Polyvalent Metal Cations Research Articles

Saccharina japonica – её технохимическая характеристика для применения в технологии пищевых и лечебно-профилактических продуктов

Data are presented that determine the directions of processing and use of brown algae, including the hydration coefficient (HC) of dried thalli or crushed into pieces of various sizes, which is an important indicator used in setting the parameters of technological processes, as well as the yield of finished products. The results are presented demonstrating the ability of the dried algae Saccharina japonica to limit hydration. It has been shown that during deep treatment of S. japonica in order to increase the HC, about 80% of biologically active substances are lost, with the exception of fiber, some part of the protein, the organic form of iodine, as well as alginates associated with polyvalent metal cations in water-insoluble complexes with alginic acids. It was determined that when soaking dried S. japonica in water, the relative content of alginic acid increases, while the HC of kelp also increases. It has been established that HC equal to 20-26 corresponds to a significant removal of extractive biologically active substances (BAS) from S. japonica. At HC 14-16, up to 50% of biologically active substances remain in the tissues of algae, giving taste to kelp algae and their biological value. It has been shown that with the content of biologically active substances in algae up to 50% of the initial value, a real opportunity is created to obtain food, therapeutic and prophylactic products from dried S. japonica.

Viscoelastic systems for well construction

One of the most important factors ensuring the required quality of well cementing is the use of effective flushing fluids (spacers). Among these fluids are viscoelastic systems (VES), which provide the best displacement of the drilling fluid during the cementing process.
 The article discusses the mechanism of polymerization of viscoelastic systems when using polyacrylamide cross-linked with polyvalent metal cations and the prospects for using these systems for oil and gas wells cementing. Models of the viscoelastic systems flow and their differences due to the presence of normal stresses in viscoelastic systems are shown in this article. The substantiation of the component composition of viscoelastic systems and their main properties, ensuring their efficiency as flushing fluids are given. The article also provides a description of the scientific instruments that were used during the research.
 It has been experimentally confirmed that it is necessary to use additives with the highest oxidation state when choosing a polyvalent cation as a "cross-linker" for viscoelastic systems. This will help to increase the rate of strength characteristics development. The most adequate ratios of components have been experimentally substantiated and the best solids-carrying capacity of a viscoelastic flushing fluid in comparison with other types has been proven. This eliminates the possibility of cement slurry flowing down in the annular space after the completion of the cementing process.
 The special installations proved the best degree of wellbore cleaning in vugular formation zones with a laminar flow regime. In order to minimize the negative effect of polymer films from viscoelastic systems on the adhesion of the cement stone to the casing strings it is recommended to inject a portion of the liquid containing the polymer destructor after a portion of the viscoelastic fluid.

Facile preparation of sodium alginate-based gel spheres by droplet polymerization method for removal of levofloxacin from aqueous solution

Abstract The extensive use of fluoroquinolones antibiotics (FQs) makes great contributions to human society, but it also brings serious threats due to its stable chemical properties and difficulty in natural degradation. Since FQs can form stable chelates with polyvalent metal cations, the new adsorbents based on this chelating agent can not only remove FQs effectively, but also have the characteristics of selective identification on target pollutants. In this paper, novel sodium alginate-based gel spheres were prepared by droplet polymerization with sodium alginate (SA) as functional monomer, AlCl3/CaCl2 solutions and glutaraldehyde (GA) as crosslinking agents. The SA-Al/Ca gel spheres and GA (SA-Al/Ca) gel spheres were successively prepared for adsorption of levofloxacin (S-OFX) from aqueous solution. The results showed that after ion crosslinking with AlCl3/CaCl2 solutions and covalent crosslinking with GA, the prepared SA-Al/Ca and GA (SA-Al/Ca) gel spheres showed high adsorption capacity and good reusability, respectively. The equilibrium adsorption capacity of SA-Al/Ca gel spheres reached up to 176.26 mg∙L−1 with the initial concentration of S-OFX as 100 mg∙L−1. The maximum removal rate of S-OFX was 92.10%. The GA (SA-Al/Ca) gel spheres had a certain degree of tolerance in temperature, pH, and ionic strength. The adsorption of S-OFX by both SA-Al/Ca and GA (SA-Al/Ca) gel spheres had fast kinetics. Moreover, the prepared GA (SA-Al/Ca) gel spheres also showed good reusability and stability.

