Some studies on the occurrence of sialic acid in human cartilage

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Abstract
The specificities of the diphenylamine and resorcinol reactions for sialic acid in the presence of protein and acid mucopolysaccharide components were investigated, and the violet and blue chromogens absorbing strongly at 525 m[mu] and 575 m[mu] respectively were found specific for this compound. Disintegration of human cartilage was carried out mechanically at -196[degree] and the amounts of water-soluble material extractable at 3 pH values were determined. Sialic acid-containing components were present in these fractions, increasing amounts of which could be extracted from cartilage as the pH was increased. Three fractions were extracted from the disintegrated cartilage a major fraction at pH 10.6 and two smaller fractions at pH 11.6. Analysis for protein, sulphate, sialic acid, hexosamine and total non-nitrogenous hexoses accounted for 85% by weight of the total solids. No sulphur-containing amino acids were detected. Sialic acid was detected in certain mucopolysaccharide-peptide complexes. The difficulties attending the separation of protein from acid mucopolysaccharide preparations applied equally to the removal of the sialic acid-containing components. The significance of this is discussed.