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Solid-state NMR

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https://www.readbyqxmd.com/read/29155581/phosphorescence-control-mediated-by-molecular-rotation-and-aurophilic-interactions-in-amphidynamic-crystals-of-1-4-bis-tri-p-fluorophenyl-phosphane-gold-i-ethynyl-benzene
#1
Mingoo Jin, Tim S Chung, Tomohiro Seki, Hajime Ito, Miguel A Garcia-Garibay
Here we present a structural design aimed at the control of phosphorescence emission as the result of changes in molecular rotation in a crystalline material. The proposed strategy includes the use of aurophilic interactions, both as a crystal engineering tool and as sensitive emission probe, and the use of a dumbbell-shaped architecture intended to create a low packing density region that permits the rotation of a central phenylene. Molecular rotor 1 with of a central 1,4-diethynylphenylene rotator linked to two gold(I) triphenylphosphane complexes was prepared and its structure confirmed by single crystal X-ray diffraction (XRD), which revealed chains mediated by dimeric aurophilic interactions...
November 20, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29152977/local-disorder-and-tunable-luminescence-in-sr1-x-2al2-xsixo4-0-2-%C3%A2-x-%C3%A2-0-5-transparent-ceramics
#2
Alberto J Fernandez-Carrion, Kholoud Al Saghir, Emmanuel Veron, Ana I Becerro, Florence Porcher, Wolfgang Wisniewski, Guy Matzen, Franck Fayon, Mathieu Allix
Eu-doped Sr1-x/2Al2-xSixO4 (x = 0.2, 0.4, and 0.5) transparent ceramics have been synthesized by full and congruent crystallization from glasses prepared by aerodynamic levitation and laser-heating method. Structural refinements from synchrotron and neutron powder diffraction data show that the ceramics adopt a 1 × 1 × 2 superstructure compared to the SrAl2O4 hexagonal polymorph. While the observed superstructure reflections indicate a long-range ordering of the Sr vacancies in the structure, (29)Si and (27)Al solid-state NMR measurements associated with DFT computations reveal a significant degree of disorder in the fully polymerized tetrahedral network...
November 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29151676/jim-hyde-and-the-endor-connection-a-personal-account
#3
Klaus Möbius, Wolfgang Lubitz, Anton Savitsky
In this minireview, we report on our year-long EPR work, such as electron-nuclear double resonance (ENDOR), pulse electron double resonance (PELDOR) and ELDOR-detected NMR (EDNMR) at X-band and W-band microwave frequencies and magnetic fields. This report is dedicated to James S. Hyde and honors his pioneering contributions to the measurement of spin interactions in large (bio)molecules. From these interactions, detailed information is revealed on structure and dynamics of macromolecules embedded in liquid-solution or solid-state environments...
2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29151208/strategies-for-efficient-sample-preparation-for-dynamic-nuclear-polarization-solid-state-nmr-of-biological-macromolecules
#4
Boris Itin, Ivan V Sergeyev
Solid-state NMR (SSNMR) is a powerful tool for the elucidation of structure and dynamics in biological macromolecules. Over the years, SSNMR spectroscopists have developed an array of techniques enabling the measurement of internuclear correlations, distances, and torsional angles; these have been applied to the study of a number of biological systems that are difficult to study by X-ray crystallography and solution NMR, including key biological targets such as membrane proteins and amyloid fibrils. Applications of SSNMR to other topic areas, including materials science, pharmaceuticals, and small molecules, have also flourished in recent years...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29151207/rapid-prediction-of-multi-dimensional-nmr-data-sets-using-fandas
#5
Siddarth Narasimhan, Deni Mance, Cecilia Pinto, Markus Weingarth, Alexandre M J J Bonvin, Marc Baldus
Solid-state NMR (ssNMR) can provide structural information at the most detailed level and, at the same time, is applicable in highly heterogeneous and complex molecular environments. In the last few years, ssNMR has made significant progress in uncovering structure and dynamics of proteins in their native cellular environments [1-4]. Additionally, ssNMR has proven to be useful in studying large biomolecular complexes as well as membrane proteins at the atomic level [5]. In such studies, innovative labeling schemes have become a powerful approach to tackle spectral crowding...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29151205/filamentous-bacteriophage-viruses-preparation-magic-angle-spinning-solid-state-nmr-experiments-and-structure-determination
#6
Omry Morag, Nikolaos G Sgourakis, Gili Abramov, Amir Goldbourt
Filamentous bacteriophages are elongated semi-flexible viruses that infect bacteria. They consist of a circular single-stranded DNA (ssDNA) wrapped by a capsid consisting of thousands of copies of a major coat protein subunit. Given the increasing number of discovered phages and the existence of only a handful of structures, the development of methods for phage structure determination is valuable for biophysics and structural virology. In recent years, we developed and applied techniques to elucidate the 3D atomic-resolution structures of intact bacteriophages using experimental magic-angle spinning (MAS) solid-state NMR data...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29151204/afterglow-solid-state-nmr-spectroscopy
#7
Gili Abramov, Nathaniel J Traaseth
