Analysis of the pH-Dependent Fe(III) Ion Chelating Activity of Anthocyanin Extracted from Black Soybean [Glycine max (L.) Merr.] Coats.

PubMed

Xie, Yanli; Zhu, Xiaolu; Li, Yuan; Wang, Chen

2018-02-07

The Fe(III) chelating activity of anthocyanin extracted from black soybean coats was investigated at pH 3.0, 5.0, 6.5, 7.0, and 7.4 with fluorescence spectroscopy and microscale thermophoresis (MST). Cyanidin-3-glucoside (C3G) was determined to be 98% of the total anthocyanin by high-performance liquid chromatography. The binding affinity (K a ) exhibited significant pH-dependent behavior: K a was 9.7167 × 10 4 , 1.0837 × 10 4 , 1.4284 × 10 4 , 5.4550 × 10 4 , and 3.0269 × 10 4 M -1 at pH 3.0, 5.0, 6.5, 7.0, and 7.4, respectively (p < 0.05). The MST data showed that ΔG < 0 and ΔH < 0, demonstrating that chelation is spontaneous and exothermic. Because both ΔH and ΔS < 0, the chelation involves hydrogen bonds and/or van der Waals forces for pH 3.0, 5.0, and 6.5. Electrostatic interactions contributed to chelation at pH 7.0 and 7.4 with ΔH < 0 and ΔS > 0. With the formation of chelates, C3G improved the solubility of Fe(III) at pH 6.5, 7.0, and 7.4 to enhance the ferric ion bioavailability, except for aggregation observed at pH 5.0.

Effect of the chelation of metal cation on the antioxidant activity of chondroitin sulfates.

PubMed

Ajisaka, Katsumi; Oyanagi, Yutaka; Miyazaki, Tatsuo; Suzuki, Yasuhiro

2016-06-01

The antioxidant potencies of chondroitin sulfates (CSs) from shark cartilage, salmon cartilage, bovine trachea, and porcine intestinal mucosa were compared by three representative methods for the measurement of the antioxidant activity; DPPH radical scavenging activity, superoxide radical scavenging activity, and hydroxyl radical scavenging activity. CSs from salmon cartilage and bovine trachea showed higher potency in comparison with CSs from shark cartilage and porcine intestinal mucosa. Next, CS from salmon cartilage chelating with Ca(2+), Mg(2+), Mn(2+), or Zn(2+) were prepared, and their antioxidant potencies were compared. CS chelating with Ca(2+) or Mg(2+) ions showed rather decreased DPPH radical scavenging activity in comparison with CS of H(+) form. In contrast, CS chelating with Ca(2+) or Mg(2+) ion showed remarkably enhanced superoxide radical scavenging activity than CS of H(+) or Na(+) form. Moreover, CS chelating with divalent metal ions, Ca(2+), Mg(2+), Mn(2+), or Zn(2+), showed noticeably higher hydroxyl radical scavenging activity than CS of H(+) or Na(+) form. The present results revealed that the scavenging activities of, at least, superoxide radical and hydroxyl radical were enhanced by the chelation with divalent metal ions.

Potential of ethylenediaminedi(o-hydroxyphenylacetic acid) and N,N'-bis(hydroxybenzyl)ethylenediamine-N,N'-diacetic acid for the determination of metal ions by capillary electrophoresis.

PubMed

Krokhin, O V; Kuzina, O V; Hoshino, H; Shpigun, O A; Yotsuyanagi, T

2000-08-25

Two aromatic polyaminocarboxylate ligands, ethylenediaminedi(o-hydroxyphenylacetic acid) (EDDHA) and N,N'-bis(hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED), were applied for the separation of transition and heavy metal ions by the ion-exchange variant of electrokinetic chromatography. EDDHA structure contains two chiral carbon centers. It makes it impossible to use the commercially available ligand. All the studied metal ions showed two peaks, which correspond to meso and rac forms of the ligand. The separation of metal-HBED chelates was performed using poly(diallyldimethylammonium) polycations in mixed acetate-hydroxide form. Simultaneous separation of nine single- and nine double-charged HBED chelates, including In(III), Ga(III), Co(II)-(III) and Mn(II)-(III) pairs demonstrated the efficiency of 40,000-400,000 theoretical plates. The separation of Co(III), Fe(III) complexes with different arrangements of donor groups and oxidation of Co(II), Mn(H), Fe(II) ions in reaction with HBED have been discussed.

Interactions of flavonoids with iron and copper ions: a mechanism for their antioxidant activity.

PubMed

Mira, Lurdes; Fernandez, M Tereza; Santos, Marta; Rocha, Rui; Florêncio, M Helena; Jennings, Keith R

2002-11-01

The metal chelating properties of flavonoids suggest that they may play a role in metal-overload diseases and in all oxidative stress conditions involving a transition metal ion. A detailed study has been made of the ability of flavonoids to chelate iron (including Fe3+) and copper ions and its dependence of structure and pH. The acid medium may be important in some pathological conditions. In addition, the ability of flavonoids to reduce iron and copper ions and their activity-structure relationships were also investigated. To fulfill these objectives, flavones (apigenin, luteolin, kaempferol, quercetin, myricetin and rutin), isoflavones (daidzein and genistein), flavanones (taxifolin, naringenin and naringin) and a flavanol (catechin) were investigated. All flavonoids studied show higher reducing capacity for copper ions than for iron ions. The flavonoids with better Fe3+ reducing activity are those with a 2,3-double bond and possessing both the catechol group in the B-ring and the 3-hydroxyl group. The copper reducing activity seems to depend largely on the number of hydroxyl groups. The chelation studies were carried out by means of ultraviolet spectroscopy and electrospray ionisation mass spectrometry. Only flavones and the flavanol catechin interact with metal ions. At pH 7.4 and pH 5.5 all flavones studied appear to chelate Cu2+ at the same site, probably between the 5-hydroxyl and the 4-oxo groups. Myricetin and quercetin, however, at pH 7.4, appear to chelate Cu2+ additionally at the ortho-catechol group, the chelating site for catechin with Cu2+ at pH 7.4. Chelation studies of Fe3+ to flavonoids were investigated only at pH 5.5. Only myricetin and quercetin interact strongly with Fe3+, complexation probably occurring again between the 5-hydroxyl and the 4-oxo groups. Their behaviour can be explained by their ability to reduce Fe3+ at pH 5.5, suggesting that flavonoids reduce Fe3+ to Fe2+ before association.

Analysis of Supercritical-Extracted Chelated Metal Ions From Mixed Organic-Inorganic Samples

NASA Technical Reports Server (NTRS)

Sinha, Mahadeva P. (Inventor)

1996-01-01

Organic and inorganic contaminants of an environmental sample are analyzed by the same GC-MS instrument by adding an oxidizing agent to the sample to oxidize metal or metal compounds to form metal ions. The metal ions are converted to chelate complexes and the chelate complexes are extracted into a supercritical fluid such as CO2. The metal chelate extract after flowing through a restrictor tube is directly injected into the ionization chamber of a mass spectrometer, preferably containing a refractory metal filament such as rhenium to fragment the complex to release metal ions which are detected. This provides a fast, economical method for the analysis of metal contaminants in a sample and can be automated. An organic extract of the sample in conventional or supercritical fluid solvents can be detected in the same mass spectrometer, preferably after separation in a supercritical fluid chromatograph.

Hydroxypyridonate chelating agents and synthesis thereof

DOEpatents

Raymond, K.N.; Scarrow, R.C.; White, D.L.

1985-11-12

Chelating agents having 1-hydroxy-2-pyridinone (HOPO) and related moieties incorporated within their structures, including polydentate HOPO-substituted polyamines such as spermidine and spermine, and HOPO-substituted desferrioxamine. The chelating agents are useful in selectively removing certain cations from solution, and are particularly useful as ferric ion and actinide chelators. Novel syntheses of the chelating agents are provided. 4 tabs.

Chelating agents.

PubMed

Bergan, T; Klaveness, J; Aasen, A J

2001-01-01

The antibacterial activity of metal ions, metal chelates, and molecules with chelating ability for polyvalent cations have been evaluated. The chelator N, N'-ethylenebis[2-(2-hydroxyphenyl)-glycine] (EHPG) exerted moderate-to-good activity against isolates of pathogenic bacteria and fungi. Other chelating agents such as ethylenediamine-tetraacetic acid (EDTA) and diethylene-triamine-pentaacetic acid (DTPA) revealed weak-to-moderate activity. Metal chelation of ligands reduced the activity of EDTA and DTPA. Copyright 2001 S. Karger AG, Basel

Catalytic superoxide scavenging by metal complexes of the calcium chelator EGTA and contrast agent EHPG.

PubMed

Fisher, Anna E O; Hague, Theresa A; Clarke, Charlotte L; Naughton, Declan P

2004-10-08

Metal ion chelators widely used in experimental protocols and clinical diagnosis are generally assumed to be inert. We previously reported that the ubiquitous chelator EDTA has high levels of superoxide suppressing activity. Here, we report that the common chelators calcium chelator EGTA and contrast agent EHPG have significant activities in suppressing superoxide levels depending on the nature of metal ion chelated. The most active species is Mn(II)-EGTA which exhibited an IC50 value of 0.19 microM for superoxide destruction. In addition, IC50 values for Mn(II)-EHPG and 2Cu(II)-EGTA were 0.69 and 0.60 microM, respectively. In conclusion, Mn(II) and Cu(II) complexes of the common chelators EGTA and EHPG exhibit considerable superoxide scavenging activities. Caution should be employed in their use in biological systems where superoxide has a key role and they may be useful for the development of catalytic anti-oxidants. Copyright 2004 Elsevier Inc.

Biological and Clinical Aspects of Lanthanide Coordination Compounds

PubMed Central

Misra, Sudhindra N.; M., Indira Devi; Shukla, Ram S.

2004-01-01

The coordinating chemistry of lanthanides, relevant to the biological, biochemical and medical aspects, makes a significant contribution to understanding the basis of application of lanthanides, particularly in biological and medical systems. The importance of the applications of lanthanides, as an excellent diagnostic and prognostic probe in clinical diagnostics, and an anticancer material, is remarkably increasing. Lanthanide complexes based X-ray contrast imaging and lanthanide chelates based contrast enhancing agents for magnetic resonance imaging (MRI) are being excessively used in radiological analysis in our body systems. The most important property of the chelating agents, in lanthanide chelate complex, is its ability to alter the behaviour of lanthanide ion with which it binds in biological systems, and the chelation markedly modifies the biodistribution and excretion profile of the lanthanide ions. The chelating agents, especially aminopoly carboxylic acids, being hydrophilic, increase the proportion of their complex excreted from complexed lanthanide ion form biological systems. Lanthanide polyamino carboxylate-chelate complexes are used as contrast enhancing agents for Magnetic Resonance Imaging. Conjugation of antibodies and other tissue specific molecules to lanthanide chelates has led to a new type of specific MRI contrast agents and their conjugated MRI contrast agents with improved relaxivity, functioning in the body similar to drugs. Many specific features of contrast agent assisted MRI make it particularly effective for musculoskeletal and cerebrospinal imaging. Lanthanide-chelate contrast agents are effectively used in clinical diagnostic investigations involving cerebrospinal diseases and in evaluation of central nervous system. Chelated lanthanide complexes shift reagent aided 23Na NMR spectroscopic analysis is used in cellular, tissue and whole organ systems. PMID:18365075

beta-Citryl-L-glutamate is an endogenous iron chelator that occurs naturally in the developing brain.

PubMed

Hamada-Kanazawa, Michiko; Kouda, Makiko; Odani, Akira; Matsuyama, Kaori; Kanazawa, Kiyoka; Hasegawa, Tatsuya; Narahara, Masanori; Miyake, Masaharu

2010-01-01

The compound beta-citryl-L-glutamate (beta-CG) was initially isolated from developing brains, while it has also been found in high concentrations in testes and eyes. However, its functional roles are unclear. To evaluate its coordination with metal ions, we performed pH titration experiments. The stability constant, logbeta(pqr) for M(p)(beta-CG)(q)H(r) was calculated from pH titration data, which showed that beta-CG forms relatively strong complexes with Fe(III), Cu(II), Fe(II) and Zn(II). beta-CG was also found able to solubilize Fe more effectively from Fe(OH)(2) than from Fe(OH)(3). Therefore, we examined the effects of beta-CG on Fe-dependent reactive oxygen species (ROS)-generating systems, as well as the potential ROS-scavenging activities of beta-CG and metal ion-(beta-CG) complexes. beta-CG inhibited the Fe-dependent degradation of deoxyribose and Fe-dependent damage to DNA or plasmid DNA in a dose-dependent manner, whereas it had no effect on Cu-mediated DNA damage. In addition, thermodynamic data showed that beta-CG in a physiological pH solution is an Fe(II) chelator rather than an Fe(III) chelator. Taken together, these findings suggest that beta-CG is an endogenous low molecular weight Fe chelator.

The Stoichiometry of Isoquercitrin Complex with Iron or Copper Is Highly Dependent on Experimental Conditions

PubMed Central

Tvrdý, Václav; Karlíčková, Jana; Migkos, Thomas; Mladěnka, Přemysl

2017-01-01

Interaction of flavonoids with transition metals can be partially responsible for their impact on humans. Stoichiometry of the iron/copper complex with a flavonoid glycoside isoquercitrin, a frequent component of food supplements, was assessed using competitive and non-competitive methods in four (patho)physiologically-relevant pH values (4.5. 5.5, 6.8, and 7.5). Isoquercitrin chelated all tested ions (Fe2+, Fe3+, Cu2+, and Cu+) but its affinity for Cu+ ions proved to be very low. In general, the chelation potency dropped with pH lowering. Metal complexes of 1:1 stoichiometry were mostly formed, however, they were not stable and the stoichiometry changed depending on conditions. Isoquercitrin was able to reduce both Cu2+ and Fe3+ ions at low ratios, but its reducing potential was diminished at higher ratios (isoquercitrin to metal) due to the metal chelation. In conclusion, this study emphasizes the need of using multiple different methods for the assessment of chelation potential in moderately-active metal chelators, like flavonoids. PMID:29084179

Headgroup interactions and ion flotation efficiency in mixtures of a chelating surfactant, different foaming agents, and divalent metal ions.

PubMed

Svanedal, Ida; Boija, Susanne; Norgren, Magnus; Edlund, Håkan

2014-06-10

The correlation between interaction parameters and ion flotation efficiency in mixtures of chelating surfactant metal complexes and different foaming agents was investigated. We have recently shown that chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) forms strong coordination complexes with divalent metal ions, and this can be utilized in ion flotation. Interaction parameters for mixed micelles and mixed monolayer formation for Mg(2+) and Ni(2+) complexes with the chelating surfactant 4-C12-DTPA and different foaming agents were calculated by Rubingh's regular solution theory. Parameters for the calculations were extracted from surface tension measurements and NMR diffusometry. The effects of metal ion coordination on the interactions between 4-C12-DTPA and the foaming agents could be linked to a previously established difference in coordination chemistry between the examined metal ions. As can be expected from mixtures of amphoteric surfactants, the interactions were strongly pH-dependent. Strong correlation was found between interaction parameter β(σ) for mixed monolayer formation and the phase-transfer efficiency of Ni(2+) complexes with 4-C12-DTPA during flotation in a customized flotation cell. In a mixture of Cu(2+) and Zn(2+), the significant difference in conditional stability constants (log K) between the metal complexes was utilized to selectively recover the metal complex with the highest log K (Cu(2+)) by ion flotation. Flotation experiments in an excess concentration of metal ions confirmed the coordination of more than one metal ion to the headgroup of 4-C12-DTPA.

Transition metal-chelating surfactant micelle templates for facile synthesis of mesoporous silica nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hye Sun; Department of Materials Science and Engineering, Yonsei University, Seoul 120-749; Kim, Won Hee

2012-01-15

Highly ordered mesoporous silica nanoparticles with tunable morphology and pore-size are prepared by the use of a transition metal-chelating surfactant micelle complex using Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} ions. These metal ions formed a metal-P123 micelle complex in an aqueous solution, while the metal ions are chelated to the hydrophilic domain such as the poly(ethylene oxide) group of a P123 surfactant. The different complexation abilities of the utilized transition metal ions play an important role in determining the formation of nano-sized ordered MSNs due to the different stabilization constant of the metal-P123 complex. Consequently, from amore » particle length of 1700 nm in the original mesoporous silica materials, the particle length of ordered MSNs through the metal-chelating P123 micelle templates can be reduced to a range of 180-800 nm. Furthermore, the variation of pore size shows a slight change from 8.8 to 6.6 nm. In particular, the Cu{sup 2+}-chelated MSNs show only decreased particle size to 180 nm. The stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism of MSNs by the metal-chelating P123 complex templates. In addition, solid-state {sup 29}Si, {sup 13}C-NMR and ICP-OES measurements are used for quantitative characterization reveal that the utilized metal ions affect only the formation of a metal-P123 complex in a micelle as a template. - Graphical abstract: Metal-chelating surfactant micelle templates support a simple and facile preparations of size-tunable ordered MSNs. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Facile preparation of mesoporous silica nanoparticles (MSNs) was achieved by metal-chelating surfactant micelle complex using Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} ions. Black-Right-Pointing-Pointer Different complexation of metal ions plays an important role in determining the formation of nano-sized ordered MSNs. Black-Right-Pointing-Pointer Systematic characterization of the synthesized materials was achieved by solid-state {sup 29}Si and {sup 13}C-NMR techniques, BET, FT-IR, and XPS. Black-Right-Pointing-Pointer Stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism.« less

Chelation of heavy group 2 (radio)metals by p-tert-butylcalix[4]arene-1,3-crown-6 and logK determination via NMR

NASA Astrophysics Data System (ADS)

Bauer, David; Gott, Matthew; Steinbach, Jörg; Mamat, Constantin

2018-06-01

A crown-bridged calix[4]arene scaffold was investigated as lead compound for the ligation of heavy alkaline earth metals such as strontium and barium, which appear to be useful for radiopharmaceutical applications in diagnosis as well as in radiotherapy. In particular barium, due to its chemical similarities, could serve as a surrogate for radium, a metal of high radiopharmaceutical interest. The ability of p-tert-butylcalix[4]arene-1,3-crown-6 (1) in particular to chelate cations, such as group 1 and 2 metal ions or ammonium ions is well known. Also, the manifold possibilities of structural modification on the upper- and lower-rim as well as on the crown itself produce properties that may lead to a highly selective and effective chelating agent. In this work, titration experiments of the perchlorate salts of Ba2+, Sr2+ and Pb2+ with ligand 1 were performed to determine their stability constants (logK = 4.7, 4.3, and 3.3, respectively) by 1H NMR measurements in acetonitrile-d3.

Supercritical Fluid Extraction of Metal Chelate: A Review.

PubMed

Ding, Xin; Liu, Qinli; Hou, Xiongpo; Fang, Tao

2017-03-04

Supercritical fluid extraction (SFE), as a new green extraction technology, has been used in extracting various metal species. The solubilities of chelating agents and corresponding metal chelates are the key factors which influence the efficiency of SFE. Other main properties of them such as stability and selectivity are also reviewed. The extraction mechanisms of mainly used chelating agents are explained by typical examples in this paper. This is the important aspect of SFE of metal ions. Moreover, the extraction efficiencies of metal species also depend on other factors such as temperature, pressure, extraction time and matrix effect. The two main complexation methods namely in-situ and on-line chelating SFE are described in detail. As an efficient chelating agent, tributyl phosphate-nitric acid (TBP-HNO 3 ) complex attracts much attention. The SFE of metal ions, lanthanides and actinides as well as organometallic compounds are also summarized. With the proper selection of ligands, high efficient extraction of metal species can be obtained. As an efficient sample analysis method, supercritical fluid chromatography (SFC) is introduced in this paper. Recently, the extraction method combining ionic liquids (ILs) with supercritical fluid has been becoming a novel technology for treating metal ions. The kinetics related to SFE of metal species is discussed with some specific examples.

Determination of trace labile copper in environmental waters by magnetic nanoparticle solid phase extraction and high-performance chelation ion chromatography.

PubMed

Wei, Z; Sandron, S; Townsend, A T; Nesterenko, P N; Paull, B

2015-04-01

Cobalt magnetic nanoparticles surface functionalised with iminodiacetic acid were evaluated as a nano-particulate solid phase extraction absorbent for copper ions (Cu(2+)) from environmental water samples. Using an external magnetic field, the collector nanoparticles could be separated from the aqueous phase, and adsorbed ions simply decomplexed using dilute HNO3. Effects of pH, buffer concentration, sample and sorbent volume, extraction equilibrium time, and interfering ion concentration on extraction efficiency were investigated. Optimal conditions were then applied to the extraction of Cu(2+) ions from natural water samples, prior to their quantitation using high-performance chelation ion chromatography. The limits of detection (LOD) of the combined extraction and chromatographic method were ~0.1 ng ml(-1), based upon a 100-fold preconcentration factor (chromatographic performance; LOD=9.2 ng ml(-1) Cu(2+)), analytical linear range from 20 to 5000 ng mL(-1), and relative standard deviations=4.9% (c=1000 ng ml(-1), n=7). Accuracy and precision of the combined approach was verified using a certified reference standard estuarine water sample (SLEW-2) and comparison of sample determinations with sector field inductively coupled plasma mass spectrometry. Recoveries from the addition of Cu(2+) to impacted estuarine and rain water samples were 103.5% and 108.5%, respectively. Coastal seawater samples, both with and without prior UV irradiation and dissolved organic matter removal were also investigated using the new methodology. The effect of DOM concentration on copper availability was demonstrated. Copyright © 2015. Published by Elsevier B.V.

Ion-pairing HPLC methods to determine EDTA and DTPA in small molecule and biological pharmaceutical formulations.

PubMed

Wang, George; Tomasella, Frank P

2016-06-01

Ion-pairing high-performance liquid chromatography-ultraviolet (HPLC-UV) methods were developed to determine two commonly used chelating agents, ethylenediaminetetraacetic acid (EDTA) in Abilify® (a small molecule drug with aripiprazole as the active pharmaceutical ingredient) oral solution and diethylenetriaminepentaacetic acid (DTPA) in Yervoy® (a monoclonal antibody drug with ipilimumab as the active pharmaceutical ingredient) intravenous formulation. Since the analytes, EDTA and DTPA, do not contain chromophores, transition metal ions (Cu 2+ , Fe 3+ ) which generate highly stable metallocomplexes with the chelating agents were added into the sample preparation to enhance UV detection. The use of metallocomplexes with ion-pairing chromatography provides the ability to achieve the desired sensitivity and selectivity in the development of the method. Specifically, the sample preparation involving metallocomplex formation allowed sensitive UV detection. Copper was utilized for the determination of EDTA and iron was utilized for the determination of DTPA. In the case of EDTA, a gradient mobile phase separated the components of the formulation from the analyte. In the method for DTPA, the active drug substance, ipilimumab, was eluted in the void. In addition, the optimization of the concentration of the ion-pairing reagent was discussed as a means of enhancing the retention of the aminopolycarboxylic acids (APCAs) including EDTA and DTPA and the specificity of the method. The analytical method development was designed based on the chromatographic properties of the analytes, the nature of the sample matrix and the intended purpose of the method. Validation data were presented for the two methods. Finally, both methods were successfully utilized in determining the fate of the chelates.

Thermodynamic stability and relaxation studies of small, triaza-macrocyclic Mn(II) chelates.

PubMed

de Sá, Arsénio; Bonnet, Célia S; Geraldes, Carlos F G C; Tóth, Éva; Ferreira, Paula M T; André, João P

2013-04-07

Due to its favorable relaxometric properties, Mn(2+) is an appealing metal ion for magnetic resonance imaging (MRI) contrast agents. This paper reports the synthesis and characterization of three new triazadicarboxylate-type ligands and their Mn(2+) chelates (NODAHep, 1,4,7-triazacyclononane-1,4-diacetate-7-heptanil; NODABA, 1,4,7-triazacyclononane-1,4-diacetate-7-benzoic acid; and NODAHA, 1,4,7-triazacyclononane-1,4-diacetate-7-hexanoic acid). The protonation constants of the ligands and the stability constants of the chelates formed with Mn(2+) and the endogenous Zn(2+) ion have been determined by potentiometry. In overall, the thermodynamic stability of the chelates is lower than that of the corresponding NOTA analogues (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetate), consistent with the decreased number of coordinating carboxylate groups. Variable temperature (1)H NMRD and (17)O NMR measurements have been performed on the paramagnetic chelates to provide information on the water exchange rates and the rotational dynamics. The values of the (17)O chemical shifts are consistent with the presence of one water molecule in the first coordination sphere of Mn(2+). The three complexes are in the slow to intermediate regime for the water exchange rate, and they all display relatively high rotational correlation times, which explain the relaxivity values between 4.7 and 5.8 mM(-1) s(-1) (20 MHz and 298 K). These relaxivities are higher than expected for Mn(2+) chelates of such size and comparable to those of small monohydrated Gd(3+) complexes. The amphiphilic [Mn(NODAHep)] forms micelles above 22 mM (its critical micellar concentration was determined by relaxometry and fluorescence), and interacts with HSA via its alkylic carbon chain providing a 60% relaxivity increase at 20 MHz due to a longer tumbling time.

Comparing potential copper chelation mechanisms in Parkinson's disease protein

NASA Astrophysics Data System (ADS)

Rose, Frisco; Hodak, Miroslav; Bernholc, Jerry

2011-03-01

We have implemented the nudged elastic band (NEB) as a guided dynamics framework for our real-space multigrid method of DFT-based quantum simulations. This highly parallel approach resolves a minimum energy pathway (MEP) on the energy hypersurface by relaxing intermediates in a chain-of-states. As an initial application we present an investigation of chelating agents acting on copper ion bound to α -synuclein, whose misfolding is implicated in Parkinson's disease (PD). Copper ions are known to act as highly effective misfolding agents in a-synuclein and are thus an important target in understanding PD. Furthermore, chelation therapy has shown promise in the treatment of Alzheimer's and other neuro-degenerative diseases with similar metal-correlated pathologies. At present, our candidate chelating agents include nicotine, curcumin and clioquinol. We examine their MEP activation barriers in the context of a PD onset mechanism to assess the viability of various chelators for PD remediation.

Metal chelate process to remove pollutants from fluids

DOEpatents

Chang, Shih-Ger T.

1994-01-01

The present invention relates to improved methods using an organic iron chelate to remove pollutants from fluids, such as flue gas. Specifically, the present invention relates to a process to remove NO.sub.x and optionally SO.sub.2 from a fluid using a metal ion (Fe.sup.2+) chelate wherein the ligand is a dimercapto compound wherein the --SH groups are attached to adjacent carbon atoms (HS--C--C--SH) or (SH--C--CCSH) and contain a polar functional group so that the ligand of DMC chelate is water soluble. Alternatively, the DMC' is covalently attached to a water insoluble substrate such as a polymer or resin, e.g., polystyrene. The chelate is regenerated using electroreduction or a chemical additive. The dimercapto compound bonded to a water insoluble substrate is also useful to lower the concentration or remove hazardous metal ions from an aqueous solution.

Metal chelate process to remove pollutants from fluids

DOEpatents

Chang, S.G.T.

1994-12-06

The present invention relates to improved methods using an organic iron chelate to remove pollutants from fluids, such as flue gas. Specifically, the present invention relates to a process to remove NO[sub x] and optionally SO[sub 2] from a fluid using a metal ion (Fe[sup 2+]) chelate wherein the ligand is a dimercapto compound wherein the --SH groups are attached to adjacent carbon atoms (HS--C--C--SH) or (SH--C--CCSH) and contain a polar functional group so that the ligand of DMC chelate is water soluble. Alternatively, the DMC is covalently attached to a water insoluble substrate such as a polymer or resin, e.g., polystyrene. The chelate is regenerated using electroreduction or a chemical additive. The dimercapto compound bonded to a water insoluble substrate is also useful to lower the concentration or remove hazardous metal ions from an aqueous solution. 26 figures.

Cellular conditions of weakly chelated magnesium ions strongly promote RNA stability and catalysis.

PubMed

Yamagami, Ryota; Bingaman, Jamie L; Frankel, Erica A; Bevilacqua, Philip C

2018-06-01

Most RNA folding studies have been performed under non-physiological conditions of high concentrations (≥10 mM) of Mg 2+ free , while actual cellular concentrations of Mg 2+ free are only ~1 mM in a background of greater than 50 mM Mg 2+ total . To uncover cellular behavior of RNA, we devised cytoplasm mimic systems that include biological concentrations of amino acids, which weakly chelate Mg 2+ . Amino acid-chelated Mg 2+ (aaCM) of ~15 mM dramatically increases RNA folding and prevents RNA degradation. Furthermore, aaCM enhance self-cleavage of several different ribozymes, up to 100,000-fold at Mg 2+ free of just 0.5 mM, indirectly through RNA compaction. Other metabolites that weakly chelate magnesium offer similar beneficial effects, which implies chelated magnesium may enhance RNA function in the cell in the same way. Overall, these results indicate that the states of Mg 2+ should not be limited to free and bound only, as weakly bound Mg 2+ strongly promotes RNA function under cellular conditions.

Removal of heavy metal ions from wastewaters using dendrimer-functionalized multi-walled carbon nanotubes.

PubMed

Iannazzo, Daniela; Pistone, Alessandro; Ziccarelli, Ida; Espro, Claudia; Galvagno, Signorino; Giofré, Salvatore V; Romeo, Roberto; Cicero, Nicola; Bua, Giuseppe D; Lanza, Giuseppe; Legnani, Laura; Chiacchio, Maria A

2017-06-01

Dendrimer-functionalized multi-walled carbon nanotubes (MWCNT) for heavy metal ion removal from wastewaters were developed. Triazole dendrimers (TD) were built directly onto the carbon nanotube surface by successive click chemistry reactions affording the zero- and first-generation dendrimer-functionalized MWCNT (MWCNT-TD1 and MWCNT-TD2). The Moedritzer-Irani reaction carried out on the amino groups present on the MWCNT-TD2 sample gave the corresponding α-aminophosphonate nanosystem MWCNT-TD2P. Both MWCNT-TD2 and MWCNT-TD2P nanosystems have been characterized by physical, chemical, and morphological analyses. Their chelating abilities towards the toxic metal ions Pb 2+ , Hg 2+ , and Ni 2+ and the harmless Ca 2+ ion have been experimentally evaluated in the two different sets of experiments and at the salt concentrations of 1 mg/mL or 1 μg/mL by inductively coupled plasma mass spectrometry (ICP-MS). The results of these studies pointed out the interesting chelating behavior for the phosphonated nanosystem towards the Hg 2+ ion. The complexation mode of the best chelating system MWCNT-TD2P with mercury was investigated through density functional theory (DFT) calculations, suggesting a chelation mechanism involving the two oxygen atoms of the phosphate group. The synthesized dendrimers, supported on the multi-walled carbon nanotubes, have shown the potential to be used for the selective toxic metal ion removal and recovery.

Novel Cu(I)-selective chelators based on a bis(phosphorothioyl)amide scaffold.

PubMed

Amir, Aviran; Ezra, Alon; Shimon, Linda J W; Fischer, Bilha

2014-08-04

Bis(dialkyl/aryl-phosphorothioyl)amide (BPA) derivatives are versatile ligands known by their high metal-ion affinity and selectivity. Here, we synthesized related chelators based on bis(1,3,2-dithia/dioxaphospholane-2-sulfide)amide (BTPA/BOPA) scaffolds targeting the chelation of soft metal ions. Crystal structures of BTPA compounds 6 (N(-)R3NH(+)) and 8 (NEt) revealed a gauche geometry, while BOPA compound 7 (N(-)R3NH(+)) exhibited an anti-geometry. Solid-state (31)P magic-angle spinning NMR spectra of BTPA 6-Hg(II) and 6-Zn(II) complexes imply a square planar or tetrahedral geometry of the former and a distorted tetrahedral geometry of the latter, while both BTPA 6-Ni(II) and BOPA 7-Ni(II) complexes possibly form a polymeric structure. In Cu(I)-H2O2 system (Fenton reaction conditions) BTPA compounds 6, 8, and 10 (NCH2Ph) were identified as most potent antioxidants (IC50 32, 56, and 29 μM, respectively), whereas BOPA analogues 7, 9 (NEt), and 11 (NCH2Ph) were found to be poor antioxidants. In Fe(II)-H2O2 system, IC50 values for both BTPA and BOPA compounds exceeded 500 μM indicating high selectivity to Cu(I) versus the borderline Fe(II)-ion. Neither BTPA nor BOPA derivatives showed radical scavenging properties in H2O2 photolysis, implying that inhibition of the Cu(I)-induced Fenton reaction by both BTPA and BOPA analogues occurred predominantly through Cu(I)-chelation. In addition, NMR-monitored Cu(I)- and Zn(II)-titration of BTPA compounds 8 and 10 showed their high selectivity to a soft metal ion, Cu(I), as compared to a borderline metal ion, Zn(II). In summary, lipophilic BTPA analogues are promising highly selective Cu(I) ion chelators.

DFT study of the interaction between DOTA chelator and competitive alkali metal ions.

PubMed

Frimpong, E; Skelton, A A; Honarparvar, B

2017-09-01

1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetracetic acid (DOTA) is an important chelator for radiolabeling of pharmaceuticals. The ability of alkali metals found in the body to complex with DOTA and compete with radio metal ions can alter the radiolabeling process. Non-covalent interactions between DOTA complexed with alkali metals Li + , Na + , K + and Rb + , are investigated with density functional theory using B3LYP and ωB97XD functionals. Conformational possibilities of DOTA were explored with a varying number of carboxylic pendant arms of DOTA in close proximity to the ions. It is found that the case in which four arms of DOTA are interacting with ions is more stable than other conformations. The objective of this study is to explore the electronic structure properties upon complexation of alkali metals Li + Na + , K + and Rb + with a DOTA chelator. Interaction energies, relaxation energies, entropies, Gibbs free energies and enthalpies show that the stability of DOTA, complexed with alkali metals decreases down the group of the periodic table. Implicit water solvation affects the complexation of DOTA-ions leading to decreases in the stability of the complexes. NBO analysis through the natural population charges and the second order perturbation theory, revealed a charge transfer between DOTA and alkali metals. Conceptual DFT-based properties such as HOMO/LUMO energies, ΔE HOMO-LUMO and chemical hardness and softness indicated a decrease in the chemical stability of DOTA-alkali metal complexes down the alkali metal series. This study serves as a guide to researchers in the field of organometallic chelators, particularly, radiopharmaceuticals in finding the efficient optimal match between chelators and various metal ions. Copyright © 2017 Elsevier Inc. All rights reserved.

Methylenediphosphonotetrathioate: synthesis, characterization, and chemical properties.

PubMed

Amir, Aviran; Sayer, Alon Haim; Ezra, Alon; Fischer, Bilha

2013-03-18

Metal chelators are potential therapeutic agents for treating diseases such as Wilson's and Alzheimer's where the pathology involves an excess of metal-ions (Cu(II) and Zn(II)/Cu(II)/Fe(II/III), respectively). In addition to the high affinity of the metal-ion to the chelators, metal selectivity of the chelators is essential to achieve the therapeutic goal, that is, the successful removal of excess of harmful metal-ions in a physiological extracellular medium rich in alkali and alkali earth metal-ions. For this purpose, we synthesized a novel chelator, methylenediphosphonotetrathioate (MDPT) which is the tetrathio analogue of methylenediphosphonic acid (MDP). MDPT was synthesized from bis-methylene(phosphonicdichloride) in a 3-step synthesis and a 31% overall yield. MDPT formed a stable complex with Zn(II) (log K = 10.84), which is 10(7) times more stable than the corresponding Ca(II) complex. Moreover, the MDPT-Zn(II) complex was 50-fold more stable than the MDP-Zn(II) complex. In addition, MDPT was found to inhibit the Cu(I)-catalyzed Fenton reaction (IC50 26 μM) 2.5 times more potently than a Fe(II)-catalyzed Fenton reaction, and 2.5 times more potently than EDTA (IC50 64 μM) in the Cu(I)/H2O2 system, as monitored by electron spin resonance (ESR). Furthermore, MDPT was found to be relatively stable in both acidic (pD 1.9, t(½) = 71.5 h) and basic media (pD 12.4, t(½) = 81 h) as monitored by (31)P/(1)H NMR. However, MDPT was not stable in air because of intramolecular oxidation and disulfide formation (33% oxidation after 27 h). In conclusion, MDPT was found to be a water-soluble chelator showing a clear preference to soft/borderline metal-ions and a remarkable selectivity to those metal-ions vs Ca(II) ions. The relative sensitivity of MDPT to oxidation may limit its use; however, the application of MDPT in acidic or basic media will increase its lifetime.

Metal ion promoted hydrogels for bovine serum albumin adsorption: Cu(II) and Co(II) chelated poly[(N-vinylimidazole)-maleic acid].

PubMed

Pekel, Nursel; Salih, Bekir; Güven, Olgun

2005-05-10

Poly[(N-vinylimidazole)-maleic acid] (poly(VIm-MA)), copolymeric hydrogels were prepared by gamma-irradiating ternary mixtures of N-vinylimidazole-maleic acid-water in a (60)Co-gamma source. Cu(II) and Co(II) ions were chelated within the gels at pH=5.0. The maximum adsorption capacity of the gels were 3.71 mmol/g dry gel for Cu(II) and 1.25 mmol/g dry gel for Co(II) at pH=5.0. The swelling ratios of the gels were 1200% for poly(VIm-MA), 60 and 45% for Cu(II) and Co(II)-chelated poly(VIm-MA) gels at pH=5.0 in acetate buffer solution. These affinity gels with different swelling ratios for plain poly(VIm-MA), Cu(II)-, and Co(II)-chelated poly(VIm-MA), in acetate and phosphate buffers were used in the bovine serum albumin (BSA) adsorption/desorption studies in batch reactor. The maximum BSA adsorption capacities of the gels were 0.38 g/g dry gel for plain, 0.88 g/g dry gel for Cu(II)-chelated poly(VIm-MA) and 1.05 g/g dry gel for Co(II)-chelated poly(VIm-MA) gels. Adsorption capacity of BSA by the gels was reduced dramatically by increasing the ionic strength adjusted with NaCl. More than 95% of BSA were desorbed in 10 h in desorption medium containing 0.1M of EDTA for metal ion-chelated gels at pH=4.7.

The preparation and antioxidant activity of glucosamine sulfate

NASA Astrophysics Data System (ADS)

Xing, Ronge; Liu, Song; Wang, Lin; Cai, Shengbao; Yu, Huahua; Feng, Jinhua; Li, Pengcheng

2009-05-01

Glucosamine sulfate was prepared from glucosamine hydrochloride that was produced by acidic hydrolysis of chitin by ion-exchange method. Optical rotation and elemental analysis characterized the degree of its purity. In addition, the antioxidant potency of chitosan derivative-glucosamine sulfate was investigated in various established in vitro systems, such as superoxide (O{2/-})/hydroxyl (·OH) radicals scavenging, reducing power, iron ion chelating. The following results are obtained: first, glucosamine sulfate had pronounced scavenging effect on superoxide radical. For example the O{2/-} scavenging activity of glucosamine sulfate was 92.11% at 0.8 mg/mL. Second, the ·OH scavenging activity of glucosamine sulfate was also strong, and was about 50% at 3.2 mg/mL. Third, the reducing power of glucosamine sulfate was more pronounced. The reducing power of glucosamine sulfate was 0.643 at 0.75 mg/mL. However, its potency for ferrous ion chelating was weak. Furthermore, except for ferrous ion chelating potency, the scavenging rate of radical and reducing power of glucosamine sulfate were concentration-dependent and increased with their increasing concentrations, but its ferrous ion chelating potency decreased with the increasing concentration. The multiple antioxidant activities of glucosamine sulfate were evidents of reducing power and superoxide/hydroxyl radicals scavenging ability. These in vitro results suggest the possibility that glucosamine sulfate could be used effectively as an ingredient in health or functional food, to alleviate oxidative stress.

Simultaneous determination of copper, cobalt, and mercury ions in water samples by solid-phase extraction using carbon nanotube sponges as adsorbent after chelating with sodium diethyldithiocarbamate prior to high performance liquid chromatography.

PubMed

Wang, Lei; Zhou, Jia-Bin; Wang, Xia; Wang, Zhen-Hua; Zhao, Ru-Song

2016-06-01

Recently, a sponge-like material called carbon nanotube sponges (CNT sponges) has drawn considerable attention because it can remove large-area oil, nanoparticles, and organic dyes from water. In this paper, the feasibility of CNT sponges as a novel solid-phase extraction (SPE) adsorbent for the enrichment and determination of heavy metal ions (Co(2+), Cu(2+), and Hg(2+)) was investigated for the first time. Sodium diethyldithiocarbamate (DDTC) was used as the chelating agent and high performance liquid chromatography (HPLC) for the final analysis. Important factors which may influence extraction efficiency of SPE were optimized, such as the kind and volume of eluent, volume of DDTC, sample pH, flow rate, etc. Under the optimized conditions, wide range of linearity (0.5-400 μg L(-1)), low limits of detection (0.089~0.690 μg L(-1); 0.018~0.138 μg), and good repeatability (1.27~3.60 %, n = 5) were obtained. The developed method was applied for the analysis of the three metal ions in real water samples, and satisfactory results were achieved. All of these findings demonstrated that CNT sponges will be a good choice for the enrichment and determination of target ions at trace levels in the future.

New approach for the quantification of metallic species in healthcare products based on optical switching of a Schiff base possessing ONO donor set.

PubMed

Singh, Jaswant; Parkash, Jyoti; Kaur, Varinder; Singh, Raghubir

2017-10-05

A new method is reported for the quantification of some metallic components of healthcare products utilizing a Schiff base chelator derived from 2-hydroxyacetophenone and ethanolamine. The Schiff base chelator recognizes some metallic species such as iron, copper and zinc (important components of some healthcare products), and cadmium (common contaminant in healthcare products) giving colorimetric/fluorimetric response. It coordinates with Fe 2+ /Fe 3+ and Cu 2+ ions via ONO donor set and switches the colour to bright red, green and orange, respectively. Similarly, it switches 'ON' a fluorometric response when coordinates with Zn 2+ and Cd 2+ ions. In the present approach, detailed studies on the colorimetric and fluorimetric response of ONO Schiff base is investigated in detail. The Job plot for the complexation of ONO switch with various metal ions suggested formation of 1:1 (metal-chelator) complex with Fe 2+ , Fe 3+ , and Cu 2+ while 1:2 (metal-chelator) for Zn 2+ and Cd 2+ ions. The limit of detection, limit of quantification are 6.73, 18.0, 25.0, 0.65, 1.10μM and 27.0, 72.0, 100.0, 2.60 and 4.40μM for Fe 2+ , Fe 3+ , Cu 2+ , Zn 2+ and Cd 2+ ions, respectively. Under the optimized conditions, chelator was used for the quantification of important metals present in healthcare products via direct dissolution and furnace treatment during sample preparation. The results were found precise and accurate for both sample preparation techniques using the developed method. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis and thermal characterization of new ternary chelates of piroxicam and tenoxicam with glycine and DL-phenylalanine and some transition metals.

PubMed

Zayed, M A; El-Dien, F A Nour; Mohamed, Gehad G; El-Gamel, Nadia E A

2006-05-01

The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various amino acids such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates. Different thermodynamic parameters are calculated using Coats-Redfern method and the results are interpreted.

Synthesis and thermal characterization of new ternary chelates of piroxicam and tenoxicam with glycine and DL-phenylalanine and some transition metals

NASA Astrophysics Data System (ADS)

Zayed, M. A.; El-Dien, F. A. Nour; Mohamed, Gehad G.; El-Gamel, Nadia E. A.

2006-05-01

The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various amino acids such as glycine (Gly) or DL-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine- N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates. Different thermodynamic parameters are calculated using Coats-Redfern method and the results are interpreted.

In Situ Chelating Synthesis of Hierarchical LiNi1/3 Co1/3 Mn1/3 O2 Polyhedron Assemblies with Ultralong Cycle Life for Li-Ion Batteries.

PubMed

Zhang, Yue; Jia, Dianzeng; Tang, Yakun; Huang, Yudai; Pang, Weikong; Guo, Zaiping; Zhou, Zhen

2018-06-03

Layered lithium transition-metal oxides, with large capacity and high discharge platform, are promising cathode materials for Li-ion batteries. However, their high-rate cycling stability still remains a large challenge. Herein, hierarchical LiNi 1/3 Co 1/3 Mn 1/3 O 2 polyhedron assemblies are obtained through in situ chelation of transition metal ions (Ni 2+ , Co 2+ , and Mn 2+ ) with amide groups uniformly distributed along the backbone of modified polyacrylonitrile chains to achieve intimate mixing at the atomic level. The assemblies exhibit outstanding electrochemical performances: superior rate capability, high volumetric energy density, and especially ultralong high-rate cyclability, due to the superiority of unique hierarchical structures. The polyhedrons with exposed active crystal facets provide more channels for Li + diffusion, and meso/macropores serve as access shortcuts for fast migration of electrolytes, Li + and electrons. The strategy proposed in this work can be extended to fabricate other mixed transition metal-based materials for advanced batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Increased Uptake of Chelated Copper Ions by Lolium perenne Attributed to Amplified Membrane and Endodermal Damage

PubMed Central

Johnson, Anthea; Singhal, Naresh

2015-01-01

The contributions of mechanisms by which chelators influence metal translocation to plant shoot tissues are analyzed using a combination of numerical modelling and physical experiments. The model distinguishes between apoplastic and symplastic pathways of water and solute movement. It also includes the barrier effects of the endodermis and plasma membrane. Simulations are used to assess transport pathways for free and chelated metals, identifying mechanisms involved in chelate-enhanced phytoextraction. Hypothesized transport mechanisms and parameters specific to amendment treatments are estimated, with simulated results compared to experimental data. Parameter values for each amendment treatment are estimated based on literature and experimental values, and used for model calibration and simulation of amendment influences on solute transport pathways and mechanisms. Modeling indicates that chelation alters the pathways for Cu transport. For free ions, Cu transport to leaf tissue can be described using purely apoplastic or transcellular pathways. For strong chelators (ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA)), transport by the purely apoplastic pathway is insufficient to represent measured Cu transport to leaf tissue. Consistent with experimental observations, increased membrane permeability is required for simulating translocation in EDTA and DTPA treatments. Increasing the membrane permeability is key to enhancing phytoextraction efficiency. PMID:26512647

Evaluation of the chelating performance of biopolyelectrolyte green complexes (NIBPEGCs) for wastewater treatment from the metal finishing industry.

PubMed

López-Maldonado, Eduardo A; Zavala García, Oscar Gabriel; Escobedo, Kevin Cruz; Oropeza-Guzman, Mercedes T

2017-08-05

In this paper nonstoichiometric interbiopolyelectrolyte green complexes (NIBPEGCs) were prepared using chitosan (Ch), alginate (AG) and poly(acrylic acid)(PAA). They are proposed as innovative formulations (polyelectrolytes and chelating agents) suitable for the elimination heavy metals contained in wastewater. This application may represent an integral solution for industries rejecting solid and aqueous metallic materials; however, it has not been previously reported. NIBPEGCs physicochemical performance was evaluated based on pH, particle size, surface charge, isoelectric point, dose, coagulation-flocculation kinetics and chemical affinity with seven metal ions. The experimental results showed that NIBPEGCs composed by AG/Ch and PAA/Chitosan have all the three complementary functions: chemical affinity, electrostatic interaction and particle entrapment anticipating more simple operation units to remove heavy metals. Complexes of AG/Ch (negative) were higher performance in removing heavy metals, with a dose window (150-180mg/L), lower dose of 410mg/L PAA/Ch (negative). Investigation of chelating performances of NIBPEGCs show that the efficiency of metal removal is: Ca˃Cr˃Cu˃Pb˃Ni˃Zn˃Cd. Transmittance vs time profiles, metals and zeta potential analysis showed that chelation capacity is the crucial factor to ensure metallic species removal, followed by physical entrapment of the metallic colloids. Integrating all presented results allow to sustain the development of excellent metals removal formulations. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of ionic complexation on release rate profiles from multiple water-in-oil-in-water (W/O/W) emulsions.

PubMed

Bonnet, Marie; Cansell, Maud; Placin, Frédéric; David-Briand, Elisabeth; Anton, Marc; Leal-Calderon, Fernando

2010-07-14

Water-in-oil-in-water (W/O/W) double emulsions were prepared, and the kinetics of release of magnesium ions from the internal to the external water phase was followed. Different chelating agents (phosvitin and gluconate) were used to bind magnesium within the prospect of improving the ion retention in the internal aqueous droplets. Magnesium release was monitored for 1 month of storage, for each formulation, with and without chelation, at two storage temperatures (4 and 25 degrees C). Leakage occurred without film rupturing (coalescence) and was mainly due to entropically driven diffusion/permeation phenomena. The experimental results revealed a clear correlation between the effectiveness of chelating agents to delay the delivery and their binding capacity characterized by the equilibrium affinity constant. The kinetic data (percent released versus time curves) were interpreted within the framework of a kinetic model based on diffusion and taking into account magnesium chelation.

Reactions in glass-ionomer cements: IV. Effect of chelating comonomers on setting behavior.

PubMed

Wilson, A D; Crisp, S; Ferner, A J

1976-01-01

The oscillating rheometer is a valuable instrument for studying the effects of additives on the setting behavior of a cement system. Using this instrument, it was found that certain chelating comonomers, the hydroxycarboxylic acids, could improve the setting characteristics of the glass-ionomer cement system when added to the PAA solution. The acid chelates probably assign the extraction of metal ions from the glass and also tend to hold them in solution, preventing premature ion binding of the polyanion chains. The effect is to increase the rate of hardening without reducing the working time, which may indeed by slightly increased. Tartaric acid, the most effective of the comonomers, can form a chelate bridge between aluminum atoms, and this metal complex probably acts as a flexible bridge structure linking polyanion chains. This mechanism offers some steric advantages over a simple salt bridge.

Investigation of molecular mechanisms of action of chelating drugs on protein-lipid model membranes by X-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novikova, N. N., E-mail: nn_novikova@ns.crys.ras.ru; Zheludeva, S. I.; Koval'chuk, M. V.

Protein-lipid films based on the enzyme alkaline phosphatase were subjected to the action of chelating drugs, which are used for accelerating the removal of heavy metals from the human body, and the elemental composition of the resulting films was investigated. Total-reflection X-ray fluorescence measurements were performed at the Berlin Electron Storage Ring Company for Synchrotron Radiation (BESSY) in Germany. A comparative estimation of the protective effect of four drugs (EDTA, succimer, xydiphone, and mediphon) on membrane-bound enzymes damaged by lead ions was made. The changes in the elemental composition of the protein-lipid films caused by high doses of chelating drugsmore » were investigated. It was shown that state-of-the-art X-ray techniques can, in principle, be used to develop new methods for the in vitro evaluation of the efficiency of drugs, providing differential data on their actions.« less

Combined NO/sub x//SO/sub 2/ removal from flue gas using ferrous chelates of SH-containing amino acids and alkali

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, D.K.; Chang, S.G.

1987-04-01

We report herein the use of ferrous chelates of SH-containing amino acids including cysteine, penicillamine, N-acetylcysteine, and N-acetylpenicillamine in neutral or alkaline solutions for the combined removal of NO and SO/sub 2/ in wet flue gas clean-up systems. These SH-containing amino acids not only can stabilize ferrous ions in alkaline solutions to promote the absorption of NO, but are also capable of rapidly reducing ferric ions formed during the scrubbing process back to ferrous ions. The disulfide form of the above amino acids can be reduced by SO/sub 2/ and H/sub 2/S to regenerate the starting monomeric species. The chemistrymore » relevant to the absorption of NO by the above ferrous chelates and the ligand regeneration process will be discussed.« less

Combined NO/sub x//SO/sub 2/ removal from flue gas using ferrous chelates of SH-containing amino acids and alkali

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, D.K.; Chang, S.G.

1987-01-01

We report herein the use of ferrous chelates of SH-containing amino acids including cysteine, penicillamine, N-acetylcysteine, and N-acetylpenicillamine in neutral or alkaline solutions for the combined removal of NO and SO/sub 2/ in wet flue gas clean-up systems. These SH-containing amino acids not only can stabilize ferrous ions in alkaline solutions to promote the absorption of NO, but are also capable of rapidly reducing ferric ions formed during the scrubbing process back to ferrous ions. The disulfide from of the above amino acids can be reduced by SO/sub 2/ and H/sub 2/S to regenerate the starting monomeric species. The chemistrymore » relevant to the absorption of NO by the above ferrous chelates and the ligand regeneration process will be discussed.« less

Langmuir-Blodgett deposition selects carboxylate headgroup coordination

NASA Astrophysics Data System (ADS)

Mukherjee, Smita; Datta, Alokmay

2011-10-01

Infrared reflection-absorption spectroscopy results on stearic acid Langmuir monolayers containing Mn, Co, and Cd ions show that on the water surface, the ions induce unidentate and bidentate (both chelate and bridged) coordination in the carboxylate headgroup with some trace of undissociated acid. Moreover, with Cd and Mn ions in subphase, the preferred coordination is found to be unidentate, whereas for Co, bidentate chelate is most preferred. After transfer onto amorphous substrate, not all coordinations are found to exist in the same ratio for the deposited metal stearate monolayers. More specifically, after transfer, Mn is found to coordinate with the carboxylate group as bidentate chelate, Cd as unidentate and bidentate bridged (with unidentate as the preferred coordination), and Co as preferably bidentate bridged (although all coordinations are present). Results suggest a specific interaction in each case, as the metal-carboxylate pair at the water surface is transferred to the substrate surface during Langmuir-Blodgett deposition.

Antimicrobial Polymer

DOEpatents

McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

2004-09-28

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

Regulation of copper and iron homeostasis by metal chelators: a possible chemotherapy for Alzheimer's disease.

PubMed

Robert, Anne; Liu, Yan; Nguyen, Michel; Meunier, Bernard

2015-05-19

With the increase of life expectancy of humans in more than two-thirds of the countries in the World, aging diseases are becoming the frontline health problems. Alzheimer's disease (AD) is now one of the major challenges in drug discovery, since, with the exception of memantine in 2003, all clinical trials with drug candidates failed over the past decade. If we consider that the loss of neurons is due to a high level of oxidative stress produced by nonregulated redox active metal ions like copper linked to amyloids of different sizes, regulation of metal homeostasis is a key target. The difficulty for large copper-carrier proteins to directly extract copper ions from metalated amyloids might be considered as being at the origin of the rupture of the copper homeostasis regulation in AD brains. So, there is an urgent need for new specific metal chelators that should be able to regulate the homeostasis of metal ions, specially copper and iron, in AD brains. As a consequence of that concept, chelators promoting metal excretion from brain are not desired. One should favor ligands able to extract copper ions from sinks (amyloids being the major one) and to transfer these redox-active metal ions to copper-carrier proteins or copper-containing enzymes. Obviously, the affinity of these chelators for the metal ion should not be a sufficient criterion, but the metal specificity and the ability of the chelators to release the metal under specific biological conditions should be considered. Such an approach is still largely unexplored. The requirements for the chelators are very high (ability to cross the brain-blood barrier, lack of toxicity, etc.), few chemical series were proposed, and, among them, biochemical or biological data are scarce. As a matter of fact, the bioinorganic pharmacology of AD represents less than 1% of all articles dedicated to AD drug research. The major part of these articles deals with an old and rather toxic drug, clioquinol and related analogs, that do not efficiently extract copper from soluble amyloids. We have designed and developed new tetradendate ligands such as 21 and PA1637 based on bis(8-aminoquinolines) that are specific for copper chelation and are able to extract copper(II) from amyloids and then can release copper ion upon reduction with a biological reducing agent. These studies contribute to the understanding of the physicochemical properties of the tetradentate copper ligands compared with bidentate ligands like clioquinol. One of these copper ligands, PA1637, after selection with a nontransgenic mouse model that is able to efficiently monitor the loss of episodic memory, is currently under preclinical development.

Triplin, a small molecule, reveals copper ion transport in ethylene signaling from ATX1 to RAN1.

PubMed

Li, Wenbo; Lacey, Randy F; Ye, Yajin; Lu, Juan; Yeh, Kuo-Chen; Xiao, Youli; Li, Laigeng; Wen, Chi-Kuang; Binder, Brad M; Zhao, Yang

2017-04-01

Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human.

Surface Engineering of PAMAM-SDB Chelating Resin with Diglycolamic Acid (DGA) Functional Group for Efficient Sorption of U(VI) and Th(IV) from Aqueous Medium.

PubMed

Ilaiyaraja, P; Deb, A K Singha; Ponraju, D; Ali, Sk Musharaf; Venkatraman, B

2017-04-15

A novel chelating resin obtained via growth of PAMAM dendron on surface of styrene divinyl benzene resin beads, followed by diglycolamic acid functionalization of the dendrimer terminal. Batch experiments were conducted to study the effects of pH, nitric acid concentration, amount of adsorbent, shaking time, initial metal ion concentration and temperature on U(VI) and Th(IV) adsorption efficiency. Diglycolamic acid terminated PAMAM dendrimer functionalized styrene divinylbenzene chelating resin (DGA-PAMAM-SDB) is found to be an efficient candidate for the removal of U(VI) and Th(IV) ions from aqueous (pH >4) and nitric acid media (>3M). The sorption equilibrium could be reached within 60min, and the experimental data fits with pseudo-second-order model. Langmuir sorption isotherm model correlates well with sorption equilibrium data. The maximum U(VI) and Th(IV) sorption capacity onto DGA-PAMAMG 5 -SDB was estimated to be about 682 and 544.2mgg -1 respectively at 25°C. The interaction of actinides and chelating resin is reversible and hence, the resin can be regenerated and reused. DFT calculation on the interaction of U(VI) and Th(IV) ions with chelating resin validates the experimental findings. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, investigation and spectroscopic characterization of piroxicam ternary complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with glycine and DL-phenylalanine.

PubMed

Mohamed, Gehad G; El-Gamel, Nadia E A

2004-11-01

The ternary piroxicam (Pir; 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide) complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with various amino acids (AA) such as glycine (Gly) or DL-phenylalanine (PhA) were prepared and characterized by elemental analyses, molar conductance, IR, UV-Vis, magnetic moment, diffuse reflectance and X-ray powder diffraction. The UV-Vis spectra of Pir and the effect of metal chelation on the different interligand transitions are discussed in detailed manner. IR and UV-Vis spectra confirm that Pir behaves as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its carboxylic group, in addition PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its carboxylic and amino groups. All the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. The molar conductance data reveal that most of these chelates are non electrolytes, while Fe(III)-Pir-Gly, Co(II)-, Ni(II)-, Cu(II)- and Zn(II)-Pir-PhA chelates were 1:1 electrolytes. X-ray powder diffraction is used as a new tool to estimate the crystallinity of chelates as well as to elucidate their geometrical structures.

Preparation and Evaluation of the Chelating Nanocomposite Fabricated with Marine Algae Schizochytrium sp. Protein Hydrolysate and Calcium.

PubMed

Lin, Jiaping; Cai, Xixi; Tang, Mengru; Wang, Shaoyun

2015-11-11

Marine algae have been becoming a popular research topic because of their biological implication. The algae peptide-based metal-chelating complex was investigated in this study. Schizochytrium sp. protein hydrolysate (SPH) possessing high Ca-binding capacity was prepared through stepwise enzymatic hydrolysis to a degree of hydrolysis of 22.46%. The nanocomposites of SPH chelated with calcium ions were fabricated in aqueous solution at pH 6 and 30 °C for 20 min, with the ratio of SPH to calcium 3:1 (w/w). The size distribution showed that the nanocomposite had compact structure with a radius of 68.16 ± 0.50 nm. SPH was rich in acidic amino acids, accounting for 33.55%, which are liable to bind with calcium ions. The molecular mass distribution demonstrated that the molecular mass of SPH was principally concentrated at 180-2000 Da. UV scanning spectroscopy and Fourier transform infrared spectroscopy suggested that the primary sites of calcium-binding corresponded to the carboxyl groups, carbonyl groups, and amino groups of SPH. The results of fluorescent spectroscopy, size distribution, atomic force microscope, and (1)H nuclear magnetic resonance spectroscopy suggested that calcium ions chelated with SPH would cause intramolecular and intermolecular folding and aggregating. The SPH-calcium chelate exerted remarkable stability and absorbability under either acidic or basic conditions, which was in favor of calcium absorption in the gastrointestinal tracts of humans. The investigation suggests that SPH-calcium chelate has the potential prospect to be utilized as a nutraceutical supplement to improve bone health in the human body.

Preparation, spectral, X-ray powder diffraction and computational studies and genotoxic properties of new azo-azomethine metal chelates

NASA Astrophysics Data System (ADS)

Bitmez, Şirin; Sayin, Koray; Avar, Bariş; Köse, Muhammet; Kayraldız, Ahmet; Kurtoğlu, Mükerrem

2014-11-01

A new tridentate azo-azomethine ligand, N‧-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, (sbH·H2O) (1), is prepared by condensation of benzohydrazide and 2-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde (a) with treatment of a solution of diazonium salt of p-nitroaniline and 2-hydroxybenzaldehyde in EtOH. The five coordination compounds, [Co(sb)2]·4H2O (2), [Ni(sb)2]·H2O (3), [Cu(sb)2]·4H2O (4), [Zn(sb)2]·H2O (5) and [Cd(sb)2]·H2O (6) are prepared by reacting the Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions with the ligand. The structures of the compounds are elucidated from the elemental analyses data and spectroscopic studies. It is found the ligand acts as a tridentate bending through phenolic and carbonyl oxygens and nitrogen atom of the Cdbnd Nsbnd group similar to the most of salicylaldimines. Comparison of the infrared spectra of the ligand and its metal complexes confirm that azo-Schiff base behaves as a monobasic tridentate ligand towards the central metal ion with an ONO donor sequence. Upon complexation with the ligand, the Cd(II), and Zn(II) ions form monoclinic structures, while Co(II), Cu(II) and Ni(II) ions form orthorhombic structures. Quantum chemical calculations are performed on tautomers and its metal chelates by using DFT/B3LYP method. Most stable tautomer is determined as tautomer (1a). The geometrical parameters of its metal chelates are obtained as theoretically. The NLO properties of tautomer (1a) and its metal complexes are investigated. Finally, the ligand and its metal complexes are assessed for their genotoxicity.

Metal regeneration of iron chelates in nitric oxide scrubbing

DOEpatents

Chang, Shih-Ger; Littlejohn, David; Shi, Yao

1997-08-19

The present invention relates to a process of using metal particles to reduce NO to NH.sub.3. More specifically, the invention concerns an improved process to regenerate iron (II) (CHELATE) by reduction of iron (II) (CHELATE) (NO) complex, which process comprises: a) contacting an aqueous solution containing iron (II) (CHELATE) (NO) with metal particles at between about 20.degree. and 90.degree. C. to reduce NO present, produce ammonia or an ammonium ion, and produce free iron (II) (CHELATE) at a pH of between about 3 and 8. The process is useful to remove NO from flue gas and reduce pollution.

Metal regeneration of iron chelates in nitric oxide scrubbing

DOEpatents

Chang, S.G.; Littlejohn, D.; Shi, Y.

1997-08-19

The present invention relates to a process of using metal particles to reduce NO to NH{sub 3}. More specifically, the invention concerns an improved process to regenerate iron (II) (CHELATE) by reduction of iron (II) (CHELATE) (NO) complex, which process comprises: (a) contacting an aqueous solution containing iron (II) (CHELATE) (NO) with metal particles at between about 20 and 90 C to reduce NO present, produce ammonia or an ammonium ion, and produce free iron (II) (CHELATE) at a pH of between about 3 and 8. The process is useful to remove NO from flue gas and reduce pollution. 34 figs.

Structural dependence of flavonoid interactions with Cu2+ ions: implications for their antioxidant properties.

PubMed Central

Brown, J E; Khodr, H; Hider, R C; Rice-Evans, C A

1998-01-01

The flavonoids constitute a large group of polyphenolic phytochemicals with antioxidant properties in vitro. The interactions of four structurally related flavonoids (quercetin, kaempferol, rutin and luteolin) with Cu2+ ions were investigated in terms of the extent to which they undergo complex formation through chelation or modification through oxidation, as well as in their structural dependence. The ortho 3',4'-dihydroxy substitution in the B ring is shown to be important for Cu2+-chelate formation, thereby influencing the antioxidant activity. The presence of a 3-hydroxy group in the flavonoid structure enhances the oxidation of quercetin and kaempferol, whereas luteolin and rutin, each lacking the 3-hydroxy group, do not oxidize as readily in the presence of Cu2+ ions. The results also demonstrate that the reactivities of the flavonoids in protecting low-density lipoprotein (LDL) against Cu2+ ion-induced oxidation are dependent on their structural properties in terms of the response of the particular flavonoid to Cu2+ ions, whether chelation or oxidation, their partitioning abilities between the aqueous compartment and the lipophilic environment within the LDL particle, and their hydrogen-donating antioxidant properties. PMID:9494082

Computational Assessment of Potassium and Magnesium Ion Binding to a Buried Pocket in GTPase-Associating Center RNA

PubMed Central

2016-01-01

An experimentally well-studied model of RNA tertiary structures is a 58mer rRNA fragment, known as GTPase-associating center (GAC) RNA, in which a highly negative pocket walled by phosphate oxygen atoms is stabilized by a chelated cation. Although such deep pockets with more than one direct phosphate to ion chelation site normally include magnesium, as shown in one GAC crystal structure, another GAC crystal structure and solution experiments suggest potassium at this site. Both crystal structures also depict two magnesium ions directly bound to the phosphate groups comprising this controversial pocket. Here, we used classical molecular dynamics simulations as well as umbrella sampling to investigate the possibility of binding of potassium versus magnesium inside the pocket and to better characterize the chelation of one of the binding magnesium ions outside the pocket. The results support the preference of the pocket to accommodate potassium rather than magnesium and suggest that one of the closely binding magnesium ions can only bind at high magnesium concentrations, such as might be present during crystallization. This work illustrates the complementary utility of molecular modeling approaches with atomic-level detail in resolving discrepancies between conflicting experimental results. PMID:27983843

Computational Assessment of Potassium and Magnesium Ion Binding to a Buried Pocket in GTPase-Associating Center RNA.

