Adsorption kinetic, isotherm and thermodynamic studies of Sr2+ onto hexagonal tungsten oxide

Hexagonal tungsten oxide (hex-WO₃) with exchangeable sodium and ammonium cations located in hexagonal channel was synthesized by a facile hydrothermal treatment of sodium tungstate dihydrate in concentrated HCl solution in the presence of ammonium sulfate. An attempt was made to assess the potential of hex-WO₃ for the adsorption of Sr²⁺ ions from acidic radioactive waste solutions. Adsorption of Sr²⁺ reached equilibrium very quickly in 2 h in acidic aqueous solution. Maximum removal of Sr²⁺ ions occurred at pH 4. Equilibrium studies showed that the extent of Sr²⁺ ions uptake by hex-WO₃ was better described by the Freundlich isotherm in comparison with the Langmuir model. The thermodynamic parameters showed that the adsorption of Sr²⁺ ions onto hex-WO₃ was spontaneous and exothermic under the studied conditions.     

Zingipain, a Ginger Protease with Acetylcholinesterase Inhibitory Activity

In order to search for new acetylcholinesterase inhibitors (AChEIs), 15 Zingiberaceae plants were tested for AChEI activity in rhizome extracts. The crude homogenate and ammonium sulfate cut fraction of Zingiber officinale contained a significant AChEI activity. Eighty percent saturation ammonium sulfate precipitation and diethylaminoethyl cellulose ion exchange chromatography (unbound fraction) enriched the protein to a single band on nondenaturing and reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (approximately 33.5 kDa). Gelatin-degrading zymography showed that the AChEI-containing band also contained cysteine protease activity. The AChEI activity was largely stable between ?20 and 60 °C (at least over 120 min) and over a broad pH range (2–12). The AChEI activity was stimulated strongly by Mn²⁺ and Cu²⁺ at 1–10 mM and weakly by Ca²⁺, Fe²⁺, Mg²⁺, and Zn²⁺ at 1 mM, but was inhibited at 10 mM. In contrast, Hg²⁺ and ethylenediaminetetraacetic acid were very and moderately strongly inhibitory, respectively. In-gel tryptic digestion with liquid chromatography–tandem mass spectroscopy resolution revealed two heterogeneous peptides, a 16-amino-acid-long fragment with 100 % similarity to zingipain-1, which is a cysteine protease from Z. officinale, and a 9-amino-acid-long fragment that was 100 % identical to actinidin Act 2a, suggesting that the preparation was heterogeneous. AChEI exhibited noncompetitive inhibition of AChE for the hydrolysis of acetylthiocholine iodide with a K _i value of 9.31 mg/ml.     

Stability and Detergent Compatibility of a Predominantly β-Sheet Serine Protease from Halotolerant B. aquimaris VITP4 Strain

The present study deals with the characterization of halotolerant protease produced by Bacillus aquimaris VITP4 strain isolated from Kumta coast, Karnataka, India. The studies were performed at 40 °C and pH 8 in Tris buffer. Metal ions such as Mn²⁺ and Ca²⁺ increased the proteolytic activity of the enzyme by 34 and 30 %, respectively, at 10 mM concentration. Cu²⁺ at 1 mM concentration was found to enhance the enzyme activity by 16 %, whereas inhibition was observed at higher concentration (>5 mM). Slight inhibition was observed even with lower (>1 mM) concentrations of Zn²⁺, Hg²⁺, Fe³⁺, Ni²⁺, and Co²⁺.The activity of protease was completely inhibited by phenylmethylsulfonyl fluoride, indicating that the VITP4 protease is a serine protease. The presence of ethylenediaminetetraacetic acid and 1,10-phenanthroline (>5 mM) moderately inhibited the activity, suggesting that the enzyme is activated by metal ions. The protease was purified to homogeneity with a purification fold of 15.7 with ammonium sulfate precipitation and 46.65 with gel filtration chromatography using Sephadex G-100, resulting in a specific activity of 424?±?2.6 U mg^?1. The VITP4 protease consists of a single polypeptide chain with a molecular mass of 34.7 kDa as determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization–time of flight. Among the different substrates used (casein, egg albumin, gelatin, and bovine serum albumin), the activity was higher with casein with V _max, K _m, and k _cat values of 0.817 mg ml min^?1, 0.472 mg ml^?1, and 2.31 s^?1, respectively. Circular dichroism studies revealed that the VITP4 protease has a predominantly β-sheet structure (51.6 %) with a temperature for half denaturation of 85.8 °C in the presence of 1 mM CaCl₂. Additionally, the VITP4 protease was found to retain more than 70 % activity in the presence of 10 mM concentration of different detergents (CTAB, urea, and sodium dodecyl sulfate) and surfactants (Triton X-100, Tween-20, and Tween-80), and the results of wash performance test with various commercial detergents confirmed that it can be used in detergent formulations.     

