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FREE RADICALS FROM THE PHOTODECOMPOSITION OF BLEOMYCIN
Author(s) -
Antholine William E.,
Sarna Tadeusz,
Sealy Roger C.,
Kalyanaraman Balaraman,
Shields Glen D.,
Petering David H.
Publication year - 1985
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1985.tb03503.x
Subject(s) - radical , photochemistry , chemistry , irradiation , oxygen , spin trapping , adduct , moiety , bleomycin , hydroxyl radical , catalase , electron paramagnetic resonance , superoxide dismutase , ion , metal ions in aqueous solution , stereochemistry , enzyme , organic chemistry , nuclear magnetic resonance , medicine , physics , surgery , chemotherapy , nuclear physics
— Irradiation of bleomycin with light (λ > 320 nm) leads to a decrease in absorbance at 290 nm, which is suppressed by metal ions and by oxygen. Light‐induced oxygen consumption is diminished by the enzymes superoxide dismutase and catalase, implying that toxic reduced species of oxygen (O 2 and H 2 O 2 ) are formed during irradiation. Spin‐trapping measurements with 5,5‐dimethyl‐1‐pyrroline‐1‐oxide and 2‐methyl‐2‐nitrosopropane demonstrated that hydroxyl radical and methyl radical adducts also are generated in the system. In addition, direct ESR measurements have shown that methyl radicals are produced during irradiation of bleomycin solutions at low temperatures, together with radicals probably derived from the bithiazole moiety of the bleomycin. The latter are also produced from irradiation of the model compound bithia. Radical production is diminished by complexation of bleomycin with metal ions.