CONFORMATION AND DYNAMICS OF GLYCOPROTEIN OLIGOSACCHARIDES AS STUDIED BY H-1-NMR SPECTROSCOPY

Most complex carbohydrates can take a large number of shapes in solution. Determining the favored solution conformations and characterizing the internal motions of complex carbohydrates is essential to understanding their biological function, particularly their interactions with proteins. This paper describes an NMR spectroscopic study of the internal dynamics of a mucin glycoprotein-derived di-antennary octasaccharide, [GRAPHICS] H-1 NMR spectra of this oligosaccharide in D2O and H2O were completely assigned by the combination of TOCSY, ROESY and triple-quantum spectroscopy experiments. Specific {H-1,H-1} cross-relaxation rates and H-1 longitudinal relaxation times were measured at various temperatures and magnetic field strengths. The data show that the NeuAcalpha(2 --> 3)Galbeta arm of the octasaccharide can adopt two conformations around the (2 --> 3)-bond. Most important, the NeuAcalpha(2 --> 3)Galbeta and Galalpha(1 --> 4)Galbeta linkages both have pronounced conformational flexibility; their rearrangements are fast on the time scale of the overall molecular tumbling.