2022年06月, 第26回RADIOISOTOPES誌 論文奨励賞, マウス精巣器官培養法を活用した放射線不妊メカニズムの解析, 日本アイソトープ協会
神長 輝一;横谷 明徳;福永 久典

2020年12月, 優秀発表賞, X線照射ストレス下における細胞内Caイオンダイナミクスの測定法の検討, 量子生命科学会第2回大会
鈴木碧海;横谷明徳

2020年10月, 日本放射線影響学会賞, 放射線DNA損傷生成の物理化学的初期過程、及びマイクロビームとライブセル観察を組み合わせた細胞の放射線に対する応答システムの研究, 日本放射線影響学会
横谷 明徳

2019年05月, 優秀賞, X線小角散乱法によるDNA修復タンパク質（XRCC4）複合体形成過程の研究, 量子生命科学会第1回大会
長谷川真保;西久保開;藤原悟;松尾龍人;横谷明徳

Computational analysis of the spatial distributions of low-energy electrons generated via water photolysis and photoinjection into electrodes in water
Takeshi Kai; Tomohiro Toigawa; Yusuke Matsuya; Yuho Hirata; Hidetsugu Tsuchida; Akinari Yokoya, ラスト(シニア)オーサー
The Journal of Chemical Physics, 2025年04月21日, ［査読有り］

チューブリン重合反応に対するX 線影響の検討 —インビトロ再構成実験系を用いたアプローチ—
阿部紀宜; 清野良輔; 横谷明徳; 福永久典, Japan Radioisotope Association
RADIOISOTOPES, 2025年03月15日, ［査読有り］

Multiple DNA damages induced by water radiolysis demonstrated using a dynamic Monte Carlo code
Takeshi Kai; Tomohiro Toigawa; Yusuke Matsuya; Yuho Hirata; Hidetsugu Tsuchida; Yuma Ito; Akinari Yokoya, ラスト(シニア)オーサー, Multiple DNA damage resulting from different nearby ionizations of water molecules is an important process of the initial step of radiobiological effects. Several important characteristics of the damaged DNA site such as the critical size and types of chemical lesions are not well-known. We investigated this long-term issue by developing a dynamic Monte Carlo code for the chemical process. The reaction probabilities and the spatial distribution of lesions were theoretically solved as a function of the spur radius and distance between DNA and the initial ionisation position. From our previous reported results, we suggest that a hydroxyl radical and a hydrated electron from a single spur can concomitantly react within a 10 base pairs DNA to induce a multiple DNA damage site comprising a DNA single-strand break and reductive nucleobase damage; however, the reaction probability is 0.4% or less. Once this combination arises, it may result in a DNA double-strand break (DSB). DSBs are difficult to repair, which may lead to cell death or misrepair, and could lead to point mutations in the genome., NATURE PORTFOLIO
COMMUNICATIONS CHEMISTRY, 2025年03月06日, ［査読有り］

Distribution of the dose response in a silicone-based radio-fluorogenic dosimeter and FWT-60 irradiated with monochromatic low-energy X-rays
Seiko Nakagawa; Takuya Maeyama; Akinari Yokoya; Maki Ohara; Noriko Usami, Elsevier BV
Radiation Measurements, 2025年02月, ［査読有り］

Super-competition as a Novel Mechanism of the Dose-rate Effect in Radiation Carcinogenesis: A Mathematical Model Study.
Yuya Hattori; Kento Nagata; Ritsuko Watanabe; Akinari Yokoya; Tatsuhiko Imaoka, Data from animal experiments show that the radiation-related risk of cancer decreases if the dose rate is reduced, even though the cumulative dose is unchanged (i.e., a dose-rate effect); however, the underlying mechanism is not well understood. To explore factors underlying the dose-rate effect observed in experimental rat mammary carcinogenesis, we developed a mathematical model that accounts for cellular dynamics during carcinogenesis, and then examined whether the model predicts cancer incidence. A mathematical model of multistage carcinogenesis involving radiation-induced cell death and mutagenesis was constructed using differential equations. The mutation rate was changed depending on the dose rate. The model also considered competition among cells with various mutation levels. The main parameters of the model were determined using previous experimental data. The parameters of the model were consistent with experimental observations. A dose-rate effect on carcinogenesis became apparent when the relationship between dose rate and mutation rate was linear quadratic or quadratic. The dose-rate effect became prominent when cells with more mutations preferentially compensated for the radiation-induced death of cells with fewer mutations. The phenomenon by which mutated cells gain a competitive advantage over normal cells is known as super-competition. Here, we identified super-competition as a novel mechanism underlying the dose-rate effects on carcinogenesis. The data also confirmed the relevance of the shape of the relationship between dose rate and the mutation rate. Thus, this study provides new evidence for the mechanism underlying the dose-rate effect, which is important for predicting the cancer-related risks of low-dose-rate irradiation.
Radiation Research, 2025年01月20日, ［査読有り］

Significant role of secondary electrons in the formation of a multi-body chemical species spur produced by water radiolysis
Takeshi Kai; Tomohiro Toigawa; Yusuke Matsuya; Yuho Hirata; Tomoya Tezuka; Hidetsugu Tsuchida; Akinari Yokoya, ラスト(シニア)オーサー, Abstract

Scientific insights into water photolysis and radiolysis are essential for estimating the direct and indirect effects of deoxyribonucleic acid (DNA) damage. Secondary electrons from radiolysis intricately associated with both effects. In our previous paper, we simulated the femtosecond (1 × 10^− 15 s) dynamics of secondary electrons ejected by energy depositions of 11−19 eV into water via high-energy electron transport using a time-dependent simulation code. The results contribute to the understanding of simple “intra-spur” chemical reactions of tree-body chemical species (hydrated electrons, hydronium ion and OH radical) in subsequent chemical processes. Herein, we simulate the dynamics of the electrons ejected by energy depositions of 20−30 eV. The present results contribute to the understanding of complex “inter-spur” chemical reactions of the multi-body chemical species as well as for the formation of complex DNA damage with redox site and strand break on DNA. The simulation results present the earliest formation mechanism of an unclear multi-body chemical species spur when secondary electrons induce further ionisations or electronic excitations. The formation involves electron–water collisions, i.e. ionisation, electronic excitation, molecular excitation and elastic scattering. Our simulation results indicate that (1) most secondary electrons delocalise to ~ 12 nm, and multiple collisions are sometimes induced in a water molecule at 22 eV deposition energy. (2) The secondary electrons begin to induce diffuse band excitation of water around a few nm from the initial energy deposition site and delocalise to ~ 8 nm at deposition energies ~ 25 eV. (3) The secondary electron can cause one additional ionisation or electronic excitation at deposition energies > 30 eV, forming a multi-body chemical species spur. Thus, we propose that the type and density of chemical species produced by water radiolysis strongly depend on the deposition energy. From our results, we discuss formation of complex DNA damage., Springer Science and Business Media LLC
Scientific Reports, 2024年10月21日, ［査読有り］

Luminal progenitor and mature cells are more susceptible than basal cells to radiation-induced DNA double-strand breaks in rat mammary tissue.
Kento Nagata; Mayumi Nishimura; Kazuhiro Daino; Yukiko Nishimura; Yuya Hattori; Ritsuko Watanabe; Daisuke Iizuka; Akinari Yokoya; Keiji Suzuki; Shizuko Kakinuma; Tatsuhiko Imaoka, Ionizing radiation promotes mammary carcinogenesis. Induction of DNA double-strand breaks (DSBs) is the initial event after radiation exposure, which can potentially lead to carcinogenesis, but the dynamics of DSB induction and repair are not well understood at the tissue level. In this study, we used female rats, which have been recognized as a useful experimental model for studying radiation effects on the mammary gland. We focused on differences in DSB kinetics among basal cells, luminal progenitor and mature cells in different parts of the mammary duct. 53BP1 foci were used as surrogate markers of DSBs, and 53BP1 foci in each mammary epithelial cell in immunostained tissue sections were counted 1-24 h after irradiation and fitted to an exponential function of time. Basal cells were identified as cytokeratin (CK) 14+ cells, luminal progenitor cells as CK8 + 18low cells and luminal mature cells as CK8 + 18high cells. The number of DSBs per nucleus tended to be higher in luminal cells than basal cells at 1 h post-irradiation. A model analysis indicated that basal cells in terminal end buds (TEBs), which constitute the leading edge of the mammary duct, had significantly fewer initial DSBs than the two types of luminal cells, and there was no significant difference in initial amount among the cell types in the subtending duct. The repair rate did not differ among mammary epithelial cell types or their locations. Thus, luminal progenitor and mature cells are more susceptible to radiation-induced DSBs than are basal cells in TEBs.
Journal of Radiation Research, 2024年09月05日, ［査読有り］

〔主要な業績〕Consideration of the dielectric response for radiation chemistry simulations.
Tomohiro Toigawa; Takeshi Kai; Yuta Kumagai; Akinari Yokoya, ラスト(シニア)オーサー, The spur reaction, a spatially nonhomogeneous chemical reaction following ionization, is crucial in radiolysis or photolysis in liquids, but the spur expansion process has yet to be elucidated. One reason is the need to understand the role of the dielectric response of the solvating molecules surrounding the charged species generated by ionization. The dielectric response corresponds to the time evolution of the permittivity and might affect the chemical reaction-diffusion of the species in a spur expansion process. This study examined the competitive relationship between reaction-diffusion kinetics and the dielectric response by solving the Debye-Smoluchowski equation while considering the dielectric response. The Coulomb force between the charged species gradually decreases with the dielectric response. Our calculation results found a condition where fast recombination occurs before the dielectric response is complete. Although it has been reported that the primary G-values of free electrons depend on the static dielectric constant under low-linear-energy transfer radiation-induced ionization, we propose that considering the dielectric response can provide a deeper insight into fast recombination reactions under high-linear-energy transfer radiation- or photo-induced ionization. Our simulation method enables the understanding of fast radiation-induced phenomena in liquids.
The Journal of chemical physics, 2024年06月07日, ［査読有り］

Ultrafast fragmentation of highly-excited doubly-ionized deoxyribose: role of the liquid water environment.
Marie-Anne Hervé du Penhoat; Alexandre Souchaud; Aashini Rajpal; Rodolphe Vuilleumier; Marie-Pierre Gaigeot; Ivano Tavernelli; Kentaro Fujii; Akinari Yokoya; Sergio Díaz-Tendero; Marie-Françoise Politis, Ab initio molecular dynamics simulations are used to investigate the fragmentation dynamics following the double ionization of 2-deoxy-D-ribose (DR), a major component in the DNA chain. Different ionization scenarios are considered to provide a complete picture. First focusing on isolated DR2+, fragmentation patterns are determined for the ground electronic state, adding randomly distributed excitation energy to the nuclei. These patterns differ for the two isomers studied. To compare thermal and electronic excitation effects, Ehrenfest dynamics are also performed, allowing to remove the two electrons from selected molecular orbitals. Two intermediate-energy orbitals, localized on the carbon chain, were selected. The dissociation pattern corresponds to the most frequent pattern obtained when adding thermal excitation. On the contrary, targeting the four deepest orbitals, localized on the oxygen atoms, leads to selective ultrafast C-O and/or O-H bond dissociation. To probe the role of environment, a system consisting of a DR molecule embedded in liquid water is then studied. The two electrons are removed from either the DR or the water molecules directly linked to the sugar through hydrogen bonds. Although the dynamics onset is similar to that of isolated DR when removing the same deep orbitals localized on the sugar oxygen atoms, the subsequent fragmentation patterns differ. Sugar damage also occurs following the Coulomb explosion of neighboring H2O2+ molecules due to interaction with the emitted O or H atoms.
Physical chemistry chemical physics : PCCP, 2024年05月29日, ［査読有り］

Decomposition characteristics of a hypervalent iodine compound, 2-iodosobenzoic acid, exposed to monochromatic X-rays around the iodine L3-edge energy region
Maki Ohara; Yudai Izumi; Hideo Takakura; Shosei Enomoto; Kentaro Fujii; Akinari Yokoya; Mikako Ogawa, Elsevier BV
Radiation Physics and Chemistry, 2024年03月, ［査読有り］

X-ray photoemission and absorption spectroscopy of a hypervalent iodine compound, 2-iodosobenzoic acid
Yudai Izumi; Maki Ohara; Kentaro Fujii; Akinari Yokoya; Mikako Ogawa, Elsevier BV
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2024年02月, ［査読有り］

Electronic states of fluorinated DNA components revealed by X-ray photoelectron spectroscopy
S. Onuma; Y. Izumi; M. Ohara; A. Yokoya, ラスト(シニア)オーサー
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2024年02月, ［査読有り］

ゲノムの構造と機能、およびエネルギー代謝に及ぼす 放射線の長期影響
廣瀬 エリ; 横谷 明徳; 野口 実穂; Lucie Huar; 鈴木 啓司
放射線生物研究, 2024年, ［査読有り］

Comparison of core and valence band electronic structures of bulk uracil and 5-halouracils
Yudai Izumi; Maki Ohara; Yuji Baba; Akinari Yokoya, ラスト(シニア)オーサー
Physical Chemistry Chemical Physics, 2024年, ［査読有り］

High linear energy transfer (LET) nature of alanine radical yield by soft X-ray irradiations studied by electron spin resonance (ESR) applications
Seiko Nakagawa; Akinari Yokoya; Maki Ohara; Noriko Usami; Mizue Asada; Motoyasu Fujiwara; Toshikazu Nakamura; Kenji Ishikawa, Elsevier BV
Radiation Physics and Chemistry, 2024年01月, ［査読有り］

Temporal Dynamic Regulation of Autophagy and Senescence Induction in Response to Radiation Exposure.
Miho Noguchi; Tomokazu Ihara; Keiji Suzuki; Akinari Yokoya, ラスト(シニア)オーサー, Autophagy and senescence are closely related cellular responses to genotoxic stress, and play significant roles in the execution of cellular responses to radiation exposure. However, little is known about their interplay in the fate-decision of cells receiving lethal doses of radiation. Here, we report that autophagy precedes the establishment of premature senescence in normal human fibroblasts exposed to lethal doses of radiation. Activation of the p53-dependent DNA damage response caused sustained dephosphorylation of RB proteins and consequent cell cycle arrest, concurrently with Ulk1 dephosphorylation at Ser638 by PPM1D, which promoted autophagy induction 1-2 days after irradiation. In addition, mitochondrial fragmentation became obvious 1-2 days after irradiation, and autophagy was further enhanced. However, Ulk1 levels decreased significantly after 2 days, resulting in lower LC3-II levels. An autophagic flux assay using chloroquine (CQ) also revealed that the flux in irradiated cells gradually decreased over 30 days. In contrast, lysosomal augmentation started at 1 day, became significantly upregulated after 5 days, and continued for over 30 days. After a rapid decrease in autophagy, p16 expression increased and senescence was established, but autophagic activity remained reduced. These results demonstrated that X-ray irradiation triggered two processes, autophagy and senescence, with the former being temporary and regulated by DNA damage response and mitophagy, and the latter being sustained and regulated by persistent cell cycle arrest. The interplay between autophagy and senescence seems to be essential for the proper implementation of the cellular response to radiation exposure.
Radiation research, 2023年10月30日, ［査読有り］

First-principles simulation of an ejected electron produced by monochromatic deposition energy to water at the femtosecond order.
Takeshi Kai; Tomohiro Toigawa; Yusuke Matsuya; Yuho Hirata; Tomoya Tezuka; Hidetsugu Tsuchida; Akinari Yokoya, ラスト(シニア)オーサー, This study uses a time-dependent first-principles simulation code to investigate the transient dynamics of an ejected electron produced in the monochromatic deposition energy from 11 to 19 eV in water. The energy deposition forms a three-body single spur comprising a hydroxyl radical (OH˙), hydronium ion (H3O+), and hydrated electron (eaq-). The earliest formation involves electron thermalization and delocalization dominated by the molecular excitation of water. Our simulation results show that the transient electron dynamics primarily depends on the amount of deposition energy to water; the thermalization time varies from 200 to 500 fs, and the delocalization varies from 3 to 10 nm in this energy range. These features are crucial for determining the earliest single-spur formation and facilitating a sequential simulation from an energy deposition to a chemical reaction in water photolysis or radiolysis. The spur radius obtained from the simulation correlates reasonably with the experimental-based estimations. Our results should provide universalistic insights for analysing ultrafast phenomena dominated by the molecular excitation of water in the femtosecond order.
RSC advances, 2023年10月29日, ［査読有り］

放射線DNA損傷の量子過程とその難修復性評価の試み
横谷明徳, 筆頭著者, 放射線によるDNA損傷の物理化学的初期過程の解明は,低線量放射線のリスク評価のみならずメカニズムに基づいた放射線治療の基盤を提供すると考えられる。本稿ではミクロな世界を支配する量子的性質のひとつである電子物性に焦点を当て,DNA内に臭素(Br)原子を取り込ませた細胞の持つ大きな放射線増感の起源を,X線光電子分光による物理計測と量子化学計算の両面から探る研究を紹介する。さらにDNA損傷の難修復性を評価するための,EGFP発現プラスミドDNAを放射線照射した後非照射細胞へ導入する新しい試みについても併せて紹介する。(著者抄録), (株)北隆館
Bio Clinica, 2023年08月, ［招待有り］

X-ray irradiation-induced ligand cleavage of a phthalocyanine derivative, tin (IV) phthalocyanine dichloride: A potential for X-ray activation of caged compounds
Yudai Izumi; Maki Ohara; Kentaro Fujii; Akinari Yokoya; Mikako Ogawa, The X-ray dissociation of tin (IV) phthalocyanine dichloride (SnCl2Pc) was investigated using X-ray photoemission spectroscopy. The photoemission spectra of SnCl2Pc after X-ray irradiation exhibited additional components assigned as chloride ions and tin (II) phthalocyanine, as well as decomposition products from the phthalocyanine framework, indicating that X-ray irradiation induced the release of chloride ions as ligands from SnCl2Pc. Although the ligand releases were caused not by a simple cleavage between Cl-Sn bonding but by accompanying the molecular framework destruction, these reactions may robustly facilitate a novel application of X-rays to activate caged compounds in tissues.
Chemical Physics Letters, 2023年07月, ［査読有り］

〔主要な業績〕Incorporation of a bromine atom into DNA-related molecules changes their electronic properties.
Misaki Hirato; Akinari Yokoya; Yuji Baba; Seiji Mori; Kentaro Fujii; Shin-Ichi Wada; Yudai Izumi; Yoshinori Haga, 責任著者, To understand the mechanism underlying the high radio-sensitisation of living cells possessing brominated genomic DNA, X-ray photoelectron spectroscopy (XPS) using synchrotron X-rays with energies of 2000 or 2500 eV was used to study brominated and nonbrominated nucleobases, nucleosides and nucleotides. The bromine atom significantly reduced the energy gap between the valence and conduction states, although the core level states were not greatly affected. This finding was supported by quantum chemical calculation for the nucleobases and nucleosides. Our findings strongly indicate that the energy gaps between the valence and conduction levels of the molecules are significantly reduced by bromination. Furthermore, the brominated molecules are more likely to produce inelastic scattering low energy electrons upon exposure to 2000 or 3000 eV X-rays. This modification of electronic properties around the brominated group may both facilitate electron transfer to the brominated site in DNA and increase the probability of reaction with low energy electrons. These processes can induce DNA damage, presumably resulting in debromination of the uracil moiety and a subsequent cytotoxic effect.
Physical chemistry chemical physics : PCCP, 2023年05月31日, ［査読有り］

Structural study of wild-type and phospho-mimic XRCC4 dimer and multimer proteins using circular dichroism spectroscopy.
Kai Nishikubo; Maho Hasegawa; Yudai Izumi; Kentaro Fujii; Koichi Matsuo; Yoshihisa Matsumoto; Akinari Yokoya, ラスト(シニア)オーサー, PURPOSE: To investigate the structural features of wild-type and phospho-mimicking mutated XRCC4 protein, a protein involved in DNA double-strand break repair. MATERIALS AND METHODS: XRCC4 with a HisTag were expressed by E. coli harboring plasmid DNA and purified. Phospho-mimicking mutants in which one phosphorylation site was replaced with aspartic acid were also prepared in order to reproduce the negative charge resulting from phosphorylation. The proteins were separated into dimers and multimers by gel filtration chromatography. Circular dichroism (CD) spectroscopy was performed in the region from ultraviolet to vacuum-ultraviolet. The CD spectra were analyzed with two analysis programs to evaluate the secondary structures of the wild-type and phospho-mimicked dimers and multimers. RESULT AND DISCUSSION: The proportion of β-strand in the wild-type dimers was very low, particularly in their C-terminal region, including the five phosphorylation sites. The secondary structure of the phospho-mimic hardly changed from the monomeric to dimeric forms. In contrast, the β-strand content increased and the α-helix content decreased upon multimerization of the wild-type protein. The structural change of multimers slightly depended on the phospho-mimic site. These results suggest that the β-strand structure stabilizes the multimerization of XRCC4 and it is regulated by phosphorylation at the C-terminal site in living cells. CONCLUSION: An increase in the β-strand content in XRCC4 is essential for stabilization of the multimeric form through C-terminal phosphorylation, allowing formation of the large double-strand break repair machinery.
International journal of radiation biology, 2023年05月12日, ［査読有り］

Nature of the physicochemical process in water photolysis uncovered by a computer simulation.
Takeshi Kai; Tomohiro Toigawa; Masatoshi Ukai; Kentaro Fujii; Ritsuko Watanabe; Akinari Yokoya, ラスト(シニア)オーサー, In this work, we investigate the physicochemical process of water photolysis to bridge physical and chemical processes by a newly developed first-principles calculation code. The deceleration, thermalization, delocalization, and initial hydration of the extremely low-energy electrons ejected by water photolysis are sequentially tracked in the condensed phase. We show herein the calculated results for these sequential phenomena during 300 fs. Our results indicate that the mechanisms heavily depend on the intermolecular vibration and rotation modes peculiar to water and the momentum transfer between the electrons and the water medium. We suggest that using our results for the delocalized electron distribution will reproduce successive chemical reactions measured by photolysis experiments using a chemical reaction code. We expect our approach to become a powerful technique for various scientific fields related to water photolysis and radiolysis.
The Journal of chemical physics, 2023年04月28日, ［査読有り］

Secondary structural analyses of histone H2A-H2B proteins extracted from heated cells.
Yudai Izumi; Koichi Matsuo; Akinari Yokoya, ラスト(シニア)オーサー, Histone proteins, building blocks of chromatins, participate in enzymatic reactions in cells heated at around 45°C though in vitro the denaturation of histones significantly proceeds at a similar temperature. It implies that unidentified mechanisms prevent thermal denaturation of histones in vivo. However, studies on the histone structures in the heated cells have been scarce. Here, we analyzed the secondary structures of histone H2A-H2B proteins originating from the heated cells using circular dichroism spectroscopy. The secondary structure contents of the H2A-H2B extracted from the heated cells differed from those of H2A-H2B both native and denatured in vitro but reverted to the native structures by incubating the heated cells at 37°C within 2 h. Such structural flexibility may play a role in protecting genomic functions governed by chromatin structures from heat stresses.
Chirality, 2023年03月, ［査読有り］

Initial yield of hydrated electron production from water radiolysis based on first-principles calculation
Takeshi Kai; Tomohiro Toigawa; Yusuke Matsuya; Yuho Hirata; Tomoya Tezuka; Hidetsugu Tsuchida; Akinari Yokoya, ラスト(シニア)オーサー, For water radiolysis, conventional simulation methods estimate free radical yields based on the cross-sections. Our results indicated that electron dynamic motion must be further solved to predict the initial yields of hydrated electrons., Royal Society of Chemistry (RSC)
RSC Advances, 2023年02月, ［査読有り］

Mitochondrial Metabolism in X-Irradiated Cells Undergoing Irreversible Cell-Cycle Arrest.
Eri Hirose; Miho Noguchi; Tomokazu Ihara; Akinari Yokoya, ラスト(シニア)オーサー, Irreversible cell-cycle-arrested cells not undergoing cell divisions have been thought to be metabolically less active because of the unnecessary consumption of energy for cell division. On the other hand, they might be actively involved in the tissue microenvironment through an inflammatory response. In this study, we examined the mitochondria-dependent metabolism in human cells irreversibly arrested in response to ionizing radiation to confirm this possibility. Human primary WI-38 fibroblast cells and the BJ-5ta fibroblast-like cell line were exposed to 20 Gy X-rays and cultured for up to 9 days after irradiation. The mitochondrial morphology and membrane potential were evaluated in the cells using the mitochondrial-specific fluorescent reagents MitoTracker Green (MTG) and 5,5',6,6'-tetraethyl-benzimidazolylcarbocyanine iodide (JC-1), respectively. The ratio of the mean MTG-stained total mitochondrial area per unit cell area decreased for up to 9 days after X-irradiation. The fraction of the high mitochondrial membrane potential area visualized by JC-1 staining reached its minimum 2 days after irradiation and then increased (particularly, WI-38 cells increased 1.8-fold the value of the control). Their chronological changes indicate that the mitochondrial volume in the irreversible cell-cycle-arrested cells showed significant increase concurrently with cellular volume expansion, indicating that the mitochondria-dependent energy metabolism was still active. These results indicate that the energy metabolism in X-ray-induced senescent-like cells is active compared to nonirradiated normal cells, even though they do not undergo cell divisions.
International journal of molecular sciences, 2023年01月17日, ［査読有り］

Analysis of differentially expressed genes on human X chromosome harboring large deletion induced by X-rays.
Eri Hirose; Akinari Yokoya; Kasumi Kawamura; Keiji Suzuki, We examined here normal human cells with large deletions encompassing the hypoxanthine-phosphoribosyltransferase 1 (HPRT1) gene on X chromosome. Expression levels of genes on X chromosome were analyzed by microarray and RT-qPCR method, and differentially expressed genes (DEGs) were extracted. We found that DEGs were not limited to the genes flanking deleted regions but spread over the entire X chromosome. Interestingly, the gene regulation patterns were similar to a large extent among independent clones that have similar-sized large deletions involving the HPRT1 gene. Thus, it is indicated that an impact of large deletion on possible epigenetic transcriptional regulation is not limited to the regions proximal to the deletion region.
Journal of radiation research, 2023年01月06日, ［査読有り］

Core level ionization or excitation and Auger relaxation induce clustered DNA damage.
Akinari Yokoya; Yui Obata, 筆頭著者, Ionizing radiation causes various types of DNA damage, such as single- (SSBs) and double-strand breaks (DSBs), nucleobase lesions, abasic sites (AP sites), and cross-linking between complementary strands of DNA or DNA and proteins. DSBs are among the most harmful type of DNA damage, inducing serious genetic effects such as cell lethality and mutation. Nucleobase lesions and AP sites, on the other hand, may be less deleterious and are promptly repaired by base excision repair (BER) pathways. Recently, biochemical approaches to quantify nucleobase lesions and AP sites have revealed certain types of non-strand break lesions as harmful DNA damage, called clustered DNA damage. Such clusters can retard nucleobase excision repair enzymes, and can sometimes be converted to DSBs by BER catalysis. This unique character of clustered DNA damage strongly depends on the spatial density of ionization or excitation events occurring at the track end of initial radiation or low energy secondary electrons. In particular, the photoelectric effect of elements comprising biological molecules, followed by emission of Auger electrons, are key factors in determining the future fate of each clustered damage site. This chapter describes biological studies of clustered nucleobase lesions with SSBs or AP sites, and mechanistical studies on core level excitation and Auger relaxation giving rise to clustered DNA damage.
The Enzymes, 2022年10月07日, ［査読有り］, ［招待有り］

X-ray photoelectron spectroscopy of Thymine and 5-Bromouracil studied by Symmetry-Adapted-Cluster Configuration-Interaction (SAC-CI) theory
Yusaku I. Kurokawa; Hiroshi Nakatsuji; Misaki Hirato; Akinari Yokoya, ラスト(シニア)オーサー, Elsevier BV
Chemical Physics Letters, 2022年10月, ［査読有り］

Establishment of a Method for Investigating Direct and Indirect Actions of Ionizing Radiation Using Scavenger-free Plasmid DNA.
Hao Yu; Yusuke Kondo; Kentaro Fujii; Akinari Yokoya; Shinichi Yamashita, In this study, an improved method using scavenger-free plasmid DNA was established to accurately determine yields of DNA damage induced by direct and indirect actions of ionizing radiation. The scavenger-free plasmid DNA was obtained by dialysis over 5-7 days, and the DNA solvent was replaced with phosphate buffer to completely remove impurities, which could be scavengers of radicals produced as a result of water radiolysis. DNA samples of films and dilute aqueous solutions were used to separately evaluate contributions of the direct and indirect actions of X rays (150-160 kVp). The irradiated DNA was analyzed by agarose gel electrophoresis to quantify strand-break yields. The yields of single-strand breaks (SSBs), n(SSB), were determined to be (6.5 ± 2.0) × 10-10 and (3.1 ± 0.9) × 10-7 SSBs/Gy/Da for the film and solution samples, respectively, showing a significant contribution of hydroxyl radicals (•OH) compared with direct energy depositions from ionizing radiation to DNA. As observed in SSBs, the yields of double-strand breaks (DSBs), n(DSB), were (5.6 ± 1.1) × 10-11 and (1.3 ± 0.2) × 10-8 DSBs/Gy/Da for the film and solution samples, respectively. The yield ratio of DSBs to SSBs, that is, n(DSB)/n(SSB), was 0.091 ± 0.026 for the film samples, while it was much lower for the solution samples (0.045 ± 0.010), indicating that direct actions result in more localized strand breaks relative to indirect actions. Base excision repair enzymes, namely, endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg), were utilized after irradiations to convert base lesions and apurinic/apyrimidinic (AP) sites into strand breaks. The amounts of Nth and Fpg for the conversion were optimized to a few units per µg of DNA, although the optimal concentrations can differ among conditions.
Radiation Research, 2022年06月01日, ［査読有り］

Molecular Interactions of Normal and Irradiated Tubulins During Polymerization
Hisanori Fukunaga; Yuka Kimura; Ami Suzuki; Yuki Kawabata; Akinari Yokoya, ラスト(シニア)オーサー, Microtubules, one of the cytoskeletons, are highly dynamic structures that play a variety of roles in maintaining cell morphology, cell division and intracellular transport. Microtubules are composed of heterodimers of α- and β-tubulins, which are repeatedly polymerized and depolymerized. To investigate the radiation-induced impacts on the polymerization reaction of tubulins, we evaluated the molecular interactions between normal and irradiated tubulins. First, the polymerization reaction of the tubulins was measured after stepwise irradiation from 0 Gy to 1,000 Gy of X rays. The polymerization was inhibited in a dose-dependent manner. Next, the tubulins' polymerization reaction was then measured after the tubulin that was damaged from the exposure to 1,000 Gy of X rays was mixed with the normal tubulins. Our findings reveal that the radiation dose-dependent change in the degree of overall microtubule polymerization progression depends on the ratio of damaged tubulin. This result is biochemical evidence that non-DNA damage (in this case, cytoskeletal damage) from cytoplasmic radiation exposure may inhibit cell division, suggesting that some cytoskeletal damage may also affect the fate of the entire cell., Radiation Research Society
Radiation Research, 2022年05月23日, ［査読有り］

マウス精巣器官培養法を活用した放射線不妊メカニズムの解析
神長輝一; 横谷明徳; 福永久典, Japan Radioisotope Association
RADIOISOTOPES, 2022年03月15日, ［査読有り］, ［招待有り］

A Brief Overview of Radiation-Induced Effects on Spermatogenesis and Oncofertility.
Hisanori Fukunaga; Akinari Yokoya; Kevin M Prise, The genotoxicity of radiation on germ cells may be passed on to the next generation, thus its elucidation is not only a scientific issue but also an ethical, legal, and social issue in modern society. In this article, we briefly overview the effects of radiation on spermatogenesis and its associated genotoxicity, including the latest findings in the field of radiobiology. The potential role of transgenerational effects is still poorly understood, and further research in this area is desirable. Furthermore, from the perspective of oncofertility, we discuss the historical background and clinical importance of preserving male fertility during radiation treatment and the potential of microbeam radiotherapy. We hope that this review will contribute to stimulating further discussions and investigations for therapies for pediatric and adolescent/young adult patients.
Cancers, 2022年02月04日, ［査読有り］

No Intercellular Regulation of the Cell Cycle among Human Cervical Carcinoma HeLa Cells Expressing Fluorescent Ubiquitination-Based Cell-Cycle Indicators in Modulated Radiation Fields.
Hisanori Fukunaga; Kiichi Kaminaga; Eri Hirose; Ritsuko Watanabe; Noriko Usami; Kevin M Prise; Akinari Yokoya, ラスト(シニア)オーサー, The non-targeted effects of radiation have been known to induce significant alternations in cell survival. Although the effects might govern the progression of tumor sites following advanced radiotherapy, the impacts on the intercellular control of the cell cycle following radiation exposure with a modified field, remain to be determined. Recently, a fluorescent ubiquitination-based cell-cycle indicator (FUCCI), which can visualize the cell-cycle phases with fluorescence microscopy in real time, was developed for biological cell research. In this study, we investigated the non-targeted effects on the regulation of the cell cycle of human cervical carcinoma (HeLa) cells with imperfect p53 function that express the FUCCI (HeLa-FUCCI cells). The possible effects on the cell-cycle phases via soluble factors were analyzed following exposure to different field configurations, which were delivered using a 150 kVp X-ray irradiator. In addition, using synchrotron-generated, 5.35 keV monochromatic X-ray microbeams, high-precision 200 μm-slit microbeam irradiation was performed to investigate the possible impacts on the cell-cycle phases via cell-cell contacts. Collectively, we could not detect the intercellular regulation of the cell cycle in HeLa-FUCCI cells, which suggested that the unregulated cell growth was a malignant tumor. Our findings indicated that there was no significant intercellular control system of the cell cycle in malignant tumors during or after radiotherapy, highlighting the differences between normal tissue and tumor characteristics.
International journal of molecular sciences, 2021年11月26日, ［査読有り］

〔主要な業績〕Expression of an X-Ray Irradiated EGFP-Expressing Plasmid Transfected into Nonirradiated Human Cells.
Yui Obata; Hiroki Nakaue; Keishiro Hirasaki; Nobuyoshi Akimitsu; Akinari Yokoya, ラスト(シニア)オーサー, To investigate the repairability of X-ray induced DNA damage, particularly non-double-strand breaks in living cells, enhanced green fluorescent protein (EGFP)-expressing plasmids X-ray irradiated and then transfected into nonirradiated human cells, MCF7 and MCF10A. Live-cell imaging of EGFP fluorescence was performed to measure the efficiency of plasmid repair in cells. The number of EGFP-expressing cells significantly decreased with increasing X-ray dose for both cell lines. The obtained kinetic curves of EGFP expression indicating plasmid repair were quantitatively compared against algebraically calculated ones based on the values of the transfected plasmids that had been treated with nicking or restriction enzymes. Then, assuming a Poisson distribution of single-strand breaks (SSBs), the number of cells carrying these nicked plasmids that could express EGFP were estimated. Our experimental results revealed considerably fewer cells expressing EGFP compared to the expected values we had calculated. These results suggest that the lower proportion of cells expressing EGFP as a measure of plasmid repair was due not only to the complex chemical structures of termini created by SSBs compared to those created by enzyme treatments, but also that base lesions or AP sites proximately arising at the strand-break termini might compromise EGFP expression. These results emphasize that radiation-induced DNA breaks are less repairable than enzymatically induced DNA breaks, which is not apparent when using conventional gel electrophoresis assays of plasmid DNA.
Radiation research, 2021年09月01日, ［査読有り］

〔主要な業績〕X-ray induced luminescence spectroscopy for DNA damaging intermediates aided by a monochromatic synchrotron radiation
Yusaku Terao; Yoshiaki Kumagai; Issei Suzuki; Takahiro Tsuchiya; Masatoshi Ukai; Akinari Yokoya; Kentaro Fujii; Yoshihiro Fukuda; Yuji Saitoh, Informa UK Limited
International Journal of Radiation Biology, 2021年08月23日, ［査読有り］

〔主要な業績〕Molecular Configuration of Human Genome Neighboring Megabase-Sized Large Deletions Induced by X-Ray Irradiation.
Eri Hirose; Keiji Suzuki; Akinari Yokoya, ラスト(シニア)オーサー, The genomic landscape neighboring large deletions including the hypoxanthine-guanine phosphoribosyl transferase (HPRT) locus on human X chromosome in 6-thioguanine-resistant mutants originating from immortalized human fibroblast cells exposed to X rays was characterized by real-time quantitative PCR (qPCR)-based analyses. Among the 13 mutant clones with large deletions extending over several Mb, including the HPRT locus, revealed by 10 conventional sequence-tagged site (STS) markers, three clones bearing the largest deletions were selected for further qPCR analysis using another 21 STS markers and 15 newly designed PCR primer pairs. The results indicated that the major deletions were in very specific regions between the 130-Mb and 140-Mb positions containing the HPRT locus on the X chromosome and, contrary to our initial expectations, additional minor deletions were distributed in a patchwork pattern. These findings strongly indicate that the complex deletion patterns in the affected chromosome are related to the radiation track structure with spatially heterogeneous energy deposition and the specific structure of the chromatin-nuclear membrane complex. The uncovered complex deletion patterns are in agreement with the idea of complex chromatin damage, which is frequently associated with carcinogenesis.
Radiation research, 2021年06月01日, ［査読有り］

