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acid base strong ion

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https://www.readbyqxmd.com/read/28102930/modulation-of-the-thermodynamic-signatures-of-an-rna-thermometer-by-osmolytes-and-salts
#1
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
https://www.readbyqxmd.com/read/28099805/the-importance-of-cannizzaro-type-reactions-during-electrocatalytic-reduction-of-carbon-dioxide
#2
Yuvraj Y Birdja, Marc T M Koper
A seemingly catalytic inactive electrode as boron doped diamond 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...
January 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28099170/exploring-the-ability-of-the-nalidixate-to-sensitize-visible-and-near-infrared-emitting-lanthanide-iii-cations
#3
Svetlana V Eliseeva, Valerii S Liasotkyi, Iurii P Golovach, Pavel G Doga, Valery P Antonovich, Stéphane Petoud, Svetlana B Meshkova
Recently, a strong interest has been directed towards near-infrared (NIR) emitting lanthanide(III) compounds as they do possess complementary advantages in respect to organic molecules and semi-conductor nanocrystals, especially in the fields of biological analysis and imaging. To benefit from their emission, a key requirement to fulfill is the sensitization of lanthanide(III) cations with an appropriate chromophore. This condition is especially challenging to address for the lanthanide(III) cations emitting in the NIR...
January 18, 2017: Methods and Applications in Fluorescence
https://www.readbyqxmd.com/read/28070588/a-silica-based-sers-chip-for-rapid-and-ultrasensitive-detection-of-fluoride-ions-triggered-by-a-cyclic-boronate-ester-cleavage-reaction
#4
Jian Zhang, Lifang He, Peirong Chen, Chao Tian, Jianping Wang, Bianhua Liu, Changlong Jiang, Zhongping Zhang
Chemical sensing for the convenient detection of trace aqueous fluoride ions (F(-)) has been widely explored with the use of various sensing materials and techniques. It still remains a challenge to achieve ultrasensitive but simple, rapid, and inexpensive detection of F(-) for environmental monitoring and protection. Here we reported a novel surface-enhanced Raman scattering (SERS) nanosensor, fluorescein phenylboronic acid covalently linked to 1,4-dimercapto-2,3-butanediol modified Au@Ag NPs by a cyclic boronate ester (Flu-PBA-Diol-Au@Ag NPs), for the rapid and ultrasensitive detection of F(-)...
January 10, 2017: Nanoscale
https://www.readbyqxmd.com/read/28063295/role-of-calcium-ions-on-the-removal-of-haloacetic-acids-from-swimming-pool-water-by-nanofiltration-mechanisms-and-implications
#5
Linyan Yang, Jin Zhou, Qianhong She, Man Pun Wan, Rong Wang, Victor W-C Chang, Chuyang Y Tang
We investigated the removal of haloacetic acids (HAAs) from swimming pool waters (SPWs) by two nanofiltration membranes NF270 and NF90. The strong matrix effect (particularly by Ca(2+)) on membrane rejection prompts us to systematically investigate the mechanistic role of Ca(2+) in HAA rejection. At typical SPW pH of 7.5, NF90 maintained consistently high rejection of HAAs (>95%) with little influence by Ca(2+), thanks to the dominance of size exclusion effect for this tight membrane (pore radius ∼ 0...
November 14, 2016: Water Research
https://www.readbyqxmd.com/read/28034959/counting-the-ions-surrounding-nucleic-acids
#6
David R Jacobson, Omar A Saleh
Nucleic acids are strongly negatively charged, and thus electrostatic interactions-screened by ions in solution-play an important role in governing their ability to fold and participate in biomolecular interactions. The negative charge creates a region, known as the ion atmosphere, in which cation and anion concentrations are perturbed from their bulk values. Ion counting experiments quantify the ion atmosphere by measuring the preferential ion interaction coefficient: the net total number of excess ions above, or below, the number expected due to the bulk concentration...