PubMed

Hayatshahi, Hamed S; Roe, Daniel R; Galindo-Murillo, Rodrigo; Hall, Kathleen B; Cheatham, Thomas E

2017-01-26

An experimentally well-studied model of RNA tertiary structures is a 58mer rRNA fragment, known as GTPase-associating center (GAC) RNA, in which a highly negative pocket walled by phosphate oxygen atoms is stabilized by a chelated cation. Although such deep pockets with more than one direct phosphate to ion chelation site normally include magnesium, as shown in one GAC crystal structure, another GAC crystal structure and solution experiments suggest potassium at this site. Both crystal structures also depict two magnesium ions directly bound to the phosphate groups comprising this controversial pocket. Here, we used classical molecular dynamics simulations as well as umbrella sampling to investigate the possibility of binding of potassium versus magnesium inside the pocket and to better characterize the chelation of one of the binding magnesium ions outside the pocket. The results support the preference of the pocket to accommodate potassium rather than magnesium and suggest that one of the closely binding magnesium ions can only bind at high magnesium concentrations, such as might be present during crystallization. This work illustrates the complementary utility of molecular modeling approaches with atomic-level detail in resolving discrepancies between conflicting experimental results.

Functional, mesoporous, superparamagnetic colloidal sorbents for efficient removal of toxic metals.

PubMed

Sinha, Arjyabaran; Jana, Nikhil R

2012-09-25

γ-Fe(2)O(3) incorporated mesoporous silica particles of 50-100 nm size have been synthesized which are functionalized with chelating agents of metal ions. These particles are water dispersible but aggregate in response to the external magnetic field and have been used for high performance and selective removal of Cd, Pb, Hg and As.

Rates of nickel(II) capture from complexes with NTA, EDDA, and related tetradentate chelating agents by the hexadentate chelating agents EDTA and CDTA: Evidence of a "semijunctive" ligand exchange pathway

NASA Astrophysics Data System (ADS)

Boland, Nathan E.; Stone, Alan T.

2017-09-01

Many siderophores and metallophores produced by soil organisms, as well as anthropogenic chelating agent soil amendments, rely upon amine and carboxylate Lewis base groups for metal ion binding. UV-visible spectra of metal ion-chelating agent complexes are often similar and, as a consequence, whole-sample absorbance measurements are an unreliable means of monitoring the progress of exchange reactions. In the present work, we employ capillary electrophoresis to physically separate Ni(II)-tetradentate chelating agent complexes (NiL) from Ni(II)-hexadentate chelating agent complexes (NiY) prior to UV detection, such that progress of the reaction NiL + Y → NiY + L can be conveniently monitored. Rates of ligand exchange for Ni(II) are lower than for other +II transition metal ions. Ni(II) speciation in environmental media is often under kinetic rather than equilibrium control. Nitrilotriacetic acid (NTA), with three carboxylate groups all tethered to a central amine Lewis base group, ethylenediamine-N,N‧-diacetic acid (EDDA), with carboxylate-amine-amine-carboxylate groups arranged linearly, plus four structurally related compounds, are used as tetradentate chelating agents. Ethylenediaminetetraacetic acid (EDTA) and the structurally more rigid analog trans-cyclohexaneethylenediaminetetraacetic acid (CDTA) are used as hexadentate chelating agents. Effects of pH and reactant concentration are explored. Ni(II) capture by EDTA was consistently more than an order of magnitude faster than capture by CDTA, and too fast to quantify using our capillary electrophoresis-based technique. Using NiNTA as a reactant, Ni(II) capture by CDTA is independent of CDTA concentration and greatly enhanced by a proton-catalyzed pathway at low pH. Using NiEDDA as reactant, Ni(II) capture by CDTA is first order with respect to CDTA concentration, and the contribution from the proton-catalyzed pathway diminished by CDTA protonation. While the convention is to assign either a disjunctive pathway or adjunctive pathway to multidentate ligand exchange reactions, our results indicate that a third "semijunctive" pathway is necessary to account for slow reactions progressing through Lsbnd Nisbnd Y ternary complexes. Ligand exchange pathways with NTA-type chelating agents are assigned a disjunctive pathway, while pathways with EDDA-type chelating agents are assigned a semijunctive pathway. Based upon operative mechanism(s), magnitudes of exchange rates and effects of ambient geochemical conditions can be predicted.

Chelation in Metal Intoxication

PubMed Central

Flora, Swaran J.S.; Pachauri, Vidhu

2010-01-01

Chelation therapy is the preferred medical treatment for reducing the toxic effects of metals. Chelating agents are capable of binding to toxic metal ions to form complex structures which are easily excreted from the body removing them from intracellular or extracellular spaces. 2,3-Dimercaprol has long been the mainstay of chelation therapy for lead or arsenic poisoning, however its serious side effects have led researchers to develop less toxic analogues. Hydrophilic chelators like meso-2,3-dimercaptosuccinic acid effectively promote renal metal excretion, but their ability to access intracellular metals is weak. Newer strategies to address these drawbacks like combination therapy (use of structurally different chelating agents) or co-administration of antioxidants have been reported recently. In this review we provide an update of the existing chelating agents and the various strategies available for the treatment of heavy metals and metalloid intoxications. PMID:20717537

Triplin, a small molecule, reveals copper ion transport in ethylene signaling from ATX1 to RAN1

PubMed Central

Li, Wenbo; Ye, Yajin; Lu, Juan; Yeh, Kuo-Chen; Xiao, Youli; Li, Laigeng; Binder, Brad M.

2017-01-01

Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human. PMID:28388654

Quantitative Determination of NTA and Other Chelating Agents in Detergents by Potentiometric Titration with Copper Ion Selective Electrode.

PubMed

Ito, Sana; Morita, Masaki

2016-01-01

Quantitative analysis of nitrilotriacetate (NTA) in detergents by titration with Cu 2+ solution using a copper ion selective electrode was achieved. This method tolerates a wide range of pH and ingredients in detergents. In addition to NTA, other chelating agents, having relatively lower stability constants toward Cu 2+ , were also qualified with sufficient accuracy by this analytical method for model detergent formulations. The titration process was automated by automatic titrating systems available commercially.

Tripeptide GGH as the Inhibitor of Copper-Amyloid-β-Mediated Redox Reaction and Toxicity.

PubMed

Hu, Xiaoyu; Zhang, Qian; Wang, Wei; Yuan, Zhi; Zhu, Xushan; Chen, Bing; Chen, Xingyu

2016-09-21

The Aβ complexes of some redox-active species, such as Cu, cause oxidative stress and induce severe toxicity by generating reactive oxygen species (ROS). Thus, Cu chelation therapy should be considered as a valuable strategy for the treatment of Alzheimer's disease (AD). However, more attention should be paid to the specific chelating ability of these chelating agents. Herein, a tripeptide GGH was used to selectively chelate the Cu(2+) in Aβ-Cu complex in the presence of other metal ions (e.g., K(+), Ca(2+), Ni(2+), Mg(2+), and Zn(2+)) as shown by isothermal titration calorimetry results. GGH decreased the level of HO(•) radicals by preventing the formation of intermediate Cu(I) ion. Thus, the Cu species completely lost its catalytic activity at a superequimolar GGH/Cu(II) ratio (4:1) as observed by UV-visible spectroscopy, coumarin-3-carboxylic acid fluorescence, and BCA assay. Moreover, (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay indicates that GGH increased PC-12 cell viability from 36% to 63%, and neurotoxicity partly triggered by ROS decreased. These results indicate potential development of peptide chelation therapy for AD treatment.

A facile synthesis of zinc oxide/multiwalled carbon nanotube nanocomposite lithium ion battery anodes by sol-gel method

NASA Astrophysics Data System (ADS)

Köse, Hilal; Karaal, Şeyma; Aydın, Ali Osman; Akbulut, Hatem

2015-11-01

Free standing zinc oxide (ZnO) and multiwalled carbon nanotube (MWCNT) nanocomposite materials are prepared by a sol gel technique giving a new high capacity anode material for lithium ion batteries. Free-standing ZnO/MWCNT nanocomposite anodes with two different chelating agent additives, triethanolamine (TEA) and glycerin (GLY), yield different electrochemical performances. Field emission gun scanning electron microscopy (FEG-SEM), energy dispersive X-ray spectrometer (EDS), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analyses reveal the produced anode electrodes exhibit a unique structure of ZnO coating on the MWCNT surfaces. Li-ion cell assembly using a ZnO/MWCNT/GLY free-standing anode and Li metal cathode possesses the best discharge capacity, remaining as high as 460 mAh g-1 after 100 cycles. This core-shell structured anode can offer increased energy storage and performance over conventional anodes in Li-ion batteries.

Enhanced in vitro activity of tigecycline in the presence of chelating agents.

PubMed

Deitchman, Amelia N; Singh, Ravi Shankar Prasad; Rand, Kenneth H; Derendorf, Hartmut

2018-05-01

The lack of availability of novel antibiotic agents and the rise of resistance to existing therapies has led clinicians to utilise combination therapy to adequately treat bacterial infections. Here we examined how chelators may impact the in vitro activity of tigecycline (TIG) against Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. Minimum inhibitory concentrations (MICs) were determined by broth dilution with and without various combinations of chelators (EDTA and other tetracyclines) and metal ions (i.e. calcium, magnesium). Trimethoprim (TMP) was used as a non-chelating control. Addition of metal ions led to increases in MICs, whilst addition of EDTA led to decreases in MICs. The chelating effects of EDTA were reversed by addition of magnesium and most profoundly calcium. Similar effects of EDTA and calcium were observed for tetracycline (TET) and TMP. When other tetracyclines (TET, oxytetracycline (OXY) and chlortetracycline (CHL)) were used as chelators at concentrations below their MICs, TIG MICs decreased for P. aeruginosa but not for E. coli. Some decreases in TIG MICs were observed for K. pneumoniae when TET and CHL were added. A dose-dependent decrease in TIG MIC was observed for TET and was reversed by the addition of calcium. The presence of effects of EDTA and calcium on TMP MICs indicates that mechanisms outside of TIG chelation likely play a role in enhanced activity. Full characterisation of an unexpected interaction such as TIG-TET with different microorganisms could provide valuable insights into the underlying mechanisms and design of physiologically viable chelators as candidates for future combinations regimens. Copyright © 2018 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

Optical response measurements of a new class of upconverting luminescent reporters

NASA Astrophysics Data System (ADS)

Xiao, Xudong; Haushalter, Jeanne P.; Weiss, Michael; Faris, Gregory W.

2004-06-01

We have prepared and characterized several lanthanide ion complexes of multidentate ligands or chelates in an effort to develop new luminescent reporters that will be immune to autofluorescence and photobleaching. Our study has involved the characterization of various chelates of Eu, Er, and Tm with respect to relative luminescent efficiency and excited state lifetimes. Included in the list of chelates studied are TTFA, EDTA, DPA, DOTA and DTPA as well as mixed and double chelates. In addition to determining the relative efficiencies and luminescence lifetimes of the lanthanide chelates, we have explored various excitation mechanisms and determined optimum excitation wavelengths. This paper will address the various hurdles encountered in the development of this new class of reporters.

Time-resolved delayed luminescence image microscopy using an europium ion chelate complex.

PubMed Central

Marriott, G.; Heidecker, M.; Diamandis, E. P.; Yan-Marriott, Y.

1994-01-01

Improvements and extended applications of time-resolved delayed luminescence imaging microscopy (TR-DLIM) in cell biology are described. The emission properties of europium ion complexed to a fluorescent chelating group capable of labeling proteins are exploited to provide high contrast images of biotin labeled ligands through detection of the delayed emission. The streptavidin-based macromolecular complex (SBMC) employs streptavidin cross-linked to thyroglobulin multiply labeled with the europium-fluorescent chelate. The fluorescent chelate is efficiently excited with 340-nm light, after which it sensitizes europium ion emission at 612 nm hundreds of microseconds later. The SBMC complex has a high quantum yield orders of magnitude higher than that of eosin, a commonly used delayed luminescent probe, and can be readily seen by the naked eye, even in specimens double-labeled with prompt fluorescent probes. Unlike triplet-state phosphorescent probes, sensitized europium ion emission is insensitive to photobleaching and quenching by molecular oxygen; these properties have been exploited to obtain delayed luminescence images of living cells in aerated medium thus complementing imaging studies using prompt fluorescent probes. Since TR-DLIM has the unique property of rejecting enormous signals that originate from scattered light, autofluorescence, and prompt fluorescence it has been possible to resolve double emission images of living amoeba cells containing an intensely stained lucifer yellow in pinocytosed vesicles and membrane surface-bound SBMC-labeled biotinylated concanavalin A. Images of fixed cells represented in terms of the time decay of the sensitized emission show the lifetime of the europium ion emission is sensitive to the environment in which it is found. Through the coupling of SBMC to streptavidin,a plethora of biotin-based tracer molecules are available for immunocytochemical studies. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 PMID:7811952

Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism.

PubMed

Ali, Mubarak; Ramirez, Patricio; Duznovic, Ivana; Nasir, Saima; Mafe, Salvador; Ensinger, Wolfgang

2017-02-01

We design and characterize a nanofluidic device for the label-free specific detection of histamine neurotransmitter based on a metal ion displacement mechanism. The sensor consists of an asymmetric polymer nanopore fabricated via ion track-etching technique. The nanopore sensor surface having metal-nitrilotriacetic (NTA-Ni 2+ ) chelates is obtained by covalent coupling of native carboxylic acid groups with N α ,N α -bis(carboxymethyl)-l-lysine (BCML), followed by exposure to Ni 2+ ion solution. The BCML immobilization and subsequent Ni 2+ ion complexation with NTA moieties change the surface charge concentration, which has a significant impact on the current-voltage (I-V) curve after chemical modification of the nanopore. The sensing mechanism is based on the displacement of the metal ion from the NTA-Ni 2+ chelates. When the modified pore is exposed to histamine solution, the Ni 2+ ion in NTA-Ni 2+ chelate recognizes histamine through a metal ion coordination displacement process and formation of stable Ni-histamine complexes, leading to the regeneration of metal-free NTA groups on the pore surface, as shown in the current-voltage characteristics. Nanomolar concentrations of the histamine in the working electrolyte can be detected. On the contrary, other neurotransmitters such as glycine, serotonin, gamma-aminobutyric acid, and dopamine do not provoke significant changes in the nanopore electronic signal due to their inability to displace the metal ion and form a stable complex with Ni 2+ ion. The nanofluidic sensor exhibits high sensitivity, specificity and reusability towards histamine detection and can then be used to monitor the concentration of biological important neurotransmitters. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis, investigation and spectroscopic characterization of piroxicam ternary complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with glycine and DL-phenylalanine

NASA Astrophysics Data System (ADS)

Mohamed, Gehad G.; El-Gamel, Nadia E. A.

2004-11-01

The ternary piroxicam (Pir; 4-hydroxy-2-methyl- N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide) complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with various amino acids (AA) such as glycine (Gly) or DL-phenylalanine (PhA) were prepared and characterized by elemental analyses, molar conductance, IR, UV-Vis, magnetic moment, diffuse reflectance and X-ray powder diffraction. The UV-Vis spectra of Pir and the effect of metal chelation on the different interligand transitions are discussed in detailed manner. IR and UV-Vis spectra confirm that Pir behaves as a neutral bidentate ligand coordinated to the metal ions via the pyridine- N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its carboxylic group, in addition PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its carboxylic and amino groups. All the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. The molar conductance data reveal that most of these chelates are non electrolytes, while Fe(III)-Pir-Gly, Co(II)-, Ni(II)-, Cu(II)- and Zn(II)-Pir-PhA cheletes were 1:1 electrolytes. X-ray powder diffraction is used as a new tool to estimate the crystallinity of chelates as well as to elucidate their geometrical structures.

Iron-chelating agents never suppress Fenton reaction but participate in quenching spin-trapped radicals.

PubMed

Li, Linxiang; Abe, Yoshihiro; Kanagawa, Kiyotada; Shoji, Tomoko; Mashino, Tadahiko; Mochizuki, Masataka; Tanaka, Miho; Miyata, Naoki

2007-09-19

Hydroxyl radical formation by Fenton reaction in the presence of an iron-chelating agent such as EDTA was traced by two different assay methods; an electron spin resonance (ESR) spin-trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and high Performance liquid chromatography (HPLC)-fluorescence detection with terephthalic acid (TPA), a fluorescent probe for hydroxyl radicals. From the ESR spin-trapping measurement, it was observed that EDTA seemed to suppress hydroxyl radical formation with the increase of its concentration. On the other hand, hydroxyl radical formation by Fenton reaction was not affected by EDTA monitored by HPLC assay. Similar inconsistent effects of other iron-chelating agents such as nitrylotriacetic acid (NTA), diethylenetriamine penta acetic acid (DTPA), oxalate and citrate were also observed. On the addition of EDTA solution to the reaction mixture 10 min after the Fenton reaction started, when hydroxyl radical formation should have almost ceased but the ESR signal of DMPO-OH radicals could be detected, it was observed that the DMPO-OH* signal disappeared rapidly. With the simultaneous addition of Fe(II) solution and EDTA after the Fenton reaction ceased, the DMPO-OH* signal disappeared more rapidly. The results indicated that these chelating agents should enhance the quenching of [DMPO-OH]* radicals by Fe(II), but they did not suppress Fenton reaction by forming chelates with iron ions.

Preparation and adsorption behavior of aminated electrospun polyacrylonitrile nanofiber mats for heavy metal ion removal.

PubMed

Kampalanonwat, Pimolpun; Supaphol, Pitt

2010-12-01

Polyacrylonitrile (PAN) nanofiber mats were prepared by electrospinning and they were further modified to contain amidino diethylenediamine chelating groups on their surface via heterogeneous reaction with diethylenetriamine (DETA). The obtained aminated PAN (APAN) nanofiber mats were evaluated for their chelating property with four types of metal ions, namely Cu(II), Ag(I), Fe(II), and Pb(II) ions. The amounts of the metal ions adsorbed onto the APAN nanofiber mats were influenced by the initial pH and the initial concentration of the metal ion solutions. Increasing the contact time also resulted in a monotonous increase in the adsorbed amounts of the metal ions, which finally reached equilibria at about 10 h for Cu(II) ions and about 5 h for Ag(I), Fe(II), and Pb(II) ions. The maximal adsorption capacities of the metal ions on the APAN nanofiber mats, as calculated from the Langmuir model, were 150.6, 155.5, 116.5, and 60.6 mg g(-1), respectively. Lastly, the spent APAN nanofiber mats could be facilely regenerated with a hydrochloric acid (HCl) aqueous solution.

IR, UV-Vis, magnetic and thermal characterization of chelates of some catecholamines and 4-aminoantipyrine with Fe(III) and Cu(II)

NASA Astrophysics Data System (ADS)

Mohamed, Gehad G.; Zayed, M. A.; El-Dien, F. A. Nour; El-Nahas, Reham G.

2004-07-01

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. α-Methyldopa (α-MD) in tablets is used in medication of hypertension. The Fe(III) and Cu(II) chelates with coupled products of adrenaline hydrogen tartarate (AHT), levodopa (LD), α-MD and carbidopa (CD) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical methods like IR, magnetic and UV-Vis spectra are used to investigate the structure of these chelates. Fe(III) form 1:2 (M:catecholamines) chelates while Cu(II) form 1:1 chelates. Catecholamines behave as a bidentate mono- or dibasic ligands in binding to the metal ions. IR spectra show that the catecholamines are coordinated to the metal ions in a bidentate manner with O,O donor sites of the phenolic - OH. Magnetic moment measurements reveal the presence of Fe(III) chelates in octahedral geometry while the Cu(II) chelates are square planar. The thermal decomposition of Fe(III) and Cu(II) complexes is studied using thermogravimetric (TGA) and differential thermal analysis (DTA) techniques. The water molecules are removed in the first step followed immediately by decomposition of the ligand molecules. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Macrocycles

DOEpatents

Raymond, Kenneth N.; Xu, Jide; Pham, Tiffany A.

2016-09-13

The invention provides macrocycles useful in chelating metal ions, particularly radionuclides, to provide metal ion complexes. The invention also provides methods of using the compounds and complexes of the invention, such as in therapeutic and diagnostic applications.

Synthesis of Iminodiacetate Functionalized Polypropylene Films and Their Efficacy as Antioxidant Active-Packaging Materials.

PubMed

Lin, Zhuangsheng; Roman, Maxine J; Decker, Eric A; Goddard, Julie M

2016-06-08

The introduction of metal-chelating ligands to the food-contact surface of packaging materials may enable the removal of synthetic chelators (e.g., ethylenediamine tetra-acetic acid (EDTA)) from food products. In this study, the metal-chelating ligand iminodiacetate (IDA) was covalently grafted onto polypropylene surfaces to produce metal-chelating active-packaging films. The resulting films were able to chelate 138.1 ± 26 and 210.0 ± 28 nmol/cm(2) Fe(3+) and Cu(2+) ions, respectively, under acidic conditions (pH 3.0). The films demonstrated potent antioxidant efficacy in two model food systems. In an emulsified-oil system, the chelating materials extended the lag phase of both lipid hydroperoxide and hexanal formation from 5 to 25 days and were as effective as EDTA. The degradation half-life of ascorbic acid in an aqueous solution was extended from 5 to 14 days. This work demonstrates the potential application of surface-grafted chelating IDA ligands as effective antioxidant active food-packaging materials.

Colour and stability assessment of blue ferric anthocyanin chelates in liquid pectin-stabilised model systems.

PubMed

Buchweitz, M; Brauch, J; Carle, R; Kammerer, D R

2013-06-01

The formation of blue coloured ferric anthocyanin chelates and their colour stability during storage and thermal treatment were monitored in a pH range relevant to food (3.6-5.0). Liquid model systems were composed of different types of Citrus pectins, juices (J) and the respective phenolic extracts (E) from elderberry (EB), black currant (BC), red cabbage (RC) and purple carrot (PC) in the presence of ferric ions. For EB, BC and PC, pure blue colours devoid of a violet tint were exclusively observed for the phenolic extracts and at pH values ≥ 4.5 in model systems containing high methoxylated and amidated pectins, respectively. Colour and its stability strongly depended on the amount of ferric ions and the plant source; however, colour decay could generally be described as a pseudo-first-order kinetics. Despite optimal colour hues for RC-E and RC-J, storage and heat stabilities were poor. Highest colour intensities and best stabilities were observed for model systems containing PC-E at a molar anthocyanin:ferric ion ratio of 1:2. Ascorbic and lactic acids interfered with ferric ions, thus significantly affecting blue colour evolution and stability. Colour loss strongly depended on heat exposure with activation energies ranging between 60.5 and 78.4 kJ/mol. The comprehensive evaluation of the interrelationship of pigment source, pH conditions and pectin type on chelate formation and stability demonstrated that ferric anthocyanin chelates are promising natural blue food colourants. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of hydroxycinnamic acids on blue color expression of cyanidin derivatives and their metal chelates.

PubMed

Sigurdson, G T; Robbins, R J; Collins, T M; Giusti, M M

2017-11-01

Mechanisms to recreate many anthocyanin blue hues in nature are not fully understood, but interactions with metal ions and phenolic compounds are thought to play important roles. Bluing effects of hydroxycinnamic acids on cyanidin and chelates were investigated by addition of the acids to triglycosylated cyanidin (0-50×[anthocyanin]) and by comparison to hydroxycinnamic acid monoacylated and diacylated Cy fractions by spectrophotometry (380-700nm) and colorimetry in pH 5-8. With no metal ions, λ max and absorbance was greatest for cyanidin with diacylation>monoacylation>increasing [acids]. Hydroxycinnamic acids added to cyanidin solutions weakly impacted color characteristics (ΔE<5); while acylation (covalent acid attachment) resulted in ΔE 5-15. Triglycosylated cyanidin expressed blue color (pH 7-8), suggesting glycosylation pattern also plays a role. Al 3+ chelation increased absorbance 2-42× and λ max ≳40nm (pH 5-6) compared to added hydroxycinnamic acids. Metal chelation and aromatic diacylation resulted in the most blue hues. Copyright © 2017 Elsevier Ltd. All rights reserved.

Curcumin derivatives as metal-chelating agents with potential multifunctional activity for pharmaceutical applications.

PubMed

Ferrari, Erika; Benassi, Rois; Sacchi, Stefania; Pignedoli, Francesca; Asti, Mattia; Saladini, Monica

2014-10-01

Curcuminoids represent new perspectives for the development of novel therapeutics for Alzheimer's disease (AD), one probable mechanism of action is related to their metal complexing ability. In this work we examined the metal complexing ability of substituted curcuminoids to propose new chelating molecules with biological properties comparable with curcumin but with improved stability as new potential AD therapeutic agents. The K2T derivatives originate from the insertion of a -CH2COOC(CH3)3 group on the central atom of the diketonic moiety of curcumin. They retain the diketo-ketoenol tautomerism which is solvent dependent. In aqueous solution the prevalent form is the diketo one but the addition of metal ion (Ga(3+), Cu(2+)) causes the dissociation of the enolic proton creating chelate complexes and shifting the tautomeric equilibrium towards the keto-enol form. The formation of metal complexes is followed by both NMR and UV-vis spectroscopy. The density functional theory (DFT) calculations on K2T21 complexes with Ga(3+) and Cu(2+) are performed and compared with those on curcumin complexes. [Ga(K2T21)2(H2O)2](+) was found more stable than curcumin one. Good agreement is detected between calculated and experimental (1)H and (13)C NMR data. The calculated OH bond dissociation energy (BDE) and the OH proton dissociation enthalpy (PDE), allowed to predict the radical scavenging ability of the metal ion complexed with K2T21, while the calculated electronic affinity (EA) and ionization potential (IP) represent yardsticks of antioxidant properties. Eventually theoretical calculations suggest that the proton-transfer-associated superoxide-scavenging activity is enhanced after binding metal ions, and that Ga(3+) complexes display possible superoxide dismutase (SOD)-like activity. Copyright © 2014 Elsevier Inc. All rights reserved.

Antimicrobial Properties of Copper Nanoparticles and Amino Acid Chelated Copper Nanoparticles Produced by Using a Soya Extract.

PubMed

DeAlba-Montero, I; Guajardo-Pacheco, Jesús; Morales-Sánchez, Elpidio; Araujo-Martínez, Rene; Loredo-Becerra, G M; Martínez-Castañón, Gabriel-Alejandro; Ruiz, Facundo; Compeán Jasso, M E

2017-01-01

This paper reports a comparison of the antibacterial properties of copper-amino acids chelates and copper nanoparticles against Escherichia coli , Staphylococcus aureus , and Enterococcus faecalis . These copper-amino acids chelates were synthesized by using a soybean aqueous extract and copper nanoparticles were produced using as a starting material the copper-amino acids chelates species. The antibacterial activity of the samples was evaluated by using the standard microdilution method (CLSI M100-S25 January 2015). In the antibacterial activity assays copper ions and copper-EDTA chelates were included as references, so that copper-amino acids chelates can be particularly suitable for acting as an antibacterial agent, so they are excellent candidates for specific applications. Additionally, to confirm the antimicrobial mechanism on bacterial cells, MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) was carried out. A significant enhanced antimicrobial activity and a specific strain were found for copper chelates over E. faecalis . Its results would eventually lead to better utilization of copper-amino acids chelate for specific application where copper nanoparticles can be not used.

Antimicrobial Properties of Copper Nanoparticles and Amino Acid Chelated Copper Nanoparticles Produced by Using a Soya Extract

PubMed Central

DeAlba-Montero, I.; Morales-Sánchez, Elpidio; Araujo-Martínez, Rene

2017-01-01

This paper reports a comparison of the antibacterial properties of copper-amino acids chelates and copper nanoparticles against Escherichia coli, Staphylococcus aureus, and Enterococcus faecalis. These copper-amino acids chelates were synthesized by using a soybean aqueous extract and copper nanoparticles were produced using as a starting material the copper-amino acids chelates species. The antibacterial activity of the samples was evaluated by using the standard microdilution method (CLSI M100-S25 January 2015). In the antibacterial activity assays copper ions and copper-EDTA chelates were included as references, so that copper-amino acids chelates can be particularly suitable for acting as an antibacterial agent, so they are excellent candidates for specific applications. Additionally, to confirm the antimicrobial mechanism on bacterial cells, MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) was carried out. A significant enhanced antimicrobial activity and a specific strain were found for copper chelates over E. faecalis. Its results would eventually lead to better utilization of copper-amino acids chelate for specific application where copper nanoparticles can be not used. PMID:28286459

Use of ferrous chelates of SH-containing amino acids and peptides for the removal of NO/sub x/ and SO/sub 2/ from flue gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, S.G.; Littlejohn, D.; Liu, D.K.

1988-11-01

The use of ferrous complexes of SH-containing amino acids and peptides for the removal of NO and SO/sub 2/ in wet flue gas clean-up systems is reported. The ferrous chelates investigated in the present study include those of cysteine, N-acetylcysteine, penicillamine, N-acetylpenicillamine, glutathine, and cysteinylglycine. Compared to conventional chelates such as EDTA, these thioamino acids/peptides not only can stabilize ferrous ion in alkaline solutions to promote the absorption of NO but are also capable of rapidly reducing any ferric ions formed during the scrubbing process back to ferrous ions so that continual absorption of NO can be achieved. In themore » case of ferrous cysteine and ferrous penicillamine, most of the absorbed NO is reduced to N/sub 2/. The disulfide form of several of the thioamino acids/peptides produced upon oxidation can be conveniently reduced by SO/sub 2/ and H/sub 2/S to regenerate the starting materials, thus making possible the recycling of the reagents.« less

Docking modes of BB-3497 into the PDF active site--a comparison of the pure MM and QM/MM based docking strategies.

PubMed

Kumari, Tripti; Issar, Upasana; Kakkar, Rita

2014-01-01

Peptide deformylase (PDF) has emerged as an important antibacterial drug target. Considerable effort is being directed toward developing peptidic and non-peptidic inhibitors for this metalloprotein. In this work, the known peptidic inhibitor BB-3497 and its various ionization and tautomeric states are evaluated for their inhibition efficiency against PDF using a molecular mechanics (MM) approach as well as a mixed quantum mechanics/molecular mechanics (QM/MM) approach, with an aim to understand the interactions in the binding site. The evaluated Gibbs energies of binding with the mixed QM/MM approach are shown to have the best predictive power. The experimental pose is found to have the most negative Gibbs energy of binding, and also the smallest strain energy. A quantum mechanical evaluation of the active site reveals the requirement of strong chelation by the ligand with the metal ion. The investigated ligand chelates the metal ion through the two oxygens of its reverse hydroxamate moiety, particularly the N-O(-) oxygen, forming strong covalent bonds with the metal ion, which is penta-coordinated. In the uninhibited state, the metal ion is tetrahedrally coordinated, and hence chelation with the inhibitor is associated with an increase of the metal ion coordination. Thus, the strong binding of the ligand at the binding site is accounted for.

Assessment of Antioxidant and Cytotoxicity Activities of Saponin and Crude Extracts of Chlorophytum borivilianum

PubMed Central

Abd Aziz, Maheran; Stanslas, Johnson; Abdul Kadir, Mihdzar

2013-01-01

The present paper focused on antioxidant and cytotoxicity assessment of crude and total saponin fraction of Chlorophytum borivilianum as an important medicinal plant. In this study, three different antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH), ferrous ion chelating (FIC), and β-carotene bleaching (BCB) activity) of crude extract and total saponin fraction of C. borivilianum tubers were performed. Crude extract was found to possess higher free radical scavenging activity (ascorbic acid equivalents 2578 ± 111 mg AA/100 g) and bleaching activity (IC50 = 0.7 mg mL−1), while total saponin fraction displayed higher ferrous ion chelating (EC50 = 1 mg mL−1). Cytotoxicity evaluation of crude extract and total saponin fraction against MCF-7, PC3, and HCT-116 cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) cell viability assay indicated a higher cytotoxicity activity of the crude extract than the total saponin fraction on all cell lines, being most effective and selective on MCF-7 human breast cancer cell line. PMID:24223502

A microextraction procedure based on a task-specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves.

PubMed

Saljooqi, Asma; Shamspur, Tayebeh; Mohamadi, Maryam; Afzali, Daryoush; Mostafavi, Ali

2015-05-01

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task-specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho-positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0-24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of Cu(II), Hg(II), and Ni(II) ions by modified natural wool chelating fibers.

PubMed

Monier, M; Ayad, D M; Sarhan, A A

2010-04-15

The graft copolymerization of ethyl acrylate (EA) onto natural wool fibers initiated by potassium persulphate and Mohr's salt redox initiator system in limited aqueous medium was carried out in heterogeneous media. Ester groups of the grafted copolymers were partially converted into hydrazide function groups followed by hydrazone formation through reaction with isatin. Also the application of the modified fibers for metal ion uptake was studied using Cu(II), Hg(II) and Ni(II). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction. 2009 Elsevier B.V. All rights reserved.

Molecular engineering of lanthanide ion chelating phospholipids generating assemblies with a switched magnetic susceptibility.

PubMed

Isabettini, Stéphane; Massabni, Sarah; Hodzic, Arnel; Durovic, Dzana; Kohlbrecher, Joachim; Ishikawa, Takashi; Fischer, Peter; Windhab, Erich J; Walde, Peter; Kuster, Simon

2017-08-09

Lanthanide ion (Ln 3+ ) chelating amphiphiles are powerful molecules for tailoring the magnetic response of polymolecular assemblies. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA) complexed to Ln 3+ deliver highly magnetically responsive bicelles. Their magnetic properties are readily tuned by changing the bicellar size or the magnetic susceptibility Δχ of the bilayer lipids. The former technique is intrinsically bound to the region of the phase diagram guarantying the formation of bicelles. Methods aiming towards manipulating the Δχ of the bilayer are comparatively more robust, flexible and lacking. Herein, we synthesized a new Ln 3+ chelating phospholipid using glutamic acid as a backbone: DMPE-Glu-DTPA. The chelate polyhedron was specifically engineered to alter the Δχ, whilst remaining geometrically similar to DMPE-DTPA. Planar asymmetric assemblies hundreds of nanometers in size were achieved presenting unprecedented magnetic alignments. The DMPE-Glu-DTPA/Ln 3+ complex switched the Δχ, achieving perpendicular alignment of assemblies containing Dy 3+ and parallel alignment of those containing Tm 3+ . Moreover, samples with chelated Yb 3+ were more alignable than the Tm 3+ chelating counterparts. Such a possibility has never been demonstrated for planar Ln 3+ chelating polymolecular assemblies. The physico-chemical properties of these novel assemblies were further studied by monitoring the alignment behavior at different temperatures and by including 16 mol% of cholesterol (Chol-OH) in the phospholipid bilayer. The DMPE-Glu-DTPA/Ln 3+ complex and the resulting assemblies are promising candidates for applications in numerous fields including pharmaceutical technologies, structural characterization of membrane biomolecules by NMR spectroscopy, as contrasting agents for magnetic resonance imaging, and for the development of smart optical gels.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmieri, M.D.; Fritz, J.S.

Metal ions are determined by adding N-methylfurohydroxamic acid to an aqueous sample and then separating the metal chelates by direct injection onto a liquid chromatographic column. Separations on a C/sub 8/ silica column and a polystyrene-divinylbenzene column are compared, with better separations seen on the polymeric column. The complexes formed at low pH values are cationic and are separated by an ion pairing mechanism. Retention times and selectivity of the metal complexes can be varied by changing the pH. Several metal ions can be separated and quantified; separation conditions, linear calibration curve ranges, and detection limits are presented for Zr(IV),more » Hf(IV), Fe(III), Nb(V), Al(III), and Sb(III). Interferences due to the presence of other ions in solution are investigated. Finally, an antiperspirant sample is analyzed for zirconium by high-performance liquid chromatography.« less

Effect of Ca2+ ion concentration on adsorption of poly(carboxylate ether)-based (PCE) superplasticizer on mica.

PubMed

Wu, Bo; Chun, Byong-Wa; Gu, Le; Kuhl, Tonya L

2018-05-09

Poly(carboxylate ether)-based (PCE) superplasticizers consist of a carboxylic acid backbone and grafted poly(ethylene glycol) (PEG) side chains. Ca 2+ ion bridging mechanism is commonly purported to control PCE's adsorption on negatively charged cement particle surfaces in cement suspension, thus PCE was expected to adsorb on negatively charged surfaces in synthetic pore solutions via Ca 2+ /COO - interactions. Adsorption behaviors of a commercial PCE on negatively charged mica were studied in aqueous electrolyte solutions by a surface forces apparatus. Direct force measurements indicated that the PCE adsorbed onto mica from 0.1 M K 2 SO 4 due to K + ion chelation by the ether oxygen units CH 2 CH 2 O on the PEG chains, but surprisingly did not adsorb from either 0.1 M K 2 SO 4 with saturated Ca(OH) 2 or 0.1 M Ca(NO 3 ) 2 . The adsorption in K 2 SO 4 was weak, enabling the adsorbed PCE layers to be squeezed out under modest compression. Upon separating the surfaces, the PCE immediately achieved an identical re-adsorption. In high-calcium conditions, the PCE was highly positively charged due to Ca 2+ ion chelation by PEG chains and backbone carboxylic groups COO - , and mica also underwent charge reversal due to electrostatic adsorption/binding of Ca 2+ ions. Consequently, the interaction between mica and PCE was electrostatically repulsive and no PCE adsorption occurred. These findings can be explained by the complex interplay of ion chelation by PEG chains, electrostatic binding and screening interactions with charged surfaces in the presence of monovalent and divalent counterions, and ultimately charge reversal of both the charged surfaces and polyelectrolyte in high divalent ion conditions. Copyright © 2018 Elsevier Inc. All rights reserved.

Characterization of sea cucumber (stichopus japonicus) ovum hydrolysates: calcium chelation, solubility and absorption into intestinal epithelial cells.

PubMed

Sun, Na; Cui, Pengbo; Lin, Songyi; Yu, Cuiping; Tang, Yue; Wei, Ye; Xiong, Youling; Wu, Haitao

2017-10-01

Sea cucumber (Stichopus japonicus) ovum hydrolysates (SCOHs) chelated with calcium were produced to investigate the characteristics of calcium binding and solubility, as well as to study any effects on calcium absorption by human intestinal epithelial cells. The results of the present study show that the calcium-binding capacity of SCOHs depended greatly on the type of proteases. The maximum level of Ca binding (0.38 mmol L -1 ) occurred when trypsin was used, with a peptide yield of 85.7%. Investigation of the possible chelating modes between SCOHs and calcium ions indicated that calcium ions bound to SCOHs primarily via interactions with carboxyl oxygen and amino nitrogen atoms of Glu and Asp and also that the phosphoserine residues might be also responsible for SCOH-calcium chelation. Moreover, SCOH-calcium complexes maintained the solubility of calcium under simulated gastrointestinal digestion, regardless of the presence of dietary components such as oxalate. Furthermore, SCOH-Ca led to higher peak intracellular [Ca 2+ ] i in both Caco-2 cells (338.3 nmol L -1 versus 269.6 nmol L -1 ) and HT-29 cells (373.9 nmol L -1 versus 271.7 nmol L -1 ) than casein phosphopeptide-Ca. Carboxyl oxygen and amino nitrogen atoms in the SCOHs could bind calcium ions, forming SCOH-calcium complexes. These complexes improved calcium solubility under simulated gastrointestinal digestion and also promoted calcium absorption in Caco-2 and HT-29 cells. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Investigation of yeast invertase immobilization onto cupric ion-chelated, porous, and biocompatible poly(hydroxyethyl methacrylate-n-vinyl imidazole) microspheres.

PubMed

Sari, Müfrettin Murat

2011-04-01

Cupric ion-chelated poly(hydroxyethyl methacrylate-n-vinyl imidazole) (poly(HEMA-VIM)) microspheres prepared by suspension polymerization were investigated as a specific adsorbent for immobilization of yeast invertase in a batch system. They were characterized by scanning electron microscopy, surface area, and pore size measurements. They have spherical shape and porous structure. The specific surface area of the p(HEMA-VIM) spheres was found to be 81.2 m²/g with a size range of 70-120 μm in diameter, and the swelling ratio was 86.9%. Then, Cu(II) ion chelated on the microspheres (546 μmol Cu(II)/g), and they were used in the invertase adsorption. Maximum invertase adsorption was 51.2 mg/g at pH 4.5. Cu(II) chelation increases the tendency from Freundlich-type to Langmuir-type adsorption model. The optimum activity for both free and adsorbed invertase was observed at pH 4.5. The optimum temperature for the poly(HEMA-VIM)/Cu(II)-invertase system was found to be at 55 °C, 10 °C higher than that of the free enzyme at 45 °C. V(max) values were determined as 342 and 304 U/mg enzyme, for free and adsorbed invertase, respectively. K(m) values were found to be same for free and adsorbed invertase (20 mM). Thermal and pH stability and reusability of invertase increased with immobilization.

Oxidative degradation stability and hydrogen sulfide removal performance of dual-ligand iron chelate of Fe-EDTA/CA.

PubMed

Miao, Xinmei; Ma, Yiwen; Chen, Zezhi; Gong, Huijuan

2017-09-05

Catalytic oxidation desulfurization using chelated iron catalyst is an effective method to remove H 2 S from various gas streams including biogas. However, the ligand of ethylenediaminetetraacetic acid (EDTA), which is usually adopted to prepare chelated iron catalyst, is liable to be oxidative degraded, and leads to the loss of desulfurization performance. In order to improve the degradation stability of the iron chelate, a series of iron chelates composed of two ligands including citric acid (CA) and EDTA were prepared and the oxidative degradation stability as well as desulfurization performance of these chelated iron catalysts were studied. Results show that the iron chelate of Fe-CA is more stable than Fe-EDTA, while for the desulfurization performance, the situation is converse. For the dual-ligand iron chelates of Fe-EDTA/CA, with the increase of mol ratio of CA to EDTA in the iron chelate solution, the oxidative degradation stability increased while the desulfurization performance decreased. The results of this work showed that Fe-EDTA/CA with a mol ratio of CA:EDTA = 1:1 presents a relative high oxidative degradation stability and an acceptable desulfurization performance with over 90% of H 2 S removal efficiency.

Tentacle-type immobilized metal affinity cryogel for invertase purification from Saccharomyces cerevisiae.

PubMed

Çetin, Kemal; Perçin, Işık; Denizli, Fatma; Denizli, Adil

2017-11-01

The aim of this study is to investigate the usability of cryogel columns for the purification of invertase from Saccharomyces cerevisiae. Poly(2-hydroxyethyl methacrylate) monolithic columns were produced via cryogelation. Ester groups of the poly(2-hydroxyethyl methacrylate) structure were then converted to imine groups by the reaction with poly(ethylene imine) in the presence of NaHCO 3 . Transition metal ions, Cu(II), Co(II), and Ni(II), were chelated on the PEI-modified cryogel columns. Purification of invertase from natural source namely S. cerevisiae was also studied, and the purification fold values were obtained as 41.350, 44.714, and 30.302 for Cu(II)-chelated, Co(II)-chelated, and Ni(II)-chelated PHEMA/PEI columns, respectively.

Development of Ion Chemosensors Based on Porphyrin Analogues.

PubMed

Ding, Yubin; Zhu, Wei-Hong; Xie, Yongshu

2017-02-22

Sensing of metal ions and anions is of great importance because of their widespread distribution in environmental systems and biological processes. Colorimetric and fluorescent chemosensors based on organic molecular species have been demonstrated to be effective for the detection of various ions and possess the significant advantages of low cost, high sensitivity, and convenient implementation. Of the available classes of organic molecules, porphyrin analogues possess inherently many advantageous features, making them suitable for the design of ion chemosensors, with the targeted sensing behavior achieved and easily modulated based on their following characteristics: (1) NH moieties properly disposed for binding of anions through cooperative hydrogen-bonding interactions; (2) multiple pyrrolic N atoms or other heteroatoms for selectively chelating metal ions; (3) variability of macrocycle size and peripheral substitution for modulation of ion selectivity and sensitivity; and (4) tunable near-infrared emission and good biocompatibility. In this Review, design strategies, sensing mechanisms, and sensing performance of ion chemosensors based on porphyrin analogues are described by use of extensive examples. Ion chemosensors based on normal porphyrins and linear oligopyrroles are also briefly described. This Review provides valuable information for researchers of related areas and thus may inspire the development of more practical and effective approaches for designing high-performance ion chemosensors based on porphyrin analogues and other relevant compounds.

The Extracellular Domain of Human High Affinity Copper Transporter (hNdCTR1), Synthesized by E. coli Cells, Chelates Silver and Copper Ions In Vivo

PubMed Central

Sankova, Tatiana P.; Orlov, Iurii A.; Saveliev, Andrey N.; Kirilenko, Demid A.; Babich, Polina S.; Brunkov, Pavel N.; Puchkova, Ludmila V.

2017-01-01

There is much interest in effective copper chelators to correct copper dyshomeostasis in neurodegenerative and oncological diseases. In this study, a recombinant fusion protein for expression in Escherichia coli cells was constructed from glutathione-S-transferase (GST) and the N-terminal domain (ectodomain) of human high affinity copper transporter CTR1 (hNdCTR1), which has three metal-bound motifs. Several biological properties of the GST-hNdCTR1 fusion protein were assessed. It was demonstrated that in cells, the protein was prone to oligomerization, formed inclusion bodies and displayed no toxicity. Treatment of E. coli cells with copper and silver ions reduced cell viability in a dose- and time-dependent manner. Cells expressing GST-hNdCTR1 protein demonstrated resistance to the metal treatments. These cells accumulated silver ions and formed nanoparticles that contained AgCl and metallic silver. In this bacterial population, filamentous bacteria with a length of about 10 µm were often observed. The possibility for the fusion protein carrying extracellular metal binding motifs to integrate into the cell’s copper metabolism and its chelating properties are discussed. PMID:29099786

The Extracellular Domain of Human High Affinity Copper Transporter (hNdCTR1), Synthesized by E. coli Cells, Chelates Silver and Copper Ions In Vivo.

PubMed

Sankova, Tatiana P; Orlov, Iurii A; Saveliev, Andrey N; Kirilenko, Demid A; Babich, Polina S; Brunkov, Pavel N; Puchkova, Ludmila V

2017-11-03

There is much interest in effective copper chelators to correct copper dyshomeostasis in neurodegenerative and oncological diseases. In this study, a recombinant fusion protein for expression in Escherichia coli cells was constructed from glutathione-S-transferase (GST) and the N-terminal domain (ectodomain) of human high affinity copper transporter CTR1 (hNdCTR1), which has three metal-bound motifs. Several biological properties of the GST-hNdCTR1 fusion protein were assessed. It was demonstrated that in cells, the protein was prone to oligomerization, formed inclusion bodies and displayed no toxicity. Treatment of E. coli cells with copper and silver ions reduced cell viability in a dose- and time-dependent manner. Cells expressing GST-hNdCTR1 protein demonstrated resistance to the metal treatments. These cells accumulated silver ions and formed nanoparticles that contained AgCl and metallic silver. In this bacterial population, filamentous bacteria with a length of about 10 µm were often observed. The possibility for the fusion protein carrying extracellular metal binding motifs to integrate into the cell's copper metabolism and its chelating properties are discussed.

Photocatalysts Based on Cobalt-Chelating Conjugated Polymers for Hydrogen Evolution from Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Lianwei; Hadt, Ryan G.; Yao, Shiyu

Developing photocatalytic systems for water splitting to generate oxygen and hydrogen is one of the biggest chemical challenges in solar energy utilization. In this work, we report the first example of heterogeneous photocatalysts for hydrogen evolution based on in-chain cobalt-chelating conjugated polymers. Four conjugated polymers chelated with earth abundant cobalt ions were synthesized and found to evolve hydrogen photocatalytically from water. These polymers are designed to combine functions of the conjugated backbone as light-harvesting antenna and electron transfer conduit with the in-chain bipyridyl chelated transition metal centers as catalytic active sites. In addition, these polymers are soluble in organic solvents,more » enabling effective interactions with the substrates as well as detailed characterization. We also found a polymer-dependent optimal cobalt chelating concentration at which the highest photocatalytic hydrogen production (PHP) activity can be achieved.« less

Interaction of curcumin with Zn(II) and Cu(II) ions based on experiment and theoretical calculation

NASA Astrophysics Data System (ADS)

Zhao, Xue-Zhou; Jiang, Teng; Wang, Long; Yang, Hao; Zhang, Sui; Zhou, Ping

2010-12-01

Curcumin and its complexes with Zn 2+ and Cu 2+ ions were synthesized and characterized by elemental analysis, mass spectroscopy, IR spectroscopy, UV spectroscopy, solution 1H and solid-state 13C NMR spectroscopy, EPR spectroscopy. In addition, the density functional theory (DFT)-based UV and 13C chemical shift calculations were also performed to view insight into those compound structures and properties. The results show that curcumin easily chelate the metal ions, such as Zn 2+ and Cu 2+, and the Cu(II)-curcumin complex has an ability to scavenge free-radicals. We demonstrated the differences between Zn(II)-curcumin and Cu(II)-curcumin complexes in structure and properties, enhancing the comprehensions about the curcumin roles in the Alzhermer's disease treatment.

Magnetic separation of heavy metal ions and evaluation based on surface-enhanced Raman spectroscopy: copper(II) ions as a case study.

PubMed

Yan, Xue; Zhang, Xue-Jiao; Yuan, Ya-Xian; Han, San-Yang; Xu, Min-Min; Gu, Ren'ao; Yao, Jian-Lin

2013-11-01

A new approach was developed for the magnetic separation of copper(II) ions with easy operation and high efficiency. p-Mercaptobenzoic acid served as the modified tag of Fe2O3@Au nanoparticles both for the chelation ligand and Raman reporter. Through the chelation between the copper(II) ions and carboxyl groups on the gold shell, the Fe2O3@Au nanoparticles aggregated to form networks that were enriched and separated from the solution by a magnet. A significant decrease in the concentration of copper(II) ions in the supernatant solution was observed. An extremely sensitive method based on surface-enhanced Raman spectroscopy was employed to detect free copper(II) ions that remained after the magnetic separation, and thus to evaluate the separation efficiency. The results indicated the intensities of the surface-enhanced Raman spectroscopy bands from p-mercaptobenzoic acid were dependent on the concentration of copper(II) ions, and the concentration was decreased by several orders of magnitude after the magnetic separation. The present protocol effectively decreased the total amount of heavy metal ions in the solution. This approach opens a potential application in the magnetic separation and highly sensitive detection of heavy metal ions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermometric titration studies of mixed ligand complexes of thorium.

PubMed

Kugler, G C; Carey, G H

1970-10-01

Mixed-ligand chelates consisting of two different multidentate ligands linked to a central thorium(IV) ion have been prepared in aqueous solution and their heats of formation studied thermo metrically. Pyrocatechol, tiron, chromotropic acid, potassium hydrogen phthalate, 8-hydroxyquinoline-S-sulphonic acid, iminodiacetic acid, 5-sulphosalicylic acid and salicylic acid were used as the secondary ligands, while ethylenediaminetetra-acetate and 1, 2-diaminocyclohexane-N,N,N',N'-tetra-acetate were used as primary ligands. DeltaH values for the overall reactions are given, and where possible, the DeltaH and DeltaS values for the specific secondary ligand addition were calculated. The overall stability of the mixed-ligand chelates and the enhanced stability of EDTA mixed chelates relative to the analogous DCTA chelates were found to be due to entropy rather than enthalpy effects.

Metal-Chelate Immobilization of Lipase onto Polyethylenimine Coated MCM-41 for Apple Flavor Synthesis.

PubMed

Sadighi, Armin; Motevalizadeh, Seyed Farshad; Hosseini, Morteza; Ramazani, Ali; Gorgannezhad, Lena; Nadri, Hamid; Deiham, Behnaz; Ganjali, Mohammad Reza; Shafiee, Abbas; Faramarzi, Mohammad Ali; Khoobi, Mehdi

2017-08-01

An enzyme immobilized on a mesoporous silica nanoparticle can serve as a multiple catalyst for the synthesis of industrially useful chemicals. In this work, MCM-41 nanoparticles were coated with polyethylenimine (MCM-41@PEI) and further modified by chelation of divalent metal ions (M = Co 2+ , Cu 2+ , or Pd 2+ ) to produce metal-chelated silica nanoparticles (MCM-41@PEI-M). Thermomyces lanuginosa lipase (TLL) was immobilized onto MCM-41, MCM-41@PEI, and MCM-41@PEI-M by physical adsorption. Maximum immobilization yield and efficiency of 75 ± 3.5 and 65 ± 2.7% were obtained for MCM@PEI-Co, respectively. The highest biocatalytic activity at extremely acidic and basic pH (pH = 3 and 10) values were achieved for MCM-PEI-Co and MCM-PEI-Cu, respectively. Optimum enzymatic activity was observed for MCM-41@PEI-Co at 75 °C, while immobilized lipase on the Co-chelated support retained 70% of its initial activity after 14 days of storage at room temperature. Due to its efficient catalytic performance, MCM-41@PEI-Co was selected for the synthesis of ethyl valerate in the presence of valeric acid and ethanol. The enzymatic esterification yield for immobilized lipase onto MCM-41@PEI-Co was 60 and 53%, respectively, after 24 h of incubation in n-hexane and dimethyl sulfoxide media. Graphical Abstract Divalent metal chelated polyethylenimine coated MCM-41 (MCM-41@PEI-M) was used for immobilization of Thermomyces lanuginosa lipase catalyzing green apple flavor preparation.

Structural and Antioxidant Properties of Compounds Obtained from Fe2+ Chelation by Juglone and Two of Its Derivatives: DFT, QTAIM, and NBO Studies

PubMed Central

Tamafo Fouegue, Aymard Didier; Bikélé Mama, Désiré; Nkungli, Nyiang Kennet; Younang, Elie

2016-01-01

The chelating ability of juglone and two of its derivatives towards Fe2+ion and the antioxidant activity (AOA) of the resulting chelates and complexes (in the presence of H2O and CH3OH as ligands) in gas phase is reported via bond dissociation enthalpy, ionization potential, proton dissociation enthalpy, proton affinity, and electron transfer enthalpy. The DFT/B3LYP level of theory associated with the 6-31+G(d,p) and 6-31G(d) Pople-style basis sets on the atoms of the ligands and the central Fe(II), respectively, was used. Negative chelation free energies obtained revealed that juglone derivatives possessing the O-H substituent (L2) have the greatest ability to chelate Fe2+ ion. Apart from 1B, thermodynamic descriptors of the AOA showed that the direct hydrogen atom transfer is the preferred mechanism of the studied molecules. NBO analysis showed that the Fe-ligand bonds are all formed through metal to ligand charge transfer. QTAIM studies revealed that among all the Fe-ligand bonds, the O1-Fe bond of 1A is purely covalent. The aforementioned results show that the ligands can be used to fight against Fe(II) toxicity, thus preserving human health, and fight against the deterioration of industrial products. In addition, most of the complexes studied have shown a better AOA than their corresponding ligands. PMID:27774044

An efficient optical-electrochemical dual probe for highly sensitive recognition of dopamine based on terbium complex functionalized reduced graphene oxide

NASA Astrophysics Data System (ADS)

Zhou, Zhan; Wang, Qianming

2014-04-01

A novel organic-inorganic hybrid sensor based on diethylenetriaminepentaacetic acid (DTPA) modified reduced graphene oxide (RGO-DTPA) chelated with terbium ions allows detection of dopamine (DA) through an emission enhancement effect. Its luminescence, peaking at 545 nm, has been improved by a factor of 25 in the presence of DA (detection limit = 80 nM). In addition, this covalently bonded terbium complex functionalized reduced graphene oxide (RGO-DTPA-Tb) can be successfully assembled on a glassy carbon electrode. The assay performed through differential pulse voltammetry (DPV) yielded obvious peak separation between DA and excessive amounts of the interfering ascorbic acid (AA).A novel organic-inorganic hybrid sensor based on diethylenetriaminepentaacetic acid (DTPA) modified reduced graphene oxide (RGO-DTPA) chelated with terbium ions allows detection of dopamine (DA) through an emission enhancement effect. Its luminescence, peaking at 545 nm, has been improved by a factor of 25 in the presence of DA (detection limit = 80 nM). In addition, this covalently bonded terbium complex functionalized reduced graphene oxide (RGO-DTPA-Tb) can be successfully assembled on a glassy carbon electrode. The assay performed through differential pulse voltammetry (DPV) yielded obvious peak separation between DA and excessive amounts of the interfering ascorbic acid (AA). Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06156f

Monitoring the progression of calcium and protein solubilisation as affected by calcium chelators during small-scale manufacture of casein-based food matrices.

PubMed

McIntyre, Irene; O'Sullivan, Michael; O'Riordan, Dolores

2017-12-15

Calcium and protein solubilisation during small-scale manufacture of semi-solid casein-based food matrices was investigated and found to be very different in the presence or absence of calcium chelating salts. Calcium concentrations in the dispersed phase increased and calcium-ion activity (A Ca ++ ) decreased during manufacture of the matrices containing calcium chelating salts; with ∼23% of total calcium solubilised by the end of manufacture. In the absence of calcium chelating salts, these concentrations were significantly lower at equivalent processing times and remained unchanged as did A Ca ++ , throughout manufacture. The protein content of the dispersed phase was low (≤3% of total protein), but was significantly higher for matrices containing calcium chelating salts. This study elucidates the critical role of calcium chelating salts in modulating casein hydration and dispersion and gives an indication of the levels of soluble calcium and protein required to allow matrix formation during manufacture of casein-based food structures e.g. processed and analogue cheese. Copyright © 2017 Elsevier Ltd. All rights reserved.

Copper and Zinc Chelation as a Treatment of Alzheimer's Disease

NASA Astrophysics Data System (ADS)

Hodak, Miroslav; Bernholc, Jerry

2014-03-01

Alzheimer's disease (AD) is a neurodegenerative disorder affecting millions of people in the U.S. The cause of the disease remains unknown, but amyloid- β (A β), a short peptide, is considered causal its pathogenesis. At cellular level, AD is characterized by deposits mainly composed of A β that also contain elevated levels of transition metals ions. Targeting metals is a promising new strategy for AD treatment, which uses moderately strong metal chelators to sequester them from A β or the environment. PBT2 is a chelating compound that has been the most promising in clinical trials. In our work, we use computer simulations to investigate complexes of a close analog of PBT2 with Cu2+ and Zn2+ ions. The calculations employ KS/FD DFT method, which combines Kohn-Sham DFT with the frozen-density DFT to achieve efficient description of explicit solvent beyond the first solvation shell. Our work is based on recent experiments and examines both 1:1 and 2:1 chelator-metal stochiometries detected experimentally. The results show that copper attaches more strongly than zinc, find that 1:1 complexes involve water in the first coordination shell and determine which one of several possible 2:1 geometries is the most preferable.

A gadolinium(III) complex of a carboxylic-phosphorus acid derivative of diethylenetriamine covalently bound to inulin, a potential macromolecular MRI contrast agent.

PubMed

Lebdusková, Petra; Kotek, Jan; Hermann, Petr; Vander Elst, Luce; Muller, Robert N; Lukes, Ivan; Peters, Joop A

2004-01-01

A novel conjugate of a polysaccharide and a Gd(III) chelate with potential as contrast agent for magnetic resonance imaging (MRI) was synthesized. The structure of the chelate was derived from H5DTPA by replacing the central pendant arm by a phosphinic acid functional group, which was covalently bound to the polysaccharide inulin. On the average, each monosaccharide unit of the inulin was attached to approximately one (0.9) chelate moiety. The average molecular weight is 23110 and the average number of Gd3+ ions per molecule is 24. The ligand binds the Gd3+ ion in an octadentate fashion via three nitrogen atoms, four carboxylate oxygen atoms, and one P-O oxygen atom, and its first coordination sphere is completed by a water molecule. This compound shows promising properties for application as a contrast agent for MRI thanks to a favorable residence lifetime of this water molecule (170 ns at 298 K), a relatively long rotational correlation time (866 ps at 298 K), and the presence of two water molecules in the second coordination sphere of the Gd3+ ion. Furthermore, its stability toward transmetalation with Zn(II) is as high as that of the clinically used [Gd(DTPA)(H2O)]2-.

Synthesis, structurale elucidation and antioxidant study of Ortho-substituted N,N’-bis(benzamidothiocarbonyl)hydrazine derivatives

NASA Astrophysics Data System (ADS)

Firdausiah, Syadza; Hasbullah, S. A.; Yamin, B. M.

2018-03-01

Some bis(thiourea) compounds have been reported to posses excellent performance in pharmaceutical and environmental fields because of their ability to form chelating complexes with various anions and metal ions. Structurally for carbonyl thiourea derivatives, to become a chelating agent, it must adopt cis-configuration. In the present study, four new bis(thiourea) derivatives namely N,N’-bis(o-fluorobenzamidothiocarbonyl)hydrazine (1), N,N’- bis(o-chloro-benzamidothiocarbonyl)hydrazine (2), N,N’-bis(o-nitrobenzamidothiocarbonyl)-hydrazine (3), and N,N’-bis(o-methylbenzamidothiocarbonyl)hydrazine (4) were successfully synthesized and characterized by CHNS microelemental analysis, FTIR, UV-Vis, and 1H and 13C NMR spectroscopy. However chemical crystallography study showed that both thiourea moieties in compound (2) and (3) adopt trans geometry. Therefore they are potential monodentate ligand with two active moieties. DPPH radical scavenging experiment showed that compound (1), (2), and (4) exhibited higher antioxidant activity than ascorbic acid (Vitamin C).

SP70-alpha-benzoin oxime chelating resin for preconcentration-separation of Pb(II), Cd(II), Co(II) and Cr(III) in environmental samples.

PubMed

Narin, Ibrahim; Surme, Yavuz; Bercin, Erdogan; Soylak, Mustafa

2007-06-25

In the presented work, alpha-benzoin oxime immobilized SP70 chelating resin was synthesized for separation and preconcentration of Pb(II), Cd(II), Co(II) and Cr(III). The optimization procedure for analytical parameters including pH, eluent type, flow rate, etc. was examined in order to gain quantitative recoveries of analyte ions. The effects of foreign ions on the recoveries of studied metal ions were also investigated. The detection limits (3sigma) were found to be 16.0, 4.2, 1.3, 2.4microgL(-1) for Pb, Cd, Co and Cr, respectively. The preconcentration factor was 75 for Pb, 100 for Cd, Co and Cr. The optimized method was validated with certified reference materials and successfully applied to the waters, crops and pharmaceutical samples with good results (recoveries greater than 95%, R.S.D. lower than 10%).

High in Vivo Stability of 64Cu-Labeled Cross-Bridged Chelators Is a Crucial Factor in Improved Tumor Imaging of RGD Peptide Conjugates.

PubMed

Sarkar, Swarbhanu; Bhatt, Nikunj; Ha, Yeong Su; Huynh, Phuong Tu; Soni, Nisarg; Lee, Woonghee; Lee, Yong Jin; Kim, Jung Young; Pandya, Darpan N; An, Gwang Il; Lee, Kyo Chul; Chang, Yongmin; Yoo, Jeongsoo

2018-01-11

Although the importance of bifunctional chelators (BFCs) is well recognized, the chemophysical parameters of chelators that govern the biological behavior of the corresponding bioconjugates have not been clearly elucidated. Here, five BFCs closely related in structure were conjugated with a cyclic RGD peptide and radiolabeled with Cu-64 ions. Various biophysical and chemical properties of the Cu(II) complexes were analyzed with the aim of identifying correlations between individual factors and the biological behavior of the conjugates. Tumor uptake and body clearance of the 64 Cu-labeled bioconjugates were directly compared by animal PET imaging in animal models, which was further supported by biodistribution studies. Conjugates containing propylene cross-bridged chelators showed higher tumor uptake, while a closely related ethylene cross-bridged analogue exhibited rapid body clearance. High in vivo stability of the copper-chelator complex was strongly correlated with high tumor uptake, while the overall lipophilicity of the bioconjugate affected both tumor uptake and body clearance.

Semiconductor assisted metal deposition for nanolithography applications

DOEpatents

Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

2001-01-01

An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

Semiconductor assisted metal deposition for nanolithography applications

DOEpatents

Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

2002-01-01

An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

Evaluation of antioxidant potential of essential oils of some commonly used Indian spices in in vitro models and in food supplements enriched with omega-6 and omega-3 fatty acids.

