Sodium Ions In Solution Research Articles

MONTMORILLONITE SURFACE AS A CATALYST FOR THE FORMATION OF SAT METAL TETRA (P-SULPHOPHENYL) PORPHYRINS

The adsorption of the water-soluble tetra(p-sulphophenyl)porphyrin (TPPS) compound on Fe(II), Fe(III), Cu(II), Co(II), Ni(II), Zn(II), Cd(II), Sn(IV) and UO22+ metal ion-exchanged montmorillonite (MMT) facilitated the formation of the SAT metal-TPPS MMT complexes of these cations (where SAT indicates sitting atop, ie the metal is above the porphyrin plane and is bound to external ligands in this case the MMT surface). All the resulting powder samples have a brown-orange colour due to the presence of the metal-TPPS-MMT complexes of these cations. Heating the solid powder samples caused demetallation and changed the colour of the powder from brown-orange colour of the metal-TPPS-MMT complex to the green colour of the diacid porphyrin on the clay. When such samples were exposed to the open atmosphere where they could absorb water vapour, the brown-orange colour appeared again due to the remetallation. The cation remained in the vicinity of the TPPS molecule upon demetallation, which makes the metallation-demetallation process reversible. The TPPS has been found to be adsorbed only on the external surface, and can be intercalated using sodium ions in solution with the compound to open the clay lattice. The reactions were monitored using visible absorption spectra, diffuse reflectance spectra, Mössbauer spectroscopy and X-ray diffraction.

The Influence of Ionic Liquids on Micellization of Sodium Dodecyl Sulfate in Aqueous Solutions

The micellization of sodium dodecyl sulfate (SDS) in water and aqueous solutions of NaCl (0.1 M) and three ionic liquids (IL, 0.01 M) with different side-chain length, i.e. 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium chloride was investigated in the temperature range from 288.15 to 328.15 K using isothermal titration calorimetry (ITC). Thermodynamics of micellization was studied by the fitting of the mass-action model to the ITC data. The micellization of SDS in all the studied systems is an entropy-driven at lower temperatures and an enthalpy-driven at higher temperatures. It was also found that with the increasing nonpolar character of IL the interactions between the SDS should be stronger leading to more negative Gibbs free energy and enthalpy of micellization. To obtain information about the micellar charge, the conductivity and zeta-potential measurements were performed at 298.15 K. It is assumed that the charge screening between negative sulfate heads is more efficient in the presence of ILs due to their possible incorporation into the micellar structure reflecting in less negative zeta-potential of micelles comparing to SDS in water and consequently higher degrees of micelle ionization due to the larger portion of sodium ions in solution.

ГЕОЭКОЛОГИЧЕСКИЕ АСПЕКТЫ ИСПОЛЬЗОВАНИЯ ПРИРОДНЫХ ЦЕОЛИТОВ

In the paper the issues of using of natural zeolites from Eastern Transbaikal for solving geoecological problems are considered. Chemical and mineral composition of natural zeolites from Eastern Transbaikal is presented. Main directions of the application of zeolite containing rocks at mining industry and for environmental protection at atomic power provision mining enterprises are outlined. Experimental investigations for decontaminating of waste water of industrial enterprises from radionuclide and other contaminants. Characteristics of sorption with natural zeolites 137Cs from solution 0.1 and 1.0 mol/l sodium nitrate are represented. Sorption dependences 137Cs from concentration of sodium ions in solution and from size of sorbent granules are established. Results of investigation of sorption with natural zeolite of radionuclide 90Sr and ions Са2+.

Temperature effect on ion selectivity of potassium and sodium ions in solution

The effect of temperature on ion selectivity of various-diameter nanopores in an NaCl and KCl solution has been studied with molecular dynamics simulation. Our results indicate that ion selectivity is absent at high temperature, while pores become increasingly selective as the system temperature decreases, but that depends on the nano-pore diameter. By investigating how the hydration shell of ions and cation–anion interactions affect the ability of ions to access the nanopore, we reveal the mechanism behind this dependence of selectivity on temperature. The implication that ion selectivity is vulnerable to higher temperature may provide a useful selectivity-control mechanism, and may help improve the performance of permeable membranes.

Binding thermodynamics of a glutamate transporter homolog

Glutamate transporters catalyze concentrative uptake of the neurotransmitter into glial cells and neurons. Their transport cycle involves binding and release of the substrate on the extra- and intracellular sides of the plasma membranes, and translocation of the substrate-binding site across the lipid bilayers. The energy of the ionic gradients, mainly sodium, fuels the cycle. Here, we used a cross-linking approach to trap a glutamate transporter homologue from Pyrococcus horikoshii in key conformational states with substrate-binding site facing either the extracellular or intracellular sides of the membrane to study their binding thermodynamics. We show that the chemical potential of sodium ions in solution is exclusively coupled to substrate binding and release, and not to substrate translocation. Despite the structural symmetry, the binding mechanisms are distinct on the opposite sides of the membrane and more complex than the current models suggest.

