Simulation Study On DNA Strand Breakage Induced By Proton Radiation

DNA is one of the most important targets for radiation in biological tissues,so it is very important to study the interaction between the proton and the DNA molecule near the Bragg peak for the application of proton in the carcinogenesis of radiation.Cells can be approximately regarded as one composed of water and DNA,protein,and other macromolecules in the solution environment.The damage of ionizing radiation to DNA can be divided into the direct effect of the direct transfer of energy to the biological macromolecules,and the indirect effect of the high activity free radicals produced by radiolysis of water to the damage of biomolecules.Proton irradiation of the energy near Bragg peak causing DNA direct damage and indirect damage were simulated in this paper.The damage points,single strand breaks and double strand breaks were calculated,and the damage mechanism of DNA and the proportion of direct and indirect damage were calculated.Finally use the improved simulation method of direct and indirect injury,compare strand break yield and relative biological effect induced by protons and alpha particles of the same linear energy transfer,thus characterize the severity of the biological effects of two types of radiation on the human body to a certain extent.For the simulation of DNA direct and indirect total damage,this paper makes an improvement on the DNA method,which is based on the research of Francis,which can be used in the simulation of low energy and high energy domain,which is consistent with the real DNA damage mechanism.For the DNA direct damage simulation,this paper simplifies the DNA model,improves the simulation efficiency,and distinguishes SSSB,CSSB,SDSB,CDSB damage types.By comparing DNA direct damage and indirect injury simulation results induced by proton irradiation,we found that in the aqueous environment,free radicals play a leading role in the production of single and double strand breaks,the direct effect of energy deposition induce only a small part of single and double strand breaks.And the direct and indirect effect induced strand break yields are related to the linear energy transfer of incident particles and cell moisture.Based on the analysis of the change of the chain fracture yield caused by different energy proton irradiation,it is found that the DNA strand breaks are mainlydominated by the easily repaired SSB,but the low energy protons can induce more double strand breaks of DNA molecules.By comparing the results of DNA damage induced by protons and alpha particles in the same linear energy transfer,it is found that the DSB yields difficult to repair produced by the alpha particles are more than proton,and the biological effects of DNA double strand breaks are also more serious.