Molecular statistical model for adsorbed membrane particles

Indirect membrane-mediated forces influence aggregation, segregation and freezing processes of large particles inserted into a membrane or adsorbed to its surface. Colloidal particles, polymers, peptides and proteins are the source of deformations of the lipid double layer. These perturbations cause membrane-mediated attractive or repulsive forces between the particles. A molecular statistical treatment is useful for investigating the lateral organization of peripheral and trans-membrane peptides. To describe aggregation and freezing phenomena a density functional, which includes conventional short-range forces and membrane-mediated effects, is proposed. The method is applied to an ensemble of adsorbed peptides. It is investigated how the elastic splay-distortion modulus, the surface tension, the compression-expansion modulus of the bilayer and the cross-section of adsorbed particles influence aggregation and freezing. Assuming conventional values for the material parameters, membrane-mediated attractive forces are found to be sufficiently strong to enforce aggregation.