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acid base strong ion

Paula A Cristini, Eleonor Tietze, Claudio G De Francesco, Daniel E Martínez
A seasonal sampling of sediments, column and interstitial water for physico-chemical analysis were performed in littoral and open water areas in three freshwater shallow lakes (Nahuel Rucá, Las Mostazas and Los Carpinchos) from Southeastern Pampa plain, Argentina. The main objective of the present study is to evaluate how the characteristics of the depositional environments could be affecting mollusk shell preservation. These lakes are very shallow (2m) and are characterized by an extensive littoral area, dominated by the emergent macrophyte Schoenoplectus californicus, which forms a complete ring around the lake, and an open water area, in general free of vegetation...
June 15, 2017: Science of the Total Environment
Gyula Lajkó, Tímea Orosz, Imre Ugrai, Zsolt Szakonyi, Ferenc Fülöp, Wolfgang Lindner, Antal Péter, István Ilisz
The eight stereoisomers of limonene-based carbocyclic β-amino acids containing three chiral centers have been directly separated on chiral stationary phases containing Cinchona alkaloid-based zwitterionic selectors. The effects of bulk solvent composition of the mobile phase, the nature of base additives, counter-ion concentration, and the structure of selector on the enantiorecognition were studied. Experiments were performed at constant mobile phase composition in the temperature range 5-40°C to study the effect of temperature...
June 16, 2017: Journal of Separation Science
Christian Malm, Heejae Kim, Manfred Wagner, Johannes Hunger
Solutions of Brønsted acids with bases in aprotic solvents are not only common model systems to study the fundamentals of proton transfer pathways but are also highly relevant to Brønsted acid catalysis. Despite their importance the light nature of the proton makes characterization of acid-base aggregates challenging. Here, we track such acid-base interactions over a broad range of relative compositions between diphenyl phosphoric acid and the base quinaldine in dichloromethane, by using a combination of dielectric relaxation and NMR spectroscopy...
June 8, 2017: Chemistry: a European Journal
Nanna Myllys, Tinja Olenius, Theo Kurtén, Hanna Vehkamäki, Ilona Riipinen, Jonas Elm
We investigate the effect of the bisulfate anion HSO4(-), ammonium cation NH4(+), and ammonia NH3 on the clustering of sulfuric acid and pinic acid or 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA). The systems were chosen based on their expected relevance in atmospheric new particle formation. Using quantum chemical methods together with kinetic calculations, we study the ability of these compounds to enhance cluster formation and growth. The cluster structures are obtained and frequencies are calculated using three different DFT functionals (M06-2X, PW91, and ωB97X-D) with the 6-31++G(d,p) basis set...
June 19, 2017: Journal of Physical Chemistry. A
Muhammad Moazzam Naseer, Klaus Jurkschat
The field of anion recognition has developed into an area of tremendous significance over the recent decades due to the role of anions in biological and environmental systems, contributing significantly to the more general domain of supramolecular chemistry. So far, a number of receptors have been designed for anion recognition, synthesized and evaluated, most involving hydrogen bonding donors (urea, amide, pyrrole, imidazolium and hydroxyl groups), π-acidic aryl rings, Lewis acidic metals (boron, tin, aluminium, mercury and uranium) and positively charged polyammonium moieties...
June 5, 2017: Chemical Communications: Chem Comm
Weiwei Zhang, Adri C T van Duin
Hydronium (H3O(+)) and hydroxide (OH(-)) ions have anomalously large diffusion constants in aqueous solutions due to their combination of vehicular and Grotthuss hopping diffusion mechanisms. An improvement of the ReaxFF reactive water force field on the basis of our first-generation water force field (water-2010) is presented to describe the proton transfer (PT) mechanisms of H3O(+) and OH(-) in water. Molecular dynamics simulation studies with the water-2017 force field support the Eigen-Zundel-Eigen mechanism for PT in acidic aqueous solution and reproduce the hypercoordinated solvation structure of the OH(-) in a basic environment...
June 8, 2017: Journal of Physical Chemistry. B
Dejan Nikolić, Carmen Macias, David C Lankin, Richard B van Breemen
RATIONALE: Phenethylamides are a large group of naturally occurring molecules found both in the plant and animal kingdoms. In addition, they are used as intermediates for the synthesis of pharmaceutically important dihydro- and tetrahydroisoquinolines. To enable efficient characterization of this class of molecules, a detailed mass spectrometric fragmentation study of a broad series of analogs was carried out. METHODS: The test compounds were synthesized using standard methods for amide bond formation...
