Receptor-Ligand Bond Spacing and Stresses in Membrane Bulge of Cell Adhesion

In this paper, focal adhesion growth is idealized as a process assisted by thermal fluctuations and receptor-ligand binding, but resisted by repulsive bulge pressure and membrane deformation. By considering the equilibrium of these forces, we obtain a critical spacing of receptor-ligand bonds, which is around 37-103nm for a wide range of repulsive bulge pressure. The results from our analysis quantitatively match well with the experiments reported in literature. The receptor-ligand bond spacing decreases with the increase of the repulsive pressure. The stresses and deflections of bulge membrane are studied by the bulge test method. The results show that the maximum values of normal and tangential stresses occur in the apex of the bulges. The values of stresses increase with the increase of repulsive bulge pressure. The deflection of bulge increases with the decrease of the thickness of membrane, but is little affected by the repulsive—this may be because a larger repulsive pressure corresponds to a shorter receptor-ligand bond space.