Fig. 2.

Linearization and noise reduction due to NF. (A) Experimental and simulated dose–response curves for the constructs in Fig. 1. For theoretical curves, the parameters are a = 50 nM h⁻¹, b = 3.6 nM⁻¹ h⁻¹, C = 0.6 [ATc] h⁻¹, d = 0.12 h⁻¹, f = 1.2 h⁻¹, θ = 0.44, n = 4, F_x ≡ 1.5 for NR strains, and F_x = F_z for NF strains (B) Experimental, background-corrected dose–response for the NF cascade and the corresponding linear fit plotted on log–log scale, showing that linearity holds from very small to saturating ATc concentrations (0.1–60 ng/mL). Error bars corresponding to standard deviations (from 3 replicates) are smaller than the symbols. (C) Experimentally measured and simulated gene expression noise for the NR and NF gene circuits. (D and E) Experimental fluorescence histograms for the NR (D) and the NF (E) strains at increasing ATc concentrations (0–500 ng/mL).