Volumetric Properties, Compressibilities and Volume Fluctuations in Phospholipid-Cholesterol Bilayers

Abstract

Abstract We conducted detailed measurements of the apparent specific volume of dipalmitoylphosphatidylcholine (DPPC)–cholesterol mixtures in excess water as a function of pressure up to 70MPa (700bar) at 20, 38 and 50°C. The volumetric properties and the isothermal compressibility κ T of the lipid vesicles were determined at cholesterol concentrations, χchol, ranging up to 50 mol. The thermodynamic data are compared with other physico-chemical properties of phospholipid–cholesterol mixtures. Furthermore, the thermodynamic properties of the system are discussed in the light of the various T, χchol–phase diagrams and computer simulation studies published in the literature.