Effects of Ethanol on the Subtransition of Phospholipid Bilayers.

Abstract

Fluorescence spectroscopy was used to study the effects of varying concentrations of ethanol on the phase behavior of the 16-carbon acyl chain phospholipid, dipalmitoylphosphatidylcholine (DPPC).The fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), was incorporated into the bilayer to monitor the phase transitions through the displacement of DPH. Studies of up to 5.5 M ethanol showed that there was an increasing hysteresis and shift in the main transition temperature with higher ethanol concentrations.While the subtransition still existed at lower concentrations of ethanol, it disappeared along with the pretransition in the presence of 4.2 M ethanol or above.This disappearance was indicative of the differing effects of ethanol in the phase destabilization of the subgel and rippled gel phases.With even higher concentrations of ethanol, there was a decrease in relative intensity at around ~30? Celsius which may be correlated to the induction of the interdigitated phase.