DNP-NMR Literature Blog

Platforms for Stable Carbon‐Centered Radicals #DNPNMR

Kato, Kenichi, and Atsuhiro Osuka. “Platforms for Stable Carbon‐Centered Radicals.” Angewandte Chemie International Edition 58, no. 27 (July 2019): 8978–86.

https://doi.org/10.1002/anie.201900307

Organic radicals can play important roles potentially in diverse functional materials owing to an unpaired electron but are usually highly reactive and difficult to use. Therefore, stabilization of organic radicals is crucially important. Among organic radicals, carbon-centered radicals are promising because of their trivalent nature that enables structural diversity and elaborate designs but they show less stabilities because of reactivities toward carboncarbon bond formation and atmospheric oxygen. Recently, stable carbon-centered radicals have been increasingly explored on the basis of diverse molecular platforms. This minireview highlights these newly explored stable carbon-centered radicals with a particular focus on porphyrinoid-stabilized radicals owing to their remarkable spin delocalization abilities.

Field Guide to Terahertz Sources, Detectors, and Optics

I recently came across this very handy and useful publication. It is helpful to anyone who wants to understand the design of quasi-optical elements, which are for example used in many high-field EPR spectrometers.

O’Sullivan, Créidhe M., and J. Anthony Murphy. Field Guide to Terahertz Sources, Detectors, and Optics. SPIE, 2012.

https://doi.org/10.1117/3.952851.

The region of the electromagnetic spectrum between microwaves and infrared radiation has come to be known as the “THz gap,” mainly due to the lack of readily available laboratory sources and detectors. For many years technology development was driven by astronomers and planetary scientists, but other potential uses, particularly in medical and security applications, have led to increased activity by the mainstream physics and engineering community in recent times. Because diffraction is important at these frequencies, THz systems cannot be successfully designed using traditional optical techniques alone.

The primary objective of this Field Guide is to provide the reader with a concise description of the quasi-optical techniques used at THz frequencies, as well as the basic principles of operation of the most common THz system components in use today. More detailed accounts of specific devices can be found in the bibliography and references therein.

Molecular Dynamics and Hyperpolarization Performance of Deuterated β-Cyclodextrins #DNP

Caracciolo, Filippo, Efstathios Charlaftis, Lucio Melone, and Pietro Carretta. “Molecular Dynamics and Hyperpolarization Performance of Deuterated β-Cyclodextrins.” The Journal of Physical Chemistry B 123, no. 17 (May 2, 2019): 3731–37.

https://doi.org/10.1021/acs.jpcb.9b01857.

We discuss the temperature dependence of the 1H and 13C nuclear spin−lattice relaxation rate 1/T1 and dynamic nuclear polarization (DNP) performance in β-cyclodextrins with deuterated methyl groups. It is shown that 13C DNP-enhanced polarization is raised up to 10%. The temperature dependence of the buildup rate for nuclear spin polarization and of 1/T1, below 4.2 K, is analyzed in the framework of the thermal mixing regime and the origin of the deviations from the theoretical behavior discussed. 13C 1/T1 is determined at low temperature by the glassy dynamics and at high temperature by the rotational molecular motions of the deuterated methyl groups. Thanks to deuteration, relaxation times approaching 30 s are achieved at room temperature, making this material interesting for molecular imaging applications. The effect of molecular dynamics on the line width of the NMR spectra is also discussed.

Wave Guides for Micromagnetic Resonance

Yilmaz, Ali, and Marcel Utz. “Wave Guides for Micromagnetic Resonance.” In Micro and Nano Scale NMR, by Jens Anders and Jan G. Korvink, 75–108. Advanced Micro and Nanosystems. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2018.

https://doi.org/10.1002/9783527697281.ch4.

In nuclear magnetic resonance, a system of nuclear spins exposed to a static magnetic interacts with an oscillatory field, usually in the radio frequency range. In most NMR setups, including all commercially available NMR spectrometers, coherent transitions between spin states are detected by a voltage induced into a conductor surrounding the sample. Whereas other detection techniques have their advantages in certain cases, inductive detection has proven to be both robust and easy to implement.

Microscale Hyperpolarization #DNPNMR

Kiss, Sebastian, Lorenzo Bordonali, Jan G. Korvink, and Neil MacKinnon. “Microscale Hyperpolarization.” In Micro and Nano Scale NMR, by Jens Anders and Jan G. Korvink, 297–351. Advanced Micro and Nanosystems. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2018.

https://doi.org/10.1002/9783527697281.ch11.

Magnetic resonance (MR) is a tremendously powerful technique for obtaining both structural and dynamical information non-invasively and with atomic resolution. The primary limitation of MR is sensitivity, with the detected resonant exchange of energy dependent on population differences on the order of tens of parts per million as dictated by Boltzmann statistics. The MR community has implemented various strategies to overcome this inherent limitation, including maximizing the static polarizing magnetic field and cooling the probe electronics. As discussed throughout this book, an alternative strategy is to miniaturize the MR detector in order to maximize resonant energy exchange efficiency between the sample and the instrument electronics. In this chapter, we discuss approaches that aim to overcome Boltzmann population statistics. These hyperpolarization techniques rely on the transfer of a large polarization source to the target nuclear spin system, or the preparation of pure spin states that are transferred into the target spin system. The archetypal example of the former case is dynamic nuclear polarization (DNP), whereas in the latter case para-hydrogen and optically pumped 3He or 129Xe are examples.