December 29, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/28034505/high-performance-thin-layer-chromatography-mass-spectrometry-of-japanese-knotweed-flavan-3-ols-and-proanthocyanidins-on-silica-gel-plates
#7
Vesna Glavnik, Irena Vovk, Alen Albreht
On-line elution based TLC-MS is now a well-established technique, but the quality of the data obtained can sometimes be hampered by a severe spectral background or by strong ion suppression, especially when silica gel plates are used in combination with an acidic modifier in the developing solvent. We solved this issue simply and efficiently using two pre-developments of the plates, firstly with methanol-formic acid (10:1, v/v) and secondly with acetonitrile-methanol (2:1, v/v). This solution resulted in significant improvement in the sensitivity of HPTLC-MS methods...
December 21, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28033575/multi-wavelength-spectrophotometric-determination-of-cr-vi-in-water-with-abts
#8
Wenjuan Fan, Junlian Qiao, Xiaohong Guan
A new method for Cr(VI) (0.025-8.00 mg/L) determination based on the reaction of Cr(VI) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in aqueous solutions was developed. The colorless ABTS reacted with Cr(VI) under strong acidic conditions ([H(+)] = 3.0 or 6.0 M) producing a stable colored radical ABTS(+), which could be measured spectrophotometrically at 415, 649 or 732 nm. The absorbance increase at these three wavelengths for ABTS(+) generation were all linear (less than 1.0% deviation) with respect to the amount of added Cr(VI) and the sensitivity were 1...
December 1, 2016: Chemosphere
https://www.readbyqxmd.com/read/28028530/acid-base-and-hemodynamic-status-of-patients-with-intraoperative-hemorrhage-using-two-solution-types-crystalloid-ringer-lactate-and-1-3-sodium-bicarbonate-in-half-normal-saline-solution
#9
Sayed Jalal Hashemi, Sayed Morteza Heidari, Ahmad Yaraghi, Reza Seirafi
BACKGROUND: Intraoperative hemorrhage is one of the problems during surgery and, if it happens in a high volume without an immediate action to control, it can be fatal. Nowadays, various injectable solutions are used. The aim of this study was to compare the acid-base and hemodynamic status of the patient using two solutions, Ringer lactate and 1.3% sodium bicarbonate, in half saline solution. MATERIALS AND METHODS: This clinical trial was performed at the Al-Zahra Hospital in 2013 on 66 patients who were randomly selected and put in two studied groups at the onset of hemorrhage...
2016: Advanced Biomedical Research
https://www.readbyqxmd.com/read/27990831/-clinical-evaluation-of-acid-base-status-henderson-hasselbalch-or-stewart-fencl-approach
#10
Karel Matoušovic, Jan Havlín, Otto Schück
Two approaches have been used in clinical evaluation the acid-base status: traditional (bicarbonate-centered) is based on the Henderson-Hasselbalch equation complemented by calculation of the anion gap, and more recent quantitative approach proposed by Stewart and Fencl. The latter method defines the three independent variables, which regulate pH. These include: the difference between the sum of charges carried by strong plasma cations and anions termed the strong ion difference - SID (decrease causes acidosis, and vice versa); the total concentration of the weak non-volatile acids [Atot] (inorganic phosphate and albumin, decrease causes alkalosis and vice versa), and pCO2...
2016: Casopís Lékar̆ů C̆eských
https://www.readbyqxmd.com/read/27990824/surface-tension-of-acid-solutions-fluctuations-beyond-the-nonlinear-poisson-boltzmann-theory
#11
Tomer Markovich, David Andelman, Rudi Podgornik
We extend our previous study of surface tension of ionic solutions and apply it to acids (and salts) with strong ion-surface interactions, as described by a single adhesivity parameter for the ionic species interacting with the interface. We derive the appropriate nonlinear boundary condition with an effective surface charge due to the adsorption of ions from the bulk onto the interface. The calculation is done using the loop-expansion technique, where the zero loop (mean field) corresponds of the full nonlinear Poisson-Boltzmann equation...