〔主要な業績〕Targeted Nuclear Irradiation with an X-Ray Microbeam Enhances Total JC-1 Fluorescence from Mitochondria
Kiichi Kaminaga; Ryo Hamada; Noriko Usami; Keiji Suzuki; Akinari Yokoya, ラスト(シニア)オーサー, Several studies have demonstrated that mitochondria are critically involved in the pleiotropic manifestation of radiation effects. While conventional whole-cell irradiation compromises the function of mitochondria, the effects of subcellular targeted radiation are not yet fully understood. In this study, normal human diploid cells with cell-cycle indicators were irradiated using a synchrotron X-ray microbeam, and mitochondrial membrane potential was quantified by JC-1 over the 72-h period postirradiation. Cytoplasmic irradiation was observed to temporarily enlarge the mitochondrial area with high membrane potential, while the total mitochondrial area did not change significantly. Unexpectedly, cell-nucleus irradiation promoted a similar increase not only in the mitochondrial areas with high membrane potential, but also in those with low membrane potential, which gave rise to the apparent increase in the total mitochondrial area. Augmentation of the mitochondrial area with low membrane potential was predominantly observed among G1 cells, suggesting that nucleus irradiation during the G1 phase regulated the mitochondrial dynamics of the cytoplasm, presumably through DNA damage in the nucleus., Radiation Research Society
Radiation Research, 2020年10月12日, ［査読有り］

Spatially Fractionated Microbeam Analysis of Tissue-sparing Effect for Spermatogenesis
Hisanori Fukunaga; Kiichi Kaminaga; Takuya Sato; Karl T. Butterworth; Ritsuko Watanabe; Noriko Usami; Takehiko Ogawa; Akinari Yokoya; Kevin M. Prise, Spatially fractionated radiation therapy (SFRT) has been based on the delivery of a single high-dose fraction to a large treatment area that has been divided into several smaller fields, reducing the overall toxicity and adverse effects. Complementary microbeam studies have also shown an effective tissue-sparing effect (TSE) in various tissue types and species after spatially fractionated irradiation at the microscale level; however, the underlying biological mechanism remains elusive. In the current study, using the combination of an ex vivo mouse spermatogenesis model and high-precision X-ray microbeams, we revealed the significant TSE for maintaining spermatogenesis after spatially fractionated microbeam irradiation. We used the following ratios of the irradiated to nonirradiated areas: 50:50, 150:50 and 350:50 µm-slit, where approximately 50, 75 and 87.5% of the sample was irradiated (using center-to-center distances of 100, 200 and 400 µm, respectively). We found that the 50 and 75% micro-slit irradiated testicular tissues showed an almost unadulterated TSE for spermatogenesis, whereas the 87.5% micro-slit irradiated tissues showed an incomplete TSE. This suggests that the TSE efficiency for spermatogenesis is dependent on the size of the nonirradiated spermatogonial stem cell pool in the irradiated testicular tissues. In addition, there would be a spatiotemporal limitation of stem cell migration/competition, resulting in the insufficient TSE for 87.5% micro-slit irradiated tissues. These stem cell characteristics are essential for the accurate prediction of tissue-level responses during or after SFRT, indicating the clinical potential for achieving better outcomes while preventing adverse effects., Radiation Research Society
Radiation Research, 2020年08月19日, ［査読有り］

〔主要な業績〕Electronic properties of DNA-related molecules containing a bromine atom
Misaki Hirato; Misato Onizawa; Yuji Baba; Yoshinori Haga; Kentaro Fujii; Shin-ichi Wada; Akinari Yokoya, ラスト(シニア)オーサー, Purpose: To clarify the radiosensitization mechanism masking the Auger effect of the cells possessing brominated DNA, the electronic properties of DNA-related molecules containing Br were investigated by X-ray spectroscopy and specific heat measurement. Materials and Methods: X-ray absorption near-edge structure (XANES) and X-ray photoemission spectroscopy (XPS) were used to measure the electronic properties of the nucleotides with and without Br. We determined the specific heat of 5-bromouracil crystals with thymine as a reference molecule at low temperatures of 3–48 K to calculate the microscopic state numbers. Results: Obtained XANES and XPS spectra indicated that both the lowest unoccupied molecular orbital (LUMO) and the core-levels were not affected by the Br incorporation. The state numbers of 5-bromouracil calculated from the specific heats obtained around 25 K was about 1.5 times larger than that for thymine below 20 K, although the numbers were almost the same below 5 K. Discussion: Our results suggest that the Br atom may not contribute substantially to the LUMO and core-level electronic states of the molecule, but rather to the microscopic states related to the excitation of lattice vibrations, which may be involved in valence electronic states., Informa UK Limited
International Journal of Radiation Biology, 2020年08月12日, ［査読有り］

マイクロビームと組織培養を用いた放射線組織生物学―保健物理学と放射線生物学の接点として
福永久典; 横谷明徳, *Japanese, 日本保健物理学会
保健物理, 2020年07月20日, ［査読有り］

The Tissue-Sparing Effect of Spatially Fractionated X-rays for Maintaining Spermatogenesis: A Radiobiological Approach for the Preservation of Male Fertility after Radiotherapy.
Hisanori Fukunaga; Kiichi Kaminaga; Takuya Sato; Ritsuko Watanabe; Takehiko Ogawa; Akinari Yokoya; Kevin M Prise, Radiotherapy can result in temporary or permanent gonadal toxicity in male cancer patients despite the high precision and accuracy of modern radiation treatment techniques. Previous radiobiological studies have shown an effective tissue-sparing response in various tissue types and species following exposure to spatially fractionated radiation. In the present study, we used an ex vivo mouse testicular tissue culture model and a conventional X-ray irradiation device to evaluate the tissue-sparing effect (TSE) of spatially fractionated X-rays for the protection of male fertility from radiotherapy-related adverse effects. We revealed a significant TSE for maintaining spermatogenesis in the ex vivo testes model following spatially fractionated X-ray irradiation. Moreover, we experimentally propose a possible mechanism by which the migration of spermatogonial cells, from the non-irradiated areas to the irradiated ones, in irradiated testicular tissue, is essential for the TSE and maintaining spermatogenesis. Therefore, our findings demonstrate that the control of TSE following spatially fractionated X-rays in the testes has a considerable potential for clinical application. Interdisciplinary research will be essential for further expanding the applicability of this method as an approach for the preservation of male fertility during or after radiotherapy.
Journal of clinical medicine, 2020年04月11日, ［査読有り］

〔主要な業績〕Targeting Specific Sites in Biological Systems with Synchrotron X-Ray Microbeams for Radiobiological Studies at the Photon Factory
Akinari Yokoya; Noriko Usami, 筆頭著者, X-ray microbeams have been used to explore radiobiological effects induced by targeting a specific site in living systems. Synchrotron radiation from the Photon Factory, Japan, with high brilliance and highly parallel directionality is a source suitable for delivering a particular beam size or shape, which can be changed according to target morphology by using a simple metal slit system (beam size from 5 μm to several millimeters). Studies have examined the non-targeted effects, called bystander cellular responses, which are thought to be fundamental mechanisms of low-dose or low-dose-rate effects in practical radiation risk research. Narrow microbeams several tens of micrometers or less in their size targeted both the cell nucleus and the cytoplasm. Our method combined with live-cell imaging techniques has challenged the traditional radiobiological dogma that DNA damage is the only major cause of radiation-induced genetic alterations and is gradually revealing the role of organelles, such as mitochondria, in these biological effects. Furthermore, three-dimensionally cultured cell systems have been used as microbeam targets to mimic organs. Combining the spatial fractionation of X-ray microbeams and a unique ex vivo testes organ culture technique revealed that the tissue-sparing effect was induced in response to the non-uniform radiation fields. Spatially fractionated X-ray beams may be a promising tool in clinical radiation therapy., MDPI AG
Quantum Beam Science, 2020年01月09日, ［査読有り］

〔主要な業績〕Ab Initio Molecular Dynamics Simulations to Interpret the Molecular Fragmentation Induced in Deoxyribose by Synchrotron Soft X-Rays
Marie-Anne Hervé du Penhoat; Anis Hamila; Marie-Pierre Gaigeot; Rodolphe Vuilleumier; Kentaro Fujii; Akinari Yokoya; Marie-Françoise Politis, It has been suggested that core ionization in DNA atoms could induce complex, irreparable damage. Synchrotron soft X-rays have been used to probe the damage induced by such events in thin films of DNA components. In a complementary approach, we investigate the fragmentation dynamics following a carbon or oxygen K-shell ionization in 2-deoxy-D-ribose (DR), a major component in the DNA chain. Core ionization of the sugars hydration layer is also studied. To that aim, we use state-of-the-art ab initio Density Functional Theory-based Molecular Dynamics (MD) simulations. The ultrafast dissociation dynamics of the core ionized molecule, prior Auger decay, is modeled for about 10 fs. We show that the core-ionization of oxygen atoms within DR or its hydration layer may induce proton transfers towards nearby molecules, before Auger decay. In a second step, we model an Auger effect occurring either at the beginning or at the end of the core–hole dynamics. Two electrons are removed from the deepest valence molecular orbitals localized on the initially core-ionized oxygen atom (O*), and this electronic state is propagated by means of Ehrenfest MD. We show an ultrafast dissociation of the DR2+ molecule C-O* bonds, which, in most cases, seems independent of the time at which Auger decay occurs., MDPI AG
Quantum Beam Science, 2019年12月10日, ［査読有り］

〔主要な業績〕High-precision microbeam radiotherapy reveals testicular tissue-sparing effects for male fertility preservation
Fukunaga Hisanori; Kaminaga Kiichi; Sato Takuya; Butterworth Karl T; Watanabe Ritsuko; Usami Noriko; Ogawa Takehiko; Yokoya Akinari; Prise Kevin M, 責任著者,
Microbeam radiotherapy (MRT) is based on a spatial fractionation of synchrotron X-ray microbeams at the microscale level. Although the tissue-sparing effect (TSE) in response to non-uniform radiation fields was recognized more than one century ago, the TSE of MRT in the testes and its clinical importance for preventing male fertility remain to be determined. In this study, using the combination of MRT techniques and a unique ex vivo testes organ culture, we show, for the first time, the MRT-mediated TSE for the preservation of spermatogenesis. Furthermore, our high-precision microbeam analysis revealed that the survival and potential migration steps of the non-irradiated germ stem cells in the irradiated testes tissue would be needed for the effective TSE for spermatogenesis. Our findings indicated the distribution of dose irradiated in the testes at the microscale level is of clinical importance for delivering high doses of radiation to the tumor, while still preserving male fertility., Springer Science and Business Media LLC
SCIENTIFIC REPORTS, 2019年10月01日, ［査読有り］

VISUALIZATION OF THE DNA REPAIR PROCESS IN MAMMALIAN CELLS TRANSFECTED WITH EGFP-EXPRESSING PLASMID DNA AFTER EXPOSURE TO X-RAYS IN VITRO
Hiroki Nakaue; Yui Obata; Kiichi Kaminaga; Nobuyoshi Akimitsu; Akinari Yokoya, ラスト(シニア)オーサー, To investigate the repair process of DNA damage induced by ionizing radiation in isolation from various types of cytoplasmic damage, we transfected X-irradiated enhanced green fluorescent protein (EGFP)-expressing plasmid DNA into non-irradiated mammalian cells using lipofectamine. The repair kinetics of the irradiated plasmids in the cells were visualized under microscopy as the EGFP fluorescence emitted by transfected cells. Using an agarose gel electrophoresis method, the yields of single- and double-strand breaks of the plasmids were also quantified. As positive control experiments, plasmid DNA with single- or double-strand breaks induced by a nicking or restriction enzyme were also transfected into the cells. The DNA repair rates for X-ray-irradiated plasmids were significantly lower than those of the enzymatically digested positive control samples. These results indicate that X-rays could induce less repairable damage than that induced by enzymes., Oxford University Press (OUP)
Radiation Protection Dosimetry, 2019年05月01日, ［査読有り］

NOVEL ANALYTICAL STUDY FOR REACTION INTERMEDIATES IN THE PRIMARY RADIATION INTERACTION OF DNA USING A SYNCHROTRON RADIATION-INDUCED LUMINESCENCE SPECTROSCOPY
T Kojima; H Aihara; Y Kodashima; H Makishima; S Nakiri; S Takada; H Shimada; M Ukai; C Ozga; X Holzapfel; Ph Schmidt; C Küstner-Wetekam; H Otto; D Bloβ; A Knie; A Ehresmann; A Yokoya; K Fujii; Y Fukuda; Y Saitoh, Oxford University Press (OUP)
Radiation Protection Dosimetry, 2019年05月01日, ［査読有り］

STRUCTURAL ANALYSIS OF DNA REPAIR PROTEIN XRCC4 APPLYING CIRCULAR DICHROISM IN AN AQUEOUS SOLUTION
Kai Nishikubo; Yudai Izumi; Yoshihisa Matsumoto; Kentaro Fujii; Koichi Matsuo; Akinari Yokoya, ラスト(シニア)オーサー, Oxford University Press (OUP)
Radiation Protection Dosimetry, 2019年05月01日, ［査読有り］

MITOCHONDRIAL MEMBRANE POTENTIAL, MORPHOLOGY AND ATP PRODUCTION IN MAMMALIAN CELLS EXPOSED TO X-RAYS
R Hamada; K Kaminaga; K Suzuki; A Yokoya, ラスト(シニア)オーサー, Oxford University Press (OUP)
Radiation Protection Dosimetry, 2019年05月01日, ［査読有り］

Precision Radiotherapy and Radiation Risk Assessment: How Do We Overcome Radiogenomic Diversity?
Fukunaga Hisanori; Yokoya Akinari; Taki Yasuyuki; Butterworth Karl T; Prise Kevin M, Tohoku University Medical Press
TOHOKU JOURNAL OF EXPERIMENTAL MEDICINE, 2019年04月, ［査読有り］

XANES Spectral Changes of Hydrated Deoxyribose Induced by K-Shell Ionization of Oxygen
Fujii Kentaro; Yokoya Akinari
13TH INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION (SRI2018), 2019年, ［査読有り］

〔主要な業績〕Substituent effect on the yield of unpaired electrons in DNA bases studied by electron paramagnetic resonance
Oka Toshitaka; Yokoya Akinari; Fujii Kentaro; Kino Yasushi; Sekine Tsutomu, The physicochemical processes underlying the radiation sensitization of DNA by the K-shell photoabsorption of nitrogen and oxygen atoms are unclear. Accordingly, we evaluated electron paramagnetic resonance spectra of thin films of pyrimidine bases. By altering the substituents of the pyrimidine ring, we found a substituent effect on the yield of unpaired electrons induced by photo-absorption. The yield of the unpaired electrons of the DNA-base containing amino groups increased by the donation of electrons, and the yield of halogenated DNA-bases decreased by the withdrawal of electrons. These different physicochemical processes might affect DNA bases, leading to differences in DNA modification. Published by AIP Publishing., AMER INST PHYSICS
APPLIED PHYSICS LETTERS, 2018年12月10日, ［査読有り］

〔主要な業績〕Application of an Ex Vivo Tissue Model to Investigate Radiobiological Effects on Spermatogenesis
Hisanori Fukunaga; Kiichi Kaminaga; Takuya Sato; Noriko Usami; Ritsuko Watanabe; Karl T. Butterworth; Takehiko Ogawa; Akinari Yokoya; Kevin M. Prise, 責任著者, The formation of sperm by the testes through the process of spermatogenesis is highly radiosensitive and can be affected by environmental, occupational and therapeutic radiation exposures. In this study, we applied an ex vivo mouse testis organ culture as an experimental model of spermatogenesis to investigate the radiobiological effects and to demonstrate its feasibility as a tool to determine response to complex, modulated radiation fields. This model uses Acr-GFP transgenic mice, which express the marker green fluorescent proteins specific for meiosis to allow observation of functional changes in real-time that can be used to analyze radiation-induced changes in the process of spermatogenesis. Our results showed that the model can accurately reproduce radiation-induced male germ cell toxicity, such as temporary infertility and permanent sterility. Furthermore, using a monochromatic X-ray microbeam, we applied this model to investigate the effects of heterogeneous radiation fields on testis tissue ex vivo. Our model represents a unique application in the field, which offers significant potential for gaining further mechanistic insight into radiation effects on the process of spermatogenesis., Radiation Research Society
Radiation Research, 2018年06月01日, ［査読有り］

〔主要な業績〕Roles of Hydration for Inducing Decomposition of 2-Deoxy-d-ribose by Ionization of Oxygen K-Shell Electrons
Kentaro Fujii; Yudai Izumi; Ayumi Narita; Krishna Kamol Ghose; Pablo López-Tarifa; Alain Touati; Riccardo Spezia; Rodolphe Vuilleumier; Marie-Pierre Gaigeot; Marie-Françoise Politis; Marie-Anne Hervé Du Penhoat; Akinari Yokoya, To experimentally investigate the role of hydration in the initial process of the decomposition of 2-deoxy-d-ribose (dR), which is a major component of the DNA backbone, we used mass spectrometry to monitor the ions desorbing from hydrated dR films exposed to monochromatic soft X rays (560 eV). The X-ray photons preferentially ionize the K-shell electrons of the oxygen atoms in DNA. Hydrated dR samples were prepared under vacuum by exposing a cooled (~150 K) dR film deposited on a Si substrate to water vapor. Using a quadrupole mass spectrometer, we observed the desorption of ions such as H+, CHx+, C2Hx+, CHxO+, C3Hx+ and C2HxO+ (x = 1, 2, 3 and 4). In addition, the desorption of H2O+ or H3O+ was observed in the mass spectra of hydrated dR films. Except for H+, the yields of these ions decreased when one layer of water molecules was deposited onto the film. These ions are produced by C-C or C-O bond scission. This result suggests that the water molecules act as a quencher, suppressing Coulomb repulsion and thus the extensive molecular decomposition of dR. Ab initio molecular dynamics simulations were performed to rationalize the fragments observed in the experiments. The results of the dynamical process of a hydrated dR molecule after oxygen K-ionization revealed elongation of a C-O bond of dR and the O-H bonds of both dR and water molecules prior to the Auger process, resulting in the ejection of H+ ions. These results strongly suggest that the very early process contributes to reducing the dR fragmentation, producing the H3O+ and H+ detected from the hydrated dR films. These desorbed ions may be involved in the induction of other types of damage, such as oxidatively generated base lesions, concomitantly produced with a strand break when produced in DNA., Radiation Research Society
Radiation Research, 2018年03月01日, ［査読有り］

〔主要な業績〕Circular dichroism spectroscopic study on structural alterations of histones induced by post-translational modifications in DNA damage responses: lysine-9 methylation of H3
Yudai Izumi; Koichi Matsuo; Kentaro Fujii; Akinari Yokoya; Masaki Taniguchi; Hirofumi Namatame, Oxford University Press (OUP)
Journal of Radiation Research, 2018年03月01日, ［査読有り］

放射線物理化学過程に関する最近の進展(後編)
甲斐健師; 横谷明徳; 藤井健太郎; 渡邊立子
放射線化学(Web), 2018年

〔主要な業績〕A significant role of non-thermal equilibrated electrons in the formation of deleterious complex DNA damage
Takeshi Kai; Akinari Yokoya; Masatoshi Ukai; Kentaro Fujii; Tomohiro Toigawa; Ritsuko Watanabe, Although most of the radiation damage to genomic DNA could be rendered harmless using repair enzymes in a living cell, a certain fraction of the damage is persistent resulting in serious genetic effects, such as mutation induction. In order to understand the mechanisms of the deleterious DNA damage formation in terms of its earliest physical stage at the radiation track end, dynamics of low energy electrons and their thermalization processes around DNA molecules were investigated using a dynamic Monte Carlo code. The primary incident (1 keV) electrons multiply collide within 1 nm (equivalent to three DNA-base-pairs, 3bp) and generate secondary electrons which show non-Gaussian and non-thermal equilibrium distributions within 300 fs. On the other hand, the secondary electrons are mainly distributed within approximately 10 nm from their parent cations although approximately 5% of the electrons are localized within 1 nm of the cations owing to the interaction of their Coulombic fields. The mean electron energy is 0.7 eV
however, more than 10% of the electrons fall into a much lower-energy region than 0.1 eV at 300 fs. These results indicate that pre-hydrated electrons are formed from the extremely decelerated electrons over a few nm from the cations. DNA damage sites comprising multiple nucleobase lesions or single strand breaks can therefore be formed by multiple collisions of these electrons within 3bp. This multiple damage site is hardly processed by base excision repair enzymes. However, pre-hydrated electrons can also be produced resulting in an additional base lesion (or a strand break) more than 3bp away from the multi-damage site. These damage sites may be finally converted into a double strand break (DSB) when base excision enzymes process the additional base lesions. This DSB includes another base lesion(s) at their termini, and may introduce miss-rejoining by DSB repair enzymes, and hence may result in biological effects such as mutation in surviving cells., Royal Society of Chemistry
Physical Chemistry Chemical Physics, 2018年, ［査読有り］

Radiobiological Implications of Fukushima Nuclear Accident for Personalized Medical Approach
Hisanori Fukunaga; Akinari Yokoya; Yasuyuki Taki; Kevin M. Prise, On March 11, 2011, a devastating earthquake and subsequent tsunami caused serious damage to areas of the Pacific coast in Fukushima prefecture and prompted fears among the residents about a possible meltdown of the Fukushima Daiichi Nuclear Power Plant reactors. As of 2017, over six years have passed since the Fukushima nuclear crisis and yet the full ramifications of the biological exposures to this accidental release of radioactive substances remain unclear. Furthermore, although several genetic studies have determined that the variation in radiation sensitivity among different individuals is wider than expected, personalized medical approaches for Fukushima victims have seemed to be insufficient. In this commentary, we discuss radiobiological issues arising from low-dose radiation exposure, from the cell based to the population level. We also introduce the scientific utility of the Integrative Japanese Genome Variation Database (iJGVD), an online database released by the Tohoku Medical Megabank Organization, Tohoku University that covered the whole genome sequences of 2,049 healthy individuals in the northeastern part of Japan in 2016. Here we propose a personalized radiation risk assessment and medical approach, which considers the genetic variation of radiation sensitivity among individuals, for next step developments in radiological protection., TOHOKU UNIV MEDICAL PRESS
TOHOKU JOURNAL OF EXPERIMENTAL MEDICINE, 2017年05月, ［査読有り］

抗酸化物質エダラボンによる活性酸素除去およびDNA酸化損傷の化学的修復
端邦樹; LIN Mingzhang; 横谷明徳; 藤井健太郎; 山下真一; 室屋裕佐; 勝村庸介
放射線化学(Web), 2017年04月, ［査読有り］

Efficiency of radiation-induced base lesion excision and the order of enzymatic treatment
Iyo Shiraishi; Naoya Shikazono; Masao Suzuki; Kentaro Fujii; Akinari Yokoya, 責任著者, Purpose: To clarify whether initial base excision repair processes at clustered DNA damage sites comprising multiple base lesions affect subsequent excision processes via the formation of additional strand breaks by glycosylase and apurinic/apyrimidinic (AP) endonuclease base excision enzymes.Materials and methods: Plasmid DNA (pUC18) as a model DNA molecule was exposed to high-linear-energy-transfer (LET) ionizing radiation (He(2+)or C(6+)ions) or low-LET ionizing radiation (X-rays) under various conditions to produce varied radical-scavenging effects. pUC18 was then treated sequentially or simultaneously with two bacterial base excision enzymes (glycosylases), namely, endonuclease III and formamidopyrimidine-DNA glycosylase, which convert pyrimidine (or abasic [AP] site) and purine (or AP site) lesions to single-strand breaks (SSB), respectively. Yields of additional SSB or double-strand breaks (DSB) as digestion products were examined after changing the order of enzymatic treatment.Results: There were few differences among the enzymatic treatments, indicating that treatment order did not affect the final yields of additional SSB or DSB formed by glycosylase activity. This suggests that of the total damage, the fraction of clustered damage sites with a persistent base lesion dependent on the order of glycosylase treatment was insignificant if present.Conclusion: Base lesion clusters induced by high- or low-LET radiation appear three or more base pairs apart, and are promptly converted to a DSB by glycosylase, regardless of the order of enzymatic treatment., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2017年03月, ［査読有り］

高エネルギー電子線により水中で生成された2次電子の動的挙動
甲斐健師; 横谷明徳; 藤井健太郎; 渡邊立子
陽電子科学, 2017年

〔主要な業績〕DNA damage response induces structural alterations in histone H3-H4
Yudai Izumi; Kentaro Fujii; Satoshi Yamamoto; Koichi Matsuo; Hirofumi Namatame; Masaki Taniguchi; Akinari Yokoya, Synchrotron-radiation circular-dichroism spectroscopy was used to reveal that the DNA damage response induces a decrement of alpha-helix and an increment of beta-strand contents of histone H3-H4 extracted from X-ray-irradiated human HeLa cells. The trend of the structural alteration was qualitatively opposite to that of our previously reported results for histone H2A-H2B. These results strongly suggest that histones share roles in DNA damage responses, particularly in DNA repair processes and chromatin remodeling, via a specific structural alteration of each histone., OXFORD UNIV PRESS
JOURNAL OF RADIATION RESEARCH, 2017年01月, ［査読有り］

〔主要な業績〕Photon-induced Auger effect in biological systems: a review
Akinari Yokoya; Takashi Ito, 筆頭著者, Purpose: In this paper, we review interesting findings reported in the studies of the biological effects induced by inner-shell ionization with the aim of interpreting them from a mechanistic viewpoint, in particular, of the Auger effect of atoms on different biological systems.
Materials and methods: More than 70 published papers are cited on the Auger effects ranging from DNA-related elements (carbon, nitrogen, oxygen and phosphorus) to mammalian cells. Externally administrated bromine, iodine, and platinum have also been cited for the present endeavor. Those significant works all needed a highly monochromatized X-rays from brilliant synchrotron light sources.
Results: We have assembled a coherent view on the inner-shell effects of the Auger process that contrasts to the overall effects with the outer-shell ionization processes.
Conclusion: Some of these studies have reported that the Auger effect significantly enhances biological effects as compared with irradiation at below K-ionization energy. The Auger-specific molecular degradation mode of DNA, involving extensive fragmentation of the deoxypentose moiety, has also been revealed. We conclude that the selectively localized effect on the specified atoms through inner-shell ionization followed by the Auger process should have a definite impact on the current radiation effect studies, which are largely based on non-selective outer-shell ionizations., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2017年, ［査読有り］

Low-dose radiation-induced risk in spermatogenesis
Hisanori Fukunaga; Karl T. Butterworth; Akinari Yokoya; Takehiko Ogawa; Kevin M. Prise, Purpose: To discuss low-dose radiation-induced risks to male fertility focusing on potential mechanisms of low-dose radiation-induced damage on spermatogenesis, epidemiological studies of environmental radiation effects on sperm parameters and transgenerational effects following exposure of spermatogonial stem cells (SSCs).Background: Spermatogenesis produces mature male gametes, spermatozoa, which fertilize their counterpart female gametes, oocytes. The robust maintenance system of spermatogenesis is essential for genomic conservation; however, male fertility can be readily impacted by exposure to environmental, chemical and physical factors including ionizing radiation. The mammalian testes are known to be radiosensitive yet the underlying molecular mechanisms of low-dose radiation-induced risks for spermatogenesis remain unclear. Furthermore, evidence characterizing transgenerational effects following exposure of SSCs remain controversial.Conclusions: Current concerns over the possible effects of low-dose radiation exposure on spermatogenesis requires further elucidation that may be resolved comparing and integrating observed experimental and epidemiological data., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2017年, ［査読有り］

The 8th Auger Symposium: Preface
Akinari Yokoya, 筆頭著者, TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2016年11月, ［査読有り］, ［招待有り］

Enhancement of DNA double-strand break induction and cell killing by K-shell absorption of phosphorus in human cell lines
Masanori Tomita; Munetoshi Maeda; Noriko Usami; Akinari Yokoya; Ritsuko Watanabe; Katsumi Kobayashi, Purpose: To investigate an enhancement of DNA double-strand break (DSB) induction and cell killing effect by K-shell ionization of phosphorus atoms and Auger electrons on human cell lines.Materials and methods: Induction of DSB, DNA damage responses, cell cycle distributions, and cell killing effects were investigated after exposures of the cells with monochromatic synchrotron radiation soft X-rays of 2153 and 2147eV, which were the resonance peak and off peak, respectively, of the K-shell photoabsorption of phosphorus.Results: Higher biological effects in the cells irradiated with soft X-rays at 2153eV than at 2147eV were observed in (i) the efficiency of 53BP1/-H2AX co-localized foci formation per dose and residual number of foci, (ii) prolonged phosphorylation levels of DSB repair and/or cell cycle checkpoint related proteins and G2 arrest, (iii) the cell killing effects at the 10% survival level of normal human fibroblasts, HeLa cells, and human glioblastoma M059K cells (1.2-1.5 times higher) and that of human ataxia telangiectasia mutated (ATM)-defective cells and glioblastoma DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-defective cells (1.2 times).Conclusion: The yield of DSB and partly less-reparable complex DNA damage induction in human cells was enhanced by K-shell photoabsorption of phosphorus and low-energy Auger electrons., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2016年11月, ［査読有り］

Deceleration processes of secondary electrons produced by a high-energy Auger electron in a biological context
Takeshi Kai; Akinari Yokoya; Masatoshi Ukai; Kentaro Fujii; Ritsuko Watanabe, Purpose: To simulate the deceleration processes of secondary electrons produced by a high-energy Auger electron in water, and particularly to focus on the spatial and temporal distributions of the secondary electron and the collision events (e.g. ionization, electronic excitation, and dissociative electron attachment) that are involved in the multiplication of lesions at sites of DNA damage.Materials and methods: We developed a dynamic Monte Carlo code that considers the Coulombic force between an ejected electron and its parent cation produced by the Auger electron in water. Thus our code can simulate some return electrons to the parent cations. Using the code, we calculated to within the order of femtoseconds the temporal evolution of collision events, the mean energy, and the mean traveling distance (including its spatial probability distribution) of the electron at an ejected energy of 20eV.Results: Some of the decelerating electrons in water in the Coulombic field were attracted to the ionized atoms (cations) by the Coulombic force within hundreds of femtoseconds, although the force did not significantly enhance the number of ionization, electronic excitation, and dissociative electron attachment collision events leading to water radiolysis.Conclusions: The secondary electrons are decelerated in water by the Coulombic force and recombined to the ionized atoms (cations). Furthermore, the some return electrons might be prehydrated in water layer near the parent cation in DNA if the electrons might be emitted from the DNA. The prehydrated electron originated from the return electron might play a significant role in inducing DNA damage., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2016年11月, ［査読有り］

Cell cycle tracking for irradiated and unirradiated bystander cells in a single colony with exposure to a soft X-ray microbeam
Kiichi Kaminaga; Miho Noguchi; Ayumi Narita; Yuya Hattori; Noriko Usami; Akinari Yokoya, 責任著者, Purpose: To establish a new experimental technique to explore the photoelectric and subsequent Auger effects on the cell cycles of soft X-ray microbeam-irradiated cells and unirradiated bystander cells in a single colony.Materials and methods: Several cells located in the center of a microcolony of HeLa-Fucci cells consisting of 20-80 cells were irradiated with soft X-ray (5.35keV) microbeam using synchrotron radiation as a light source. All cells in the colony were tracked for 72h by time-lapse microscopy imaging. Cell cycle progression, division, and death of each cell in the movies obtained were analyzed by pedigree assay. The number of cell divisions in the microcolony was also determined.Results: The fates of these cells were clarified by tracking both irradiated and unirradiated bystander cells. Irradiated cells showed significant cell cycle retardation, explosive cell death, or cell fusion after a few divisions. These serious effects were also observed in 15 and 26% of the bystander cells for 10 and 20Gy irradiation, respectively, and frequently appeared in at least two daughter or granddaughter cells from a single-parent cell.Conclusions: We successfully tracked the fates of microbeam-irradiated cells and unirradiated bystander cells with live cell recordings, which have revealed the dynamics of soft X-ray irradiated and unirradiated bystander cells for the first time. Notably, cell deaths or cell cycle arrests frequently arose in closely related cells. These details would not have been revealed by a conventional immunostaining imaging method. Our approach promises to reveal the dynamic cellular effects of soft X-ray microbeam irradiation and subsequent Auger processes from various endpoints in future studies., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2016年11月, ［査読有り］

Now Is the Time to Consider Personalized Effective Dose
Hisanori Fukunaga; Akinari Yokoya; Yasuyuki Taki, ELSEVIER SCIENCE INC
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 2016年10月, ［査読有り］

〔主要な業績〕Dynamic Behavior of Secondary Electrons in Liquid Water at the Earliest Stage upon Irradiation: Implications for DNA Damage Localization Mechanism
Takeshi Kai; Akinari Yokoya; Masatoshi Ukai; Kentaro Fujii; Ritsuko Watanabe, To clarify the formation of radiation damage in DNA, the dynamic behavior of low-energy secondary electrons produced by ionizing radiation in water was studied by using a dynamic Monte Carlo code that considers the Coulombic force between electrons and their parent cations. The calculated time evolution of the mean energy, total track length, and mean traveling distance of the electrons indicated that the prehydration of the electrons occurs competitively with thermalization on a time scale of hundreds of femtoseconds. The decelerating electrons are gradually attracted to their parent cations by Coulombic force within hundreds of femtoseconds, and finally about 12.6% electrons are distributed within 2 nm of the cations. The collision fraction for ionization and electronic excitation within 1 nm of the cation was estimated to be about 40%. If these electrons are decelerated in a living cell, they may cause highly localized lesions around a cation in a DNA molecule through additional dissociative electron transfer (DET) as well as ionization and electronic excitation (EXC), possibly resulting in cell death or mutation., AMER CHEMICAL SOC
JOURNAL OF PHYSICAL CHEMISTRY A, 2016年10月, ［査読有り］

〔主要な業績〕Structure Change from beta-Strand and Turn to alpha-Helix in Histone H2A-H2B Induced by DNA Damage Response
Yudai Izumi; Kentaro Fujii; Frank Wien; Chantal Houee-Levin; Sandrine Lacombe; Daniela Salado-Leza; Erika Porcel; Rawand Masoud; Satoshi Yamamoto; Matthieu Refregiers; Marie-Anne Herve du Penhoat; Akinari Yokoya, Using synchrotron radiation-based circular dichroism spectroscopy, we found that the DNA damage response induces an increase of alpha-helix structure and a decrease of beta-strand and turn structures in histone H2A-H2B extracted from x-irradiated human HeLa cells. The structural alterations correspond to the assumption that an average of eight amino acid residues form new alpha-helix structures at 310 K. We propose the structural transition from beta-strand and turn structures to an a-helix structure in H2A-H2B as a novel, to our knowledge, process involved in the DNA damage response., CELL PRESS
BIOPHYSICAL JOURNAL, 2016年07月, ［査読有り］

紫外円二色性スペクトルを用いたタンパク質構造研究
泉雄大; 山本悟史; 藤井健太郎; 横谷明徳; 横谷明徳, ラスト(シニア)オーサー
放射線生物研究, 2016年03月, ［査読有り］, ［招待有り］

放射線物理化学過程に関する最近の進展(前編)
甲斐健師; 横谷明徳; 藤井健太郎; 渡邊立子
放射線化学(Web), 2016年

放射線物理化学過程に関する最近の進展(中編)
甲斐健師; 横谷明徳; 藤井健太郎; 渡邊立子
放射線化学(Web), 2016年

水溶液環境下における生体分子放射線損傷の分光研究
島田紘行; 横谷明徳; 鵜飼正敏
日本物理学会誌, 2016年, ［査読有り］, ［招待有り］

〔主要な業績〕Low-dose radiation risk and individual variation in radiation sensitivity in Fukushima
Hisanori Fukunaga; Akinari Yokoya, OXFORD UNIV PRESS
JOURNAL OF RADIATION RESEARCH, 2016年01月, ［査読有り］

