Figure 2. Dynamic ranges of the HTRF assay for purified Stx2a and Stx2e.

In the left panels, delta ratio (DR) values at each Stx2 concentration ranging from 1 ng/ml to 256 ng/ml are shown. All measurements were conducted in triplicate, and data are presented as the mean values ± standard deviation. In the right panels, DR values at Stx2 concentrations ranging from 1 ng/ml to 64 ng/ml in a representative assay are shown. A weighted four parameter logistic (4PL) curve can be applied to the analysis of the DRs in this range of Stx2 concentrations.