DNP-NMR Literature Blog

Water-soluble BDPA radicals with improved persistence #DNPNMR

Mandal, Sucharita, and Snorri Th. Sigurdsson. “Water-Soluble BDPA Radicals with Improved Persistence.” Chemical Communications, 2020, 10.1039.D0CC04920D. 

https://doi.org/10.1039/D0CC04920D.

1,3-Bis(diphenylene)-2-phenylallyl (BDPA) radicals are promising polarizing agents for increasing the sensitivity of NMR spectroscopy through dynamic nuclear polarization (DNP), but have low persistence and solubility in aqueous media. New tetraalkyl/aryl-ammonium derivatives of BDPA are soluble in polar solvents and are highly persistent, with 5–20-fold lower initial rates of degradation than BDPA.

Hyperpolarization of Nitrile Compounds Using Signal Amplification by Reversible Exchange

Kim, Sarah, Sein Min, Heelim Chae, Hye Jin Jeong, Sung Keon Namgoong, Sangwon Oh, and Keunhong Jeong. “Hyperpolarization of Nitrile Compounds Using Signal Amplification by Reversible Exchange.” Molecules 25, no. 15 (July 23, 2020): 3347.

https://doi.org/10.3390/molecules25153347.

Signal Amplification by Reversible Exchange (SABRE), a hyperpolarization technique, has been harnessed as a powerful tool to achieve useful hyperpolarized materials by polarization transfer from parahydrogen. In this study, we systemically applied SABRE to a series of nitrile compounds, which have been rarely investigated. By performing SABRE in various magnetic fields and concentrations on nitrile compounds, we unveiled its hyperpolarization properties to maximize the spin polarization and its transfer to the next spins. Through this sequential study, we obtained a ~130-fold enhancement for several nitrile compounds, which is the highest number ever reported for the nitrile compounds. Our study revealed that the spin polarization on hydrogens decreases with longer distances from the nitrile group, and its maximum polarization is found to be approximately 70 G with 5 µL of substrates in all structures. Interestingly, more branched structures in the ligand showed less effective polarization transfer mechanisms than the structural isomers of butyronitrile and isobutyronitrile. These first systematic SABRE studies on a series of nitrile compounds will provide new opportunities for further research on the hyperpolarization of various useful nitrile materials.

Analysis of 1-aminoisoquinoline using the signal amplification by reversible exchange hyperpolarization technique #SABRE

Jeong, Hye Jin, Sein Min, and Keunhong Jeong. “Analysis of 1-Aminoisoquinoline Using the Signal Amplification by Reversible Exchange Hyperpolarization Technique.” The Analyst, 2020, 10.1039.D0AN00967A.

https://doi.org/10.1039/D0AN00967A

Signal amplification by reversible exchange (SABRE), a parahydrogen-based hyperpolarization technique, is valuable in detecting low concentrations of chemical compounds, which facilitates the understanding of their functions at molecular level as well as their applicability in nuclear magnetic resonance (NMR) and magentic resource maging (MRI). SABRE of 1- aminoisoquinoline (1-AIQ) is significant because isoquinoline derivatives are the fundamental structures in compounds with notable biological activity and are basic organic building blocks. Through this study, we explain how SABRE is applied to hyperpolarize 1-AIQ for diverse solvent systems such as deuterium and non-deuterium solvents. We observed the amplification of individual protons of 1-AIQ at various magnetic fields. Further, we describe the polarization transfer mechanism of 1-AIQ compared to pyridine using density functional theory (DFT) calculations. These hyperpolarization techniques, including the polarization transfer mechanism investigation on 1-AIQ, will provide a firm basis for the future application of the hyperpolarization study on various bio-friendly materials.

Basics of EPR for NMR spectroscopists

Dear NMR Enthusiast,

The 16th Global NMR Educational Tutorial will be given by Nino Wili, PhD student in Prof. Gunnar Jeschke’s lab at ETH Zurich, Switzerland, on the topic:

“Basics of EPR for NMR spectroscopists”.

