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Dynamic nuclear polarization

Peter Niedbalski, Christopher R Parish, Qing Wang, Zahra Hayati, Likai Song, Andre F Martins, A Dean Sherry, Lloyd Laporca Lumata
Optimal efficiency of dissolution dynamic nuclear polarization (DNP) is essential to provide the required high sensitivity enhancements for in vitro and in vivo hyperpolarized 13C nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI). At the nexus of the DNP process are the free electrons which provide the high spin alignment that is transferred to the nuclear spins. Without changing DNP instrumental conditions, one way to improve 13C DNP efficiency is by adding trace amounts of paramagnetic additives such as lanthanide (e...
November 10, 2017: Journal of Physical Chemistry. A
Thomas Wiegand, Wei-Chih Liao, Ta Chung Ong, Alexander Däpp, Riccardo Cadalbert, Christophe Copéret, Anja Böckmann, Beat H Meier
DNP (dynamic nuclear polarization)-enhanced solid-state NMR is employed to directly detect protein-DNA and protein-ATP interactions and identify the residue type establishing the intermolecular contacts. While conventional solid-state NMR can detect protein-DNA interactions in large oligomeric protein assemblies in favorable cases, it typically suffers from low signal-to-noise ratios. We show here, for the oligomeric DnaB helicase from Helicobacter pylori complexed with ADP and single-stranded DNA, that this limitation can be overcome by using DNP-enhanced spectroscopy...
November 8, 2017: Journal of Biomolecular NMR
Rivkah Tamar Rogawski, Ivan V Sergeyev, Yinglu Zhang, Timothy Hoang Tran, Yongjun Li, Liang Tong, Ann E McDermott
We characterize the effect of specifically bound biradicals on the NMR spectra of dihydrofolate reductase (DHFR) from E. coli. Dynamic nuclear polarization methods enhance the signal-to-noise of solid state NMR experiments by transferring polarization from unpaired electrons of biradicals to nuclei. There has been recent interest in co-localizing the paramagnetic polarizing agents with the analyte of interest through covalent or non-covalent specific interactions. This experimental approach broadens the scope of dynamic nuclear polarization methods by offering the possibility of selective signal enhancements and the potential to work in a broad range of environments...
November 8, 2017: Journal of Physical Chemistry. B
Susan K Lutgendorf, Premal H Thaker, Jesusa M Arevalo, Michael J Goodheart, George M Slavich, Anil K Sood, Steve W Cole
BACKGROUND: Social factors in the patient macroenvironment have been shown to influence molecular events in the tumor microenvironment and thereby influence cancer progression. However, biomarkers providing a window into the longitudinal effects of biobehavioral factors on tumor biology over time are lacking. Exosome analysis is a novel strategy for in vivo monitoring of dynamic changes in tumor cells. This study examined exosomal profiles from patients with low or high levels of social support for epithelial-mesenchymal transition (EMT) polarization and gene expression related to inflammation and β-adrenergic signaling...
November 7, 2017: Cancer
James Eills, Javier Alonso-Valdesueiro, David Enrique Salazar Marcano, Jesse Ferreira da Silva, Shamim Alom, Gregory Jon Rees, John Vincent Hanna, Marina Carravetta, Malcolm Harris Levitt
We demonstrate that non-equilibrium nuclear spin order survives precipitation from solution and redissolution. The effect is demonstrated on 13C- and 2H-labeled sodium fumarate, with precipitation and dissolution achieved by altering the pH. The lifetime of the spin magnetization in the precipitate suspension is found to be much longer than in solution. Our preliminary results show an extension of the effective T1 for the metabolite fumarate by a factor of ~6. We show that when the free radical agent TEMPO is present in the solution, it is not incorporated into the precipitate, suggesting that this procedure may provide a means to store and transport agents polarized by dynamic nuclear polarization...
November 3, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Qian Wang, Xiaoxia Yan, Yanjiao Chang, Lili Ren, Jiang Zhou
Chitin nanofibers were prepared from commercially available chitin powder via esterification modification and subsequent ultrasound treatment. The obtained chitin nanofibers were characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), (13)C CP-MAS (cross-polarization under magic-angle spinning) solid state nuclear magnetic resonance (NMR), elemental analysis, and X-ray diffraction (XRD). Results showed that the esterification of chitin with maleic anhydride significantly improved the ultrasound disintegration of chitin fibrils into nanofibers...
