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.

EPR Studies of Mn2+-Doped Diammonium Hexaaqua Magnesium(II) Sulfate

2006 ◽  
Vol 61 (12) ◽  
pp. 683-687 ◽  
Author(s):  
Ram Kripal ◽  
Ashutosh Kumar Shukla
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fine Structure ◽  
Single Crystals ◽  
Room Temperature ◽  
Spin Hamiltonian ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

Electron paramagnetic resonance (EPR) studies of Mn2+ impurity in single crystals of diammonium hexaaqua magnesium(II) sulfate have been carried out at 9.3 GHz (X-band) at room temperature. The EPR spectra exhibit a group of five fine structure transitions. The spin-Hamiltonian parameters were determined. Mn2+ enters the lattice interstitially. The EPR spectrum of a powder sample supports the data obtained by single crystal studies. - PACS number: 76.30

Electron Paramagnetic Resonance of the V3+ Ion in CsAl(SO4)2∙12H2O

1971 ◽  
Vol 49 (11) ◽  
pp. 1539-1541 ◽  
Author(s):  
J. G. Clarke ◽  
J. A. MacKinnon
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectrum ◽  
Single Crystals ◽  
Resonance Spectrum ◽  
Paramagnetic Resonance ◽  
Microwave Spectrometer ◽  
X Band ◽  
Electron Paramagnetic

The electron paramagnetic resonance spectrum of the V3+ ion in CsAl(SO4)2∙12H2O single crystals has been studied in the {100} and {111} planes at 4.2 °K with an X-band microwave spectrometer.

Electron Paramagnetic Resonance of Ti3+ Ions in KAl(SO4)2∙12H2O

1975 ◽  
Vol 53 (8) ◽  
pp. 841-842 ◽  
Author(s):  
John A. MacKinnon ◽  
M. Shannon
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Single Crystals ◽  
Resonance Spectrum ◽  
Point Group ◽  
Spin Hamiltonian ◽  
Potassium Alum ◽  
Paramagnetic Resonance ◽  
Microwave Spectrometer ◽  
X Band ◽  
Electron Paramagnetic

The paramagnetic resonance spectrum of Ti3+ ions in potassium alum (KAl(SO4)2∙12H2O) single crystals has been studied in the {100} planes at 4.2 K with an X band microwave spectrometer. The spectrum is an analogue of that reported by Dionne for Ti3+ ions in rubidium alum (RbAl(SO4)2∙12H2O) and by MacKinnon and Dionne for Ti3+ ions in the thallium alum (TlAl(SO4)2∙12H2O). The spectrum was explained with a model of 12 magnetic complexes, the complexes being related to each other through the symmetry elements of the [Formula: see text] point group of the alum lattice. The three g factors for the spin Hamiltonian with S = 1/2 were found to be 1.979, 1.898, and 1.828, with an accuracy of ±0.005.

The neutral complex [CrIII4(μ3-O)2(μ2-CH3CO2)7(tbpy0)(tbpy•)]0 — a tetranuclear Cr(III) species containing a neutral (bpy0) and a π-radical anion (bpy•)1–

2014 ◽  
Vol 92 (10) ◽  
pp. 913-917 ◽  
Author(s):  
Mei Wang ◽  
Eckhard Bill ◽  
Thomas Weyhermüller ◽  
Karl Wieghardt
Keyword(s):  
Quantum Interference ◽  
Radical Anion ◽  
Resonance Spectrum ◽  
Coupling Model ◽  
Superconducting Quantum Interference Device ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
X Band ◽  
Electron Paramagnetic

The tetranuclear neutral species [CrIII4(μ3-O)2(μ2-CH3CO2)7(tbpy0)(tbpy•)]0·3THF has been prepared from a mixture of [CrII2(μ2-CH3CO2)4]·2H2O and 4,4′-di-tert-butyl-2,2′-bipyridine (1:2) in tetrahydrofuran (THF) under anaerobic conditions. Black crystals of [CrIII4(μ-O)2(μ-CH3CO2)7(tbpy)2]0 were grown and investigated by X-ray crystallography: a [Cr4O2]8+ butterfly core structure has been identified. In addition, the presence of seven μ2-acetate bridges, a neutral (tbpy0) ligand, and a single π-radical anion (tbpy•)1– have been clearly identified. The magnetic properties have been investigated by solid-state SQUID (superconducting quantum interference device) measurements (2–300 K) and a coupling model is presented. Its X-band electron paramagnetic resonance spectrum has been recorded at 10 and 300 K in toluene solution and successfully simulated. The spin of the (tbpy•)1– radical couples strongly antiferromagnetically to one Cr(III) center (J4 = –129 cm−1). These properties are compared with those reported previously for the monocationic species [CrIII4(μ3-O)2(μ2-CH3CO2)7(bpy0)2](PF6) in Bino et al. (Inorg. Chem. 1991, 30, 856).

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