Oxidation of nitroxide radicals by an iron-hydrogen peroxide-amino acid system

The oxidation of nitroxide radicals by the reaction of hemoglobin with hydrogen peroxide occurred using both FeSO4 and amino acids instead of hemoglobin. Tyrosine, phenylalanine, tryptophan, methionine and cysteine in globin were connected with the formation of the oxoammonium cation. Of these amino acids, tyrosine was especially effective in its oxidation. It was found that both the binding of nitroxide radicals to ferric iron and the activation of amino acids by hydroxyl radicals were important in the radical oxidation.