Friday, August 17, 2018

Dynamic Nuclear Polarization Surface Enhanced NMR spectroscopy (DNP SENS): Principles, protocols, and practice #DNPNMR

Liao, Wei-Chih, Behnaz Ghaffari, Christopher P. Gordon, Jun Xu, and Christophe Copéret. “Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS): Principles, Protocols, and Practice.” Current Opinion in Colloid & Interface Science 33 (January 1, 2018): 63–71.


Dynamic Nuclear Polarization Surface Enhanced NMR spectroscopy has been demonstrated to significantly improve NMR sensitivity on materials by 1 to 2 orders of magnitude at high magnetic fields. The preferential surface enhancement also allows for selectively probing the solid surface. In this review, we will briefly describe the main mechanism used nowadays, i.e. cross effect, for DNP enhanced solid-state NMR. We will show the typical protocols of sample formulation leading to effective DNP surface enhancements and the key experimental factors in performing DNP SENS experiments. Other important developments in DNP, i.e. shielded polarizing agents for reactive surfaces, hyperpolarizing solid matrices, and high-temperature and high-field DNP, will be discussed as well. Finally, we close the review with a short summary and our perspectives on the directions of future developments in this field.

Wednesday, August 15, 2018

Considering low-rank, sparse and gas-inflow effects constraints for accelerated pulmonary dynamic hyperpolarized 129Xe MRI

Xiao, Sa, He Deng, Caohui Duan, Junshuai Xie, Huiting Zhang, Xianping Sun, Chaohui Ye, and Xin Zhou. “Considering Low-Rank, Sparse and Gas-Inflow Effects Constraints for Accelerated Pulmonary Dynamic Hyperpolarized 129Xe MRI.” Journal of Magnetic Resonance 290 (May 1, 2018): 29–37.


Dynamic hyperpolarized (HP) 129Xe MRI is able to visualize the process of lung ventilation, which potentially provides unique information about lung physiology and pathophysiology. However, the longitudinal magnetization of HP 129Xe is nonrenewable, making it difficult to achieve high image quality while maintaining high temporal-spatial resolution in the pulmonary dynamic MRI. In this paper, we propose a new accelerated dynamic HP 129Xe MRI scheme incorporating the low-rank, sparse and gas-inflow effects (L + S + G) constraints. According to the gas-inflow effects of HP gas during the lung inspiratory process, a variable-flip-angle (VFA) strategy is designed to compensate for the rapid attenuation of the magnetization. After undersampling k-space data, an effective reconstruction algorithm considering the low-rank, sparse and gas-inflow effects constraints is developed to reconstruct dynamic MR images. In this way, the temporal and spatial resolution of dynamic MR images is improved and the artifacts are lessened. Simulation and in vivo experiments implemented on the phantom and healthy volunteers demonstrate that the proposed method is not only feasible and effective to compensate for the decay of the magnetization, but also has a significant improvement compared with the conventional reconstruction algorithms (P-values are less than 0.05). This confirms the superior performance of the proposed designs and their ability to maintain high quality and temporal-spatial resolution.

Monday, August 13, 2018

Magic angle spinning NMR with metallized rotors as cylindrical microwave resonators #DNPNMR

Scott, Faith J., Erika L. Sesti, Eric J. Choi, Alexander J. Laut, Jagadishwar R. Sirigiri, and Alexander B. Barnes. “Magic Angle Spinning NMR with Metallized Rotors as Cylindrical Microwave Resonators.” Magnetic Resonance in Chemistry, May 16, 2018.


