Fluid-fluid coexistence in phospholipid membranes induced by decanol.

We have observed fluid-fluid coexistence in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane containing 1-decanol, using different experimental techniques and membrane morphologies. This phase behavior is reversible and occurs over a temperature range just above the chain melting transition temperature of the membrane. Although earlier experimental studies and computer simulations have shown the ability of decanol to enhance lipid chain ordering, its potential to induce fluid-fluid coexistence in membranes has not been hitherto recognized. Being the only binary membrane system known so far to exhibit fluid-fluid coexistence, the present system can serve as a simple model to gain a better understanding of mechanisms that drive this unusual phase behavior, which is believed to play an important role in the functioning of cell membranes.