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Dynamic nuclear polarization

Meng Shen, Honghao Li, Monica Olvera de la Cruz
Surface polarization in ion-containing heterogeneous dielectric media such as cell media and emulsions is determined by and determines the positions of the ions. We compute the surface polarization self-consistently as the ions move and analyze their effects on the interactions between electro-neutral, ion-containing droplets using coarse-grained molecular dynamics simulations based on the true energy functional. For water droplets immersed in oil, the interdroplet interaction is attractive, and the surface polarization makes the major contribution...
September 29, 2017: Physical Review Letters
N Lokesh, Andreas Seegerer, Johnny Hioe, Ruth M Gschwind
The low sensitivity of NMR and transient key intermediates below detection limit are the central problems studying reaction mechanisms by NMR. Sensitivity can be enhanced by hyperpolarization techniques such as dynamic nuclear polarization or the incorporation/interaction of special hyperpolarized molecules. However, all of these techniques require special equipment, are restricted to selective reactions or undesirably influence the reaction pathways. Here, we apply the Chemical Exchange Saturation Transfer (CEST) technique for the first time to NMR detect and characterize previously unobserved transient reaction intermediates in organocatalysis...
January 16, 2018: Journal of the American Chemical Society
Keith J Fritzsching, Boris Itin, Ann E McDermott
We demonstrate that N,N-Diethylmethylamine (DEMA) is a useful compound for shimming the magnetic field when doing NMR experiments at room temperature and 130 K, near the temperature used in many dynamic nuclear polarization (DNP) experiments. The resonance assigned to the N-methyl carbon in DEMA at 14.7 T and 140 K has a full-width-half-max linewidth of <4 Hz and has a spin-lattice relaxation time of 0.17 ± 0.03 s.
December 30, 2017: Journal of Magnetic Resonance
Jasmine Viger-Gravel, Anna Schantz, Arthur C Pinon, Aaron J Rossini, Staffan Schantz, Lyndon Emsley
Here we show how dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy experiments permit the atomic level structural characterization of loaded and empty lipid nanoparticles (LNPs). The LNPs used here were synthesized by microfluidic mixing technique and are composed of ionizable cationic lipid (DLin-MC3-DMA), a phospholipid (DSPC), cholesterol and PEG (DMPE-PEG 2000), as well as encapsulated cargoes which are either phosphorothioated-siRNA (50 or 100%) or mRNA. We show that LNPs form physically stable complexes with bioactive drug siRNA for a period of 94 days...
January 14, 2018: Journal of Physical Chemistry. B
Kasper Wigh Lipsø, Esben Søvsø Szocska Hansen, Rasmus Stilling Tougaard, Christoffer Laustsen, Jan Henrik Ardenkjaer-Larsen
PURPOSE: To investigate dynamic coronary MR angiography using hyperpolarized water as a positive contrast agent. Hyperpolarization can increase the signal by several orders of magnitude, and has recently been translated to human cardiac application. The aim was to achieve large 1 H signal enhancement to allow high-resolution imaging of the coronary arteries. METHODS: Protons in D2 O were hyperpolarized by dissolution dynamic nuclear polarization. A total of 18 mL of hyperpolarized water was injected into the coronary arteries of healthy pigs (N = 9; 3 injections in 3 animals)...
January 12, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Jian Zhang, Zhaofeng Ding, Cheng Tan, Kevin Huang, Oscar O Bernal, Pei-Chun Ho, Gerald D Morris, Adrian D Hillier, Pabitra K Biswas, Stephen P Cottrell, Hui Xiang, Xin Yao, Douglas E MacLaughlin, Lei Shu
The origin of the pseudogap region below a temperature T* is at the heart of the mysteries of cuprate high-temperature superconductors. Unusual properties of the pseudogap phase, such as broken time-reversal and inversion symmetry are observed in several symmetry-sensitive experiments: polarized neutron diffraction, optical birefringence, dichroic angle-resolved photoemission spectroscopy, second harmonic generation, and polar Kerr effect. These properties suggest that the pseudogap region is a genuine thermodynamic phase and are predicted by theories invoking ordered loop currents or other forms of intra-unit-cell (IUC) magnetic order...
January 2018: Science Advances
Sharon E Ashbrook, John M Griffin, Karen E Johnston
The sensitivity of nuclear magnetic resonance (NMR) spectroscopy to the local atomic-scale environment offers great potential for the characterization of a diverse range of solid materials. Despite offering more information than its solution-state counterpart, solid-state NMR has not yet achieved a similar level of recognition, owing to the anisotropic interactions that broaden the spectral lines and hinder the extraction of structural information. Here, we describe the methods available to improve the resolution of solid-state NMR spectra and the continuing research in this area...
