Figure 3.

Determination of the Fos:H2O2 reaction stoichiometry. A, LC-MS chromatograms monitoring m/z = 141 for the HppE-generated d4-Fos product (black) and m/z = 137 for the commercial Fos internal standard (gray). B, quantity of d4-Fos produced by HppE as a function of [H2O2] added. The error bars are the standard deviations from the mean values of six measurements at each concentration. The slope gives the Fos:H2O2 reaction stoichiometry (1.00 ± 0.05). Reaction conditions were the same as in Figure 2, with the exception of the [H2O2] added.