Figure 2
From: Confidence from uncertainty - A multi-target drug screening method from robust control theory
Case study model. (A) Topology of the network. U is the enzyme catalyzing the conversion of X to product Y, through the intermediate UX. The open arrows indicate the chemical reactions, and the oval arrow a negative regulation. k's represent the parameters involved in each step. Ø is the null component to indicate production and degradation. Input to the system is given by the total enzyme, U tot , concentration, constant over time and given by u tot = u+ux (lower-case component names indicate the corresponding concentrations). Output of the system is y. Inputs and outputs are highlighted in red. (B) Nonlinear model equations. The reaction rates are given by mass-action, negative feedback is described by the multiplicative term containing k 5 . The nominal values of the parameters are: k 1 = 1, k 2 = 2, k 3 = 10, k 4 = 0.5, k 5 = 0.5, k -1 = 3, k -3 = 1.