Modeling and analysis of single cell characteristics of the ppERK dynamics and dose response. A. Schematic of a mechanistic model of ERK activation and its steady-state response properties. The positive feedback (PF), no-feedback, ultrasensitive (US), and negative feedback (NF) models have the feedback strength F
set to different values (5, 1 and 0.5, respectively). The input is RasGTP, and the output is ppERK. B-D. Steady-state, deterministic input/output response curves for the PF, US and NF models. E-G. Steady-state, cell population input/output response curves for the PF, US and NF models. In B-G, red denotes increasing input from low levels, while blue denotes decreasing input from high levels. When only one color is shown, there is no difference between the increasing and decreasing input curves. Dashed lines indicate the 95th percentile of all simulations, and dotted lines indicate the 5th percentile.