研究者詳細 - 熊谷　純

論文 - 熊谷　純

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Electron spin resonance study on H6+, H5D+, H4D2+, and H2D4+ in solid parahydrogen 査読有り

Jun Kumagai, Hiroki Inagaki, Susumu Kariya, Takahiro Ushida, Yuta Shimizu, Takayuki Kumada

J. Chem. Phys. 127 巻 ( 2 ) 頁： 024505 2007年7月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We carried out an electron spin resonance (ESR) study on hydrogen ion radicals produced by radiolysis of solid para-H-2. In addition to quartet ESR lines proposed to be H-2(+)-core H-6(+) (D-2d) ions in solid para-H-2 [T. Kumada , Phys. Chem. Chem. Phys. 7, 776 (2005)], we newly observed totally more than 50 resolved lines in gamma-ray irradiated solid para-H-2-ortho-D-2 (1 mol %) and para-H-2-HD (1 mol %) mixtures. We assigned these lines to be isotope substituents of H-2(+)-core H-6(+) ions such as H5D+, H4D2+, and H2D4+ throughout the comparison of their ESR parameters with theoretical results. These results provide a conclusive evidence that H-2(+)-core H-6(+) ions are generated in irradiated solid hydrogens. Analysis of the EPR spectrum and ab initio calculations predicts D-2d symmetry of the H-6(+) ions, whereas a lowering symmetry (D-2d -> C-2v) induced by asymmetric nuclear wave function is observed in H5D+ and H4D2+. We also observed isotope-substitution reactions such as H-6(+)+D-2 -> H4D2++H-2 and H-6(+)+HD -> H5D++H-2, which are analogous to the well-known isotope-condensation reactions of H-3(+) in dark nebula, H-3(+)+HD -> HD2++H-2 and HD2++HD -> D-3(+)+H-2.

DOI： 10.1063/1.2748046

固体パラ水素中に生成したH6+のESR分光研究査読有り

熊田高之、牛田考洋、清水裕太、熊谷　純

電子スピンサイエンス 5 巻頁： 134-139 2007年

ESR study of H₆⁺ and H₄D₂⁺ produced in irradiated solid hydrogens 査読有り

T. Kumada, T. Takayanagi, J. Kumagai

J. Mol. Struc. 786 巻 ( 2-3 ) 頁： 130-133 2006年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

We reinvestigated the quartet ESR lines with g-valueg=2.002 and hyperfine coupling constant A approximate to 20 mT produced in gamma-ray irradiated solid pH, in order to determine to which the lines should be assigned, H-2(-) or H-6(+). We newly found further splitting of each of the quartet lines into quintet ones in irradiated solid p-H-2 containing o-D-2 at 1 mol%. ESR parameters of these new lines were found to be consistent with those of H4D2+ calculated. This result supports the assignment to H-6(+) rather than H-2(-).

DOI： 10.1016/j.molstruc.2005.08.036

Is the ESR spectrum attributable to H2- or H2+(H2)2? Precise measurement of the g-value and anisotropic hyperfine structure in gamma-irradiated solid parahydrogen 査読有り

Jun Kumagai, Masatsugu Hanabusa, Hiroki Inagaki and Susumu Kariya

Phys. Chem. Chem. Phys. 6 巻 ( 17 ) 頁： 4363-4368 2004年6月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Four ESR lines, found by Miyazaki et al. in 1995 in irradiated solid parahydrogen (ca. 92% para-purity) at 4.2 K, assigned as "H-2(-),'' were precisely re-measured with highly pure solid parahydrogen (>99.9%) and compared with calculated g-value and hyperfine coupling constants of H-2(+)(H-2)(2). The g-value of I,M-I=0,0 feature, reported previously as 2.0033 or 2.0023, was found to be incorrect and has now been corrected to 2.002120+/-0.000012. This corrected value is clearly smaller than that of free electron. We also found that the remaining three lines corresponding to I, M-I=1,0; 1, +1; and 1, -1 features have axially symmetric hyperfine anisotropic structure i.e., A(parallel to)=20.318 and A(perpendicular to)=20.502 mT. This anisotropy corresponds to the rotation of the species in solid parahydrogen. Although the experimental g-value and isotropic hyperfine coupling constants are in good agreement with those of H-2(+)(H-2)(2) estimated by ab initio calculation, it is still difficult to explain why H-2(+)(H-2)(2) clusters turned into ESR inactive species by addition of 0.1similar to1% D-2 in the present system. In this regard, we still maintain that the species in solid parahydrogen are H-2(-).

