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Dynamic nuclear polarization

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https://www.readbyqxmd.com/read/28445055/the-molecular-mechanism-of-overhauser-dynamic-nuclear-polarization-in-insulating-solids
#1
Svetlana Pylaeva, Konstantin L Ivanov, Marc Baldus, Daniel Sebastiani, Hossam Elgabarty
Dynamic Nuclear Polarization (DNP), a technique that significantly enhances NMR signals, is experiencing a renaissance owing to enormous methodological developments. In the heart of DNP is a polarization transfer mechanism that endows nuclei with the much larger electronic spin polarization. Polarization transfer via the Overhauser effect is traditionally known to be operative only in liquids and conducting solids. Very recently, surprisingly strong Overhauser effect DNP in insulating solids has been reported, with a DNP efficiency that increases with the magnetic field strength...
April 26, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28444914/dynamic-nuclear-polarization-studies-on-deuterated-nitroxyl-spin-probes
#2
David Jebaraj D, Hideo Utsumi, Milton Franklin Benial A
Detailed dynamic nuclear polarization and electron spin resonance studies were carried out for 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl,3-methoxycarbonyl-2,2,5,5-tetramethy pyrolidine-1-oxyl nitroxyl radicals and their corresponding deuterated nitroxyl radicals, used in Overhauser-enhanced magnetic resonance imaging for the first time. The dynamic nuclear polarization parameters such as DNP factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for deuterated nitroxyl radicals...
April 26, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28439549/observation-of-current-induced-long-lived-persistent-spin-polarization-in-a-topological-insulator-a-rechargeable-spin-battery
#3
Jifa Tian, Seokmin Hong, Ireneusz Miotkowski, Supriyo Datta, Yong P Chen
Topological insulators (TIs), with their helically spin-momentum-locked topological surface states (TSSs), are considered promising for spintronics applications. Several recent experiments in TIs have demonstrated a current-induced electronic spin polarization that may be used for all-electrical spin generation and injection. We report spin potentiometric measurements in TIs that have revealed a long-lived persistent electron spin polarization even at zero current. Unaffected by a small bias current and persisting for several days at low temperature, the spin polarization can be induced and reversed by a large "writing" current applied for an extended time...
April 2017: Science Advances
https://www.readbyqxmd.com/read/28433011/ramped-amplitude-novel
#4
T V Can, R T Weber, J J Walish, T M Swager, R G Griffin
We present a pulsed dynamic nuclear polarization (DNP) study using a ramped-amplitude nuclear orientation via electron spin locking (RA-NOVEL) sequence that utilizes a fast arbitrary waveform generator (AWG) to modulate the microwave pulses together with samples doped with narrow-line radicals such as 1,3-bisdiphenylene-2-phenylallyl (BDPA), sulfonated-BDPA (SA-BDPA), and trityl-OX063. Similar to ramped-amplitude cross polarization in solid-state nuclear magnetic resonance, RA-NOVEL improves the DNP efficiency by a factor of up to 1...
April 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28429936/electron-decoupling-with-dynamic-nuclear-polarization-in-rotating-solids
#5
Edward P Saliba, Erika L Sesti, Faith J Scott, Brice J Albert, Eric J Choi, Nicholas Alaniva, Chukun Gao, Alexander B Barnes
Dynamic nuclear polarization (DNP) can enhance NMR sensitivity by orders of magnitude by transferring spin polarization from electron paramagnetic resonance (EPR) to NMR. However, paramagnetic DNP polarizing agents can have deleterious effects on NMR signals. Electron spin decoupling can mitigate these paramagnetic relaxation effects. We demonstrate electron decoupling experiments in conjunction with DNP and magic angle spinning (MAS) NMR spectroscopy. Following a DNP and spin diffusion period, the microwave irradiation frequency is quickly tuned on-resonance with electrons on the DNP polarizing agent...
April 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28425462/role-of-chiral-quantum-hall-edge-states-in-nuclear-spin-polarization
#6
Kaifeng Yang, Katsumi Nagase, Yoshiro Hirayama, Tetsuya D Mishima, Michael B Santos, Hongwu Liu
Resistively detected NMR (RDNMR) based on dynamic nuclear polarization (DNP) in a quantum Hall ferromagnet (QHF) is a highly sensitive method for the discovery of fascinating quantum Hall phases; however, the mechanism of this DNP and, in particular, the role of quantum Hall edge states in it are unclear. Here we demonstrate the important but previously unrecognized effect of chiral edge modes on the nuclear spin polarization. A side-by-side comparison of the RDNMR signals from Hall bar and Corbino disk configurations allows us to distinguish the contributions of bulk and edge states to DNP in QHF...
