Characterization of bioflocculant MBF3-3 produced by an isolated <Emphasis Type="Italic">Bacillus </Emphasis>sp.

Summary  The characteristics of bioflocculant MBF3-3 produced by Bacillus sp. BF3-3 were investigated here. MBF3-3 showed excellent flocculating activity on real and synthetic wastewaters, and consumed a much lower dosage than that of the widely used polyaluminum chloride (PAC) when flocculating brewery wastewater. Except Fe³⁺, metal ions, including Al³⁺, Mg²⁺, Ca²⁺, K⁺ and Na⁺, can stimulate the flocculating activity of MBF3-3 obviously, and the stimulating effects increased in the order: monovalent < bivalent < trivalent. MBF3-3 was mainly composed of acidic polysaccharide (66.1%) and protein (29.3%), in which acidic polysaccharide was the main effective flocculating component. OH and COO– groups may play a vital role in the flocculation of suspended particles.     

Effects of some trivalent metal ions on the fluoride‐induced chemiluminescence from a phenylphosphate‐substituted dioxetane Lumigen PPD

The chemiluminescene generated from the reaction of a thermally stable phenylphosphate‐substituted dioxetane Lumigen PPD at ambient temperature was studied in DMSO solution. The presence of trivalent metal ions Cr³⁺, Ga³⁺, Fe³⁺ and Al³⁺ was found to quench the resulting chemiluminescence dramatically. The system resulted in nice Stern–Volmer plots in the quencher concentration range 1.5 × 10^?4–1.8 × 10^?3 mol/L. The K _Q values decreased in the order Cr³⁺ > Ga³⁺ > Fe³⁺ > Al³⁺. Copyright © 2002 John Wiley & Sons, Ltd.     

Yersiniabactin metal binding characterization and removal of nickel from industrial wastewater

Yersiniabactin (Ybt) is a metal‐binding natural product that has been re‐purposed for water treatment. The early focus of this study was the characterization of metal binding breadth attributed to Ybt. Using LC‐MS analysis of water samples exposed to aqueous and surface‐localized Ybt, quantitative assessment of binding was completed with metals that included Pd²⁺, Mg²⁺, and Zn²⁺. In total, Ybt showed affinity for 10 metals. Next, Ybt‐modified XAD‐16N resin (Ybt‐XAD) was utilized to quantify the affinity for metal removal, showing a rank order of Fe³⁺ > Ga³⁺ > Ni²⁺ > Cu²⁺ > Cr²⁺≈Zn²⁺ > Co²⁺ > Pd²⁺ > Mg²⁺ > Al³⁺, and in the applied treatment of wastewater from a local precious metal plating company, showing selective removal of nickel from the aqueous effluent. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1548–1554, 2017     

Iron transport by proteoliposomes containing mitochondrial F1Fo ATP synthase isolated from rat heart

In this work, we present evidence of Fe²⁺ transport by rat heart mitochondrial F₁F_o ATP synthase. Iron uptake by the vesicles containing the enzyme was concentration- and temperature-dependent, with an optimum temperature of 37 °C. Both ATP and ADP stimulated iron uptake in a concentration-dependent manner, whereas AMP, AMPPCP, and mADP did not. Inhibitors of the enzyme, oligomycin, and resveratrol similarly blocked iron transport. The iron uptake was confirmed by inhibition using specific antibodies against the α, β, and c subunits of the enzyme. Interestingly, slight transport of common divalent and trivalent metal ions such as Mg⁺², Ca⁺², Mn⁺², Zn⁺², Cu⁺², Fe⁺³, and Al⁺³ was observed. Moreover, Cu⁺², even in the nM range, inhibited iron uptake and attained maximum inhibition of approximately 56%. Inorganic phosphate (Pi) in the medium exerted an opposite effect depending on the type of adenosine nucleotide, which was suppressed with ATP, but enhanced with ADP. A similarly stimulating effect of ATP and ADP with an inverse effect of Pi suggests that the activity of ATPase and ATP synthase may be associated with iron uptake in a different manner, probably via antiport of H⁺.     

