THE T,X,P-PHASE DIAGRAM OF BINARY PHOSPHOLIPID MIXTURES

High pressure differential thermal analysis (DTA) has been applied to the study of the temperature-composition-pressure phase diagram of the binary saturated phospholipid mixtures dimyristoyl/palmitoyl phosphatidylcholine (DMPC/DPPC) and dimyristoyl/stearoyl phosphatidylcholine (DMPC/DPPC) in excess water. A temperature range from 10 to 100-degrees-C and a pressure range from ambient up to 1500 bar has been covered. The experimentally obtained phase equilibria of these binary systems are compared with thermodynamic calculations for ideal and non-ideal mixing behaviour, and with recent results from Monte Carlo computer simulation studies, which not only permit determination of the phase diagram but also reveal a pictorial view of the local structure of the mixtures in the different parts of the phase diagrams.