Studies on certain peptide fractions isolated from human dentine

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The acid-soluble nitrogenous components of human dentine were fractionated by gel filtration and ion-exchange chromatography. The fraction believed to be in the molecular weight range 750–5000, but later found to contain some free amino acids, comprized approximately 0.08 per cent of dentine and contained 20 per cent glycine, 25 per cent dicarboxylic amino acids and 15 per cent basic amino acids which included ornithine. High-voltage paper electrophoresis was used to obtain nine fractions which were then analysed. Five of the peptide fractions were predominantly acidic and were also rich in hydroxy amino acids, while three, though containing dicarboxylic amino acids, were richer in basic amino acids. One highly basic fraction was also found. The peptide fractions were considered to be comparable to fractions previously isolated from ox bone and, although clearly not fragments of the main tropocollagen chains, were thought likely to be either associated with collagen at physiological pH or possibly to have been originally associated with glycoprotein or mucopolysaccharide.