Effect of cholesteryl hemisuccinate on the interfacial properties of phosphatidylcholine bilayers

Cholesteryl hemisuccinate (CHEMS) is an amphipathic lipid that can regulate cell growth. A comparison of the effects of CHEMS and cholesterol on 1-pal mitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-g lycero-3-phosphocholine (DPPC) bilayers was investigated using fluorescence techniques. In liquid-crystalline phase POPC bilayers, CHEMS increased the interfacial surface charge, but was less effective than cholesterol in red ucing acyl chain mobility and interfacial hydration. In liquid-crystalline phase DPPC bilayers, CHEMS and cholesterol were equally effective in reduci ng acyl chain mobility. Similar to the POPC matrix, CHEMS increased the int erfacial surface charge and cholesterol decreased the surface hydration. Th e different effect of cholesterol and CHEMS on acyl chain mobility may be d ue to a preferential interaction of cholesterol with POPC. In gel phase DPP C bilayers, CHEMS and a succinylated pyrenyl cholesterol analog exhibited d ifferent effects on membrane physical-chemical properties than cholesterol. Succinylation also increased the rate of transfer of the pyrenyl cholester ol analog between single unilamellar vesicles approximately seven fold. Thi s process demonstrated first-order kinetics which indicated that transbilay er migration was not a rate-limiting step. The succinylation of cholesterol places a carboxyl group at the lipid-water interface and the sterol ring d eeper in the bilayer. For a structural model to explain its biological prop erties, CHEMS should be considered a bulky fatty acid. (C) 1998 Elsevier Sc ience B.V. All rights reserved.