Fig. 1

TGF- β model: panel a shows the model sensitivities with respect to the parameters in logarithmic scale. In panel b the maximum number of identifiable parameters is depicted depending on the collinearity threshold. The group-size does not change much by the threshold. The red vertical line indicates our choice (CI =20) for the further analysis. In panel c the mathematical model is depicted. Nodes indicate states (yellow), identifiable (green) and not identifiable (red) parameters, and observables (blue). In panel d the interplay among the collinear parameters are indicated. There are 5 groups of parameters: in the first 4 groups triplets of parameters show large collinearity, while in the fifth group 5 parameters are collinear