Effect of sterol structure on the partition of sterol between phospholipid vesicles of different composition.

The partition of cholesterol analogues between dipalmitoylphosphatidylcholine and egg phosphatidylcholine vesicles was examined. Cholesterol, trans- and cis-22-dehydrocholesterols, and 24 alpha-ethyl,trans-22-dehydrocholesterol (stigmasterol) showed a preference from gel phase dipalmitoylphosphatidylcholine over fluid phase egg phosphatidylcholine at 37 degrees C. Within this group, the sterol concentration in DPPC relative to that in egg PC ranged from about 1.5 to 2.0. Cholesterol analogues with a 24 alpha-methyl or ethyl substituent (campesterol and beta-sitosterol, respectively) and cholestanol (dihydrocholesterol) distributed about equally between the two types of phospholipid. Thus, in this study involving two kinds of phospholipid and a small number of cholesterol analogues, there was no simple correlation between the sterol structure and its partition behavior. The combined results from studies on sterol partition behavior and on sterol interaction with individual phospholipids (Rujanavech, C., Henderson, P.A., and Silbert, D.F. (1986) J. Biol. Chem. 261, 7204-7214) provide an adequate basis to explain the different patterns of membrane lipid adaptation which accompany growth of LM cells on various cholesterol analogues (Rujanavech, C., and Silbert, D.F. (1986) J. Biol. Chem. 261, 7196-7203).