The identification of terminal alpha (1----3)-linked galactose in N-acetyllactosamine type of glycopeptides by means of 500-MHz 1H-NMR spectroscopy.

500-MHz 1H-NMR spectroscopy was employed to study two N-acetyllactosamine-type glycopeptide fractions which were derived from a bovine thyroglobulin preparation (Cummings, R.D., and Kornfeld, S. (1982) J. Biol. Chem. 257, 11230-11234). By this method, their branches were found to be terminated either by NeuAc in alpha (2----6)-linkage or by Gal in alpha (1----3)-linkage. For the first time, the Gal alpha (1----3) Gal beta (1----4) GlcNAc beta (1----.) sequence is characterized by 1H-NMR to occur in N-glycosidic carbohydrate chains of glycoproteins. Moreover, this approach made possible the branch localization of such a unit. Microheterogeneity with respect to the presence of alpha-linked Gal or NeuAc in terminal position of a certain branch in one of the preparations, could be adequately assessed in terms of structures by 1H-NMR.