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.

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 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 inhibitor complex of sulphite oxidase from electron-paramagnetic-resonance studies using oxygen-17

1980 ◽  
Vol 191 (1) ◽  
pp. 285-288 ◽  
Author(s):  
S Gutteridge ◽  
M T Lamy ◽  
R C Bray
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Active Site ◽  
Detectable Effect ◽  
Paramagnetic Resonance ◽  
Enzyme Reactions ◽  
Inhibitor Complex ◽  
Sulphite Oxidase ◽  
Oxygen Ligand ◽  
Normal Water ◽  
Electron Paramagnetic

Studies of the effect of substitution with 17O on the e.p.r. spectra at 9 and 35 GHz of Mo(V) in the phosphate complex of sulphite oxidase are reported. Substitution of 17O-enriched water for normal water, for samples of the enzymes reduced by sulphite in the presence of normal phosphate, produced no detectable effect on the e.p.r. signal. If phosphate substituted with 17O was used, coupling due to 17O, producing large anisotropic splittings in the spectrum, was clearly detectable. It is concluded that phosphate is co-ordinated directly to molybdenum in the active site of the enzyme, in an equatorial type of ligand position. An oxygen ligand must be displaced from the molybdenum in the process of binding the phosphate. Implications concerning the mechanism of the enzyme reactions are discussed.

scholarly journals Triarylmethyl Radicals: An EPR Study of 13C Hyperfine Coupling Constants

2017 ◽  
Vol 231 (4) ◽  
Author(s):  
Andrey A. Kuzhelev ◽  
Victor M. Tormyshev ◽  
Olga Yu. Rogozhnikova ◽  
Dmitry V. Trukhin ◽  
Tatiana I. Troitskaya ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Epr Spectroscopy ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Spin Labels ◽  
Spin Probes ◽  
Paramagnetic Resonance ◽  
Hyperfine Coupling Constants ◽  
Electron Paramagnetic ◽  
Triarylmethyl Radicals

AbstractTriarylmethyl (TAM) radicals are widely used in electron paramagnetic resonance (EPR) spectroscopy as spin labels and in EPR imaging as spin probes for

scholarly journals Direct enantiomeric discrimination through antisymmetric hyperfine coupling

2021 ◽  
Author(s):  
Piotr Garbacz ◽  
Juha Vaara
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Hyperfine Coupling ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Molecular Chirality ◽  
Enantiomeric Discrimination ◽  
Electron Paramagnetic

A chirality-sensitive effect induced by antisymmetric hyperfine coupling, which lifts the intrinsic insensitivity of electron paramagnetic resonance spectroscopy to molecular chirality, is described.

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