Features of the Sorption Process of Polyvalent Metal Cations in Soils

The issue of migration and accumulation of harmful and toxic compounds in soils is considered. Particular attention is paid to the study of the rate of ion-exchange process of cations of copper, iron, zinc, aluminum on humic acids, since these elements constitute a significant mass of harmful emissions from industrial enterprises in the form of drainage effluents to be cleaned. The results of studies of mass transfer processes in soils for various compounds are presented. An approach is proposed based on the calculation of the average dynamic value of the charge of a polyvalent metal cation extinguished when interacting with a specific sorbent, which allows a predictive estimate of the migration and accumulation of this cation within the spill of its salt solution on the soil.

Effects of Thylakoid-Rich Spinach Extract on the Pharmacokinetics of Drugs in Rats.

Thylakoid-rich spinach extract is being used as dietary weight-loss supplements in Japan. A recent rat study has suggested that intake of thylakoid-rich spinach extract with dietary oil inhibits dietary fat absorption via binding to bile acids, which promotes excretion of bile acids in feces. While, we confirmed that a serving size of thylakoid-rich spinach extract contains a large amount of calcium (130 mg/5 g). Therefore, using rats, we evaluated whether one-time ingestion of thylakoid-rich spinach extract affects the gastrointestinal absorption of water-insoluble drugs, such as griseofulvin (GF) and indomethacin (IM), or ciprofloxacin (CPFX) that chelate with polyvalent metal cations. Pretreatment of the rats with thylakoid-rich spinach extract (100 or 300 mg/kg) for 15 min prior to oral administration of GF (50 mg/kg) or IM (10 mg/kg) did not significantly alter the pharmacokinetic properties of either drug. Meanwhile, co-administration of thylakoid-rich spinach extract (500 mg/kg) and CPFX (20 mg/kg) significantly reduced the peak plasma concentration and the area under the plasma concentration-time curve of CPFX to 25 and 40%, respectively in rats. In vitro studies demonstrated that when a mixture of thylakoid-rich spinach extract and CPFX was centrifuged, there was a significant reduction in the supernatant concentration of CPFX relative to the control. When the experiment was repeated in the presence of ethylenediaminetetraacetic acid, the concentration of CPFX was unchanged. These results suggest that the intake of thylakoid-rich spinach extract may reduce the absorption of drugs that form a chelate with polyvalent metal cations, such as CPFX.

Food intake attenuates the drug interaction between new quinolones and aluminum

BackgroundIntestinal absorption of new quinolones is decreased by oral administration of polyvalent metal cations. Some clinical studies have demonstrated this drug - drug interaction is more prominent under fasted condition. However, the effect of food intake on the extent of drug - drug interaction between new quinolones and metal cations remains to be investigated quantitatively and systematically. The aim of this study was to develop an animal model that enables to evaluate the effect of food intake on the extent of drug - drug interaction in the gastrointestinal tract by chelation and to apply the model to evaluate quantitatively the effect of food intake on the drug - drug interaction between two new quinolones, ofloxacin or ciprofloxacin and sucralfate.MethodsThe rats were orally administered new quinolones (5.3 mg/kg of ofloxacin or 10 mg/kg of ciprofloxacin) with or without 13.3 mg/kg of sucralfate under fasted or fed condition and plasma concentration profiles of new quinolones were monitored. To the fed group, standard breakfast used in human studies was pasted and administered at a dose of 8.8 g/kg.ResultsThe area under the plasma concentration - time curves (AUC0–6) of ofloxacin and ciprofloxacin under the fasted condition were significantly decreased to 28.8 and 17.1% by co-administration of sucralfate, respectively. On the contrary, sucralfate moderately decreased the AUC0–6 of ofloxacin and ciprofloxacin to 54.9 and 33.2%, respectively, under fed condition. The effects of sucralfate and food intake on the kinetics of ofloxacin in this study were well consistent with the results of previous clinical trial.ConclusionsThe developed animal model quantitatively reproduced the effect of food intake on the drug - drug interaction between ofloxacin and sucralfate. The similar influences were observed for the drug - drug interaction between ciprofloxacin and sucralfate, suggesting that the extent of drug - drug interaction caused by chelation is generally attenuated by food intake.

