Visualization of simplifications 5 and 6. See Figure 3 and 4 for comments on the notation. In iteration 5 the association and dissociation plus phosphorylation of the active receptor IFN_R_JAKPhos_2_STAT1c and STAT1c are replaced by a simplified reaction (highlighted in yellow). In the simplified reaction with the new parameter k5new, phosphorylation of STAT1c by the active receptor is modeled without considering complex formation of both species. In the last iteration the dissociation and dephosphorylation of STAT1cPhos_y2 is removed from the model. A mathematical description of the models created in steps 5 and 6 are given in Additional file 1.