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https://www.readbyqxmd.com/read/28089491/satellite-and-central-transitions-selective-1-h-27-al-d-hmqc-experiments-at-very-fast-mas-for-quadrupolar-couplings-determination
#1
Nghia Tuan Duong, Yusuke Nishiyama
Recent study has demonstrated the application of the proton-detected heteronuclear multi-quantum coherence (HMQC) at ultrafast Magic Angle Spinning (MAS) to probe quadrupolar nuclei including (14)N and (35)Cl. In addition, for half-integer quadrupolar nucleus like (35)Cl, the quadrupolar product can be calculated based on the shift difference between the center band of satellite transition (ST) and the central transition (CT) peaks. The applicability of this technique is further investigated on spin I=5/2, namely (27)Al nucleus, and kaolin is chosen as the testing sample...
January 4, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28059506/local-and-global-dynamics-in-klebsiella-pneumoniae-outer-membrane-protein-a-in-lipid-bilayers-probed-at-atomic-resolution
#2
Olivier Saurel, Iordan Orlinov Iordanov, Guillaume Nars, Pascal Demange, Tanguy Le Marchand, Loren B Andreas, Guido Pintacuda, Alain Milon
The role of membrane proteins in cellular mechanism strongly depends on their dynamics and solid-state Magic-Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) is a unique method to exhaustively characterize motions of proteins in a lipid environment. Herein, we make use of advances in 1H-detected MAS NMR to describe the dynamics of the membrane domain of the Outer membrane protein A of Klebsiella pneumoniae (KpOmpA). By measuring 1H-15N dipolar-coupling as well as 15N R1 and R1ρ relaxation rates at fast (60 kHz) MAS and high magnetic field (1 GHz), we were able to describe the motions of the residues of the β-barrel as a collective rocking of low amplitude and of hundreds of nano-seconds time scale...
January 6, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28054096/tuning-the-dipolar-second-order-nonlinear-optical-properties-of-5-%C3%AF-delocalized-donor-1-3-di-2-pyridyl-benzenes-related-cyclometallated-platinum-ii-complexes-and-methylated-salts
#3
Filippo Nisic, Elena Cariati, Alessia Colombo, Claudia Dragonetti, Simona Fantacci, Eleonora Garoni, Elena Lucenti, Stefania Righetto, Dominique Roberto, J A Gareth Williams
The synthesis and characterization of three 5-π-delocalized-donor-1,3-di(2-pyridyl)benzenes is reported along with that of their related cyclometallated platinum(ii) complexes and N,N-dimethylated iodide salts. The second-order nonlinear optical (NLO) properties of all the compounds have been determined by the Electric Field Induced Second Harmonic generation technique, showing how the μβEFISH absolute value of 1,3-di(2-pyridyl)benzenes can be tuned by the nature of the substituent on position 5 of the central benzene ring, and greatly increased by cyclometallation to Pt or by N-methylation...
January 5, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28040572/new-blue-emissive-conjugated-small-molecules-with-low-lying-homo-energy-levels-for-optoelectronic-applications
#4
C Trupthi Devaiah, B Hemavathi, T N Ahipa
Versatile conjugated small molecules bearing cyanopyridone core (CP1-5), composed of various donor/acceptor moieties at position -4 and -6 have been designed, developed and characterized. Their solvatochromic studies were conducted and analyzed using Lippert-Mataga, Kamlet-Taft and Catalan solvent scales and interesting results were obtained. The polarizability/dipolarity of the solvent greatly influenced the spectra. The electrochemical studies were carried out using cyclic voltammetry to calculate the HOMO-LUMO energy levels...