Increased Solubility and Bioavailability of Hydroxy-Cr(III) Precipitates in the Presence of Hydroxamate Siderophores

Siderophores are a diverse group of low molecular weight biogenic metallophores with a particular affinity for Fe(III) but they also have potential to complex a number of other polyvalent metal cations, including Cr(III). Here we show that two hydroxamate siderophores, desferrioxamine B and rhodotorulic acid, at environmentally relevant concentrations, facilitate the dissolution of hydroxy-Cr(III) precipitates from a common layer silicate. Desferrioxamine B and rhodotorulic acid induced maximum initial Cr dissolution rates of 11.3 ± 1.7 × 10− 4 and 9.03 ± 0.68 × 10− 4 µmol m− 2 h− 1, respectively, yielding maximum solution Cr concentrations of 0.26 ± 0.01 and 0.20 ± 0.02 µmol m− 2, respectively. These data demonstrate that hydroxamate siderophores may play an important role increasing the dispersal of Cr in natural environments, thus facilitating greater bioavailability of this potential toxin.

Research of interaction between metronidazole tablets and metal salts `in vitro`

Introduction: Along with the efficacy and safety of drugs, the interaction of drugs with each other and with other accompanying substances is important, too. There are no data about the interaction or influence of antacids and other drugs with polyvalent cations on the metronidazole bioavailability. The purpose of this research was the studying of the metronidazole release kinetics from the tablets in an environment that simulates stomach conditions with the addition of metal salts, which are part of the widespread drugs. The research was conducted to assess the impact of possible interactions between the active substance and polyvalent metal cations on their bioavailability and efficacy. Material and methods : Metronidazole tablets were chosen as research object. 0.1 N HCl solution with addition of metal salts was chosen as medium dissolution. The “PharmaTest-DT70” Device with basket, the “Evolution 60S” Spectrophotometer as well as the “AB 204 S/A METTLER TOLEDO” analytical balances were used in the study. Results : Research of chemical interaction between metronidazole and metal salts, which are part of the widespread drugs, in the experiment “in vitro” was carried out. Metal salts don’t influence the metronidazole release from the tablets, as evidenced by dissolution profiles and similarity factors for each of the cases. Conclusions : The chemical interactions between the chosen medicines were not observed in the “in vitro” experiment. Thus, separate intake of metronidazole with other drugs, containing metal cations, is important for further research in the “in vivo” experiment.

Decrease in Ciprofloxacin Absorption by Polyvalent Metal Cations Is Not Fully Attributable to Chelation or Adsorption

The drug interaction between new quinolone antibiotics (NQs) and polyvalent metal cation products, leading to a significant decrease in the absorption of NQ, is considered to be attributable to the formation of poorly absorbable chelate and physicochemical adsorption of NQs to cation products. To clarify the mechanisms of this drug interaction in detail, we investigated the effects of Al(3+) or Mg(2+) on the membrane permeation profile of ciprofloxacin (CPFX) across human colon carcinoma cell lines (Caco-2) in monolayer culture, and characterized the adsorption nature of CPFX to polyvalent metal cation products under physiological conditions. As a result, Al(3+) or Mg(2+) partially but not fully impaired the permeation of CPFX across Caco-2 monolayer up to 30% or 60% of control, respectively. Physicochemical adsorption of CPFX to cation products was not observed under physiological pH. In conclusion, two possible mechanisms investigated, the decrease in the permeability of CPFX by chelate formation and adsorption of CPFX to polyvalent metal cation products, may partially but not fully explain the extent of the drug interaction clinically observed.

Cytotoxicity study of novel water‐soluble chitosan derivatives applied as membrane material of alginate microcapsules

The majority of cell encapsulation systems applied so far are based on polyelectrolyte complexes of alginate and polyvalent metal cations. Although widely used, these systems suffer from the risk of disintegration. This can be partially solved by applying chitosan as additional outer membrane. However, chitosan can be dissolved in water only at a low pH, which limits its use in the field of bioencapsulation. In this study, novel primary and tertiary amine chitosan derivatives have been synthesized, which may be dissolved at pH 7.0, and retain the ability to effectively form additional membrane on the surface of alginate beads. As aqueous solutions tertiary amines dimethylamino-1-propyl-chitosan and dimethylethylamine-chitosan with linear hydrochloride aliphatic chains had the lowest toxicity, whereas dimethylpropylamine-chitosan, diethylaminoethyl-chitosan, and diisopropylaminoethyl-chitosan with branched hydrochloride aliphatic were cytotoxic to the majority of tested cells. When applied as polyelectrolyte complexation agent on the surface of alginate beads, none of the derivates had any negative effect on the metabolic activity of encapsulated beta-cells.

