A comparative study of the sorption of serum albumin, lysozyme, and cytochrome C at phospholipid membranes using surface tensiometry, electrophoresis, and leakage of probe molecules

Protein sorption at phospholipid membranes is studied when proteins are injected into the solution, by measuring the change in the surface tension of lipid monolayers spread on the water surface. A method for analyzing the surface tension data is proposed. The results of this analysis are in agreement with the results of experiments on liposomes: an investigation of the change in electrophoretic mobilities and leakage tests of probe molecules from inside the liposomes, when proteins are added to the dispersion medium. The conclusion is that serum albumin, a rather flexible protein, absorbs into lipid membranes through non-electrostatic forces, whereas cytochrome C and lysozyme adsorb onto the membranes mainly by electrostatic attraction.