研究者詳細 - 熊谷　純

論文 - 熊谷　純

分割表示 79 件中 21 - 40 件目／全件表示 >>

Suppressive effect of ascorbic acid on the mutagenesis induced by the bystander effect through mitochondrial function 査読有り

G. Kashino, Y. Tamari, J. Kumagai, K. Tano, M. Watanabe

Free Radic. Res. 47 巻 ( 6-7 ) 頁： 474-479 2013年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

We focused on suppressive effect of ascorbic acid (AsA) on changes in mitochondrial function and mutagenesis by the radiation-induced bystander eff ect (RIBE). In mammalian cell lines, medium transfer assay was performed and conditioned medium including secreted factors after X-irradiation were examined to detect the RIBE. We found that the membrane potential and increased levels of superoxide radical (O-2(-)) in mitochondria were modulated in cells treated with conditioned medium from irradiated cells. The result of the present study also demonstrated that increases in reactive oxygen species (ROS) levels led to the induction of gene mutations. Interestingly, the modulations in mitochondria, in addition to mutation inductions by RIBE, were completely suppressed by treatment with AsA in cells treated with conditioned medium. These results suggest that mutagenesis, which may have resulted from secreted factors involving the RIBE, may be induced by ROS that are localized in mitochondria and may be relieved by AsA.

DOI： 10.3109/10715762.2013.791025

Reaction Mechanism of Aromatic Ring Amination of Benzene and Substituted Benzenes by Aqueous Ammonia over Platinum-Loaded Titanium Oxide Photocatalyst 査読有り

H. Yuzawa, J. Kumagai, H. Yoshida

J. Phys. Chem. C 117 巻 ( 21 ) 頁： 11047-11058 2013年5月

A heterogeneous palladium catalyst hybridised with a titanium dioxide photocatalyst for direct C-C bond formation between an aromatic ring and acetonitrile 査読有り

H. Yoshida, Y. Fujimura, H. Yuzawa, J. Kumagai, T. Yoshida

Chem. Commun. 49 巻 ( 36 ) 頁： 3793-3795 2013年3月

Electrical properties of lead-free ferroelectric Mn-Doped K0.5Na0.5NbO3-CaZrO3 thin films prepared by chemical solution deposition 査読有り

T. Matsuda, W. Sakamoto, B.Y. Lee, T. Iijima, J. Kumagai, M. Moriya, T. Yogo

51 巻 ( 9 ) 頁： 09LA03 2012年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

Lead-free ferroelectric K0.5Na0.5NbO3-CaZrO3 thin films were prepared by chemical solution deposition. Chemically optimized K0.5Na0.5NbO3-CaZrO3 precursor thin films crystallized in the perovskite single phase on Pt/TiOx/SiO2/Si substrates at 650 degrees C. The K0.5Na0.5NbO3-CaZrO3 thin films showed poor ferroelectric polarizations due to the insufficient insulating resistance. The leakage current of the K0.5Na0.5NbO3-CaZrO3 films, especially in the high-applied-field region, was markedly reduced by 1 mol % Mn doping for the Nb site. Also, the ferroelectric properties of the K0.5Na0.5NbO3-CaZrO3 thin films depended on CaZrO3 concentration. 1 mol % Mn-doped K0.5Na0.5NbO3-CaZrO3 thin films exhibited slim and small ferroelectric polarization-electric field (P-E) hysteresis loops at room temperature with an increase in CaZrO3 amount. Furthermore, these films showed a typical field-induced displacement curve with a small hysteresis, and the estimated effective d(33) values were 32 pm/V for the 1 mol % Mn-doped 0.95K(0.5)Na(0.5)NbO(3)-0.05CaZrO(3) thin films and 21 pm/V for the 1 mol % Mn-doped 0.9K(0.5)Na(0.5)NbO(3)-0.1CaZrO(3) thin films.

DOI： 10.1143/JJAP.51.09LA03

The Bystander Effect is a Novel Mechanisms of UVA-Induced Melanogenesis 査読有り

H. Nishiura, J. Kumagai, G. Kashino, T. Okada, K. Tano, M. Watanabe

88 巻 ( 2 ) 頁： 389-397 2012年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

We successfully identified the bystander effect in B16 murine melanoma cells exposed to UVA irradiation. The effect was identified based on melanogenesis following the medium transfer of the B16 cells, which had been cultured for 24 h after being exposed to UVA irradiation, to nonirradiated cells (bystander cells). Our confirmation study of the functional mechanism of bystander cells confirmed the reduced levels of mitochondrial membrane potential 14 h after the medium transfer. In addition, we observed increased levels of intracellular oxidation after 912 h, and the generation of melanin radicals, including long-lived radicals, 24 h after medium transfer. Further analysis of bystander factors revealed that the administration of EGTA treatment at the time of medium transfer led to an inhibition of melanogenesis and to neutralization of the mitochondrial membrane potential level, as well as to the restoration of intracellular oxidation levels to those of controls. The results demonstrated that the UVA irradiation bystander effect in B16 cells, as indicated by melanogenesis, was induced by the increase in intracellular oxidation due to the mitochondrial activity of calcium ions, which were among the bystander factors involved in the increase.

