title: A direct electron spin resonance and spin-trapping investigation of peroxyl free radical formation by hematin/hydroperoxide systems.
abstract: Direct electron spin resonance was used to detect tert-alkylperoxyl radicals generated by hematin and the corresponding hydroperoxides at near-physiological pH values. The spin-trapping method was necessary to detect the less persistent primary ethylperoxyl radical. Under a nitrogen atmosphere, the electron spin resonance signal of the tert-alkylperoxyl radicals decreased, and the ethylperoxyl spin-adduct concentration did not change. Concomitant studies, using a Clark oxygen electrode, show that oxygen was consumed by the hematin-tert-alkyl hydroperoxide systems, but was released by the hematin-ethyl hydroperoxide reaction. Thus, molecular oxygen seems to play a subsidiary role in the hematin-catalyzed decomposition of hydroperoxides. Based on the electron spin resonance and oxygen electrode results, a mechanism for the continuous production of the peroxyl free radicals is proposed for hematin/hydroperoxide systems. The present spectroscopic methodology can be used to search for peroxyl free radical formation by hemoprotein/hydroperoxide systems.
mesh_terms: D000818:Animals; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006418:Heme / Q000031:analogs & derivatives; D006427:Hemin; D006861:Hydrogen Peroxide; D007700:Kinetics; D010101:Oxygen Consumption
chemical_list: D005609:Free Radicals; D006418:Heme; D006427:Hemin; D006861:Hydrogen Peroxide