Polyvalent Metal Ions Research Articles

Self-assembling peptide amphiphile nanofiber matrices for cell entrapment

We have developed a class of peptide amphiphile (PA) molecules that self-assemble into three-dimensional nanofiber networks under physiological conditions in the presence of polyvalent metal ions. The assembly can be triggered by adding PA solutions to cell culture media or other synthetic physiological fluids containing polyvalent metal ions. When the fluids contain suspended cells, PA self-assembly entraps cells in the nanofibrillar matrix, and the cells survive in culture for at least three weeks. We also show that entrapment does not arrest cell proliferation and motility. Biochemical and ultrastructural analysis by electron microscopy indicate that entrapped cells internalize the nanofibers and possibly utilize PA molecules in their metabolic pathways. These results demonstrate that PA nanofibrillar matrices have the potential to be used for cell transplantation or other tissue engineering applications.

AFM of Iron Oxide Particles Attachment on Mica

The attachment of iron oxide colloidal particles on a mica surface in the presence of humic acid (HA) and/or aluminum ions (Al3+) was investigated with atomic force microscopy (AFM). In the absence of both HA and Al3+, adhesion of some individual colloidal particles onto the solid substrate increased with time as clusters formed and grew. HA substances present in the colloidal suspension considerably reduced the attachment of iron oxide colloidal particles onto the mica surface. In addition, most attached colloidal particles tended to aggregate following long immersion times forming big clusters on specific areas of the mica sheet, thus displaying a selective way of attaching to the mica surface. The presence of Al3+ greatly increased the attachment of iron oxide colloidal particles whether in the absence or in the presence of HA. These observations carry significance in the colloid‐facilitated transport and mobilization of contaminants in subsurface environments, where humic substances have previously been known to enhance transport, while polyvalent metal ions are noted as promoters of particle aggregation in suspensions and slurries.

An investigation of valence state and structural geometry of polyvalent Fe and Ti ions in sodium borosilicate glasses by x-ray absorption spectroscopy

Valence states and structural environments of polyvalent Fe and Ti ions in two different borosilicate glasses have been studied by X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The results indicate that different valence states of polyvalent metal ions usually exist simultaneously in glass matrix. Doping C favours the formation of reduced state of metal ion. Especially, Fe2+ ion can be reduced into neutral iron atom. Fe2+ ion generally occupies octahedrally coordinated site. Fe3+ ion tends to be in tetrahedral coordination with increasing total iron concentration. Adding oxidising agent can transfer the octahedral iron ions into tetrahedral Fe3+ ions. Ti4+ ions mainly occupy five-fold coordination sites in NBS1 and four-fold coordination sites in NBS2, depending on the existence of non-bridging oxygen ions in the glass matrix.

Sorption of apolar aromatic compounds to soil humic acid particles affected by aluminum(III) ion Cross-Linking.

Sorption of hydrophobic compounds in soils often shows nonlinearity, competition, and hysteresis. Since such behaviors have been associated with organic polymers in glassy state, it has been postulated that some forms of soil humic substances are glassy. The glassy state is favored by properties that decrease the flexibility of macromolecules, such as cross-linking, presence of unsaturated bonds, and high molecular weight. Polyvalent metal ions, which are abundant in soils, may cross-link humic substances by coordinating to multiple functional groups on different strands. Accordingly, we prepared an Al(3+)-cross-linked humic acid (Al-HA) from the H(+) form (H-HA) of a soil humic acid by a flocculation technique that leaves Al ions bound to organic groups. Sorption of naphthalene and 1,2,4-trichlorobenzene (TCB) on H-HA was nonlinear, competitive, and slightly hysteretic, in agreement with previous studies showing glass transition temperatures of humic acids that lie above room temperature. Nonlinearity, competition, and hysteresis were all enhanced in Al-HA, validating the hypothesis that metal ion cross-linking enhances nonideal sorption. Application of a glassy polymer sorption model reveals that cross-linking increases the affinity of solutes for the hole domain relative to the dissolution domain. The results (i) indicate that isolated, purified soil humic acid behaves like a glassy solid, (ii) indicate that metal-ion cross-linking creates a more rigid-chain structure and supports a link between nonideal sorption and the glassy character of soil organic matter, and (iii) underscore the importance of metal ions on humic structure in relation to sorption of hydrophobic organic compounds.