January 11, 2018: Annual Review of Analytical Chemistry
Miguel Mompeán, Rosa M Sánchez-Donoso, Antonio de la Hoz, Vittorio Saggiomo, Aldrik H Velders, M Victoria Gomez
Among the methods to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy, small-diameter NMR coils (microcoils) are promising tools to tackle the study of mass-limited samples. Alternatively, hyperpolarization schemes based on dynamic nuclear polarization techniques provide strong signal enhancements of the NMR target samples. Here we present a method to effortlessly perform photo-chemically induced dynamic nuclear polarization in microcoil setups to boost NMR signal detection down to sub-picomole detection limits in a 9...
January 9, 2018: Nature Communications
Dmitry Shishmarev, Alan J Wright, Tiago B Rodrigues, Giuseppe Pileio, Gabriele Stevanato, Kevin M Brindle, Philip W Kuchel
Fumarate is an important probe of metabolism in hyperpolarized magnetic resonance imaging and spectroscopy. It is used to detect the release of fumarase in cancer tissues, which is associated with necrosis and drug treatment. Nevertheless, there are limited reports describing the detailed kinetic studies of this enzyme in various cells and tissues. Thus, we aimed to evaluate the sub-minute kinetics of human red blood cell fumarase using nuclear magnetic resonance (NMR) spectroscopy, and to provide a quantitative description of the enzyme that is relevant to the use of fumarate as a probe of cell rupture...
January 8, 2018: NMR in Biomedicine
Aleksandra Andreevna Ageeva, Ekaterina Khramtsova, Ilya Magin, Denis Rychkov, Peter Purtov, Miguel Miranda, Tatyana Leshina
This work has shown spin selectivity in electron transfer (ET) of diastereomers of (R,S)-naproxen-(S)-N-methylpyrrolidine and (R,S)-naproxen-(S)-tryptophan dyads. Photoinduced (ET) in these dyads is interesting due to still unexplained phenomenon of stereoselectivity in drug activity of enantiomers. The chemically induced dynamic nuclear polarization (CIDNP) enhancement coefficients of (R,S)-diastereomers twice exceeds those for the (S,S)-analogue. These facts are also interesting because spin effects are one of the most sensitive to subtle changes in spin and molecular dynamics of paramagnetic particles...
January 4, 2018: Chemistry: a European Journal
Yuki Imakura, Hiroshi Nonaka, Yoichi Takakusagi, Kazuhiro Ichikawa, Nesmine Maptue, Alexander Funk, Chalermchai Khemtong, Shinsuke Sando
Dynamic nuclear polarization (DNP) is a technique to polarize the nuclear spin population. As a result of the hyperpolarization, NMR sensitivity of the nuclei in molecules can be enhanced dramatically. Recent application of the hyperpolarization technique has led to advances in biochemical and molecular studies. A major problem is the short lifetime of the polarized nuclear spin state. Generally, in solution, the polarized nuclear spin state decays to a thermal spin equilibrium, resulting in loss of the enhanced NMR signal...
December 31, 2017: Chemistry, An Asian Journal
Hsueh-Ying Chen, Robert Tycko
We demonstrate the feasibility of high-resolution 1H magnetic resonance imaging (MRI) at low temperatures by obtaining an MRI image of 20 μm diameter glass beads in glycerol/water at 28 K with 2.8 μm isotropic resolution. The experiments use a recently-described MRI apparatus (Moore and Tycko, 2015) with minor modifications. The sample is contained within a radio-frequency microcoil with 150 μm inner diameter. Sensitivity is additionally enhanced by paramagnetic doping, optimization of the sample temperature, three-dimensional phase-encoding of k-space data, pulsed spin-lock detection of 1H nuclear magnetic resonance signals, and spherical sampling of k-space...
December 20, 2017: Journal of Magnetic Resonance
Li Wang, Dong-Sheng Zhai, Ban-Jun Ruan, Cheng-Ming Xu, Zi-Chen Ye, Huan-Yu Lu, Ying-Hao Jiang, Zhen-Yu Wang, An Xiang, Yuan Yang, Jian-Lin Yuan, Zi-Fan Lu
Macrophages, characterized by considerable diversity and plasticity, play a crucial role in a broad spectrum of biological processes, including inflammation. However, the molecular mechanisms underlying the diverse phenotypes of macrophages are not well defined. Here, we show that the RNA-binding protein, quaking (QKI), dynamically modulates macrophage polarization states. After lipopolysaccharide (LPS) stimulation, QKI-silenced RAW 264.7 cells displayed a pro-inflammatory M1 phenotype characterized by increased expression of iNOS, TNF-α, and IL-6 and decreased expression of anti-inflammatory factors, such as IL-10, found in inflammatory zone (Fizz1), and chitinase-like 3 (Chil3 or Ym1)...
