Insight into Photoactive Sites for the Ethylene Oxidation on Commercial HZSM-5 Zeolites with Iron Impurities by UV Raman, X-ray Absorption Fine Structure, and Electron Paramagnetic Resonance Spectroscopies

2007 ◽  
Vol 111 (13) ◽  
pp. 5195-5202 ◽  
Author(s):  
Guiyang Yan ◽  
Jinlin Long ◽  
Xuxu Wang ◽  
Zhaohui Li ◽  
Xinchen Wang ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fine Structure ◽  
Ethylene Oxidation ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Absorption Fine ◽  
Uv Raman ◽  
X Ray Absorption ◽  
Electron Paramagnetic ◽  
Insight Into

scholarly journals [FeFe]-Hydrogenase Maturation: H-Cluster Assembly Intermediates Tracked by Electron Paramagnetic Resonance, Infrared, and X-Ray Absorption Spectroscopy

2020 ◽  
Author(s):  
Brigitta Németh ◽  
Moritz Senger ◽  
Holly J. Redman ◽  
Pierre Ceccaldi ◽  
Joan Broderick ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Absorption Spectroscopy ◽  
Cluster Assembly ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Hydrogenase Maturation ◽  
Catalytically Active ◽  
X Ray Absorption ◽  
Electron Paramagnetic

[FeFe]-hydrogenase enzymes employ a unique organometallic cofactor for efficient and reversible hydrogen conversion. This so-called H-cluster consists of a [4Fe-4S] cubane cysteine-linked to a diiron complex coordinated by carbon monoxide and cyanide ligands and an azadithiolate ligand (adt = NH(CH2S)2). [FeFe]-hydrogenase apo-protein binding only the [4Fe-4S] sub-complex can be fully activated in vitro by the addition of a synthetic diiron site precursor complex ([2Fe]adt,). Elucidation of the mechanism of cofactor assembly will aid in the design of improved hydrogen processing synthetic catalysts. We combined in situ electron paramagnetic resonance, Fourier-transform infrared, and X-ray absorption spectroscopy to characterize intermediates of H-cluster assembly as initiated by mixing of the apo-protein (HydA1) from the green alga Chlamydomonas reinhardtii with [2Fe]adt. The three methods consistently show rapid formation of a complete H-cluster in the oxidized, CO-inhibited state (Hox-CO) already within seconds after the mixing. Moreover, FTIR spectroscopy support a model in which Hox-CO formation is preceded by a short-lived Hred´-CO like intermediate. Accumulation of Hox-CO was followed by CO release resulting in the slower conversion to the catalytically active state (Hox) as well as formation of reduced states of the H-cluster.

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