Synthesis and extension/contraction motion of spiroborate-based double-stranded helicates consisting of substituted oligophenol strands

A new class of ortho- and meta-substituted tetraphenols at the terminal phenyl residues with a biphenylene unit in the middle were synthesized and the effect of the substitution position on the spiroborate-based double-stranded helicate formation with sodium borohydride was investigated. The ortho-substitution considerably hampered the spiroborate formation between the terminal biphenol units and the boron atoms, whereas the meta-substituted oligomers formed a double-stranded helicate bridged by spiroborate groups accommodating a sodium cation in the center, which displayed an extension and contraction motion triggered by the removal and addition of sodium ions in solution.

Ion-triggered spring-like motion of a double helicate accompanied by anisotropic twisting

Molecules that extend and contract under external stimuli are used to build molecular machines with nanomechanical functions. But although common in biological systems, such extension and contraction motions with helical molecules have rarely been accompanied by unidirectional twisting in synthetic systems. Here we show that sodium ions can trigger the reversible anisotropic twisting of an enantiomeric double-stranded helicate, without racemization. An optically active helicate consisting of two tetraphenol strands bridged by two spiroborate groups sandwiches a sodium ion. On removal of the central sodium-through addition of a cryptand [2.2.1] in solution-the double helicate extends. Crystallographic and nuclear magnetic resonance studies reveal that the extended helicate is over twice as long as the initial molecule, and is twisted in the right-handed direction. Circular dichroism analysis suggests that the twisting doesn't affect the helicate's handedness. This anisotropic extension-contraction process is reversibly triggered by the successive addition and removal of sodium ions in solution.

Electrochemical recognition of analytes using quaternary ammonium binaphthyl salts.

The electrooxidation of quaternary ammonium binaphthyl salts is shown to proceed by a quasi-reversible one-electron process. The oxidation of an aza-crown ether substituted binaphthyl salt is affected by the presence of lithium and sodium ions in solution and there is shown to be a linear relationship between the limiting current for the process and the concentration of Li+ and Na+. The electrochemistry of the binaphthyl salt is also shown to be affected by the addition of organic cations to the solution, showing that these receptors could form the basis of analytical devices which could be made specific to a range of analytes.

Desilication veins in the Cadillac Mountain granite (Maine, USA): a record of reversals in the SiO2 solubility of H2O-rich vapour released during subsolidus cooling

Late-stage hydrous fluids, which evolved during the cooling of the Cadillac Mountain granite, Maine, USA, produced narrow veins that transect the pluton. The vein margins contain microstructures transitional between granite and the vein centre. They preserve the vestige shapes of original Na-rich alkali feldspar crystals that have been pseudomorphed by cordierite+quartz+K-rich alkali feldspar. Closer to the centres of the veins, the minerals change from an outer zone with cordierite, hercynitic–galaxite spinel, minor corundum, K-feldspar and plagioclase to an inner zone with remnant cordierite, hercynitic gahnite, strongly zoned almandine–spessartine garnet, chlorite and quartz. Three allochemical reactions are inferred to have occurred with the influx of hydrous fluids during the replacement process. Reaction (1) is Na-rich alkali feldspar+iron ions in solution=Fe-cordierite+quartz+K-feldspar+sodium ions in solution. Reactions (2) and (3) occurred during desilication. Reaction (2) is Fe-cordierite=hercynite+silica in solution, and reaction (3)isFe-cordierite+water=corundum+iron hydroxide in solution+silicic acid in solution.Two independent techniques, experimental silica-solubility data and spinel–cordierite thermobarometry, constrain the conditions of vein formation to c. 1.0 kbar and both methods indicate that the progressive mineral reactions occurred during cooling of the hydrous fluids from c. 775° to 400–340 °C. This cooling trend is consistent with the petrographic evidence, which demonstrates that reactions occurred before desilication, during desilication, and then diminished with a final phase of resilication. Although the veins are minor features of the Cadillac Mountain granite, they provide insight into the conditions that prevailed during cooling of the pluton, and similar features may be important for constraining the cooling history of shallow-level plutonic complexes elsewhere.

Molecular dynamics simulation of the adsorption of benzene on charged metal electrodes in the presence of aqueous electrolyte

Abstract Classical molecular dynamics was used to model the adsortion of benzene on metal electrodes in a thin electrochemical cell containing aqueous NaCl solution. On uncharged electrodes benzene was adsorbed mostly flat and the ions formed a neural diffuse region between the electrodes. As the charge on the electrode was increased the diffuse layer rearranged to shield the center of the film from the electric field. The remaining high electric field at the surface caused ordering of water molecules next to the metal, and this in turn promoted benzene desorption. Desorption occurred first from the cathode because of a higher surface electric field between the hydrate sodium ion in solution and the negative electrode. At the anode the field across the water layer was lower because the chloride ion was adsorbed in contact closer to metal than the water layer. At the highest electrode charge density both ions were adsorbed in contact on their respective electrodes and benzene was desorbed from both surfaces into the central aqueous region.

