Critical mixing in monomolecular films : pressure-composition phase diagram of a two-dimensional binary mixture

Abstract

The pressure-composition phase diagram of mixed monolayers of dimyristoyl phosphatidylcholine (DMPC) and cholesterol at a temperature of 23.5 °C is derived by numerical analysis of pressure-area isotherms and corroborated by direct fluorescence microscopic observations. We identify a fluid-fluid miscibility gap, terminated by an upper critical point which is accessible near room temperature. We propose that the coexisting mixed phases of cholesterol and DMPC contain the phospholipid in two distinct states