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. Author manuscript; available in PMC: 2010 Dec 11.
Published in final edited form as: Mol Cell. 2009 Dec 11;36(5):894–899. doi: 10.1016/j.molcel.2009.11.018

Figure 3. I1-FFL shows fold-change detection over a wide range of parameters.

Figure 3

(A) Model parameters were varied. For each choice of parameters, we provided two step inputs with the same fold-change F=10, and different absolute levels X0’=10 X0. As a measure of the fold-change detection property, we computed the relative difference (ε) in the amplitude of the Z response (Zmax) for the two step inputs.

(B-D) Three detailed designs of the Z promoter input function were considered, in which binding of X and Y is exclusive (B), independent (C), or cooperative (D). In all cases, the light region indicates the parameter range where fold-change detection occurs, in the sense that the two step inputs produce identical outputs within 10% (contour line delineates ε=0.1).

Parameters: Ki’s are binding constants, X0 is the basal input level, and Y0= β1X0/α1, with β1 and α1 defined in equation 3 in Box.