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https://www.readbyqxmd.com/read/28821133/single-helix-in-v-type-starch-carrier-determines-the-encapsulation-capacity-of-ethylene
#1
Linfan Shi, Xiong Fu, Qiang Huang, Bin Zhang
V-type starch carriers with different single helix contents were prepared using alcoholic-alkaline treatment followed by ethanol precipitation. Ethylene gas was entrapped into V-type starch carriers using a solid encapsulation method. The morphological and structural properties of inclusion complexes (ICs) were characterized using scanning electron and light microscopy, X-ray diffractometry, (13)C solid-state nuclear magnetic resonance (NMR) and Raman spectroscopy. Aqueous ethanol treatment resulted in swelling and aggregation of starch granules, and B-type diffraction reflections were either reduced or completely lost with evolution of V-type pattern...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28821093/urea-free-synthesis-of-chitin-based-acrylate-superabsorbent-polymers-under-homogeneous-conditions-effects-of-the-degree-of-deacetylation-and-the-molecular-weight
#2
T G Liu, Y T Wang, B Li, H B Deng, Z L Huang, L W Qian, X Wang
In order to understand the chemical structure of chitin-based acrylate superabsorbent polymers (SAP), chitin was dissolved in NaOH aqueous solution via freezing-thawing cyclic treatment without urea, subsequently, a transparent hydrogel was prepared by copolymerizing the alkali-chitin solution and acrylic acid directly. The effects of the degree of deacetylation (DDA) and the molecular weight (Mw) of chitin on the properties of SAP were investigated in detail. With increasing the DDA and Mw, the yield improved while the water absorbency decreased, yet the effect of DDA is insignificant if the Mw is smaller enough...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28821081/direct-characterization-of-cotton-fabrics-treated-with-di-epoxide-by-nuclear-magnetic-resonance
#3
Min Xiao, Joronia Chéry, Ivan Keresztes, David B Zax, Margaret W Frey
A non-acid-based, di-functional epoxide, neopentyl glycol diglycidyl ether (NPGDGE), was used to modify cotton fabrics. Direct characterization of the modified cotton was conducted by Nuclear Magnetic Resonance (NMR) without grinding the fabric into a fine powder. NaOH and MgBr2 were compared in catalyzing the reaction between the epoxide groups of NPGDGE and the hydroxyl groups of cellulose. Possible reaction routes were discussed. Scanning electron microscopy (SEM) images showed that while the MgBr2-catalyzed reaction resulted in self-polymerization of NPGDGE, the NaOH-catalyzed reaction did not...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28820940/polyoxometalate-cationic-cluster-and-%C3%AF-%C3%AE-cyclodextrin-from-primary-interactions-to-supramolecular-hybrid-materials
#4
Mhamad Aly Moussawi, Nathalie Leclerc-Laronze, Sébastien Floquet, Pavel A Abramov, Maxim Nailyevich Sokolov, Stephane Cordier, Anne Ponchel, Eric Monflier, Herve Bricout, David Landy, Mohamed Haouas, Jerome Marrot, Emmanuel Cadot
Herein, we report on a three-component supramolecular hybrid system built from specific recognition processes involving a Dawson type polyoxometalate [P2W18O62](6-,) a cationic electron-rich cluster {[Ta6Br12(H6O)6]@2CD}(2+) and γ-cyclodextrin. Investigations of such a class of materials have been conducted using bottom-up approach by studying the specific interactions between -CD and both types of inorganic units. Their ability to interact has been investigated in the solid state by single-crystal X-ray diffraction and in solution using multinuclear NMR methods (including DOSY, EXSY and COSY), ESI-mass and UV-vis spectroscopies, electrochemistry and ITC experiments...
August 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28820582/pathogenic-mutations-induce-partial-structural-changes-in-native-%C3%AE-sheet-structure-of-transthyretin-and-accelerate-aggregation
#5
Kwang Hun Lim, Anvesh K R Dasari, Renze Ma, Ivan Hung, Zhehong Gan, Jeffery W Kelly, Michael C Fitzgerald
Amyloid formation of natively folded proteins involves global and/or local unfolding of the native state to form aggregation-prone intermediates. Here we report solid-state NMR structural studies of amyloid derived from wild-type (WT) and more aggressive mutant forms of transthyretin (TTR) to investigate the structural changes associated with effective TTR aggregation. We employed selective 13C-labeling schemes to investigate structural features of β-structured core regions in amyloid states of WT and two mutant forms (V30M and L55P) of TTR...
