Category Archives: EPR

[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.

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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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NMR web database:

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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.

Postdoctoral Position: EPR Spectroscopic Studies of Membrane Proteins #EPR

Postdoctoral Position: EPR Spectroscopic Studies of Membrane Proteins

Miami University, Oxford, OH, USA

A Postdoctoral research position is available immediately to study the structural and dynamic properties of integral membrane proteins in the laboratory of Prof. Gary A. Lorigan in the Department of Chemistry and Biochemistry at Miami University in Ohio. The postdoctoral position is funded through a NIH MIRA R35 grant.

Candidates who are interested in studying the structural and dynamic properties of membrane proteins are encouraged to apply. Experience in two of the following areas is desirable: molecular biology and biochemistry of membrane proteins, protein purification, and EPR spectroscopy. 2 pulsed EPR spectrometers (X-band/Q-band) for DEER and ESEEM experiments, 2 CW-EPR spectrometers, and a 500 MHz solid-state NMR instrument are available for this project. Miami University is home to the Ohio Advanced EPR Lab (http://epr.miamioh.edu). Please send a CV and two letters of recommendation to: Professor Gary A. Lorigan, Department of Chemistry and Biochemistry, Miami University gary.lorigan@miamioh.edu. A Ph.D. in Chemistry/Biochemistry or related fields is required. Contact phone is 513-529-3338. 

Miami University, an Equal Opportunity/Affirmative Action employer, encourages applications from minorities, women, protected veterans and individuals with disabilities. Miami University prohibits harassment, discrimination and retaliation on the basis of sex/gender (including sexual harassment, sexual violence, sexual misconduct, domestic violence, dating violence, or stalking), race, color, religion, national origin (ancestry), disability, age (40 years or older), sexual orientation, gender identity, pregnancy, status as a parent or foster parent, military status, or veteran status in its recruitment, selection, and employment practices. Requests for all reasonable accommodations for disabilities related to employment should be directed to ADAFacultyStaff@miamioh.edu or 513-529-3560.

As part of the University’s commitment to maintaining a healthy and safe living, learning, and working environment, we encourage you to read Miami University’s Annual Security & Fire Safety Report at http://www.MiamiOH.edu/campus-safety/annual-report/index.html(http://www.miamioh.edu/campus-safety/annual-report/index.html), which contains information about campus safety, crime statistics, and our drug and alcohol abuse and prevention program designed to prevent the unlawful possession, use, and distribution of drugs and alcohol on campus and at university events and activities. This report also contains information on programs and policies designed to prevent and address sexual violence, domestic violence, dating violence, and stalking. Each year, email notification of this website is made to all faculty, staff, and enrolled students. Written notification is also provided to prospective students and employees. Hard copies of the Annual Security & Fire Safety Report may be obtained from the Miami University Police Department at (513) 529-2225.

Gary A. Lorigan

John W. Steube Professor 

Department of Chemistry and Biochemistry

Miami University

651 E. High St.

Oxford, Ohio 45056

Office: 137 Hughes Laboratories

Phone: (513) 529-3338

Fax: (513) 529-5715

e-mail: gary.lorigan@miamioh.edu

web: www.users.muohio.edu/lorigag/index.html

EPR facility: epr.muohio.edu

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NMR web database:

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[NMR] PhD position in magnetic resonance at the University of Freiburg #EPR

Dear colleagues,

I would be grateful if you could forward the following announcement for a PhD position at the University of Freiburg to any students in your institution potentially interested in pursuing a doctorate in magnetic resonance and optical spectroscopy.

PhD position in magnetic resonance and optical spectroscopy

Applications are invited for a doctoral position to work in the group of Dr. S. Richert within the Institute of Physical Chemistry at the University of Freiburg. The position is initially limited to three years and funded by the German Research Foundation (DFG).

