Single-molecule measurements of DNA with nanopores have advanced substantially since their inception three decades ago. Recently, nanopores have been used to quantify the amount of intact DNA after gamma irradiation. In this scenario, hydroxyl radicals generated by irradiation create single-strand breaks in DNA. These breaks can combine over a length scale l to give a double-strand break, resulting in a reduction of intact DNA. Other processes, such as enzymatic nicking, give an analogous biophysical process. We develop a theory of l, discussing how it depends on temperature and ionic strength. Moreover, we present the fragmentation patterns expected for the generation of random single-strand breaks. Optimized single-molecule measurements should be able to detect these patterns and validate the theoretical model of l.
Zwolak et al. (Sun,) studied this question.