August 18, 2017: Biochemistry
https://www.readbyqxmd.com/read/28820260/thermally-induced-self-assembly-and-cyclization-of-l-leucyl-l-leucine-in-solid-state
#6
Marat A Ziganshin, Aisylu S Safiullina, Alexander Vladimirovich Gerasimov, Sufia A Ziganshina, Alexander E Klimovitskii, Khasan R Khayarov, Valery V Gorbatchuk
The thermal treatment of oligopeptides is one of the methods for synthesis of organic nanostructures. However, heating may lead not only to self-assembly of the initial molecules, but also to chemical reactions resulting in the formation of new unexpected nanostructures or changing in the properties of the existing ones. In the present work, the reaction of cyclization of dipeptide L-leucyl-L-leucine in solid state under heating was studied. The change in morphology of dipeptide thin film and formation of nanostructures after heating was visualized using atomic force microscopy...
August 18, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28820241/interactions-of-verkade-s-superbase-with-strong-lewis-acids-from-labile-mono-and-binuclear-lewis-acid-base-complexes-to-phosphenium-cations
#7
Suresh Mummadi, Dustin Kenefake, Rony Diaz, Daniel K Unruh, Clemens Krempner
A series of mono- and binuclear Lewis acid-base complexes of the formulas N[CH2CH2N(Pr(i))]3P→LA [LA = BH3 (8), Ga(C6F5)3 (10), GaCl3 (11)], LA←N[CH2CH2N(Pr(i))]3P [LA = Al(C6F5)3 (6a), AlMe3 (6b), AlEt3 (6c), AlBu(i)3 (6d), BF3 (13)], and LA←N[CH2CH2N(Pr(i))]3P→LA [Lewis acid (LA) = Al(C6F5)3 (7a), AlMe3 (7b), AlEt3 (7c), AlBu(i)3 (7d), AlCl3 (7e), BH3 (9)] were generated from reactions of Verkade's base, N[CH2CH2N(Pr(i))]3P (1), with various boron-, aluminum-, and gallium-containing Lewis acids, and characterized by multinuclear NMR spectroscopy...
August 18, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28818654/water-based-fractionation-of-a-commercial-humic-acid-solid-state-and-colloidal-characterization-of-the-solubility-fractions
#8
Weronika M Swiech, Ian Hamerton, Huang Zeng, David J Watson, Eleonore Mason, Spencer E Taylor
BACKGROUND AND HYPOTHESIS: Humic acid (HA) is of considerable environmental significance, being a major component of soil, as well as being considered for application in other technological areas. However, its structure and colloidal properties continue to be the subject of debate, largely owing to its molecular complexity and association with other humic substances and mineral matter. As a class, HA is considered to comprise supramolecular assemblies of heterogeneous species, and herein we consider a simple route for the separation of some HA sub-fractions...
August 12, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28817269/the-chemistry-of-co2-capture-in-an-amine-functionalized-metal-organic-framework-under-dry-and-humid-conditions
#9
Robinson W Flaig, Thomas M Osborn Popp, Alejandro M Fracaroli, Eugene A Kapustin, Markus J Kalmutzki, Rashid M Altamimi, Farhad Fathieh, Jeffrey A Reimer, Omar M Yaghi
The use of two primary alkylamine functionalities covalently tethered to the linkers of IRMOF-74-III results in a material which can uptake CO2 at low pressures through a chemisorption mechanism. In contrast to other primary amine-functionalized solid adsorbents which uptake CO2 primarily as ammonium carbamates, we observe using solid state NMR that the major chemisorption product for this material is carbamic acid. The equilibrium of reaction products also shifts to ammonium carbamate when water vapor is present; a new finding that has impact on control of the chemistry of CO2 capture in MOF materials and one that highlights the importance of geometric constraints and the mediating role of water within the pores of MOFs...
August 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28816463/signaling-related-mobility-changes-in-bacterial-chemotaxis-receptors-revealed-by-solid-state-nmr
#10
Maryam Kashefi, Lynmarie K Thompson
Bacteria employ remarkable membrane-bound nanoarrays to sense their environment and direct their swimming. Arrays consist of chemotaxis receptor trimers of dimers that are bridged at their membrane-distal tips by rings of two cytoplasmic proteins, a kinase CheA and a coupling protein CheW. It is not clear how ligand binding to the periplasmic domain of the receptor deactivates the CheA kinase bound to the cytoplasmic tip ~300 Å away, but the mechanism is thought to involve changes in dynamics within the cytoplasmic domain...