〔主要な業績〕Cellular automaton-based model for radiation-induced bystander effects
Yuya Hattori; Akinari Yokoya; Ritsuko Watanabe, Background: The radiation-induced bystander effect is a biological response observed in non-irradiated cells surrounding an irradiated cell. The bystander effect is known to be induced by two intercellular signaling pathways, the medium-mediated pathway (MDP) and the gap junctional pathway (GJP). To investigate the relative contribution of each signaling pathway, we have developed a mathematical model of the cellular response through these two pathways, with a particular focus on cell-cycle modification.
Methods: The model is based on a cellular automaton and consists of four components: (1) irradiation, (2) generation and diffusion of intercellular signals, (3) induction of DNA double-strand breaks (DSBs), and (4) cell-cycle modification or cell death. The intercellular signals are generated in and released from irradiated cells. The signals through the MDP and the GJP are modeled independently based on diffusion equations. The irradiation and both signals raise the number of DSBs, which determines transitions of cellular states, such as cell-cycle arrest or cell death.
Results: Our model reproduced fairly well previously reported experimental data on the number of DSBs and cell survival curves. We examined how radiation dose and intercellular signaling dynamically affect the cell cycle. The analysis of model dynamics for the bystander cells revealed that the number of arrested cells did not increase linearly with dose. Arrested cells were more efficiently accumulated by the GJP than by the MDP.
Conclusions: We present here a mathematical model that integrates various bystander responses, such as MDP and GJP signaling, DSB induction, cell-cycle arrest, and cell death. Because it simulates spatial and temporal conditions of irradiation and cellular characteristics, our model will be a powerful tool to predict dynamical radiobiological responses of a cellular population in which irradiated and non-irradiated cells co-exist., BIOMED CENTRAL LTD
BMC SYSTEMS BIOLOGY, 2015年12月, ［査読有り］

〔主要な業績〕Secondary Structure Alterations of Histones H2A and H2B in X-Irradiated Human Cancer Cells: Altered Histones Persist in Cells for at Least 24 Hours
Yudai Izumi; Satoshi Yamamoto; Kentaro Fujii; Akinari Yokoya, We measured and compared the circular dichroism (CD) spectra and secondary structures of histone proteins H2A, H2B and their variants extracted from X-irradiated and unirradiated human HeLa cells. Compared to unirradiated cells, a relative increase in alpha-helix structure and decrease in other secondary structures was observed in X-irradiated cells. These structural alterations persisted for at least 24 h, which is substantially longer than the 2 h generally known to be required for DNA double-strand break repair. (C) 2015 by Radiation Research Society, RADIATION RESEARCH SOC
RADIATION RESEARCH, 2015年11月, ［査読有り］

Thermal equilibrium and prehydration processes of electrons injected into liquid water calculated by dynamic Monte Carlo method
Takeshi Kai; Akinari Yokoya; Masatoshi Ukai; Kentaro Fujii; Ritsuko Watanabe, The thermalization length and spatial distribution of electrons in liquid water were simulated for initial electron energies ranging from 0.1 eV to 100 keV using a dynamic Monte Carlo code. The results showed that electrons were decelerated for thermalization over a longer time period than was previously predicted. This long thermalization time significantly contributed to the series of processes from initial ionization to hydration. We further studied the particular deceleration process of electrons at an incident energy of 1 eV, focusing on the temporal evolution of total track length, mean traveling distance, and energy distributions of decelerating electrons. The initial prehydration time and thermalization periods were estimated to be approximately 50 and 220 fs, respectively, indicating that the initial prehydration began before or contemporaneously with the thermal equilibrium. Based on these results, the prehydrated electrons were suggested to play an important role during multiple DNA damage induction. (C) 2015 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2015年10月, ［査読有り］

Real-time observation of irradiated HeLa-cell modified by fluorescent ubiquitination-based cell-cycle indicator using synchrotron X-ray microbeam
A. Narita; K. Kaminaga; A. Yokoya; M. Noguchi; K. Kobayashi; N. Usami; K. Fujii, Fluorescent ubiquitination-based cell-cycle indicator (FUCCI) human cancer (HeLa) cells (red indicates G1; green, S/G2) were exposed to a synchrotron X-ray microbeam. Cells in either G1 or S/G2 were irradiated selectively according to their colour in the same microscopic field. Time-lapse micrographs of the irradiated cells were acquired for 24 h after irradiation. For fluorescent immunostaining, phosphorylated histone proteins (gamma-H2AX) indicated the induction of DNA double-strand breaks. The cell cycle was arrested by irradiation at S/G2. In contrast, cells irradiated at G1 progressed to S/G2. The foci were induced in cells irradiated at both G1 and S/G2, suggesting that the G1-S (or S) checkpoint pathway does not function in HeLa cells due to the fact that the cells are functionally p53 deficient, even though X-ray microbeam irradiation significantly induces double-strand breaks. These results demonstrate that single FUCCI cell exposure and live cell imaging are powerful methods for studying the effects of radiation on the cell cycle., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2015年09月, ［査読有り］

Visualisation of cell cycle modifications by X-ray irradiation of single HeLa cells using fluorescent ubiquitination-based cell cycle indicators
K. Kaminaga; M. Noguchi; A. Narita; Y. Sakamoto; Y. Kanari; A. Yokoya, 責任著者, To explore the effects of X-ray irradiation on mammalian cell cycle dynamics, single cells using the fluorescent ubiquitination-based cell cycle indicator (Fucci) technique were tracked. HeLa cells expressing Fucci were used to visualise cell cycle modifications induced by irradiation. After cultured HeLa-Fucci cells were exposed to 5 Gy X-rays, fluorescent cell images were captured every 20 min for 48 h using a fluorescent microscope. Time dependence of the fluorescence intensity of S/G2 cells was analysed to examine the cell cycle dynamics of irradiated and non-irradiated control cells. The results showed that irradiated cells could be divided into two populations: one with similar cell cycle dynamics to that of non-irradiated cells, and another displaying a prolonged G2 phase. Based on these findings, it is proposed in this article that an underlying switch mechanism is involved in cell cycle regulation and the G2/M checkpoint of HeLa cells., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2015年09月, ［査読有り］

A mathematical model of radiation-induced responses in a cellular population including cell-to-cell communications
Yuya Hattori; Michiyo Suzuki; Tomoo Funayama; Yasuhiko Kobayashi; Akinari Yokoya; Ritsuko Watanabe, Cell-to-cell communication is an important factor for understanding the mechanisms of radiation-induced responses such as bystander effects. In this study, a new mathematical model of intercellular signalling between individual cells in a cellular population is proposed. The authors considered two types of transmission of signals: via culture medium and via gap junction. They focus on the effects that radiation and intercellular signalling have on cell-cycle modification. The cell cycle is represented as a virtual clock that includes several checkpoint pathways within a cyclic process. They also develop a grid model and set up diffusion equations to model the propagation of signals to and from spatially located cells. The authors have also considered the role that DNA damage plays in the cycle of cells which can progress through the cell cycle or stop at the G1, S, G2 or M-phase checkpoints. Results of testing show that the proposed model can simulate intercellular signalling and cell-cycle progression in individual cells during and after irradiation., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2015年09月, ［査読有り］

LIVE-CELL IMAGING STUDY OF MITOCHONDRIAL MORPHOLOGY IN MAMMALIAN CELLS EXPOSED TO X-RAYS
M. Noguchi; Y. Kanari; A. Yokoya; A. Narita; K. Fujii, Morphological changes in mitochondria induced by X-irradiation in normal murine mammary gland cells were studied with a live-cell microscopic imaging technique. Mitochondria were visualised by staining with a specific fluorescent probe in the cells, which express fluorescent ubiquitination-based cell-cycle indicator 2 (Fucci2) probes to visualise cell cycle. In unirradiated cells, the number of cells with fragmented mitochondria was about 20 % of the total cells through observation period (96 h). In irradiated cells, the population with fragmented mitochondria significantly increased depending on the absorbed dose. Particularly, for 8 Gy irradiation, the accumulation of fragmentation persists even in the cells whose cell cycle came to a stand (80 % in G1 (G0-like) phase). The fraction reached to a maximum at 96 h after irradiation. The kinetics of the fraction with fragmented mitochondria was similar to that for cells in S/G2/M phase (20 %) through the observation period (120 h). The evidences show that, in irradiated cells, some signals are continually released from a nucleus or cytoplasm even in the G0-like cells to operate some sort of protein machineries involved in mitochondrial fission. It is inferred that this delayed mitochondrial fragmentation is strongly related to their dysfunction, and hence might modulate radiobiological effects such as mutation or cell death., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2015年09月, ［査読有り］

〔主要な業績〕Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution
Hiroyuki Shimada; Hirotake Minami; Naoto Okuizumi; Ichiro Sakuma; Masatoshi Ukai; Kentaro Fujii; Akinari Yokoya; Yoshihiro Fukuda; Yuji Saitoh, X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5'-monophosphate (CMP), 2'-deoxythymidine 5'-monophosphate (dTMP), and uridine 5'-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations. This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms. (C) 2015 AIP Publishing LLC., AMER INST PHYSICS
JOURNAL OF CHEMICAL PHYSICS, 2015年05月, ［査読有り］

Cross sections, stopping powers, and energy loss rates for rotational and phonon excitation processes in liquid water by electron impact
Takeshi Kai; Akinari Yokoya; Masatoshi Ukai; Ritsuko Watanabe, We calculated cross sections, stopping powers, and energy loss rates for rotational and phonon-mode excitations caused by the impact of an electron in an energy region from 0.1 meV to 100 eV injected into liquid water. The spatial distribution of the decelerated electron depends on these cross sections. We performed calculations assuming an optical approximation with the dielectric functions that are experimentally reported in the literature. We observed that the cross sections lie below 1 x 10(-16) cm(2) over the considered energy region. The values for rotational excitation processes in the liquid phase are less by three orders of magnitude than those in the gas phase because of the screening effect of neighboring water molecules on the interaction between the incident electron and water molecules. These results suggest that the cross sections in the liquid phase are significantly different from those in the gas phase. The values for phonon-mode excitations in the liquid phase are close to those reported for amorphous ice. Furthermore, we observed that the stopping power shows a maximum around 200 meV, and the energy loss rates, which are derived from the stopping power, depend significantly on the electron energy, particularly below 1 eV. The values obtained here will allow us to precisely estimate the decelerating process of an electron in liquid water to predict radiation effects such as chemical processes in water radiolysis or biomolecular damage induction strongly involved in low energy electron processes. (C) 2014 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2015年03月, ［査読有り］

〔主要な業績〕Investigation of the fragmentation of core-ionised deoxyribose: a study as a function of the tautomeric form
Marie-Anne Herve du Penhoat; Krishna Kamol Ghose; Marie-Pierre Gaigeot; Rodolphe Vuilleumier; Kentaro Fujii; Akinari Yokoya; Marie-Francoise Politis, We have investigated the gas phase fragmentation dynamics following the core ionisation of 2-deoxy-Dribose (dR), a major component in the DNA chain. To that aim, we use state-of-the-art ab initio Density Functional Theory-based Molecular Dynamics simulations. The ultrafast dissociation dynamics of the core-ionised biomolecule, prior Auger decay, is first modelled for 10 fs to generate initial configurations (atomic positions and velocities) for the subsequent dynamics of the doubly ionised biomolecule in the ground state. The furanose, linear and pyranose conformations of dR were investigated. We show that fragmentation is relatively independent of the atom struck or of the duration of the core vacancy, but depends rather critically on the molecular orbital removed following Auger decay., ROYAL SOC CHEMISTRY
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 2015年, ［査読有り］

〔主要な業績〕Live-cell imaging study of radiation effect on cell cycles of three-dimensional cultured cells exposed to synchrotron soft X-ray microbeam　　　　　　　　　　　　　　　
坂本由佳; 神長輝一; 嘉成由紀子; 宇佐美徳子; 野口実穂; 横谷明徳, 責任著者
乳癌基礎研究, 2015年, ［査読有り］

〔主要な業績〕Chemical repair activity of free radical scavenger edaravone: reduction reactions with dGMP hydroxyl radical adducts and suppression of base lesions and AP sites on irradiated plasmid DNA
Kuniki Hata; Ayumi Urushibara; Shinichi Yamashita; Mingzhang Lin; Yusa Muroya; Naoya Shikazono; Akinari Yokoya; Haiying Fu; Yosuke Katsumura, Reactions of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) with deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts were investigated by pulse radiolysis technique. Edaravone was found to reduce the dGMP hydroxyl radical adducts through electron transfer reactions. The rate constants of the reactions were greater than 4 x 10(8) dm(3) mol(-1) s(-1) and similar to those of the reactions of ascorbic acid, which is a representative antioxidant. Yields of single-strand breaks, base lesions, and abasic sites produced in pUC18 plasmid DNA by gamma ray irradiation in the presence of low concentrations (10-1000 mu mol dm(-3)) of edaravone were also quantified, and the chemical repair activity of edaravone was estimated by a method recently developed by the authors. By comparing suppression efficiencies to the induction of each DNA lesion, it was found that base lesions and abasic sites were suppressed by the chemical repair activity of edaravone, although the suppression of single-strand breaks was not very effective. This phenomenon was attributed to the chemical repair activity of edaravone toward base lesions and abasic sites. However, the chemical repair activity of edaravone for base lesions was lower than that of ascorbic acid., OXFORD UNIV PRESS
JOURNAL OF RADIATION RESEARCH, 2015年01月, ［査読有り］

Dynamics of low-energy electrons in liquid water with consideration of Coulomb interaction with positively charged water molecules induced by electron collision
Takeshi Kai; Akinari Yokoya; Masatoshi Ukai; Kentaro Fujii; Mariko Higuchi; Ritsuko Watanabe, To explain the electron energy relaxation process in water, we performed dynamical calculations of electrons in water using a simulation code developed in this study to calculate mean diffusion distances and mean energies of incident and secondary electrons released by the impact of the incident electron, as well as spatial probability-distribution of the secondary electrons. In addition to the following molecular processes of water: ionization: electronic, vibrational, and rotational excitation by electron impact; dissociative electron attachment; and elastic electron scattering, which were basic parameters used by Monte Carlo simulation, we newly took into account Coulomb interactions between electrons and positively ionized water molecules to calculate classical electron trajectories. We found that the Coulomb interactions enhance the number of collisions for the vibrational and rotational excitation processes at the incident 500 eV electron energy. The secondary electrons diffuse to an average of 3 nm from their original position, resulting much different spatial probability-distribution of those electrons in comparison to those previously reported. We also found that approximately 20% of the secondary electrons were returned to the parent ions within 100 fs. By the electron re-capturing to either bonding or antibionding orbital, the molecules might be converted to some electronic excitation states. We suggest that the spatial probability-distribution of electrons, taken into account the re-capturing process, should be essential for detailed analysis of following chemical process arising in nanometer scales, such as biomolecular damage caused by radiation. (C) 2014 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2014年09月, ［査読有り］

Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution
Hiroyuki Shimada; Taishi Fukao; Hirotake Minami; Masatoshi Ukai; Kentaro Fujii; Akinari Yokoya; Yoshihiro Fukuda; Yuji Saitoh, The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5'-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to pi* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5'-monophosphate, and adenosine 5'-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety. (C) 2014 AIP Publishing LLC., AMER INST PHYSICS
JOURNAL OF CHEMICAL PHYSICS, 2014年08月, ［査読有り］

〔主要な業績〕Induction of genetic instability by transfer of a UV-A-irradiated chromosome
Ayumi Urushibara; Seiji Kodama; Akinari Yokoya, Exposure of cells to ultraviolet (UV)-A radiation induces oxidative damage in DNA, such as 8-oxo-7,8-dihydroguanine (8-oxoG), single-strand breaks, a-basic sites, and DNA-protein cross-links, via reactions with reactive oxygen species (ROS). In this study we examine whether the damage other than double-strand breaks (non-DSB damage), which is UV-A-induced oxidative damage, plays a role in the induction of chromosomal instability. We exposed human chromosome 21 to UV-A and transferred the chromosome into non-irradiated mouse recipient cells by microcell-mediated chromosome transfer. The chromosomal instability of both the transferred human chromosome and the recipient mouse chromosomes was examined by whole-chromosome painting and fluorescence in situ hybridization (WCP-FISH). The ploidy of the mouse recipient cells increased, and chromosomal aberrations occurred not only in the UV-A-irradiated human chromosome but also in the non-irradiated mouse chromosomes. The frequencies of these abnormalities increased with the radiation dose received by the transferred human chromosome. In contrast, in the control experiment, in which an non-irradiated human chromosome was transferred, the micro-cell hybrids remained diploid, and the frequency of chromosomal aberrations in both the transferred human chromosome and recipient mouse chromosomes remained low. Thus, the present study indicates that a chromosome harboring non-DSB damage induced by UV-A irradiation is unstable and transmits instability to chromosomes of non-irradiated recipient mouse cells. (C) 2014 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS, 2014年05月, ［査読有り］

〔主要な業績〕Structural changes of nucleic acid base in aqueous solution as observed in X-ray absorption near edge structure (XANES)
Hiroyuki Shimada; Taishi Fukao; Hirotake Minami; Masatoshi Ukai; Kentaro Fujii; Akinari Yokoya; Yoshihiro Fukuda; Yuji Saitoh, X-ray absorption near edge structure (XANES) spectra for adenine-containing nucleotides, adenosine 5'-monophosphate (AMP) and adenosine 5'-triphosphate (ATP) in aqueous solutions at the nitrogen K-edge region were measured. The two intense peaks in XANES spectra are assigned to transitions of 1s electrons to the pi* orbitals of different types of N atoms with particular bonding characteristics. The difference between their spectra is ascribed to protonation of a particular N atom. Similarity observed in XANES spectra of guanosine 5'-monophosphate (GMP) and ATP is also interpreted as similar bonding characters of the N atoms in the nucleobase moiety. (C) 2013 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
CHEMICAL PHYSICS LETTERS, 2014年01月, ［査読有り］

Bond cleavages of adenosine 5 '-triphosphate induced by monochromatic soft X-rays
K. Fujii; A. Narita; A. Yokoya, To investigate which type of bond is likely to be cleaved by soft X-ray exposure to an adenosine 5'-triphosphate (ATP), we observed spectral changes in X-ray absorption near edge structure (XANES) around nitrogen and oxygen K-edge of an ATP film by soft X-ray irradiation. Experiments were performed at a synchrotron soft X-ray beamline at SPring-8, Japan. The XANES spectra around the nitrogen and oxygen K-edge slightly varied by exposure to 560 eV soft X-rays. These changes are originated from the cleavage of C-N bonds between a sugar and a nucleobase site and of C-O, P-O or O-H bond of sugar and phosphate site. From the comparison between the change in XANES intensity of sigma* peak at nitrogen and that at oxygen K-edges, it is inferred that the C-O, P-O or O-H bond of sugar and phosphate is much efficiently cleaved than the C-N of N-glycoside bond by the exposure of 560 eV soft X-ray to ATP film., IOP PUBLISHING LTD
1ST CONFERENCE ON LIGHT AND PARTICLE BEAMS IN MATERIALS SCIENCE 2013 (LPBMS2013), 2014年, ［査読有り］

DNA damage by soft X-ray exposure at oxygen K-edge
Y. Sugaya; A. Narita; K. Fujii; A. Yokoya, 責任著者, In order to obtain detailed insights into the physicochemical mechanism of DNA damage induction in terms of photoabsorption modes, we have prepared thin DNA films of closed circular plasmid (pUC18) on a cover slip without any additives. Using this film, we have performed preliminary experiments by exposing to soft X-rays with energies around oxygen K-shell ionization threshold. The DNA damage yields of strand breaks and base lesions or AP sites were quantified by biochemical treatments. We confirmed that the DNA film can work as a specimen irradiation. The DNA damage yields induced by pi* excitation of a K-shell electron of oxygen atoms in DNA were significantly larger those for oxygen K-ionization., IOP PUBLISHING LTD
1ST CONFERENCE ON LIGHT AND PARTICLE BEAMS IN MATERIALS SCIENCE 2013 (LPBMS2013), 2014年, ［査読有り］

Significance of DNA polymerase I in in vivo processing of clustered DNA damage
Naoya Shikazono; Ken Akamatsu; Momoko Takahashi; Miho Noguchi; Ayumi Urushibara; Peter O'Neill; Akinari Yokoya, We examined the biological consequences of bi-stranded clustered damage sites, consisting of a combination of DNA lesions, such as a 1-nucleotide gap (GAP), an apurinic/apyrimidinic (AP) site, and an 8-oxo-7,8-dihydroguanine (8-oxoG), using a bacterial plasmid-based assay. Following transformation with the plasmid containing bi-stranded clustered damage sites into the wild type strain of Escherichia coli, transformation frequencies were significantly lower for the bi-stranded clustered GAP/AP lesions (separated by 1 bp) than for either a single GAP or a single AP site. When the two lesions were separated by 10-20 bp, the transformation efficiencies were comparable with those of the single lesions. This recovery of transformation efficiency for separated lesions requires DNA polymerase I (Pol I) activity. Analogously, the mutation frequency was found to depend on the distance separating lesions in a bi-stranded cluster containing a GAP and an 8-oxoG, and Poll was found to play an important role in minimising mutations induced as a result of clustered lesions. The mutagenic potential of 8-oxoG within the bi-stranded lesions does not depend on whether it is situated on the leading or lagging strand. These results indicate that the biological consequences of clustered DNA damage strongly depend on the extent of repair of the strand breaks as well as the DNA polymerase in lesion-avoidance pathways during replication. (C) 2013 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS, 2013年09月, ［査読有り］

〔主要な業績〕Chemical repair of base lesions, AP-sites, and strand breaks on plasmid DNA in dilute aqueous solution by ascorbic acid
Kuniki Hata; Ayumi Urushibara; Shinichi Yamashita; Naoya Shikazono; Akinari Yokoya; Yosuke Katsumura, We quantified the damage yields produced in plasmid DNA by gamma-irradiation in the presence of low concentrations (10-100 mu M) of ascorbic acid, which is a major antioxidant in living systems, to clarify whether it chemically repairs radiation damage in DNA. The yield of DNA single strand breaks induced by irradiation was analyzed with agarose gel electrophoresis as conformational changes in closed circular plasmids. Base lesions and abasic sites were also observed as additional conformational changes by treating irradiated samples with glycosylase proteins.
By comparing the suppression efficiencies to the induction of each DNA lesion, in addition to scavenging of the OH radicals derived from water radiolysis, it was found that ascorbic acid promotes the chemical repair of precursors of AP-sites and base lesions more effectively than those of single strand breaks. We estimated the efficiency of the chemical repair of each lesion using a kinetic model. Approximately 50-60% of base lesions and AP-sites were repaired by 10 mu M ascorbic acid, although strand breaks were largely unrepaired by ascorbic acid at low concentrations. The methods in this study will provide a route to understanding the Mechanistic aspects of antioxidant activity in living systems. (C) 2013 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 2013年05月, ［査読有り］

〔主要な業績〕Induction of DNA damage, including abasic sites, in plasmid DNA by carbon ion and X-ray irradiation
Takuya Shiina; Ritsuko Watanabe; Iyo Shiraishi; Masao Suzuki; Yuki Sugaya; Kentaro Fujii; Akinari Yokoya, 責任著者, DNA from plasmid pUC18 was irradiated with low-LET (13 keV/mu m) or high-LET (60 keV/mu m) carbon ions or X-rays (4 keV/mu m) in solutions containing several concentrations of Tris (0.66-200 mM) to determine the yield of abasic (AP) sites and the effect of scavenging capacity. The yield of AP sites, detected as single-strand breaks (SSB) after digestion with E. coli endonuclease IV (Nfo), was compared with that of SSB and base lesions. At higher concentrations of Tris, the yields of single or clustered AP sites were significantly lower than those of single or clustered base lesions. The relative yields of single AP sites and AP clusters were less than 10 and 7 %, respectively, of the total damage produced at a scavenger capacity mimicking that in cells. The dependence of the yield of AP sites on scavenging capacity was similar to that of prompt strand breaks. The ratios of the yield of isolated AP sites to that of SSB induced by carbon ion or X-ray irradiation were relatively constant at 0.45 +/- A 0.15 over the tested range of scavenger capacity, although the ratio of SSB to double-strand breaks (DSB) showed the characteristic dependence on both scavenging capacity and radiation quality. These results indicate that the reaction of water radiolysis products, presumably OH radicals, with the sugar-phosphate moieties in the DNA backbone induces both AP sites and SSB with similar efficiency. Direct ionization of DNA is notably more involved in the production of DSB and base lesion clusters than in the production of AP site clusters., SPRINGER
RADIATION AND ENVIRONMENTAL BIOPHYSICS, 2013年03月, ［査読有り］

Lifetime of the unpaired electron species in calf thymus DNA thin films induced by nitrogen and oxygen K-shell photoabsorption
Toshitaka Oka; Akinari Yokoya; Kentaro Fujii, Purpose : To study the lifetime of the short-lived unpaired electron species induced in a calf thymus DNA film by soft X-rays in the energy regions around nitrogen and oxygen K-edge.
Materials and methods : Dry calf thymus DNA films were measured by electron paramagnetic resonance (EPR) spectrometer during the monochromatic soft X-ray irradiation provided from a synchrotron accelerator (SPring-8, Super Photon ring-8 GeV). Two operation modes of SPring-8 with different electron bunch structures were used to explore dependence of EPR intensity on pulse interval of soft X-rays.
Results : Observed EPR spectra did not show significant difference, in the spectral shape, intensity, g-factor and photon energy dependence, between the two bunch modes.
Conclusions : The total yield of the unpaired electron species were estimated by assuming the exponential relaxation of the unpaired electrons with two different bunch modes of the synchrotron. The lifetime of the unpaired electron species is estimated to be in the range of a few tens to several hundreds of mu s., INFORMA HEALTHCARE
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2012年12月, ［査読有り］

Observation of cleavage in DNA and nucleotides following oxygen K-shell ionization by measuring X-ray absorption near edge structure
Kentaro Fujii; Yoshihiro Fukuda; Akinari Yokoya, Purpose: To investigate which type of bond is more likely to be cleaved in functional groups in DNA including the nucleobases by the K-shell ionization of oxygen of DNA, and to determine whether the production of propenal is specific to the oxygen resonant excitation. To investigate the degradation pattern which depends on the type of nucleobase in the DNA monomer.
Materials and methods: Calf thymus DNA film and four nucleotides (dAMP, TMP, dGMP, and dCMP) films were used as samples. Soft X-rays with energy of 560 eV were used to irradiate the samples, and the changes in the X-ray absorption near edge structure (XANES) spectra during the irradiation were measured. The XANES measurements were performed by using a 0.02 eV scanning photon energy step.
Results: The difference spectra for DNA and nucleotides were similar to those for pyridine deprotonation. The oxygen K-edge regions in the difference spectra were all similar apart from the spectrum obtained at the resonant excitation energy of oxygen in DNA. The spectral change did not depend on the type of nucleotide.
Conclusion: (1) Deprotonation of the nucleobase -NH is usually induced by core ionization of carbon, nitrogen, and oxygen; (2) propenal production is specific to the oxygen K-shell resonant excitation; and (3) the pattern of XANES spectral changes does not significantly depend on the type of nucleobase., INFORMA HEALTHCARE
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2012年12月, ［査読有り］

Development of a simulation method for dynamics of electrons ejected from DNA molecules irradiated with X-rays
Takeshi Kai; Mariko Higuchi; Kentaro Fujii; Ritsuko Watanabe; Akinari Yokoya, Purpose: To develop a method for simulating the dynamics of the photoelectrons and Auger electrons ejected from DNA molecules irradiated with pulsed monochromatic X-rays.
Materials and methods: A 30-base-pair (bp) DNA molecule was used as the target model, and the X-rays were assumed to have a Gaussian-shaped time distribution. Photoionization and Auger decay were considered as the atomic processes. The atoms from which the photoelectrons or Auger electrons were emitted were specified in the DNA molecule (or DNA ion) using the Monte Carlo method, and the trajectory of each electron in the electric field formed around the positively charged DNA molecule was calculated with a Newtonian equation. The kinetics of the electrons produced by irradiation with X-rays at an intensity ranging from 1 x 10(12) to 1 x 10(16) photons/mm(2) and energies of 380 eV (below the carbon K-edge), 435 eV (above the nitrogen K-edge), and 560 eV (above the oxygen K-edge) were evaluated.
Results: It was found that at an X-ray intensity of 1 x 10(14) photons/mm(2) or less, all the produced electrons escaped from the target. However, above an X-ray intensity of 1 x 10(15) photons/mm(2) and an energy of 560 eV, some photoelectrons that were ejected from the oxygen atoms were trapped near the target DNA.
Conclusions: A simulation method for studying the trajectories of electrons ejected from a 30-bp DNA molecule irradiated with pulsed monochromatic X-rays has been developed. The present results show that electron dynamics are strongly dependent on the charged density induced in DNA by pulsed X-ray irradiation., INFORMA HEALTHCARE
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2012年12月, ［査読有り］

〔主要な業績〕Unpaired Electron Species in Thin Films of Calf-Thymus DNA Molecules Induced by Nitrogen and Oxygen K-Shell Photoabsorption
T. Oka; A. Yokoya; K. Fujii; Y. Fukuda; M. Ukai, The mechanism of DNA modification induced by K-shell photoabsorption of nitrogen and oxygen atoms was investigated by electron paramagnetic resonance and x-ray absorption near edge structure measurements of calf thymus DNA. A g factor of 2.000 for the unpaired electron species, which only arises during irradiation, was measured. The EPR intensities for DNA zwere twofold times larger than those estimated based on the photoabsorption cross section. This suggests that the DNA film itself forms unpaired electron species through the excitation of enhanced electron recapturing, known as the postcollision interaction process., AMER PHYSICAL SOC
PHYSICAL REVIEW LETTERS, 2012年11月, ［査読有り］

〔主要な業績〕Yield of Single- and Double-Strand Breaks and Nucleobase Lesions in Fully Hydrated Plasmid DNA Films Irradiated with High-LET Charged Particles
Takeshi Ushigome; Naoya Shikazono; Kentaro Fujii; Ritsuko Watanabe; Masao Suzuki; Chizuru Tsuruoka; Hiroshi Tauchi; Akinari Yokoya, 責任著者, We measured the yield and spectrum of strand breaks and nucleobase lesions produced in fully hydrated plasmid DNA films to determine the linear energy transfer (LET) dependence of DNA damage induced by ion-beam irradiation in relation to the change in the atomic number of ions. The yield of isolated damage was revealed as a decrease in prompt SSBs with increasing LET of He2+, C5+6+ and Ne-8+,Ne-10+ ions. On the other hand, the yields of prompt DSBs increased with increasing ion LET. SSBs were additionally induced in ion-irradiated DNA film by treatment with two kinds of base excision repair proteins (glycosylases), Nth and Fpg, indicating that base lesions are produced in the hydrated DNA film. This result shows that nucleobase lesions are produced via both chemical reactions with diffusible water radicals, such as OH radicals, and direct energy deposition onto DNA and the hydrated water layer. Nth-sensitive sites deduced to be pyrimidine lesions, such as 5,6-dihydrothymine (DHT), showed a relatively larger yield than Fpg-sensitive sites deduced to be purine lesions, such as 7,8-dihydro-8-oxo-2'deoxyguanine (8-oxoGua), for all ion exposures tested. The yield of SSBs or DSBs observed by enzyme treatment decreased noticeably with increasing LET for all tested ions. These results indicated that higher-LET ions preferentially produce a complex type of damage that might compromise the activities of the glycosylases used in this study. These findings are biologically important since, under cell mimicking conditions, persistent DNA damage occurs in part due to direct energy deposition on the DNA or hydrated water shell that is specifically induced by dense ionization in the track. (C) 2012 by Radiation Research Society, RADIATION RESEARCH SOC
RADIATION RESEARCH, 2012年05月, ［査読有り］

〔主要な業績〕The mutagenic potential of 8-oxoG/single strand break-containing clusters depends on their relative positions
Miho Noguchi; Ayumi Urushibara; Akinari Yokoya; Peter O'Neill; Naoya Shikazono, The biological consequences of clusters containing a single strand break and base lesion(s) remain largely unknown. In the present study we determined the mutagenicities of two- and three-lesion clustered damage sites containing a 1-nucleotide gap (GAP) and 8-oxo-7,8-dihydroguanine(s) (8-oxoG(s)) in Escherichia coli. The mutation frequencies (MFs) of bi-stranded two-lesion clusters (GAP/8-oxoG), especially in mutY-deficient strains, were high and were similar to those for bi-stranded clusters with 8-oxoG and base lesions/AP sites, suggesting that the GAP is processed with an efficiency similar to the efficiency of processing a base lesion or an AP site within a cluster. The MFs of tandem two-lesion clusters comprised of a GAP and an 8-oxoG on the same strand were comparable to or less than the MF of a single 8-oxoG. The mutagenic potential of three-lesion clusters, which were comprised of a tandem lesion (a GAP and an 8-oxoG) and an opposing single 8-oxoG, was higher than that of a single 8-oxoG, but was no more than that of a bi-stranded 8-oxoGs. We suggest that incorporation of a nucleotide opposite 8-oxoG is less mutagenic when a GAP is present in a cluster than when a GAP is absent. Our observations indicate that the repair of a GAP is retarded by an opposing 8-oxoG, but not by a tandem 8-oxoG, and that the extent of GAP repair determines the biological consequences. (C) 2012 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS, 2012年04月, ［査読有り］

〔主要な業績〕Electron paramagnetic resonance study of unpaired electron species in thin films of pyrimidine bases induced by nitrogen and oxygen K-shell photoabsorption
T. Oka; A. Yokoya; K. Fujii, In order to clarify the mechanism of DNA-base modification induced by K-shell photoabsorption of nitrogen and oxygen atoms, we measured electron paramagnetic resonance (EPR) spectra of two DNA pyrimidine bases, thymine, and cytosine. The g-factor of 2.000 of the unpaired electron species arising only during irradiation is determined. The EPR intensities for cytosine are two times larger than those simply estimated based on the photoabsorption cross section, whereas those for thymine show similar energy dependence to photoabsorption spectra, suggesting that cytosine favors to form unpaired electron species, rather than thymine, presumably due to the excitation of the enhanced electron capturing. (C) 2011 American Institute of Physics. [doi:10.1063/1.3563712], AMER INST PHYSICS
APPLIED PHYSICS LETTERS, 2011年03月, ［査読有り］

A MODEL FOR ANALYSIS OF THE YIELD AND THE LEVEL OF CLUSTERING OF RADIATION-INDUCED DNA-STRAND BREAKS IN HYDRATED PLASMIDS
N. Shikazono; A. Yokoya; A. Urushibara; M. Noguchi; K. Fujii, Although it is widely accepted that the spatial distribution of strand breaks is highly relevant to the biological consequences of radiation, the extent to which strand breaks are clustered is not usually demonstrated directly from the experimental data. To evaluate the spatial distribution of radiation-induced strand breaks, the authors have developed a model for the generation of strand breaks after irradiation. The model assumes that (1) a radiation track has a certain probability of ` hitting' a plasmid, (2) the radiation generates strand break(s) by chance within a relatively small region that could produce doublestrand breaks and (3) the number of strand breaks generated within the region follows a Poisson distribution. To find out whether the model is valid, the authors compared the calculated values with the experimental data obtained by a plasmid DNA assay. Taking into account the inherent bias of the plasmid assay, the model described well the experimental results of hydrated plasmids exposed to radiation., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2011年02月, ［査読有り］

A NOVEL TECHNIQUE USING DNA DENATURATION TO DETECT MULTIPLY INDUCED SINGLE-STRAND BREAKS IN A HYDRATED PLASMID DNA MOLECULE BY X-RAY AND He-4(2+) ION IRRADIATION
Akinari Yokoya; Naoya Shikazono; Kentaro Fujii; Miho Noguchi; Ayumi Urushibara, 筆頭著者, To detect multiple single-strand breaks (SSBs) produced in plasmid DNA molecules by direct energy deposition from radiation tracks, we have developed a novel technique using DNA denaturation by which irradiated DNA is analysed as single-strand DNA (SS-DNA). The multiple SSBs that arise in both strands of DNA, but do not induce a double-strand break, are quantified as loss of SS-DNA using agarose gel electrophoresis. We have applied this method to X-ray and He-4(2+) ion-irradiated samples of fully hydrated pUC18 plasmid DNA. The fractions of both SS-DNA and closed circular DNA (CCDNA) exponentially decrease with the increasing dose of X rays and He-4(2+) ions. The efficiency of the loss of SS-DNA was half that of CC-DNA for both types of irradiation, indicating that one of two strands in DNA is not broken when one SSB is produced in CC-DNA by irradiation. Contrary to our initial expectation, these results indicate that SSBs are not multiply induced even by high linear energy transfer radiation distributed in both strands., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2011年02月, ［査読有り］

Protective effects of silybin and analogues against X-ray radiation-induced damage
Haiying Fu; Mingzhang Lin; Yosuke Katsumura; Akinari Yokoya; Kuniki Hata; Yusa Muroya; Kentaro Fujii; Naoya Shikazono, Silybin (SLB) and similar analogues, namely, hesperetin (HESP), naringenin (NAN) and naringin (NAR), are believed to be active constituents of natural flavonoids that have been reported as chemopreventive agents for certain cancers. Moreover, SLB and analogues have been determined to fast repair DNA bases from oxidative damage by pulse radiolysis techniques. The present study was designed to evaluate the protective effects of SLB and analogues on soft X-ray-induced damage to plasmid DNA in vitro. The DNA damage was determined by agarose gel electrophoresis. SLB and analogues were found to protect DNA from radiation damage at micromolar concentrations. Among the compounds tested, HESP and SLB were the most effective in preventing X-ray-induced formation of DNA single-strand breaks (SSB). A comparison of these results with other experiments showed that the ability of SLB and analogues to inhibit DNA damage in vitro correlated with the ability of the compounds to scavenge free radicals. Our work revealed that natural flavonoids, SLB and analogues may be used as potent radioprotectors against radiation damage., OXFORD UNIV PRESS
ACTA BIOCHIMICA ET BIOPHYSICA SINICA, 2010年07月, ［査読有り］