Single particle analysis of tau oligomer formation induced by metal ions and organic solvents

Pathological aggregates of tau protein are found in several neurodegenerative diseases termed ‘tauopathies’. Increasing evidence indicates that tau oligomer species rather than the large amyloid cytoplasmic inclusions relevant for histopathological diagnosis might be crucial for cellular damage and neurodegeneration. Trivalent metal ions and polyanionic structures like heparin or arachidonic acid have been shown to induce tau aggregation. However, little is known about early processes of tau aggregation. In this study, we applied fluorescence correlation spectroscopy (FCS) and scanning for intensely fluorescent targets (SIFT) to investigate oligomer formation of tau protein at nanomolar protein concentrations at the single-particle level. Our results indicate that the formation of distinct tau oligomers is induced by the trivalent metal ions Fe³⁺ and Al³⁺ and by organic solvents like DMSO, respectively. In contrast, bivalent metal ions (Cu²⁺, Zn²⁺, Mn²⁺, Ca²⁺, Mg²⁺) had no effect. While DMSO-induced small tau oligomers are relatively stable in solution, dynamic remodeling can be initiated by non-ionic detergents. Moreover Al³⁺ induces rapid formation of a different oligomer species of larger size. Our results provide further insights into early tau oligomerization and aggregation dynamics.     

Colorimetric chiral fluorescent sensors for Eu3+ and sequential enantioselective sensing of malate anion

Novel phenanthroline Schiff base fluorescent sensors L1 , L2 , and D1 were designed and synthesized. The sensing abilities of the compounds in the presence of metal cations (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ba²⁺, Ca²⁺, Mn²⁺, Pb²⁺, Hg²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Co²⁺, Cu²⁺, Cr³⁺, Fe³⁺, Fe²⁺, Al³⁺, and Eu³⁺) were studied by UV‐vis and fluorescent spectroscopy. The compounds L1 , L2 , and D1 could act as Eu³⁺ ion turn‐off fluorescent sensors based on ligand‐to‐metal binding mechanism in DMSO‐H₂O solution (v/v = 1:1, 10 mM Tris, pH = 7.4). Additionally, the L1 –Eu³⁺ and D1 –Eu³⁺ complexes could be applied as turn‐on enantioselective sensors sensing of malate anion isomers with color changes. Furthermore, biological experiments using living PC‐12 cells demonstrated that L1 and D1 had excellent membrane permeability and could be used as effective fluorescent sensors for detecting Eu³⁺ and malate anion in living cells.     

Ion Permeation and Block of P2X2 Purinoceptors: Single Channel Recordings

P2X₂ purinoceptors are cation-selective channels activated by ATP and its analogues. Using single channel measurements we studied the channel's selectivity for the alkali metal ions and organic monovalent cations NMDG⁺, Tris⁺, TMA⁺, and TEA⁺. The selectivity sequence for currents carried by alkali metal ions is: K⁺ > Rb⁺ > Cs⁺ > Na⁺ > Li⁺, which is Eisenman sequence IV. This is different from the mobility sequence of the ions in free solution suggesting there is weak interaction between the ions and the channel interior. The relative conductance for alkali ions increases linearly in relation to the Stokes radius. The organic ions NMDG⁺, Tris⁺, TMA⁺ and TEA⁺ were virtually impermeant. The divalent ions (Mn²⁺, Mg²⁺, Ca²⁺ and Ba²⁺) induced a fast block visible as a reduction in amplitude of the unitary currents. Using a single-site binding model, the divalent ions exhibited an equilibrium affinity sequence of Mn²⁺ > Mg²⁺ > Ca²⁺ > Ba²⁺. Received: 3 May 1999/Revised: 23 August 1999     

Characterization of Mg2+-ATPase from sheep kidney medulla: purification.

