ABSTRACT
The packing of amphiphiles in an aggregate obeys some simple rules following the consideration that, except for surface roughness, no water can exist inside the hydrophobic domain, so that one of its dimensions cannot exceed twice the monomer hydrophobic length, while contact with water is allowed by the hydrophilic headgroup. Gangliosides have been shown to be a good example of such amphiphiles, since they have large hydrophobic and hydrophilic parts in the same molecule. The availability of a considerable number of high-purity gangliosides, prepared by specific chromatographic procedures in order to obtain molecules containing similar lipid moieties, allows, therefore, a significant test of the influence of the headgroup geometry on the final shape of the aggregate. The lipid moiety of gangliosides is called ceramide and is constituted by a long chain amino alcohol, generally called sphingosine, connected to a fatty acid by an amide linkage.
