Structure Determination by 360-MHz 1H-NMR Spectroscopy and Methylation Analysis of a Biantennary Glycan of the N-Acetyllactosaminic Type Isolated from Rat-Liver Plasma Membrane

Glycopeptides obtained by exhaustive pronase digestion of delipidated rat liver plasmic membranes were purified by gel filtration on Sephadex G-25. These glycopeptides were further fractionated by affinity chromatography on a concanavalin-A--Sepharose 4B column into the following fractions: (a) glycopeptides which did not bind to the column (fraction 1); (b) glycopeptides with weak affinity for concanavalin-A--Sepharose, which could be eluted with buffer only (fraction 2); (c) glycopeptides retained on the column and which could be eluted specifically with buffer containing 0.2 M methyl alpha-glucoside (fraction 3). On the basis of the carbohydrate composition, methylation analysis and 360-MHz 1H-NMR spectroscopy, the following primary structure of a glycan in fraction 2 is proposed: (see formula in text).