Conformational entropy of a bilayer membrane derived from a molecular dynamics simulation

Abstract

The conformational entropy of the disordered hydrocarbon chains in a bilayer membrane is calculated from a molecular dynamics simulation. We find that one chain in the mean field of the others is very well described by a trans-gauche model with adjacent gauches of opposite sign forbidden. The effective gauche energy depends, however, on the density of chains and may for realistic densities be between 4·5 and 5·7 kJ mol-1. This gives a conformational entropy of the disordered phase close to the gel-liquid crystalline phase transition temperature that is in rough agreement with the experimental phase transition entropy.