Asparagine-linked sugar chains of glycoproteins in calf thymocyte plasma membrane. Isolation and fractionation of oligosaccharides liberated by hydrazinolysis.

The plasma membrane glycoproteins of calf thymocytes were converted to glycopeptides by exhaustive pronase digestion. Glycopeptides with asparagine-linked sugar chains were separated from those with mucine-type sugar chains by Bio-Gel P-10 column chromatography. The asparagine-linked sugar chains were released as oligosaccharides from the peptide moiety by hydrazinolysis and labeled by reduction with NaB[3H]4. The radioactive oligosaccharides were fractionated into fifteen acidic components and ten neutral components by combination of paper electrophoresis and Bio-Gel P-4 column chromatography. The acidic nature of all fifteen acidic components can be ascribed to their N-acetylneuraminic acid residues. The Bio-Gel P-4 column chromatographic patterns of the neutral oligosaccharide fraction and of the neutral fraction obtained on sialidase treatment of the pooled acidic oligosaccharide fraction were totally different, indicating that the acidic oligosaccharides are not simple sialyl derivatives of the neutral oligosaccharides.