Physicochemical Properties of Aqueous Solutions of Binary Mixtures of Lignin Derivatives and Sodium Dodecyl Sulfate

Physicochemical properties of aqueous solutions of binary mixtures of lignosulfonates and sodium dodecyl sulfate were studied. Introduction of sodium dodecyl sulfate into solutions of high-molecular-mass lignosulfonates at certain ratios causes macrophase separation of the systems with the formation of loose precipitates. A synergistic effect of a decrease in the surface tension is observed in the mixed solutions. This effect increases with increasing lignosulfonate molecular mass and temperature. The revealed relationships are caused by hydrophobic interactions of hydrocarbon radicals of sodium dodecyl sulfate with hydrophobic segments of lignosulfonate polymer chains with the formation of micellar associates. Aqueous solutions of binary mixtures of lignosulfonates (с_LS ≥ 0.2 g dm^–3) and sodium dodecyl sulfate (с_DSNa ≥ 0.08 g dm^–3) can be recommended for use as surfactant formulations for high-temperature autoclave leaching of polymetal ores.     

Metal Ion Buffer Systems for Ionometry in Water-Ethanol Mixtures and Micellar Medium of Sodium Dodecyl Sulfate

The concentration dissociation constants of nitrilotriacetic acid and the concentration stability constants of Cd(II) complexes with the nitrilotriacetic acid anion in water-ethanol mixtures and of Cu(II) and Cd(II) complexes with o-phenanthroline and 2,2′-bipyridine in micellar solutions of sodium dodecyl sulfate were determined potentiometrically. Based on the concentration constants determined, Cd²⁺ and Cu²⁺ buffer solutions were developed for calibration of a Cd²⁺-selective electrode in water-ethanol mixtures and Cd²⁺ and Cu²⁺-selective electrodes in micellar solutions of sodium dodecyl sulfate within the ranges pCu 9.7–13.5 and pCd 7.5–11.8.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 273–278.Original Russian Text Copyright © 2005 by Chernysheva, Loginova, Bazilyanskaya.     

Protolytic properties of <Emphasis Type="Italic">DL</Emphasis>-alanyl-<Emphasis Type="Italic">DL</Emphasis>-methionine and its complexation in aqueous solutions and micellar solutions

Dissociation constants of DL-alanyl-DL-methionine have been determined in water and micellar solutions of surfactants (anionic sodium n-dodecyl sulfate, cationic cetylpyridinium chloride, and nonionic Brij 35). It has been established that CuA⁺ and CuH_–1A complexes are formed in water and micellar solutions of sodium n-dodecyl sulfate, while CuA⁺, CuH_–1A, and Cu_–2A^– complexes are formed in micellar solutions of cetylpyridinium chloride and Brij 35. Stability of the complexes depends on micelle surface charge and degrees of binding of individual chemical forms by a micellar pseudophase.     

Novel method for the preparation of core-shell nanoparticles with movable Ag core and polystyrene loop shell

Core/shell nanoparticles with movable silver (Ag) core and polystyrene (PSt) shell (Ag@PSt nanoparticle) were successfully synthesized at room temperature and under ambient pressure via two steps: γ-irradiation and interfacial-initiated polymerization. Firstly, mono-dispersed Ag nanoparticles with diameters 20 nm were synthesized in inversed microemulsion by reducing silver nitrate under γ-irradiation. Then, Ag nanoparticles were coated with PSt via interfacial-initiated polymerization with cumene hydroperoxide/ferrous sulfate/disodium ethylenediaminetetraacetate/sodium formaldehyde sulfoxylate (CHPO-Fe²⁺-EDTA-SFS) as the redox initiation pair. The resulted Ag@PSt nanoparticles were identified by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).     

