Theoretical Model for the Phospholipid Bilayer System: Single Component Phase Transition and Binary Mixture Phase Diagram

Abstract

An interesting and important problem in statistical mechanics is the phospholipid main phase transition and related phenomena. A phospholipid molecule may be thought of as being composed of a polar head group molecular subunit to which are attached two alkyl chain “tails.”1 In aqueous solution, under conditions of excess water, these molecules are organized into bilayer structures. The bilayer may be viewed as a planar assembly with thickness approximately twice the length of the chain tails (~ 60 A). The polar head groups are confined to the two planes which define the surface of the bilayer and are in contact with the water on the outside of the bilayer. The hydrophobic alkyl chains are confined to the interior of the bilayer and extend from the polar head group to which they are attached to the plane which is the mid plane of the bilayer. Water is almost totally excluded from the interior of the bilayer.