Time and frequency domain representations of the behaviour of NF-κBn, p53a, p21 and CycE-CDK2-p21. Individual time courses (left) and average frequency spectra (right). A Left panel: time courses of stochastically simulated NF-κBn (red) and p53a (blue). Quasi-deterministic time courses superimposed in black. Right panel: average frequency spectra of NF-κBn (red), p53a (blue) and E2F-Rbpp perturbed by NF-κBn alone (black). B Evidence of crosstalk in time (left) and frequency domain (right) of p21 in the fully coupled network (red), in comparison to the isolated cell cycle (black). C Stochasticity in time (left) and frequency domain (right) of CycE-CDK2-p21 in isolated cell cycle, using quasi-deterministic (black) and fully stochastic models (red).