Figure 4.

Dependence of unbinding force of the first peak (corresponding to μ1 in Fig. 3) on retrace velocity plotted in the inset on a logarithmic scale. Each point represents the average value of at least 300 unbinding events measured at a given retrace velocity. The solid line is a numerical fit of the data to modified Bell's expression (τ(f_u) = τ₀ exp(−l_r f_u/k_BT), where τ₀ is the lifetime of unstressed bonds, l_r the unbinding width between adhering cadherins, k_B Boltzman's constant, T is the absolute temperature, and f_u is the unbinding force. The fit yields for τ₀ ≈ 0.55 s and for l_r ≈ 0.59 nm.