Modelling of radiation-induced DNA damage: the early physical and chemical event.

A Monte Carlo track structure calculation of single- and double-strand breaks induced by direct energy deposition in DNA and by interacting diffusible .OH radicals with DNA has been made for low energy electrons. The .OH radicals generated within 4 nm of linear segments of DNA were diffused in order to mimic the mean diffusion distance in the cellular environment. The reactions of the radical species .OH, .H and e-aq were included in this study. The calculated values for the yield of single- and double-strand breaks have been compared with experimentally determined values from the literature. The calculations indicate, too, that the majority of dsb have additional associated damage, constituting clustered lesions of varying complexity.