Stripe phases in lipid monolayers near a miscibility critical point

Some mixtures of lipids in monolayers at the air-water interface exhibit im miscible liquid phases. Theory predicts an exponential scaling for the widt h of liquid domains that depends on a competition between line tension and electrostatic dipolar repulsion. It is shown that the scaling law is valid for the stripe phase in a binary mixture of lipids, dihydrocholesterol, and dimyristoylphosphatidylcholine. This stripe phase appears only near a misc ibility critical point. The agreement of observed widths with theoretical s caling provides strong evidence for equilibrium in such mixtures, an essent ial condition for using data from monolayers to model the liquid regions of bilayers and biological membranes.[S0031-9007(99)08450-1].