August 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28816462/-1-h-detected-redor-with-fast-magic-angle-spinning-of-a-deuterated-protein
#11
Manali Ghosh, Chad M Rienstra
Rotational echo double resonance (REDOR) is a highly successful method for heteronuclear distance determination in biological solid-state NMR, and 1H detection methods have emerged in recent years as a powerful approach to improving sensitivity and resolution for small sample quantities by utilizing fast magic-angle spinning (>30 kHz) and deuteration strategies. In theory, involving 1H as one of the spins for measuring REDOR effects can greatly increase the distance measurement range, but few experiments of this type have been reported...
August 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28815866/catalytic-intramolecular-cycloaddition-reactions-using-a-discrete-molecular-architecture
#12
Partha Sarathi Mukherjee, Bijan Roy, Anthonisamy Devaraj, Rupak Saha, Suprita Jharimune, Ki-Whan Chi
A discrete tetragonal tube-shaped complex (MT-1) has been synthesized by coordination-driven self-assembly of a carbazole-based tetraimidazole donor L and a Pd(II) 90° acceptor, viz. [cis-(dppf)Pd(OTf)2] (dppf = diphenylphosphino ferrocene, OTf = CF3SO3-). Complex MT-1 was characterized by multinuclear NMR, ESI-MS and single crystal X-ray diffraction analysis (SCXRD), which showed its symmetrical tetrafacial tube-shaped architecture possessing a large cavity described by four aromatic walls. This coordination cage was successfully utilized as a molecular vessel to perform intramolecular cycloaddition reactions of O-allylated benzylidinebarbituric acid derivatives inside its confined nanospace...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815397/detecting-and-accounting-for-multiple-sources-of-positional-variance-in-peak-list-registration-analysis-and-spin-system-grouping
#13
Andrey Smelter, Eric C Rouchka, Hunter N B Moseley
Peak lists derived from nuclear magnetic resonance (NMR) spectra are commonly used as input data for a variety of computer assisted and automated analyses. These include automated protein resonance assignment and protein structure calculation software tools. Prior to these analyses, peak lists must be aligned to each other and sets of related peaks must be grouped based on common chemical shift dimensions. Even when programs can perform peak grouping, they require the user to provide uniform match tolerances or use default values...
August 16, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28812886/room-temperature-ring-opening-of-quinoline-isoquinoline-and-pyridine-with-low-valent-titanium
#14
Seung-Yeol Baek, Takashi Kurogi, Dahye Kang, Masahiro Kamitani, Seongyeon Kwon, Douglas Solowey, Chun-Hsing Chen, Maren Pink, Patrick J Carroll, Daniel J Mindiola, Mu-Hyun Baik
The complex (PNP)Ti=CHtBu(CH2tBu) (PNP = N[2-PiPr2-4-methylphenyl]2-) dehydrogenates cyclohexane to cyclohexene by forming a transient low-valent titanium-alkyl species, [(PNP)Ti(CH2tBu)], which reacts with two equivalents of quinoline (Q) at room temperature to form H3CtBu and a Ti(IV) species where the less hindered C2=N1 bond of Q is ruptured and coupled to another equivalent of Q. The product isolated from this reaction is an imide with a tethered cycloamide group, (PNP)Ti=N[C18H13N] (1). Under photolytic conditions, intramolecular C-H bond activation across the imide-moiety in 1 occurs to form 2, and thermolysis reverses this process...
August 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28812758/a-metalloporphyrin-based-porous-organic-polymer-as-an-efficient-catalyst-for-the-catalytic-oxidation-of-olefins-and-arylalkanes
#15
Zheng-Dong Ding, Wei Zhu, Tao Li, Rui Shen, Yunxing Li, Zaijun Li, Xuehong Ren, Zhi-Guo Gu
A metalloporphyrin-based porous organic polymer, Mn-PPOP-1, was constructed in high yield via the ketoenamine condensation of robust porphyrin tetraamines (TBPP) with 1,3,5-triformylphloroglucinol. The stable keto-enamine form in the synthesized polymer was unambiguously confirmed by (13)C CP-MAS solid state NMR. Noticeably, besides the high thermal and chemical stability, this material contains both micropores and mesopores, which are favorable for mass transfer in the catalytic application. Mn-PPOP-1 exhibits significantly high catalytic oxidation of olefins and arylalkanes at room temperature...
