Fig. 2.

Fraction of bound ligand θ as a function of the net charge (q_l) and the number of phosphorylations (n) on the ligand. (A) Variation of θ for different ligand concentrations in the mean-field model with E_b = −10 k_BT, q_r = 3, q_l⁰ = 11 and 〈r〉 = 12 Å. Ligand concentrations, ρ_l, equal [in units of (δV)⁻¹] 10⁻⁶ (short-dashed line), 10⁻⁷ (long-dashed line), and 10⁻⁸ (solid line). (B) Variation of θ for different numbers of binding motifs, n, for an alternate model in which K_d = (nδV)⁻¹ exp(E_b/k_BT), with E_b values −12 (solid line), −15 (long-dashed line), and −20 (short-dashed line) k_BT, and ρ_l = 10⁻⁷ (δV)⁻¹. The parameters n and q_l are shown as continuous variables; however, only integer numbers of n and the corresponding values of q_l are of physical interest. Numerical results presented in this and subsequent plots are for γ = 1, as discussed in the text, and T = 298 K.