Figure 2.

Reproducibility of the phosphomolybdate blue (PMB) assay for RecA-DNA ATPase activity under optimal conditions. The absorbance at 650 nm (A₆₅₀) was measured after 35 min in each well of a 384-well plate in the presence (open circles) or absence (filled circles) of 5 μM-nts poly(dT). The concentration of ATP was 0.75 mM in the experiments. Each data point indicates the A₆₅₀ signal for each well from three different experiments on three different days; the error bars indicate the standard deviation of each mean value. The overall means for the positive signal control (no inhibitor added; open circles) and negative background control (no poly(dT) added; filled circles) were 1.153 ± 0.038 (CV = 3.3%) and 0.622 ± 0.010 (CV = 1.6%), respectively. The signal-to-background ratio was 1.8 and the signal-to-noise ratio was 14. The overall Z' factor was 0.73.