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https://www.readbyqxmd.com/read/28060513/water-induced-phase-transition-in-cyclohexane-n-hexanol-triton-x-100-mixtures-at-a-molar-composition-of-1-16-74-studied-by-nmr
#1
Mario E Flores, Francisco Martinez, Andres F Olea, Toshimichi Shibue, Natsuhiko Sugimura, Hiroyuki Nishide, Ignacio Moreno-Villoslada
Molecular aggregation in a mixture of Triton X-100 / n-hexanol / cyclohexane at a molar ratio of 1 / 16 / 74 is studied upon addition of small amounts of water. The composition of organic components has been chosen at a ratio n-hexanol / cyclohexane where a well-formed hydrogen bond network has been described. The ratio Triton X-100 / n-hexanol has been chosen to afford a stoichiometry of ethylene oxide (EO) residues / n-hexanol of 1 / 2. At these conditions the addition of water consecutively produces the appearance of three defined phases: a clear solution, a lamellar phase, and a microemulsion...
January 6, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28046809/su-f-t-31-shape-and-isodose-distributions-in-co60-hdr-brachytherapy-for-different-utero-vaginal-time-ratios
#2
G Gonzalez-Sprinberg, G Piriz
PURPOSE: To optimize the dose in bladder and rectum and show the different shapes of the isodose volumes in Co60-HDR brachytherapy, considering different utero and vaginal sources dwell ratio times (TU:TV). METHODS: Besides Ir192-HDR, new Co60-HDR sources are being incorporated. We considered different TU:TV times and computed the dosis in bladder, rectum and at the reference points of the Manchester system. Also, we calculated the isodose volume and shape in each case...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28032881/alopecia-frontal-fibrosante-una-enfermedad-en-auge
#3
A De Quintana Sancho, X Piris García, J N Valle García, M Hierro Cámara
La alopecia frontal fibrosante (AFF) es un tipo de alopecia cicatricial cuya incidencia está aumentando de forma significativa en nuestro país. Se caracteriza por un retroceso en la línea de implantación del pelo a nivel frontotemporal que afecta mayoritariamente a mujeres postmenopaúsicas, con un impacto negativo en su calidad de vida. Se asocia a menopausia precoz en un 14% de los casos y a hipotiroidismo en un 15%. Con respecto al tratamiento, son los inhibidores de la 5α-reductasa, los fármacos que han demostrado mejoría de la enfermedad en un mayor número de casos...
December 30, 2016: Anales del Sistema Sanitario de Navarra
https://www.readbyqxmd.com/read/28026805/-conformational-polymorphysm-of-g-rich-fragments-of-dna-alu-repeats-ii-the-putative-role-of-g-quadruplex-structures-in-genomic-rearrangements
#4
A M Varizhuk, A V Sekridova, M V Tankevich, V S Podgorsky, I P Smirnov, G E Pozmogova
Three evolutionary conserved sites of Alu repeats (PQS2, PQS3 and PQS4) were shown to form stable inter- and intramolecular G-quadruplexes (GQs) in vitro. Structures and topologies of these GQs were elucidated using spectral methods. Self-association of G-rich Alu fragments was studied. Dimeric GQ formation from two distal identical or different putative quadruplex sites - (PQS2)2, (PQS3)2 or PQS2-PQS3 - within one lengthy DNA strand was demonstrated by a FRET-based method. Oligomer PQS4 (folded into a parallel intramolecular GQ) was shown to form stacks of quadruplexes that are stabilized by stacking interactions of external G-tetrads (this was confirmed by DOSY NMR, AFM microscopy and differential CD spectroscopy)...
November 2016: Biomedit︠s︡inskai︠a︡ Khimii︠a︡
https://www.readbyqxmd.com/read/28001408/ultrathin-monomolecular-films-and-robust-assemblies-based-on-cyclic-catechols
#5
Markus M Zieger, Ognen Pop-Georgievski, Andres de Los Santos Pereira, Elisseos Verveniotis, Corinna M Preuss, Matthias Zorn, Bernd Reck, Anja S Goldmann, Cesar Rodriguez-Emmenegger, Christopher Barner-Kowollik
We introduce a newly designed catechol-based compound and its application for the preparation of homogeneous monomolecular layers as well as for robust assemblies on various substrates. The precisely defined cyclic catechol material (CyCat) was prepared from ortho-dimethoxybenzene in a phenolic resin-like synthesis and subsequent deprotection, featuring molecules with up to 32 catechol units. The CyCat's chemical structure was carefully assessed via matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), proton nuclear magnetic resonance ((1)H NMR), diffusion ordered spectroscopy (2D DOSY) and high resolution electrospray ionization mass spectrometry (ESI MS) experiments...
