Behavior of the two primary oscillators. The molar concentrations of the protein products of the two primary oscillators, P1 and P3, are shown as a function of time. The data were generated using the system of equations described in the text, with the parameters given below, and in constant darkness. The period over which the relative positions of the two primary oscillators repeat corresponds to the slow circadian frequency seen for the system overall (26.7 hours). Parameters used in the model: k11 = 1 × 109/(M • h), k12 = 0.3/h, k13 = 2000/h, k14 = 5.2/h, k15 = 500/h, k16 = 4.1/h, k17 = 5 × 105/(M • h), k18 = 15/h, k21 = 1.2 × 106/(M • h), k22 = 2/h, k23 = 600/h, k25 = 400/h, k29 = 4, k52 = 0.7/h, k53 = 1500/h, k54 = 2.55/h, k55 = 8/h, k56 = 2/h, k57 = 5 × 106/(M • h), k58 = 10/h, k61 = 2 × 105/(M • h), k62 = 2/h, DNA = 1 × 10-9 M, δ = 1.125, L1 = 2 × 10-9M/h, L2 = 6 × 10-10M/h, L5 = 1.5 × 10-9M/h.