Room temperature ordering of dipalmitoyl phosphatidylserine bilayers induced by short chain alcohols

Using differential scanning calorimetry and small and wide angle X-ray diffraction, we show that, following extended incubation at room temperature, methanol, propanol, and three of the isomers of butanol can induce ordering in dipalmitoyl phosphatidylserine (DPPS) gel phase bilayers. The organization of the bilayers in the presence of ethanol, described previously, is now observed to be a general effect of short chain alcohols. Evidence is presented for tilting of the acyl chains with respect to the bilayer normal in the presence of ethanol or propanol. However, the different chain lengths of the alcohols, and isomeric form, influence the thermal stability of the ordered gel to different extents. This behavior is unlike that of the gel state phosphatidylcholine analog which, in the presence of short chain alcohols, undergoes hydrocarbon chain interdigitation. Dipalmitoyl phosphatidylcholine added to DPPS in the presence of 20 vol% ethanol, acts to suppress the ordered gel phase.