January 12, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28000994/lithium-dihydropyridine-dehydrogenation-catalysis-a-group%C3%A2-1-approach-to-the-cyclization-of-diamine-boranes
#6
Ross McLellan, Alan R Kennedy, Samantha A Orr, Stuart D Robertson, Robert E Mulvey
In reactions restricted previously to a ruthenium catalyst, a 1-lithium-2-alkyl-1,2-dihydropyridine complex is shown to be a competitive alternative dehydrogenation catalyst for the transformation of diamine boranes into cyclic 1,3,2-diazaborolidines, which can in turn be smoothly arylated in good yields. This study established the conditions and solvent dependence of the catalysis through NMR monitoring, with mechanistic insight provided by NMR (including DOSY) experiments and X-ray crystallographic studies of several model lithio intermediates...
December 21, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27958755/amphiphilic-ferrocene-containing-peg-block-copolymers-as-micellar-nanocarriers-and-smart-surfactants
#7
Arda Alkan, Sarah Wald, Benoit Louage, Bruno G De Geest, Katharina Landfester, Frederik R Wurm
An important and usually the only function of most surfactants in heterophase systems is stabilizing one phase in another, for example, droplets or particles in water. Surfactants with additional chemical or physical handles are promising in controlling the colloidal properties by external stimuli. The redox stimulus is an attractive feature; however, to date only a few ionic redox-responsive surfactants have been reported. Herein, the first nonionic and noncytotoxic ferrocene-containing block copolymers are prepared, carrying a hydrophilic poly(ethylene glycol) (PEG) chain and multiple ferrocenes in the hydrophobic segment...
December 29, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/27930812/assessing-2d-electrophoretic-mobility-spectroscopy-2d-mosy-for-analytical-applications
#8
Yuan Fang, Pavel V Yushmanov, István Furó
Electrophoretic displacement of charged entities phase modulates the spectrum acquired in electrophoretic NMR experiments and this modulation can be presented via 2D FT transformation as 2D MOSY (MObility SpectroscopY) spectra. We compare in various mixed solutions the chemical selectivity provided by 2D MOSY spectra to that provided by 2D DOSY (Diffusion Ordered SpectroscopY) spectra and demonstrate, under the conditions explored, a superior performance of the former method. 2D MOSY compares also favourably to closely related LC-NMR methods...
December 8, 2016: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/27918010/spatially-encoded-2d-and-3d-diffusion-ordered-nmr-spectroscopy
#9
Ludmilla Guduff, Ilya Kuprov, Carine van Heijenoort, Jean-Nicolas Dumez
We show that the acquisition of 3D diffusion-ordered NMR spectroscopy (DOSY) experiments can be accelerated significantly with the use of spatial encoding (SPEN). The SPEN DOSY approach is discussed, analysed with numerical simulation, and illustrated on a mixture of small molecules.
December 5, 2016: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/27879043/uncovering-key-structural-features-of-an-enantioselective-peptide-catalyzed-acylation-utilizing-advanced-nmr-techniques
#10
Eliška Procházková, Andreas Kolmer, Julian Ilgen, Mira Schwab, Lukas Kaltschnee, Maic Fredersdorf, Volker Schmidts, Raffael C Wende, Peter R Schreiner, Christina M Thiele
We report on a detailed NMR spectroscopic study of the catalyst-substrate interaction of a highly enantioselective oligopeptide catalyst that is used for the kinetic resolution of trans-cycloalkane-1,2-diols via monoacylation. The extraordinary selectivity has been rationalized by molecular dynamics as well as density functional theory (DFT) computations. Herein we describe the conformational analysis of the organocatalyst studied by a combination of nuclear Overhauser effect (NOE) and residual dipolar coupling (RDC)-based methods that resulted in an ensemble of four final conformers...
