Akamatsu, K. and Yokoya, A. X-Ray Absorption near Edge Structures of DNA or its Components around the Oxygen K-shell Edge.

The initial process of radiation damage in DNA was investigated by measuring the X-ray absorption near edge structures (XANES) within the energy region around the oxygen K-shell absorption edge for DNA, cytosine and 2-deoxy-d-ribose. Irradiation and XANES experiments were performed with the BL23SU soft X-ray beamline, using synchrotron radiation from the 8 GeV electron storage ring at SPring-8. Samples were mounted on gold-coated plates in a vacuum chamber. The XANES spectra were obtained by measuring the photoelectron current of the samples. 2-Deoxy-d-ribose was exposed to X rays at the absorption peak corresponding to the oxygen (O) 1s→σ* transition energy (538 eV); the XANES spectra were obtained after each irradiation. DNA and cytosine, possessing characteristic XANES spectra, both had two major energy bands corresponding to the O 1s→π* and 1s→σ* transitions. Two new peaks appeared and gradually increased in the XANES spectra of 2-deoxy-d-ribose during irradiation. These results suggest that C–O bonds in 2-deoxy-d-ribose are transformed to C=O bonds by O 1s→σ* transition, suggesting that the molecules undergo chemical changes into carbonyl-containing compounds.