Cholesterol-induced alterations of the packing properties of gangliosides:an EPR study

The effect of cholesterol (Chol) on two kinds of glycolipid assemblies, one composed of monosialogangliosides (G(M1a)) and the other formed by a natur al mixture of bovine brain gangliosides (TBG), has been analysed. The exper imental approach involves spin label electron paramagnetic resonance (EPR) in aqueous lipid dispersions. The employment of a hydrosoluble spin label a nd a 'quencher' of the EPR signal that is not able to permeate lipid interf aces, allowed us to conclude that G(M1a)/Chol mixtures give rise to vesicle s at Chol proportions for which TBG/Chol mixtures form micelles. The use of different liposoluble spin labels reveals that cholesterol produces a stra ightening of the hydrocarbon chains in both lipid systems. In G(M1a)/Chol m ixtures, this feature is more pronounced and it is coupled with a decrease in polarity at the chain ends. (C) 2000 Elsevier Science Ireland Ltd. All r ights reserved.