Electron and Spin Density Topology of the H‐Cluster and Its Biomimetic Complexes

Giles, Logan J.; Grigoropoulos, Alexios; Szilágyi, Róbert K.

doi:10.1002/ejic.201100318

Cited by 15 publications

(12 citation statements)

References 47 publications

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“…Similar experimental studies of a H-cluster model complex containing an azadithiolate-bridging ligand without any other nitrogen atoms in its environment yielded similar hyperfine coupling components as the enzyme, providing additional support for nitrogen as the bridgehead atom (Erdem et al, 2011). Further computational analysis of the H-cluster embedded in a 3.5 Å protein environment and compared to analogous model complexes has demonstrated notable distinctions between the paramagnetic properties of the bridgehead group in the enzyme and the models, suggesting that the network of interactions housing the H-cluster acts to limit the localization of atomic spin density at the bridgehead atom position (Giles et al, 2011). Clearly, there are still questions to be answered with regard to the composition and the potential mechanistic relevance of the nonprotein dithiolate of the H-cluster, ambiguities that would be resolved by some direct chemical composition analysis of the ligand itself or the elucidation of the mechanism of its biosynthesis.…”

Section: Structurementioning

confidence: 78%

Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

et al. 2011

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Hydrogenases are metalloenzymes that are key to energy metabolism in a variety of microbial communities. Divided into three classes based on their metal content, the [Fe]-, [FeFe]-, and [NiFe]-hydrogenases are evolutionarily unrelated but share similar nonprotein ligand assemblies at their active site metal centers that are not observed elsewhere in biology. These nonprotein ligands are critical in tuning enzyme reactivity, and their synthesis and incorporation into the active site clusters require a number of specific maturation enzymes. The wealth of structural information on different classes and different states of hydrogenase enzymes, biosynthetic intermediates, and maturation enzymes has contributed significantly to understanding the biochemistry of hydrogen metabolism. This review highlights the unique structural features of hydrogenases and emphasizes the recent biochemical and structural work that has created a clearer picture of the [FeFe]-hydrogenase maturation pathway.

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Section: Structurementioning

confidence: 78%

Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

et al. 2011

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“…The surrounding protein framework finely-tunes the H-cluster and is considered to play an important role in regulating its catalytic activity, electronic properties, and potential hydride binding sites [14,23,130,[140][141][142][143]. Within the catalytic site are several conserved, charged residues that form the secondary coordination sphere, with exchangeable groups proposed to function in the transfer of protons, water coordination, and bonding interactions with the H cluster (Fig.…”

Section: Catalytic Site Structure and Coordination Spherementioning

confidence: 99%

[FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation

Peters

Schut

Boyd

et al. 2015

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

424

397

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The [FeFe]- and [NiFe]-hydrogenases catalyze the formal interconversion between hydrogen and protons and electrons, possess characteristic non-protein ligands at their catalytic sites and thus share common mechanistic features. Despite the similarities between these two types of hydrogenases, they clearly have distinct evolutionary origins and likely emerged from different selective pressures. [FeFe]-hydrogenases are widely distributed in fermentative anaerobic microorganisms and likely evolved under selective pressure to couple hydrogen production to the recycling of electron carriers that accumulate during anaerobic metabolism. In contrast, many [NiFe]-hydrogenases catalyze hydrogen oxidation as part of energy metabolism and were likely key enzymes in early life and arguably represent the predecessors of modern respiratory metabolism. Although the reversible combination of protons and electrons to generate hydrogen gas is the simplest of chemical reactions, the [FeFe]- and [NiFe]-hydrogenases have distinct mechanisms and differ in the fundamental chemistry associated with proton transfer and control of electron flow that also help to define catalytic bias. A unifying feature of these enzymes is that hydrogen activation itself has been restricted to one solution involving diatomic ligands (carbon monoxide and cyanide) bound to an Fe ion. On the other hand, and quite remarkably, the biosynthetic mechanisms to produce these ligands are exclusive to each type of enzyme. Furthermore, these mechanisms represent two independent solutions to the formation of complex bioinorganic active sites for catalyzing the simplest of chemical reactions, reversible hydrogen oxidation. As such, the [FeFe]- and [NiFe]-hydrogenases are arguably the most profound case of convergent evolution. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.

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“…The near-identical TM-S(TU) pre-edge intensities within the error of XAS data collection and analysis (Giles et al, 2011) do not correspond to identical S 3p contributions, since the Co 2+ complex has three d-electron holes and four absorbers, while the Ni 2+ complex has two holes for six absorbers. The renormalized intensity values are 0.8 units and 1.7 units per hole for [Co(TU) 4 ] 2+ and [Ni(TU) 6 ] 2+ , respectively, which now clearly indicate a ca double TM-S bond covalency in the octahedral Ni 2+ versus tetrahedral Co 2+ complex, as expected from the difference in the number of ligands and the efficiency of the M-L overlap between the two coordination environments.…”

Section: Determination Of Normalized Pre-edge Intensity (D 0 ) For Coordinated Ligandsmentioning

confidence: 96%

Ground electronic state description of thiourea coordination in homoleptic Zn²⁺, Ni²⁺ and Co²⁺ complexes using sulfur K-edge X-ray absorption spectroscopy

Queen¹,

Jalilehvand²,

Szilágyi³

2021

J Synchrotron Radiat

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Sulfur K-edge X-ray absorption spectroscopy (XAS) was employed to experimentally characterize the coordinative bond between the thiourea (TU) or thiocarbamide ligand and transition metal (TM) ions Zn2+, Co2+ and Ni2+ in distorted tetrahedral and octahedral homoleptic coordination environments. Comparisons of XAS spectra of the free TU ligand and [Zn(TU)4]2+, [Co(TU)4]2+ and [Ni(TU)6]2+ complexes clearly identify spectral features unique to TM2+–S(TU) bonding. Quantitative analysis of pre-edge intensities describes the covalency of Ni2+—S(TU) and Co2+—S(TU) bonding to be at most 21% and 9% as expressed by the S 3p contributions per TM 3d electron hole. Using relevant Ni2+ complexes with dithiocarbamate and thioether ligands, we evaluated the empirical S 1s → 3p transition dipole integrals developed for S-donor ligands and their dependence on heteroatom substitutions. With the aid of density functional theory-based ground electronic state calculations, we found evidence for the need of using a transition dipole that is dependent on the presence of conjugated heteroatom (N) substitution in these S-donor ligands.

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Electron and Spin Density Topology of the H‐Cluster and Its Biomimetic Complexes

Cited by 15 publications

References 47 publications

Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

[FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation

Ground electronic state description of thiourea coordination in homoleptic Zn²⁺, Ni²⁺ and Co²⁺ complexes using sulfur K-edge X-ray absorption spectroscopy

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Electron and Spin Density Topology of the H‐Cluster and Its Biomimetic Complexes

Cited by 15 publications

References 47 publications

Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

Insights into [FeFe]-Hydrogenase Structure, Mechanism, and Maturation

[FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation

Ground electronic state description of thiourea coordination in homoleptic Zn2+, Ni2+ and Co2+ complexes using sulfur K-edge X-ray absorption spectroscopy

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Product

Resources

About

Ground electronic state description of thiourea coordination in homoleptic Zn²⁺, Ni²⁺ and Co²⁺ complexes using sulfur K-edge X-ray absorption spectroscopy