Biomolecular solid-state NMR experiments have traditionally been collected through detection of (13)C or (15)N nuclei. Since these nuclei have relatively low sensitivity stemming from their smaller gyromagnetic ratios relative to (1)H, the time required to collect multi-dimensional datasets serves as a limitation to resonance assignment and structure determination. One improvement in the field has been to employ simultaneous or parallel acquisition techniques with the goal of acquiring more than one dataset at a time and therefore speeding up the overall data collection process...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29151203/experimental-aspects-of-polarization-optimized-experiments-poe-for-magic-angle-spinning-solid-state-nmr-of-microcrystalline-and-membrane-bound-proteins
#8
T Gopinath, Gianluigi Veglia
Conventional NMR pulse sequences record one spectrum per experiment, while spending most of the time waiting for the spin system to return to the equilibrium. As a result, a full set of multidimensional NMR experiments for biological macromolecules may take up to several months to complete. Here, we present a practical guide for setting up a new class of MAS solid-state NMR experiments (POE or polarization optimized experiments) that enable the simultaneous acquisition of multiple spectra of proteins, accelerating data acquisition...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29151202/nmr-of-macromolecular-assemblies-and-machines-at-1-ghz-and-beyond-new-transformative-opportunities-for-molecular-structural-biology
#9
Caitlin M Quinn, Mingzhang Wang, Tatyana Polenova
As a result of profound gains in sensitivity and resolution afforded by ultrahigh magnetic fields, transformative applications in the fields of structural biology and materials science are being realized. The development of dual low temperature superconducting (LTS)/high-temperature superconducting (HTS) magnets has enabled the achievement of magnetic fields above 1 GHz (23.5 T), which will open doors to an unprecedented new range of applications. In this contribution, we discuss the promise of ultrahigh field magnetic resonance...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29151190/elucidation-of-functional-chemical-groups-responsible-of-compost-phytotoxicity-using-solid-state-13-c-nmr-spectroscopy-under-different-initial-c-n-ratios
#10
Khalid Azim, Youssef Faissal, Brahim Soudi, Claude Perissol, Sevastianos Roussos, Imane Thami Alami
More than 1 million tons of fresh organic wastes is produced in the Souss-Massa region in Morocco. Tomato organic residues represent more than 25% of the total organic wastes and are deposited in uncontrolled landfills. Thus, composting can represent a valuable and pertinent solution to this environmental problem. The objectives of this experiment are to identify the potential functional groups responsible for compost phytotoxicity and to determine the optimum initial carbon to nitrogen ratio (C/N) for maximum recovery of tomato residues...
November 19, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/29150138/new-hybrid-adsorbent-based-on-porphyrin-functionalized-silica-for-heavy-metals-removal-synthesis-characterization-isotherms-kinetics-and-thermodynamics-studies
#11
Smaail Radi, Chahrazad El Abiad, Nuno M M Moura, Maria A F Faustino, M Graça P M S Neves
The pollution of water resources due to the disposal of toxic heavy metals has been a growing global concern for the last decades. For this purpose, the search for effective and economic material based adsorbents is required, due to the efficiency of the process. In this work, a novel inorganic-organic hybrid material based on silica chemically modified with a porphyrin (SiNTPP), with a high metal removal efficiency, was developed. The new material was characterized using a set of suitable techniques such as (13)C NMR of the solid state, elemental analysis, FTIR, nitrogen adsorption-desorption isotherm, BET surface area, BJH pore sizes and scanning electron microscopy (SEM)...
November 7, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/29149466/microsecond-timescale-protein-dynamics-a-combined-solid-state-nmr-approach
#12
Petra Rovó, Rasmus Linser
Conformational exchange in proteins is a major determinant in protein functionality. In particular, the μs-ms timescale is associated with enzymatic activity and interactions between biological molecules. We show here that a comprehensive data set of R1ρ relaxation dispersion profiles employing multiple effective fields and tilt angles can be easily obtained in perdeuterated, partly back-exchanged proteins at fast magic-angle spinning and further complemented with chemical-exchange saturation transfer NMR experiments...
November 17, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/29148785/rapid-quantitative-measurements-of-paramagnetic-relaxation-enhancements-in-cu-ii-tagged-proteins-by-proton-detected-solid-state-nmr-spectroscopy
#13
Dwaipayan Mukhopadhyay, Philippe S Nadaud, Matthew D Shannon, Christopher P Jaroniec
We demonstrate rapid quantitative measurements of site-resolved paramagnetic relaxation enhancements (PREs), which are a source of valuable structural restraints corresponding to electron-nucleus distances in the ~10-20 Å regime, in solid-state nuclear magnetic resonance (NMR) spectra of proteins containing covalent Cu(2+)-binding tags. Specifically, using protein GB1 K28C-EDTA-Cu(2+) mutant as a model, we show the determination of backbone amide (15)N longitudinal and (1)H transverse PREs within a few hours of experiment time based on proton-detected 2D or 3D correlation spectra recorded with magic-angle spinning frequencies ≥ ~60 kHz for samples containing ~10-50 nanomoles of (2)H,(13)C,(15)N-labeled protein back-exchanged in H2O...
