Effects of alcohols on lipid bilayers with and without cholesterol: the dipalmitoylphosphatidylcholine system

Differential scanning calorimetry is a useful method to study the thermotro pic phase transitions of a phospholipid bilayer. In the present study DSC i s used to determine the effects of methanol and ethanol on DPPC and DPPC/2 mol% cholesterol bilayers. The biphasic effect of the main transition and t he presence of an extra peak on the DSC cooling scans were observed above c ertain alcohol concentrations. In the presence of 2% cholesterol, the conce ntration at which the biphasic effect occurs is increased by both short-cha in alcohols. 1,6-Diphenyl-1,3,5-hexatriene (DPH) is used as a fluorescent p robe to directly determine the onset of interdigitation in these systems as reflected by a drop in the DPH fluorescence intensity. (C) 1999 Elsevier S cience B.V. All rights reserved.