Computer simulation of damage induced in DNA by radiation with high linear energy transfer

The molecular nature of primary lesions in DNA is important for an understanding of cellular responses to radiation exposure and their dependence on dose, dose rate, and radiation quality. Full characterization of the physicochemical alterations induced by absorption of radiation in mammalian chromatin will ultimately require a much larger data base of interaction probabilities and reaction rates than is presently available; however, progress can be made on the basis of their current understanding of spatial patterns of energy deposition by ionizing radiation and their geometric relation to chromatin structure. Since energy transfer from radiation to matter is a stochastic process, research in this area generally involves (i) computer simulation by Monte Carlo techniques of the slowing down of ions and electrons in biologically relevant materials, (ii) scoring energy deposited in well-defined volumes that model the elements of chromatin structure, and (iii) mathematical models of the chemical and biological changes induced by the absorbed energy. These techniques have been successfully employed to predict the yield of free radicals in oriented fibers of DNA by exposure to neutrons and the production of single- and double-strand breaks in DNA by 125I decays