January 15, 2018: Carbohydrate Polymers
Sheetal K Jain, Guinevere Mathies, Robert G Griffin
Dynamic nuclear polarization (DNP) is theoretically able to enhance the signal in nuclear magnetic resonance (NMR) experiments by a factor γe/γn, where γ's are the gyromagnetic ratios of an electron and a nuclear spin. However, DNP enhancements currently achieved in high-field, high-resolution biomolecular magic-angle spinning NMR are well below this limit because the continuous-wave DNP mechanisms employed in these experiments scale as ω0(-n) where n ∼ 1-2. In pulsed DNP methods, such as nuclear orientation via electron spin-locking (NOVEL), the DNP efficiency is independent of the strength of the main magnetic field...
October 28, 2017: Journal of Chemical Physics
Saikat Das, Edward Davis Oldham, Hans-Joachim Lehmler, Barbara L Knutson, Stephen E Rankin
HYPOTHESIS: Emerging applications of carbohydrate/cationic surfactant mixtures require not only synergistic mixing, but also accessible sugar headgroups at the exterior of micelles. A previous study showed that the glucoside headgroups of octyl-β-d-glucopyranoside aggregate at the interior of mixed micelles with equimolar cetyltrimethylammonium bromide rather than mixing with trimethylammonium groups at the corona. The current study tests the hypothesis that structural characteristics of the surfactants (the relative lengths of the alkyl tails and the type of linker) can be tuned to shift the carbohydrate groups to micelle surfaces...
October 18, 2017: Journal of Colloid and Interface Science
Douglas H Fabini, Ting Ann Siaw, Constantinos C Stoumpos, Geneva Laurita, Daniel Olds, Katharine Page, Jerry G Hu, Mercouri G Kanatzidis, Songi Han, Ram Seshadri
The role of organic molecular cations in the high-performance perovskite photovoltaic absorbers, methylammonium lead iodide (MAPbI3) and formamidinium lead iodide (FAPbI3), has been an enigmatic subject of great interest. Beyond aiding in the ease of processing of thin films for photovoltaic devices, there have been suggestions that many of the remarkable properties of the halide perovskites can be attributed to the dipolar nature and the dynamic behavior of these cations. Here, we establish the dynamics of the molecular cations in FAPbI3 between 4 K and 340 K and the nature of their interaction with the surrounding inorganic cage using a combination of solid state nuclear magnetic resonance and dielectric spectroscopies, neutron scattering, calorimetry, and ab initio calculations...
November 2, 2017: Journal of the American Chemical Society
Ryan Barnes, Sheng Sun, Yann Fichou, Frederick W Dahlquist, Matthias Heyden, Songi Han
Hydration water on the surface of a protein is thought to mediate the thermodynamics of protein-ligand interaction. For hydration water to play a role beyond modulating global protein solubility or stability, the thermodynamic properties of hydration water must reflect on the properties of the heterogeneous protein surface, and thus spatially vary over the protein surface. A potent read-out of local variations in thermodynamic properties of hydration water is its equilibrium dynamics spanning picosecond to nanosecond timescales...
November 1, 2017: Journal of the American Chemical Society
A Karabanov, D C Rose, W Köckenberger, J P Garrahan, I Lesanovsky
We study an ensemble of strongly coupled electrons under continuous microwave irradiation interacting with a dissipative environment, a problem of relevance to the creation of highly polarized nonequilibrium states in nuclear magnetic resonance. We analyze the stationary states of the dynamics, described within a Lindblad master equation framework, at the mean-field approximation level. This approach allows us to identify steady-state phase transitions between phases of high and low polarization controlled by the distribution of disordered electronic interactions...
October 13, 2017: Physical Review Letters
David Guarin, Sina Marhabaie, Alberto Rosso, Daniel Abergel, Geoffrey Bodenhausen, Konstantin L Ivanov, Dennis Kurzbach
Dynamic nuclear polarization (DNP) embraces a family of methods to increase signal intensities in nuclear magnetic resonance (NMR) spectroscopy. Despite extensive theoretical work that allows one to distinguish at least five distinct mechanisms, it remains challenging to determine the relative weights of the processes that are responsible for DNP in state-of-the-art experiments operating with stable organic radicals like nitroxides at high magnetic fields and low temperatures. Specifically, determining experimental conditions where DNP involves thermal mixing, which denotes a spontaneous heat exchange between different spin reservoirs, remains challenging...
November 1, 2017: Journal of Physical Chemistry Letters
J A Jarvis, I Haies, M Lelli, A J Rossini, I Kuprov, M Carravetta, P T F Williamson
The quadrupolar interaction experienced by the spin-1 (14)N nucleus is known to be extremely sensitive to local structure and dynamics. Furthermore, the (14)N isotope is 99.6% naturally abundant, making it an attractive target for characterisation of nitrogen-rich biological molecules by solid-state NMR. In this study, dynamic nuclear polarization (DNP) is used in conjunction with indirect (14)N detected solid-state NMR experiments to simultaneously characterise the quadrupolar interaction at multiple (14)N sites in the backbone of the microcrystalline protein, GB3...
