The phase diagram of dimyristoyl phosphatidylcholine and chain-perdeuterated distearoyl phosphatidylcholine A deuterium NMR spectral difference study

Abstract

The phase diagram for mixtures of the lipids dimyristoylphosphatidylcholine (DMPC) and chain perdeuterated distearoylphosphatidylcholine (DSPC- d 70) is determined using 2H-NMR difference spectroscopy. It is found that the temperature of the solidus line increases monotonically with DSPC- d 70 concentration and thus that there is no evidence for peritectic behavior in this mixture. This phase diagram is compared to others that have been determined for DMPC/DSPC mixtures and for mixtures of perdeuterated DMPC (DMPC- d 54) with DSPC some of which do display peritectic behavior. The possibility that different isotopic compositions give rise to qualitatively different phase diagrams for this system is discussed