Cross-sectional view of the time evolution of membrane shape as a result of receptor-ligand binding. Already by t = 20 s, we can see that the membrane separation distance center of the contact zone has more or less attained a uniform value of z ∼ 40 nm. This image sequence was obtained with PA(BA) = 100 (KA ≈ 106 M−1), PA(LI) = 1000 (KA ≈ 107 M−1), A0 = I0 = 2000 molecules, κBA = κLI = 40 μN/m, zeq(BA) = zeq(LI) = 42 nm, pdiff(F) = 1, pdiff(C) = 0.1, M ∼ 10−12 m4/Js, γ = 24 μN/m, β = 5 × 10−20 J.