Fig. 5

Conversion of λ between two PWM matrices for the lmd transcription factor. The flow chart shows the procedure to obtain an optimised λ, given two different PWMs and one known and one unknown λ (a). Subfigure b illustrates the two alternate PWMs for lmd which are available in the FLYFACTORSURVEY database [24]. Equation 6 suggests that PWM1 has a λ of 1.6, and we are trying to find a λ for PWM2. Subfigure c is a heatmap of the residence time distribution of PWM2 for different values of λ and different binding site strength level. Each column of the heatmap represents a specific λ value and each row represents a specific binding site strength level measured by the −l o g ₁₀ of the corresponding top quantiles from low affinity to high affinity sites. Blank regions in the heatmap indicate λ values which lead to residence time out of the reference scale that is an indication of unsuitable λ values. d, e and f show the correlation of residence time between PWM1 and PWM2 using specific λ values of 0.8, 1.4 and 2.0, respectively. The curve in Subfigure E has the lowest mean square error, and so we assign PWM2 to have a λ=1.4