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https://www.readbyqxmd.com/read/29322123/dehydrogenation-of-dimethylamine-borane-mediated-by-group-1-pincer-complexes
#1
Roberto Nolla-Saltiel, Ana M Geer, William Lewis, Alexander J Blake, Deborah L Kays
Group 1 salts containing carbazolido NNN pincer ligands are precatalysts for the dehydrogenation of Me2NH·BH3. NMR monitoring and DOSY studies show a heavy dependence on the metal and solvent, allowing in some cases selective formation of dehydrogenation products consistent with hydrogen liberation.
January 11, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29278508/are-keggin-s-poms-charged-nano-colloids-or-multicharged-anions
#2
Alla Malinenko, Alban Jonchere, Luc Girard, Sandra Parrès-Maynadié, Olivier Diat, Pierre Bauduin
Owing to their multiple charges and their nanometric size polyoxometalates (POMs) are at the frontier between ions and charged colloids. We investigated here the effect of POM-POM electrostatics repulsions on their self-diffusion in water by varying POM and supporting salt concentrations. The self-diffusion coefficients of two Keggin's POMs: silicotungstate (SiW4-) and phosphotungstate (PW3-) were determined by dynamic light scattering (DLS) and DOSY 1H/31P NMR whereas POM-POM electrostatic repulsions were investigated by the determination of the static structure factors using small angle X-ray scattering (SAXS)...
December 26, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29245075/evidence-of-coexisting-microemulsion-droplets-in-oil-in-water-emulsions-revealed-by-2d-dosy-1h-nmr
#3
Tarek S Awad, Dalal Asker, Laurence S Romsted
Optimizing the macroscopic properties, shelf-life and stability of emulsion products requires a better understanding of the microstructural characteristics such as the type (nano, micro and macro) and the relative distribution of components (i.e., oil and surfactant) within the emulsion droplets. We used Diffusion-Ordered NMR Spectroscopy (DOSY NMR) to evaluate these characteristics in model oil-in-water emulsion containing Tween 80 and medium chain triglycerides (MCT). At low MCT concentrations, the solutions were transparent but from 1 to 5 wt% MCT, they became translucent then opaque...
December 7, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/29193969/synthesis-and-study-at-a-solid-liquid-interface-of-porphyrin-dimers-linked-by-metal-ions
#4
Mary-Ambre Carvalho, Hervé Dekkiche, Lydia Karmazin, Fabien Sanchez, Bruno Vincent, Masatoshi Kanesato, Yoshihiro Kikkawa, Romain Ruppert
Several porphyrin dimers linked by metal ions were prepared. One trimeric compound was also isolated and one porphyrin dimer linked by palladium(II) could be structurally characterized. In solution, the size of the new compounds was estimated by DOSY NMR techniques. These compounds all contained long aliphatic chains (O-C12H25), which were used to assemble them at a highly oriented pyrolytic graphite (HOPG)/liquid interface. The highly ordered arrays were visualized by scanning tunneling microscopy (STM).
December 1, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29152789/automatic-differential-analysis-of-nmr-experiments-in-complex-samples
#5
Laure Margueritte, Petar Markov, Lionel Chiron, Jean-Philippe Starck, Catherine Vonthron-Sã nà Cheau, Mã Lanie Bourjot, Marc-Andrà Delsuc
Liquid state NMR is a powerful tool for the analysis of complex mixtures of unknown molecules. This capacity has been used in many analytical approaches: metabolomics, identification of active compounds in natural extracts, characterization of species, and such studies require the acquisition of many diverse NMR measurements on series of samples. While acquisition can easily be performed automatically, the number of NMR experiments involved in these studies increases very rapidly and this data avalanche requires to resort to automatic processing and analysis...
November 20, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/29143029/triphenylsulfonium-topophotochemistry
#6
E Despagnet-Ayoub, W W Kramer, W Sattler, A Sattler, P J LaBeaume, J W Thackeray, J F Cameron, T Cardolaccia, A A Rachford, J R Winkler, H B Gray
The products from the 193 nm irradiation of triphenylsulfonium nonaflate (TPS) embedded in a poly(methyl methacrylate) (PMMA) film have been characterized. The analysis of the photoproduct formation was performed using chromatographic techniques including HPLC, GPC and GC-MS as well as UV-vis and NMR spectroscopic methods. Two previously unreported TPS photoproducts, triphenylene and dibenzothiophene, were detected; additionally, GPC and DOSY-NMR spectroscopic analyses after irradiation suggested that TPS fragments had been incorporated into the polymer film...
