title: Metal ion-induced activation of molecular oxygen in pigmented polymers.
abstract: Diamagnetic and paramagnetic metal ions enhanced the rate of production of hydrogen peroxide during autoxidation of melanin pigments, as measured using an oxidase electrode. However, redox-active metal ions, such as Fe3+ and Cu2+, caused a marked decrease in H2O2 production. Evidence for redox-active metal ion-dependent formation of hydroxyl radicals during autoxidation of melanin pigments has been obtained using the electron spin resonance-spin trapping method. Evidence for direct reduction of Fe3+ by melanin polymers also has been obtained using optical spectroscopy. Mechanisms of molecular activation of oxygen induced by metal ions on melanin polymers are discussed.
mesh_terms: D000818:Animals; D002412:Cations; D002417:Cattle; D003300:Copper / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000378:metabolism; D006878:Hydroxides / Q000378:metabolism; D017665:Hydroxyl Radical; D007501:Iron / Q000494:pharmacology; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008543:Melanins / Q000378:metabolism*; D008670:Metals / Q000494:pharmacology*; D009532:Nickel / Q000494:pharmacology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
chemical_list: D002412:Cations; D006878:Hydroxides; D008543:Melanins; D008670:Metals; D017665:Hydroxyl Radical; D008345:Manganese; D007811:Lanthanum; D003300:Copper; D009532:Nickel; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D008274:Magnesium; D015032:Zinc; D010100:Oxygen