Gene Cloning,Expression, and Characterization of an Exo-inulinase from Paenibacillus polymyxa ZJ-9

An inulinase-producing strain, Paenibacillus polymyxa ZJ-9, was isolated from natural sources to produce R,R-2,3-butanediol via one-step fermentation of raw inulin extracted from Jerusalem artichoke tubers. The inulinase gene from P. polymyxa ZJ-9 was cloned and overexpressed in Escherichia coli BL21 (DE3), and the purified recombinant inulinase was estimated to be approximately 56 kDa by both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) and gel filtration chromatography. This result suggests that the active form of the inulinase is probably a monomer. Terminal hydrolysis fructose units from the inulin indicate that enzymes are exo-inulinase. The purified recombinant enzyme showed maximum activity at 25 °C and pH 6.0, which indicate its extreme suitability for industrial applications. Zn²⁺, Fe²⁺, and Mg²⁺ stimulated the activity of the purified enzyme, whereas Co²⁺, Cu²⁺, and Ni²⁺ inhibited enzyme activity. The K _m and V _max values for inulin hydrolysis were 1.72 mM and 21.69 μmol min^?1 mg^?1 protein, respectively. The same parameters toward sucrose were 41.09 mM and 78.7 μmol min^?1 mg^?1 protein, respectively. Considering its substrate specificity and other enzymatic characteristics, we believe that this inulinase gene from P. polymyxa ZJ-9 could be transformed into other special bacterial strains to allow inulin conversion to other biochemicals and bioenergy through one-step fermentation.     

Use of Cr(phen)33+ as luminescence probe to study the binding constants of phenols to micelles of SDS

Steady-state and time resolved luminescence quenching measurements of (²T/²E)Cr(phen)₃³⁺ were used to investigate the association of phenols to sodium dodecyl sulfate (SDS) micelles. Steady-state results show the quenching process occurs in the micellar pseudo phase. Scatchard plots indicate that the process is a partition between aqueous and micelles. The k₊ and k₋ rate constant have been evaluated from time resolved data and the binding constants were obtained. The trend found in the K's were 4-H-Ph < 2,6-diMe-Ph < 4-Br-Ph. We concluded that it is possible to use *Cr(phen)₃³⁺ as a luminescent probe to determine association parameters for quenchers to micelles of SDS.     

Trace fluoride determination with specific ion electrode

A method is described for determining 10^-5–10^-4M fluoride in a variety of solutions potentiometrically with a fluoridc-specific electrode, by a standard addition method. Any change of ionic strength or the nature of the solution that might alter activity coefficients or junction potentials is minimized. The relationship between potential and fluoride concentration thus follows the Nernst equation, and the unknown concentration can be calculated. Experimental data are given for solutions of sodium choride, sodium nitrate, acidified sodium silicate and sodium hydroxide, lithium chloride, and phosphoric acid. Metal ions (e.g., Al³⁺, UO₂²⁺, Fe³⁺, Th⁴⁺) that interfere by forming complexes with fluoride can be precomplexed with phosphoric acid. The relative error is estimated at 10%, and the relative standard deviation is less than 5% over the concentration range 10^-5–10^-4M fluoride.     

The stability and solubility of cadmium(II)-8-oxyquinoline complexes in water and micellar solutions of sodium dodecyl sulfate

The formation of cadmium 8-oxyquinoline (HOx) complexes in water and a 0.01 M aqueous solution of sodium dodecyl sulfate (293 K, 0.01) was studied by pH-metric titration. Mathematical simulation of the most probable equilibria gave complex formation constants logβ₁ = 6.17 ± 0.32 (CdOx⁺) and logβ₂ = 14.60 ± 0.14 (CdOx₂) in aqueous solution and apparent stability constants logβ₁ = 8.64 (CdOx⁺) and logβ₂ = 17.59 (CdOx₂) in a solution of dodecyl sulfate. The solubility of cadmium dioxyquinolate in water at pH from 3 to 6 and a micellar sodium dodecyl sulfate medium was determined by the method of saturated solutions. The solubility product pL _p = 21.3 ± 0.9 (H₂O, 293 K) was calculated by modeling the solution of CdOx₂ with taking into account all acid-base interactions and complex formation reactions.     