The project

The project aims at investigating the factors influencing spin-information transfer in organic multi-spin systems by combining modern optical spectroscopy, pulse electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR). The long-term goal is to provide design principles for materials to be used for molecular spintronics applications. All of these future applications require the search for new materials, new devices, and design rules, to enable a fundamental understanding of the underlying physical processes and to reveal the importance of specific molecular properties for an efficient generation, transfer and storage of spin information.

What we offer

The successful candidate will work at the University of Freiburg, one of the leading research and teaching institutions in Germany. S/he will work as part of a small team, in direct contact with the members of other research groups at the Institute of Physical Chemistry. Through the work on the project, the candidate will be made familiar with (i) state-of-the-art pulse EPR methods, (ii) photo-induced NMR and (iii) modern optical spectroscopic techniques from the femtosecond to the microsecond time scale and learn about their applicability to current research challenges in the field of molecular spintronics.

Depending on the strengths and interests of the successful applicant, the focus of the individually designed subproject may either lie on the theoretical (programming, data analysis and simulations, method development) or practical (spectroscopic measurements, synthesis) aspects of the project.

The candidate

Highly motivated candidates with a master’s degree in either chemistry or physics are strongly encouraged to apply. Successful applicants should have a solid background in physical chemistry (spectroscopy), good presentation and writing skills in English and/or German and must be able to work independently as part of a team in an interdisciplinary environment. Previous experience with programming (MATLAB, Python), advanced optical spectroscopy, or magnetic resonance spectroscopy, is advantageous, but not required.

The application

Applications (in English or German) including a letter of motivation, curriculum vitæ, degree certificates and grades, and full contact details of at least two referees, should be sent in a single PDF document (no more than 10 MB) via email to sabine.richert@pc.unifreiburg.de. Although the starting date is flexible, interested candidates should get in touch as soon as possible. For further information please also see: http://www.richert.uni-freiburg.de.

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

This article is not directly related to DNP but it is about a small EPR resonator for nanoliter size samples. However, I find it fascinating how sow far you can push instrumentation to miniaturize EPR spectroscopy.

Sidabras, Jason W., Jifu Duan, Martin Winkler, Thomas Happe, Rana Hussein, Athina Zouni, Dieter Suter, Alexander Schnegg, Wolfgang Lubitz, and Edward J. Reijerse. “Extending Electron Paramagnetic Resonance to Nanoliter Volume Protein Single Crystals Using a Self-Resonant Microhelix.” Science Advances 5, no. 10 (October 2019): eaay1394.

https://doi.org/10.1126/sciadv.aay1394.

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.

Rutile dielectric loop-gap resonator for X-band EPR spectroscopy of small aqueous samples

Mett, Richard R., Jason W. Sidabras, James R. Anderson, Candice S. Klug, and James S. Hyde. “Rutile Dielectric Loop-Gap Resonator for X-Band EPR Spectroscopy of Small Aqueous Samples.” Journal of Magnetic Resonance 307 (October 2019): 106585.

https://doi.org/10.1016/j.jmr.2019.106585

The performance of a metallic microwave resonator that contains a dielectric depends on the separation between metallic and dielectric surfaces, which affects radio frequency currents, evanescent waves, and polarization charges. The problem has previously been discussed for an X-band TE011 cylindrical cavity resonator that contains an axial dielectric tube (Hyde and Mett, 2017). Here, a short rutile dielectric tube inserted into a loop-gap resonator (LGR) at X-band, which is called a dielectric LGR (dLGR), is considered. The theory is developed and experimental results are presented. It was found that a central sample loop surrounded by four ‘‘flux-return” loops (i.e., 5-loop–4-gap) is preferable to a 3-loop–2-gap configuration. For sufficiently small samples (less than 1 mL), a rutile dLGR is preferred relative to an LGR both at constant K (B1= Pl) and at constant incident power. Introduction of LGR technology to X-band EPR was a significant advance for site-directed spin labeling because of small sample size and high K. The rutile dLGR introduced in this work offers further extension to samples that can be as small as 50 nL when using typical EPR acquisition times.

