Molecular Theory of Acyl Chain Packing in Lipid and Lipid-Protein Membranes

Abstract

This chapter describes the molecular level theory of lipid packing and chain statistics in membrane bilayers and demonstrate some of its recent biophysical applications. In MD simulations of a lipid membrane one solves the classical equations of motion governing the dynamics of all the atoms of all the constituent lipid molecules, as well as those of the surrounding water molecules. The uncertainties in intermolecular potentials also affect the applicability of MC simulations. In these simulations, unlike in MD, one does solve the equations of motions, but, rather, tries to sample as many equilibrium configurations of the system in question as possible. The formalism outlined below can be applied to a bilayer membrane of arbitrary lipid composition, whether symmetric or nonsymmetric with respect to the two monolayers, as well as to an arbitrary membrane thickness and/or curvature. The variational derivation of the singlet probability distribution started indeed with the mean field free energy expression.