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https://www.readbyqxmd.com/read/28644665/giant-paramagnetism-induced-valley-polarization-of-electrons-in-charge-tunable-monolayer-mose_-2
#1
Patrick Back, Meinrad Sidler, Ovidiu Cotlet, Ajit Srivastava, Naotomo Takemura, Martin Kroner, Atac Imamoğlu
For applications exploiting the valley pseudospin degree of freedom in transition metal dichalcogenide monolayers, efficient preparation of electrons or holes in a single valley is essential. Here, we show that a magnetic field of 7 T leads to a near-complete valley polarization of electrons in a MoSe_{2} monolayer with a density 1.6×10^{12}  cm^{-2}; in the absence of exchange interactions favoring single-valley occupancy, a similar degree of valley polarization would have required a pseudospin g factor of 38...
June 9, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28644466/characterization-of-a-selenocysteine-ligated-p450-compound-i-reveals-direct-link-between-electron-donation-and-reactivity
#2
Elizabeth L Onderko, Alexey Silakov, Timothy H Yosca, Michael T Green
Strong electron-donation from the axial thiolate ligand of cytochrome P450 has been proposed to increase the reactivity of compound I with respect to C-H bond activation. However, it has proven difficult to test this hypothesis, and a direct link between reactivity and electron donation has yet to be established. To make this connection, we have prepared a selenolate-ligated cytochrome P450 compound I intermediate. This isoelectronic perturbation allows for direct comparisons with the wild-type enzyme. Selenium incorporation was achieved using a cysteine auxotrophic Escherichia coli strain...
July 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28644026/pb0-65mn2-85ga3s8-and-pb0-72mn2-84ga2-95se8-two-quaternary-metal-chalcognides-with-open-tunnel-framework-structures-displaying-intense-second-harmonic-generation-responses-and-interesting-magnetic-properties
#3
Molin Zhou, Xingxing Jiang, Yangwu Guo, Zheshuai Lin, Jiyong Yao, Yicheng Wu
By combining different nonlinear optical-active structural chromophores with transition metal Mn into a crystal structure, two novel quaternary metal chalcogenides Pb0.65Mn2.85Ga3S8 (1) and Pb0.72Mn2.84Ga2.95Se8 (2) were successfully synthesized. Compounds 1 and 2 are isostructural, and they represent a new structure type that crystallizes in the space group P6̅ (No. 174) in the hexagonal system. Their structures feature an interesting three-dimensional open-tunnel framework composed of bridged infinite chains with Pb(2+) cations filling in the biggest tunnels...
June 23, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28640289/consensus-structures-of-the-mo-v-sites-of-sulfite-oxidizing-enzymes-derived-from-variable-frequency-pulsed-epr-spectroscopy-isotopic-labelling-and-dft-calculations
#4
John H Enemark
Sulfite-oxidizing enzymes from eukaryotes and prokaryotes have five-coordinate distorted square-pyramidal coordination about the molybdenum atom. The paramagnetic Mo(v) state is easily generated, and over the years four distinct CW EPR spectra have been identified, depending upon enzyme source and the reaction conditions, namely high and low pH (hpH and lpH), phosphate inhibited (Pi) and sulfite (or blocked). Extensive studies of these paramagnetic forms of sulfite-oxidizing enzymes using variable frequency pulsed electron spin echo (ESE) spectroscopy, isotopic labeling and density functional theory (DFT) calculations have led to the consensus structures that are described here...
June 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28640222/albumin-and-hyaluronic-acid-coated-superparamagnetic-iron-oxide-nanoparticles-loaded-with-paclitaxel-for-biomedical-applications
#5
Elena Vismara, Chiara Bongio, Alessia Coletti, Ravit Edelman, Andrea Serafini, Michele Mauri, Roberto Simonutti, Sabrina Bertini, Elena Urso, Yehuda G Assaraf, Yoav D Livney
Super paramagnetic iron oxide nanoparticles (SPION) were augmented by both hyaluronic acid (HA) and bovine serum albumin (BSA), each covalently conjugated to dopamine (DA) enabling their anchoring to the SPION. HA and BSA were found to simultaneously serve as stabilizing polymers of Fe₃O₄·DA-BSA/HA in water. Fe₃O₄·DA-BSA/HA efficiently entrapped and released the hydrophobic cytotoxic drug paclitaxel (PTX). The relative amount of HA and BSA modulates not only the total solubility but also the paramagnetic relaxation properties of the preparation...
