Since we could qualitatively reproduce the UV-vis spectra of 2, we additionally calculated the UV-vis spectrum of 3 for both TaAA9 and LsAA9 (Figures S6 and S7 in the SI). Intermediate 3 has only been observed for LsAA9 and the peak that experimentally is assigned the histidyl intermediate 41 is obtained at 360 nm (3.44 eV). The TD-DFT calculations do predict intense transitions involving orbitals of histidyl character (further discussions are provided in the SI). However, these are at somewhat lower energies at 427 nm (2.91 eV) for the triplet and 406 nm (3.05 eV) for the open-shell singlet. The correspondence with the experimental values was clearly better for the tyrosyl radical (2). Intriguingly, the calculated spectrum for 3 in TaAA9 is broader with two intense transitions at 342 nm (3.63 eV) and 395 nm (3.15 eV). Particularly, the former corresponds well to the observed band in LsAA9, but we cannot presently explain why the calculated spectrum for TaAA9 fits better with the experimental spectrum of LsAA9. More benchmarks of the accuracy of TD-DFT -and preferably also investigations with multiconfigurational wave functions -will be required to confidently assign the spectrum of 3. Along these lines, Zhao et al. find that 17% exact exchange is optimal to reproduce relative intensities for HERFD-XAS spectra, but we have refrained from attempting to re-parameterize the functional at this point.