Nonequilibrium Lipid Domain Growth in the Gel−Fluid Two-Phase Region of a DC16PC−DC22PC Lipid Mixture Investigated by Monte Carlo Computer Simulation, FT-IR, and Fluorescence Spectroscopy

The nonequilibrium ordering dynamics of lipid domains in the gel−fluid coexistence region of an equimolar DC16PC−DC22PC lipid mixture has been studied by means of Monte Carlo computer simulation, fluorescence, and Fourier transform infrared spectroscopy. The results reveal that the nonequilibrium phase separation process after a sudden temperature or pressure quench of the binary mixture from the one-phase fluid region into the two-phase gel−fluid coexistence region has a strong influence on the lateral membrane organization on different length scales. This is manifested as the formation of a heterogeneous lateral bilayer structure composed of long-living gel and fluid lipid domains characterized by a relaxation time on the order of hours. In the early time stage of the phase separation process a distinct local lipid structure of ordered DC16PC lipids is formed at the dynamically changing network of domain boundaries. Our combined theoretical and experimental investigations suggest that nonequilibrium eff...