Gangliosides, surface viscosity

Influence of the Sugar Moiety on Surface Viscosity of Glycosphin-golipids. The series ceramide > gluco- or galactocerebroside > lacto-cerebroside > hematoside > ganglioside (Figure 3) indicates a decrease in surface viscosity with an increase in monosaccharide units. 

The surface viscosity of gangliosides may be discussed in relation to their surface potentials. The higher surface potential of gangliosides on CaCl2 compared with that on NaCl indicates that the carboxyl group of the NANA moiety of the ganglioside probably binds Ca2+ in this case a bidentate lipid-Ca-lipid complex of MW 3,000 (about six times ceramide)... 

Molecular Area and Film Pressure. A smaller area/molecule and a greater film pressure caused an increase of surface viscosity (Figures 3-8). However, at the same area/molecule, ceramide was more viscous than ganglioside. A more striking contrast is seen in Figures 9 and 10. When modest quantities of DPL or cholesterol are added to saturated films of BSA and RNase, the pressure increases markedly (e.g., from 21 to 45 dynes/cm with BSA) whereas the viscosity dropped from large, immeasurable values to practically zero. 

Surface viscosity does not depend generally on the molecular weight of the surfactant. Indeed at all film pressures, the viscosity decreased in the order dihydroceramide (MW 702) > dihydrolactoside (MW 864) >> RNase (MW 14,000) > ganglioside (MW 1,500). 

Formation of the lipid-Ca-lipid bidentate complex does not cause an increase in surface viscosity as shown by the low viscosity of the ganglioside—Ca—ganglioside system. 

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