Dynamics and spatial organization of surface gangliosides

Model surfaces in a water environment suitable for the study of membrane ganglioside properties have been developed. They, together with ganglioside micelles of large molecular mass, consist of ganglioside-phosphatidylcholine mixed micelles of small molecular mass and ceramide-modified ganglioside micelles of intermediate molecular mass. The experimental information on the conformational and geometrical properties of ganglio-series gangliosides inserted into these model surfaces is discussed, compared and integrated with that obtained using multilamellar aggregate models. The results show that the conformational properties of the chain are determined by interresidual interactions between the sialic acid and N-acetylgalactosamine units, regardless of the total oligosaccharide structure, the structure of the ganglioside ceramide, possible phospholipid head group or Ca++ interactions, a highly enriched ganglioside environment, the presence of cholesterol in the membrane or temperature variation. Furthermore, the oligosaccharide chain seems to be well extended beyond the bilayer surface with a well defined average conformation and motional order, common to all the investigated gangliosides.