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.

scholarly journals The nature of the phosphate complex of sulphite oxidase from electron-paramagnetic-resonance studies

1988 ◽  
Vol 256 (1) ◽  
pp. 307-309 ◽  
Author(s):  
G N George ◽  
R C Prince ◽  
C A Kipke ◽  
R A Sunde ◽  
J H Enemark
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Hyperfine Coupling ◽  
Hyperfine Interactions ◽  
Structural Detail ◽  
Paramagnetic Resonance ◽  
Phosphate Complex ◽  
Derivative Spectra ◽  
Sulphite Oxidase ◽  
Electron Paramagnetic ◽  
Third Derivative

The phosphate complex of sulphite oxidase in the Mo(V) oxidation state was investigated by e.p.r. spectroscopy. Third-derivative spectra reveal a wealth of structural detail previously unobserved in this spectrum. Most notable is the presence of hyperfine coupling from two inequivalent I = 1/2 nuclei, which we tentatively attribute to two 31P nuclei. Unresolved hyperfine interactions from at least one exchangeable 1H nucleus are also present.

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni2+ — Cu2+ Exchange-Coupled Pairs

1984 ◽  
Vol 39 (11) ◽  
pp. 1061-1065 ◽  
Author(s):  
E. Buluggiu
Keyword(s):  
Single Crystals ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Magnetic Behaviour ◽  
Coupling Constant ◽  
Paramagnetic Resonance ◽  
Strongly Coupled ◽  
Definite Difference ◽  
Electron Paramagnetic ◽  
Made In

Electron paramagnetic resonance measurements on nickel(ll) doped copper(ll) acetate mono­hydrate single crystals have been made. In the liquid helium temperature range, spectra have been observed which may be assigned to Ni2+-Cu2+ strongly coupled mixed pairs in the state of total spin S = 1/2. This result represents a definite difference of magnetic behaviour from the case of the nickel(II) doped dicopper(II) tetra(μ-benzoato-O,O′)bis(quinoline) complex, which has the same sandwich dimeric structure but shows spectra indicative of a S=3/2 state. Apart from this difference, unusual EPR data are found such as pronounced misalignments of g with respect to the relevant pair axes and very large values of the hyperfine coupling constant of the copper nucleus, which characteristically recall that case.

A Study of the Effect of Solvent and Temperature on the Electron Paramagnetic Resonance Parameters and Linewidths of Copper(II)bis(Diethyldithiocarbamate)

1974 ◽  
Vol 52 (24) ◽  
pp. 4016-4024 ◽  
Author(s):  
F. Geoffrey Herring ◽  
Robert L. Tapping
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Rotational Correlation Time ◽  
Coupling Constant ◽  
Paramagnetic Resonance ◽  
Axial Ligation ◽  
Effect Of Solvent ◽  
Isotropic Hyperfine Coupling ◽  
Electron Paramagnetic

The effect of varying solvent and temperature on the e.s.r. parameters and linewidths of copper(II) bis(diethyldithiocarbamate) has been studied. The temperature and solvent dependences of the isotropic hyperfine coupling constant (a0) have been interpreted in terms of vibronic and axial ligation effects. The rotational correlation time, τR, of Cu(DEDC)2 has been measured in the solvents employed. The values of τR measured at 300 K have been used to obtain the anisotropic interaction parameter, κ, which is found to correlate roughly with the dipole moment and molar refractivity of the solvent.

scholarly journals Electron Paramagnetic Resonance (EPR) Detection of Nitric Oxide Produced during Forebrain Ischemia of the Rat

1994 ◽  
Vol 14 (5) ◽  
pp. 715-722 ◽  
Author(s):  
Teiji Tominaga ◽  
Shinya Sato ◽  
Tomoko Ohnishi ◽  
S. Tsuyoshi Ohnishi
Keyword(s):  
Nitric Oxide ◽  
Electron Paramagnetic Resonance ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Forebrain Ischemia ◽  
Coupling Constant ◽  
Paramagnetic Resonance ◽  
Rat Forebrain ◽  
Electron Paramagnetic

