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Dynamic nuclear polarization

Kazutoshi Yamamoto, Marc A Caporini, Sang-Choul Im, Lucy Waskell, Ayyalusamy Ramamoorthy
The dynamic protein-protein and protein-ligand interactions of integral bitopic membrane proteins with a single membrane-spanning helix play a plethora of vital roles in the cellular processes associated with human health and diseases, including signaling and enzymatic catalysis. While an increasing number of high-resolution structural studies of membrane proteins have successfully manifested an in-depth understanding of their biological functions, intact membrane-bound bitopic protein-protein complexes pose tremendous challenges for structural studies by crystallography or solution NMR spectroscopy...
June 23, 2017: Scientific Reports
Guoquan Liu, Marcel Levien, Niels Karschin, Giacomo Parigi, Claudio Luchinat, Marina Bennati
Nuclear magnetic resonance (NMR) is a fundamental spectroscopic technique for the study of biological systems and materials, molecular imaging and the analysis of small molecules. It detects interactions at very low energies and is thus non-invasive and applicable to a variety of targets, including animals and humans. However, one of its most severe limitations is its low sensitivity, which stems from the small interaction energies involved. Here, we report that dynamic nuclear polarization in liquid solution and at room temperature can enhance the NMR signal of (13)C nuclei by up to three orders of magnitude at magnetic fields of ∼3 T...
July 2017: Nature Chemistry
Julia H Ortony, Baofu Qiao, Christina J Newcomb, Timothy J Keller, Liam C Palmer, Elad Deiss-Yehiely, Monica Olvera de la Cruz, Songi Han, Samuel I Stupp
Water within and surrounding the structure of a biological system adopts context-specific dynamics that mediate virtually all of the events involved in the inner workings of a cell. These events range from protein folding and molecular recognition to the formation of hierarchical structures. Water dynamics are mediated by the chemistry and geometry of interfaces where water and biomolecules meet. Here we investigate experimentally and computationally the translational dynamics of vicinal water molecules within the volume of a supramolecular peptide nanofiber measuring 6...
June 21, 2017: Journal of the American Chemical Society
Peter Niedbalski, Christopher Parish, Qing Wang, Andhika Kiswandhi, Zahra Hayati, Likai Song, Lloyd Laporca Lumata
Dissolution dynamic nuclear polarization (DNP) is one of the most successful techniques that resolves the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) by amplifying the signal by several thousand-fold. One way to further improve the DNP signal is the inclusion of trace amounts of lanthanides in DNP samples doped with trityl OX063 free radical as the polarizing agent. In practice, stable monomeric gadolinium complexes such as Gd-DOTA or Gd-HP-DO3A are used as beneficial additives in DNP samples, further boosting the DNP-enhanced solid-state 13C polarization by a factor of 2 or 3...
June 20, 2017: Journal of Physical Chemistry. A
Rivkah Rogawski, Ann McDermott
Magic angle spinning solid state NMR studies of biological macromolecules [1-3] have enabled exciting studies of membrane proteins [4,5], amyloid fibrils [6], viruses, and large macromolecular assemblies [7]. Dynamic nuclear polarization (DNP) provides a means to enhance detection sensitivity for NMR, particularly for solid state NMR, with many recent biological applications and considerable contemporary efforts towards elaboration and optimization of the DNP experiment. This review explores precedents and innovations in biological DNP experiments, especially highlighting novel chemical biology approaches to introduce the radicals that serve as a source of polarization in the DNP experiments...
June 13, 2017: Archives of Biochemistry and Biophysics
Jihyun Kim, Mengxiao Liu, Christian Hilty
Water-protein interactions play a central role in protein structure, dynamics, and function. These interactions, traditionally, have been studied using nuclear magnetic resonance (NMR) by measuring chemical exchange and nuclear Overhauser effect (NOE). Polarization transferred from hyperpolarized water can result in substantial transient signal enhancements of protein resonances due to these processes. Here, we use dissolution dynamic nuclear polarization and flow-NMR for measuring the pH dependence of transferred signals to the protein trypsin...
June 14, 2017: Journal of Physical Chemistry. B
Armand Masion, Anne Alexandre, Fabio Ziarelli, Stéphane Viel, Guaciara M Santos
The determination of the chemical nature of the organic matter associated with phytoliths remains a challenge. This difficulty mainly stems from amounts of organic carbon (C) that are often well below the detection limit of traditional spectroscopic tools. Conventional solid-state (13)C Nuclear Magnetic Resonance (NMR) is widely used to examine the nature and structure of organic molecules, but its inherent low sensitivity prohibits the observation of diluted samples. The recent advent of commercial microwave source in the terahertz range triggered a renewed interest in the Dynamic Nuclear Polarization (DNP) technique to improve the signal to noise ratio of solid-state NMR experiments...
