Electrostatic Potentials at Membrane-Solution Interfaces

Abstract

This chapter discusses electrostatic potentials at membrane solution interfaces. Lipids in the membranes of all cells and subcellular organelles are arranged in the form of a bilayer with the hydrocarbon tails sequestered away from the water and the polar head groups exposed to the aqueous environment. About 10%–20% of the lipids in the membranes of many cells and organelles bear a net negative charge, whereas positively charged lipids are extremely rare. The concentration of monovalent cations at the surface of the bilayer will be an order of magnitude higher than the concentration of these ions in the bulk aqueous phase. The surface potential produced by charged lipids is dependent on the salt concentration in the bulk aqueous phase and a seminal paper. The absence of proteins, polysaccharides, and other macromolecules present in biological membranes can be considered an advantage to test how well the theory of the diffuse double layer describes the electrostatic potential produced by charges on lipids. The chapter describes hydrophobic adsorption of charged molecules to bilayer membranes, the electrostatic potential produced by molecular dipoles at membrane-solution interfaces, and the electrostatic boundary potential produced by charges located in the interior of the membrane, a few angstroms from the interface. Few examples of the possible biological significance of these electrostatic surface potentials are also described.