CARBOHYDRATE DYNAMICS AT A MICELLAR SURFACE - GD1A HEADGROUP TRANSFORMATIONS REVEALED BY NMR-SPECTROSCOPY

The conformational dynamics of the carbohydrate headgroup of ganglioside GD1a, NeuAc alpha 2-->3Gal beta 1-->3GalNAc beta 1-->4[NeuAc alpha 2-->3]Gal beta 1-->4Glc beta 1-1Cer, anchored in a perdeuterated dodecylphosphocholine micelle in aqueous solution, were probed by high resolution NMR spectroscopy. The observed H-1/H-1 NOE interactions revealed conformational averaging of the terminal NeuAc alpha 2-->3Gal and Gal beta 1-->3GalNAc glycosidic linkages. The pronounced flexibility of this trisaccharide moiety was substantiated further by two-dimensional proton-detected C-13 T-1, T-1p and H-1/C-13 NOE measurements. The anchoring effect of the micelle allowed the detection of conformational fluctuations of the headgroup on the time scale of a few hundred picoseconds. NMR experiments performed on the GD1a/DPC micelles in H2O at low temperatures permitted the observation of hydroxyl proton resonances, contributing valuable conformational information.