Influence of molecular flexibility on DNA radiosensitivity: A simulation study

Radiation damage in DNA is caused mainly by hydroxyl radicals which are gen erated by ionizing radiation in water and removing hydrogen atoms from the DNA chain. This damage affects certain nucleotide sequences more than other s due to differences in the local structure of the DNA chains. This sequenc e dependence has been analyzed experimentally and calculated theoretically for a rigid DNA model. In this paper we take into account the flexibility o f the DNA chain and show how it modifies the strand breakage probabilities. We use a simple harmonic model for DNA flexibility which permits the study of a long (68 base pair) fragment with modest computational effort. The es sential influence of flexibility is an increased breakage probability towar ds the ends of the fragment, which can also be identified in the experiment al data.