We introduce a novel design for millimeter wave electromagnetic structures within magic angle spinning (MAS) rotors. In this demonstration, a copper coating is vacuum deposited onto the outside surface of a sapphire rotor at a thickness of 50 nanometers. This thickness is sufficient to reflect 197 GHz microwaves, yet not too thick as to interfere with radiofrequency fields at 300 MHz or prevent sample spinning due to eddy currents. Electromagnetic simulations of an idealized rotor geometry show a microwave quality factor of 148. MAS experiments with sample rotation frequencies of ωr/2π = 5.4 kHz demonstrate that the drag force due to eddy currents within the copper does not prevent sample spinning. Spectra of sodium acetate show resolved 13C J-couplings of 60 Hz and no appreciable broadening between coated and uncoated sapphire rotors, demonstrating that the copper coating does not prevent shimming and high-resolution NMR spectroscopy. Additionally, 13C Rabi nutation curves of ω1/2π = 103 kHz for both coated and uncoated rotors indicate no detrimental impact of the copper coating on radiofrequency coupling of the nuclear spins to the sample coil. We present this metal coated rotor as a first step towards an MAS resonator. MAS resonators are expected to have a significant impact on developments in electron decoupling, pulsed DNP, room temperature DNP, DNP with low power microwave sources, and EPR detection.

[NMR] DNP postdoctoral position at UCSD

The Debelouchina lab at the University of California, San Diego is looking for a postdoctoral researcher with experience and/or interest in DNP to join our growing team. The position will involve the development of new DNP biradical polarization agents and their application to biological systems and materials. Candidates must hold a Ph.D. in chemistry, physics or a related discipline and have experience in solid-state NMR, hyperpolarization techniques or EPR. The project will take advantage of a new 600 MHz DNP spectrometer, scheduled for installation in the fall of 2018.

In addition, the University of California, San Diego has outstanding resources for high-field NMR spectroscopy, including 900 MHz, 750 MHz, 700 MHz and 500 MHz solid-state NMR spectrometers equipped with MAS and static probes, as well as solution spectrometers operating at 800 MHz, 600 MHz and 500 MHz dedicated to biomolecular NMR applications. The large UCSD scientific community and several research institutes nearby (The Salk Institute for Biological Studies, the Scripps Research Institute and the Sanford Burnham Prebys Medical Discovery Institute) provide a vast network and potential for collaborations and scientific exchange. In addition to a vibrant scientific environment, San Diego also offers beautiful weather all year round and many opportunities for nature and ocean exploration.

Interested candidates should contact Dr. Debelouchina directly at gdebelouchina@ucsd.edu with a cover letter, CV and email addresses of two references.

Representative publications:

  • Debelouchina GT, Bayro MJ, Fitzpatrick AWP, Ladizhansky V, Colvin MT, Caporini MA, Jaroniec CP, Bajaj VS, Rosay M, MacPhee C, Vendruscolo M, Maas WE, Dobson CM, Griffin RG (2013). Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy. J. Am. Chem. Soc. 135, 19237-47.
  • Debelouchina GT, Bayro MJ, van der Wel PCA, Caporini MA, Barnes AB, Rosay M, Maas WE, Griffin RG (2010). Dynamic Nuclear Polarization Enhanced Solid-State NMR Spectroscopy of GNNQQNY Crystals and Amyloid Fibrils. Phys. Chem. Chem. Phys. 12, 5911-9.
  • Hu KN, Debelouchina GT, Smith AA, Griffin RG (2011). Quantum Mechanical Theory of Dynamic Nuclear Polarization in Solid Dielectrics. J. Chem. Phys. 134, 125105.
  • Dane EL, Maly T, Debelouchina GT, Griffin RG, Swager TM (2009). Synthesis of a BDPA-TEMPO Biradical. Org. Lett. 11, 1871-4.
___________________________
Galia Debelouchina, Ph.D.
Assistant Professor
Department of Chemistry and Biochemistry
University of California, San Diego
9500 Gilman Drive
La Jolla, CA 92093











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A message from the International EPR Society

Below is a message from the International EPR Society to members for the EPR and Magnetic Resonance Community. I typically don't post these kind of advertisements but I do believe the International EPR Society has done a lot of great work for the community over the many years.

Take a look at https://www.ieprs.org. Membership fees are very low and the EPR Newsletter is a nice treat.



Dear EPR users,

To continue to have a vibrant, diverse, and active EPR community, we will all benefit from a scientific organization that offers a support and communication infrastructure for EPR -- this is what the International EPR Society (https://www.ieprs.org) aspires to offer. 

The most familiar faces of IES may be the EPR Newsletters and the Silver and Gold Medals for EPR. 