〔主要な業績〕X-ray absorption spectra of nucleotides (AMP, GMP, and CMP) in liquid water solutions near the nitrogen K-edge
Masatoshi Ukai; Akinari Yokoya; Kentaro Fujii; Yuji Saitoh, The X-ray absorption of nucleotides (adenosine-5'-monophosphate, guanosine 5'-monophosphate, and cytidine 5'-monophosphate) are measured in both water solutions and thin solid films at X-ray energies near the nitrogen K-edge in the 'water-window' region. Each spectrum corresponds to the selective excitation of a nucleobase site in a nucleotide, and thus has features similar to the spectrum of the corresponding nucleobase. An additional new peak in the energy region of the nitrogen 1s -> pi* resonance is observed for each nucleotide. No significant difference between the water solutions and thin solid films is found, which might be attributable to the hydrophobic properties of a nucleobase in a nucleotide. (C) 2010 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
CHEMICAL PHYSICS LETTERS, 2010年07月, ［査読有り］

Spectral change in X-ray absorption near edge structure of DNA thin films irradiated with monochromatic soft X-rays
Kentaro Fujii; Akinari Yokoya, To reveal the chemical changes induced in DNA by irradiation with ionizing radiation, we have investigated the spectral change in the X-ray absorption near edge structure (XANES) of DNA resulting from exposure to monochromatic soft X-rays. We used a thin film of calf thymus DNA as a sample and observed nitrogen K-shell and oxygen K-shell XANES spectra. The typical monochromatic soft X-ray energies used for the irradiation (395, 408, 528, and 538 eV) were obtained from a soft X-ray beamline (BL23SU, SPring-8). These energies correspond to those just below or just above the nitrogen and oxygen K-shell ionization energy, respectively. The obtained XANES spectra show significant changes by irradiation. Particularly a new pi* resonance peak in oxygen XANES spectra evidently appeared by the irradiation above oxygen K-shell ionization potential. These results suggest that carbonyl groups, presumably a propenal group (O=C-C=C), may be produced in the sample by oxygen ionization. Thus characteristic damage induced by induction in the DNA molecule would be predicted following exposure to monochromatized synchrotron soft X-rays. (C) 2009 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2009年12月, ［査読有り］

Free radical scavenging and radioprotective effects of carnosine and anserine
Haiying Fu; Yosuke Katsumura; Mingzhang Lin; Yusa Muroya; Kuniki Hata; Kentaro Fujii; Akinari Yokoya; Yoshihiko Hatano, Two histidine-containing natural dipeptides, carnosine and anserine (beta-alanyl-1-methyl-L-histidine), have been examined for their antioxidant and radioprotective abilities. Pulse radiolysis studies indicated the antioxidative properties of carnosine and anserine aqueous solutions at different pH. The rate constants for the reaction CH radical with carnosine at neutral pH were determined to be 5.3 x 10(9) M-1 s(-1) at 300 nm, and 4.1 x 10(9) M-1 s(-1) at 400 nm, respectively. Carnosine and anserine also protected plasmid pUC18 DNA from X-ray radiation-induced strand breaks as evidenced from the studies by agarose gel electrophoresis, Carnosine showed higher protective efficiency under the experimental conditions. Our data demonstrated that carnosine and anserine may play an important role in the maintenance of the antioxidant system. (C) 2009 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2009年12月, ［査読有り］

Synchrotron radiation photoelectron studies for primary radiation effects using a liquid water jet in vacuum: Total and partial photoelectron yields for liquid water near the oxygen K-edge
Masatoshi Ukai; Akinari Yokoya; Yusuke Nonaka; Kentaro Fujii; Yuji Saitoh, A new spectroscopy to identify the hydration structure playing important role in liquid-phase radiation damage is in progress using a laminar liquid water jet sample in vacuum in combination with soft X-ray synchrotron radiation. We present the total and partial electron yields for liquid water using a photoelectron spectroscopy. Partial electron yields for the K-1 1b(1) 1b(1), Auger transition are obtained for the first time by measuring the electrostatically dispersed electron kinetic energy spectra as a function of photon energy of synchrotron radiation. (C) 2009 Published by Elsevier Ltd., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2009年12月, ［査読有り］

EPR study of radiation damage to DNA irradiated with synchrotron soft X-rays around nitrogen and oxygen K-edge
A. Yokoya; K. Fujii; Y. Fukuda; M. Ukai, 筆頭著者, In order to obtain detailed insights into the physicochemical mechanism of DNA damage induction, "in situ" measurement of electron paramagnetic resonance (EPR) signal from DNA constituent nucleobases, guanine and adenine, has been performed in a vacuum using monochromatic synchrotron soft X-rays. We found that short-lived unpaired electron species arise only during irradiation to the evaporated thin film on a surface. The EPR spectrum of the short-lived species significantly depends on the photon energy irradiated, and the spin concentration obtained from the EPR spectra shows a similar fine structure to the X-ray photoabsorption spectra (X-ray absorption near edge structure: XANES). For the adenine sample, the spin concentration alters strikingly by water absorption on the sample surface. Trapping of photo- or Auger electrons into a newly generated potential in the nucleobases as the consequence of photoelectric effect is suggested as mechanisms of the induction of the short-lived species. (C) 2009 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2009年12月, ［査読有り］

Nucleobase Lesions and Strand Breaks in Dry DNA Thin Film Selectively Induced by Monochromatic Soft X-rays
Kentaro Fujii; Naoya Shikazono; Akinari Yokoya, To verify the possibility of "selective damage induction" in DNA, the yields of base lesions as well as strand breaks have been measured in dry plasmid DNA films irradiated with highly monochromatized soft X-rays in the energy region of 270-760 eV, which includes the carbon, nitrogen, and oxygen K-edges. The yields of both pyrimidine and purine base lesions, observed as Nth-sensitive and Fpg-sensitive sites, respectively, are strikingly high at the oxygen K-edge (560 eV) but extremely low at an energy just below the nitrogen K-edge (380 eV) as compared with the yields observed at other photon energies. The yields at 560 eV are enhanced 9.6-fold and 27-fold for Nth-sensitive and Fpg-sensitive sites, respectively, compared with those at 380 eV. The yield of prompt single strand breaks is also enhanced at the oxygen K-ionization energy, but only 2-fold, as compared with that at 380 eV. Our results strongly suggest that (1) the K-shell ionization of oxygen in both the nucleobases as well as in other parts of DNA and in the hydrating water molecules bound to DNA, but not the K-shell ionization of nitrogen in the nucleobases, most likely contributes to the induction of nucleobase lesions and that (2) migration of electrons and holes is involved differentially in the production of each type of DNA lesion. These results could potentially lead to new methods for "partially selective induction" of specific types of DNA damage through tuning the energy of soft X-rays., AMER CHEMICAL SOC
JOURNAL OF PHYSICAL CHEMISTRY B, 2009年12月, ［査読有り］

〔主要な業績〕Induction of DNA Strand Breaks, Base Lesions and Clustered Damage Sites in Hydrated Plasmid DNA Films by Ultrasoft X Rays around the Phosphorus K Edge
Akinari Yokoya; Siobhan M. T. Cunniffe; Ritsuko Watanabe; Katsumi Kobayashi; Peter O' Neill, 筆頭著者, To characterize the DNA damage induced by K-shell ionization of phosphorus atom in DNA backbone on the level of hydration, the yields of DNA strand breaks and base lesions arising from the interaction of ultrasoft X rays with energies around the phosphorus K edge were determined using dry and fully hydrated pUC18 plasmid DNA samples. Base lesions and bistranded clustered DNA damage sites were revealed by postirradiation treatment with the base excision repair proteins endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). The yield of prompt single-strand breaks (SSBs) with dry DNA irradiated at the phosphorus K resonance energy (2153 eV) is about one-third that below the phosphorus K edge (2147 eV). The yields of prompt double-strand breaks (DSBs) were found to be less dependent on the X-ray energy, with the yields being about two times lower when irradiated at 2153 eV. Heat-labile sites were not produced in detectable amounts. The yields of base lesions were dependent on the energy of the X rays, especially when the DNA was fully hydrated. Bistranded clustered DNA damage sites, revealed enzymatically as additional DSBs, were produced in dry as well as in hydrated DNA with all three energies of X rays. The yields of these enzyme-sensitive sites were also lower when irradiated at the phosphorus K resonance energy. On the other hand, the yields of prompt SSBs and enzyme-sensitive sites for the two off-resonance energies were, larger than those determined previously for gamma radiation. The results indicate that the photoelectric effect caused by X rays and dense ionization and excitation events along the tracks of low-energy secondary electrons are more effective at inducing SSBs and enzyme-sensitive sites. The complex types of damage, prompt and enzymatically induced DSBs, are preferentially induced by phosphorus K resonance at 2153 eV rather than simple SSBs and isolated base lesions, particularly in hydrated conditions. It is concluded that not only the phosphorus K resonance and resulting emission of low-energy LMM-Auger electrons (similar to 120 eV) but also the level of hydration plays an important role in the induction of complex damage in plasmid DNA. (C) 2009 by Radiation Research Society, RADIATION RESEARCH SOC
RADIATION RESEARCH, 2009年09月, ［査読有り］

The Yield, Processing, and Biological Consequences of Clustered DNA Damage Induced by Ionizing Radiation
Naoya Shikazono; Miho Noguchi; Kentaro Fujii; Ayumi Urushibara; Akinari Yokoya, After living cells are exposed to ionizing radiation, a variety of chemical modifications of DNA are induced either directly by ionization of DNA or indirectly through interactions with water-derived radicals. The DNA lesions include single strand breaks (SSB), base lesions, sugar damage, and apurinic/apyrimidinic sites (AP sites). Clustered DNA damage, which is defined as two or more of such lesions within one to two helical turns of DNA induced by a single radiation track, is considered to be a unique feature of ionizing radiation. A double strand break (DSB) is a type Of Clustered DNA damage, in which single strand breaks arc formed on opposite strands in close proximity. Fort-nation and repair of DSBs have been studied in great detail over the years as they have been linked to important biological endpoints, such as cell death, loss of genetic material, chromosome aberration. Although non-DSB clustered DNA damage has received less attention, there is growing evidence of its biological significance. This review focuses on the current understanding of (1) the yield of non-DSB clustered damage induced by ionizing radiation (2) the processing, and (3) biological consequences of non-DSB clustered DNA damage., JAPAN RADIATION RESEARCH SOC
JOURNAL OF RADIATION RESEARCH, 2009年01月, ［査読有り］

Free radical scavenging reactions and antioxidant activities of silybin: Mechanistic aspects and pulse radiolytic studies
Haiying Fu; Mingzhang Lin; Yusa Muroya; Kuniki Hata; Yosuke Katsumura; Akinari Yokoya; Naoya Shikazono; Yoshihiko Hatano, Silybin (extracted from Silybum marianum) is the major active constituent of silymarin which possesses a wide range of medicinal properties. These properties may be, in part, due to the potent scavenging capacity of oxidizing free radicals. In this context, scavenging radicals (hydroxyl, azide, dibromide anion radicals, nitrite, carbonate, etc.) of silybin have been studied to understand the mechanistic aspects of its action against free radicals. The transients produced in these reactions have been assigned and the rate constants have been measured by pulse radiolysis techniques. Reduction potential determined both by cyclic voltammetry gave a value 0.62 +/- 0.02 V vs NHE at pH 9. Quantum chemical calculations have been performed to further confirm the different activities of individual hydroxyl groups with the difference of heat of formation. Moreover, silybin also protected plasmid pUC18 DNA from soft X-ray radiation which induced strand breaks. These results are expected to be helpful for a better understanding of the anti-oxidative properties of silybin., TAYLOR & FRANCIS LTD
FREE RADICAL RESEARCH, 2009年, ［査読有り］

Studies of soft X-ray-induced Auger effect on the induction of DNA damage
A. Yokoya; K. Fuji; N. Shikazono; K. Akamatsu; A. Urushibara; R. Watanabe, Purpose: To understand the characteristics of DNA damage induced by Auger effect in DNA by ultrasoft X-irradiation. In situ electron paramagnetic resonance (EPR) spectroscopy as well as biochemical analysis has been applied to examine the DNA damage induction in both viewpoints of intermediate species and final products.
Materials and methods: Unpaired electron species induced in a calf thymus DNA film irradiated with monochromatic ultrasoft X-rays (270-580 eV) was observed using an X-band EPR spectrometer installed in a synchrotron beamline. To determine the yield of single strand break (SSB), pUC18 plasmid DNA was irradiated and then analyzed by agarose gel electrophoresis. To analyze molecular change in a single strand DNA, a new technique using DNA-denaturation-treatment has been applied to quantify multiple SSB arising in both DNA strands.
Results: Short-lived EPR spectra were observed during irradiation. The intensity of transient EPR spectrum shows the similar energy dependence with that of the SSB yield around oxygen K-edge in particular. The fraction of the single-strand plasmid DNA (SS-DNA) after irradiation could be determined using a low-temperature-denaturation condition. The obtained slope of the dose-response for SS-DNA shows half of that of closed circular DNA as expected under the diluted solution condition.
Conclusion: The availability of an EPR apparatus installed in a synchrotron beamline is demonstrated by detecting very short-lived unpaired electron species. Transient EPR spectra of DNA show the similar energy dependence to that of the SSB yield. The proposed DNA-denaturation assay works as expected using the low-temperature-denaturation condition., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2008年12月, ［査読有り］

Characterization of lesions induced in linear-formed plasmid DNA by valence ionization and Auger decay at carbon, nitrogen and oxygen
Ken Akamatsu; Kentaro Fujii; Akinari Yokoya, Purpose: To study the DNA lesions induced by the Auger decay of carbon, nitrogen, and oxygen using ultrasoft X-rays (USX) that are expected to be important with the DNA repair system of living cells.
Materials and methods: pUC19 plasmid DNA dry samples were irradiated with USX photons at 270 and 560 eV and (60)Co gamma-rays in vacuum at room temperature. The amounts of unaltered base release by the direct radiation effects were quantified using high-performance liquid chromatography. To quantify and characterize the strand break termini the rate at which snake venom phosphodiesterase (SVPD) digested irradiated DNA pretreated with and without calf intestine alkaline phosphatase was measured. Moreover, the pipcridine-labile base lesions and abasic sites of the irradiated DNA were estimated using the SVPD method.
Results: The yields of unaltered base release for 270, 560 eV photons and (60)Co gamma-rays were 0.0 16, 0.014, and 0.0 18 mu mol/J, respectively. The total 3' termini for the three kinds of photons were around 0.1 mu mol/J. The production of 3' termini with phosphate was found to be predominant with respect to that of 3'OH termini for the three kinds of radiation. The yield of piperidine-labile sites for 270 eV (similar to 0.1 mu mol/J) was slightly larger than that for 560 eV (similar to 0.07 mu mol/J) and also for gamma-rays (similar to 0. 082 mu mol/J).
Conclusion: Although the Auger process in DNA-constituent atoms was expected to induce Auger-specific lesions in the molecule the chemical endpoints would have been covered with a large number of lesions produced from secondary electrons in the surrounding bulk DNA molecules. The present results, however, suggest that a low-energy electron field produced by the USX photons in the bulk DNA is basically not at all specific to DNA damage being produced when compared with the high-energy electron field produced by (60)Co gamma-rays., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2008年12月, ［査読有り］

Induction of single strand breaks, and base lesions in plasmid DNA films induced by carbon, nitrogen, and oxygen KLL Auger process
Kentaro Fujii; Akinari Yokoya; Naoya Shikazono, Purpose: To reveal the reaction process in DNA by Auger electrons using the observed single strand breaks (SSB) and base lesions induced by monochromatic ultrasoft X-rays in dry plasmid DNA film. Desorbed ions from DNA and 2-deoxy-Dribose thin films were also measured to ascertain the decomposition site in DNA.
Materials and methods: Dry plasmid DNA (pUC18) films were irradiated with synchrotron monochromatic ultrasoft X-rays (USX). Two photon energies, 270, and 560 eV, were chosen for the irradiation experiments. Irradiated plasmid DNA was analyzed by agarose gel electrophoresis. The yield of base lesions was determined by the post-irradiation-treatment of the DNA with enzymatic probes (formamidpyrimidine DNA glycosylase [Fpg] and endonuclease III [Nth]). Desorbed ions induced by 540 eV USX irradiation from calf thymus DNA and 2-deoxy-D-ribose thin films were detected by quadrupolemass spectrometer.
Results: Yield of strand breaks and base lesions were obtained by 270 and 560 eV photon energies, respectively. Each yield showed characteristic of the photon energy spectrum. The characteristics of the desorbed ion mass spectra from 2-deoxy-Dribose and DNA films were strikingly similar with each other.
Conclusions: In this paper we report, for the first time, the yields of base lesions and SSB induced by monochromatic USX. The yield of SSB induced by core-ionization of carbon, nitrogen, and oxygen was two times more frequent than that of valence-electrons. From the comparison of desorbed ion mass spectra of 2-deoxy-D-ribose with DNA films we predict these breaks are likely to be induced by the decomposition of the sugar sites in DNA backbone., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2008年12月, ［査読有り］

ASR2007 - International symposium on "Charged Particle and Photon Interactions with Matter", November 6-9, 2007
Y. Katsumura; M. Lin; A. Yokoya; Y. Hatano, PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2008年10月, ［査読有り］, ［招待有り］

X-ray absorption spectrum for guanosine-5 '-monophosphate in water solution in the vicinity of the nitrogen K-edge observed in free liquid jet in vacuum
Masatoshi Ukai; Akinari Yokoya; Kentaro Fujii; Yuji Saitoh, A new spectroscopy for direct effect of radiation damage to nucleic acids such as DNA and RNA is underway using a liquid beam sample in vacuum combined with soft-X-ray synchrotron radiation. We show the X-ray absorption spectrum (XANES) of liquid phase water at X-ray photon energy in the vicinity of oxygen K-shell absorption edge obtained from total photoelectron yields ejected from a pure water beam. We confirm a "liquid sample in vacuum" for the present experiment by the measurements of the temperature dependence of the XANES spectrum for a liquid beam of pure water. Shown is the first measurement of the XANES spectrum for guanosine-5'-monophosphate (GMP), which is one of the fundamental nucleotide unit for RNA, in water solution at X-ray photon energy in the vicinity of nitrogen K-shell absorption edge involved in the 'water-window' region, which corresponds to a selective excitation of guanine site. (C) 2008 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2008年10月, ［査読有り］

DNA damage induced by the direct effect of radiation
A. Yokoya; N. Shikazono; K. Fujii; A. Urushibara; K. Akamatsu; R. Watanabe, 筆頭著者, We have studied the nature of DNA damage induced by the direct effect of radiation. The yields of single- (SSB) and double-strand breaks (DSB), base lesions and clustered damage were measured using the agarose gel electrophoresis method after exposing to various kinds of radiations to a simple model DNA molecule, fully hydrated closed-circular plasmid DNA (pUC18). The yield of SSB does not show significant dependence on linear energy transfer (LET) values. On the other hand, the yields of base lesions revealed by enzymatic probes, endonuclease III (Nth) and formamidopyrimidine DNA glycosylase (Fpg), which excise base lesions and leave a nick at the damage site, strongly depend on LET values. Soft X-ray photon (150 kVp) irradiation gives a maximum yield of the base lesions detected by the enzymatic probes as SSB and clustered damage, which is composed of one base lesion and proximate other base lesions or SSBs. The clustered damage is visualized as an enzymatically induced DSB. The yields of the enzymatically additional damages strikingly decrease with increasing levels of LET. These results suggest that in higher LET regions, the repair enzymes used as probes are compromised because of the dense damage clustering. The studies using simple plasmid DNA as a irradiation sample, however, have a technical difficulty to detect multiple SSBs in a plasmid DNA. To detect the additional SSBs induced in opposite strand of the first SSB, we have also developed a novel technique of DNA-denaturation assay. This allows us to detect multiply induced SSBs in both strand of DNA, but not induced DSB. (C) 2008 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
RADIATION PHYSICS AND CHEMISTRY, 2008年10月, ［査読有り］

〔主要な業績〕LET dependence of the yield of single-, double-strand breaks and base lesions in fully hydrated plasmid DNA films by He-4(2+) ion irradiation
Ayumi Urushibara; Naoya Shikazono; Peter O'Neill; Kentaro Fujii; Seiichi Wada; Akinari Yokoya, Purpose: To characterize the complexity of DNA damage through determination of the yields of single (SSB) and double strand breaks (DSB), base lesions and clustered damage sites induced in fully hydrated plasmid DNA by direct radiation effects as a function of the ionizing density of the radiation using He-4(2+) ion irradiation with linear energy-transfer (LET) values in the range 19 to 148 keV/mu m.
Materials and methods: Hydrated plasmid DNA (pUC 18) containing 34.5 water molecules/nucleotide was irradiated with He2+ ions with LET values of 19, 63, 95, 121 and 148 keV/mu m. From quantification of the conformational changes of the irradiated samples (closed circular, open or linear forms) analyzed by agarose gel electrophoresis, the yields of SSB and DSB were obtained. Base lesions were visualized as additional strand breaks by treatment with base excision repair enzymes (enclonuclease III (Nth) and formamidpyrimidine DNA glycosylase (Fpg)).
Results: The yield of prompt SSB does not depend significantly on LET of the He-4(2+) ions, whereas the yield of prompt DSB increases with increasing LET. The yields of isolated base lesions, revealed by Nth and Fpg as additional SSB, decrease drastically with increasing LET. The sum of the yields of DSB and additional DSB revealed by Nth and Fpg increase with increasing LET of the He-4(2+) ions except at the highest LET investigated.
Conclusion: The yields of clustered damage, revealed as DSB and non-DSB clustered damage sites, but not isolated lesions, namely SSB, increase with increasing ionization density of the He-4(2+) ions except at the highest LET investigated., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2008年01月, ［査読有り］

DNA damage induced by the direct effect of HE ion particles
Ayumi Urushibara; Naoya Shikazono; Ritsuko Watanabe; Kentaro Fujii; Peter O'Neill; Akinari Yokoya, We present here evidence showing that the yields of DNA lesions induced by He 21 ions strongly depend on Linear energy transfer (LET). In this study, hydrated plasmid DNA was irradiated with He2+ ions with LET values of 19, 63 and 95 keV mu m(-1). The yields of prompt single-strand breaks (SSBs) are very similar at the varying LET values, whereas the yields of prompt double-strand breaks (DSBs) increase with increasing LET. Further, base lesions were revealed as additional strand breaks by post-irradiation treatment of the DNA with endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). The reduction in the yield of these enzymatically induced SSBs and DSBs becomes significant as the LET increases. These results suggest that the clustering of DNA lesions becomes more probable in regions of high LET., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2006年12月, ［査読有り］

Yields of strand breaks and base lesions induced by soft X-rays in plasmid DNA
A. Yokoya; K. Fujii; T. Ushigome; N. Shikazono; A. Urushibara; R. Watanabe, 筆頭著者, The yields of soft-X-ray-induced DNA damages have been measured by using closed-circular plasmid DNA. Several DNA solutions with three kinds of radical scavenger capacity and also fully hydrated DNA samples were irradiated to compare the contribution by indirect reaction of diffusible water radicals, such as OH center dot, with those by direct action of secondary electrons. The yields of prompt single- (SSBs) and double-strand breaks (DSBs) decrease with increasing scavenging capacity. The SSB yields for soft X-rays are approximately midway those between gamma-ray and ultrasoft X-ray data previously reported. Heat labile sites are observed only in the low scavenger condition. The yields of the base lesions revealed by post irradiation treatment with base excision repair enzymes showed a similar value for Nth and Fpg protein except in the hydrated sample. These results indicate that the direct effect of soft X-rays induces the damages with different efficiency from those by indirect effect., OXFORD UNIV PRESS
RADIATION PROTECTION DOSIMETRY, 2006年12月, ［査読有り］

Natural circular dichroism of amino acid films observed in soft X-ray and VUV region using polarizing undulator
K Nakagawa; F Kaneko; Y Ohta; M Tanaka; T Kitada; A Agui; F Fujii; A Yokoya; K Yagi-Watanabe; T Yamada, We observed the natural circular dichroism NCD of amino acid films in the soft X-ray region for the first time [M. Tanaka, K. Nakagawa, A. Agui, K. Fujii, A. Yokoya, Physica Scripta, in press]. Based on the success, a new generation of detection system is now under preparation. Vacuum ultraviolet NCD of amino acid films was measured successfully using a polarizing undulator [H. Onuki, Nucl. Instrum. Meth. A 246 (1986) 94] installed at the TERAS electron storage ring at AIST, Tsukuba, Japan. A result of NCD measurement for alanine films is described in detail. (c) 2005 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 2005年06月, ［査読有り］

Chemical evolution of amino acid induced by soft X-ray with synchrotron radiation
F Kaneko; M Tanaka; S Narita; T Kitada; T Matsui; K Nakagawa; A Agui; K Fujii; A Yokoya, Soft X-ray induced chemical evolution from glycine (Gly) to glycyl-glycine (glycine dimer or Gly-Gly) was studied for sublimated films of Gly. Values of quantum yield of Gly dimer formation were determined by high performance liquid chromatography (HPLC) technique to be: (1.2 +/- 0.2) x 10(-1) for 400 eV, (4.6 +/- 0.5) x 10(-2) for 407 eV and (3.2 +/- 1.5) x 10(-2) for 860 eV irradiation, respectively. We measured X-ray absorption spectra of irradiated Gly films at near edge region of nitrogen K-edge, as a function of X-ray dose. Formation of Gly-Gly was confirmed by the appearance and growth of 402 eV peak, which is a fingerprint of the peptide bond. The important role of surface to chemical evolution is discussed. (c) 2005 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 2005年06月, ［査読有り］

〔主要な業績〕First observation of natural circular dichroism for biomolecules in soft x-ray region studied with a polarizing undulator
Masahito Tanaka; Kazumichi Nakagawa; Akane Agui; Kentaro Fujii; Akinari Yokoya, We measured natural circular dichroism (CD) for biomolecules in soft X-ray region for the first time. Natural linear dichroism (LD) for K(TiO)PO4 (KTP) crystal was also measured at the K-edge energy of oxygen. Measurements of CD and LD spectra were performed at the soft X-ray undulator beamline BL23SU of S Pring-8 in Japan. In this beamline, an APPLE-2 type variable undulator was installed as a light source. This undulator was operated under the phase modulation mode in which left and right circularly polarized light (LCPL and RCPL) was switched with about 0.1 Hz.
As a sample for CD measurement, we used sublimated film of L-, D- and DL-phenylalanine (Phe) and L- and D-serine (Ser) (thickness similar to 300 nm) and measured CD (A(L)-A(R)) spectra in the nitrogen and the oxygen K-edge region, respectively. Here, A(L) and A(R) mean the abbreviation of absorption for LCPL and RCPL, respectively. For the Phe film, we observed a negative peak at about 407 eV for the L-Phe spectra. On the contrary, a positive peak for the D- Phe spectra and no spectral feature for the DL-Phe were observed. For the Ser film, we observed positive CD peaks at around 540 eV and 548eV at the L-Ser spectra, on the contrary, negative peaks for the D- Ser. These results are the first CD spectra for biomolecules in the soft X-ray region.
We also used KTP crystal cut parallel to the plane (1,2,0) or (1,-2,0) as a sample of LD measurement and measured (A(L)-A(R)) spectra in the oxygen Kedge region and observed some peaks at about 530 eV. Since sign of these peaks were dependent on sample rotation angle in a plane perpendicular to the incident light, we concluded that these peaks are derived from linear anisotropy of crystal. Because of a weak linear polarization component of incident light, we could measure such LD spectra., IOP PUBLISHING LTD
PHYSICA SCRIPTA, 2005年, ［査読有り］

〔主要な業績〕DNA strand breaks by direct energy deposition by Auger and photo-electrons ejected from DNA constituent atoms following K-shell photoabsorption
R Watanabe; A Yokoya; K Fujii; K Saito, Purpose: To study DNA strand breaks induced by direct energy deposition by photo- and Auger electrons ejected following K-shell photoabsorption of DNA constituent atoms (carbon, nitrogen, oxygen and phosphorus).
Method. Using a Monte Carlo code which has been developed to simulate the photoelectric effect on plasmid DNA pBR322, the energy deposition pattern of secondary electrons ejected after photoabsorption in DNA constituent atoms (not including the hydration shell) was calculated. Experimentally obtained X-ray absorption near edge structures were considered of the cross-sections at the K-shell resonant absorption (1s-->sigma*) of carbon, nitrogen and oxygen, and the K-shell resonant absorption (1s-->t2*) of phosphorus. Direct energy deposition by secondary electrons was scored using two different DNA models with and without the hydrated shell. The yields of SSB, DSB per photoabsorption events as well as break complexity were estimated for monochromatic X-rays around the K-edges of DNA constituent atoms (200-3000 eV).
Results: Higher SSB and DSB yields were obtained below the carbon, nitrogen and oxygen K-edges compared to at or above the resonance, and at the K-shell resonant absorption of phosphorus compared to below the resonance. The number of electrons with sufficient energy to induce strand breaks was found to change depending on the photon energy. Electrons with 120 and 250 eV are shown to be rather more effective in SSB and DSB induction than electrons with higher energy. Inclusion of hydrated water in the DNA volume did not affect the photon energy dependence of the strand break yields.
Conclusion: The small difference of photon energies around K-absorption edges of the carbon, nitrogen, oxygen and phosphorus is indicated to induce variation in strand break yields by direct effect. Higher SSB and DSB induction efficiencies could be due to a higher yield of more than two electrons with around 120 eV to 250 eV per photoabsorption event., INFORMA HEALTHCARE
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2004年11月, ［査読有り］

"In situ" observation of guanine radicals induced by ultrasoft X-ray irradiation around the K-edge regions of nitrogen and oxygen
A Yokoya; K Akamatsu; K Fujii; M Ukai, 筆頭著者, Purpose: In order to understand the molecular mechanism of nucleobase damage caused by ultrasoft X-ray irradiation, guanine radicals have been studied using an X-band EPR (electron paramagnetic resonance) spectrometer installed in a synchrotron soft X-ray beamline.
Materials and Methods: Guanine pellets were irradiated under vacuum with ultrasoft X-rays obtained from a soft X-ray beamline (BL23SU) in SPring-8. The energy regions around the nitro en (0.4 keV) and oxygen (0.5 keV) K-edges were chosen for the irradiation. The ultrasoft X-ray irradiation and EPR measurements were carried out simultaneously at low temperature, 20 K and 77 K.
Results: The EPR spectrum observed during irradiation was clearly distinguishable from that of the stable radical, which still exists after exposure to ultrasoft X-rays at 7 7 K. The spectrum of the short-lived radicals consisted of two components, which exhibited different EPR microwave power saturation. The EPR signal intensities increased linearly with increasing dose rate (photon flux density). These signals immediately disappeared when the beam was turned off, even when irradiated at lower temperature (20 K). At the energy of the oxygen K-resonance excitation (539 eV) the signal intensity was clearly increased to more than five times that obtained on the lower energy side (526 eV). On the other hand, the enhancement was insignificant above and below the nitrogen K-edge (401 eV). The singlet EPR signal of the stable radical was similar to that reported previously in the literature for gamma-irradiated guanine.
Conclusions: The short-lived radical species observed were mainly induced as a result of the final state of the resonant Auger process oil oxygen atoms existing solely in the carbonyl group in guanine. Auger events at the other atoms in guanine (namely, carbon and nitrogen) do not induce this radical process to any great extent, even though the abundance of these atoms (i.e. the sum of their photoabsorption cross sections) is dominant in the guanine molecule., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2004年11月, ［査読有り］

Low-energy Auger- and photo-electron effects on the degradation of thymine by ultrasoft X-irradiation
K Akamatsu; K Fujii; A Yokoya, Purpose: To investigate quantitatively and qualitatively the production of thymine radicals produced by monochromatic ultrasoft X (USX) - or Co-60 gamma-rays using electron paramagnetic resonance (EPR) spectroscopy.
Materials and Methods: Thymine was chosen as the DNA component for the irradiation. The EPR experiments of irradiated thymine were performed using an X-band EPR device installed in a soft X-ray beamline (BL23SU) in SPring-8. Sample pellets were irradiated with USX photons in a microwave cavity in a vacuum chamber. EPR measurements of thymine powder pellets irradiated with USX photons at energies of 407 and 538 eV were performed at 77 K or room temperature. For reference, Co-60 gamma-irradiation to a pellet was also performed at room temperature.
Results: The following three features were found: 1) comparison between the two energies shows that the EPR dose-response curves are clearly distinguishable from each other: the curve for 407 eV saturated at a lower dose and spin number than that for 538 eV, 2) no evident qualitative difference between the radical species produced at the two energies was observed. 3) the EPR signal of the 538 eV USX-irradiated sample measured after annealing for 12 days is similar to that obtained with Co-70 gamma-irradiation.
Conclusions: The difference observed in the EPR dose-response relationship reflects the difference in the K-absorption cross-sections of carbon, nitrogen and oxygen in the thymine molecule which govern the photo-/Auger electron energy spectrum., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2004年11月, ［査読有り］

Decomposition of 2-deoxy-D-ribose by irradiation with 0.6 keV electrons and by 0.5 keV ultrasoft X-rays
K Fujii; K Akamatsu; A Yokoya, Purpose: To compare the molecular decomposition of 2-deoxy-D-ribose induced by 0.6 keV electron irradiation or by 0.5 keV ultrasoft X-ray irradiation.Materials and methods: A thin film of 2-deoxy-D-ribose was irradiated by two radiation sources: low-energy (similar to 0.6 keV) electrons and ultrasoft X-rays (similar to 0.5 keV). The positive ions that were desorbed from the sample during the irradiation were measured using a quadrupole mass spectrometer. The spectral changes in the X-ray absorption near edge structure (XANES) were also examined after the irradiation.Results and discussion: The ions that were desorbed from 2-deoxy-D-ribose due to electron irradiation were mainly H+, CHx+, C2Hx+, CO+, CHxO+, C3Hx+, C2HxO+ and C-3,HxO+ (x= 1, 2, and 3) ions. These ions were the same as those observed in desorption due to ultrasoft X-ray irradiation. The XANES spectral changes induced by electron irradiation showed GO bond cleavage in the molecule and C = O bond formation in the surface residues. These results show that intensive molecular decomposition of the furanose ring structure was induced by both types of irradiation. It is inferred that these irradiation products are primarily produced by secondary electrons (several tens of eV), which are thought to be generated by both types of irradiation when they are applied to the 2-deoxy-D-ribose sample., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 2004年11月, ［査読有り］

〔主要な業績〕EPR studies of 5-bromouracil crystal after irradiation with X rays in the bromine K-edge region
A Yokoya; K Takakura; R Watanabe; K Akamatsu; T Ito, 筆頭著者, Radicals induced in a single crystal of 5-bromouracil (BrUra) by synchrotron soft X rays in the bromine K-edge region (13.461-13.482 keV) were investigated using the X-band EPR method. The crystal was irradiated at three peak energies of the absorption spectrum at room temperature or at 80 K. A hydrogen abstraction radical derived from N1 of the pyrimidine ring was commonly observed for all of the energies used, though with some variation in quantity. Similar characteristics were also observed in the EPR signal for the off-K-edge low-energy (13.42 keV) and (CO)-C-60 gamma rays used for comparison. When irradiated at 80 K, a much larger exposure (roughly 10 times) of soft X rays was needed to obtain the same signal intensity as that observed at room temperature. EPR signals were not detectable with gamma irradiation at liquid nitrogen temperature. (C) 2004 by Radiation Research Society., RADIATION RESEARCH SOC
RADIATION RESEARCH, 2004年10月, ［査読有り］

Near-edge X-ray absorption fine structure of DNA nucleobases thin film in the nitrogen and oxygen K-edge region
K Fujii; K Akamatsu; A Yokoya, The near-edge X-ray absorption fine structure (NEXAFS) of evaporated thin films of DNA nucleobases on an Au-coated Si surface at room temperature has been investigated in the regions around the nitrogen and oxygen K-edges using highly monochromatic synchrotron soft X-rays. Each nucleobase shows a specific absorption spectrum originating from the resonant excitation of 1s electrons of nitrogen or oxygen to antibonding states, some of which strongly depend on the polarization angle of incident soft X-rays. From an analysis of the polarization angle dependences of the pi* resonance absorption intensity, it is found that purines are orientated to the multilayer surface with an angle of 15 +/- 6degrees for adenine and 38 +/- 1degrees for guanine. Uracil has an orientation of 16 +/- 4degrees, although other pyrimidines such as thymine and cytosine are randomly orientated with respect to the surface. These characteristics of the obtained NEXAFS spectra not only reveal the electrical structure of the nucleobases but also provide us with knowledge of the thermal stability of the self-organized base-stacking structure, which might play an important role in retaining the conformation of an intact or base-damaged DNA molecule., AMER CHEMICAL SOC
JOURNAL OF PHYSICAL CHEMISTRY B, 2004年06月, ［査読有り］

