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1.
Cristian Faralli Marco Pagliai Gianni Cardini Vincenzo Schettino 《Theoretical chemistry accounts》2007,118(2):417-423
The structure of the solvation shell of Na+ and K+ in fully deuterated liquid methanol has been studied by ab initio Car-Parrinello molecular dynamics simulations. The solvent
cage has been found relatively stable and this property has been explained by means of charge transfer and electrostatic interactions
as was previously done for Li+ in the same solvent. The differences with Li+ such as the increase of the coordination number going from Li+ to K+ and the reduced stability of the cage have been ascribed to the increase in the ionic radius. 相似文献
2.
Background
When cells are exposed to high salinity conditions, they develop a mechanism to extrude excess Na+ from cells to maintain the cytoplasmic Na+ concentration. Until now, the ATPase involved in Na+ transport in cyanobacteria has not been characterized. Here, the characterization of ATPase and its role in Na+ transport of alkaliphilic halotolerant Aphanothece halophytica were investigated to understand the survival mechanism of A. halophytica under high salinity conditions. 相似文献3.
H. N. Altshuler L. P. Abramova N. V. Malyshenko G. Yu. Shkurenko E. V. Ostapova 《Russian Chemical Bulletin》2005,54(8):1978-1981
The ion-exchange equilibrium in network polymers obtained from cis-2,8,14,20-tetraphenyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene by template synthesis on cations Na+, K+, and Ba2+ as matrices was studied. The selectivity coefficients of ion exchanges Ba2+-H+, Na+-H+, K+-H+, Na+-K+, and Na+-NH4
+ were determined. The template synthesis enhanced the affinity of the polymers to matrix-forming cations by 6–8 kJ mol−1.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1919–1922, August, 2005. 相似文献
4.
Yu. A. Karavanova I. A. Stenina A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2008,53(4):520-523
The kinetics of solid-phase reaction between iron(III) hydrogen sulfate and sodium chloride was studied by thermal analysis followed by analysis of leaving gases. The exchange kinetics are described by the soft cylinder model. The hydrogen and sodium ion interdiffusion coefficients were determined for various temperatures, as well as the activation energy of interdiffusion. Sodium ion diffusion through the product layer is the rate-controlling stage of the reaction. 相似文献
5.
G. I. Smirnov L. M. Dimova A. A. Redchenko 《Russian Journal of Applied Chemistry》2004,77(8):1259-1262
Ion-exchange sorption of K+ and Na+ from their mixture on X-ray-amorphous and crystalline Sn(IV) hydrophosphates was studied. These sorbents exhibit a high selectivity for K+. Amorphous Sn(IV) hydrophosphate can be used for efficient purification of aqueous sodium salt solutions to remove potassium impurity.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1275–1278.Original Russian Text Copyright © 2004 by Smirnov, Dimova, Redchenko. 相似文献
6.
V. Vasić D. Kojić K. Krinulović M. Čolović A. Vujačić D. Stojić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(9):1402-1406
Time-dependent interactions of Na+/K+-ATPase, isolated from rat brain synaptic plasma membranes (SPMs), with Cd2+ and Pb2+ ions in a single exposure and in a mixture were investigated in vitro. The interference of the enzyme with these metal ions
was studied as a function of different protein concentrations and exposure time. The aim of the work was to investigate the
possibility of selective recognition of Cd2+ and Pb2+ ions in a mixture, on the basis of the different rates of their protein-ligand interactions. Decreasing protein concentration
increased the sensitivity of Na+/K+-ATPase toward both metals. The selectivity in protein-ligand interactions was obtained by variation of preincubation time
(incubation before starting the enzymatic reaction).
The text was submitted by the authors in English. 相似文献
7.
Saeedeh Hashemian 《Russian Journal of Inorganic Chemistry》2011,56(3):397-401
The imidazol side group of histidine has two nitrogen atoms capable of being protonated or participating in metal binding.
Hence, histidine can take on various metal-bound and protonated forms in proteins. Because of its variable structural state,
histidine often functions as a key amino acid residue in enzymatic reactions. Ab initio (HF and MP2) calculations were done
in modeling the cation (H+, Li+, Na+, K+, Mg2+, Ca2+) interaction with side chain of histidine. The region selectivity of metal ion complexation is controlled by the affinity
of the side of attack. In the imidazol unite of histidine the ring nitrogen has much higher metal ion (as well as proton)
affinity. The complexation energies with the model systems decrease in the following order: Mg2+ > Ca2+ > Li+ > Na+ > K+. The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction
energies. 相似文献
8.
