Dataset Information

Fe-mediated HER vs N2RR: Exploring Factors that Contribute to Selectivity in P3 EFe(N2) (E = B, Si, C) Catalyst Model Systems.

ABSTRACT: Mitigation of the hydrogen evolution reaction (HER) is a key challenge in selective small molecule reduction catalysis. This is especially true of catalytic nitrogen (N2) and carbon dioxide (CO2) reduction reactions (N2RR and CO2RR, respectively) using H+/e- currency. Here we explore, via DFT calculations, three iron model systems, P3 EFe (E = B, Si, C), known to mediate both N2RR and HER, but with different selectivity depending on the identity of the auxiliary ligand. It is suggested that the respective efficiencies of these systems for N2RR trend with the predicted N-H bonds strengths of two putative hydrazido intermediates of the proposed catalytic cycle, P3 EFe(NNH2)+ and P3 EFe(NNH2). Further, a mechanism is presented for undesired HER consistent with DFT studies, and previously reported experimental data, for these systems; bimolecular proton-coupled-electron-transfer (PCET) from intermediates with weak N-H bonds is posited as an important source of H2' instead of more traditional scenarios that proceed via metal hydride intermediates and proton transfer/electron transfer (PT/ET) pathways. Wiberg bond indices provide additional insight into key factors related to the degree of stabilization of P3 EFe(NNH2) species, factors that trend with overall product selectivity.

SUBMITTER: Matson BD

PROVIDER: S-EPMC6289286 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Fe-mediated HER vs N2RR: Exploring Factors that Contribute to Selectivity in P3 EFe(N2) (E = B, Si, C) Catalyst Model Systems.

Matson Benjamin D BD Peters Jonas C JC

ACS catalysis 20180103 2

Mitigation of the hydrogen evolution reaction (HER) is a key challenge in selective small molecule reduction catalysis. This is especially true of catalytic nitrogen (N2) and carbon dioxide (CO2) reduction reactions (N2RR and CO2RR, respectively) using H+/e- currency. Here we explore, via DFT calculations, three iron model systems, P3 EFe (E = B, Si, C), known to mediate both N2RR and HER, but with ...[more]

PMID: 30555733

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Project description:Ethylene is one of the most used chemical monomers derived from non-renewable sources and we are investigating the possibility of producing it in yeast via the ethylene forming enzyme (EFE) from Pseudomonas syringae. To enable engineering strategies to improve the enzyme, it is necessary to identify the regions and amino acid residues involved in ethylene formation.We identified the open reading frame for the EFE homolog in Penicillium digitatum and also showed its capability of mediating ethylene production in yeast. The sequence of the EFE homologs from P.digitatum and P. syringae was compared to that of the non-functional EFE-homolog from Penicillium chrysogenum and ten amino acids were found to correlate with ethylene production. Several of these amino acid residues were found to be important for ethylene production via point mutations in P. syringae EFE. The EFE homolog from P. chrysogenum was engineered at 10 amino acid residues to mimic the P. syringae EFE, but this did not confer ethylene producing capability.Furthermore, we predicted the structure of EFE by homology to known structures of 2-oxoglutarate/Fe(II) dependent dioxygenases. Three of the amino acids correlating with ethylene production are located in the predicted 2-oxoglutarate binding domain. A protein domain specific for the EFE-class was shown to be essential for activity. Based on the structure and alanine substitutions, it is likely that amino acids (H189, D191 and H268) are responsible for binding the Fe(II) ligand.We provide further insight into the structure and function of the ethylene forming (EFE) - subclass of 2-oxoglutarate/Fe(II) dependent dioxygenases. We conclude that residues in addition to the 10 identified positions implicated in ethylene production by sequence comparison, are important for determining ethylene formation. We also demonstrate the use of an alternative EFE gene. The data from this study will provide the basis for directed protein engineering to enhance the ethylene production capability and properties of EFE.

Dataset Information

Fe-mediated HER vs N2RR: Exploring Factors that Contribute to Selectivity in P3 EFe(N2) (E = B, Si, C) Catalyst Model Systems.

Publications

Fe-mediated HER vs N<sub>2</sub>RR: Exploring Factors that Contribute to Selectivity in P<sub>3</sub> <sup>E</sup>Fe(N<sub>2</sub>) (E = B, Si, C) Catalyst Model Systems.

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