Raising the Efficiency of Electroflotation Extraction of Metals in Multicomponent Systems from Aqueous Media

Specific features of the electroflotation extraction of hydroxides of nonferrous metals (Cu²⁺, Ni²⁺, Zn²⁺, Cr³⁺, Fe³⁺) from a five-component system in the presence of sodium sulfate as supporting electrolyte were examined. The fundamental aspects of the extraction process upon introduction into the system of surfactants of varied nature and flocculants were determined. It was shown that addition of a nonionogenic flocculant N-300 makes it possible to raise the efficiency and stabilize the process of the electroflotation extraction of difficultly soluble metal hydroxides contained in multicomponent systems from wastewater formed in various galvanic shops, with the degrees of extraction possibly reaching a value of 97%.     

Purification and Characterization of Alkaline Pectin Lyase from a Newly Isolated Bacillus clausii and Its Application in Elicitation of Plant Disease Resistance

Alkaline pectin lyase (PNL) shows potential as a biological control agent against several plant diseases. We isolated and characterized a new Bacillus clausii strain that can produce 4,180?U/g of PNL using sugar beet pulp as a carbon source and inducer. The PNL was purified to apparent homogeneity using ultrafiltration, ammonium sulfate fractionation, DEAE Sepharose Fast Flow, and Sephadex G-75 gel filtration. The purified PNL was found to be a monomeric protein with a molecular weight of 35?kDa, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). It demonstrated optimal activity with K _m of 0.87?mg/ml at pH?10.0 and 60?°C. The enzyme is stable in the pH range of 8.0?C10.0 and temperature ??40?°C. Ca²⁺ was found to stimulate the enzymatic activity of the PNL by up to 410?%. Mass spectrometric results gave 38?% match coverage with pectate lyase from B. clausii KSM-K16 (gi|56961845). The PNL was found to elicit disease resistance in cucumber seedlings, suggesting that it may have applications in biocontrol and sustainable agriculture.     

Interaction of calcium ion with sodium triphosphate determined by potentiometric and calorimetric techniques

The stoichiometry of the interaction of Ca²⁺ with sodium triphosphate was determined using a Ca²⁺ sensitive electrode, divalent ion sensitive electrode, a glass electrode and by titration calorimetry, A 2:1 and 1:1 complex of Ca²⁺ and P₃O^5?₁₀ is found when titrating calcium chloride with sodium triphosphate by the calcium ion sensitive electrode and tritation calorimetry. However, only by titration calorimetry is the 2:1 and 1:1 complex found when titrating sodium triphosphate with calcium chloride. Thermodynamic value (log K, ΔH and ΔS) are reported for the formation of CaP(in3)O^?3₁₀ and Ca₂P₃O^?₁₀ in aqueous solution.     

Production and Purification of Pectinase from Bacillus subtilis 15A-B92 and Its Biotechnological Applications

Enzymes that degrade pectin are called pectinases. Pectinases of microbial origin are used in juice clarification as the process is cost-effective. This study screened a pectinase-producing bacterium isolated from soil and identified as Bacillus subtilis 15A B-92 based on the 16S rRNA molecular technique. The purified pectinase from the isolate showed 99.6 U/mg specific activity and 11.6-fold purity. The molecular weight of the purified bacterial pectinase was 14.41 ± 1 kD. Optimum pectinase activity was found at pH 4.5 and 50 °C, and the enzyme was 100% stable for 3.5 h in these conditions. No enzymatic inhibition or activation effect was seen with Fe²⁺, Ca²⁺, or Mg²⁺. However, a slight inhibition was seen with Cu²⁺, Mn²⁺, and Zn²⁺. Tween 20 and 80 slightly inhibited the pectinase, whereas iodoacetic acid (IAA), ethylenediaminetetraacetate (EDTA), urea, and sodium dodecyl sulfate (SDS) showed potent inhibition. The bacterial pectinase degraded citrus pectin (100%); however, it was inactive in the presence of galactose. With citrus pectin as the substrate, the Km and Vmax were calculated as 1.72 mg/mL and 1609 U/g, respectively. The high affinity of pectinase for its substrate makes the process cost-effective when utilized in food industries. The obtained pectinase was able to clarify orange and apple juices, justifying its application in the food industry.     

