Abstract
DNA base radicals were examined around oxygen K-edge region using an EPR spectrometer installed in a synchrotron soft X-ray beamline (BL23SU) in SPring-8. In situ measurements of EPR spectrum of guanine and thymine revealed that short-lived transient radical species are induced by photoexcitation of O 1s electron to σ * orbital. They promptly disappear by “beam-off”. On the other hand, long-lived radicals whose EPR spectra are consistent with previous reports for guanine cation and thymine anion radical are accumulated during the irradiation. These results indicate that chemically stable DNA base lesions, such as 8-oxo-G, would result from transient species that are inferred to be one electron oxidized radicals after decay of Auger final state.
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