Competition experiments of NSC120927, NSC132279, NSC133071 and NSC132277 against substrate NADPH for E. coli DHFR. The plots show the fit of the primary data to the uncompetitive inhibition model and double reciprocal Lineweaver-Burk plot for NADPH titration at several fixed concentrations of (A) NSC120927, (B) NSC132279, (C) NSC133071 and (D) NSC132277. The y-axis shows the kcat and kcat−1 value and the x-axis shows the [NADPH] and 1/[NADPH] values for the primary and LB plot, respectively. The experimental data points were fit to the respective models using the non-linear curve-fitting algorithm of GraphPad Prism v 6.0e.