Piezoelectricity of phospholipids: Are cell membranes also piezoelectric?

Abstract

Recently it was foundi that mechanical deformation of films of L-α-phosphatidylcholine in the La phase induces an electric polarization. It was suggested that this effect is due to the chiral smectic A (SmA∗) type liquid crystal structure of the bilayers, which under molecular tilt becomes a ferroelectric (SmC∗) phase, where the electric polarization is normal to the tilt plane. However no control measurement on the racemic material has been presented to prove this suggestion. Here we demonstrate that indeed the chirality of phospholipids makes fluid lipid bilayers piezoelectric. By periodically shearing and compressing nonaqueous lamellar phases of synthetic right enantiomer 2,3-Dihexadecanoyl-sn-glycero-1-phosphocholine (D-DPPC) the synthetic left enantiomer 1,2-Dihexadecanoyl-sn-glycero-3-phosphocholine (L-DPPC) lipids and their racemic mixture (DL-DPPC) ,we induced a tilt of the molecules with respect to the bilayer normal and produced electric current perpendicular to the tilt plane, with the chiral lipids only. Because most of the living cell membranes contain chiral lipids, we hypothesize that piezoelectricity may have a role in the function of cell membranes. For example, this coupling allows for a wide variety of sensory possibilities of cell membranes such as mechano-reception, magneto-sensitivity, and proton membrane transport. Preliminary results on electromechanical couplings in Saccharomyces cerevisiae (Baker's yeast) and their protoplasts will be also reported and discussed.Endnotesi A. Jakli, J. Harden, C. Notz and C. Bailey, Liquid Crystals, 35 (4), 395-400 (2008).