May 30, 2017: Rapid Communications in Mass Spectrometry: RCM
Cui Liu, Dianhua Ning, Cheng Zhang, Zhengjie Liu, Ruilong Zhang, Jun Zhao, Tingting Zhao, Bianhua Liu, Zhongping Zhang
Classical pH test papers are widely used to measure the acid-base degree of media in a qualitative or semiquantitative manner. However, the extension of portable and inexpensive methods to a wide range of analytes so as to eliminate the tediousness of instrumental assays remains unsuccessful. Here, we report a novel kind of dual-colored carbon dot (CD) ratiometric fluorescent test paper for the semiquantitative assay of copper ions (Cu(2+)) by a dose-sensitive color evolution. The preparation of the test paper is based on the following two interesting findings: on the one hand, residual p-phenylenediamine at the surface of as-synthesized red CDs (r-CDs) efficiently binds Cu(2+) ions to produce a strong visible absorption that overlaps the emission of blue CDs (b-CDs); on the other hand, the Cu(2+) ions render the adsorption of small b-CDs onto the surface of larger r-CDs through their dual-coordinating interactions with the surface ligands of both r-CDs and b-CDs...
June 7, 2017: ACS Applied Materials & Interfaces
Jie Yang, Anna-Lena Gustavsson, Martin Haraldsson, Göran Karlsson, Thomas Norberg, Lars Baltzer
A high-affinity polypeptide conjugate 4-C25L22-DQ, has been developed for the molecular recognition of the human C-reactive protein, CRP, a well-known inflammation biomarker. CRP is one of the most frequently quantified targets in diagnostic applications and a target in drug development. With the exception of antibodies, most molecular constructs take advantage of the known affinity for CRP of phosphocholine that depends on Ca(2+) for its ability to bind. 4-C25L22-DQ which is unrelated to phosphocholine binds in the absence of Ca(2+) with a dissociation constant of 760 nM, an order of magnitude lower than that of phosphocholine, the KD of which is 5 μM...
May 31, 2017: Organic & Biomolecular Chemistry
Joseph A B Abdalla, Rémi C Tirfoin, Haoyu Niu, Simon Aldridge
A versatile synthetic route has been developed to access strongly Lewis acidic borenium cations (and heavier group 13 analogues) featuring a pendant weakly-coordinating borate function. The hydrocarbon-soluble borenium/borate zwitterion is more strongly Lewis acidic than B(C6F5)3, despite featuring a pendant (non-fluorinated) aryl group and two flanking N-donors.
May 17, 2017: Chemical Communications: Chem Comm
Kai Lv, Chu-Ting Yang, Jun Han, Sheng Hu, Xiao-Lin Wang
Combining the merits of soft-templating and perchlorate oxidation methods, the first-case investigation of niobium alkylphosphonates has uncovered their unique morphology, backbone composition, thermal behavior and huge potentiality as radioanalytical separation materials. These hierarchically porous solids are random aggregates of densely stacked nanolayers perforated with worm-like holes or vesicular voids, manifesting the massif-, tower-like "polymer brush" elevated up to ∼150nm driven by the minimal surface free energy principle...
May 8, 2017: Journal of Chromatography. A
Jing Zhang, Qing Tang, Zhongzheng Gao, Sheng Chao Qiu, Ying Huang, Zhu Tao
A water-soluble fluorescent sensor based on the interaction of the twisted cucurbit[14]uril (tQ[14]) and thiazole orange (TO) in aqueous solution has been developed. Formation of the tQ[14]/TO complex gives rise to strong fluorescence in both of neutral and acidic aqueous solutions compared with that of free TO. Further experiments on the interaction of the tQ[14]/TO complex with metal ions revealed that from a series of nineteen selected common metal ions, 1) only Hg2+ ion can lead to the fluorescence enhancement and then quenching of the tQ[14]/TO complex (2:1) in neutral aqueous solution; 2) only Ba2+ can induce fluorescence quenching of the tQ[14]/TO (2:1) complex in aqueous HCl solution (pH 2)...
May 16, 2017: Chemistry: a European Journal
Xian Zhou, Min Zhou, Xian Wu, Yi Han, Junjun Geng, Teng Wang, Sha Wan, Haobo Hou
Fly ash is a hazardous byproduct of municipal solid waste incineration (MSWI). Cementitious material that is based on ground-granulated blast furnace slag (GGBFS) has been tested and proposed as a binder to stabilize Pb, Cd, and Zn in MSWI fly ash (FA). Cr, however, still easily leaches from MSWI FA. Different reagents, such as ascorbic acid (VC), NaAlO2, and trisodium salt nonahydrate, were investigated as potential Cr stabilizers. The results of the toxicity characteristic leaching procedure (TCLP) showed that VC significantly improved the stabilization of Cr via the reduction of Cr(VI) to Cr(III)...
