Comparison of potency of sildenafil and tadalafil for WT PDE11 versus the Q869A mutant
Values are given as mean ± S.E.M. The concentration at IC50 value for WT PDE11A4 and the Q869A mutant and calculation of the loss of free energy of binding (ΔΔG) were determined as described under Materials and Methods. ΔΔG values were calculated from the Ki values and not independently measured. -Fold change was calculated by dividing the Q869A value by that for the WT PDE11. Results are derived from at least three experiments in which each was assayed in triplicate. Ki for tadalafil and sildenafil for PDE11 and the Q869A mutant were calculated as described previously (Cheng and Prusoff, 1973).