Thin-proteolipid films: A new approach to the reconstitution of biological membranes

The extraction into n-decane of proteolipids composed of cytochrome c and a mixture of acidic and zwitter-ionic phospholipids, studied as a function of aqueous-phase pH, showed that optimal extraction occurred below pH 4.0 regardless of the anionic phospholipid used. The decane-soluble proteolipid readily allowed the formation of ultrathin black films whose electrical resistance was of the same magnitude as bilayers composed only of lipids. However significant differences in film capacitance were detected, being lower for the proteolipid than for equivalent lipid films. This model study establishes principles upon which the extraction of membrane proteins must be based and indicates the feasibility of reconstituting complex membrane functions in model thin-proteolipid films.