DOI： 10.1111/j.1751-1097.2011.01046.x

放射線誘導長寿命ラジカルが DNA 損傷を起源としない発がん経路の引き金招待有り査読有り

渡邉正己, 菓子野元郎, 熊谷　純

放射線化学 93 巻頁： 15-22 2012年3月

Negative and positive ion trapping by isotopic molecules in cryocrystals in case of solid parahydrogen containing electrons and H6+ radical cations 査読有り

Y. Shimizu, M. Inagaki, T. Kumada, J. Kumagai

132 巻 ( 24 ) 頁： 244503 2010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）

We performed electron spin resonance studies of trapped electrons and H-6(+) radical cations produced by radiolysis of solid parahydrogen (p-H-2), p-H-2-ortho-D-2 (o-D-2), and p-H-2-HD mixtures. Yields of trapped electrons, H-6(+) radical cations, and its isotopic analogs H6-nD(n)(+) (4 >= n >= 1) increased with increasing o-D-2 and HD concentrations in solid p-H-2. Electrons were found trapped near an o-D-2 or an HD in solid p-H-2 due to the long-range charge-induced dipole and quadrupole interactions between electrons and isotopic hydrogen molecules. H-6(+) radical cations diffuse in solid p-H-2 by repetition of H-6(+)+H-2 -> H-2+H-6(+) and are trapped by ortho-D-2 or HD to form H6-nDn+ (4 >= n >= 1) as isotope condensation reactions. Decay behaviors of these cations by the repetition, isotope condensation, and geminate recombination between electrons and H6-nDn+ (4 >= n >= 0) were reproduced by determining the corresponding reaction rate constants k(1), k(2), and k(3). Values of 0.045 and 0.0015 L mol(-1) min(-1) were obtained for k1 (H-6(+)+D-2 -> H-2+H4D2+) and k(2) (H4D2++D-2 -> H-2+H(2)D4+), respectively, and the value was quasinull for k(3) (H(2)D4++D-2 -> H-2+D6+). These rate constants suggest that hole mobility drastically decreased in the repetition reaction when H-6(+) radical cations acting as hole carriers formed H4D2+ or H(2)D4+. HD and D-2 molecules, therefore, act as electron and hole acceptors in irradiated solid p-H-2-o-D-2 and p-H-2-HD mixtures.

DOI： 10.1063/1.3432780

照射培地移動による放射線バイスタンダー効果を遅発性長寿命ラジカルから探る査読有り

熊谷　純、菓子野元郎

放射線化学 89 巻頁： 20-24 2010年3月

Improvement in Ferroelectric Properties of Chemically Synthesized Lead-Free Piezoelectric (K,Na)(Nb,Ta)O3 Thin Films by Mn Doping 査読有り

N. Kondo,W . Sakamoto, B.Y. Lee, T. Iijima, J. Kumagai, M. Moriya T. Yogo

Jpn. J. Appl. Phys. 49 巻頁： 09MA04 2010年

*固体パラ水素中の H6+同位体イオンと捕捉電子の放射線化学招待有り査読有り

清水裕太、熊谷　純

放射線化学 87 巻頁： 23-33 2009年3月

Electron spin resonance spectroscopy of molecules in large precessional motion: A case of H6+ and H4D2+ in solid parahydrogen 査読有り

Yuta Shimizu, Takayuki Kumada, Jun Kumagai

J. Mag. Reson. 194 巻 ( 1 ) 頁： 76–80 2008年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

We have measured electron spin resonance (ESR) spectra of H-6(+) and H4D2+ tons produced in gamma-ray irradiated solid parahydrogen. Anisotropic hyperfine-coupling constants for H-6(+) and H4D2+ determined by the analysis of ESR lines at 4.2 K were -0.06 and -0.12 mT, respectively, which were opposite in sign to and much smaller than theoretical results of 1.17-1.25 mT. Although no change was observed in H-6(+), the constant for H4D2- increased to be 1.17 mT at 1.7 K, which is very close to the theoretical value. We concluded that H-6(-) both at 4.2 and 1.7 K and H4D2+ at 4.2 K should be in a large precessional motion with the angle of 57-59 degrees, but the precession of H4D2+ is stopped at 1.7 K.

DOI： 10.1016/j.jmr.2008.05.024

*放射線照射後に細胞中で生じてくる遅発性長寿命ラジカルと遅延放射線生物影響招待有り

熊谷　純

電子スピンサイエンス 6 巻 ( 11 ) 頁： 109-115 2008年9月

H atom, e(-), and H(6)(+) ions produced in irradiated solid hydrogens: An electron spin resonance study 査読有り

T. Kumada, Y. Shimizu, T. Ushida, J. Kumagai

Radiat. Phys. Chem. 77 巻 ( 10-12 ) 頁： 1318-1322 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）

We carried out electron spin resonance (ESR) study of irradiated solid H(2) and para-H(2). H-atom, e(-), and H(6)(+) lines were observed. The H-atom radicals diffuse in solid H2 by the tunneling chemical reaction H+H(2) -> H(2)+H below 4 K, and by the thermally activated process above 5 K. These decay via H-H recombination. Yield of trapped electrons e- produced by the radiolysis of solid para-H2 increases with increase in the concentration of added isotopic hydrogen, HD or D(2). These decay via geminate recombination with positive ions with a half-life of 8 h at 4 K. H(6)(+) ion is an ionic hydrogen radical whose spectrum has firstly been observed in irradiated solid para-H(2). H(6)(+) ions diffuse in solid H2 by sequence of H(6)(+)+H(2) -> H(2)+H(6)(+) reactions, and terminate by the isotope-exchange reaction H(6)(+)+HD -> H(5)D(+)+H(2) or H(6)(+)D(2) -> H(4)D(2)(+)+H(2). Unlike H(6)(+), isotopically substituted H(5)D(+) and H(4)D(2)(+) cannot diffuse in solid para-H(2). Rate-determining step of their decay is charge recombination with e(-).

DOI： 10.1016/j.radphyschem.2008.05.026

放射線照射後に細胞中で生じてくる遅発性長寿命ラジカルと遅延放射線生物影響招待有り

熊谷　純

電子スピンサイエンス 6 巻頁： 109-115 2008年

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

　前のページ - 次のページ　

<熊谷 純>

論文 - 熊谷 純

<熊谷　純>

論文 - 熊谷　純