PubMed

Bag, Anwesa; Chattopadhyay, Rabi Ranjan

2018-01-01

The aim of this study was to evaluate and compare the antioxidant potential of essential oils of some commonly used Indian spices (black pepper, cinnamon, clove, coriander and cumin) in various in vitro models and in food supplements enriched with omega-6 and omega-3 fatty acids. In vitro antioxidant potential was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging and Fe 2+ ion-chelating methods and lipid oxidation stabilisation potential was evaluated in bulk soybean oil-fish oil mixture and their oil-in-water emulsions using peroxide value (PV), p-anisidine value (p-AV) and total oxidation value as indicators of oxidation. Combination effects using DPPH radical scavenging and Briggs-Rauscher oscillating reaction methods were also evaluated. Test essential oils showed varying degrees of radical scavenging and Fe 2+ ion-chelating efficacy. Clove and coriander oils showed significantly higher (P < 0.05) radical scavenging and Fe 2+ ion-chelating potential over other tested essential oils as well as BHT and ∞-tocopherol. The anti-lipid peroxidative potential of test essential oils was found in the following decreasing order: clove > coriander > BHT > cinnamon > α-tocopherol > cumin > black pepper. Furthermore, clove and coriander oils showed synergistic antioxidant activity in combination both in DPPH radical scavenging and Briggs-Rauscher oscillating reaction methods whereas other possible combinations showed additive effects. Strong radical scavenging and Fe 2+ -chelating as well as anti-lipid peroxidative activities of clove and coriander oils provide evidence that clove and coriander oils may serve as a potential source of natural antioxidants for retarding lipid oxidation of food supplements enriched with omega-6 and omega-3 fatty acids.

Chemical evaluation of HBED/Fe(3+) and the novel HJB/Fe(3+) chelates as fertilizers to alleviate iron chlorosis.

PubMed

López-Rayo, Sandra; Hernández, Diana; Lucena, Juan J

2009-09-23

Iron chelates such as ethylenediamine-N,N'-bis(2-hydroxyphenylacetic) acid (o,o-EDDHA) and their analogues are the most efficient soil fertilizers to treat iron chlorosis in plants growing in calcareous soil. A new chelating agent, HJB (N,N'-bis(2-hydroxy-5-methylphenyl)ethylendiamine-N,N'-diacetic acid) may be an alternative to o,o-EDDHA since its synthesis yields a purer product, but its chemical behavior and efficiency as chlorosis corrector should be evaluated. In this research, a known analogous HBED (N,N'-bis(2-hydroxyphenyl)ethylendiamine-N,N'-diacetic acid) has also been considered. First, an ion-pair high performance liquid chromatography (HPLC) method has been tested for the HJB/Fe(3+) and HBED/Fe(3+) determination. The ability of HJB and HBED to maintain Fe in solution has been compared with respect to o,o-EDDHA. Theoretical modelization for HBED and HJB in agronomic conditions has been done after the determination of the protonation and Ca(II), Mg(II), Fe(III), and Cu(II) stability constants for HJB. Also, batch interaction experiments with soils and soil materials have been conducted. According to our results, HJB/Fe(3+) and HBED/Fe(3+) present high stability, even when competing cations (Cu(2+), Ca(2+)) are present, and have low reactivity with soils and soil components. The chelating agent HJB dissolves a higher amount of Fe than o,o-EDDHA, and it seems as effective as o,o-EDDHA in keeping Fe in solution. These results indicate that these chelates may be very efficient products to correct Fe chlorosis, and additional plant experiments should demonstrate plants' ability to assimilate Fe from HJB/Fe(3+) and HBED/Fe(3+).

Structure and in vitro activities of a Copper II-chelating anionic peptide from the venom of the scorpion Tityus stigmurus.

PubMed

Melo, Menilla M A; Daniele-Silva, Alessandra; Teixeira, Diego G; Estrela, Andréia B; Melo, Karolline R T; Oliveira, Verônica S; Rocha, Hugo A O; Ferreira, Leandro de Santis; Pontes, Daniel L; Lima, João P M S; Silva-Júnior, Arnóbio A; Barbosa, Euzebio G; Carvalho, Eneas; Fernandes-Pedrosa, Matheus F

2017-08-01

Anionic Peptides are molecules rich in aspartic acid (Asp) and/or glutamic acid (Glu) residues in the primary structure. This work presents, for the first time, structural characterization and biological activity assays of an anionic peptide from the venom of the scorpion Tityus stigmurus, named TanP. The three-dimensional structure of TanP was obtained by computational modeling and refined by molecular dynamic (MD) simulations. Furthermore, we have performed circular dichroism (CD) analysis to predict TanP secondary structure, and UV-vis spectroscopy to evaluate its chelating activity. CD indicated predominance of random coil conformation in aqueous medium, as well as changes in structure depending on pH and temperature. TanP has chelating activity on copper ions, which modified the peptide's secondary structure. These results were corroborated by MD data. The molar ratio of binding (TanP:copper) depends on the concentration of peptide: at lower TanP concentration, the molar ratio was 1:5 (TanP:Cu 2+ ), whereas in concentrated TanP solution, the molar ratio was 1:3 (TanP:Cu 2+ ). TanP was not cytotoxic to non-neoplastic or cancer cell lines, and showed an ability to inhibit the in vitro release of nitric oxide by LPS-stimulated macrophages. Altogether, the results suggest TanP is a promising peptide for therapeutic application as a chelating agent. Copyright © 2017 Elsevier Inc. All rights reserved.

SEPARATION PROCESS FOR PROTACTINIUM AND COMPOUNDS THEREOF

DOEpatents

Van Winkle, A.

1959-07-21

The separation of protactinium from aqueous solutions from its mixtures with thorium, uranium and fission products is described. The process for the separation comprises preparing an ion nitric acid solution containing protactinium in the pentavalent state and contacting the solution with a fluorinated beta diketone, such as trifluoroacetylacetone, either alone or as an organic solvent solution to form a pentavalent protactinium chelate compound. When the organic solvent is present the chelate compound is extracted; otherwise it is separated by filtration.

Speciation in Metal Toxicity and Metal-Based Therapeutics

PubMed Central

Templeton, Douglas M.

2015-01-01

Metallic elements, ions and compounds produce varying degrees of toxicity in organisms with which they come into contact. Metal speciation is critical to understanding these adverse effects; the adjectives “heavy” and “toxic” are not helpful in describing the biological properties of individual elements, but detailed chemical structures are. As a broad generalization, the metallic form of an element is inert, and the ionic salts are the species that show more significant bioavailability. Yet the salts and other chelates of a metal ion can give rise to quite different toxicities, as exemplified by a range of carcinogenic potential for various nickel species. Another important distinction comes when a metallic element is organified, increasing its lipophilicity and hence its ability to penetrate the blood brain barrier, as is seen, for example, with organic mercury and tin species. Some metallic elements, such as gold and platinum, are themselves useful therapeutic agents in some forms, while other species of the same element can be toxic, thus focusing attention on species interconversions in evaluating metal-based drugs. The therapeutic use of metal-chelating agents introduces new species of the target metal in vivo, and this can affect not only its desired detoxification, but also introduce a potential for further mechanisms of toxicity. Examples of therapeutic iron chelator species are discussed in this context, as well as the more recent aspects of development of chelation therapy for uranium exposure. PMID:29056656

Study of Anti-Fatigue Effect in Rats of Ferrous Chelates Including Hairtail Protein Hydrolysates

PubMed Central

Huang, Saibo; Lin, Huimin; Deng, Shang-gui

2015-01-01

The ability of ferrous chelates including hairtail protein hydrolysates to prevent and reduce fatigue was studied in rats. After hydrolysis of hairtail surimi with papain, the hairtail protein hydrolysates (HPH) were separated into three groups by range of relative molecular weight using ultrafiltration membrane separation. Hairtail proteins were then chelated with ferrous ions, and the antioxidant activity, the amino acid composition and chelation rate of the three kinds of ferrous chelates including hairtail protein hydrolysates (Fe-HPH) were determined. Among the three groups, the Fe-HPH chelate showing the best conditions was selected for the anti-fatigue animal experiment. For it, experimental rats were randomly divided into seven groups. Group A was designated as the negative control group given distilled water. Group B, the positive control group, was given glutathione. Groups C, D and E were designated as the Fe-HPH chelate treatment groups and given low, medium, and high doses, respectively. Group F was designated as HPH hydrolysate treatment group, and Group G was designated as FeCl2 treatment group. The different diets were orally administered to rats for 20 days. After that time, rats were subjected to forced swimming training after 1 h of gavage. Rats given Fe-FPH chelate had higher haemoglobin regeneration efficiency (HRE), longer exhaustive swimming time and higher SOD activity. Additionally, Fe-FPH chelate was found to significantly decrease the malondialdehyde content, visibly enhance the GSH-Px activity in liver and reduce blood lactic acid of rats. Fe-HPH chelate revealed an anti-fatigue effect, similar to or better than the positive control substance and superior to HPH or Fe when provided alone. PMID:26633476

Demetallization of Enterococcus faecalis biofilm: a preliminary study

PubMed Central

ESTRELA, Carlos; COSTA E SILVA, Rodrigo; URBAN, Roberta Cerasi; GONÇALVES, Pablo José; SILVA, Júlio A.; ESTRELA, Cyntia R.A.; PECORA, Jesus Djalma; PETERS, Ove A.

2018-01-01

Abstract Objectives To determine the concentration of calcium, iron, manganese and zinc ions after the application of chelator to Enterococcus faecalis biofilms. Material and Methods Fifty bovine maxillary central incisors were prepared and inoculated with E. faecalis for 60 days. The following were used as irrigation solutions: 17% EDTA (pH 3, 7 and 10), 2.5% sodium hypochlorite (NaOCl) combined with 17% EDTA (pH 3, 7 and 10), distilled water (pH 3, 7 and 10), and 2.5% NaOCl. Each solution was kept in the root canal for five minutes. Fifteen uncontaminated root canals were irrigated with 17% EDTA (pH 3, 7 and 10). Six teeth were used as bacterial control. The number of calcium, iron, manganese and zinc ions was determined using flame atomic absorption spectrometry. Mean ± standard deviation (SD) values were used for descriptive statistics. Results Calcium chelation using 17% EDTA at pH 7 was higher than at pH 3 and 10, regardless of whether bacterial biofilm was present. The highest concentration of iron occurred at pH 3 in the presence of bacterial biofilm. The highest concentration of manganese found was 2.5% NaOCl and 17% EDTA at pH 7 in the presence of bacterial biofilm. Zinc levels were not detectable. Conclusions The pH of chelating agents affected the removal of calcium, iron, and manganese ions. The concentration of iron ions in root canals with bacterial biofilm was higher after the use of 17% EDTA at pH 3 than after the use of the other solutions at all pH levels. PMID:29451651

Dynamics of paramagnetic agents by off-resonance rotating frame technique in the presence of magnetization transfer effect

NASA Astrophysics Data System (ADS)

Zhang, Huiming; Xie, Yang

2007-02-01

The simple method for measuring the rotational correlation time of paramagnetic ion chelates via off-resonance rotating frame technique is challenged in vivo by the magnetization transfer effect. A theoretical model for the spin relaxation of water protons in the presence of paramagnetic ion chelates and magnetization transfer effect is described. This model considers the competitive relaxations of water protons by the paramagnetic relaxation pathway and the magnetization transfer pathway. The influence of magnetization transfer on the total residual z-magnetization has been quantitatively evaluated in the context of the magnetization map and various difference magnetization profiles for the macromolecule conjugated Gd-DTPA in cross-linked protein gels. The numerical simulations and experimental validations confirm that the rotational correlation time for the paramagnetic ion chelates can be measured even in the presence of strong magnetization transfer. This spin relaxation model also provides novel approaches to enhance the detection sensitivity for paramagnetic labeling by suppressing the spin relaxations caused by the magnetization transfer. The inclusion of the magnetization transfer effect allows us to use the magnetization map as a simulation tool to design efficient paramagnetic labeling targeting at specific tissues, to design experiments running at low RF power depositions, and to optimize the sensitivity for detecting paramagnetic labeling. Thus, the presented method will be a very useful tool for the in vivo applications such as molecular imaging via paramagnetic labeling.

Metal-chelating active packaging film enhances lysozyme inhibition of Listeria monocytogenes.

PubMed

Roman, Maxine J; Decker, Eric A; Goddard, Julie M

2014-07-01

Several studies have demonstrated that metal chelators enhance the antimicrobial activity of lysozyme. This study examined the effect of metal-chelating active packaging film on the antimicrobial activity of lysozyme against Listeria monocytogenes. Polypropylene films were surface modified by photoinitiated graft polymerization of acrylic acid (PP-g-PAA) from the food contact surface of the films to impart chelating activity based on electrostatic interactions. PP-g-PAA exhibited a carboxylic acid density of 113 ± 5.4 nmol cm(-2) and an iron chelating activity of 53.7 ± 9.8 nmol cm(-2). The antimicrobial interaction of lysozyme and PP-g-PAA depended on growth media composition. PP-g-PAA hindered lysozyme activity at low ionic strength (2.48-log increase at 64.4 mM total ionic strength) and enhanced lysozyme activity at moderate ionic strength (5.22-log reduction at 120 mM total ionic strength). These data support the hypothesis that at neutral pH, synergy between carboxylate metal-chelating films (pKa(bulk) 6.45) and lysozyme (pI 11.35) is optimal in solutions of moderate to high ionic strength to minimize undesirable charge interactions, such as lysozyme absorption onto film. These findings suggest that active packaging, which chelates metal ions based on ligand-specific interactions, in contrast to electrostatic interactions, may improve antimicrobial synergy. This work demonstrates the potential application of metal-chelating active packaging films to enhance the antimicrobial activity of membrane-disrupting antimicrobials, such as lysozyme.

Evaluation of Complexation Ability Using a Sensor Electrode Chip Equipped with a Wireless Screening System

PubMed Central

Isoda, Takaaki; Urushibara, Ikuko; Sato, Hikaru; Yamauchi, Noriyoshi

2012-01-01

We fabricated an electrode chip with a structure coated by an insulation layer that contains dispersed SiO2 adsorbent particles modified by an amino-group on a source-drain electrode. Voltage changes caused by chelate molecule adsorption onto electrode surfaces and by specific cation interactions were investigated. The detection of specific cations without the presence of chelate molecules on the free electrode was also examined. By comparing both sets of results the complexation ability of the studied chelate molecules onto the electrode was evaluated. Five pairs of source-drain electrodes(×8 arrays) were fabricated on a glass substrate of 20 × 30mm in size. The individual Au/Cr (1.0/0.1μm thickness) electrodes had widths of 50 μm and an inter-electrode interval of 100μm.The fabricated source-drain electrodes were further coated with an insulation layer comprising a porous SiO2 particle modified amino-group to adsorb the chelate molecules. The electrode chip was equipped with a handy-type sensor signal analyzer that was mounted on an amplifier circuit using a Miniship™ or a system in a packaged LSI device. For electrode surfaces containing different adsorbed chelate molecules an increase in the sensor voltage depended on a combination of host-guest reactions and generally decreased in the following order:5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine, tetrakis(p-toluenesulfonate) (TMPyP)as a Cu2+chelator and Cu2+>2-nitroso-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol(nitroso-PSAP) as an Fe2+chelator and Fe2+>4,7-diphenyl-1,10-phenanthrolinedisulfonic acid, disodium salt (BPDSA) as an Fe2+chelatorand Fe2+>3-[3-(2,4-dimethylphenylcarbamoyl)-2-hydroxynaphthalene-1-yl-azo]-4-hydroxybenzenesulfonic acid, sodium salt (XB-1) as a Mg2+chelator and Mg2+>2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonic acid, disodium salt (BCIDSA) as a Cu2+chelator and Cu2+, respectively. In contrast, for the electrode surfaces with adsorbed O,O′-bis(2-aminoethyl)ethyleneglycol-N,N,N′,N′-tetraacetic acid (GEDTA) or O,O′-bis(2-aminophenyl)ethyleneglycol-N,N,N′,N′-tetraacetic acid, tetrapotassium salt, hydrate (BAPTA) as a Ca2+chelator no increase in the detection voltage was found for all the electrode tests conducted in the presence of Ca2+.To determine the differences in electrode detection, molecular orbital (MO) calculations of the chelate molecules and surface molecular modeling of the adsorbents were carried out. In accordance with frontier orbital theory, the lowest unoccupied MO (LUMO) of the chelate molecules can accept two lone pair electrons at the highest occupied MO (HOMO) of the amino group on the model surface structure of the SiO2 particle. As a result, a good correlation was obtained between the LUMO-HOMO difference and the ion response of all the electrodes tested. Based on the results obtained, the order of adsorbed chelate molecules on adsorption particles reflects the different metal ion detection abilities of the electrode chips. PMID:22969407

Ethylenediaminetetraacetic acid in endodontics

PubMed Central

Mohammadi, Zahed; Shalavi, Sousan; Jafarzadeh, Hamid

2013-01-01

Ethylenediaminetetraacetic acid (EDTA) is a chelating agent can bind to metals via four carboxylate and two amine groups. It is a polyamino carboxylic acid and a colorless, water-soluble solid, which is widely used to dissolve lime scale. It is produced as several salts, notably disodium EDTA and calcium disodium EDTA. EDTA reacts with the calcium ions in dentine and forms soluble calcium chelates. A review of the literature and a discussion of the different indications and considerations for its usage are presented. PMID:24966721

Copper Reduction and Contact Killing of Bacteria by Iron Surfaces

PubMed Central

Mathews, Salima; Kumar, Ranjeet

2015-01-01

The well-established killing of bacteria by copper surfaces, also called contact killing, is currently believed to be a combined effect of bacterial contact with the copper surface and the dissolution of copper, resulting in lethal bacterial damage. Iron can similarly be released in ionic form from iron surfaces and would thus be expected to also exhibit contact killing, although essentially no contact killing is observed by iron surfaces. However, we show here that the exposure of bacteria to iron surfaces in the presence of copper ions results in efficient contact killing. The process involves reduction of Cu2+ to Cu+ by iron; Cu+ has been shown to be considerably more toxic to cells than Cu2+. The specific Cu+ chelator, bicinchoninic acid, suppresses contact killing by chelating the Cu+ ions. These findings underline the importance of Cu+ ions in the contact killing process and infer that iron-based alloys containing copper could provide novel antimicrobial materials. PMID:26150470

Investigation of DOTA-Metal Chelation Effects on the Chemical Shift of 129 Xe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, Keunhong; Slack, Clancy C.; Vassiliou, Christophoros C.

2015-09-17

Recent work has shown that xenon chemical shifts in cryptophane-cage sensors are affected when tethered chelators bind to metals. Here in this paper, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) linked to cryptophane-A. The shifts induced by the binding of Ca 2+, Cu 2+, Ce 3+, Zn 2+, Cd 2+, Ni 2+, Co 2+, Cr 2+, Fe 3+, and Hg 2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding withmore » a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. Lastly, these sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs.« less

Lateral cis-1,3,5,7-tetraazadecalin podands and their complexes: synthesis, structure, and strong binding with Pb(II) and other heavy metal ions.

PubMed

Reany, Ofer; Fuchs, Benzion

2013-02-18

The chemistry and complexation behavior of diaminal podands based on cis-1,3,5,7-tetraazadecalin (cis-TAD) were elaborated, reassessed, and extended. The synthesis of 2,6-bis(hydroxymethylene)-cis-TAD (9) and 2,6-bis(α,α'-dimethyl-β- hydroxyethyl)-cis-TAD (10) as well as of suitably substituted 2,6-diaryl-cis-TAD podands is laid out. For the latter, the effect of electron donating or withdrawing substituents on the benzaldehyde reagents was examined while 9 and 10 were probed and showed considerable propensity for heavy metal-ion chelation. The [Cd(II)·(9)] and [Pb(II)·(9)] complexes stood out indeed, and their structure and properties show a particularly interesting 5-amino-1,3-diazane chelation type and strong ligand-ion binding mode, with intramolecular donor exchange in solution, all strongly influenced by the anomeric effect in the ligand.

Depletion of intracellular zinc from neurons by use of an extracellular chelator in vivo and in vitro.

PubMed

Frederickson, Christopher J; Suh, Sang W; Koh, Jae-Young; Cha, Yoo K; Thompson, Richard B; LaBuda, Christopher J; Balaji, Rengarajan V; Cuajungco, Math P

2002-12-01

The membrane-impermeable chelator CaEDTA was introduced extracellularly among neurons in vivo and in vitro for the purpose of chelating extracellular Zn(2+). Unexpectedly, this treatment caused histochemically reactive Zn(2+) in intracellular compartments to drop rapidly. The same general result was seen with intravesicular Zn(2+), which fell after CaEDTA infusion into the lateral ventricle of the brain, with perikaryal Zn(2+) in Purkinje neurons (in vivo) and with cortical neurons (in vitro). These findings suggest either that the volume of zinc ion efflux and reuptake is higher than previously suspected or that EDTA can enter cells and vesicles. Caution is therefore warranted in attempting to manipulate extracellular or intracellular Zn(2+) selectively.

The use of dihexyldithiocarbamate in reverse-phase HPLC of metal chelates

NASA Astrophysics Data System (ADS)

Fatimah, S. S.; Bahti, H. H.; Hastiawan, I.; Permanasari, A.

2018-05-01

Dialkyldithiocarbamates have long been used as chelating agents in reverse-phase HPLC of transition metals. In the previous study, an alkyl homolog of this type of ligand, namely dihexyldithiocarbamate (DHDTC), was synthesized and characterized. The use of this particular ligand in the revese-phase HPLC of some selected transition metal ions is now reported for the first time. The mobile phase comprising of the flow rate and of the detection, in the separation of the metal chelates of Cd (II), Fe (III), Cu (II), and Co (III), were investigated on a C-18 column. The results showed that dihexylditiocarbamate could be used for separating Cd (II), Fe(III), Cu(II), and Co(III). Therefore, it could be used in simultaneous analysis.

Synthesis and Electrochemical Performance of Urea Assisted Pristine LiMn2O4 Cathode for Li Ion Batteries

NASA Astrophysics Data System (ADS)

Iqbal, Azhar; Iqbal, Yousaf; Khan, Abdul Majeed; Ahmed, Safeer

2017-12-01

We report the synthesis of electrochemically active LiMn2O4 nanoparticles at varied temperature and pH values by sol-gel method using urea as a chelating and combusting agent. The effect of pH and annealing temperature on the structure, morphology and electrochemical performance was evaluated. The results obtained by XRD, SEM, TEM, and FTIR show that LiMn2O4 has uniform porous morphology and highly crystalline particles that can be obtained at pH 7.0 and 8.0 and at a relatively lower temperature of 600°C. Cyclic voltammetry measurements showed reversible redox reactions with fast kinetics corresponding to Li ions intercalation/deintercalation at 600°C at neutral pH 7.0. Charge/discharge studies carried out at a current rate of 40 mA g-1 reveal that LiMn2O4 synthesized at 600°C and pH 7.0 has the best structural stability and excellent cycling performance.

Measurement of Polycyclic Aromatic Hydrocarbons in Airborne Particulate Matter at Low Concentrations

DTIC Science & Technology

2012-03-01

Soil & Water Colorimetric (diphenylcarbazide) 7199 Hexavalent Chromium by Ion Chromatography 218.6 Low level chelation & extraction NATTS...Hexane:Dichloromethane:Methanol Dionex ASE 200 Sample Concentration Evaporation in Ultrapure Nitrogen Stream Zymark Turbovap Solid Phase Extraction Supelco Custom...Glass Silica SPE Cartridge 1% Dichloromethane + 1% Acetone in Hexane GCMS Analysis Conventional Splitless Injection Selective Ion Monitoring

Physicochemical characterization, and relaxometry studies of micro-graphite oxide, graphene nanoplatelets, and nanoribbons.

PubMed

Paratala, Bhavna S; Jacobson, Barry D; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn(2+) ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents.

Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

PubMed Central

Paratala, Bhavna S.; Jacobson, Barry D.; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents. PMID:22685555

Post-hypoxic cellular disintegration in glycine-preserved renal tubules is attenuated by hydroxyl radical scavengers and iron chelators.

PubMed

Moussavian, Mohammed R; Slotta, Jan E; Kollmar, Otto; Menger, Michael D; Gronow, Gernot; Schilling, Martin K

2008-05-01

Cellular stress during reoxygenation is a common phenomenon in solid organ transplantation and is characterized by production of reactive oxygen species. Herein, we studied in isolated tubular segments of rat kidney cortex the impact of oxygen radical scavengers and an iron chelator on post-hypoxic recovery. Tubules, suspended in Ringer's solution containing 5 mM glycine, underwent 30 min hypoxia and 60 min reoxygenation. Untreated tubules served as controls. Hypoxia-reoxygenation injury was measured by membrane leakage, lipid peroxidation and cellular functions. In hypoxia-reoxygenated-isolated tubular segments, protective effects of different scavengers and of the iron chelator deferoxamine on hypoxia-reoxygenation injury were analyzed. Scavengers protected isolated tubular segments from hypoxia-reoxygenation-induced cellular disintegration and dysfunction. Deferoxamine was found to exert the most distinct protection. It was further found to exert a dose-dependent protection on hypoxia-reoxygenation damage in isolated tubular segments, which was critically mediated by chelating tissue and bond iron. Our data demonstrate that radical scavengers effectively protect from hypoxia-reoxygenation injury in isolated tubular segments and that the iron chelator deferoxamine is especially a potent inhibitor of iron ion-mediated hypoxia-reoxygenation damage. Thus, inclusion of this iron chelator in organ storage solutions might improve post-transplant organ function and protect from reperfusion injury.

Fluoride ion recognition by chelating and cationic boranes.

PubMed

Hudnall, Todd W; Chiu, Ching-Wen; Gabbaï, François P

2009-02-17

Because of the ubiquity of fluoride ions and their potential toxicity at high doses, researchers would like to design receptors that selectively detect this anion. Fluoride is found in drinking water, toothpaste, and osteoporosis drugs. In addition, fluoride ions also can be detected as an indicator of uranium enrichment (via hydrolysis of UF(6)) or of the chemical warfare agent sarin, which releases the ion upon hydrolysis. However, because of its high hydration enthalpy, the fluoride anion is one of the most challenging targets for anion recognition. Among the various recognition strategies that are available, researchers have focused a great deal of attention on Lewis acidic boron compounds. These molecules typically interact with fluoride anions to form the corresponding fluoroborate species. In the case of simple triarylboranes, the fluoroborates are formed in organic solvents but not in water. To overcome this limitation, this Account examines various methods we have pursued to increase the fluoride-binding properties of boron-based receptors. We first considered the use of bifunctional boranes, which chelate the fluoride anion, such as 1,8-diborylnaphthalenes or heteronuclear 1-boryl-8-mercurio-naphthalenes. In these molecules, the neighboring Lewis acidic atoms can cooperatively interact with the anionic guest. Although the fluoride binding constants of the bifunctional compounds exceed those of neutral monofunctional boranes by several orders of magnitude, the incompatibility of these systems with aqueous media limits their utility. More recently, we have examined simple triarylboranes whose ligands are decorated by cationic ammonium or phosphonium groups. These cationic groups increase the electrophilic character of these boranes, and unlike their neutral analogs, they are able to complex fluoride in aqueous media. We have also considered cationic boranes, which form chelate complexes with fluoride anions. Our work demonstrates that Coulombic and chelate effects are additive and can be combined to boost the anion affinity of Lewis acidic hosts. The boron compounds that we have investigated present a set of photophysical and electrochemical properties that can serve to signal the fluoride-binding event. We can also apply this approach to cyanide complexation and are continuing our investigations in that area.

Metal-chelating polymers by anionic ring-opening polymerization and their use in quantitative mass cytometry.

PubMed

Illy, Nicolas; Majonis, Daniel; Herrera, Isaac; Ornatsky, Olga; Winnik, Mitchell A

2012-08-13

Metal-chelating polymers (MCPs) are important reagents for multiplexed immunoassays based on mass cytometry. The role of the polymer is to carry multiple copies of individual metal isotopes, typically as lanthanide ions, and to provide a reactive functionality for convenient attachment to a monoclonal antibody (mAb). For this application, the optimum combination of chain length, backbone structure, end group, pendant groups, and synthesis strategy has yet to be determined. Here we describe the synthesis of a new type of MCP based on anionic ring-opening polymerization of an activated cyclopropane (the diallyl ester of 1,1-cyclopropane dicarboxylic acid) using a combination of 2-furanmethanethiol and a phosphazene base as the initiator. This reaction takes place with rigorous control over molecular weight, yielding a polymer with a narrow molecular weight distribution, reactive pendant groups for introducing a metal chelator, and a functional end group with orthogonal reactivity for attaching the polymer to the mAbs. Following the ring-opening polymerization, a two-step transformation introduced diethylenetriaminepentaacetic acid (DTPA) chelating groups on each pendant group. The polymers were characterized by NMR, size exclusion chromatography (SEC), and thermogravimetric analysis (TGA). The binding properties toward Gd(3+) as a prototypical lanthanide (Ln) ion were also studied by isothermal titration calorimetry (ITC). Attachment to a mAb involves a Diels-Alder reaction of the terminal furan with a bismaleimide, followed by a Michael addition of a thiol on the mAb, generated by mild reduction of a disulfide bond in the hinge region. Polymer samples with a number average degree of polymerization of 35, with a binding capacity of 49.5 ± 6 Ln(3+) ions per chain, were loaded with 10 different types of Ln ions and conjugated to 10 different mAbs. A suite of metal-tagged Abs was tested by mass cytometry in a 10-plex single cell analysis of human adult peripheral blood, allowing us to quantify the antibody binding capacity of 10 different cell surface antigens associated with specific cell types.

Phenomenon of hot-cold hemolysis: chelator-induced lysis of sphingomyelinase-treated erythrocytes.

PubMed Central

Smyth, C J; Möllby, R; Wadström, T

1975-01-01

Staphylococcus aureus produces a phospholipase C specific for sphingomyelin (beta-hemolysin). Erythrocytes with approximately 50% sphingomyelin in their membranes, e.g., from sheep, have been shown to have up to 60% of this phospholipid hydrolyzed by this enzyme at 37 C in isotonic buffered saline without hemolysis. Cooling of sphingomyelinase C-treated erythrocytes to 4 C causes complete lysis of the cells, a phenomenon known as hot-cold hemolysis. The addition of ethylenediaminetetraacetate (EDTA) to sheep erythrocytes preincubated with sphingomyelinase C was found to induce rapid hemolysis at 37 C. The treated cells became susceptible to chelator-induced hemolysis and to hot-cold hemolysis simultaneously, and the degree of lysis of both mechanisms increased equally with prolonged preincubation with sphingomyelinase C. Erythrocytes of species not readily susceptible to hot-cold hemolysis were equally insusceptible to chelator-induced lysis. Chelators of the EDTA series were the most effective, whereas chelators more specific for Ca2+, Zn2+, Fe2+, Cu2+, and Mg2+ were without effect. The rate of chelator-induced lysis was dependent on the preincubation period with beta-hemolysin and on the concentration of chelator added. The optimal concentration of EDTA was found to equal the amount of exogenously added Mg2+, a cation necessary for sphingomyelinase C activity. Hypotonicity increased the rate of chelator-induced hemolysis, whereas increasing the osmotic pressure to twice isotonic completely inhibited chelator-induced lysis. The data suggest that exogenously added and/or membrane-bound divalent cations are important for the stability of sphingomyelin-depleted membranes. The phenomenon of hot-cold hemolysis may be a consequence of the temperature dependence of divalent ion stabilization. Images PMID:333

Lanthanide-IMAC enrichment of carbohydrates and polyols.

PubMed

Schemeth, Dieter; Rainer, Matthias; Messner, Christoph B; Rode, Bernd M; Bonn, Günther K

2014-03-01

In this study a new type of immobilized metal ion affinity chromatography resin for the enrichment of carbohydrates and polyols was synthesized by radical polymerization reaction of vinyl phosphonic acid and 1,4-butandiole dimethacrylate using azo-bis-isobutyronitrile as radical initiator. Interaction between the chelated trivalent lanthanide ions and negatively charged hydroxyl groups of carbohydrates and polyols was observed by applying high pH values. The new method was evaluated by single standard solutions, mixtures of standards, honey and a more complex extract of Cynara scolymus. The washing step was accomplished by acetonitrile in excess volumes. Elution of enriched carbohydrates was successfully performed with deionized water. The subsequent analysis was carried out with matrix-free laser desorption/ionization-time of flight mass spectrometry involving a TiO2 -coated steel target, especially suitable for the measurement of low-molecular-weight substances. Quantitative analysis of the sugar alcohol xylitol as well as the determination of the maximal loading capacity was performed by gas chromatography in conjunction with mass spectrometric detection after chemical derivatization. In a parallel approach quantum mechanical geometry optimizations were performed in order to compare the coordination behavior of various trivalent lanthanide ions. Copyright © 2013 John Wiley & Sons, Ltd.

Potassium fulvate-modified graft copolymer of acrylic acid onto cellulose as efficient chelating polymeric sorbent.

PubMed

Mohamed, Magdy F; Essawy, Hisham A; Ammar, Nabila S; Ibrahim, Hanan S

2017-01-01

Acrylic acid (AA) was graft copolymerized from cellulose (Cell) in presence of potassium fulvate (KF) in order to enhance the chemical activity of the resulting chelating polymer and the handling as well. Fourier transform infrared (FTIR) proved that KF was efficiently inserted and became a permanent part of the network structure of the sorbent in parallel during the grafting copolymerization. Scanning electron microscopy (SEM) revealed intact homogeneous structure with uniform surface. This indicates improvement of the handling, however, it was not the case for the graft copolymer of acrylic acid onto cellulose in absence of KF, which is known to be brittle and lacks mechanical integrity. Effective insertion of this co-interpenetrating agent provided more functional groups, such as OH and COOH, which improved the chelating power of the produced sorbent as found for the removal of Cu 2+ ions from its aqueous solutions (the removal efficiency reached ∼98.9%). Different models were used to express the experimental data. The results corroborated conformity of the pseudo-second order kinetic model and Langmuir isotherm model to the sorption process, which translates into dominance of the chemisorption. Regeneration of the chelating polymers under harsh conditions did not affect the efficiency of copper ions uptake up to three successive cycles. A thermodynamic investigation ensured exothermic nature of the adsorption process that became less favourable at higher temperatures. Copyright © 2016 Elsevier B.V. All rights reserved.

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: Spectroscopic and thermal characterization

NASA Astrophysics Data System (ADS)

Mohamed, Gehad G.; Nour El-Dien, F. A.; El-Nahas, R. G.

2011-10-01

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic- OH, -NH and carbonyl- O, while VMA is coordinated with OO donor sites of the phenolic- OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Pistachio (Pistacia vera L.) gum: a potent inhibitor of reactive oxygen species.

PubMed

Sehitoglu, M Hilal; Han, Hatice; Kalin, Pınar; Gülçin, İlhami; Ozkan, Ali; Aboul-Enein, Hassan Y

2015-04-01

In the present study, in order to evaluate antioxidant and radical scavenging properties of Pistachio gum (P-Gum), different bioanalytical methods such as DPPH(•) scavenging activity, DMPD(•+) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, reducing ability Fe(3+)-Fe(2+) transformation, Cuprac and FRAP assays, O2(•-) scavenging by riboflavin-methionine-illuminate system and ferrous ions (Fe(2+)) chelating activities by 2,2'-bipyridyl reagent were performed separately. P-Gum inhibited 54.2% linoleic acid peroxidation at 10 µg/ml concentration. On the other hand, BHA, BHT, α-tocopherol and trolox, pure antioxidant compounds, indicated inhibition of 80.3%, 73.5%, 36.2% and 72.0% on peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, all of sample had an effective DPPH(•), DMPD(•+) and O2(•-) scavenging, Fe(3+) reducing power by Fe(3+)-Fe(2+) transformation and FRAP assay, Cu(2+) reducing ability by Cuprac method and Fe(2+) chelating activities.

Determination of residual fluoroquinolones in honey by liquid chromatography using metal chelate affinity chromatography.

PubMed

Yatsukawa, Yoh-Ichi; Ito, Hironobu; Matsuda, Takahiro; Nakamura, Munetomo; Watai, Masatoshi; Fujita, Kazuhiro

2011-01-01

A new analytical method for the simultaneous determination of seven fluoroquinolones, namely, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, orbifloxacin, sarafloxacin, and difloxacin, especially in dark-colored honey, has been developed. Fluoroquinolone antibiotics were extracted from samples with MacIlvaine buffer solution (pH 4.0) containing EDTA disodium salt dihydrate. The extracts were treated with both a polymeric cartridge and a metal chelate affinity column preloaded with ferric ion (Fe3+). LC separation with fluorescence detection was performed at 40 degrees C using an Inertsil ODS-4 analytical column (150 x 4.6 mm, 3 microm). The mobile phase was composed of 20 mM/L citrate buffer solution (pH 3.1)-acetonitrile mixture (70 + 30, v/v) containing 1 mM/L sodium dodecyl sulfate. Lomefloxacin was used as an internal standard. The developed method was validated according to the criteria of European Commission Decision 2002/657/EC. Decision limits and detection capabilities were below 2.9 and 4.4 microg/kg, respectively.

Spectral, biological screening of metal chelates of chalcone based Schiff bases of N-(3-aminopropyl) imidazole.

PubMed

Kalanithi, M; Rajarajan, M; Tharmaraj, P; Sheela, C D

2012-02-15

Tridentate chelate complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the chalcone based ligands 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol(HL(1)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-p-tolylallyl]phenol(HL(2)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol(HL(3)). Microanalytical data, UV-vis spectrophotometric method, magnetic susceptibility measurements, IR, 1H NMR, Mass, and EPR techniques were used to characterize the structure of chelates. The electronic absorption spectra and magnetic susceptibility measurements suggest a distorted square planar geometry for the copper(II) ion. The other metal complexes show distorted tetrahedral geometry. The coordination of the ligands with metal(II) ions was further confirmed by solution fluorescence spectrum. The antimicrobial activity of the ligands and metal(II) complexes against the species Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albigans and Aspergillus niger has been carried out and compared. The electrochemical behavior of copper(II) complex is studied by cyclic voltammetry. Copyright © 2011 Elsevier B.V. All rights reserved.

Evaluation of immobilized metal-ion affinity chromatography (IMAC) as a technique for IgG(1) monoclonal antibodies purification: the effect of chelating ligand and support.

PubMed

Bresolin, I T L; Borsoi-Ribeiro, M; Tamashiro, W M S C; Augusto, E F P; Vijayalakshmi, M A; Bueno, S M A

2010-04-01

Monoclonal antibodies (MAbs) have been used for therapies and some analytical procedures as highly purified molecules. Many techniques have been applied and studied, focusing on monoclonal antibodies purification. In this study, an immobilized metal affinity chromatography membrane was developed and evaluated for the purification of anti-TNP IgG(1) mouse MAbs from cell culture supernatant after precipitation with a 50% saturated ammonium sulfate solution. The chelating ligands iminodiacetic acid, carboxymethylated aspartic acid (CM-Asp), nitrilotriacetic acid, and tris (carboxymethyl) ethylenediamine in agarose gels with immobilized Ni(II) and Zn(II) ions were compared for the adsorption and desorption of MAbs. The most promising chelating ligand--CM-Asp--was then coupled to poly(ethylene vinyl alcohol) (PEVA) hollow fiber membranes. According to SDS-PAGE and ELISA analyses, a higher selectivity and a purification factor of 85.9 (fraction eluted at 500 mM Tris) were obtained for IgG(1) using PEVA-CM-Asp-Zn(II). The anti-TNP MAb could be eluted under mild pH conditions causing no loss of antigen binding capacity.

Iron Chelation Nanoparticles with Delayed Saturation as an Effective Therapy for Parkinson Disease.

PubMed

Wang, Nan; Jin, Xin; Guo, Dongbo; Tong, Gangsheng; Zhu, Xinyuan

2017-02-13

Iron accumulation in substantia nigra pars compacta (SNpc) has been proved to be a prominent pathophysiological feature of Parkinson's diseases (PD), which can induce the death of dopaminergic (DA) neurons, up-regulation of reactive oxygen species (ROS), and further loss of motor control. In recent years, iron chelation therapy has been demonstrated to be an effective treatment for PD, which has shown significant improvements in clinical trials. However, the current iron chelators are suboptimal due to their short circulation time, side effects, and lack of proper protection from chelation with ions in blood circulation. In this work, we designed and constructed iron chelation therapeutic nanoparticles protected by a zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) to delay the saturation of iron chelators in blood circulation and prolong the in vivo lifetime, with HIV-1 trans-activating transcriptor (TAT) served as a shuttle to enhance the blood-brain barrier (BBB) permeability. We explored and investigated whether the Parkinsonian neurodegeneration and the corresponding symptoms in behaviors and physiologies could be prevented or reversed both in vitro and in vivo. The results demonstrated that iron chelator loaded therapeutic nanoparticles could reverse functional deficits in Parkinsonian mice not only physiologically but also behaviorally. On the contrary, both untreated PD mice and non-TAT anchored nanoparticle treated PD mice showed similar loss in DA neurons and difficulties in behaviors. Therefore, with protection of zwitterionic polymer and prolonged in vivo lifetime, iron chelator loaded nanoparticles with delayed saturation provide a PD phenotype reversion therapy and significantly improve the living quality of the Parkinsonian mice.

Clioquinol-zinc chelate: a candidate causative agent of subacute myelo-optic neuropathy.

PubMed Central

Arbiser, J. L.; Kraeft, S. K.; van Leeuwen, R.; Hurwitz, S. J.; Selig, M.; Dickersin, G. R.; Flint, A.; Byers, H. R.; Chen, L. B.

1998-01-01

BACKGROUND: 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol) was used clinically three decades ago as an oral antiparasitic agent and to increase intestinal absorption of zinc in patients with acrodermatitis enteropathica, a genetic disorder of zinc absorption. Use of clioquinol was epidemiologically linked to subacute myelo-optic neuropathy (SMON), characterized by peripheral neuropathy and blindness, which affected 10,000 patients in Japan. Discontinuation of oral clioquinol use led to elimination of SMON, however, the mechanism of how clioquinol induces neurotoxicity is unclear. MATERIALS AND METHODS: We tested the effect of clioquinol-metal chelates on neural crest-derived melanoma cells. The effect of clioquinol chelates on cells was further studied by electron microscopy and by a mitochondrial potential-sensitive fluorescent dye. RESULTS: Of the ions tested, only clioquinol-zinc chelate demonstrated cytotoxicity. The cytotoxicity of clioquinol-zinc chelate was extremely rapid, suggesting that its primary effect was on the mitochondria. Electron microscopic analysis demonstrated that clioquinol-zinc chelate caused mitochondrial damage. This finding was further confirmed by the observation that clioquinol-zinc chelate caused a decrease in mitochondrial membrane potential. CONCLUSIONS: We demonstrate that clioquinol, in the presence of zinc, is converted to a potent mitochondrial toxin. The phenomenon of clioquinol mediated toxicity appears to be specific to zinc and is not seen with other metals tested. Since clioquinol has been shown to cause increased systemic absorption of zinc in humans, it is likely that clioquinol-zinc chelate was present in appreciable levels in patients with SMON and may be the ultimate causative toxin of SMON. Images Fig. 2 Fig. 3 PMID:9848083

Modelling studies in aqueous solution of lanthanide (III) chelates designed for nuclear magnetic resonance biomedical applications

NASA Astrophysics Data System (ADS)

Henriques, E. S.; Geraldes, C. F. G. C.; Ramos, M. J.

Molecular dynamics simulations and complementary modelling studies have been carried out for the [Gd(DOTA)·(H2O)]- and [Tm(DOTP)]5- chelates in aqueous media, to provide a better understanding of several structural and dynamical properties of these versatile nuclear magnetic resonance (NMR) probes, including coordination shells and corresponding water exchange mechanisms, and interactions of these complexes with alkali metal ions. This knowledge is of key importance in the areas of 1H relaxation and shift reagents for NMR applications in medical diagnosis. A new refinement of our own previously developed set of parameters for these Ln(III) chelates has been used, and is reported here. Calculations of water mean residence times suggest a reassessment of the characterization of the chelates' second coordination shell, one where the simple spherical distribution model is discarded in favour of a more detailed approach. Na+ probe interaction maps are in good agreement with the available site location predictions derived from 23Na NMR shifts.

Zinc chelation with hydroxamate in histone deacetylases modulated by water access to the linker binding channel.

PubMed

Wu, Ruibo; Lu, Zhenyu; Cao, Zexing; Zhang, Yingkai

2011-04-27

It is of significant biological interest and medical importance to develop class- and isoform-selective histone deacetylase (HDAC) modulators. The impact of the linker component on HDAC inhibition specificity has been revealed but is not understood. Using Born-Oppenheimer ab initio QM/MM MD simulations, a state-of-the-art approach to simulating metallo-enzymes, we have found that the hydroxamic acid remains to be protonated upon its binding to HDAC8, and thus disproved the mechanistic hypothesis that the distinct zinc-hydroxamate chelation modes between two HDAC subclasses come from different protonation states of the hydroxamic acid. Instead, our simulations suggest a novel mechanism in which the chelation mode of hydroxamate with the zinc ion in HDACs is modulated by water access to the linker binding channel. This new insight into the interplay between the linker binding and the zinc chelation emphasizes its importance and gives guidance regarding linker design for the development of new class-IIa-specific HDAC inhibitors.

Nucleic acid nanomaterials: Silver-wired DNA

NASA Astrophysics Data System (ADS)

Auffinger, Pascal; Ennifar, Eric

2017-10-01

DNA double helical structures are supramolecular assemblies that are typically held together by classical Watson-Crick pairing. Now, nucleotide chelation of silver ions supports an extended silver-DNA hybrid duplex featuring an uninterrupted silver array.

Synthesis, characterization and physicochemical studies of new chelating resin 1, 8-(3, 6-dithiaoctyl)-4-polyvinylbenzenesulphonate (dpvbs) and its metallopolymer Cu(II), Ni(II), Co(II) and Fe(III) complexes

NASA Astrophysics Data System (ADS)

Khalil, Tarek E.; Elbadawy, Hemmat A.; El-Dissouky, Ali

2018-02-01

A new chelating resin, 1,8-(3,6-dithiaoctyl)-4-polyvinylbenzenesulphonate (dpvbs) has been synthesized by coupling Amberlite XAD-16 with (2,2‧-ethylenedithio) diethanol using pyridine/CH2Cl2 mixture as a solvent. The chelating resin and its metallopolymer Cu(II), Ni(II), Co(II) and Fe(III) complexes have been synthesized and characterized by EDS, SEM, XPS, elemental analysis, spectral (IR, UV/Vis, EPR). The thermal analysis of the resin and its metallopolymer complexes indicated an endothermic spontaneous sorption mechanism with the liberation of water of hydration of the metal ions and that adsorbed by the free resin. At the solid liquid interface, the degrees of freedom increased during the sorption of the metal ions onto the resin. The surface area of polymer support and its metallopolymer complexes are estimated by (BJH) method. The batch equilibrium method was used for studying the metal sorption and selectivity at different pH values and different contact times at room temperature. ICP-AES was used to estimate the metal capacity of the resin for sorption of Cu(II), Ni(II), Co(II) and Fe(III) from aqueous solutions utilizing the batch equilibrium method. The sorption tendency of the metal ions by the resin was found to be: Cu(II) > Fe(III) > Co(II) > Ni(II). Adsorption kinetics was found to be fit the pseudo-second order model.

The ALMT family of organic acid transporters in plants and their involvement in detoxification and nutrient security

USDA-ARS?s Scientific Manuscript database

About a decade ago, members of a new protein family of anion channels were discovered on the basis of their ability to confer on plants the tolerance towards toxic aluminum ions in the soil. The efflux of Al3+ chelating malate anions through these channels is stimulated by external Al3+ ions. This f...

Efficient removal of heavy metal ions from aqueous solution using salicylic acid type chelate adsorbent.

PubMed

An, Fuqiang; Gao, Baojiao; Dai, Xin; Wang, Min; Wang, Xiaohua

2011-09-15

In this study, 5-aminosalicylic acid was successfully grafted onto the poly(glycidyl methacrylate) (PGMA) macromolecular chains of PGMA/SiO(2) to obtain a novel adsorbent designated as ASA-PGMA/SiO(2). The adsorption properties of ASA-PGMA/SiO(2) for heavy metal ions were studied through batch and column methods. The experimental results showed that ASA-PGMA/SiO(2) possesses strong chelating adsorption ability for heavy metal ions, and its adsorption capacity for Cu(2+), Cd(2+), Zn(2+), and Pb(2+) reaches 0.42, 0.40, 0.35, and 0.31 mmol g(-1), respectively. In addition, pH has a great influence on the adsorption capacity in the studied pH range. The adsorption isotherm data greatly obey the Langmuir and Freundlich model. The desorption of metal ions from ASA-PGMA/SiO(2) is effective using 0.1 mol l(-1) of hydrochloric acid solution as eluent. Consecutive adsorption-desorption experiments showed that ASA-PGMA/SiO(2) could be reused almost without any loss in the adsorption capacity. Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis and characterization of an N-(2-hydroxyethyl)-ethylenediaminetriacetic acid resin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Yuet Fan

1977-10-01

A chelating ion-exchange resin with N-(2-hydroxyethyl)ethylene-diaminetriacetic acid (HEDTA) used as the ligand chemically bonded to XAD-4 by an ester linkage, HEDTA-4, was synthesized. It is stable under normal experimental conditions with the liquid chromatograph. The structure of the resin was confirmed by an infrared spectrum, and by potentiometric titrations. The capacity of the resin was also obtained by potentiometric titration and by a nitrogen analysis. The resin was used to pack a column of 5 mm internal diameter and 5 cm long. The effect of pH on the retention of different metal ions on the resin was studied. It wasmore » found that the resin was most selective for chromium(III), copper(II), lead(II), mercury(II), uranium(VI), zirconium(IV) and zinc(II) at a pH of less than 3. Furthermore, the resin proves to be functioning with a chelating mechanism rather than ion-exchange, and it can concentrate trace metal ions in the presence of a large excess of calcium and magnesium. This makes the resin potentially useful for purifying and analyzing drinking water.« less

Method and apparatus for back-extracting metal chelates

DOEpatents

Wai, Chien M.; Smart, Neil G.; Lin, Yuehe

1998-01-01

A method of extracting metal and metalloid species from a solid or liquid substrate using a supercritical fluid solvent containing one or more chelating agents followed by back-extracting the metal and metalloid species from the metal and metalloid chelates formed thereby. The back-extraction acidic solution is performed utilizing an acidic solution. Upon sufficient exposure of the metal and metalloid chelates to the acidic solution, the metal and metalloid species are released from the chelates into the acid solution, while the chelating agent remains in the supercritical fluid solvent. The chelating agent is thereby regenerated and the metal and metalloid species recovered.

Assessment of iron chelates efficiency for photo-Fenton at neutral pH.

PubMed

De Luca, Antonella; Dantas, Renato F; Esplugas, Santiago

2014-09-15

In this study, homogeneous photo-Fenton like at neutral pH was applied to remove sulfamethoxazole from water. The process was performed using different chelating agents in order to solubilize iron in a neutral water solution. The chelating agents tested were: ethylenediaminetetraacetic acid (EDTA); nitrilotriacetic acid (NTA); oxalic acid (OA) and tartaric acid (TA). The iron leaching was monitored over reaction time to evaluate the chelates stability and their resistance to HO· and UV-A radiation. Chelates of EDTA and NTA presented more stability than OA and TA, which also confirmed their higher efficiency. Total Organic Carbon (TOC) analyses were also performed to evaluate the contribution in terms of solution contamination related to the use of chelating agents. The better properties of biodegradability in respect of EDTA combined with better efficiency in terms of microcontaminant removal and the smallest TOC contribution indicate that NTA could represent a useful option to perform photo-Fenton processes at neutral pH. Copyright © 2014 Elsevier Ltd. All rights reserved.

Economical recycling process for spent lithium-ion batteries and macro- and micro-scale mechanistic study

NASA Astrophysics Data System (ADS)

Li, Li; Bian, Yifan; Zhang, Xiaoxiao; Xue, Qing; Fan, Ersha; Wu, Feng; Chen, Renjie

2018-02-01

An economical effective method is developed for recycling spent LiNi1/3Co1/3Mn1/3O2 cathodes, where more than 98% Li, Co, Ni and Mn can be leached out with different organic acids, and resynthesized to LiNi1/3Co1/3Mn1/3O2. The leaching mechanism is investigated at macro- and micro-scales. The particles undergo a loosening-breaking-shrinking change for two acids, while the FTIR and UV-vis spectra indicate different coordination reactions. The performance of LiNi1/3Co1/3Mn1/3O2 resynthesized from the leachate of the acetic acid leaching (NCM-Ac) and maleic acid leaching (NCM-Ma) are compared. The first discharge capacity of NCM-Ma and NCM-Ac at 0.2C are 151.6 and 115.0 mA h g-1, respectively. The much better performance of NCM-Ma than NCM-Ac results from the different coordination of the two acids in the sol-gel process, where the maleic acid can esterify to establish a stable network to chelate metal ions, while the weak chelation of acetic acid leads to the formation of impurities. The economics analysis including the cost of leaching acid and energy consumption shows that the price of organic acids and reducing agents, short leaching time, low temperature and high-valued products are the effective way to increase recycling and environmental benefits, which shows advantages in terms of resources cost and added value.

Development of peptoid-based ligands for the removal of cadmium from biological media

DOE PAGES

Knight, Abigail S.; Zhou, Effie Y.; Francis, Matthew B.

2015-05-14

Cadmium poisoning poses a serious health concern due to cadmium's increasing industrial use, yet there is currently no recommended treatment. The selective coordination of cadmium in a biological environment—i.e. in the presence of serum ions, small molecules, and proteins—is a difficult task. To address this challenge, a combinatorial library of peptoid-based ligands has been evaluated to identify structures that selectively bind to cadmium in human serum with minimal chelation of essential metal ions. Eighteen unique ligands were identified in this screening procedure, and the binding affinity of each was measured using metal titrations monitored by UV-vis spectroscopy. To evaluate themore » significance of each chelating moiety, sequence rearrangements and substitutions were examined. Analysis of a metal–ligand complex by NMR spectroscopy highlighted the importance of particular residues. Depletion experiments were performed in serum mimetics and human serum with exogenously added cadmium. These depletion experiments were used to compare and demonstrate the ability of these peptoids to remove cadmium from blood-like mixtures. In one of these depletion experiments, the peptoid sequence was able to deplete the cadmium to a level comparable to the reported acute toxicity limit. Evaluation of the metal selectivity in buffered solution and in human serum was performed to verify minimal off-target binding. These studies highlight a screening platform for the identification of metal–ligands that are capable of binding in a complex environment. They additionally demonstrate the potential utility of biologically-compatible ligands for the treatment of heavy metal poisoning.« less

Development of peptoid-based ligands for the removal of cadmium from biological media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knight, Abigail S.; Zhou, Effie Y.; Francis, Matthew B.

Cadmium poisoning poses a serious health concern due to cadmium's increasing industrial use, yet there is currently no recommended treatment. The selective coordination of cadmium in a biological environment—i.e. in the presence of serum ions, small molecules, and proteins—is a difficult task. To address this challenge, a combinatorial library of peptoid-based ligands has been evaluated to identify structures that selectively bind to cadmium in human serum with minimal chelation of essential metal ions. Eighteen unique ligands were identified in this screening procedure, and the binding affinity of each was measured using metal titrations monitored by UV-vis spectroscopy. To evaluate themore » significance of each chelating moiety, sequence rearrangements and substitutions were examined. Analysis of a metal–ligand complex by NMR spectroscopy highlighted the importance of particular residues. Depletion experiments were performed in serum mimetics and human serum with exogenously added cadmium. These depletion experiments were used to compare and demonstrate the ability of these peptoids to remove cadmium from blood-like mixtures. In one of these depletion experiments, the peptoid sequence was able to deplete the cadmium to a level comparable to the reported acute toxicity limit. Evaluation of the metal selectivity in buffered solution and in human serum was performed to verify minimal off-target binding. These studies highlight a screening platform for the identification of metal–ligands that are capable of binding in a complex environment. They additionally demonstrate the potential utility of biologically-compatible ligands for the treatment of heavy metal poisoning.« less

In silico strategies for the selection of chelating compounds with potential application in metal-promoted neurodegenerative diseases

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, Cristina; Rimola, Albert; Alí-Torres, Jorge; Sodupe, Mariona; González-Duarte, Pilar

2011-01-01

The development of new strategies to find commercial molecules with promising biochemical features is a main target in the field of biomedicine chemistry. In this work we present an in silico-based protocol that allows identifying commercial compounds with suitable metal coordinating and pharmacokinetic properties to act as metal-ion chelators in metal-promoted neurodegenerative diseases (MpND). Selection of the chelating ligands is done by combining quantum chemical calculations with the search of commercial compounds on different databases via virtual screening. Starting from different designed molecular frameworks, which mainly constitute the binding site, the virtual screening on databases facilitates the identification of different commercial molecules that enclose such scaffolds and, by imposing a set of chemical and pharmacokinetic filters, obey some drug-like requirements mandatory to deal with MpND. The quantum mechanical calculations are useful to gauge the chelating properties of the selected candidate molecules by determining the structure of metal complexes and evaluating their stability constants. With the proposed strategy, commercial compounds containing N and S donor atoms in the binding sites and capable to cross the BBB have been identified and their chelating properties analyzed.

Influence of the environment on the [4Fe-4S]2+ to [2Fe-2S]2+ cluster switch in the transcriptional regulator FNR.

PubMed

Crack, Jason C; Gaskell, Alisa A; Green, Jeffrey; Cheesman, Myles R; Le Brun, Nick E; Thomson, Andrew J

2008-02-06

In Escherichia coli, the switch between aerobic and anaerobic metabolism is primarily controlled by the fumarate and nitrate reduction transcriptional regulator FNR. In the absence of O2, FNR binds a [4Fe-4S]2+ cluster, generating a transcriptionally active dimeric form. Exposure to O2 results in the conversion of the cluster to a [2Fe-2S]2+ form, leading to dissociation of the protein into transcriptionally inactive monomers. The [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion proceeds in two steps. Step 1 involves the one-electron oxidation of the cluster, resulting in the release of Fe2+, generating a [3Fe-4S]1+ cluster intermediate, and a superoxide ion. In step 2, the cluster intermediate spontaneously rearranges to form the [2Fe-2S]2+ cluster, with the release of a Fe3+ ion and two sulfide ions. Here, we demonstrate that, in both native and reconstituted [4Fe-4S] FNR, the reaction environment and, in particular, the presence of Fe2+ and/or Fe3+ chelators can influence significantly the cluster conversion reaction. We demonstrate that while the rate of step 1 is largely insensitive to chelators, that of step 2 is significantly enhanced by both Fe2+ and Fe3+ chelators. We show that, for reactions in Fe3+-coordinating phosphate buffer, step 2 is enhanced to the extent that step 1 becomes the rate determining step and the [3Fe-4S]1+ intermediate is no longer detectable. Furthermore, Fe3+ released during this step is susceptible to reduction in the presence of Fe2+ chelators. This work, which may have significance for the in vivo FNR cluster conversion reaction in the cell cytoplasm, provides an explanation for apparently contradictory results reported from different laboratories.

Chelate-modified polymers for atmospheric gas chromatography

NASA Technical Reports Server (NTRS)

Christensen, W. W.; Mayer, L. A.; Woeller, F. H. (Inventor)

1980-01-01

Chromatographic materials were developed to serve as the stationary phase of columns used in the separation of atmospheric gases. These materials consist of a crosslinked porous polymer matrix, e.g., a divinylbenzene polymer, into which has been embedded an inorganic complexed ion such as N,N'-ethylene-bis-(acetylacetoniminato)-cobalt (2). Organic nitrogenous bases, such as pyridine, may be incorporated into the chelate polymer complexes to increase their chromatographic utility. With such materials, the process of gas chromatography is greatly simplified, especially in terms of time and quantity of material needed for a gas separation.

Chelator free gallium-68 radiolabelling of silica coated iron oxide nanorods via surface interactions

NASA Astrophysics Data System (ADS)

Burke, Benjamin P.; Baghdadi, Neazar; Kownacka, Alicja E.; Nigam, Shubhanchi; Clemente, Gonçalo S.; Al-Yassiry, Mustafa M.; Domarkas, Juozas; Lorch, Mark; Pickles, Martin; Gibbs, Peter; Tripier, Raphaël; Cawthorne, Christopher; Archibald, Stephen J.

2015-09-01

The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron-oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T2 MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging.The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron-oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T2 MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02753e

Antioxidant Contents and Antioxidant Activities of White and Colored Potatoes (Solanum tuberosum L.).

PubMed

Lee, Sang Hoon; Oh, Seung Hee; Hwang, In Guk; Kim, Hyun Young; Woo, Koan Sik; Woo, Shun Hee; Kim, Hong Sig; Lee, Junsoo; Jeong, Heon Sang

2016-06-01

This study was performed to evaluate and compare the antioxidant substance content and antioxidant activities of white (Superior) and colored (Hongyoung, Jayoung, Jasim, Seohong, and Jaseo) potatoes. The potatoes were extracted with 80% ethanol and were evaluated for the total polyphenol, flavonoid, and anthocyanin contents and for 1,1-diphenyl- 2-picrylhydrazyl (DPPH)/2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activity, reducing power, and ferrous metal ion chelating effect. The total polyphenol, flavonoid, and anthocyanin contents of Hongyoung and Jayoung were higher than white and other colored potatoes. All colored potato extracts, except for Jaseo and Seohong, showed higher ABTS radical scavenging activities than the general white potato extract. Hongyoung and Jayoung had the highest ABTS and DPPH radical scavenging activities. Optical density values for the reducing power of Jayoung and Jaseo at concentration of 2 mg/mL were 0.148 and 0.090, respectively. All colored potato extracts had lower ferrous metal ion chelating effect than the white potato. A significant (P<0.05) positive correlation was observed between total polyphenol content and total flavonoid content (r=0.919), anthocyanin content (r=0.992), and ABTS radical scavenging activity (r=0.897). Based on these results, this research may be useful in developing the Hongyoung and Jayoung cultivars with high antioxidant activities.

Inert Reassessment Document for Ethylenediaminetetracetric acid (EDTA)

EPA Pesticide Factsheets

EDTA is a chelating agent. Its ability to bind heavy metal ions can be used to sequester these trace metals. However, trace amounts of various metals are necessary for the proper functioning of the body.

Understanding interaction of curcumin and metal ions on electrode surfaces using EDXRF

NASA Astrophysics Data System (ADS)

Joseph, Daisy; Kumar, K. Krishna; Narayanan, S. Sriman

2018-04-01

A chemically modified electrode was developed for determination of metal ions (Cd, Pb, Zn, Co, Hg). The modifier used for the study was Curcumin. Curcumin acts as a complexing agent at the surface of the electrode for preconcentration of metal ions from electrolyte to electrode surface and stripped back to electrolyte during analysis. EDXRF was used to analyze these electrodes and it was concluded that the PCR modified electrode favored effective chelation for lead and mercury.

Reversible adsorption of catalase onto Fe(3+) chelated poly(AAm-GMA)-IDA cryogels.

PubMed

Aktaş Uygun, Deniz; Uygun, Murat; Akgöl, Sinan; Denizli, Adil

2015-05-01

In this presented study, poly(acrylamide-glycidyl methacrylate) [poly(AAm-GMA)] cryogels were synthesized by cryopolymerization technique at sub-zero temperature. Prepared cryogels were then functionalized with iminodiacetic acid (IDA) and chelated with Fe(3+) ions in order produce the metal chelate affinity matrix. Synthesized cryogels were characterized with FTIR, ESEM and EDX analysis, and it was found that the cryogel had sponge like structure with interconnected pores and their pore diameter was about 200 μm. Fe(3+) chelated poly(AAm-GMA)-IDA cryogels were used for the adsorption of catalase and optimum adsorption conditions were determined by varying the medium pH, initial catalase concentration, temperature and ionic strength. Maximum catalase adsorption onto Fe(3+) chelated poly(AAm-GMA)-IDA cryogel was found to be 12.99 mg/g cryogel at 25 °C, by using pH 5.0 acetate buffer. Adsorbed catalase was removed from the cryogel by using 1.0M of NaCl solution and desorption yield was found to be 96%. Additionally, reusability profile of the Fe(3+) chelated poly(AAm-GMA)-IDA cryogel was also investigated and it was found that, adsorption capacity of the cryogels didn't decrease significantly at the end of the 40 reuses. Catalase activity studies were also tested and it was demonstrated that desorbed catalase retained 70% of its initial activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Method and apparatus for back-extracting metal chelates

DOEpatents

Wai, C.M.; Smart, N.G.; Lin, Y.

1998-08-11

A method is described for extracting metal and metalloid species from a solid or liquid substrate using a supercritical fluid solvent containing one or more chelating agents followed by back-extracting the metal and metalloid species from the metal and metalloid chelates formed thereby. The back-extraction acidic solution is performed utilizing an acidic solution. Upon sufficient exposure of the metal and metalloid chelates to the acidic solution, the metal and metalloid species are released from the chelates into the acid solution, while the chelating agent remains in the supercritical fluid solvent. The chelating agent is thereby regenerated and the metal and metalloid species recovered. 3 figs.

Using amino acids for the chromatofocusing of metal ions on silica with bonded tetraethylenepentamine groups

NASA Astrophysics Data System (ADS)

Ivanov, A. V.

2014-09-01

Amino acid-based eluents are used for the chromatofocusing of metal ions on Tetren-SiO2 chelating sorbent (silica with bonded tetraethylenepentamine groups) for the first time. The smoothest quasilinear pH gradients form for eluents based on glutamic and aspartic acids. The separation of Mn2+, Cr3+, Co2+, Ni2+, and Cu2+ is achieved.

Design, synthesis and biological evaluation of multifunctional tacrine-curcumin hybrids as new cholinesterase inhibitors with metal ions-chelating and neuroprotective property.