Starch‐graft copolymers of N‐vinylformamide and acrylamide modified with montmorillonite manufactured by reactive extrusion

AbstractGraft copolymers of potato starch with acrylamide, acrylamide, and acrylic acid or N‐vinylformamide in the presence of 1–16 wt % montmorillonite were manufactured via reactive extrusion. XRD and TEM measurements exhibited intercalated structure of clay dispersion (d001 distance up to 2.3 nm). The influence of graft polymer(s) system and montmorillonite content on thermal properties, water sorption as well as polyvalent metal cation (Cd2+ and Fe3+) sorption of obtained starch graft copolymers has been determined. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Iron Stabilization with Phytic Acid in Model Wine and Wine

When present in high concentrations in wine and other beverages, polyvalent metal cations such as iron may cause objectionable sensory and physicochemical properties including metallic taste, discoloration, oxidative changes, and formation of haze and cloudiness. Reducing metal concentrations in beverages, especially wines, has long been desirable. In this investigation, phytic acid was added to red, white, or model wine to chelate polyvalent iron cations in a phytic acid to iron molar ratio of 1:1, which corresponds to 0.018 mM phytic acid or 11.8 mg/L phytic acid for each 1 mg/L iron present. A calcium salt was then added to coprecipitate the complex quantitatively, at a calcium to phytic acid molar ratio of 5:1, which corresponds to 9.0 mg/L CaCO₃ for each 1 mg/L iron subsequently removed by filtration. The method removes excessive iron in wine, sparkling wine, and other beverages and overcomes the problems of alternative methods; for example, it binds iron to the most complete extent possible, produces no toxic products even with overclarification, and acts selectively on iron and calcium ions but not on copper or potassium ions. Color and phenolic attributes were measured spectrophotometrically and were not greatly affected by phytic acid and calcium carbonate treatments. Titratable acidity and pH were slightly changed after treatment; however, such changes could likely be diminished with further work.

Soybean peroxidase-catalyzed removal of phenylenediamines and benzenediols from water

Crude soybean peroxidase (SBP), isolated from soybean seed coats (hulls), catalyzes the oxidative polymerization of hazardous aqueous phenylenediamines and benzenediols in the presence of hydrogen peroxide. Experiments were conducted to investigate the optimum operating conditions including pH, hydrogen peroxide-to-substrate concentration ratio and the minimum SBP concentration required to achieve at least 95% conversion of these pollutants in synthetic wastewaters. The substrate conversion and hydrogen peroxide consumption were monitored over the period of the reactions. Polyethylene glycol (PEG) was ineffective as an additive in enhancing the conversion efficiency. The enzymatically generated polymeric products from phenylenediamines could be removed with the aid of a surfactant, sodium dodecyl sulfate (SDS), whereas the polyvalent metal cation salt, aluminum sulfate (alum), was able to remove the products from benzenediols, except hydroquinone. Enzyme-catalyzed polymerization with SBP and subsequent removal of the polymeric products generated can provide an alternative means to the conventional methods for treating many aromatic wastewater pollutants, including the title compounds.

Investigation of the Effect of Various Fluoride Compounds and Preparations Thereof on Erosive Tissue Loss in Enamel in vitro

