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Vibrational spectroscopy reveals the initial steps of biological hydrogen evolution
Katz, Sagie; Noth, Jens; Horch, Marius; Shafaat, Hannah; Happe, Thomas; Hildebrandt, Peter; Zebger, Ingo
[FeFe] hydrogenases are biocatalytic model systems for the exploitation and investigation of catalytic hydrogen evolution. Here, we used vibrational spectroscopic techniques to characterize, in detail, redox transformations of the [FeFe] and [4Fe4S] sub-sites of the catalytic centre (H-cluster) in a monomeric [FeFe] hydrogenase. Through the application of low-temperature resonance Raman spectroscopy, we discovered a novel metastable intermediate that is characterized by an oxidized [(FeFeII)-Fe-I] centre and a reduced [4Fe4S](1+) cluster. Based on this unusual configuration, this species is assigned to the first, deprotonated H-cluster intermediate of the [FeFe] hydrogenase catalytic cycle. Providing insights into the sequence of initial reaction steps, the identification of this species represents a key finding towards the mechanistic understanding of biological hydrogen evolution.