PubMed

Liu, Zhikun; Fang, Lei; Zhang, Huan; Gou, Shaohua; Chen, Li

2017-04-15

Total sixteen tacrine-curcumin hybrid compounds were designed and synthesized for the purpose of searching for multifunctional anti-Alzheimer agents. In vitro studies showed that these hybrid compounds showed good cholinesterase inhibitory activity. Particularly, the potency of K 3-2 is even beyond tacrine. Some of the compounds exhibited different selectivity on acetylcholinesterase or butyrylcholinesterase due to the structural difference. Thus, the structure and activity relationship is summarized and further discussed based on molecular modeling studies. The ORAC and MTT assays indicated that the hybrid compounds possessed pronounced antioxidant activity and could effectively protect PC12 cells from the H 2 O 2 /Aβ42-induced toxicity. Moreover, the hybrid compounds also showed positive metal ions-chelating ability in vitro, suggesting a potential to halt ion-induced Aβ aggregation. All the obtained results demonstrated that the tacrine-curcumin hybrid compounds, in particular compound K 3-2 , can be considered as potential therapeutic agents for Alzheimer's disease. Copyright © 2017 Elsevier Ltd. All rights reserved.

A novel, highly sensitive, selective, reversible and turn-on chemi-sensor based on Schiff base for rapid detection of Cu(II)

NASA Astrophysics Data System (ADS)

Saleh, Sayed M.; Ali, Reham; Ali, Ibrahim A. I.

2017-08-01

In this work, a novel optical fluoro-chemisensor was designed and synthesized for copper (II) ions detection. The sensor film is created by embedded N,N-Bis(2-hydroxo-5-bromobenzyl)ethylenediamine in poly vinyl chloride (PVC) film in presence of dioctyl phthalate (DOP) as plasticizer. The receptor Schiff base reveals "off-on" mode with high selectivity, significant sensitivity to Cu(II) ions. The selectivity of optical sensor for Cu(II) ions is the result of chelation enhanced fluorescence (CHEF). The optimal conditions of pH and response time at which higher efficiency of sensor film is performed was found to be 6.8 and 2.48 min. The possible interference of other metal ions in solution was examined in presence of different types of metal ions. This film shows high selectivity and ultra-sensitivity with low detection limit LOD (1.1 × 10- 8 M). Thus, these considerable properties make it viable to monitor copper metal ions within very low concentration range (0-15 × 10- 6 M Cu(II)) and highly selective even in the presence of different types of metal ions. The sensor reversibility was achieved by utilizing EDTA solution with concentration of 0.1 M solution.

Electrogenerated chemiluminescence. 58. Ligand-sensitized electrogenerated chemiluminescence in europium labels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, M.M.; Bard, A.J.

The electrochemistry and electrogenerated chemiluminescence (ECL) of a series of europium chelates, cryptates, and mixed-ligand chelate/cryptand complexes were studied. The complexes were of the following general forms: EuL{sub 4}{sup -}, where L = {beta}-diketonate, a bis-chelating ligand (such as dibenzoylmethide), added as salts (A)EuL{sub 4}, where A= tetrabutylammonium ion or piperidinium ion (pipH{sup +}); Eu(crypt){sup 3+}, where crypt = a cryptand ligand, e.g., 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8,8,5]-tricosa ne; and Eu(crypt)(L){sup 2+} for the mixed-ligand systems. ECL was obtained for the chelates and mixed-ligand systems by reducing the complexes at a Pt electrode in the presence of peroxydisulfate in acetonitrile solutions and was attributedmore » to the electron-transfer reaction between the reduced bound ligands and SO{sub 4}{sup .-}, followed by intramolecular excitation transfer from the excited ligand orbitals to the metal-centered 4f states. No ECL was observed under the same conditions for the europium complexes incorporating only the cryptand ligands in aqueous solution. The ECL spectra matched the photoluminescence spectra with a narrow emission band observed at 612 nm, corresponding to a metal-centered 4f-4f transition. The ECL efficiencies for the ECL-active species were low, about 10{sup -1}-10{sup -4}% of that of the Ru-(bpy){sub 3}{sup 2+}/S{sub 2}O{sub 8}{sup 2-} system under similar conditions. 38 refs., 6 figs., 2 tabs.« less

Covalent Organic Frameworks as a Decorating Platform for Utilization and Affinity Enhancement of Chelating Sites for Radionuclide Sequestration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Qi; Aguila, Briana; Earl, Lyndsey D.

The potential consequences of nuclear events and the complexity of nuclear waste management motivate the development of selective solid-phase sorbents to provide enhanced protection. In this paper, it is shown that 2D covalent organic frameworks (COFs) with unique structures possess all the traits to be well suited as a platform for the deployment of highly efficient sorbents such that they exhibit remarkable performance, as demonstrated by uranium capture. The chelating groups laced on the open 1D channels exhibit exceptional accessibility, allowing significantly higher utilization efficiency. In addition, the 2D extended polygons packed closely in an eclipsed fashion bring chelating groupsmore » in adjacent layers parallel to each other, which may facilitate their cooperation, thereby leading to high affinity toward specific ions. As a result, the amidoxime-functionalized COFs far outperform their corresponding amorphous analogs in terms of adsorption capacities, kinetics, and affinities. Specifically, COF-TpAb-AO is able to reduce various uranium contaminated water samples from 1 ppm to less than 0.1 ppb within several minutes, well below the drinking water limit (30 ppb), as well as mine uranium from spiked seawater with an exceptionally high uptake capacity of 127 mg g -1. Finally, these results delineate important synthetic advances toward the implementation of COFs in environmental remediation.« less

Covalent Organic Frameworks as a Decorating Platform for Utilization and Affinity Enhancement of Chelating Sites for Radionuclide Sequestration

DOE PAGES

Sun, Qi; Aguila, Briana; Earl, Lyndsey D.; ...

2018-03-27

The potential consequences of nuclear events and the complexity of nuclear waste management motivate the development of selective solid-phase sorbents to provide enhanced protection. In this paper, it is shown that 2D covalent organic frameworks (COFs) with unique structures possess all the traits to be well suited as a platform for the deployment of highly efficient sorbents such that they exhibit remarkable performance, as demonstrated by uranium capture. The chelating groups laced on the open 1D channels exhibit exceptional accessibility, allowing significantly higher utilization efficiency. In addition, the 2D extended polygons packed closely in an eclipsed fashion bring chelating groupsmore » in adjacent layers parallel to each other, which may facilitate their cooperation, thereby leading to high affinity toward specific ions. As a result, the amidoxime-functionalized COFs far outperform their corresponding amorphous analogs in terms of adsorption capacities, kinetics, and affinities. Specifically, COF-TpAb-AO is able to reduce various uranium contaminated water samples from 1 ppm to less than 0.1 ppb within several minutes, well below the drinking water limit (30 ppb), as well as mine uranium from spiked seawater with an exceptionally high uptake capacity of 127 mg g -1. Finally, these results delineate important synthetic advances toward the implementation of COFs in environmental remediation.« less

TCE degradation in groundwater by chelators-assisted Fenton-like reaction of magnetite: Sand columns demonstration.

PubMed

Jia, Daqing; Sun, Sheng-Peng; Wu, Zhangxiong; Wang, Na; Jin, Yaoyao; Dong, Weiyang; Chen, Xiao Dong; Ke, Qiang

2018-03-15

Trichloroethylene (TCE) degradation in sand columns has been investigated to evaluate the potential of chelates-enhanced Fenton-like reaction with magnetite as iron source for in situ treatment of TCE-contaminated groundwater. The results showed that successful degradation of TCE in sand columns was obtained by nitrilotriacetic acid (NTA)-assisted Fenton-like reaction of magnetite. Addition of ethylenediaminedisuccinic acid (EDDS) resulted in an inhibitory effect on TCE degradation in sand columns. Similar to EDDS, addition of ethylenediaminetetraacetic acid (EDTA) also led to an inhibition of TCE degradation in sand column with small content of magnetite (0.5 w.t.%), but enhanced TCE degradation in sand column with high content of magnetite (7.0 w.t.%). Additionally, the presence of NTA, EDDS and EDTA greatly decreased H 2 O 2 uptake in sand columns due to the competition between chelates and H 2 O 2 for surface sites on magnetite (and sand). Furthermore, the presented results show that magnetite in sand columns remained stable in a long period operation of 230 days without significant loss of performance in terms of TCE degradation and H 2 O 2 uptake. Moreover, it was found that TCE was degraded mainly to formic acid and chloride ion, and the formation of chlorinated organic intermediates was minimal by this process. Copyright © 2017 Elsevier B.V. All rights reserved.

Micellar liquid chromatography

NASA Astrophysics Data System (ADS)

Basova, Elena M.; Ivanov, Vadim M.; Shpigun, Oleg A.

1999-12-01

Background and possibilities of practical applications of micellar liquid chromatography (MLC) are considered. Various retention models in MLC, the effects of the nature and concentration of surfactants and organic modifiers, pH, temperature and ionic strength on the MLC efficiency and selectivity are discussed. The advantages and limitations of MLC are demonstrated. The performance of MLC is critically evaluated in relationship to the reversed-phase HPLC and ion-pair chromatography. The potential of application of MLC for the analysis of pharmaceuticals including that in biological fluids and separation of inorganic anions, transition metal cations, metal chelates and heteropoly compounds is described. The bibliography includes 146 references.

Iron and copper chelation by flavonoids: an electrospray mass spectrometry study.

PubMed

Fernandez, M Tereza; Mira, M Lurdes; Florêncio, M Helena; Jennings, Keith R

2002-11-11

Flavonoids are well known as effective free radical scavengers exhibiting therefore an antioxidant behaviour. Another antioxidant mechanism however may result from the ability they have to chelate metal ions, rendering them inactive to participate in free radical generating reactions. Electrospray mass spectrometry has been used to study metal ion interactions with a set of flavonoids from different classes. Complexes with a range of stoichiometries, of metal: flavonoid, 1:1, 1:2, 2:2, 2:3 have been observed. The stoichiometry 1:2 is in general the preferred one. It is established for flavones and for the flavanone naringenin that the binding metal sites are preferentially at the 5-hydroxyl and 4-oxo groups. Redox reactions are also observed through the change of the oxidation state of the metal, jointly with the oxidation of the flavonoid by loss of hydrogen. Structures of the oxidized species of some flavonoids are proposed.

Use of Chelex-100 for selectively removing Y-90 from its parent Sr-90

DOEpatents

Huntley, Mark W.

1996-01-01

A method for selectively removing yttrium-90 from its parent strontium-90 contained in an environmental sample includes loading the sample onto a column containing a chelating ion-exchange resin capable of retaining yttrium-90; washing the column with a solution capable of removing strontium, calcium, and other contaminants from the yttrium-90 fraction retained on the column; removing excess acetate salts from the column; eluting yttrium-90 solution from the column and adjusting the pH of this solution to about 2.7; filtering the yttrium-90 solution and weighing this solution for gravimetric yield; and, counting the yttrium-90 containing solution with a radiological counter for a time sufficient to achieve the statistical accuracy desired. It is preferred that the chelating ion-exchange resin is a bidente ligand having the chemical name iminodiacetic acid mounted on a divinyl benzene substrate, converted from sodium form to ammonia form.

Use of Chelex-100 for selectively removing Y-90 from its parent Sr-90

DOEpatents

Huntley, M.W.

1996-02-27

A method for selectively removing yttrium-90 from its parent strontium-90 contained in an environmental sample includes loading the sample onto a column containing a chelating ion-exchange resin capable of retaining yttrium-90; washing the column with a solution capable of removing strontium, calcium, and other contaminants from the yttrium-90 fraction retained on the column; removing excess acetate salts from the column; eluting yttrium-90 solution from the column and adjusting the pH of this solution to about 2.7; filtering the yttrium-90 solution and weighing this solution for gravimetric yield; and, counting the yttrium-90 containing solution with a radiological counter for a time sufficient to achieve the statistical accuracy desired. It is preferred that the chelating ion-exchange resin is a ligand having the chemical name iminodiacetic acid mounted on a divinyl benzene substrate, converted from sodium form to ammonia form.

Fusaric acid induces a notochord malformation in zebrafish via copper chelation.

PubMed

Yin, Emily S; Rakhmankulova, Malika; Kucera, Kaury; de Sena Filho, Jose Guedes; Portero, Carolina E; Narváez-Trujillo, Alexandra; Holley, Scott A; Strobel, Scott A

2015-08-01

Over a thousand extracts were tested for phenotypic effects in developing zebrafish embryos to identify bioactive molecules produced by endophytic fungi. One extract isolated from Fusarium sp., a widely distributed fungal genus found in soil and often associated with plants, induced an undulated notochord in developing zebrafish embryos. The active compound was isolated and identified as fusaric acid. Previous literature has shown this phenotype to be associated with copper chelation from the active site of lysyl oxidase, but the ability of fusaric acid to bind copper ions has not been well described. Isothermal titration calorimetry revealed that fusaric acid is a modest copper chelator with a binding constant of 4.4 × 10(5) M(-1). These results shed light on the toxicity of fusaric acid and the potential teratogenic effects of consuming plants infected with Fusarium sp.

Site-activated chelators derived from anti-Parkinson drug rasagiline as a potential safer and more effective approach to the treatment of Alzheimer's disease.

PubMed

Zheng, Hailin; Fridkin, Mati; Youdim, Moussa B H

2010-12-01

chelators can modulate β-amyloid accumulation, protect against tau hyperphosphorylation, and block metal-related oxidative stress, and thereby hold considerable promise as effective anti-AD drugs. At present, a growing interest is focusing on increasing the efficacy and targeting of chelators through drug design. To this end, we have developed a new class of multifunctional prochelators from three FDA- approved drugs rasagiline, rivastigmine, and donepezil or tacrine. HLA20 A was designed by merging the important pharmacophores of rasagiline, rivastigmine, and donepezil into our newly developed multifunctional chelator HLA20. M30D was constructed using the key pharmacophoric moieties from rasagiline, rivastigmine, and tacrine. Experiments showed that both compounds possess potent anti-acetylcholinesterase (AChE) activity in vitro with weak inhibition of butyrylcholinesterase (BuChE), and without significant metal-binding activity. M30D was found also to be a highly potent MAO A inhibitor with moderate inhibition of MAO B in vitro. Both HLA20 and M30D can be activated by inhibition of AChE to release active chelators HLA20 and M30, respectively. HLA20 and M30 have been shown to be able to modulate amyloid precursor protein regulation and beta-amyloid reduction, suppress oxidative stress, and passivate excess metal ions (Fe, Cu, and Zn). Compared with the activated chelator HLA20 or M30, both HLA20A and M30D exhibited lower cytotoxicity in SH-SY5Y neuroblastoma cells, substantiating the prochelator strategy for minimizing toxicity associated with poor targeted chelators.

Rapid, quantitative and sensitive immunochromatographic assay based on stripping voltammetric detection of a metal ion label

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Fang; Wang, Kaihua; Lin, Yuehe

2005-10-10

A novel, sensitive immunochromatographic electrochemical biosensor (IEB) which combines an immunochromatographic strip technique with an electrochemical detection technique is demonstrated. The IEB takes advantages of the speed and low-cost of the conventional immunochromatographic test kits and high-sensitivity of stripping voltammetry. Bismuth ions (Bi3+) have been coupled with the antibody through the bifunctional chelating agent diethylenetriamine pentaacetic acid (DTPA). After immunoreactions, Bi3+ was released and quantified by anodic stripping voltammetry at a built-in single-use screen-printed electrode. As an example for the applications of such novel device, the detection of human chorionic gonadotronphin (HCG) in a specimen was performed. This biosensor providesmore » a more user-friendly, rapid, clinically accurate, and less expensive immunoassay for such analysis in specimens than currently available test kits.« less

Exploration of the Ca2+ interaction modes of the nifedipine calcium channel antagonist.

PubMed

Liu, Huichun; Zhang, Liang; Li, Ping; Cukier, Robert I; Bu, Yuxiang

2007-02-02

A comprehensive study is carried out using quantum chemical computation and molecular dynamics (MD) simulations to gain insight into the interaction between Ca(2+) ions and the most important class of calcium channel antagonists--nifedipine. First, the chelating structures and energetic characters of nifedipine-Ca(2+) in the gas phase are explored, and 25 isomers are found. The most favorable chelating mode is a tridentate one, that is, Ca(2+) binds to two carbonyl O atoms and one nitryl O atom, where Ca(2+) is above the plane of the three O atoms to form a pyramidal structure. Accurate geometric structures, relative stabilities, vertical and adiabatic binding energies, and charge distributions are discussed. The differences in the geometries and energies among these isomers are analyzed from the contributions of chelating sites, electrostatics and polarizations, steric repulsions, and charge distributions. The interconversions among isomers with similar geometries and energies are also investigated because of the importance of the geometric transformation in the biological system. Furthermore, certain numbers of water molecules are added to the nifedipine-Ca(2+) system to probe the effect of water. A detailed study is performed on the hydrated geometries on the basis of the most stable isomer 1. Stepwise hydration can weaken the nifedipine-Ca(2+) interaction, and the chelating sites of nifedipine are gradually replaced by the added water molecules. Hexacoordination is found to be the most favorable geometry no matter how many water molecules were added, which can be verified by the MD simulations. The transfer of water molecules from the inner shell to the outer shell is also supported by MD simulations of the hexahydrated complexes.

Nanopore Device for Reversible Ion and Molecule Sensing or Migration

NASA Technical Reports Server (NTRS)

Seger, R. Adam (Inventor); Pourmand, Nader (Inventor); Actis, Paolo (Inventor); Singaram, Bakthan (Inventor); Vilozny, Boaz (Inventor)

2015-01-01

Disclosed are methods and devices for detection of ion migration and binding, utilizing a nanopipette adapted for use in an electrochemical sensing circuit. The nanopipette may be functionalized on its interior bore with metal chelators for binding and sensing metal ions or other specific binding molecules such as boronic acid for binding and sensing glucose. Such a functionalized nanopipette is comprised in an electrical sensor that detects when the nanopipette selectively and reversibly binds ions or small molecules. Also disclosed is a nanoreactor, comprising a nanopipette, for controlling precipitation in aqueous solutions by voltage-directed ion migration, wherein ions may be directed out of the interior bore by a repulsing charge in the bore.

Silver Recovery and Power Generation from Ammonia Chelated Silver Solution in a Bio-Electrochemical Reactor

NASA Astrophysics Data System (ADS)

Ho, N. A. D.; Babel, S.

2017-06-01

Silver has valuable features and limited availability, and thus recovery from wastewater or aqueous solutions plays an important role in environmental protection and economic profits. In this study, silver recovery along with power generation and COD removal were investigated in a bio-electrochemical system (BES). The BES comprised of an anode and a cathode chamber which were separated by a cation exchange membrane to prevent the cross-over of electrolytes. During the biological oxidation of acetate as an electron donor in the anode chamber, the reduction of ammonia chelated silver ions as electron acceptors in the cathode side occurred spontaneously. Results showed that a silver recovery of 99% and COD removal efficiency of 60% were achieved at the initial silver concentration of 1,000 mg/L after 48 hours of operation. The power generation improved 4.66%, from 3,618 to 3,795 mW/m3, by adding NaNO3 of 850 mg/L to the catholyte containing 2,000 mg/L of silver ions. Deposits on the cathode surface were characterized using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Metallic silver with dendritic structures and high purity were detected. This study demonstrated that BES technology can be employed to recover silver from complex chelating solution, produce electricity, and treat wastewater.

Structural diversity of benzil bis(benzoylhydrazone): Mononuclear, binuclear and trinuclear complexes.

PubMed

López-Torres, Elena; Mendiola, M Antonia

2009-10-07

The coordination behaviour of the Schiff-base, benzil bis(benzoylhydrazone), LH(2) towards divalent nickel, lead, cadmium, zinc and copper ions has been investigated. The complexes have been fully characterized by techniques including (113)Cd and (207)Pb NMR, as well as (13)C and (113)Cd CP/MAS NMR and by single crystal X-ray diffraction. All the complexes have the general formula [ML](n) (n = 1-3 depending on the metal ion), with the ligand doubly deprotonated. The nickel complex [NiL] is a monomeric compound, the lead complex [PbL](2) shows a binuclear structure, whereas zinc [ZnL](3) and copper [CuL](3) complexes are trinuclear helicates. The cadmium complex seems to be a dimer with a structure similar to that of . In the nickel and lead derivatives, the ligand behaves as a tetradentate N(2)O(2) chelate and in complex also as a bridge through one of the O atoms. In the crystal structures of Zn and Cu complexes [ML](3) each metal is in a pentadentate N(3)O(2) environment formed by two different ligands, one tridentate chelate and the other bidentate chelate, giving rise to trinuclear helicates. These results point out the versatility of benzil bis(benzoylhydrazone) on its coordination.

Solid-state chelation of metal ions by ethylenediaminetetraacetate intercalated in a layered double hydroxide.

PubMed

Tarasov, Konstantin A; O'Hare, Dermot; Isupov, Vitaly P

2003-03-24

The solid-state chelation of transition metal ions (Co(2+), Ni(2+), and Cu(2+)) from aqueous solutions into the lithium aluminum layered double hydroxide ([LiAl(2)(OH)(6)]Cl x 0.5H(2)O or LDH) which has been pre-intercalated with EDTA (ethylenediaminetetraacetate) ligand has been investigated. The intercalated metal cations form [M(edta)](2)(-) complexes between the LDH layers as indicated by elemental analysis, powder X-ray diffraction, and IR and UV-vis spectroscopies. If metal chloride or nitrate salts are used in the reaction with the LDH then co-intercalation of either the Cl(-) or NO(3)(-) anions is observed. In the case of metal acetate salts the cations intercalate without the accompanying anion. This can be explained by the different intercalation selectivity of the anions in relation to the LDH. In the latter case the introduction of the positive charge into LDH structure was compensated for by the release from the solid of the equivalent quantity of lithium and hydrogen cations. Time-resolved in-situ X-ray diffraction measurements have revealed that the chelation/intercalation reactions proceed very quickly. The rate of the reaction found for nickel acetate depends on concentration as approximately k[Ni(Ac)(2)](3).

Poly(ethylene imine)-based granular sorbents by a new process of templated gel-filling. High capacity and selectivity of copper sorption in acidic and alkaline media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chanda, M.; Rempel, G.L.

A new process has been developed for making granular gel-type sorbents from chelating resins using metal ion as template. Named as templated gel-filling, the process uses the chosen metal as templating host ion on high-surface-area silica to build a templated gel layer from a solution of the chelating resin in a suitable solvent in which the resin is soluble but its metal complex is insoluble. After cross-linking the templated gel layer, the silica support is removed by alkali to produce a hollow shell of the templated gel. The shells are then soaked in a concentrated aqueous solution of the samemore » metal ion and suspended in the same resin solution to afford gel-filling. The shells thus filled with metal-templated gel are treated with cross-linking agent, followed by acid to remove the template ion and activate the resin for metal sorption. Poly(ethyleneimine) and its partially ethylated derivative have been used to produce granular gel-type sorbents by this process, with Cu(II) as the template ion. These sorbents are found to offer high capacity and selectivity for copper over nickel, cobalt, and zinc in both acidic and alkaline media. Containing a relatively high fraction of imbibed water, the sorbents exhibit markedly enhanced rate behavior, in both sorption and stripping.« less

Degradation of S-nitrosocysteine in vascular tissue homogenates: role of divalent ions.

PubMed

Kostka, P; Xu, B; Skiles, E H

1999-04-01

The objective of the study was to inquire about the mechanism(s) involved in the catabolism of S-nitrosothiols by vascular tissue under in vitro conditions. Incubations of S-nitrosocysteine (CYSNO) or S-nitrosoglutathione (GSNO) with homogenates isolated from porcine aortic smooth muscle resulted in only a marginal depletion of S-nitrosothiols from the reaction mixtures, which became statistically significant at relatively high concentrations of homogenate (> or =300 microg of protein/ml). Degradation of CYSNO (but not GSNO) was found to be potentiated several-fold by millimolar concentrations of either Mg2+ or Ca2+ ions. Under such conditions, the degradation of CYSNO was significantly suppressed by the removal of proteins by ultrafiltration (>80% inhibition) and eliminated completely by the alkylation of thiol groups with 1 mM N-ethylmaleimide. The potentiating effect of divalent ions on the degradation of CYSNO was insensitive to 0.1 mM neocuproine (selective chelator of Cu+ ions), although it was enhanced in the presence of 0.1 mM o-phenanthroline (selective chelator of Fe2+ ions). It is concluded that the degradation of CYSNO by tissue homogenate involves the interaction with protein-bound sulfhydryl groups, which is stimulated by Mg2+ or Ca2+ ions. The potentiating effect of o-phenanthroline suggests that the liberation of the nitrosonium moiety in such a process may be accompanied by its transfer to sulfur center(s) by transient formation of dinitrosyl-iron complexes.

Performance of Nonmigratory Iron Chelating Active Packaging Materials in Viscous Model Food Systems.

PubMed

Roman, Maxine J; Decker, Eric A; Goddard, Julie M

2015-09-01

Many packaged food products undergo quality deterioration due to iron promoted oxidative reactions. Recently, we have developed a nonmigratory iron chelating active packaging material that represents a novel approach to inhibit oxidation of foods while addressing consumer demands for "cleanˮ labels. A challenge to the field of nonmigratory active packaging is ensuring that surface-immobilized active agents retain activity in a true food system despite diffusional limitations. Yet, the relationship between food viscosity and nonmigratory active packaging activity retention has never been characterized. The objective of this study was to investigate the influence of food viscosity on iron chelation by a nonmigratory iron chelating active packaging material. Methyl cellulose was added to aqueous buffered iron solutions to yield model systems with viscosities ranging from ∼1 to ∼10(5)  mPa·s, representing viscosities ranging from beverage to mayonnaise. Iron chelation was quantified by material-bound iron content using colorimetry and inductively coupled plasma-optical emission spectrometry (ICP-OES).  Maximum iron chelation was reached in solutions up to viscosity ∼10(2)  mPa·s. In more viscous solutions (up to ∼10(4)  mPa·s), there was a significant decrease in iron chelating capacity (P < 0.05). However, materials still retained at least 76% iron chelating capacity. Additionally, the influence of different food hydrocolloids on the performance of nonmigratory iron chelating active packaging was characterized. Methyl cellulose and carrageenan did not compete with the material for specific iron chelation (P > 0.05). Materials retained 32% to 45% chelating capacity when in contact with competitively chelating hydrocolloids guar gum, locust bean gum, and xanthan gum. This work demonstrates the potential application of nonmigratory iron chelating active packaging in liquid and semi-liquid foods to allow for the removal of synthetic chelators, while maintaining food quality. © 2015 Institute of Food Technologists®

Antioxidant properties of various solvent extracts from purple basil

NASA Astrophysics Data System (ADS)

Yeşiloğlu, Yeşim; Şit, Latifşah

2012-09-01

Water, ethanol and acetone extracts from leaves and flowers of purple basil, one of the most popular spices consumed in the Thrace region of Turkey, were tested in vitro for their ability to inhibit peroxidation of lipids, to scavenge DPPH, hydrogen peroxide, superoxide anion, to reduce Fe(III) to Fe(II) and to chelate Fe(II) ions. The results showed that purple basil contained naturally occurring antioxidant components and possessed antioxidant activity which may be attributed to its lipid peroxidation inhibitory, radical scavenging and metal chelating activities. It was concluded that purple basil might be a potential source of antioxidants.

Flame Atomic Absorption Spectrometric Determination of Trace Metal Ions in Environmental and Biological Samples After Preconcentration on a Newly Developed Amberlite XAD-16 Chelating Resin Containing p-Aminobenzene Sulfonic Acid.

PubMed

Islam, Aminul; Ahmad, Akil; Laskar, Mohammad Asaduddin

2015-01-01

Amberlite® XAD-16 was functionalized with p-aminobenzene sulfonic acid via an azo spacer in order to prepare a new chelating resin, which was then characterized by water regain value, hydrogen ion capacity, elemental analyses, and IR spectral and thermal studies. The maximum uptake of Cu(II), Ni(II), Zn(II), Co(II), Cr(III), Fe(III), and Pb(II) ions was observed in the pH range 4.0-6.0 with the corresponding half-loading times of 6.5, 7.0, 8.0, 9.0, 11.0, 8.5, and 16.5 min. The sorption data followed Langmuir isotherms and a pseudo-second-order model. Thermodynamic quantities, ΔH and ΔS, based on the variation of the distribution coefficient with temperature were also evaluated. High preconcentration factors of 60-100 up to a low preconcentration limit of 4.0-6.6 μg/L have been achieved for the metal ions. The validity of the method was checked by analyzing standard reference materials and recoveries of trace metals after spiking. The analytical applications of the method were explored by analyzing natural water, mango pulp, mint leaves, and fish.

Selective Solid-Phase Extraction of Zinc(II) from Environmental Water Samples Using Ion Imprinted Activated Carbon.

PubMed

Moniri, Elham; Panahi, Homayon Ahmad; Aghdam, Khaledeh; Sharif, Amir Abdollah Mehrdad

2015-01-01

A simple ion imprinted amino-functionalized sorbent was synthesized by coupling activated carbon with iminodiacetic acid, a functional compound for metal chelating, through cyanoric chloride spacer. The resulting sorbent has been characterized using FTIR spectroscopy, elemental analysis, and thermogravimetric analysis and evaluated for the preconcentration and determination of trace Zn(II) in environmental water samples. The optimum pH value for sorption of the metal ion was 6-7.5. The sorption capacity of the functionalized sorbent was 66.6 mg/g. The chelating sorbent can be reused for 10 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 100% was obtained for the metal ion with 0.5 M nitric acid as the eluent. Compared with nonimprinted polymer particles, the prepared Zn-imprinted sorbent showed high adsorption capacity, significant selectivity, and good site accessibility for Zn(II). Scatchard analysis revealed that the homogeneous binding sites were formed in the polymer. The equilibrium sorption data of Zn(II) by modified resin were analyzed by Langmuir, Freundlich, Temkin, and Redlich-Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.139, 12.82, and 2.34, respectively, at 25°C.

Removal of heavy metals from aqueous waste streams using surface-modified nanosized TiO{sub 2} photocatalysts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meshkov, N. K.

1998-08-27

Titanium dioxide (TiO{sub 2}) colloidal particles ({approximately}45{angstrom}) whose surfaces were modified with chelating agents for photocatalytic removal of heavy-metal ions and their subsequent reduction to metallic form were investigated. Experiments were performed on nanoparticle TiO{sub 2} colloids derivatized with bidentate and tridentate ligands (thiolactic acid [TLA], cysteine, and alanine [ALA]) in batch mode in a photoreactor with 254nm light. We used catalysts designed and synthesized for selective and efficient removal of Pb and Cu with and without added hole scavenger (methanol). Parallel experiments also have been carried out in the dark to study metal ion adsorption properties. Solutions have beenmore » filtered to remove TiO{sub 2}, and metal particulates. Both the native solution and the metal deposited on the nanocrystalline TiO{sub 2} particles were analyzed. Results demonstrate that for the case of lead, the most effective TiO{sub 2} surface modifier was TLA (>99% Pb(II) removed from solution). Experiments performed to study Cn removal using TiO{sub 2} colloids modified with alanine showed that copper ions were effectively removed and reduced to metallic form in the presence of methanol.« less

Generic tags for Mn(ii) and Gd(iii) spin labels for distance measurements in proteins.

PubMed

Yang, Yin; Gong, Yan-Jun; Litvinov, Aleksei; Liu, Hong-Kai; Yang, Feng; Su, Xun-Cheng; Goldfarb, Daniella

2017-10-11

High-affinity chelating tags for Gd(iii) and Mn(ii) ions that provide valuable high-resolution distance restraints for biomolecules were used as spin labels for double electron-electron resonance (DEER) measurements. The availability of a generic tag that can bind both metal ions and provide a narrow and predictable distance distribution for both ions is attractive owing to their different EPR-related characteristics. Herein we introduced two paramagnetic tags, 4PSPyMTA and 4PSPyNPDA, which are conjugated to cysteine residues through a stable thioether bond, forming a short and, depending on the metal ion coordination mode, a rigid tether with the protein. These tags exhibit high affinity for both Mn(ii) and Gd(iii) ions. The DEER performance of the 4PSPyMTA and 4PSPyNPDA tags, in complex with Gd(iii) or Mn(ii), was evaluated for three double cysteine mutants of ubiquitin, and the Gd(iii)-Gd(iii) and Mn(ii)-Mn(ii) distance distributions they generated were compared. All three Gd(iii) complexes of the ubiquitin-PyMTA and ubiquitin-PyNPDA conjugates produced similar and expected distance distributions. In contrast, significant variations in the maxima and widths of the distance distributions were observed for the Mn(ii) analogs. Furthermore, whereas PyNPDA-Gd(iii) and PyNPDA-Mn(ii) delivered similar distance distributions, appreciable differences were observed for two mutants with PyMTA, with the Mn(ii) analog exhibiting a broader distance distribution and shorter distances. ELDOR (electron-electron double resonance)-detected NMR measurements revealed some distribution in the Mn(ii) coordination environment for the protein conjugates of both tags but not for the free tags. The broader distance distributions generated by 4PSPyMTA-Mn(ii), as compared with Gd(iii), were attributed to the distributed location of the Mn(ii) ion within the PyMTA chelate owing to its smaller size and lower coordination number that leave the pyridine nitrogen uncoordinated. Accordingly, in terms of distance resolution, 4PSPyNPDA can serve as an effective generic tag for Gd(iii) and Mn(ii), whereas 4PSPyMTA is efficient for Gd(iii) only. This comparison between Gd(iii) and Mn(ii) suggests that PyMTA model compounds may not predict sufficiently well the performance of PyMTA-Mn(ii) as a tag for high-resolution distance measurements in proteins because the protein environment can influence its coordination mode.

Strong adsorbability of mercury ions on aniline/sulfoanisidine copolymer nanosorbents.

PubMed

Li, Xin-Gui; Feng, Hao; Huang, Mei-Rong

2009-01-01

The highest Hg-ion adsorbance so far, namely up to 2063 mg g(-1), has been achieved by poly(aniline-co-5-sulfo-2-anisidine) nanosorbents. Sorption of Hg ions occurs mainly by redox and chelation mechanisms (see scheme), but also by ion exchange and physisorption.Poly(aniline (AN)-co-5-sulfo-2-anisidine (SA)) nanoparticles were synthesized by chemical oxidative copolymerization of AN and SA monomers, and their extremely strong adsorption of mercury ions in aqueous solution was demonstrated. The reactivity ratios of AN and SA comonomers were found to be 2.05 and 0.02, respectively. While AN monomer tends to homopolymerize, SA monomer tends to copolymerize with AN monomer because of the great steric hindrance and electron-attracting effect of the sulfo groups, despite the effect of conjugation of the methoxyl group with the benzene ring. The effects of initial mercury(II) concentration, sorption time, sorption temperature, ultrasonic treatment, and sorbent dosage on mercury-ion sorption onto AN/SA (50/50) copolymer nanoparticles with a number-average diameter of around 120 nm were significantly optimized. The results show that the maximum Hg-ion sorption capacity on the particulate nanosorbents can even reach 2063 mg of Hg per gram of sorbent, which would be the highest Hg-ion adsorbance so far. The sorption data fit to the Langmuir isotherm, and the process obeys pseudo-second-order kinetics. The IR and UV/Vis spectral data of the Hg-loaded copolymer particles suggest that some mercury(II) was directly reduced by the copolymer to mercury(I) and even mercury(0). A mechanism of sorption between the particles and Hg ions in aqueous solution is proposed, and a physical/ion exchange/chelation/redox sorption ratio of around 2/3/45/50 was found. Copolymer nanoparticles may be one of the most powerful and cost-effective sorbents of mercury ions, with a wide range of potential applications for the efficient removal and even recovery of the mercury ions from aqueous solution.

Beneficial effects of humic acid on micronutrient availability to wheat

NASA Technical Reports Server (NTRS)

Mackowiak, C. L.; Grossl, P. R.; Bugbee, B. G.

2001-01-01

Humic acid (HA) is a relatively stable product of organic matter decomposition and thus accumulates in environmental systems. Humic acid might benefit plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA on growth and micronutrient uptake in wheat (Triticum aestivum L.) grown hydroponically. Four root-zone treatments were compared: (i) 25 micromoles synthetic chelate N-(4-hydroxyethyl)ethylenediaminetriacetic acid (C10H18N2O7) (HEDTA at 0.25 mM C); (ii) 25 micromoles synthetic chelate with 4-morpholineethanesulfonic acid (C6H13N4S) (MES at 5 mM C) pH buffer; (iii) HA at 1 mM C without synthetic chelate or buffer; and (iv) no synthetic chelate or buffer. Ample inorganic Fe (35 micromoles Fe3+) was supplied in all treatments. There was no statistically significant difference in total biomass or seed yield among treatments, but HA was effective at ameliorating the leaf interveinal chlorosis that occurred during early growth of the nonchelated treatment. Leaf-tissue Cu and Zn concentrations were lower in the HEDTA treatment relative to no chelate (NC), indicating HEDTA strongly complexed these nutrients, thus reducing their free ion activities and hence, bioavailability. Humic acid did not complex Zn as strongly and chemical equilibrium modeling supported these results. Titration tests indicated that HA was not an effective pH buffer at 1 mM C, and higher levels resulted in HA-Ca and HA-Mg flocculation in the nutrient solution.

Structured copolymers and their use as absorbents, gels and carriers of metal ions

DOEpatents

Hedstrand, David M.; Helmer, Bradley J.; Tomalia, Donald A.

1996-01-01

Dense star polymers or dendrimers having a highly branched interior structure capable of associating or chelating with metal ions are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell. The modified dendrimers are useful for dispersing metal ions in a non-aqueous polymer matrix. Also dense star polymers or dendrimers having a highly branched hydrophilic interior structure are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell, which modified polymers are useful as gels and surfactants.

Structured copolymers and their use as absorbents, gels and carriers of metal ions

DOEpatents

Hedstrand, D.M.; Helmer, B.J.; Tomalia, D.A.

1996-10-01

Dense star polymers or dendrimers having a highly branched interior structure capable of associating or chelating with metal ions are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell. The modified dendrimers are useful for dispersing metal ions in a non-aqueous polymer matrix. Also dense star polymers or dendrimers having a highly branched hydrophilic interior structure are modified by capping with a hydrophobic group capable of providing a hydrophobic outer shell, which modified polymers are useful as gels and surfactants.

Derivatizations of Sgc8-c aptamer to prepare metallic radiopharmaceuticals as imaging diagnostic agents: Syntheses, isolations, and physicochemical characterizations.

PubMed

Sicco, Estefanía; Báez, Jessica; Margenat, Jimena; García, Fernanda; Ibarra, Manuel; Cabral, Pablo; Moreno, María; Cerecetto, Hugo; Calzada, Victoria

2018-03-01

Aptamers, oligonucleotides with the capability to bind to a target through non-covalent bonds with high affinity and specificity, have a great number of advantages as scaffold to prepare molecular imaging agents. In this sense, we have performed post-SELEX modifications of a truncated aptamer, Sgc8-c, which bind to protein tyrosine kinase 7 to obtain a specific molecular targeting probe for in vivo diagnosis and in vivo therapy. Herein, we describe the synthetic efforts to prepare conjugates between Sgc8-c and different metallic ions chelator moieties in short times, high purities, and adequate yields. The selected chelator moieties, derived from 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, 2-benzyl-1,4,7-triazacyclononane-1,4,7-triacetic acid, and 6-hydrazinonicotinic acid, were covalently attached at the 5'-aptamer position yielding the expected products which were stable in aqueous solution up to 75°C and in typical aptamer storage conditions at least for 30 days. © 2017 John Wiley & Sons A/S.

Triamines and their derivatives as bifunctional chelating agents

DOEpatents

Troutner, David E.; John, Christy S.; Pillai, Maroor R. A.

1992-03-31

A group of functionalized triamine chelants and their derivatives that form complexes with radioactive metal ions are disclosed. The complexes can be covalently attached to a protein or an antibody or antibody fragment and used for therapeutic and/or diagnostic purposes.

Solution-processed Al-chelated gelatin for highly transparent non-volatile memory applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Yu-Chi; Wang, Yeong-Her, E-mail: yhw@ee.ncku.edu.tw

2015-03-23

Using the biomaterial of Al-chelated gelatin (ACG) prepared by sol-gel method in the ITO/ACG/ITO structure, a highly transparent resistive random access memory (RRAM) was obtained. The transmittance of the fabricated device is approximately 83% at 550 nm while that of Al/gelatin/ITO is opaque. As to the ITO/gelatin/ITO RRAM, no resistive switching behavior can be seen. The ITO/ACG/ITO RRAM shows high ON/OFF current ratio (>10{sup 5}), low operation voltage, good uniformity, and retention characteristics at room temperature and 85 °C. The mechanism of the ACG-based memory devices is presented. The enhancement of these electrical properties can be attributed to the chelate effect ofmore » Al ions with gelatin. Results show that transparent ACG-based memory devices possess the potential for next-generation resistive memories and bio-electronic applications.« less

Cyclodextrin Nanoparticles Bearing 8-Hydroxyquinoline Ligands as Multifunctional Biomaterials.

PubMed

Oliveri, Valentina; Bellia, Francesco; Vecchio, Graziella

2017-03-28

Cyclodextrins are used as building blocks for the development of a host of polymeric biomaterials. The cyclodextrin polymers have found numerous applications as they exhibit unique features such as mechanical properties, stimuli responsiveness and drug loading ability. Notwithstanding the abundance of cyclodextrin polymers studied, metal-chelating polymers based on cyclodextrins have been poorly explored. Herein we report the synthesis and the characterization of the first metal-chelating β-cyclodextrin polymer bearing 8-hydroxyquinoline ligands. The metal ions (Cu 2+ or Zn 2+ ) can modulate the assembly of the polymer nanoparticles. Moreover, the protective activity of the new chelating polymer against self- and metal-induced Aβ aggregation and free radical species are significantly higher than those of the parent compounds. These synergistic effects suggest that the incorporation of hydroxyquinoline moieties into a soluble β-cyclodextrin polymer could represent a promising strategy to design multifunctional biomaterials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Soluble organic substances extracted from compost as amendments for Fenton-like oxidation of contaminated sites.

PubMed

Zingaretti, Daniela; Lombardi, Francesco; Baciocchi, Renato

2018-04-01

The Fenton process is a well known treatment that proved to be effective for the remediation of sites contaminated by a wide range of organic pollutants. Its application to soil-water systems typically requires the addition of a stabilizer, in order to increase the H 2 O 2 lifetime and thus the radius of influence of the treatment, and a chelating agent, aimed to extract and maintain in solution the iron present in the soil. However, as the use of these compounds has been debated for their environmental impact, efforts have been placed to test new "greener" amendments. Namely, in line with the concept of circular economy introduced by the European Council, in this study we have tested the use of humic acids extracted from compost as amendment in a Fenton-like process. These substances are of potential interest as can form complexes with metal ions and act as sorbents for hydrophobic organic compounds. Fenton-like lab-scale tests with the extracted humic acids were performed on a soil-water system artificially contaminated by chlorophenol. The obtained results were compared with those achieved applying commercial humic acids or traditional amendments (i.e. KH 2 PO 4 or EDTA) used as reference. The humic acids extracted from compost allowed to achieve a H 2 O 2 lifetime close to the one obtained with traditional stabilizing agent; besides, humic acids proved also effective in removing chlorophenol, with performance close to the one achieved using a traditional chelating agent. These findings hence suggest that the use of the humic acids extracted from wastes in a Fenton-like process could allow to replace at the same time the H 2 O 2 stabilizer and the chelating agent. Copyright © 2017 Elsevier B.V. All rights reserved.

Purification of yeast alcohol dehydrogenase by using immobilized metal affinity cryogels.

PubMed

Akduman, Begüm; Uygun, Murat; Uygun, Deniz Aktaş; Akgöl, Sinan; Denizli, Adil

2013-12-01

In this study, poly(2-hydroxyethyl methacrylate-glycidylmethacrylate) [poly(HEMA-GMA)] cryogels were prepared by radical cryocopolymerization of HEMA with GMA as a functional comonomer and N,N'-methylene-bisacrylamide (MBAAm) as a crosslinker. Iminodiacetic acid (IDA) functional groups were attached via ring opening of the epoxy group on the poly(HEMA-GMA) cryogels and then Zn(II) ions were chelated with these structures. Characterization of cryogels was performed by FTIR, SEM, EDX and swelling studies. These cryogels have interconnected pores of 30-50 μm size. The equilibrium swelling degree of Zn(II) chelated poly(HEMA-GMA)-IDA cryogels was approximately 600%. Zn(II) chelated poly(HEMA-GMA)-IDA cryogels were used in the adsorption of alcohol dehydrogenase from aqueous solutions and adsorption was performed in continuous system. The effects of pH, alcohol dehydrogenase concentration, temperature, and flow rate on adsorption were investigated. The maximum amount of alcohol dehydrogenase adsorption was determined to be 9.94 mg/g cryogel at 1.0mg/mL alcohol dehydrogenase concentration and in acetate buffer at pH5.0 with a flow rate of 0.5 mL/min. Desorption of adsorbed alcohol dehydrogenase was carried out by using 1.0M NaCI at pH8.0 phosphate buffer and desorption yield was found to be 93.5%. Additionally, these cryogels were used for purification of alcohol dehydrogenase from yeast with a single-step. The purity of desorbed alcohol dehydrogenase was shown by silver-stained SDS-PAGE. This purification process can successfully be used for the purification of alcohol dehydrogenase from unclarified yeast homogenates and this work is the first report about the usage of the cryogels for purification of alcohol dehydrogenase. © 2013 Elsevier B.V. All rights reserved.

Chelating DTPA amphiphiles: ion-tunable self-assembly structures and gadolinium complexes.

PubMed

Moghaddam, Minoo J; de Campo, Liliana; Kirby, Nigel; Drummond, Calum J

2012-10-05

A series of chelating amphiphiles and their gadolinium (Gd(III)) metal complexes have been synthesized and studied with respect to their neat and lyotropic liquid crystalline phase behavior. These amphiphiles have the ability to form ion-tunable self-assembly nanostructures and their associated Gd(III) complexes have potential as magnetic resonance imaging (MRI) contrast enhancement agents. The amphiphiles are composed of diethylenetriaminepentaacetic acid (DTPA) chelates conjugated to one or two oleyl chain(s) (DTPA-MO and DTPA-BO), or isoprenoid-type chain(s) of phytanyl (DTPA-MP and DTPA-BP). The thermal phase behavior of the neat amphiphiles was examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross polarizing optical microscopy (POM). Self-assembly of neat amphiphiles and their associated Gd complexes, as well as their lyotropic phase behavior in water and sodium acetate solutions of different ionic strengths, were examined by POM and small and wide angle X-ray scattering (SWAXS). All neat amphiphiles exhibited lamellar structures. The non-complexed amphiphiles showed a variety of lyotropic phases depending on the number and nature of the hydrophobic chain in addition to the ionic state of the hydration. Upon hydration with increased Na-acetate concentration and the subtle changes in the effective headgroup size, the interfacial curvature of the amphiphile increased, altering the lyotropic liquid crystalline structures towards higher order mesophases such as the gyroid (Ia3d) bicontinuous cubic phase. The chelation of Gd with the DTPA amphiphiles resulted in lamellar crystalline structures for all the neat amphiphiles. Upon hydration with water, the Gd-complexed mono-conjugates formed micellar or vesicular self-assemblies, whilst the bis-conjugates transformed only partially into lyotropic liquid crystalline mesophases.

Towards a selective adsorbent for arsenate and selenite in the presence of phosphate: Assessment of adsorption efficiency, mechanism, and binary separation factors of the chitosan-copper complex.

PubMed

Yamani, Jamila S; Lounsbury, Amanda W; Zimmerman, Julie B

2016-01-01

The potential for a chitosan-copper polymer complex to select for the target contaminants in the presence of their respective competitive ions was evaluated by synthesizing chitosan-copper beads (CCB) for the treatment of (arsenate:phosphate), (selenite:phosphate), and (selenate:sulfate). Based on work by Rhazi et al., copper (II) binds to the amine moiety on the chitosan backbone as a monodentate complex (Type I) and as a bidentate complex crosslinking two polymer chains (Type II), depending on pH and copper loading. In general, the Type I complex exists alone; however, beyond threshold conditions of pH 5.5 during synthesis and a copper loading of 0.25 mol Cu(II)/mol chitosan monomer, the Type I and Type II complexes coexist. Subsequent chelation of this chitosan-copper ligand to oxyanions results in enhanced and selective adsorption of the target contaminants in complex matrices with high background ion concentrations. With differing affinities for arsenate, selenite, and phosphate, the Type I complex favors phosphate chelation while the Type II complex favors arsenate chelation due to electrostatic considerations and selenite chelation due to steric effects. No trend was exhibited for the selenate:sulfate system possibly due to the high Ksp of the corresponding copper salts. Binary separation factors, α12, were calculated for the arsenate-phosphate and selenite-phosphate systems, supporting the mechanistic hypothesis. While, further research is needed to develop a synthesis method for the independent formation of the Type II complexes to select for target contaminants in complex matrices, this work can provide initial steps in the development of a selective adsorbent. Copyright © 2015 Elsevier Ltd. All rights reserved.

Identification of a Pyridoxine-Derived Small-Molecule Inhibitor Targeting Dengue Virus RNA-Dependent RNA Polymerase.

PubMed

Xu, Hong-Tao; Colby-Germinario, Susan P; Hassounah, Said; Quashie, Peter K; Han, Yingshan; Oliveira, Maureen; Stranix, Brent R; Wainberg, Mark A

2016-01-01

The viral RNA-dependent RNA polymerase (RdRp) activity of the dengue virus (DENV) NS5 protein is an attractive target for drug design. Here, we report the identification of a novel class of inhibitor (i.e., an active-site metal ion chelator) that acts against DENV RdRp activity. DENV RdRp utilizes a two-metal-ion mechanism of catalysis; therefore, we constructed a small library of compounds, through mechanism-based drug design, aimed at chelating divalent metal ions in the catalytic site of DENV RdRp. We now describe a pyridoxine-derived small-molecule inhibitor that targets DENV RdRp and show that 5-benzenesulfonylmethyl-3-hydroxy-4-hydroxymethyl-pyridine-2-carboxylic acid hydroxyamide (termed DMB220) inhibited the RdRp activity of DENV serotypes 1 to 4 at low micromolar 50% inhibitory concentrations (IC50s of 5 to 6.7 μM) in an enzymatic assay. The antiviral activity of DMB220 against DENV infection was also verified in a cell-based assay and showed a 50% effective concentration (EC50) of <3 μM. Enzyme assays proved that DMB220 was competitive with nucleotide incorporation. DMB220 did not inhibit the enzymatic activity of recombinant HIV-1 reverse transcriptase and showed only weak inhibition of HIV-1 integrase strand transfer activity, indicating high specificity for DENV RdRp. S600T substitution in the DENV RdRp, which was previously shown to confer resistance to nucleoside analogue inhibitors (NI), conferred 3-fold hypersusceptibility to DMB220, and enzymatic analyses showed that this hypersusceptibility may arise from the decreased binding/incorporation efficiency of the natural NTP substrate without significantly impacting inhibitor binding. Thus, metal ion chelation at the active site of DENV RdRp represents a viable anti-DENV strategy, and DMB220 is the first of a new class of DENV inhibitor. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Antioxidant and cytotoxic activity of new di- and polyamine caffeine analogues.

PubMed

Jasiewicz, Beata; Sierakowska, Arleta; Jankowski, Wojciech; Hoffmann, Marcin; Piorońska, Weronika; Górnicka, Agnieszka; Bielawska, Anna; Bielawski, Krzysztof; Mrówczyńska, Lucyna

2018-04-18

A series of new di- and polyamine-caffeine analogues were synthesized and characterized by NMR, FT-IR and MS spectroscopic methods. To access stability of the investigated caffeine analogues Molecular Dynamic simulations were performed in NAMD 2.9 assuming CHARMM36 force field. To evaluate the antioxidant capacity of new compounds, three different antioxidant assays were used, namely 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH • ) scavenging activity, ferrous ions (Fe 2+ ) chelating activity and Fe 3+ →Fe 2+ reducing ability. In vitro, the ability of new derivatives to protect human erythrocytes against oxidative haemolysis induced by free radical from 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) was estimated. The cytotoxic activity was tested using MCF-7 breast cancer cells and human erythrocytes. All compounds showed the antioxidant capacity depending mostly on their ferrous ions chelating activity. In the presence of AAPH, some derivatives were able to effectively inhibit the oxidative haemolysis. Two derivatives, namely 8-(methyl(2-(methylamino)ethyl)-amino)caffeine and 8-(methyl(3-(methylamino)propyl)amino)caffeine, showed cytotoxic activity against MCF-7 breast cancer cells but not against human erythrocytes. Therefore, it is concluded that the selected di- and polyamine caffeine analogues, depending on their chemical structure, were able to minimize the oxidative stress and to inhibit the tumour cell grow. The confirmed antioxidant and cytotoxic properties of some caffeine derivatives make them attractive for potential applications in food or pharmaceutical industries.

SEPARATION PROCESS USING COMPLEXING AND ADSORPTION

DOEpatents

Spedding, J.H.; Ayers, J.A.

1958-06-01

An adsorption process is described for separating plutonium from a solution of neutron-irradiated uranium containing ions of a compound of plutonium and other cations. The method consists of forming a chelate complex compound with plutoniunn ions in the solution by adding a derivative of 8- hydroxyquinoline, which derivative contains a sulfonic acid group, and adsorbing the remaining cations from the solution on a cation exchange resin, while the complexed plutonium remains in the solution.

Triamines and their derivatives as bifunctional chelating agents

DOEpatents

Troutner, D.E.; John, C.S.; Pillai, M.R.A.

1992-03-31

A group of functionalized triamine chelants and their derivatives that form complexes with radioactive metal ions are disclosed. The complexes can be covalently attached to a protein or an antibody or antibody fragment and used for therapeutic and/or diagnostic purposes. No Drawings

Optimization of Layered Cathode Materials for Lithium-Ion Batteries

PubMed Central

Julien, Christian; Mauger, Alain; Zaghib, Karim; Groult, Henri

2016-01-01

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi2MnO3•(1 − y)LiNi½Mn½O2 layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling. PMID:28773717

Interaction of curcumin with Al(III) and its complex structures based on experiments and theoretical calculations

NASA Astrophysics Data System (ADS)

Jiang, Teng; Wang, Long; Zhang, Sui; Sun, Ping-Chuan; Ding, Chuan-Fan; Chu, Yan-Qiu; Zhou, Ping

2011-10-01

Curcumin has been recognized as a potential natural drug to treat the Alzheimer's disease (AD) by chelating baleful metal ions, scavenging radicals and preventing the amyloid β (Aβ) peptides from the aggregation. In this paper, Al(III)-curcumin complexes with Al(III) were synthesized and characterized by liquid-state 1H, 13C and 27Al nuclear magnetic resonance (NMR), mass spectroscopy (MS), ultraviolet spectroscopy (UV) and generalized 2D UV-UV correlation spectroscopy. In addition, the density functional theory (DFT)-based UV and chemical shift calculations were also performed to view insight into the structures and properties of curcumin and its complexes. It was revealed that curcumin could interact strongly with Al(III) ion, and form three types of complexes under different molar ratios of [Al(III)]/[curcumin], which would restrain the interaction of Al(III) with the Aβ peptide, reducing the toxicity effect of Al(III) on the peptide.

Fabrication of Co3O4 mesoporous thin films by using cobalt/chitosan precursor on fluorine-doped tin oxide glass

NASA Astrophysics Data System (ADS)

Yang, Hui-Chia; Tsai, Jung-Che

2017-06-01

For the development of high-performance and low-cost electrode materials, many alternative materials have been fabricated by various groups. Among these materials, Co3O4 has been demonstrated to be a promising candidate for pseudocapacitors because of its low potential environmental pollution, low cost, and extremely high theoretical specific capacitance. Chitosan, a linear polysaccharide produced by the deacetylation of chitin, is a nontoxic, tissue-compatible polymeric biomaterial. It is usually used to eliminate or filter the heavy metals in wastewater. That is, chitosan can act as a deliverer of metal ions and a nanostructure constructer of metals (or metal oxides). In this study, a facile approach is developed to synthesize mesoporous cobalt oxide thin films on fluorine-doped tin oxide (FTO)-coated glass with environmentally friendly chitosan, which chelates cobalt ions.

Crystal structures reveal metal-binding plasticity at the metallo-β-lactamase active site of PqqB from Pseudomonas putida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tu, Xiongying; Latham, John A.; Klema, Valerie J.

PqqB is an enzyme involved in the biosynthesis of pyrroloquinoline quinone and a distal member of the metallo-β-lactamase (MBL) superfamily. PqqB lacks two residues in the conserved signature motif HxHxDH that makes up the key metal-chelating elements that can bind up to two metal ions at the active site of MBLs and other members of its superfamily. Here, we report crystal structures of PqqB bound to Mn2+, Mg2+, Cu2+, and Zn2+. These structures demonstrate that PqqB can still bind metal ions at the canonical MBL active site. The fact that PqqB can adapt its side chains to chelate a widemore » spectrum of metal ions with different coordination features on a uniform main chain scaffold demonstrates its metal-binding plasticity. This plasticity may provide insights into the structural basis of promiscuous activities found in ensembles of metal complexes within this superfamily. Furthermore, PqqB belongs to a small subclass of MBLs that contain an additional CxCxxC motif that binds a structural Zn2+. Our data support a key role for this motif in dimerization.« less

The fluorescence of a chelating two-photon-absorbing dye is enhanced with the addition of transition metal ions but quenched in the presence of acid

NASA Astrophysics Data System (ADS)

Stewart, David J.; Long, Stephanie L.; Yu, Zhenning; Kannan, Ramamurthi; Mikhailov, Alexandr; Rebane, Aleksander; Tan, Loon-Seng; Haley, Joy E.

2016-09-01

A pseudo-symmetric two-photon absorbing dye (1) containing a central piperazine unit substituted with (benzothiazol-2- yl)-9,9-diethylfluoren-2-yl pendant groups has been synthesized and characterized. The molecule has a two-photonabsorption cross-section of σ2 = 140 GM in tetrahydrofuran at 740 nm and shows significant solvatochromism in the excited-state fluorescence spectra. The emission spectra broaden and the maxima bathochromically shift from 411 nm to 524 nm in n-hexane and acetonitrile, respectively. Moreover, the central piperazine moiety serves as a potential chelation site for ions. Addition of copper(I) hexafluorophosphate and zinc(II) triflate in acetonitrile indicate ground-state complexation with a shift in the emission maximum from 524 nm to 489 nm and 487 nm, respectively. Interestingly, the newly formed Cu and Zn complexes are more strongly emissive than the free dye. Finally, addition of p-toluenesulfonic acid in tetrahydrofuran also blue-shifts the emission maximum, but the intensity is quenched. Due to the photophysical changes induced by addition of metal ions and protons, the dye shows promise as a potential sensor.

Carbon-coated ZnO mat passivation by atomic-layer-deposited HfO2 as an anode material for lithium-ion batteries.

PubMed

Jung, Mi-Hee

2017-11-01

ZnO has had little consideration as an anode material in lithium-ion batteries compared with other transition-metal oxides due to its inherent poor electrical conductivity and large volume expansion upon cycling and pulverization of ZnO-based electrodes. A logical design and facile synthesis of ZnO with well-controlled particle sizes and a specific morphology is essential to improving the performance of ZnO in lithium-ion batteries. In this paper, a simple approach is reported that uses a cation surfactant and a chelating agent to synthesize three-dimensional hierarchical nanostructured carbon-coated ZnO mats, in which the ZnO mats are composed of stacked individual ZnO nanowires and form well-defined nanoporous structures with high surface areas. In order to improve the performance of lithium-ion batteries, HfO 2 is deposited on the carbon-coated ZnO mat electrode via atomic layer deposition. Lithium-ion battery devices based on the carbon-coated ZnO mat passivation by atomic layer deposited HfO 2 exhibit an excellent initial discharge and charge capacities of 2684.01 and 963.21mAhg -1 , respectively, at a current density of 100mAg -1 in the voltage range of 0.01-3V. They also exhibit cycle stability after 125 cycles with a capacity of 740mAhg -1 and a remarkable rate capability. Copyright © 2017 Elsevier Inc. All rights reserved.

Quantum dot nanocrystals having guanosine imprinted nanoshell for DNA recognition.

PubMed

Diltemiz, Sibel Emir; Say, Ridvan; Büyüktiryaki, Sibel; Hür, Deniz; Denizli, Adil; Ersöz, Arzu

2008-05-30

Molecular imprinted polymers (MIPs) as a recognition element for sensors are increasingly of interest and MIP nanoparticles have started to appear in the literature. In this study, we have proposed a novel thiol ligand-capping method with polymerizable methacryloylamido-cysteine (MAC) attached to CdS quantum dots (QDs), reminiscent of a self-assembled monolayer and have reconstructed surface shell by synthetic host polymers based on molecular imprinting method for DNA recognition. In this method, methacryloylamidohistidine-platinium (MAH-Pt(II)) is used as a new metal-chelating monomer via metal coordination-chelation interactions and guanosine templates of DNA. Nanoshell sensors with guanosine templates give a cavity that is selective for guanosine and its analogues. The guanosine can simultaneously chelate to Pt(II) metal ion and fit into the shape-selective cavity. Thus, the interaction between Pt(II) ion and free coordination spheres has an effect on the binding ability of the CdS QD nanosensor. The binding affinity of the guanosine imprinted nanocrystals has investigated by using the Langmuir and Scatchard methods, and experiments have shown the shape-selective cavity formation with O6 and N7 of a guanosine nucleotide (K(a) = 4.841x10(6) mol L(-1)) and a free guanine base (K(a) = 0.894x10(6) mol L(-1)). Additionally, the guanosine template of the nanocrystals is more favored for single stranded DNA compared to double stranded DNA.

Gadolinium chelate coated gold nanoparticles as contrast agents for both X-ray computed tomography and magnetic resonance imaging.

PubMed

Alric, Christophe; Taleb, Jacqueline; Le Duc, Géraldine; Mandon, Céline; Billotey, Claire; Le Meur-Herland, Alice; Brochard, Thierry; Vocanson, Francis; Janier, Marc; Perriat, Pascal; Roux, Stéphane; Tillement, Olivier

2008-05-07

Functionalized gold nanoparticles were applied as contrast agents for both in vivo X-ray and magnetic resonance imaging. These particles were obtained by encapsulating gold cores within a multilayered organic shell which is composed of gadolinium chelates bound to each other through disulfide bonds. The contrast enhancement in MRI stems from the presence of gadolinium ions which are entrapped in the organic shell, whereas the gold core provides a strong X-ray absorption. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in the lungs, spleen, and liver.

8-Hydroxyquinolines: a review of their metal chelating properties and medicinal applications

PubMed Central

Prachayasittikul, Veda; Prachayasittikul, Supaluk; Ruchirawat, Somsak; Prachayasittikul, Virapong

2013-01-01

Metal ions play an important role in biological processes and in metal homeostasis. Metal imbalance is the leading cause for many neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis. 8-Hydroxyquinoline (8HQ) is a small planar molecule with a lipophilic effect and a metal chelating ability. As a result, 8HQ and its derivatives hold medicinal properties such as antineurodegenerative, anticancer, antioxidant, antimicrobial, anti-inflammatory, and antidiabetic activities. Herein, diverse bioactivities of 8HQ and newly synthesized 8HQ-based compounds are discussed together with their mechanisms of actions and structure–activity relationships. PMID:24115839

Culturing Selenastrum capricornutum (Chlorophyta) in a synthetic algal nutrient medium with defined mineral particulates

USGS Publications Warehouse

Kuwabara, J.S.; Davis, J.A.; Chang, Cecily C.Y.

1985-01-01

Algal nutrient studies in chemically-defined media typically employ a synthetic chelator to prevent iron hydroxide precipitation. Micronutrient-particulate interactions may, however, significantly affect chemical speciation and hence biovailability of these nutrients in natural waters. A technique is described by which Selenastrum capricornutum Printz (Chlorophyta) may be cultured in a medium where trace metal speciation (except iron) is controlled, not by organic chelation, but by sorption onto titanium dioxide. Application of this culturing protocol in conjunction with results from sorption studies of nutrient ions on mineral particles provides a means of studying biological impacts of sorptive processes in aquatic environments. ?? 1985 Dr W. Junk Publishers.

Confirmation of heavy metal ions in used lubricating oil from a passenger car using chelating self-assembled monolayer.

PubMed

Ko, Young Gun; Kim, Choong Hyun

2006-09-01

In order to prevent engine failure, the oil must be changed before it loses its protective properties. It is necessary to monitor the actual physical and chemical condition of the oil to reliably determine the optimum oil-change interval. Our study focuses on the condition of the lubricating oil in an operated car engine. Shear stress curves and viscosity curves as a function of the shear rate for fresh and used lubricating oil were examined. Metal nitrate was detected in the lubricating oil from the operated car engine through the use of a chelating self-assembled monolayer.

Determination of traces of silver in waters by anion exchange and atomic absorption spectrophotometry

USGS Publications Warehouse

Chao, T.T.; Fishman, M. J.; Ball, J.W.

1969-01-01

A method has been developed for the accurate determination of 0.1-1 ??g of silver per liter of water. The method permits stabilization of silver in water without loss to container walls. Optimum conditions have been established for the complete recovery of silver from water with an anion-exchange column, for quantitative elution of silver from the resin, and for measurement of silver by atomic absorption spectrophotometry after chelation with ammonium pyrrolidine dithiocarbamate and extraction of the chelate with MIBK. Silver in the 1-10 ??g 1 range can be determined by extraction without pre-concentration on an ion-exchange resin. ?? 1969.

The solution structure of Ln (DOTP) 5- complexxes. A comparison of lanthanide-induced paramagnetic shifts with the MMX energy-minimized structure

NASA Astrophysics Data System (ADS)

Geraldes, Carlos F. G. C.; Sherry, A. Dean; Kiefer, Garry E.

