Results of the parameter fit. (A-D) Simulation of the continuous model (solid lines) for high (red), medium (blue) and low (green) concentrations of ligand L144 and experimentally measured concentrations, cf. markers '+', '×' and '○'. (A) ERK. (B) JNK. (C) NFAT. (D) IKK. (E, F) Distribution of the Hill parameters in the best fit parameter set for ligand L144 (Table 1). (E) Distribution of the thresholds k. The markers '+' indicate the position of the parameters which we set to kfast (blue) and kslow (red) at the beginning of the optimization. The marker '○' indicates the position of kL144; for comparability the thresholds kQ144 and kY144 are also indicated, cf. the markers '◇' and '□', respectively. (F) Distribution of the Hill exponents n.