November 16, 2017: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/29124821/ring-chain-morphology-control-in-overall-neutral-internally-ion-paired-supramolecular-polymers
#7
Nadia Manganaro, Ilenia Pisagatti, Anna Notti, Andrea Pappalardo, Salvatore Patanè, Norberto Micali, Valentina Villari, Melchiorre F Parisi, Giuseppe Gattuso
The self-assembly of internally-ion-paired neutral AA/BB-type supramolecular polymers composed of complementary di-ionizable homoditopic pairs of monomers is reported. Host-to-guest double proton transfer mediates the recognition between bis-calix[5]arene-dicarboxylic acids and α,ω-diaminoalkanes, yielding cyclic, doughnut-shaped assemblies whose morphology (i.e., cyclic vs. linear) can be controlled by means of external chemical stimuli. The behavior of these intriguing aggregates both in solution and on surface was investigated by a combination of 1H and DOSY NMR, light scattering and AFM techniques...
November 10, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29112901/novel-method-for-the-determination-of-average-molecular-weight-of-natural-polymers-based-on-2d-dosy-nmr-and-chemometrics-example-of-heparin
#8
Yulia B Monakhova, Bernd W K Diehl, Tung X Do, Margit Schulze, Steffen Witzleben
Apart from the characterization of impurities, the full characterization of heparin and low molecular weight heparin (LMWH) also requires the determination of average molecular weight, which is closely related to the pharmaceutical properties of anticoagulant drugs. To determine average molecular weight of these animal-derived polymer products, partial least squares regression (PLS) was utilized for modelling of diffused-ordered spectroscopy NMR data (DOSY) of a representative set of heparin (n=32) and LMWH (n=30) samples...
November 4, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/29112387/aggregates-of-defined-stereochemical-scaffolds-a-study-in-solution-of-a-zinc-ii-schiff-base-complex-derived-from-the-enantiopure-trans-1-2-cyclopentanediamine
#9
Ivan Pietro Oliveri, Giuseppe Forte, Giuseppe Consiglio, Salvatore Failla, Santo Di Bella
Molecular aggregation of bis(salicylaldiminato) Zn(II) Schiff base, ZnL, complexes is a topic of current interest. In this paper, we report a novel complex derived from the enantiopure trans-1,2-cyclopentanediamine, (R)-1, in order to probe the effect of the defined stereochemistry on its coordination geometry and aggregation properties, through detailed (1)H NMR, DOSY NMR, UV/vis, and circular dichroism spectroscopic studies and accurate DFT calculations. This complex shows several peculiarities in solution, behaving very differently from ZnL complexes and more importantly from the related trans-1,2-diaminocyclohexane derivative...
November 7, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29111065/complexes-between-methyltestosterone-and-%C3%AE-cyclodextrin-for-application-in-aquaculture-production
#10
Lucas Bragança de Carvalho, Kepa Koldo Burusco, Carlos Jaime, Tiago Venâncio, Aline Ferreira Souza de Carvalho, Luis David Solis Murgas, Luciana de Matos Alves Pinto
The inclusion complexes between 17-α-methyltestosterone (MT) and β-cyclodextrin (bCD) were prepared and characterized in dissolution and solid phase. The complex promoted a sixfold increment in solubility of the hormone. It has a limited solubility and stoichiometry of 2:1 (bCD:MT) determined by DSC, NMR and solubility experiments, the association constant Ka=2846Lmol(-1) and complex fraction of 76% (assessed by DOSY-NMR, in (1:3) DMSO/D2O). The association constant obtained in water by the solubility isotherms is 7540Lmol(-1)...
January 1, 2018: Carbohydrate Polymers
https://www.readbyqxmd.com/read/29074350/effects-of-charge-and-hydrophobicity-on-the-oligomerization-of-peptides-derived-from-iapp
#11
Yilin Wang, Nicholas L Truex, Ngoc D P Vo, James S Nowick
Changes in pH resulting in modifications of charge can dramatically alter the folding and interaction of proteins. This article probes the effects of charge and hydrophobicity on the oligomerization of macrocyclic β-sheet peptides derived from residues 11-17 of IAPP (RLANFLV). Previous studies have shown that a macrocyclic β-sheet peptide containing this IAPP sequence (peptide 1Arg) does not form oligomers in aqueous solution at low millimolar concentrations. Replacing arginine with the uncharged isostere citrulline generates a homologue (peptide 1Cit) that forms a tetramer consisting of a sandwich of hydrogen-bonded dimers...