Complexes between the trivalent lanthanide ions and the macrocyclic chelate 1,4,7,10-tetraazacyclododecane- N,N',N″,N‴-tetra(methylene phosphonate) (DOTP) have been examined by high-resolution NMR spectroscopy. The proton spectra of the diamagnetic La(DOTP) 5- and Lu(DOTP) 5- complexes provide evidence for very rigid chelate structures with the ethylenediamine-containing chelate rings essentially locked into a single conformation at room temperature. The activation energy for ethylenediamine chelate ring interconversions in these complexes is approximately 100 kJ mol -1, considerably higher than that reported previously for the corresponding Ln(DOTA) - complexes (DOTA is the tetraacetate analog of DOTP). Lanthanide-induced shifts are reported for all 1H, 13C, and 31P nuclei in 11 Ln(DOTP) 5- complexes. The proton spectra of these complexes display unusually large lanthanide-induced shifts, one showing a spectrum in which the 1H resonances span 900 ppm. The contact and pseudocontact contributions to these shifts were separated using Reilley's temperature-independent method and the resulting pseudocontact lanthanide-induced NMR shifts were in excellent agreement with those calculated for a structure derived using MMX molecular modeling methods. The pseudocontact shifts provide evidence for Ln (DOTP) 5- chelates which have virtually identical structures along the lanthanide series, with the possible exception of Tm(DOTP) 5-.

Antioxidant and chelating capacity of Maillard reaction products in amino acid-sugar model systems: applications for food processing.

PubMed

Mondaca-Navarro, Blanca A; Ávila-Villa, Luz A; González-Córdova, Aarón F; López-Cervantes, Jaime; Sánchez-Machado, Dalia I; Campas-Baypoli, Olga N; Rodríguez-Ramírez, Roberto

2017-08-01

Maillard reaction products (MRP) have gained increasing interest owing to their both positive and negative effects on human health. Aqueous amino acid-sugar model systems were studied in order to evaluate the antioxidant and chelating activity of MRP under conditions similar to those of food processing. Amino acids (cysteine, glycine, isoleucine and lysine) combined with different sugars (fructose or glucose) were heated to 100 and 130 °C for 30, 60 and 90 min. Antioxidant capacity was evaluated via ABTS and DPPH free radical scavenging assays, in addition to Fe 2+ and Cu 2+ ion chelating capacity. In the ABTS assay, the cysteine-fructose model system presented the highest antioxidant activity at 7.05 µmol mL -1 (130 °C, 60 min), expressed in Trolox equivalents. In the DPPH assay, the cysteine-glucose system presented the highest antioxidant activity at 3.79 µmol mL -1 (100 °C, 90 min). The maximum rate of chelation of Fe 2+ and Cu 2+ was 96.31 and 59.44% respectively in the lysine-fructose and cysteine-glucose systems (100 °C, 30 min). The model systems presented antioxidant and chelating activity under the analyzed temperatures and heating times, which are similar to the processing conditions of some foods. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Nickel(II) Inhibits Tet-Mediated 5-Methylcytosine Oxidation by High Affinity Displacement of the Cofactor Iron(II).

PubMed

Yin, Ruichuan; Mo, Jiezhen; Dai, Jiayin; Wang, Hailin

2017-06-16

Ten-eleven translocation (Tet) family proteins are Fe(II)- and 2-oxoglutarate-dependent dioxygenases that regulate the dynamics of DNA methylation by catalyzing the oxidation of DNA 5-methylcytosine (5mC). To exert physiologically important functions, redox-active iron chelated in the catalytic center of Tet proteins directly involves the oxidation of the multiple substrates. To understand the function and interaction network of Tet dioxygenases, it is interesting to obtain high affinity and a specific inhibitor. Surprisingly, here we found that natural Ni(II) ion can bind to the Fe(II)-chelating motif (HXD) with an affinity of 7.5-fold as high as Fe(II). Consistently, we further found that Ni(II) ion can displace the cofactor Fe(II) of Tet dioxygenases and inhibit Tet-mediated 5mC oxidation activity with an estimated IC 50 of 1.2 μM. Essentially, Ni(II) can be used as a high affinity and selective inhibitor to explore the function and dynamics of Tet proteins.

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

NASA Astrophysics Data System (ADS)

Wang, Yongliang; Li, Baoqiang; Zhou, Yu; Jia, Dechang

2009-09-01

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS-Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4 and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3 and hydroxyapatite.

A morphological screening of protein crystals for interferon delivery by metal ion-chelate technology.

PubMed

Jiang, Yanbo; Shi, Kai; Wang, Shuo; Li, Xuefeng; Cui, Fude

2010-12-01

This study presents a preliminary exploration on extending the half-life of therapeutic proteins by crystallization strategy without new molecular entities generation. Recombinant human interferon (rhIFN) α-2b, a model protein drug in this case, was crystallized using a hanging-drop vapor diffusion method. A novel chelating technique with metal ions was employed to promote crystals formation. The effects of key factors such as seeding protein concentration, pH of the hanging drop, ionic strength of the equilibration solution, and precipitants were investigated. Size-exclusion liquid chromatography, antiviral activity determination, and enzyme-linked immunosorbent assay indicated that both the molecular integrity and biological potency of rhIFN were not significantly affected by crystallization process. In addition, the in vitro release behavior of rhIFN from crystal lattice was characterized by an initial fast release, followed by a sustained release up to 48 hour. The work described here suggested an exciting possibility of therapeutic protein crystals as a long-acting formulation.

Synthesis and evaluation of nanoglobular macrocyclic Mn(II) chelate conjugates as non-gadolinium(III) MRI contrast agents.

PubMed

Tan, Mingqian; Ye, Zhen; Jeong, Eun-Kee; Wu, Xueming; Parker, Dennis L; Lu, Zheng-Rong

2011-05-18

Because of the recent observation of the toxic side effects of Gd(III) based MRI contrast agents in patients with impaired renal function, there is strong interest on developing alternative contrast agents for MRI. In this study, macrocyclic Mn(II) chelates were conjugated to nanoglobular carriers, lysine dendrimers with a silsesquioxane core, to synthesize non-Gd(III) based MRI contrast agents. A generation 3 nanoglobular conjugate of Mn(II)-1,4,7-triaazacyclononane-1,4,7-triacetate-GA amide (G3-NOTA-Mn) was also synthesized and evaluated. The per ion T(1) and T(2) relaxivities of G2, G3, G4 nanoglobular Mn(II)-DOTA monoamide conjugates decreased with increasing generation of the carriers. The T(1) relaxivities of G2, G3, and G4 nanoglobular Mn(II)-DOTA conjugates were 3.3, 2.8, and 2.4 mM(-1) s(-1) per Mn(II) chelate at 3 T, respectively. The T(1) relaxivity of G3-NOTA-Mn was 3.80 mM(-1) s(-1) per Mn(II) chelate at 3 T. The nanoglobular macrocyclic Mn(II) chelate conjugates showed good in vivo stability and were readily excreted via renal filtration. The conjugates resulted in much less nonspecific liver enhancement than MnCl(2) and were effective for contrast-enhanced tumor imaging in nude mice bearing MDA-MB-231 breast tumor xenografts at a dose of 0.03 mmol Mn/kg. The nanoglobular macrocyclic Mn(II) chelate conjugates are promising nongadolinium based MRI contrast agents.

Effects of ionised or chelated water-soluble mineral mixture supplementation on growth performance, nutrient digestibility, blood characteristics, meat quality and intestinal microbiota in broilers.

PubMed

Upadhaya, S D; Lee, B R; Kim, I H

2016-04-01

An experiment was conducted to study the effects of dietary supplementation of water-soluble ionised or chelated mineral mixture on growth performance, nutrient digestibility, blood characteristics, relative organ weight, meat quality and excreta microflora in broilers. A total of 408 Arbor Acres broilers (17 birds in 8 replicate pens) were randomly allocated into one of the following three treatments: (1) Control/basal diet (CON), (2) T1 (basal diet + 0.5% ionised mineral mixture solution, pH 3.0) and (3) T2 (basal diet + 0.5% chelated mineral mixture solution, pH 3.0). The body weight gain was greater and feed conversion ratio was lower in broilers supplemented with ionised or chelated mineral liquid complex compared to CON during the grower and overall phase of the experiment. No significant effect in the concentration of Ca and P in the blood was observed in birds supplemented with ionised or chelated mineral mixture solution. No adverse effects were observed in organ weight and meat quality with ionised or chelated mineral mixture supplementation. Regarding intestinal microbiota counts there was a reduction of Escherichia coli counts in the small intestine in ionised mineral supplemented birds. In the large intestine, E. coli as well as Salmonella populations were reduced in ionised mineral supplemented birds. In conclusion, ionised or chelated minerals have partial positive effects in improving growth performance and reducing pathogenic bacteria load in the gastro-intestinal tract.

Iron uptake in Mycelia sterilia EP-76.

PubMed Central

Adjimani, J P; Emery, T

1987-01-01

The cyclic trihydroxamic acid, N,N',N''-triacetylfusarinine C, produced by Mycelia sterilia EP-76, was shown to be a ferric ionophore for this organism. The logarithm of the association constant k for the ferric triacetylfusarinine C chelate was determined to be 31.8. Other iron-chelating agents, such as rhodotorulic acid, citric acid, and the monomeric subunit of triacetylfusarinine C, N-acetylfusarinine, delivered iron to the cells by an indirect mechanism involving iron exchange into triacetylfusarinine C. In vitro ferric ion exchange was found to be rapid with triacetylfusarinine C. Gallium uptake rates comparable to those of iron were observed with the chelating agents that transport iron into the cell. Ferrichrome, but not ferrichrome A, was also capable of delivering iron and gallium to this organism, but not by an exchange mechanism. Unlike triacetylfusarinine C, the 14C-ligand of ferrichrome was retained by the cell. A midpoint potential of -690 mV with respect to the saturated silver chloride electrode was obtained for the ferric triacetylfusarinine C complex, indicating that an unfavorable reduction potential was not the reason for the use of a hydrolytic mechanism of intracellular iron release from the ferric triacetylfusarinine C chelate. PMID:3611025

Influence of structural and surface properties of whey-derived peptides on zinc-chelating capacity, and in vitro gastric stability and bioaccessibility of the zinc-peptide complexes.

PubMed

Udechukwu, M Chinonye; Downey, Brianna; Udenigwe, Chibuike C

2018-02-01

Gastrointestinal stability of zinc-peptide complexes is essential for zinc delivery. As peptide surface charge can influence their metal complex stability, we evaluated the zinc-chelating capacity and stability of zinc complexes of whey protein hydrolysates (WPH), produced with Everlase (WPH-Ever; ζ-potential, -39mV) and papain (WPH-Pap; ζ-potential, -7mV), during simulated digestion. WPH-Ever had lower amount of zinc-binding amino acids but showed higher zinc-chelating capacity than WPH-Pap. This is attributable to the highly anionic surface charge of WPH-Ever for electrostatic interaction with zinc. Release of zinc during peptic digestion was lower for WPH-Ever-zinc, and over 50% of zinc remained bound in both peptide complexes after peptic-pancreatic digestion. Fourier transform infrared spectroscopy suggests the involvement of carboxylate ion, and sidechain carbon-oxygen of aspartate/glutamate and serine/threonine in zinc-peptide complexation. The findings indicate that strong zinc chelation can promote gastric stability and impede intestinal release, for peptides intended for use as dietary zinc carriers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structure-Based Design and Synthesis of Potent and Selective Matrix Metalloproteinase 13 Inhibitors.

PubMed

Choi, Jun Yong; Fuerst, Rita; Knapinska, Anna M; Taylor, Alexander B; Smith, Lyndsay; Cao, Xiaohang; Hart, P John; Fields, Gregg B; Roush, William R

2017-07-13

We describe the use of comparative structural analysis and structure-guided molecular design to develop potent and selective inhibitors (10d and (S)-17b) of matrix metalloproteinase 13 (MMP-13). We applied a three-step process, starting with a comparative analysis of the X-ray crystallographic structure of compound 5 in complex with MMP-13 with published structures of known MMP-13·inhibitor complexes followed by molecular design and synthesis of potent but nonselective zinc-chelating MMP inhibitors (e.g., 10a and 10b). After demonstrating that the pharmacophores of the chelating inhibitors (S)-10a, (R)-10a, and 10b were binding within the MMP-13 active site, the Zn 2+ chelating unit was replaced with nonchelating polar residues that bridged over the Zn 2+ binding site and reached into a solvent accessible area. After two rounds of structural optimization, these design approaches led to small molecule MMP-13 inhibitors 10d and (S)-17b, which bind within the substrate-binding site of MMP-13 and surround the catalytically active Zn 2+ ion without chelating to the metal. These compounds exhibit at least 500-fold selectivity versus other MMPs.

Spectroscopic studies on the antioxidant activity of ellagic acid

NASA Astrophysics Data System (ADS)

Kilic, Ismail; Yeşiloğlu, Yeşim; Bayrak, Yüksel

2014-09-01

Ellagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2‧-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 μg/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), α-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH• scavenging, ABTSrad + scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that EA can be used in the pharmacological, food industry and medicine because of these properties.

Spectroscopic studies on the antioxidant activity of p-coumaric acid

NASA Astrophysics Data System (ADS)

Kiliç, Ismail; Yeşiloğlu, Yeşim

2013-11-01

p-coumaric acid (4-hydroxycinnamic acid), a phenolic acid, is a hydroxyl derivative of cinnamic acid. It decreases low density lipoprotein (LDL) peroxidation and reduces the risk of stomach cancer. In vitro radical scavenging and antioxidant capacity of p-coumaric acid were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2‧-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. p-Coumaric acid inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 μg/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and ascorbic acid displayed 66.8%, 69.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, p-coumaric acid had an effective DPPHrad scavenging, ABTSrad + scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that p-coumaric acid can be used in the pharmacological and food industry because of these properties.

Exploration research on synthesis and application of a new dye containing di-2-picolyamine

NASA Astrophysics Data System (ADS)

Zhang, Huihui; Wei, Zeyue; Xia, Ying; Fang, Min; Zhu, Weiju; Yang, Xingyuan; Li, Fei; Tian, Yupeng; Zhang, Xuanjun; Zhou, Hongping

2018-05-01

A newly designed fluorescence dye L based on di-2-picolyamine (DPA) moiety as a chelator was obtained under the protection of N2 at 120 °C, and KI as catalyst with relatively better yield. More interestingly, L not only could selectively and sensitively detect Cu2+ ions in aqueous medium but also examine the Cu2+ ions of the actual water samples. Nevertheless, L could be visual in Hela cells with excellent cell permeability, viz, monitoring exogenous Cu2+ ions as well as realizing an "on-off-on" process.

The influence of functional groups on the permeation and distribution of antimycobacterial rhodamine chelators.

PubMed

Moniz, T; Leite, A; Silva, T; Gameiro, P; Gomes, M S; de Castro, B; Rangel, M

2017-10-01

We formerly hypothesized a mechanism whereby the antimycobacterial efficiency of a set of rhodamine labelled iron chelators is improved via the rhodamine fluorophore which enhances the chelators' permeation properties through membranes. To validate our hypothesis in a cellular context and to understand the influence of the structure of the fluorophore on the chelator's uptake and distribution within macrophages we now report comparative confocal microscopy studies performed with a set of rhodamine labelled chelators. We identify the functional groups of the chelator's framework that favor uptake by macrophages and conclude that the antimycobacterial effect is strongly related with the capacity of the chelator to distribute within the host cell and its compartments, a property that is closely related with the chelators' ability to interact with membranes. The quantification of the chelators' interaction with membranes was assessed through measurement of the corresponding partition constants in liposomes. The overall results support that the compounds which are preferentially taken up are the most efficient antimycobacterial chelators and for that reason we infer that the biological activity is modulated by the structural features of the fluorophore. Copyright © 2017 Elsevier Inc. All rights reserved.

Discrimination of fluorescence light-up effects induced by pH and metal ion chelation on a spirocyclic derivative of rhodamine B.

PubMed

Leite, Andreia; Silva, Ana M G; Cunha-Silva, Luís; de Castro, Baltazar; Gameiro, Paula; Rangel, Maria

2013-05-07

In the present work we describe the structure and the spectroscopic characterization of a spirocyclic derivative of a rhodamine B ligand whose properties allow discrimination of light-up effects induced by metal ion chelation and variation of pH. Distinction of the two effects is important for the use of this type of ligand to detect and monitor metal ions in aqueous solutions. The synthesis of the ligand was performed in two steps, which involve the reaction of rhodamine B with hydrazine hydrate to form rhodamine B hydrazide followed by condensation with 2-pyridinecarboxaldehyde and was successfully optimized using a solvent free approach under microwave irradiation. The ligand was obtained in the expected spirolactam form and was characterized in the solid state by EA, MS and single-crystal X-ray diffraction. The ligand was characterized in solution by NMR and absorption and fluorescence spectroscopies and its properties were found to be sensitive to pH and concentration of iron(III). The study of the fluorescence properties at variable pH shows that the compound is fluorescent in the range 2 < pH < 4 with maximum intensity at pH 3 and allowed the determination of two pK(a) values (pK(a1) = 2.98, pK(a2) = 2.89) and establishment of the corresponding distribution diagram. The very low pK(a) values guarantee that above pH equal to 4 the ligand is mostly present in the fully non-protonated and non-fluorescent form L. The study of the interaction of the ligand with iron(iii) was performed in DMSO and DMSO-H(2)O to exclude the influence of pH and due to the low solubility of the compound. The results indicate that the presence of iron(III) triggers the opening of the spirolactam form of the ligand and the maximum intensity obtained at a metal : ligand ratio of 1 : 2 is consistent with the formation of an iron(III) complex with the tridentate ligand.

Method of removing nitrogen monoxide from a nitrogen monoxide-containing gas using a water-soluble iron ion-dithiocarbamate, xanthate or thioxanthate

DOEpatents

Liu, D. Kwok-Keung; Chang, Shih-Ger

1987-08-25

The present invention relates to a method of removing of nitrogen monoxide from a nitrogen monoxide-containing gas which method comprises contacting a nitrogen oxide-containing gas with an aqueous solution of water soluble organic compound-iron ion chelate complex. The NO absorption efficiency of ferrous urea-dithiocarbamate and ferrous diethanolamine-xanthate as a function of time, oxygen content and solution ph is presented. 3 figs., 1 tab.

C-H oxidation and chelation of a dipyrromethane mediated rapid colorimetric naked-eye Cu(ii) chemosensor.

PubMed

Rajmohan, Rajamani; Ayaz Ahmed, Khan Behlol; Sangeetha, Sampathkumar; Anbazhagan, Veerappan; Vairaprakash, Pothiappan

2017-09-08

Copper(ii) ion mediated C-H oxidation of dipyrromethanes (DPMs) to the corresponding dipyrrins followed by complexation invoked the selective sensing of copper(ii) ions in aqueous solutions. On the addition of copper, the colour of the DPM solution instantaneously changes from yellow to pink with the detection limit of 0.104 μM measured by absorption spectroscopy, whereas visible colour changes could be observed by the naked eye for concentrations as low as 3 μM.

Development of an upconverting chelate assay

NASA Astrophysics Data System (ADS)

Xiao, Xudong; Haushalter, Jeanne P.; Kotz, Kenneth T.; Faris, Gregory W.

2005-04-01

We report progress on performing a cell-based assay for the detection of EGFR on cell surfaces by using upconverting chelates. An upconversion microscope has been developed for performing assays and testing optical response. A431 cells are labeled with europium DOTA and imaged using this upconverting microscope.

Metal-Chelate Polymers: Structural/Property Relationships as a Function of the Metal Ion.

DTIC Science & Technology

1984-03-01

and Stein;17 yield, 39%. This compound was simultaneously decarboxylated and dehydrogenated with palladium on 7 charcoal in 1,2,4-trichlorobenzene...Minnesota 55455 Dr. Theodore E. Madey Dr. Keith H. Johnson Surface Chemistry Section Department of Metallurgy and Department of Commerce Materials

Aromatic triamide-lanthanide complexes

DOEpatents

Raymond, Kenneth N; Petoud, Stephane; Xu, Jide

2013-10-08

The present invention provides luminescent lanthanide metal chelates comprising a metal ion of the lanthanide series and a complexing agent comprising at least one phthalamidyl moiety. Also provided are probes incorporating the phthalamidyl ligands of the invention and methods utilizing the ligands of the invention and probes comprising the ligands of the invention.

Discovery of novel PDE9 inhibitors capable of inhibiting Aβ aggregation as potential candidates for the treatment of Alzheimer's disease.

PubMed

Su, Tao; Zhang, Tianhua; Xie, Shishun; Yan, Jun; Wu, Yinuo; Li, Xingshu; Huang, Ling; Luo, Hai-Bin

2016-02-25

Recently, phosphodiesterase-9 (PDE9) inhibitors and biometal-chelators have received much attention as potential therapeutics for the treatment of Alzheimer's disease (AD). Here, we designed, synthesized, and evaluated a novel series of PDE9 inhibitors with the ability to chelate metal ions. The bioassay results showed that most of these molecules strongly inhibited PDE9 activity. Compound 16 showed an IC50 of 34 nM against PDE9 and more than 55-fold selectivity against other PDEs. In addition, this compound displayed remarkable metal-chelating capacity and a considerable ability to halt copper redox cycling. Notably, in comparison to the reference compound clioquinol, it inhibited metal-induced Aβ(1-42) aggregation more effectively and promoted greater disassembly of the highly structured Aβ fibrils generated through Cu(2+)-induced Aβ aggregation. These activities of 16, together with its favorable blood-brain barrier permeability, suggest that 16 may be a promising compound for treatment of AD.

Lanthanides caged by the organic chelates; structural properties

NASA Astrophysics Data System (ADS)

Smentek, Lidia

2011-04-01

The structure, in particular symmetry, geometry and morphology of organic chelates coordinated with the lanthanide ions are analyzed in the present review. This is the first part of a complete presentation of a theoretical description of the properties of systems, which are widely used in technology, but most of all, in molecular biology and medicine. The discussion is focused on the symmetry and geometry of the cages, since these features play a dominant role in the spectroscopic activity of the lanthanides caged by organic chelates. At the same time, the spectroscopic properties require more formal presentation in the language of Racah algebra, and deserve a separate analysis. In addition to the parent systems of DOTA, DOTP, EDTMP and CDTMP presented here, their modifications by various antennas are analyzed. The conclusions that have a strong impact upon the theory of the energy transfer and the sensitized luminescence of these systems are based on the results of numerical density functional theory calculations.

Particulate nanocomposite from oyster (Crassostrea rivularis) hydrolysates via zinc chelation improves zinc solubility and peptide activity.

PubMed

Zhang, Ziran; Zhou, Feibai; Liu, Xiaoling; Zhao, Mouming

2018-08-30

An oyster protein hydrolysates-zinc complex (OPH-Zn) was prepared and investigated to improve zinc bioaccessibility. Zinc ions chelating with oyster protein hydrolysates (OPH) cause intramolecular and intermolecular folding and aggregation, homogeneously forming the OPH-Zn complex as nanoclusters with a Z-average at 89.28 nm (PDI: 0.16 ± 0.02). The primary sites of zinc-binding in OPH were carboxyl groups, carbonyl groups, and amino groups, and they were related to the high number of charged amino acid residues. Furthermore, formation of the OPH-Zn complex could significantly enhance zinc solubility both under specific pH conditions as well as during simulated gastrointestinal digestion, compared to the commonly used ZnSO 4 . Additionally, after digestion, either preserved or enhanced antioxidant activity of OPH was found when chelated with zinc. These results indicated that the OPH-Zn complex could be a potential functional ingredient with improved antioxidant bioactivity and zinc bioaccessibility. Copyright © 2018. Published by Elsevier Ltd.

Metal chelate affinity precipitation of RNA and purification of plasmid DNA

NASA Technical Reports Server (NTRS)

Balan, Sindhu; Murphy, Jason; Galaev, Igor; Kumar, Ashok; Fox, George E.; Mattiasson, Bo; Willson, Richard C.

2003-01-01

The affinity of metal chelates for amino acids, such as histidine, is widely used in purifying proteins, most notably through six-histidine 'tails'. We have found that metal affinity interactions can also be applied to separation of single-stranded nucleic acids through interactions involving exposed purines. Here we describe a metal affinity precipitation method to resolve RNA from linear and plasmid DNA. A copper-charged copolymer of N-isopropyl acrylamide (NIPAM) and vinyl imidazole (VI) is used to purify plasmid from an alkaline lysate of E. coli. The NIPAM units confer reversible solubility on the copolymer while the imidazole chelates metal ions in a manner accessible to interaction with soluble ligands. RNA was separated from the plasmid by precipitation along with the polymer in the presence of 800 mM NaCl. Bound RNA could be recovered by elution with imidazole and separated from copolymer by a second precipitation step. RNA binding showed a strong dependence on temperature and on the type of buffer used.

Production and Characterization of Desmalonichrome Relative Binding Affinity for Uranyl Ions in Relation to Other Siderophores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mo, Kai-For; Dai, Ziyu; Wunschel, David S.

2016-06-24

Siderophores are Fe binding secondary metabolites that have been investigated for their uranium binding properties. Much of the previous work has focused on characterizing hydroxamate types of siderophores, such as desferrioxamine B, for their uranyl binding affinity. Carboxylate forms of these metabolites hold potential to be more efficient chelators of uranyl, yet they have not been widely studied and are more difficult to obtain. Desmalonichrome is a carboxylate siderophore which is not commercially available and so was obtained from the ascomycete fungus Fusarium oxysporum cultivated under Fe depleted conditions. The relative affinity for uranyl binding of desmalonichrome was investigated usingmore » a competitive analysis of binding affinities between uranyl acetate and different concentrations of iron(III) chloride using electrospray ionization mass spectrometry (ESI-MS). In addition to desmalonichrome, three other siderophores, including two hydroxamates (desferrioxamine B and desferrichrome) and one carboxylate (desferrichrome A) were studied to understand their relative affinities for the uranyl ion at two pH values. The binding affinities of hydroxymate siderophores to uranyl ion were found to decrease to a greater degree at lower pH as the concentration of Fe (III) ion increases. On the other hand, lowering pH has little impact on the binding affinities between carboxylate siderophores and uranyl ion. Desmalonichrome was shown to have the greatest relative affinity for uranyl at any pH and Fe(III) concentration. These results suggest that acidic functional groups in the ligands are critical for strong chelation with uranium at lower pH.« less

Functional magnetic microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Landel, Robert F. (Inventor); Yen, Shiao-Ping S. (Inventor)

1981-01-01

Functional magnetic particles are formed by dissolving a mucopolysaccharide such as chitosan in acidified aqueous solution containing a mixture of ferrous chloride and ferric chloride. As the pH of the solution is raised magnetite is formed in situ in the solution by raising the pH. The dissolved chitosan is a polyelectrolyte and forms micelles surrounding the granules at pH of 8-9. The chitosan precipitates on the granules to form microspheres containing the magnetic granules. On addition of the microspheres to waste aqueous streams containing dissolved ions, the hydroxyl and amine functionality of the chitosan forms chelates binding heavy metal cations such as lead, copper, and mercury and the chelates in turn bind anions such as nitrate, fluoride, phosphate and borate.

Boric acid reversibly inhibits the second step of pre-mRNA splicing.

PubMed

Shomron, Noam; Ast, Gil

2003-09-25

Several approaches have been used to identify the factors involved in mRNA splicing. None of them, however, comprises a straightforward reversible method for inhibiting the second step of splicing using an external reagent other than a chelator. This investigation demonstrates that the addition of boric acid to an in vitro pre-mRNA splicing reaction causes a dose-dependent reversible inhibition effect on the second step of splicing. The mechanism of action does not involve chelation of several metal ions; hindrance of 3' splice-site; or binding to hSlu7. This study presents a novel method for specific reversible inhibition of the second step of pre-mRNA splicing.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop for preconcentration and determination of trace amounts of copper by flame atomic absorption spectrometry.

PubMed

Karadaş, Cennet; Kara, Derya

2017-04-01

A novel, simple, rapid, sensitive, inexpensive and environmentally friendly dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO) was developed for the determination of copper by flame atomic absorption spectrometry (FAAS). N-o-Vanillidine-2-amino-p-cresol was used as a chelating ligand and 1-undecanol was selected as an extraction solvent. The main parameters affecting the performance of DLLME-SFO, such as sample pH, volume of extraction solvent, extraction time, concentration of the chelating ligand, salt effect, centrifugation time and sample volume were investigated and optimized. The effect of interfering ions on the recovery of copper was also examined. Under the optimum conditions, the detection limit (3σ) was 0.93μgL -1 for Cu using a sample volume of 20mL, yielding a preconcentration factor of 20. The proposed method was successfully applied to the determination of Cu in tap, river and seawater, rice flour and black tea samples as well as certified reference materials. Copyright © 2016. Published by Elsevier Ltd.

Consequence of the antioxidant activities and tyrosinase inhibitory effects of various extracts from the fruiting bodies of Pleurotus ferulae

PubMed Central

Alam, Nuhu; Yoon, Ki Nam; Lee, Jae Seong; Cho, Hae Jin; Lee, Tae Soo

2011-01-01

This study was initiated to screen the antioxidant activities, tyrosinase inhibitory effects on the fruiting bodies of Pleurotus ferulae extracted with acetone, methanol and hot water. The antioxidant activities were performed on β-carotene–linoleic acid, reducing power, DPPH, ferrous ions chelating abilities, and xanthine oxidase. In addition to this, phenolic compounds were also analyzed. The methanolic extract showed the strongest β-carotene–linoleic acid inhibition and high reducing power as compared to other extracts. The scavenging effects on DPPH radicals, the acetonic and methanolic extracts were more effective than hot water extracts. The strongest chelating effect was obtained from the methanolic extract as compared to the tested synthetic antioxidant. Gallic acid, protocatechuic acid, caffeic acid, vanillin, ferulic acid, naringin, resveratrol, naringenin, hesperetin, formononetin and biochanin-A were detected from acetonitrile and hydrochloric acid (5:1) solvent extract. Xanthine oxidase and tyrosinase inhibitory activities of acetonic, methanolic, and hot water extracts of P. ferulae increased with increasing concentration. The results suggested that consumption of P. ferulae might be beneficial to the antioxidant, xanthine oxidase, and tyrosinase protection system of the human body against oxidative damage and others complications. PMID:23961169

Swelling and Softening of the Cowpea Chlorotic Mottle Virus in Response to pH Shifts

PubMed Central

Wilts, Bodo D.; Schaap, Iwan A.T.; Schmidt, Christoph F.

2015-01-01

Cowpea chlorotic mottle virus (CCMV) forms highly elastic icosahedral protein capsids that undergo a characteristic swelling transition when the pH is raised from 5 to 7. Here, we performed nano-indentation experiments using an atomic force microscope to track capsid swelling and measure the shells’ Young’s modulus at the same time. When we chelated Ca2+ ions and raised the pH, we observed a gradual swelling of the RNA-filled capsids accompanied by a softening of the shell. Control experiments with empty wild-type virus and a salt-stable mutant revealed that the softening was not strictly coupled to the swelling of the protein shells. Our data suggest that a pH increase and Ca2+ chelation lead primarily to a loosening of contacts within the protein shell, resulting in a softening of the capsid. This appears to render the shell metastable and make swelling possible when repulsive forces among the capsid proteins become large enough, which is known to be followed by capsid disassembly at even higher pH. Thus, softening and swelling are likely to play a role during inoculation. PMID:25992732

Rhelogical, dermal wound healing and in vitro antioxidant properties of exopolysaccharide hydrogel from Pseudomonas stutzeri AS22.

PubMed

Maalej, Hana; Moalla, Dorsaf; Boisset, Claire; Bardaa, Sana; Ben Ayed, Hanen; Sahnoun, Zouheir; Rebai, Tarek; Nasri, Moncef; Hmidet, Noomen

2014-11-01

The in vitro antioxidant activity and the in vivo wound healing performance of the exopolysaccharide EPS22, produced by Pseudomonas stutzeri AS22, were investigated. Antioxidant activity was evaluated by three different tests. The scavenging effect on DPPH radicals at a concentration of 1mg/ml was 80±1.41%. The reducing power reached a maximum of 1.26±0.02 at 2 mg/ml. Moreover, EPS22 showed good chelating ability and chelated almost 88.5±0.7% of ferrous ions at 0.75 mg/ml. The rheological characterization of EPS22 gel (0.5%) showed a pseudoplastic behavior, high elasticity, good mechanical strength and stability with high water-absorption ability. The application of the EPS22 gel on dermal full-thickness excision wounds in a rat model every two days, enhanced significantly wound healing activity and a total closure was achieved after 12 days of wound induction. Further, histological examination of biopsies showed advanced tissue regeneration, characterized by the presence of well-organized stratum of both derma and epidermis. Copyright © 2014 Elsevier B.V. All rights reserved.

Biodegradable gadolinium-chelated cationic poly(urethane amide) copolymers for gene transfection and magnetic resonance imaging.

PubMed

Gao, Xiaolong; Wang, Gangmin; Shi, Ting; Shao, Zhihong; Zhao, Peng; Shi, Donglu; Ren, Jie; Lin, Chao; Wang, Peijun

2016-08-01

Theranostic nano-polyplexes containing gene and imaging agents hold a great promise for tumor diagnosis and therapy. In this work, we develop a group of new gadolinium (Gd)-chelated cationic poly(urethane amide)s for gene delivery and T1-weighted magnetic resonance (MR) imaging. Cationic poly(urethane amide)s (denoted as CPUAs) having multiple disulfide bonds, urethane and amide linkages were synthesized by stepwise polycondensation reaction between 1,4-bis(3-aminopropyl)piperazine and a mixture of di(4-nitrophenyl)-2, 2'-dithiodiethanocarbonate (DTDE-PNC) and diethylenetriaminepentaacetic acid (DTPA) dianhydride at varied molar ratios. Then, Gd-chelated CPUAs (denoted as GdCPUAs) were produced by chelating Gd(III) ions with DTPA residues of CPUAs. These GdCPUAs could condense gene into nanosized and positively-charged polyplexes in a physiological condition and, however, liberated gene in an intracellular reductive environment. In vitro transfection experiments revealed that the GdCPUA at a DTDE-PNC/DTPA residue molar ratio of 85/15 induced the highest transfection efficiency in different cancer cells. This efficiency was higher than that yielded with 25kDa branched polyethylenimine as a positive control. GdCPUAs and their polyplexes exhibited low cytotoxicity when an optimal transfection activity was detected. Moreover, GdCPUAs may serve as contrast agents for T1-weighted magnetic resonance imaging. The results of this work indicate that biodegradable Gd-chelated cationic poly(urethane amide) copolymers have high potential for tumor theranostics. Copyright © 2016 Elsevier B.V. All rights reserved.

Organic composite-mediated surface coating of human acellular bone matrix with strontium.

PubMed

Huang, Yi-Zhou; Wang, Jing-Jing; Huang, Yong-Can; Wu, Cheng-Guang; Zhang, Yi; Zhang, Chao-Liang; Bai, Lin; Xie, Hui-Qi; Li, Zhao-Yang; Deng, Li

2018-03-01

Acellular bone matrix (ACBM) provides an osteoconductive scaffold for bone repair, but its osteoinductivity is poor. Strontium (Sr) improves the osteoinductivity of bone implants. In this study, we developed an organic composite-mediated strontium coating strategy for ACBM scaffolds by using the ion chelating ability of carboxymethyl cellulose (CMC) and the surface adhesion ability of dopamine (DOPA). The organic coating composite, termed the CMC-DOPA-Sr composite, was synthesized under a mild condition, and its chemical structure and strontium ion chelating ability were then determined. After surface decoration, the physicochemical properties of the strontium-coated ACBM (ACBM-Sr) scaffolds were characterized, and their biocompatibility and osteoinductivity were determined in vitro and in vivo. The results showed that the CMC-DOPA-Sr composite facilitated strontium coating on the surface of ACBM scaffolds. The ACBM-Sr scaffolds possessed a sustained strontium ion release profile, exhibited good cytocompatibility, and enhanced the osteogenic differentiation of mesenchymal stem cells in vitro. Furthermore, the ACBM-Sr scaffolds showed good histocompatibility after subcutaneous implantation in nude mice. Taken together, this study provided a simple and mild strategy to realize strontium coating for ACBM scaffolds, which resulted in good biocompatibility and improved osteoinductivity. Copyright © 2017 Elsevier B.V. All rights reserved.

Separation of heavy metals: Removal from industrial wastewaters and contaminated soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, R.W.; Shem, L.

1993-01-01

This paper reviews the applicable separation technologies relating to removal of heavy metals from solution and from soils in order to present the state-of-the-art in the field. Each technology is briefly described and typical operating conditions and technology performance are presented. Technologies described include chemical precipitation (including hydroxide, carbonate, or sulfide reagents), coagulation/flocculation, ion exchange, solvent extraction, extraction with chelating agents, complexation, electrochemical operation, cementation, membrane operations, evaporation, adsorption, solidification/stabilization, and vitrification. Several case histories are described, with a focus on waste reduction techniques and remediation of lead-contaminated soils. The paper concludes with a short discussion of important research needsmore » in the field.« less

Separation of heavy metals: Removal from industrial wastewaters and contaminated soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, R.W.; Shem, L.

1993-03-01

This paper reviews the applicable separation technologies relating to removal of heavy metals from solution and from soils in order to present the state-of-the-art in the field. Each technology is briefly described and typical operating conditions and technology performance are presented. Technologies described include chemical precipitation (including hydroxide, carbonate, or sulfide reagents), coagulation/flocculation, ion exchange, solvent extraction, extraction with chelating agents, complexation, electrochemical operation, cementation, membrane operations, evaporation, adsorption, solidification/stabilization, and vitrification. Several case histories are described, with a focus on waste reduction techniques and remediation of lead-contaminated soils. The paper concludes with a short discussion of important research needsmore » in the field.« less

An efficient optical-electrochemical dual probe for highly sensitive recognition of dopamine based on terbium complex functionalized reduced graphene oxide.

PubMed

Zhou, Zhan; Wang, Qianming

2014-05-07

A novel organic-inorganic hybrid sensor based on diethylenetriaminepentaacetic acid (DTPA) modified reduced graphene oxide (RGO-DTPA) chelated with terbium ions allows detection of dopamine (DA) through an emission enhancement effect. Its luminescence, peaking at 545 nm, has been improved by a factor of 25 in the presence of DA (detection limit = 80 nM). In addition, this covalently bonded terbium complex functionalized reduced graphene oxide (RGO-DTPA-Tb) can be successfully assembled on a glassy carbon electrode. The assay performed through differential pulse voltammetry (DPV) yielded obvious peak separation between DA and excessive amounts of the interfering ascorbic acid (AA).

Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria

2015-07-01

A systematic study of the absorption spectra of Fricke Xylenol Orange gel dosimeters has been performed, in the wavelength range from 300 nm to 700 nm. The spectrum of Xylenol Orange (without ferrous sulphate solution) has been achieved, in order to subtract its contribution from the absorption spectra of the irradiated Fricke Xylenol Orange gel dosimeters. The absorbance due to ferric ions chelated by Xylenol Orange has been studied for various irradiation doses. Two absorbance peaks are visible, mainly at low doses: the first peak increases with the dose more slowly than the second one. This effect can explain themore » apparent threshold dose that was frequently evidenced. (authors)« less

Superabsorbing gel for actinide, lanthanide, and fission product decontamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaminski, Michael D.; Mertz, Carol J.

The present invention provides an aqueous gel composition for removing actinide ions, lanthanide ions, fission product ions, or a combination thereof from a porous surface contaminated therewith. The composition comprises a polymer mixture comprising a gel forming cross-linked polymer and a linear polymer. The linear polymer is present at a concentration that is less than the concentration of the cross-linked polymer. The polymer mixture is at least about 95% hydrated with an aqueous solution comprising about 0.1 to about 3 percent by weight (wt %) of a multi-dentate organic acid chelating agent, and about 0.02 to about 0.6 molar (M)more » carbonate salt, to form a gel. When applied to a porous surface contaminated with actinide ions, lanthanide ions, and/or other fission product ions, the aqueous gel absorbs contaminating ions from the surface.« less

Bioconjugation of luminescent silicon quantum dots to gadolinium ions for bioimaging applications

NASA Astrophysics Data System (ADS)

Erogbogbo, Folarin; Chang, Ching-Wen; May, Jasmine L.; Liu, Liwei; Kumar, Rajiv; Law, Wing-Cheung; Ding, Hong; Yong, Ken Tye; Roy, Indrajit; Sheshadri, Mukund; Swihart, Mark T.; Prasad, Paras N.

2012-08-01

Luminescent imaging agents and MRI contrast agents are desirable components in the rational design of multifunctional nanoconstructs for biological imaging applications. Luminescent biocompatible silicon quantum dots (SiQDs) and gadolinium chelates can be applied for fluorescence microscopy and MRI, respectively. Here, we report the first synthesis of a nanocomplex incorporating SiQDs and gadolinium ions (Gd3+) for biological applications. The nanoconstruct is composed of a PEGylated micelle, with hydrophobic SiQDs in its core, covalently bound to DOTA-chelated Gd3+. Dynamic light scattering reveals a radius of 85 nm for these nanoconstructs, which is consistent with the electron microscopy results depicting radii ranging from 25 to 60 nm. Cellular uptake of the probes verified that they maintain their optical properties within the intracellular environment. The magnetic resonance relaxivity of the nanoconstruct was 2.4 mM-1 s-1 (in terms of Gd3+ concentration), calculated to be around 6000 mM-1 s-1 per nanoconstruct. These desirable optical and relaxivity properties of the newly developed probe open the door for use of SiQDs in future multimodal applications such as tumour imaging.Luminescent imaging agents and MRI contrast agents are desirable components in the rational design of multifunctional nanoconstructs for biological imaging applications. Luminescent biocompatible silicon quantum dots (SiQDs) and gadolinium chelates can be applied for fluorescence microscopy and MRI, respectively. Here, we report the first synthesis of a nanocomplex incorporating SiQDs and gadolinium ions (Gd3+) for biological applications. The nanoconstruct is composed of a PEGylated micelle, with hydrophobic SiQDs in its core, covalently bound to DOTA-chelated Gd3+. Dynamic light scattering reveals a radius of 85 nm for these nanoconstructs, which is consistent with the electron microscopy results depicting radii ranging from 25 to 60 nm. Cellular uptake of the probes verified that they maintain their optical properties within the intracellular environment. The magnetic resonance relaxivity of the nanoconstruct was 2.4 mM-1 s-1 (in terms of Gd3+ concentration), calculated to be around 6000 mM-1 s-1 per nanoconstruct. These desirable optical and relaxivity properties of the newly developed probe open the door for use of SiQDs in future multimodal applications such as tumour imaging. Electronic supplementary information (ESI) available: SEM images of MSiQD-Gd3+, DLS plot of MSiQD-NH2, images of Gd3+-functionalized Si QDs micelles in water, plot of percentages of Gd3+ leaked from original sample, and determination of free Gd3+ in solutions of Gd chelates. See DOI: 10.1039/c2nr31002c

Spectroscopic studies on the antioxidant activity of p-coumaric acid.

PubMed

Kiliç, Ismail; Yeşiloğlu, Yeşim

2013-11-01

p-coumaric acid (4-hydroxycinnamic acid), a phenolic acid, is a hydroxyl derivative of cinnamic acid. It decreases low density lipoprotein (LDL) peroxidation and reduces the risk of stomach cancer. In vitro radical scavenging and antioxidant capacity of p-coumaric acid were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe(2+)) chelating activity and ferric ions (Fe(3+)) reducing ability. p-Coumaric acid inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45μg/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and ascorbic acid displayed 66.8%, 69.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, p-coumaric acid had an effective DPPH scavenging, ABTS(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that p-coumaric acid can be used in the pharmacological and food industry because of these properties. Copyright © 2013 Elsevier B.V. All rights reserved.

Molecular recognition modes between adenine or adeniniun(1+) ion and binary M(II)(pdc) chelates (MCoZn; pdc=pyridine-2,6-dicarboxylate(2-) ion).

PubMed

Del Pilar Brandi-Blanco, María; Choquesillo-Lazarte, Duane; Domínguez-Martín, Alicia; Matilla-Hernández, Antonio; González-Pérez, Josefa María; Castiñeiras, Alfonso; Niclós-Gutiérrez, Juan

2013-10-01

Mixed ligand M(II)-complexes (MCoZn) with pyridine-2,6-dicarboxylate(2-) chelator (pdc) and adenine (Hade) have been synthesized and studied by X-ray diffraction and other spectral and thermal methods: [Cu(pdc)(H(N9)ade)(H2O)] (1), [Cu2(pdc)2(H2O)2(μ2-N3,N7-H(N9)ade)]·3H2O (2), trans-[M(pdc)(H(N9)ade)(H2O)2]·nH2O for MCo (3-L, 3-M, 3-H) or Zn (4-L, 4-H), where n is 0, 1 or 3 for the 'lowest' (L), 'medium' (M) and 'highest' (H) hydrated forms, and the salt trans-[Ni(pdc)(H2(N1,N9)ade)(H2O)2]Cl·2H2O (5). In all the nine compounds, both neutral and cationic adenine exist as their most stable tautomer and the molecular recognition pattern between the metal-pdc chelates and the adenine or adeninium(1+) ligands involves the MN7 bond in cooperation with an intra-molecular N6H⋯O(coordinated carboxylate) interligand interaction. In addition the dinuclear copper(II) compound (2) has the CuN3 bond and the N9H⋯O(coord. carboxylate) interaction. The structures of mononuclear ternary complexes proved that the molecular recognition pattern is the same irrespective of (a) the coordination geometry of the complex molecule, (b) the different hydrated forms of crystals with Co or Zn, and (c) the neutral of cationic form of the adenine ligand. These features are related to the mer-NO2 chelating ligand conformation (imposed by the planar rigidity of pdc) as a driving force for the observed metal binding mode. Copyright © 2013 Elsevier Inc. All rights reserved.

Salicylamide-lanthanide complexes for use as luminescent markers

DOEpatents

Raymond, Kenneth N.; Petoud, Stephane; Cohen, Seth; Xu, Jide

2002-01-01

The present invention provides luminescent lanthanide metal chelates comprising a metal ion of the lanthanide series and a complexing agent comprising at least one salicylamidyl moiety. Also provided are probes incorporating the salicylamidyl ligands of the invention and methods utilizing the ligands of the invention and probes comprising the ligands of the invention.

The Radiation Sensitivity of Select Metal Chelate Polymers: Mechanistic Changes at Higher Energies.

DTIC Science & Technology

1987-10-01

mass croducticn necessary for the lo-; cost devices currently on the market . Ai’houan electron beat litho- graphy can provide hiaher resolution, tne...nhotochemistrv of the uranvi ion. Them Soc Rev 3: 139-165 Charlesby A (195Ř) Molecular weight changes in degradation onln - chain polymers. Proc Royal Soc

Salicylamide-lanthanide complexes for use as luminescent markers

DOEpatents

Raymond, Kenneth N [Berkeley, CA; Petoud, Stephane [Berkeley, CA; Cohen, Seth [Boston, MA; Xu, Jide [Berkeley, CA

2008-07-29

The present invention provides luminescent lanthanide metal chelates comprising a metal ion of the lanthanide series and a complexing agent comprising at least one salicylamidyl moiety. Also provided are probes incorporating the salicylamidyl ligands of the invention and methods utilizing the ligands of the invention and probes comprising the ligands of the invention.

Supercritical Carbon Dioxide Extraction of Bioactive Compounds from Ampelopsis grossedentata Stems: Process Optimization and Antioxidant Activity

PubMed Central

Wang, Yuefei; Ying, Le; Sun, Da; Zhang, Shikang; Zhu, Yuejin; Xu, Ping

2011-01-01

Supercritical carbon dioxide (SC-CO2) extraction of bioactive compounds including flavonoids and phenolics from Ampelopsis grossedentata stems was carried out. Extraction parameters such as pressure, temperature, dynamic time and modifier, were optimized using an orthogonal array design of L9 (34), and antioxidant activities of the extracts were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and ferrous ion chelating (FIC) assay. The best conditions obtained for SC-CO2 extraction of flavonoids was 250 bar, 40 °C, 50 min, and with a modifier of methanol/ethanol (1:3, v/v), and that for phenolics extraction was 250 bar, 40 °C, 50 min, and with a modifier of methanol/ethanol (1:1, v/v). Meantime, flavonoids and phenolics were found to be mainly responsible for the DPPH scavenging activity of the extracts, but not for the chelating activity on ferrous ion according to Pearson correlation analysis. Furthermore, several unreported flavonoids such as apigenin, vitexin, luteolin, etc., have been detected in the extracts from A. grossedentata stems. PMID:22072923

Theoretical Study of Oxovanadium(IV) Complexation with Formamidoximate: Implications for the Design of Uranyl-Selective Adsorbents

DOE PAGES

Mehio, Nada; Ivanov, Alexander S.; Ladshaw, Austin P.; ...

2015-11-22

Poly(acrylamidoxime) fibers are the current state of the art adsorbent for mining uranium from seawater. However, the competition between uranyl (UO 2 2+) and vanadium ions poses a challenge to mining on the industrial scale. In this work, we employ density functional theory (DFT) and coupled-cluster methods (CCSD(T)) in the restricted formalism to investigate potential binding motifs of the oxovanadium(IV) ion (VO 2+) with the formamidoximate ligand. Consistent with experimental EXAFS data, the hydrated six-coordinate complex is predicted to be preferred over the hydrated five-coordinate complex. Here, our investigation of formamidoximate-VO 2+ complexes universally identified the most stable binding motifmore » formed by chelating a tautomerically rearranged imino hydroxylamine via the imino nitrogen and hydroxylamine oxygen. The alternative binding motifs for amidoxime chelation via a non-rearranged tautomer and 2 coordination are found to be ~11 kcal/mol less stable. Ultimately, the difference in the most stable VO 2+ and UO 2 2+ binding conformation has important implications for the design of more selective UO 2 2+ ligands.« less

Insights into cholinesterase inhibitory and antioxidant activities of five Juniperus species.

PubMed

Orhan, Nilufer; Orhan, Ilkay Erdogan; Ergun, Fatma

2011-09-01

In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory and antioxidant activities of the aqueous and ethanol extracts of the leaves, ripe fruits, and unripe fruits of Juniperus communis ssp. nana, Juniperus oxycedrus ssp. oxycedrus, Juniperus sabina, Juniperus foetidissima, and Juniperus excelsa were investigated in the present study. Cholinesterase inhibition of the extracts was screened using ELISA microplate reader. Antioxidant activity of the extracts was tested by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging, ferrous ion-chelating, and ferric-reducing antioxidant power (FRAP) assays. Total phenol and flavonoid contents of the extracts were determined spectrophotometrically. The extracts had low or no inhibition towards AChE, whereas the leaf aqueous extract of J. foetidissima showed the highest BChE inhibition (93.94 ± 0.01%). The leaf extracts usually exerted higher antioxidant activity. We herein describe the first study on anticholinesterase and antioxidant activity by the methods of ferrous ion-chelating, superoxide radical scavenging, and ferric-reducing antioxidant power (FRAP) assays of the mentioned Juniperus species. Copyright © 2011 Elsevier Ltd. All rights reserved.

Gelatin hydrolysates from farmed Giant catfish skin using alkaline proteases and its antioxidative function of simulated gastro-intestinal digestion.

PubMed

Ketnawa, Sunantha; Martínez-Alvarez, Oscar; Benjakul, Soottawat; Rawdkuen, Saroat

2016-02-01

This work aims to evaluate the ability of different alkaline proteases to prepare active gelatin hydrolysates. Fish skin gelatin was hydrolysed by visceral alkaline-proteases from Giant catfish, commercial trypsin, and Izyme AL®. All antioxidant activity indices of the hydrolysates increased with increasing degree of hydrolysis (P<0.05). The hydrolysates obtained with Izyme AL® and visceral alkaline-proteases showed the highest and lowest radical scavenging capacity, while prepared with commercial trypsin was the most effective in reducing ferric ions and showed the best metal chelating properties. The hydrolysate obtained with Izyme AL® showed the lowest iron reducing ability, but provided the highest average molecular weight (⩾ 7 kDa), followed by commercial trypsin (2.2 kDa) and visceral alkaline-proteases (1.75 kDa). After in vitro gastrointestinal digestion, the hydrolysates showed significant higher radical scavenging, reducing ferric ions and chelating activities. Gelatin hydrolysates, from fish skin, could serve as a potential source of functional food ingredients for health promotion. Copyright © 2015 Elsevier Ltd. All rights reserved.

One-pot synthesis of transition metal ion-chelating ordered mesoporous carbon/carbon nanotube composites for active and durable fuel cell catalysts

NASA Astrophysics Data System (ADS)

Dombrovskis, Johanna K.; Palmqvist, Anders E. C.

2017-07-01

Development of non-precious metal catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells with high activity and durability and with optimal water management properties is of outmost technological importance and highly challenging. Here we study the possibilities offered through judicious selection of small molecular precursors used for the formation of ordered mesoporous carbon-based non-precious metal ORR catalysts. By combining two complementary precursors, we present a one-pot synthesis that leads to a composite material consisting of transition metal ion-chelating ordered mesoporous carbon and multi-walled carbon nanotubes (TM-OMC/CNT). The resulting composite materials show high specific surface areas and a carbon structure that exhibits graphitic signatures. The synthesis procedure allows for tuning of the carbon structure, the surface area, the pore volume and the ratio of the two components of the composite. The TM-OMC/CNT composites were processed into membrane electrode assemblies and evaluated in single cell fuel cell measurements where they showed a combination of good ORR activity and very high durability.

Iron restriction and the growth of Salmonella enteritidis.

PubMed Central

Chart, H.; Rowe, B.

1993-01-01

Strains of Salmonella enteritidis were examined for their ability to remove ferric-ions from the iron chelating agents ovotransferrin, Desferal and EDDA. Growth of S. enteritidis phage type (PT) 4 (SE4) in trypticase soy broth containing ovotransferrin resulted in the expression of iron regulated outer membrane proteins (OMPs) of 74, 78 and 81 kDa, and unexpectedly the repression of expression of OMP C. The 38 MDa 'mouse virulence' plasmid was not required for the expression of the iron-regulated OMPs (IROMPs). SE4 was able to obtain iron bound to the iron chelator Desferal and EDDA without expressing a high-affinity iron uptake system. Strains of S. enteritidis belonging to PTs 7, 8, 13a, 23, 24 and 30 were also able to remove ferric ions from Desferal and EDDA without expressing a high-affinity iron uptake system. We conclude that strains of SE4 possess a high-affinity iron sequestering mechanism that can readily remove iron from ovotransferrin. It is likely that iron limitation, and not iron restriction, is responsible for the bacteriostatic properties of fresh egg whites. Images Fig. 2 PMID:8432322

Synthesis, spectroscopic, thermal and anticancer studies of metal-antibiotic chelations: Ca(II), Fe(III), Pd(II) and Au(III) chloramphenicol complexes

NASA Astrophysics Data System (ADS)

Al-Khodir, Fatima A. I.; Refat, Moamen S.

2016-09-01

Four Ca(II), Fe(III), Pd(II) and Au(III) complexes of chloramphenicol drug have been synthesized and well characterized using elemental analyses, (infrared, electronic, and 1H-NMR) spectra, magnetic susceptibility measurement, and thermal analyses. Infrared spectral data show that the chloramphenicol drug coordinated to Ca(II), Pd(II) and Au(III) metal ions through two hydroxyl groups with 1:1 or 1:2 M ratios, but Fe(III) ions chelated towards chloramphenicol drug via the oxygen and nitrogen atoms of amide group with 1:2 ratio based on presence of keto↔enol form. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques were used to identify the nano-size particles of both iron(III) and gold(III) chloramphenicol complexes. The antimicrobial assessments of the chloramphenicol complexes were scanned and collected the results against of some kind of bacteria and fungi. The cytotoxic activity of the gold(III) complex was tested against the human colon carcinoma (HCT-116) and human hepatocellular carcinoma (HepG-2) tumor cell lines.

Comparison of methionine hydroxy analogue chelated versus sulfate forms of copper, zinc, and manganese on growth performance and pregnancy rates in yearling beef replacement heifers

USDA-ARS?s Scientific Manuscript database

Our objectives were to compare growth performance and pregnancy rates of heifers supplemented with Cu, Zn, and Mn as either methionine hydroxy analog chelate (provided as MINTREX) or in the S04 form. The experiment used 3 ranches, each having 2 replicate pens per treatment. Performance data were ana...

Iron oxide nanomatrix facilitating metal ionization in matrix-assisted laser desorption/ionization mass spectrometry.

PubMed

Obena, Rofeamor P; Lin, Po-Chiao; Lu, Ying-Wei; Li, I-Che; del Mundo, Florian; Arco, Susan dR; Nuesca, Guillermo M; Lin, Chung-Chen; Chen, Yu-Ju

2011-12-15

The significance and epidemiological effects of metals to life necessitate the development of direct, efficient, and rapid method of analysis. Taking advantage of its simple, fast, and high-throughput features, we present a novel approach to metal ion detection by matrix-functionalized magnetic nanoparticle (matrix@MNP)-assisted MALDI-MS. Utilizing 21 biologically and environmentally relevant metal ion solutions, the performance of core and matrix@MNP against conventional matrixes in MALDI-MS and laser desorption ionization (LDI) MS were systemically tested to evaluate the versatility of matrix@MNP as ionization element. The matrix@MNPs provided 20- to >100-fold enhancement on detection sensitivity of metal ions and unambiguous identification through characteristic isotope patterns and accurate mass (<5 ppm), which may be attributed to its multifunctional role as metal chelator, preconcentrator, absorber, and reservoir of energy. Together with the comparison on the ionization behaviors of various metals having different ionization potentials (IP), we formulated a metal ionization mechanism model, alluding to the role of exciton pooling in matrix@MNP-assisted MALDI-MS. Moreover, the detection of Cu in spiked tap water demonstrated the practicability of this new approach as an efficient and direct alternative tool for fast, sensitive, and accurate determination of trace metal ions in real samples.

Functionalized Nanocellulose-Integrated Heterolayered Nanomats toward Smart Battery Separators.

PubMed

Kim, Jung-Hwan; Gu, Minsu; Lee, Do Hyun; Kim, Jeong-Hoon; Oh, Yeon-Su; Min, Sa Hoon; Kim, Byeong-Su; Lee, Sang-Young

2016-09-14

Alternative materials obtained from natural resources have recently garnered considerable attention as an innovative solution to bring unprecedented advances in various energy storage systems. Here, we present a new class of heterolayered nanomat-based hierarchical/asymmetric porous membrane with synergistically coupled chemical activity as a nanocellulose-mediated green material strategy to develop smart battery separator membranes far beyond their current state-of-the-art counterparts. This membrane consists of a terpyridine (TPY)-functionalized cellulose nanofibril (CNF) nanoporous thin mat as the top layer and an electrospun polyvinylpyrrolidone (PVP)/polyacrylonitrile (PAN) macroporous thick mat as the support layer. The hierarchical/asymmetric porous structure of the heterolayered nanomat is rationally designed with consideration of the trade-off between leakage current and ion transport rate. The TPY (to chelate Mn(2+) ions) and PVP (to capture hydrofluoric acid)-mediated chemical functionalities bring a synergistic coupling in suppressing Mn(2+)-induced adverse effects, eventually enabling a substantial improvement in the high-temperature cycling performance of cells.

Gadolinium released by the linear gadolinium-based contrast-agent Gd-DTPA decreases the activity of human epithelial Na+ channels (ENaCs).

PubMed

Knoepp, Fenja; Bettmer, Joerg; Fronius, Martin

2017-05-01

Gadolinium-based-contrast-agents (GBCAs) are used for magnetic-resonance-imaging and associated with renal and cardiovascular adverse reactions caused by released Gd 3+ ions. Gd 3+ is also a modulator of mechano-gated ion channels, including the epithelial Na + channel (ENaC) that is expressed in kidney epithelium and the vasculature. ENaC is important for salt-/water homeostasis and blood pressure regulation and a likely target of released Gd 3+ from GBCAs causing the above-mentioned adverse reactions. Therefore this study examined the effect of Gd 3+ and GBCAs on ENaC's activity. Human αβγENaC was expressed in Xenopus laevis oocytes and exposed to Gd 3+ , linear (Gd-DTPA, Magnevist) or cyclic (Dotarem) GBCAs. Transmembrane ion-currents (I M ) were recorded by the two-electrode-voltage-clamp technique and Gd 3+ -release by Gd-DTPA was confirmed by inductively coupled plasma-mass spectrometry. Gd 3+ exerts biphasic effects on ENaC's activity: ≤0.3mmol/l decreased I M which was preventable by DEPC (modifies histidines). Strikingly Gd 3+ ≥0.4mmol/l increased I M and this effect was prevented by cysteine-modifying MTSEA. Linear Gd-DTPA and Magnevist mimicked the effect of ≤0.3mmol/l Gd 3+ , whereas the chelator DTPA showed no effect. Gd 3+ and Gd-DTPA increased the IC 50 for amiloride, but did not affect ENaC's self-inhibition. Interestingly, cyclic Gd-DOTA (Dotarem) increased I M to a similar extent as its chelator DOTA, suggesting that the chelator rather than released Gd 3+ is responsible for this effect. These results confirm Gd 3+ -release from linear Gd-DTPA and indicate that the released Gd 3+ amount is sufficient to interfere with ENaC's activity to provide putative explanations for GBCA-related adverse effects. Copyright © 2017 Elsevier B.V. All rights reserved.

Appropriate Handling, Processing and Analysis of Blood Samples Is Essential to Avoid Oxidation of Vitamin C to Dehydroascorbic Acid

PubMed Central

Pullar, Juliet M.; Carr, Anitra C.

2018-01-01

Vitamin C (ascorbate) is the major water-soluble antioxidant in plasma and its oxidation to dehydroascorbic acid (DHA) has been proposed as a marker of oxidative stress in vivo. However, controversy exists in the literature around the amount of DHA detected in blood samples collected from various patient cohorts. In this study, we report on DHA concentrations in a selection of different clinical cohorts (diabetes, pneumonia, cancer, and critically ill). All clinical samples were collected into EDTA anticoagulant tubes and processed at 4 °C prior to storage at −80 °C for subsequent analysis by HPLC with electrochemical detection. We also investigated the effects of different handling and processing conditions on short-term and long-term ascorbate and DHA stability in vitro and in whole blood and plasma samples. These conditions included metal chelation, anticoagulants (EDTA and heparin), and processing temperatures (ice, 4 °C and room temperature). Analysis of our clinical cohorts indicated very low to negligible DHA concentrations. Samples exhibiting haemolysis contained significantly higher concentrations of DHA. Metal chelation inhibited oxidation of vitamin C in vitro, confirming the involvement of contaminating metal ions. Although EDTA is an effective metal chelator, complexes with transition metal ions are still redox active, thus its use as an anticoagulant can facilitate metal ion-dependent oxidation of vitamin C in whole blood and plasma. Handling and processing blood samples on ice (or at 4 °C) delayed oxidation of vitamin C by a number of hours. A review of the literature regarding DHA concentrations in clinical cohorts highlighted the fact that studies using colourimetric or fluorometric assays reported significantly higher concentrations of DHA compared to those using HPLC with electrochemical detection. In conclusion, careful handling and processing of samples, combined with appropriate analysis, is crucial for accurate determination of ascorbate and DHA in clinical samples. PMID:29439480

Ratiometric and turn-on monitoring for heavy and transition metal ions in aqueous solution with a fluorescent peptide sensor.

PubMed

Joshi, Bishnu Prasad; Park, Junwon; Lee, Wan In; Lee, Keun-Hyeung

2009-05-15

A novel fluorescent peptide sensor containing tryptophan (donor) and dansyl fluorophore (acceptor) was synthesized for monitoring heavy and transition metal (HTM) ions on the basis of metal ion binding motif (Cys-X-X-X-Cys). The peptide probe successfully exhibited a turn on and ratiometric response for several heavy metal ions such as Hg(2+), Cd(2+), Pb(2+), Zn(2+), and Ag(+) in aqueous solution. The enhancements of emission intensity were achieved in the presence of the HTM ions by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The detection limits of the sensor for Cd(2+), Pb(2+), Zn(2+), and Ag(+) were lower than the EPA's drinking water maximum contaminant levels (MCL). We described the fluorescent enhancement, binding affinity, and detection limit of the peptide probe for HTM ions.

Synthesis of Copper-Chelates Derived from Amino Acids and Evaluation of Their Efficacy as Copper Source and Growth Stimulator for Lactuca sativa in Nutrient Solution Culture.

PubMed

Kaewchangwat, Narongpol; Dueansawang, Sattawat; Tumcharern, Gamolwan; Suttisintong, Khomson

2017-11-15

Five tetradentate ligands were synthesized from l-amino acids and utilized for the synthesis of Cu(II)-chelates 1-5. The efficacy of Cu(II)-chelates as copper (Cu) source and growth stimulator in hydroponic cultivation was evaluated with Lactuca sativa. Their stability test was performed at pH 4-10. The results suggested that Cu(II)-chelate 3 is the most pH tolerant complex. Levels of Cu, Zn, and Fe accumulated in plants supplied with Cu(II)-chelates were compared with those supplied with CuSO 4 at the same Cu concentration of 8.0 μM. The results showed that Cu(II)-chelate 3 significantly enhanced Cu, Zn, and Fe content in shoot by 35, 15, and 48%, respectively. Application of Cu(II)-chelate 3 also improved plant dry matter yield by 54%. According to the results, Cu(II)-chelate 3 demonstrated the highest stimulating effect on plant growth and plant mineral accumulation so that it can be used as an alternative to CuSO 4 for supplying Cu in nutrient solutions and enhancing the plant growth.