Selective production of rat mutant selenoprotein W with and without bound glutathione

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) and electrospray ionization mass spectrometry (ESI MS) analysis of a 6× His-tagged recombinant form of rat mutant selenoprotein W (RMSW) reveals that aerobic growth conditions primarily produce a form of RMSW without bound glutathione (10,305 Da) whereas anaerobic conditions produce a glutathione-bound (305 Da) form (10,610 Da). Purification of RMSW was achieved with a procedure employing acetone precipitation and DEAE-cellulose chromatography, in addition to Ni–NTA agarose chromatography. Additional steps, including polyvalent metal ion binding (PMIB) resin chromatography and CM-cellulose chromatography, were necessary after elution from the Ni–NTA agarose column, in order to maintain solubility of the purified protein.

Aquatic colloids relevant to radionuclide migration: characterization by size fractionation and ICP-mass spectrometric detection

The application of the flow-field flow fractionation (FFFF) combined with on-line ICP-mass spectrometry (ICP-MS) to the characterization of aquatic colloids is described. The capabilities and drawbacks of the technique are discussed with the aid of two examples. (1) The size distribution of smectitic colloids dispersed from a natural bentonite is determined by FFFF and laser light scattering (LLS) and compared with the size information obtained by ICP-MS detection. Due to the pronounced size dependency of the scatter light intensity, the LLS detection tends to overestimate the larger sized particles. Therefore, the FFFF-ICP-MS fractogram delivers more reliable size information. (2) Groundwater humic/fulvic colloids and the humic matter extracted from the corresponding sediment, both taken from the Gorleben aquifer (Lower Saxony, Northern Germany), are analysed by FFFF-ICP-MS. The location of REE, U, Th and Ca in different colloid size fractions appears to be very similar in both samples. The element specific fractograms suggest in agreement with earlier studies the location of Th and the REE mainly in inorganic colloids>17 nm containing also Fe and/or Al. U and Ca appear to be distributed between larger colloids and the fulvic/humic acid fraction with a size <3 nm. The results demonstrate that even in groundwater/sediment systems with high humic/fulvic content, inorganic colloids may play an important role as carrier for polyvalent metal ions. The consequences of this finding on the applicability of in-situ K d values for U, Th and REE, taken as naturally abundant representatives of the nuclear waste derived actinides, for the assessment of laboratory sorption data is discussed.

Humic colloid-borne natural polyvalent metal ions: dissociation experiment.

The natural association nature of the humic colloid-borne trace elements is investigated. Rare earth elements (REE) Th and U are chosen as naturally occurring representatives and chemical homologues for actinides of different oxidation states present in nuclear waste. Tri- and tetravalent elements in two investigated Gorleben groundwaters (Gohy-532 and -2227) almost exclusively occur as humic or fulvic colloid-borne species. Their desorption behavior from colloids is examined in the unperturbed groundwater (pH approximately 8) under anaerobic conditions (Ar/1% CO2) by addition of a chelating cation exchanger resin. Particularly, the dissociation process of naturally occurring Eu(III) in the groundwater is compared with the Eu(III) desorption from its humate complex prepared with purified Aldrich humic acid in a buffered aqueous solution at pH approximately 8. The Eu(III) dissociation from the groundwater colloids is found to be considerably slower than found for the humate complex synthesized in the laboratory. This suggests that under natural aquatic conditions the Eu(III) binding in colloids is chemically different from the simple humate complexation as observed in the laboratory experiment. The colloid characterization bythe size exclusion chromatography (SEC) and the flow field-flow fractionation (FFFF) indicates that natural colloid-borne trace elements are found predominantly in colloids of larger size (>15 nm in size), while Eu(III) in its humate complex is found mainly in colloids of hydrodynamic diameters <5 nm. The slower desorption kinetics and the larger colloid size suggest that the polyvalent metal ion binding in natural humic colloids is associated to polynucleation with other co-present trace metal ions. Radiotracer experiments reveal that isotopic equilibria with the naturally colloid-borne trace elements are not attained within a period of more than 100 days, indicating irreversible binding of at least a part of colloid-borne polyvalent trace elements. The different kinetic properties of colloid-bound Eu(III) are discussed taking the aqueous speciation based on thermodynamic data into account.

Metal-triggered structural transformations, aggregation, and fibrillation of human alpha-synuclein. A possible molecular NK between Parkinson's disease and heavy metal exposure.

