Conformational studies of the glycopeptide Ac-Tyr-[Man5GlcNAc-β-(1 → 4)GlcNAc-β-(1 → Nδ)]-Asn-Leu-Thr-Ser-OBz and the constituent peptide and oligosaccharide

Glycopeptides of desired structure can be conveniently prepared by the coupling of reducing oligosaccharides to aspartic acid of peptides via their glycosylamines formed in the presence of saturated aqueous ammonium hydrogen carbonate. The resulting oligosaccharide chains are N-linked to asparagine as in natural glycoproteins, allowing different peptide oligosaccharide combinations to be analysed for conformational effects. In the present paper, a pentapeptide of ovalbumin was coupled to Man(5)GlcNAc(2) oligosaccharide and the glycopeptide and the two parent compounds compared by NMR ROESY experiments and molecular dynamics simulations. Despite the small size of the peptide, conformational effects were observed suggestive of the oligosaccharide stabilising the peptide in solution and of the peptide influencing oligosaccharide conformation. These effects are relevant to the function of glycosylation and the enzymic processing of oligosaccharide chains. (C) 2000 Elsevier Science Ltd. All rights reserved.