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Solid-state NMR

Henry H Wilson, Connor A Koellner, Zain M Hannan, Caroline B Endy, Mark W Bezpalko, Nicholas A Piro, W Scott Kassel, Matthew D Sonntag, Christopher R Graves
The synthesis and full characterization of a series of neutral ligand α-diimine complexes of aluminum are reported. The compounds [Al(LAr )2 Cl2 )][AlCl4 ] [LAr = N, N'-bis(4-R-C6 H4 )-2,3-dimethyl-1,4-diazabutadiene] are structurally analogous, as determined by multinuclear NMR spectroscopy and solid-state X-ray diffraction, across a range of electron-donating [R = Me (2),t Bu (3), OMe (4), and NMe2 (5)] and electron-withdrawing [R = Cl (6), CF3 (7), and NO2 (8)] substituents in the aryl side arm of the ligand...
March 19, 2018: Inorganic Chemistry
Ken Xuan Wei, Chandrasekhar Ramanathan, Paola Cappellaro
Characterizing out-of-equilibrium many-body dynamics is a complex but crucial task for quantum applications and understanding fundamental phenomena. A central question is the role of localization in quenching thermalization in many-body systems and whether such localization survives in the presence of interactions. Probing this question in real systems necessitates the development of an experimentally measurable metric that can distinguish between different types of localization. While it is known that the localized phase of interacting systems [many-body localization (MBL)] exhibits a long-time logarithmic growth in entanglement entropy that distinguishes it from the noninteracting case of Anderson localization (AL), entanglement entropy is difficult to measure experimentally...
February 16, 2018: Physical Review Letters
Lauriane Lecoq, Shishan Wang, Thomas Wiegand, Stéphane Bressanelli, Michael Nassal, Beat H Meier, Anja Böckmann
The hepatitis B virus (HBV) icosahedral nucleocapsid is assembled from 240 chemically identical core protein molecules and, structurally, comprises four groups of symmetrically nonequivalent subunits. We show here that this asymmetry is reflected in solid-state NMR spectra of the capsids in which peak splitting is observed for a subset of residues. We compare this information to dihedral angle variations from available 3D structures, and also to computational predictions of dynamic domains and molecular hinges...
March 15, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
David R Glenn, Dominik B Bucher, Junghyun Lee, Mikhail D Lukin, Hongkun Park, Ronald L Walsworth
Quantum systems that consist of solid-state electronic spins can be sensitive detectors of nuclear magnetic resonance (NMR) signals, particularly from very small samples. For example, nitrogen-vacancy centres in diamond have been used to record NMR signals from nanometre-scale samples, with sensitivity sufficient to detect the magnetic field produced by a single protein. However, the best reported spectral resolution for NMR of molecules using nitrogen-vacancy centres is about 100 hertz. This is insufficient to resolve the key spectral identifiers of molecular structure that are critical to NMR applications in chemistry, structural biology and materials research, such as scalar couplings (which require a resolution of less than ten hertz) and small chemical shifts (which require a resolution of around one part per million of the nuclear Larmor frequency)...
March 14, 2018: Nature
Fatimah Alahmari, Bambar Davaasuren, Abdul-Hamid Emwas, Alexander Rothenberger
The new thioaluminogermanate Na(AlS2 )(GeS2 )4 (1) was successfully synthesized by a direct combination reaction. The compound crystallizes in the monoclinic space group P21 / n (no. 14) with unit cell parameters a = 6.803(3) Å, b = 38.207(2) Å, c = 6.947(4) Å, and β = 119.17(3)°. The crystal structure is composed of a [(AlS2 )(GeS2 )4 ]- 3D polyanionic network, in which Al and Ge atoms share the atomic positions and Na cations occupy the channels and voids formed by the connection of (Ge/Al)S4 tetrahedra...
March 14, 2018: Inorganic Chemistry
Arisu Shigeta, Shota Ito, Rina Kaneko, Sahoko Tomida, Keiichi Inoue, Hideki Kandori, Izuru Kawamura
Krokinobacter rhodopsin 2 (KR2), a light-driven Na+ pump, is a dual-functional protein, pumping protons in the absence of Na+ when K+ or larger alkali metal ions are present. A specific mutation in helix A near the extracellular Na+ binding site, H30A, eliminates its proton pumping ability. We induced structural changes in H30A by altering the alkali metal ion bound at the extracellular binding site, and observed a strong electrostatic interaction between the Schiff base and counterion and torsion around the Schiff base as revealed by solid-state nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies...
