ON THE BINDING OF DIRECT COTTON DYES BY AMYLOID

Application of 30 direct cotton dyes in aqueous salt solution to amyloid in human tissues yielded different staining patterns. Only dyes with good wool reserve without reactive metal atoms, i.e., dyes which stain cellulose but not proteins or polyamides, colored amyloid selectively without differentiation. Direct dyes for union fabrics, i.e., dyes which color cellulose and protein fibers, stained all tissue structures. The effects of deamination and acetylation on the binding of direct dyes with good wool reserve indicate interaction of these dyes with hydroxyl groups of amyloid. The increase in intensity of staining upon addition of NaCl to the dye solution suggests a nonionic type linkage. According to chemical data on the direct dyeing of cellulose, direct dyes are adsorbed by hydrogen bonding between hydroxyl groups of the polysaccharide chains and suitable groups in the dye. It seems probable that a similar mechanism is involved in the binding of these dyes by amyloid. The selective staining of amyloid with direct dyes with good wool reserve, which do not color proteins, suggests that the polysaccharide moiety of amyloid may play a major role in the binding of direct dyes.