Radiation effects in living cells

Insult from ionizing radiation is in the form of microscopic tracks that are highly structured from the atomic level upwards. The internal composition of mammalian cells, too, is highly structured, from dimensions smaller than the DNA molecule (diameter ~2 nm) up to the entire cell [Formula: see text]. There is a wide spectrum of initial physical and chemical damage, subsequent biochemical modification, and final cellular response. The vast majority of the physical, chemical, and biochemical damage is apparently of little relevance to final observable cellular effects. This predominance of "irrelevant" damage masks the nature of that which is of prime relevance. Nevertheless, systematic studies of the effects of radiations on cells have revealed that there are unifying features in the observed responses of different cell types to induction of different effects, and by different radiations. This implies that there are dominant mechanisms that are open to kinetic analysis. Relevant processes may be dominated by the non-linear kinetics of clusters of ionizations and excitations that are within the macromolecule of interest (DNA) or shared with closely adjacent bound molecules. Quantitative models of radiobiological action have concentrated on the relative kinetics of single-track versus multitrack modes and describe the elementary damage either in terms of single ionizations or of clusters of energy depositions.