Structure determination of glycolipids using two dimensional proton nmr spectroscopy: Globoside

High resolution one and two dimensional proton nuclear magnetic resonance (2D-NMR) spectra of the glycosphingolipid globoside (the P blood group antigen) have been obtained at 500 WHz and 40–50 degrees C in dimethylsulfoxide-d₆-deuterium oxide (98:2 v/v). Analysis of a scalar coupling correlated spectrum (SECSY) allows assignment of resonances to residue types. Analysis of the oligosaccharide anomeric proton signals in the 3–6 ppm region of the 2D nuclear Overhauser effect (2D-N0E) spectrum of globoside reveals inter-residue couplings that allow identification of glycosidic linkage interactions and hence a primary structure. The diversity of linkage types in globoside demonstrates that oligosaccharide sequence determination via 2D-NMR spectroscopy may be considered a general approach, regardless of the type of anomeric linkage involved. Measurement of the intra-oligosaccharide and inter-oligosaccharide NOE-couplings allows an estimation of the glycosidic interproton distances for each glycosidic linkage. These distances are shown to be consistent with current views of preferred glycosidic bond conformations.