scholarly journals Atomic-scale evidence for highly selective electrocatalytic N−N coupling on metallic MoS2

2020 ◽  
Vol 117 (50) ◽  
pp. 31631-31638
Author(s):  
Daoping He ◽  
Hideshi Ooka ◽  
Yujeong Kim ◽  
Yamei Li ◽  
Fangming Jin ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Continuous Wave ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Molybdenum Sulfide ◽  
Nitrite Reduction ◽  
Atomic Scale ◽  
Resonance Spectroscopy ◽  
Transition Metal Dichalcogenide ◽  
Protonation Site ◽  
Phase Engineering

Molybdenum sulfide (MoS2) is the most widely studied transition-metal dichalcogenide (TMDs) and phase engineering can markedly improve its electrocatalytic activity. However, the selectivity toward desired products remains poorly explored, limiting its application in complex chemical reactions. Here we report how phase engineering of MoS2 significantly improves the selectivity for nitrite reduction to nitrous oxide, a critical process in biological denitrification, using continuous-wave and pulsed electron paramagnetic resonance spectroscopy. We reveal that metallic 1T-MoS2 has a protonation site with a pKa of ∼5.5, where the proton is located ∼3.26 Å from redox-active Mo site. This protonation site is unique to 1T-MoS2 and induces sequential proton−electron transfer which inhibits ammonium formation while promoting nitrous oxide production, as confirmed by the pH-dependent selectivity and deuterium kinetic isotope effect. This is atomic-scale evidence of phase-dependent selectivity on MoS2, expanding the application of TMDs to selective electrocatalysis.

scholarly journals Protein Conformational Dynamics upon Association with the Surfaces of Lipid Membranes and Engineered Nanoparticles: Insights from Electron Paramagnetic Resonance Spectroscopy

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5393
Author(s):  
Elka R. Georgieva
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Continuous Wave ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Conformational Dynamics ◽  
Engineered Nanoparticles ◽  
Resonance Spectroscopy ◽  
Functional Protein ◽  
Paramagnetic Resonance ◽  
Conformational Rearrangements ◽  
Electron Paramagnetic

Detailed study of conformational rearrangements and dynamics of proteins is central to our understanding of their physiological functions and the loss of function. This review outlines the applications of the electron paramagnetic resonance (EPR) technique to study the structural aspects of proteins transitioning from a solution environment to the states in which they are associated with the surfaces of biological membranes or engineered nanoobjects. In the former case these structural transitions generally underlie functional protein states. The latter case is mostly relevant to the application of protein immobilization in biotechnological industries, developing methods for protein purification, etc. Therefore, evaluating the stability of the protein functional state is particularly important. EPR spectroscopy in the form of continuous-wave EPR or pulse EPR distance measurements in conjunction with protein spin labeling provides highly versatile and sensitive tools to characterize the changes in protein local dynamics as well as large conformational rearrangements. The technique can be widely utilized in studies of both protein-membrane and engineered nanoobject-protein complexes.

scholarly journals The NosX and NirX Proteins of Paracoccus denitrificans Are Functional Homologues: Their Role in Maturation of Nitrous Oxide Reductase

2000 ◽  
Vol 182 (18) ◽  
pp. 5211-5217 ◽  
Author(s):  
Neil F. W. Saunders ◽  
Jorrit J. Hornberg ◽  
Willem N. M. Reijnders ◽  
Hans V. Westerhoff ◽  
Simon de Vries ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Nitrous Oxide ◽  
Double Mutant ◽  
Paracoccus Denitrificans ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Nitrous Oxide Reductase ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Functional Homologues

ABSTRACT The nos (nitrous oxide reductase) operon ofParacoccus denitrificans contains a nosX gene homologous to those found in the nos operons of other denitrifiers. NosX is also homologous to NirX, which is so far unique to P. denitrificans. Single mutations of these genes did not result in any apparent phenotype, but a double nosX nirX mutant was unable to reduce nitrous oxide. Promoter-lacZ assays and immunoblotting against nitrous oxide reductase showed that the defect was not due to failure of expression of nosZ, the structural gene for nitrous oxide reductase. Electron paramagnetic resonance spectroscopy showed that nitrous oxide reductase in cells of the double mutant lacked the CuA center. A twin-arginine motif in both NosX and NirX suggests that the NosX proteins are exported to the periplasm via the TAT translocon.

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