December 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/27987757/in-situ-production-of-silver-nanoparticles-for-high-sensitive-detection-of-ascorbic-acid-via-inner-filter-effect
#12
B Rezaei, M Shahshahanipour, Ali A Ensafi
In the present research, a sensitive biosensing method was proposed for the detection of trace amounts of ascorbic acid (AA). Herein, colloidal silver nanoparticles (SNPs) were successfully in-situ produced by chemical reduction of silver ion in the presence of AA, as a reducing agent. The one-pot in-situ produced silver nanoparticles were characterized by UV-vis, dynamic light scattering (DLS), zeta potential and transmission electron microscopic (TEM). SNPs act as a strong fluorescence quencher for the CdTe quantum dots via an inner filter effect (IFE)...
February 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/27979313/high-resolution-of-racemic-phenylalanine-with-dication-imidazolium-based-chiral-ionic-liquids-in-a-solid-liquid-two-phase-system
#13
Xiaoxia Huang, Haoran Wu, Zhixia Wang, Yingjie Luo, Hang Song
A novel solid-liquid two-phase system was developed for the chiral separation of racemic phenylalanine with new dication imidazolium-based chiral ionic liquids. Preliminary experiments showed distinct enantioselectivity in amino acid extraction with the novel solid-liquid two-phase system, more L-enantiomer of amino acid cooperatively interacted with ionic liquids and copper ions to be the solid phase. Various factors, including the alkyl chain length of cations of ionic liquids, the amount of copper acetate, the ratio of n(ILs)/n(Cu(2+)), the amount of water and racemic phenylalanine, the resolution time together with the resolution temperature, were systematically investigated for their influence on resolution efficiency...
January 6, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/27976871/metabolism-of-the-tobacco-carcinogen-2-amino-9h-pyrido-2-3-b-indole-a%C3%AE-c-in-primary-human-hepatocytes
#14
Medjda Bellamri, Ludovic Le Hegarat, Robert J Turesky, Sophie Langouët
2-Amino-9H-pyrido[2,3-b]indole (AαC) is the most abundant carcinogenic heterocyclic aromatic amine (HAA) formed in mainstream tobacco smoke. AαC is a liver carcinogen in rodents, but its carcinogenic potential in humans is not known. To obtain a better understanding of the genotoxicity of AαC in humans, we have investigated its metabolism and its ability to form DNA adducts in human hepatocytes. Primary human hepatocytes were treated with AαC at doses ranging from 0.1-50 μM, and the metabolites were characterized by ultra-performance LC/ion trap multistage mass spectrometry (UPLC/MS(n))...
December 15, 2016: Chemical Research in Toxicology
https://www.readbyqxmd.com/read/27966707/mesoporous-stilbene-based-lanthanide-metal-organic-frameworks-synthesis-photoluminescence-and-radioluminescence-characteristics
#15
Stephan R Mathis Ii, Saki T Golafale, John Bacsa, Alexander Steiner, Conrad W Ingram, F Patrick Doty, Elizabeth Auden, Khalid Hattar
Ultra large pore isostructural metal organic frameworks (MOFs) which exhibit both photoluminescence and scintillation properties, were synthesized from trans-4,4'-stilbenedicarboxylic acid (H2L) and trivalent lanthanide (Ln) metal salts under solvothermal conditions (Ln = Er(3+) (1) and Tm(3+) (2)). This new class of mesoporous materials is a non-interpenetrating network that features ultra-large diamond shaped pores of dimensions with approximate cross-sectional dimensions of 28 Å × 12 Å. The fully deprotonated ligand, L, is isolated and rigidified as it serves as the organic linker component of the MOF structure...
