Category Archives: EPR

[NMR] Bruker ESR Thesis Prize – call for applications

Dear Colleagues,

the ESR Group of the Royal Society of Chemistry and Bruker Corporation are pleased to invite applications for the 2021 Bruker ESR Thesis Prize – a monetary award and a prize lecture at the ESR Group Meeting in April 2021, set up to recognize outstanding work by PhD students in the field of Electron Spin Resonance. Further information is here:

http://www.esr-group.org/bruker-thesis-prize/

The deadline for the 2021 Bruker Thesis Prize applications is 12:00 (UK time) on 01 December 2020. Applications should be sent, in the form of PDF files (1-page summary, full thesis, supervisor support letter, examiner support letter) to the ESR Group Secretary – Dr Ilya Kuprov (i.kuprov@soton.ac.uk).

Best wishes,

Ilya.

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Dr Ilya Kuprov FRSC

Associate Professor of Chemical Physics

Secretary to the RSC ESR Spectroscopy Group

Associate Editor, Science Advances

Office 3041, Building 30,

School of Chemistry, FNES,

University of Southampton,

Southampton, SO17 1BJ, UK.

Tel: +44 2380 594 140

Email: i.kuprov@soton.ac.uk

Web: http://spindynamics.org

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http://www.drorlist.com/nmrlist.html

NMR web database:

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Continuous wave electron paramagnetic resonance of nitroxide biradicals in fluid solution

Eaton, Sandra S., Lukas B. Woodcock, and Gareth R. Eaton. “Continuous Wave Electron Paramagnetic Resonance of Nitroxide Biradicals in Fluid Solution.” Concepts in Magnetic Resonance Part A 47A, no. 2 (March 2018): e21426.

https://doi.org/10.1002/cmr.a.21426

Nitroxide biradicals have been prepared with electron-electron spin-spin exchange interaction, J, ranging from weak to very strong. EPR spectra of these biradicals in fluid solution depend on the ratio of J to the nitrogen hyperfine coupling, AN, and the rates of interconversion between conformations with different values of J. For relatively rigid biradicals EPR spectra can be simulated as the superposition of AB splitting patterns arising from different combinations of nitrogen nuclear spin states. For more flexible biradicals spectra can be simulated with a Liouville representation of the dynamics that interconvert conformations with different values of J on the EPR timescale. Analysis of spectra, factors that impact J, and examples of applications to chemical and biophysical problems are discussed.

Electron Paramagnetic Resonance Instrumentation #DNPNMR

Instrumentation for DNP-NMR spectroscopy has many similar components to instrumentation for EPR spectroscopy. This is a comprehensive review of the current state-of-the-art in EPR instrumentation, covering all aspects from magnet technology, pulse generation, detection and resonator design.

Reijerse, Edward, and Anton Savitsky. “Electron Paramagnetic Resonance Instrumentation.” In EMagRes, edited by Robin K. Harris and Roderick L. Wasylishen, 187–206. Chichester, UK: John Wiley & Sons, Ltd, 2017.

https://doi.org/10.1002/9780470034590.emrstm1511

The article gives a general overview of instrumentation commonly used in electron paramagnetic resonance. It includes magnet systems, microwave bridge configurations, and sample cryostats. A special focus has been placed on the discussion of various resonator and sample probe designs used in CW as well as pulsed EPR. Specialized EPR applications such as very high frequency EPR, electrochemistry, stopped flow, and the application to volume limited samples are briefly discussed.

New limits of sensitivity of site-directed spin labeling electron paramagnetic resonance for membrane proteins #DNPNMR

A nice overview how spinlabels can be used for structural biology studies. This includes pulsed EPR techniques such as PELDOR (DEER) and ODNP spectroscopy.

