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. 2006 Dec 12;2:68. doi: 10.1038/msb4100099

Figure 2.

Figure 2

Characterization of switches and feedforward circuits. The total concentration of the source So1 or the switch template T12 is 100 nM, and the total concentration of the source So2 or the switch template T21 is 75 nM. Downstream activator concentration is 1 μM. The ratio of maximum to minimum fluorescence signals before normalization is greater than 10 for both TAMRA and Texas Red dyes. (A) Normalized fluorescence time courses for the DNA inhibitor dI1 inhibiting switch Sw21 with the total concentration of activator A1 at 1 μM. The enzymes are added at 10 min and different amounts of DNA inhibitor dI1 inputs are added at 35 min. Additional DNA inhibitor dI1 is added at 4 h to generate maximal fluorescence levels. The concentrations of DNA inhibitor dI1 inputs are marked on the time courses. (B, C) The normalized fluorescence signals immediately prior to the addition of excess dI as shown in (A) are used for the construction of transfer curves. Experimental data points are plotted as circles and the model fits (see Box 1 for model and parameters) are plotted as lines. (B) The transfer curves of switch Sw21 with the total concentration of DNA inhibitor dI1 as inputs. (C) The transfer curve of switch Sw12 with the total concentration of DNA inhibitor dI2 as inputs. (D) Normalized fluorescence time courses for the feedforward circuit of source So1 inhibiting switch Sw21 with the total concentration of activator A1 at 1 μM. The enzymes are added at 20 min and excess DNA inhibitor dI1 is added at 210 min to generate maximal fluorescence levels. The concentrations of ON state source So1 are marked on the time courses. (E, F) The normalized fluorescence signals immediately prior to the addition of excess dI as shown in (D) are used for the construction of transfer curves. Experimental data points are plotted as circles and the model fits are plotted as lines. (E) The transfer curves of switch Sw21 with the source So1 activity as inputs. (F) The transfer curve of switch Sw12 with the source So2 activity as inputs.