Virtual coupling in the 1H NMR spectrum of N,N'-diacetyl chitobioside. Application to glycopeptides.

The unexplained line shape for the anomeric hydrogen resonance of the core GlcNAc observed in the 1H NMR spectra of high mannose N-linked glycopeptides (Bruch, R. C., and Bruch, M. D. (1982) J. Biol. Chem. 257, 3409-3413) can be accounted for by virtual coupling. Complete assignment, at various temperatures, of the 360-MHz 1H NMR spectrum of beta-methyl N,N'-diacetyl chitobioside confirms this interpretation. This analysis has revealed the existence of a long range chemical shift perturbation in these glycopeptides which is interpreted as arising from their specific three-dimensional structure.