March 14, 2018: Physical Chemistry Chemical Physics: PCCP
Shixiang Dai, Ling Zhao, Ying Teng, Xiaomi Wang, Wenjie Ren
The fate and transport of polychlorinated biphenyls (PCBs), a class of persistent organic compounds, in soils was markedly affected by their sorption/desorption on soil organic matters (SOM) due to high hydrophobicity of PCBs. Humic acid (HA), an important fraction of SOM, has no steady composition and microstructure from different origins, resulting in their diverse sorption capacity. Therefore, the effect of composition and microstructure of HA on sorption of 3,3',4,4'-tetrachlorobiphenyl (PCB77) was investigated in this study...
March 12, 2018: Environmental Science and Pollution Research International
J J Wittmann, T V Can, M Eckardt, W Harneit, R G Griffin, B Corzilius
The electronic g factor carries highly useful information about the electronic structure of a paramagnetic species, such as spin-orbit coupling and dia- or paramagnetic (de-)shielding due to local fields of surrounding electron pairs. However, in many cases, a near "spin-only" case is observed, in particular for light elements, necessitating accurate and precise measurement of the g factors. Such measurement is typically impeded by a "chicken and egg situation": internal or external reference standards are used for relative comparison of electron paramagnetic resonance (EPR) Larmor frequencies...
March 6, 2018: Journal of Magnetic Resonance
Maria Zakharova, Nima Masoumifard, Yimu Hu, Jongho Han, Freddy Kleitz, Frédéric-Georges Fontaine
Conventional amines and phosphines, such as diethylenetriamine, diphenylpropylphosphine, triethylamine, and tetramethylpyperidine, were grafted or impregnated on the surface of metalated SBA-15 materials, such as Ti-, Al-, Zr-SBA-15, to generate air-stable solid-supported Lewis acid-base pairs. The Lewis acidity of the metalated materials before and after the introduction of Lewis bases was verified by means of pyridine adsorption-FTIR technique. Detailed characterization of the materials was achieved by solid state 13C, 31P and 1H MAS NMR spectroscopy, low temperature N2 physisorption, XPS and EDX mapping analyses...
March 9, 2018: ACS Applied Materials & Interfaces
Albert A Smith, Emilie Testori, Riccardo Cadalbert, Beat H Meier, Matthias Ernst
In our recent publication (Smith et al., J Biomol NMR 65:171-191, 2016) on the dynamics of HET-s(218-289), we reported on page 176, that calculation of solid-state NMR R1ρ rate constants using analytical equations based on Redfield theory (Kurbanov et al., J Chem Phys 135:184104:184101-184109, 2011) failed when the correlation time of motion becomes too long.
March 8, 2018: Journal of Biomolecular NMR
Pegah Khanjani, Alistair William Thomas King, Gabriel J Partl, Leena-Sisko Johansson, Mauri A Kostiainen, Robin H A Ras
The development of economically and ecologically viable strategies for superhydrophobization offers a vast variety of interesting applications in self-cleaning surfaces. Examples include packaging materials, textiles, outdoor clothing, and microfluidic devices. In this work, we produced superhydrophobic paper by spin-coating a dispersion of nanostructured fluorinated cellulose esters. Modification of cellulose nanocrystals (CNCs) was accomplished using 2H,2H,3H,3H-perfluorononanoyl chloride and 2H,2H,3H,3H-perfluoroundecanoyl chloride, which are well-known for their ability to reduce surface energy...
March 8, 2018: ACS Applied Materials & Interfaces
Ming Xiao, Wei Chen, Weiyao Li, Jiuzhou Zhao, You-Lee Hong, Yusuke Nishiyama, Toshikazu Miyoshi, Matthew D Shawkey, Ali Dhinojwala
Eumelanin is one of the most ubiquitous pigments in living organisms and plays an important role in coloration and UV protection. Because eumelanin is highly cross-linked and insoluble in solvents, the chemical structure is still not completely known. In this study, we used atomic force microscopy, X-ray photoelectron spectroscopy and solid-state nuclear magnetic resonance (NMR) to compare intact eumelanosomes (pigment granules mostly made of eumelanin) from four phylogentically distant species: cuttlefish ( Sepia officinalis ) inks, black fish crow ( Corvus ossifragus ) feathers, iridescent wild turkey ( Melleagris gallopavo ) feathers and black human hair...
