Figure 5. The high Hes1 steady state can be readily excited into transient oscillations.

(a) The model is initiated in the high Hes1 state in a bistable regime (parameters as default and p₁=220, initial conditions m=14.6766, p=465.8128, r=33.1285). At 5,000 min, the Hes1 mRNA levels are instantaneously set to a value 10% higher than at this steady state (that is, m=16.1433). The system is excited into transient oscillations. (b) The model is initiated in the low Hes1 steady state (initial conditions m=28.9, p=0.4, r=1442.6). To excite the system, at t=5,000 min, a perturbation of 15 units of protein (an initial 30-fold increase) is added every minute for 4,000 min. Other parameters are p₀=390, τ=29 min, b_l=ln(2)/20 min⁻¹, b_u=ln(2)/35 min⁻¹, n₀=n₁=m₀=m₁=5, r₀=100, r₁=300, μ_p=22 min, μ_r=1,000 min.