DOI： 10.1039/b402756f

Long-lived mutagenic radicals induced in mammalian cells by ionizing radiation are mainly localized to proteins 査読有り

J. Kumagai, K. Masui, Y. Itagaki, M. Shiotani, S. Kodama, M. Watanabe, T. Miyazaki

Radiat. Res. 160 巻 ( 1 ) 頁： 95-102 2003年7月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We have provided evidence that long-lived radicals, produced by ionizing radiation, are highly mutagenic and transforming in mammalian cells. Long-lived radicals are scavenged effectively by vitamin C or by epigallocatechin-3-O-gallate (EGCG). Long-lived radicals are not involved in lethality or in the induction of chromosome aberrations. We now report the results of experiments that define the relative amounts of long-lived radicals in DNA and proteins and identify the major protein radicals as sulfinyl radicals (R-CH2-S-O-.). To make these assignments, yields of long-lived radicals in gamma-irradiated salmon sperm DNA and albumin were compared by ESR. ESR spectra of long-lived radicals produced in irradiated Syrian hamster embryo (SHE) cells were analyzed precisely and compared with ESR parameters obtained by density functional theory calculations. Long-lived radicals yields of 99.8% were produced in proteins. We also identified a new type of long-lived radical as H-added phenylalanine radicals. While our evidence does not rule out the possibility of important biological consequences of the low-level long-lived radicals created by radiation, it implicates radicals in proteins as playing a key role in genetic effects of ionizing radiation. We suggest that these novel radicals, wherever they reside, need to be considered in explanations of biological sequela of radiation.

DOI： 10.1667/RR3015

Active sites and active oxygen species for photocatalytic epoxidation of propene by molecular oxygen over TiO₂-SiO₂ binary oxides 査読有り

C. Murata, H. Yoshida, J. Kumagai, T. Hattori

J. Phys. Chem. B 107 巻 ( 18 ) 頁： 4364-4373 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

TiO2-SiO2 binary oxides of low Ti content promoted photocatalytic epoxidation of propene by molecular oxygen. By catalytic runs and UV spectra, it was revealed that the isolated tetrahedral Ti species on the TiO2-SiO2 samples are active for the photoepoxidation of propene, while the aggregated titanium oxide species are active mainly for the side reactions. By ESR and stoichiometric reaction tests of radical species, the following mechanism was proposed. Over the isolated tetrahedral Ti species, a [Ti3+-O-L(-)]* radical pair is formed by UV irradiation. The Ti3+ moiety reacts with O-2 to form O-2(-), which could not activate propene by itself. The O-L(-) moiety, a hole center on lattice oxygen, reacts with O-2 to form O-3(-), and the O-3(-) reacts with propene to yield PO. It is first suggested that the O-3(-) is the electrophilic oxygen species effective for the epoxidation of propene. When the O-L(-) moiety reacts with propene, acrolein or ethanal is produced through H abstraction or CC bond fission. The lower selectivity of the aggregated titanium oxide species was attributed to the lower stability of the O-3(-) and high activity for the consecutive reaction of PO.

DOI： 10.1021/jp0277006

Test for antioxidant ability by scavenging long-lived mutagenic radicals in mammalian cells and by blood test with intentional radicals: an application of gallic acid 査読有り

J. Kumagai, T. Kawaura, T. Miyazaki, M. Prost, E. Prost, M. Watanabe, J. Q. Leclercq

Radiat. Phys. Chem. 66 巻 ( 1 ) 頁： 17-25 2003年1月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Antioxidant ability of gallic acid (GA) are determined both by electron spin resonance measurement of long-lived radicals produced in gamma-ray irradiated Syrian golden hamster embryo cells with GA and by hemolysis measurement with GA when blood cells are submitted to radicals. Scavenging properties of GA are determined by the reaction rate constant with long-lived mutagenic radicals in the cells while the blood test allows to analyze the global effects of this compound: radical scavenger + metal ion chelator + regeneration of intra- and extra-cellular antioxidant.

