Entropy-driven aggregation in multilamellar membranes

Membrane-fluctuation-induced attraction between ligand--receptor sites binding neighboring membranes is studied using meshless membrane simulations and the Weil--Farago two-dimensional lattice model. For the adhesion sites binding two membranes, this entropic interaction is too weak by itself for the adhesion sites to form a large stable domain. However, it is found that this attraction is enhanced sufficiently to induce large domains either when the sites bind three or more neighboring membranes together or have anchors that harden surrounding membranes. The latter effect is understood by the Asakura--Oosawa type of effective potential in the depletion theory.