June 22, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28639791/insight-into-the-final-step-of-the-supramolecular-buildup-of-eumelanin
#6
Anne Büngeler, Benjamin Hämisch, Klaus Huber, Wolfgang Bremser, Oliver Ingolf Strube
The final step in the supramolecular buildup of eumelanin particles is investigated regarding involved species and mechanism. Time resolved in situ light scattering and scanning electron microscopy reveal an aggregation of particles with narrow size distribution around 40 nm, previously only observed as substructures. These form larger particles with again very uniform size and diameters around 200 nm. Aggregation of each single particle takes only a few minutes to complete, whereas the entire process goes on for at least three hours, partly due to kinetics of the precursors...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28639638/a-combined-optical-and-epr-spectroscopy-study-azobenzene-based-biradicals-as-reversible-molecular-photoswitches
#7
Eva A Jaumann, Sabrina Steinwand, Szabina Klenik, Jörn Plackmeyer, Jan W Bats, Josef Wachtveitl, Thomas F Prisner
Azobenzene compounds are known as versatile examples for photoswitchable systems because of their isomeric cis- and trans-configurations. The switching between these isomers can be reversibly controlled by light excitation. In this study we characterize two members of this class by joining the azobenzene moiety with each two paramagnetic nitroxide spin labels. Two different linkers were chosen to tune the molecular properties. The combined approach using optical and EPR spectroscopy proved the reversibility of photoexcitation and high fatigue resistance...
June 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28636384/role-of-crystal-structure-and-chalcogenide-redox-properties-on-the-oxidative-assembly-of-cadmium-chalcogenide-nanocrystals
#8
Jessica Davis, Aaron M Chalifoux, Stephanie L Brock
Oxidative assembly of metal chalcogenide nanocrystals (NCs) enables formation of 2-D (dense) and 3-D porous structures without the presence of intervening ligands between particles that can moderate transport properties. This route has been demonstrated successful for a range of single component structures including CdQ, PbQ and ZnQ (Q = S, Se, Te). En route to controllable assembly of multicomponent nanostructures, the roles of Q redox properties (2Q2-  Q22- + 2e), responsible for particle crosslinking, and the native structure (cubic zinc blende vs...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28636366/oxygenation-via-c-h-c-c-bond-activation-with-molecular-oxygen
#9
Yu-Feng Liang, Ning Jiao
The selective oxidation of organic molecules is a fundamentally important component of modern synthetic chemistry. In the past decades, direct oxidative C-H and C-C bond functionalization has proved to be one of the most efficient and straightforward methods to synthesize complex products from simple and readily available starting materials. Among these oxidative processes, the use of molecular oxygen as a green and sustainable oxidant has attracted considerable attention because of its highly atom-economical, abundant, and environmentally friendly characteristics...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636359/relativistic-approximations-to-paramagnetic-nmr-chemical-shift-and-shielding-anisotropy-in-transition-metal-systems
#10
Syed Awais Rouf, Jiří Mareš, Juha Vaara
We apply approximate relativistic methods to calculate the magnetic property tensors, i.e., the g-tensor, zero-field splitting (ZFS) tensor (D), and hyperfine coupling (HFC) tensors, for the purpose of constructing paramagnetic nuclear magnetic resonance (pNMR) shielding tensors. The chemical shift and shielding anisotropy are calculated by applying a modern implementation of the classic Kurland-McGarvey theory (J. Magn. Reson. 1970, 2, 286), which formulates the shielding tensor in terms of the g- and HFC tensors obtained for the ground multiplet, in the case of higher than doublet multiplicity defined by the ZFS interaction...
June 21, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28635269/the-reduction-potentials-of-fefe-hydrogenase-accessory-iron-sulfur-clusters-provide-insights-into-the-energetics-of-proton-reduction-catalysis
#11
Jacob H Artz, David W Mulder, Michael W Ratzloff, Carolyn E Lubner, Oleg A Zadvornyy, Axl X LeVan, S Garrett Williams, Michael W W Adams, Anne K Jones, Paul W King, John W Peters
An [FeFe]-hydrogenase from Clostridium pasteurianum, CpI, is a model system for biological H2 activation. In addition to the catalytic H-cluster, CpI contains four accessory iron-sulfur [FeS] clusters in a branched series that transfer electrons to and from the active site. In this work, potentiometric titrations have been employed in combination with electron paramagnetic resonance (EPR) spectroscopy at defined electrochemical potentials to gain insights into the role of the accessory clusters in catalysis...