DOI： 10.1016/S0969-806X(02)00288-8

磁気共鳴法を用いた照射生体中の長寿命ラジカルの観測と生物効果との関連性の解明招待有り査読有り

熊谷　純

放射線化学 75 巻頁： 3-11 2003年

Long-lived radicals produced by gamma-irradiation or vital activity in plants, animals, cells, and protein solution: their observation and inhomogeneous decay dynamics 査読有り

T. Miyazaki, A. Morikawa, J. Kumagai, M. Ikehata, T. Koana, S. Kikuchi

Radiat. Phys. Chem. 65 巻 ( 2 ) 頁： 151-157 2002年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

Long-lived radicals produced by gamma-irradiation or vital activity in plants, animals, cells, and protein (albumin) solution were studied by electron spin resonance spectroscopy. Long-lived radicals produced by vital activity exist in biological systems, such as plants, animals, and cells, in the range of 0.1-20 nmol g(-1). Since vital organs keep the radicals at a constant concentration, the radicals are probably related to life conservation. Long-lived radicals are also produced by gamma-irradiation of cells or protein solution. The radicals decay after death of living things or after gamma-irradiation. We found that the decay dynamics in all biological systems can be expressed by the same kinetic equation of an inhomogeneous reaction

DOI： 10.1016/S0969-806X(02)00198-6

Suppression and enhancement of tunneling ion recombination of electron bubbles in solid para-hydrogen-ortho-hydrogen mixtures at 4.2 K: controlling factors of tunneling reaction 査読有り

T. Miyazaki, H. Fukuta, M. Hanabusa, T. Kumada, J. Kumagai

Chem. Phys. Lett. 360 巻 ( 1-2 ) 頁： 8-12 2002年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

The decay of electron bubbles due to a tunneling ion recombination was studied by ESR in gamma-ray irradiated solid para-hydrogen (p-H-2)-ortho-hydrogen (o-H-2) mixtures at 4.2 K. In the range of 10-75% o-H-2 (region I), the decay rates of the electron bubbles increase with decreasing o-H-2 concentration. The decay rate constant shows the maximum around 10% o-H-2. Then, the decay rates decrease with decreasing o-H-2 concentration below 10% o-H-2 (region II). The results were interpreted by two different rate-determining steps: a tunneling process in region I and an energy-dissipation process in region II. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(02)00823-0

Scavenging of long-lived radicals by (-)-epigallocatechin-3-O-gallate and simultaneous suppression of mutation in irradiated mammalian cells 査読有り

J. Kumagai, M. Nakama, T. Miyazaki, T. Ise, S. Kodama, M. Watanabe

64 巻 ( 4 ) 頁： 293-297 2002年7月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Effect of (-)-epigallocatechin-3-O-gallate (EGCg) on scavenging long-lived radicals and its biological significance were investigated using electron-spin-resonance spectroscopy and mutation assay in cultured human embryo cells. EGCg scavenged long-lived radicals in irradiated golden hamster embryo cells and albumin solution, and simultaneously reduced mutation frequency in the irradiated human embryo cells. These results indicate that long-lived radials are involved in the induction of mutation by radiation.

DOI： 10.1016/S0969-806X(01)00501-1

Absence of recombination of neighboring H atoms in highly purified solid parahydrogen: Electron spin resonance, electron-nuclear double resonance, and electron spin echo studies 査読有り

