Phospholipid monolayers at hydrocarbon/water interfaces

Abstract Monolayers of the phospholipid dipalmitoylphosphatidylethanolamine are investigated at interfaces of water with the hydrocarbons n -dodecane, n -hexadecane, and bicyclohexyl. For the first time thermodynamic data and data from quantitative analysis of fluorescence microscopic observations are compared and discussed consistently. We observe the fluid/condensed phase transition with condensed phase domain shapes and interactions depending on the type of hydrocarbon. The hydrocarbon is shown to partition in the condensed lipid phase only if lipid and hydrocarbon chain lengths agree. The isotherms can be consistently simulated considering only entropic interactions and a removal of hydrocarbon from the interface upon compression.