title: An approach to modelling radiation damage by fast ionizing particles.
abstract: This paper presents a statistical approach to modelling the damaging effects of radiation by fast heavy ionizing particles in small biological structures such as enzymes, viruses, and some cells. Irreparable damage is assumed to be caused by the occurrence of ionizations within sensitive regions of a structure. For structures containing double-stranded DNA, one or more ionizations occurring within each strand of the DNA will cause inactivation; for simpler structures without double-stranded DNA a single ionization within the structure will be sufficient for inactivation. Damaging ionizations occur along tracks of primary irradiating particles or along tracks of secondary particles released at primary ionizations. An inactivation probability is derived for each damage mechanism, and is expressed in integral form in terms of the radius of the biological structure (assumed spherical), the rate of ionization along primary tracks, and the maximum energy for secondary particles. The performance of each model is assessed by comparing results from the model with results derived from data from various experimental studies extracted from the literature. For the simpler structures, where a single ionization is sufficient for inactivation, the model gives qualitatively promising results. However, for larger more complex structures containing double-stranded DNA, the model requires some further refinements.
mesh_terms: D004247:DNA / Q000528:radiation effects; D004249:DNA Damage; D004798:Enzymes / Q000528:radiation effects; D008954:Models, Biological; D008962:Models, Theoretical; D011832:Radiation Injuries / Q000209:etiology*; D014780:Viruses / Q000528:radiation effects
chemical_list: D004798:Enzymes; D004247:DNA