Normal Ganglioside Micelles in Aqueous Solution: Interaction with Phospholipid Planar Bilayers
Gangliosides are membrane-bound glycosphingolipids with oligosaccharide chains which contain one or several residues of sialic acid, a negatively charged sugar (Figure 1). In animal tissues the most abundant gangliosides are monosialoganglioside GM1, disialogangliosides, GD1a and GD1b, and trisialoganglioside, GT. Most of them are localized on the outer surface of the plasma membrane and are ubiquitous but minor components of the cell surface, with the major exception of the mammalian central nervous system where they comprise up to 5–10% of the total lipid, and where lipid-bound sialic acid often exceeds that bound to glycoproteins1,2. Gangliosides have been shown to interact with several bacterial toxins3, peptide hormones and other external ligands4,5 probably through association with membrane proteins6. Most likely they are involved in functional activities of the cell surface, such as regulation of growth and structural plasticity. All these functions are likely to be mediated by ganglioside head group dynamics with a strong tendency for cooperative associations with each other and with glycoproteins6,8,9,10. This behavior appears to be strongly enhanced by divalent cations and affected by crosslinking agents6,8, as observed with both native and articial membrances.
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