A calorimetric investigation of the interaction of short chain alcohols with unilamellar DMPC liposomes

The molecular mechanisms by which ethanol and other short-chain alcohols perturb biological systems have been suggested to involve specific interactions with proteins and/or nonspecific interactions with the lipid bilayer part of biological membranes. To gain insight into the influence of alcohols on well-defined lipid bilayers, isothermal titration calorimetry (ITC) is used to determine the excess partial molar enthalpy of alcohol in liposome suspensions as well as the excess partial molar enthalpy of liposomes in dilute alcohol−water mixtures at temperatures above the main phase transition of dimyristoyl phosphatidylcholine (DMPC). The alcohols investigated were ethanol, 1-propanol, and 1-butanol. The calorimetric data were used to evaluate molecular interactions and based on a simple partitioning model the standard molar enthalpy of transferring alcohol from water into unilamellar DMPC liposomes was determined. The results reveal that the interaction of short-chain alcohols with the DMPC lipid bilayer ...