August 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28812063/self-organization-of-amino-acid-derived-ndi-assemblies-into-a-nanofibrillar-superstructure-with-humidity-sensitive-n-type-semiconducting-properties
#16
Marco A Squillaci, Grzegorz Markiewicz, Anna Walczak, Artur Ciesielski, Artur R Stefankiewicz, Paolo Samorì
The hierarchical self-assembly of l-tyrosine substituted naphthalenediimide has been explored in solution by NMR spectroscopy and in the solid-state by atomic force microscopy. Spontaneous non-covalent polymerisation led to the formation of a three-dimensional fibre-like supramolecular polymer with n-type semiconducting properties.
August 16, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28809493/macroscopic-structural-compositions-of-%C3%AF-conjugated-polymers-combined-insights-from-solid-state-nmr-and-molecular-dynamics-simulations
#17
Anton Melnyk, Matthias Junk, Michael D McGehee, Bradley F Chmelka, Michael Ryan Hansen, Denis Andrienko
Molecular dynamics simulations are combined with solid-state NMR measurements to gain insight into the macroscopic structural composition of the π-conjugated polymer poly(2,5-bis(3-tetradecyl-thiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). The structural and dynamical properties, as established by the NMR analyses, were used to test the local structure of three constitutient mesophases with: (i) crystalline backbones and side chains, (ii) lamellar backbones and disordered side chains, or (iii) amorphous backbones and side chains...
August 15, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28809485/dispersion-and-halogen-bonding-interactions-binding-of-the-axial-conformers-of-monohalo-and-%C3%A2-trans-1-2-dihalocyclohexanes-in-enantiopure-alleno-acetylenic-cages
#18
Cornelius Gropp, Tamara Husch, Nils Trapp, Markus Reiher, François Diederich
Enantiopure alleno-acetylenic cage (AAC) receptors with a resorcin[4]arene scaffold, from which four homochiral alleno-acetylenes converge to shape a cavity closed by a four-fold OH-hydrogen-bonding array, form a highly ordered porous network in the solid state. They enable the complexation and co-crystallization of otherwise non-crystalline small molecules. This paper analyzes the axial conformers of monohalo- and (±)-trans-1,2-dihalocyclohexanes, bound in the interior cavity of the AACs, on the atomic level in the solid state and in solution, accompanied by accurate calculations...
August 15, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28809415/stimuli-responsive-emissive-behavior-of-1-and-1-3-connectivities-in-azulene-based-imine-ligands-cycloplatination-and-pt-tl-dative-bond-formation
#19
Sirous Jamali, Narges-Alsadat Mousavi, Mojtaba Bagherzadeh, Reza Kia, Hamidreza Samouei
The preparation of two new azulene-based imine ligands N-(2,6-diisopropylphenyl)-6-(t)Bu-1-azulenylmethaneimine, 3, and N-(2,6-diisopropylphenyl)-6-(t)Bu-3-(2,6-diisopropylphenyliminomethyl)-1-azulenylmethaneimine, 4, is described. These imine ligands display stimuli responsive emissive behavior and their fluorescence can be switched on and off by protonation and neutralization with trifluoroacetic acid and trimethylamine, respectively. The cyclometalation of the monoimine ligand by platinum gave the cyclometalated complex [PtMe(SMe2)(3')], 5, (where the prime denotes the cyclometalated ligand 3)...
August 15, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28806512/painkiller-isoxicam-and-its-copper-complex-can-form-inclusion-complexes-with-different-cyclodextrins-a-fluorescence-fourier-transform-infra-red-spectroscopy-and-nuclear-magnetic-resonance-study
#20
Sathi Goswami, Anupa Majumdar, Munna Sarkar
The interaction of a painkiller Isoxicam, belonging to the oxicam group of Non Steroidal Anti-Inflammatory Drugs (NSAIDs) and its copper complex with different cyclodextrins (β-CD, γ-CD, HPβCD and HPγCD ) has been investigated in both solution and the solid state. Steady state and time resolved fluorescence spectroscopy, fluorescence anisotropy, 1H NMR and FTIR spectroscopy are used. Both the drug and its copper complex form host-guest inclusion complex with all CDs. Fluorescence spectroscopy is used to determine binding constants and stoichiometries of the host-guest complex...
August 14, 2017: Journal of Physical Chemistry. B
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