scholarly journals Denaturation studies of active-site labeled papain using electron paramagnetic resonance and fluorescence spectroscopy

1991 ◽  
Vol 60 (3) ◽  
pp. 623-628 ◽  
Author(s):  
Z.A. Ping ◽  
D.A. Butterfiel
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fluorescence Spectroscopy ◽  
Active Site ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

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.

Reacted copper(II) concentrations in earlywood and latewood of micronized copper-treated Canadian softwood species

Holzforschung ◽  
2015 ◽  
Vol 69 (4) ◽  
pp. 509-512 ◽  
Author(s):  
Wei Xue ◽  
Pierre Kennepohl ◽  
John N.R. Ruddick
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fluorescence Spectroscopy ◽  
Copper Content ◽  
Red Pine ◽  
Western Hemlock ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Total Copper ◽  
Electron Paramagnetic ◽  
Softwood Species

Abstract Electron paramagnetic resonance was used in conjunction with X-ray fluorescence spectroscopy to quantify total copper and reacted copper retentions in MCQ and MCA treated Canadian red pine sapwood and western hemlock heartwood. Total copper retentions were distinctly different between earlywood and latewood of both softwood species examined. Earlywood of red pine sapwood had higher total copper content than the latewood, while western hemlock heartwood had higher total copper contents in latewood than earlywood. The reacted copper concentrations were similar in earlywood and latewood, reflecting a similar capacity of each to solubilize and complex the reacted copper.

scholarly journals Extending electron paramagnetic resonance to nanoliter volume protein single crystals using a self-resonant microhelix

2019 ◽  
Vol 5 (10) ◽  
pp. eaay1394 ◽  
Author(s):  
Jason W. Sidabras ◽  
Jifu Duan ◽  
Martin Winkler ◽  
Thomas Happe ◽  
Rana Hussein ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Single Crystals ◽  
Active Site ◽  
Measured Signal ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
X Band ◽  
Electron Paramagnetic ◽  
Epr Experiments

Electron paramagnetic resonance (EPR) spectroscopy on protein single crystals is the ultimate method for determining the electronic structure of paramagnetic intermediates at the active site of an enzyme and relating the magnetic tensor to a molecular structure. However, crystals of dimensions typical for protein crystallography (0.05 to 0.3mm) provide insufficient signal intensity. In this work, we present a microwave self-resonant microhelix for nanoliter samples that can be implemented in a commercial X-band (9.5 GHz) EPR spectrometer. The self-resonant microhelix provides a measured signal-to-noise improvement up to a factor of 28 with respect to commercial EPR resonators. This work opens up the possibility to use advanced EPR techniques for studying protein single crystals of dimensions typical for x-ray crystallography. The technique is demonstrated by EPR experiments on single crystal [FeFe]-hydrogenase (Clostridium pasteurianum; CpI) with dimensions of 0.3 mm by 0.1 mm by 0.1 mm, yielding a proposed g-tensor orientation of the Hox state.

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