Abstract
The object of the study is to reveal whether the induction process of an abasic site (AP site) and the clustered DNA damage which contain AP sites (AP cluster) depends on ionizing density of radiation. Many studies using synthetic AP clusters incorporated into oligonucleotides reported that AP clusters retard base excision repair processes. Sutherland et al. (2002) reported that AP clusters are induced efficiently in human cells by low LET X-irradiation with the similar yields with those for the clusters which contain pyrimidine or purine base lesions. There, however, has been very little knowledge of AP sites and AP clusters induced by heavy ion beam irradiation. In order to clarify the relation between track structure of C ions (290MeV/nucleon, LET 13, 60keV/um) or X-rays and the induction processes of an AP or AP clusters, we measure the yield of AP sites visualized by the treatment of irradiated pUC18 plasmid DNA with the AP endonuclease (Nfo), which converts an AP site to detectable single strand break. Several scavenging capacities of the samples are tested to estimate the effect of indirect action of diffusible OH radicals in the induction of AP site. These experimental data will be discussed with theoretical radiation track structure in the respect of repair susceptibility of the AP cluster.
