Repair of the double-strand breaks induced by low energy electrons: A modelling approach

Purpose: We propose a biochemical mathematical model for the repair of double-strand breaks (DSB) induced by low energy electron tracks, and determine the repair time for simple and complex DSB. Materials and methods: The track structure code KURBUC_liq was used to simulate electron tracks in liquid water. All possible sites of energy depositions and reactions of water radicals in the nucleobases of an atomistic model of DNA were located, and the types of damage were determined. The initial induced DSB were subjected to a mechanistic model of Nonhomologous end-joining (NHEJ) repair. Results: Data are presented for the initial and residual yield of DSB induced by low energy electrons. The model of repair was verified by comparing the kinetics of the unrejoined DSB with the experimental data for the V79-4 hamster cells irradiated with 15 Gy of Carbon-K (C-K) 278 eV ultrasoft X-rays. The residual unrepaired DSB in the duplex DNA is presented in the time interval up to 3 hours. The calculated repair time for the simple and complex DSB are presented. Conclusion: With the hypothesis that complex DSB take longer time to repair than the simple type DSB, the model provides an estimate of DSB repair kinetics of experimental data.