〔主要な業績〕Ion desorption from DNA components irradiated with 0.5 keV ultrasoft X-ray photons
K Fujii; K Akamatsu; A Yokoya, Positive ion desorption from thin films of DNA components, 2-deoxy-D-ribose, thymine, thymidine (dThd), and thymidine 5'-monophosphate (dTMP) was investigated in the oxygen K-shell edge excitation region using synchrotron ultrasoft X rays (538 eV). A large number of molecular fragments, H+, CHx+, C2Hx+, CO+, CHxO+, C3Hx+, C2HxO+ and C3HxO+ (x = 1, 2 and 3), were observed as desorbed ions from 2-deoxy-D-ribose. Some of these ions are related to simultaneous bond scission at particular C-C and C-O (or C-C) bonds in the furanose ring structure in the 2-deoxy-D-ribose molecule, indicating that the impact of photons on the oxygen atom and the impact of ejected secondary electrons (e.g. Auger electrons) cause an intense destruction of the furanose ring structure. In thymine thin films, H+, CHx+, CO+, CHxO+, C2HxN+ and CHxNO+ (x = 1, 2 and 3) fragments were observed. The yields of these ions were smaller than the yields from 2-deoxy-D-ribose. The desorption of CH3+ from thymine might induce a molecular conversion from thymine to uracil. The mass patterns of dThd and dTMP, and especially that of dTMP, were similar to that of 2-deoxy-D-ribose, indicating that a number of ions were generated at the sugar site, even in the nucleotide molecule. It is therefore predicted that the sugar moiety is more fragile than the thymine base. (C) 2004 by Radiation Research Society., RADIATION RESEARCH SOC
RADIATION RESEARCH, 2004年04月, ［査読有り］

Qualitative and quantitative analyses of the decomposition products that arise from the exposure of thymine to monochromatic ultrasoft X rays and Co-60 gamma rays in the solid state
K Akamatsu; K Fujii; A Yokoya, HPLC analyses of condensed thymine irradiated with monochromatic synchrotron ultrasoft X rays in the energy region around nitrogen and oxygen K-shell edges were performed. Cobalt-60 gamma rays were used as a reference radiation. The radiation chemical dose response of each separated thymine decomposition product was also determined. Uracil (U), 5-(hydroxymethyl)uracil (HMU), 5,6-dihydrothymine (DHT), 5-formyluracil (foU) and four main unknown products were found in the HPLC chromatogram of the sample irradiated with ultrasoft X rays in vacuo. Similar spectra of the products were also found in the gamma-ray experiment; however, some unknown products that appeared after elution of the thymine peak were significantly larger than those in the ultrasoft Xray experiment. This result indicates the difference in radiation quality. The G value of DHT produced by gamma radiation was 10 times larger than those produced by the ultrasoft Xray photons with energies of 395 and 407 eV corresponding to below and on the nitrogen K-shell edge, respectively. This result suggests that the differences in the photon energy and/ or in the energy spectra of the secondary electron between ultrasoft X rays and gamma rays are causing differences in the process of the radiation chemistry. Moreover, the yields of all the thymine decomposition products induced by 538 eV photons (oxygen K-shell edge) were significantly smaller than those induced by photons around the nitrogen K-shell edge. The K-shell excitation of oxygen in thymine may efficiently promote the production of small thymine fragments susceptible to desorption from the sample. (C) 2004 by Radiation Research Society., RADIATION RESEARCH SOC
RADIATION RESEARCH, 2004年04月, ［査読有り］

The measurement of molecular fragments from DNA components using synchrotron radiation
K Fujii; K Akamatsu; A Yokoya, Photon-stimulated desorption of positive ions from thin film DNA components, 2-deoxy-D-ribose, thymine and guanine, were investigated in the oxygen K-edge excitation region. H+, CH2+, C2H2+, CHO+, C3H3+ and CHO+ were desorbed mainly from the 2-deoxy-D-ribose thin film following oxygen K-edge excitation. The ion yields were obtained as a function of the photon energy. Each spectrum showed a prominent peak structure coinciding with the O1s --> sigma*(C-O) excitation energy. These results indicate that the observed ions are produced not only by direct photodecomposition but also by the impact of secondary electrons that the core excitation generates. On the other hand, H+ has been observed by irradiation of thymine and guanine thin films, while only insignificant amounts of the other ions were observed. It is shown that the core excitation more drastically degraded the 2-deoxy-D-ribose molecule into small fragments than is the case with the nucleobases. The sugar moiety in DNA is likely to be one of the nor fragile molecular sites, conducive to a single-strand DNA break. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
SURFACE SCIENCE, 2003年03月, ［査読有り］

〔主要な業績〕Effects of hydration on the induction of strand breaks, base lesions, and clustered damage in DNA films by alpha-radiation
A Yokoya; SMT Cunniffe; DL Stevens; P O'Neill, 筆頭著者, The yields of DNA single (ssb)- and double-strand breaks (dsb) as well as base lesions, which are converted into detectable ssb by base excision repair enzymes, induced at 278 K by densely ionizing alpha-radiation have been determined as a function of the level of hydration (Gamma, number of water molecules per nucleoticle) of films of supercoiled plasmid DNA (pUC 18). The yields of prompt ssb induced by alpha-radiation are independent of Gamma, from vacuum-dried up to 35 water molecules per nucleotide, indicating that diffusible hydroxyl radicals or H2O.+, if induced in the hydrated layer by alpha-radiation, do not significantly contribute to the induction of ssb. In contrast, the yield of prompt dsb does increase with increasing hydration level. At a Gamma of 35, the yield of dsb is about twice that for gamma-irradiation. Treatment of alpha-particle-irradiated DNA with the enzymatic probes, endonuclease III (Nth), and formamidopyrimicline-DNA glycosylase (Fpg), does not lead to significant levels of additional ssb and dsb. It is proposed that (i) base lesions induced by direct energy deposition in the DNA-water complex by high LET radiation, such as cc-particles, are generally present in clustered DNA damage, e.g., two or more lesions produced within a few tens of base pairs, and (ii) the complexity of the clustered damage, lesion density, is greater for densely (compared with sparsely) ionizing radiation. As a consequence, the majority of DNA base lesions induced by high LET radiation, in contrast to those by low LET radiation, and which are substrates for Fpg and Nth become refractory to excision repair due to their formation within more complex, clustered DNA damage., AMER CHEMICAL SOC
JOURNAL OF PHYSICAL CHEMISTRY B, 2003年01月, ［査読有り］

X-ray absorption near edge structure of DNA bases around oxygen and nitrogen K-edge
K Fujii; K Akamatsu; Y Muramatsu; A Yokoya, X-ray absorption near edge structure (XANES) spectra of DNA and the nucleobases (adenine, guanine, cytosine, thymine and uracil) are observed using monochromatic soft X-rays (400-560 eV). The photon energy range includes the electron binding energy of the core orbital of nitrogen and oxygen K shell. Obtained XANES spectra showing a characteristic structure were theoretically analyzed by the discrete variational density functional formalism (DV-Xalpha) method. These results clearly indicate that the photo-excitation of oxygen and nitrogen Is electron to pi* orbitals shows a sharp resonance profile rather than that to sigma* orbitals, enough to realize selecting a photochemical reaction site at specific nucleobases in a DNA molecule. Novel experiments are proposed based on the obtained spectra to understand the molecular mechanisms of radiation damages on DNA bases. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 2003年01月, ［査読有り］

Infrared spectral change in 2-deoxy-D-ribose by irradiation with monochromatic photons around oxygen K-edge
K Akamatsu; K Fujii; A Yokoya, Analyses of chemical changes in DNA by energy deposition from ionizing radiation are quite important to strictly know characteristics of radiobiological effects. Monochromatic photons from synchrotron radiation are one of the powerful probes to investigate the effects. As a step for the aim, chemical analyses by Fourier-transform infrared spectroscopy of the samples irradiated with the monochromatic photons were performed. It appeared that 2-deoxy-D-ribose irradiated around the energy of oxygen K-edge contained C=O or C=C, which would be responsible for a direct strand break of DNA. These data are noteworthy to find not only the strand scission at 2-deoxy-D-ribose moiety by the direct energy deposition by photon but also the following radiobiological responses such as cell killing or mutation. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 2003年01月, ［査読有り］

〔主要な業績〕Electron paramagnetic resonance induced by K-shell resonance excitation in DNA bases in solid state
A Yokoya; K Akamatsu; K Fujii, 筆頭著者, DNA base radicals were examined around oxygen K-edge region using an EPR spectrometer installed in a synchrotron soft X-ray beamline (BL23SU) in SPring-8. In situ measurements of EPR spectrum of guanine and thymine revealed that short-lived transient radical species are induced by photoexcitation of O 1s electron to sigma* orbital. They promptly disappear by "beam-off". On the other hand, long-lived radicals whose EPR spectra are consistent with previous reports for guanine cation and thymine anion radical are accumulated during the irradiation. These results indicate that chemically stable DNA base lesions, such as 8-oxo-G, would result from transient species that are inferred to be one electron oxidized radicals after decay of Auger final state. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 2003年01月, ［査読有り］

〔主要な業績〕Effect of hydration on the induction of strand breaks and base lesions in plasmid DNA films by gamma-radiation
A Yokoya; SMT Cunniffe; P O'Neill, 筆頭著者, The yields of gamma-radiation-induced single- and double-strand breaks (ssb's and dsb's) as well as base lesions, which are converted into detectable ssb by the base excision repair enzymes endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg), at 278 K have been measured as a function of the level of hydration of closed-circular plasmid DNA (pUC18) films. The yields of ssb and dsb increase slightly on increasing the level of hydration (Gamma) from vacuum-dried DNA up to DNA containing 15 mol of water per mole of nucleotide. At higher levels of hydration (15 < Gamma < 35), the yields are constant, indicating that H2O.+ or diffusible hydroxyl radicals, if produced in the hydrated layer, do not contribute significantly to the induction of strand breaks. In contrast, the yields of base lesions, recognized by Nth and Fpg, increase with increasing hydration of the DNA over the range studied. The maximum ratios of the yields of base lesions to that of ssb are 1.7:1 and 1.4:1 for Nth- and Fpg-sensitive sites, respectively. The yields of additional dsb, revealed after enzymatic treatment, increase with increasing level of hydration of DNA. The maximum yield of these enzymatically induced dsb is almost the same as that for prompt, radiation-induced dsb's, indicating that certain types of enzymatically revealed, clustered DNA damage, e.g., two or more lesions closely located, one on each DNA strand, are induced in hydrated DNA by radiation. It is proposed that direct energy deposition in the hydration layer of DNA produces H2O.+ and an electron, which react with DNA to produce mainly base lesions but not ssb. The nucleobases are oxidized by H2O.+ in competition with its conversion to hydroxyl radicals, which if formed do not produce ssb's, presumably due to their scavenging by Tris present in the samples. This pathway plays an important role in the induction of base lesions and clustered DNA damage by direct energy deposition in hydrated DNA and is important in understanding the processes that lead to radiation degradation of DNA in cells or biological samples., AMER CHEMICAL SOC
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2002年07月, ［査読有り］

First results from the actinide science beamline BL23SU at SPring-8
Y Saitoh; T Nakatani; T Matsushita; A Agui; A Yoshigoe; Y Teraoka; A Yokoya, The present performance of a soft X-ray beamline BL23SU at SPring-8 is described. The resolving power realized on a varied-line-spacing plane grating monochromator connected to a variably polarizing undulator was estimated to be better than 10 000 at 400 eV and similar to 6500 at 867 eV. In addition, reasonable photon flux of more than 10(11) photons/s/100 mA/0.02% b.w. is available in the energy range of 0.5-1.8 keV at experimental stations. (C) 2001 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 2001年12月, ［査読有り］

Reparability of lethal lesions produced by phosphorus photoabsorption in yeast cells
N Usami; A Yokoya; S Ishizaka; K Kobayashi, The characteristics of DNA lesions produced by the photoabsorption of phosphorus in yeast cells were studied using monochromatized soft X-rays tuned to the absorption peak of the phosphorus K-edge (2153 eV) and below the peak energy (2147 eV). The repaired fractions of DNA double-strand breaks (dsb) were measured relatively by using both a mutant, rad 54-3, which shows the temperature-sensitive dsb repair-deficient phenotype, and a wild-type strain. The repaired fraction of lesion in rad 54-3, which corresponds to the relative yield of dsb reparable by the RAD 54 pathway, was not affected by the phosphorus photo absorption. Repair of the produced lesions in the wild-type cells was also measured by comparing the surviving fraction of the immediately plated cells to that of those cells plated after holding in a non-nutrient medium for 80 hrs. The recovery of the surviving fraction after the holding treatment was dependent upon the irradiated X-ray energy. These results suggest that irreparable lesions are produced by the inner-shell photoabsorption of phosphorus in DNA, although its yield is small., JAPAN RADIATION RESEARCH SOC
JOURNAL OF RADIATION RESEARCH, 2001年09月, ［査読有り］

First operation of circular dichroism measurements with periodic photon-helicity switching by a variably polarizing undulator at BL23SU at SPring-8
A Agui; A Yoshigoe; T Nakatani; T Matsushita; Y Saitoh; A Yokoya; H Tanaka; Y Miyahara; T Shimada; M Takeuchi; T Bizen; S Sasaki; M Takao; H Aoyagi; TP Kudo; K Satoh; S Wu; Y Hiramatsu; H Ohkuma, This article presents the first operation of the magnetic circular dichroism (MCD) measurement system with periodic photon-helicity switching. The measurements were performed at the newly constructed soft x-ray beamline-BL23SU- at the third-generation synchrotron radiation facility, SPring-8. The monochromator control system was synchronized to the movement of the magnetic row (phase shift) of an APPLE-2 (Sasaki) type variably polarizing undulator. The periodic phase shift of the undulator provided the switching of helicity polarizing soft x rays up to 0.1 Hz. The closed-orbit distortion of the storage ring was controlled to avoid optical axis disturbances at this beamline as well as at other beamlines. The circular dichroism spectra with helicity switching by APPLE-2 show the possibility of high-sensitivity MCD measurements. This method promotes precise MCD measurements and can be a powerful technique to study magnetism as well as dichroism. (C) 2001 American Institute of Physics., AMER INST PHYSICS
REVIEW OF SCIENTIFIC INSTRUMENTS, 2001年08月, ［査読有り］

Synchronous beam diagnostic system using cordless telephones at SPring-8
TP Kudo; H Aoyagi; K Sato; S Wu; H Tanaka; S Sasaki; T Nakatani; M Takeuchi; T Shimada; Y Hiramatsu; A Yokoya; A Agui; A Yoshigoe; H Ohkuma; Y Miyahara; T Ishikawa; H Kitamura, Recently, we have developed a synchronous SR beam position diagnostic system. In this system, more than one X-ray beam position monitor is used synchronously and an oscillation of the SR beam position all through the storage ring can be detected. For an example, during the high speed driving of the insertion device, beam oscillation and shift can be simultaneously observed at different beamlines. To start the measurements simultaneously at the different beamlines, a trigger signal was conveyed by a cordless telephone. This paper describes the system and performance tests of it. (C) 2001 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 2001年07月, ［査読有り］

EPR spectrometer installed in a soft X-ray beamline at SPring-8 for biophysical studies
A Yokoya; K Akamatsu, 筆頭著者, We have developed an Electron paramagnetic resonance (EPR) system combined with a synchrotron beamline (Synchrotron Light Excited Electron Paramagnetic Resonance Spectrometer (SLEEPRS)) to detect radicals in biomolecules caused by irradiating with soft X-rays below 2keV. SLEEPRS was installed in a soft X-ray undulator beamline equipped with a grazing incidence grating monochromator (BL23SU, SPring-8). The cavity of the X-band microwave was set in a high vacuum chamber connected with the beamline transport channel. The sample temperature was controlled from 10 to 300 K by a closed-cycle cryogenic system during the soft X-ray irradiation and the EPR measurements. Typical EPR signals of a deaminated alanine radical from L-a-alanine were observed by irradiating 1.5 keV soft X-rays, The calculated absorbed dose shows that a dose of the same order or less gives the same EPR signal intensity as that generated by a conventional 100 kVp X-ray source. Thus the combination of an EPR spectrometer and synchrotron soft X-ray beamline may open a way for investigating the radical processes involved in biomolecular damages induced by a selective K-photoabsorption of a specific atom. (C), 2001 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 2001年07月, ［査読有り］

X-ray absorption near-edge structure (XANES) spectral changes of 2-deoxy-D-ribose by irradiation within the energy region around the oxygen K-shell absorption edge
K Akamatsu; A Yokoya, The physicochemical characteristics of 2-deoxy-D-ribose moieties in DNA strands are important to understand biological radiation stress. So, the X-ray absorption near edge structure (XANES) of 2-deoxy-D-ribose within the energy region around the oxygen K-shell absorption edge was measured. 2-deoxy-D-ribose was exposed to 3 energies of X-rays, i.e., 526.3 eV (below O 1s-->pi*), 537.8 eV (at the absorption peak of O 1s-->sigma*) and 552.6 eV (above O 1s-->sigma*) for given periods. Slight differences in spectral changes were seen in the each irradiation energy, suggesting in fact that the chemical state and following rearranged chemical structure of 2-deoxy-D-ribose may be different between the 3 irradiation energies., MUNKSGAARD INT PUBL LTD
JOURNAL OF SYNCHROTRON RADIATION, 2001年03月, ［査読有り］

A grating monochromator of BL23SU at SPring-8 covering silicon and oxygen K-edges
A Yoshigoe; A Agui; T Nakatani; T Matsusita; Y Saitoh; A Yokoya, We report the present performance of a grating monochromator at the newly constructed soft x-ray beamline (BL23SU at the SPring-8), which can measure both silicon and oxygen K-edges. That provides new opportunities for XAFS measurements of solids up to 2100 eV., MUNKSGAARD INT PUBL LTD
JOURNAL OF SYNCHROTRON RADIATION, 2001年03月, ［査読有り］

X-ray absorption near edge structures of DNA or its components around the oxygen K-shell edge
K Akamatsu; A Yokoya, The initial process of radiation damage in DNA was investigated by measuring the X-ray absorption near edge structures (XANES) within the energy region around the oxygen K-shell absorption edge for DNA, cytosine and 2-deoxy-D-ribose. Irradiation and XANES experiments were performed with the BL23SU soft X-ray beamline, using synchrotron radiation from the 8 GeV electron storage ring at SPring-8. Samples were mounted on gold-coated plates in a vacuum chamber. The XANES spectra were obtained by measuring the photoelectron current of the samples. 2-Deoxy-D-ribose was exposed to X rays at the absorption peak corresponding to the oxygen (O) 1s-->sigma* transition energy (538 eV); the XANES spectra were obtained after each irradiation. DNA and cytosine, possessing characteristic XANES spectra, both had two major energy bands corresponding to the O 1s-->pi* and 1s-->sigma* transitions, Two new peaks appeared and gradually increased in the XANES spectra of 2-deoxy-D-ribose during irradiation. These results suggest that C-O bonds in 2-deoxy-D-ribose are transformed to C=O bonds by O 1s-->sigma* transition, suggesting that the molecules undergo chemical changes into carbonyl-containing compounds. (C) 2001 By Radiation Research Society., RADIATION RESEARCH SOC
RADIATION RESEARCH, 2001年03月, ［査読有り］

Photoionization of Ne3+ ions in the region of the 1s -> 2p autoionizing resonance
M Oura; H Yamaoka; K Kawatsura; J Kimata; T Hayaishi; T Takahashi; T Koizumi; T Sekioka; M Terasawa; Y Itoh; Y Awaya; A Yokoya; A Agui; A Yoshigoe; Y Saitoh, Photoion yields of Ne4+ from Ne3+ ions were successfully measured in the region of the 1s --> 2p autoionizing resonance by a photon-ion mer ed-beam technique. A broad structure centered at 864.5 eV, which is composed of several transitions, was observed in the photoion-yield spectrum. The spectrum was analyzed with the results of multiconfiguration Dirac-Fock calculations. The calculations revealed that the lines contained in the broad structure can be attributed to possible transitions from the 2s(2)2p(3) S-4(3/2), D-2(3/2) and D-2(5/2) initial levels. The calculated spectrum satisfactorily shows an overall agreement with the experimental one., AMERICAN PHYSICAL SOC
PHYSICAL REVIEW A, 2001年01月, ［査読有り］

酸素K殻領域でのアミノ酸蒸着膜のNEXAFS測定
田中真人; 古結俊行; 児玉洋子; 横谷明徳; 安居院あかね; 赤松憲; 中川和道, Oxygen K-edge X-ray absorption near edge structures (XANES) spectra of amino acids (glycine, L-alpha -alanine, beta -alanine, L-serine, L-asparic acid and L-tyrosine) were measured. Several peaks of XANES spectra were successfully assigned on the basis of DV-X alpha calculation., MUNKSGAARD INT PUBL LTD
放射線化学討論会講演要旨集, 2000年, ［査読有り］

〔主要な業績〕Single- and double-strand breaks in solid pBR322 DNA induced by ultrasoft X-rays at photon energies of 388, 435 and 573 eV
A Yokoya; R Watanabe; T Hara, 筆頭著者, We measured strand breaks of pBR322 plasmid DNA irradiated with ultrasoft X-rays using monochromatic synchrotron radiation as a light source. Three photon energies, 388, 435 and 573 eV, a value below and above the nitrogen K-edge and above the oxygen K-edge, respectively, were chosen for the irradiation experiments as they have an equivalent photon transmittance of the sample. Irradiated DNA was analyzed by agarose gel electrophoresis and the numbers of single-and double-strand breaks (ssb and dsb) were determined by measuring the band intensity on the gel after ethidium bromide staining. The action cross-sections for the ssb and dsb slightly increased with the photon energy. The ratio between 388 and 573 eV was about 1.5 for both forms of strand breaks. The absorbed energy required far a strand break was about 60 eV for ssb and 1 keV for dsb, less than one fifth of the values obtained previously in the 2 keV region. On the other hand, the absorbed energies per strand break, as well as the ratio of the action cross-section for the ssb to that for the dsb, were constant regardless of the photon energy used. The K-shell photoabsorption on carbon, nitrogen and oxygen atoms in the DNA molecule, followed by an Auger cascade, induced DNA strand breaks with a constant efficiency in terms of the absorbed energy. These results indicate that the strand breaks of the DNA molecule in the solid state are mainly caused by the photo- and Auger-electrons and the efficiency of the strand breaks little depends on the atoms ejecting these secondary electrons., JAPAN RADIATION RESEARCH SOC
JOURNAL OF RADIATION RESEARCH, 1999年06月, ［査読有り］

Construction of the JAERI soft X-ray beamline for actinide material sciences
T Nakatani; Y Saitoh; Y Teraoka; T Okane; A Yokoya, An undulator beamline for spectroscopy studies focusing on the electronic structure of actinide materials is under construction. Linearly or circularly polarized soft X-rays are provided by employing a variably polarizing undulator. Varied-line-spacing plane gratings and a sagittal-focusing system are used to monochromatize the undulator beam, whose energy ranges from 0.3 to 1.5 keV. A resolving power of 10(4) is expected in the whole energy region. These components are methodically operated by the SPring-8 beamline control system. There are three experimental stations in the beamline. In one of the stations the photoemission spectroscopy experiments are carried out at a radioisotope-controlled area where actinide compounds as well as unsealed radioactive materials are usable. Other experimental stations are planned in the beamline for surface photochemical reactions and biological applications., MUNKSGAARD INT PUBL LTD
JOURNAL OF SYNCHROTRON RADIATION, 1998年05月, ［査読有り］

〔主要な業績〕Soft X-ray beamline specialized for actinides and radioactive materials equipped with a variably polarizing undulator
A Yokoya; T Sekiguchi; Y Saitoh; T Okane; T Nakatani; T Shimada; H Kobayashi; M Takao; Y Teraoka; Y Hayashi; S Sasaki; Y Miyahara; T Harami; TA Sasaki, 筆頭著者, This report presents the design of an undulator beamline at SPring-s to be used for soft X-ray spectroscopy focused on radioactive materials. Photoemission spectroscopy experiments are carried out in a radioisotope (RI)-controlled area where actinide compounds as well as unsealed radioactive materials are usable. Intrusion of the radioactive materials into the electron storage ring or to the outside of the evacuated beamline components can be avoided by a specially devised RI protection/inspection mechanism. The combination of a variably polarizing undulator and a varied-line-spacing plane-grating monochromator provides linearly or circularly polarized soft X-rays with a high resolving power in the energy range 0.28-1.5 keV. The beamline will become operational in December 1997., MUNKSGAARD INT PUBL LTD
JOURNAL OF SYNCHROTRON RADIATION, 1998年01月, ［査読有り］

Single- and double-strand breaks in pBR322 plasmid DNA by monochromatic X-rays on and off the K-absorption peak of phosphorus
K Hieda; T Hirono; A Azami; M Suzuki; Y Furusawa; H Maezawa; N Usami; A Yokoya; K Kobayashi, Using a synchrotron irradiation system pBR322 plasmid DNA was irradiated under vacuum by monochromatic X-rays having five specific photon energies (2.147, 2.153, 2.159, 2.168 and 2.199 KeV) both on and off the It-absorption peak (2.153 keV) of phosphorus. The single-and double-strand breaks (ssb and dsb) were measured as conversions of the closed circular form of DNA (form I) to open circular (form II) and linear (form III) forms respectively. Exposures to induce one strand break per molecule were lowest at the peak (2.153 keV), and highest at 2.147 KeV; the ratios were 2.7 for ssb and 3.0 for dsb. The exposures for dsb were 21-26 times higher than those for ssb. When the exposures were converted to absorbed doses in grays the absorbed doses per ssb were almost independent of photon energy. This result indicates that a certain absorbed dose was necessary to induce a ssb, regardless of whether photons were absorbed by the It-shell of phosphorus or by other shells, or by other atoms. However, the absorbed dose per dsb at 2.147 keV was 1.17 times higher than that averaged over four X-ray energies above 2.153 keV, indicating that the Ii-shell absorption, and the subsequent Auger event, efficiently induce dsb. The results are also discussed concerning the number of photo-absorptions of the constituent atoms pel DNA strand break., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 1996年10月, ［査読有り］

Synchrotron radiation beamline to study radioactive materials at the photon factory
H Konishi; A Yokoya; H Shiwaku; H Motohashi; T Makita; Y Kashihara; S Hashimoto; T Harami; TA Sasaki; H Maeta; H Ohno; H Maezawa; S Asaoka; N Kanaya; K Ito; N Usami; K Kobayashi, Design and construction of a new beamline have been described. The beamline is housed in a specially designed area controlled for radioactive materials at the Photon Factory (PF) in the National Laboratory for High Energy Physics (KEK). The beamline system consists of a front-end and two branchlines. One of the branchlines is used for X-ray photoelectron spectroscopy and radiation biology in the energy range of 1.8-6 keV and the other for X-ray diffractometry and XAFS studies as well as radiation biology in the range of 4-20 keV. The former was particularly equipped for the protection against accidental scattering of radioactive materials both inside and outside of the vacuum system., ELSEVIER SCIENCE BV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1996年03月, ［査読有り］

Lethal effect of K-shell absorption of intracellular phosphorus on wild-type and radiation sensitive mutants of Escherichia coli
H Maezawa; Y Furusawa; K Kobayashi; K Hieda; M Suzuki; N Usami; A Yokoya; T Mori, The present study was conducted to clarify the lethality of Auger cascades induced by the K-shell photoabsorption of phosphorus in Escherichia coli. Killing of wild-type and radiation-sensitive mutants of E. coli was examined. Three x-ray energies were chosen for irradiation; at 2.153 keV: the resonance peak of K-shell photoabsorption of phosphorus; at 2.146 and 2.160 keV: off-peak. Enhancement ratio, which was defined as the ratio of the killing sensitivity of 2.153 keV to that at 2.146 keV, were 1.32 to 1.54 for examined strains. Increment of absorbed energy calculated in entire cells for 2.153 keV radiation could not explain the degree of observed enhancement of killing. Lethality of Anger cascades depended on the killing sensitivity with x-rays which did not induce Auger cascades. The lethality for wild-type was lower than that for recombination repair-deficient mutants. It was concluded that one part of damages produced by Auger cascades was repaired in wild-type strains., SCANDINAVIAN UNIVERSITY PRESS
ACTA ONCOLOGICA, 1996年, ［査読有り］

INACTIVATION ACTION SPECTRA OF BACILLUS-SUBTILIS SPORES WITH MONOCHROMATIC SOFT X-RAYS (0.1-0.6 NM) OF SYNCHROTRON RADIATION
N MUNAKATA; K HIEDA; N USAMI; A YOKOYA; K KOBAYASHI, RADIATION RESEARCH SOC
RADIATION RESEARCH, 1992年07月, ［査読有り］

MUTAGENIC AND TRANSFORMING EFFECTS OF SOFT-X-RAYS WITH RESONANCE ENERGY OF PHOSPHORUS K-ABSORPTION EDGE
M WATANABE; M SUZUKI; K WATANABE; K SUZUKI; N USAMI; A YOKOYA; K KOBAYASHI, Syrian golden hamster embryo (SHE) cells were exposed to synchrotron-produced monochromatic X-rays at 5.747 (2.159 keV), 5.763 (2.153 keV) and 5.779 angstrom (2.147 keV). Although X-rays of all wavelengths induced mutations and chromatid aberrations in a dose-dependent manner, when cells were irradiated with 2.153 keV X-rays, which correspond to the resonance energy of the phosphorus K-absorption edge, the frequencies of mutation and chromatid aberration at equal dose levels were higher than for X-rays of the other wavelengths. At equal survival levels, however, there was no difference in the frequencies of mutations and chromatid aberrations in cells irradiated with soft X-rays. On the other hand, the frequency of morphological transformation in cells irradiated with 2.147 keV X-rays was higher than those irradiated with 2.153 keV and 2.159 keV X-rays. The relative biological effectiveness compared to cobalt-60 gamma-rays in morphological transformation was 2.8 for 2.147 keV, 1.1 for 2.159 keV and 1.0 for 2.153 keV at a 37% survival level., TAYLOR & FRANCIS LTD
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY, 1992年02月, ［査読有り］

RADIOLYTIC DEGRADATION OF CYSTATHIONINE IRRADIATED WITH MONOCHROMATIC SOFT X-RAYS AT THE K-SHELL RESONANCE-ABSORPTION OF SULFUR
A YOKOYA; K KOBAYASHI; N USAMI; S ISHIZAKA, 筆頭著者, The degradation of cystathionine was investigated using irradiation with monochromatized synchrotron X-rays at 2472 eV and 2466 eV. 2472 eV corresponds to the energy of the K-shell resonance absorption peak of the sulfur atom. The energy at 2466 eV was adopted as a reference. Cystathionine has a sulfur atom which joins two amino acid residues. This form is useful for analyzing the effect of degradation that originates from photoexcitation in the sulfur atom. The degradation products of cystathionine were detected by high performance liquid chromatography (HPLC). Of the products present, alpha-aminobutyric acid was produced threefold on irradiation with 2472 eV X-rays, as compared with the value for irradiation at 2466 eV and the same exposure. Almost the same amount of glycine was produced at the two irradiation energies. The yields of these two products were analyzed on the basis of the amount of cystathionine degraded and the number of photons absorbed by sulfur and the other elements in cystathionine. Cleavage of a bond was shown to depend on whether the bond includes an atom that absorbs the X-ray photon., JAPAN RADIATION RESEARCH SOC
JOURNAL OF RADIATION RESEARCH, 1991年06月, ［査読有り］

TARGET SIZE FOR A FIBRONECTIN-CELL ADHESION SYSTEM DETERMINED BY THE X-RAY INACTIVATION METHOD
A YOKOYA; K KOBAYASHI; Y MIYAMOTO; S ISHIZAKA, 筆頭著者, In order to elucidate the mechanism of cell adhesion, the size of the functional site, both in the fibronectin molecule and in the mouse fibroblast cell, responsible for cell adhesion activity, was determined. The size was assumed to be equivalent to the target size, that can be determined from the X-ray inactivation dose. The target size of the cell-binding site in the fibronectin molecule was 32 kdalton. The molecular weight was much larger than that of the tripeptide, which has been reported to be the minimum peptides having a cell-binding activity. This suggests that submolecular regions in fibronectin other than the tripeptide are necessary for cell adhesion. The target size in the cell responsible for the adhesion to the fibronectin-coated surface was 4300 kdalton. The large molecular weight of the target could be explained by assuming that a complex protein system is involved in the cell-adhesion process in the cell., JAPAN SOC CELL BIOLOGY
CELL STRUCTURE AND FUNCTION, 1991年02月, ［査読有り］

INTERACTION BETWEEN CELL-BINDING DOMAIN AND EXTRACELLULAR MATRIX-BINDING DOMAIN OF FIBRONECTIN DETERMINED BY FLUORESCENCE DEPOLARIZATION
Y MIYAMOTO; A YOKOYA; S ISHIZAKA, ELSEVIER SCIENCE BV
BIOCHIMICA ET BIOPHYSICA ACTA, 1988年04月, ［査読有り］

放射線照射ストレス時の細胞内の熱生産と熱流のモデル化
花澤恵子; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2024年

X線照射に対するストレス応答性長鎖ノンコーディングRNA(MALAT1)のがん細胞及び正常細胞における核内分布の違い
竹下敬祐; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2024年

放射線で誘発される老化様細胞に特異的な代謝機構の解明
三浦颯; 野口実穂; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2024年

ブロモウラシルの軟X線照射による電子状態変化
小沼草太; 大原麻希; 泉雄大; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2024年

光免疫治療標的分子のX線内殻励起による分解評価
横谷明徳; 泉雄大; 大原麻希; 小河原浩輝; 我喜屋祥; 家田直弥; 小川美香子
アイソトープ・放射線研究発表会(Web), 2024年

ヒト単層培養細胞集団に対する不均一なX線照射が与える遊走速度の変化
山口海希; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2024年

酵素的に二本鎖切断を誘発したEGFPプラスミドDNAのin vivoおよびin vitro再結合の可能性の検討
江田脩真; 伊東裕真; 小畑結衣; 廣瀬エリ; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2024年

放射線により不可逆的に細胞周期停止した細胞の温度変化
伊原智一; 伊原智一; 伊原智一; 花澤恵子; 横谷明徳; 横谷明徳
Thermal Medicine, 2024年

光電子スペクトル変化として検出されたDNA関連分子の軟X線照射効果
小沼草太; 横谷明徳; 横谷明徳
KEK Progress Report (Web), 2024年

フッ化DNA関連分子の電子状態についてのX線光電子分光研究
小沼草太; 泉雄大; 大原麻希; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2024年
ラスト(シニア)オーサー

超原子価ヨウ素化合物2-ヨードソ安息香酸のX線吸収・光電子分光スペクトル
泉雄大; 大原麻希; 藤井健太郎; 横谷明徳; 小川美香子
量子ビームサイエンスフェスタ(Web), 2024年

ハロゲン化ウラシル表面状態の第一原理電子状態計算
関川卓也; 甲斐健師; 小沼草太; 芳賀芳範; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2024年
ラスト(シニア)オーサー

軟X線照射で生成するアラニンラジカルのESRイメージング
中川清子; 横谷明徳; 大原麻希; 宇佐美徳子; 浅田瑞枝; 藤原基靖; 中村敏和; 石川健治
電子スピンサイエンス学会年会講演要旨集, 2023年

ラット乳腺における放射線発がんに至る初期細胞動態の解析
永田健斗; 西村まゆみ; 臺野和広; 臺野和広; 飯塚大輔; 飯塚大輔; 西村由希子; 西村由希子; 服部佑哉; 渡邊立子; 横谷明徳; 柿沼志津子; 柿沼志津子; 今岡達彦; 今岡達彦
日本癌学会学術総会抄録集(Web), 2023年

XPS法によるフッ化DNA関連分子の電子物性研究
小沼草太; 大原麻希; 横谷明徳; 横谷明徳
KEK Progress Report (Web), 2023年
ラスト(シニア)オーサー

まばらに当たった放射線はラット乳腺細胞の競合に影響するのか
西村由希子; 神長輝一; 宇佐美徳子; 横谷明徳; 今岡達彦
KEK Progress Report (Web), 2023年

リンK殻共鳴励起によるEGFP発現プラスミドDNAの損傷と細胞内における修復
小畑結衣; 小畑結衣; 木名瀬暁理; 横谷明徳; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2023年
ラスト(シニア)オーサー

軟X線照射におけるアラニンラジカル生成効率のX線エネルギー依存性
中川清子; 横谷明徳; 大原麻希; 宇佐美徳子
量子ビームサイエンスフェスタ(Web), 2023年

単色X線照射による超原子価ヨウ素化合物の分解
大原麻希; 泉雄大; 高倉栄男; 榎本将聖; 藤井健太郎; 横谷明徳; 小川美香子
量子ビームサイエンスフェスタ(Web), 2023年

コヒーレントX線を含めた2ビーム利用による新しいサイエンス
横谷明徳
KEK Proceedings (Web), 2023年, ［招待有り］
筆頭著者

マイクロビーム放射線治療における組織代償効果のメカニズム(A Possible Mechanism for the Tissue-Sparing Effect of Microbeam Radiotherapy)
福永 久典; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月
ラスト(シニア)オーサー

