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Dynamic nuclear polarization

You Kure Wu, Hiroki Umeshima, Junko Kurisu, Mineko Kengaku
Nuclear migration of newly born neurons is essential for cortex formation in the brain. The nucleus is translocated by actin and microtubules, yet the actual force generated by the interplay of these cytoskeletons remains elusive. High-resolution time-lapse observation of migrating murine cerebellar granule cells revealed that the nucleus actively rotates along the direction of its translocation, independently of centrosome motion. Pharmacological and molecular perturbation indicated that spin torque is primarily generated by microtubule motors through the LINC complex in the absence of actomyosin contractility...
March 8, 2018: Development
Fabian Cadiz, Abdelhak Djeffal, Delphine Lagarde, Andrea Balocchi, Bingshan Tao, Bo Xu, Shiheng Liang, Mathieu Stoffel, Xavier Devaux, Henri Jaffres, Jean-Marie George, Michel Hehn, Stéphane Mangin, Helene Carrere, Xavier Marie, Thierry Amand, Xiufeng Han, Zhanguo Wang, Bernhard Urbaszek, Yuan Lu, Pierre Renucci
The emission of circularly polarized light from a single quantum dot relies on the injection of carriers with well-defined spin polarization. Here we demonstrate single dot electroluminescence (EL) with a circular polarization degree up to 35 % at zero applied magnetic field. The injection of spin polarized electrons is achieved by combining ultrathin CoFeB electrodes on top of a spin-LED device with p-type InGaAs quantum dots in the active region. We measure an Overhauser shift of several μeV at zero magnetic field for the positively charged exciton (trion X+) EL emission, which changes sign as we reverse the injected electron spin orientation...
March 8, 2018: Nano Letters
Alex M Schrader, Jacob I Monroe, Ryan Sheil, Howard A Dobbs, Timothy J Keller, Yuanxin Li, Sheetal Jain, M Scott Shell, Jacob N Israelachvili, Songi Han
An in-depth knowledge of the interaction of water with amorphous silica is critical to fundamental studies of interfacial hydration water, as well as to industrial processes such as catalysis, nanofabrication, and chromatography. Silica has a tunable surface comprising hydrophilic silanol groups and moderately hydrophobic siloxane groups that can be interchanged through thermal and chemical treatments. Despite extensive studies of silica surfaces, the influence of surface hydrophilicity and chemical topology on the molecular properties of interfacial water is not well understood...
March 5, 2018: Proceedings of the National Academy of Sciences of the United States of America
Bence Daniel, Gergely Nagy, Attila Horvath, Zsolt Czimmerer, Ixchelt Cuaranta-Monroy, Szilard Poliska, Tristan T Hays, Sascha Sauer, Jean Francois-Deleuze, Laszlo Nagy
Retinoid X receptor (RXR) is an obligate heterodimeric partner of several nuclear receptors (NRs), and as such a central component of NR signaling regulating the immune and metabolic phenotype of macrophages. Importantly, the binding motifs of RXR heterodimers are enriched in the tissue-selective open chromatin regions of resident macrophages, suggesting roles in subtype specification. Recent genome-wide studies revealed that RXR binds to thousands of sites in the genome, but the mechanistic details how the cistrome is established and serves ligand-induced transcriptional activity remained elusive...
February 28, 2018: Nucleic Acids Research
Kent R Thurber, Thanh-Ngoc Le, Victor Changcoco, David J R Brook
Solid-state dynamic nuclear polarization (DNP) using the cross-effect relies on radical pairs whose electron spin resonance (ESR) frequencies differ by the nuclear magnetic resonance (NMR) frequency. We measure the DNP provided by a new water-soluble verdazyl radical, verdazyl-ribose, under both magic-angle spinning (MAS) and static sample conditions at 9.4 T, and compare it to a nitroxide radical, 4-hydroxy-TEMPO. We find that verdazyl-ribose is an effective radical for cross-effect DNP, with the best relative results for a non-spinning sample...
