EPR studies of 5-bromouracil crystal after irradiation with X-rays in the bromine K-edge region

Yokoya, Akinari; Takakura, Kaoru*; Watanabe, Ritsuko; Akamatsu, Ken*; Ito, Takashi*

Radiation Research, 162(4), p.469 - 473, 2004/10

https://doi.org/10.1667/RR3230

Radicals induced in a single crystal of 5-bromouracil (BrUra) by synchrotron soft X-rays in the Br K-edge region (13.461-13482 keV) were investigated using the X-band EPR method. The crystal was irradiated at three peak energies in the absorption spectrum at room temperature or at 80K. A hydrogen abstraction radical derived from N1 atom of the pyrimidine ring was commonly observed for all of the energies used, though with some variation in quantity. Similar characteristics were also observed in the EPR signal for the off-K-edge low energy (13.42 keV) and when Co -ray irradiation was employed as the reference. When irradiated at 80K, a much larger exposure (roughly 10 times) of soft X-rays was needed to obtain the same signal intensity as that observed at room temperature. EPR signals were not detectable with g-irradiation at liquid nitrogen temperature.