電子状態の物理学的理解による放射線生体分子変異プロセスの探索(Radiation damage processes explored based on physical property of electronic states of biological molecules)
横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月, ［招待有り］
筆頭著者

放射線はラット乳腺の内腔細胞の分化を線量率依存的に阻害する(Radiation inhibits differentiation of luminal cells in the rat mammary gland in a dose-rate-dependent manner)
永田 健斗; 西村 まゆみ; 臺野 和宏; 飯塚 大輔; 西村 由希子; 服部 佑哉; 渡邊 立子; 横谷 明徳; 柿沼 志津子; 今岡 達彦
日本放射線影響学会大会講演要旨集, 2022年09月

ヒト細胞中に導入された線形プラスミドDNAは遺伝子発現をするのか?(Does linear plasmid DNA express genes in it after transfected into human cells)
小畑 結衣; 木名瀬 暁理; 伊東 祐真; 秋光 信佳; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月
ラスト(シニア)オーサー

軟X線を照射したEGFP発現プラスミドDNAの非照射細胞内におけるDNA修復の難易性(DNA repair susceptibility in non-irradiated cells transfected with EGFP expressing plasmid DNA irradiated with various soft X-rays)
木名瀬 暁理; 小畑 結衣; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月
ラスト(シニア)オーサー

Brから放出される低エネルギー二次電子がプラスミドDNAの鎖切断に与える効果(Effect of low-energy secondary electrons emitted from bromine atoms on the strand breaks of plasmid DNA)
伊東 祐真; 小畑 結衣; 木名瀬 暁理; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月
ラスト(シニア)オーサー

放射線誘発老化様増殖停止を起こした細胞は二相性のオートファジー活性化を示す(Biphasic activation of autophagy in X-irradiated cells undergoing senescence-like growth arrest)
野口 実穂; 伊原 智一; 鈴木 啓司; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月
ラスト(シニア)オーサー

ヨウ素L吸収端近傍の単色X線照射による超原子価ヨウ素化合物の分解特性(Decomposition characteristics of caged compounds harboring a hypervalent iodine atom exposed to monochromatic X-rays around iodine L-edge)
大原 麻希; 泉 雄大; 高倉 栄男; 榎本 将聖; 藤井 健太郎; 横谷 明徳; 小川 美香子
日本放射線影響学会大会講演要旨集, 2022年09月

不均一なX線照射野での細胞移動を視覚化するためのFucci化および非Fucci化ヒト線維芽細胞の共培養(Co-culture of the Fucci and non-Fucci human fibroblast cells for visualizing cell migration in a heterogeneously X-ray-exposed field)
松本 萌; 福永 久典; 鈴木 啓司; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2022年09月
ラスト(シニア)オーサー

マウス精巣器官培養法を活用した放射線不妊メカニズムの解析
神長輝一; 横谷明徳; 福永久典
RADIOISOTOPES, 2022年03月15日, ［査読有り］

1.5keV軟X線照射した重水素化アラニン中での高密度ラジカル生成
中川清子; 岡壽崇; 藤井健太郎; 横谷明徳
放射線化学討論会講演要旨集, 2022年03月
ラスト(シニア)オーサー

超原子価ヨウ素化合物2-ヨードソ安息香酸(IBA)のX線光電子分光測定
泉雄大; 大原麻希; 横谷明徳
KEK Progress Report (Web), 2022年
ラスト(シニア)オーサー

蛍光標識二次元培養ラット乳腺細胞へのX線マイクロビーム照射におけるビーム位置補正法の開発
西村由希子; 神長輝一; 宇佐美徳子; 横谷明徳; 今岡達彦
KEK Progress Report (Web), 2022年

ハロゲン化ウラシルのX線光電子分光
泉雄大; 大原麻希; 馬場祐治; 横谷明徳
KEK Progress Report (Web), 2022年
ラスト(シニア)オーサー

プラスミドDNAの放射線誘発損傷:1.フィルムと水溶液での線量評価
YU Hao; 篠原俊輔; 横谷明徳; 横谷明徳; 山下真一
アイソトープ・放射線研究発表会(Web), 2022年

X線照射した細胞内のNADH量の経時変化
山野下佳輝; 山野下佳輝; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2022年
ラスト(シニア)オーサー

放射線照射細胞中のCa²⁺濃度ダイナミクスと小胞体の形態変化
斉藤智幸; 鈴木碧海; 鈴木碧海; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2022年
ラスト(シニア)オーサー

放射線はラット乳腺内腔細胞の分化を線量率依存的に抑制する
永田健斗; 西村まゆみ; 臺野和広; 飯塚大輔; 西村由希子; 服部佑哉; 渡辺立子; 横谷明徳; 柿沼志津子; 今岡達彦
アイソトープ・放射線研究発表会(Web), 2022年

放射線によるプラスミドDNAの損傷誘発:フィルムと希薄水溶液での吸収線量の補正
YU H.; YU H.; 篠原俊輔; 横谷明徳; 横谷明徳; 山下真一
放射線化学討論会講演要旨集, 2022年

放射線照射された細胞の内部の温度変化
横谷明徳
放射線化学討論会講演要旨集, 2022年
筆頭著者

軟X線照射におけるアラニンラジカル生成効率とスピン緩和時間のX線エネルギー依存性(1)
中川清子; 横谷明徳; 大原麻希; 宇佐美徳子
放射線化学討論会講演要旨集, 2022年

光免疫がん治療のための超原子価ヨウ素化合物のXANES測定による評価
大原麻希; 泉雄大; 高倉栄男; 榎本将聖; 藤井健太郎; 横谷明徳; 小川美香子
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2022年

内殻空孔緩和に伴う水和ヌクレオチドからの発光
寺尾優作; 熊谷嘉晃; 鈴木一世; 土屋貴寛; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2022年

5-クロロウラシルの塩素K殻XANESスペクトル測定
泉雄大; 大原麻希; 馬場裕治; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2022年
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軟X線XPSによるBr-ヌクレオチド分子の価電子状態計測とDNA分子内電荷移動機構
平戸未彩紀; 平戸未彩紀; 横谷明徳; 横谷明徳; 馬場祐治; 和田真一; 芳賀芳範; 藤井健太郎; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2022年
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超原子価ヨウ素化合物のヨウ素L₃殻XANES測定
大原麻希; 泉雄大; 高倉栄男; 榎本将聖; 藤井健太郎; 横谷明徳; 小川美香子
量子ビームサイエンスフェスタ(Web), 2022年

5-ハロゲン化ウラシルのX線光電子分光測定
泉雄大; 大原麻希; 馬場祐治; 馬場祐治; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2022年
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水溶液中分子における放射線効果理解を目指したイオン質量分析法
熊谷嘉晃; 土屋貴寛; 宮後海帆; 寺尾優作; 鈴木一世; 金井唯; 黒瀬研二; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
日本物理学会講演概要集(CD-ROM), 2022年

DNA修復タンパク質XRCC4及びその変異体タンパク質のSAXS構造解析
長谷川真保; 西久保開; 藤原悟; 松尾龍人; 松本義久; 横谷明徳
Photon Factory Activity Report 2020, 2021年04月, ［査読有り］
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放射線ストレスによる細胞内Ca²⁺濃度変化のライブセルイメージング法の検討
鈴木碧海; 鈴木碧海; 大塚将太郎; 大塚将太郎; 横谷明徳; 横谷明徳
アイソトープ・放射線研究発表会(Web), 2021年
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放射線誘発DNA損傷の捕捉剤による選択的な防護効果と含水率による違い
YU Hao; 近藤勇佑; 藤井健太郎; 横谷明徳; 山下真一
アイソトープ・放射線研究発表会(Web), 2021年

様々な条件下におけるパーキンソン病発症と関係する蛋白質α-シヌクレインのX線小角散乱測定
藤原悟; 西久保開; 長谷川真保; 横谷明徳
KEK Progress Report (Web), 2021年

二次元培養ラット乳腺細胞へのX線マイクロビーム照射におけるビーム位置補正法の開発
西村由希子; 西村由希子; 神長輝一; 宇佐美徳子; 横谷明徳; 今岡達彦
KEK Progress Report (Web), 2021年

X線誘起発光計測によるDNAの放射線損傷中間体の研究
寺尾優作; 熊谷嘉晃; 鈴木一世; 土屋貴寛; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
日本物理学会講演概要集(CD-ROM), 2021年

放射線誘発DNA損傷における含水率の影響:2.塩基損傷およびAP部位
YU Hao; 近藤勇佑; 山下真一; 藤井健太郎; 横谷明徳
放射線化学(Web), 2021年, ［査読有り］
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水和DNAに対する放射線効果解明のための飛行時間型イオン質量分析法の開発
土屋貴寛; 熊谷嘉晃; 熊谷嘉晃; 宮後海帆; 寺尾優作; 鈴木一世; 金井唯; 黒瀬研二; 鵜飼正敏; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
原子衝突学会年会講演概要集, 2021年

液相における内殻空孔緩和に伴う水分子解離プロセス
宮後海帆; 熊谷嘉晃; 土屋貴寛; 寺尾優作; 鈴木一世; 金井唯; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
原子衝突学会年会講演概要集, 2021年

温熱処理した細胞から抽出したヒストンの円二色性測定
泉雄大; 泉雄大; 松尾光一; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2021年
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活性化XRCC4のSAXS構造解析とDNA修復
長谷川真保; 西久保開; 西久保開; 藤原悟; 松尾龍人; 松本義久; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2021年
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軟X線光電子分光法を用いた臭素化DNA関連分子の電子状態の研究
平戸未彩紀; 馬場祐治; 和田真一; 藤井健太郎; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2021年
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放射線誘発DNA損傷における含水率の影響:損傷収率の損傷タイプによる分離評価
YU H.; 近藤勇佑; 藤井健太郎; 横谷明徳; 横谷明徳; 山下真一
放射線化学討論会講演要旨集, 2021年

水和ヌクレオチド分子のX線誘起発光
寺尾優作; 熊谷嘉晃; 鈴木一世; 土屋貴寛; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
放射線化学討論会講演要旨集, 2021年

放射線損傷DNAの細胞内修復ダイナミクス可視化のための新たなベクターDNA系の開発(Development of a vector DNA system for visualization of intracellular repair dynamics of DNA damage by ionizing radiation)
小畑 結衣; 平嵜 敬志朗; 秋光 信佳; 鈴木 雅雄; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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X線照射による広範囲ゲノム欠失の様式解析(Genome signature analysis of Megabase-sized large deletions induced by X-irradiation)
廣瀬 エリ; 鈴木 啓司; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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X線により老化した細胞内の温度計測の試み(An approach of intracellular measurements of temperature in senescent cells after X-ray exposure)
伊原 智一; 野口 実穂; 岡部 弘基; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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放射線損傷DNAの細胞内修復ダイナミクス可視化のための新たなベクターDNA系の開発(Development of a vector DNA system for visualization of intracellular repair dynamics of DNA damage by ionizing radiation)
小畑 結衣; 平嵜 敬志朗; 秋光 信佳; 鈴木 雅雄; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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水和水に対するX線エネルギー付与により誘発されたEGFPプラスミドDNA損傷の修復のライブセルイメージング(Live cell imaging of repair of EGFP plasmid DNA damage induced by X-ray energy deposition on hydrated waters)
平嵜 敬志朗; 小畑 結衣; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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DNA損傷と細胞応答に対する線量率効果のシミュレーション(Simulation of dose-rate effect on DNA damage and cellular responses)
渡辺 立子; 服部 佑哉; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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DNA修復タンパク質XRCC4多量体のリン酸化による構造変化(Structural changes of DNA repair protein XRCC4 due to phosphorylation and its role for multimerization)
西久保 開; 長谷川 真保; 泉 雄大; 藤井 健太郎; 松尾 光一; 松本 義久; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月
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X線照射された細胞内部の温度測定(Measurement of the temperature inside X-ray irradiated cells)
重清 壯登; 宇佐美 徳子; 岡部 弘基; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月

X線照射された細胞内におけるストレス応答シグナルとしてのCa2+濃度変化(Ca2+ waves as stress signals in X-irradiated cells)
鈴木 碧海; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月

X線照射による広範囲ゲノム欠失の様式解析(Genome signature analysis of Megabase-sized large deletions induced by X-irradiation)
廣瀬 エリ; 鈴木 啓司; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月

放射線誘発老化細胞におけるオートファジー関連タンパク質の経時的な発現変動(Temporal expression analysis of autophagy-related proteins in radiation-induced senescence)
野口 実穂; 伊原 智一; 鈴木 啓司; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月

X線により老化した細胞内の温度計測の試み(An approach of intracellular measurements of temperature in senescent cells after X-ray exposure)
伊原 智一; 野口 実穂; 岡部 弘基; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2020年10月

光免疫治療に資するX線誘導による生体深部腫瘍での選択的分子解離の探索(Explore of X-ray induced selective molecular degradation for photoimmuno-therapy targeting deep tissues)
横谷 明徳; 藤井 健太郎; 渡辺 立子; 平戸 未彩紀; 中川 桂一; 稲波 修; 武次 徹也; 小川 美香子
日本放射線影響学会大会講演要旨集, 2020年10月

X線マイクロビーム照射及び非照射細胞の化学プローブを用いた温度計測の試み
重清壯登; 重清壯登; 清野晃平; 清野晃平; 神長輝一; 宇佐美徳子; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2020年

軟X線分光法を用いたハロゲン化DNA関連分子の電子状態の研究
平戸未彩紀; 平戸未彩紀; 馬場祐治; 和田真一; 藤井健太郎; 本田充紀; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2020年

放射線生物影響メカニズムのマルチモーダル解析
横谷明徳; 横谷明徳; 鵜飼正敏; 宇佐美徳子; 西久保開; 西久保開; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2020年

微量添加薬剤による放射線防護効果の検討~防護剤フリーなDNA試料を用いた損傷収率測定~
近藤勇佑; YU Hao; 横谷明徳; 藤井健太郎; 山下真一
日本原子力学会春の年会予稿集(CD-ROM), 2020年

マイクロビームと組織培養を用いた放射線組織生物学 -保健物理学と放射線生物学の接点として-
福永久典; 横谷明徳
保健物理(Web), 2020年

二次元培養ラット乳腺細胞へのX線マイクロビーム照射及びその動態追跡
西村由希子; 西村由希子; 神長輝一; 宇佐美徳子; 横谷明徳; 今岡達彦
KEK Progress Report (Web), 2020年

VUV-CDで見えてきたリン酸化によるXRCC4会合体の構造変化解析
西久保開; 西久保開; 長谷川真保; 長谷川真保; 泉雄大; 藤井健太郎; 松尾光一; 松本義久; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2020年

X線小角散乱法を用いたリン酸化XRCC4の活性化構造解析
長谷川真保; 長谷川真保; 西久保開; 西久保開; 藤原悟; 松尾龍人; 松本義久; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2020年

放射線誘発DNA損傷における含水率の影響:2.塩基損傷およびAP部位
YU H.; 近藤勇佑; 藤井健太郎; 横谷明徳; 山下真一
放射線化学討論会講演要旨集, 2020年

放射線誘発DNA損傷における含水率の影響:1.収率測定精度の向上および鎖切断収率の測定
近藤勇佑; YU H.; 藤井健太郎; 横谷明徳; 山下真一
放射線化学討論会講演要旨集, 2020年

重粒子線によるDNA損傷形成における水和水の役割
山下真一; YU H.; 近藤勇佑; 永井菜月; 横谷明徳; 平山亮一
量子科学技術研究開発機構研究報告書(Web), 2020年

Micro-slit X-ray irradiation reveals testicular tissue-sparing effects: an attempt for high-precision radiotherapy for male fertility preservation
Hisanori Fukunaga; Kevin M. Prise; Akinari Yokoya
PF Highlights 2019, 2020年, ［招待有り］
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ストライプ状照射を用いた精子形成能維持と臨床応用
福永久典; 横谷明徳
Isotope News (Web), 2020年, ［招待有り］
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コルヒチン投与またはX線照射によって阻害される哺乳動物細胞におけるミトコンドリア動態(Mitochondrial Dynamics in Mammalian Cells Modified by Colchicine Administration or X-irradiation)
木村 由佳; 大内 則幸; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2019年11月

非照射ヒト細胞におけるin vitro X線照射プラスミドDNAのEGFP発現のライブセル観察(Live cell observation of EGFP expression of in vitro X-irradiated plasmid DNA in non-irradiated human cells)
小畑 結衣; 平嵜 敬志朗; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2019年11月

正常ヒト線維芽細胞における放射線照射後のオートファジー及び老化誘導の分子的プロセスについて(Molecular processes of Radiation induced autophagy and senescence of a normal human fibroblast)
野口 実穂; 伊原 智一; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2019年11月

ヒト細胞中に移入されたX線照射水和EGFP発現プラスミドDNAの修復感受性(Repair susceptibility of hydrated EGFP-expressing plasmid DNA transfected into human cells after exposure to X-rays)
平嵜 敬志朗; 小畑 結衣; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2019年11月

X線照射後の老化誘発における細胞内環境及びオートファジー活性の変化(Changes of intracellular environment and autophagy activity during senescence induction after X-ray exposure)
伊原 智一; 野口 実穂; 横谷 明徳
日本放射線影響学会大会講演要旨集, 2019年11月

最先端の研究開発 量子科学技術研究開発機構 第4回「量子生命科学」の発進
藤巻秀; 五十嵐龍治; 高草木洋一; 安達基泰; 横谷明徳; 玉田太郎; 河野秀俊; 鹿園直哉; 今岡達彦; 赤松憲; 小西輝昭; 山田真希子; 八幡憲明
ΑΤΟΜΟΣ, 2019年06月01日

放射線照射による線量分布と生物影響の初期過程で生じるDNA損傷応答のシミュレーション研究
渡邊立子; 服部佑哉; 横谷明徳
放射線, 2019年

放射線DNA損傷と生物影響の関係
横谷明徳
日本物理学会講演概要集(CD-ROM), 2019年

DNA損傷修復の時間変化を考慮した放射線誘発の標的論モデル
服部佑哉; 渡辺立子; 横谷明徳; 倉林大輔
日本数理生物学会年会(Web), 2019年

糖転移フラボノイドの重粒子線に対する防護メカニズム
YU H.; 永井菜月; 山下真一; 横谷明徳; 平山亮一
量子科学技術研究開発機構研究報告書(Web), 2019年

防護剤フリーな条件での放射線の直接作用によるDNA損傷
永井菜月; YU Hao; 山下真一; 藤井健太郎; 横谷明徳; 平山亮一
アイソトープ・放射線研究発表会要旨集, 2019年

放射線によるDNA変異誘発における微量添加剤の影響:高純度DNA試料へのX線照射
YU Hao; 山下真一; 永井菜月; 藤井健太郎; 横谷明徳
アイソトープ・放射線研究発表会要旨集, 2019年

三次元培養ラット乳腺細胞コロニーへのX線マイクロビーム照射及びその動態追跡
西村由希子; 神長輝一; 宇佐美徳子; 横谷明徳; 今岡達彦
KEK Progress Report (Web), 2019年

放射光X線マイクロビームを用いた細胞内局所照射に対するミトコンドリアの放射線応答研究
神長輝一; 宇佐美徳子; 鈴木啓司; 横谷明徳
KEK Progress Report (Web), 2019年

XANESスペクトルによる放射線DNA鎖切断の観測
藤井健太郎; 横谷明徳; DU PENHOAT M.A. Herve; POLITIS M.F.
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2019年

CDスペクトル測定を用いたリン酸化XRCC4タンパク質の活性化構造の探索
西久保開; 西久保開; 長谷川真保; 長谷川真保; 泉雄大; 藤井健太郎; 松尾光一; 松本義久; 横谷明徳; 横谷明徳
日本分子生物学会年会プログラム・要旨集(Web), 2019年

DNA修復タンパク質複合体形成過程に関する小角散乱研究の試み
長谷川真保; 長谷川真保; 西久保開; 西久保開; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2019年

VUV-CDで見えてきたXRCC4活性中心に対するリン酸化の分子内遠隔制御
西久保開; 西久保開; 長谷川真保; 長谷川真保; 泉雄大; 藤井健太郎; 松尾光一; 松本義久; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2019年

X線照射で誘発されるDNA安定変異収率への抗酸化剤添加の影響
YU H.; 永井菜月; 近藤勇佑; 藤井健太郎; 横谷明徳; 山下真一
放射線化学討論会講演要旨集, 2019年

DNA修復タンパク質のリン酸化構造のSAXS解析
長谷川真保; 長谷川真保; 西久保開; 西久保開; 松尾龍人; 藤原悟; 横谷明徳; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2019年

Brを含むDNA関連分子の内殻電子状態の研究
平戸未彩紀; 平戸未彩紀; 横谷明徳; 横谷明徳; 馬場祐治; 藤井健太郎
量子ビームサイエンスフェスタ(Web), 2019年

VUV-CDを用いたリン酸化XRCC4の構造変化解析
西久保開; 西久保開; 長谷川真保; 長谷川真保; 泉雄大; 藤井健太郎; 松尾光一; 松本義久; 横谷明徳; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2019年

器官培養したマウス精巣に対するすだれ状X線マイクロビーム照射と精子形成に与える影響
福永久典; 神長輝一; BUTTERWORTH Karl T.; 佐藤卓也; 渡辺立子; 宇佐美徳子; 小川毅彦; 横谷明徳; PRISE Kevin M.
KEK Progress Report (Web), 2019年07月

放射線複雑DNA損傷を誘発する低エネルギー電子の役割:動的モンテカルロ計算解析
甲斐健師; 米谷佳晃; 横谷明徳
日本物理学会講演概要集(CD-ROM), 2018年

DNAの溶媒和構造と放射線損傷サイトの関係:分子動力学シミュレーション解析
米谷佳晃; 中川洋; 横谷明徳; 甲斐健師
日本物理学会講演概要集(CD-ROM), 2018年

セルオートマトンをベースとした放射線適応応答解析モデルの構築
服部佑哉; 小宮山裕人; 倉林大輔; 横谷明徳; 渡辺立子
自律分散システム・シンポジウム(CD-ROM), 2018年

糖転移フラボノイドMGルチンによるラジカル捕捉と化学回復:パルスラジオリシスによる直接観測
YU Hao; 山下真一; 藤井健太郎; 横谷明徳; 上坂充
アイソトープ・放射線研究発表会要旨集, 2018年

DNAの水和構造と放射線損傷サイトの関係:分子動力学シミュレーション解析
米谷佳晃; 中川洋; 横谷明徳; 甲斐健師
日本物理学会講演概要集(CD-ROM), 2018年

DNA放射線損傷中間体分析のための発光測定
寺尾優作; 百鬼壮大; 高田秀一郎; 小島拓也; 相原大樹; 小田島嘉孝; 槇島煕; 島田紘行; 鵜飼正敏; OZGA C.; HOLZAPFEL X.; SCHIMIDT Ph.; KUESTNER-WETEKAMM C.; OTTO H.; KNIE A.; EHRESMANN A.; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
放射線化学討論会講演要旨集, 2018年

放射線によるDNA変異誘発における微量添加剤の影響:透析によるDNAの高純度化
YU Hao; 山下真一; 横谷明徳; 藤井健太郎; 上坂充
放射線化学討論会講演要旨集, 2018年

放射線照射後の乳腺末梢芽状突起の細胞数動態推定モデル
服部佑哉; 今岡達彦; 横谷明徳; 渡辺立子
日本放射線影響学会大会抄録(Web), 2018年

DNA損傷生成・応答に対する線量・線量率の影響モデル
渡辺立子; 服部佑哉; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

三次元乳腺細胞コロニーに対するX線マイクロビーム照射
今岡達彦; 西村由希子; 神長輝一; 神長輝一; 宇佐美徳子; 横谷明徳
KEK Progress Report (Web), 2018年

電子物性に着目したハロゲン化ピリミジンの放射線増感メカニズム解明の試み
鬼澤美智; 芳賀芳範; 田中成典; 平戸未彩紀; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

ヒト線維芽細胞におけるX線照射によるミトコンドリアへの影響
浜田涼; 杉本理峻; 木村由佳; 神長輝一; 鈴木啓司; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

正常ヒト線維芽細胞における放射線照射後の老化誘導に伴うオートファジー活性の変動
野口実穂; 伊原智一; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

X線光電子分光法によるBrを含むDNA関連分子の内殻電子状態の研究
平戸未彩紀; 横谷明徳; 馬場祐治; 藤井健太郎
日本放射線影響学会大会抄録(Web), 2018年

Ca²⁺濃度変化をパラメータとする放射線適応応答反応ネットワークのモデル化の試み
杉本理峻; 浜田涼; 服部佑哉; 渡辺立子; 立花章; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

酸素K殻イオン化によって起こるデオキシリボースの分解過程
藤井健太郎; HERVE DU PENHOAT Marie-Anne; POLITIS Marie-Francoise; 横谷明徳
分子科学討論会講演プログラム&要旨(Web), 2018年

水和ヌクレオチドの放射線誘起反応経路分析のための発光励起関数測定
寺尾優作; 百鬼壮大; 高田秀一郎; 小島拓也; 相原大樹; 小田島嘉孝; 槇島煕; 島田紘行; 鵜飼正敏; OZGA C.; HOLZAPFEL X.; SCHIMIDT Ph.; KUESTNER-WETEKAMM C.; OTTO H.; KNIE A.; EHRESMANN A.; 横谷明徳; 藤井健太郎; 福田義博
原子衝突学会年会講演概要集, 2018年

X線マイクロビームを用いた細胞内照射部位特異的なミトコンドリア応答の研究
神長輝一; 浜田涼; 宇佐美徳子; 鈴木啓司; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2018年

ラット乳腺の腫瘍試料からの小角X線散乱
大和田謙二; 今岡達彦; 藤井健太郎; 町田晃彦; 綿貫徹; 西村由希子; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2018年

電離放射線によって生じるDNA鎖切断に対する水和水分子の役割
藤井健太郎; 横谷明徳; DU PENHOAT M-A Herve; POLITIS M-F
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2018年

放射線照射による線量分布とDNA損傷応答のシミュレーション研究
渡辺立子; 服部佑哉; 横谷明徳
応用物理学会春季学術講演会講演予稿集(CD-ROM), 2018年

ライブセルイメージングで観るX線マイクロビーム照射・非照射細胞の細胞周期変調
神長輝一; 神長輝一; 野口美穂; 宇佐美徳子; 横谷明徳; 横谷明徳
応用物理学会春季学術講演会講演予稿集(CD-ROM), 2018年

蛍光ナノダイヤによるマウス受精卵内環境変化のリアルタイム計測に向けた試み
神長輝一; 塚本智史; 相澤竜太郎; 藤咲貴大; 横谷明徳; 柿沼志津子; 白川昌弘; 白川昌弘; 五十嵐龍治
日本分子生物学会年会プログラム・要旨集(Web), 2018年

XRCC4タンパク質の擬似リン酸化による構造変化の解析
西久保開; 長谷川真保; 泉雄大; 藤井健太郎; 松尾光一; 松本義久; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

X線照射したEGFPプラスミドの非照射細胞への導入とDNA修復難易度の研究
小畑結衣; 平嵜敬志朗; 横谷明徳
日本放射線影響学会大会抄録(Web), 2018年

放射光円二色性分光によるメチル化ヒストンH3の構造解析
泉雄大; 松尾光一; 藤井健太郎; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2018年

VUV-CDスペクトル測定によるDNA修復タンパク質XRCC4の二次構造解析
西久保開; 泉雄大; 藤井健太郎; 松本義久; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2018年

精巣器官培養法を用いた精子形成に対する不均一放射線照射場影響に関する検討
福永久典; 神長輝一; 宇佐美徳子; 小川毅彦; PRISE Kevin; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2018年

X線マイクロビームを用いたDNA損傷に開始される細胞周期変調のライブセルイメージング
神長輝一; 宇佐美徳子; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2018年

(量子物理学+生化学)×生物学=?～"量子生物学"とは何か～ シンクロトロン放射をツールとする放射線によるDNA損傷と細胞学的応答の研究
横谷 明徳; 藤井 健太郎; 島田 紘行; 鵜飼 正敏; 神長 輝一; 大和田 謙二; 町田 晃彦; 西村 由希子; 今岡 達彦
生命科学系学会合同年次大会, 2017年12月

精巣組織器官培養法を用いた放射線照射影響の検討と治療への応用
福永久典; 神長輝一; 佐藤卓也; Butterworth KT; 横谷明徳; 小川毅彦; Prise KM
生命科学系学会合同年次大会 2017年度, 2017年12月

大規模ゲノムバンクiJGVDを用いた放射線感受性遺伝子変異の検討と個別化放射線被ばくリスク評価
福永久典; 横谷明徳; 瀧靖之
アイソトープ・放射線研究発表会要旨集, 2017年

水中でエネルギー付与された電子の動的挙動
甲斐健師; 樋川智洋; 鵜飼正敏; 藤井健太郎; 渡邊立子; 横谷明徳
放射線化学討論会講演要旨集, 2017年

抗酸化剤MG-Rutinの放射線防護効果:パルスラジオリシス法によるラジカル捕捉と化学回復の観測
YU Hao; 山下真一; 横谷明徳; 藤井健太郎; 上坂充
放射線化学討論会講演要旨集, 2017年

軟X線照射によってDNA核酸塩基中に生じる不対電子のESR測定
岡壽崇; 横谷明徳; 藤井健太郎; 木野康志; 関根勉
分子科学討論会講演プログラム&要旨(Web), 2017年

細胞内局所X線照射法を用いたミトコンドリアの放射線応答研究
神長輝一; 浜田涼; 宇佐美徳子; 鈴木啓司; 横谷明徳
日本生化学会大会(Web), 2017年
ラスト(シニア)オーサー

乳腺の末梢芽状突起の低線量放射線応答モデルの構築
服部佑哉; 今岡達彦; 横谷明徳; 渡辺立子
日本放射線影響学会大会抄録(Web), 2017年

X線マイクロビームを用いた細胞小器官への放射線影響研究
神長輝一; 浜田涼; 宇佐美徳子; 鈴木啓司; 横谷明徳
日本放射線影響学会大会抄録(Web), 2017年
ラスト(シニア)オーサー

正常ヒト細胞へのX線照射によるミトコンドリア量及びATP産生量の変化
浜田涼; 浜田涼; 小野莉菜; 小野莉菜; 神長輝一; 神長輝一; 木村由佳; 木村由佳; 鈴木啓司; 横谷明徳; 横谷明徳
日本放射線影響学会大会抄録(Web), 2017年

ハロゲン化ピリミジンを含むDNAの放射線増感の電子物性の研究
鬼澤美智; 鬼澤美智; 芳賀芳範; 田中成典; 鯉渕誠也; 横谷明徳; 横谷明徳
日本放射線影響学会大会抄録(Web), 2017年

X線マイクロビーム照射後のミトコンドリア活性の変化
横谷明徳; 横谷明徳; 神長輝一; 神長輝一; 浜田涼; 浜田涼; 宇佐美徳子; 鈴木啓司
日本放射線影響学会大会抄録(Web), 2017年

シンクロトロン放射を用いたCDスペクトル測定によるDNA修復タンパク質XRCC4の溶液中での構造解析
西久保開; 泉雄大; 藤井健太郎; 松本義久; 横谷明徳
日本放射線影響学会大会抄録(Web), 2017年

非照射細胞への放射線誘発DNA損傷の導入とライブセル観察による修復動態の観察
中上裕貴; 中上裕貴; 小畑結衣; 神長輝一; 神長輝一; 横谷明徳; 横谷明徳
日本放射線影響学会大会抄録(Web), 2017年

Ca²⁺オシレーションを含む細胞内ネットワークシステムの変化をパラメータとした放射線適応応答誘導経路のモデル化に向けた取組み
杉本理峻; 杉本理峻; 小林涼香; 服部佑哉; 渡辺立子; 立花章; 横谷明徳; 横谷明徳
日本放射線影響学会大会抄録(Web), 2017年

放射線による細胞競合を解析するための蛍光タンパク発現ラット乳腺細胞培養技術
西村由希子; 横谷明徳; 横谷明徳; 神長輝一; 神長輝一; 工藤健一; 宇佐美徳子; 柿沼志津子; 今岡達彦; 今岡達彦
日本放射線影響学会大会抄録(Web), 2017年

放射線適応応答に関する細胞内シグナリングの数理モデル化
服部佑哉; 渡辺立子; 倉林大輔; 横谷明徳
日本数理生物学会年会(Web), 2017年

放射光円二色性分光によるDNA損傷誘起ヒストン二次構造変化の観測
泉雄大; 山本悟史; 藤井健太郎; 松尾光一; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2017年

水溶液中ピリミジン塩基の軟X線光電子およびオージェ電子スペクトル
島田紘行; 武田泰明; 三浦亮介; 篠澤柚衣; 柏田拓臣; 村井龍司; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; KNIE A.; OZGA C.; EHRESMANN A.
日本放射光学会年会・放射光科学合同シンポジウム(Web), 2017年

X線マイクロビームを用いたDNA損傷に開始される細胞周期変調のライブセルイメージング
神長輝一; 神長輝一; 宇佐美徳子; 横谷明徳; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2017年

水溶液中ヌクレオチドのオージェ崩壊のpH依存性
島田紘行; 武田泰明; 三浦亮介; 柏田拓臣; 篠澤柚衣; 村井龍司; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; OZGA C.; KNIE A.
日本物理学会講演概要集(CD-ROM), 2016年

電子線トラックエンドの放射線最初期過程の研究
甲斐健師; 横谷明徳; 鵜飼正敏; 藤井健太郎; 渡邊立子; 米谷佳晃; 樋川智洋; 佐藤達彦
放射線化学討論会講演要旨集, 2016年

内殻励起された水溶液中ヌクレオチドからの発光の観測
島田紘行; 柏田拓臣; 篠澤柚衣; 村井龍司; 小田島嘉孝; 槇島熙; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
日本物理学会講演概要集(CD-ROM), 2016年

バイスタンダー効果によるDNA二本鎖切断生成数の数理解析
服部佑哉; 横谷明徳; 渡辺立子
日本放射線影響学会大会抄録(Web), 2016年

X線マイクロビームを使用した細胞質への放射線影響の研究
神長輝一; 神長輝一; 宇佐美徳子; 鈴木啓司; 横谷明徳; 横谷明徳
日本放射線影響学会大会抄録(Web), 2016年

X線マイクロビームを用いた細胞質への放射線生物影響研究
神長輝一; 神長輝一; 宇佐美徳子; 鈴木啓司; 横谷明徳; 横谷明徳
日本分子生物学会年会プログラム・要旨集(Web), 2016年

DNA損傷により誘起されるヒストンタンパク質の二次構造変化
泉雄大; 山本悟史; 藤井健太郎; 松尾光一; 横谷明徳; 横谷明徳
放射線化学討論会講演要旨集, 2016年

DNA損傷応答により生じるヒストンの二次構造変化
泉雄大; 山本悟史; 藤井健太郎; 松尾光一; 横谷明徳
日本放射線影響学会大会抄録(Web), 2016年

放射線生体影響のメカニズム解明に向けた放射光利用研究
横谷明徳; 横谷明徳; 神長輝一; 神長輝一; 渡辺立子; 服部佑哉; 福永久典; 福永久典; 鈴木啓司; 泉雄大; 藤井健太郎
KEK Proceedings (Web), 2016年

固体表面に作製したSAM-DNA二重膜の軟X線照射効果
成田あゆみ; 藤井健太郎; 横谷明徳; 馬場祐治; 下山巖
量子ビームサイエンスフェスタ(Web), 2016年

X線マイクロビームを用いたDNA損傷に開始させる細胞周期変調のライブセルイメージング
神長輝一; 神長輝一; 野口実穂; 宇佐美徳子; 横谷明徳; 横谷明徳
量子ビームサイエンスフェスタ(Web), 2016年

放射光を用いたゲノムDNA損傷の初期過程と生体修復
横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2015年

スフェロイドに対するX線マイクロビームを用いたバイスタンダー効果の研究
坂本由佳; 坂本由佳; 嘉成由紀子; 嘉成由紀子; 神長輝一; 神長輝一; 成田あゆみ; 野口実穂; 宇佐美徳子; 小林克己; 藤井健太郎; 横谷明徳; 横谷明徳
物構研サイエンスフェスタ要旨集, 2015年

自己組織化単分子膜を介した無機表面へのオリゴヌクレオチドの固定化
成田あゆみ; 藤井健太郎; 横谷明徳; 馬場祐治; 下山巌
日本化学会講演予稿集, 2015年

バイスタンダー効果が細胞周期に与える影響の解明
神長輝一; 神長輝一; 成田あゆみ; 野口実穂; 嘉成由紀子; 嘉成由紀子; 坂本由佳; 坂本由佳; 宇佐美徳子; 横谷明徳; 横谷明徳
物構研サイエンスフェスタ要旨集, 2015年

有機自己組織化膜をアンカーとした透明酸化物表面へのオリゴヌクレオチドの固定化
成田あゆみ; 藤井健太郎; 横谷明徳; 馬場祐治; 下山巖
物構研サイエンスフェスタ要旨集, 2015年

