The significance of the histochemical reaction for carboxyl groups of protein in cartilage matrix.

Abstract

A major component of cartilage matrix reacting in the histochemical reaction for protein-bound carboxyl groups is the protein moiety of chondromucoprotein. C-terminal carboxyl groups in cartilage matrix are too sparse to contribute to the histochemical reaction; the side-chain carboxyls are responsible for all of the color developed. It is suggested that variation in staining reaction in the matrix reflects differences in the state of aggregation of chondromucoprotein. Thus the presence of an intense reaction for protein-bound carboxyl groups in cartilage matrix may be explained on the basis of aggregation of chondromucoprotein into high molecular weight complexes, yielding a high local concentration of requisite side-chain carboxyl groups for dye-coupling.