December 23, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/27976673/br%C3%A3-nsted-acid-sites-based-on-penta-coordinated-aluminum-species
#5
Zichun Wang, Yijiao Jiang, Olivier Lafon, Julien Trébosc, Kyung Duk Kim, Catherine Stampfl, Alfons Baiker, Jean-Paul Amoureux, Jun Huang
Zeolites and amorphous silica-alumina (ASA), which both provide Brønsted acid sites (BASs), are the most extensively used solid acid catalysts in the chemical industry. It is widely believed that BASs consist only of tetra-coordinated aluminum sites (Al(IV)) with bridging OH groups in zeolites or nearby silanols on ASA surfaces. Here we report the direct observation in ASA of a new type of BAS based on penta-coordinated aluminum species (Al(V)) by (27)Al-{(1)H} dipolar-mediated correlation two-dimensional NMR experiments at high magnetic field under magic-angle spinning...
December 15, 2016: Nature Communications
https://www.readbyqxmd.com/read/27966496/recent-excitements-in-protein-nmr-large-proteins-and-biologically-relevant-dynamics
#6
Sai Chaitanya Chiliveri, Mandar V Deshmukh
The advent of Transverse Relaxation Optimized SpectroscopY (TROSY) and perdeuteration allowed biomolecular NMR spectroscopists to overcome the size limitation barrier (approx. 20 kDa) in de novo structure determination of proteins. The utility of these techniques was immediately demonstrated on large proteins and protein complexes (e.g. GroELGroES, ClpP protease, Hsp90-p53, 20S proteasome, etc.). Further, recent methodological developments such as Residual Dipolar Couplings and Paramagnetic Relaxation Enhancement allowed accurate measurement of long-range structural restraints...
December 2016: Journal of Biosciences
https://www.readbyqxmd.com/read/27941753/emergent-weyl-excitations-in-systems-of-polar-particles
#7
Sergey V Syzranov, Michael L Wall, Bihui Zhu, Victor Gurarie, Ana Maria Rey
Weyl fermions are massless chiral particles first predicted in 1929 and once thought to describe neutrinos. Although never observed as elementary particles, quasiparticles with Weyl dispersion have recently been experimentally discovered in solid-state systems causing a furore in the research community. Systems with Weyl excitations can display a plethora of fascinating phenomena and offer great potential for improved quantum technologies. Here, we show that Weyl excitations generically exist in three-dimensional systems of dipolar particles with weakly broken time-reversal symmetry (by for example a magnetic field)...
December 12, 2016: Nature Communications
https://www.readbyqxmd.com/read/27941225/the-3d-kasteleyn-transition-in-dipolar-spin-ice-a-numerical-study-with-the-conserved-monopoles-algorithm
#8
M L Baez, R A Borzi
We study the three-dimensional Kasteleyn transition in both nearest neighbours and dipolar spin ice models using an algorithm that conserves the number of excitations. We first limit the interactions range to nearest neighbours to test the method in the presence of a field applied along [Formula: see text], and then focus on the dipolar spin ice model. The effect of dipolar interactions, which is known to be greatly self screened at zero field, is particularly strong near full polarization. It shifts the Kasteleyn transition to lower temperatures, which decreases  ≈0...
February 8, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/27936795/behavior-of-deep-eutectic-solvents-under-external-electric-fields-a-molecular-dynamics-approach
#9
Mert Atilhan, Santiago Aparicio
The properties of selected deep eutectic solvents (DESs) comprising choline chloride as a hydrogen bond acceptor and several types of hydrogen bond donors under static and dynamic external electric fields (EEFs) have been studied in this work using classical molecular dynamics simulations. The effects of field intensities under static conditions and of field frequencies under dynamic conditions were simulated. The response of the fluids to the external fields was analyzed from the changes in dipolar arrangements, intermolecular interaction energies, nanoscopic arrangements, and molecular diffusion...
