Irreversible vs. reversible bridging:: When is kinetics relevant for adhesion?

We study theoretically the adhesion between two approaching surfaces, one containing tethered ligands and the other receptors. Using the reaction-diffusion formalism, we show that the range of adhesion l(r) is generally determined by a combination of tether dynamics, ligand-receptor affinity and experimental speed of approach v. Contrary to previous studies, we fully account for back reactions and are thus able to describe the crossover between irreversible adhesion at large affinities or high speed v and reversible adhesion at small affinities or low speed. We also briefly discuss the case of rupture and show that in the limit of irreversible adhesion the rupture occurs always at a larger distance than l(r) determined for approaching surfaces.