Fig. 4.

Strength and dynamics of the SdrC homophilic interaction. (A) Adhesion forces together with representative curves (Inset) obtained in PBS between 13 different L. lactis SdrC⁽⁺⁾ cells and AFM tips labeled with the recombinant SdrC_N2N3 protein. Curves were obtained using a contact time of 100 ms, an applied force of 250 pN, and an approach and retraction speed of 1.0 µm/s. (B) Control experiments on SdrC⁽⁻⁾ cells showing the specificity of the SdrC–SdrC forces. (C) Dependence of the adhesion force on the loading rate applied during retraction, measured on six different cells from four independent cultures, using a contact time of 100 ms. The mean adhesion force, F, increased linearly with the logarithm of the loading rate (r): F = 7.84 10⁻¹² ln(r) + 2.07 10⁻¹⁰. (C, Inset) Force-vs.-time curve, which was used to estimate the effective loading rate. (D) Dependence of the adhesion frequency on the interaction time, measured at a constant approach and retraction speed of 1.0 µm/s on five different cells from five independent cultures.