Instances of three-component negative feedback loops with positive feedback in biochemical oscillators and the generic motifs studied in this work.

<p>(A) Some biochemical oscillators utilizing the three-component negative feedback loop motif. Positive feedback loops (in blue) are often found along with the core negative feedback loop (in orange) (B) Oscillatory motifs involving the three-component negative feedback loop (<i>top</i>) with all possible auxiliary positive feedback loops (in blue). The motifs encountered in biochemical oscillators are clearly recognizable. The kinetic model formulation for each motif is also listed with the term representing the positive feedback in blue. The three components of the negative feedback loop are activator , intermediate and repressor . The parameter tunes the strength of the positive feedback, with a value of representing no positive feedback. (C) Waveform of the Goodwin oscillator with equal degradation in all steps with cooperativity increased from 3 (<i>left</i>) to 10 (<i>right</i>).