Simulation of ionisation clusters formed in nanometric volumes of the deoxyribose-substitute tetrahydrofuran
Purpose: To investigate the implications of using interaction cross sections of liquid water for the target volume when studying radiation action at the DNA level by particle track structure simulations. Materials and methods: Absolute interaction cross sections for low energy electrons between 20 eV and 1 keV were measured for tetrahydrofuran (THF), which is a substitute for deoxyribose. From these data a complete interaction cross section data set was derived and integrated in our PTB Track structure Monte Carlo code 'PTra'. Simulations of electron track structure in THF and water were performed and ionisation cluster size distributions in nanometric target volumes were determined. From these a nanodosimetric estimate for the probability to produce a double strand break was derived. Results: The probability distribution of ionisation cluster sizes was found to be shifted towards smaller values for a THF-filled target as compared to a water-filled one. For all electron energies investigated, the nanodosimetric estimates for double-strand break probability in the THF-filled target have lower values than for a target of liquid water. Conclusion: The preliminary results indicate that simulations based on cross sections of water would overestimate the initial direct radiation damage to the DNA.