scholarly journals The Hydricity and Reactivity Relationship in [ FeFe ]-hydrogenases

2020 ◽  
Author(s):  
Jacob Artz ◽  
David Mulder ◽  
Michael Ratzloff ◽  
John Peters ◽  
Paul King
Keyword(s):  
Catalytic Activity ◽  
Transition Metal ◽  
Thermodynamic Properties ◽  
Chemical Reactivity ◽  
Chemical Compounds ◽  
Transition Metal Catalysts ◽  
Metal Cofactor ◽  
Non Covalent Interactions ◽  
Metal Cofactors ◽  
Covalent Interactions

Abstract Reactivity of transition metal catalysts is controlled by covalent and non-covalent interactions that tune thermodynamic properties including hydricity. Hydricity is critical to catalytic activity and for modulating the reduction or oxidation of chemical compounds. Likewise, enzymes can employ transition metal cofactors and use metal-hydride intermediates tuned by protein frameworks to selectively control reactivity. One example, the [FeFe]-hydrogenases, catalyze reversible H2 activation with H2 oxidation to H+ reduction ratios spanning ~107 in rate, offering a model to determine the extent that hydricity controls reactivity. To address this question, the hydricity of the catalytic H cluster of two [FeFe]-hydrogenases, CpI and CpII, were compared. We show that for CpI, the higher rates of H+ reduction correspond to a more hydridic H cluster, whereas CpII, which strongly favors H2 oxidation, has a less hydridic H cluster. The results demonstrate that enzymes manipulate metal cofactor hydricity to enable an extraordinary range of chemical reactivity.

scholarly journals 1,3,5-Triaza-7-Phosphaadamantane (PTA) as a 31P NMR Probe for Organometallic Transition Metal Complexes in Solution

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1390 ◽  
Author(s):  
Ilya G. Shenderovich
Keyword(s):  
Chemical Shift ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
Molecular Structures ◽  
Basis Sets ◽  
Functional Theory ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Due to the rigid structure of 1,3,5-triaza-7-phosphaadamantane (PTA), its 31P chemical shift solely depends on non-covalent interactions in which the molecule is involved. The maximum range of change caused by the most common of these, hydrogen bonding, is only 6 ppm, because the active site is one of the PTA nitrogen atoms. In contrast, when the PTA phosphorus atom is coordinated to a metal, the range of change exceeds 100 ppm. This feature can be used to support or reject specific structural models of organometallic transition metal complexes in solution by comparing the experimental and Density Functional Theory (DFT) calculated values of this 31P chemical shift. This approach has been tested on a variety of the metals of groups 8–12 and molecular structures. General recommendations for appropriate basis sets are reported.

scholarly journals A co-opted ISG15-USP18 binding mechanism normally reserved for deISGylation controls type I IFN signalling

2021 ◽  
Author(s):  
Andri Vasou ◽  
Katie Nightingale ◽  
Vladimira Cetkovska ◽  
Connor GG Bamford ◽  
Jelena Andrejeva ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Autoinflammatory Disease ◽  
Type I Interferon ◽  
Negative Regulator ◽  
Regulatory Function ◽  
Type I ◽  
Binding Mechanism ◽  
Tight Control ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Type I interferon (IFN) signalling induces the expression of several hundred IFN-stimulated genes that provide an unfavourable environment for viral replication. To prevent an overexuberant response and autoinflammatory disease, IFN signalling requires tight control. One critical regulator is the ubiquitin-like protein ISG15, evidenced by autoinflammatory disease in patients with inherited ISG15 deficiencies. Current models suggest that ISG15 stabilises USP18, a well-established negative regulator of IFN signalling. USP18 also functions as an ISG15-specific peptidase, however its catalytic activity is dispensable for controlling IFN signalling. Here, we show that the ISG15-dependent stabilisation of USP18 is necessary but not sufficient for regulation of IFN signalling and that USP18 requires non-covalent interactions with ISG15 to enhance its regulatory function. Intriguingly, this trait has been acquired through co-option of a binding mechanism normally reserved for deISGylation, identifying an unexpected new function for ISG15.

Solvent-Free Assembled Fe-Chitosan Chelates Derived N-Doped Carbon Layer-Encapsulated Fe/Fe3C for ORR and OER

NANO ◽  
2020 ◽  
Vol 15 (06) ◽  
pp. 2050070
Author(s):  
Renxing Huang ◽  
Ying Lei ◽  
Dandan Zhang ◽  
Huaming Xie ◽  
Xingyong Liu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Transition Metal ◽  
Nitrogen Source ◽  
Small Molecule ◽  
Carbon Layer ◽  
Transition Metal Catalysts ◽  
Solvent Free ◽  
Metal Catalyst ◽  
High Peak Power ◽  
High Catalytic Activity

Carbon encapsulated transition metal catalysts receive extensive attention in electrochemical catalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to the unique structure and highly adjustable electronic configuration. Herein, we synthesized 3D porous Active-N-rich graphene-like carbon layer-encapsulated Fe/Fe3C (Fe@NCG) via pyrolysis of a mixture of solvent-free assembled Fe-chitosan chelates and additional small molecule nitrogen source urea, wherein space-confinement effect of chelates suppressed agglomeration of [Formula: see text] ions and small molecule nitrogen source facilitated regulation of N configurations. The optimized catalyst Fe@NCG shows remarkable ORR/OER bifunctional catalytic activity with a half-wave potential of 0.86 V for ORR and a moderate potential difference of 0.85 V in alkaline medium. Comparative studies revealed that Active-N-rich carbon layer and inner well-dispersed Fe/Fe3C nanoparticles and the favorable interface structures between them were responsible for high catalytic activity. Excitingly, the assembled zinc-air battery with Fe@NCG catalysts exhibits a high open-circuit potential (1.45 V), extremely high peak power density (204.50[Formula: see text][Formula: see text] and energy density (814.70[Formula: see text]Wh[Formula: see text][Formula: see text]) as well as robust charge–discharge durability, surpassing those of noble metal catalyst. This proposed simple and universal strategy can also be extended to synthesize carbon encapsulated other transition metal electrocatalysts.

Topological aspects of chemical reactivity. Catalytic reactions

1986 ◽  
Vol 51 (9) ◽  
pp. 1843-1855 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Transition Metal ◽  
Detailed Analysis ◽  
Chemical Reactivity ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Catalytic Reactions ◽  
Pericyclic Reactions

Recently proposed overlap determinant method is applied to the description of reactions induced by the presence of the transition metal catalysts. The use of this technique is demonstrated on a detailed analysis of a number of examples of thermally forbidden pericyclic reactions in which the interaction with the catalyst removes the symmetry restrictions imposed by Woodward-Hoffmann rules.

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