December 22, 2016: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/27923764/applications-of-deep-eutectic-solvents-in-biotechnology-and-bioengineering-promises-and-challenges
#10
REVIEW
Yves Paul Mbous, Maan Hayyan, Adeeb Hayyan, Won Fen Wong, Mohd Ali Hashim, Chung Yeng Looi
Deep eutectic solvents (DESs) have been touted recently as potential alternatives to ionic liquids (ILs). Although they possess core characteristics that are similar to those of ILs (e.g., low volatility, non-flammability, low melting points, low vapor pressure, dipolar nature, chemical and thermal stability, high solubility, and tuneability), DESs are superior in terms of the availability of raw materials, the ease of storage and synthesis, and the low cost of their starting materials. As such, they have become the subject of intensive research in various sectors, notably the chemical, electrochemical, and biological sectors...
December 3, 2016: Biotechnology Advances
https://www.readbyqxmd.com/read/27917231/magnetotail-energy-dissipation-during-an-auroral-substorm
#11
E V Panov, W Baumjohann, R A Wolf, R Nakamura, V Angelopoulos, J M Weygand, M V Kubyshkina
Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere...
December 2016: Nature Physics
https://www.readbyqxmd.com/read/27911819/programmable-and-reversible-plasmon-mode-engineering
#12
Ankun Yang, Alexander J Hryn, Marc R Bourgeois, Won-Kyu Lee, Jingtian Hu, George C Schatz, Teri W Odom
Plasmonic nanostructures with enhanced localized optical fields as well as narrow linewidths have driven advances in numerous applications. However, the active engineering of ultranarrow resonances across the visible regime-and within a single system-has not yet been demonstrated. This paper describes how aluminum nanoparticle arrays embedded in an elastomeric slab may exhibit high-quality resonances with linewidths as narrow as 3 nm at wavelengths not accessible by conventional plasmonic materials. We exploited stretching to improve and tune simultaneously the optical response of as-fabricated nanoparticle arrays by shifting the diffraction mode relative to single-particle dipolar or quadrupolar resonances...
December 13, 2016: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/27910450/first-order-reversal-curves-forc-analysis-of-individual-magnetic-nanostructures-using-micro-hall-magnetometry
#13
Merlin Pohlit, Paul Eibisch, Maryam Akbari, Fabrizio Porrati, Michael Huth, Jens Müller
Alongside the development of artificially created magnetic nanostructures, micro-Hall magnetometry has proven to be a versatile tool to obtain high-resolution hysteresis loop data and access dynamical properties. Here we explore the application of First Order Reversal Curves (FORC)-a technique well-established in the field of paleomagnetism for studying grain-size and interaction effects in magnetic rocks-to individual and dipolar-coupled arrays of magnetic nanostructures using micro-Hall sensors. A proof-of-principle experiment performed on a macroscopic piece of a floppy disk as a reference sample well known in the literature demonstrates that the FORC diagrams obtained by magnetic stray field measurements using home-built magnetometers are in good agreement with magnetization data obtained by a commercial vibrating sample magnetometer...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27908109/perturbation-of-hydration-layer-in-solvated-proteins-by-external-electric-and-electromagnetic-fields-insights-from-non-equilibrium-molecular-dynamics
#14
Prithwish K Nandi, Zdenek Futera, Niall J English
Given the fundamental role of water in governing the biochemistry of enzymes, and in regulating their wider biological activity (e.g., by local water concentration surrounding biomolecules), the influence of extraneous electric and electromagnetic (e/m) fields thereon is of central relevance to biophysics and, more widely, biology. With the increase in levels of local and atmospheric microwave-frequency radiation present in modern life, as well as other electric-field exposure, the impact upon hydration-water layers surrounding proteins, and biomolecules generally, becomes a particularly pertinent issue...
November 28, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/27906313/experimental-study-on-the-transition-of-plasmonic-resonance-modes-in-double-ring-dimers-by-conductive-junctions-in-the-terahertz-regime
#15
Huifang Zhang, Chun Li, Caihong Zhang, Xueqian Zhang, Jianqiang Gu, Biaobing Jin, Jiaguang Han, Weili Zhang
Plasmonic dimers that made from two subwavelength particles have drawn much attention in the recent years, which are quite promising in local field enhancement, sensing, high frequency conductance probing and electron tunneling. In this work, we experimentally investigate the mode transition effect of different plasmonic resonances in double-ring dimers when introducing conductive junction at the dimer gap in the terahertz regime. Without the junction, the dimers support a single dipolar bonding dimer plasmonic (BDP) mode...
