The effect of H
concentration on inducing fluorescence in the probes. In the presence of 0.2 μM HRP, 50 mM phosphate pH 7.4 buffer and H2O2, oxidation of the probes results in an increase in fluorescence. On the left side of the vertical axis are the fluorescence intensities when no HRP nor H2O2 are added to the probe and pH buffer. The fluorometer was calibrated so that pure water resulted in a zero fluorescence and the reaction involving the probe with HRP, pH buffer, and 100 nM H2O2 resulted in a fluorescence reading of 1000. The fluorescence intensity results presented in the next two figures are calibrated using two points: the fluorescence intensity of the probe without H2O2 or HRP added, and the fluorescence intensity at 1000 nM H2O2. The measurements were repeated four times and standard deviation error bars have been added. Many of the error bars, however, are within the size of the points.