Bordignon, Enrica, and Stephanie Bleicken. “New Limits of Sensitivity of Site-Directed Spin Labeling Electron Paramagnetic Resonance for Membrane Proteins.” Biochimica et Biophysica Acta (BBA) – Biomembranes 1860, no. 4 (April 2018): 841–53. https://doi.org/10.1016/j.bbamem.2017.12.009

Site-directed spin labeling electron paramagnetic resonance is a biophysical technique based on the specific introduction of spin labels to one or more sites in diamagnetic proteins, which allows monitoring dynamics and water accessibility of the spin-labeled side chains, as well as nanometer distances between two (or more) labels. Key advantages of this technique to study membrane proteins are addressed, with focus on the recent developments which will expand the range of applicability. Comparison with other biophysical methods is provided to highlight the strength of EPR as complementary tool for structural biology. This article is part of a Special Issue entitled: Beyond the Structure-Function Horizon of Membrane Proteins edited by Ute Hellmich, Rupak Doshi and Benjamin McIlwain.

Uniform Field Resonators for EPR Spectroscopy: A Review #EPR #DNPNMR

This is an excellent review about uniform field resonators for EPR. These resonators typically have larger filling factors and therefore increased sensitivity. Not directly related to DNP-NMR spectroscopy, but definitely an inspiring article to think about high (and low) field resonators for DNP-NMR.

Hyde, James S., Jason W. Sidabras, and Richard R. Mett. “Uniform Field Resonators for EPR Spectroscopy: A Review.” Cell Biochemistry and Biophysics 77, no. 1 (March 2019): 3–14.

https://doi.org/10.1007/s12013-018-0845-6

Cavity resonators are often used for electron paramagnetic resonance (EPR). Rectangular TE102 and cylindrical TE011 are common modes at X-band even though the field varies cosinusoidally along the Z-axis. The authors found a way to create a uniform field (UF) in these modes. A length of waveguide at cut-off was introduced for the sample region, and tailored end sections were developed that supported the microwave resonant mode. This work is reviewed here. The radio frequency (RF) magnetic field in loop-gap resonators (LGR) at X-band is uniform along the Z-axis of the sample, which is a benefit of LGR technology. The LGR is a preferred structure for EPR of small samples. At Q-band and W-band, the LGR often exhibits nonuniformity along the Z-axis. Methods to trim out this nonuniformity, which are closely related to the methods used for UF cavity resonators, are reviewed. In addition, two transmission lines that are new to EPR, dielectric tube waveguide and circular ridge waveguide, were recently used in UF cavity designs that are reviewed. A further benefit of UF resonators is that cuvettes for aqueous samples can be optimum in cross section along the full sample axis, which improves quantification in EPR spectroscopy of biological samples.

Improving B1 field homogeneity in dielectric tube resonators for EPR spectroscopy via controlled shaping of the dielectric insert

Syryamina, Victoria N., Anna G. Matveeva, Yan V. Vasiliev, Anton Savitsky, and Yuri A. Grishin. “Improving B1 Field Homogeneity in Dielectric Tube Resonators for EPR Spectroscopy via Controlled Shaping of the Dielectric Insert.” Journal of Magnetic Resonance 311 (February 2020): 106685.

https://doi.org/10.1016/j.jmr.2020.106685

We propose an approach for improving the homogeneity of microwave magnetic field amplitude in a dielectric tube resonator for electron paramagnetic resonance spectroscopy at X-band. The improvement is achieved by “shaping” (controllable variation of the outer diameter of a dielectric insert along its axial direction). Various shaping scenarios based on the principle of discrete solenoids and electromagnetic calculations have been considered. The dielectric insert having the most promising shape was manufactured from a bismuth germanate single crystal. The shaped insert increases the area at B1 > 0.9 B1max from 5.06 to 7.36 mm. Higher sensitivity and lower likelihood of quantitative errors have been achieved in pulse EPR experiments for “long” samples (whose length was comparable to that of the dielectric insert) in a shaped dielectric insert.

1st International EPR-on-a-chip Workshop

EPR-on-a-chip is an emerging technology that aims at providing the analytical power of electron paramagnetic resonance (EPR) spectroscopy in the tiny form factor of a millimeter-sized microchip.

