分光学的アプローチによる放射線によるゲノム損傷と生体修復の研究

Spectroscopic approaches to study DNA damage induced in genome exposed to ionizing radiation and its enzymatic repair

横谷 明徳; 藤井 健太郎; 岡 壽崇   ; 渡辺 立子

Yokoya, Akinari; Fujii, Kentaro; Oka, Toshitaka; Watanabe, Ritsuko

It has been predicted by computer track simulation studies that complex DNA damage, so called clustered DNA damage sites, is produced along the tack particularly of high LET ions. The clustered DNA damage is thought to compromise DNA repair enzymes. We have revealed that the nucleobase lesions produced by He ion impact to simple model DNA (plasmid) are hardly processed by base excision repair enzymes. Using a synchrotron radiation facility (SPring-8), we have studied unpaired electron species or desorbed ions as intermediates of DNA damage using an EPR apparatus or mass spectrometer installed in a soft X-ray beamline. These aspects are compared with the yields of final products of DNA strand breaks or base lesions revealed biochemical techniques. Models of complex DNA damage induction will be proposed considering various modification factors of the damage induction, ionization of valence and inner-shell electrons, OH radicals, hydration layer and the impact of secondary electrons.