Results from stopped-flow mixing of 14 μM CYP119 with 8.6 μM mCPBA at 4 °C. (A) Observed spectra at 1.0, 7.0, 13, 26, and 65 ms after mixing. (B) Observed spectra at 65, 180, 290, 390, and 700 ms after mixing. (C–F) Simulated spectra of the intermediate as found from unconstrained minimizations with different initial guesses for the rate constants. The program-derived final values for kC in the deconvolutions are 17.4 s−1 (C), 9.2 s−1 (D), 6.7 s−1 (E), and 2.3 s−1 (F). The Supporting Information has more information.