Metal fluoride preparations are promising in view of protection against dental erosion. The aim of this study was to screen the effect fluoride preparations containing various polyvalent metal cations had on erosion progression under increasingly severe erosive conditions in human enamel in vitro. Specimens were subjected to a cyclic de- and remineralisation procedure. Demineralisation (experiment E1 and E2a: 6 × 2 min/day, experiment E2b: 6 × 5 min/day) was performed with 0.05 M citric acid (pH 2.3). Fluoridation directly followed demineralisation and was reduced stepwise (E1: 6 × 2 min/day, E2a and E2b: 2 × 2 min/day). The test solutions were: ZnF₂(E1), AmF/NaF/CuSO₄ (E1), TiF₄/AmF/Zn lactate (E1), TiF₄ (E1, E2a), TiF₄/AmF (E2a), TiF₄/AmF/NaF (E2a), TiF₄/AmF/ZnF₂ (E1, E2a, E2b), AmF/NaF/SnCl₂ (2,800 mg/l Sn²⁺; E1, E2a, E2b), AmF/NaF/SnCl₂-1 (700 mg/l Sn²⁺; E2a, E2b), all 1,500 ppm F^–, pH 4.5, and AmF/SnF₂ (positive control, pH 4.2, 250 ppm F^–; E1, E2a, E2b). In the negative control group, specimens were not fluoridated. Tissue loss was determined by profilometry after the last experimental day. Under mild conditions (E1), tin- and titanium-containing solutions were of marked efficacy and could nearly completely inhibit erosive tissue loss (reduction between 94.2 and 97.5%). With increasingly severe conditions (E2a, E2b), titanium lost its efficacy. Only the highly concentrated tin preparation (2,800 mg/l Sn²⁺) was able to reduce erosive tissue loss by 93.1%, even under severe conditions (E2b), with less frequent application of the experimental preparations. It should be considered for approaches for a symptomatic therapy of dental erosion.

Metal-ion complexation effects in C 1s-NEXAFS spectra of carboxylic acids—Evidence by quantum chemical calculations

Previous systematic C 1s-NEXAFS studies carried out for humic acid (HA) loaded with polyvalent metal cations (M n+ ) reveal spectral features which were postulated to result from metal ion complexation: a strong decrease of the C 1s (COO −) → π* C O transition intensity and the appearance of a new absorption feature at slightly lower energy adjacent to the carboxyl resonance. Although spectroscopic results for the M n+ -PAA (polyacrylic acid) system (selected as model for structurally ill-defined HA) reveal the same spectral features, evidence by an independent approach for interpretation of these features is desirable. It is well established that quantum chemical calculations are capable of reproducing transition features in C 1s core excitation spectra of small organic molecules, e.g., acetate, which is chosen here as a fragment containing the complexing group to model the macromolecular HA and PAA systems. In this study, the RI-ADC(2) approach, as implemented in the TURBOMOLE program package, is applied to calculate vertical core excitation spectra of various metal acetates and the acetate anion. An energy shift (Δ f) between the C 1s (COO −) → π* C O transition of the acetate anion and various metal cation acetates is established. Calculated shifts are very similar to the experimentally observed values for the energy difference between the C 1s (COO −) → π* C O peak and the absorption feature appearing after metal ion complexation in M n+ -PAA/PAA. According to our computations, structural changes of the acetate complexes (e.g., the O–C–O bond angle) compared to the free acetate anion are predominantly responsible for the spectral changes observed upon metal ion complexation.

Interaction with Al and Zn induces structure formation and aggregation in natively unfolded caseins

Caseins are phosphoproteins that form the principal protein component of milk, their chief function being the transport of inorganic calcium and phosphate to the neonates. The four major members of the casein family are α s1-, α s2- (together referred to as α s-casein), β- and κ-casein, each having a characteristic high negative net charge as well as high hydrophobicity and preferring extended conformational states in solution. We have investigated the influence of the polyvalent metal cations Zn(II) and Al(III) on the structure of bovine caseins, using fluorescence and circular dichroic (CD) spectroscopy and light scattering. Changes in Trp and ANS fluorescence parameters (blue shifts of the emission maxima and enhancement of fluorescence intensity) and in the far-UV CD spectra of the caseins caused by the presence of both metals suggest that conformational changes are induced in them by low concentrations (20–40 μM) of the metal cations. These changes lead to formation of solvent-accessible hydrophobic clusters or cavities that, in turn, cause self-association and precipitation of caseins at higher concentration of the metals. These conclusions are supported by increased binding of ThT to the caseins, as well as enhancement of light scattering intensity, observed in presence of Al(III). The chaperonic property of α s-casein, which enables it to inhibit thermal aggregation of alcohol dehydrogenase, is shown to be partially destroyed by Zn(II)-induced structural alterations, due possibly to loss of flexibility of the natively unfolded casein chains.

