The properties of lipid bilayer membranes separating two aqueous phases: Formation of a membrane of simple composition

Abstract

The formation of a lipid membrane 61 Å in thickness from a system composed of a highly purified egg phosphatidyl choline and n-tetradecane dissolved in a chloroform-methanol solvent is described. This membrane, which is formed in aqueous 0·1 M-NaCl at 36°C in a manner analogous to the generation in air of so-called “black” soap films, has a D.C. ohmic resistance of about 1 × 1×10⁶ Ω cm², a dielectric breakdown voltage of 200 mv, a surface tension of 0·5 dyne cm⁻¹ and a water permeability coefficient of 0·16 microns min⁻¹ atm⁻¹. The effects of lipid composition, solvent composition and temperature on the formation and stability of the membrane are investigated. The physical properties together with the composition and the extreme thinness of the membrane suggest that the structure is very similar to the bimolecular lipid leaflet which is widely accepted to constitute an integral part of membranes of natural origin.