Magnesium-dependent adenosine triphosphatase has been purified from sheep kidney medulla plasma membranes. The purification, which is based on treatment of a kidney plasma membrane fraction with 0.5% digitonin in 3 mm MgCl₂, effectively separates the Mg²⁺-ATPase from (Na⁺ + K⁺)-ATPase present in the same tissue and yields the Mg²⁺-ATPase in soluble form. The purified enzyme is activated by a variety of divalent cations and trivalent cations, including Mg²⁺, Mn²⁺, Ca²⁺, Co²⁺, Fe²⁺, Zn²⁺, Eu³⁺, Gd³⁺, and VO²⁺. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme shows two bands with R_f values corresponding to molecular weights of 150,000 and 77,000. The larger peptide is phosphorylated by [γ-³²P]ATP, suggesting that this peptide may contain the active site of the Mg²⁺-ATPase. The Mg²⁺-ATPase activity is unaffected by the specific (Na⁺ + K⁺)-ATPase inhibitor ouabain.     

Probing the coordination properties of glutathione with transition metal ions (Cr2+,Mn2+,Fe2+,Co2+, Ni2+,Cu2+,Zn2+,Cd2+,Hg2+) by density functional theory

Complexes formed by reduced glutathione (GSH) with metal cations (Cr²⁺, Mn²⁺,Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺,Zn²⁺,Cd²⁺,Hg²⁺) were systematically investigated by the density functional theory (DFT). The results showed that the interactions of the metal cations with GSH resulted in nine different stable complexes and many factors had an effect on the binding energy. Generally, for the same period of metal ions, the binding energies ranked in the order of Cu²⁺>Ni²⁺>Co²⁺>Fe²⁺>Cr²⁺>Zn²⁺>Mn²⁺; and for the same group of metal ions, the general trend of binding energies was Zn²⁺>Hg²⁺>Cd²⁺. Moreover, the amounts of charge transferred from S or N to transition metal cations are greater than that of O atoms. For Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺,Zn²⁺,Cd²⁺ and Hg²⁺ complexes, the values of the Wiberg bond indices (WBIs) of M-S (M denotes metal cations) were larger than that of M-N and M-O; for Cr²⁺ complexes, most of the WBIs of M-O in complexes were higher than that of M-S and M-N. Furthermore, the changes in the electron configuration of the metal cations before and after chelate reaction revealed that Cu²⁺, Ni²⁺,Co²⁺ and Hg²⁺ had obvious tendencies to be reduced to Cu⁺,Ni⁺,Co⁺ and Hg⁺ during the coordination process.     

Using Taguchi experimental design methods to optimize trace element composition for enhanced surfactin production by Bacillus subtilis ATCC 21332

In this work, optimizing trace element composition was attempted as a primary strategy to improve surfactin production from Bacillus subtilis ATCC 21332. Statistical experimental design (Taguchi method) was applied for the purpose of identifying optimal trace element composition in the medium. Of the five trace elements examined, Mg²⁺, K⁺, Mn²⁺, and Fe²⁺ were found to be more significant factors affecting surfactin production by the B. subtilis strain. In the absence of Mg²⁺ or K⁺, surfactin yield decreased to 0.4 g/l, which was only 25% of the value obtained from the control run. When Mn²⁺ and Fe²⁺ were both absent, the production yield also dropped to ca. 0.6 g/l, approximately one-third of the control value. However, when only one of the two metal ions (Fe²⁺ or Mn²⁺) was missing, the B. subtilis ATCC 21332 strain was able to remain over 80% of original surfactin productivity, suggesting that some interactive correlations among the selected metal ions may involve. Taguchi method was thus applied to reveal the interactive effects of Mg²⁺, K⁺, Mn²⁺, Fe²⁺ on surfactin production. The results show that interaction of Mg²⁺ and K⁺ reached significant level. By further optimizing Mg²⁺ and K⁺ concentrations in the medium, the surfactin production was boosted to 3.34 g/l, which nearly doubled the yield obtained from the original control.     

