Yields of SSB and DSB induced in DNA by Al K ultrasoft X-rays and α-particles: comparison of experimental and simulated yields

Abstract

Purpose : To compare experimental yields of single strand breaks (SSB) and double strand breaks (DSB) induced in plasmid DNA in aqueous solution by f -particles and Al K ultrasoft X-rays (USX) with the corresponding yields, generated via computer simulations, for a range of mean diffusion distances of the hydroxyl radical (OH). Materials and methods : Aerobic, aqueous solutions of plasmid DNA were irradiated at 277K with 238 Pu f -particles or USX in the presence of 10 -4 to 0.33 mol dm -3 Tris and the yields of SSB and DSB determined by gel electrophoresis. Computer simulations, using Monte Carlo track-structure codes for 1.5keV electrons (CPA100) and 3.2MeV f -particle track segments (PITS), were used to obtain yields of DNA SSB and DSB at different OH scavenger conditions. Results : The experimental yield of SSB and DSB induced by AlK USX and SSB induced by f -particles and the dependences on the mean diffusion distance of the OH are in reasonable agreement with the corresponding simulated yields and their corresponding dependences. However, for DSB induced by f -particles, a significant systematic difference exists between the simulated and experimental yields over the full OH scavenging range, with the simulated yields being a factor of two to three greater than the experimental values. Conclusion : That the simulated yields of strand breaks are generally in reasonable agreement with those determined experimentally over a wide range of OH scavenging capacities, increases confidence in the use of these simulations as a valuable source of quantitative, mechanistic information on DNA damage induced at very low radiation doses.