Metal chelates of phosphonate-containing ligands-III Analytical applications of N,N,N',N'-ethylenediaminetetra(methylenephosphonic) acid.

PubMed

Zaki, M T; Rizkalla, E N

1980-05-01

N,N*,N',N'-Ethylenediaminetetra(methylenephosphonic) acid is used as a titrant for the direct determination of Cu, Co and Ni, with murexide as indicator. Indirect titrimetric procedures are suggested for the determination of silver, mercury, zinc and cyanide and both direct and indirect methods are applied for the analysis of binary mixtures of silver (or mercury) and copper (cobalt or nickel). The stoichiometry of the reaction, interferences of some metal ions and the pH effects on the complexation reactions are discussed. The values of the equilibrium constants of the protonated CuH(n)L (n = 1, 2, 3 and 4) as well as the unprotonated CuL chelates have been measured.

Selective ion exchange governed by the Irving-Williams series in K2Zn3[Fe(CN)6]2 nanoparticles: toward a designer prodrug for Wilson's disease.

PubMed

Kandanapitiye, Murthi S; Wang, Fan Jennifer; Valley, Benjamin; Gunathilake, Chamila; Jaroniec, Mietek; Huang, Songping D

2015-02-16

The principle of the Irving-Williams series is applied to the design of a novel prodrug based on K2Zn3[Fe(CN)6]2 nanoparticles (ZnPB NPs) for Wilson's disease (WD), a rare but fatal genetic disorder characterized by the accumulation of excess copper in the liver and other vital organs. The predetermined ion-exchange reaction rather than chelation between ZnPB NPs and copper ions leads to high selectivity of such NPs for copper in the presence of the other endogenous metal ions. Furthermore, ZnPB NPs are highly water-dispersible and noncytotoxic and can be readily internalized by cells to target intracellular copper ions for selective copper detoxification, suggesting their potential application as a new-generation treatment for WD.

MA-NOTMP: A Triazacyclononane Trimethylphosphinate Based Bifunctional Chelator for Gallium Radiolabelling of Biomolecules.

PubMed

Poty, Sophie; Désogère, Pauline; Šimeček, Jakub; Bernhard, Claire; Goncalves, Victor; Goze, Christine; Boschetti, Frédéric; Notni, Johannes; Wester, Hans J; Denat, Franck

2015-09-01

In the past few years, gallium-68 has demonstrated significant potential as a radioisotope for positron emission tomography (PET), and the optimization of chelators for gallium coordination is a major goal in the development of radiopharmaceuticals. Methylaminotriazacyclononane trimethylphosphinate (MA-NOTMP), a new C-functionalized triazacyclononane derivative with phosphinate pendant arms, presents excellent coordination properties for (68) Ga (low ligand concentration, labelling at low pH even at room temperature). A "ready-to-be-grafted" bifunctional chelating agent (p-NCS-Bz-MA-NOTMP) was prepared to allow (68) Ga labelling of sensitive biological vectors. Conjugation to a bombesin(7-14) derivative was performed, and preliminary in vitro experiments demonstrated the potential of MA-NOTMP in the development of radiopharmaceuticals. This new chelator is therefore of major interest for labelling sensitive biomolecules, and further in vivo experiments will soon be performed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Automation of flow injection gas diffusion-ion chromatography for the nanomolar determination of methylamines and ammonia in seawater and atmospheric samples

PubMed Central

Gibb, Stuart W.; Wood, John W.; Fauzi, R.; Mantoura, C.

1995-01-01

The automation and improved design and performance of Flow Injection Gas Diffusion-Ion Chromatography (FIGD-IC), a novel technique for the simultaneous analysis of trace ammonia (NH3) and methylamines (MAs) in aqueous media, is presented. Automated Flow Injection Gas Diffusion (FIGD) promotes the selective transmembrane diffusion of MAs and NH3 from aqueous sample under strongly alkaline (pH > 12, NaOH), chelated (EDTA) conditions into a recycled acidic acceptor stream. The acceptor is then injected onto an ion chromatograph where NH3 and the MAs are fully resolved as their cations and detected conductimetrically. A versatile PC interfaced control unit and data capture unit (DCU) are employed in series to direct the selonoid valve switching sequence, IC operation and collection of data. Automation, together with other modifications improved both linearily (R2 > 0.99 MAs 0-100 nM, NH3 0-1000 nM) and precision (<8%) of FIGD-IC at nanomolar concentrations, compared with the manual procedure. The system was successfully applied to the determination of MAs and NH3 in seawater and in trapped particulate and gaseous atmospheric samples during an oceanographic research cruise. PMID:18925047

Chelating ionic liquids for reversible zinc electrochemistry.

PubMed

Kar, Mega; Winther-Jensen, Bjorn; Forsyth, Maria; MacFarlane, Douglas R

2013-05-21

Advanced, high energy-density, metal-air rechargeable batteries, such as zinc-air, are of intense international interest due to their important role in energy storage applications such as electric and hybrid vehicles, and to their ability to deal with the intermittency of renewable energy sources such as solar and wind. Ionic liquids offer a number of ideal thermal and physical properties as potential electrolytes in such large-scale energy storage applications. We describe here the synthesis and characterisation of a family of novel "chelating" ILs designed to chelate and solubilize the zinc ions to create electrolytes for this type of battery. These are based on quaternary alkoxy alkyl ammonium cations of varying oligo-ether side chains and anions such as p-toluene sulfonate, bis(trifluoromethylsulfonyl)amide and dicyanoamides. This work shows that increasing the ether chain length in the cation from two to four oxygens can increase the ionic conductivity and reduce the melting point from 67 °C to 15 °C for the tosylate system. Changing the anion also plays a significant role in the nature of the zinc deposition electrochemistry. We show that zinc can be reversibly deposited from [N(222(20201))][NTf2] and [N(222(202020201))][NTf2] beginning at -1.4 V and -1.7 V vs. SHE, respectively, but not in the case of tosylate based ILs. This indicates that the [NTf2] is a weaker coordinating anion with the zinc cation, compared to the tosylate anion, allowing the coordination of the ether chain to dominate the behavior of the deposition and stripping of zinc ions.

[(Nitrato-κO,O')(nitrito-κO,O')(0.25/1.75)]bis-(1,10-phenanthroline-κN,N')cadmium(II).

PubMed

Najafi, Ezzatollah; Amini, Mostafa M; Ng, Seik Weng

2011-01-22

The reaction of cadmium nitrate and sodium nitrite in the presence of 1,10-phenanthroline yields the mixed nitrate-nitrite title complex, [Cd(NO(2))(1.75)(NO(3))(0.25)(C(12)H(8)N(2))(2)]. The metal ion is bis-chelated by two N-heterocycles as well as by the nitrate/nitrite ions in a distorted dodeca-hedral CdN(4)O(4) coordination environment. One nitrite group is ordered; the other is disordered with respect to a nitrate group (ratio 0.75:0.25) concerning the O atom that is not involved in bonding to the metal ion.

Removal of Hg(II) from aqueous solution by resin loaded magnetic β-cyclodextrin bead and graphene oxide sheet: Synthesis, adsorption mechanism and separation properties.

PubMed

Cui, Limei; Wang, Yaoguang; Gao, Liang; Hu, Lihua; Wei, Qin; Du, Bin

2015-10-15

Resin loaded magnetic β-cyclodextrin bead and graphene oxide sheet (MCD-GO-R) was synthesized successfully and found to be an excellent adsorbent for Hg(II) removal. The as-prepared adsorbent was characterized by SEM, FTIR, BET, magnetization curve and zeta potential analysis respectively. Good magnetic performance made MCD-GO-R simply recover from aqueous solution at low magnetic field within 30s. And also, the rich functional groups and outstanding dispersity play an important role in the adsorption process. The maximum adsorption capacity was 88.43 mg g(-1) at 323 K and pH 7.1. The as-prepared adsorbent could perform well in a wide pH range from 4.0 to 10.0. Static adsorption experimental data showed good correlation with pseudo-second-order model and Freundlich isotherm models. It was found that the contaminant adsorption was accomplished mainly via chelation or ion exchange and come to equilibrium in only 30 min. All experimental results, especially the excellent reproducibility and resistance to ion interference, suggest that MCD-GO-R has promising applications in water treatment. Copyright © 2015 Elsevier Inc. All rights reserved.

Tetra-ammine-(carbonato-κ(2) O,O')cobalt(III) nitrate: a powder X-ray diffraction study.

PubMed

Le Bail, Armel

2013-01-01

Practical chemistry courses at universities very frequently propose the synthesis and characterization of [Co(CO3)(NH3)4]NO3, but this goal is never achieved since students only obtain the hemihydrated form. The anhydrous form can be prepared, however, and its structure is presented here. Similar to the hemihydrate form, the anhydrous phase contains the Co(III) ion in an octahedral O2N4 coordination by a chelating carbonate group and four ammine ligands. The structure reveals an intricate array of N-H⋯O hydrogen bonds involving both the chelating and the non-chelating O atoms of the carbonate ligand as hydrogen-bond acceptors of the amine H atoms, which are also involved in hydrogen-bonding inter-actions with the nitrate O atoms. The structure of the anhydrous form is close to that of the hemihydrate phase, suggesting a probable topotactic reaction with relatively small rotations and translations of the [Co(CO3)(NH3)4](+) and NO3 (-) groups during the dehydration process, which produces an unusual volume increase of 4.3%.

Tetra­ammine­(carbonato-κ2 O,O′)cobalt(III) nitrate: a powder X-ray diffraction study

PubMed Central

Le Bail, Armel

2013-01-01

Practical chemistry courses at universities very frequently propose the synthesis and characterization of [Co(CO3)(NH3)4]NO3, but this goal is never achieved since students only obtain the hemihydrated form. The anhydrous form can be prepared, however, and its structure is presented here. Similar to the hemihydrate form, the anhydrous phase contains the CoIII ion in an octahedral O2N4 coordination by a chelating carbonate group and four ammine ligands. The structure reveals an intricate array of N—H⋯O hydrogen bonds involving both the chelating and the non-chelating O atoms of the carbonate ligand as hydrogen-bond acceptors of the amine H atoms, which are also involved in hydrogen-bonding inter­actions with the nitrate O atoms. The structure of the anhydrous form is close to that of the hemihydrate phase, suggesting a probable topotactic reaction with relatively small rotations and translations of the [Co(CO3)(NH3)4]+ and NO3 − groups during the dehydration process, which produces an unusual volume increase of 4.3%. PMID:24046543

[Distribution of electric charges in 2 substances inducing tumor cell regression].

PubMed

Smeyers, Y G; Huertas, A

1983-01-01

The charge distribution of anti-cancer molecules 4-thiazolidine-carboxylic acid and 2-amino-2-thiazoline hydrochloride was calculated with a CNDO/2 semiempiral quantum mechanic method. The activity seems to be related with the formation of Zn2+ and Mn2+ ions. Both molecules show local isosterism, origin of their chelating properties.

Luminescent 1-hydroxy-2-pyridinone chelates of lanthanides

DOEpatents

Raymond, Kenneth N.; Xu, Jide; Moore, Evan G.; Werner, Eric J.

2013-10-15

The present invention provides luminescent complexes between a lanthanide ion and an organic ligand which contains 1,2-hydroxypyridinone units. The complexes of the invention are stable in aqueous solutions and are useful as molecular probes, for example in medical diagnostics and bioanalytical assay systems. The invention also provides methods of using the complexes of the invention.

Antimicrobial Mechanism of Action of Surfactant Lipid Preparations in Enteric Gram-Negative Bacilli

DTIC Science & Technology

2001-12-25

The addition of EDTA/Tris to the reaction the bacterial cells in the assay time (15min). W60C (1%) mixture results in chelation of ions, facilitating... Maillard , J.Y. (1999) Do antisep- Hamouda, T., Hayes, M.M., Cao, Z. et al. (1999) A novel surfac- tics and disinfectants select for antibiotic resistance

Luminescent 1-hydroxy-2-pyridinone chelates of lanthanides

DOEpatents

Raymond, Kenneth N.; Xu, Jide; Moore, Evan G.; Werner, Eric J.

2017-01-31

The present invention provides luminescent complexes between a lanthanide ion and an organic ligand which contains 1,2-hydroxypyridinone units. The complexes of the invention are stable in aqueous solutions and are useful as molecular probes, for example in medical diagnostics and bioanalytical assay systems. The invention also provides methods of using the complexes of the invention.

Effect of chaotropes on the kinetics of iron release from ferritin by flavin nucleotides.

PubMed

Johnson, Lindsay E; Wilkinson, Tyler; Arosio, Paolo; Melman, Artem; Bou-Abdallah, Fadi

2017-12-01

Ferritins are ubiquitous multi-subunit iron storage and detoxification proteins that play a critical role in iron homeostasis. Ferrous ions that enter the protein's shell through hydrophilic channels are rapidly oxidized at dinuclear centers on the H-subunit before transfer to the protein's cavity for storage. The mechanisms of iron loading have been extensively studied, but little is known about iron mobilization. Fe(III) reduction can occur via rapid reduction by suitable reducing agents followed by chelation of Fe(II) ions or via direct and slow Fe(III) chelation. Here, the iron release kinetics from ferritin by FMNH 2 in the presence of various chaotropic agents are studied and their in-vivo physiological significance discussed. The iron release kinetics from horse and human ferritins by FMNH 2 were monitored at 522nm where the Fe(II)-bipyridine complex absorbs. The experiments were performed in the presence of different concentrations of three chaotropic agents, urea, guanidine HCl, and triton. Under our experimental conditions, iron reductive mobilization by the non-enzymatic FMN/NAD(P)H system is limited by the concentration of FMNH 2 and is independent on the type or amount of chaotropes present. Diffusion of FMNH 2 through the ferritin pores is an unlikely mechanism for ferritin iron reduction. An iron mobilization mechanism involving rapid electron transfer through the protein shell is discussed. Caution must be exercised when interpreting the kinetics of iron mobilization from ferritin using the FMN/NAD(P)H system. The kinetics are highly dependent on the amount of dissolved oxygen and the concentration of reagents used. Copyright © 2017 Elsevier B.V. All rights reserved.

Sulphur-containing Amino Acids: Protective Role Against Free Radicals and Heavy Metals.

PubMed

Colovic, Mirjana B; Vasic, Vesna M; Djuric, Dragan M; Krstic, Danijela Z

2018-01-30

Sulphur is an abundant element in biological systems, which plays an important role in processes essential for life as a constituent of proteins, vitamins and other crucial biomolecules. The major source of sulphur for humans is plants being able to use inorganic sulphur in the purpose of sulphur-containing amino acids synthesis. Sulphur-containing amino acids include methionine, cysteine, homocysteine, and taurine. Methionine and cysteine are classified as proteinogenic, canonic amino acids incorporated in protein structure. Sulphur amino acids are involved in the synthesis of intracellular antioxidants such as glutathione and N-acetyl cysteine. Moreover, naturally occurring sulphur-containing ligands are effective and safe detoxifying agents, often used in order to prevent toxic metal ions effects and their accumulation in human body. Literature search for peer-reviewed articles was performed using PubMed and Scopus databases, and utilizing appropriate keywords. This review is focused on sulphur-containing amino acids - methionine, cysteine, taurine, and their derivatives - glutathione and N-acetylcysteine, and their defense effects as antioxidant agents against free radicals. Additionally, the protective effects of sulphur-containing ligands against the toxic effects of heavy and transition metal ions, and their reactivation role towards the enzyme inhibition are described. Sulphur-containing amino acids represent a powerful part of cell antioxidant system. Thus, they are essential in the maintenance of normal cellular functions and health. In addition to their worthy antioxidant action, sulphur-containing amino acids may offer a chelating site for heavy metals. Accordingly, they may be supplemented during chelating therapy, providing beneficial effects in eliminating toxic metals. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosario-Amorin, Daniel; Ouizem, Sabrina; Dickie, D. A.

Syntheses for new ligands based upon dibenzothiophene and dibenzothiophene sulfone platforms, decorated with phosphine oxide and methylphosphine oxide donor groups, are described. Coordination chem. of 4, 6- bis(diphenylphosphinoylmethyl) dibenzothiophene (8) , 4, 6- bis(diphenylphosphinoylmethyl) dibenzothiophene- 5, 5- dioxide (9) and 4, 6- bis(diphenylphosphinoyl) dibenzothiophene- 5, 5- dioxide (10) with lanthanide nitrates, Ln(NO3) 3 (H2O) n is outlined, and crystal structure detns. reveal a range of chelation interactions on Ln(III) ions. The HNO3 dependence of the solvent extn. performance of 9 and 10 in 1, 2- dichloroethane for Eu(III) and Am(III) is described and compared against the extn. behavior of relatedmore » dibenzofuran ligands (2, 3; R = Ph) and n- octyl(phenyl) - N, N- diisobutylcarbamoylmethyl phosphine oxide (4) measured under identical conditions.« less

Review—Multifunctional Materials for Enhanced Li-Ion Batteries Durability: A Brief Review of Practical Options

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Anjan; Shilina, Yuliya; Ziv, Baruch

Transition metal (TM) ions dissolution from positive electrodes, migration to and deposition on negative electrodes, followed by Mn-catalyzed reactions of solvents and anions, with loss of Li+ ions, is a major degradation (DMDCR) mechanism in Li-ion batteries (LIBs) with spinel positive electrode materials. While the details of the DMDCR mechanism are still under debate, it is clear that HF and other acid species’ attack is the main cause in solutions with LiPF6 electrolyte. We first review the work on various mitigation measures for the DMDCR mechanism, now spanning more than two decades. We then discuss recent progress on our understandingmore » of Mn species in electrolyte solutions and the extension of a mitigation measure first proposed by Tarascon and coworkers in 1999, namely chelation of TM cations, to Mn cation trapping, HF scavenging, and alkali metal ions dispensing multi-functional materials. We focus on practicable, drop-in technical solutions, based on placing such materials in the inter-electrode space, with significant benefits for LIBs performance: increased capacity retention during operation at room and above-ambient temperatures as well as robust (both maximally ionically conducting and electronically insulating) solid-electrolyte interfaces, having reduced charge transfer and film resistances at both negative and positive electrodes. We illustrate the multifunctional materials approach with both new and previously published data. We also discuss and offer our evaluation regarding the merits and drawbacks of the various mitigation measures, with an eye for practically relevant technical solutions capable to meet both the performance requirements and cost constraints for commercial LIBs, and end with recommendations for future work.« less

Dipotassium tetra­kis­(thio­cyanato-κS)palladate(II)–(2,2′-bipyrimidine-κ2 N 1,N 1′)bis­(thio­cyanato-κS)palladium(II) (1/2)

PubMed Central

Ha, Kwang

2012-01-01

The asymmetric unit of the title compound, K2[Pd(NCS)4]·2[Pd(NCS)2(C8H6N4)], contains two crystallographically independent half-mol­ecules of the anionic PdII complex, two K+ cations and two independent neutral PdII complexes; an inversion centre is located at the centroid of each anionic complex. In the anionic complexes, each PdII ion is four-coordinated in an almost regular square-planar environment by four S atoms from four SCN− anions, and the PdS4 unit is exactly planar. In the neutral complexes, the PdII ion has a slightly distorted square-planar coordination environment defined by two pyrimidine N atoms derived from a chelating 2,2′-bipyrimidine ligand and two mutually cis S atoms from two SCN− anions. Both 2,2′-bipyrimidine ligands are almost planar [dihedral angle between the rings = 3.98 (16) and 4.57 (17)°] and also chelate to a potassium ion from their other two N atoms. In the crystal, the K+ ions inter­act with various S and N atoms of the ligands, forming a three-dimensional polymeric network, in which the shortest K⋯K contacts between the KN7S polyhedra are 4.4389 (17) and 4.4966 (18) Å. Intra- and inter­molecular C—H⋯S and C—H⋯N hydrogen bonds are also observed. PMID:22590117

Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lendrum, Conrad D.; Ingham, Bridget; Lin, Binhua

2012-02-06

2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position {alpha} to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of {approx}6. Themore » role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.« less

Photoluminescence and Coordination Behaviour of Lanthanide Complexes of Tris (Aminomethyl)Ethane-5-Oxine in Aqueous Solution.

PubMed

Akbar, Rifat; Baral, Minati; Kanungo, B K

2017-01-01

Photophysical properties of a multidentate tripodal ligand, 5,5'-(2-(((8-hydroxyquinolin-5-yl) methylamino)methyl)-2-methylpropane-1,3-diyl) bis (azanediyl)bis (methylene)diquinolin-8-ol, (TAME5OX), with La 3+ and Er 3+ ions have been examined for photonics applications. The change in behavior in electronic spectra of these complexes reveals the use of TAME5OX as a sensitive optical pH based sensor to detect Ln 3+ ions whereas indication of strong green fluorescence allows simultaneous sensing within the visible region in competitive medium. The intense fluorescence intermittently gets quenched under acidic and basic conditions due to photoinduced intramolecular electron transfer from the excited 8-hydroxyquinoline (8-HQ) moiety to the metal ion. This renders these compounds the OFF-ON-OFF type of pH-dependent fluorescent sensor. The thermodynamic stability and coordination behaviour of the chelator with the said lanthanide ions have also been probed by potentiometric, UV - visible and fluorescence spectrophotometric method. TAME5OX forms protonated complex [Ln (H 4 L)] 4+ below pH ~4.0 which sequentially deprotonates through one proton process with increase of pH. The stability constants of neutral complexes have been determined to be in the range log β 110  = 32-34 and pLn in the range of 14-20, indicating TAME5OX is a good synthetic lanthanide chelator. Theoretical spectra were also calculated by ZINDO/s methodology at single excitations (CIS) level on PM7 as sparkle energy-minimized geometries.

Chelation of Cu(II), Zn(II), and Fe(II) by Tannin Constituents of Selected Edible Nuts

PubMed Central

Karamać, Magdalena

2009-01-01

The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II) and Zn(II) was determined by the reaction with tetramethylmurexide, whereas for Fe(II), ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II). The Fe(II) complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II) by ~90%. The capacity to chelate Zn(II) was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II), whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II) chelation took place at the levels tested. PMID:20054482

Chelation of Cu(II), Zn(II), and Fe(II) by tannin constituents of selected edible nuts.

PubMed

Karamać, Magdalena

2009-12-22

The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II) and Zn(II) was determined by the reaction with tetramethylmurexide, whereas for Fe(II), ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II). The Fe(II) complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II) by approximately 90%. The capacity to chelate Zn(II) was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II), whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II) chelation took place at the levels tested.

Iron Requirement and Iron Uptake from Various Iron Compounds by Different Plant Species

PubMed Central

Christ, Rudolf A.

1974-01-01

The Fe requirements of four monocotyledonous plant species (Avena sativa L., Triticum aestivum L., Oryza sativa L., Zea mays L.) and of three dicotyledonous species (Lycopersicum esculentum Mill., Cucumis sativus L., Glycine maxima (L.) Merr.) in hydroponic cultures were ascertained. Fe was given as NaFe-EDDHA chelate (Fe ethylenediamine di (O-hydroxyphenylacetate). I found that the monocotyledonous species required a substantially higher Fe concentration in the nutrient solution in order to attain optimum growth than did the dicotyledonous species. Analyses showed that the process of iron uptake was less efficient with the monocotyledonous species. When the results obtained by using chelated Fe were compared with those using ionic Fe, it was shown that the inefficient species were equally inefficient in utilizing Fe3+ ions. However, the differences between the efficient and the inefficient species disappeared when Fe2+ was used. This confirms the work of others who postulated that Fe3+ is reduced before uptake of chelated iron by the root. In addition, it was shown that reduction also takes place when Fe is used in ionic form. The efficiency of Fe uptake seems to depend on the efficiency of the root system of the particular plant species in reducing Fe3+. The removal of Fe from the chelate complex after reduction to Fe2+ seems to present no difficulties to the various plant species. PMID:16658933

Effects of iron and iron chelation in vitro on mucosal oxidant activity in ulcerative colitis.

PubMed

Millar, A D; Rampton, D S; Blake, D R

2000-09-01

Reactive oxygen species may be pathogenic in ulcerative colitis. Oral iron supplements anecdotally exacerbate inflammatory bowel disease and iron levels are elevated in the inflamed mucosa. Mucosal iron may enhance hydroxyl ion production via Fenton chemistry. Conversely, the iron chelator, desferrioxamine, is reportedly beneficial in Crohn's disease. To assess the in vitro effects of exogenous iron and of iron chelators on the production of reactive oxygen species by colonic biopsies from normal control subjects and patients with ulcerative colitis. Luminol-amplified chemiluminescence was used to measure mucosal reactive oxygen species production both before and after addition in vitro of ferric citrate (100 microM), desferrioxamine (1 mM) and 1,10-phenanthroline (1 mM). Ferric citrate had no effect on the chemiluminescence produced by human colonic mucosa. However, desferrioxamine and phenanthroline reduced chemiluminescence by 47% (n=7, P=0.018) and by 26% (n=10, P=0.005), respectively, in inactive ulcerative colitis, and by 44% (n=9, P=0. 008) and 42% (n=11, P=0.006) in active disease. The lack of effect of ferric citrate suggests that sufficient free iron is already present in inflamed biopsies to drive the Fenton reaction maximally. The effects of desferrioxamine and 1,10-phenanthroline on the chemiluminescence of biopsies from patients with ulcerative colitis suggest that a clinical trial of topical iron chelation in active disease is indicated.

Rational Design, Development, and Stability Assessment of a Macrocyclic Four-Hydroxamate-Bearing Bifunctional Chelating Agent for 89 Zr.

PubMed

Seibold, Uwe; Wängler, Björn; Wängler, Carmen

2017-09-21

Zirconium-89 is a positron-emitting radionuclide of high interest for medical imaging applications with positron emission tomography (PET). For the introduction of this radiometal into biologically active targeting vectors, the chelating agent desferrioxamine B (DFO) is commonly applied. However, DFO is known to form 89 Zr complexes of limited in vivo stability. Herein we describe the rational design and chemical development of a new macrocyclic four-hydroxamate-bearing chelating agent-1,10,19,28-tetrahydroxy-1,5,10,14,19,23,28,32-octaazacyclohexatriacontan-2,6,11,15,20,24,29,33-octaone (CTH36)-for the stable complexation of Zr 4+ . For this purpose, we first performed computational studies to determine the optimal chelator geometry before we developed different synthesis pathways toward the target structures. The best results were obtained using an efficient solution-phase-based synthesis strategy toward the target chelating agent. To enable efficient and chemoselective conjugation to biomolecules, a tetrazine-modified variant of CTH36 was also developed. The excellent conjugation characteristics of the so-functionalized chelator were demonstrated on the example of the model peptide TCO-c(RGDfK). We determined the optimal 89 Zr radiolabeling parameters for CTH36 as well as its bioconjugate, and found that 89 Zr radiolabeling proceeds efficiently under very mild reaction conditions. Finally, we performed comparative complex stability tests for 89 Zr-CHT36-c(RGDfK) and 89 Zr-DFO-c(RGDfK), showing improved complex stability for the newly developed chelator CTH36. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The chemical deposition of semiconductor thin-films for photovoltaic devices

NASA Astrophysics Data System (ADS)

Breen, Marc Louis

Initially, possible precursors to metal sulfide films formed by metal-organic chemical vapor deposition (MOCVD), the standard commercial technique for manufacturing photovoltaic semiconductors, were synthesized. Triple-junction GaInP 2/GaAs/Ge solar cells, prepared by this method, were studied to understand how chemical properties and material defects can effect the performance of photovoltaic devices. Finally, novel methods for the low-temperature, solution growth of CdS, CdSe, and CuInSe2 photovoltaic materials were targeted which will reduce manufacturing costs and increase the economic feasibility of solar energy conversion. A series of dialkyldithiocarbamate copper, gallium and indium compounds were studied as possible metal sulfide MOCVD precursors. Metal powders were oxidized by dialkylthiurams in 3- or 4-methylpyridine using standard techniques for handling air and moisture-sensitive compounds. Metal chlorides reacted directly with the sodium dialkyldithiocarbamate salts. In these complexes, the metal was found in a roughly octahedral orientation, surrounded by dithiocarbamate ligands and/or solvent molecules. Triple-junction GaInP2/GaAs/Ge cells were composed of thin-films of GaInP2 and GaAs grown monolithically on top of a germanium substrate. Each layer of semiconductor material had a different bandgap and absorbed a different portion of the solar spectrum, thus improving the overall efficiency of the cell. Work focused on dark current-voltage behavior which is known to limit solar cell open-circuit voltage, fill factor, and conversion efficiency. Cells were studied using microscopic and spectroscopic techniques to correlate the effect of physical defects in the materials with poor performance of the devices as evaluated through current vs. voltage measurements. Films of US and CdSe were readily prepared in solution through an "ion-by-ion" deposition of Cd2+ and S2- (or Se 2-) generated from the slow hydrolysis of thiourea (or dimethylthiourea). The bath chemistry was carefully controlled by the adjustment of pH to slow hydrolysis and with chelating agents to sequester the cadmium ions. Triethanolamine and ethylenediamine were both effective chelators with the latter producing thicker, clearer films. Finally, US films were grown over electrodeposited CuInSe2 to form working photovoltaic devices. In summary, contributions were made which (a) advance current methods for manufacturing photovoltaic semiconductors and (b) offer an alternative route to producing new forms of thin-film solar cell devices.

Gd(III) complexes for electron-electron dipolar spectroscopy: Effects of deuteration, pH and zero field splitting.

PubMed

Garbuio, Luca; Zimmermann, Kaspar; Häussinger, Daniel; Yulikov, Maxim

2015-10-01

Spectral parameters of Gd(III) complexes are intimately linked to the performance of the Gd(III)-nitroxide or Gd(III)-Gd(III) double electron-electron resonance (DEER or PELDOR) techniques, as well as to that of relaxation induced dipolar modulation enhancement (RIDME) spectroscopy with Gd(III) ions. These techniques are of interest for applications in structural biology, since they can selectively detect site-to-site distances in biomolecules or biomolecular complexes in the nanometer range. Here we report relaxation properties, echo detected EPR spectra, as well as the magnitude of the echo reduction effect in Gd(III)-nitroxide DEER for a series of Gadolinium(III) complexes with chelating agents derived from tetraazacyclododecane. We observed that solvent deuteration does not only lengthen the relaxation times of Gd(III) centers but also weakens the DEER echo reduction effect. Both of these phenomena lead to an improved signal-to-noise ratios or, alternatively, longer accessible distance range in pulse EPR measurements. The presented data enrich the knowledge on paramagnetic Gd(III) chelate complexes in frozen solutions, and can help optimize the experimental conditions for most types of the pulse measurements of the electron-electron dipolar interactions. Copyright © 2015 Elsevier Inc. All rights reserved.

Regulation of the catalytic behavior of pullulanases chelated onto nickel (II)-modified magnetic nanoparticles.

PubMed

Wang, Jianfeng; Liu, Zhongmei; Zhou, Zhemin

2017-06-01

Chelating of pullulanases onto nickel (II)-modified magnetic nanoparticles results in one-step purification and immobilization of pullulanase, and facilitates the commercial application of pullulanase in industrial scale. To improve the catalytic behavior, especially the operational stability, of the nanocatalyst in consecutive batch reactions, we prepared various iminodiacetic acid-modified magnetic nanoparticles differed in surface polarity and spacer length, on which the His6-tagged pullulanases were chelated via nickel ions, and then studied the correlation between the MNPs surface property and the corresponding catalyst behavior. When pullulanases were chelated onto the surface-modified MNPs, the thermostability of all pullulanase derivatives were lower than that of free counterpart, being not relevant to the protein orientation guided by the locality of the His6-tag, but related to the MNPs basal surface polarity and the grafted spacer length. After chelating of pullulanases onto MNPs, there were changes observed in the pH-activity profile and the apparent Michaelis constant toward pullulan. The changing tendencies were mainly dependent on the His6-tagged pullulanase orientation, and the changing extents were tuned by the spacer length. The reusability of pullulanase immobilized by N-terminal His6-tag was higher than that of pullulanase immobilized by C-terminal His6-tag. Moreover, the reusability of the immobilized pullulanase tested increased till grafting polyether amine-400 as spacer-arm, therefore the N-terminal His6-tagged pullulanase chelating MNPs grafted polyether amine-400 gave the best reusability, which retained 60% of initial activity after 18 consecutive cycles with a total reaction time of 9h. Additionally, the correlation analysis of the catalyst behaviors indicated that the reusability was independent from other catalytic properties such as thermostability and substrate affinity. All the results revealed that the catalyst behavior can be mainly controlled by the His6-tagged pullulanase orientation than by the MNPs surface property which can tune the catalyst function. Copyright © 2017. Published by Elsevier Inc.

Macrocyclic receptor showing extremely high Sr(II)/Ca(II) and Pb(II)/Ca(II) selectivities with potential application in chelation treatment of metal intoxication.

PubMed

Ferreirós-Martínez, Raquel; Esteban-Gómez, David; Tóth, Éva; de Blas, Andrés; Platas-Iglesias, Carlos; Rodríguez-Blas, Teresa

2011-04-18

Herein we report a detailed investigation of the complexation properties of the macrocyclic decadentate receptor N,N'-Bis[(6-carboxy-2-pyridil)methyl]-4,13-diaza-18-crown-6 (H(2)bp18c6) toward different divalent metal ions [Zn(II), Cd(II), Pb(II), Sr(II), and Ca(II)] in aqueous solution. We have found that this ligand is especially suited for the complexation of large metal ions such as Sr(II) and Pb(II), which results in very high Pb(II)/Ca(II) and Pb(II)/Zn(II) selectivities (in fact, higher than those found for ligands widely used for the treatment of lead poisoning such as ethylenediaminetetraacetic acid (edta)), as well as in the highest Sr(II)/Ca(II) selectivity reported so far. These results have been rationalized on the basis of the structure of the complexes. X-ray crystal diffraction, (1)H and (13)C NMR spectroscopy, as well as theoretical calculations at the density functional theory (B3LYP) level have been performed. Our results indicate that for large metal ions such as Pb(II) and Sr(II) the most stable conformation is Δ(δλδ)(δλδ), while for Ca(II) our calculations predict the Δ(λδλ)(λδλ) form being the most stable one. The selectivity that bp18c6(2-) shows for Sr(II) over Ca(II) can be attributed to a better fit between the large Sr(II) ions and the relatively large crown fragment of the ligand. The X-ray crystal structure of the Pb(II) complex shows that the Δ(δλδ)(δλδ) conformation observed in solution is also maintained in the solid state. The Pb(II) ion is endocyclically coordinated, being directly bound to the 10 donor atoms of the ligand. The bond distances to the donor atoms of the pendant arms (2.55-2.60 Å) are substantially shorter than those between the metal ion and the donor atoms of the crown moiety (2.92-3.04 Å). This is a typical situation observed for the so-called hemidirected compounds, in which the Pb(II) lone pair is stereochemically active. The X-ray structures of the Zn(II) and Cd(II) complexes show that these metal ions are exocyclically coordinated by the ligand, which explains the high Pb(II)/Cd(II) and Pb(II)/Zn(II) selectivities. Our receptor bp18c6(2-) shows promise for application in chelation treatment of metal intoxication by Pb(II) and (90)Sr(II).

A napthelene-pyrazol conjugate: Al(III) ion-selective blue shifting chemosensor applicable as biomarker in aqueous solution.

PubMed

Mukherjee, Manjira; Pal, Siddhartha; Lohar, Somenath; Sen, Buddhadeb; Sen, Supriti; Banerjee, Samya; Banerjee, Snehasis; Chattopadhyay, Pabitra

2014-10-07

A newly synthesized and crystalographically characterized napthelene–pyrazol conjugate, 1-[(5-phenyl-1H-pyrazole-3-ylimino)-methyl]-naphthalen-2-ol (HL) behaves as an Al(III) ion-selective chemosensor through internal charge transfer (ICT)-chelation-enhanced fluorescence (CHEF) processes in 100 mM HEPES buffer (water–DMSO 5:1, v/v) at biological pH with almost no interference of other competitive ions. This mechanism is readily studied from electronic, fluorimetric and (1)H NMR titration. The probe (HL) behaved as a highly selective fluorescent sensor for Al(III) ions as low as 31.78 nM within a very short response time (15–20 s). The sensor (HL), which has no cytotoxicity, is also efficient in detecting the distribution of Al(III) ions in HeLa cells via image development under fluorescence microscope.

Succinate, iron chelation, and monovalent cations affect the transformation efficiency of Acinetobacter baylyi ATCC 33305 during growth in complex media.

PubMed

Leong, Colleen G; Boyd, Caroline M; Roush, Kaleb S; Tenente, Ricardo; Lang, Kristine M; Lostroh, C Phoebe

2017-10-01

Natural transformation is the acquisition of new genetic material via the uptake of exogenous DNA by competent bacteria. Acinetobacter baylyi is model for natural transformation. Here we focus on the natural transformation of A. baylyi ATCC 33305 grown in complex media and seek environmental conditions that appreciably affect transformation efficiency. We find that the transformation efficiency for A. baylyi is a resilient characteristic that remains high under most conditions tested. We do find several distinct conditions that alter natural transformation efficiency including addition of succinate, Fe 2+ (ferrous) iron chelation, and substitution of sodium ions with potassium ones. These distinct conditions could be useful to fine tune transformation efficiency for researchers using A. baylyi as a model organism to study natural transformation.

Radiometals (non-Tc, non-Re) and Bifunctional Labeling Chemistry

NASA Astrophysics Data System (ADS)

Fani, M.; Good, S.; Maecke, H. R.

Radiometals are of increased current interest because of the growing use of targeted radiotherapy for tumors and the development of generators that produce positron-emitting radiometals. In addition, biomedical cyclotrons allow the cheap production of some relevant radiometals. The design of the corresponding radiopharmaceuticals includes the synthesis of bifunctional chelators, which carry a functional unit for the immobilization of the radiometal and a functional group for the covalent attachment to a vector molecule. Radiometals of interest for therapeutic applications are some lanthanides, 67Cu, and 90Y. For diagnostic applications 61Cu, 62Cu, 64Cu, 89Zr, and 68Ga are currently used and corresponding radiopharmaceuticals are being designed. In this chapter, some properties and the synthesis of bifunctional chelators including metal ion selectivity and special aspects of coupling chemistry are being described.

Ligand exchange and MIP-based paraoxon memories onto QCM sensor

NASA Astrophysics Data System (ADS)

Birlik Özkütük, Ebru; Emir Diltemiz, Sibel; Özalp, Elif; Uzun, Lokman; Ersöz, Arzu

2015-04-01

In this study, we have aimed to prepare quartz crystal microbalance (QCM) sensor using paraoxon-imprinted particles. Firstly, methacryloyl antipyrine (MAAP)-based metal-chelate-coordinated pre-complex has been prepared and used for paraoxon templation. Then, paraoxon-imprinted nanofilms were formed on QCM sensor after modification of the gold surfaces with allyl mercaptan. By this way, specific and selective memories, which depend on metal-chelate interactions between Eu(III) ions and template, for paraoxon molecules have been obtained on the electrode surface. QCM sensor has characterized using AFM and ellipsometer. The detection limit and the affinity constant have found to be 0.09 μM and 5.71 × 103 M-1 for MAAP-Eu paraoxon-based nanofilm, respectively. The specificity of the QCM sensor has shown using parathion as a competitor molecule.

“Straining” to Separate the Rare Earths: How the Lanthanide Contraction Impacts Chelation by Diglycolamide Ligands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellis, Ross J.; Brigham, Derek M.; Delmau, Laetitia

The subtle energetic differences underpinning adjacent lanthanide discrimination are explored with diglycolamide ligands. Our approach converges liquid–liquid extraction experiments with solution-phase X-ray absorption spectroscopy (XAS) and density functional theory (DFT) simulations, spanning the lanthanide series. The homoleptic [(DGA)3Ln]3+ complex was confirmed in the organic extractive solution by XAS, and this was modeled using DFT. An interplay between steric strain and coordination energies apparently gives rise to a nonlinear trend in discriminatory lanthanide ion complexation across the series. Our results highlight the importance of optimizing chelate molecular geometry to account for both coordination interactions and strain energies when designing new ligandsmore » for efficient adjacent lanthanide separation for rare-earth refining.« less

“Straining” to Separate the Rare Earths: How the Lanthanide Contraction Impacts Chelation by Diglycolamide Ligands

DOE PAGES

Ellis, Ross J.; Brigham, Derek M.; Delmau, Laetitia; ...

2016-11-23

The subtle energetic differences underpinning adjacent lanthanide discrimination are explored with diglycolamide ligands. Our approach converges liquid–liquid extraction experiments with solution-phase X-ray absorption spectroscopy (XAS) and density functional theory (DFT) simulations, spanning the lanthanide series. The homoleptic [(DGA)3Ln]3+ complex was confirmed in the organic extractive solution by XAS, and this was modeled using DFT. An interplay between steric strain and coordination energies apparently gives rise to a nonlinear trend in discriminatory lanthanide ion complexation across the series. Our results highlight the importance of optimizing chelate molecular geometry to account for both coordination interactions and strain energies when designing new ligandsmore » for efficient adjacent lanthanide separation for rare-earth refining.« less

Phosphinic acid functionalized polyazacycloalkane chelators for radiodiagnostics and radiotherapeutics: unique characteristics and applications.

PubMed

Notni, Johannes; Šimeček, Jakub; Wester, Hans-Jürgen

2014-06-01

Given the wide application of positron emission tomography (PET), positron-emitting metal radionuclides have received much attention recently. Of these, gallium-68 has become particularly popular, as it is the only PET nuclide commercially available from radionuclide generators, therefore allowing local production of PET radiotracers independent of an on-site cyclotron. Hence, interest in optimized bifunctional chelators for the elaboration of (68) Ga-labeled bioconjugates has been rekindled as well, resulting in the development of improved triazacyclononane-triphosphinate (TRAP) ligand structures. The most remarkable features of these ligands are unparalleled selectivity for Ga(III) , rapid Ga(III) complexation kinetics, extraordinarily high thermodynamic stability, and kinetic inertness of the respective Ga(III) chelates. As a result, TRAP chelators exhibit very favorable (68) Ga-labeling properties. Based on the scaffolds NOPO (1,4,7-triazacyclononane-1,4-bis[methylene(hydroxymethyl)phosphinic acid]-7-[methylene(2-carboxyethyl)phosphinic acid]) and TRAP-Pr, tailored for convenient preparation of (68) Ga-labeled monomeric and multimeric bioconjugates, a variety of novel (68) Ga radiopharmaceuticals have been synthesized. These include bisphosphonates, somatostatin receptor ligands, prostate-specific membrane antigen (PSMA)-targeting peptides, and cyclic RGD pentapeptides, for in vivo PET imaging of bone, neuroendocrine tumors, prostate cancer, and integrin expression, respectively. Furthermore, TRAP-based (68) Ga-labeled gadolinium(III) complexes have been proposed as bimodal probes for PET/MRI, and a cyclen-based analogue of TRAP-Pr has been suggested for the elaboration of targeted radiotherapeutics comprising radiolanthanide ions. Thus, polyazacycloalkane-based polyphosphinic acid chelators are a powerful toolbox for pharmaceutical research, particularly for the development of (68) Ga radiopharmaceuticals. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zinc chelation decreases IFN-β-induced STAT1 upregulation and iNOS expression in RAW 264.7 macrophages.

PubMed

Reiber, Cathleen; Brieger, Anne; Engelhardt, Gabriela; Hebel, Silke; Rink, Lothar; Haase, Hajo

2017-12-01

One consequence of lipopolysaccharide (LPS)-induced stimulation of macrophages is the release of Interferon (IFN)-β, and subsequently the activation of the JAK-STAT1 pathway, resulting in the expression of inducible nitric oxide synthase (iNOS). Free intracellular zinc ions (Zn 2+ ) have a profound impact as a second messenger in LPS-dependent gene expression. Previous work had indicated a Zn 2+ -dependent upregulation of STAT1 mRNA in response to LPS and IFN-β, potentially affecting STAT1-dependent downstream signaling upon pre-incubation with these agents. The aim of the present study was to investigate the long-term influence of Zn 2+ chelation on cellular STAT1 levels and their effect on protein levels and activity of iNOS. The LPS- and IFN-β-mediated increase of STAT1 mRNA and protein levels was abrogated by chelation of Zn 2+ with the membrane permeable chelator N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) in RAW 264.7 macrophages. After 48h pre-incubation together with IFN-β, TPEN also led to reduced nitric monoxide formation in response to a second stimulation with LPS. Nonetheless, the latter was observed regardless of any pre-incubation with IFN-β, suggesting that the effect of treatment with TPEN negatively affects iNOS induction independently from cellular STAT1 levels. In conclusion, long term Zn 2+ chelation does affect STAT1 protein expression, but interferes with NO production by a different, yet unknown pathway not involving STAT1. However, as there are many additional STAT1-dependent genes, there might still be effects on targets other than iNOS. Copyright © 2017 Elsevier GmbH. All rights reserved.

CHEMICAL CHARACTERIZATION OF A CHELATOR-TREATED SOIL HUMATE BY SOLUTION-STATE MULTINUCLEAR TWO-DIMENSIONAL NMR WITH FTIR AND PYROLYSIS-GCMS. (R825960)

EPA Science Inventory

A California forest soil used for contaminant bioavailability
studies was extracted for humic substances (HS) and
then treated with 4,5-dihydroxy-1,3-benzene disulfonate
("Tiron") to remove exchangeable metal ions. This yielded
HS that was readily water-soluble at ...

Transition metal coordination chemistry ofN,N-bis(2-{pyrid-2-ylethyl})hydroxylamine.

PubMed

Belock, Christopher W; Cetin, Anil; Barone, Natalie V; Ziegler, Christopher J

2008-08-18

Although directly relevant to metal mediated biological nitrification as well as the coordination chemistry of peroxide, the metal complexes of hydroxylamines and their functionalized variants remain largely unexplored. The chelating hydroxylamine ligand N,N-bis(2-{pyrid-2-ylethyl})hydroxylamine can be readily generated via a solvent free reaction in high purity; however, the ligand is prone to decomposition which can hamper metal reaction. N,N-bis(2-{pyrid-2-ylethyl})hydroxylamine forms stable complexes with chromium(III), manganese(II), nickel(II), and cadmium(II) ions, coordinating in a side-on mode in the case of chromium and via the nitrogen in the case of the latter three metal ions. The hydroxylamine ligand can also be reduced to form N,N-bis(2-{pyrid-2-ylethyl})amine upon exposure to a stoichiometric amount of the metal salts cobalt(II) nitrate, vanadium(III) chloride, and iron(II) chloride. In the reaction with cobalt nitrate, the reduced ligand then chelates to the metal to form [N,N-bis(2-{pyrid-2-ylethyl})amine]dinitrocobalt(II). Upon reaction with vanadium(III) chloride and iron(III) chloride, the reduced ligand is isolated as the protonated free base, resulting from a metal-mediated decomposition reaction.

Calixarene cleansing formulation for uranium skin contamination.

PubMed

Phan, Guillaume; Semili, Naïma; Bouvier-Capely, Céline; Landon, Géraldine; Mekhloufi, Ghozlene; Huang, Nicolas; Rebière, François; Agarande, Michelle; Fattal, Elias

2013-10-01

An oil-in-water cleansing emulsion containing calixarene molecule, an actinide specific chelating agent, was formulated in order to improve the decontamination of uranium from the skin. Commonly commercialized cosmetic ingredients such as surfactants, mineral oil, or viscosifying agents were used in preparing the calixarene emulsion. The formulation was characterized in terms of size and apparent viscosity measurements and then was tested for its ability to limit uranyl ion permeation through excoriated pig-ear skin explants in 24-h penetration studies. Calixarene emulsion effectiveness was compared with two other reference treatments consisting of DTPA and EHBP solutions. Application of calixarene emulsion induced the highest decontamination effect with an 87% decrease in uranium diffusion flux. By contrast, EHBP and DTPA solutions only allowed a 50% and 55% reduction of uranium permeation, respectively, and had the same effect as a simple dilution of the contamination by pure water. Uranium diffusion decrease was attributed to uranyl ion-specific chelation by calixarene within the formulation, since no significant effect was obtained after application of the same emulsion without calixarene. Thus, calixarene cleansing emulsion could be considered as a promising treatment in case of accidental contamination of the skin by highly diffusible uranium compounds.

Antioxidant activity of raw, cooked and Rhizopus oligosporus fermented beans of Canavalia of coastal sand dunes of Southwest India.

PubMed

Niveditha, Vedavyas R; Sridhar, Kandikere R

2014-11-01

The raw and processed (cooked and cooked + solid-state fermented with Rhizopus oligosporus) split beans of two landraces of coastal sand dune wild legumes (Canavalia cathartica and Canavalia maritima) of the southwest coast of India were examined for bioactive compounds (total phenolics, tannins and vitamin C) and antioxidant potential (total antioxidant activity, ferrous-ion chelating capacity, DPPH free radical-scavenging activity and reducing activity). One-way ANOVA revealed significant elevation of bioactive compounds as well as antioxidant activities in fermented beans compared to raw and cooked beans in both legumes (p < 0.001). The EC50 values in fermented beans of both legumes were significantly lowest compared to raw and cooked beans (p < 0.001). In principal component analysis, total phenolics along with antioxidant activities (total antioxidant, ferrous-ion chelating and free radical-scavenging activities) of fermented beans of C. cathartica, while total antioxidant and free radical-scavenging activities of fermented beans of C. maritima were clustered. The present study demonstrated that split beans of coastal sand dune Canavalia fermented by R. oligosporus endowed with high bioactive principles as well as antioxidant potential and thus serve as future nutraceutical source.

Robust surface coating for a fast, facile fluorine-18 labeling of iron oxide nanoparticles for PET/MR dual-modality imaging

DOE PAGES

Sun, Ziyan; Cheng, Kai; Wu, Fengyu; ...

2016-10-31

Grafting a robust organic shell around inorganic nanoparticles can optimize their colloidal features to dramatically improve their physicochemical properties. Here, we have developed a polymer coating procedure for providing colloidal stability to the nanoparticles and, more importantly, for applying a fast, facile fluorine-18 labeling of iron oxide nanoparticles (IONPs) for positron emission tomography (PET)/magnetic resonance (MR) dual-modality imaging. The structure of the amphiphilic polymer is based on a backbone of polyacrylic acid, conjugated with multiple oleylamines to form a comb-like branched structure. The dense polymer shell provides high colloidal stability to the IONPs against harsh conditions such as high temperature,more » low pH value, and high ion strength. By incorporating a 1,4,7-triazacyclononane (NOTA) chelator to the comb-like amphiphilic polymer for the chelation of aluminum fluoride ions, we applied a one-step radiolabeling approach for a fast, facile radiofluorination of magnetic nanoparticles. The new strategy can significantly reduce the procedure time and radiation exposure. In conclusion, the PET/MR dual modality imaging was successfully achieved in living subjects by using 18F labeled magnetic nanoparticles.« less

Robust surface coating for a fast, facile fluorine-18 labeling of iron oxide nanoparticles for PET/MR dual-modality imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Ziyan; Cheng, Kai; Wu, Fengyu

Grafting a robust organic shell around inorganic nanoparticles can optimize their colloidal features to dramatically improve their physicochemical properties. Here, we have developed a polymer coating procedure for providing colloidal stability to the nanoparticles and, more importantly, for applying a fast, facile fluorine-18 labeling of iron oxide nanoparticles (IONPs) for positron emission tomography (PET)/magnetic resonance (MR) dual-modality imaging. The structure of the amphiphilic polymer is based on a backbone of polyacrylic acid, conjugated with multiple oleylamines to form a comb-like branched structure. The dense polymer shell provides high colloidal stability to the IONPs against harsh conditions such as high temperature,more » low pH value, and high ion strength. By incorporating a 1,4,7-triazacyclononane (NOTA) chelator to the comb-like amphiphilic polymer for the chelation of aluminum fluoride ions, we applied a one-step radiolabeling approach for a fast, facile radiofluorination of magnetic nanoparticles. The new strategy can significantly reduce the procedure time and radiation exposure. In conclusion, the PET/MR dual modality imaging was successfully achieved in living subjects by using 18F labeled magnetic nanoparticles.« less

Changes in antioxidant and biochemical activities in castor oil-coated Capsicum annuum L. during postharvest storage.

PubMed

Panigrahi, Jitendriya; Patel, Mansi; Patel, Niyati; Gheewala, Bhumi; Gantait, Saikat

2018-06-01

This study, for the first time, evaluates the efficiency of castor oil when used as an external coating on Capsicum annuum L., to increase postharvest storage-life at 4 ± 1 °C. The castor oil-coated fruits were successfully stored for 36 days, while the non-coated fruits could only sustain for 18 days. Throughout the storage period (at 9-day intervals), different antioxidants and biochemical assays (allied with storage) such as titratable acidity, ascorbic acid content, ferrous ion chelating activity, reducing power, DPPH scavenging activity, hydroxyl radical scavenging activity, total phenolic content, total sugar estimation, and enzymatic study of polyphenol oxidase and pectate lyase, were assessed. During storage, the castor oil-coated fruits showed a substantial decrease in titratable acidity, ascorbic acid content, total phenolic content, including antioxidant activities such as reducing power and DPPH activity; however, an increase in ferrous ion chelating activity, total soluble sugar content, polyphenol oxidase activity and initial pectate lyase activity was observed, in contrast to that of the non-coated fruits. The application of castor oil proved to be effective in delaying the ripening process of fruits during storage.

Paramagnetic Gd IIIFe III heterobimetallic complexes of DTPA-bis-salicylamide

NASA Astrophysics Data System (ADS)

Aime, S.; Botta, M.; Fasano, M.; Terreno, E.

1993-08-01

The reaction between DTPA (diethylenetriaminepenta-acetic acid)-anhydride and p-aminosalicylic acid (PAS) affords a novel ligand, [DTPA(PAS) 2], able to form stable heterobimetallic complexes with Gd 3+ and Fe 3+ ions. The lanthanide ion occupies an internal coordination cage formed by three nitrogen atoms, two carboxylate and two carboxoamido groups of the ligand, whereas the outer salicylic moieties form stable chelate rings with Fe III ions. The stoichiometry of the resulting heterobimetallic complexes, established by measurements of water proton relaxation enhancement, is [(H 2O)-Gd-DTPA(PAS) 2] 2-Fe(H 2O) 2 or [(H 2O)-Gd-DTPA(PAS) 2] 3-Fe depending on the pH of the aqueous solution. The individual contributions to the observed relaxation enhancement from Gd 3+ and Fe 3+ paramagnetic ions have been clearly distinguished and analysed.

A Novel Coordination Polymer Constructed by Hetero-Metal Ions and 2,3-Pyridine Dicarboxylic Acid: Synthesis and Structure of [NiNa2(PDC)2(μ-H2O)(H2O)2] n

NASA Astrophysics Data System (ADS)

Dou, Ming-Yu; Lu, Jing

2017-12-01

A novel coordination polymer containing hetero-metal ions, [NiNa2(PDC)2(μ-H2O)(H2O)2] n , where PDC is 2,3-pyridine dicarboxylate ion, has been synthesized. In the structure, the PDC ligand chelates and bridges two Ni(II) and two Na(I) centers. Two kinds of metal centers are connected by μ4-PDC and μ2-H2O to form 2D coordination layers. Hydrogen bonds between coordination water molecules and carboxylate oxygen atoms further link these 2D coordination layers to form 3D supramolecular network.

Synthesis of a ratiometric fluorescent peptide sensor for the highly selective detection of Cd2+.

PubMed

Li, Yan; Li, Lianzhi; Pu, Xuewei; Ma, Guolin; Wang, Erqiong; Kong, Jinming; Liu, Zhipeng; Liu, Yangzhong

2012-06-15

A novel ratiometric fluorescent peptidyl chemosensor (Dansyl-Cys-Pro-Gly-Cys-Trp-NH(2), D-P5) for metal ions detection has been synthesized via Fmoc solid-phase peptide synthesis. The chemosensor exhibited a high selectivity for Cd(2+) over other metal ions including competitive transition and Group I and II metal ions in neutral pH. The fluorescence emission intensity of D-P5 was significantly enhanced in the presence of Cd(2+) by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The binding stoichiometry, detection limit, binding affinity, reversibility and pH sensitivity of the sensor for Cd(2+) were investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

[(Nitrato-κ2 O,O′)(nitrito-κ2 O,O′)(0.25/1.75)]bis­(1,10-phenanthroline-κ2 N,N′)cadmium(II)

PubMed Central

Najafi, Ezzatollah; Amini, Mostafa M.; Ng, Seik Weng

2011-01-01

The reaction of cadmium nitrate and sodium nitrite in the presence of 1,10-phenanthroline yields the mixed nitrate–nitrite title complex, [Cd(NO2)1.75(NO3)0.25(C12H8N2)2]. The metal ion is bis-chelated by two N-heterocycles as well as by the nitrate/nitrite ions in a distorted dodeca­hedral CdN4O4 coordination environment. One nitrite group is ordered; the other is disordered with respect to a nitrate group (ratio 0.75:0.25) concerning the O atom that is not involved in bonding to the metal ion. PMID:21522904

Enhancement effects of chelating agents on the degradation of tetrachloroethene in Fe(III) catalyzed percarbonate system

PubMed Central

Miao, Zhouwei; Gu, Xiaogang; Lu, Shuguang; Brusseau, Mark L.; Zhang, Xiang; Fu, Xiaori; Danish, Muhammad; Qiu, Zhaofu; Sui, Qian

2015-01-01

The performance of Fe(III)-based catalyzed sodium percarbonate (SPC) for stimulating the oxidation of tetrachloroethene (PCE) for groundwater remediation applications was investigated. The chelating agents citric acid monohydrate (CIT), oxalic acid (OA), and Glutamic acid (Glu) significantly enhanced the degradation of PCE. Conversely, ethylenediaminetetraacetic acid (EDTA) had a negative impact on PCE degradation, which may due to its strong Fe chelation and HO• scavenging abilities. However, excessive SPC or chelating agent will retard PCE degradation. In addition, investigations using free radical probe compounds and radical scavengers revealed that PCE was primarily degraded by HO• radical oxidation in both the chelated and non-chelated systems, while O2•− also participated in the non-chelated system and the OA and Glu modified systems. According to the electron paramagnetic resonance (EPR) studies, the presence of HO• in the Fe(III)/SPC system was maintained much longer than that in the Fe(II)/SPC system. The results indicated that the addition of CIT, OA or Glu indeed enhanced the generation of HO• in the first 10 min and promoted degradation efficiency by increasing the amount of Fe(III) and maintaining the concentration of HO• radicals in solution. In conclusion, chelated Fe(III)-based catalyzed SPC oxidation is a promising method for the remediation of PCE-contaminated groundwater. PMID:26549979

Spectroscopic investigation of the influence of calcium ion on the structures of casein micelles.

PubMed

Wang, Peng-Jie; Wu, Jian-Ping; Zhang, Hao; Guo, Hui-Yuan; Liu, Hong-Na; Ren, Fa-Zheng

2014-01-01

The effects of calcium ion on the structural properties of casein micelles in the course of heat treatment were synthetically examined by non-structure-invasive spectrometry. The hydrophobicity, reflected by extrinsic fluorescence (ANS fluorescence), was positively correlated with the concentration of the calcium ion, within the range of 0 to 12 mmol x L(-1). Meanwhile, the turbidity and stability of casein micelles also increased with the growth of calcium concentrations. However, opposite results were observed for hydrodynamic diameter and polydispersity index. Compared with the calcium ion, the calcium-chelator (citrate) has an opposite effect on the structural characteristics of casein micelles. Within the calcium concentrations range of 0 to 12 mmol x L(-1), the hydrophobicity, stability and turbidity were negatively correlated with the concentration of the calcium ion, nevertheless, opposite results were observed for hydrodynamic diameter and polydispersity index. All the results indicate that the calcium ion could be used to modify the structures of casein micelles during heat heatment.

Relevant interactions of antimicrobial iron chelators and membrane models revealed by nuclear magnetic resonance and molecular dynamics simulations.

PubMed

Coimbra, João T S; Moniz, Tânia; Brás, Natércia F; Ivanova, Galya; Fernandes, Pedro A; Ramos, Maria J; Rangel, Maria

2014-12-18

The dynamics and interaction of 3-hydroxy-4-pyridinone fluorescent iron chelators, exhibiting antimicrobial properties, with biological membranes were evaluated through NMR and molecular dynamics simulations. Both NMR and MD simulation results support a strong interaction of the chelators with the lipid bilayers that seems to be strengthened for the rhodamine containing compounds, in particular for compounds that include ethyl groups and a thiourea link. For the latter type of compounds the interaction reaches the hydrophobic core of the lipid bilayer. The molecular docking and MD simulations performed for the potential interaction of the chelators with DC-SIGN receptors provide valuable information regarding the cellular uptake of these compounds since the results show that the fluorophore fragment of the molecular framework is essential for an efficient binding. Putting together our previous and present results, we put forward the hypothesis that all the studied fluorescent chelators have access to the cell, their uptake occurs through different pathways and their permeation properties correlate with a better access to the cell and its compartments and, consequently, with the chelators antimicrobial properties.

Process for the displacement of cyanide ions from metal-cyanide complexes

DOEpatents

Smith, Barbara F.; Robinson, Thomas W.

1997-01-01

The present invention relates to water-soluble polymers and the use of such water-soluble polymers in a process for the displacement of the cyanide ions from the metal ions within metal-cyanide complexes. The process waste streams can include metal-cyanide containing electroplating waste streams, mining leach waste streams, mineral processing waste streams, and related metal-cyanide containing waste streams. The metal ions of interest are metals that give very strong complexes with cyanide, mostly iron, nickel, and copper. The physical separation of the water-soluble polymer-metal complex from the cyanide ions can be accomplished through the use of ultrafiltration. Once the metal-cyanide complex is disrupted, the freed cyanide ions can be recovered for reuse or destroyed using available oxidative processes rendering the cyanide nonhazardous. The metal ions are released from the polymer, using dilute acid, metal ion oxidation state adjustment, or competing chelating agents, and collected and recovered or disposed of by appropriate waste management techniques. The water-soluble polymer can then be recycled. Preferred water-soluble polymers include polyethyleneimine and polyethyleneimine having a catechol or hydroxamate group.

Versatile chelating behavior of benzil bis(thiosemicarbazone) in zinc, cadmium, and nickel complexes.

PubMed

López-Torres, Elena; Mendiola, Ma Antonia; Pastor, César J; Pérez, Beatriz Souto

2004-08-23

Reactions of benzil bis(thiosemicarbazone), LH(6), with M(NO(3))(2).nH(2)O (M = Zn, Cd, and Ni), in the presence of LiOH.H(2)O, show the versatile behavior of this molecule. The structure of the ligand, with the thiosemicarbazone moieties on opposite sides of the carbon backbone, changes to form complexes by acting as a chelating molecule. Complexes of these metal ions with empirical formula [MLH(4)] were obtained, although they show different molecular structures depending on their coordinating preferences. The zinc complex is the first example of a crystalline coordination polymer in which a bis(thiosemicarbazone) acts as bridging ligand, through a nitrogen atom, giving a 1D polymeric structure. The coordination sphere is formed by the imine nitrogen and sulfur atoms, and the remaining position, in a square-based pyramid, is occupied by an amine group of another ligand. The cadmium derivative shows the same geometry around the metal ion but consists of a dinuclear structure with sulfur atoms acting as a bridge between the metal ions. However, in the nickel complex LH(6) acts as a N(2)S(2) ligand yielding a planar structure for the nickel atom. The ligand and its complexes have been characterized by X-ray crystallography, microanalysis, mass spectrometry, IR, (1)H, and (13)C NMR spectroscopies and for the cadmium complex by (113)Cd NMR in solution and in the solid state.

Gadolinium-based nanoparticles to improve the hadrontherapy performances.

PubMed

Porcel, Erika; Tillement, Olivier; Lux, François; Mowat, Pierre; Usami, Noriko; Kobayashi, Katsumi; Furusawa, Yoshiya; Le Sech, Claude; Li, Sha; Lacombe, Sandrine

2014-11-01

Nanomedicine is proposed as a novel strategy to improve the performance of radiotherapy. High-Z nanoparticles are known to enhance the effects of ionizing radiation. Recently, multimodal nanoparticles such as gadolinium-based nanoagents were proposed to amplify the effects of x-rays and g-rays and to improve MRI diagnosis. For tumors sited in sensitive tissues, childhood cases and radioresistant cancers, hadrontherapy is considered superior to x-rays and g-rays. Hadrontherapy, based on fast ion radiation, has the advantage of avoiding damage to the tissues behind the tumor; however, the damage caused in front of the tumor is its major limitation. Here, we demonstrate that multimodal gadolinium-based nanoparticles amplify cell death with fast ions used as radiation. Molecular scale experiments give insights into the mechanisms underlying the amplification of radiation effects. This proof-of-concept opens up novel perspectives for multimodal nanomedicine in hadrontherapy, ultimately reducing negative radiation effects in healthy tissues in front of the tumor. Gadolinium-chelating polysiloxane nanoparticles were previously reported to amplify the anti-tumor effects of x-rays and g-rays and to serve as MRI contrast agents. Fast ion radiation-based hadrontherapy avoids damage to the tissues behind the tumor, with a major limitation of tissue damage in front of the tumor. This study demonstrates a potential role for the above nanoagents in optimizing hadrontherapy with preventive effects in healthy tissue and amplified cell death in the tumor. Copyright © 2014 Elsevier Inc. All rights reserved.

Conformation of the Phosphate D-alanine Zwitterion in Bacterial Teichoic Acid from Nuclear Magnetic Resonance Spectroscopy

PubMed Central

Garimella, Ravindranath; Halye, Jeffrey L.; Harrison, William; Klebba, Phillip E.; Rice, Charles V.