Abstract: 

In this tutorial lecture, I will describe similarities and differences between NMR and EPR. Continuous-wave EPR will be introduced, as well as basic pulse sequences for hyperfine spectroscopy (ESEEM, ENDOR, ELDOR-detected NMR) and pulsed dipolar spectroscopy (DEER, RIDME, DQC). I will assume previous knowledge about the Bloch equations, the spin Hamiltonian description, product operator formalism, and anisotropic interactions. Examples will focus on molecular systems in chemistry and biology.

Speaker’s biography:

2016: MSc, ETH Zurich (Prof. Matthias Ernst)

2017-present: PhD, ETH Zurich (Prof. Gunnar Jeschke)

Webinar details:

Time: Tuesday, October 13, 2020, 08:00 AM California or 11:00 am Boston or 5:00 PM Paris or 8:30 PM Delhi

Join Meeting: https://ucsb.zoom.us/j/92480496788

Meeting ID: 924 8049 6788

Best regards,

Global NMR Discussion Meetings

YouTube Channel: https://www.youtube.com/c/GlobalNMRDiscussionMeetings/videos

[Organizers:

Adrian Draney (Guido Pintacuda Lab, CRMN lyon)

Amrit Venkatesh (Aaron Rossini Lab, Iowa State Uni)

Asif Equbal (Songi Han Lab, UCSB)

Blake Wilson (Robert Tycko Lab, NIH)

Michael Hope (Lyndon Emsley Lab, EPFL)

PinelopiMoutzouri (Lyndon Emsley Lab, EPFL) ]

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NMR web database:

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Dynamic nuclear polarization and ESR hole burning in As doped silicon #DNPNMR

Järvinen, J., D. Zvezdov, J. Ahokas, S. Sheludiakov, L. Lehtonen, S. Vasiliev, L. Vlasenko, Y. Ishikawa, and Y. Fujii. “Dynamic Nuclear Polarization and ESR Hole Burning in As Doped Silicon.” Physical Chemistry Chemical Physics 22, no. 18 (2020): 10227–37.

https://doi.org/10.1039/C9CP06859G

We present an experimental study of the Dynamic Nuclear Polarization (DNP) of 29Si nuclei in silicon crystals of natural abundance doped with As in the temperature range 0.1-1 K and in strong magnetic field of 4.6 T. This ensures very high degree of electron spin polarization, extremely slow nuclear relaxation and optimal conditions for realization of Overhauser and resolved solid effects. We found that the solid effect DNP leads to an appearance of a pattern of holes and peaks in the ESR line, separated by the super-hyperfine interaction between the donor electron and 29Si nuclei closest to the donor. On the contrary, the Overhauser effect DNP mainly affects the remote 29Si nuclei having the weakest interaction with the donor electron. This leads to an appearance of a very narrow ( 3 mG wide) hole in the ESR line. We studied relaxation of the holes after burning, which is caused by the nuclear spin diffusion. Analyzing the dynamics of the hole in the spectrum with a simple one-dimensional diffusion model leads to a value of the diffusion coefficient D = 8(3)10􀀀9 G2/s. Our data indicate that the spin diffusion is not completely prevented even in the frozen core near the donors. The emergence of the narrow hole after the Overhauser DNP may be explained by a partial “softening” of the frozen core caused by decoupling of the donor electron and remote 29Si nuclei.

[NMR] Postdoc position in NMR/DNP of heterogeneous catalysts at

Dear Colleagues,

We are seeking a postdoctoral associate with a background in solid-state NMR spectroscopy for the solid-state NMR investigations of heterogeneous catalysts, by conventional as well as dynamic nuclear polarization (DNP) enhanced solid-state NMR spectroscopy. A significant portion of the work will involve solid-state NMR methods development for instance through the development of novel data analysis tools, pulse sequence development, and the advancement and application of emerging technologies including ultra-fast (100 kHz+) magic-angle-spinning, dynamic nuclear polarization, and ultrahigh magnetic fields. The main focus of the work will be geared towards gaining a dynamic understanding of the structures of heterogeneous catalyst surfaces through multidimensional NMR spectroscopy.

