Monte Carlo simulation of direct and indirect effects of radiation on DNA target structure

A new theoretical model for estimating yields of DNA strand break induced by several monoenergetic electrons is presented. It is based on the Monte-Carlo track structure simulation and on new DNA structure models (1 turn of double-strand DNA, nucleosome, solenoid), and links physical and chemical stages of radiation action. Direct and indirect effects are strictly distinguished. Some results of calculations indicated: (i) The number of single strand breaks per nucleus (6 μmφ) per Gy in pure water was about ten times that in a cell environment. (ii) The contribution of indirect effects to total damage decreased as the order of the DNA target model structure used in the simulation increased (e.g., a 1-turn model of double-strand DNA, ∼98.4%; but 30 nm solenoid model, ∼86.1%). The present study indicated that the information from morphological and biochemical examinations of the cell environment must be considered more carefully in computer simulation