PHASE BEHAVIOR OF DIPALMITOYLPHOSPHATIDYLGLYCEROL BILAYER MEMBRANE IN SALINE WATER UNDER HIGH PRESSURE

The phase transitions of dipalmitoylphosphatidylglycerol (DPPG) bilayer membrane in the aqueous NaCl solution were observed by means of an optical method under atmospheric and high pressures. The temperature-pressure phase diagram of the DPPG bilayer showed that the phase behavior of the DPPG bilayer was similar to that of dipalmitoylphosphatidylcholine (DPPC) bilayer except for the interdigitated gel (LβI) phase. Comparing the phase diagram with the diagram obtained in a phosphate buffer, it turned out that the formation of the LβI phase is suppressed by the shielding effect of NaCl on the repulsive interaction among polar headgroups.