EPR experiments to elucidate the structure of the ready and unready states of the [NiFe] hydrogenase of Desulfovibrio vulgaris Miyazaki F

2005 ◽  
Vol 33 (1) ◽  
pp. 7-11 ◽  
Author(s):  
M. van Gastel ◽  
C. Fichtner ◽  
F. Neese ◽  
W. Lubitz
Keyword(s):  
Dft Calculations ◽  
Hyperfine Coupling ◽  
Epr Spectra ◽  
Desulfovibrio Vulgaris ◽  
Aerobic Conditions ◽  
Isolation And Purification ◽  
Bridging Ligand ◽  
Exchangeable Proton ◽  
Activation Times ◽  
Epr Experiments

Isolation and purification of the [NiFe] hydrogenase of Desulfovibrio vulgaris Miyazaki F under aerobic conditions leads to a mixture of two states, Ni-A (unready) and Ni-B (ready). The two states are distinguished by different activation times and different EPR spectra. HYSCORE and ENDOR data and DFT calculations show that both states have an exchangeable proton, albeit with a different 1H hyperfine coupling. This proton is assigned to the bridging ligand between Ni and Fe. For Ni-B, a hydroxo ligand is found. For Ni-A, either a hydroxo in a different orientation or a hydroperoxo-bridging ligand is present.

scholarly journals Electron-paramagnetic-resonance parameters of molybdenum(V) in sulphite oxidase from chicken liver

1980 ◽  
Vol 185 (2) ◽  
pp. 397-403 ◽  
Author(s):  
M T Lamy ◽  
S Gutteridge ◽  
R C Bary
Keyword(s):  
Hyperfine Coupling ◽  
Chemical Species ◽  
Hyperfine Coupling Constant ◽  
Chicken Liver ◽  
Paramagnetic Resonance ◽  
Phosphate Complex ◽  
Exchangeable Proton ◽  
Weakly Coupled ◽  
Sulphite Oxidase ◽  
Single Chemical

A study has been made of e.p.r. signals due to Mo(V) in reduced sulphite oxidase (EC 1.8.3.1) from chicken liver. Reduction by SO3(2-), or photochemically in the presence of a deazaflavin derivative, produces spectra indistinguishable from one another. Three types of spectra from the enzyme were distingusihed and shown to correspond to single chemical species, since they could be simulated at both 9 and 35 GHz by using the same parameters. These were the low-pH form of the enzyme, with gav. 1.9805, the high-pH form, with gav. 1.9681 and a phosphate complex, with gav. 1.9741. The low-H form shows interaction with a single exchangeable proton, with A(1H)av. (hyperfine coupling constant) = 0.98 mT, probably in the form of an MoOH group. Parameters of the signals are compared with those for signals from xanthine oxidase and nitrate reductase. The signal from the phosphate complex of sulphite oxidase in unique among anion complexes of Mo-containing enzymes in showing no hyperfine coupling to protons. There is no evidence for additional weakly coupled protons or nitrogen nuclei in the sulphite oxidase signals. The possibility is considered that the enzymic mechanism involves abstraction of a proton and two electrons from HSO3- by a Mo = O group in the enzyme.

Combined analysis of chemical bonding in a CuIIdimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches

2015 ◽  
Vol 71 (5) ◽  
pp. 543-554 ◽  
Author(s):  
Anna V. Vologzhanina ◽  
Svitlana V. Kats ◽  
Larisa V. Penkova ◽  
Vadim A. Pavlenko ◽  
Nikolay N. Efimov ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Voronoi Tessellation ◽  
Quantitative Description ◽  
Hirshfeld Surface ◽  
Epr Spectra ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Spin Distribution ◽  
X Ray

Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform–IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathwayviathe bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant −2Jis equal to 220 cm−1, which compares well with the experimental value of 203 ± 2 cm−1. Chemical connectivity was derived by Bader's `quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

Paramagnetic centers in graphite oxide according to EPR spectra and DFT calculations

2020 ◽  
Vol 754 ◽  
pp. 137722
Author(s):  
Andrey Kh Vorobiev ◽  
Dmitriy A. Astvatsaturov ◽  
Alexander V. Fionov ◽  
Natalia A. Chumakova
Keyword(s):  
Dft Calculations ◽  
Graphite Oxide ◽  
Epr Spectra ◽  
Paramagnetic Centers

Unusually large hyperfine structure of the electron spin levels in an endohedral dimetallofullerene and its spin coherent properties

Nanoscale ◽  
2020 ◽  
Vol 12 (39) ◽  
pp. 20513-20521
Author(s):  
Ruslan B. Zaripov ◽  
Yuri E. Kandrashkin ◽  
Kev M. Salikhov ◽  
Bernd Büchner ◽  
Fupin Liu ◽  
...  
Keyword(s):  
Hyperfine Structure ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Broad Temperature Range ◽  
Epr Spectra ◽  
Coupling Constant ◽  
Spin Coherence ◽  
Temperature Range

Sc2@C80(CH2Ph) with giant 45Sc hyperfine coupling constant yields fully-resolved EPR spectra and maintains spin coherence in a broad temperature range.

Radical non-radical states of the [Ru(PIQ)] core in complexes (PIQ = 9,10-phenanthreneiminoquinone)

2016 ◽  
Vol 45 (19) ◽  
pp. 8236-8247 ◽  
Author(s):  
Sachinath Bera ◽  
Suvendu Maity ◽  
Thomas Weyhermüller ◽  
Prasanta Ghosh
Keyword(s):  
Cyclic Voltammetry ◽  
Dft Calculations ◽  
Single Crystal ◽  
Electronic States ◽  
Epr Spectra ◽  
X Ray ◽  
Structure Determinations

The electronic states of types [RuII(PIQ˙−)], [RuIII(PIQ˙−)], [RuIII2(PIQ˙−)2], [RuIII2(PIQ˙−)(PIQ)] and [RuIII(PIQ)] (PIQ = 9,10-phenanthreneiminoquinone) were substantiated by the single crystal X-ray structure determinations, EPR spectra, cyclic voltammetry, DFT calculations and compared with those of 9,10-phenanthrenequinone (PQ) analogues.

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