Ames Laboratory is equipped with 9.4 and 14.1 T solid-state NMR spectrometers with MAS probes for rotor diameters ranging from 5 to 0.7-mm. Aside from these instruments, the lab is also equipped with a 9.4 T Bruker MAS-DNP NMR spectrometer with both 3.2 and 1.3-mm MAS-DNP probes. Access to computational resources and synthetic resources will also be available.

Interested people are encouraged to apply for the position. More details can be found at this link:

https://isu.wd1.myworkdayjobs.com/en-US/IowaStateJobs/job/Ames-IA/Postdoctoral-Research-Associate—Ames-Laboratory_R2763

Best,

Frédéric Perras, PhD

Ames Laboratory

US Department of Energy

Ames, IA, 50011

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[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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Enabling Natural Abundance 17O Solid-State NMR by Direct Polarization from Paramagnetic Metal Ions #DNPNMR

Jardón-Álvarez, Daniel, Guy Reuveni, Adi Harchol, and Michal Leskes. “Enabling Natural Abundance 17O Solid-State NMR by Direct Polarization from Paramagnetic Metal Ions.” The Journal of Physical Chemistry Letters 11, no. 14 (July 16, 2020): 5439–45.

https://doi.org/10.1021/acs.jpclett.0c01527.

Dynamic nuclear polarization (DNP) significantly enhances the sensitivity of nuclear magnetic resonance (NMR), increasing applications and quality of NMR as a characterization tool for materials. Efficient spin diffusion among the nuclear spins is considered to be essential for spreading the hyperpolarization throughout the sample enabling large DNP enhancements. This scenario mostly limits the polarization enhancement of low sensitivity nuclei in inorganic materials to the surface sites when the polarization source is an exogenous radical. In metal ions based DNP, the polarization agents are distributed in the bulk sample and act as both source of relaxation and of polarization enhancement. We have found that as long as the polarization agent is the main source of relaxation, the enhancement does not depend on the distance between the nucleus and dopant. As a consequence, the requirement of efficient spin diffusion is lifted and the entire sample can be directly polarized. We exploit this finding to measure high quality NMR spectra of 17O in the electrode material Li4Ti5O12 doped with Fe(III) despite its low abundance and long relaxation time.

Open Position: Junior Scientist – Magnetic Resonance

Bridge12 is hiring.

We are seeking to fill an open position in our team for a Junior Scientist. You will work on multidisciplinary projects covering many different aspects of magnetic resonance, instrumentation design, development of prototypes and conduct research. This is a junior position and while some experience or a background in magnetic resonance spectroscopy (e.g. NMR, EPR, MRI, DNP) is desired, it is not necessary.

We are looking for a creative, highly motivated, highly organized individual who enjoys an innovative, interdisciplinary environment and the challenges that come with manufacturing high-tech, scientific instrumentation. This position requires the ability to apply sound scientific fundamentals to the design and characterization of magnetic resonance instruments.

For more information visit: JUNIOR SCIENTIST – MAGNETIC RESONANCE SPECTROSCOPY

A temperature-controlled sample shuttle for field-cycling NMR

Today, something that has nothing to do with DNP-NMR spectroscopy, but is a cool piece of equipment.

Hall, Andrew M.R., Topaz A.A. Cartlidge, and Giuseppe Pileio. “A Temperature-Controlled Sample Shuttle for Field-Cycling NMR.” Journal of Magnetic Resonance 317 (August 2020): 106778. https://doi.org/10.1016/j.jmr.2020.106778

We present a design for a temperature-controlled sample shuttle for use in NMR measurements at variable magnetic field strength. Accurate temperature control was achieved using a mixture of waterethylene glycol as a heat transfer fluid, reducing temperature gradients across the sample to <0.05 °C and minimising convection. Using the sample shuttle, we show how the longitudinal (T1) and singlet order (TS) relaxation time constants were measured for two molecules capable of supporting long-lived states, with new record lifetimes observed at low field and above ambient temperatures.

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