Theory of Self-Assembled Bilayers Near a Cylindrical Hydrophobic Insertion

Abstract

We develop a coarse-grained model of lipids and proteins in which the lipids are modelled as diblock copolymers and the proteins as rigid cylinders. The generic protein model allows the possibility of amphipathic proteins with intrinsic curvature. Self-consistent field theory (SCFT) is used to determine the morphology of the lipid bilayer in the vicinity of the proteins. In particular, we focus on the case of a long transmembrane protein inserted perpendicular to the bilayer. For this system we use SCFT to determine the mechanical properties of the membrane and the thickness profile as a function of distance from the protein inclusion. The mechanical constants are also used in an elastic theory to predict the thickness profile. Good agreement between the full SCFT and elastic theory is obtained. We also use SCFT to determine systematic trends of the boundary conditions for the thickness profile at the protein interface. Such results could be used as boundary conditions for the description of bilayers using elastic theory. We show that this system undergoes a second order wetting transition as the interaction strength between the protein and membrane is varied.