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acid base strong ion

Sunil Nath
Theories of biological energy coupling in oxidative phosphorylation (OX PHOS) and photophosphorylation (PHOTO PHOS) are reviewed and applied to ATP synthesis by an experimental system containing purified ATP synthase reconstituted into liposomes. The theories are critically evaluated from the standpoint of the principle of electrical neutrality. It is shown that the obligatory requirement to maintain overall electroneutrality of bulk aqueous phases imposes strong constraints on possible theories of energy coupling and molecular mechanisms of ATP synthesis...
March 8, 2017: Biophysical Chemistry
Shuai Wang, Iker Agirrezabal-Telleria, Aditya Bhan, Dante Simonetti, Kazuhiro Takanabe, Enrique Iglesia
This account illustrates concepts in chemical kinetics underpinned by the formalism of transition state theory using catalytic processes that enable the synthesis of molecules suitable as fuels from C1 and oxygenate reactants. Such feedstocks provide an essential bridge towards a carbon-free energy future, but their volatility and low energy density require the formation of new C-C bonds and the removal of oxygen. These transformations are described here through recent advances in our understanding of the mechanisms and site requirements in catalysis by surfaces, with emphasis on enabling concepts that tackle ubiquitous reactivity and selectivity challenges...
March 16, 2017: Faraday Discussions
Yu Shao, Haoyang Jia, Tianyang Cao, Dongsheng Liu
Extracellular matrix (ECM) provides essential supports three dimensionally to the cells in living organs, including mechanical support and signal, nutrition, oxygen, and waste transportation. Thus, using hydrogels to mimic its function has attracted much attention in recent years, especially in tissue engineering, cell biology, and drug screening. However, a hydrogel system that can merit all parameters of the natural ECM is still a challenge. In the past decade, deoxyribonucleic acid (DNA) has arisen as an outstanding building material for the hydrogels, as it has unique properties compared to most synthetic or natural polymers, such as sequence designability, precise recognition, structural rigidity, and minimal toxicity...
March 16, 2017: Accounts of Chemical Research
Rikard Emanuelsson, Mia Sterby, Maria Strømme, Martin Sjödin
Rechargeable batteries that use organic matter as the capacity-carrying material have previously been considered a technology for the future. Earlier batteries in which both the anode and cathode consisted of organic material required significant amounts of conductive additives and were often based on metal-ion electrolytes containing Li(+) or Na(+). However, we have used conducting poly(3,4-ethylenedioxythiophene) (PEDOT), functionalized with anthraquinone (PEDOT-AQ) or benzonquinone (PEDOT-BQ) pendant groups as the negative and positive electrode materials, respectively, to make an all-organic proton battery devoid of metals...
March 15, 2017: Journal of the American Chemical Society
Tomomichi Kasagi, Hirokazu Imai, Naoto Miura, Keisuke Suzuki, Masabumi Yoshino, Hironobu Nobata, Takuhito Nagai, Shogo Banno
BACKGROUND: The Stewart model for analyzing acid-base disturbances emphasizes serum albumin levels, which are ignored in the traditional Boston model. We compared data derived using the Stewart model to those using the Boston model in patients with nephrotic syndrome. METHODS: Twenty-nine patients with nephrotic syndrome and six patients without urinary protein or acid-base disturbances provided blood and urine samples for analysis that included routine biochemical and arterial blood gas tests, plasma renin activity, and aldosterone...
March 13, 2017: Clinical and Experimental Nephrology
Hua Chen, Lin Chen, Dan Liu, Dan-Qian Chen, Nosratola D Vaziri, Xiao-Yong Yu, Li Zhang, Wei Su, Xu Bai, Ying-Yong Zhao
Chronic kidney disease (CKD) results in significant dyslipidemia and profound changes in lipid and lipoprotein metabolism. The associated dyslipidemia, in turn, contributes to progression of CKD and its cardiovascular complications. To gain an in-depth insight into the disorders of lipid metabolism in advanced CKD, we applied UPLC-HDMS-based lipidomics to measure serum lipid metabolites in 180 patients with advanced CKD and 120 age-matched healthy controls. We found significant increases in the levels of total free fatty acids, glycerolipids and glycerophospholipids in patients with CKD...