IES is the only international scientific organization that represents the whole range of important research fields of electron paramagnetic resonance (EPR) spectroscopy and EPR imaging (EMRI). These methods are used as the main research tools over a very wide range of fields, including physics, chemistry, life sciences, materials research and medicine.

IES is a world-wide association of scientists, and the IES mailing list serves the community to help spread EPR-related information (jobs, post-doc and PhD positions, conferences, etc.) to the world-wide EPR community. It provides public networking, available to IES members, where one can post messages via the EPR Newsletter (EPRNL), the official IES publication. EPRNL not only provides information on the availability of second-hand EPR instrumentation, it also publishes advertisements of prominent manufacturers of EPR instrumentation.

Members of IES have free access to the EPRNL! See: http://www.epr-newsletter.ethz.ch

IES also awards prizes and honors for outstanding contributions to EPR spectroscopy, from senior to young investigators! The newly created IES poster prizes honor excellent young scientists and PhD students for their contributions to international EPR conferences. All these achievements are reported in the EPRNL, and you can find more about "Why IES" here: http://www.ieprs.org/whyjoin.php

The member fees are encouragingly low: $6/year for students, $12/year for emeritus and post-doctoral fellows, and $36/year for full members. We will be happy if you paid the membership dues for several years. See: http://www.apes-ies2018.org/registration
Your membership of the IES is what will keep IES relevant, vibrant and impactful, and give IES the necessary tools to be responsive to the ever emerging field of EPR spectroscopy. 

Sincerely,
Songi Han, Vice President (America) of IES
Thomas Prisner, President of IES

Friday, August 3, 2018

High-Resolution 2D NMR of Disordered Proteins Enhanced by Hyperpolarized Water

Szekely, O., G. L. Olsen, I. C. Felli, and L. Frydman. “High-Resolution 2D NMR of Disordered Proteins Enhanced by Hyperpolarized Water.” Analytical Chemistry, March 26, 2018.


This study demonstrates the usefulness derived from relying on hyperpolarized water obtained by dissolution DNP, for site-resolved biophysical NMR studies of intrinsically disordered proteins. Thanks to the facile amide-solvent exchange experienced by protons in these proteins, 2D NMR experiments that like HMQC rely on the polarization of the amide protons, can be enhanced using hyperpolarized water by several orders of magnitude over their conventional counterparts. Optimizations of the DNP procedure and of the subsequent injection into the protein sample are necessary to achieve these gains while preserving state-of-the-art resolution; procedures enabling this transfer of the hyperpolarized water and the achievement of foamless hyperpolarized protein solutions are demonstrated. These protocols are employed to collect 2D (15)N-(1)H HMQC NMR spectra of alpha-synuclein, showing residue-specific enhancements >/=100x over their thermal counterparts. These enhancements, however, vary considerably throughout the residues. The biophysics underlying this residue-specific behavior upon injection of hyperpolarized water is theoretically examined, the information that it carries is compared with results arising from alternative methods, and its overall potential is discussed.

Wednesday, August 1, 2018

Hyperpolarized Laplace NMR

Telkki, Ville-Veikko. “Hyperpolarized Laplace NMR.” Magnetic Resonance in Chemistry 0, no. 0 (2018).


Laplace nuclear magnetic resonance (NMR), dealing with NMR relaxation and diffusion experiments, reveals details of molecular motion and provides chemical resolution complementary to NMR spectra. Laplace NMR has witnessed a great progress in past decades due to the development of methodology and signal processing, and it has lots of extremely interesting applications in various fields, including chemistry, biochemistry, geology, archaeology, and medicine. The aim of this minireview is to give a pedagogically oriented overview of Laplace NMR. It does not provide a full literature review of the field, but, instead, it elucidate the benefits and features of Laplace NMR methods through few selected examples. The minireview describes also recent progress in multidimensional Laplace NMR and Laplace inversion methods. Furthermore, the potential of modern hyperpolarization methods as well as ultrafast approach to increase the sensitivity and time-efficiency of the Laplace NMR experiments is highlighted.