Biochemical mechanisms and clusters of damage for high-LET radiation.

Using mechanisms of indirect and direct radiation, a generalized theory has been developed to account for strand break yields by high-LET particles. The major assumptions of this theory are: (i) damage at deoxyribose sites results primarily in strand break formation and (2) damage to bases leads to a variety of base alterations. Results of the present theory compare well with cellular data without enzymatic repair. As an extension of this theory, we show that damage clusters are formed near each double strand break for high-LET radiation only. For 10 MeV/n (LET = 450 keV/micrometer) neon ions, the results show that on average there are approximately 3 additional breaks and approximately 3 damaged bases formed near each double strand break. For 100 MeV/n helium ions (LET = 3 keV/micrometer), less than 1% of the strand breaks have additional damage within 10 base pairs.