FREE RADICALS FROM THE PHOTODECOMPOSITION OF BLEOMYCIN |
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| Authors: | William E Antholine Tadeusz Sarna † Roger C Sealy Balaraman Kalyanaraman Glen D Shields David H Petering |
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| Institution: | National Biomedical ESR Center, Department of Radiology, The Medical College of Wisconsin, 8700 West Wisconsin Avenue, Milwaukee, WI 53226, USA;S. C. Johnson and Sons, Inc., Racine, WI 53403, USA;Department of Chemistry, University of Wisconsin–Milwaukee, Milwaukee, WI 53201, USA |
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| Abstract: | Abstract— 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 (O2 and H2O2) 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. |
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