December 19, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27862747/ultrahigh-resolution-diffusion-ordered-spectroscopy
#11
Mohammadali Foroozandeh, Laura Castañar, Lucas G Martins, Davy Sinnaeve, Guilherme Dal Poggetto, Claudio F Tormena, Ralph W Adams, Gareth A Morris, Mathias Nilsson
Diffusion-ordered spectroscopy (DOSY) is an effective method for the analysis of intact mixtures, but the quality of results is critically limited by resolution in the NMR dimension. A new experiment integrating diffusion weighting into the PSYCHE method for pure shift NMR spectroscopy allows DOSY spectra to be measured with ultrahigh NMR resolution at improved sensitivity.
December 12, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27862424/synthesis-of-structurally-varied-1-3-disiloxanediols-and-their-activity-as-anion-binding-catalysts
#12
Kayla M Diemoz, Sean O Wilson, Annaliese K Franz
A series of new 1,3-disiloxanediols has been synthesized, including naphthyl-substituted and unsymmetrical siloxanes, and demonstrated as a new class of anion-binding catalysts. In the absence of anions, diffusion-ordered spectroscopy (DOSY) displays self-association of 1,3-disiloxanediols through hydrogen-bonding interactions. Binding constants determined for 1,3-disiloxanediol catalysts indicate strong hydrogen-bonding and anion-binding abilities with unsymmetrical siloxanes displaying different hydrogen-bonding abilities for each silanol group...
December 19, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27854348/oxidatively-locked-co%C3%A2-l%C3%A2-6-cylinders-derived-from-bis-bidentate-2-pyridyl-1-2-3-triazole-click-ligands-synthesis-stability-and-antimicrobial-studies
#13
Roan A S Vasdev, Dan Preston, Synøve Ø Scottwell, Heather J L Brooks, James D Crowley, Michael P Schramm
A small family of [Co₂(Lpytrz)₃](6+) cylinders was synthesised from bis(bidentate) 2-pyridyl-1,2,3-triazole "click" ligands (Lpytrz) through an "assembly-followed-by-oxidation" method. The cylinders were characterised using ¹H, (13)C, and DOSY NMR, IR, and UV-Vis spectroscopies, along with electrospray ionisation mass spectrometry (ESMS). Stability studies were conducted in dimethyl sulfoxide (DMSO) and D₂O. In contrast to similar, previously studied, [Fe₂(Lpytrz)₃](4+) helicates the more kinetically inert [Co₂(Lpytrz)₃](6+) systems proved stable (over a period of days) when exposed to DMSO and were even more stable in D₂O...
November 16, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/27842812/interactions-between-quaternized-chitosan-and-surfactant-studied-by-diffusion-nmr-and-conductivity
#14
Tonimar D A Senra, Abdel Khoukh, Jacques Desbrières
Surfactant-polysaccharide complexes (SPEC) based on oppositely charged sodium 1-decanesulfonate and quaternized chitosan were studied using two techniques. The first one, the conductivity, is a very often used even when diffusion NMR (DOSY) technique was considered for the first time for such systems involving surfactant and chitosan derivatives and more generally polysaccharides. The physico-chemical characteristics of pure surfactant solutions as well as SPECs were determined and compared according to the considered experimental technique...
January 20, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/27805760/paramagnetic-dosy-an-accurate-tool-for-the-analysis-of-the-supramolecular-interactions-between-lanthanide-complexes-and-proteins
#15
Sandrine Denis-Quanquin, François Riobé, Marc-André Delsuc, Olivier Maury, Nicolas Giraud
Diffusion ordered NMR is implemented to determine accurately the mobility of paramagnetic tris-dipicolinate lanthanide complexes that are versatile probes of protein structure. It is shown that diffusion coefficient ratios can be measured with an accuracy of 1 % using a standard BPPLED pulse sequence, which allows for observing significant, though weak, variations when different species are interacting with the paramagnetic compound. We demonstrate that this approach is complementary to classical chemical shift titration experiments, and that it can be applied successfully to probe the supramolecular dynamic interactions between lanthanide complexes and small molecules on the one hand, or to determine rapidly their affinity for a targeted protein...
