Dilatometric study of binary mixtures of phosphatidylcholines

Abstract

Volumes of lipid dispersions as a function of temperature were measured for 2 different kinds of binary mixtures of lecithins, DMPC [dimyristoylphosphatidylcholine] and DSPC [distearoylphosphatidylcholine], and DMPC and DC20PC [dieicosanoylphosphatidylcholine]. Emphasis was placed on DMPC-rich compositions so as to resolve ambiguities regarding solid-phase immiscibility in DMPC-DSPC mixtures. Special attention was paid to problems of equilibration in the low-temperature phase and to methods of mixing the lipids. There is no solid-solid immiscibility in DMPC-DSPC mixtures, although this system to close to exhibiting such immiscibility, and DMPC-DC20PC mixtures exhibit pronounced solid immiscibility.