ROLE OF CHOLESTEROL IN THE MODULATION OF INTERDIGITATION IN PHOSPHATIDYLETHANOLS

Phosphatidylethanol (Peth) is formed in biological membranes when etha nol replaces water in the transphosphatidylation reaction catalyzed by phospholipase D. This charged lipid accumulates in the presence of et hanol, and it has unusual properties that can influence membrane struc ture and function. We have previously shown that dimyristoylphosphatid ylethanol (DMPeth) and dipalmitoylphosphatidylethanol (DPPeth) form th e interdigitated gel phase in the presence of Tris-HCl [O.P. Bondar, E .S. Rowe, Biophys. J., 71 (1996) 1440-1449]. In the present investigat ion, differential scanning calorimetry (DSC) and fluorescence have bee n used to investigate the effect of cholesterol on the phase behavior of DPPeth and DMPeth. Our results show that cholesterol prevents the f ormation of the interdigitated phase in the presence of Tris-HCl, and that ethanol counters this influence and restores the ability of these lipids to interdigitate. Pyrene-PC fluorescence probe was used in thi s investigation and gave results that were in agreement with the concl usions based on the DSC study. (C) 1998 Elsevier Science B.V.