2009-01-01

The conformation of D-alanine (D-Ala) groups of bacterial teichoic acid is a central, yet untested, paradigm of microbiology. The D-Ala binds via the C-terminus, thereby allowing the amine to exist as a free cationic NH3+ group with the ability to form a contact-ion-pair with the nearby anionic phosphate group. This conformation hinders metal chelation by the phosphate because the zwitterion pair is charge neutral. To the contrary, the repulsion of cationic antimicrobial peptides (CAMPs) is attributed to the presence of the D-Ala cation; thus the ion-pair does not form in this model. Solid-state nuclear magnetic resonance (NMR) spectroscopy has been used to measure the distance between amine and phosphate groups within cell wall fragments of Bacillus subtilis. The bacteria were grown on media containing 15N D-Ala and β-chloroalanine racemase inhibitor. The rotational-echo double-resonance (REDOR) pulse sequence was used to measure the internuclear dipolar coupling and the results demonstrate: 1) the metal-free amine-to-phosphate distance is 4.4 Å and 2) the amine-to-phosphate distance increases to 5.4 Å in the presence of Mg2+ ions. As a result, the zwitterion exists in a nitrogen-oxygen ion-pair configuration providing teichoic acid with a positive charge to repel CAMPs. Additionally, the amine of D-Ala does not prevent magnesium chelation in contradiction to the prevailing view of teichoic acids in metal binding. Thus, the NMR-based description of teichoic acid structure resolves the contradictory models, advances the basic understanding of cell wall biochemistry, and provides possible insight into the creation of new antibiotic therapies. PMID:19746945

Oxidation of nitroxyl anion to nitric oxide by copper ions

PubMed Central

Nelli, Silvia; Hillen, Mark; Buyukafsar, Kansu; Martin, William

2000-01-01

This study made use of a nitric oxide-sensitive electrode to examine possible means of generating nitric oxide from nitroxyl anion (NO−) released upon the decomposition of Angeli's salt. Our results show that copper ions (from CuSO4) catalyze the rapid and efficient oxidation of nitroxyl to nitric oxide. Indeed, the concentrations of copper required to do so (0.1–100 μM) are roughly 100-times lower than those required to generate equivalent amounts of nitric oxide from S-nitroso-N-acetyl-D,L-penicillamine (SNAP). Experiments with ascorbate (1 mM), which reduces Cu2+ ions to Cu+, and with the Cu2+ chelators, EDTA and cuprizone, and the Cu+ chelator, neocuproine, each at 1 mM, suggest that the oxidation is catalyzed by copper ions in both valency states. Some compounds containing other transition metals, i.e. methaemoglobin, ferricytochrome c and Mn(III)TMPyP, were much less efficient than CuSO4 in catalyzing the formation of nitric oxide from nitroxyl, while FeSO4, FeCl3, MnCl2, and ZnSO4 were inactive. Of the copper containing enzymes examined, Cu-Zn superoxide dismutase and ceruloplasmin were weak generators of nitric oxide from nitroxyl, even at concentrations (2500 and 30 u ml−1, respectively) vastly greater than are present endogenously. Two others, ascorbate oxidase (10 u ml−1) and tyrosinase (250 u ml−1) were inactive. Our findings suggest that a copper-containing enzyme may be responsible for the rapid oxidation of nitroxyl to nitric oxide by cells, but the identity of such an enzyme remains elusive. PMID:10991931

Influence of copper ions on the viability and cytotoxicity of Pseudomonas aeruginosa under conditions relevant to drinking water environments.

PubMed

Dwidjosiswojo, Zenyta; Richard, Jessica; Moritz, Miriam M; Dopp, Elke; Flemming, Hans-Curt; Wingender, Jost

2011-11-01

Copper plumbing materials can be the source of copper ions in drinking water supplies. The aim of the current study was to investigate the influence of copper ions on the viability and cytotoxicity of the potential pathogen Pseudomonas aeruginosa that presents a health hazard when occurring in building plumbing systems. In batch experiments, exposure of P. aeruginosa (10(6)cells/mL) for 24h at 20°C to copper-containing drinking water from domestic plumbing systems resulted in a loss of culturability, while total cell numbers determined microscopically did not decrease. Addition of the chelator diethyldithiocarbamate (DDTC) to copper-containing water prevented the loss of culturability. When suspended in deionized water with added copper sulfate (10 μM), the culturability of P. aeruginosa decreased by more than 6 log units, while total cell counts, the concentration of cells with intact cytoplasmic membranes, determined with the LIVE/DEAD BacLight kit, and the number of cells with intact 16S ribosomal RNA, determined by fluorescent in situ hybridization, remained unchanged. When the chelator DDTC was added to copper-stressed bacteria, complete restoration of culturability was observed to occur within 14 d. Copper-stressed bacteria were not cytotoxic towards Chinese hamster ovary (CHO-9) cells, while untreated and resuscitated bacteria caused an almost complete decrease of the concentration of viable CHO-9 cells within 24 h. Thus, copper ions in concentrations relevant to drinking water in plumbing systems seem to induce a viable but non-culturable (VBNC) state in P. aeruginosa accompanied by a loss of culturability and cytotoxicity, and VBNC cells can regain both culturability and cytotoxicity, when copper stress is abolished. Copyright © 2011 Elsevier GmbH. All rights reserved.

Pressure-Assisted Chelating Extraction as a Teaching Tool in Instrumental Analysis

ERIC Educational Resources Information Center

Sadik, Omowunmi A.; Wanekaya, Adam K.; Yevgeny, Gelfand

2004-01-01

A novel instrumental-digestion technique using pressure-assisted chelating extraction (PACE), for undergraduate laboratory is reported. This procedure is used for exposing students to safe sample-preparation techniques, for correlating wet-chemical methods with modern instrumental analysis and comparing the performance of PACE with conventional…

A new morphological approach for removing acid dye from leather waste water: preparation and characterization of metal-chelated spherical particulated membranes (SPMs).

PubMed

Şenay, Raziye Hilal; Gökalp, Safiye Meriç; Türker, Evren; Feyzioğlu, Esra; Aslan, Ahmet; Akgöl, Sinan

2015-03-15

In this study, p(HEMA-GMA) poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) spherical particulated membranes (SPMs) were produced by UV-photopolymerization and the synthesized SPMs were coupled with iminodiacetic acid (IDA). Finally the novel SPMs were chelated with Cr(III) ions as ligand and used for removing acid black 210 dye. Characterizations of the metal-chelated SPMs were made by SEM, FTIR and swelling test. The water absorption capacities and acid dye adsorption properties of the SPMs were investigated and the results were 245.0, 50.0, 55.0 and 51.9% for p(HEMA), p(HEMA-GMA), p(HEMA-GMA)-IDA and p(HEMA-GMA)-IDA-Cr(III) SPMs respectively. Adsorption properties of the p(HEMA-GMA)-IDA-Cr(III) SPMs were investigated under different conditions such as different initial dye concentrations and pH. The optimum pH was observed at 4.3 and the maximum adsorption capacity was determined as 885.14 mg/g at about 8000 ppm initial dye concentration. The concentrations of the dyes were determined using a UV/Vis Spectrophotometer at a wavelength of 435 nm. Reusability of p(HEMA-GMA)-IDA-Cr(III) SPMs was also shown for five adsorption-desorption cycles without considerable decrease in its adsorption capacity. Finally, the results showed that the metal-chelated p(HEMA-GMA)-IDA SPMs were effective sorbent systems removing acid dye from leather waste water. Copyright © 2014 Elsevier Ltd. All rights reserved.

Relaxivity enhancement of aquated Tris(β-diketonate)gadolinium(III) chelates by confinement within ultrashort single-walled carbon nanotubes.

PubMed

Law, Justin J; Guven, Adem; Wilson, Lon J

2014-01-01

Ultrashort single-walled carbon nanotubes loaded with gadolinium ions (gadonanotubes) have been previously shown to exhibit extremely high T1 -weighted relaxivities (>100 mm(-1) s(-1) ). To further examine the effect of nanoconfinement on the relaxivity of gadolinium-based contrast agents for magnetic resonance imaging, a series of ultrashort single-walled carbon nanotube (US-tube) materials internally loaded with gadolinium chelates have been prepared and studied. US-tubes were loaded with Gd(acac)3  · 2H2 O, Gd(hfac)3  · 2H2 O, and Gd(thd)3 (acac = acetylacetone, hfac = hexafluoroacetylacetone, thd = tetramethylheptanedione). The longitudinal relaxivities of the prepared materials determined at 25°C in a 1.5 T field were 103 mm(-1) s(-1) for Gd(acac)3  · 2H2 O@US-tubes, 105 mm(-1) s(-1) for Gd(hfac)3  · 2H2 O@US-tubes and 26 mm(-1) s(-1) for Gd(thd)3 @US-tubes. Compared with the relaxivities obtained for the unloaded chelates (<10 mm(-1) s(-1) ) as well as accounting for the T1 reduction observed for the empty US-tubes, the boost in relaxivity for chelate-loaded US-tubes is attributed to confinement within the nanotube and depends on the number of coordinated water molecules. Copyright © 2014 John Wiley & Sons, Ltd.

Physicochemical impact studies of gamma rays on "aspirin" analgesics drug and its metal complexes in solid form: Synthesis, spectroscopic and biological assessment of Ca(II), Mg(II), Sr(II) and Ba(II) aspirinate complexes

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Sharshar, T.; Elsabawy, Khaled M.; Heiba, Zein K.

2013-09-01

Metal aspirinate complexes, M2(Asp)4, where M is Mg(II), Ca(II), Sr(II) or Ba(II) are formed by refluxed of aspirin (Asp) with divalent non-transition metal ions of group (II) and characterized by elemental analysis and spectroscopic measurements (infrared, electronic, 1H NMR, Raman, X-ray powder diffraction and scanning electron microscopy). Elemental analysis of the chelates suggests the stoichiometry is 1:2 (metal:ligand). Infrared spectra of the complexes agree with the coordination to the central metal atom through three donation sites of two oxygen atoms of bridge bidentate carboxylate group and oxygen atom of sbnd Cdbnd O of acetyl group. Infrared spectra coupled with the results of elemental analyzes suggested a distorted octahedral structure for the M(II) aspirinate complexes. Gamma irradiation was tested as a method for stabilization of aspirin as well as their complexes. The effect of gamma irradiation, with dose of 80 Gy, on the properties of aspirinate complexes was studied. The aspirinate chelates have been screened for their in vitro antibacterial activity against four bacteria, gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two strains of fungus (Aspergillus flavus and Candida albicans). The metal chelates were shown to possess more antibacterial activity than the free aspirin chelate.

Immobilization of ionophore and surface characterization studies of the titanium(III) ion in a PVC-membrane sensor.

PubMed

Rezayi, Majid; Heng, Lee Yook; Kassim, Anuar; Ahmadzadeh, Saeid; Abdollahi, Yadollah; Jahangirian, Hossein

2012-01-01

Novel ionophores comprising various hydroxide and amine structures were immobilized onto poly(vinyl chloride) (PVC) matrices, and these were examined to determine Ti(III) selectivity. To predict the selectivity of Ti(III), a PVC membrane was used to investigate the binding of Ti(III) to c-methylcalix[4]resorcinarene (CMCR). The study showed that the chelating ligand, CMCR, was coordinated selectively to Ti(III) at eight coordination sites involving the oxygen atoms at the interface of the membrane/solution. The membrane was prepared, based on CMCR as an ionophore, sodium tetrakis(4-fluorophenyl) borate (NaTFPB) as a lipophilic ionic additive, and dioctylphthalate (DOP) as a plasticizer. The immobilization of the ionophore and surface characterization studies revealed that the performance of CMCR-immobilized PVC was equivalent to that of mobile ionophores in supported liquid membranes (SLMs). The strengths of the ion-ionophore (CMCR-Ti(OH)(OH(2))(5) (2+)) interactions and the role of ionophores on membranes were studied via UV-Vis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and and X-ray diffraction (XRD).

Zinc and Copper Effects on Stability of Tubulin and Actin Networks in Dendrites and Spines of Hippocampal Neurons.

PubMed

Perrin, Laura; Roudeau, Stéphane; Carmona, Asuncion; Domart, Florelle; Petersen, Jennifer D; Bohic, Sylvain; Yang, Yang; Cloetens, Peter; Ortega, Richard

2017-07-19

Zinc and copper ions can modulate the activity of glutamate receptors. However, labile zinc and copper ions likely represent only the tip of the iceberg and other neuronal functions are suspected for these metals in their bound state. We performed synchrotron X-ray fluorescence imaging with 30 nm resolution to image total biometals in dendrites and spines from hippocampal neurons. We found that zinc is distributed all along the dendrites while copper is mainly pinpointed within the spines. In spines, zinc content is higher within the spine head while copper is higher within the spine neck. Such specific distributions suggested metal interactions with cytoskeleton proteins. Zinc supplementation induced the increase of β-tubulin content in dendrites. Copper supplementation impaired the β-tubulin and F-actin networks. Copper chelation resulted in the decrease of F-actin content in dendrites, drastically reducing the number of F-actin protrusions. These results indicate that zinc is involved in microtubule stability whereas copper is essential for actin-dependent stability of dendritic spines, although copper excess can impair the dendritic cytoskeleton.

Lectin conjugates as biospecific contrast agents for MRI. Coupling of Lycopersicon esculentum agglutinin to linear water-soluble DTPA-loaded oligomers.

PubMed

Pashkunova-Martic, Irena; Kremser, Christian; Galanski, Markus; Schluga, Petra; Arion, Vladimir; Debbage, Paul; Jaschke, Werner; Keppler, Bernhard

2011-06-01

Magnetic resonance imaging (MRI) requires synthesis of contrast media bearing targeting groups and numerous gadolinium chelating groups generating high relaxivity. This paper explores the results of linking the gadolinium chelates to the targeting group, a protein molecule, via various types of linkers. Polycondensates of diethylenetriaminepentaacetic acid (DTPA) with either diols or diamines were synthesised and coupled to the targeting group, a lectin (Lycopersicon esculentum agglutinin, tomato lectin) which binds with high affinity to specific oligosaccharide configurations in the endothelial glycocalyx. The polycondensates bear up to four carboxylic groups per constitutive unit. Gd-chelate bonds are created through dative interactions with the unshared pair of electrons on each oxygen and nitrogen atom on DTPA. This is mandatory for complexation of Gd(III) and avoidance of the severe toxicity of free gadolinium ions. The polymer-DTPA compounds were characterised by (1)H NMR and mass spectrometry. The final lectin-DTPA-polycondensate conjugates were purified by fast protein liquid chromatography (FPLC). The capacity for specific binding was assessed, and the MRI properties were examined in order to evaluate the use of these oligomers as components of selective perfusional contrast agents.

Spectrophotometric Study of the Complex Formation of Anionic Chelates of Cobalt(II) with Monotetrazolium Cations

NASA Astrophysics Data System (ADS)

Divarova, V. V.; Stojnova, K. T.; Racheva, P. V.; Lekova, V. D.

2017-05-01

The complex formation and extraction of anionic chelates of Co(II)-4-(2-thiazolylazo)resorcinol (TAR) with cations of monotetrazolium salts (TS) — (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and 3-(2-naphthyl)-2,5-diphenyl-2H-tetrazolium chloride (TV) — in the liquid-liquid extraction system Co(II)-TAR-TS-H2O-CHCl3 were studied by spectrophotometric methods. The optimum conditions for the extraction of Co(II) were found. The molar ratio of the components and the form of the anionic chelates of Co(II) in the extracted compounds were determined by independent methods. The association process in the aqueous phase and the extraction process were investigated and quantitatively characterized. The following key constants were calculated: association constant, distribution constant, extraction constant, and recovery factor. The validity of the Beer's law was checked, and some analytical characteristics were calculated. Based on the obtained results and the lower price of the monotetrazolium salt MTT compared with that of TV, the ion-associated complex of Co(II)-TAR-MTT can be implemented for determination of cobalt(II) traces in alloys and biological, medical, and pharmaceutical samples.

Benzyl and Methyl Fatty Hydroxamic Acids Based on Palm Kernel Oil as Chelating Agent for Liquid-Liquid Iron(III) Extraction

PubMed Central

Haron, Md Jelas; Jahangirian, Hossein; Silong, Sidik; Yusof, Nor Azah; Kassim, Anuar; Rafiee-Moghaddam, Roshanak; Mahdavi, Behnam; Peyda, Mazyar; Abdollahi, Yadollah; Amin, Jamileh

2012-01-01

Liquid-liquid iron(III) extraction was investigated using benzyl fatty hydroxamic acids (BFHAs) and methyl fatty hydroxamic acids (MFHAs) as chelating agents through the formation of iron(III) methyl fatty hydroxamate (Fe-MFHs) or iron(III) benzyl fatty hydroxamate (Fe-BFHs) in the organic phase. The results obtained under optimized conditions, showed that the chelating agents in hexane extract iron(III) at pH 1.9 were realized effectively with a high percentage of extraction (97.2% and 98.1% for MFHAs and BFHAs, respectively). The presence of a large amount of Mg(II), Ni(II), Al(III), Mn(II) and Co(II) ions did affect the iron(III) extraction. Finally stripping studies for recovering iron(III) from organic phase (Fe-MFHs or Fe-BFHs dissolved in hexane) were carried out at various concentrations of HCl, HNO3 and H2SO4. The results showed that the desired acid for recovery of iron(III) was 5 M HCl and quantitative recovery of iron(III) was achieved from Fe(III)-MFHs and Fe(III)-BFHs solutions in hexane containing 5 mg/L of Fe(III). PMID:22408444

Synthesis, characterization and application of a new chelating resin for solid phase extraction, preconcentration and determination of trace metals in some dairy samples by flame atomic absorption spectrometry.

PubMed

Daşbaşı, Teslima; Saçmacı, Şerife; Çankaya, Nevin; Soykan, Cengiz

2016-11-15

In this study, a simple and rapid solid phase extraction/preconcentration procedure was developed for determination of Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Pb(II), and Zn(II) trace metals by flame atomic absorption spectrometry (FAAS). A new chelating resin, poly(N-cyclohexylacrylamide-co-divinylbenzene-co-2-acrylamido-2-methyl-1-propanesulfonic acid) (NCA-co-DVB-co-AMPS) (hereafter CDAP) was synthesized and characterized. The influences of the analytical parameters such as pH of the sample solution, type and concentration of eluent, flow rates of the sample and eluent, volume of the sample and eluent, amount of chelating resin, and interference of ions were examined. The limit of detection (LOD) of analytes were found (3s) to be in the range of 0.65-1.90μgL(-1). Preconcentration factor (PF) of 200 and the relative standard deviation (RSD) of ⩽2% were achieved (n=11). The developed method was applied for determination of analytes in some dairy samples and certified reference materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Switchable polarity solvent for liquid phase microextraction of Cd(II) as pyrrolidinedithiocarbamate chelates from environmental samples.

PubMed

Yilmaz, Erkan; Soylak, Mustafa

2015-07-30

A switchable polarity solvent was synthesized from triethylamine (TEA)/water/CO2 (Dry ice) via proton transfer reaction has been used for the microextraction of cadmium(II) as pyrrolidinedithiocarbamate (APDC) chelate. Cd(II)-APDC chelate was extracted into the switchable polarity solvent drops by adding 2 mL 10 M sodium hydroxide solution. Analytical parameters affecting the complex formation and microextraction efficiency such as pH, amount of ligand, volume of switchable polarity solvent and NaOH, sample volume were optimized. The effects of foreign ions were found tolerably. Under optimum conditions, the detection limit was 0.16 μg L(-1) (3Sb/m, n = 7) and the relative standard deviation was 5.4% (n = 7). The method was validated by the analysis of certified reference materials (TMDA-51.3 fortified water, TMDA-53.3 fortified water and SPS-WW2 waste water, 1573a Tomato Leaves and Oriental Basma Tobacco Leaves (INCT-OBTL-5)) and addition/recovery tests. The method was successfully applied to determination of cadmium contents of water, vegetable, fruit and cigarette samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Cell-permeable Ln(III) chelate-functionalized InP quantum dots as multimodal imaging agents.

PubMed

Stasiuk, Graeme J; Tamang, Sudarsan; Imbert, Daniel; Poillot, Cathy; Giardiello, Marco; Tisseyre, Céline; Barbier, Emmanuel L; Fries, Pascal Henry; de Waard, Michel; Reiss, Peter; Mazzanti, Marinella

2011-10-25

Quantum dots (QDs) are ideal scaffolds for the development of multimodal imaging agents, but their application in clinical diagnostics is limited by the toxicity of classical CdSe QDs. A new bimodal MRI/optical nanosized contrast agent with high gadolinium payload has been prepared through direct covalent attachment of up to 80 Gd(III) chelates on fluorescent nontoxic InP/ZnS QDs. It shows a high relaxivity of 900 mM(-1) s(-1) (13 mM(-1 )s(-1) per Gd ion) at 35 MHz (0.81 T) and 298 K, while the bright luminescence of the QDs is preserved. Eu(III) and Tb(III) chelates were also successfully grafted to the InP/ZnS QDs. The absence of energy transfer between the QD and lanthanide emitting centers results in a multicolor system. Using this convenient direct grafting strategy additional targeting ligands can be included on the QD. Here a cell-penetrating peptide has been co-grafted in a one-pot reaction to afford a cell-permeable multimodal multimeric MRI contrast agent that reports cellular localization by fluorescence and provides high relaxivity and increased tissue retention with respect to commercial contrast agents.

Synthesis, structure and magnetic study of a novel mixed-valent Co(II)10Co(III)4 shield constructed by mixed pyridine-alcoholate ligands.

PubMed

Peng, Yan; Tian, Chong-Bin; Zhang, Hua-Bin; Li, Zhi-Hua; Lin, Ping; Du, Shao-Wu

2012-04-28

A novel tetradecanuclear mixed-valent cobalt cluster, formulated as [Co(II)(10)Co(III)(4)(OH)(2)O(6)(hmp)(10)(pdm)(4)(CH(3)OH)(2)]·5H(2)O (1), was obtained using mixed ligands of 2-(hydroxymethyl)pyridine (hmpH) and 2,6-pyridinedimethanol (pdmH(2)). The cobalt ions in 1 are connected by ten chelating hmp(-) ligands, four tris-chelating pdm(2-) ligands and six μ(3)-oxide/hydroxide anions, forming a unique shield-like planar structure that is rarely observed for Co-based clusters. Compound 1 displays slight frequency dependence at static zero field below 4.5 K, suggesting that it might be a single molecule magnet (SMM). This journal is © The Royal Society of Chemistry 2012

Thermometric studies on the Fe(III)-EDTA chelate.

PubMed

Dot, K

1978-02-01

A DeltaH of -11.5 +/- 0.5 kJ/mole has been determined for the formation of the Fe(III)-EDTA chelate at 25.0 degrees and mu = 0.1(= [HClO(4)] + [NaClO(4)]) by a direct thermometric titration procedure. The entropy change, DeltaS, has been calculated to be 440 J.mole(-1) .deg(-1) by combining the result of the heat measurements with the free energy change obtained from the stability constant previously determined. A relationship between the DeltaS values and the standard partial molal entropies of the tervalent metal ions is discussed. In addition, conditions for the thermometric titration of Fe(III) with NA(4)EDTA at room temperature have been investigated. Iron(III) can be determined in the presence of fairly large amounts of phosphate, Cr(III), Mn(II) and Al(III).

Determining the EDTA Content in a Consumer Shower Cleaner. An Introductory Chemistry Laboratory Experiment

NASA Astrophysics Data System (ADS)

Weigand, Willis A.

2000-10-01

At Altoona College, Chemistry 11 is offered to students as a preparatory course for the University's Chemical Principles course, Chem 12. A relevant laboratory is a source of motivation for the students to learn the chemistry. One way of making the laboratory relevant is to analyze the chemical components of consumer products. Several new shower-cleaning products have been introduced, which advertise that cleaning the shower is no longer necessary. The cleaners work using a combination of surfactants, alcohols, and a chelating agent. The Web site of a popular shower cleaner lists EDTA (ethylenediamine tetraacetate ion) as the chelating agent. The classic EDTA/calcium complexometric titration can be used to determine the EDTA content of the cleaner. This article describes the experiment to determine the EDTA content in a shower-cleaning product.

An improved method for emergent decontamination of ocular and dermal hydrofluoric acid splashes.

PubMed

Soderberg, Kjell; Kuusinen, Petri; Mathieu, Laurence; Hall, Alan H

2004-08-01

Accidental hydrofluoric acid (HF) splashes often occur in industrial settings. HF easily penetrates into tissues by initial acid action allowing fluoride ions to penetrate deeply, chelating calcium and magnesium. Resultant hypocalcemia and hypomagnesemia can be fatal. This report describes the utilization of Hexafluorine--a hypertonic, amphoteric, chelating decontamination solution--in workplaces where water decontamination followed by calcium gluconate inunction failed to prevent HF burns and systemic toxicity. Between 1998 and 1999, 16 cases of ocular and dermal HF splashes with either 70% HF or 6% HF/15% nitric acid (HNO3) were decontaminated with Hexafluorine at the worksite. HF burns did not develop and medical treatment other than initial decontamination was not reQuired in 12/16 (75%). In 7/16 (44%) cases, lost work time corresponded to duration of hospital observation (mean < 1 d).

Chelating Tendencies of Bioactive Aminophosphonates

PubMed Central

Lázár, István; Kafarski, Pawel

1994-01-01

The metal-binding abilities of a wide variety of bioactive aminophosphonates, from the simple aminoethanephosphonic acids to the rather large macrocyclic polyaza derivatives, are discussed with special emphasis on a comparison of the analogous carboxylic acid and phosphonic acid systems. Examples are given of the biological importance of metal ion – aminophosphonate interactions in living systems, and also of their actual and potential applicability in medicine. PMID:18476237

Radiopharmaceuticals for imaging the heart

DOEpatents

Green, Mark A.; Tsang, Brenda W.

1994-01-01

Radiopharmaceuticals for imaging myocardial tissues are prepared by forming lipophilic, cationic complexes of radioactive metal ions with metal chelating ligands comprising the Schiff base adducts of triamines and tetraamines with optionally substituted salicylaldehydes. The lipophilic, cationic, radioactive complexes of the invention exhibit high uptake and retention in myocardial tissues. Preferred gallium-68(III) complexes in accordance with this invention can be used to image the heart using positron emission tomography.

Crystal and electronic structures of magnesium(II), copper(II), and mixed magnesium(II)-copper(II) complexes of the quinoline half of styrylquinoline-type HIV-1 integrase inhibitors.

PubMed

Courcot, B; Firley, D; Fraisse, B; Becker, P; Gillet, J-M; Pattison, P; Chernyshov, D; Sghaier, M; Zouhiri, F; Desmaële, D; d'Angelo, J; Bonhomme, F; Geiger, S; Ghermani, N E

2007-05-31

A new target in AIDS therapy development is HIV-1 integrase (IN). It was proven that HIV-1 IN required divalent metal cations to achieve phosphodiester bond cleavage of DNA. Accordingly, all newly investigated potent IN inhibitors contain chemical fragments possessing a high ability to chelate metal cations. One of the promising leads in the polyhydroxylated styrylquinolines (SQLs) series is (E)-8-hydroxy-2-[2-(4,5-dihydroxy-3-methoxyphenyl)-ethenyl]-7-quinoline carboxylic acid (1). The present study focuses on the quinoline-based progenitor (2), which is actually the most probable chelating part of SQLs. Conventional and synchrotron low-temperature X-ray crystallographic studies were used to investigate the chelating power of progenitor 2. Mg2+ and Cu2+ cations were selected for this purpose, and three types of metal complexes of 2 were obtained: Mg(II) complex (4), Cu(II) complex (5) and mixed Mg(II)-Cu(II) complexes (6 and 7). The analysis of the crystal structure of complex 4 indicates that two tridentate ligands coordinate two Mg2+ cations, both in octahedral geometry. The Mg-Mg distance was found equal to 3.221(1) A, in agreement with the metal-metal distance of 3.9 A encountered in the crystal structure of Escherichia coli DNA polymerase I. In 5, the complex is formed by two bidentate ligands coordinating one copper ion in tetrahedral geometry. Both mixed Mg(II)-Cu(II) complexes, 6 and 7 exhibit an original arrangement of four ligands linked to a central heterometallic cluster consisting of three octahedrally coordinated magnesium ions and one tetrahedrally coordinated copper ion. Quantum mechanics calculations were also carried out in order to display the electrostatic potential generated by the dianionic ligand 2 and complex 4 and to quantify the binding energy (BE) during the formation of the magnesium complex of progenitor 2. A comparison of the binding energies of two hypothetical monometallic Mg(II) complexes with that found in the bimetallic magnesium complex 4 was made.

Molecular Mechanism of Action for Allosteric Modulators and Agonists in CC-chemokine Receptor 5 (CCR5).

PubMed

Karlshøj, Stefanie; Amarandi, Roxana Maria; Larsen, Olav; Daugvilaite, Viktorija; Steen, Anne; Brvar, Matjaž; Pui, Aurel; Frimurer, Thomas Michael; Ulven, Trond; Rosenkilde, Mette Marie

2016-12-23

The small molecule metal ion chelators bipyridine and terpyridine complexed with Zn 2+ (ZnBip and ZnTerp) act as CCR5 agonists and strong positive allosteric modulators of CCL3 binding to CCR5, weak modulators of CCL4 binding, and competitors for CCL5 binding. Here we describe their binding site using computational modeling, binding, and functional studies on WT and mutated CCR5. The metal ion Zn 2+ is anchored to the chemokine receptor-conserved Glu-283 VII:06/7.39 Both chelators interact with aromatic residues in the transmembrane receptor domain. The additional pyridine ring of ZnTerp binds deeply in the major binding pocket and, in contrast to ZnBip, interacts directly with the Trp-248 VI:13/6.48 microswitch, contributing to its 8-fold higher potency. The impact of Trp-248 was further confirmed by ZnClTerp, a chloro-substituted version of ZnTerp that showed no inherent agonism but maintained positive allosteric modulation of CCL3 binding. Despite a similar overall binding mode of all three metal ion chelator complexes, the pyridine ring of ZnClTerp blocks the conformational switch of Trp-248 required for receptor activation, thereby explaining its lack of activity. Importantly, ZnClTerp becomes agonist to the same extent as ZnTerp upon Ala mutation of Ile-116 III:16/3.40 , a residue that constrains the Trp-248 microswitch in its inactive conformation. Binding studies with 125 I-CCL3 revealed an allosteric interface between the chemokine and the small molecule binding site, including residues Tyr-37 I:07/1.39 , Trp-86 II:20/2.60 , and Phe-109 III:09/3.33 The small molecules and CCL3 approach this interface from opposite directions, with some residues being mutually exploited. This study provides new insight into the molecular mechanism of CCR5 activation and paves the way for future allosteric drugs for chemokine receptors. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Application of a thiourea-containing task-specific ionic liquid for the solid-phase extraction cleanup of lead ions from red lipstick, pine leaves, and water samples.

PubMed

Saljooqi, Asma; Shamspur, Tayebeh; Mohamadi, Maryam; Mostafavi, Ali

2014-07-01

Here, task-specific ionic liquid solid-phase extraction is proposed for the first time. In this approach, a thiourea-functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid-phase extraction column are used for the selective extraction and preconcentration of ultra-trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5-40.0 ng/mL with the detection limit of 0.13 ng/mL (3(Sb)/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization and quantification of racemic and meso-ethylenediamine-N,N'-bis(2-hydroxy-5-sulfophenylacetic) acid/iron (III) by ion-pair ultra-high performance liquid chromatography coupled with diode array detector and electrospray tandem mass spectrometry.

PubMed

Biasone, Alessandro; Cianci, Giusto; Di Tommaso, Donata; Piaggesi, Alberto; Tagliavini, Emilio; Galletti, Paola; Moretti, Fabio

2013-03-22

EDDHSA/Fe is a promising substitute of EDDHA/Fe to fight iron chlorosis. o,o-EDDHSA structure contains two chiral carbons giving the racemic and meso couples of stereoisomers. Ion-pair HPLC and UHPLC-UV/Vis-ESI-MS/MS methods were developed for the determination of racemic and meso-o,o-EDDHSA/Fe in commercial samples of chelates. The lack of a commercial EDDHSA standard was overcome by sulfonation of a commercial available o,o-EDDHA standard and subsequent quantification by (1)H-NMR. Assignment of configurations was carried out starting from racemic and meso-o,o-EDDHA/Fe by direct sulfonation to give the corresponding o,o-EDDHSA/Fe isomers. The performances of these methods were assessed in terms of intra and inter-day precision, linearity and selectivity. The high selectivity and lower detection limit (nanomolar) of the UHPLC-ESI-MS/MS method could allow to deepen the knowledge relative to meso and rac-o,o-EDDHSA/Fe interactions with plants, its fate in different soil conditions, its mobility and other environmental aspects. Copyright © 2013 Elsevier B.V. All rights reserved.

Radiation induced deposition of copper nanoparticles inside the nanochannels of poly(acrylic acid)-grafted poly(ethylene terephthalate) track-etched membranes

NASA Astrophysics Data System (ADS)

Korolkov, Ilya V.; Güven, Olgun; Mashentseva, Anastassiya A.; Atıcı, Ayse Bakar; Gorin, Yevgeniy G.; Zdorovets, Maxim V.; Taltenov, Abzal A.

2017-01-01

Poly(ethylene terephthalate) PET, track-etched membranes (TeMs) with 400 nm average pore size were UV-grafted with poly(acrylic acid) (PAA) after oxidation of inner surfaces by H2O2/UV system. Carboxylate groups of grafted PAA chains were easily complexed with Cu2+ ions in aqueous solutions. These ions were converted into metallic copper nanoparticles (NPs) by radiation-induced reduction of copper ions in aqueous-alcohol solution by gamma rays in the dose range of 46-250 kGy. Copper ions chelating with -COOH groups of PAA chains grafted on PET TeMs form polymer-metal ion complex that prevent the formation of agglomerates during reduction of copper ions to metallic nanoparticles. The detailed analysis by X-Ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) confirmed the deposition of copper nanoparticles with the average size of 70 nm on the inner surface of nanochannels of PET TeMs. Samples were also investigated by FTIR, ESR spectroscopies to follow copper ion reduction.

Development of a fluorescent chelating ligand for scandium ion having a Schiff base moiety

NASA Astrophysics Data System (ADS)

Yamada, Hiroshi; Kojo, Masahito; Nakahara, Tomomi; Murakami, Kumi; Kakima, Takashi; Ichiba, Hideaki; Yajima, Takehiko; Fukushima, Takeshi

2012-05-01

A fluorescent ligand, 1-(2-hydroxy-3-methoxybenzaldehyde)-4-aminosalicylhydrazone (HMB-ASH), was newly designed and synthesized, and its fluorescence characteristics for metal ions were investigated in the pH range 3.0-10.5 (at a difference of 0.5 for each metal). After testing 31 different metal ions, it was found that HMB-ASH was able to emit fluorescence intensely at 512 nm with an excitation wavelength of 353 nm in the presence of Sc3+, one of the rare earth metals, at pH values around 3.5 and 8.0. The other metal ions hardly showed fluorescence with HMB-ASH. The fluorescence was more intense at pH 8.0, and the detection limit of Sc3+ in a buffer solution (pH 8.0) was approximately 18.8 nmol L-1 (0.85 ppb).

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance.

PubMed

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-25

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)-a chelating agent of copper II ions-was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

The Ca(2+)-EDTA chelation as standard reaction to validate Isothermal Titration Calorimeter measurements (ITC).

PubMed

Ràfols, Clara; Bosch, Elisabeth; Barbas, Rafael; Prohens, Rafel

2016-07-01

A study about the suitability of the chelation reaction of Ca(2+)with ethylenediaminetetraacetic acid (EDTA) as a validation standard for Isothermal Titration Calorimeter measurements has been performed exploring the common experimental variables (buffer, pH, ionic strength and temperature). Results obtained in a variety of experimental conditions have been amended according to the side reactions involved in the main process and to the experimental ionic strength and, finally, validated by contrast with the potentiometric reference values. It is demonstrated that the chelation reaction performed in acetate buffer 0.1M and 25°C shows accurate and precise results and it is robust enough to be adopted as a standard calibration process. Copyright © 2016 Elsevier B.V. All rights reserved.

Preservation of glutamic acid-iron chelate into montmorillonite to efficiently degrade Reactive Blue 19 in a Fenton system under sunlight irradiation at neutral pH

NASA Astrophysics Data System (ADS)

Huang, Zhujian; Wu, Pingxiao; Gong, Beini; Yang, Shanshan; Li, Hailing; Zhu, Ziao; Cui, Lihua

2016-05-01

To further enhance the visible light responsive property and the chemical stability of Fe/clay mineral catalysts, glutamic acid-iron chelate intercalated montmorillonite (G-Fe-Mt) was developed. The physiochemical properties of G-Fe-Mt were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), etc. The results showed that glutamic acid-iron chelates were successfully intercalated into the gallery of montmorillonite and the intercalated glutamic acid-iron chelate molecules were well preserved. The product G-Fe-Mt displayed excellent catalytic performance in heterogeneous photo-Fenton reaction under sunlight irradiation at acidic and neutral pH values. The chelation and the visible light responsiveness of glutamic acid produce a synergistic effect leading to greatly enhanced sunlight-Fenton reaction catalyzed by the heterogeneous G-Fe-Mt under neutral pH. G-Fe-Mt is a promising catalyst for advanced oxidation processes.

Ga(III) chelates of amphiphilic DOTA-based ligands: synthetic route and in vitro and in vivo studies.

PubMed

Fontes, André; Prata, M Isabel M; Geraldes, Carlos F G C; André, João P

2011-04-01

In this work, we report on a synthetic strategy using amphiphilic DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)-based chelators bearing a variable-sized α-alkyl chain at one of the pendant acetate arms (from 6 to 14 carbon atoms), compatible with their covalent coupling to amine-bearing biomolecules. The amphiphilic behavior of the micelles-forming Ga(III) chelates (critical micellar concentration), their stability in blood serum and their lipophilicity (logP) were investigated. Biodistribution studies with the (67)Ga-labeled chelates were performed in Wistar rats, which showed a predominant liver uptake with almost no traces of the radiochelates in the body after 24 h. Copyright © 2011 Elsevier Inc. All rights reserved.

Synthesis and characterization of novel ion-imprinted guanyl-modified cellulose for selective extraction of copper ions from geological and municipality sample.

PubMed

Kenawy, I M; Ismail, M A; Hafez, M A H; Hashem, M A

2018-04-21

The new ion-imprinted guanyl-modified cellulose (II.Gu-MC) was prepared for the separation and determination of Cu (II) ions in different real samples. Several techniques such as Fourier Transform Infrared (FT-IR), scanning electron microscope (SEM), thermal analysis, potentiograph and elemental analysis have been utilized for the characterization of II.Gu-MC. The adsorption behavior of the ion imprinted polymer (II.Gu-MC) was evaluated and compared to the non ion-imprinted polymer (NII.Gu-MC) at the optimum conditions. The selectivity and the adsorption capacity were greatly enhanced by using the ion-imprinted polymer, indicating its validation for the separation and determination of Cu 2+ ions in different matrices. The adsorption capacity by chelating fibers II.Gu-MC & NII.Gu-MC agreed with the second-order model, and the sorption-isotherm experiments revealed best agreement with Langmuir model. The adsorption capacity of II.Gu-MC and NII.Gu-MC were 115 and 55 mg·g -1 , respectively. The II.Gu-MC was successfully employed for the selective separation and determination of Cu(II) ions with high accuracy. Copyright © 2018 Elsevier B.V. All rights reserved.

Effectiveness of FeEDDHA, FeEDDHMA, and FeHBED in Preventing Iron-Deficiency Chlorosis in Soybean.

PubMed

Bin, Levi M; Weng, Liping; Bugter, Marcel H J

2016-11-09

The performance of FeHBED in preventing Fe deficiency chlorosis in soybean (Glycine max (L.) Merr.) in comparison to FeEDDHA and FeEDDHMA was studied, as well as the importance of the ortho-ortho and ortho-para/rest isomers in defining the performance. To this end, chlorophyll production (SPAD), plant dry matter yield, and the mass fractions of important mineral elements in the plant were quantified in a greenhouse pot experiment. All three Fe chelates increased SPAD index and dry matter yield compared to the control. The effect of FeHBED on chlorophyll production was visible over a longer time span than that of FeEDDHA and FeEDDHMA. Additionally, FeHBED did not suppress Mn uptake as much as the other Fe chelates. Compared to the other Fe chelates, total Fe content in the young leaves was lower in the FeHBED treatment; however, total Fe content was not directly related to chlorophyll production and biomass yield. For each chelate, the ortho-ortho isomer was found to be more effective than the other isomers evaluated.

Polymer-grafted QCM chemical sensor and application to heavy metalions real time detection.

PubMed

Sartore, Luciana; Barbaglio, Marzia; Borgese, Laura; Bontempi, Elza

2011-07-20

A flow type quartz crystal microbalance (QCM) chemical sensor was developed for monitoring of heavy metal ions in aqueous solutions (that is suitable for environmental monitoring). The sensor is based upon surface chelation of the metal ions at multifunctional polymer modified gold electrodes on 9 MHz AT-cut quartz resonators, functioning as a QCM. New processes have been developed which enable to obtain surface-modified gold electrodes with high heavy metal ions complexing ability. These polymer grafted QCM sensors can selectively adsorb heavy metal ions, such as copper lead chrome and cadmium, from solution over a wide range from 0.01 to 1000 ppm concentration by complexation with functional groups in the polymers. Cations typically present in natural water did not interfere with the detection of heavy metals. X-Ray Reflectivity (XRR) and Total Reflection X-ray Fluorescence (TXRF) were carried out to characterise the unmodified and modified gold surfaces as well as to verify the possibility to selectively bond and remove metal ions.

Antioxidant mechanism of milk mineral-high-affinity iron binding.

PubMed

Allen, K; Cornforth, D

2007-01-01

Milk mineral (MM), a by-product of whey processing, is an effective antioxidant in meat systems, but the antioxidant mechanism has not been established. MM has been postulated to chelate iron and prevent iron-catalysis of lipid oxidation. The objective of this research was to examine this putative mechanism. MM was compared to sodium tripolyphosphate (STPP), calcium phosphate monobasic (CPM), and calcium pyrophosphate (CPP) to determine iron-binding capacity, sample solubility, and eluate soluble phosphorus after treating samples with a ferrous chloride standard. Scanning electron microscopy with energy-dispersive X-ray analysis was used to localize minerals on iron-treated MM particle surfaces. Histochemical staining for calcium was performed on raw and cooked ground beef samples with added MM. MM bound more iron per gram (P < 0.05) than the other compounds, and was much less soluble (P < 0.05) than either STPP or CPM. Mineral localization showed an even distribution of calcium, phosphorus, oxygen, and iron across the MM particle surface, directly demonstrating iron binding to MM particles. Unlike other common chelating agents, such as STPP and citrate, histochemical staining demonstrated that MM remained insoluble in ground beef, even after cooking. The ability of MM to bind iron and remain insoluble may enhance its antioxidant effect by removing iron ions from solution. However, MM particles must be small and well distributed in order to adequately bind iron throughout the food system.

Self-assembly of PEGylated tetra-phenylalanine derivatives: structural insights from solution and solid state studies

PubMed Central

Diaferia, Carlo; Mercurio, Flavia Anna; Giannini, Cinzia; Sibillano, Teresa; Morelli, Giancarlo; Leone, Marilisa; Accardo, Antonella

2016-01-01

Water soluble fibers of PEGylated tetra-phenylalanine (F4), chemically modified at the N-terminus with the DOTA chelating agent, have been proposed as innovative contrast agent (CA) in Magnetic Resonance Imaging (MRI) upon complexation of the gadolinium ion. An in-depth structural characterization of PEGylated F4-fibers, in presence (DOTA-L6-F4) and in absence of DOTA (L6-F4), is reported in solution and at the solid state, by a multiplicity of techniques including CD, FTIR, NMR, DLS, WAXS and SAXS. This study aims to better understand how the aggregation process influences the performance of nanostructures as MRI CAs. Critical aggregation concentrations for L6-F4 (43 μM) and DOTA-L6-F4 (75 μM) indicate that self-aggregation process occurs in the same concentration range, independently of the presence of the CA. The driving force for the aggregation is the π-stacking between the side chains of the aromatic framework. CD, FTIR and WAXS measurements indicate an antiparallel β-sheet organization of the monomers in the resulting fibers. Moreover, WAXS and FTIR experiments point out that in solution the nanomaterials retain the same morphology and monomer organizations of the solid state, although the addition of the DOTA chelating agent affects the size and the degree of order of the fibers. PMID:27220817

Atypical Presentation of Iridocorneal Endothelial Syndrome With Band Keratopathy but No Corneal Edema Managed With Descemet Membrane Endothelial Keratoplasty.

PubMed

Zygoura, Vasiliki; Lavy, Itay; Verdijk, Robert M; Santander-García, Diana; Baydoun, Lamis; Dapena, Isabel; Melles, Gerrit R J

2018-04-17

To report an unusual presentation of iridocorneal endothelial (ICE) syndrome associated with band keratopathy and its management with ethylenediamine-tetraacetic acid (EDTA) chelation and Descemet membrane endothelial keratoplasty (DMEK). A 57-year-old female patient presented with unilateral progressive painless visual impairment, corneal band keratopathy, and morphological corneal endothelial changes without corneal edema or any previous ophthalmic, medical, or family history. Routine specular and confocal microscopy imaging, as well as biomicroscopy, best-corrected visual acuity, and pachymetry measurements were performed before and after the surgical procedures. Histopathologic and immunohistochemical evaluations of the surgically excised diseased DM-endothelium were performed. Superficial epithelial keratectomy with EDTA chelation was performed. After an initial period of a few months of corneal clearance, the patient presented with recurrence of visually significant band keratopathy. After 1 year, she underwent retreatment with superficial epithelial keratectomy and EDTA chelation, followed by DMEK. Histopathologic and immunohistochemical analysis showed ICE syndrome. Two years after DMEK surgery, the cornea was still clear and band keratopathy had not recurred. To the best of our knowledge, this is the first case in the literature that reports the association of ICE syndrome with band keratopathy. As band keratopathy recurred shortly after EDTA chelation, endothelial keratoplasty (DMEK) may be indicated to successfully treat such cases.

Radiopharmaceuticals for imaging the heart

DOEpatents

Green, M.A.; Tsang, B.W.

1994-06-28

Radiopharmaceuticals for imaging myocardial tissues are prepared by forming lipophilic, cationic complexes of radioactive metal ions with metal chelating ligands comprising the Schiff base adducts of triamines and tetraamines with optionally substituted salicylaldehydes. The lipophilic, cationic, radioactive complexes of the invention exhibit high uptake and retention in myocardial tissues. Preferred gallium-68(III) complexes in accordance with this invention can be used to image the heart using positron emission tomography. 6 figures.

Coumarin Derivative Directly Coordinated to Lanthanides Acts as an Excellent Antenna for UV-Vis and Near-IR Emission.

PubMed

Guzmán-Méndez, Óscar; González, Federico; Bernès, Sylvain; Flores-Álamo, Marcos; Ordóñez-Hernández, Javier; García-Ortega, Héctor; Guerrero, Joselin; Qian, Wenjie; Aliaga-Alcalde, Nuria; Gasque, Laura

2018-02-05

A chelating coumarin-derived ligand sensitizes all emitting lanthanide ions in the solid state and gives high absolute quantum yields for ethanol solutions of complexes of Sm, Eu, Tb, and Dy, above 20% for the last two. Crystal structures of these four complexes are [Ln(Cum) 3 (H 2 O)(X)]·X where X = MeOH or EtOH.

Influence of Botanical Origin and Chemical Composition on the Protective Effect against Oxidative Damage and the Capacity to Reduce In Vitro Bacterial Biofilms of Monofloral Honeys from the Andean Region of Ecuador

PubMed Central

García-Tenesaca, Marilyn; Navarrete, Eillen S.; Iturralde, Gabriel A.; Villacrés Granda, Irina M.; Tejera, Eduardo; Beltrán-Ayala, Pablo

2017-01-01

Three types of monofloral honey from the Andean regions of Ecuador (Avocado, Eucalyptus, and Rapeseed honey) were analyzed to determine their floral origin, physicochemical parameters, chemical composition, antioxidant capacity, and their capacity to reduce in vitro bacterial biofilms. The chemical composition varied considerably depending on floral origin. The highest values of bioactive compounds were found in Avocado honey, classified as dark amber in color, while the lowest values were found in Eucalyptus honey followed by Rapeseed honey, both classified as extra light amber. When compared to Eucalyptus and Rapeseed honey, Avocado honey showed a more effective superoxide scavenging activity, chelating metal ions capacity, and a higher ability to protect human erythrocyte membranes against lipid peroxidation. For antimicrobial activity, the hydrogen peroxide content and the capacity to inhibit the biofilm formation, and to remove preformed biofilm from Staphylococcus aureus and Klebsiella pneumoniae was determined. Avocado honey showed the highest values of hydrogen peroxide content, as well as the highest capacity to reduce in vitro bacterial biofilms. A correlation between color vs. phenolics content vs. superoxide scavenging activity vs. chelating metal ions capacity, and the capacity to protect human erythrocyte membranes against lipid peroxidation was found. PMID:29295525

Influence of Botanical Origin and Chemical Composition on the Protective Effect against Oxidative Damage and the Capacity to Reduce In Vitro Bacterial Biofilms of Monofloral Honeys from the Andean Region of Ecuador.

PubMed

García-Tenesaca, Marilyn; Navarrete, Eillen S; Iturralde, Gabriel A; Villacrés Granda, Irina M; Tejera, Eduardo; Beltrán-Ayala, Pablo; Giampieri, Francesca; Battino, Maurizio; Alvarez-Suarez, José M

2017-12-23

Three types of monofloral honey from the Andean regions of Ecuador (Avocado, Eucalyptus, and Rapeseed honey) were analyzed to determine their floral origin, physicochemical parameters, chemical composition, antioxidant capacity, and their capacity to reduce in vitro bacterial biofilms. The chemical composition varied considerably depending on floral origin. The highest values of bioactive compounds were found in Avocado honey, classified as dark amber in color, while the lowest values were found in Eucalyptus honey followed by Rapeseed honey, both classified as extra light amber. When compared to Eucalyptus and Rapeseed honey, Avocado honey showed a more effective superoxide scavenging activity, chelating metal ions capacity, and a higher ability to protect human erythrocyte membranes against lipid peroxidation. For antimicrobial activity, the hydrogen peroxide content and the capacity to inhibit the biofilm formation, and to remove preformed biofilm from Staphylococcus aureus and Klebsiella pneumoniae was determined. Avocado honey showed the highest values of hydrogen peroxide content, as well as the highest capacity to reduce in vitro bacterial biofilms. A correlation between color vs. phenolics content vs. superoxide scavenging activity vs. chelating metal ions capacity, and the capacity to protect human erythrocyte membranes against lipid peroxidation was found.

[Resistance of Lactobacillus casei subsp. casei SY13 and Lactobacillus delbrueckii subsp. bulgaricus LJJ to reactive oxygen species].

PubMed

Zhang, Shuwen; Lv, Jiaping; Menghe, Bilige; Zhang, Heping; Zhang, Liyu; Song, Jinhui; Wang, Zhifei

2009-02-01

We evaluated antioxidative effect of two antioxidative strains, isolated from the traditional fermented dairy products. Both intact cells and cell-free extract of Lactobacillus casei subsp. casei SY13 and Lactobacillus delbrueckii subsp. bulgaricus LJJ were used to study the inhibited effect of linoleic acid peroxidation, the ability of scavenging 1,1-diphenyl-2-picrylhydrazyl radical, hydroxyl radical, superoxide anion radical,the ability of tolerancing hydrogen peroxide and the chelating capacity of ferrous ion and reducting activity. Lactobacillus casei subsp. casei SY13 and Lactobacillus delbrueckii subsp. bulgaricus LJJ demonstrated highest inhibition on linoleic acid peroxidation by 62.95% and 66.16%, respectively. The cell-free extract showed excellent scavenging superoxide anion and hydroxyl radicals activity. However, the intact cells of Lactobacillus delbrueckii subsp. bulgaricus LJJ scavenging superoxide and hydroxyl radicals capacity were not detected. The intact cells of Lactobacillus casei subsp. casei SY13 and Lactobacillus delbrueckii subsp. bulgaricus LJJ on 1,1-diphenyl-2-picrylhydrazyl radical scavenging ability and chelating ferrous ion capacity were superior to cell-free extract. The highest reduced activety was equivalent to 305 micromol/L and 294 micromol/L L-cysteine. Two latobacilli strains had good antioxidant capacity. As potential probiotics, it can be used in future.

Antioxidant activities of methanol extract of Sambucus ebulus L. flower.

PubMed

Ebrahimzadeh, M A; Nabavi, S F; Nabavi, S M

2009-03-01

In this study antioxidant activity of methanol extract of Sambucus ebulus L. flower was investigated employing various in vitro assay systems, i.e., DPPH and nitric oxide radical scavenging, hydrogen peroxide scavenging, reducing power, iron ion chelating power and linoleic acid. IC50 for DPPH radical-scavenging activity was 228 +/- 12 microg mL(-1). The extract showed very high activity in the reducing power assay that was comparable with positive control, vitamin C. The extract showed good nitric oxide-scavenging activity (IC50 = 309 +/- 14 microg mL(-1). It was found that antioxidant activity was dose dependent i.e., activity was increased with the increase of their concentrations. The extract showed very weak activity in iron ion chelating (IC50 = 1.3 +/- 0.07 mg mL(-1)). It is showed very good activity in scavenging of hydrogen'peroxide. IC50 for scavenging of extract was 59.5 +/- 3.3 mcirog mL(-1). The extracts exhibited no activity in linoleic acid model. The total phenolic content of flower was 56.3 +/- 2.81 mg gallic acid equivalent g(-1) of extract powder and total flavonoid content was 14.5 +/- 0.72 mg quercetin equivalent g(-1) of extract powder by reference to standard curve.

Evaluation of different iron compounds in chlorotic Italian lemon trees (Citrus lemon).

PubMed

Ortiz, Patricio Rivera; Castro Meza, Blanca I; de la Garza Requena, Francisco R; Flores, Guillermo Mendoza; Etchevers Barra, Jorge D

2007-05-01

The severe deficiency of iron or ferric chlorosis is a serious problem of most citrus trees established in calcareous soils, as a result of the low availability of iron in these soils and the poor uptake and limited transport of this nutrient in trees. The objective of this study was to evaluate the response of chlorotic Italian lemon trees (Citrus lemon) to the application of iron compounds to roots and stems. On comparing the effects of aqueous solutions of ferric citrate, ferrous sulphate and FeEDDHA chelate, applied to 20% of the roots grown in soil and sand, of trees that were planted in pots containing calcareous soil, it was observed that the chelate fully corrected ferric chlorosis, while citrate and sulphate did not solve the problem. EDDHA induced the root uptake of iron as well as the movement of the nutrient up to the leaves. With the use of injections of ferric solutions into the secondary stem of adult trees, ferric citrate corrected chlorosis but ferrous sulphate did not. The citrate ion expanded the mobility of iron within the plant, from the injection points up to the leaves, whereas the sulphate ion did not sufficiently improve the movement of iron towards the leaf mesophyll.

Antioxidant and Toxicity Studies of 50% Methanolic Extract of Orthosiphon stamineus Benth

PubMed Central

Lim, Chung Pin; Fung Ang, Lee; Por, Lip Yee; Wong, Siew Tung; Asmawi, Mohd. Zaini

2013-01-01

The present study evaluated the antioxidant activity and potential toxicity of 50% methanolic extract of Orthosiphon stamineus (Lamiaceae) leaves (MEOS) after acute and subchronic administration in rats. Superoxide radical scavenging, hydroxyl radical scavenging, and ferrous ion chelating methods were used to evaluate the antioxidant properties of the extract. In acute toxicity study, single dose of MEOS, 5000 mg/kg, was administered to rats by oral gavage, and the treated rats were monitored for 14 days. While in the subchronic toxicity study, MEOS was administered orally, at doses of 1250, 2500, and 5000 mg/kg/day for 28 days. From the results, MEOS showed good superoxide radical scavenging, hydroxyl radical scavenging, ferrous ion chelating, and antilipid peroxidation activities. There was no mortality detected or any signs of toxicity in acute and subchronic toxicity studies. Furthermore, there was no significant difference in bodyweight, relative organ weight, and haematological and biochemical parameters between both male and female treated rats in any doses tested. No abnormality of internal organs was observed between treatment and control groups. The oral lethal dose determined was more than 5000 mg/kg and the no-observed-adverse-effect level (NOAEL) of MEOS for both male and female rats is considered to be 5000 mg/kg per day. PMID:24490155

The Role of Copper in Neurodegenerative Disease

NASA Astrophysics Data System (ADS)

Rose, Francis M.

My research concerns the fundamental atomistic mechanisms of neurodegenerative diseases and the methodologies by which they may be discerned. This thesis consists of three primary parts. The introductory material is the raison d'etre for this work and a critical overview of the specific physics, mathematics and algorithms used in this research. The methods are presented along with specific details in order to facilitate future replication and enhancement. With the groundwork of mechanisms and methods out of the way, we then explore a nouveau atomistic mechanism describing the onset of Parkinson's disease, a disease that has been closely linked to misfolded metalloproteins. Further exploration of neurodegeneration takes place in the following chapter, where a remedial approach to Alzheimer's disease via a simulated chelation of a metalloprotein is undertaken. Altogether, the methods and techniques applied here allow for simulated exploration of both the atomistic mechanisms of neurodegeneration and their potential remediation strategies. The beginning portion of the research efforts explore protein misfolding dynamics in the presence a copper ion. Misfolding of the human alpha-synuclein (aS) protein has been implicated as a central constituent in neurodegenerative disease. In Parkinson's disease (PD) in particular, aS is thought to be the causative participant when found concentrated into neuritic plaques. Here we propose a scenario involving the metal ion Cu2+ as the protein misfolding initiator of fibrillized aS, the chief component of neuritic plaques. From experimental results we know these misfolded proteins have a rich beta--sheet signature, a marker that we reproduce with our simulated model. This model identifies a process of structural modifications to a natively unfolded alpha-synuclein resulting in a partially folded intermediate with a well defined nucleation site. It serves as a precursor to the fully misfolded protein. Understanding the nucleation mechanism is of critical importance, as it enables the study of reversal mechanisms and inhibitory agents, leading to development of effective PD therapies. Following the PD work we then explore simulated chelation of a metalloprotein as a potential remediation scheme in neurodegeneration. Misfolded metalloproteins are potential causal agents in the onset of neurodegenerative diseases, such as Alzheimer's and Parkinson's Diseases (AD and PD, respectively). Experimental results involving molecules capable of metal chelation have shown significant promise in AD symptom reduction and neuritic plaque clearance. We explore, through atomistic simulations, potential reaction pathways for the chelation of Cu2+ from the metal binding site in our metalloprotein model, amyloid--beta1--42. Our simulations use an ab-initio-based nudged elastic band (NEB) algorithm to obtain the activation barrier energies in these reactions. The NEB implementation provides a guided dynamics framework for our real-space multigrid method of density-functional-theory-based quantum simulations. This highly parallel approach resolves a minimum energy pathway (MEP) on the energy hypersurface by relaxing intermediates in a chain-of-states approach. In using NEB to explore copper chelation in Alzheimer's disease protein, we find that there exists a sequence of unbonding and rebonding events as well as proton transfers that make up an energetically viable chelation process. These findings provide fundamental insight into the process of metalloprotein chelation in AD and can lead to the development of more effective AD therapeutic drugs.

Hydroxypyridinone Chelators: From Iron Scavenging to Radiopharmaceuticals for PET Imaging with Gallium-68

PubMed Central

Cusnir, Ruslan; Imberti, Cinzia; Hider, Robert C.; Blower, Philip J.; Ma, Michelle T.

2017-01-01

Derivatives of 3,4-hydroxypyridinones have been extensively studied for in vivo Fe3+ sequestration. Deferiprone, a 1,2-dimethyl-3,4-hydroxypyridinone, is now routinely used for clinical treatment of iron overload disease. Hexadentate tris(3,4-hydroxypyridinone) ligands (THP) complex Fe3+ at very low iron concentrations, and their high affinities for oxophilic trivalent metal ions have led to their development for new applications as bifunctional chelators for the positron emitting radiometal, 68Ga3+, which is clinically used for molecular imaging in positron emission tomography (PET). THP-peptide bioconjugates rapidly and quantitatively complex 68Ga3+ at ambient temperature, neutral pH and micromolar concentrations of ligand, making them amenable to kit-based radiosynthesis of 68Ga PET radiopharmaceuticals. 68Ga-labelled THP-peptides accumulate at target tissue in vivo, and are excreted largely via a renal pathway, providing high quality PET images. PMID:28075350

Chelation and stabilization of berkelium in oxidation state +IV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deblonde, Gauthier J. -P.; Sturzbecher-Hoehne, Manuel; Rupert, Peter B.

Berkelium (Bk) has been predicted to be the only transplutonium element able to exhibit both +III and +IV oxidation states in solution, but evidence of a stable oxidized Bk chelate has so far remained elusive. Here, in this work, we describe the stabilization of the heaviest 4+ ion of the periodic table, under mild aqueous conditions, using a siderophore derivative. The resulting Bk(IV) complex exhibits luminescence via sensitization through an intramolecular antenna effect. This neutral Bk(IV) coordination compound is not sequestered by the protein siderocalin - a mammalian metal transporter - in contrast to the negatively charged species obtained withmore » neighbouring trivalent actinides americium, curium and californium (Cf). The corresponding Cf(III)-ligand-protein ternary adduct was characterized by X-ray diffraction analysis. Finally, combined with theoretical predictions, these data add significant insight to the field of transplutonium chemistry, and may lead to innovative Bk separation and purification processes.« less

Chelation and stabilization of berkelium in oxidation state +IV

DOE PAGES

Deblonde, Gauthier J. -P.; Sturzbecher-Hoehne, Manuel; Rupert, Peter B.; ...

2017-04-10

Berkelium (Bk) has been predicted to be the only transplutonium element able to exhibit both +III and +IV oxidation states in solution, but evidence of a stable oxidized Bk chelate has so far remained elusive. Here, in this work, we describe the stabilization of the heaviest 4+ ion of the periodic table, under mild aqueous conditions, using a siderophore derivative. The resulting Bk(IV) complex exhibits luminescence via sensitization through an intramolecular antenna effect. This neutral Bk(IV) coordination compound is not sequestered by the protein siderocalin - a mammalian metal transporter - in contrast to the negatively charged species obtained withmore » neighbouring trivalent actinides americium, curium and californium (Cf). The corresponding Cf(III)-ligand-protein ternary adduct was characterized by X-ray diffraction analysis. Finally, combined with theoretical predictions, these data add significant insight to the field of transplutonium chemistry, and may lead to innovative Bk separation and purification processes.« less

Gadolinium Endohedral Metallofullerene-Based MRI Contrast Agents

NASA Astrophysics Data System (ADS)

Bolskar, Robert D.

With the ability to encapsulate and carry the highly paramagnetic Gd3+ ion, gadolinium endohedral metallofullerenes or "gadofullerenes" are being explored as alternatives to the chelate complexes that are currently used for contrast-enhanced magnetic resonance imaging (MRI). Reviewed here are the various water-soluble derivatives of the gadofullerenes Gd@C82, Gd@C60, and Gd3N@C80 that have been investigated as MRI contrast agents. The water proton r1 relaxivities of gadofullerenes can be more than an order of magnitude higher than those of clinically used chelate agents. Gadofullerene relaxivity mechanisms have been studied, and multiple factors are found to contribute to their high relaxivities. In vitro and in vivoT1-weighted MRI tests of gadofullerene derivatives have shown their utility as bright image-enhancing agents. The gadofullerene MRI contrast agents are a promising new and unique style of gadolinium carrier for advanced imaging applications, including cellular and molecular imaging.

Hydroxypyridinone Chelators: From Iron Scavenging to Radiopharmaceuticals for PET Imaging with Gallium-68.

PubMed

Cusnir, Ruslan; Imberti, Cinzia; Hider, Robert C; Blower, Philip J; Ma, Michelle T

2017-01-08

Derivatives of 3,4-hydroxypyridinones have been extensively studied for in vivo Fe 3+ sequestration. Deferiprone, a 1,2-dimethyl-3,4-hydroxypyridinone, is now routinely used for clinical treatment of iron overload disease. Hexadentate tris(3,4-hydroxypyridinone) ligands (THP) complex Fe 3+ at very low iron concentrations, and their high affinities for oxophilic trivalent metal ions have led to their development for new applications as bifunctional chelators for the positron emitting radiometal, 68 Ga 3+ , which is clinically used for molecular imaging in positron emission tomography (PET). THP-peptide bioconjugates rapidly and quantitatively complex 68 Ga 3+ at ambient temperature, neutral pH and micromolar concentrations of ligand, making them amenable to kit-based radiosynthesis of 68 Ga PET radiopharmaceuticals. 68 Ga-labelled THP-peptides accumulate at target tissue in vivo, and are excreted largely via a renal pathway, providing high quality PET images.

N,N',N"-tris(dihydroxyphosphorylmethyl)-1,4,7-triazacyclononane (Deofix) - a high-affinity, high-specificity chelator for first transition series metal cations with significant deodorant, antimicrobial, and antioxidant activity.

