Impact of polymer tether length on multiple ligand-receptor bond formation

The promoters of cell adhesion are ligands, which are often attached to fle xible tethers that bind to surface receptors on adjacent cells. Using a com bination of Monte Carte simulations, diffusion reaction theory, and direct experiments (surface force measurements) of the biotin-streptavidin system, we have quantified polymer chain dynamics and the kinetics and spatial ran ge of tethered ligand-receptor binding. The results show that the efficienc y of strong binding does not depend solely on the molecular architecture or binding energy of the receptor-ligand pair, nor on the equilibrium configu ration of the polymer tether, but rather on its "rare" extended conformatio ns.