59—THE OXIDATIVE INSOLUBILIZATION OF PROTEINS

Abstract

Many proteins become coloured after oxidation with reagents such as potassium permanganate or chlorine dioxide and these colorations are associated with insolubilization of the protein. It is considered that the insolubility on oxidation is probably due to cross-links of a melanin-type structure, derived from tyrosine residues. This conclusion is based on chemical and ultraviolet absorption analysis of substances isolated from oxidized proteins, and experiments on tyrosine and its derivatives. Further information has been obtained from the reactions of potassium nitroso disulphonate, which oxidizes phenols quantitatively to quinones, and which has been used for the first time to oxidize proteins.