To detect if nitric oxide (NO) is produced in rat forebrain ischemia, we applied an electron paramagnetic resonance (EPR) NO-trapping technique. We also performed a detailed characterization of the technique. Diethyldithiocarbamate (DETC) and Fe-citrate were used as NO-trapping reagents. Under controlled ventilation, forebrain ischemia was produced by occlusion of both carotid arteries combined with hemorrhagic hypotension at 50 mm Hg for 15 min. DETC and Fe were administered 30 min prior to the onset of ischemia. During ischemia, the cerebral cortex was removed, and EPR samples were prepared. At liquid nitrogen temperatures, the NO-Fe-DETC signal (a triplet signal centered at g = 2.039 with the hyperfine coupling constant aN of 13 G) was detected overlapping Cu-DETC signals. By perfusing various concentrations of an NO-generating agent, 1,1-diethyl-2-hydroxy-2-nitrosohydrazine, into the rat brains, the amount of the “trapped NO” was calibrated. The size of the NO-Fe-DETC signal was well correlated with the NO concentrations in the perfusate (correlation coefficient r = 0.998, p < 0.01). Based on this calibration curve, it was found that the amount of trapped NO during forebrain ischemia increased to seven times that of the control (control n = 5, forebrain ischemia n = 4, p < 0.005).

The β-phosphorus hyperfine coupling constant in nitroxide: part 3: titration of water by electron paramagnetic resonance

2015 ◽  
Vol 13 (46) ◽  
pp. 11393-11400 ◽  
Author(s):  
Gérard Audran ◽  
Lionel Bosco ◽  
Paul Brémond ◽  
Teddy Butscher ◽  
Jean-Michel Franconi ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Organic Solvent ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Coupling Constant ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

Titration of a few percent of water in an organic solvent is possible due to a large difference in aP.

scholarly journals Binding of Oxovanadium(IV) Complexes to Blood Serum Albumins

2017 ◽  
Vol 57 (3) ◽  
Author(s):  
Enoch Cobbina ◽  
Sameena Mehtab ◽  
Isabel Correia ◽  
Gisela Gonçalves ◽  
Isabel Tomaz ◽  
...  
Keyword(s):  
Serum Albumin ◽  
Binding Sites ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Coupling Constants ◽  
Serum Albumins ◽  
Visible Absorption ◽  
Paramagnetic Resonance ◽  
Porcine Serum ◽  
X Band

In this work the binding of V<sup>IV</sup>O<sup>2+</sup> and V<sup>IV</sup>O-complexes to serum albumins {human serum albumin (HSA), bovine serum albumin (BSA) and porcine serum albumin (PSA)} are studied using circular dichroism (CD), electron paramagnetic resonance (EPR) and visible absorption spectroscopy. The results confirm previous findings that V<sup>IV</sup>O<sup>2+</sup> occupies at least two types of binding sites on albumin: ‘the strong vanadium binding site’ (designated by VBS1) and ‘the weak vanadium binding sites’ (designated by VBS2). VBS1 binds 1 mol equivalent of V<sup>IV</sup>O<sup>2+</sup>. On the other hand VBS2 correspond to binding of several mol equivalents of V<sup>IV</sup>O, and studies done with PSA in the presence of excess Zn<sup>II</sup> ions indicate that VSB2 corresponds to two distinct types of sites. The hyperfine coupling constant A<sub>z</sub> for V<sup>IV</sup>O<sup>2+</sup> binding at VBS2 on HSA and BSA are all very similar (~168 × 10-4 cm<sup>-1</sup>) but differ slightly on PSA (~166 × 10-4 cm<sup>-1</sup>) due to differences in the binding sets. When (V<sup>IV</sup>O)-HSA systems are titrated with maltol ternary species of (maltol)<sub>m</sub>(V<sup>IV</sup>O)<sub>m</sub>HSA and (maltol)<sub>2m</sub>(V<sup>IV</sup>O)<sub>m</sub>HSA stoichiometry form which are clearly distinguishable from the binary (V<sup>IV</sup>O)-HSA system by the type and intensity of the CD spectra recorded. Changes are also observable in the intensity of the X-band EPR spectra, but not much in the hyperfine coupling constants A<sub>z</sub>, which are all in the range 166-167 × 10-4 cm<sup>-1</sup>. The results further demonstrate that the presence of maltol may enhance the binding of VIVO to albumin.