June 13, 2017: Scientific Reports
Frédéric A Perras, Aaron D Sadow, Marek Pruski
Numerical calculations of enhancement factors offered by dynamic nuclear polarization in solids under magic angle spinning (DNP-MAS) were performed to determine the optimal EPR parameters for a dinitroxide polarizing agent. We found that the DNP performance of a biradical is more tolerant to the relative orientation of the two nitroxide moieties than previously thought. Generally, any condition in which the gyy tensor components of both radicals are perpendicular to one another is expected to have near-optimal DNP performance...
June 9, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
V Meenakumari, Hideo Utsumi, Fuminori Hyodo, A Jawahar, A Milton Franklin Benial
Agarose is a tissue-equivalent material and its imaging characteristics similar to those of real tissues. Hence the dynamic nuclear polarization studies of carboxy-PROXYL in agarose gel were carried out. The DNP parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy-PROXYL in PBS solution and water/agarose mixture (99:1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy-PROXYL in water/agarose mixture (99:1) compared with PBS solution...
June 9, 2017: Magnetic Resonance in Chemistry: MRC
E M M Weber, H Vezin, J G Kempf, G Bodenhausen, D Abergél, D Kurzbach
We report the observation of anisotropic longitudinal electronic relaxation in nitroxide radicals under typical dynamic nuclear polarization conditions. This anisotropy affects the efficiency of dynamic nuclear polarization at cryogenic temperatures of 4 K and high magnetic fields of 6.7 T. Under our experimental conditions, the electron paramagnetic resonance spectrum of nitroxides such as TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) is only partly averaged by electronic spectral diffusion, so that the relaxation times T1e(ω) vary across the spectrum...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
Corinne E Isaac, Christine M Gleave, Paméla T Nasr, Hoang L Nguyen, Elizabeth A Curley, Jonilyn L Yoder, Eric W Moore, Lei Chen, John A Marohn
Correction for 'Dynamic nuclear polarization in a magnetic resonance force microscope experiment' by Corinne E. Isaac et al., Phys. Chem. Chem. Phys., 2016, 18, 8806-8819.
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
Zijian Zhou, Jin Yu, Johannes F P Colell, Raul Laasner, Angus W J Logan, Danila A Barskiy, Roman V Shchepin, Eduard Y Chekmenev, Volker Blum, Warren S Warren, Thomas Theis
Parahydrogen is an inexpensive and readily available source of hyperpolarization used to enhance magnetic resonance signals by up to 4 orders of magnitude above thermal signals obtained at ~10 T. A significant challenge for applications is fast signal decay after hyperpolarization. Here, we use parahydrogen based polarization transfer catalysis at micro-Tesla fields (first introduced as SABRE-SHEATH) to hyperpolarize (13)C2 spin pairs and find decay time constants of 12 s for magnetization at 0.3 mT, which are extended to 2 minutes at that same field, when long lived singlet states are hyperpolarized instead...
June 8, 2017: Journal of Physical Chemistry Letters
Andhika Kiswandhi, Peter Niedbalski, Christopher Parish, Qing Wang, Lloyd Lumata
We report on the assembly and performance evaluation of a 180 GHz/6.4 T dynamic nuclear polarization (DNP) system based on a cryogen-free superconducting magnet. The DNP system utilizes a variable-field superconducting magnet that can be ramped up to 9 T and equipped with cryocoolers that can cool the sample space with the DNP assembly down to 1.8 K via the Joule-Thomson effect. A homebuilt DNP probe insert with top-tuned NMR coil and microwave port was incorporated into the sample space in which the effective sample temperature is approximately 1...
June 7, 2017: Magnetic Resonance in Chemistry: MRC
Naranamangalam R Jagannathan, Uma Sharma
Metabolic alterations are known to occur with oncogenesis and tumor progression. During malignant transformation, the metabolism of cells and tissues is altered. Cancer metabolism can be studied using advanced technologies that detect both metabolites and metabolic activities. Identification, characterization, and quantification of metabolites (metabolomics) are important for metabolic analysis and are usually done by nuclear magnetic resonance (NMR) or by mass spectrometry. In contrast to the magnetic resonance imaging that is used to monitor the tumor morphology during progression of the disease and during therapy, in vivo NMR spectroscopy is used to study and monitor tumor metabolism of cells/tissues by detection of various biochemicals or metabolites involved in various metabolic pathways...
