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

The conformational dynamics of the carbohydrate headgroup of gangliosi de 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 dodec ylphosphocholine micelle in aqueous solution, were probed by high reso lution NMR spectroscopy. The observed H-1/H-1 NOE interactions reveale d conformational averaging of the terminal NeuAc alpha 2-->3Gal and Ga l 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 anc horing effect of the micelle allowed the detection of conformational f luctuations of the headgroup on the time scale of a few hundred picose conds. NMR experiments performed on the GD1a/DPC micelles in H2O at lo w temperatures permitted the observation of hydroxyl proton resonances , contributing valuable conformational information.