March 1, 2018: Journal of Magnetic Resonance
Venkata S Mandala, Jonathan K Williams, Mei Hong
Solid-state nuclear magnetic resonance (SSNMR) spectroscopy elucidates membrane protein structures and dynamics in atomic detail to yield mechanistic insights. By interrogating membrane proteins in phospholipid bilayers that closely resemble the biological membrane, SSNMR spectroscopists have revealed ion conduction mechanisms, substrate transport dynamics, and oligomeric interfaces of seven-transmembrane helix proteins. Research has also identified conformational plasticity underlying virus-cell membrane fusions by complex protein machineries, and β-sheet folding and assembly by amyloidogenic proteins bound to lipid membranes...
March 2, 2018: Annual Review of Biophysics
Sten O Nilsson Lill, Cory M Widdifield, Anna Pettersen, Anna Svensk Ankarberg, Maria Lindkvist, Peter Aldred, Sandra Gracin, Norman Shankland, Kenneth Shankland, Staffan Schantz, Lyndon Emsley
By the combined use of powder and single crystal X-ray diffraction, solid-state NMR, and molecular modelling, the crystal structures of two systems containing the unusually large tenapanor drug molecule have been determined: the free form, ANHY and a dihydrochloride salt form, 2HCl. Dynamic nuclear polarization (DNP) assisted solid-state NMR (SSNMR) crystallography investigations were found essential for the final assignment, and were used to validate the crystal structure of ANHY. From the structural informatics analysis of ANHY and 2HCl, conformational ring differences in one part of the molecule were observed which influences the relative orientation of a methyl group on a ring nitrogen and thereby impacts the crystallizability of the dihydrochloride salt...
February 28, 2018: Molecular Pharmaceutics
Jeffrey Camacho-Bunquin, Magali S Ferrandon, Hyuntae Sohn, Dali Yang, Cong Liu, Patricia Ignacio-de Leon, Frédéric A Perras, Marek Pruski, Peter C Stair, Massimiliano Delferro
Well-defined organoplatinum(IV) sites were grafted on a Zn(II)-modified SiO2 support via surface organometallic chemistry in toluene at room temperature. Solid-state spectroscopies including XAS, DRIFTS, DRUV-Vis, and solid-state (SS)NMR enhanced by dynamic nuclear polarization (DNP), as well as TPR-H2 and TEM techniques revealed highly dispersed (methylcyclopentadienyl)methylplatinum(IV) sites on the surface ((MeCp)PtMe/Zn/SiO2, 1). In addition, computational modelling suggests that the surface reaction of (MeCp)PtMe3 with Zn(II)-modified SiO2 support is thermodynamically favorable (∆G = -12...
February 27, 2018: Journal of the American Chemical Society
Bertrand Plainchont, Pierrick Berruyer, Jean-Nicolas Dumez, Sami Jannin, Patrick Giraudeau
Dynamic nuclear polarization (DNP) can boost sensitivity in nuclear magnetic resonance (NMR) experiments by several orders of magnitude. This review illustrates how the coupling of DNP with both liquid- and solid-state NMR spectroscopy has the potential to considerably extend the range of applications of NMR in analytical chemistry.
February 26, 2018: Analytical Chemistry
Faith J Scott, Edward P Saliba, Brice J Albert, Nicholas Alaniva, Erika L Sesti, Chukun Gao, Natalie C Golota, Eric J Choi, Anil P Jagtap, Johannes J Wittmann, Michael Eckardt, Wolfgang Harneit, Björn Corzilius, Snorri Th Sigurdsson, Alexander B Barnes
We describe a frequency-agile gyrotron which can generate frequency-chirped microwave pulses. An arbitrary waveform generator (AWG) within the NMR spectrometer controls the microwave frequency, enabling synchronized pulsed control of both electron and nuclear spins. We demonstrate that the acceleration of emitted electrons, and thus the microwave frequency, can be quickly changed by varying the anode voltage. This strategy results in much faster frequency response than can be achieved by changing the potential of the electron emitter, and does not require a custom triode electron gun...
