Critical Micelle Concentrations of Gangliosidest

The micellar properties of mixed, bovine gangliosides and purified galactosyl-N-acetylgalactosaminyl(Nacetylneuramin yl)galactosylglucosylceramide were studied by gel filtration, equilibrium dialysis, and band and boundary centrifugation in sucrose gradients. The dissociation of micelles is very slow (days) in water and required us to approach equilibrium by association of monomers rather than by the dissociation of micelles. The gangliosides were therefore first converted into very low molecular weight aggregates (1-3 molecules) by dissolving them in Me,SO. Galactosyl-Nacetylgalactosaminyl(N-acetylneuraminyl)galactosylglucoGang l ios ides were originally described as acylsphingosyl oligosaccharides containing sialic acid (Klenk, 1942). It was later shown that higher order gangliosides (GMI, GD,,, GDlb, GT1, etc.)’ have a common basic structure, Le., N-acylsphingosineglucosegalactose-N-acetylgalactosaminegalactose, with one or more molecules of N-acetylneuraminic acid (Svennerholm, 1962). GMZ and GM3 are biosynthetic precursors with deletions at the terminal galactose and galactosaminegalactose residues, respectively. Gangliosides have been implicated in the binding or function of many biologically important molecules, Le., cholera toxin (Sattler et al., 1977), tetanus toxin (Helting et al., 1977), botulinum toxin (Haberman & Heller, 1975), thyrotropin (Mullin et al., 1976), human chorionic gonadotropin (Lee et al., 1976), luteinizing hormone (Lee et al., 1977), serotonin (Ochoa & Bangham, 1976), interferon (Vengris et a]., 1976), bilirubin (Kahan et al., 1968), and wheat germ agglutinin (Redwood & Polefka, 1976). From the Clinical Endocrinology Branch (S.F., M.L.J., and H.E.) and the Laboratory of Biochemical Pharmacology (G.L. and S.M.A.), National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014. Received July 27, 1978. ‘Present address: Centro di Endocrinologia ed Oncologia Sperimentale del C.N.R., Naples, Italy. Abbreviations used: cmc, critical micelle concentration; Me2S0, dimethyl sulfoxide; ganglioside nomenclature is according to Svennerholm ( 1964)-G,,, galactosyl-N-acetylgalactosaminyl(N-acety~neuraminyl)galactosylglucosylceramide; G,,,,, N-acetylneuraminylgalactosylN-acetylgalactosaminyl(N-acetylneuraminyl)galactosylglucosylcerimide; G D l b , galactosyl-N-acetylgalactosaminyl(~-acetylneuraminyl-~acetylneuraminyl)galactosylglucosylcerimide; G T I , N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl(N-acetylneuraminyl-~acetylneuraminyl)galactosylglucosylceramide; GM,, N-acetylgalactosaminyl(N-acetylneuraminyl)galactosylglucosylcerimide; GM), N acetylneuraminylgalactosylglucosylcerimide. sylceramide was then diluted into aqueous sucrose gradients and sedimented by the boundary centrifugation technique. This gave a sedimenting micelle and a nonsedimenting monomer concentration of (1-2) X M (or less) which corresponds to the critical micelle concentration value. The mixed gangliosides revealed two micellar sizes (i.e., 10 and 4.5 S), the slower sedimenting species being formed from the larger one with time (days). The critical micelle concentration of the mixed gangliosides was found to be approximately M by gel filtration, equilibrium dialysis, and band centrifugation. Table I : Literature Values for the cmc of Gangliosides cmc (M) ganglioside technique reference 1 X mixed surface Gammack (1963) tension 1 X 10” mixed conductance Howard & Burton (1964) 1 X GM, neuraminidase Rauvala (1976) 7.5 X lo-’ G M ~ triiodide Yohe & Rosenberg (1972) 8.5 X lo-’ G M ~ triiodide Yohe & Rosenberg (1972) 9.5 X lo-’ G D , ~ triiodide Yohe & Rosenberg (1972) 1 X G T , triiodide Yohe & Rosenberg(l972) method