FIG. 1.

(A) Whole-plate scatter plot: columns 1, 2, and 5–48 represent complete reaction samples; columns 3 and 4 contain no-enzyme controls. Z′ factor of 0.70 and signal-to-background ratio of 3.5 were calculated based on the absorbance increase over 8 min (n = 64 wells each for the positive and negative controls). AU, absorbance units. (B) Single-well reaction time courses in the presence of furoxan (12 concentrations ranging from 57 μM [bottom line] to 28 nM [top line] in twofold dilution steps). The zero-time point refers to the first plate read, while the actual reaction initiation is estimated to take place approximately 1.5 min earlier. Reaction time-course data from a no-enzyme control, overlapping with those from the top furoxan concentrations, are provided as larger-size open circles. (C) Concentration-response curves of four furoxan samples delivered as 12-point dilution series with final concentrations ranging from 28 nM to 57 μM. (Inset) Structure of furoxan.