On lipid monolayer-bilayer correspondence - a theoretical molecular biomechanics of biomembranes

摘要

Lipid bilayer vesicles play important physiological function and have wide applications in drug delivery, gene therapy, and artificial blood. Vesicles are difficult to handle in experiment. Various measurements, however, can be conveniently made on the monolayer at the air/water or oil/water interface. The monolayer-bilayer correspondence problem is firstly to pursue under what condition a leaflet of a bilayer can be mechanochemically equivalent to the monolayer at the interface. It is then extended to find a way to obtain mechanochemical properties of the monolayer and bilayer vesicles from the Pressure-area (π-a) relationship of the monolayer at the interface. We attack the problem starting from defining the intrinsic surface pressure for a bilayer leaflet. The difference between a bilayer leaflet and the monolayer at the air/water interface is merely that the latter, but not the former, exhibits a microscopic interfacial tension between the air or the oil and the hydrocarbon layer. It is concluded that the equilibrium pressure between the monolayer and bilayer vesicles is equal in magnitude to the microscopic water-monolayer interfacial tension. A procedure is developed to obtain from the π-a relationship of the monolayer at the air/water interface and various mechanochemical properties of the monolayer and bilayer vesicles.