January 3, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/27936618/continuous-separation-of-dna-molecules-by-size-using-insulator-based-dielectrophoresis
#16
Paul Vernon Jones, Gabriel L Salmon, Alexandra Ros
Separation of nucleic acids has long served as a central goal of analytical research. Innovations in this field may soon enable the development of rapid, on-site sequencing devices that significantly improve both the availability and accuracy of detailed bioinformatics. However, achieving efficient continuous-flow operation and size-based fractionation of DNA still presents considerable challenges. Current methods have not yet satisfied the need for rapid fractionation of size-heterogeneous nucleic acid samples into specific and narrow size distributions...
December 12, 2016: Analytical Chemistry
https://www.readbyqxmd.com/read/27935129/performance-comparison-of-esi-and-apci-in-untargeted-and-targeted-lc-ms-based-metabolomics-analysis-of-grapeberry-metabolites
#17
Mauro Commisso, Andrea Anesi, Silvia Dal Santo, Flavia Guzzo
RATIONALE: Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are both used to generate ions for the analysis of metabolites by liquid chromatography/mass spectrometry (LC-MS). We compared the performance of these methods for the analysis of Corvina grapevine berry methanolic extracts, which are complex mixtures of diverse metabolites. METHODS: Corvina berries representing three ripening stages (veraison, early-ripening and full-ripening) were collected during two growing seasons, powdered and extracted with methanol...
December 9, 2016: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/27934986/a-unique-copper-ii-assisted-transformation-of-acetylacetone-dioxime-in-acetone-that-leads-to-one-dimensional-quinoxaline-bridged-coordination-polymers
#18
Zoi G Lada, Amaia Soto Beobide, Aikaterini Savvidou, Catherine P Raptopoulou, Vassilis Psycharis, George A Voyiatzis, Mark M Turnbull, Spyros P Perlepes
The reactions of copper(ii) carboxylate sources with acetylacetone dioxime (acacdoH2) in Me2CO have been studied and a novel, metal ion-assisted ligand transformation has been discovered. The reaction of [Cu2(diba)4(dibaH)2] and acacdoH2 (1 : 1.5) in Me2CO has provided access to the complex {[Cu2(diba)4(qunx)]}n (1) in low yield (25-30%), where dibaH is 3,3-dimethylbutyric acid and qunx is quinoxaline. The [Cu2(piv)4(pivH)2]/acacdoH2 (1 : 1.5) reaction system in warm Me2CO, where pivH is pivalic acid, gave the analogous complex {[Cu2(piv)4(qunx)]}n (2) in moderate yield (∼50%)...
December 20, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/27924036/folding-and-misfolding-pathways-of-g-quadruplex-dna
#19
Adrien Marchand, Valérie Gabelica
G-quadruplexes adopt various folding topologies, but information on their folding pathways remains scarce. Here, we used electrospray mass spectrometry to detect and quantify the specifically bound potassium ions, and circular dichroism to characterize the stacking topology of each ensemble. For human telomeric (hTel) sequences containing the d((GGGTTA)3GGG) core, K(+) binding affinity and cooperativity strongly depends on the chosen construct. The shortest sequences bind only one K(+) at low KCl concentration, and this 2-quartet G-quadruplex is antiparallel...
December 15, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27918643/electrostatic-assembly-guided-synthesis-of-highly-luminescent-carbon-nanodots-baso4-hybrid-phosphors-with-improved-stability
#20
Ding Zhou, Yuechen Zhai, Songnan Qu, Di Li, Pengtao Jing, Wenyu Ji, Dezhen Shen, Andrey L Rogach
Carbon nanodots (CNDs)@BaSO4 hybrid phosphors are fabricated in an easy and low-cost process by sequentially assembling Ba(2+) and SO4(2-) ions onto the surface of carbon nanodots through electrostatic attraction. CNDs act as the nucleus to attract these reactive ions and provide the luminescent centers in the hybrid phosphors. This strategy is versatile for a variety of negatively charged CNDs with different emission colors. The advantage of the resultant hybrid phosphors is that their luminescence exhibits excellent thermal and photostability, as well as remarkable resistance to strong acid/alkali and common organic solvents...
December 5, 2016: Small
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