HIGH-PRESSURE VOLUMETRIC MEASUREMENTS ON PHOSPHOLIPID-BILAYERS

We report on a new apparatus which allows to perform high pressure volumetric measurements on biochemical systems at temperatures ranging from 0 to 100-degrees-C and at pressures from ambient up to 2500 bar. As an example, we present PVT-data of dilute aqueous dispersions of the model biomembrane dimyristoylphosphatidylcholine. The thermal expansion coefficient, isothermal compressibility and the lipid volume fluctuations of the lipid bilayer in its various thermotropic and barotropic phases have been determined and an accurate temperature-pressure phase diagram of the liquid-crystalline to gel phase transition of the lipid membrane could be obtained. The experimental results are compared with theoretical models for phospholipid bilayer phase transitions and for the thermomechanical properties of the lipid in its various phases.