Illustration of a re-entrant dose response predicted by the thermostatistical model for a double-binding-site promoter.

<p>The solid line ‘DS’ was computed from Eq. (25) and represents the fold change of the transcriptional activity of a double binding site promoter for a given relative transcription factor concentrations . The solid line labeled ‘SS’ represents the transcriptional activity of a corresponding single binding site promoter (as computed from Eq. (82) given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034439#pone.0034439.s001" target="_blank">Text S1</a>). The dashed line represents two times the the activity calculated for the single binding site promoter. Diamonds indicate the critical transcription factor concentrations calculated from Eq. (91) in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034439#pone.0034439.s001" target="_blank">Text S1</a>. As expected, these critical value correspond to the critical values that can be obtained directly from the intersections of the ‘2× SS’ and ‘DS’ graphs. Parameters: , . , and .