December 12, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27804286/ph-responsive-nanometric-polydiacetylenic-micelles-allow-for-efficient-intracellular-sirna-delivery
#16
Manon Ripoll, Patrick Neuberg, Antoine Kichler, Nassera Tounsi, Alain Wagner, Jean-Serge Remy
A novel generation of pH-responsive photopolymerized diacetylenic amphiphile (PDA) micelles with a diameter of 10 nm was designed and optimized for the intracellular delivery of siRNAs. Dialysis and photopolymerization of the micelles allowed a strong reduction of the cytotoxicity of the nanovector, while the hydrophilic histidine headgroup permitted enhancing the siRNA delivery potential by improving the endosomal escape via imidazole protonation. These PDA-micellar systems were fully characterized by DLS, TEM, and DOSY-NMR experiments...
November 16, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27800558/high-throughput-excipient-discovery-enables-oral-delivery-of-poorly-soluble-pharmaceuticals
#17
Jeffrey M Ting, Swapnil Tale, Anatolii A Purchel, Seamus D Jones, Lakmini Widanapathirana, Zachary P Tolstyka, Li Guo, Steven J Guillaudeu, Frank S Bates, Theresa M Reineke
Polymeric excipients are crucial ingredients in modern pills, increasing the therapeutic bioavailability, safety, stability, and accessibility of lifesaving products to combat diseases in developed and developing countries worldwide. Because many early-pipeline drugs are clinically intractable due to hydrophobicity and crystallinity, new solubilizing excipients can reposition successful and even failed compounds to more effective and inexpensive oral formulations. With assistance from high-throughput controlled polymerization and screening tools, we employed a strategic, molecular evolution approach to systematically modulate designer excipients based on the cyclic imide chemical groups of an important (yet relatively insoluble) drug phenytoin...
October 26, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27792454/gene-dosis-and-the-timing-of-mitosis
#18
Victor A Tallada, Jürg Bähler
No abstract text is available yet for this article.
November 16, 2016: Cell Cycle
https://www.readbyqxmd.com/read/27791294/a-phosphorescent-platinum-ii-bipyridyl-supramolecular-polymer-based-on-quadruple-hydrogen-bonds
#19
Fang-Wei Liu, Li-Ya Niu, Yong Chen, Vaidhyanathan Ramamurthy, Li-Zhu Wu, Chen-Ho Tung, Yu-Zhe Chen, Qing-Zheng Yang
A platinum(II) bipyridyl complex bearing bis-ureidopyrimidinone (Pt-bisUPy) has been designed and its self-assembling behavior has been thoroughly investigated by (1) H NMR, DOSY NMR, Ubbelohde viscometry analysis, UV/Vis, and emission spectroscopies. Pt-bisUPy underwent concentration-dependent ring-chain polymerization in apolar solvents. Hydrogen-bonding interactions play an important role during the formation of the supramolecular polymers. Hydrogen-bonded supramolecular polymers were transformed to nanoparticles in water through the miniemulsion method...
December 12, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27785845/isomerization-of-keggin-al13-ions-followed-by-diffusion-rates
#20
Anna F Oliveri, Christopher A Colla, Cory K Perkins, Noushin Akhavantabib, Joseph R Callahan, Corey D Pilgrim, Scott E Smart, Paul H-Y Cheong, Long Pan, William H Casey
The solution chemistry of aluminum has long interested scientists due to its relevance to materials chemistry and geochemistry. The dynamic behavior of large aluminum-oxo-hydroxo clusters, specifically [Al13 O4 (OH)24 (H2 O)12 ](7+) (Al13 ), is the focus of this paper. (27) Al NMR, (1) H NMR, and (1) H DOSY techniques were used to follow the isomerization of the ϵ-Al13 in the presence of glycine and Ca(2+) at 90 °C. Although the conversion of ϵ-Al13 to new clusters and/or Baker-Figgis-Keggin isomers has been studied previously, new (1) H NMR and (1) H DOSY analyses provided information about the role of glycine, the ligated intermediates, and the mechanism of isomerization...
December 23, 2016: Chemistry: a European Journal
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