Parkinson's disease involves the aggregation of alpha-synuclein to form fibrils, which are the major constituent of intracellular protein inclusions (Lewy bodies and Lewy neurites) in dopaminergic neurons of the substantia nigra. Occupational exposure to specific metals, especially manganese, copper, lead, iron, mercury, zinc, aluminum, appears to be a risk factor for Parkinson's disease based on epidemiological studies. Elevated levels of several of these metals have also been reported in the substantia nigra of Parkinson's disease subjects. We examined the effect of various metals on the kinetics of fibrillation of recombinant alpha-synuclein and in inducing conformational changes, as monitored by biophysical techniques. Several di- and trivalent metal ions caused significant accelerations in the rate of alpha-synuclein fibril formation. Aluminum was the most effective, along with copper(II), iron(III), cobalt(III), and manganese(II). The effectiveness correlated with increasing ion charge density. A correlation was noted between efficiency in stimulating fibrillation and inducing a conformational change, ascribed to formation of a partially folded intermediate. The potential for ligand bridging by polyvalent metal ions is proposed to be an important factor in the metal-induced conformational changes of alpha-synuclein. The results indicate that low concentrations of some metals can directly induce alpha-synuclein fibril formation.

Mobilization of soil organic matter by complexing agents and implications for polycyclic aromatic hydrocarbon desorption

Complexing agents are frequently used in treatment technologies to remediate soils, sediments and wastes contaminated with toxic metals. The present study reports results that indicate that the rate and extent of soil organic matter (SOM) as represented by dissolved natural organic carbon (DNOC) and polycyclic aromatic hydrocarbon (PAH) desorption from a contaminated soil from a manufactured gas plant (MGP) site can be significantly enhanced with the aid of complexing agents. Desorption of DNOC and PAH compounds was pH dependent, with minimal release occurring at pH 2–3 and maximal release at pH 7–8. At pH∼6, chelate solutions were shown to dissolve large amounts of humic substances from the soil compared to controls. The complexing agents mobilized polyvalent metal ions, particularly Fe and Al from the soil. Metal ion chelation may disrupt humic–(metal ion)–mineral linkages, resulting in mobilization of SOM and accompanying PAH molecules into the aqueous phase; and/or reduce the degree of cross-linking in the soil organic matter phase, which could accelerate PAH diffusion.

Influence of Humic Substances on the Sorption Interactions between Lanthanide and Actinide Ions and Clay Minerals

Lanthanide (Eu, Nd, Gd) and actinide (Th, U) adsorption in a system consisting of fulvic acid, metal ions and clay minerals (montmorillonite, kaolinite, illite) was studied as a function of pH, metal ion concentration and fulvic acid concentration using spectrophotometric analysis and 152Eu tracer methods. Increasing metal ion adsorption on to the clay minerals was observed when humic substances were present in the system. The bridging of polyvalent metal ions between clay minerals and humic substance complexes was proposed as the possible adsorption mechanism.

Adsorption of Ionic Surfactants at the Air−Solution Interface

Neutron reflection (NR) and surface tension methods were compared for accessing the equilibrium adsorption isotherm of various ionic surfactants at the air−water interface. Four custom-synthesized anionics were investigated in detail: sodium dihexyl sulfosuccinate (di-C6SS), bis(1H,1H-perfluoro-n-pentyl)sodium sulfosuccinate (di-CF4), bis(1H,1H,5H-octafluoro-n-pentyl)sodium sulfosuccinate (di-HCF4), and bis(1H,1H,5H-octafluoropentyl)-2-sulfoglutaconate (di-HCF4GLU). Commercial n-alkyltrimethylammonium bromide (Cn-TAB) cationic surfactants with C12, C14, and C16 chain lengths were also studied. The experiments examined the validity of the Gibbs equation, and the prefactor 2, for these seven compounds. Effects of contaminants, trace levels of polyvalent metal ions, and hydrophobic impurities were assessed for the anionics. When added at low levels, tetrasodium ethylenediaminetetraacetate (EDTA) was effective for eliminating effects of metallic impurities, and foam fractionation was used to remove hydrophob...

Removal of heavy metal ions from aqueous solutions by alkaline-earth metal phosphates

The possibility of utilization of calcium or magnesium phosphates of various composition for heavy and non-ferrous metal extraction from aqueous solutions has been studied. The efficiency of the phosphates in removal of Pb(II), Cr(III) and Fe(III) ions has been shown to decrease in the following sequence: Mg 3(PO 4) 2>MgNH 4PO 4>Ca 3(PO 4) 2>CaHPO 4>Ca 10(PO 4) 6(OH) 2 which is inverse to their hydrolytic stability series. It has been established that phosphates of non-apatite structure are capable of binding up to 12 mmol g −1 of the named heavy metals by a chemical interaction. Hydroxyapatite interacts with the polyvalent metal ions via either the above mentioned or ion-exchange mechanism, depending on preparation method used for the apatite and the nature of metal.

