The Influence of DNA Configuration on the Direct Strand Break Yield.

M A Bernal,C Champion,Z Francis,C E Dealmeida,V Ivanchenko,S Incerti

doi:10.1155/2015/417501

Abstract

Purpose. To study the influence of DNA configuration on the direct damage yield. No indirect effect has been accounted for. Methods. The GEANT4-DNA code was used to simulate the interactions of protons and alpha particles with geometrical models of the A-, B-, and Z-DNA configurations. The direct total, single, and double strand break yields and site-hit probabilities were determined. Certain features of the energy deposition process were also studied. Results. A slight increase of the site-hit probability as a function of the incident particle linear energy transfer was found for each DNA configuration. Each DNA form presents a well-defined site-hit probability, independently of the particle linear energy transfer. Approximately 70% of the inelastic collisions and ~60% of the absorbed dose are due to secondary electrons. These fractions are slightly higher for protons than for alpha particles at the same incident energy. Conclusions. The total direct strand break yield for a given DNA form depends weakly on DNA conformation topology. This yield is practically determined by the target volume of the DNA configuration. However, the double strand break yield increases with the packing ratio of the DNA double helix; thus, it depends on the DNA conformation.

Highlights

The mechanisms by which ionizing radiation induces damage in DNA are very complex and multifaceted, going through physical, physicochemical, and biological stages, from the chronological point of view
It can be observed that, for the 7 MeV alpha particle case (LET∼100 keV/μm), there is an appreciable increase in the total strand break (TSB) yield for all the DNA conformations
For a given event cluster size and extension, which is related to the LET, the DNA conformation with the highest linear bp density would exhibit the highest probability of producing a double strand break (DSB), as seen in Figure 2

Summary

Introduction

The mechanisms by which ionizing radiation induces damage in DNA are very complex and multifaceted, going through physical, physicochemical, and biological stages, from the chronological point of view. In atomistic DNA geometrical models [3], the volume of the target to be impacted by the radiation to induce a strand break is defined by the union of all the atoms making up the sugar-phosphate groups. This target definition will be used throughout this document. The atom size can be estimated by the corresponding van der Waals radius

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