E. Yu. Safronova V. I. Volkov A. A. Pavlov A. V. Chernyak E. V. Volkov A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2011,56(2):156-162
The hydration, state, and mobility of protons and Li+, Na+, and Cs+ ions in MF-4SK perfluorinated sulfonic acid cation-exchange membranes doped with silicon dioxide and phosphotungstic acid
have been investigated by NMR and impedance spectroscopy. The dopants increase the moisture content of the membrane and change
the system of pores and channels in which ion transport takes place. At low humidities, the dopant particles are involved
in ion transport. The greatest effect is observed for the membranes doped with both SiO2 and phosphotungstic acid. The water molecules sorbed by dopant particles as a material participate in the hydration of alkali
metal cations in the membrane. 相似文献
9.
A. V. Mamchenko I. M. Kosygina O. A. Savchenko 《Russian Journal of Applied Chemistry》2010,83(5):801-805
Nonequilibrium dynamics of the Na+-Ca2+ exchange in water softening on a Lewatit CNP 80 carboxylic cation-exchanger was studied at a widely varying linear velocity
of water filtration. The kinetic coefficient of the pore-diffusion mass-transfer was determined at various flow rates of the
model solution. 相似文献
10.
E. S. Zakaria 《Journal of Radioanalytical and Nuclear Chemistry》2005,264(3):629-635
Summary This paper reports the radiochemical study of the ion-exchange of Cs+, Na+, Sr2+ and Eu3+ ions with H+ by chromium hexacyanoferrate(II) which was prepared in a granular form using a gel method. The slow steps which determine the rate of exchange of these ions are directly proportional to the particle diameter and this is confirmed from the linearity test of Bt vs. t plots at different particle diameters. Boyed’s equation and Reichenberg’s tables were used for evaluating all the kinetic parameters. The results reveal that the effective particle radii are unchanged for both chromium hexacyanoferrate(II) dried at 60 and 120 °C. The obtained data were analyzed using McKay plots and Arrhenius equation and the kinetic and thermodynamic parameters, e.g., effective diffusion coefficient, activation energies and entropies of activation have been evaluated. The mobility of these ions inside the particles of chromium hexacyanoferrate(II) decrease in the order of Eu3+>Sr2+>Na+⊃Cs+. 相似文献
11.
Krivec S Buchmayr M Detzel T Froemling T Fleig J Hutter H 《Analytical and bioanalytical chemistry》2011,400(3):649-657
The action of Na+ incorporation into thin insulating films and transport therein under influence of a bias voltage and temperature (BT stress)
is the subject of this work. Deposited onto highly n-doped Si wafers, the insulators get BT stressed and subsequently investigated by means of time-of-flight–secondary ion mass
spectrometry (ToF-SIMS). A thin PMMA film, spin-coated onto the insulator, serves as host matrix for a defined amount of Na+, provided via sodium triflate. Combining BT stress and ToF-SIMS depth profiling enables the unambiguous detection of Na+, incorporated into the insulating material. The insulators of interest vary in their nitride content: SiO2, SiOxNy, and Si3N4. For SiO2, it is shown that once a threshold BT stress is exceeded, Na+ gets quantitatively incorporated from PMMA into the underlying insulator, finally accumulating at the SiO2/Si interface. A quantitative assessment by combination of Butler–Volmer kinetics with hopping dynamics reveals activation
energies of E
a = 1.55 − 2.04 eV for Na+ transport in SiO2 with varying thickness. On the other hand, SiOxNy and Si3N4 films show a different Na+ incorporation characteristic in this type of experiment, which can be explained by the higher coordination of nitrogen and
hence the reduced Na+ permeability within these insulators. 相似文献
12.
V. P. Korolev 《Journal of Structural Chemistry》2011,52(4):737-742
The relations for the calculation of the partial molar volumes of NaCl, NaBPh4, and Ph4AsCl in an aqueous urea solution are obtained. The salt characteristics are divided into ionic components. Different methods
of the division are discussed. It is shown that the hydration numbers of Na+ and Cl− ions decrease with increasing urea concentration; therewith, the dehydration of Cl− ion occurs relatively faster. 相似文献
13.
G. N. Altshuler E. V. Ostapova L. A. Sapozhnikova O. G. Altshuler 《Russian Chemical Bulletin》2004,53(12):2670-2673
The corrected selectivity coefficients of the ion exchange H+-Na+ and H+-NH4
+ on ion-exchange resins based on C-tetramethylcalix[4]resorcinarene were calculated from the experimental data obtained from studying ion-exchange equilibria. The preference of the ion-exchange resins for cations increases in the sequence: Na+ < NH4
+ < < H+, and the ion-exchange resin based on (2-furyl)hydroxymethyltetramethylcalix[4]resorcinarene has a higher preference for ammonium cations. According to the results of microcalorimetric measurements, the exchange H+-Na+ on this ion-exchange resin is accompanied by the highest change in the differential enthalpy. It follows from the quantum-chemical calculations that the introduction of a (2-furyl)hydroxymethyl group into the structure of the polymer induces additional electrostatic interactions between an ammonium cation and an elementary unit of the ion-exchange resin.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2560–2563, December, 2004. 相似文献
14.
