Nucleobase lesions and strand breaks in dry DNA thin film selectively induced by monochromatic soft X-rays

Fujii, Kentaro; Shikazono, Naoya; Yokoya, Akinari

In order to verify the possibility of selective damage induction in DNA, the yields of base lesions as well as strand breaks have been measured in dry plasmid DNA films irradiated with highly monochromatized soft X-rays in the energy region of 270-760 eV, which includes the carbon, nitrogen and oxygen K-edges. Our results strongly suggest that (1) the K-shell ionization of oxygen in both the nucleobases as well as in other parts of DNA and in the hydrating water molecules bound to DNA, but not the K-shell ionization of nitrogen in the nucleobases, most likely contributes to the induction of nucleobase lesions, and (2) migration of electrons and holes are involved differentially in the production of each type of DNA lesion. These results could potentially lead to new methods for selective induction of specific types of DNA damage through tuning the energy of soft X-rays.