June 7, 2017: Metabolites
Karilyn E Sant, Jason M Hansen, Larissa M Williams, Nancy L Tran, Jared V Goldstone, John J Stegeman, Mark E Hahn, Alicia Timme-Laragy
Redox signaling is important for embryogenesis, guiding pathways that govern processes crucial for embryo patterning, including cell polarization, proliferation, and apoptosis. Exposure to pro-oxidants during this period can be deleterious, resulting in altered physiology, teratogenesis, later-life diseases, or lethality. We previously reported that the glutathione antioxidant defense system becomes increasingly robust, including a doubling of total glutathione and dynamic shifts in the glutathione redox potential at specific stages during embryonic development in the zebrafish, Danio rerio...
May 30, 2017: Redox Biology
Murielle F Delley, Giuseppe Lapadula, Francisco Núñez-Zarur, Aleix Comas-Vives, Vidmantas Kalendra, Gunnar Jeschke, Dirk Baabe, Marc D Walter, Aaron J Rossini, Anne Lesage, Lyndon Emsley, Olivier Maury, Christophe Copéret
Grafting molecular precursors on partially dehydroxylated silica followed by a thermal treatment yields silica-supported M(III) sites for a broad range of metals. They display unique properties such as high activity in olefin polymerization and alkane dehydrogenation (M = Cr) or efficient luminescence properties (M = Yb and Eu) essential for bioimaging. Here, we interrogate the local structure of the M(III) surface sites obtained from two molecular precursors, amides M(N(SiMe3)2)3 vs siloxides (M(OSi(O(t)Bu)3)3·L with L = (THF)2 or HOSi(O(t)Bu)3 for M = Cr, Yb, Eu, and Y, by a combination of advanced spectroscopic techniques (EPR, IR, XAS, UV-vis, NMR, luminescence spectroscopies)...
June 21, 2017: Journal of the American Chemical Society
Olivier Ouari, Evgeniy S Salnikov, Sébastien Abel, Ganesan Karthikeyan, Hakim Karoui, Fabien Aussenac, Paul Tordo, Burkhard Bechinger
Dynamic Nuclear Polarization boosts the sensitivity of NMR spectroscopy by orders of magnitude making possible investigations previously out of scope. For MAS solid-state NMR studies the samples are typically mixed with biradicals dissolved in glass forming solvent and investigated at 100K. Here we present new biradical polarizing agents developed for matrix-free samples such as supported lipid bilayers, which are systems widely used for the investigation of membrane proteins of high biomedical importance. A series of 11 biradicals with different structure, geometry and physico-chemical properties was comprehensively tested for DNP performance in lipid bilayers, some of them developed specifically for membranes investigations...
June 2, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Andrea Capozzi, Tian Cheng, Giovanni Boero, Christophe Roussel, Arnaud Comment
Hyperpolarization via dynamic nuclear polarization (DNP) is pivotal for boosting magnetic resonance imaging (MRI) sensitivity and dissolution DNP can be used to perform in vivo real-time (13)C MRI. The type of applications is however limited by the relatively fast decay time of the hyperpolarized spin state together with the constraint of having to polarize the (13)C spins in a dedicated apparatus nearby but separated from the MRI magnet. We herein demonstrate that by polarizing (13)C with photo-induced radicals, which can be subsequently annihilated using a thermalization process that maintains the sample temperature below its melting point, hyperpolarized (13)C-substrates can be extracted from the DNP apparatus in the solid form, while maintaining the enhanced (13)C polarization...
June 1, 2017: Nature Communications
Jasmine Viger-Gravel, Pierrick Berruyer, David Gajan, Jean-Marie Basset, Anne Lesage, Paul Tordo, Olivier Ouari, Lyndon Emsley
We show that aqueous acrylamide gels can be used to provide dynamic nuclear polarization (DNP) NMR signal enhancements of around 200 at 9.4 T and 100 K. The enhancements are shown to increase with cross linker concentration and low concentrations of the AMUPol biradical. We show that this DNP matrix can be used in situations where conventional incipient wetness methods fail, such as to obtain DNP surface enhanced NMR spectra from inorganic nanoparticles. In particular, we obtain 113Cd spectra from CdTe-COOH NPs in minutes...
May 23, 2017: Angewandte Chemie
György Pintér, Harald Schwalbe
We shall overcome: As a result of efforts to overcome the sensitivity challenge of liquid-state NMR spectroscopy, a thousand-fold signal enhancement was achieved by dynamic nuclear polarization (DNP) for (13) C signals at high magnetic field (3.4 T) and room temperature, thereby exceeding the predicted limitations of high-field liquid-state in situ DNP.
May 23, 2017: Angewandte Chemie
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