Calculation of range and distributions of damage to DNA by high- and low-LET radiations

Data are presented for the distribution and complexity of damage in DNA by radiations of high- and low-LET. The results of two methods of calculation are described: (a) tracks of alpha particles and electrons were examined for clusters of ionizations of differing complexity in spherical volumes of DNA size targets; (b) patterns of energy depositions in sugar/phosphate moiety and the bases were converted to events which may or may not lead to DNA damage. The patterns were examined for the distribution of a number of damage sites and the lengths of the damage segments in DNA. The results indicate that the majority of damage in short segments of DNA are simple and the frequency of more complex damage types is very low. The data suggest that biophysical modeling should be carried-out in higher order structures of DNA such as chromatin fiber