T. Kumada, M. Sakakibara, T. Nagasaka, H. Fukuta, J. Kumagai, T. Miyazaki

J. Chem. Phys. 116 巻 ( 3 ) 頁： 1109-1119 2002年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

Diffusion and recombination of H atoms were studied in solid hydrogen containing ortho-H(2) molecules at relative concentration X(o)=0.001 -->0.75 using electron spin resonance (ESR), electron-nuclear double resonance (ENDOR), and electron spin echo (ESE) methods at around 4 K. When the rate-determining step for recombination is assumed to be the diffusion of H atoms, the rate constant for recombination at X(o)greater than or equal to0.1 is consistent with the diffusion coefficient estimated from the analysis of ENDOR spectra and longitudinal spin relaxation behaviors. The recombination rate constant at X(o)<0.1, however, is too slow to be explained using the diffusion coefficient estimated from longitudinal spin relaxation and forbidden spin-flip satellite transition studies. This result suggests that, even if one H atom finds another H in its immediate neighborhood, these H atoms do not react to form a H(2) molecule at X(o)<<0.1. The absence of recombination of H atoms is due to lack of the energy dispersion path required for the recombination of diatomic molecules. Since the absence of recombination becomes less significant at higher X(o), ortho-H(2) molecules are found to play an important role in the energy dispersion which accompanies the recombination reaction

DOI： 10.1063/1.1426410

An ESR and ESEEM study of long-lived radicals which cause mutation in irradiated mammalian cells 査読有り

J. Kumagai, T. Miyazaki, S. Kodama, M. Watanabe

Int. Congress Series 1236 巻頁： 351-354 2002年

突然変異やガン化を誘発する長寿命タンパク質ラジカル　〜電子スピン共鳴法・電子スピンエコー法による解析〜招待有り

熊谷　純

放射線生物研究 37 巻頁： 85-103 2002年

A role of long-lived radicals in radiation mutagenesis and its suppression by epigallocatechin gallate 査読有り

1236 巻頁： 355-358 2002年

High-resolution electron spin resonance spectroscopy of ethyl radicals in solid parahydrogen 査読有り

T. Kumada, J. Kumagai, T. Miyazaki

J. Chem. Phys. 114 巻 ( 22 ) 頁： 10024-10030 2001年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

High-resolution electron spin resonance (ESR) spectrum of ethyl radicals isolated in solid parahydrogen (> 99.5 mol %) has been measured in the temperature range between 3.1 and 6.7 K. This study was carried out by UV photolysis of ethyl iodide doped in solid parahydrogen. Although ESR linewidth of the spectrum is broadened due to anisotropic terms of hyperfine interactions, the linewidth measured in parahydrogen remains comparable to that of the isotropic spectrum measured in liquid ethane [R. W. Fessenden, J. Chem. Phys. 37, 747 (1962)]. Small splittings were found in the resolved ESR signals and assigned as ethyl radicals with A(A',A') and E(E',E') symmetries, respectively. The ratio in the ESR intensities is not proportional to that of the degeneracy of each symmetry but varies as a function of temperature. We measured the signal intensities as a function of temperature and determined the rotational energy level splitting of methyl groups between the lowest with the A(A('),A(')) symmetry and the second-lowest with the E(E-',E-') symmetry in solid parahydrogen to be 5.3 +/-0.7 K. The level splitting is close to that measured by infrared-absorption study in gas phase and theoretical calculation, whereas the splitting measured in conventional matrices have been much smaller. Intermolecular interaction between guest radicals and surroundings in solid parahydrogen are found to be much smaller than those in other conventional matrices giving less shifted spectral parameters.

DOI： 10.1063/1.1370080

ESR, ENDOR and ESEEM spectroscopy study on local structure and motion of reactants: highly selective tunneling radical abstraction in neopentane-ethane mixture 査読有り

Jun Kumagai, Yoshiteru Itagaki, Masanobu Ishizuka, Takayuki Kumada, Anders Lund, Tetsuo Miyazaki

J. Phys. Chem. A 105 巻 ( 14 ) 頁： 3652-3657 2001年4月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Local structures and motions of radical reactants in highly selective tunneling abstraction reaction in neopentane-ethane mixture are investigated with CW-ESR, ENDOR, and ESEEM spectroscopy at different temperatures. H atoms produced by the radiolysis of neo-C5H12 in the neo-C5H12-C2H6 (2 mol %) mixtures above 40 K react selectively with the solute C2H6 to give ethyl radicals. The selective reaction is suppressed below 30 K. The local structures of neopentane matrix around neopentyl and ethyl radicals are approximately the same in the temperature range from 4.4 to 45 K. Although neopentyl radicals are rigidly trapped below 100 K, ethyl radicals in neopentane matrix begin to librate even at 6 K and increase the degree of motion up to 30 K, Finally, the librating motion of the ethyl radicals in neopentane matrix is vigorous above 40 K. The ethane molecule can take more favorable orientation for the hydrogen abstraction reaction by H atoms than rigid neopentane molecules by the vigorous libration motion, resulting in the selective reaction with H atoms.

