Figure 4

Bell-shaped dose-response for the basic model. (a) Bell-shaped dose response for the basic model when S _t is varied. Parameters used are: λ₋₁ = λ₁ = λ₂ = λ₋₂ = 0. 1s⁻¹,k₁ = 1 s⁻¹,k₂ = 0. 1s⁻¹,K _t = 2000μ M,E _p = 0. 1001E _k (−),E _p = 0. 2E _k (−−),E _p = 0. 08E _k (−.) (b) 2D parameter plot when α and P _t /K _t are varied. Parameters used are λ₋₁ = λ₁ = λ₂ = λ₋₂ = 0. 1 s⁻¹,α = 0. 1,K _t = 2000μ M.$R_{\max }^{S_t}$ denotes the maximum of R with respect to S _t and $R_0=\underset{S_t\to 0_{+}}{\text{lim}}R$. Within a narrow region above the line P _t /K _t = α the ratio $R_{max}^{S_t}/R_0>1.05$, i.e., there is at least a 5% increase in $R_{max}^{S_t}/R_0$ compared to R₀.