The Formation of Photoreactivable Damage by Direct Excitation of DNA in X-irradiatedE. ColiCells

Abstract
The role of the direct excitation process in the formation of photoreactivable damage (pyrimidine dimers) in E. coli WP2 hcrexr cells has been studied. The pyrimidine dimers were detected by photoreactivation following anoxic irradiation by X-rays (220 kVp). The dose modifying factor (DMF) is 1·28 ± 0·09. A biophysical model is used for a theoretical examination of the importance of the direct excitation process in the formation of photoreactivable damage and the experimental data are consistent with this model.