Binding of Pyrene to Hydrophobic Fractions of Dissolved Organic Matter: Effect of Polyvalent Metal Complexation

The effects of polyvalent metal cations on pyrene binding to hydrophobic acid and neutral fractions (HoA and HoN, respectively) of dissolved organic matter (DOM) were elucidated. The DOM was isolated from sewage sludge; pyrene binding was estimated from fluorescence measurements. Isotherms of pyrene binding to both fractions were nonlinear. Pyrene binding was higher for HoN due to the combined effect of greater hydrophobicity, aromaticity and the large molecular size of this fraction relative to HoA. The complexation of HoA with Cu2+, Al3+, and Fe3+ increased the binding of pyrene only when the HoA was equilibrated with polyvalent cations before pyrene was added. The maximal increase in pyrene binding to HoA was 56%, 64%, and 118% when pre-equilibrated with Cu2+, Fe3+, and Al3+, respectively. Pyrene binding to HoN was not affected by the presence of metal cations. HoA complexation with metal cations increased the apparent molecular size of this fraction. We suggest that the presence of metal cations induces the formation of pseudomicelles, which are more efficient in binding pyrene than the low-molecular-weight components. Our results demonstrate that HoA and HoN components can significantly affect the transport of organic contaminants in soils irrigated with treated wastewater or amended with sewage sludge.

The influence of polyvalent metal cations on the corrosion rate of molybdenum in molten glass

The corrosion behavior of molybdenum in a silicate melt has been studied using electrochemical techniques. The aim was to examine whether or not polyvalent metal ions such as iron (Fe 3+), nickel (Ni 2+) and cobalt (Co 2+) are able to influence the corrosion behavior of molybdenum and, if so, to which extent. In addition the impact of the temperature of the melt on the corrosion rate has been addressed.

Oxytetracycline Sorption to Organic Matter by Metal‐Bridging

The sorption of oxytetracycline to metal-loaded ion exchange resin and to natural organic matter by the formation of ternary complexes between polyvalent metal cations and sorbent- and sorbate ligand groups was investigated. Oxytetracycline (OTC) sorption to Ca- and Cu-loaded Chelex-100 resin increased with increasing metal/sorbate ratio at pH 7.6 (OTC speciation: 55% zwitterion, 45% anion). Greater sorption to Cu- than Ca-loaded resin was observed, consistent with the greater stability constants of Cu with both the resin sites and with OTC. Oxytetracycline sorption to organic matter was measured at pH 5.5 (OTC speciation: 1% cation, 98% zwitterion, 1% anion). No detectable sorption was measured for cellulose or lignin sorbents that contain few metal-complexing ligand groups. Sorption to Aldrich humic acid increased from "clean" < "dirty" (no cation exchange pretreatment) < Al-amended < Fe(III)-amended clean humic acid with K(d) values of 5500, 32000, 48000, and 250000 L kg(-1) C, respectively. Calcium amendments of clean humic acid suggested that a portion of the sorbed OTC was interacting by cation exchange. Oxytetracycline sorption coefficients for all humic acid sorbents were well-correlated with the total sorbed Al-plus-Fe(III) concentrations (r(2) = 0.87, log-log plot), suggesting that sorption by ternary complex formation with humic acid is important. Results of this research indicate that organic matter may be an important sorbent phase in soils and sediments for pharmaceutical compounds that can complex metals by the formation of ternary complexes between organic matter ligand groups and pharmaceutical ligand groups.

The design, fabrication and characterization of rare-earth containing multilayer supramolecular films with nanometer-scale controlled composition, structure and properties

We demonstrate the controlled formation of highly-ordered rare-earth stearate multilayer Langmuir–Blodgett films, novel supramolecular organized structures: hybrid polyanion/rare-earth metal cation/anionic surfactant metal–organic superlattice thin films with separating acidic amphiphile bilayers by highly rare-earth-doped polymeric interlayers and fabrication of closely packed, homogeneous and stable rare-earth metal cation/polyanion complex self-assembled multilayer films in which molecular polyelectrolyte building blocks are held together by complexed polyvalent metal cations. The design and fabrication strategies developed to construct those films are based on the surface and interface trivalent rare-earth metal cation complexation with consecutive formation of multilayer superstructures on the solid substrates. The structure and morphology of the built-up multilayer films were characterized by atomic force microscopy and X-ray diffraction.