Near edge X-ray absorption fine structure of DNA thin film irradiated with soft X-rays

Fujii, Kentaro; Yokoya, Akinari

To in-vestigate the mechanism of the molecular change in DNA irradiated with the soft X-rays, we have measured the spectra of the near edge X-ray absorption fine structure (NEXAFS) of DNA caused by exposure to monochromatic soft X-rays. We used a calf thymus DNA and oligonucleotide 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 760 eV) were obtained from SPring-8, BL23SU. The observed spectra showed that initiation of the new products by the irradiation in the irradiated sample and the dissociation of molecular structure of the DNA by the irradiation. By comparison of these NEXAFS spectral changes with the yields of base lesions and strand breaks as final products, we will discuss the molecular structure of DNA damage site and the site selectivity of damage induction in DNA by soft X-rays.