scholarly journals The stereochemical configuration of Mn(II) . ADP at the active site of creatine kinase elucidated by electron paramagnetic resonance with Rp [alpha-17O]ADP and Sp [alpha-17O]ADP.

1982 ◽  
Vol 257 (24) ◽  
pp. 15047-15053
Author(s):  
T S Leyh ◽  
R D Sammons ◽  
P A Frey ◽  
G H Reed
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Creatine Kinase ◽  
Active Site ◽  
Paramagnetic Resonance ◽  
Stereochemical Configuration ◽  
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.

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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