March 13, 2017: Journal of Proteome Research
Caroline West, Jodie Melin, Hassna Ansouri, Maïly Mengue Metogo
The mobile phases employed in current supercritical fluid chromatography (SFC) are usually composed of a mixture of pressurized carbon dioxide and a co-solvent. The co-solvent is most often an alcohol and may contain a third component in small proportions, called an additive (acid, base or salt). The polarity of such mobile phase compositions is here re-evaluated with a solvatochromic dye (Nile Red), particularly to assess the contribution of additives. It appears that additives, when employed in usual concentration range (0...
March 1, 2017: Journal of Chromatography. A
Eleni C Mazarakioti, Jeffery Regier, Luís Cunha-Silva, Wolfgang Wernsdorfer, Melanie Pilkington, Jinkui Tang, Theocharis C Stamatatos
The introduction of the Schiff base ligand N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2) in 4f-metal chemistry has afforded a new dinuclear complex, [Dy2(NO3)4(sacbH)2(H2O)2(MeCN)2] (1), with the metal ions adopting a rare spherical tricapped trigonal prismatic coordination geometry. The deprotonated phenoxido O atoms of the organic chelate occupy the axial triangular faces of the prism and were found to be very close to the main anisotropy axes of the two Dy(III) ions. As a result, the {Dy(III)2} compound exhibits frequency- and temperature-dependent out-of-phase ac signals below ∼25 K in the absence of a static dc field, yielding an energy barrier of 109...
March 7, 2017: Inorganic Chemistry
Scott E Denmark, David J P Kornfilt
The catalytic, enantioselective, cyclization of phenols with electrophilic sulfenophthalimides onto isolated or conjugated alkenes affords 2,3-disubstituted benzopyrans and benzoxepins. The reaction is catalyzed by a BINAM-based phosphoramide Lewis base catalyst which assists in the highly enantioselective formation of a thiiranium ion intermediate. The influence of nucleophile electron density, alkene substitution pattern, tether length and Lewis base functional groups on the rate, enantio- and site-selectivity for the cyclization is investigated...
March 17, 2017: Journal of Organic Chemistry
Huaixu Cheng, Zhidan Luo, Mingsheng Lu, Song Gao, Shujun Wang
The hyperthermophilic α-amylase from Thermococcus sp. HJ21 does not require exogenous calcium ions for thermostability, and is a promising alternative to commercially available α-amylases to increase the efficiency of industrial processes like the liquefaction of starch. We analyzed the amino acid sequence of this α-amylase by sequence alignments and structural modeling, and found that this α-amylase closely resembles the α-amylase from Pyrococcus woesei. The gene of this α-amylase was cloned in Escherichia coli and the recombinant α-amylase was overexpressed and purified with a combined renaturation-purification procedure...
March 1, 2017: Journal of Microbiology / the Microbiological Society of Korea
Yanti, Madriena, Soegianto Ali
BACKGROUND: Cosmeceuticals refer to natural cosmetics with medical-like benefits due to their bioactive contents. Sugar palm fruit (Arenga pinnata) extract has been claimed for its anti-aging effect in vitro. However, its active compounds for cosmeceuticals is still unclear. OBJECTIVE: This study was aimed to extract galactomannan from A. pinnata fruits and test its efficacy for tyrosinase inhibition, antioxidant, and anti-photoaging activities in vitro. MATERIALS AND METHODS: Galactomannan from A...
January 2017: Pharmacognosy Research
Cailong Zhou, Zhaodan Chen, Hao Yang, Kun Hou, Xinjuan Zeng, Yanfen Zheng, Jiang Cheng
Phytic acid, which is a naturally occurring component that is widely found in many plants, can strongly bond toxic mineral elements in the human body, because of its six phosphate groups. Some of the metal ions present the property of bonding with phytic acid to form insoluble coordination complexes aggregations, even at room temperature. Herein, a superhydrophobic cotton fabric was prepared using a novel and facile nature-inspired strategy that introduced phytic acid metal complex aggregations to generate rough hierarchical structures on a fabric surface, followed by PDMS modification...