June 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28633971/manganese-enhanced-magnetic-resonance-imaging-depicts-brain-activity-in-models-of-acute-and-chronic-pain-a-new-window-to-study-experimental-spontaneous-pain
#12
I M Devonshire, J J Burston, L Xu, A Lillywhite, M J Prior, D J G Watson, C M Greenspon, S J Iwabuchi, D P Auer, V Chapman
Application of functional imaging techniques to animal models is vital to understand pain mechanisms, but is often confounded by the need to limit movement artefacts with anaesthesia, and a focus on evoked responses rather than clinically relevant spontaneous pain and related hyperalgesia. The aim of the present study was to investigate the potential of manganese-enhanced magnetic resonance imaging (MEMRI) to measure neural responses during on-going pain that underpins hyperalgesia in pre-clinical models of nociception...
June 17, 2017: NeuroImage
https://www.readbyqxmd.com/read/28633562/advances-in-imaging-brain-metabolism
#13
Fahmeed Hyder, Douglas L Rothman
Metabolism is central to neuroimaging because it can reveal pathways by which neuronal and glial cells use nutrients to fuel their growth and function. We focus on advanced magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) methods used in brain metabolic studies. (17)O-MRS and (31)P-MRS, respectively, provide rates of oxygen use and ATP synthesis inside mitochondria, whereas (19)F-MRS enables measurement of cytosolic glucose metabolism. Calibrated functional MRI (fMRI), an advanced form of fMRI that uses contrast generated by deoxyhemoglobin, provides maps of oxygen use that track neuronal firing across brain regions...
June 21, 2017: Annual Review of Biomedical Engineering
https://www.readbyqxmd.com/read/28631929/-13-c-dynamic-nuclear-polarization-using-a-trimeric-gd-3-complex-as-an-additive
#14
Peter Niedbalski, Christopher Parish, Qing Wang, Andhika Kiswandhi, Zahra Hayati, Likai Song, Lloyd Laporca Lumata
Dissolution dynamic nuclear polarization (DNP) is one of the most successful techniques that resolves the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) by amplifying the signal by several thousand-fold. One way to further improve the DNP signal is the inclusion of trace amounts of lanthanides in DNP samples doped with trityl OX063 free radical as the polarizing agent. In practice, stable monomeric gadolinium complexes such as Gd-DOTA or Gd-HP-DO3A are used as beneficial additives in DNP samples, further boosting the DNP-enhanced solid-state 13C polarization by a factor of 2 or 3...
June 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28631141/cell-labeling-with-magneto-endosymbionts-and-the-dissection-of-the-subcellular-location-fate-and-host-cell-interactions
#15
Kayla R Lee, Abdul Wakeel, Papia Chakraborty, Chandler S Foote, Lauren Kajiura, Joyce C Barrozo, Andrea C Chan, Alexey V Bazarov, Ryan Spitler, Peter M Kutny, Jim M Denegre, Rob A Taft, Joachim Seemann, Bradley W Rice, Christopher H Contag, Brian K Rutt, Caleb B Bell
PURPOSE: The purposes of this study are to characterize magneto-endosymbiont (ME) labeling of mammalian cells and to discern the subcellular fate of these living contrast agents. MEs are novel magnetic resonance imaging (MRI) contrast agents that are being used for cell tracking studies. Understanding the fate of MEs in host cells is valuable for designing in vivo cell tracking experiments. PROCEDURES: The ME's surface epitopes, contrast-producing paramagnetic magnetosomal iron, and genome were studied using immunocytochemistry (ICC), Fe and MRI contrast measurements, and quantitative polymerase chain reaction (qPCR), respectively...
June 19, 2017: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/28630417/ultrarapid-measurement-of-diagnostic-antibodies-by-magnetic-capture-of-immune-complexes
#16
Peter D Burbelo, Sreenivasulu Gunti, Jason M Keller, Caryn G Morse, Steven G Deeks, Michail S Lionakis, Amit Kapoor, Qingxue Li, Jeffrey I Cohen, Abner L Notkins, Ilias Alevizos
Rapid point-of-care, antibody-based testing is not currently available for the diagnosis of most autoimmune and infectious diseases. Here we report a simple, robust and ultrafast fluid-phase immunocapture method for clinical measurements of antibody levels. This method employs neodymium magnetic sticks that capture protein A/G-coated paramagnetic beads bound to antibody-luciferase-labeled antigen complexes. We demonstrate the ability to effectively measure specific antibody levels in serum samples from patients with varied infectious or autoimmune disorders, and in the case of Sjögren's syndrome directly in saliva, requiring about a minute per assay...
