Effect of bilayer morphology on the subgel phase formation.

We examined how morphology of bilayer assemblies affects the kinetics of the subgel phase formation in dimyristoylphosphatidylglycerol (DMPG) bilayers, which change their morphology depending on NaCl concentration. Quantitative analysis of the kinetics revealed that in flat sheet-like structures (bilayer sheets) the subgel phase forms in a simple two-state manner with the relaxation time of about 3 min at -10 degrees C while in vesicles it forms much slower under a multi-step process. Freeze-etch electron microscopic observations suggested that the kinetics of the subgel phase formation is directly correlated with the morphology of bilayer assemblies. It is likely that the bilayer sheet structure is more favorable to the subgel phase formation in DMPG bilayers than the vesicular structure.