Aqua-Impregnated Resins. 2. Separation of Polyvalent Metal Ions on Iminodiacetic and Polyacrylic Resins Using Bis(2-ethylhexyl) Phosphoric and Bis(2-ethylhexyl) Dithiophosphoric Acids as Organic Eluents

This paper dedicated to the further development of the novel aqua-impregnated-resin (AIR) technique reports the results obtained by studying the column separation of equimolar mixtures of Cu(2+), Al(3+), and Zn(2+) on iminodiacetic (IDA) and polyacrylic (PAR) resins by using 0.2 M heptane solutions of either bis(2-ethylhexyl) phosphoric acid (DEHPA) or bis(2-ethyhexyl) dithiophosphoric acid (DEHDTPA) as selective eluents for extractive desorption of metal ions from the resin phase. The quantitative separation of Cu(2+)-Al(3+) mixtures has been achieved by sequential elution of metals from PAR with DEHDTPA and H(2)SO(4) solutions. Purification of Cu(2+) from Al(3+) and/or Zn(2+) and Al(3+) from Cu(2+) and Zn(2+) is achieved by extractive elution of metal mixtures from IDAR or PAR with DEHPA or DEHDTPA solutions, respectively, followed by stripping of the purified metals with 1.1 M H(2)SO(4). The resulting purity of metals obtained with the yield of >96% exceed 95%.

Gas/Diffusion Flow Injection Determination of Ammonium Ions in River and Waste Waters by Conductometry

An FIA conductometric method for monitoring of ammonium ions in river and waste waters is proposed. A very good detection limit (xD 5.6 μmol l-1) was obtained at 100/20 s preconcentration/rinsing times and 2 ml sample consumption per analysis at the flow rate 0.8 ml min-1. The detection limit xD can be further improved at longer preconcentration/ rinsing times. Precipitation of polyvalent metal ions (mainly Fe(III)) was eliminated by addition of 0.5 mmol l-1 EDTA prior to injection. The results are comparable with those obtained by spectrophotometry (Nessler's reagent).

Absorption/release of polyvalent metal ions by a polyelectrolyte gel

The swelling/contraction dynamics of a strongly charged gel immersed in a copper sulphate solution were studied. Changes in the size of the gel particle and the penetration of metal ions inside the network were monitored by optical microscopy. The equilibrium state was attained in two steps: First, the gel swells, mainly by absorbing water, and then it collapses, to the almost dry state. The release of copper ions from the contracted gel when it was placed in acidic medium was studied as a function of time using optical microscopy. The influence of the acid concentration on the rate of ion release and on changes in the particle size of the gel are discussed.

OPTIMIZATION OF SORPTION PURIFICATION OF INDUSTRIAL EFFLUENTS, WASTE WATERS AND TECHNOLOGICAL SOLUTIONS FROM POLYVALENT METAL IONS

ABSTRACT The paper critically reviews the existing methods which are applied for the sorption purification of industrial effluents, waste waters and technological solutions from polyvalent metal ions (such as mercury, cadmium, calcium, copper, nickel and zinc), and also describes the novel purification processes developed recently by the authors. Particular attention is paid to the optimization of purification processes through the use of specially selected ion-exchange materials with the optimal equilibrium, kinetic, mechanical and other properties, application of the most effective apparatus design, and optimization of the process flowsheets. The approach proposed is illustrated by the results of both laboratory and the pilot-plant experiments including the final flowsheet of the purification processes. One of the examples given is the tailor-made modification of the commercial VP-1AP polyvinylpyridine resins with l,3-dichlor-5-dimethyl hydantoin, which combines high selectivity and oxidation capability towards different mercury species (including mercury organic compounds) in the same ion-exchange material. The paper includes also examples of purification of the native waste waters of different types from mercury and cadmium on organic and inorganic ion exchangers; deep purification of the NaCI brines from calcium on polyampholytes, purification of rinsing waters of electroplating industry from copper, nickel and zinc on mixed beds of ion exchangers, and other information which may be of interest for environmental and applied chemists.