October 5, 2017: Bioorganic & Medicinal Chemistry
https://www.readbyqxmd.com/read/29065692/diffusion-ordered-nuclear-magnetic-resonance-spectroscopy-dosy-nmr-a-novel-tool-for-identification-of-phosphorus-compounds-in-soil-extracts
#12
Liming Wang, Wulf Amelung, Sabine Willbold
Liquid-state, one-dimension (31)P nuclear magnetic resonance spectroscopy (NMR) has greatly advanced our understanding of the composition of organic phosphorus in the environment. However, the correct assignment of signals is complicated by overlapping and shifting signals in different types of soils. We applied therefore for the first time diffusion-ordered spectroscopy (DOSY) to soil extracts, allowing us to separate phosphorus components in the second domain based on their translational diffusion coefficients...
November 7, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/29052357/critical-sized-full-thickness-skin-defect-regeneration-using-ovine-small-intestinal-submucosa-with-or-without-mesenchymal-stem-cells-in-rat-model
#13
Morteza Rashtbar, Jamshid Hadjati, Jafar Ai, Sadegh Shirian, Issa Jahanzad, Mahmoud Azami, Shiva Asadpuor, Esmaeil Sadroddiny
Decellularized extracellular matrices (ECM) based materials are routinely used for a variety of clinical applications. Hereof, in vivo application of decellularized ovine small intestinal submucosal (DOSIS) layer as, a scaffold is yet to be investigated. In this study, the effectiveness of the DOSIS scaffold, with or without rat bone marrow mesenchymal stem cells (BM-MSCs), in full-thickness wound healing of critical-sized defect was experimentally studied in a rat model. The experimental groups included; group I (control), group II (DOSIS), and group III (BM-MSCs-seeded DOSIS)...
October 20, 2017: Journal of Biomedical Materials Research. Part B, Applied Biomaterials
https://www.readbyqxmd.com/read/29048381/self-assembly-with-2-6-bis-1-pyridin-4-ylmethyl-1h-1-2-3-triazol-4-yl-pyridine-silver-i-and-iron-ii-complexes
#14
Daniel A W Ross, Dan Preston, James D Crowley
A new "click" ligand, 2,6-bis(1-(pyridin-4-ylmethyl)-1H-1,2,3-triazol-4-yl)pyridine (L) featuring a tridentate 2,6-bis(1,2,3-triazol-4-yl)pyridine (tripy) pocket and two pyridyl (py) units was synthesized in modest yield (42%) using the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The coordination chemistry of the ligand with silver(I) and iron(II) ions was examined using a battery of solution (¹H and DOSY (diffusion ordered spectroscopy) nuclear magnetic resonance (NMR), infrared and absorption spectroscopies, high-resolution electrospray ionization mass spectrometry (HR-ESI-MS)), and solid state (X-ray crystallography, elemental analysis) techniques...
October 19, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29044341/the-use-of-antimicrobials-in-septic-patients-with-acute-kidney-injury
#15
Fernanda Moreira de Freitas, Welder Zamoner, Durval Sampaio de Souza Garms, Mariele Gobo de Oliveira, André Luis Balbi, Daniela Ponce
Sepsis is the most common cause of death in critically ill patients and it may be associated with multiorgan failure, including acute kidney injury (AKI). This situation can require acute renal support and increase mortality. Therefore, it is essential to administrate antimicrobials in dosis to achieve adequate serum levels, preventing overdosis and drug toxicity or underdosing and risk for resistance to antibiotics and higher mortality. To date, there aren't validated guidelines on antibiotic dosis adjustment in septic patients with AKI and the recommendations are extrapolated from studies conducted in non-critical patients with chronic kidney disease in end stage receiving chronic renal replacement therapy...
