DNA CLEAVAGE INDUCED BY ALKOXYL RADICALS GENERATED IN THE PHOTOLYSIS OF N-ALKOXYPYRIDINETHIONES

The photolysis of N-isopropoxypytidine-2-thione (1b) and of N-tert-but oxypyridine-2-thione (1c) generated alkoxyl radicals as confirmed by t rapping experiments with DMPO and subsequent EPR spectroscopy. Upon UV A irradiation, the alkoxyl-radical sources induce strand breaks in sup ercoiled pBR 322 DNA, which was analyzed by gel electrophoresis. The p articipation of type I (electron transfer, H abstraction) or type II ( O-1(2)) photosensitization in the DNA cleavage by the oxyl-radical sou rces 1a-d or their photoproducts could be excluded. The present study establishes uneqivocally that alkoxyl and benzoyloxyl, as well as hydr oxyl radicals, cause strand breaks in DNA and, thus, may play a signif icant role in the DNA cleavage by peroxides. (C) 1998 Elsevier Science Inc.