Functionally Relevant Interplay between the Fe4S4 Cluster and CN− Ligands in the Active Site of [FeFe]-Hydrogenases

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• 作者：Maurizio Bruschi ; Claudio Greco ; Luca Bertini ; Piercarlo Fantucci ; Ulf Ryde ; Luca De Gioia
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：April 14, 2010
• 年：2010
• 卷：132
• 期：14
• 页码：4992-4993
• 全文大小：146K
• 年卷期：v.132,no.14(April 14, 2010)
• ISSN：1520-5126

文摘

[FeFe]-hydrogenases are highly efficient H₂-evolving metalloenzymes that include cyanides and carbonyls in the active site. The latter is an Fe₆S₆ cluster (the so-called H-cluster) that can be subdivided into a binuclear portion carrying the CO and CN⁻ groups and a tetranuclear subcluster. The fundamental role of cyanide ligands in increasing the basicity of the H-cluster has been highlighted previously. Here a more subtle but crucial role played by the two CN⁻ ligands in the active site of [FeFe]-hydrogenases is disclosed. In fact, QM/MM calculations on all-atom models of the enzyme from Desulfovibrio desulfuricans show that the cyanide groups fine-tune the electronic and redox properties of the active site, affecting both the protonation regiochemistry and electron transfer between the two subclusters of the H-cluster. Despite the crucial role of cyanides in the protein active site, the currently available bioinspired electrocatalysts generally lack CN⁻ groups in order to avoid competition between the latter and the catalytic metal centers for proton binding. In this respect, we show that a targeted inclusion of phosphine ligands in hexanuclear biomimetic clusters may restore the electronic and redox features of the wild-type H-cluster.