Formation of insoluble and colloidally dispersed tannic acid complexes in the midgut fluid ofManduca sexta (Lepidoptera: Sphingidae): An explanation for the failure of tannic acid to cross the peritrophic envelopes of lepidopteran larvae

Magnesium and calcium ions, in concentrations comparable to those reported in the midgut fluids of lepidopteran larvae, bring about the precipitation of most of the tannic acid present in simple solutions buffered at pH 8.0 and 10.0, but not at pH 6.5. In contrast, when tannic acid is added to Manduca sexta midgut fluid, less than 31% of the tannic acid added to the gut fluid is converted to a form that can be centrifuged into a pellet. The rest remains in the supernatant solution in the form of a colloidal suspension. Very little of the tannic acid, if any, remains in true solution. We suggest that the tannic acid-containing phase that is produced when tannic acid is added to midgut fluid is a complex multi-molecular aggregate of indefinite chemical composition, incorporating varying amounts of tannic acid, surface-active phospholipids, proteins, and polyvalent metal ions. On the basis of this study, we further suggest that the failure of tannins to diffuse across the peritrophic envelopes of lepidopteran larvae is a result of the capacity of the peritrophic envelope to act as a physical barrier to insoluble and colloidally dispersed particles, not the presence of substances in the matrix that strongly adsorb polyphenols or the presence of an extensive network of fixed anionic sites in the matrix that acts as an electrostatic barrier to the passage of polyphenolate anions. Arch. Insect Biochem. Physiol. 39:109–117, 1998.© 1998 Wiley-Liss, Inc.

Formation of insoluble and colloidally dispersed tannic acid complexes in the midgut fluid of Manduca sexta (Lepidoptera: Sphingidae): An explanation for the failure of tannic acid to cross the peritrophic envelopes of lepidopteran larvae

Magnesium and calcium ions, in concentrations comparable to those reported in the midgut fluids of lepidopteran larvae, bring about the precipitation of most of the tannic acid present in simple solutions buffered at pH 8.0 and 10.0, but not at pH 6.5. In contrast, when tannic acid is added to Manduca sexta midgut fluid, less than 31% of the tannic acid added to the gut fluid is converted to a form that can be centrifuged into a pellet. The rest remains in the supernatant solution in the form of a colloidal suspension. Very little of the tannic acid, if any, remains in true solution. We suggest that the tannic acid-containing phase that is produced when tannic acid is added to midgut fluid is a complex multi-molecular aggregate of indefinite chemical composition, incorporating varying amounts of tannic acid, surface-active phospholipids, proteins, and polyvalent metal ions. On the basis of this study, we further suggest that the failure of tannins to diffuse across the peritrophic envelopes of lepidopteran larvae is a result of the capacity of the peritrophic envelope to act as a physical barrier to insoluble and colloidally dispersed particles, not the presence of substances in the matrix that strongly adsorb polyphenols or the presence of an extensive network of fixed anionic sites in the matrix that acts as an electrostatic barrier to the passage of polyphenolate anions. Arch. Insect Biochem. Physiol. 39:109–117, 1998.© 1998 Wiley-Liss, Inc.

Growth Inhibition of Listeria monocytogenes by Sodium Polyphosphate as Affected by Polyvalent Metal Ions

ABSTRACTSodium polyphosphate (SPP, average chain length = 13) increased the lag time of L. monocytogenes Scott A (Lm) in brain‐heart infusion broth (BHI). Polyvalent metal ions (1–10 mM) reversed inhibition of Lm growth by 0.5% SPP (nominal 3.6 mM). 10 mM Ca2+ or Mg2+, 5 mM Fe3+, 2 mM Mn2+ or 1 mM Zn2+ added to SPP‐containing BHI, pH 6.0, at 19°C resulted in growth comparable to control cultures. Fe2+ partially restored growth; Ni2+, Co2+, Cu2+ or Al3+ were ineffective. SPP inhibited growth at 28°C in BHI, pH 5.0, and Lm grew upon addition of Ca2+, Mg2+ or Mn2+, but not Zn2+ or Fe3+. Addition of 0.5% SPP to mineral‐rich foods, such as pureed beef, green beans or sweet potatoes, did not delay growth.

A Sensor for Measuring Gel Phase-Transition Temperature, with Potential as a Metal Ion Detector

This paper describes a sensor employing a gel formed from an interpenetrating polymer network of poly(vinyl alcohol) and a copolymer of N-isopropylacrylamide and acrylic acid. This gel exhibits a continuous volume-phase transition that is strongly dependent on the presence of polyvalent metal ions in the gel solvent. A sensor apparatus has been constructed that estimates, in real time, the transition temperature of a gel. When this sensor is loaded with a gel sensitive to metal ions, it could be used to detect the presence and identity of metal ions in a solution.