DNA damage spectra for He ion beam and ultrasoft X-rays compared with that for Co-60 -rays

Akamatsu, Ken; Fujii, Kentaro; Yokoya, Akinari; Wada, Seiichi*; Kobayashi, Yasuhiko

High-dense radical field formed by high- LET radiations and short track electrons emitted from DNA constituent atoms by ultrasoft X- (USX-) irradiation have been suggested to produce severe DNA damage. The aim of this study is to clarify the difference of DNA damage induced by 4He ion beam and USX from that by Co-60 -rays. We have recently attended to unaltered base release, strand break terminus and base lesion, focusing on the effect of nitrogen and oxygen K-shell electron ionization in the USX experiments. The yields of unaltered bases released were determined by HPLC. To quantify and characterize the strand break termini, the digestion rates of the irradiated DNA pretreated with or without calf intestinal alkaline phosphatase by snake venom phosphodiesterase (SVPD) were measured.