Orientational Order within Biological Membranes

Recently developed approaches analyzing the degree of in-plane orientational  ordering are compared. The first one originates from an intrinsic anisotropic shape of membrane constituents, based on which the mismatch curvature tensor M is introduced. The second one originates from the nematic tensor order parameter Q reflecting average local degree of orientational ordering. Based on these tensors free energy of systems are derived taking into account symmetry allowed combinations of tensors. From both approaches the degree of local orientational ordering is determined as a function of membrane shape. In the paper we discuss relevance of these approaches