April 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/28423212/persistent-radicals-of-self-assembled-benzophenone-bis-urea-macrocycles-characterization-and-application-as-a-polarizing-agent-for-solid-state-dnp-mas-spectroscopy
#7
Baillie A DeHaven, John T Tokarski, Arthur A Korous, Frederic Mentink-Vigier, Thomas M Makris, Alexander M Brugh, Malcolm D E Forbes, Johan van Tol, Clifford Russ Bowers, Linda S Shimizu
UV-irradiation of a self-assembled benzophenone bis-urea macrocycle generates μM amounts of radicals that persist for weeks under ambient conditions. High-Field EPR and variable temperature X-band EPR studies suggest a resonance stabilized radical pair through H-abstraction. These endogenous radicals were applied as a polarizing agent for magic angle spinning (MAS) dynamic nuclear polarization (DNP) NMR enhancement. The field-stepped DNP enhancement profile exhibits a sharp peak with a maximum enhancement of εon/off = 4 superimposed on a nearly constant DNP enhancement of εon/off = 2 over a broad field range...
April 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28422500/influence-of-13-c-isotopic-labeling-location-on-dynamic-nuclear-polarization-of-acetate
#8
Peter Niedbalski, Christopher Parish, Andhika Kiswandhi, Zoltan Kovacs, Lloyd Lumata
Dynamic nuclear polarization (DNP) via the dissolution method has alleviated the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy by amplifying the signals by several thousand-fold. This NMR signal amplification process emanates from the microwave-mediated transfer of high electron spin alignment to the nuclear spins at high magnetic field and cryogenic temperature. Since the interplay between the electrons and nuclei is crucial, the chemical composition of a DNP sample such as the type of free radical used, glassing solvents, or the nature of the target nuclei can significantly affect the NMR signal enhancement levels that can be attained with DNP...
April 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28407455/construction-and-13-c-hyperpolarization-efficiency-of-a-180%C3%A2-ghz-dissolution-dynamic-nuclear-polarization-system
#9
Andhika Kiswandhi, Peter Niedbalski, Christopher Parish, Sarah Ferguson, David Taylor, George McDonald, Lloyd Lumata
Dynamic nuclear polarization (DNP) via the dissolution method has become one of the rapidly emerging techniques to alleviate the low signal sensitivity in nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI). In this paper, we report on the development and (13) C hyperpolarization efficiency of a homebuilt dynamic nuclear polarization (DNP) system operating at 6.423 T and 1.4 K. The DNP hyperpolarizer system was assembled on a wide-bore superconducting magnet, equipped with a standard continuous-flow cryostat, and a 180 GHz microwave source with 120 mW power output and wide 4 GHz frequency tuning range...
April 13, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28373720/purification-of-an-unpolarized-spin-ensemble-into-entangled-singlet-pairs
#10
Johannes N Greiner, Durga Bhaktavatsala Rao Dasari, Jörg Wrachtrup
Dynamical polarization of nuclear spin ensembles is of central importance for magnetic resonance studies, precision sensing and for applications in quantum information theory. Here we propose a scheme to generate long-lived singlet pairs in an unpolarized nuclear spin ensemble which is dipolar coupled to the electron spins of a Nitrogen Vacancy center in diamond. The quantum mechanical back-action induced by frequent spin-selective readout of the NV centers allows the nuclear spins to pair up into maximally entangled singlet pairs...
April 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28365821/couplings-and-recouplings-of-four-angular-momenta-alternative-9j-symbols-and-spin-addition-diagrams
#11
Robenilson F Santos, Ana Carla P Bitencourt, Mirco Ragni, Frederico V Prudente, Cecilia Coletti, Annalisa Marzuoli, Vincenzo Aquilanti
The Wigner 9j symbols of the first kind-also known as Fano X-coefficients-serve to connect different addition schemes of four angular momenta, widely known examples being the LS and the jj couplings in atomic, molecular, and nuclear spectroscopies. Here, we also consider alternative sequences of binary couplings of four angular momenta, which are dealt through the 9j symbols of the second kind, and are explicitly given by the pentagonal (or Biedenharn-Elliott) identity. These coefficients are essential ingredients in the quantum-mechanical treatments of rotational and polarization phenomena in reaction dynamics and photoinduced processes...
April 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28365491/solvent-signal-suppression-for-high-resolution-mas-dnp
#12
Daniel Lee, Sachin R Chaudhari, Gaël De Paëpe
Dynamic nuclear polarization (DNP) has become a powerful tool to substantially increase the sensitivity of high-field magic angle spinning (MAS) solid-state NMR experiments. The addition of dissolved hyperpolarizing agents usually results in the presence of solvent signals that can overlap and obscure those of interest from the analyte. Here, two methods are proposed to suppress DNP solvent signals: a Forced Echo Dephasing experiment (FEDex) and TRAnsfer of Populations in DOuble Resonance Echo Dephasing (TRAPDORED) NMR...