February 12, 2018: Journal of Magnetic Resonance
Chia-Hsiu Chen, Yunyi Wang, Christian Hilty
The nuclear Overhauser effect (NOE) is a primary means to characterize intermolecular interactions using modern NMR spectroscopy. Multiple experiments measured using different mixing time can be used for quantifying NOE buildup and measuring cross-relaxation rates. However, this approach using conventional multi-dimensional NMR is time consuming. Hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) can generate deviations from equilibrium spin polarization by orders of magnitude, thereby enhancing signals and allowing to characterize NOE build up in real-time...
February 19, 2018: Methods: a Companion to Methods in Enzymology
Pelayo Fernandez-Acebal, Oded Rosolio, Jochen Scheuer, Christoph Müller, Samuel Müller, Simon Schmitt, Liam P McGuinness, Ilai Schwartz, Qiong Chen, Alex Retzker, Boris Naydenov, Fedor Jelezko, Martin B Plenio
Efficient polarization of organic molecules is of extraordinary relevance when performing nuclear magnetic resonance (NMR) and imaging. Commercially available routes to dynamical nuclear polarization (DNP) work at extremely low-temperatures, relying on the solidification of organic samples and thus bringing the molecules out of their ambient thermal conditions. In this work we investigate polarization transfer from optically-pumped nitrogen vacancy centers in diamond to external molecules at room temperature...
February 22, 2018: Nano Letters
Sebastien Alphonse, Boris Itin, Reza Khayat, Ranajeet Ghose
While solid-state NMR (ssNMR) has emerged as a powerful technique to study viral capsids, current studies are limited to capsids formed from single proteins or single polyproteins. The ability to selectively label individual protein components within multi-protein viral capsids and the resulting spectral simplification will facilitate the extension of ssNMR techniques to complex viruses. In vitro capsid assembly by combining individually purified, labeled and unlabeled components in NMR quantities is not a viable option for most viruses...
February 21, 2018: Biochemistry
Inés Rodríguez-Arias, Alberto Rosso, Andrea De Luca
The solid effect is one of the simplest and most effective mechanisms for Dynamic Nuclear Polarization. It involves the exchange of polarization between one electron and one nuclear spin coupled via the hyperfine interaction. Even for such a small spin system, the theoretical understanding is complicated by the contact with the lattice and the microwave irradiation. Both being weak, they can be treated within perturbation theory. In this work, we analyze the two most popular perturbation schemes: the Zeeman and the eigenstate-based approaches which differ in the way the hyperfine interaction is treated...
February 20, 2018: Magnetic Resonance in Chemistry: MRC
Thierry Dubroca, Adam N Smith, Kevin J Pike, Stuart Froud, Richard Wylde, Bianca Trociewitz, Johannes McKay, Frederic Mentink-Vigier, Johan van Tol, Sungsool Wi, William Brey, Joanna R Long, Lucio Frydman, Stephen Hill
Nuclear magnetic resonance (NMR) is an intrinsically insensitive technique, with Boltzmann distributions of nuclear spin states on the order of parts per million in conventional magnetic fields. To overcome this limitation, dynamic nuclear polarization (DNP) can be used to gain up to three orders of magnitude in signal enhancement, which can decrease experimental time by up to six orders of magnitude. In DNP experiments, nuclear spin polarization is enhanced by transferring the relatively larger electron polarization to NMR active nuclei via microwave irradiation...
