Table 3.
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 |
Values represent the data from 3 traces (SF) or 2-4 experiments (RFQ-EPR). Similar rate constants were obtained in SF studies at lower NrdIhq and NrdF concentrations (Figure S13).
For phases involving MnIIIMnIV 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 MnIIIMnIV by simulation at 3 timepoints (section 2.9).
NA: not applicable (not observable at this wavelength). Given that the MnIIIMnIV 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).
Uncertainty includes uncertainties in fit and in concentration of MnIIIMnIV (~30%)
Concentrations of MnIII2-Y• (27 μM) and MnIII2 (11 μM) are taken as given (section 2.8.1)