Initial events in the cellular effects of ionizing radiations: clustered damage in DNA.

TLDR: Track structure analysis has revealed that clustered DNA damage of severity greater than simple double-strand breaks is likely to occur at biologically relevant frequencies with all ionizing radiations.

Abstract: General correlations are found between the detailed spatial and temporal nature of the initial physical features of radiation insult and the likelihood of final biological consequences. These persist despite the chain of physical, chemical and biological processes that eliminate the vast majority of the early damage. Details of the initial conditions should provide guidance to critical features of the most relevant early biological damage and subsequent repair. Ionizing radiations produce many hundreds of different simple chemical products in DNA and also multitudes of possible clustered combinations. The simple products, including single-strand breaks, tend to correlate poorly with biological effectiveness. Even for initial double-strand breaks, as a broad class, there is apparently little or no increase in yield with increasing ionization density, in contrast with the large rise in relative biological effectiveness for cellular effects. Track structure analysis has revealed that clustered DNA damage of ...