FIGURE 8.

The simulations show the impact of different arrestin binding scenarios for the toad rod scenario defined in Table 2. The behavior of the phosphorylation and transducin activation rates are given by Eqs. 48 and 49 with ω_λ = ω_act = 0.1 and N_p = 6. In the optimal scenario, arrestin binds only when rhodopsin is fully phosphorylated and the rate is given by Eq. 50. In the exp. scenario, the arrestin binding rates increase twofold with each phosphorylation step according to μ_n = 1.8 s⁻¹ e^{−0.7(n–1)} for n < N and μ_N = 0. In the linear scenario, the arrestin biding rates increase linearly according to μ_n = (N − n) 0.3 s⁻¹. The arrestin binding rates are chosen such that in each scenario they reach the final value μ₁ = 1.8 s⁻¹. For the (optimal, exp., linear) scenarios, the rates λ_N and k_act(N) are given by (3.2, 2.05, 0.9) s⁻¹ and (245, 237, 227) s⁻¹.