EPR Spectroscopy

doi:10.1007/978-3-642-28347-5

Cited by 39 publications

(2 citation statements)

References 22 publications

(22 reference statements)

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“…Most commonly, a pair of nitroxide radicals, incorporated into the molecule of interest by site-directed spin labelling, has been used for these type of experiments. 17–21 On the other hand, if the excitation bandwidth of the available microwave pulses is large enough to excite the whole EPR spectrum, e.g. in case of trityls, the usage of single frequency techniques like double-quantum coherence (DQC), 22 or the single frequency technique for refocusing dipolar couplings (SIFTER) 23 is preferred due to higher sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

Akhmetzyanov

Schöps

Marko

et al. 2015

Phys. Chem. Chem. Phys.

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Pulsed electron paramagnetic resonance (EPR) spectroscopy is a valuable technique for the precise determination of distances between paramagnetic spin labels that are covalently attached to macromolecules. Nitroxides have commonly been utilised as paramagnetic tags for biomolecules, but trityl radicals have recently been developed as alternative spin labels. Trityls exhibit longer electron spin relaxation times and higher stability than nitroxides under in vivo conditions. So far, trityl radicals have only been used in pulsed EPR dipolar spectroscopy (PDS) at X-band (9.5 GHz), Ku-band (17.2 GHz) and Q-band (34 GHz) frequencies. In this study we investigated a trityl biradical by PDS at Q-band (34 GHz) and G-band (180 GHz) frequencies. Due to the small spectral width of the trityl (30 MHz) at Q-band frequencies, single frequency PDS techniques, like double-quantum coherence (DQC) and single frequency technique for refocusing dipolar couplings (SIFTER), work very efficiently. Hence, Q-band DQC and SIFTER experiments were performed and the results were compared; yielding a signal to noise ratio for SIFTER four times higher than that for DQC. At G-band frequencies the resolved axially symmetric g-tensor anisotropy of the trityl exhibited a spectral width of 130 MHz. Thus, pulsed electron electron double resonance (PELDOR/DEER) obtained at different pump-probe positions across the spectrum was used to reveal distances. Such a multi-frequency approach should also be applicable to determine structural information on biological macromolecules tagged with trityl spin labels.

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Section: Introductionmentioning

confidence: 99%

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

Akhmetzyanov

Schöps

Marko

et al. 2015

Phys. Chem. Chem. Phys.

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“…EPR spectroscopy is a commonly used tool in many areas of chemistry. , Its ability to detect unpaired electrons, and yield detailed information on structure and bonding of paramagnetic species has led to EPR becoming indispensable within chemistry and biochemistry. Also within catalysis, EPR is a popular method. , However, throughout this Review, only few examples employed EPR spectroscopy. ,,,, In these examples, EPR was used to detect and quantify states that can be related to oxygen vacancies and other defects within zinc oxide. This ability of EPR to be sensitive to O-vacancies but not the metallic zinc, which would be present in any CuZn alloy, makes the method extremely interesting in relation to aspects of methanol synthesis over industrial-type CZA catalysts.…”

Section: Underutilized Methodsmentioning

confidence: 99%

The Enigma of Methanol Synthesis by Cu/ZnO/Al₂O₃-Based Catalysts

Beck,

Newton,

van de Water

et al. 2024

Chem. Rev.

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The activity and durability of the Cu/ZnO/Al 2 O 3 (CZA) catalyst formulation for methanol synthesis from CO/CO 2 /H 2 feeds far exceed the sum of its individual components. As such, this ternary catalytic system is a prime example of synergy in catalysis, one that has been employed for the large scale commercial production of methanol since its inception in the mid 1960s with precious little alteration to its original formulation. Methanol is a key building block of the chemical industry. It is also an attractive energy storage molecule, which can also be produced from CO 2 and H 2 alone, making efficient use of sequestered CO 2 . As such, this somewhat unusual catalyst formulation has an enormous role to play in the modern chemical industry and the world of global economics, to which the correspondingly voluminous and ongoing research, which began in the 1920s, attests. Yet, despite this commercial success, and while research aimed at understanding how this formulation functions has continued throughout the decades, a comprehensive and universally agreed upon understanding of how this material achieves what it does has yet to be realized. After nigh on a century of research into CZA catalysts, the purpose of this Review is to appraise what has been achieved to date, and to show how, and how far, the field has evolved. To do so, this Review evaluates the research regarding this catalyst formulation in a chronological order and critically assesses the validity and novelty of various hypotheses and claims that have been made over the years. Ultimately, the Review attempts to derive a holistic summary of what the current body of literature tells us about the fundamental sources of the synergies at work within the CZA catalyst and, from this, suggest ways in which the field may yet be further advanced.

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Electron Paramagnetic Resonance Spectroscopy

Jeschke¹

2013

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Principles of EPR 2.1. Electron and Nuclear Spins 2.2. High‐Field Approximation and Forbidden Transitions 2.3. Relaxation and Linewidths 3. The EPR Experiment 3.1. Continuous‐Wave EPR 3.1.1. Continuous‐Wave ENDOR and Triple Resonance 3.1.2. Progressive Saturation 3.1.3. Saturation‐Transfer EPR 3.2. Pulse EPR 3.2.1. Fourier‐Transform EPR 3.2.2. Echo‐Detected EPR 3.2.3. Relaxation Measurements 3.2.4. ESEEM and HYSCORE 3.2.5. Pulse ENDOR 3.2.6. Pulse ELDOR and Double‐Quantum EPR 3.3. EPR Imaging 4. Spectral Parameters 4.1. g ‐Factor 4.2. Hyperfine Interaction 4.3. Zero‐Field Splitting 4.4. Exchange Interaction 4.5. Dipole–Dipole Interaction 4.6. Spin Concentration 5. EPR in the Liquid State and in Soft Matter 5.1. Slow Molecular Tumbling and Local Order 5.2. Heisenberg Spin Exchange 6. Computation of Parameters and Spectra 6.1. Parameter Prediction 6.2. Data Analysis and Spectrum Simulation 7. Specialist Techniques 7.1. Spin Trapping 7.2. Spin Probing and Labeling 7.3. EPR Oxymetry 7.4. EPR Dosimetry and Dating

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EPR Spectroscopy

Cited by 39 publications

References 22 publications

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

The Enigma of Methanol Synthesis by Cu/ZnO/Al₂O₃-Based Catalysts

Electron Paramagnetic Resonance Spectroscopy

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EPR Spectroscopy

Cited by 39 publications

References 22 publications

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

The Enigma of Methanol Synthesis by Cu/ZnO/Al2O3-Based Catalysts

Electron Paramagnetic Resonance Spectroscopy

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The Enigma of Methanol Synthesis by Cu/ZnO/Al₂O₃-Based Catalysts