Cooperative effects. Simulations performed using the two-state model described in Fig 1 and the k₁ slow and k₋₁ slow rate functions. Left-hand panels show calculations with k_plus = 100 s⁻¹ and k_minus = 0 s⁻¹. Right-hand panels show calculations with k_minus = 15 s⁻¹ and k_plus = 0 s⁻¹. Additional parameters are as defined in Table S1. (A) Calculated force values. (B) Number of binding sites that are available (solid lines) and the number of sites that are bound (dotted lines). (C) Ca²⁺ concentrations.