Flexoelectric Model for Active Transport

Abstract

A general model of active transport is proposed, based on the flexoelectric membrane properties, with regard to liquid crystalline membrane structure. The physical principles of the flexoelectric effect are briefly reviewed and it is admitted that the spherical deformation of planar membrane produces a flexoelectric polarization which results in depolarizing electric field. The orientational state of integral protein globuli in this field is considered and it is found to be similar to that of a trigger. It is shown that a change of the globula dipole moment by adhering to the negative end of a proton may cause its reorientation accompanied with translocation of the proton to the outer membrane side. The theoretical formulae describing such a mechanism are derived and both the value and the sign of transmembrane potential are calculated as a function of flexoelectric membrane coefficients. Two chanal feedback control leading to stable self-regulation both of the membrane curvature and transmembrane potential, is involved in this model. In view of such mechanism a natural explanation may be given for a number of active transport features: curved membrane sectors are found to be metabolitically active; transport energy is secured by membrane itself; assymmetry and vector character of the transport are clearly demonstrated. There exist at least two experiments which are consistent with the notion of flexoelectricity and permit in principle to measure the value of flexoelectric membrane coefficient.