A method for fast field settling in cryogen-free superconducting magnets for NMR

Cryogen-free magnets are around for EPR spectroscopy for a while already, however, in recent years they also become more popular for NMR spectroscopy (solids and solutions). This article greatly demonstrate the potential of the technology.

Kryukov, Eugeny, Yury Bugoslavsky, Angel Joaquin Perez Linde, Thomas Holubar, Stephen Burgess, David Marlow, and Jeremy Good. “A Method for Fast Field Settling in Cryogen-Free Superconducting Magnets for NMR.” Solid State Nuclear Magnetic Resonance 109 (October 2020): 101684.

https://doi.org/10.1016/j.ssnmr.2020.101684.

We propose a fast algorithm to energise a cryogen free magnet to a highly persistent state. A decay rate as low as 0.021 ppm/h can be achieved in less than an hour after reaching the target field. The decay rate drops further to 0.0004 ppm/h in the following 48 h. This procedure can be applied at different values of target field, which makes it feasible to use a single magnet for study of various NMR lines at different fields. The mechanism of establishing a highly stable magnetic field can be understood on the basis of the magnetic properties of the superconducting wire, which were studied using a vibrating sample magnetometer. The results confirm the high quality of the superconducting wire and joints.

XeUS: A second-generation automated open-source batch-mode clinical-scale hyperpolarizer

Birchall, Jonathan R., Robert K. Irwin, Panayiotis Nikolaou, Aaron M. Coffey, Bryce E. Kidd, Megan Murphy, Michael Molway, et al. “XeUS: A Second-Generation Automated Open-Source Batch-Mode Clinical-Scale Hyperpolarizer.” Journal of Magnetic Resonance 319 (October 2020): 106813.

https://doi.org/10.1016/j.jmr.2020.106813.

We present a second-generation open-source automated batch-mode 129Xe hyperpolarizer (XeUS GEN2), designed for clinical-scale hyperpolarized (HP) 129Xe production via spin-exchange optical pumping (SEOP) in the regimes of high Xe density (0.66–2.5 atm partial pressure) and resonant photon flux (~170 W, Dk = 0.154 nm FWHM), without the need for cryo-collection typically employed by continuous-flow hyperpolarizers. An Arduino micro-controller was used for hyperpolarizer operation. Processing open-source software was employed to program a custom graphical user interface (GUI), capable of remote automation. The Arduino Integrated Development Environment (IDE) was used to design a variety of customized automation sequences such as temperature ramping, NMR signal acquisition, and SEOP cell refilling for increased reliability. A polycarbonate 3D-printed oven equipped with a thermoelectric cooler/heater provides thermal stability for SEOP for both binary (Xe/N2) and ternary (4He-containing) SEOP cell gas mixtures. Quantitative studies of the 129Xe hyperpolarization process demonstrate that near-unity polarization can be achieved in a 0.5 L SEOP cell. For example, %PXe of 93.2 ± 2.9% is achieved at 0.66 atm Xe pressure with polarization build-up rate constant cSEOP = 0.040 ± 0.005 minÀ1, giving a max dose equivalent % 0.11 L/h 100% hyperpolarized, 100% enriched 129Xe; %PXe of 72.6 ± 1.4% is achieved at 1.75 atm Xe pressure with cSEOP of 0.041 ± 0.001 minÀ1, yielding a corresponding max dose equivalent of 0.27 L/h. Quality assurance studies on this device have demonstrated the potential to refill SEOP cells hundreds of times without significant losses in performance, with average %PXe = 71.7%, (standard deviation rP = 1.52%) and mean polarization lifetime T1 = 90.5 min, (standard deviation rT = 10.3 min) over the first ~200 gas mixture refills, with sufficient performance maintained across a further ~700 refills. These findings highlight numerous technological developments and have significant translational relevance for efficient production of gaseous HP 129Xe contrast agents for use in clinical imaging and bio-sensing techniques.

[NMR] PhD and postdoc positions at MPI Göttingen

Dear colleagues, I have three position to fill in my group at the Max Planck Institute for Biophysical Chemistry in Göttingen. Please see the postings below and feel free to forward this mail to interested candidates.
Best regards,

Stefan Glöggler
Max Planck Institute for Biophysical Chemistry
NMR Signal Enhancement
Dr. Stefan Glöggler
Am Fassberg 11
37077 Göttingen, Germany
https://www.mpibpc.mpg.de/gloeggler

Open positions:

Postdoc for hyperpolarized in vivo magnetic resonance imaging (preclinical):We are looking for a highly motivated postdoc with experience in preclinical hyperpolarized magnetic resonance in vivo who wants to work in a multidisciplinary team on magnetic resonance spectroscopy and imaging of metabolism in the brain. The successful candidate will benefit from state-of-the-art high field NMR and microimaging equipment and a team of chemists dedicated to develop new hyperpolarized contrast agents.Your Profile