Within the BMBF sponsored research project EPRoC, the possibilities of this new and fascinating technology are evaluated in the context of operando EPR measurements on energy materials.

The goal of the 1st International EPR-on-a-chip Workshop is to serve as a forum for discussing the possibilities of the EPR-on-a-chip technology in other disciplines, including catalysis, biology and medicine.

For more information visit: https://www.iis.uni-stuttgart.de/institute/news-and-events/eproc2020

[NMR] 53rd Royal Society of Chemistry ESR Group Meeting

Meet the Bridge12 team at the ESR/EPR group meeting in Manchester. Bridge12 is an official sponsor of this exciting event.

Dear Colleagues,

on behalf of the Scientific Committee of the ESR Group of the Royal Society of Chemistry, it is my pleasure to invite you to our 53rd annual Meeting:

http://www.esr-group.org/conferences/2020-conference-manchester/

The Meeting is the longest running EPR spectroscopy conference in the world, as well as the occasion on which the EPR Bruker Prizes are awarded for the best PhD thesis (junior level) and the best scientific accomplishment (senior level). The meeting also hosts IES Poster Prizes, and the JEOL Medal, awarded for the best student presentation. In the annual cycle of the EPR spectroscopy community, this conference is the central event.

This year’s Meeting will take place in Manchester between 29th Mar and 2nd Apr 2020. The registration is now open and may be accessed via the link above.

Best wishes,

Ilya.

—————————————–

Dr Ilya Kuprov FRSC

Associate Professor of Chemical Physics

Secretary to the RSC ESR Spectroscopy Group

Associate Editor, Science Advances

Office 3041, Building 30,

School of Chemistry, FNES,

University of Southampton,

Southampton, SO17 1BJ, UK.

Tel: +44 2380 594 140

Email: i.kuprov@soton.ac.uk

Web: http://spindynamics.org

—————————————–

====================================

This is the AMPERE MAGNETIC RESONANCE mailing list:

http://www.drorlist.com/nmrlist.html

NMR web database:

http://www.drorlist.com/nmr.html

Towards Low-Cost, High-Sensitivity Point-of-Care Diagnostics Using VCO-Based ESR-on-a-Chip Detectors

This article is not directly related to DNP-NMR spectroscopy, but shows the potential of miniaturizing the required instrumentation for EPR. Very impressive technology.

Schlecker, Benedikt, Alexander Hoffmann, Anh Chu, Maurits Ortmanns, Klaus Lips, and Jens Anders. “Towards Low-Cost, High-Sensitivity Point-of-Care Diagnostics Using VCO-Based ESR-on-a-Chip Detectors.” IEEE Sensors Journal 19, no. 20 (October 15, 2019): 8995–9003.

https://doi.org/10.1109/JSEN.2018.2875767.

In this paper, we present a new architecture for VCO-based ESR detection for a future use in portable, point-ofcare ESR spectrometers. The proposed architecture is centered around an ASIC containing a VCO-based ESR detector with two distinct tuning ports with largely different VCO gains to enable wide frequency sweeps and small-signal frequency modulations while keeping the requirements on the digital-to-analog converter driving the ports manageable. Additionally, the proposed ASIC features a second VCO for an on-chip frequency downconversion via mixing. To allow for a precise derivation of the operating frequency from an external reference as it is required for quantitative ESR experiments, the two on-chip VCOs are embedded into an offset phase-locked loop. The proposed architecture is verified with ESR experiments on commonly used ESR standard samples (DPPH and BDPA). In these experiments, a spin sensitivity of 1.7*10^9 spins/(G sqrt(Hz)) has been achieved at B0 = 450mT, which is comparable to the state of the art, using a permanent magnet and low-cost signal processing on an FPGA. The presented proof-of-concept experiments clearly demonstrate the potential of the proposed VCO-based ESR detection system for future point-of-care applications.

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