scholarly journals Evidence from electron-paramagnetic-resonance spectroscopy for a complex of sulphite ions with the molybdenum centre of sulphite oxidase

1982 ◽  
Vol 201 (1) ◽  
pp. 241-243 ◽  
Author(s):  
R C Bray ◽  
M T Lamy ◽  
S Gutteridge ◽  
T Wilkinson
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Hyperfine Coupling ◽  
Resonance Spectrum ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Low Ph ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Ph Values ◽  
Sulphite Oxidase ◽  
Electron Paramagnetic

Reduction of sulphite oxidase by sulphite at low pH values in Mes (4-morpholine-ethanesulphonic acid) buffer gives rise to a new molybdenum(V) electron-paramagnetic-resonance spectrum different from that obtained by photoreduction of the enzyme in the same medium. The spectrum is attributed to a sulphite complex of the enzyme, showing g-values of about 2.000, 1.972 and 1.963. The complex is analogous to that with the inhibitor phosphate in that it gives rise to no observable hyperfine coupling of Mo(V) to exchangeable protons.

scholarly journals New Polyporphyrin Arrays with Controlled Fluorescence Obtained by Diaxial Sn(IV)-Porphyrin Phenolates Chelation with Cu2+ Cation

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 829
Author(s):  
Galina M. Mamardashvili ◽  
Dmitriy A. Lazovskiy ◽  
Ilya A. Khodov ◽  
Artem E. Efimov ◽  
Nugzar Z. Mamardashvili
Keyword(s):  
Chemical Species ◽  
Ultra Violet ◽  
X Rays ◽  
Structure And Properties ◽  
Paramagnetic Resonance ◽  
1H Nuclear Magnetic Resonance ◽  
Infra Red ◽  
Connection Type ◽  
Chelation Reaction ◽  
Electron Paramagnetic

New coordination oligomers and polymers of Sn(IV)-tetra(4-sulfonatophenyl)porphyrin have been constructed by the chelation reaction of its diaxialphenolates with Cu2+. The structure and properties of the synthesized polyporphyrin arrays were investigated by 1H Nuclear Magnetic Resonance (1H NMR), Infra Red (IR), Ultra Violet - Visible (UV-Vis) and fluorescence spectroscopy, mass spectrometry, Powder X-Rays Diffraction (PXRD), Electron Paramagnetic Resonance (EPR), thermal gravimetric, elemental analysis, and quantum chemical calculations. The results show that the diaxial coordination of bidentate organic ligands (L-tyrazine and diaminohydroquinone) leads to the quenching of the tetrapyrrole chromophore fluorescence, while the chelation of the porphyrinate diaxial complexes with Cu2+ is accompanied by an increase in the fluorescence in the organo-inorganic hybrid polymers formed. The obtained results are of particular interest to those involved in creating new ‘chemo-responsive’ (i.e., selectively interacting with other chemical species as receptors, sensors, or photocatalysts) materials, the optoelectronic properties of which can be controlled by varying the number and connection type of monomeric fragments in the polyporphyrin arrays.

Simple Test of the Effect of an Electric Field on the14N-Hyperfine Coupling Constant in Nitroxide Spin Probes

1997 ◽  
Vol 101 (43) ◽  
pp. 8735-8739 ◽  
Author(s):  
Robert N. Schwartz ◽  
Miroslav Peric ◽  
Steven A. Smith ◽  
Barney L. Bales
Keyword(s):  
Electric Field ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Simple Test ◽  
Coupling Constant ◽  
Spin Probes ◽  
Nitroxide Spin Probes
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