Fig. 3
From: Crystallographic and spectroscopic assignment of the proton transfer pathway in [FeFe]-hydrogenases
Infrared spectra of wild types and PT pathway variants. The frequency regime of the H-clusters’ CO ligands is shown (2000–1785 cm−1). For ATR-FTIR spectroscopy, the buffer was set to pH 8 and the rehydrated samples were purged with 100% H2 for 5 min. a, c Auto-oxidation in absence of H2 (i.e. purged with N2) was exploited to likewise enrich for all examined proteins the oxidized resting state, Hox (gray bands). Some CpI variants tend to accumulate HoxH in parallel with Hox (e.g. C299A bands at frequencies 1975/1953/1809)34. b, d When shifting from N2 to H2 the spectrum of wild-type protein changes to different fractions of reduced species including Hred (cyan) and Hsred (red) as well as Hred´ (magenta). Most PT pathway variants accumulate Hhyd (blue) instead or in addition to a mix of reduced states. For precise state-specific vibrational signals of CpI and HydA1 see Supplementary Table 7