May 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28330994/combining-dnp-nmr-with-segmental-and-specific-labeling-to-study-a-yeast-prion-protein-strain-that-is-not-parallel-in-register
#13
Kendra K Frederick, Vladimir K Michaelis, Marc A Caporini, Loren B Andreas, Galia T Debelouchina, Robert G Griffin, Susan Lindquist
The yeast prion protein Sup35NM is a self-propagating amyloid. Despite intense study, there is no consensus on the organization of monomers within Sup35NM fibrils. Some studies point to a β-helical arrangement, whereas others suggest a parallel in-register organization. Intermolecular contacts are often determined by experiments that probe long-range heteronuclear contacts for fibrils templated from a 1:1 mixture of (13)C- and (15)N-labeled monomers. However, for Sup35NM, like many large proteins, chemical shift degeneracy limits the usefulness of this approach...
April 4, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28327736/a-dnp-supported-solid-state-nmr-study-of-carbon-species-in-fluid-catalytic-cracking-catalysts
#14
Deni Mance, Johan van der Zwan, Marjolein E Z Velthoen, Florian Meirer, Bert M Weckhuysen, Marc Baldus, Eelco T C Vogt
A combination of solid-state NMR techniques supported by EPR and SEM-EDX experiments was used to localize different carbon species (coke) in commercial fluid catalytic cracking catalysts. Aliphatic coke species formed during the catalytic process and aromatic coke species deposited directly from the feedstock respond differently to dynamic nuclear polarization signal enhancement in integral and crushed FCC particles, indicating that aromatic species are mostly concentrated on the outside of the catalyst particles, whereas aliphatic species are also located on the inside of the FCC particles...
March 22, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28319293/bis-gadolinium-complexes-for-solid-effect-and-cross-effect-dynamic-nuclear-polarization
#15
Monu Kaushik, Mian Qi, Adelheid Godt, Björn Corzilius
High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined Gd⋅⋅⋅Gd distances in the range of 1.2-3.4 nm allowed us to elucidate the Gd⋅⋅⋅Gd distance dependence of the DNP mechanism and NMR signal enhancement. We found that Gd⋅⋅⋅Gd distances above 2...
April 3, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28304028/nmr-signal-enhancement-of-50%C3%A2-000-times-in-fast-dissolution-dynamic-nuclear-polarization
#16
L F Pinto, I Marín-Montesinos, V Lloveras, J L Muñoz-Gómez, M Pons, J Veciana, J Vidal-Gancedo
Herein, we report the synthesis and the study of a novel mixed biradical with BDPA and TEMPO radical units that are covalently bound by an ester group (BDPAesterTEMPO) as a polarizing agent for fast dissolution DNP. The biradical exhibits an extremely high DNP NMR enhancement of >50 000 times, which constitutes one of the largest signal enhancements observed so far, to the best of our knowledge.
March 17, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28290535/continuous-flow-dnp-polarizer-for-mri-applications-at-1-5%C3%A2-t
#17
V Denysenkov, M Terekhov, R Maeder, S Fischer, S Zangos, T Vogl, T F Prisner
Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1...
March 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28282137/enhanced-performance-of-blended-polymer-excipients-in-delivering-a-hydrophobic-drug-through-the-synergistic-action-of-micelles-and-hpmcas
#18
Ziang Li, Lindsay M Johnson, Ralm G Ricarte, Letitia J Yao, Marc A Hillmyer, Frank S Bates, Timothy P Lodge
Blends of hydroxypropyl methylcellulose acetate succinate (HPMCAS) and dodecyl (C12)-tailed poly(N-isopropylacrylamide) (PNIPAm) were systematically explored as a model system to dispense the active ingredient phenytoin by rapid dissolution, followed by the suppression of drug crystallization for an extended period. Dynamic and static light scattering revealed that C12-PNIPAm polymers, synthesized by reversible addition-fragmentation chain-transfer polymerization, self-assembled into micelles with dodecyl cores in phosphate-buffered saline (PBS, pH 6...
March 10, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28260385/dynamic-nuclear-polarization-of-%C3%AE-cyclodextrin-macromolecules
#19
Filippo Caracciolo, Pietro Carretta, Marta Filibian, Lucio Melone
(1)H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of β-cyclodextrins doped with different concentrations of the TEMPO radical. Nuclear polarization increased up to 10% in the optimal case, with a behavior of the buildup rate (1/TPOL) and of the nuclear spin-lattice relaxation rate (1/T1n) consistent with a thermal mixing regime. The temperature dependence of 1/T1n and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics...
March 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28242746/torsina-regulates-the-linc-to-moving-nuclei
#20
Daniel A Starr, Lesilee S Rose
How LINC complexes are regulated to connect nuclei to the cytoskeleton during nuclear migration is unknown. Saunders et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201507113) show that the AAA+ ATPase torsinA and its partner LAP1 are required for nuclear migration during fibroblast polarization by mediating the dynamics of LINC complexes.
March 6, 2017: Journal of Cell Biology
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