A novel fluorescent probe based on rhodamine hydrazone derivatives bearing a thiophene group for Al3+

In the present work, a novel 5‐methyl‐thiophene‐carbaldehyde‐functionalized rhodamine 6G Schiff base (RA) was designed and easily prepared as an Al³⁺ fluorescent and colorimetric probe, which could selectively and sensitively detect Al³⁺ by showing enhanced fluorescence emission. Meanwhile distinct color variation from colorless to pink also provided ‘naked eye’ detection of Al³⁺, due to the ring spirolactam opening of the rhodamine derivative. Other metal ions (including K⁺, Mg²⁺, Na⁺, Ba²⁺, Mn²⁺, Cd²⁺, Fe²⁺, Ni²⁺, Pb²⁺, Zn²⁺, Hg²⁺, Co²⁺, Li⁺, Sr²⁺ and Cu²⁺) could only induce limited interference. The detection limit of the fluorescent probe was estimated to be 4.17 × 10^?6 M, the binding constant of the RA–Al³⁺ complex was 1.4 × 10⁶ M^?1. Moreover, this fluorescent probe RA possessed high reversibility. As aluminum is a ubiquitous metal in nature and plays vital roles in many biological processes, this chemosensor could be explored for biological study applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Correlations between projection area of ectomycorrhizae and H<Subscript>2</Subscript>O extractable nutrients in organic soil layers

Most of the fine root tips of boreal and temperate forests are colonized by ectomycorrhizal fungi. Thus ectomycorrhizal (ECM) symbiosis is an important factor in supplying trees with water and a wide range of nutrients. ECM are frequently patchily distributed and often form dense systems in small areas. One of the reasons for this uneven distribution might be a heterogeneous and patchy distribution of nutrients. The present study compares the occurrence of ECM of Cortinarius obtusus, Lactarius decipiens, L. theiogalus, and Russula ochroleuca and soil nutrient concentrations at a micro-scale (1 cm²) in the O_F layer of a pure Norway spruce stand. In addition to the macronutrients K⁺, Mg²⁺, Ca²⁺, NO₃ ⁻, NH₄ ⁺, the concentrations of Na⁺, Fe³⁺+Mn²⁺, Al³⁺, Cl⁻, SO₄ ²⁻ are studied, as well as pH. Whereas Russula ochroleuca and Lactarius decipiens did not reveal any significant correlation with any of the tested nutrients or pH, the occurrence of L. theiogalus was significantly (p < 5 %) positively correlated with NH₄ ⁺, K⁺, Na⁺, Mg²⁺, Fe³⁺+Mn²⁺, and pH. Cortinarius obtusus was positively correlated at the same significance level only with NH₄ ⁺ and Mg²⁺.     

The action of certain polyvalent cations on the voltage-clamped lobster axon

Calcium appears to be an essential participant in axon excitation processes. Many other polyvalent metal ions have calcium-like actions on axons. We have used the voltage-clamped lobster giant axon to test the effect of several of these cations on the position of the peak initial (sodium) and steady-state (potassium) conductance vs. voltage curves on the voltage axis as well as on the rate parameters for excitation processes. Among the alkaline earth metals, Mg⁺² is a very poor substitute for Ca⁺², while Ba⁺² behaves like "high calcium" when substituted for Ca⁺² on a mole-for-mole basis. The transition metal ions, Ni⁺², Co⁺², and Cd⁺² also act like high calcium when substituted mole-for-mole. Among the trivalent ions, La⁺³ is a very effective Ca⁺² replacement. Al⁺³ and Fe⁺³ are extremely active and seem to have some similar effects. Al⁺³ is effective at concentrations as low as 10^-5 M. The data suggest that many of these ions may interact with the same cation-binding sites on the axon membrane, and that the relative effects on the membrane conductance and rate parameters depend on the relative binding constants of the ions. The total amount of Na⁺ transferred during a large depolarizing transient is nearly independent of the kind or amount of polyvalent ion applied.     

