SLOW NONEQUILIBRIUM DYNAMICAL REARRANGEMENT OF THE LATERAL STRUCTURE OF A LIPID-MEMBRANE

The lipid bilayer of the biological membrane is a multicomponent molec ular mixture capable of exhibiting compositional and structural hetero geneity. Using Fourier transform infrared spectroscopy and Monte Carlo computer simulation techniques, we report here for the first time the existence of a long-lived nonequilibrium heterogeneous lateral membra ne structure composed of gel and fluid domains in a binary lphosphatid ylcholine-dibehenoylphosphatidylcholine (DC16 PC-DC22 PC) lipid membra ne. The nonequilibrium dynamic ordering process of coexisting phases f ollowing a thermal quench from the fluid state into the gel-fluid phas e coexistence region is characterized by a relaxation time on the orde r of hours. This slow process leads to a long-lived compartmentalized percolative lateral membrane structure with a dynamic network of inter facial regions having properties different from the coexisting gel and fluid bulk phases.