An investigation of the physics mechanism based on DNA damage produced by protons and alpha particles in a realistic DNA model

Abstract

The direct effect of monoenergetic protons and alpha particles on DNA molecules, as the biological endpoint, were investigated using the Geant4-DNA extensions of the Geant4 Toolkit. two different geometries of B-DNA were simulated to confirm the importance of DNA geometry, namely an atomic model of the Protein Data Bank (PDB) and a simple water cylinder. A direct damage is produced when incident radiations deposit energy in the DNA molecule. Further, the yields of DNA Direct Single-Strand Breaks (SSB), Double-Strand Breaks (DSB), and Total-Strand Breaks (TSB) were calculated for protons and alpha particles with different incident energies. The relative biological effectiveness for the induction of direct DNA double-strand breaks (RBEDSB) was evaluated in the human cell. The SSBevent ratio was determined for each incident particle. The results from the models indicated that TSB, SSB, and DSB yields are higher for simple geometry, compared to the atomic model, and a strong dependence was found by selecting the DNA geometrical model. The SSB yield incorporated the weak dependence of SSB on the type and energy of the incident particles. In addition, based on the results, the TSB yield was approximately independent of the linear energy transfer (LET) of the incident energies while the DSB yield increased as a function of the LET. Further, the results demonstrated that the DSB yield and RBEDSB of the protons were higher for iso-LET ions, compared to the alpha particles. Finally, the contribution of secondary electrons to the creation of DSBs was equal to 83 and 74% for protons and alpha particles at the same LET value, respectively.