Three-dimensional structure of the oligosaccharide chain of GM1 ganglioside revealed by a distance-mapping procedure: a rotating and laboratory frame nuclear overhauser enhancement investigation of native glycolipid in dimethyl sulfoxide and in water-dodecylphosphocholine solutions

Three-dimensional structure of the oligosaccharide part of the GM 1 ganglioside, Galpl-3GalNAcßl -(NeuAca2-3)4Galßl-4GlcßI -1Cer. was modeled with use of a distance-mapping procedure that was based on NOE contacts between amido. hydroxy, and C-linked protons, observed for the intact ganglioside dissolved in Me2SO-d6. The glycosidic linkages of the branched core trisaccharide segment are significantly more rigid than the linkages of the external disaccharide Galßl-3GalNAc and Galßl-4GIc segments, which exist in several conformations. The conformation of the sialic acid side chain seems to be predominantly determined by the hydrogen bond between the C(8)-OH proton and either the carboxylic or ring oxygen. whereas the presence of the acetyl substituent of the C(5)-amino group is irrelevant for this conformation. Similar conformations were found for GM I anchored in mixed D2O/dodecylphosphocholine-d38 micelles