Extended Data Fig. 9. Kinetic traces showing the accumulation and decay of the absorbing intermediates.

a,b, 625-nm absorbing intermediate as a function of time and O₂ concentration c,d, 510-nm absorbing intermediate as a function of time and O₂ concentration. Experimental conditions: O₂-free solution AetD (0.30 mM), 5,7-dibromo-L-tryptophan (2 mM), Fe(II) (0.60 mM, 2 molar eq), temperature: 5 °C. Concentrations are reported prior to mixing (2-fold dilution).