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https://www.readbyqxmd.com/read/29143029/triphenylsulfonium-topophotochemistry
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
Liming Wang, Wulf Amelung, Sabine Willbold
Liquid-state, one-dimension 31P nuclear magnetic resonance spectrometry (NMR) has greatly advanced our understanding of the composition of organic phosphorous 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 nuclear magnetic spectroscopy (DOSY) to soil extracts, allowing us to separate phosphorus components in the second domain based on their translational diffusion coefficient...
October 25, 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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
https://www.readbyqxmd.com/read/28917893/carboxymethyl-cyclosophoraoses-as-a-flexible-ph-responsive-solubilizer-for-pindolol
#16
Yiluo Hu, Hwanhee Kim, Vijay Vilas Shinde, Daham Jeong, Youngjin Choi, Eunae Cho, Seunho Jung
In the present study, cyclosophoraoses (CyS) (β-1,2 linked cyclic glucans, with glucopyranose units ranging from 17 to 23) isolated from Rhizobium leguminosarum biovar viciae VF-39 were modified with carboxymethyl (CM) groups, and the pH-sensitive complexation of CM CyS with pindolol was investigated. The solubility of pindolol increased 32-fold by its complexation with 5mM CM CyS at pH 10, whereas it shows no significant change at pH 3. Pindolol, a β-adrenergic blocking agent, has a hydrophobic nature at non-ionized state, and CM CyS could solubilize efficiently pindolol in a high alkaline solution...
November 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28872843/diffusion-controllable-biomineralization-conducted-in-situ-in-hydrogels-based-on-reversibly-cross-linked-hyperbranched-polyglycidol
#17
Mateusz Gosecki, Slawomir Kazmierski, Monika Gosecka
We present biocompatible hydrogel systems suitable for biomineralization processes based on hyperbranched polyglycidol cross-linked with acrylamide copolymer bearing carbonyl-coordinated boronic acid. At neutral pH, diol functional groups of HbPGL react with boronic acid of polyacrylamide to generate 3D network in water by the formation of boronic ester cross-links. The dynamic associative/dissociative characteristics of the cross-links makes the network reversible. The presented hydrogels display self-healing properties and are injectable, facilitating gap filing of bone tissue...
September 13, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/28869269/mono-bht-heteroleptic-magnesium-complexes-synthesis-molecular-structure-and-catalytic-behavior-in-the-ring-opening-polymerization-of-cyclic-esters
#18
I E Nifant'ev, A V Shlyakhtin, V V Bagrov, M E Minyaev, A V Churakov, S G Karchevsky, K P Birin, P V Ivchenko
Numerous heteroleptic 2,6-di-tert-butyl-4-methylphenolate (BHT) magnesium complexes have been synthesized by treatment of (BHT)MgBu(THF)2 with various alcohols. Molecular structures of the complexes have been determined by X-ray diffraction. The magnesium coordination number in [(BHT)Mg(μ-OBn)(THF)]2 (3) and [(BHT)Mg(μ-O-tert-BuC6H4)(THF)]2 (4) is equal to 4. Complexes formed from esters of glycolic and lactic acids, [(BHT)Mg(μ-OCH2COOEt)(THF)]2 (5) and [(BHT)Mg(μ-OCH(CH3)COOCH2COO(t)Bu)(THF)]2 (6) contain chelate fragments with pentacoordinated magnesium...
September 28, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28862280/the-templation-effect-as-a-driving-force-for-the-self-assembly-of-hydrogen-bonded-peptidic-capsules-in-competitive-media
#19
M Grajda, M J Lewińska, A Szumna
Peptide-based cavitands (resorcin[4]arenes substituted with histidine and glutamine hydrazides) exist as monomeric species in polar solvents (DMSO and methanol). Upon complexation of fullerenes, the cavitands wrap around the hydrophobic guests forming dimeric capsular shells (as evidenced by DOSY). The self-assembly of the cavitands is based on the formation of beta-sheet-like binding motifs around the hydrophobic core. In a polar environment, these hydrogen bonded structures are kinetically stable and highly ordered as manifested by a 100-fold increase of intensity of circular dichroism bands, as well as a separate set of signals and substantial differences in chemical shifts in NMR spectra...
October 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28858342/pulsed-field-gradient-nuclear-magnetic-resonance-measurements-pfg-nmr-for-diffusion-ordered-spectroscopy-dosy-mapping
#20
REVIEW
G Pagès, V Gilard, R Martino, M Malet-Martino
While NMR is the most used analytical method for determining the molecular structure of isolated chemical entities, small compounds as well as macromolecules, its capability of analysing complex mixtures is less known. The advent of Diffusion Ordered SpectroscopY (DOSY) NMR has made diffusion experiments popular, enabling diffusion coefficients to be routinely measured and used to characterize chemical systems in solution. Indeed, since the translational diffusion coefficients of molecular species reflect their effective sizes and shapes, DOSY NMR allows the separation of the chemical entities present in multicomponent systems and, as in all diffusion NMR experiments, provides information on their intermolecular interactions as well as on their size and shape...
August 31, 2017: Analyst
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