Protein-DNA crosslinks induced by primary and secondary radicals

Double-stranded DNA from calf thymus was irradiated in the presence of bovine serum albumin (BSA) at a ratio of 1:10 by mass under air, N2 or N2O, with and without ethanol, tert-butanol or isopropanol in 10(-2) mol dm-3 sodium phosphate buffer, pH 7.0. The irradiated solutions were analysed by a nitrocellulose filter assay and by high-performance liquid gel chromatography. The results show that OH. radicals as well as hydrated electrons induce protein-DNA crosslinks. Further, alcohol radicals react with BSA producing protein radicals which become crosslinked to DNA. If OH radicals are scavenged by alcohol, strand breakage of DNA does not occur.