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Kai, Takeshi; Higuchi, Mariko; Fujii, Kentaro; Watanabe, Ritsuko; Yokoya, Akinari
International Journal of Radiation Biology, 88(12), p.928 - 932, 2012/12
Times Cited Count：1 Percentile：12.53(Biology)Fujii, Kentaro; Yokoya, Akinari
no journal, ,
Inner-shell photoabsorption spectroscopy has been used as one of powerful technique providing us information of chemical environment around a target atom. We have investigated the change of the spectra of the near edge X-ray absorption fine structure (NEXAFS) of DNA exposed to monochromatic soft X-rays. We used calf thymus DNA thin films as samples and observed N K-shell and O K-shell NEXAFS spectral changes. The typical monochromatic soft X-ray energies used for the irradiation (380, 435, 560, and 760eV) were obtained from SPring-8, BL23SU. The observed spectra show the initiation of the new products and the dissociation of molecular structure of the DNA by the irradiation. By comparing the spectral changes in NEXAFS with the yields of base lesions and strand breaks, we will discuss the molecular structure of DNA damage site and the site-selectivity of damage induction in DNA by soft X-rays.
Fujii, Kentaro; Fujii, Shinichiro*; Akimitsu, Nobuyoshi*; Tsukimoto, Mitsutoshi*; Kojima, Shuji*
no journal, ,
ATP (Adenosine tri-phosphate), one of ribonucleic acids, acts as an intracellular energy transfer. ATP is used as a substrate to synthesized messenger RNA and as a ligand of inter-cellular signaling. SPring-8 beam line BL23SU can produce high resolution monochromatic soft X-rays. In this study, we analyzed the soft X-ray induced radiation damage of ATP by various biological assessments, such as energy donor activity, genetic information transfer activity and inter-cellular signaling activity.
Oka, Toshitaka; Yokoya, Akinari; Fujii, Kentaro
no journal, ,
no abstracts in English
Yokoya, Akinari; Sugaya, Yuki; Fujii, Kentaro; Oka, Toshitaka; Watanabe, Ritsuko; Kai, Takeshi
no journal, ,
In order to obtain experimental evidences of an AP site produced by soft X-ray absorption and succeeding Auger effect in a vacuum condition, we measure the yield of AP sites visualized by the treatment of irradiated plasmid DNA with endonuclease IV (Nfo), which converts an AP site to detectable single strand break. Several photon energies around oxygen K-edge regions are tested to estimate the yield of AP site. The irradiated plasmid DNA samples have also been analyzed to determine the yield of SSBs and nucleobase lesions visualized by base excision repair proteins. The yield of AP site is significantly smaller than the other damage yields (15% or less of total damage). These experimental evidences show that direct effect of photoabsorption and impact of succeeding Auger electrons to DNA does not significantly produce an AP site. AP sites might be mainly induced via reaction with OH radicals produced in water layer surrounding DNA.
