AN ION-TRACK STRUCTURE MODEL APPLIED TO ESTIMATE CROSS SECTIONS FOR SV40 DNA STRAND BREAKS IN SOLUTION

摘要

A track structure model, previously reported based on experimental measurements of the spatial dose distribution in low-pressure gases, was applied to calculate cross sections for DNA strand breaks in solution. The results give a good description of the compiled data of Taucher-Scholz and Kraft for DNA single- and double-strand breaks (SSB and DSB) with a wide range of ion species in SV40 DNA irradiated in solution in vitro. For each particle the track radius t(D_(37)) was defined and calculated from the present track structure model so as that the dose at t(D_(37)) is equal to the characteristic dose D_(37) experimentally obtained using X-ray irradiation and thus within this radius the reaction occurs. Using a target radius R_0 for a SV40 viral DNA (5243 bp) molecule in solution as a parameter, the cross section is simply given: σ = π[t(D_(37)) + R_0]~2. The agreement with experiments is quite satisfactory. The present model may help us to understand the reason why "hooks" or "maximum RBE" appear when cross sections are plotted vs LET-values of bombarding particles.