Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yokoya, Akinari
Hoshako, 17(3), p.111 - 117, 2004/05
To reveal the mechanism of oxidative base damages, such as 8-oxo-G, in DNA molecule by ionizing radiation, DNA base radicals were examined around oxygen and nitrogen 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 base revealed that short-lived transient radical species are specifically induced by photoexcitation of a 1s electron to 
* antibonding orbital at carbonyl oxygen atom. They promptly disappear by "beam-off". On the other hand, a long-lived radical whose EPR spectrum is consistent with previous reports for guanine cation radical was accumulated during the irradiation. The yield of the stable radical decreased by 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.
Yokoya, Akinari; Akamatsu, Ken*; Fujii, Kentaro
Nuclear Instruments and Methods in Physics Research B, 99, p.366 - 369, 2003/01
no abstracts in English
Usami, Noriko*; Yokoya, Akinari; Ishizaka, Shozo*; Kobayashi, Katsumi*
Journal of Radiation Research, 42(3), p.317 - 331, 2001/09
Times Cited Count：8 Percentile：27.65(Biology)The characteristics of DNA lesions produced by the phosphorus K-shell absorption in yeast cells were studied using monochromatized soft X-rays tuned to the phosphorus K-edge peak (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, (
), which shows the temperature-sensitive dsb repair-deficient, and a wild-type strain. The repaired fraction of lesion in , which corresponds to the relative yield of dsb reparable by the 
pathway, was not affected by the phosphorus photoabsorption. 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 soft X-ray energy. These results suggest that irrepairable lesions are produced by the inner-shell photoabsorption of phosphorus in DNA, although its yield is small.
; Kawatsura, Kiyoshi; ; ; Ozawa, K.;
Journal of the Physical Society of Japan, 53(3), p.1001 - 1005, 1984/00
Times Cited Count：5 Percentile：52.21(Physics, Multidisciplinary)no abstracts in English
Kawatsura, Kiyoshi; ; Ozawa, K.; ; ;
Nuclear Instruments and Methods, 170(1-3), p.265 - 268, 1980/00
no abstracts in English
Kawatsura, Kiyoshi
Rev.Phys.Chem.Jpn., 47(2), p.69 - 79, 1977/02
no abstracts in English
Kawatsura, Kiyoshi
Rev.Phys.Chem.Jpn., 47(2), p.53 - 68, 1977/02
no abstracts in English