July 2017: Jornal Brasileiro de Nefrologia: ʹorgão Oficial de Sociedades Brasileira e Latino-Americana de Nefrologia
https://www.readbyqxmd.com/read/29035038/dynamics-and-morphology-of-nanoparticle-linked-polymers-elucidated-by-nuclear-magnetic-resonance
#16
Yongqian Zhang, Charles G Fry, Joel A Pedersen, Robert J Hamers
Nanoparticles are frequently modified with polymer layers to control their physical and chemical properties, but little is understood about the morphology and dynamics of these polymer layers. We report here an NMR-based investigation of a model polymer-modified nanoparticle, using multiple NMR techniques including (1)H NMR, diffusion-ordered spectroscopy (DOSY), total correlation spectroscopy (TOCSY), and T2 relaxometry to characterize the dynamics of the nanoparticle-polymer interface. Using 5 nm detonation nanodiamond covalently linked to poly(allylamine) hydrochloride as a model system, we demonstrate the use of NMR to distinguish between free and bound polymer and to characterize the degree to which the segments of the nanoparticle-wrapping polymer are mobile (loops and tails) versus immobile (trains)...
November 7, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/29027961/dosis-facit-sanitatem-concentration-dependent-effects-of-resveratrol-on-mitochondria
#17
REVIEW
Corina T Madreiter-Sokolowski, Armin A Sokolowski, Wolfgang F Graier
The naturally occurring polyphenol, resveratrol (RSV), is known for a broad range of actions. These include a positive impact on lifespan and health, but also pro-apoptotic anti-cancer properties. Interestingly, cell culture experiments have revealed a strong impact of RSV on mitochondrial function. The compound was demonstrated to affect mitochondrial respiration, structure and mass of mitochondria as well as mitochondrial membrane potential and, ultimately, mitochondria-associated cell death pathways. Notably, the mitochondrial effects of RSV show a very strict and remarkable concentration dependency: At low concentrations, RSV (<50 μM) fosters cellular antioxidant defense mechanisms, activates AMP-activated protein kinase (AMPK)- and sirtuin 1 (SIRT1)-linked pathways and enhances mitochondrial network formation...
October 13, 2017: Nutrients
https://www.readbyqxmd.com/read/28991469/non-metal-catalyzed-heterodehydrocoupling-of-phosphines-and-hydrosilanes-mechanistic-studies-of-b-c6f5-3-mediated-formation-of-p-si-bonds
#18
Lipeng Wu, Saurabh S Chitnis, Haijun Jiao, Vincent T Annibale, Ian Manners
Non-metal-catalyzed heterodehydrocoupling of primary and secondary phosphines (R(1)R(2)PH, R(2) = H or R(1)) with hydrosilanes (R(3)R(4)R(5)SiH, R(4), R(5) = H or R(3)) to produce synthetically useful silylphosphines (R(1)R(2)P-SiR(3)R(4)R(5)) has been achieved using B(C6F5)3 as the catalyst (10 mol %, 100 °C). Kinetic studies demonstrated that the reaction is first-order in hydrosilane and B(C6F5)3 but zero-order in phosphine. Control experiments, DFT calculations, and DOSY NMR studies suggest that a R(1)R(2)HP·B(C6F5)3 adduct is initially formed and undergoes partial dissociation to form an "encounter complex"...
November 14, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28944665/kinetic-study-of-living-ring-opening-metathesis-polymerization-with-third-generation-grubbs-catalysts
#19
Dylan J Walsh, Sii Hong Lau, Michael G Hyatt, Damien Guironnet
The rate of living ring-opening metathesis polymerization (ROMP) of N-hexyl-exo-norbornene-5,6-dicarboximide initiated by Grubbs third-generation catalyst precursors [(H2IMes)(py)2(Cl)2Ru═CHPh] and [(H2IMes)(3-Br-py)2(Cl)2Ru═CHPh] is measured to be independent of catalyst concentration. This result led to the development of a rate law describing living ROMP initiated by a Grubbs third-generation catalyst that includes an inverse first-order dependency in pyridine. Additionally, it is demonstrated that one of the two pyridines coordinated to the solid catalyst is fully dissociated in solution...
September 25, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28931277/radical-cage-effects-the-prediction-of-radical-cage-pair-recombination-efficiencies-using-microviscosity-across-a-range-of-solvent-types
#20
Justin T Barry, Daniel J Berg, David R Tyler
This study reports a method for correlating the radical recombination efficiencies (FcP) of geminate radical cage pairs to the properties of the solvent. Although bulk viscosity (macroviscosity) is typically used to predict or interpret radical recombination efficiencies, the work reported here shows that microviscosity is a much better parameter. The use of microviscosity is valid over a range of different solvent system types, including nonpolar, aromatic, polar, and hydrogen bonding solvents. In addition, the relationship of FcP to microviscosity holds for solvent systems containing mixtures of these solvent types...
October 3, 2017: Journal of the American Chemical Society
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