放射光X線マイクロビームを利用した細胞部分照射によるミトコンドリア活性への影響
嘉成由紀子; 嘉成由紀子; 神長輝一; 神長輝一; 坂本由佳; 坂本由佳; 成田あゆみ; 野口実穂; 宇佐美徳子; 小林克己; 鈴木啓司; 横谷明徳; 横谷明徳; 藤井健太郎
物構研サイエンスフェスタ要旨集, 2015年

軟X線分光による水溶液中ヌクレオチドの内殻励起・脱励起状態の観測
島田紘行; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
日本物理学会講演概要集(CD-ROM), 2015年

水溶液中ヌクレオチドからのN1sオージェ電子スペクトル
島田紘行; 鵜飼正敏; 武田泰明; 三浦亮介; 篠澤柚衣; 柏田拓臣; 村井龍司; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; KNIE A.; OZGA C.; EHRESMANN A.
日本物理学会講演概要集(CD-ROM), 2015年

X線マイクロビーム照射コロニーのライブセルイメージング
神長輝一; 宇佐美徳子; 野口実穂; 横谷明徳; 横谷明徳
日本生化学会大会(Web), 2015年

X線マイクロビーム照射後の細胞周期のタイムラプスイメージング
神長輝一; 神長輝一; 宇佐美徳子; 野口実穂; 横谷明徳; 横谷明徳
放射線ワークショップ講演論文集, 2015年

水溶液中ピリミジン塩基の軟X線吸収スペクトルに現れるpHおよび水和の影響
島田紘行; 佐久間一郎; 奥泉直人; 武田泰明; 三浦亮介; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; 鵜飼正敏
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2015年

Visualization of cell-cycle modification by ionizing irradiation in single HeLa cells using fluorescent ubiquitination-based cell-cycle indicator
K. Kaminaga; Y. Sakamoto; Y. Kanari; M. Noguchi; A. Yokoya
Journal of Radiation Research, 2014年03月01日
ラスト(シニア)オーサー

Three-dimensional culture of HeLa-FUCCI cells for study of bystander cell-cycle effect of high LET particles
Y. Sakamoto; K. Kaminaga; Y. Kanari; M. Noguchi; A. Yokoya
Journal of Radiation Research, 2014年03月01日
ラスト(シニア)オーサー

Live-cell imaging study of mitochondrial morphology in mammalian cells irradiated
Y. Kanari; M. Noguchi; K. Kaminaga; Y. Sakamoto; A. Yokoya
Journal of Radiation Research, 2014年03月01日
ラスト(シニア)オーサー

Order effect of repair processes to clustered DNA damage
I. Shiraishi; M. Suzuki; N. Shikazono; K. Fujii; A. Yokoya
Journal of Radiation Research, 2014年03月01日
ラスト(シニア)オーサー

Dependence of the yields of AP sites and AP clusters produced in plasmid DNA on scavenging capacity and LET
T. Shiina; R. Watanabe; M. Suzuki; A. Yokoya
Journal of Radiation Research, 2014年03月01日
ラスト(シニア)オーサー

X線マイクロビームを用いた細胞周期影響観察
成田あゆみ; 神長輝一; 神長輝一; 横谷明徳; 野口実穂; 小林克己; 宇佐美徳子; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2014年

水和デオキシリボース分子の軟X線による分解過程
藤井健太郎; 泉雄大; 成田あゆみ; 横谷明徳; HERVE DU PENHOAT M. A.; TOUATI A.; VUILLEUMIOER R.; GAIGEOT M. P.; POLITIS M. F.
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2014年

水溶液中のプリンヌクレオチドの軟X線吸収スペクトルおよびそのpH依存性
島田紘行; 深尾太志; 南寛威; 佐久間一郎; 奥泉直人; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; 鵜飼正敏
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2014年

ピリミジン塩基のK殻イオン化閾値領域における不対電子生成
岡壽崇; 岡壽崇; 横谷明徳; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2014年

酸化物表面に作製した有機自己組織化膜へのオリゴヌクレオチド固定化
成田あゆみ; 藤井健太郎; 横谷明徳; 馬場祐治; 下山巖
物構研サイエンスフェスタ要旨集, 2014年

タイムラプスイメージング法で観察したFucci発現細胞へのX線マイクロビーム照射の影響
神長輝一; 神長輝一; 成田あゆみ; 野口実穂; 嘉成由紀子; 坂本由佳; 横谷明徳; 嘉成由紀子; 坂本由佳; 横谷明徳
物構研サイエンスフェスタ要旨集, 2014年

X線照射によるミトコンドリアの動態変化と膜電位の関係
嘉成由紀子; 嘉成由紀子; 野口実穂; 神長輝一; 坂本由佳; 横谷明徳; 神長輝一; 坂本由佳; 横谷明徳; 鈴木啓司
物構研サイエンスフェスタ要旨集, 2014年

スフェロイドに対するX線マイクロビーム照射及び細胞応答の観察
坂本由佳; 嘉成由紀子; 神長輝一; 坂本由佳; 嘉成由紀子; 神長輝一; 野口実穂; 横谷明徳; 横谷明徳
物構研サイエンスフェスタ要旨集, 2014年

X線マイクロビームを用いた細胞周期に依存した照射影響のリアルタイム観察
成田あゆみ; 神長輝一; 神長輝一; 横谷明徳; 野口実穂; 小林克己; 宇佐美徳子; 藤井健太郎
物構研サイエンスフェスタ要旨集, 2014年

軟X線照射ピリミジン塩基の不対電子収量の置換基依存性
岡壽崇; 岡壽崇; 横谷明徳; 藤井健太郎; 木野康志; 関根勉
日本放射化学会年会・放射化学討論会研究発表要旨集, 2014年

マイクロビームを用いた細胞核照射と細胞質照射によるミトコンドリアへの影響
嘉成由紀子; 嘉成由紀子; 神長輝一; 神長輝一; 成田あゆみ; 宇佐美徳子; 鈴木啓司; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2014年

スフェロイドに対するX線マイクロビームを用いたバイスタンダー効果の研究
坂本由佳; 横谷明徳; 坂本由佳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2014年

DNA二本鎖切断の修復と細胞周期制御の放射線応答モデルの構築
服部佑哉; 横谷明徳; 渡辺立子
日本放射線影響学会大会講演要旨集, 2014年

軟X線照射ピリミジン塩基の不対電子収量の置換基による影響
岡壽崇; 岡壽崇; 横谷明徳; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2014年

Cs-137γ線およびβ線による微視的線量分布とDNA損傷のシミュレーション
渡辺立子; 甲斐健師; 横谷明徳
日本放射線影響学会大会講演要旨集, 2014年

X線マイクロビーム照射・非照射細胞の細胞分裂のライブセルイメージング
神長輝一; 成田あゆみ; 嘉成由紀子; 坂本由佳; 嘉成由紀子; 坂本由佳; 宇佐美徳子; 小林克己; 野口実穂; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2014年

数理モデルを用いた放射線照射後の細胞生存率に対する細胞間シグナル伝達の影響解析
服部佑哉; 横谷明徳; 渡辺立子
日本放射線影響学会大会講演要旨集, 2014年

放射線によるゲノム大規模欠失部位の経世代エピジェネティック痕跡の探索
横谷明徳; 鈴木啓司
日本放射線影響学会大会講演要旨集, 2014年

内殻イオン化による水和デオキシリボースの分解初期物理過程
藤井健太郎; 泉雄大; 成田あゆみ; 横谷明徳; ペンホート マリーアンハーベ; グース クリスナ; ブレモア ロドルフ; ガイゴー マリーピエール; ポリティス マリーフランソア
日本放射線影響学会大会講演要旨集, 2014年

細胞周期選択的に照射した動物培養細胞のリアルタイム観察
成田あゆみ; 神長輝一; 神長輝一; 横谷明徳; 野口実穂; 小林克己; 宇佐美徳子; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2014年

X線マイクロビーム照射細胞のライブイメージング追跡
横谷明徳; 横谷明徳; 成田あゆみ; 神長輝一; 神長輝一; 嘉成由紀子; 嘉成由紀子; 坂本由佳; 坂本由佳; 野口実穂; 藤井健太郎; 宇佐美徳子; 小林克己; 鈴木啓司
日本放射線影響学会大会講演要旨集, 2014年

ナノカーボン薄膜を用いた放射線損傷に伴うATP分子変異の電気化学分析
加藤大; 藤井健太郎; 藤井紳一郎; 月本光俊; 秋光信佳; 成田あゆみ; 小島周二; 横谷明徳; 丹羽修
Chemical Sensors, 2014年

放射場生体分子科学研究グループの主な成果
横谷明徳
基礎科学ノート, 2014年

リン酸化ヒストンの放射光円二色性スペクトル
泉雄大; 松尾光一; 藤井健太郎; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2014年

X線照射細胞中におけるリン酸化ヒストンの2次構造変化
山本悟史; 山本悟史; 泉雄大; 藤井健太郎; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2014年

DNA損傷応答により生じるヒストンH2A/H2Bの二次構造変化
泉雄大; 山本悟史; 藤井健太郎; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2014年

Circular Dichroism Study on Structural Change of Proteins Triggering DNA Repair
IZUMI Yudai; YAMAMOTO Satoshi; YAMAMOTO Satoshi; FUJII Kentaro; YOKOYA Akinari
放射線化学討論会講演要旨集, 2014年

Substituent Effect for Pyrimidine DNA-base Induced by Soft X-ray Irradiation
OKA Toshitaka; YOKOYA Akinari; FUJII Kentaro; KINO Yasushi; SEKINE Tsutomu
放射線化学討論会講演要旨集, 2014年

VUV-CD Measurements of Modified Histone Proteins
IZUMI Yudai; MATSUO Koichi; FUJII Kentaro; YOKOYA Akinari
Proc Hiroshima Int Symp Synchrotron Radiat, 2014年

Unpaired electrons of pyrimidine-base induced by high intense soft X-ray irradiation studied by ESR
OKA Toshitaka; YOKOYA Akinari; FUJII Kentaro; KINO Yasushi; SEKINE Tsutomu
原子衝突学会年会講演概要集, 2014年

Initial Process of DNA Base Damage Induction Explored by Soft X-ray Spectroscopies
SHIMADA Hiroyuki; TAKEDA Yasuaki; MIURA Ryosuke; KASHIWADA Takumi; SHINOZAWA Yui; MURAI Ryuji; FUJII Kentaro; YOKOYA Akinari; FUKUDA Yoshihiro; SAITOH Yuji; UKAI Masatoshi
原子衝突学会年会講演概要集, 2014年

Destruction of Deoxyribose Induced by Core-ionization-Experimental and Theoretical Approach to Reveal Physical Processes of DNA Strand Breakage-
FUJII Kentaro; IZUMI Yudai; NARITA Ayumi; YOKOYA Akinari; HERVE DU; PENHOAT Marie‐Anne; GHOSE K; VUILLEUMIER Rodolphe; GAIGEOT Marie‐Pierre; POLITIS Marie‐Francoise
放射線化学討論会講演要旨集, 2014年

DNA薄膜のNEXAFSスペクトル
藤井健太郎; 小林英一; 横谷明徳; 岡島敏浩
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2013年

酸素K殼XANES領域の軟X線照射によるDNA損傷の収率変化
菅谷雄基; 菅谷雄基; 成田あゆみ; 椎名卓也; 椎名卓也; 白石伊世; 白石伊世; 藤井健太郎; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2013年

X線マイクロビームによる細胞周期を選択した照射効果研究
成田あゆみ; 野口実穂; 横谷明徳; 小林克己; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2013年

タイムラプスイメージング法で観察したFucci発現細胞へのX線照射の影響
神長輝一; 神長輝一; 成田あゆみ; 野口美穂; 嘉成由紀子; 嘉成由紀子; 坂本由佳; 坂本由佳; 横谷明徳; 横谷明徳
日本原子力学会秋の大会予稿集(CD-ROM), 2013年

細胞間コミュニケーションに着目した細胞集団の放射線応答モデルの構築
服部佑哉; 鈴木芳代; 舟山知夫; 小林泰彦; 横谷明徳; 渡辺立子
日本放射線影響学会大会講演要旨集, 2013年

HeLa細胞で作製したスフェロイドのX線に対する感受性
坂本由佳; 野口実穂; 藤井健太郎; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2013年

Fucci発現細胞を用いたX線照射による細胞周期変化
神長輝一; 神長輝一; 成田あゆみ; 野口実穂; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2013年

X線照射によるミトコンドリアの動態変化と膜電位の関係
嘉成由紀子; 嘉成由紀子; 野口実穂; 藤井健太郎; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2013年

DNA及びDNA関連分子のK殻イオン化閾値領域における不対電子生成
岡壽崇; 岡壽崇; 横谷明徳; 藤井健太郎; 鵜飼正敏
放射線化学討論会講演要旨集, 2013年

軟X線による水和デオキシリボースの分解過程
藤井健太郎; 泉雄大; 成田あゆみ; 横谷明徳
放射線化学討論会講演要旨集, 2013年

水中におけるフェムト秒オーダーでの電離電子のダイナミクス
甲斐健師; 横谷明徳; 鵜飼正敏; 藤井健太郎; 樋口真理子; 渡邊立子
放射線化学討論会講演要旨集, 2013年

窒素K吸収端近傍X線吸収スペクトルのpH依存性にみる水溶液ヌクレオチドの構造変化
島田紘行; 深尾太志; 南寛威; 佐久間一郎; 奥泉直人; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; 鵜飼正敏
放射線化学討論会講演要旨集, 2013年

X線マイクロビームを利用した細胞周期に対する照射影響
成田あゆみ; 野口実穂; 横谷明徳; 小林克己; 藤井健太郎
物構研サイエンスフェスタ要旨集, 2013年

X線吸収スペクトルに見る水溶液中のプリンヌクレオチドの構造変化
奥泉直人; 島田紘行; 深尾大志; 南寛威; 佐久間一郎; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児
原子衝突学会年会講演概要集, 2013年

ピリミジンヌクレオチドの窒素K殻吸収端近傍におけるX線吸収スペクトル
佐久間一郎; 島田紘行; 南寛威; 奥泉直人; 鵜飼正敏; 横谷明徳; 藤井健太郎; 福田義博; 斉藤裕児
原子衝突学会年会講演概要集, 2013年

軟X線を用いた水溶液中のヌクレオチドの幾何・電子構造の研究
島田紘行; 深尾太志; 南寛威; 佐久間一郎; 奥泉直人; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; 鵜飼正敏
原子衝突学会年会講演概要集, 2013年

細胞周期の違いによる放射線感受性とミトコンドリア形態および機能との関連性
野口実穂; 嘉成由紀子; 嘉成由紀子; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2013年

単色軟X線を用いたリンK殻吸収によるDNA2重鎖切断生成・修復効率と細胞致死効果の解析
冨田雅典; 前田宗利; 前田宗利; 宇佐美徳子; 横谷明徳; 渡辺立子; 小林克己
日本分子生物学会年会プログラム・要旨集(Web), 2013年

低線量放射線の健康影響 初期過程から細胞応答まで 放射線トラック構造に依存したクラスターDNA損傷の誘発(Dependence of induction of clustered DNA damage on radiation track structure)
横谷 明徳; O'Neill Peter
日本放射線影響学会大会講演要旨集, 2012年09月

酸素・窒素のK殻イオン化でDNA薄膜中に生じた不対電子とDNA変異の関係
岡壽崇; 横谷明徳; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2012年

DNA分子のK殻イオン化閾値領域における光電子再捕獲確率の半古典諭的解析
横谷明徳; 鵜飼正敏; 岡壽崇; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2012年

DNA薄膜のNEXAFSスペクトル
藤井健太郎; 小林英一; 菅谷雄基; 岡壽崇; 福田義博; 横谷明徳; 横谷明徳; 岡島敏浩
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2012年

UV-A照射染色体の移入による遺伝的不安定性の誘発
漆原あゆみ; 児玉靖司; 横谷明徳
日本放射線影響学会大会講演要旨集, 2012年

タイムラプス法で観測したFucci発現細胞の細胞周期へのX線照射の影響
横谷明徳; 横谷明徳; 野口実穂; 神長輝一; 神長輝一; 坂本由佳; 坂本由佳; 嘉成由紀子; 嘉成由紀子; 成田あゆみ; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2012年

X線照射が細胞周期に与える影響の放射光マイクロビームを用いた研究
成田あゆみ; 野口実穂; 横谷明徳; 小林克己; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2012年

DNA分子上の放射線損傷分布とDNA損傷修復経路干渉の相関
白石伊世; 白石伊世; 椎名卓也; 椎名卓也; 菅谷雄基; 菅谷雄基; 鹿園直哉; 鹿園直哉; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2012年

酸素K殼イオン化エネルギー領域の軟X線照射によるDNA損傷の収率変化
菅谷雄基; 椎名卓也; 白石伊世; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2012年

放射線照射による細胞周期変化とミトコンドリア形態変化の関係
野口実穂; 嘉成由紀子; 神長輝一; 坂本由佳; 成田あゆみ; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2012年

APサイト及びこれを含むクラスターDNA損傷収率の放射線の線質およびLET依存性
椎名卓也; 椎名卓也; 白石伊世; 白石伊世; 菅谷雄基; 菅谷雄基; 渡邊立子; 鈴木雅雄; 横谷明徳; 横谷明徳
日本放射線影響学会大会講演要旨集, 2012年

水溶液アデニンヌクレオチドの軟X線吸収スペクトルのpH依存性と構造変化
島田紘行; 深尾太志; 南寛威; 佐久間一郎; 奥泉直人; 横谷明徳; 藤井健太郎; 福田義博; 斎藤祐児; 鵜飼正敏
放射線化学討論会講演要旨集, 2012年

水中における自由電子の衝突イベント及び軌道の時間発展計算
甲斐健師; 横谷明徳; 鵜飼正敏; 藤井健太郎; 樋口真理子; 渡邊立子
放射線化学討論会講演要旨集, 2012年

軟X線により変異したATPの生物効果
藤井健太郎; 藤井紳一郎; 加藤大; 秋光信佳; 月本光俊; 横谷明徳; 丹羽修; 小島周二
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2012年

酸素・窒素のK殻イオン化でDNA関連分子薄膜中に生じた不対電子種のESRによる測定
岡壽崇; 横谷明徳; 福田義博; 藤井健太郎
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2011年

軟X線照射したDNA薄膜のXANESスペクトル変化
藤井健太郎; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2011年

酸素K殻共鳴励起によりプラスミドDNA中に生成する鎖切断,塩基変異及びAPサイト
菅谷雄基; 菅谷雄基; 白石伊世; 白石伊世; 椎名卓也; 椎名卓也; 藤井健太郎; 横谷明徳; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2011年

抗酸化物質エダラボンによるDNA損傷前駆体の化学回復
端邦樹; 端邦樹; 端邦樹; 漆原あゆみ; 山下真一; 山下真一; 鹿園直哉; 横谷明徳; 室屋裕佐; 勝村庸介
日本放射線影響学会大会講演要旨集, 2011年

モンテカルロ飛跡計算に基づくBNCTにおけるDNA損傷評価
冠城雅晃; 冠城雅晃; 渡邊立子; 佐藤達彦; 横谷明徳; PINAK Miroslav; 勝村庸介; 上坂充
日本放射線影響学会大会講演要旨集, 2011年

放射線の飛跡に沿ったDNA損傷生成位置の解析
渡邊立子; 椎名卓也; 椎名卓也; 横谷明徳
日本放射線影響学会大会講演要旨集, 2011年

クラスターDNA損傷の修復におけるPollの役割
鹿園直哉; 野口実穂; 漆原あゆみ; 横谷明徳
日本放射線影響学会大会講演要旨集, 2011年

APサイト及びこれを含むクラスターDNA損傷収率の放射線線質およびLET依存性
椎名卓也; 椎名卓也; 菅谷雄基; 菅谷雄基; 白石伊世; 白石伊世; 渡邊立子; 渡邊立子; 横谷明徳; 鶴岡千鶴; 鈴木雅雄
日本放射線影響学会大会講演要旨集, 2011年

クラスターDNA損傷に対する塩基除去修復酵素の作用順序の効果 II
白石伊世; 白石伊世; 椎名卓也; 椎名卓也; 菅谷雄基; 菅谷雄基; 鹿園直哉; 鹿園直哉; 横谷明徳
日本放射線影響学会大会講演要旨集, 2011年

酸素K殻イオン化エネルギー領域の軟X線照射によるDNA損傷の収率変化
菅谷雄基; 菅谷雄基; 椎名卓也; 椎名卓也; 白石伊世; 白石伊世; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2011年

窒素及び酸素のK殻吸収によってDNA及びDNA核酸塩基中に生じる不対電子種
岡壽崇; 横谷明徳; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2011年

染色体不安定性誘発における紫外線の影響
漆原あゆみ; 児玉靖司; 横谷明徳
日本放射線影響学会大会講演要旨集, 2011年

DNA構成原子の内殻イオン化閾値領域における光電子再捕獲確率の半古典論的解析
横谷明徳; 鵜飼正敏; 岡壽崇; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2011年

窒素・酸素のK殻イオン化によるDNA変異と不対電子の関係
岡壽崇; 横谷明徳; 藤井健太郎
放射線化学討論会講演要旨集, 2011年

軟X線照射したDNA薄膜の軟X線吸収スペクトル変化
藤井健太郎; 横谷明徳
放射線化学討論会講演要旨集, 2011年

生体分子損傷の“その場修復”の研究のための高圧雰囲気下における放射光電子分光・二次イオン質量分析法の開発
鵜飼正敏; 住谷亮輔; 安廣哲; 横谷明徳; 藤井健太郎; 斎藤祐児
日本原子力研究開発機構JAEA-Review(Web), 2011年

分子動力学法を用いた軟X線照射によるDNA損傷解析
甲斐健師; 樋口真理子; 藤井健太郎; 渡邊立子; 横谷明徳
日本物理学会講演概要集, 2011年08月24日

Research Group for Radiation and Biomolecular Sciences
YOKOYA Akinari; FUJII Kentaro; NOGUCHI Miho; URUSHIBARA Ayumi; OKA Toshitaka; SUGAYA Yuki; SHIRAISHI Iyo; SHIINA Takuya
Ann Rep ASRC, 2011年
筆頭著者

ガンマ線照射により生成した水分解ラジカルのCYPMPOによる捕捉
岡壽崇; 山下真一; 佐伯誠一; 横谷明徳; 勝村庸介; 上林將人
放射線化学討論会講演要旨集, 2010年

プラスミドDNAの変性-アニーリングを利用した多重塩基損傷検出のための新しい方法の開発
横谷明徳; 鹿園直哉; 鹿園直哉; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2010年

スピントラップ剤CYPMPOによるガンマ線照射水分解生成物捕捉とその安定性
岡壽崇; 山下真一; 佐伯誠一; 横谷明徳; 勝村庸介; 上林將人
日本放射線影響学会大会講演要旨集, 2010年

DNA損傷の空間分布と難修復性を考慮した生存率曲線の解析
渡邊立子; 横谷明徳; 鈴木雅雄; 鶴岡千鶴; 平山亮一; 古澤佳也
日本放射線影響学会大会講演要旨集, 2010年

AP site及びこれを含むクラスターDNA損傷収率の放射線の線質及びスキャベンジャー能に対する依存性
椎名卓也; 菅谷雄基; 白石伊世; 椎名卓也; 菅谷雄基; 白石伊世; 渡辺立子; 横谷明徳; 横谷明徳; 横谷明徳; 鶴岡千鶴; 鈴木雅雄
日本放射線影響学会大会講演要旨集, 2010年

軟X線及び電子線照射によりプラスミドDNA中に生成する塩基損傷及びAPサイト
菅谷雄基; 白石伊世; 椎名卓也; 横谷明徳; 菅谷雄基; 白石伊世; 椎名卓也; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2010年

非2重鎖切断型損傷による遺伝的不安定性の誘発
漆原あゆみ; 児玉靖司; 横谷明徳
日本放射線影響学会大会講演要旨集, 2010年

希簿プラスミドDNA水溶液へのガンマ線照射:放射線誘起損傷の抗酸化剤エダラボンによる化学回復
端邦樹; 漆原あゆみ; 山下真一; 鹿園直哉; 横谷明徳; 勝村庸介
日本放射線影響学会大会講演要旨集, 2010年

8-oxoGを含むクラスターDNA損傷の誘発突然変異
野口実穂; 漆原あゆみ; 横谷明徳; 鹿園直哉; 鹿園直哉
日本放射線影響学会大会講演要旨集, 2010年

クラスターDNA損傷に対する塩基除去修復酵素の作用順序の効果
白石伊世; 椎名卓也; 菅谷雄基; 鹿園直哉; 横谷明徳; 白石伊世; 椎名卓也; 菅谷雄基; 鹿園直哉; 横谷明徳
日本放射線影響学会大会講演要旨集, 2010年

DNA変性を利用した分子切断損傷を検出するための新しい方法の開発
横谷明徳
基礎科学ノート, 2010年02月

CYPMPOによるガンマ線照射水分解ラジカル捕捉と安定性評価
岡壽崇; 山下真一; 横谷明徳; 勝村庸介; 上林將人
電子スピンサイエンス学会年会講演要旨集, 2010年

酸素及び窒素のK殻イオン化でDNA関連分子薄膜中に生じた不対電子種の測定
岡壽崇; 横谷明徳; 福田義博; 藤井健太郎
電子スピンサイエンス学会年会講演要旨集, 2010年

シリビンの抗酸化作用とラジカル捕捉作用に関する研究
端邦樹; FU Haiying; LIN Mingzhang; 室屋裕佐; 勝村庸介; 勝村庸介; 横谷明徳; 籏野嘉彦
アイソトープ・放射線研究発表会要旨集, 2009年

水液体分子線に対するOK-殻吸収端近傍での光電子分光
鵜飼正敏; 横谷明徳; 野中裕介; 藤井健太郎; 斎藤祐児
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2009年

生体溶液試料に対する二次イオン質量分析法の開発
住谷亮輔; 安廣哲; 野中裕介; 鵜飼正敏; 横谷明徳; 藤井健太郎
原子衝突研究協会年会講演概要集, 2009年

生体分子損傷の“その場修復”の研究のための高圧雰囲気下における放射光電子分光・二次イオン質量分析法の開発
鵜飼正敏; 野中裕介; 住谷亮輔; 横谷明徳; 藤井健太郎; 斎藤祐児
日本原子力研究開発機構JAEA-Review, 2009年

DNA二本鎖切断はLET増加に伴い増加するのか?減少するのか?:(1)増加するという立場からの考察
横谷明徳
日本放射線影響学会大会講演要旨集, 2009年

イオンビーム照射により高水和DNAフィルム中に誘発されるDNA鎖切断及び塩基損傷収率のLET依存性
横谷明徳; 牛込剛史; 牛込剛史; 田内広; 鈴木雅雄; 鶴岡千鶴; 野口実穂; 藤井健太郎; 鹿園直哉; 渡邊立子
日本放射線影響学会大会講演要旨集, 2009年

大腸菌におけるクラスターDNA損傷誘発突然変異
鹿園直哉; 野口実穂; 漆原あゆみ; O’NEILL Peter; 横谷明徳
日本放射線影響学会大会講演要旨集, 2009年

同一鎖上に配置されたクラスターDNA損傷のプロセシングについて
野口実穂; 漆原あゆみ; 横谷明徳; 鹿園直哉
日本放射線影響学会大会講演要旨集, 2009年

微視的線量分布からみたDNA二本鎖切断のLET依存性
渡邊立子; 平山亮一; 横谷明徳; 寺東宏明; 鶴岡千鶴; 江口清美; 古澤佳也; 小林克也
日本放射線影響学会大会講演要旨集, 2009年

単色軟X線によるDNA鎖切断および塩基損傷の選択的誘発
藤井健太郎; 鹿園直哉; 横谷明徳
日本放射線影響学会大会講演要旨集, 2009年

酸素及び窒素のK殻イオン化によりDNA関連分子薄膜中に生じた不対電子種のEPR観測
横谷明徳; 藤井健太郎; 福田義博; 鵜飼正敏
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2009年

単色軟X線により乾燥DNA中に生じる分子変化の照射エネルギー依存性
藤井健太郎; 鹿園直哉; 横谷明徳
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 2009年

酸素K殻吸収端付近における水の光電子分光
鵜飼正敏; 横谷明徳; 野中裕介; 藤井健太郎; 斎藤祐児
原子衝突研究協会研究会講演概要集, 2008年

8-oxoGを含むクラスターDNA損傷誘発突然変異における一本鎖切断の影響
野口実穂; 漆原あゆみ; 横谷明徳; 鹿園直哉
日本放射線影響学会大会講演要旨集, 2008年

X線誘発損傷に対するシリビンとその類似体のin vitroでのDNA防護効果
FU Haiying; LIN Mingzhang; 端邦樹; 室屋裕佐; 藤井健太郎; 勝村庸介; 勝村庸介; 横谷明徳; 鹿園直哉; 籏野嘉彦
日本放射線影響学会大会講演要旨集, 2008年

鎖切断と脱塩基部位からなるクラスターDNA損傷の生物効果
鹿園直哉; 野口実穂; 漆原あゆみ; O’NEILL Peter; 横谷明徳
日本放射線影響学会大会講演要旨集, 2008年

プラスミドDNAに対する高LET放射線による非DSB性多重SSB誘発の可能性
横谷明徳; 鹿園直哉; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2008年

イオンビームにより誘発される難修復性のクラスターDNA損傷
横谷明徳
法政大学イオンビーム工学研究所シンポジウム講演予稿集, 2008年

液体分子線光電子分光法による酸素K殼吸収端近傍における水の光電子スペクトル
野中裕介; 横谷明徳; 藤井健太郎; 斎藤祐児; 鵜飼正敏
放射線化学討論会講演要旨集, 2008年

軟X線照射によって乾燥プラスミドDNAに生じる分子損傷の収率
藤井健太郎; 横谷明徳; 鹿園直哉
放射線化学討論会講演要旨集, 2008年

軟X線によってDNA分子内に生じるサイト選択的分子変化
藤井健太郎; 横谷明徳; 鹿園直哉
分子科学討論会講演プログラム&要旨(Web), 2008年

21pTC-4 液体分子線を用いた、水溶液状態にあるヌクレオチドの軟X線放射光分光研究(化学物理一般(光応答・電子状態・シミュレーション),領域12,ソフトマター物理,化学物理,生物物理)
鵜飼 正敏; 横谷 明徳; 藤井 健太郎; 斎藤 祐児
日本物理学会講演概要集, 2007年02月28日

放射光単色軟X線によりDNA中に生じる主鎖切断収量および修復酵素をプローブとして用いた塩基損傷の定量
藤井健太郎; 横谷明徳; 鹿園直哉
放射線化学討論会講演要旨集, 2007年

非二本鎖切断型クラスター損傷(8-oxoGと鎖切断)の突然変異誘発
野口実穂; 漆原あゆみ; 横谷明徳; 鹿園直哉
日本放射線影響学会大会講演要旨集, 2007年

SPring-8原子力機構軟X線ビームラインBL23SUにおける再集光ミラーの導入
福田義博; 福田義博; 斎藤祐児; 横谷明徳; 寺岡有殿
日本原子力研究開発機構JAEA-Technology, 2007年

放射線によりプラスミドDNAの両鎖に生じた非DSB性多重SSBのDNA変性を利用した新しい定量法
横谷明徳; 漆原あゆみ; 藤井健太郎; 鹿園直哉
日本放射線影響学会大会講演要旨集, 2007年

水溶液ヌクレオチドの窒素K殻吸収端近傍吸収スペクトル
鵜飼正敏; 横谷明徳; 横谷明徳; 藤井健太郎; 藤井健太郎; 斎藤祐児
分子科学討論会講演要旨集(CD-ROM), 2007年

アミノ酸の軟X線自然二色性スペクトル(SXNCD):初測定とその後の発展
中川和道; 田中真人; 泉雄大; 安居院あかね; 横谷明徳; 藤井健太郎; 室隆桂之; 松下智裕
分子科学討論会講演要旨集(CD-ROM), 2007年

光子及びイオン粒子照射により生じるDNA鎖切断及び塩基損傷の収率のLET依存性
横谷明徳; 牛込剛史; 牛込剛史; 鹿園直哉; 藤井健太郎; 漆原あゆみ; 鈴木雅雄; 田内広; 渡邊立子
日本放射線影響学会大会講演要旨集, 2006年

軟X線(270-560eV)照射により乾燥DNA中に生じる鎖切断,塩基損傷およびクラスター損傷の照射エネルギー依存性
藤井健太郎; 横谷明徳; 鹿園直哉
日本放射線影響学会大会講演要旨集, 2006年

軟X線照射により乾燥DNA中に生じる主鎖切断および塩基損傷の光子エネルギー依存性
藤井健太郎; 横谷明徳; 鹿園直哉
放射線化学討論会講演要旨集, 2006年

大腸菌における8-オキソグアニンとチミングリコールから成るクラスターDNA損傷の突然変異誘発効果
漆原あゆみ; 鹿園直哉; 横谷明徳
日本放射線影響学会大会講演要旨集, 2006年

放射光・液体分子線分光法による水溶液ヌクレオチドの内殻吸収スペクトル
鵜飼正敏; 横谷明徳; 藤井健太郎; 斎藤祐児
化学反応討論会講演要旨集, 2006年

生体溶液試料に対する軟X線放射線効果の分光研究
鵜飼正敏; 横谷明徳; 横谷明徳; 藤井健太郎; 藤井健太郎; 斎藤祐児
原子衝突研究協会研究会講演概要集, 2006年

窒素K吸収端近傍における水溶液ヌクレオチドのX線吸収スペクトル
鵜飼正敏; 横谷明徳; 横谷明徳; 藤井健太郎; 斎藤祐児
放射線化学討論会講演要旨集, 2006年

8 77Kでの真空紫外線照射によるグリシン2量体からオリゴペプチドへの化学進化(一般講演,第31回学術講演会講演要旨集)
松井 貴弘; 中川 和道; 泉 雄大; 蒲原 真澄; 横谷 明徳
Viva origino, 2006年

A model for analysis of the yield and the level of clustering of radiation-induced DNA strand breaks in hydrated plasmids
Shikazono, N; Yokoya, A; Urushibara, A; Noguchi, M; Fujii. K
Radiat. Prot. Dosimetry, 2006年

Synchrotron-radiation photoelectron study for bio-solution using liquid water jet
UKAI Masatoshi; YOKOYA Akinari; FUJII Kentaro; SAITOH Yuji
日本原子力研究開発機構JAEA-Review, 2006年01月

Unstable radical in evaporated DNA-bases onto surface irradiated with soft X-rays around nitrogen and oxygen K-edge region
YOKOYA Akinari; FUJII Kentaro
日本原子力研究開発機構JAEA-Review, 2006年01月

液体の水に対する放射光電子分光
鵜飼正敏; 横谷明徳; 横谷明徳; 藤井健太郎; 斎藤祐児
原子衝突研究協会研究会講演概要集, 2005年

シンクロトロン放射光電子分光法による溶液分子の研究
鵜飼正敏; 横谷明徳; 横谷明徳; 藤井健太郎; 斎藤祐児
放射線化学討論会講演要旨集, 2005年

イオン照射によって生成するクラスターDNA損傷
漆原あゆみ; 牛込剛史; 牛込剛史; 鹿園直哉; 藤井健太郎; 田内広; 横谷明徳
日本放射線影響学会大会講演要旨集, 2005年

低温環境下での真空紫外線照射および軟X線照射によるグリシン2量体の化学進化
松井貴弘; 中川和道; 泉雄大; 蒲原真澄; 横谷明徳
放射線化学討論会講演要旨集, 2005年

軟X線領域の分光学的手法を用いた放射線DNA分子損傷の分析
藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2005年

シンクロトロン放射光励起・液体分子線分光法による水の光電子分光
鵜飼正敏; 横谷明徳; 藤井健太郎; 斎藤祐児
化学反応討論会講演要旨集, 2005年

Circular dichroism and Asymmetric reaction of amino acid films in vacuum ultraviolet and soft X-ray region(Chemical Evolution, International Symposium on Origins of Life and Astrobiology) :
Kodama Yoko; Ohta Yoshimi; Tanaka Masahito; Kaneko Fusae; Kitada Tomo; Nakagawa Kazumichi; Yagi (Watanabe) Kazutoshi; Yamada Toru; Onuki Hideo; Agui Akane; Fujii Kentaro; Yokoya Akinari
Viva origino, 2005年

Chemical evolution of amino acid induced by soft X-ray with Synchrotron Radiation(Chemical Evolution, International Symposium on Origins of Life and Astrobiology) :
Kaneko F.; Tanaka M.; Matsui T.; Nakagawa K.; Agui A.; Fujii K.; Yokoya A.
Viva origino, 2005年

CHEMICAL EVOLUTION TO OLIGOPEPUTIDE IN SOLID PHASE IRRADIATED WITH VACUUM ULTRAVIOLET LIGHT AND SOFT X-RAY(Chemical Evolution, International Symposium on Origins of Life and Astrobiology) :
Matsui T.; Nakagawa K.; Kaneko F.; Tanaka M.; Kitada T.; Izumi Y.; Kamohara M.; Yokoya A.
Viva origino, 2005年