Naked Eye Detection of Cr3+ and Co2+ Ions by Gold Nanoparticle Modified with Azomethine

This paper reports the synthesis of azomethine-modified gold nanoparticles with azomethine (azomethine-AuNPs) in aqueous media, which were characterized by FT-IR spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The azomethine-AuNPs were employed as colorimetric for Cr³⁺ and Co²⁺ ions at pH 6.2–7.5 and 8.1–9.1, at room temperature in aqueous solution. In the presence of Cr³⁺ and Co²⁺, the azomethine-AuNPs induce aggregation of the nanoparticles. Upon aggregation, the surface plasmon absorption band red-shifts so that the nanoparticle solution appears a blue color. The sensitivity of azomethine-AuNPs towards other metal ions, Mg²⁺, Mn²⁺, Cr⁶⁺, Na⁺, Ni²⁺, Ag⁺, Al³⁺, Ca²⁺, Cd²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Cd²⁺, K⁺, Co³⁺, Ni²⁺, Pb²⁺, and Zn²⁺ are negligible. This highly selective sensor allows a direct quantitative assay of Co²⁺ and Cr³⁺ with colorimetric detection limits of 83.22 and 108 nM, respectively.

     

Terbium binding to axonal membrane vesicles from lobster (Homarus Americanus) peripheral nerve. A probe of calcium binding sites

Tb³⁺, a fluorescent trivalent cation with physicochemical properties similar to Ca²⁺, binds to peripheral nerve membrane vesicles prepared from the walking leg nerve bundle of the lobster (Homarus americanus). Saturable binding is measured for at least two classes of binding site. Bound Tb³⁺ can be displaced by other cations in the order: Ca²⁺ > Mg²⁺ = Zn²⁺ > NH₄⁺. The binding of Tb³⁺ to the lower affinity site (K_D(app) = 6.0 μM) is inhibitable by Na⁺, Mg²⁺ and Ca²⁺, whereas the higher affinity site (K_D(app) = 2.2 μM) is only sensitive to Ca²⁺. Using this spectral probe the role of Ca²⁺ in peripheral nerve membrane function can be investigated.     

A ditopic receptor for cation binding and facilitated transport through a supported liquid membrane

The binding properties of an artificial receptor towards a series of cations including Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Fe²⁺ and Al³⁺ in acetonitrile are described. The receptor comprises a photo-responsive pyrene unit connected via a short spacer to a 2,2′:6′,2″-terpyridine metal ion binding site. Interaction of cations with the receptor was monitored by changes in absorption profile and the association constants calculated for 1:1 and 1:2 cation:ligand binding fall within the range log β = 3-12. The receptor is highly fluorescent and quenching of the emission is observed upon cation binding. The potassium picrate transport properties of the membrane-bound receptor are also described. This receptor when immobilised in a polymer support, which separates two aqueous solutions, has been shown to transport potassium ions in the dark with a flux rate of 1.5 × 10⁸ mol/s m². In contrast, when the membrane-bound receptor is selectively illuminated with light (λ > 400 nm), the flux increases to 2.0 × 10⁸ mol/s m². The transport efficiency depends on the nature of the trap used in the receiver phase.     

A highly selective and sensitive boronic acid-based sensor for detecting Pd2+ ion under mild conditions

Herein, a boronic acid-based sensor was reported selectively to recognize Pd²⁺ ion. The fluorescence intensity increased 36-fold after sensor binding with 2.47 × 10⁻⁵ M of Pd²⁺ ion. It was carried out in the 99% aqueous solution for binding tests, indicating sensor having good water solubility. In addition, it is discernible that Pd²⁺ ion turned on the blue fluorescence of sensor under a UV–lamp (365 nm), while other ions (Ag⁺, Al³⁺, Ba²⁺, Ca²⁺, Cr²⁺, Cd²⁺, Co²⁺, Cs²⁺, Cu²⁺, Fe²⁺, Fe³⁺, K⁺, Li⁺, Mg²⁺, Mn²⁺, Na⁺, Ni²⁺ and Zn²⁺) did not show the similar change. Furthermore, sensor has a low limit of detection (38 nM) and high selectivity, which exhibits the potential for the development of Pd²⁺ recognition in practical environments.     

