Inclusion-Induced Bilayer Deformation: An Effect of Surface Tension

Hydrophobic interactions between an inclusion, such as a protein, and a lipid bilayer play an important role in conformational changes of the inclusion and the bilayer, We analyze a deformation energy related to a hydrophobic mismatch by using a continuum theory in which compression, tension, and bending energies are considered, Differently from previous works in which the effect of surface tension was usually neglected, we concentrate on the effect of the tension on the membrane deformation. We solve the Euler-Lagrange equation of a local deformation profile by using modified boundary conditions and a finite-difference approximation. With well-known information for three kinds of lipid bilayers, we numerically calculate the deformation energies with and without the surface tension. We find that the contribution of the surface tension to the deformation energy cannot always be neglected, implying a strong dependence on the lipid composition. The surface tension plays a negligible role in the dimyristoyl phosphatidylcholine (DMPC) bilayer; however, it does not in the glycerolmonooleate(GMO) bilayer which has a longer hydrophobic length and relatively weaker compression and bending rigidities than the DMPC bilayer.