Jadwiga Ostrowska-Czubenko 《Colloid and polymer science》2002,280(11):1015-1020
The competitive binding of monovalent and divalent counterions to poly(alkylene phosphate) related to bacterial teichoic acids and poly(styrenesulfonate) was studied experimentally by potentiometry with ion-selective electrodes. The binding of calcium ions and the release of sodium ions accompanying calcium ions binding in aqueous solutions of the polyelectrolytes was analysed and the mean exchange ratio Na+/Ca2+ was estimated. It was found that in the process of addition of calcium ions to sodium poly(alkylene phosphate) and sodium poly(styrenesulfonate) solutions all the Ca2+ ions added are bound to polyions and the initially condensed Na+ ions are released proportionally to the concentration of the added Ca2+ ions up to the critical concentration of the Ca2+ ions added. For a molar concentration ratio of calcium counterions to charged groups on the polyion up to 0.20 the exchange ratio was approximately equal to 1 or 2 for the sodium poly(alkylene phosphate)/CaCl2 and sodium poly(styrenesulfonate)/CaCl2 systems, respectively. 相似文献
15.
V. A. Volynkin A. V. Pachuev A. N. Pirogova V. T. Panyushkin A. Ya. Shurygin 《Journal of Structural Chemistry》2011,52(5):892-896
The forms and structure of comenic acid and its salts with Na+ and Li+ in solution and solid state are studied by multinuclear NMR spectroscopy. The formation of dimeric structures of comenic
acid in the solid state is shown. It is found that disubstituted sodium and lithium salts have different structures. 相似文献
16.
A. N. Khazipova R. R. Il’yasova A. A. Tantseva B. I. Kutepov 《Russian Journal of Applied Chemistry》2011,84(4):577-581
Effect of parameters of the ion exchange of Na+ cations for La3+ in Y zeolites with SiO2/Al2O3 molar ratios of 5.1 and 6.0 on the degree of exchange and physicochemical properties of the resulting LaNaY samples was studied.
The conditions in which deeply substituted La-forms of a Y zeolite with high degree of crystallinity can be obtained were
determined. 相似文献
17.
Yu. A. Karavanova I. A. Stenina A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2009,54(7):995-1001
The kinetics of solid-phase reactions between hafnium hydrogen phosphate and alkali metal chlorides were studied by thermogravimetry with subsequent analysis of leaving gases. For sodium and potassium chlorides, the reaction occurs in two stages; the first stages produces MHHf(PO4)2, and the second yields the MHf2(PO4)3 NASICON phosphate. For rubidium chloride, the reaction is one stage and produces Rb2Hf(PO4)2. For cesium chloride, the reaction is an analogue of the reaction for rubidium chloride, but has two stages. Kinetic data were used to determine interdiffusion coefficients for hydrogen and alkali-metal ions at various temperatures and the activation energies of interdiffusion. 相似文献
18.
D. G. Samsonenko O. A. Gerasko A. V. Virovets V. P. Fedin 《Russian Chemical Bulletin》2005,54(7):1557-1562
The compound of composition [{Mo3O4(H2O)6Cl3}2(Na2Cl⊂ C30H30N 20O10)]Cl3⋅14H2O (1) was prepared by evaporation of a hydrochloric acid solution containing NaCl, the trinuclear aqua complex [Mo3O4(H2O)9]4+, and the macrocyclic cavitand cucurbit[5]uril (C30H30N20O10). X-ray diffraction analysis demonstrated that the cucurbit[5]uril molecule is closed on both sides by the cluster cations
through hydrogen bonding between the CO groups of the cucurbit[5]uril portals and the aqua ligands of the oxo cluster. The
inner cavity of the supramolecular adduct includes an unusual ionic associate Na+...Cl...Na+. The sodium cations are coordinated by five carbonyl oxygen atoms of each portal of the macrocycle. Compound 1 is the first structurally characterized complex, in which the macrocyclic cucurbit[5]uril ligand is directly coordinated
to the alkali metal cation.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1513–1517, July, 2005. 相似文献
19.
20.
Structure of a Na<Superscript>+</Superscript> cation hydration shell on heating in a planar nanopore
S. V. Shevkunov 《Journal of Structural Chemistry》2017,58(7):1368-1376
Resistance to heating above the boiling point of water of the molecular structure of a single-charged sodium cation hydration shell growing under the conditions of a model planar nanopore with a width of 5 Å is studied by computer simulation. Monte Carlo calculations of spatial correlation functions are performed in a detailed model with regard to many-body interactions between the ion and water molecules. The system demonstrates an increased resistance to thermal fluctuations along the pore plane and a decreased one in the transverse direction. The heating is accompanied by an enhanced coating effect of molecules around the ion and a diminished effect of extruding the ion out of its own hydration shell. The orientational molecular order due to strong spatial anisotropy inside the nanopore is much more stable than the hydrogen bonds between the molecules. 相似文献