Mass spectrometric investigation of the side-arm lariat effect of ortho- and para-methoxyphenoxymethyl-15-crown-5 in the gas phase

Mixtures of unsubstituted 15-crown-5 and its analogues containing ortho- and para-methoxyphenoxymethyl substituents with sodium salts were investigated by matrix assisted laser desorption/ionization (MALDI) mass spectrometry. Peaks of cationized molecules [M+Na]⁺ and cluster ions [2M+2Na+An]⁺, where M is the crown ether molecule and An is monobasic acid anion, were observed in the mass spectra. It was shown that an increase of the shielding degree of the sodium cation in complexes with crown ethers, i.e., the lariat effect, led to a significant decrease in the intensity of peaks of the cluster ions.     

Sodium magnesium sulfate decahydrate,Na2Mg(SO4)2·10H2O,a new sulfate salt

The structure of synthetic disodium magnesium disulfate decahydrate at 180 K consists of alternating layers of water‐coordinated [Mg(H₂O)₆]²⁺ octahedra and [Na₂(SO₄)₂(H₂O)₄]²⁻ sheets, parallel to [100]. The [Mg(H₂O)₆]²⁺ octahedra are joined to one another by a single hydrogen bond, the other hydrogen bonds being involved in inter‐layer linkage. The Mg²⁺ cation occupies a crystallographic inversion centre. The sodium–sulfate sheets consist of chains of water‐sharing [Na(H₂O)₆]⁺ octahedra along b, which are then connected by sulfate tetrahedra through corner‐sharing. The associated hydrogen bonds are the result of water–sulfate interactions within the sheets themselves. This is believed to be the first structure of a mixed monovalent/divalent cation sulfate decahydrate salt.     

Volumetric properties, structural effects, and hydration of amino acids in aqueous salt solutions

The dependence of the standard partial volumes of glycine, α-alanine, and serine on the ionic strength of aqueous sodium chloride and sulfate solutions is modeled by the extended Masson equation: {ie534-1}. The error of less than 0.2 cm³/mol is a result of using five values of the A and B parameters: the two values of A are determined by the type of salt and the three values of B by the type of amino acid. A new variation of the additive-group approach is proposed for {ie534-2}. The partial volumes of the CH₃ group (α-alanine) and the CH₂ group (serine) are found not to depend on the salt concentration. The partial volume of the CH₂ group of glycine grows with concentration. The structural characteristics of the hydrated complexes of the NH ₃ ⁺ and COO^? groups are calculated: the hydration numbers, the molar volumes of water inside and outside the hydration sphere, and the intrinsic volume of NH ₃ ⁺ in COO^? in solution. Given the same ionic strength, the aqueous sodium sulfate solution produces a somewhat stronger dehydration of the charged groups.     

Effects of surface-active substances in square-wave voltammetry and potentiometric stripping analysis of amalgam-forming metal ions

The influence of surface active substances (SAS) (Triton X-100, sodium dodecyl sulfate and dodecyl pyridinium chloride (DPC)) on the potentiometric stripping analysis (PSA), square-wave voltammetry (SWV) and anodic stripping square-wave voltammetry (ASSWV) of Cd²⁺, Cu²⁺, Zn²⁺ and Bi(III) are measured for various contact times and detergent concentrations. Diagnostic criteria for the presence of SAS in electrolytes are reported. Zinc ions accumulate in the adsorbed layer of DPC, probably as a ZnCl⁺ complex. An anomalous dependence of zinc SWV peak currents on the delay time is observed.