November 17, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29145080/comparing-the-efficacy-of-solid-and-magic-echo-refocusing-sequences-applications-to-1-h-nmr-echo-spectroscopy-of-shale-rock
#14
Gregory S Boutis, Ravinath Kausik
Quantitative evaluation of the solid and viscous components of unconventional shale rock, namely kerogen and bitumen, is important for understanding reservoir quality. Short transverse coherence times, due to strong (1)H-(1)H dipolar interactions, motivates the application of solid state refocusing pulse sequences that allow for investigating components of the free-induction decay that are otherwise obscured by instrumental effects such as probe ringdown. This work reports on static, wide-line (1)H spectroscopy of shale rock and their extracted components, which include kerogen and bitumen, by the application of solid echo and magic echo pulse sequences...
November 3, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29144126/highly-active-carbene-potassium-complexes-for-the-ring-opening-polymerization-of-%C3%AE%C2%B5-caprolactone
#15
Mrinal Bhunia, Gonela Vijaykumar, Debashis Adhikari, Swadhin K Mandal
Herein we report the synthesis of two complexes of potassium employing strongly nucleophilic carbenes, such as cyclic "(alkyl)(amino)carbene (cAAC) and abnormal N-heterocyclic carbene (aNHC). Both complexes are dimeric in the solid state and the two potassium centers are bridged by trimethylsilylamide. In these complexes, the carbene- - -K interaction is predominantly electrostatic in character, which has been probed thoroughly by NBO and AIM analyses. Indeed, the delocalization energy of the cAAC lone pair calculated from the second-order perturbation theory was only 5...
November 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29140279/free-standing-and-self-crosslinkable-hybrid-films-by-core-shell-particle-design-and-processing
#16
Steffen Vowinkel, Stephen Paul, Torsten Gutmann, Markus Gallei
The utilization and preparation of functional hybrid films for optical sensing applications and membranes is of utmost importance. In this work, we report the convenient and scalable preparation of self-crosslinking particle-based films derived by directed self-assembly of alkoxysilane-based cross-linkers as part of a core-shell particle architecture. The synthesis of well-designed monodisperse core-shell particles by emulsion polymerization is the basic prerequisite for subsequent particle processing via the melt-shear organization technique...
November 15, 2017: Nanomaterials
https://www.readbyqxmd.com/read/29136880/enhanced-electrochemical-response-of-carbon-quantum-dot-modified-electrodes
#17
M Algarra, A González-Calabuig, K Radotić, D Mutavdzic, C O Ania, J M Lázaro-Martínez, J Jiménez-Jiménez, E Rodríguez-Castellón, M Del Valle
A glassy carbon electrode (GCE) was surface-modified with carbon quantum dots (CQDs) and applied for the effective enhancement of the electrochemical signal for dopamine and uric acid determination. CQDs were prepared from graphite by a green modification of the Hummers method. They were characterized by FTIR-ATR, XPS, solid-state NMR, fluorescence and Raman spectroscopies. TPD-MS analysis was applied to characterize the functionalization of the surface. The CQDs were assembled on the glassy carbon electrode by adsorption because of the large number of carboxy groups on their surface warrants effective adsorption...
February 1, 2018: Talanta
https://www.readbyqxmd.com/read/29136304/reversible-polymerization-of-adamantane-type-p4n10-10-anions-to-honeycomb-type-p2n5-5-layers-under-high-pressure
#18
Eva-Maria Bertschler, Robin Niklaus, Wolfgang Schnick
The high-pressure polymorph Li5P2N5 of Li10P4N10 (= "2 Li5P2N5") was synthesized by high-pressure/high-temperature reaction of LiPN2 and Li7PN4 or beta-Li10P4N10 at 9 GPa, using the Li3N self-flux method in a Walker-type multianvil assembly. Li5P2N5 is the first lithium nitridophosphate with a layered structure and is made up of corner sharing PN4 tetrahedra forming a corrugated honeycomb-type layer of linked sechser-rings in chair conformation. The arrangement of the P atoms is analogous to that of black phosphorus...
November 14, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29126001/a-robust-heteronuclear-dipolar-recoupling-method-comparable-to-tedor-for-proteins-in-magic-angle-spinning-solid-state-nmr
#19
Zhengfeng Zhang, Jianping Li, Yanke Chen, Huayong Xie, Jun Yang
In this letter, we propose a robust heteronuclear dipolar recoupling method for proteins in magic-angle spinning (MAS) solid-state NMR. This method is as simple, robust and efficient as the well-known TEDOR in the aspect of magnetization transfer between (15)N and (13)C. Deriving from our recent band-selective dual back-to-back pulses (DBP) (Zhang et al., 2016), this method uses new phase-cycling schemes to realize broadband DBP (Bro-DBP). For broadband (15)N-(13)C magnetization transfer (simultaneous (15)N→(13)C' and (15)N→(13)Cα), Bro-DBP has almost the same (15)N→(13)Cα efficiency while offers 30-40% enhancement on (15)N→(13)C' transfer, compared to TEDOR...
October 31, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/29125294/transition-metal-doping-reveals-link-between-electron-t1-reduction-and-13-c-dynamic-nuclear-polarization-efficiency
#20
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
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