January 31, 2018: Journal of Magnetic Resonance
Matthieu Cavaillès, Aurélien Bornet, Xavier Jaurand, Basile Vuichoud, David Baudouin, Mathieu Baudin, Laurent Veyre, Geoffrey Baudenhausen, Jean-Nicolas Dumez, Sami Jannin, Christophe Copéret, Chloé Thieuleux
Tailoring the physical features and the porous network architecture of silica-based hyperpolarizing solids containing TEMPO radicals, known as HYPSO (HYbrid Polarizing SOlids), enable unprecedented performance of dissolution Dynamic Nuclear Polarization (d-DNP). High polarization values up to P(1H) = 99 % were reached for samples impregnated with a mixture of H2O:D2O and loaded in a 6.7 T polarizer at temperatures around 1.2 K. These HYPSO materials combine the best performance of homogeneous DNP formulations with the advantages of solid polarizing matrices which provide hyperpolarized solutions free of any - potentially toxic - additives (radicals and glass-forming agents)...
February 19, 2018: Angewandte Chemie
Xiaoling Wang, Johannes E McKay, Bimala Lama, Johan van Tol, Tinghui Li, Kyle Kirkpatrick, Zhehong Gan, Stephen Hill, Joanna R Long, Harry C Dorn
We show increased dynamic nuclear polarization by adding a low dosage of a S = 15/2 Gd based endohedral metallofullerene (EMF) to DNP samples. By adding 60 μM Gd2 @C79 N, the nuclear polarization of1 H and13 C spins from 40 mM 4-oxo-TEMPO increases by approximately 40% and 50%, respectively, at 5 T and 1.2 K. Electron-electron double resonance (ELDOR) measurements show that the high spin EMF shortens the electron relaxation times and increases electron spectral diffusion leading to the increased DNP enhancement...
February 19, 2018: Chemical Communications: Chem Comm
Eleonora Cavallari, Carla Carrera, Silvio Aime, Francesca Reineri
The use of [1- 13 C]pyruvate, hyperpolarized by dissolution-Dynamic Nuclear Polarization (d-DNP), in in vivo metabolic studies has developed quickly, thanks to the imaging probe's diagnostic relevance. Nevertheless, the cost of a d-DNP polarizer is quite high and the speed of hyperpolarization process is relatively slow, meaning that its use is limited to few research laboratories. ParaHydrogen Induced Polarization Side Arm Hydrogenation (PHIP-SAH) (Reineri et al., 2015) is a cost effective and easy-to-handle method that produces 13 C-MR hyperpolarization in [1- 13 C]pyruvate and other metabolites...
January 31, 2018: Journal of Magnetic Resonance
Hesham Haffez, David R Chisholm, Natalie J Tatum, Roy Valentine, Christopher Redfern, Ehmke Pohl, Andrew Whiting, Stefan Przyborski
Retinoids, such as all-trans-retinoic acid (ATRA), regulate cellular differentiation and signalling pathways in chordates by binding to nuclear retinoic acid receptors (RARα/β/γ). Polar interactions between receptor and ligand are important for binding and facilitating the non-polar interactions and conformational changes necessary for RAR-mediated transcriptional regulation. The constraints on activity and RAR-type specificity with respect to the structural link between the polar and non-polar functions of synthetic retinoids are poorly understood...
February 10, 2018: Bioorganic & Medicinal Chemistry
Sandeep Chhabra, Patrick Fischer, Koh Takeuchi, Abhinav Dubey, Joshua J Ziarek, Andras Boeszoermenyi, Daniel Mathieu, Wolfgang Bermel, Norman E Davey, Gerhard Wagner, Haribabu Arthanari
Studies over the past decade have highlighted the functional significance of intrinsically disordered proteins (IDPs). Due to conformational heterogeneity and inherent dynamics, structural studies of IDPs have relied mostly on NMR spectroscopy, despite IDPs having characteristics that make them challenging to study using traditional 1H-detected biomolecular NMR techniques. Here, we develop a suite of 3D 15N-detected experiments that take advantage of the slower transverse relaxation property of 15N nuclei, the associated narrower linewidth, and the greater chemical shift dispersion compared with those of 1H and 13C resonances...
February 5, 2018: Proceedings of the National Academy of Sciences of the United States of America
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