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Synthesis of the H-cluster framework of iron-only hydrogenase


The metal-sulphur active sites of hydrogenases catalyse hydrogen evolution or uptake at rapid rates. Understanding the structure and function of these active sites—through mechanistic studies of hydrogenases1,2,3,4, synthetic assemblies5,6,7,8,9,10,11,12 and in silico models13,14,15—will help guide the design of new materials for hydrogen production or uptake16. Here we report the assembly of the iron-sulphur framework of the active site of iron-only hydrogenase (the H-cluster), and show that it functions as an electrocatalyst for proton reduction. Through linking of a di-iron subsite to a {4Fe4S} cluster, we achieve the first synthesis of a metallosulphur cluster core involved in small-molecule catalysis. In addition to advancing our understanding of the natural biological system, the availability of an active, free-standing analogue of the H-cluster may enable us to develop useful electrocatalytic materials for application in, for example, reversible hydrogen fuel cells. (Platinum is currently the preferred electrocatalyst for such applications, but is expensive, limited in availability and, in the long term, unsustainable17.)

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Figure 1: Composite structure of the H-cluster.
Figure 2: Synthetic pathways for assembly of the H-cluster model and related subsite-cluster materials.
Figure 3: Structure of [Fe4S4(SCH3)3{Fe2(CH3C(CH2S)3)(CO)5}]2-, derived from DFT calculations.
Figure 4: The electrochemical behaviour of the synthetic H-cluster model.


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This work was supported by the BBSRC and the John Innes Foundation. We thank D. J. Evans and J. E. Barclay for Mössbauer spectroscopy and discussions; L. Hill for ESMS; and R. R. Eady and R. A. Dixon for discussions and comments on the manuscript. Research done at Washington State University was supported by NIH and performed at EMSL, a national scientific user facility sponsored by the US DOE's Office of Biological and Environmental Research and located at PNNL, which is operated for DOE by Battelle.

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Correspondence to Christopher J. Pickett.

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Supplementary information

Supplementary Methods

Experimental, ESMS and PES information. (DOC 42 kb)

Supplementary Notes

Note on dissociation step in Supplementary Figure 4. (DOC 29 kb)

Supplementary Figure 1

X-ray structure of B. (JPG 167 kb)

Supplementary Figure 2

PES spectrum of [Fe4S4(SEt)3{Fe2(CH3C(CH2S)3)(CO)5}]2-. (DOC 30 kb)

Supplementary Figure 3

Simulation 10th scan of D. (JPG 25 kb)

Supplementary Figure 4

Proposed mechanism for electrochemistry of D. (GIF 12 kb)

Supplementary Figure Legends

(DOC 26 kb)

Supplementary Data

Crystallographic data of B. (DOC 34 kb)

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Tard, C., Liu, X., Ibrahim, S. et al. Synthesis of the H-cluster framework of iron-only hydrogenase. Nature 433, 610–613 (2005).

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