  • A completed PhD and training in hyperpolarized in vivo magnetic resonance
  • A minimum of three years experience with preclinical in vivo experiments
    (please provide evidence and certificates with your application)
  • Independent thinking, structured work organization and a good team spirit are expected
  • Postdocs hold a PhD or equivalent degree

Additional InformationThe position will be open until filled with the earliest possible starting date of January 1, 2021.The payment and benefits are based on the TVöD guidelines.The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.Please submit your application including a cover letter (explaining background and motivation), your CV, complete transcripts and two letters of recommendation send under separate cover preferably via e-mail as a single PDF file with the subject “In vivo” to
ausschreibung22-20@mpibpc.mpg.de

Postdoc or PhD student for in-cell NMR:We are looking for a highly motivated biochemist/biologist with a strong background in NMR who wants to work in a multidisciplinary team on aspects of protein aggregation related to neurodegeneration, cell metabolism and hyperpolarization. The successful candidate will benefit from state-of-the-art high field NMR equipment including a 900 MHz, 950 MHz and the recently installed 1.2 GHz spectrometer.Your Profile

  • Excellent degree in biochemistry, biology or a related discipline
  • Experience/Interest in NMR and structural biology
  • Knowledge and hands-on experience with cell culture
  • Independent thinking, structured work organization and a good team spirit are expected
  • PhD candidates hold (or expect to complete soon) a Masters or equivalent degree; Postdocs hold a PhD or equivalent degree

Additional InformationThe position will be open until filled with the earliest possible starting date of January 1, 2021. The PhD position is limited to four years with a possibility of extension.The payment and benefits are based on the TVöD guidelines.The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.Please submit your application including a cover letter (explaining background and motivation), your CV, complete transcripts and two letters of recommendation send under separate cover preferably via e-mail as a single PDF file with the subject “In-Cell” to
ausschreibung21-20@mpibpc.mpg.de

Postdoc or PhD student for singlet state magnetic resonance:We are looking for a highly motivated physicist/physical chemist/biophysicist with experience/interest in NMR and pulse sequence development who wants to work in a multidisciplinary team on magnetic resonance spectroscopy and imaging, metabolism research and hyperpolarization. The successful candidate will benefit from state-of-the-art high field NMR and microimaging equipment.Your Profile

  • Excellent degree in physics, physical chemistry, biophysics or related disciplines
  • Experience/interest in NMR and in pulse sequence development
  • Independent thinking, structured work organization and a good team spirit are expected
  • PhD candidates hold (or expect to complete soon) a Masters or equivalent degree; Postdocs hold a PhD or equivalent degree

Additional InformationThe position will be open until filled with the earliest possible starting date of January 1, 2021. The PhD position is limited to four years with a possibility of extensionThe payment and benefits are based on the TVöD guidelines.The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.Please submit your application including a cover letter (explaining background and motivation), your CV, complete transcripts and two letters of recommendation send under separate cover preferably via e-mail as a single PDF file with the subject “Singlet” to
ausschreibung23-20@mpibpc.mpg.de


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Electrochemical Overhauser dynamic nuclear polarization #DNPNMR #ODNP

Tamski, Mika, Jonas Milani, Christophe Roussel, and Jean-Philippe Ansermet. “Electrochemical Overhauser Dynamic Nuclear Polarization.” Physical Chemistry Chemical Physics 22, no. 32 (2020): 17769–76.


https://doi.org/10.1039/D0CP00984A

Nuclear Magnetic Resonance (NMR) spectroscopy suffers from low sensitivity due to the low nuclear spin polarization obtained within practically achievable external magnetic fields. Dynamic Nuclear Polarization (DNP) refers to the techniques that increases NMR signal intensity by transferring spin polarization from electrons to the nuclei.

Materials chemistry of triplet dynamic nuclear polarization #DNPNMR

Nishimura, Koki, Hironori Kouno, Yusuke Kawashima, Kana Orihashi, Saiya Fujiwara, Kenichiro Tateishi, Tomohiro Uesaka, Nobuo Kimizuka, and Nobuhiro Yanai. “Materials Chemistry of Triplet Dynamic Nuclear Polarization.” Chemical Communications 56, no. 53 (2020): 7217–32.

https://doi.org/10.1039/D0CC02258F

This Feature Article overviews the recently-emerged materials chemistry of triplet dynamic nuclear polarization (triplet-DNP) towards biological and medical applications.

Dynamic nuclear polarization with photo-excited triplet electrons (triplet-DNP) has the potential to enhance the sensitivity of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at a moderate temperature. While many efforts have been devoted to achieving a large nuclear polarization based on triplet-DNP, the application of triplet-DNP has been limited to nuclear physics experiments. The recent introduction of materials chemistry into the field of triplet-DNP has achieved air-stable and water-soluble polarizing agents as well as the hyperpolarization of nanomaterials with a large surface area such as nanoporous metal–organic frameworks (MOFs) and nanocrystal dispersion in water. This Feature Article overviews the recently-emerged materials chemistry of triplet-DNP that paves new paths towards unprecedented biological and medical applications.

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