Binding of Heparin to Metals

Heparin is a major prophylactic and treatment agent for thrombosis. Structurally, this anticoagulant is a polydisperse, highly negatively charged polysaccharide mixture that contains a variable density of sulfate group substituents per molecule. Previous study has shown that heparin molecules have a high affinity for a wide range of metal ions with varying oxidation states. However, reports in literature on binding of heparin to metals have investigated only a small sampling of heparin–metal ion interactions. Since interaction of heparin with fluid phase and cell surface macromolecules in vivo is dependent on the heparin structure when bound in a metal ion complex, a survey of the physical parameters for heparin binding to metals is imperative. Atomic absorption and spectrophotometry experiments were performed for metal quantification, and in this study, the relative values for affinity constants and number of binding sites for heparin binding to several alkaline, alkaline earth, main group, and transition metals in their most common oxidation states are reported. We found an overall trend for heparin–metal affinity to be Mn²⁺ > Cu²⁺ > Ca²⁺ > Zn²⁺ > Co²⁺ > Na⁺ > Mg²⁺ > Fe³⁺ > Ni²⁺ > Al³⁺> Sr²⁺, with the trend in N _b being opposite compared with the K _a.     

Aluminum-sensitive mutants of Saccharomyces cerevisiae

We are developing budding yeast, Saccharomyces cerevisiae, as a genetic system for the study of tolerance to the trivalent aluminum cation (Al³⁺). We have isolated eight mutants that are more sensitive to Al³⁺ than the wild type. Each mutant represented a different complementation group. A number of the mutants were pleiotropic, and showed defects in other stress responses, changes in tolerance to other metal cations, or abnormal morphology. Two mutants also showed increased dependence on supplemental Mg²⁺ and Ca²⁺. One mutant with a relatively specific sensitivity to Al³⁺ was chosen for molecular complementation. Normal Al³⁺ tolerance was restored by expression of the MAP kinase gene SLT2. Strains carrying deletions of the SLT2 gene, or of the gene for the corresponding MAP kinase–kinase SLK1, showed sensitivity to Al³⁺. These results indicate that the SLT2 MAP kinase signal transduction pathway is required for yeast to sense and respond to Al³⁺ stress. Received: 17 April 1996 / Accepted: 21 October 1996     

Activated carbon-containing alginate adsorbent for the simultaneous removal of heavy metals and toxic organics

By combining two functions of alginate gel and activated carbon, an activated carbon-containing alginate bead (AC-AB) adsorbent was developed and successfully used to simultaneously remove heavy metal ions and toxic organics. Quantitative analysis showed that almost all of the adsorption of toxic organics, such as p-toluic acid, is caused by the activated carbon in the AC-AB adsorbent, whereas the alginate component has a major role in the removal of heavy metals. A 50-L solution containing eight heavy metals (Pb²⁺, Mn²⁺, Cd²⁺, Cu²⁺, Zn²⁺, Fe²⁺, Al³⁺ and Hg²⁺) and four mineral ions was run continuously through a filter cartridge packed with 160 g of the AC-AB adsorbent. The adsorbent showed a high capacity to remove heavy metals completely from the water, while allowing essential minerals, such as K⁺, Na⁺, Mg²⁺ and Ca²⁺, to pass through the filter. The adsorbent could be regenerated using eluents, such as HNO₃, and reused repeatedly without considerable loss of its metal uptake capacity through 10 subsequent cycles of adsorption and desorption. With its high capacity and high selectivity for toxic heavy metals, the AC-AB adsorbent has enormous potential for application in drinking water treatment technologies.