2017: Frontiers in Immunology
Ralph Stadhouders, Erik Lubberts, Rudi W Hendriks
Since the original identification of the T helper 17 (Th17) subset in 2005, it has become evident that these cells do not only contribute to host defence against pathogens, such as bacteria and fungi, but that they are also critically involved in the pathogenesis of many autoimmune diseases. In contrast to the classic Th1 and Th2 cells, which represent rather stably polarized subsets, Th17 cells display remarkable heterogeneity and plasticity. This has been attributed to the characteristics of the key transcription factor that guides Th17 differentiation, retinoic acid receptor-related orphan nuclear receptor gamma (RORγ)...
December 21, 2017: Journal of Autoimmunity
Yusuke Okuno, Silvia Cavagnero
Given its short hyperpolarization time (∼10-6 s) and mostly non-perturbative nature, photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a powerful tool for sensitivity enhancement in nuclear magnetic resonance. In this study, we explore the extent of 1H-detected 13C nuclear hyperpolarization that can be gained via photo-CIDNP in the presence of small-molecule additives containing a heavy atom. The underlying rationale for this methodology is the well-known external-heavy-atom (EHA) effect, which leads to significant enhancements in the intersystem-crossing rate of selected photosensitizer dyes from photoexcited singlet to triplet...
December 5, 2017: Journal of Magnetic Resonance
Kelsey A Morrison, Brian H Clowers
Characterization of complex oligosaccharides has historically required extensive sample handling and separations before analysis using nuclear magnetic resonance spectroscopy and electron impact mass spectra following hydrolysis, derivatization, and gas chromatographic separation. Advances in liquid chromatography separations and tandem mass spectrometry have expanded the range of intact glycan analysis, but carbohydrate structure and conformation-integral chemical characteristics-are often difficult to assess with minimal amounts of sample in a rapid fashion...
December 14, 2017: Current Opinion in Chemical Biology
Ali A Sirusi, Eul Hyun Suh, Zoltan Kovacs, Matthew E Merritt
Dissolution dynamic nuclear polarization was introduced in 2003 as a method for producing hyperpolarized 13C solutions suitable for metabolic imaging. The signal to noise ratio for the imaging experiment depends on the maximum polarization achieved in the solid state. Hence, optimization of the DNP conditions is essential. To acquire maximum polarization many parameters related to sample preparation can be modulated. Recently, it was demonstrated that Ho3+, Dy3+, Tb3+, and Gd3+ complexes enhance the polarization at 1...
December 15, 2017: Physical Chemistry Chemical Physics: PCCP
Andrew G M Rankin, Paul B Webb, Daniel M Dawson, Jasmine Viger-Gravel, Brennan J Walder, Lyndon Emsley, Sharon E Ashbrook
Isotopic enrichment of 29Si and DNP-enhanced NMR spectroscopy are combined to determine the detailed surface structure of a silicated alumina catalyst. The significant sensitivity enhancement provided by DNP is vital to the acquisition of multinuclear and multidimensional experiments that provide information on the atomic-level structure of the species present at the surface. Isotopic enrichment not only facilitates spectral acquisition, particularly given the low (1.5 wt %) Si loading, but also enables spectra with higher resolution than those acquired using DNP to be obtained...
October 19, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Mengxiao Liu, Christian Hilty
Hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) has emerged as a technique for enhancing NMR signals by several orders of magnitude, thereby facilitating the characterization of metabolic pathways both in vivo and in vitro. Following the introduction of an externally hyperpolarized compound, real-time NMR enables the measurement of metabolic flux in the corresponding pathway. Spin relaxation however limits the maximum experimental time and prevents the use of this method with compounds exhibiting slow membrane transport rates...
December 11, 2017: Analytical Chemistry
Ryosuke Nakata, Fuminori Hyodo, Masaharu Murata, Hinako Eto, Tomoko Nakaji, Takahito Kawano, Sayoko Narahara, Keiji Yasukawa, Tomohiko Akahoshi, Morimasa Tomikawa, Makoto Hashizume
Given the rising incidence of non-alcoholic fatty liver disease (NAFLD) in both adults and children, the development of a non-invasive diagnostic method for assessing disease progression to non-alcoholic steatohepatitis (NASH) has become an important research goal. Currently available non-invasive imaging technologies are only able to assess fat accumulation in the liver. Therefore, these methods are not suitable for a precise diagnosis of NASH. The standard diagnostic technique for NASH, liver biopsy, has several drawbacks, including the higher risk of complications that accompanies invasive procedures...
December 7, 2017: Scientific Reports
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