March 2018: Journal of the Royal Society, Interface
Rupal Gupta, John Stringer, Jochem Struppe, Dieter Rehder, Tatyana Polenova
Electronic and structural properties of short-lived metal-peroxido complexes, which are key intermediates in many enzymatic reactions, are not fully understood. While detected in various enzymes, their catalytic properties remain elusive because of their transient nature, making them difficult to study spectroscopically. We integrated17 O solid-state NMR and density functional theory (DFT) to directly detect and characterize the peroxido ligand in a bioinorganic V(V) complex mimicking intermediates non-heme vanadium haloperoxidases...
February 19, 2018: Solid State Nuclear Magnetic Resonance
Martha C Mayorquín-Torres, Abraham Colin-Molina, Salvador Perez-Estrada, Annia Galano, Braulio Rodríguez-Molina, Martin A Iglesias-Arteaga
A novel steroid molecular rotor was obtained in four steps from the naturally occurring spirostane sapogenin diosgenin. The structural and dynamic characterization was carried out by solution NMR, VT X-ray diffraction, solid state 13C CPMAS and solid state 2H NMR experiments. They allowed the identification of a fast dynamic process with a frequency of 14 MHz at room temperature, featuring a barrier to rotation Ea = 7.87 kcal mol-1. The gathered experimental evidence indicated the presence of a hydrogen bond that becomes stronger as the temperature lowers...
March 5, 2018: Journal of Organic Chemistry
Robert Tycko
No abstract text is available yet for this article.
March 2018: Journal of Magnetic Resonance
Hazuki Yonashiro, Kenjirou Higashi, Chikako Morikawa, Keisuke Ueda, Tsutomu Itoh, Masataka Ito, Hyuma Masu, Shuji Noguchi, Kunikazu Moribe
The morphology and stability of amorphous nanoparticles of glibenclamide (GLB) prepared by the antisolvent method using different methods of adding hypromellose (HPMC) were evaluated. Nano-A was prepared by the injection of a dimethyl sulfoxide (DMSO) solution of GLB into the HPMC solution, whereas nano-B was obtained by the injection of a DMSO solution of GLB and HPMC into water. Cryogenic transmission electron microscopy, field-emission scanning electron microscopy, and field-emission transmission electron microscopy including energy dispersive X-ray spectrometry revealed that the particles of the nano-A and nano-B samples are hollow spheres and non-spherical nanoparticles, respectively...
March 5, 2018: Molecular Pharmaceutics
James Tolchard, Manoj Kumar Pandey, Mélanie Berbon, Abdelmajid Noubhani, Sven J Saupe, Yusuke Nishiyama, Birgit Habenstein, Antoine Loquet
We present a new solid-state NMR proton-detected three-dimensional experiment dedicated to the observation of protein proton side chain resonances in nano-liter volumes. The experiment takes advantage of very fast magic angle spinning and double quantum 13C-13C transfer to establish efficient (H)CCH correlations detected on side chain protons. Our approach is demonstrated on the HET-s prion domain in its functional amyloid fibrillar form, fully protonated, with a sample amount of less than 500 µg using a MAS frequency of 70 kHz...
March 3, 2018: Journal of Biomolecular NMR
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
Sarah E D Nelson, Kim N Ha, Tata Gopinath, Mara H Exline, Alessandro Mascioni, David D Thomas, Gianluigi Veglia
Approximately, 70% of the Ca2+ ion transport into the sarcoplasmic reticulum is catalyzed by the sarcoplasmic reticulum Ca2+ -ATPase (SERCA), whose activity is endogenously regulated by phospholamban (PLN). PLN comprises a TM inhibitory region and a cytoplasmic regulatory region that harbors a consensus sequence for cAMP-dependent protein kinase (PKA). The inhibitory region binds the ATPase, reducing its apparent Ca2+ binding affinity. β-adrenergic stimulation activates PKA, which phosphorylates PLN at Ser 16, reversing its inhibitory function...
March 1, 2018: Biochimica et Biophysica Acta
Shu Y Liao, Myungwoon Lee, Mei Hong
Many membrane proteins sense and induce membrane curvature for function, but structural information about how proteins modulate their structures to cause membrane curvature is sparse. We review our recent solid-state NMR studies of two virus membrane proteins whose conformational equilibrium is tightly coupled to membrane curvature. The influenza M2 proton channel has a drug-binding site in the transmembrane (TM) pore. Previous chemical shift data indicated that this pore-binding site is lost in an M2 construct that contains the TM domain and a curvature-inducing amphipathic helix...
February 28, 2018: Journal of Structural Biology
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