November 28, 2016: Optics Express
https://www.readbyqxmd.com/read/27903227/chemistry-of-heterocyclic-five-and-six-membered-enamino-nitriles-and-enamino-esters
#16
Moustafa Sherief Moustafa, Saleh Mohammed Al-Mousawi, Hesham R El-Seedi, Mohamed Hilmy Elnagdi
Progress in chemistry synthetic methodologies of cyclic enaminonitriles is reported. Due to this progress, it becomes possible to reactivate these molecules toward electrophiles, nucleophiles and as electron rich dienes in 2+3 dipolar additions and in 4+2 cycloadditions reactions. Synthetizing the polyfunctionalized 4H-pyrans and their fused derivatives is a fascinating field with a multitude of biological implications such as antitumor, cardiotonic, hepatoprotective, antihypertensive, antibronchitis, as well antifungal activity...
November 29, 2016: Mini Reviews in Medicinal Chemistry
https://www.readbyqxmd.com/read/27901539/colloidal-molecules-assembled-from-binary-spheres-under-an-ac-electric-field
#17
Kelley Lynch Heatley, Fuduo Ma, Ning Wu
Colloidal particles are envisioned as analogues of atoms and molecules, however they often lack the complexities present in their counterparts. In this work, we report the assembly of colloidal molecules from a binary mixture of polystyrene spheres (1, 1.6, 2, and 4 μm) under an alternating current electric field. The rich family of assembled oligomers typically consists of a large sphere that is closely surrounded by a number of smaller petal particles, driven by the dipolar attraction between large and small particles...
November 30, 2016: Soft Matter
https://www.readbyqxmd.com/read/27897195/arrangement-at-the-nanoscale-effect-on-magnetic-particle-hyperthermia
#18
E Myrovali, N Maniotis, A Makridis, A Terzopoulou, V Ntomprougkidis, K Simeonidis, D Sakellari, O Kalogirou, T Samaras, R Salikhov, M Spasova, M Farle, U Wiedwald, M Angelakeris
In this work, we present the arrangement of Fe3O4 magnetic nanoparticles into 3D linear chains and its effect on magnetic particle hyperthermia efficiency. The alignment has been performed under a 40 mT magnetic field in an agarose gel matrix. Two different sizes of magnetite nanoparticles, 10 and 40 nm, have been examined, exhibiting room temperature superparamagnetic and ferromagnetic behavior, in terms of DC magnetic field, respectively. The chain formation is experimentally visualized by scanning electron microscopy images...
November 29, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27892557/dipolar-molecules-inside-c70-an-electric-field-driven-room-temperature-single-molecule-switch
#19
Cina Foroutan-Nejad, Valery Andrushchenko, Michal Straka
We propose a two-state electric field-driven room-temperature single-molecule switch based on a dipolar molecule enclosed inside ellipsoidal fullerene C70. We show that the two low-energy minima of the molecular dipole inside the C70 cage provide distinguishable molecular states of the system that can be switched by application of an external electric field.
December 7, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27888838/five-decades-of-homonuclear-dipolar-decoupling-in-solid-state-nmr-status-and-outlook
#20
REVIEW
Kaustubh R Mote, Vipin Agarwal, P K Madhu
It has been slightly more than fifty years since the first homonuclear spin decoupling scheme, Lee-Goldburg decoupling, was proposed for removing homonuclear dipolar interactions in solid-state nuclear magnetic resonance. A family of such schemes has made observation of high-resolution NMR spectra of abundant spins possible in various applications in solid state. This review outlines the strategies used in this field and the future prospects of homonuclear spin decoupling in solid-state NMR.
November 2016: Progress in Nuclear Magnetic Resonance Spectroscopy
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