June 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28629281/noninvasive-quantitative-assessment-of-hepatic-steatosis-by-proton-magnetic-resonance-spectroscopy-among-adult-patients-receiving-home-parenteral-nutrition
#17
Angelique Huijbers, Geert Wanten, Helena Maria Dekker, Marinette van der Graaf
BACKGROUND: Intestinal failure-associated liver disease is a frequent complication in patients with chronic intestinal failure (CIF), with steatosis as a dominant feature in adults. Proton magnetic resonance spectroscopy (1H-MRS) is a noninvasive method to quantify liver fat content (LFC). In this study, LFC was assessed with 1H-MRS, taking into account the possible accumulation of paramagnetic components of home parenteral nutrition (HPN) that may disturb these measurements. METHODS: LFC was measured in 15 adult CIF patients who had been receiving HPN for >6 months...
June 1, 2017: JPEN. Journal of Parenteral and Enteral Nutrition
https://www.readbyqxmd.com/read/28628261/studying-the-conformation-of-a-receptor-tyrosine-kinase-in-solution-by-inhibitor-based-spin-labeling
#18
Dongsheng M Yin, Jeffrey S Hannam, Anton Schmitz, Olav Schiemann, Gregor Hagelueken, Michael Famulok
The synthesis of a spin label based on PD168393, a covalent inhibitor of a major anticancer drug target, the epidermal growth factor receptor (EGFR), is reported. The label facilitates the analysis of the EGFR structure in solution by pulsed electron paramagnetic resonance (EPR) spectroscopy. For various EGFR constructs, including near-full-length EGFR, we determined defined distance distributions between the two spin labels bound to the ATP binding sites of the EGFR dimer. The distances are in excellent agreement with an asymmetric dimer of the EGFR...
June 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28627400/improved-tacrolimus-skin-permeation-by-co-encapsulation-with-clobetasol-in-lipid-nanoparticles-study-of-drug-effects-in-lipid-matrix-by-electron-paramagnetic-resonance
#19
Lígia Marquez Andrade, Luis Antônio Dantas Silva, Anna Paula Krawczyk-Santos, Isabella Cristina de S M Amorim, Priscila Bianca Rodrigues da Rocha, Eliana Martins Lima, Jorge Luiz V Anjos, Antonio Alonso, Ricardo Neves Marreto, Stephânia Fleury Taveira
Combined therapy with corticosteroids and immunosuppressant-loaded nanostructured lipid carriers (NLC) could be useful in the treatment of skin diseases. To circumvent NLC loading capacity problems, loaded drugs should have different physicochemical characteristics, such as tacrolimus (TAC) and clobetasol (CLO). Therefore, in the present study, TAC and CLO were encapsulated in NLC (TAC-NLC, CLO-NLC and TAC+CLO-NLC), coated or otherwise with chitosan. Electron paramagnetic resonance (EPR) spectroscopy of different spin labels was used to investigate the impact of drug and oil incorporation on the lipid dynamic behavior of the lipid matrices...
June 13, 2017: European Journal of Pharmaceutics and Biopharmaceutics
https://www.readbyqxmd.com/read/28627037/quantitative-gd-dota-uptake-from-cerebrospinal-fluid-into-rat-brain-using-3d-vfa-spgr-at-9-4t
#20
Hedok Lee, Kristian Mortensen, Simon Sanggaard, Palle Koch, Hans Brunner, Bjørn Quistorff, Maiken Nedergaard, Helene Benveniste
PURPOSE: We propose a quantitative technique to assess solute uptake into the brain parenchyma based on dynamic contrast-enhanced MRI (DCE-MRI). With this approach, a small molecular weight paramagnetic contrast agent (Gd-DOTA) is infused in the cerebral spinal fluid (CSF) and whole brain gadolinium concentration maps are derived. METHODS: We implemented a 3D variable flip angle spoiled gradient echo (VFA-SPGR) longitudinal relaxation time (T1) technique, the accuracy of which was cross-validated by way of inversion recovery rapid acquisition with relaxation enhancement (IR-RARE) using phantoms...
June 19, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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