Table 3.

Apparent rate constants and amplitudes for Mn^IIIMn^IV formation and decay in the reaction of NrdI_hq, Mn^II-loaded NrdF, and O₂, determined by fits to single-wavelength SF (340 and 410 nm) or RFQ-EPR (10 or 77 K) data.^a

Phase	340 nm			410 nm			RFQ-EPR
	k (s−1)	ΔA	Amplitude (μM)	k (s−1)	ΔA	Amplitude (μM)	k (s−1)	Amplitude (μM)
MnIIIMnIV formation	2.5	0.17	13 ± 4 b	NAc	NA	NA	2.2 ± 0.4	19 ± 6d
MnIIIMnIV decay	0.08	−0.16	19 ± 8 e	0.09	0.054	25 ± 8 e	0.12 ± 0.02	22 ± 7d

^aValues represent the data from 3 traces (SF) or 2-4 experiments (RFQ-EPR). Similar rate constants were obtained in SF studies at lower NrdI_hq and NrdF concentrations (Figure S13).

^bFor phases involving Mn^IIIMn^IV formation or decay, we have assumed ε₃₄₀ = 13 ± 4 mM⁻¹ cm⁻¹ and ε₄₁₀ = 3 ± 1 mM⁻¹ cm⁻¹. These values were determined from Figure S14 on the basis of the estimated UV-vis spectrum of the intermediate and the quantification of the EPR spectrum of Mn^IIIMn^IV by simulation at 3 timepoints (section 2.9).

^cNA: not applicable (not observable at this wavelength). Given that the Mn^IIIMn^IV intermediate should contribute ~+0.07 to ΔA₄₁₀ (Figure S14), it is probable that this phase was not resolved from that of sq decay in the fits because its rate constant for formation is somewhat similar to that for sq decay, and of the same sign (see Table S3).

^dUncertainty includes uncertainties in fit and in concentration of Mn^IIIMn^IV (~30%)

^eConcentrations of Mn^III₂-Y• (27 μM) and Mn^III₂ (11 μM) are taken as given (section 2.8.1)