Calculation of DNA Strand Breaks by Types of Electron Interaction with Monte Carlo Simulation

In cancer treatment with radiation, the objective is to kill tumor cells by damaging their DNA. However, the DNA strand breaks are not yet understood by which types and energy of electron interactions they are caused. Most of Monte Carlo simulations reported in the literature consider an energy deposition in water-equivalent to cause DNA strand breaks. In recent years, DNA atomistic models were introduced but still the simulations consider energy deposition in volumes of DNA material. In the present work, we report advances in the understanding of DNA single and double strand breaks by low energy electrons, and the results of the simulations were compared to experimental data. We simulated a model of atomistic B-DNA, forming 1122 base pairs twisted and forming a length of 30 nm. Each atom has been represented by a sphere whose radius is equal to the radius of van der Waals. We repeatedly simulated 10 million electrons for each of the energies from 4 eV to 500 eV and counted each interaction type with its position x,y,z in the volume of DNA. Based on the number and types of interactions at the atomic level, the number of DNA single and double strand breaks were calculated. In addition, with our simulation, it is straightforward to discriminate the strand and base breaks as a function of radiation interaction type and energy. In conclusion, the knowledge of DNA damage at the atomic level helps, for example, to design internal therapeutic agents of cancer treatment.