April 21, 2017: Chemosphere
Bing Han, Wen Liu, Jingwen Li, Jin Wang, Dongye Zhao, Rui Xu, Zhang Lin
We prepared a new class of anion-exchange-resin supported Pd catalysts for efficient hydrodechlorination of triclosan in water. The catalysts were prepared through an initial ion-exchange uptake of PdCl4(2-) and subsequent reduction of Pd(II) to Pd(0) nanoparticles at ambient temperature. Two standard strong-base anion exchange resins (IRA-900 and IRA-958) with different matrices (polystyrene and polyacrylic) were chosen as the supports. SEM and TEM images showed that Pd(0) nanoparticles were evenly attached on the resin surface with a mean size of 3-5 nm...
April 26, 2017: Water Research
Kengo Asai, Aiko Fukazawa, Shigehiro Yamaguchi
A near-infrared (NIR) polymethine dye (1), consisting of a cyclohepta[1,2-b;4,3-b']dithiophene and two phenol moieties, was synthesized. This dye exhibited pH-responsive changes in its photophysical properties due to a two-step acid-base equilibrium that produced a protonated cation (1H(+) ) and an anion (1(-) ). While 1H(+) showed an intense fluorescence in the red region of the visible spectrum, 1(-) exhibited a strong absorption in the NIR region. The tropylium ion character in 1H(+) induces high pKa1 and pKa2 values for 1...
May 9, 2017: Angewandte Chemie
Tivadar Kiss, Botond Borcsa, Péter Orvos, László Tálosi, Judit Hohmann, Dezső Csupor
Aconitum diterpene alkaloids are known for their remarkable toxicity, which is due to their effect on ion channels. Activation of voltage-gated Na(+) channels is the major cause of their cardiotoxicity, however, influence on K(+) channels may also play a role in the overall effect.Here we report the synthesis of a series of lipo-alkaloids, including four new compounds, based on the 14-benzoylaconine structure, which is the core of a vast number of diterpene alkaloids naturally occurring in Aconitum species...
May 4, 2017: Planta Medica
V Sladek, J Kóňa, H Tokiwa
Golgi α-mannosidase II (GM) is a pharmaceutical target for the design of inhibitors with anticancer activity. The known potent GM inhibitors undergo complex interactions with Zn(2+) ions and the active-site amino acids, many of which contain ionisable functional groups. Herein, the physical insight into the ligandreceptor interactions has been provided based on energy decomposition techniques: SAPT (symmetry adapted perturbation theory) and FMO-PIEDA (fragment molecular orbital-pair interaction energy decomposition analysis) for a large GM active-site cluster...
May 21, 2017: Physical Chemistry Chemical Physics: PCCP
Antonino S Aricò, Mariarita Girolamo, Stefania Siracusano, David Sebastian, Vincenzo Baglio, Michael Schuster
Water-fed photo-electrolysis cells equipped with perfluorosulfonic acid (Nafion(®) 115) and quaternary ammonium-based (Fumatech(®) FAA3) ion exchange membranes as separator for hydrogen and oxygen evolution reactions were investigated. Protonic or anionic ionomer dispersions were deposited on the electrodes to extend the interface with the electrolyte. The photo-anode consisted of a large band-gap Ti-oxide semiconductor. The effect of membrane characteristics on the photo-electrochemical conversion of solar energy was investigated for photo-voltage-driven electrolysis cells...
April 29, 2017: Membranes
Kira Tiedge, Gertrud Lohaus
Floral nectar contains mainly sugars but also amino acids, organic acids, inorganic ions and secondary compounds to attract pollinators. The genus Nicotiana exhibits great diversity among species in floral morphology, flowering time, nectar compositions, and predominant pollinators. We studied nectar samples of 20 Nicotiana species, composed equally of day- and night-flowering plants and attracting different groups of pollinators (e.g. hummingbirds, moths or bats) to investigate whether sugars, amino acids, organic acids and inorganic ions are influenced by pollinator preferences...
2017: PloS One
Arkadii V Tarasevych, Anton I Kostyukov, Mark G Baronskiy, Alexander A Rastorguev, Jean-Claude Guillemin, Valeriy N Snytnikov
Luminescent spectroscopy combined with the technique of luminescent probing with rare earth ions (europium, gadolinium, terbium) and an actinide ion (uranyl) was used to differentiate enantiopure and racemic alanine, the simplest chiral proteinogenic amino acid. Using the achiral luminescent probes, small differences between pure L and DL alanine in the solid state were strongly amplified. Based on the observed electronic transitions of the probes, the position of the triplet level of the coordinated alanine was estimated...
May 3, 2017: Chirality
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