First observation of natural circular dichroism for biomolecules in soft x-ray region studied with a polarizing undulator
Masahito Tanaka; Kazumichi Nakagawa; Akane Agui; Kentaro Fujii; Akinari Yokoya
Physica Scripta T, 2005年

放射線によるクラスターDNA損傷の生成機構
横谷明徳; 鹿園直哉; 漆原あゆみ; 藤井健太郎; 赤松憲; 渡辺立子
放射線生物研究, 2005年

26pXP-13 アミノ酸(アラニン)蒸着膜の軟X線自然円二色性スペクトル測定(領域5, 領域3, 領域8合同招待講演,領域5(光物性))
北田 朋; 中川 和道; 田中 真人; 安居院 あかね; 藤井 健太郎; 横谷 明徳
日本物理学会講演概要集, 2005年

13pTE-14 シンクロトロン放射光励起・液体分子線分光法による水の軟 X 線吸収スペクトル(原子・分子, 領域 1)
鵜飼 正敏; 高畠 博嗣; 大塚 弘樹; 三矢 太亮; 藤井 健太郎; 横谷 明徳
日本物理学会講演概要集, 2004年08月25日

軟X線から真空紫外線域でのアミノ酸固相のCDスペクトル初測定
中川 和道; 田中 真人; 金子 房恵; 北田 朋; 安居院 あかね; 藤井 健太郎; 横谷 明徳; 山田 亨; 渡辺 一寿
Viva origino, 2004年02月28日

軟X線分光学的なアプローチによる放射線DNA損傷の研究
藤井健太郎; 赤松憲; 横谷明徳
分子構造総合討論会講演要旨集(CD-ROM), 2004年

シンクロトロン放射光励起・液体分子線分光法による溶液分子の研究
鵜飼正敏; 高畠博嗣; 大塚弘樹; 藤井健太郎; 横谷明徳
化学反応討論会講演要旨集, 2004年

軟X線照射により水和プラスミドDNA中に生じる鎖切断,塩基損傷及びクラスター損傷
横谷明徳; CUNNIFFE S M T; 渡辺立子; 小林克己; O’NEILL P
日本放射線影響学会大会講演要旨集, 2004年

放射線物理・化学による放射線生物学のブレークスルー 放射線エネルギーの直接付与によって生じるDNA損傷の実体とは?-酸化的DNA損傷との相違点と類似点-
赤松憲; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2004年

放射光励起・液体分子線分光法による水の酸素K殻近傍の吸収スペクトル
鵜飼正敏; 三矢太亮; 大塚弘樹; 高畠博嗣; 藤井健太郎; 横谷明徳
原子衝突研究協会研究会講演概要集, 2004年

DNAのSR軟X線光化学過程-突然変異の根源を探る-
横谷明徳; 藤井健太郎; 赤松憲; 鵜飼正敏
電気学会全国大会講演論文集, 2004年

放射線による突然変異の根源を探る-修復され難いクラスターDNA損傷の解明-
横谷明徳
基礎科学ノート, 2004年09月

X線顕微鏡によるホヤ血液細胞内のバナジウムマイクロ分布観察とXANES解析 内殻励起によるDNA塩基ラジカル生成機構
横谷明徳
放射光, 2004年05月31日

29pXF-1 生体分子の軟X線領域自然円二色性(領域5,領域12,新領域合同招待講演)(領域5)
田中 真人; 中川 和道; 安居院 あかね; 藤井 健太郎; 横谷 明徳
日本物理学会講演概要集, 2004年

SR軟X線照射によるアミノ酸の化学進化
成田 悟; ZHAOHUI Jin; 田中 真人; 北田 朋; 金子 房恵; 中川 和道; 安居院 あかね; 藤井 健太郎; 横谷 明徳
Viva origino, 2003年03月30日

シンクロトロン放射を用いたアミノ酸の化学進化研究の到達点
中川 和道; 田中 真人; ZHAOHUI Jin; 成田 悟; 北田 朋; 金子 房恵; 安居院 あかね; 藤井 健太郎; 横谷 明徳; 山田 享; 小貫 英雄
Viva origino, 2003年03月30日

29pXE-5 放射線のエネルギー付与構造と DNA 損傷
渡辺 立子; 斎藤 公明; 横谷 明徳
日本物理学会講演概要集, 2003年03月06日

0.5keV軟X線によるDNA構成分子からのイオン脱離
藤井健太郎; 赤松憲; 横谷明徳
放射線化学討論会講演要旨集, 2003年

DNAの電子状態と放射線損傷
藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2003年

DNA塩基ラジカル生成過程の放射光EPRを用いた“その場”観測
横谷明徳; 赤松憲; 藤井健太郎
日本放射線影響学会大会講演要旨集, 2003年

軟X線またはγ線照射されたチミンのHPLCおよびEPRによる分解生成物解析
赤松憲; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2003年

放射光電子分光法による液体分子の研究(提案と現状)
高畠博嗣; 藤井健太郎; 横谷明徳; 鵜飼正敏
原子衝突研究協会研究会講演概要集, 2003年

軟X線照射されたチミンのHPLCおよびEPRによる定量・定性分析-その照射エネルギー依存性-
赤松憲; 藤井健太郎; 横谷明徳
日本環境変異原学会大会プログラム・要旨集, 2003年

190 HPLC and EPR Analysis of Thymine Derivatives produced by Ultrasoft X- and ^<60>Co γ-irradiation(Environmental effects of radiation, Abstracts of the 46th Annual Meeting of the Japan Radiation Research Society) :
AKAMATSU Ken; FUJII Kentaro; YOKOYA Akinari
Journal of radiation research, 2003年

142 In situ observation of DNA base radical using an EPR spectrometer combined with a synchrotron soft X-ray beamline in SPring-8(Redox regulation, Abstracts of the 46th Annual Meeting of the Japan Radiation Research Society) :
YOKOYA Akinari; AKAMATSU Ken; FUJII Kentaro
Journal of radiation research, 2003年

W-1-3 Electronic States of DNA and Radiation Damage to DNA(Theoretical and Experimental Approaches Relative to DNA Structure and DNA Damage Production, Abstracts of the 46th Annual Meeting of the Japan Radiation Research Society) :
FUJII Kentaro; YOKOYA Akinari
Journal of radiation research, 2003年

シンクロトロン放射を用いた軟X線照射によるアミノ酸の化学進化
金子房恵; 北田朋; 中川和道; 田中真人; ZHAOHUI J; 安居院あかね; 横谷明徳; 藤井健太郎
放射線化学討論会講演要旨集, 2003年08月15日

偏光可変アンジュレーターを用いた軟X線領域における自然円二色性の初測定
田中真人; 中川和道; 北田朋; 金子房恵; 安居院あかね; 藤井健太郎; 横谷明徳
放射線化学討論会講演要旨集, 2003年

実験ステーション(原研ビームライン) BL23SU 原研 重元素科学
寺岡有殿; 吉越章隆; 藤井健太郎; 横谷明徳; 安居院あかね; 中谷健; 岡本淳; 間宮一敏; 村松康司
SPring-8年報, 2002年12月

軟X線照射によるDNA構成分子からのフラグメントイオンの観測
藤井健太郎; 赤松憲; 横谷明徳
放射線化学討論会講演要旨集, 2002年

癌治療を目的とした新規放射線増感剤の開発
赤松憲; 横谷明徳
日本原子力研究所JAERI-Research, 2002年

DNA塩基薄膜のX線吸収端近傍微細構造スペクトルの測定
藤井健太郎; 赤松憲; 横谷明徳
日本生物物理学会年会講演予稿集, 2002年

偏光放射光軟X線を用いた5-bromouracil単結晶に対するBr-K殻X線吸収及びこれにより誘発される分子損傷
横谷明徳; 高倉かほる; 渡辺立子; 赤松憲; 恵恒雄; 伊藤隆
日本放射線影響学会大会講演要旨集, 2002年

X線照射による誘発されるオージェ過程によるDNA損傷のクラスター化
渡辺立子; 斎藤公明; 横谷明徳
日本放射線影響学会大会講演要旨集, 2002年

光脱離イオン検出によるDNAフラグメントの観測
藤井健太郎; 赤松憲; 横谷明徳
日本放射線影響学会大会講演要旨集, 2002年

チミンを用いた放射線化学的dose-responseの基礎的検討
赤松憲; 内藤健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2002年

軟X線領域におけるアミノ酸,ペプチド薄膜のXANESおよび軟X線化学反応
田中真人; 成田悟; JIN Z; 北田朋; 三宅康之; 中川和道; 安居院あかね; 藤井健太郎; 横谷明徳
放射線化学討論会講演要旨集, 2002年

グリシン蒸着膜への軟X線照射によるグリシン二量体の生成
成田悟; ZHAOHUI J; 田中真人; 三宅康之; 北田朋; 中川和道; 安居院あかね; 横谷明徳; 藤井健太郎
放射線化学討論会講演要旨集, 2002年

溶液分子に対するシンクロトロン放射光電子分光の提案
鵜飼正敏; 金井秀次; 高畠博嗣; 横谷明徳
放射線化学討論会講演要旨集, 2002年

Polarized Bromine K-shell X-ray Absorption of 5-bromouracil Crystal and Induced Molecular Damage :
YOKOYA Akinari; TAKAKURA Kaoru; WATANABE Ritsuko; AKAMATSU Ken; MEGUMI Tsuneo; ITO Takashi
Journal of radiation research, 2002年

Clustering of DNA damage due to Auger process induced by photoabsorption :
WATANABE Ritsuko; SAITO Kimiaki; YOKOYA Akinari
Journal of radiation research, 2002年

A Basic Approach for Radiation Chemical Dose-Response Estimation for Thymine Derivatives :
AKAMATSU Ken; FUJII Kentaro; YOKOYA Akinari
Journal of radiation research, 2002年

The Observation of DNA Fragmentation using Desorbed Ion Detection Technique :
FUJII Kentaro; AKAMATSU Ken; YOKOYA Akinari
Journal of radiation research, 2002年

SPring-8原研軟X線ビームラインBL23SUのH13年運転・整備記録
安居院あかね; 吉越章隆; 中谷健; 藤井健太郎; 横谷明徳
日本原子力研究所JAERI-Tech, 2002年08月

APPLE-2型アンジュレータの高速位相変調を用いた高分解能円二色性実験
安居院 あかね; 吉越 章隆; 中谷 健; 松下 智裕; 斎藤 祐児; 水牧 仁一朗; 横谷 明徳; 田中 均; 宮原 義一; 島田 太平; 竹内 政雄; 高雄 勝; 佐々木 茂樹; 青柳 秀樹; 工藤 統吾; 佐藤 一道; 呉 樹奎; 大熊 春夫
放射光, 2001年11月01日

DNA構成塩基の内殻吸収端近傍X線吸収微細構造
藤井健太郎; 赤松憲; 横谷明徳; 村松康司
日本放射線影響学会大会講演要旨集, 2001年

放射線エネルギーの直接付与によるDNA分子変化のキャラクタリゼーション
赤松憲; 藤井健太郎; 横谷明徳
日本放射線影響学会大会講演要旨集, 2001年

DNA構成原子のK殻光吸収に起因するDNA損傷のモデル化
渡辺立子; 横谷明徳; 斎藤公明
日本放射線影響学会大会講演要旨集, 2001年

γ線及びα線照射により水和したプラスミドDNAに生じる鎖切断とNthとFpgにより除去される塩基損傷の収率
横谷明徳; CUNNIFFE S; STEVENS D; O’NEILL P
日本放射線影響学会大会講演要旨集, 2001年

アミノ酸,ペプチド薄膜の酸素,窒素K殻XANES測定
田中真人; 古結俊行; 児玉洋子; 中川和道; 安居院あかね; 赤松憲; 横谷明徳
放射線化学討論会講演要旨集, 2001年

DNA構成分子の軟X線照射効果
藤井健太郎; 赤松憲; 横谷明徳
分子構造総合討論会講演要旨集, 2001年

X-ray Absorption Near Edge Structure of DNA Bases :
FUJII Kentaro; AKAMATSU Ken; YOKOYA Akinari; MURAMATSU Yasuji
Journal of radiation research, 2001年

Modelling of DNA damage following K-shell photoabsorption of DNA constituent atoms :
WATANABE Ritsuko; YOKOYA Akinari; SAITO Kimiaki
Journal of radiation research, 2001年

Characterization of Chemical Changes in DNA Components by Energy Deposition from monochromatic Photons :
AKAMATSU Ken; FUJII Kentaro; YOKOYA Akinari
Journal of radiation research, 2001年

SPring-8原研軟X線ビームラインBL23SUのH12年運転・整備記録
安居院あかね; 吉越章隆; 中谷健; 斎藤祐児; 寺岡有殿; 横谷明徳
日本原子力研究所JAERI-Tech, 2001年07月

30aXA-9 窒素および酸素K殻領域でのアミノ酸蒸着膜のNEXAFS測定
田中 真人; 古結 俊行; 児玉 洋子; 中川 和道; 赤松 憲; 安居院 あかね; 横谷 明徳
日本物理学会講演概要集, 2001年

光学素子評価用試験装置の設計・製作
清水雄一; 依田修; 貴家恒男; 寺岡有殿; 横谷明徳; 柳原美広
日本原子力研究所JAERI-Tech, 2000年

DNAおよびその構成分子の酸素K殻吸収端近傍微細構造(XANES)の測定とその生物照射効果研究における意義
赤松憲; 横谷明徳
日本放射線影響学会大会講演要旨集, 2000年

X-ray absorption near edge structures (XANES) of DNA or its components around oxygen K-edge and the application for radiation biology :
AKAMATSU Ken; YOKOYA Akinari
Journal of radiation research, 2000年

電離放射線毒性作用の基礎過程解明に果たすX線吸収端近傍微細構造(XANES)の役割
赤松憲; 横谷明徳
日本環境変異原学会大会プログラム・要旨集, 2000年

25pYK-11 ネオンイオン及び酸素イオンの内殻光励起・電離実験
山岡 人志; 伊藤 陽; 粟屋 容子; 横谷 明徳; 安居院 あかね; 吉越 章隆; 大浦 正樹; 川面 澄; 木俣 潤一; 早石 達司; 高橋 武寿; 小泉 哲夫; 関岡 嗣久; 寺澤 倫孝
日本物理学会講演概要集, 2000年

22aPS-98 挿入光源の周期的位相駆動による軟X線円二色測定系の立ち上げ
安居院 あかね; 高雄 勝; 早乙女 光一; 大熊 春夫; 青柳 秀樹; 工藤 統吾; Wu S; 佐藤 一道; 竹内 政雄; 備前 輝彦; 吉越 章隆; 横谷 明徳; 斎藤 祐児; 中谷 健; 松下 智裕; 島田 太平; 宮原 義一; 田中 均
日本物理学会講演概要集, 2000年

SPring-8原研軟X線ビームラインBL23SUにおけるMCD
斎藤祐児; 水牧仁一郎; 松下智裕; 中谷健; 安居院あかね; 寺岡有殿; 横谷明徳
日本物理学会講演概要集, 1999年

X線誘発内殻光吸収によるDNA損傷生成過程のモデル化
渡辺立子; 横谷明徳; 斎藤公明
日本放射線影響学会大会講演要旨集, 1999年

SPring-8軟X線光化学ビームラインBL27SUの建設
大橋治彦; 石黒英治; 田中隆次; 岸本輝; 大浦正樹; 横谷明徳; 為則雄祐; 金島岳; 石川哲也
日本放射光学会年会・放射光科学合同シンポジウム予稿集, 1999年

原研軟X線BL23SUの現状 (高輝度光科学研究センターS)
横谷明徳; 寺岡有殿; 島田太平; 平松洋一; 斎藤祐児; 中谷健; 宮原義一; 岡根哲夫
SPring-8利用者情報, 1999年

湿潤試料用照射槽を用いた超軟X線による培養細胞の致死
伊藤敦; 前沢博; 桧枝光太郎; 小林克己; 宇佐美徳子; 横谷明徳
KEK Proceedings, 1999年

5-Bromouracil単結晶に対するBrK吸収端付近における偏光X線吸収
横谷明徳; 高倉かほる; 渡辺立子; 恵恒雄; 伊藤隆
KEK Proceedings, 1999年

Modeling of Production Process of DNA Damage by X-ray Induced Inner-Shell Photoabsorrpion :
WATANABE Ritsuko; YOKOYA Akinari; SAITO Kimiaki
Journal of radiation research, 1999年

24pYC-15 SPring-8原研軟X線ビームラインBL23SUにおけるMCD
斎藤 祐児; 水牧 仁一郎; 松下 智裕; 中谷 健; 安居院 あかね; 寺岡 有殿; 横谷 明徳
日本物理学会講演概要集, 1999年

アンジュレータ放射光を用いた超軟X線領域での生物照射効果研究
横谷明徳
日本放射線影響学会大会講演要旨集, 1998年

超軟X線領域でのDNAのXANESスペクトル測定
赤松憲; 横谷明徳
日本放射線影響学会大会講演要旨集, 1998年

リンK殻内殻電離によって生じたクロマチン切断の修復性の実験データから判ったこと
鈴木雅雄; 前沢博; 加瀬陽子; 横谷明徳; 宇佐美徳子; 小林克己
日本放射線影響学会大会講演要旨集, 1998年

Induction of non-rejoining chromatin breaks by the inner shell absorption of phosphorus in DNA. :
SUZUKI Masao; MAESAWA Hiroshi; KASE Yoko; YOKOYA Akinari; Usami Noriko; KOBAYASHI Katsumi
Journal of radiation research, 1998年

Radiobiological Study in Ultrasoft X-ray Region Using Undulator Synchrotron Radiation :
YOKOYA Akinari
Journal of radiation research, 1998年

XANES Spectra for DNA in Ultrasoft X-ray Region :
AKAMATSU Ken; YOKOYA Akinari
Journal of radiation research, 1998年

SPring-8における軟X線生物分光研究
横谷明徳
日本放射線影響学会大会講演要旨集, 1997年

リンK殻内殻電離によるクロマチン切断誘発
鈴木雅雄; 前沢博; 加瀬陽子; 横谷明徳; 宇佐美徳子; 小林克己
日本放射線影響学会大会講演要旨集, 1997年

原研軟X線ビームライン(BL23SU)の概要 (高輝度光科学研究センターS)
横谷明徳; 関口哲弘; 斎藤祐児; 岡根哲夫; 中谷健; 寺岡有殿; 島田太平; 高雄勝; 大野英雄
SPring-8利用者情報, 1997年

Soft X-ray Spectroscopy for Biology in SPring-8 : Soft X-ray Spectroscopy for Biology in SPring-8
YOKOYA Akinari
Journal of radiation research, 1997年

Chromatin-break induction in V79 cells by monochromatic soft X rays near K-shell absorption edge of phosphorus. : Chromatin-break induction in V79 cells by monochromatic soft X rays near K-shell absorption edge of phosphorus.
SUZUKI Masao; MAESAWA Hiroshi; KASE Yoko; YOKOYA Akinari; Usami Noriko; KOBAYASHI Katsumi
Journal of radiation research, 1997年

軟X線を用いた生物分光研究
横谷明徳
放射光, 1997年09月10日

原研ビームライン
原見 太幹; 小西 啓之; 横谷 明徳
放射光, 1996年11月30日

軟X線領域におけるDNAの光吸収スペクトル
横谷明徳; 原岳広; 渡辺立子; 桧枝光太郎; 小林克己
日本放射光学会年会予稿集, 1996年

湿潤生物試料のための単色超軟X線照射装置の開発 II
桧枝光太郎; 冨田雅典; 小林克己; 宇佐美徳子; 横谷明徳; 渡辺立子; 前沢博; 伊藤敦; 高倉かほる
日本放射線影響学会大会講演要旨集, 1996年

生体試料へのシンクロトロン軟X線照射のためのEPR用低温デュワーの製作
横谷明徳; 渡辺立子; 高倉かほる; 恵恒雄; 伊藤隆
放射線化学討論会講演要旨集, 1996年

軟X線領域におけるDNAの光吸収スペクトル
横谷明徳; 渡辺立子; 原岳広; 桧枝光太郎; 小林克己
日本放射線影響学会大会講演要旨集, 1996年

SPring-8原研軟x線ビームライン用挿入光源の磁場解析
小林秀樹; 佐々木茂美; 島田太平; 高雄勝; 横谷明徳; 宮原義一
日本原子力研究所JAERI-Tech, 1996年

高輝度X線(I)-SPring-8 原研ビームライン
原見太幹; 小西啓之; 横谷明徳
放射光, 1996年

Photoabsorption Spectrum of DNA in Ultrasoft X-ray Region : Photoabsorption Spectrum of DNA in Ultrasoft X-ray Region
YOKOYA Akinari; WATANABE Ritsuko; HARA Takehiro; HIEDA Kotaro; KOBAYASHI Katsumi
Journal of radiation research, 1996年

Irradiation System of Monochromatic Ultrasoft X-Rays for Wet Biological Samples. : Irradiation System of Monochromatic Ultrasoft X-Rays for Wet Biological Samples.
HIEDA Kotaro; KOBAYASHI Katsumi; USAMI Noriko; YOKOYA Akinari; WATANABE Ritsuko; MAEZAWA Hiroshi; IT0 Atsushi; TAKAKURA Kaoru; TOMITA Masanori
Journal of radiation research, 1996年

DNA主鎖切断の光子エネルギー依存性(8eV-2.2keV)
桧枝光太郎; 鈴木慶二; 横谷明徳; 小林克巳
日本放射光学会年会予稿集, 1995年

湿潤生物試料のための単色超軟X線照射装置の開発
桧枝光太郎; 小林克己; 宇佐美徳子; 横谷明徳; 前沢博; 伊藤敦; 高倉かほる
日本放射線影響学会大会講演要旨集, 1995年

Design of an Irradiation System of Monochromatic Ultrasoft X-rays for Wet Samples : Design of an Irradiation System of Monochromatic Ultrasoft X-rays for Wet Samples
HIEDA Kotaro; KOBAYASHI Katsumi; USAMI Noriko; YOKOYA Akinari; MAEZAWA Hiroshi; Ito Atsushi; TAKAKURA Kaoru
Journal of radiation research, 1995年

粉末状態及び水溶液アミノ酸のイオウK殻励起による分子変化の比較
横谷明徳; 小林克己; 宇佐美徳子
日本放射光学会年会予稿集, 1994年

単色超軟X線(60-550eV)によるDNA主鎖切断
桧枝光太郎; 鈴木慶二; 横谷明徳; 小林克巳
日本放射線影響学会大会講演要旨集, 1994年

軟X線領域における単色X線によるDNA損傷と増殖障害
中村清一; 恵恒雄; 宇佐美徳子; 横谷明徳; 小林克巳
大阪府立公衆衛生研究所研究報告 労働衛生編, 1994年

生体分子の内殻光励起による分子変化
横谷明徳
SR科学技術情報, 1994年

Single- and double-strand breaks induced by monochromatic ultra-soft X-rays from 60 to 550 eV. : Single- and double-strand breaks induced by monochromatic ultra-soft X-rays from 60 to 550 eV.
HIEDA Kotaro; SUZUKI Keiji; YOKOYA Akinari; KOBAYASHI Katsumi
Journal of radiation research, 1994年

RI・アクチノイドビームラインにおけるRI試料飛散防止対策のテスト
横谷明徳; 小西啓之; 本橋治彦; 牧田知子; 藤田利明; 大野英雄; 小林克己; 宇佐美徳子
日本放射光学会年会予稿集, 1993年

アクチノイド・RI研究用放射光ビームラインの開発
小西啓之; 本橋治彦; 横谷明徳; 藤田利明; 大野英雄
日本原子力学会春の年会要旨集, 1993年

粉末状態及び水溶液アミノ酸の単色軟X線照射による分子変化の比較
横谷明徳; 小林克己; 宇佐美徳子
日本放射線影響学会大会講演要旨集, 1993年

水溶液中のイオウを含むアミノ酸の単色軟X線照射による分子変化
横谷明徳; 小林克己; 宇佐美徳子
日本放射光学会年会予稿集, 1993年

Degradation of Amino Acid Irradiated with Monochromatized Soft X-rays in Aqueous Solution : Degradation of Amino Acid Irradiated with Monochromatized Soft X-rays in Aqueous Solution
YOKOYA Akinari; KOBAYASHI Katsumi; USAMI Noriko
Journal of radiation research, 1993年

特定元素の内殻励起によるイオウを含むアミノ酸の分子変化の機構
横谷明徳; 小林克己; 宇佐美徳子
日本放射線影響学会大会講演要旨集, 1992年

フォトンファクトリーBL-27に設置された生物照射装置の性能
小林克己; 宇佐美徳子; 横谷明徳
日本放射線影響学会大会講演要旨集, 1992年

水溶液中モノヌクレオチドの分子分解に対する分子外リン原子K殻吸収の寄与
渡辺立子; 小林克己; 宇佐美徳子; 横谷明徳
日本生物物理学会年会講演予稿集, 1992年

軟X線による水溶液中ヌクレオチドの分解機構-分子内と分子外のリン原子K殻吸収の寄与の比較
渡辺立子; 小林克己; 宇佐美徳子; 横谷明徳
日本放射線影響学会大会講演要旨集, 1992年

内殻電離原子に依存したアミノ酸の分解様式
横谷明徳; 宇佐美徳子; 小林克己
Photon Factory News, 1992年

マウス線維芽細胞における単色軟X線による潜在致死損傷の回復
横谷 明徳
日本放射線影響学会大会講演要旨集, 1989年08月

LETHAL EFFECT OF SYNCHROTRON SOFT X-RAYS AROUND K-SHELL ABSORPTION-EDGE OF PHOSPHORUS ON MOUSE 10T1/2 CELLS
A YOKOYA; K KOBAYASHI; H MAEZAWA; K HIEDA; S ISHIZAKA
JOURNAL OF RADIATION RESEARCH, 1988年03月

INACTIVATION OF REPAIR DEFICIENT YEAST-CELLS IRRADIATED WITH MONOCHROMATIC SOFT X-RAYS OF THE RESONANCE-ABSORPTION OF PHOSPHORUS
K KOBAYASHI; N USAMI; A YOKOYA; H MAEZAWA; Y FURUSAWA; K HIEDA; T ITO
JOURNAL OF RADIATION RESEARCH, 1988年03月

INACTIVATION OF CELL-ADHESION ACTIVITY MEDIATED WITH FIBRONECTIN WITH X-RAYS
A YOKOYA; K KOBAYASHI; S ISHIZAKA
JOURNAL OF RADIATION RESEARCH, 1987年03月

マイクロスフィアを用いた細胞接着機能に対する放射線効果の測定
横谷 明徳
日本放射線影響学会大会講演要旨集, 1986年10月

放射線の与える生体膜損傷測定法の開発 マイクロスフィアを用いたフィブロネクチンレセプターの定量
横谷 明徳
日本生物物理学会年会講演予稿集, 1986年08月

2-6．放射線ストレスに対する量子効果に基づくゲノム安定化機構の解明　　　　　　　　　　　　　　　
横谷 明徳; 藤井 健太郎, 分担執筆
高エネルギー加速器研究機構・放射光科学研究施設, 2016年10月31日

Spectroscopic study of radiation-induced DNA lesions and their susceptibility to enzymatic repair
Akinari Yokoya; Kentaro Fujii; Naoya Shikazono; Masatoshi Ukai, 共著
CRC Press, 2010年01月01日, ［査読有り］

放射線影響の初期過程から細胞応答のシステム的統合理解に向けて　　　　　　　　　　　　　　　
横谷明徳
令和5年東京RBC新春放談会, 2023年02月04日, ［招待有り］
20230204, 20230204

２ビーム利用による新しいサイエンス （放射線生物UG）　　　　　　　　　　　　　　　
横谷 明徳
PF研究会「開発研究多機能ビームラインの建設と利用」②, 2023年01月05日, ［招待有り］
20230105, 20230106

DNA repair response of mammary gland cells to EGFP plasmid DNA exposed to various ionizing radiations or treated with restriction enzymes　　　　　　　　　　　　　　　
Yui Obata; Akari Kinase; Keishiro Hirasaki; Nobuyoshi Akimitsu; Akinari Yokoy
68th Annual International Meeting of Radiation Research Society, 2022年10月17日
20221016, 20221019

Structural change in DNA repair protein XRCC4 by multimerization revealed by CD and SAXS　　　　　　　　　　　　　　　
Kai Nishikubo; Maho Hasegawa; Yoshihisa Matsumoto; Akinari Yokoy
68th Annual International Meeting of Radiation Research Society, 2022年10月17日
20221016, 20221019

電子状態の物理学的理解による放射線生体分子変異プロセスの探索
横谷 明徳
日本放射線影響学会第65回大会, 2022年09月16日, ［招待有り］
20220915, 20220917

クラスターDNA損傷　　　　　　　　　　　　　　　
横谷 明徳
Auger Therapy 研究会, 2022年09月05日, ［招待有り］
20220905, 20220905

Exploring active structures of DNA repair protein XRCC4 using CD and SAXS
横谷明徳; 西久保開; 長谷川真保
The 26th Hiroshima International Symposium on Synchrotron Radiation, 2022年02月18日, ［招待有り］
20220217, 20220218

放射線誘発DNA初期損傷に対する添加剤の化学修復効果　　　　　　　　　　　　　　　
于暠; 藤井健太郎; 横谷明徳; 山下真一
日本放射線影響学会第64回大会, 2021年09月23日, ［招待有り］
20210922, 20210924

放射線、生命科学、そして物理学
横谷明徳
日本放射線影響学会第64回大会, 2021年09月23日, ［招待有り］
20210922, 20210924

X線マイクロビームの可変ジオメトリックパターンと細胞・細胞集団ターゲティン グ
横谷明徳
日本放射線影響学会若手部会第1回総会・日本マイクロビーム生物研究会第11回連絡会議（総会）・高LET研究会, 2020年10月14日, ［招待有り］
20201014, 20201014

薬剤及び放射線ストレスによる動物培養細胞内のミトコンドリア動態と ATP産生の変化　　　　　　　　　　　　　　　
木村由佳; 大内則幸; 鈴木啓司; 横谷明徳
第13回Quantum Medicine研究会（茨城大学理学部公開シンポジウム）, 2020年02月23日, ［招待有り］
20200223, 20200223

Do bromine atoms incorporated into DNA obscure the photon-induced Auger effect on damage induction?　　　　　　　　　　　　　　　
Akinari Yokoya
The 9th International Symposium on Physical, Molecular, Cellular, and Medical Aspects of Auger Processes, 2019年08月23日, ［招待有り］
20190822, 20190824

Fluorescent Nanodiamonds for Intracellular Measurements　　　　　　　　　　　　　　　
Ryuji Igarashi; Kiichi Kaminaga; Daiki Terada; Takahiro Fujisaku; Takuya Genjo; Takuya F. Segawa; Akinari Yokoya; Masahiro Shirakawa
PhotonIcs & Electromagnetics Research Symposium also known as Progress In Electromagnetics Research Symposium (PIERS 2019), 2019年06月17日, ［招待有り］
20190617, 20190620

Quantum Tools to Explore Radiobiological Effects on Living Systems
Akinari Yokoya
PhotonIcs & Electromagnetics Research Symposium also known as Progress In Electromagnetics Research Symposium (PIERS 2019), 2019年06月17日, ［招待有り］
20190617, 20190620

In vitro 照射プラスミドをトランスフェクションした細胞のライブセル観察　　　　　　　　　　　　　　　
小畑結衣; 横谷明徳
第12回 Quantum Medicine 研究会（茨城大学理学部 公開シンポジウム ）, 2019年02月17日, ［招待有り］
20190217, 20190217

マイクロビームＸ線照射後のミトコンドリア活性変化のライブセル観察　　　　　　　　　　　　　　　
横谷明徳; 神長輝一; 浜田涼; 宇佐美徳子; 鈴木啓司
若⼿放射線⽣物学研究会 平成 30 年度専⾨研究会, 2018年09月01日, ［招待有り］
20180901, 20180902

放射光を量子ツールとして用いた生命・医科学研究　　　　　　　　　　　　　　　
横谷 明徳
JAEA-QST放射光科学シンポジウム2018, 2018年03月12日, ［招待有り］
20180312, 20180314

放射線による複雑なDNA損傷の生成に 関する物理化学的初期過程の研究　　　　　　　　　　　　　　　
横谷 明徳
長崎原研研究会, 2018年02月28日, ［招待有り］
20180228, 20180228

Development of the ex vivo spermatogenesis technique for advanced radiotherapeutic science　　　　　　　　　　　　　　　
Hisanori Fukunaga; Kiichi Kaminaga; Takuya Sato; Karl T. Butterworth; Akinari Yokoya; Takehiko Ogawa; Kevin M. Prise
2017年度生命科学系学会合同年次大会 （ConBio2017）, 2017年11月30日, ［招待有り］
20171128, 20171130

Synchrotron Radiation as a Quantum Tool for Studies of Radiation Damage to DNA and Resulting Cellular Responses　　　　　　　　　　　　　　　
横谷 明徳; 藤井 健太郎; 島田 紘行; 鵜飼 正敏; 神長輝一; 大和田 謙二; 町田 晃彦; 今岡 達彦; 西村 由希子
2017年度生命科学系学会合同年次大会 （ConBio2017）, 2017年11月29日, ［招待有り］
20171128, 20171130

Novel analytical study for reaction intermediates in the primary radiation interaction of DNA using a synchrotron radiation induced luminescence spectroscopy　　　　　　　　　　　　　　　
T.Kojima; H.Aihara; Y.Kodashima; H.Makishima; S.Nakiri; S.Takada; H.Shimada; C.Ozga; X.Holzapfel; Ph.Schimid; C.Küstner-Wetekamm; H.Otto; A.Knie; A.Ehresmann; A.Yokoya; K.Fujii; Y.Fukuda; M.Ukai
17th International Symposium on Microdosimetry (MICROS 2017), 2017年11月07日
20171105, 20171110

Visualization of DNA Repair Process in Mammalian Cells Transformed by Plasmid DNA Exposed to X-rays in vitro　　　　　　　　　　　　　　　
Hiroki Nakaue; Yui Obata; Kiichi Kaminaga; Akinari Yokoy
17th International Symposium on Microdosimetry (MICROS2017), 2017年11月07日
20171105, 20171110

ハロゲン化ピリミジンを含むDNA の放射線増感の電子物性の研究　　　　　　　　　　　　　　　
鬼澤 美智; 芳賀 芳範; 田中 成典; 鯉渕 誠也; 横谷 明徳
第60回 日本放射線影響学会大会, 2017年10月28日, ［招待有り］
20171025, 20171028

Ｘ線マイクロビーム照射後のミトコンドリア活性の変化　　　　　　　　　　　　　　　
横谷 明徳; 神長 輝一; 浜田 涼; 宇佐美 徳子; 鈴木 啓司
第60回 日本放射線影響学会大会, 2017年10月26日, ［招待有り］
20171025, 20171028

水中でエネルギー付与された電子の動的挙動　　　　　　　　　　　　　　　
甲斐健師; 樋川智洋; 鵜飼正敏; 藤井健太郎; 渡邊立子; 横谷明徳
第60回放射化学討論会, 2017年09月28日, ［招待有り］
20170927, 20170929

Fragmentation of Doubly-Ionized Deoxyribose. Ab Initio Molecular Dynamics Simulations　　　　　　　　　　　　　　　
Marie Anne Hervé du Penhoa; Alexandre Souchaud; Rodolphe Vuilleumier; Ivano Tavernelli; Marie Pierre Gaigeo; Kentaro Fujii; Akinari Yokoya; Marie Françoise Politis
The first International Symposium of QST - Quantum Life Sciences -, 2017年07月25日, ［招待有り］
20170725, 20170726

High Brilliance Synchrotron Radiation as a Tool for Studies of Radiation Damage to DNA and resulting cellular responses　　　　　　　　　　　　　　　
Akinari Yokoya
The first International Symposium of QST - Quantum Life Sciences -, 2017年07月25日, ［招待有り］
20170725, 20170726

Live imaging of cells exposed to ionizing radiation　　　　　　　　　　　　　　　
Akinari Yokoya; Kiichi Kaminaga; Tatsuhiko Imaoka; Takeshi Ohshima; Ryuji Igarashi
QUANTUM SENSING IN BIOLOGY WORKSHOP in University of Melbourne, 2017年03月28日, ［招待有り］
20170328, 20170328

Ｘ線マイクロビーム照射後の細胞運命とミトコンドリア活性変化　　　　　　　　　　　　　　　
横谷 明徳; 神長 輝一; 濱田 涼; 宇佐美 徳子; 鈴木 啓司
第10回Quantum Medicine研究会（茨城大学理学部公開シンポジウム）, 2017年02月12日, ［招待有り］
20170212, 20170212

Various modes of DNA damage formation by the direct effect of radiation　　　　　　　　　　　　　　　
横谷 明徳
The 56th Annual Meeting of Radiation Research Society, 2010年09月25日, ［招待有り］

2012年04月 - 現在, PFユーザーアソシエーション

量子生命科学研究会

日本放射線化学会

日本放射線影響学会

日本放射光学会