Thermodynamic study of sorption of some linear aliphatic monocarboxylic acids from aqueous solution by photografted membranes immobilizing zeolite

Sorption studies of propanoic, n-butanoic, n-pentanoic, and n-hexanoic acids from their 1.80 × 10 −4 − 2.75 × 10 −2 M aqueous solutions were carried out at 283–343 K on 1.6-–3.3 μm microporous membranes supporting 9.60 ± 0.06 mg cm −2 of photochemically grafted epoxy-diacrylate composite containing 20.0 wt.% of zeolite 13X onto a cellulose substrate. Two kinds of sorption have been ascertained: 1. i ) adsorption of alkanoic acids in the zeolite channels; 2. ii ) ion exchange paralleled by decrease of hydrogen ions and uptake of sodium ions in solutions. Thermodynamics of these two equilibria have been studied and mean enthalpies and entropies for processes i ) and ii ) evaluated. The influence of pK a of alkanoic acids was evidenced only in equilibrium constants and thermodynamic parameters of reaction ii ), while equilibrium constants for Langmuir adsorption through hydrogen bonds are practically independent of chain length. The model proposed for this complex sorption process supports soundly all experimental evidence. Competition between adsorption and ion exchange may be observed under conditions in which equilibrium constants for these two processes have comparable values. This situation may be reached owing to the endothermic adsorption process and the slightly exothermic hydrogen ion exchange.

On the discrimination of bound and free sodium ions in solutions of biomolecules by means of the T1 relaxation.

Abstract The interactions of charged macromolecules with counterions have been extensively examined previously by 23Na NMR, leading to the model that the counterions can be classified as beeing both “free” and “bound” in solution. We will demonstrate that the two dimensional time evolution approach for resolving a composite “free-induction-decay” opens the possibilities to measure both the T1 of the free sodium ion and the T1 of the sodium ion bound to a macromolecule simultaneously. A lot of various compounds as DNA and Heparin serve as models to demonstrate the usefulness of this new method.

Permeability of the integument of the horseshoe crab, Limulus polyphemus, to water, sodium, and bromide

AbstractMean water movements across the double chitin membrane of the Limulus gill are 5,000–7,000 μmoles/cm2 · h. The carapace is much less permeable to water than the gill; this difference is probably due primarily to the greater thickness of the carapace. Variations in serum sodium concentration due to salinity changes do not affect the rates of water diffusion across the gills or carapace. The cause of a substantial variation between individuals in integumental water permeability is unknown. The sodium influx across the carapace of Limulus (0.7–1.6 μmoles/cm2 · h) is only a fraction that of the unidirectional water flux under the same conditions (0.5 M NaCl on both sides). This difference may be attributed to the greater size of the sodium ion in solution. There is no apparent effect of variations in carapace thickness on the sodium influx. The double chitin gill membrane is similarly low in sodium and bromide permeability (about 0.5–0.6 μmole/cm2 · h). Thus it appears that the gills may have a relatively passive role in ionic regulation. Their low rates of ionic diffusion help to restrict the loss or intake of salts as the salinity changes. However, the high gill permeability to water must pose a severe problem for an animal coping with changes in external salinity.

Structure of the labile solvate layers of alkali metal cations and the quadrupole relaxation of the nuclei of the ions

Theoretical models and experimental data on the spin-lattice relaxation times of the nuclei of the 7Li+ and 23Na+ ions in individual and mixed solvents have been analyzed. It has been shown that the relaxation is determined by changes taking place in the configuration of the solvated complex. The rate of the quadrupole relaxation of the nuclei of ions contains information on the structure and dynamics of their solvate layers. Its use is being held back, however, by the fact that the theory has not yet been developed in sufficient detail. The present paper describes an lnvest~gation of the mechanism of the quadrupole relaxation of the nuclei of lithium and sodium ions in solution, and in particular, the determination of the type of mobility of the particles close to the ion. The general theory [i] gives an expression relating the rate of the spin-lattice relaxation (I/TI) to the correlation function G(t) of the fluctuations of the interaction of the nucleus with the environment (t is the time) co

Relationship between structure, stability of potassium complexes, and antimicrobial activity in a series of analogs of valinomycin

1. The antimicrobial activity of valinomycin and its analogs and also their capacity for forming complexes with potassium and sodium ions in solution have been investigated. 2. It has been shown that the capacity of CDPs of the valinomycin series for forming complexes with potassium ions is a necessary, but not sufficient, condition for the manifestation of antimicrobial activity by these compounds.

Simplification of the empirical relationship between melting temperature of DNA, its GC content and concentration of sodium ions in solution.

Simplification of the empirical relationship between melting temperature of DNA, its GC content and concentration of sodium ions in solution.