November 7, 2017: Chemical Communications: Chem Comm
Roberta Spadaccini, Hundeep Kaur, Johanna Becker-Baldus, Clemens Glaubitz
MsbA, a homodimeric ABC exporter, translocates its native substrate lipid A as well as a range of smaller, amphiphilic substrates across the membrane. Magic angle sample spinning (MAS) NMR, in combination with dynamic nuclear polarization (DNP) for signal enhancement, has been used to probe two specific sites in transmembrane helices 4 and 6 of full length MsbA embedded in lipid bilayers. Significant chemical shift changes in both sites were observed in the vanadate-trapped state compared to apo state MsbA...
October 22, 2017: Biochimica et Biophysica Acta
Stef Smeets, Zachariah J Berkson, Dan Xie, Stacey I Zones, Wei Wan, Xiaodong Zou, Ming-Feng Hsieh, Bradley F Chmelka, Lynne B McCusker, Christian Baerlocher
The structure of the calcined form of the high-silica zeolite SSZ-70 has been elucidated by combining synchrotron X-ray powder diffraction (XRPD), high resolution transmission electron microscopy (HRTEM), and two-dimensional (2D) dynamic nuclear polarization (DNP)-enhanced NMR techniques. The framework structure of SSZ-70 is a polytype of MWW and can be viewed as a disordered ABC-type stacking of MWW-layers. HRTEM and XRPD simulations show that the stacking sequence is almost random, with each layer being shifted by ±1/3 along the <110> direction with respect to the previous one...
October 25, 2017: Journal of the American Chemical Society
M J Moure, Y Zhuo, G J Boons, J H Prestegard
The synthesis of perdeuterated and (13)C enriched myo-inositol is presented. Myo-inositol and its derivatives are of interest as substrates for enzymes producing phosphorylated species with regulatory functions in many organisms. Its utility in monitoring real-time phosphorylation by myo-inositol-3-kinase is illustrated using dynamic nuclear polarization (DNP) to enhance NMR observation.
November 16, 2017: Chemical Communications: Chem Comm
Fred Bernard, Jean-Antoine Lepesant, Antoine Guichet
Both types of Drosophila egg chamber germ cells, i.e. oocyte and nurse cells, have to control their nucleus positions in order to produce a viable gamete. Interestingly, while actin microfilaments are crucial to position the nuclei in nurse cells, these are the microtubules that are important for oocyte nucleus to migrate and adopt the correct position. In this review, we discuss the mechanisms underlying these positioning processes in the two cell types with respect to the organization and dynamics of the actin and microtubule skeleton...
October 19, 2017: Seminars in Cell & Developmental Biology
Lingyun Wang, Feng Yan
Heterogeneous nuclear ribonucleoprotein F (hnRNP F) controls the expression of various genes through regulating the alternative splicing of pre-mRNAs in the nucleus. It uses three quasi-RNA recognition motifs (qRRMs) to recognize G-tract RNA which contains at least three consecutive guanines. The structures containing qRRMs of hnRNP F in complex with G-tract RNA have been determined by nuclear magnetic resonance (NMR) spectroscopy, shedding light on the recognition mechanism of qRRMs with G-tract RNA. However, knowledge of the recognition details is still lacking...
December 9, 2017: Biochemical and Biophysical Research Communications
Joshua R Biller, Karl F Stupic, J Moreland
We present the development of a portable dynamic nuclear polarization (DNP) instrument based on the PCI eXtensions for Instrumentation (PXI) platform. The main purpose of the instrument is for study of (1) H polarization enhancements in solution through the Overhauser mechanism at low magnetic fields. A DNP probe set was constructed for use at 6.7 mT, using a modified Alderman-Grant (MAG) resonator at 241 MHz for saturation of the electron transition. The solenoid for detection of the enhanced (1) H signal at 288 kHz was constructed with Litz wire...
October 19, 2017: Magnetic Resonance in Chemistry: MRC
W Th Wenckebach
Dynamic Nuclear Polarization (DNP) has proven itself most powerful for the orientation of nuclear spins in polarized targets and for hyperpolarization in magnetic resonance imaging (MRI). Unfortunately, the theoretical description of some of the processes involved in DNP invokes the high temperature approximation, in which Boltzmann factors are expanded up to first order, while the high electron and nuclear spin polarization required for many applications do not justify such an approximation. A previous article extended the description of one of the mechanisms of DNP-thermal mixing-beyond the high temperature approximation (Wenckebach, 2017)...
October 4, 2017: Journal of Magnetic Resonance
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