Piezoelectricity of Fluid Lipid Lamellar Phases and Their Chirality Dependence

The effects of chirality of membrane-forming lipids, has been largely ignored at present. Here we demonstrate that the chirality of phospholipids makes fluid lipid bilayers piezoelectric. This implies that chiral lipids would play a central role in the functioning of cell membranes as active mechano-transducers. By periodically shearing and compressing nonaqueous lamellar phases of left (L-alpha-Phosphatidylcholine), right (D-alpha-Phosphatidylcholine) and racemic (DL-alpha-Phosphatidylcholine) lipids, we induced a tilt of the molecules with respect to the bilayer's normal and produced an electric current perpendicular to the tilt plane with the chiral lipids but not with a racemic mixture. This effect occurs because the lipids from a SmA* phase liquid crystal structure of the bilayers. Under molecular tilt, a ferroelectric SmC* phase is formed, creating a polarization which is normal to the tilt plane. This coupling allows for a wide variety of sensory possibilities of cell membranes such as mechano-reception, magneto-sensitivity, as well as in-plane proton membrane transport and related phenomena like ATP-synthesis, soft molecular machine performance, etc.