DOI： 10.1021/jp003396+

Controlling factors of tunneling reactions in solid hydrogen at very low temperature 査読有り

Tetsuo Miyazaki, Jun Kumagai, Takayuki Kumada

Radiat. Phys. Chem. 60 巻 ( 4-5 ) 頁： 381-387 2001年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

The recent studies on tunneling reactions: of our group are;auto-reviewed. The local structure around reactants, the new temperature effect. and the impurity effect are pointed out as important controlling factors of tunneling reactions in the solid phase. The distances between H(D) atoms and H-2(HD. D,) molecules in solid hydrogen and solid argon M ere estimated by ESR, electron nuclear double resonance (ENDOR), and electron spin echo (ESE). The temperature effects on tunneling reaction were observed in a reaction D + HD --> D-2 + H in solid HD. A mechanism of a vacancy-assisted tunneling reaction has been proposed to account for the temperature effect. The strange temperature dependence of a tunneling electron-transfer-reaction H-2(-) + H-2 + H-2(-) was explained in terms elf the phonon-scattering effect and the impurity effect on the tunneling reaction. The rate constant fur a tunneling reaction H + p-H-2 --> p-H-2 + H in solid para-H-2 (p-H-2) decreases with the increase in the concentration of ortho-H-2 (o-H-2). The results were explained by the model that the orientational defects: by o-H-2 molecules affect the tunneling reaction H + p-H-2. A tunneling reaction at very low temperature gives a surprising example in control of a reaction that a small amount of energy as such 2 cal mol(-1) can affect the rate of a reaction. The tunneling reaction in the solid phase. which can be considered as a multidimensional tunneling phenomenon. is affected significantly by the condition surrounding reactants.

DOI： 10.1016/S0969-806X(00)00413-8

Resonance effect on the tunneling reaction: H+H₂ -> H₂+H in solid hydrogen 査読有り

T. Kumada, S. Mori, T. Nagasaka, J. Kumagai, T. Miyazaki

J. Low Temp. Phys. 122 巻 ( 3-4 ) 頁： 265-277 2001年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

The tunneling abstraction reaction: H + H-2 --> H-2 + H in gamma -irradiated solid hydrogen has been studied using electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) spectroscopy and gas-chromatography. The rate constant for the tunneling reaction in solid hydrogen was found to decrease with the increase in the concentration of ortho-H-2 molecules in solid hydrogen. We concluded that the decrease in the rate constant is clue to the energy level mismatching between reactant species of H + H-2 trapped and product species of H-2 + H trapped in the reverse induced by inhomogeneous intermolecular interactions between ortho-H-2 molecules in solid hydrogen. This result indicates that resonance effects play an important role in tunneling reactions in solids.

DOI： 10.1023/A:1004840631947

Electron spin echo study of long-lived radicals which cause mutation in gamma-ray irradiated mammalian cells. 査読有り

Jun Kumagai, Takayuki Kumada, Masami Watanabe, Tetsuo Miyazaki

Spctrochimica Acta. A. 56 巻 ( 13 ) 頁： 2509-2516 2000年11月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Long-lived radicals, produced by gamma -ray irradiation of mammalian cells at room temperature, cause mutation and morphological transformation in the cells. The local environment near the long-lived radicals in irradiated cells was investigated here by the analysis of electron spin echo envelope modulation (ESEEM) spectra. The number of hydrogen (deuterium) atoms surrounding the long-lived radical, which may correspond to the number of water molecules, was estimated roughly as one or two. It is postulated that the long-lived radicals are generated in the interior of biopolymers. The radicals are not produced by the reaction of OH radicals, but mainly by the decomposition of biopolymer which absorbed directly the energy of the ionizing radiation

DOI： 10.1016/S1386-1425(00)00360-7

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