Concentration dependence and structure–activity relationship of the impact of the biaryl compounds on the polymerization of SaFtsZ (A and D), EcFtsZ (B and E), and EfFtsZ (C and F), as determined by monitoring time-dependent changes in absorbance at 340 nm (A340) at 25 °C. (A–C) The time-dependent A340 polymerization profiles of each target FtsZ in the presence of 13 at the indicated concentrations. (D–F) Time-dependent A340 polymerization profiles of each target FtsZ in the presence of vehicle (DMSO) only or 40 μg/mL of 13, 14, 15, or the indicated comparator drugs. Experimental conditions for all the FtsZ polymerization studies were 10 μM protein, 50 mM Tris·HCl (pH 7.4), 50 mM KCl, 2 mM magnesium acetate, 1 mM CaCl2 (for SaFtsZ) or 10 mM CaCl2 (for EcFtsZ and EfFtsZ), and 1 mM GTP.