UV light-induced crosslinking of the complementary strands of plasmid pUC19 DNA restriction fragments

Restriction fragments of pUC19 DNA were irradiated by various doses of UV light and analyzed by denaturing (alkaline) agarose gel electrophoresis. The irradiation generated retarded species whose mobility indicated two crosslinked DNA strands. Quantitative analysis of the experimental data provided an empirical equation relating the fraction of crosslinked DNA molecules to their length and to the dose of their irradiation by UV light. This equation can be used to predict the crosslinking behavior of pUC19-like DNA molecules whose primary structures do not much differ from a random nucleotide sequence. The amount of interstrand crosslinks increased with the (A+T) content of the pUC19 DNA fragments but the dependence was not clear-cut to indicate that oligonucleotide composition of DNA played a significant role as well.