The effect of In radionuclide distance and auger electron energy on direct induction of DNA double-strand breaks: a Monte Carlo study using Geant4 toolkit.

Purpose: In this study, the effect of In position and Auger electron energy on direct induction of DSBs was investigated.

Materials And Methods: The Geant4-DNA simulation toolkit was applied using a simple B-DNA form extracted from PDBlib library. First, the simulation was performed for electrons with energies of In and equal emission probabilities to find the most effective electron energies. Then, In Auger electrons' actual spectrum was considered and their contribution in DSB induction analysed.

Results: The results showed that the most effective electron energy is 183 eV, but due to the higher emission probability of 350 eV electrons, most of the DSBs were induced by the latter electrons. Also, it was observed that most of the DSBs are induced by electrons emitted within 4 nm of the central axis of the DNA and were mainly due to breaks with <4 base pairs distance in opposing strands. Whilst, when In atoms are very close to the DNA, 1.3 DSBs have been obtained per decay of In atoms.

Conclusions: The results show that the most effective Auger electrons are the 350 eV electrons from In atoms with <4 nm distance from the central axis of the DNA which induce ∼1.3 DSBs per decay when bound to the DNA. This value seems reasonable when compared with the reported experimental data.