Figure 3.

Kinetics of the accumulation and decay of the Fe(IV) intermediate. Overlay of the quantities of Fe(IV) determined by freeze-quench Mössbauer spectroscopy (red dots, right axis) with the SF-abs trace (blue trace, left axis). Both sets of data were from the reaction of a solution of the HEPD-E176A·Fe(II)·D₂-HEP complex with O₂ as described in the legend of Figure 2. The estimated uncertainty of the total quantity of the Fe(IV) complex determined by analysis of the Mössbauer spectra is ±3% of total intensity, as determined by iterative simulations evaluated by visual inspection.