March 6, 2017: ACS Applied Materials & Interfaces
Andrea Carotti, Federica Ianni, Emidio Camaioni, Lucia Pucciarini, Maura Marinozzi, Roccaldo Sardella, Benedetto Natalini
In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C10-(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for ligand-exchange chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C10-(R)-STC-based CSP, with resolution factor (RS) values up to 8...
February 5, 2017: Journal of Pharmaceutical and Biomedical Analysis
Kimberly L Davidson, Matthew F Bush
Ion mobility (IM) separates ions based on their response to an electric field in the presence of a drift gas. Because of its speed and sensitivity, the integration of IM and mass spectrometry (MS) offers many potential advantages for the analysis of small molecules. To determine the effects that drift gas selection has on the information content of IM separations, absolute collision cross sections (Ω) with He, N2, Ar, CO2, and N2O were measured for the 20 common amino acids using low-pressure, ambient-temperature ion mobility experiments performed in a radio frequency-confining drift cell...
February 7, 2017: Analytical Chemistry
C Phillip Shelor, Purnendu K Dasgupta, Hongzhu Liao
We describe a fatty acid vapor extractor (FAVE) as a postcolumn device for sensitive detection following ion exclusion chromatographic (ICE) separation of weak acids. The device consists of a single length of a permselective membrane tube surrounded by a jacket that consists of two isolated sections. The separation column effluent flows through the lumen. A suitable strong acid is put in the upstream, short section of the jacket and permeates in, rendering the lumenal flow strongly acidic (pH ≤ 2) that suppresses eluite weak acid dissociation...
December 20, 2016: Analytical Chemistry
Anais Graff, Etienne Barrez, Philippe Baranek, Martin Bachet, Pascale Bénézeth
An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel-boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70 °C...
2017: Journal of Solution Chemistry
Amir Taghavi Nasrabadi, Lev D Gelb
Ammonium-based protic ionic liquids (PILs) have shown promising physicochemical properties as proton conductors in polymer membrane fuel cells. In this work, molecular dynamics simulations are used to study the structural, dynamic, and transport properties of a series of tertiary ammonium triflate PILs. Nonpolarizable all-atom force fields were used, including two different models for the triflate anion. Previous simulation studies of these PILs have yielded poor results for transport properties due to unrealistically slow dynamics...
February 17, 2017: Journal of Physical Chemistry. B
Ning Huang, Lipeng Zhai, Hong Xu, Donglin Jiang
The pre-designable porous structures found in covalent organic frameworks (COFs) render them attractive as a molecular platform for addressing environmental issues such as removal of toxic heavy metal ions from water. However, a rational structural design of COFs in this aspect has not been explored. Here we report the rational design of stable COFs for Hg(II) removal through elaborate structural design and control over skeleton, pore size, and pore walls. The resulting framework is stable under strong acid and base conditions, possesses high surface area, has large mesopores, and contains dense sulfide functional termini on the pore walls...
February 7, 2017: Journal of the American Chemical Society
Mimi Gao, Loana Arns, Roland Winter
Folding of ribonucleic acids (RNAs) is driven by several factors, such as base pairing and stacking, chain entropy, and ion-mediated electrostatics, which have been studied in great detail. However, the power of background molecules in the cellular milieu is often neglected. Herein, we study the effect of common osmolytes on the folding equilibrium of a hairpin-structured RNA and, using pressure perturbation, provide novel thermodynamic and volumetric insights into the modulation mechanism. The presence of TMAO causes an increased thermal stability and a more positive volume change for the helix-to-coil transition, whereas urea destabilizes the hairpin and leads to an increased expansibility of the unfolded state...
January 19, 2017: Angewandte Chemie
Yuvraj Y Birdja, Marc T M Koper
A seemingly catalytically inactive electrode, boron-doped diamond (BDD), is found to be active for CO2 and CO reduction to formaldehyde and even methane. At very cathodic potentials, formic acid and methanol are formed as well. However, these products are the result of base-catalyzed Cannizzaro-type disproportionation reactions. A local alkaline environment near the electrode surface, caused by the hydrogen evolution reaction, initiates aldehyde disproportionation promoted by hydroxide ions, which leads to the formation of the corresponding carboxylic acid and alcohol...
February 8, 2017: Journal of the American Chemical Society
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