Persistence of Nitroxide Radicals in Solution #EPR #DNPNMR

Elajaili, Hanan, Jessica Sedhom, Sandra S. Eaton, and Gareth R. Eaton. “Persistence of Nitroxide Radicals in Solution.” Applied Magnetic Resonance 50, no. 10 (October 2019): 1177–81.

https://doi.org/10.1007/s00723-019-01135-7

Data on long-term persistence of nitroxide radicals typically are focused on solid samples. Less information is available for nitroxides in fluid solution. Sealed deoxygenated solutions of a doxyl nitroxide in tetrahydrofuran and a piperidinyl nitroxide in toluene in 4 mm EPR tubes were kept in a laboratory environment at ambient temperature and without protection from light. After more than 40 years, the concentrations of the solutions had decreased by about factors of 12 and 6, respectively. The longevity in solution probably depends strongly on the purity of the solvent, but these results indicate remarkable persistence.

[NMR] Dates for the diary: 53rd ESR Group Conference in Manchester

Dear Colleagues,

the next conference in the long series of Electron Spin Resonance meetings organised by the ESR Group of the Royal Society of Chemistry will take place in Manchester between 29th March and 2nd April 2020:

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

The Meeting is the oldest EPR Spectroscopy conference in the world, as well as the occasion on which the EPR Spectroscopy Bruker Prize is awarded to eminent EPR scientists, Bruker Thesis Prize is given for the best PhD thesis in the preceding two years, and the JEOL Student Prize is awarded for the best student research work presented at the Conference.

The registration will open in November.

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

Site-Directed Spin Labeling EPR for Studying Membrane Proteins #DNPNMR #EPR

Sahu, Indra D., and Gary A. Lorigan. “Site-Directed Spin Labeling EPR for Studying Membrane Proteins.” BioMed Research International 2018 (2018): 1–13.

https://doi.org/10.1155/2018/3248289

Site-directed spin labeling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy is a rapidly expanding powerful biophysical technique to study the structural and dynamic properties of membrane proteins in a native environment. Membrane proteins are responsible for performing important functions in a wide variety of complicated biological systems that are responsible for the survival of living organisms. In this review, a brief introduction of the most popular SDSL EPR techniques and illustrations of recent applications for studying pertinent structural and dynamic properties on membrane proteins will be discussed.

1H high field electron-nuclear double resonance spectroscopy at 263 GHz/9.4 T

Tkach, Igor, Isabel Bejenke, Fabian Hecker, Annemarie Kehl, Müge Kasanmascheff, Igor Gromov, Ion Prisecaru, Peter Höfer, Markus Hiller, and Marina Bennati. “1H High Field Electron-Nuclear Double Resonance Spectroscopy at 263 GHz/9.4 T.” Journal of Magnetic Resonance 303 (June 2019): 17–27.

https://doi.org/10.1016/j.jmr.2019.04.001

We present and discuss the performance of 1H electron-nuclear double resonance (ENDOR) at 263 GHz/9.4 Tesla by employing a prototype, commercial quasi optical spectrometer. Basic instrumental features of the setup are described alongside a comprehensive characterization of the new ENDOR probe head design. The performance of three different ENDOR pulse sequences (Davies, Mims and CP-ENDOR) is evaluated using the 1H BDPA radical. A key feature of 263 GHz spectroscopy – the increase in orientiation selectivity in comparison with 94 GHz experiments – is discussed in detail. For this purpose, the resolution of 1H ENDOR spectra at 263 GHz is verified using a representative protein sample containing approximately 15 picomoles of a tyrosyl radical. Davies ENDOR spectra recorded at 5 K reveal previously obscured spectral features, which are interpreted by spectral simulations aided by DFT calculations. Our analysis shows that seven internal proton couplings are detectable for this specific radical if sufficient orientation selectivity is achieved. The results prove the fidelity of 263 GHz experiments in reporting orientation-selected 1H ENDOR spectra and demonstrate that new significant information can be uncovered in complex molecular systems, owing to the enhanced resolution combined with high absolute sensitivity and no compromise in acquisition time.

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