Studies related to the chemistry of melanins. Part 15. The electron transfer and free radical properties of dopa-melanin

Abstract

The e.s.r. signal of autoxidative dopa-melanin remained unchanged when the melanin was treated with the following reagents: potassium nitrosodisulphonate, NNN′N′-tetramethyl-p-phenylenediamine bromide, β-NADH, chlorpromazine, ascorbic acid, sodium dithionite, potassium hexacyanoferrate(III), or cerium(IV), copper(II), or zinc ions, or water, showing that the radical sites are inaccessible to chemical attack. The interaction of melanin's free radicals with copper(II) ions is not chemical in nature; the number of bound copper(II) ions was determined.