PubMed

Laden, Karl; Zaklad, Haim; Simhon, Elliot D; Klein, Joseph Y; Cyjon, Rosa L; Winchell, Harry S

2003-01-01

Deofix, N,N',N"-tris(dihydroxyphosphorylmethyl)-1,4,7-triazacyclononane, is a high-affinity, high-specificity chelator for first transition series cations such as iron, zinc, manganese, and copper. A 1% solution in 50% ethanol was found to be significantly better at reducing underarm malodor than a solution of 0.3% Triclosan in 50% ethanol. Compared to a 50% alcohol control, Deofix was found to produce a significant reduction in malodor for at least 48 hours. Deofix appears to work by reducing the concentration of first transition series metal ions below the levels needed for microbial cell reproduction and by inhibiting oxidative processes by interfering with catalytic formation of free radicals. Deofix has very low levels of toxicity when measured via a number of screening techniques.

Effect of Sterilization Process and Storage on the Antioxidative Properties of Runner Bean.

PubMed

Wołosiak, Rafał; Drużyńska, Beata; Piecyk, Małgorzata; Majewska, Ewa; Worobiej, Elwira

2018-06-11

In this study, we investigated the effect of standard preservation of bean seeds on changes in contents and activity of their selected components: dry matter, ash, different forms of nitrogen, composition of protein fractions; total phenolics and condensed tannins; ability to chelate iron(II) ions; antiradical activity against ABTS •+ and DPPH • ; and capability for inhibiting autoxidation and enzymatic oxidation of linoleic acid. The conducted technological process caused various changes in contents of nitrogen forms and partial loss of phenolic compounds. The antiradical and antioxidative activity of the extracts decreased significantly, while an increase was observed in their ability to chelate Fe(II). These changes were due to the migration of active compounds to the brine, and to their structural transformations and degradation. Longer storage of the sterilized product caused restoration of part of the antiradical activity of the seeds.

Spectroscopic studies on Solvatochromism of mixed-chelate copper(II) complexes using MLR technique

NASA Astrophysics Data System (ADS)

Golchoubian, Hamid; Moayyedi, Golasa; Fazilati, Hakimeh

2012-01-01

Mixed-chelate copper(II) complexes with a general formula [Cu(acac)(diamine)]X where acac = acetylacetonate ion, diamine = N,N-dimethyl,N'-benzyl-1,2-diaminoethane and X = BPh 4-, PF 6-, ClO 4- and BF 4- have been prepared. The complexes were characterized on the basis of elemental analysis, molar conductance, UV-vis and IR spectroscopies. The complexes are solvatochromic and their solvatochromism were investigated by visible spectroscopy. All complexes demonstrated the positive solvatochromism and among the complexes [Cu(acac)(diamine)]BPh 4·H 2O showed the highest Δ νmax value. To explore the mechanism of interaction between solvent molecules and the complexes, different solvent parameters such as DN, AN, α and β using multiple linear regression (MLR) method were employed. The statistical results suggested that the DN parameter of the solvent plays a dominate contribution to the shift of the d-d absorption band of the complexes.

(Carbonato-κO,O')bis-(di-2-pyridyl-amine-κN,N')cobalt(III) bromide.

PubMed

Czapik, Agnieszka; Papadopoulos, Christos; Lalia-Kantouri, Maria; Gdaniec, Maria

2011-04-01

In the title compound, [Co(CO(3))(C(10)H(9)N(3))(2)]Br, a distorted octa-hedral coordination of the Co(III) atom is completed by four N atoms of the two chelating di-2-pyridyl-amine ligands and two O atoms of the chelating carbonate anion. The di-2-pyridyl-amine ligands are nonplanar and the dihedral angles between the 2-pyridyl groups are 29.11 (9) and 37.15 (12)°. The coordination cation, which has approximate C(2) symmetry, is connected to the bromide ion via an N-H⋯Br(-) hydrogen bond. The ionic pair thus formed is further assembled into a dimer via N-H⋯O inter-actions about an inversion centre. A set of weaker C-H⋯O and C-H⋯Br(-) inter-actions connect the dimers into a three-dimensional network.

(Carbonato-κ2 O,O′)bis­(di-2-pyridyl­amine-κ2 N,N′)cobalt(III) bromide

PubMed Central

Czapik, Agnieszka; Papadopoulos, Christos; Lalia-Kantouri, Maria; Gdaniec, Maria

2011-01-01

In the title compound, [Co(CO3)(C10H9N3)2]Br, a distorted octa­hedral coordination of the CoIII atom is completed by four N atoms of the two chelating di-2-pyridyl­amine ligands and two O atoms of the chelating carbonate anion. The di-2-pyridyl­amine ligands are nonplanar and the dihedral angles between the 2-pyridyl groups are 29.11 (9) and 37.15 (12)°. The coordination cation, which has approximate C 2 symmetry, is connected to the bromide ion via an N—H⋯Br− hydrogen bond. The ionic pair thus formed is further assembled into a dimer via N—H⋯O inter­actions about an inversion centre. A set of weaker C—H⋯O and C—H⋯Br− inter­actions connect the dimers into a three-dimensional network. PMID:21753946

Ultrasensitive quantum dot fluorescence quenching assay for selective detection of mercury ions in drinking water.

PubMed

Ke, Jun; Li, Xinyong; Zhao, Qidong; Hou, Yang; Chen, Junhong

2014-07-09

Mercury is one of the most acutely toxic substances at trace level to human health and living thing. Developing a rapid, cheap and water soluble metal sensor for detecting mercury ions at ppb level remains a challenge. Herein, a metal sensor consisting of MPA coated Mn doped ZnSe/ZnS colloidal nanoparticles was utilized to ultrasensitively and selectively detect Hg(2+) ions with a low detection limit (0.1 nM) over a dynamic range from 0 to 20 nM. According to strong interaction between thiol(s) and mercury ions, mercaptopropionic acid (MPA) was used as a highly unique acceptor for mercury ions in the as-obtained ultrasensitive sensor. In the presence of mercury ions, colloidal nanoparticles rapidly agglomerated due to changes of surface chemical properties, which results in severe quenching of fluorescent intensity. Meanwhile, we find that the original ligands are separated from the surface of colloidal nanoparticles involving strongly chelation between mercury ion and thiol(s) proved by controlled IR analysis. The result shows that the QD-based metal ions sensor possesses satisfactory precision, high sensitivity and selectivity, and could be applied for the quantification analysis of real samples.

Ultrasensitive Quantum Dot Fluorescence quenching Assay for Selective Detection of Mercury Ions in Drinking Water

PubMed Central

Ke, Jun; Li, Xinyong; Zhao, Qidong; Hou, Yang; Chen, Junhong

2014-01-01

Mercury is one of the most acutely toxic substances at trace level to human health and living thing. Developing a rapid, cheap and water soluble metal sensor for detecting mercury ions at ppb level remains a challenge. Herein, a metal sensor consisting of MPA coated Mn doped ZnSe/ZnS colloidal nanoparticles was utilized to ultrasensitively and selectively detect Hg2+ ions with a low detection limit (0.1 nM) over a dynamic range from 0 to 20 nM. According to strong interaction between thiol(s) and mercury ions, mercaptopropionic acid (MPA) was used as a highly unique acceptor for mercury ions in the as-obtained ultrasensitive sensor. In the presence of mercury ions, colloidal nanoparticles rapidly agglomerated due to changes of surface chemical properties, which results in severe quenching of fluorescent intensity. Meanwhile, we find that the original ligands are separated from the surface of colloidal nanoparticles involving strongly chelation between mercury ion and thiol(s) proved by controlled IR analysis. The result shows that the QD-based metal ions sensor possesses satisfactory precision, high sensitivity and selectivity, and could be applied for the quantification analysis of real samples. PMID:25005836

Comparison of natural organic acids and synthetic chelates at enhancing phytoextraction of metals from a multi-metal contaminated soil.

PubMed

do Nascimento, Clístenes Williams A; Amarasiriwardena, Dula; Xing, Baoshan

2006-03-01

Chemically assisted phytoremediation has been developing to induce accumulation of metals by high biomass plants. Synthetic chelates have shown high effectiveness to reach such a goal, but they pose serious drawbacks in field application due to the excessive amount of metals solubilized. We compared the performance of synthetic chelates with naturally occurring low molecular weight organic acids (LMWOA) in enhancing phytoextraction of metals by Indian mustard (Brassica juncea) from multi-metal contaminated soils. Gallic and citric acids were able to induce removal of Cd, Zn, Cu, and Ni from soil without increasing the leaching risk. Net removal of these metals caused by LMWOA can be as much as synthetic chelates. A major reason for this is the lower phytotoxicity of LMWOA. Furthermore, supplying appropriate mineral nutrients increased biomass and metal removal.

Mn(2+)-mediated homogeneous Fenton-like reaction of Fe(III)-NTA complex for efficient degradation of organic contaminants under neutral conditions.

PubMed

Li, Yifan; Sun, Jianhui; Sun, Sheng-Peng

2016-08-05

In this work, we report a novel Mn(2+)-mediated Fenton-like process based on Fe(III)-NTA complex that is super-efficient at circumneutral pH range. Kinetics experiments showed that the presence of Mn(2+) significantly enhanced the effectiveness of Fe(III)-NTA complex catalyzed Fenton-like reaction. The degradation rate constant of crotamiton (CRMT), a model compound, by the Fe(III)- NTA_Mn(2+) Fenton-like process was at least 1.6 orders of magnitude larger than that in the absence of Mn(2+). Other metal ions such as Ca(2+), Mg(2+), Co(2+) and Cu(2+) had no impacts or little inhibitory effect on the Fe(III)-NTA complex catalyzed Fenton-like reaction. The generation of hydroxyl radical (HO) and superoxide radical anion (O2(-)) in the Fe(III)-NTA_Mn(2+) Fenton-like process were suggested by radicals scavenging experiments. The degradation efficiency of CRMT was inhibited significantly (approximately 92%) by the addition of HO scavenger 2-propanol, while the addition of O2(-) scavenger chloroform resulted in 68% inhibition. Moreover, the results showed that other chelating agents such as EDTA- and s,s-EDDS-Fe(III) catalyzed Fenton-like reactions were also enhanced significantly by the presence of Mn(2+). The mechanism involves an enhanced generation of O2(-) from the reactions of Mn(2+)-chelates with H2O2, indirectly promoting the generation of HO by accelerating the reduction rate of Fe(III)-chelates to Fe(II)- chelates. Copyright © 2016 Elsevier B.V. All rights reserved.

Novel bis-(−)-nor-meptazinol derivatives act as dual binding site AChE inhibitors with metal-complexing property

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Wei; NPFPC Key Laboratory of Contraceptives and Devices, Shanghai Institute of Planned Parenthood Research, 2140 Xietu Road, Shanghai 200032; Li, Juan

The strategy of dual binding site acetylcholinesterase (AChE) inhibition along with metal chelation may represent a promising direction for multi-targeted interventions in the pathophysiological processes of Alzheimer's disease (AD). In the present study, two derivatives (ZLA and ZLB) of a potent dual binding site AChE inhibitor bis-(−)-nor-meptazinol (bis-MEP) were designed and synthesized by introducing metal chelating pharmacophores into the middle chain of bis-MEP. They could inhibit human AChE activity with IC{sub 50} values of 9.63 μM (for ZLA) and 8.64 μM (for ZLB), and prevent AChE-induced amyloid-β (Aβ) aggregation with IC{sub 50} values of 49.1 μM (for ZLA) and 55.3more » μM (for ZLB). In parallel, molecular docking analysis showed that they are capable of interacting with both the catalytic and peripheral anionic sites of AChE. Furthermore, they exhibited abilities to complex metal ions such as Cu(II) and Zn(II), and inhibit Aβ aggregation triggered by these metals. Collectively, these results suggest that ZLA and ZLB may act as dual binding site AChEIs with metal-chelating potency, and may be potential leads of value for further study on disease-modifying treatment of AD. -- Highlights: ► Two novel bis-(−)-nor-meptazinol derivatives are designed and synthesized. ► ZLA and ZLB may act as dual binding site AChEIs with metal-chelating potency. ► They are potential leads for disease-modifying treatment of Alzheimer's disease.« less

Syntheses, structures, and magnetic properties of three new MnII-[MoIII(CN)7]4- molecular magnets.

PubMed

Wei, Xiao-Qin; Pi, Qian; Shen, Fu-Xing; Shao, Dong; Wei, Hai-Yan; Wang, Xin-Yi

2018-05-22

By reaction of K4[MoIII(CN)7]·2H2O, Mn(ClO4)2·6H2O and bidentate chelating ligands, three new cyano-bridged compounds, namely Mn2(3-pypz)(H2O)(CH3CN)[Mo(CN)7] (1), Mn2(1-pypz)(H2O)(CH3CN)[Mo(CN)7] (2) and Mn2(pyim)(H2O)(CH3CN)[Mo(CN)7] (3) (3-pypz = 2-(1H-pyrazol-3-yl)pyridine, 1-pypz = 2-(1H-pyrazol-1-yl)pyridine, pyim = 2-(1H-imidazol-2-yl)pyridine), have been synthesized and characterized structurally and magnetically. Single crystal X-ray analyses revealed that although the chelating ligands are different, compounds 1 to 3 are isomorphous and crystallize in the same monoclinic space group C2/m. Connected by the bridging cyano groups, one crystallographically unique [Mo(CN)7]4- unit and three crystallographically unique MnII ions of different coordination environments form similar three-dimensional frameworks, which have a four-nodal 3,4,4,7-connecting topological net with a vertex symbol of {43}{44·62}2{410·611}. Magnetic measurements revealed that compounds 1-3 display long-range magnetic ordering with critical temperatures of 64, 66 and 62 K, respectively. These compounds are rare examples of a small number of chelating co-ligand coordinated [Mo(CN)7]4--based magnetic materials. Specifically, the bidentate chelating ligands were successfully introduced into the heptacyanomolybdate system for the first time.

Clioquinol and vitamin B12 (cobalamin) synergistically rescue the lead-induced impairments of synaptic plasticity in hippocampal dentate gyrus area of the anesthetized rats in vivo.

PubMed

Chen, W-H; Wang, M; Yu, S-S; Su, L; Zhu, D-M; She, J-Q; Cao, X-J; Ruan, D-Y

2007-07-13

Lead (Pb(2+)) exposure in development induces impairments of synaptic plasticity in the hippocampal dentate gyrus (DG) area of the anesthetized rats in vivo. The common chelating agents have many adverse effects and are incapable of alleviating lead-induced neurotoxicity. Recently, CQ, clioquinol (5-chloro-7-iodo-8-hydroxy-quinoline), which is a transition metal ion chelator and/or ionophore with low affinity for metal ions, has yielded some promising results in animal models and clinical trials related to dysfunctions of metal ions. In addition, CQ-associated side effects are believed to be overcome with vitamin B12 (VB12) supplementation. To determine whether CQ treatment could rescue impairments of synaptic plasticity induced by chronic Pb(2+) exposure, we investigated the input/output functions (I/Os), paired-pulse reactions (PPRs) and long-term potentiation (LTP) of different treatment groups in hippocampal DG area of the anesthetized rat in vivo by recording field potentials and measured hippocampal Pb(2+) concentrations of different treatment groups by PlasmaQuad 3 inductive coupled plasma mass spectroscopy. The results show: CQ alone does not rescue the lead-induced impairments of synaptic plasticity in hippocampal DG area of the anesthetized rats in vivo; VB12 alone partly rescues the lead-induced impairments of LTP; however the co-administration of CQ and VB12 totally rescues these impairments of synaptic plasticity and moreover, the effects of CQ and VB12 co-administration are specific to the lead-exposed animals.

Different roles of glutathione in copper and zinc chelation in Brassica napus roots.

PubMed

Zlobin, Ilya E; Kartashov, Alexander V; Shpakovski, George V

2017-09-01

We investigated the specific features of copper and zinc excess action on the roots of canola (Brassica napus L.) plants. Copper rapidly accumulated in canola root cells and reached saturation during several hours of treatment, whereas the root zinc content increased relatively slowly. Excessive copper and zinc entry inside the cell resulted in significant cell damage, as evidenced by alterations in plasmalemma permeability and decreases in cellular enzymatic activity. Zinc excess specifically damaged root hair cells, which correlated with a pronounced elevation of their labile zinc level. In vitro, we showed that reduced glutathione (GSH) readily reacted with copper ions to form complexes with blocked sulfhydryl groups. In contrast, zinc ions were ineffective as glutathione blockers, and glutathione molecules did not lose their specific chemical activity in the presence of Zn 2+ ions. The effect of copper and zinc excess on the glutathione pool in canola root cells was analysed by a combination of biochemical determination of total and oxidized glutathione contents and fluorescent staining of free reduced glutathione with monochlorobimane dye. Excess copper led to dose-dependent diminution of free reduced glutathione contents in the root cells, which could not be explained by the loss of total cellular glutathione or its oxidation. In contrast, we observed little effect of much higher intracellular zinc concentrations on the free reduced glutathione content. We concluded that GSH plays an important role in copper excess, but not zinc excess chelation, in canola root cells. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Molecular Dynamics Study of Twister Ribozyme: Role of Mg(2+) Ions and the Hydrogen-Bonding Network in the Active Site.

PubMed

Ucisik, Melek N; Bevilacqua, Philip C; Hammes-Schiffer, Sharon

2016-07-12

The recently discovered twister ribozyme is thought to utilize general acid-base catalysis in its self-cleavage mechanism, but the roles of nucleobases and metal ions in the mechanism are unclear. Herein, molecular dynamics simulations of the env22 twister ribozyme are performed to elucidate the structural and equilibrium dynamical properties, as well as to examine the role of Mg(2+) ions and possible candidates for the general base and acid in the self-cleavage mechanism. The active site region and the ends of the pseudoknots were found to be less mobile than other regions of the ribozyme, most likely providing structural stability and possibly facilitating catalysis. A purported catalytic Mg(2+) ion and the closest neighboring Mg(2+) ion remained chelated and relatively immobile throughout the microsecond trajectories, although removal of these Mg(2+) ions did not lead to any significant changes in the structure or equilibrium motions of the ribozyme on the microsecond time scale. In addition, a third metal ion, a Na(+) ion remained close to A1(O5'), the leaving group atom, during the majority of the microsecond trajectories, suggesting that it might stabilize the negative charge on A1(O5') during self-cleavage. The locations of these cations and their interactions with key nucleotides in the active site suggest that they may be catalytically relevant. The P1 stem is partially melted at its top and bottom in the crystal structure and further unwinds in the trajectories. The simulations also revealed an interconnected network comprised of hydrogen-bonding and π-stacking interactions that create a relatively rigid network around the self-cleavage site. The nucleotides involved in this network are among the highly conserved nucleotides in twister ribozymes, suggesting that this interaction network may be important to structure and function.

Radical scavenging and iron-chelating activities of some greens used as traditional dishes in Mediterranean diet.

PubMed

El, Sedef Nehir; Karakaya, Sibel

2004-02-01

This study aimed at evaluating the antioxidative activity of nine different families of greens. Raphanus raphanistrum (wild radish), Anchusa azurea (bugloss), Daucus carota (wild carrot), Sonchus oleraceus (sowthistle), Papaver rhoeas (corn poppy), Malva sylvestris (blue mallow), Foeniculum vulgare (fennel), Cichorium intybus (chicory) and Salicornia europaea (jointed glasswort) are native to the Mediterranean and are commonly consumed as a salad or an ingredient in some recipes. The antioxidative activities, including the radical scavenging effects, inhibition of hydrogen peroxide (H(2)O(2)), and Fe(2+)-chelating activity, were studied. All samples showed antioxidant activity as a radical scavenger in the experiment using the DPPH* radical. The ratio between the slopes of the kinetic model was used to compare antioxidant efficiency of different greens. Greens also possessed antioxidative activity toward H(2)O(2). Especially, greens exhibited a marked scavenging effect on H(2)O(2) at 0.2 g/ml concentration. The Fe(2+) ion-chelating activities of the samples except jointed glasswort were greater than 70%. The antioxidant activity of samples with different methods based on the inhibition of different reactions could not be compared. The current dietary guidelines include recommendations for an increase in the consumption of plant foods. Greens should provide an optimal supply of antioxidant substances in the diet.

[2D correlation spectral study of a coordination polymer [Eu(PCPOA)3 (H2O)]n].

PubMed

Sun, Rui-qing; Zhang, Han-hui; Cao, Yan-ning; Chen, Yi-ping; Yang, Qi-yu; Wang, Zhi-yang

2007-05-01

A novel two dimensional coordination polymer [Eu(PCPOA)3 (H2O)], was synthesized under hydrothermal condition. Based on the determination of the structure, the 2D correlation FTIR spectra with the perturbation of magnetism and the 2D correlation fluorescence spectra with the perturbation of temperature were investigated. The energy bonds were calculated using CASTEP Program of Material studio. The Europium ions are nine-coordinated and the ligands adopted two different modes to connect the Eu3+ ions to 2D layer structure. The study of the 2D-FTIR reveals that the carboxylates coordinate with the center ions not only as monodentate, but also as bidentate chelate. The 2D fluorescence spectra indicates that the transition of (5)D0-->(7)F2 is influenced intensively by the perturbation of temperature.

Relative contribution of phytates, fibers, and tannins to low iron and zinc in vitro solubility in pearl millet (Pennisetum glaucum) flour and grain fractions.

PubMed

Lestienne, Isabelle; Caporiccio, Bertrand; Besançon, Pierre; Rochette, Isabelle; Trèche, Serge

2005-10-19

In vitro digestions were performed on pearl millet flours with decreased phytate contents and on two dephytinized or nondephytinized pearl millet grain fractions, a decorticated fraction, and a bran fraction with low and high fiber and tannin contents, respectively. Insoluble residues of these digestions were then incubated with buffer or enzymatic solutions (xylanases and/or phytases), and the quantities of indigestible iron and zinc released by these different treatments were determined. In decorticated pearl millet grain, iron was chelated by phytates and by insoluble fibers, whereas zinc was almost exclusively chelated by phytates. In the bran of pearl millet grain, a high proportion of iron was chelated by iron-binding phenolic compounds, while the rest of iron as well as the majority of zinc were chelated in complexes between phytates and fibers. The low effect of phytase action on iron and zinc solubility of bran of pearl millet grain shows that, in the case of high fiber and tannin contents, the chelating effect of these compounds was higher than that of phytates.

In vitro screening of Fe2+-chelating effect by a Fenton's reaction-luminol chemiluminescence system.

PubMed

Wada, Mitsuhiro; Komatsu, Hiroaki; Ikeda, Rie; Aburjai, Talal A; Alkhalil, Suleiman M; Kuroda, Naotaka; Nakashima, Kenichiro

2014-11-01

In vitro screening of a Fe(2+) -chelating effect using a Fenton's reaction-luminol chemiluminescence (CL) system is described. The luminescence between the reactive oxygen species generated by the Fenton's reaction and luminol was decreased on capturing Fe(2+) using a chelator. The proposed method can prevent the consumption of expensive seed compounds (drug discovery candidates) owing to the high sensitivity of CL detection. Therefore, the assay could be performed using small volumes of sample solution (150 μL) at micromolar concentrations. After optimization of the screening conditions, the efficacies of conventional chelators such as ethylenediaminetetraacetic acid (EDTA), diethylentriaminepentaacetic acid (DETAPAC), deferoxamine, deferiprone and 1,10-phenanthroline were examined. EC50 values for these compounds (except 1,10-phenanthroline) were in the range 3.20 ± 0.87 to 9.57 ± 0.64 μM (n = 3). Rapid measurement of the Fe(2+)-chelating effect with an assay run time of a few minutes could be achieved using the proposed method. In addition, the specificity of the method was discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Controlling lipid oxidation via a biomimetic iron chelating active packaging material.

PubMed

Tian, Fang; Decker, Eric A; Goddard, Julie M

2013-12-18

Previously, a siderophore-mimetic metal chelating active packaging film was developed by grafting poly(hydroxamic acid) (PHA) from the surface of polypropylene (PP) films. The objective of the current work was to demonstrate the potential applicability of this PP-g-PHA film to control iron-promoted lipid oxidation in food emulsions. The iron chelating activity of this film was investigated, and the surface chemistry and color intensity of films were also analyzed after iron chelation. In comparison to the iron chelating activity in the free Fe(3+) solution, the PP-g-PHA film retained approximately 50 and 30% of its activity in nitrilotriacetic acid (NTA)/Fe(3+) and citric acid/Fe(3+) solutions, respectively (pH 5.0), indicating a strong chelating strength for iron. The ability of PP-g-PHA films to control lipid oxidation was demonstrated in a model emulsion system (pH 3.0). PP-g-PHA films performed even better than ethylenediaminetetraacetic acid (EDTA) in preventing the formation of volatile oxidation products. The particle size and ζ potential results of emulsions indicated that PP-g-PHA films had no adverse effects on the stability of the emulsion system. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis suggested a non-migratory nature of the PP-g-PHA film surface. These results suggest that such biomimetic, non-migratory metal chelating active packaging films have commercial potential in protecting foods against iron-promoted lipid oxidation.

Nuclear Forensic Lab Interoperability and Criminal Investigation

DTIC Science & Technology

2014-08-01

34 Hydrometallurgy (3-4): 175-180 13. Kolodynska, D., H. Hubicka, et al. (2008). " Sorption of heavy metal ions from aqueous solutions in the presence of...EDTA on monodisperse anion exchangers." Desalination (1-3): 150-166 14. Kolodynska, D. (2009). "Polyacrylate anion exchangers in sorption of heavy...F. D. and A. H. Martins (2004). "Selective sorption of nickel and cobalt from sulphate solutions using chelating resins." International Journal of

Profiling of metal ions leached from pharmaceutical packaging materials.

PubMed

Fliszar, Kyle A; Walker, David; Allain, Leonardo

2006-01-01

Metal leachables from packaging components can affect the safety and efficacy of a pharmaceutical formulation. As liquid formulations continue to contain surfactants, salts, and chelating agents coupled with lower drug levels, the interaction between the formulation and the packaging material becomes more important. This study examines the interaction of commonly used packaging materials with extraction solvents representative of liquid formulations found in the pharmaceutical industry stressed under conditions encountered during accelerated stability studies.

Effect of zinc chelate and valnemulin for the treatment of swine dysentery in an experimental challenge study.

PubMed

Šperling, Daniel; Čížek, Alois; Smola, Jiří

2014-02-01

The aim of study was to determine the influence of zinc chelate, valnemulin and it's combination on Brachyspira hyodysenteriae shedding and morphological changes of colonic mucosa in an experimental model of swine dysentery (SD). The study was performed on pigs coming from a dysentery-free herd. Animals were inoculated by B. hyodysenteriae strain B204. When the clinical signs of SD and B. hyodysenteriae shedding developed, the pigs were divided into four treatment groups. The first group was treated with zinc chelate (250 ml/1000 L in water), second group was given valnemulin in feed at 75 ppm; the third group was given a combination of both and the fourth group was control. The results demonstrated therapeutic effect of valnemulin in pigs with serious SD and did not show therapeutic effect of chelated zinc. Copyright © 2013. Published by Elsevier Ltd.

Transition-metal-ion-mediated polymerization of dopamine: mussel-inspired approach for the facile synthesis of robust transition-metal nanoparticle-graphene hybrids.

PubMed

Yang, Liping; Kong, Junhua; Zhou, Dan; Ang, Jia Ming; Phua, Si Lei; Yee, Wu Aik; Liu, Hai; Huang, Yizhong; Lu, Xuehong

2014-06-16

Inspired by the high transition-metal-ion content in mussel glues, and the cross-linking and mechanical reinforcement effects of some transition-metal ions in mussel threads, high concentrations of nickel(II), cobalt(II), and manganese(II) ions have been purposely introduced into the reaction system for dopamine polymerization. Kinetics studies were conducted for the Ni(2+)-dopamine system to investigate the polymerization mechanism. The results show that the Ni(2+) ions could accelerate the assembly of dopamine oligomers in the polymerization process. Spectroscopic and electron microscopic studies reveal that the Ni(2+) ions are chelated with polydopamine (PDA) units, forming homogeneous Ni(2+)-PDA complexes. This facile one-pot approach is utilized to construct transition-metal-ion-PDA complex thin coatings on graphene oxide, which can be carbonized to produce robust hybrid nanosheets with well-dispersed metallic nickel/metallic cobalt/manganese(II) oxide nanoparticles embedded in PDA-derived thin graphitic carbon layers. The nickel-graphene hybrid prepared by using this approach shows good catalytic properties and recyclability for the reduction of p-nitrophenol. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lead sorption by waste biomass of hazelnut and almond shell.

PubMed

Pehlivan, Erol; Altun, Türkan; Cetin, Serpil; Iqbal Bhanger, M

2009-08-15

The potential to remove Pb(2+) ion from aqueous solutions using the shells of hazelnut (HNS) (Corylus avellana) and almond (AS) (Prunus dulcis) through biosorption was investigated in batch experiments. The main parameters influencing Pb(2+) ion sorption on HNS and AS were: initial metal ion concentration, amount of adsorbent, contact time and pH value of solution. The influences of initial Pb(2+) ion concentration (0.1-1.0mM), pH (2-9), contact time (10-240 min) and adsorbent amount (0.1-1.0 g) have been investigated. Equilibrium isotherms have been measured and modelled. Adsorption of Pb(2+) ions was in all cases pH-dependent showing a maximum at equilibrium pH values between 6.0 and 7.0, depending on the biomaterial, that corresponded to equilibrium pH values of 6.0 for HNS and 7.0 for AS. The equilibrium sorption capacities of HNS and AS were 28.18 and 8.08 mg/g for lead, respectively after equilibrium time of 2h. The adsorption data fit well with the Langmuir isotherm model and the experimental result inferred that adsorption, chelation and ion exchange are major adsorption mechanisms for binding Pb(2+) ion to the sorbents.

Comparison of macrocyclic and acyclic chelators for gallium-68 radiolabelling.

PubMed

Tsionou, Maria Iris; Knapp, Caroline E; Foley, Calum A; Munteanu, Catherine R; Cakebread, Andrew; Imberti, Cinzia; Eykyn, Thomas R; Young, Jennifer D; Paterson, Brett M; Blower, Philip J; Ma, Michelle T

2017-10-24

Gallium-68 ( 68 Ga) is a positron-emitting isotope used for clinical PET imaging of peptide receptor expression. 68 Ga radiopharmaceuticals used in molecular PET imaging consist of disease-targeting biomolecules tethered to chelators that complex 68 Ga 3+ . Ideally, the chelator will rapidly, quantitatively and stably coordinate 68 Ga 3+ at room temperature, near neutral pH and low chelator concentration, allowing for simple routine radiopharmaceutical formulation. Identification of chelators that fulfil these requirements will facilitate development of kit-based 68 Ga radiopharmaceuticals. Herein the reaction of a range of widely used macrocyclic and acyclic chelators with 68 Ga 3+ is reported. Radiochemical yields have been measured under conditions of varying chelator concentrations, pH (3.5 and 6.5) and temperature (25 and 90 °C). These chelators are: 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), 1,4,7-triazacyclononane macrocycles substituted with phosphonic (NOTP) and phosphinic (TRAP) groups at the amine, bis(2-hydroxybenzyl)ethylenediaminediacetic acid (HBED), a tris(hydroxypyridinone) containing three 1,6-dimethyl-3-hydroxypyridin-4-one groups (THP) and the hexadentate tris(hydroxamate) siderophore desferrioxamine-B (DFO). Competition studies have also been undertaken to assess relative complexation efficiencies of each chelator for 68 Ga 3+ under different pH and temperature conditions. Performing radiolabelling reactions at pH 6.5, 25 °C and 5-50 μM chelator concentration resulted in near quantitative radiochemical yields for all chelators, except DOTA. Radiochemical yields either decreased or were not substantially improved when the reactions were undertaken at lower pH or at higher temperature, except in the case of DOTA. THP and DFO were the most effective 68 Ga 3+ chelators at near-neutral pH and 25 °C, rapidly providing near-quantitative radiochemical yields at very low chelator concentrations. NOTP and HBED were only slightly less effective under these conditions. In competition studies with all other chelators, THP demonstrated highest reactivity for 68 Ga 3+ complexation under all conditions. These data point to THP possessing ideal properties for rapid, one-step kit-based syntheses of 68 Ga-biomolecules for molecular PET imaging. LC-MS and 1 H, 13 C{ 1 H} and 71 Ga NMR studies of HBED complexes of Ga 3+ showed that under the analytical conditions employed in this study, multiple HBED-bound Ga complexes exist. X-ray diffraction data indicated that crystals isolated from these solutions contained octahedral [Ga(HBED)(H 2 O)], with HBED coordinated in a pentadentate N 2 O 3 mode, with only one phenolic group coordinated to Ga 3+ , and the remaining coordination site occupied by a water molecule.

Efficient fabrication of high-capacity immobilized metal ion affinity chromatographic media: The role of the dextran-grafting process and its manipulation.

PubMed

Zhao, Lan; Zhang, Jingfei; Huang, Yongdong; Li, Qiang; Zhang, Rongyue; Zhu, Kai; Suo, Jia; Su, Zhiguo; Zhang, Zhigang; Ma, Guanghui

2016-03-01

Novel high-capacity Ni(2+) immobilized metal ion affinity chromatographic media were prepared through the dextran-grafting process. Dextran was grafted to an allyl-activated agarose-based matrix followed by functionalization for the immobilized metal ion affinity chromatographic media. With elaborate regulation of the allylation degree, dextran was completely or partly grafted to agarose microspheres, namely, completely dextran-grafted agarose microspheres and partly dextran-grafted ones, respectively. Confocal laser scanning microscope results demonstrated that a good adjustment of dextran-grafting degree was achieved, and dextran was distributed uniformly in whole completely dextran-grafted microspheres, while just distributed around the outside of the partly dextran-grafted ones. Flow hydrodynamic properties were improved greatly after the dextran-grafting process, and the flow velocity increased by about 30% compared with that of a commercial chromatographic medium (Ni Sepharose FF). A significant improvement of protein binding performance was also achieved by the dextran-grafting process, and partly dextran-grafted Ni(2+) chelating medium had a maximum binding capacity for His-tagged lactate dehydrogenase about 2.5 times higher than that of Ni Sepharose FF. The results indicated that this novel chromatographic medium is promising for applications in high-efficiency and large-scale protein purification. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transition-metal phosphors with cyclometalating ligands: fundamentals and applications.

PubMed

Chi, Yun; Chou, Pi-Tai

2010-02-01

One goal of this critical review is to provide advanced methodologies for systematic preparation of transition-metal based phosphors that show latent applications in the field of organic light emitting diodes (OLEDs). We are therefore reviewing various types of cyclometalating chelates for which the favorable metal-chelate bonding interaction, on the one hand, makes the resulting phosphorescent complexes highly emissive in both fluid and solid states at room temperature. On the other hand, fine adjustment of ligand-centered pi-pi* electronic transitions allows tuning of emission wavelength across the whole visible spectrum. The cyclometalating chelates are then classified according to types of cyclometalating groups, i.e. either aromatic C-H or azolic N-H fragment, and the adjacent donor fragment involved in the formation of metallacycles; the latter is an N-containing heterocycle, N-heterocyclic (NHC) carbene fragment or even diphenylphosphino group. These cyclometalating ligands are capable to react with heavy transition-metal elements, namely: Ru(II), Os(II), Ir(III) and Pt(II), to afford a variety of highly emissive phosphors, for which the photophysical properties as a function of chelate or metal characteristics are systematically discussed. Using Ir(III) complexes as examples, the C--N chelates possessing both C-H site and N-heterocyclic donor group are essential for obtaining phosphors with emission ranging from sky-blue to saturated red, while the N--N chelates such as 2-pyridyl-C-linked azolates are found useful for serving as true-blue chromophores due to their increased ligand-centered pi-pi* energy gap. Lastly, the remaining NHC carbene and benzyl phosphine chelates are highly desirable to serve as ancillary chelates in localizing the electronic transition between the metal and remaining lower energy chromophoric chelates. As for the potential opto-electronic applications, many of them exhibit remarkable performance data, which are convincing to pave a broad avenue for further development of all types of phosphorescent displays and illumination devices (94 references).

Boron removal by a composite sorbent: Polyethylenimine/tannic acid derivative immobilized in alginate hydrogel beads.

PubMed

Bertagnolli, Caroline; Grishin, Andrey; Vincent, Thierry; Guibal, Eric

2017-03-21

A novel composite material was prepared by the grafting of tannic acid on polyethylenimine (PEI), which allows an efficient sorption of boron (sorption capacity close to 0.89 mmol B g -1 ). The encapsulation of this chelating sorbent (finely crushed) facilitates its use (readily solid/liquid separation, use in fixed-bed columns) at the expense of a loss in sorption capacity (proportionally decreased by the introduction of alginate having poor efficiency for boron uptake). Sorption isotherms are modeled using the Langmuir equation, while the kinetic profiles are presented a good fit by pseudo-second order rate equation. In addition, the encapsulating matrix introduces supplementary resistance to intraparticle diffusion, especially when the resin is dried without control: freeze-drying partially limits this effect. The stability (at long-term storage) of the sorbent is improved when the sorbent is stored under nitrogen atmosphere. The presence of an excess of NaCl was investigated. The degradation of the hydrogel (by ion-exchange of Ca(II) with Na(I)) leads to a decrease in the sorption performance of composite material but the action of Ca(II) ions in the solutions re-stabilizes the hydrogel.

Porous cellulosic adsorbent for the removal of Cd (II), Pb(II) and Cu(II) ions from aqueous media

NASA Astrophysics Data System (ADS)

Barsbay, Murat; Kavaklı, Pınar Akkaş; Tilki, Serhad; Kavaklı, Cengiz; Güven, Olgun

2018-01-01

The main objective of this work is to prepare a renewable cellulosic adsorbent by γ-initiated grafting of poly(glycidyl methacrylate) (PGMA) from cellulose substrate and subsequent modification of PGMA with chelating species, iminodiacetic acid (IDA), for Cd (II), Pb(II) and Cu(II) removal from aqueous media. Modification of PGMA grafted cellulose with IDA in aqueous solution under mild conditions has proceeded efficiently to yield a natural-based and effective porous adsorbent with well-defined properties as provided by the controlled polymerization technique, namely RAFT, applied during the radiation-induced graft copolymerization step and with sufficient degree of IDA immobilization as confirmed by XPS, FTIR, contact angle measurements and elemental analysis. In order to examine the Cd (II), Pb(II) and Cu(II) removing performance of the resulting adsorbent, batch experiments were carried out by ICP-MS. The adsorption capacities were determined as 53.4 mg Cd(II)/g polymer, 52.0 mg Pb(II)/g polymer and 69.6 mg Cu(II)/g polymer at initial feed concentration of 250 ppm, showing the promising potential of the natural-based adsorbent to steadily and efficiently chemisorb toxic metal ions.

Synthesis, characterization, DFT calculations and molecular docking studies of metal (II) complexes

NASA Astrophysics Data System (ADS)

Ekennia, Anthony C.; Osowole, Aderoju A.; Olasunkanmi, Lukman O.; Onwudiwe, Damian C.; Olubiyi, Olujide O.; Ebenso, Eno E.

2017-12-01

Two novel ligands, 2-methyl-6-[(5-methyl benzothiazol-2-ylimino)-methyl]-2-methoxycyclohexa-1,5-dienol (HL1) and 2-methyl-6-[(5-floro-benzothiazol-2-ylimino)-methyl]-2-methoxycyclohexa-1,5-dienol (HL2) were synthesized from the condensation reaction of 2-hydroxy-3-methoxybenzaldehyde with 2-amino-6-methylbenzothiazole and 2-amino-6-florobenzothiazole respectively. Mononuclear Cu(II), Ni(II) and Co(II) complexes of the ligands were synthesized and characterized using elemental analysis, magnetic susceptibility, thermogravimetric, conductance, infrared and UV-visible spectroscopic measurements. The 1H NMR, 13C NMR, Dept-90 NMR spectroscopy of the ligands was also recorded to establish the formation of the Schiff bases. The analytical data of the complexes showed that the metal to ligand ratio was 1:1 for Cu(II), Ni(II) and Co(II) complexes of HL1 and Cu(II) complexes of HL2, while Ni(II) and Co(II) complexes of HL2 was 1:2. The infrared spectral data showed that the chelation behaviour of the ligands towards transition metal ions was through phenolic oxygen and azomethine nitrogen atoms. Molar conductivity revealed the non-electrolytic nature of all chelates in DMSO solution. The geometry of the complexes was deduced from thermal, magnetic susceptibility and UV-visible spectroscopic results and was further confirmed with DFT calculations. The compounds were subjected to in-vitro antibacterial screening using agar well diffusion method on some clinically isolated Gram positive and Gram negative bacteria strains. The compounds showed varied antibacterial activities. Molecular docking studies were carried out to study the molecular interaction between the compounds and different enzymes of the bacterial strains. The antioxidant potentials of the compounds were studied using ferrous ion chelating assay and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. However, the complexes had better antioxidant potentials compared to the ligands.

Antiradical capacity and polyphenol composition of asparagus spears varieties cultivated under different sunlight conditions.

PubMed

Kulczyński, Bartosz; Kobus-Cisowska, Joanna; Kmiecik, Dominik; Gramza-Michałowska, Anna; Golczak, Dorota; Korczak, Józef

2016-01-01

Asparagus officinalis has a high nutritional value. Asparagus is rich in a number of bioactive compounds, mainly flavonoids (quercetin), glutathione, vitamin C, vitamin E, fructans (inulin and fructooligosaccharides) and phytosterols (b-sitosterol). These compounds may play an important role in human health. The purpose of this study was to examine the antioxidant potential and polyphenol composition of white, pale-colored and green asparagus spears of different cultivars. Investigations were conducted on different asparagus spear extracts. The study included three colors of asparagus (white, pale-colored and green) from five different cultivars subjected to the ethanol extraction procedure. Total phenolic content was also determined by the Folin-Ciocalteu method. Polyphenol (phenolic acids and flavonols) composition was estimated using the HPLC method. The antioxidant properties of extracts were examined using DPPH, ABTS and metal ion chelating assays. The highest contents of phenolic and flavonoids were observed in green asparagus from Grolim and the lowest in pale-colored asparagus from Gyjmlin. It was found that both the color of asparagus and the cultivar had a significant effect on the composition of phenolic acid and flavonols. Radical scavenging activity toward DPPH• and ABTS was highest for green asparagus cv. Grolim and Eposs. The greatest number of Fe ions was chelated by samples of green asparagus cv. Grolim and Huchel's Alpha and pale-colored asparagus cv. Huchel's Alpha. It was shown that the antioxidant activity of asparagus spears measured by antiradical and chelating activity test depends on variety and color. The highest activity was found in green asparagus and the lowest was identified in white asparagus extracts. It has also been clarified that changes in flavonol and phenolic acid composition and increases in their diversity depends on growing with sunlight and variety. Asparagus can provide a valuable source of phenolic compounds in the human diet.

Adsorption of myoglobin to metal-chelating lipid monolayers by neutron reflectivity

NASA Astrophysics Data System (ADS)

Kent, Michael; Yim, Hyun; Sasaki, Darryl; Smith, Greg

2002-03-01

In an effort to devise simple and robust systems that can reproduce in synthetic membranes important features of biological targeting and surface assembly, a versatile system for targeting proteins to lipid membranes has been developed.1 This system utilizes metal-chelating iminodiacetate lipids loaded with divalent metal ions (Cu+2 or Ni+2) to target adsorption of specific residues in proteins. In the present work we use neutron reflection to study the adsorption of myoglobin to monolayers containing such lipids at the air-water interface. The metal-chelating lipids were mixed with deuterated DPPC at a composition of 20subphase buffered with MOPS at a pH of 7.5, compressed to a pressure of 35-40 dyn/cm, and the reflectivity was measured. Following this, a solution of CuCl2 or NiCl2 was added to the subphase, and after mixing for 1 hr the reflectivity was again collected. Finally, a solution of myoglobin was added to the subphase, and after mixing the subphase for roughly 1 hr the reflectivity was again collected. The reflectivity revealed a greater adsorbed amount of myoglobin in the case of the Cu+2 ions than for Ni+2. In addition, the conformation of the adsorbed myoglobin was quite different in the two cases, with the adsorbed layer exhibiting a large dimension ( 90 \\x81) in the case of Cu+2 but a much smaller dimension ( 20\\x81) for the case of Ni+2. Corresponding changes in the structure of the lipid layer investigated with X-ray reflectivity and grazing incidence X-ray diffraction will also be presented. 1K. Ng, D. W. Pack, D. Sasaki, F. H. Arnold, Langmuir 1995, 11, 4048. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract CE-AC04-94AL85000.

Inorganic materials and living organisms: surface modifications and fungal responses to various asbestos forms.

PubMed

Daghino, Stefania; Martino, Elena; Fenoglio, Ivana; Tomatis, Maura; Perotto, Silvia; Fubini, Bice

2005-09-19

In a previous study several strains of soil fungi were reported to remove iron in vitro from crocidolite asbestos, a process that was envisaged as a possible bioremediation route for asbestos-polluted soils. Here, we get some new insight into the chemical basis of the fiber/fungi interaction by comparing the action of the most active fungal strain Fusarium oxysporum on three kind of asbestos fibers--chrysotile, amosite, and crocidolite--and on a surface-modified crocidolite. None of the fibers examined significantly inhibited biomass production. Even the smallest fibrils were visibly removed from the supernatant following adhesion to fungal hyphae. F. oxysporum, through release of chelators, extracted iron from all fibers; the higher the amount of iron at the exposed surface, the larger the amount removed, that is, crocidolite > amosite > chrysotile. When considering the fraction of total iron extracted, however, the ranking was chrysotile > crocidolite > amosite > heated crocidolite, because of the different accessibility of the chelators to the metal ions in the crystal structure. Chrysotile was the easiest to deplete of its metal content. Iron removal fully blunted HO* radical release from crocidolite and chrysotile but only partially from amosite. The removal, in a long-term experiment, of more iron than is expected to be at the surface suggests a diffusion of ions from the bulk solid towards the surface depleted of iron by fungal activity. Thus, if the fibers could be treated with a continuous source of chelators, iron extraction would proceed up to a full inactivation of free radical release. The fungal metabolic response of F. oxysporum grown in the presence of chrysotile, amosite and crocidolite revealed that new extracellular proteins are induced--including manganese-superoxide dismutase, the typical antioxidant defense--and others are repressed, upon direct contact with the fibers. The protein profile induced by heated crocidolite was different, a result suggesting a key role for the state of the fiber/hyphae interface in protein induction.

Metal Ion-Induced Self-Assembly of a Multi-Responsive Block Copolypeptide into Well-Defined Nanocapsules.

PubMed

van Eldijk, Mark B; Schoonen, Lise; Cornelissen, Jeroen J L M; Nolte, Roeland J M; van Hest, Jan C M

2016-05-01

Protein cages are an interesting class of biomaterials with potential applications in bionanotechnology. Therefore, substantial effort is spent on the development of capsule-forming designer polypeptides with a tailor-made assembly profile. The expanded assembly profile of a triblock copolypeptide consisting of a metal ion chelating hexahistidine-tag, a stimulus-responsive elastin-like polypeptide block, and a pH-responsive morphology-controlling viral capsid protein is presented. The self-assembly of this multi-responsive protein-based block copolymer is triggered by the addition of divalent metal ions. This assembly process yields monodisperse nanocapsules with a 20 nm diameter composed of 60 polypeptides. The well-defined nanoparticles are the result of the emergent properties of all the blocks of the polypeptide. These results demonstrate the feasibility of hexahistidine-tags to function as supramolecular cross-linkers. Furthermore, their potential for the metal ion-mediated encapsulation of hexahistidine-tagged proteins is shown. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modification of porous starch for the adsorption of heavy metal ions from aqueous solution.

PubMed

Ma, Xiaofei; Liu, Xueyuan; Anderson, Debbie P; Chang, Peter R

2015-08-15

Porous starch xanthate (PSX) and porous starch citrate (PSC) were prepared in anticipation of the attached xanthate and carboxylate groups respectively forming chelation and electrostatic interactions with heavy metal ions in the subsequent adsorption process. The lead(II) ion was selected as the model metal and its adsorption by PSX and PSC was characterized. The adsorption capacity was highly dependent on the carbon disulfide/starch and citric acid/starch mole ratios used during preparation. The adsorption behaviors of lead(II) ion on PSXs and PSCs fit both the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity from the Langmuir isotherm equation reached 109.1 and 57.6 mg/g for PSX and PSC when preparation conditions were optimized, and the adsorption times were just 20 and 60 min, respectively. PSX and PSC may be used as effective adsorbents for removal of heavy metals from contaminated liquid. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Use of recombinantly produced 15N3-labelled nicotianamine for fast and sensitive stable isotope dilution ultra-performance liquid chromatography/electrospray ionization time-of-flight mass spectrometry.

PubMed

Schmidt, Holger; Böttcher, Christoph; Trampczynska, Aleksandra; Clemens, Stephan

2011-01-01

Nicotianamine (NA) is an important metal chelator, implicated in the intra- and intercellular trafficking of several transition metal ions in plants. To decipher its roles in physiological processes such as micronutrient acquisition, distribution or storage, fast and sensitive analytical techniques for quantification of this non-proteinogenic amino acid will be required. The use of a recombinant Schizosaccharomyces pombe strain expressing a nicotianamine synthase (NAS) gene allowed for the production of [(15)N(3)]-NA, which was enriched from cell extracts through cation exchange and used for stable isotope dilution analysis of NA. Such an approach should be widely applicable to important bioanalytes that are difficult to synthesize. The analytical procedure comprises mild aqueous extraction and rapid Fmoc derivatization, followed by fast separation using ultra-performance liquid chromatography (UPLC) and sensitive detection by positive ion electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) with a chromatographic cycle time of only 8 min. Derivatization was optimized with respect to incubation time and species suitable for quantification. The limit of detection was 0.14 to 0.23 pmol in biological matrices with the response being linear up to 42 pmol. Recovery rates were between 83% and 104% in various biological matrices including fission yeast cells, fungal mycelium, plant leaves and roots.

Artificial intelligence and regression analysis for Cd(II) ion biosorption from aqueous solution by Gossypium barbadense waste.

PubMed

Fawzy, Manal; Nasr, Mahmoud; Nagy, Heba; Helmi, Shacker

2018-02-01

In this study, batch biosorption experiments were conducted to determine the removal efficiency of Cd(II) ion from aqueous solutions by Gossypium barbadense waste. The biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) connected with energy dispersive X-ray (EDX). The sorption mechanism was described by complexation/chelation of Cd 2+ with the functional groups of O-H, C=O, -COO-, and C-O, as well as, cation-exchange with Mg 2+ and K + . At initial Cd(II) ion concentration (C o ), 50 mg/L, the adsorption equilibrium of 89.2% was achieved after 15 min under the optimum experimental factors of pH 6.0, biosorbent dosage 10 g/L, and particle diameter 0.125-0.25 mm. Both Langmuir and Freundlich models fitted well to the sorption data, suggesting the co-existence of monolayer coverage along with heterogenous surface biosorption. Artificial neural network (ANN) with a structure of 5-10-1 was performed to predict the Cd(II) ion removal efficiency. The ANN model provided high fit (R 2 0.923) to the experimental data and indicated that C o was the most influential input. A pure-quadratic model was developed to determine the effects of experimental factors on Cd(II) ion removal efficiency, which indicated the limiting nature of pH and biosorbent dosage on Cd(II) adsorption. Based on the regression model (R 2 0.873), the optimum experimental factors were pH 7.61, biosorbent dosage 24.74 g/L, particle size 0.125-0.25 mm, and adsorption time 109.77 min, achieving Cd 2+ removal of almost 100% at C o 50 mg/L.

Impact of sodium caseinate concentration and location on magnesium release from multiple W/O/W emulsions.

PubMed

Bonnet, Marie; Cansell, Maud; Placin, Frédéric; Anton, Marc; Leal-Calderon, Fernando

2010-06-15

Water-in-oil-in-water (W/O/W) double emulsions were prepared and the rate of release of magnesium ions from the internal to the external aqueous phase was followed. Sodium caseinate was used not only as a hydrophilic surface-active species but also as a chelating agent able to bind magnesium ions. The release occurred without film rupturing (no coalescence). The kinetics of the release process depended on the location (in only one or in both aqueous compartments) and on the concentration of sodium caseinate. The rate of release increased with the concentration of sodium caseinate in the external phase and decreased when sodium caseinate was present in the inner droplets. The experiments were interpreted within the frame of a mean-field model based on diffusion, integrating the effect of ion binding. The data could be adequately fitted by considering a time-dependent permeation coefficient of the magnesium ions across the oil phase. Our results suggested that ion permeability was influenced by the state of the protein interfacial layers which itself depended on the extent of magnesium binding.

Influence of chelation strength and bacterial uptake of gallium salicylidene acylhydrazide on biofilm formation and virulence of Pseudomonas aeruginosa.

PubMed

Hakobyan, Shoghik; Rzhepishevska, Olena; Björn, Erik; Boily, Jean-François; Ramstedt, Madeleine

2016-07-01

Development of antibiotic resistance in bacteria causes major challenges for our society and has prompted a great need for new and alternative treatment methods for infection. One promising approach is to target bacterial virulence using for example salicylidene acylhydrazides (hydrazones). Hydrazones coordinate metal ions such as Fe(III) and Ga(III) through a five-membered and a six-membered chelation ring. One suggested mode of action is via restricting bacterial Fe uptake. Thus, it was hypothesized that the chelating strength of these substances could be used to predict their biological activity on bacterial cells. This was investigated by comparing Ga chelation strength of two hydrazone complexes, as well as bacterial Ga uptake, biofilm formation, and virulence in the form of production and secretion of a toxin (ExoS) by Pseudomonas aeruginosa. Equilibrium constants for deprotonation and Ga(III) binding of the hydrazone N'-(5-chloro-2-hydroxy-3-methylbenzylidene)-2,4-dihydroxybenzhydrazide (ME0329), with anti-virulence effect against P. aeruginosa, were determined and compared to bacterial siderophores and the previously described Ga(III) 2-oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (Ga-ME0163) and Ga-citrate complexes. In comparison with these two complexes, it was shown that the uptake of Ga(III) was higher from the Ga-ME0329 complex. The results further show that the Ga-ME0329 complex reduced ExoS expression and secretion to a higher extent than Ga-citrate, Ga-ME0163 or the non-coordinated hydrazone. However, the effect against biofilm formation by P. aeruginosa, by the ME0329 complex, was similar to Ga-citrate and lower than what has been reported for Ga-ME0163. Copyright © 2016. Published by Elsevier Inc.

Theranostic Gd(III)-lipid microbubbles for MRI-guided focused ultrasound surgery.

PubMed

Feshitan, Jameel A; Vlachos, Fotis; Sirsi, Shashank R; Konofagou, Elisa E; Borden, Mark A

2012-01-01

We have synthesized a biomaterial consisting of Gd(III) ions chelated to lipid-coated, size-selected microbubbles for utility in both magnetic resonance and ultrasound imaging. The macrocyclic ligand DOTA-NHS was bound to PE headgroups on the lipid shell of pre-synthesized microbubbles. Gd(III) was then chelated to DOTA on the microbubble shell. The reaction temperature was optimized to increase the rate of Gd(III) chelation while maintaining microbubble stability. ICP-OES analysis of the microbubbles determined a surface density of 7.5 × 10(5) ± 3.0 × 10(5) Gd(III)/μm(2) after chelation at 50 °C. The Gd(III)-bound microbubbles were found to be echogenic in vivo during high-frequency ultrasound imaging of the mouse kidney. The Gd(III)-bound microbubbles also were characterized by magnetic resonance imaging (MRI) at 9.4 T by a spin-echo technique and, surprisingly, both the longitudinal and transverse proton relaxation rates were found to be roughly equal to that of no-Gd(III) control microbubbles and saline. However, the relaxation rates increased significantly, and in a dose-dependent manner, after sonication was used to fragment the Gd(III)-bound microbubbles into non-gas-containing lipid bilayer remnants. The longitudinal (r(1)) and transverse (r(2)) molar relaxivities were 4.0 ± 0.4 and 120 ± 18 mM(-1)s(-1), respectively, based on Gd(III) content. The Gd(III)-bound microbubbles may find application in the measurement of cavitation events during MRI-guided focused ultrasound therapy and to track the biodistribution of shell remnants. Copyright © 2011 Elsevier Ltd. All rights reserved.

The National Shipbuilding Research Program. Trailer Mounted Water Recovery and Reuse System

DTIC Science & Technology

2000-11-30

surfactants, and stabilize oil emulsions. • Sequestering or chelating agents bind problematic ions such as calcium or iron, which tend to form deposits on...cleaned parts. • Wetting/emulsifying agents (surfactants) help remove oil from dirty parts and stabilize the removed oil, preventing it from redepositing...neutralized; • The metal-loading can overcome the sequestering agents ’ capacity to keep the metals in solution; and • Oil and grease, if held in the emulsified

Tetraammine(carbonato-κ(2) O,O')cobalt(III) perchlorate.

PubMed

Mohan, Singaravelu Chandra; Jenniefer, Samson Jegan; Muthiah, Packianathan Thomas; Jothivenkatachalam, Kandasamy

2013-01-01

In the title complex, [Co(CO3)(NH3)4]ClO4, both the cation and anion lie on a mirror plane. The Co(III) ion is coordinated by two NH3 ligands and a chelating carbonato ligand in the equatorial sites and by two NH3 groups in the axial sites, forming a distorted octa-hedral geometry. In the crystal, N-H⋯O hydrogen bonds connect the anions and cations, forming a three-dimensional network.

A comparative evaluation of the chelators H4octapa and CHX-A″-DTPA with the therapeutic radiometal (90)Y.

PubMed

Price, Eric W; Edwards, Kimberly J; Carnazza, Kathryn E; Carlin, Sean D; Zeglis, Brian M; Adam, Michael J; Orvig, Chris; Lewis, Jason S

2016-09-01

To compare the radiolabeling performance, stability, and practical efficacy of the chelators CHX-A″-DTPA and H4octapa with the therapeutic radiometal (90)Y. The bifunctional chelators p-SCN-Bn-H4octapa and p-SCN-Bn-CHX-A″-DTPA were conjugated to the HER2-targeting antibody trastuzumab. The resulting immunoconjugates were radiolabeled with (90)Y to compare radiolabeling efficiency, in vitro and in vivo stability, and in vivo performance in a murine model of ovarian cancer. High radiochemical yields (>95%) were obtained with (90)Y-CHX-A″-DTPA-trastuzumab and (90)Y-octapa-trastuzumab after 15min at room temperature. Both (90)Y-CHX-A″-DTPA-trastuzumab and (90)Y-octapa-trastuzumab exhibited excellent in vitro and in vivo stability. Furthermore, the radioimmunoconjugates displayed high tumoral uptake values (42.3±4.0%ID/g for (90)Y-CHX-A″-DTPA-trastuzumab and 30.1±7.4%ID/g for (90)Y-octapa-trastuzumab at 72h post-injection) in mice bearing HER2-expressing SKOV3 ovarian cancer xenografts. Finally, (90)Y radioimmunotherapy studies performed in tumor-bearing mice demonstrated that (90)Y-CHX-A″-DTPA-trastuzumab and (90)Y-octapa-trastuzumab are equally effective therapeutic agents, as treatment with both radioimmunoconjugates yielded substantially decreased tumor growth compared to controls. Ultimately, this work demonstrates that the acyclic chelators CHX-A″-DTPA and H4octapa have comparable radiolabeling, stability, and in vivo performance, making them both suitable choices for applications requiring (90)Y. Copyright © 2016 Elsevier Inc. All rights reserved.

Optimization of Time-Resolved Fluorescence Assay for Detection of Eu-DOTA-labeled Ligand-Receptor Interactions

PubMed Central

De Silva, Channa R.; Vagner, Josef; Lynch, Ronald; Gillies, Robert J.; Hruby, Victor J.

2010-01-01

Lanthanide-based luminescent ligand binding assays are superior to traditional radiolabel assays due to improved sensitivity and affordability in high throughput screening while eliminating the use of radioactivity. Despite significant progress using lanthanide(III)-coordinated chelators such as DTPA derivatives, dissociation-enhanced lanthanide fluoroimmunoassays (DELFIA) have not yet been successfully used with more stable chelators, e.g. DOTA derivatives, due to the incomplete release of lanthanide(III) ions from the complex. Here, a modified and an optimized DELFIA procedure incorporating an acid treatment protocol is introduced for use with Eu(III)-DOTA labeled peptides. Complete release of Eu(III) ions from DOTA labeled ligands was observed using hydrochloric acid (2.0 M) prior to the luminescent enhancement step. NDP-α-MSH labeled with Eu(III)-DOTA was synthesized and the binding affinity to cells overexpressing the human melanocortin-4 receptors (hMC4R) was evaluated using the modified protocol. Binding data indicate that the Eu(III)-DOTA linked peptide bound to these cells with an affinity similar to its DTPA analogue. The modified DELFIA procedure was further used to monitor the binding of an Eu(III)-DOTA labeled heterobivalent peptide to the cells expressing both hMC4R and CCK-2 (Cholecystokinin) receptors. The modified assay provides superior results and is appropriate for high-throughput screening of ligand libraries. PMID:19852924

Evaluation of technetium-99m decay on Escherichia coli inactivation: effects of physical or chemical agents.

PubMed Central

Silva, C. R.; Valsa, J. O.; Caniné, M. S.; Caldeira-de-Araújo, A.; Bernardo-Filho, M.

1998-01-01

Technetium-99m (99mTc) has been used in nuclear medicine and in biomedical research to label molecular and cellular structures employed as radiotracers. Here, we have evaluated, on a DNA repair proficient Escherichia coli strain, the 99mTc decay inactivation and the influence of the (i) pre-treatment with metal ion chelators or of the (ii) treatment with a free radical scavenger on the protection of the cells against the lethal effect of the 99mTc. As SnCl2 is frequently used as a reducing agent in the 99mTc-labeling process, we have also studied the capability of SnCl2 to alter the biological effects induced by the 99mTc decay. As we are exposed to either chemical or physical agents in the nature, we have decided to study a possible influence of the ultraviolet solar radiation in the biological phenomena induced by the 99mTc decay. Our data point out (i) a very important role of the Auger and/or conversion electrons in the cytotoxicity induced by the 99mTc decay; (ii) SnCl2, the metal ion chelators and the free radical scavenger protect the cells against the lethal effect of the 99mTc; and (iii) near-UV does not alter the lethal effect of the 99mTc decay. PMID:9713950

Antioxidants Potential of the Filamentous Fungi (Mucor circinelloides)

PubMed Central

Hussain, Syed Ammar; Yang, Junhuan; Ijaz, Muhammad Umair; Liu, Qing; Song, Yuanda

2017-01-01

Three important strains of Mucor circinelloides grown in complete and minimal media for specified period (72 h, 120 h and 168 h) under submerged fermentation conditions were investigated for their potential antioxidants/secondary metabolite production. All mycelial extracts demonstrated effective antioxidant activities in terms of β-carotene/linoleic acid bleaching, radical scavenging, reduction of metal ions and chelating abilities against ferrous ions. Different extraction methods and solvent systems affected the recovery yield and antioxidant activities of the extracts significantly (p ≤ 0.05). Ethanolic extracts were found to be rich source of antioxidant components and subsequently more effective in antioxidant properties. Fermentation period and media used also significantly affected (p ≤ 0.05) the antioxidant production and the resulting antioxidant properties. The (ethanolic) extracts of all the strains from late exponential growth phase (120 h) showed highest antioxidant production with topmost reducing, chelating and radical scavenging capabilities. Strain MC277.49 was found to be the highest producer of antioxidants followed by MC108.16 and WJ11. Phenolic compounds were detected significantly in higher (p ≤ 0.05) amount succeeded by the condensed tannins and flavonoids. Total phenol content of each extract was attributed to overall antioxidant capacity. Submerged fermentation with nutritional stress conditions were found to be excellent way of producing surplus amount of natural antioxidants/secondary metabolites with their vast potential commercial application in food and pharmaceutical industries. PMID:28991177

Antioxidants Potential of the Filamentous Fungi (Mucor circinelloides).

PubMed

Hameed, Ahsan; Hussain, Syed Ammar; Yang, Junhuan; Ijaz, Muhammad Umair; Liu, Qing; Suleria, Hafiz Ansar Rasul; Song, Yuanda

2017-10-07

Three important strains of Mucor circinelloides grown in complete and minimal media for specified period (72 h, 120 h and 168 h) under submerged fermentation conditions were investigated for their potential antioxidants/secondary metabolite production. All mycelial extracts demonstrated effective antioxidant activities in terms of β-carotene/linoleic acid bleaching, radical scavenging, reduction of metal ions and chelating abilities against ferrous ions. Different extraction methods and solvent systems affected the recovery yield and antioxidant activities of the extracts significantly ( p ≤ 0.05). Ethanolic extracts were found to be rich source of antioxidant components and subsequently more effective in antioxidant properties. Fermentation period and media used also significantly affected ( p ≤ 0.05) the antioxidant production and the resulting antioxidant properties. The (ethanolic) extracts of all the strains from late exponential growth phase (120 h) showed highest antioxidant production with topmost reducing, chelating and radical scavenging capabilities. Strain MC277.49 was found to be the highest producer of antioxidants followed by MC108.16 and WJ11. Phenolic compounds were detected significantly in higher ( p ≤ 0.05) amount succeeded by the condensed tannins and flavonoids. Total phenol content of each extract was attributed to overall antioxidant capacity. Submerged fermentation with nutritional stress conditions were found to be excellent way of producing surplus amount of natural antioxidants/secondary metabolites with their vast potential commercial application in food and pharmaceutical industries.

Armillaria mellea: phenolic content, in vitro antioxidant and antihyperglycemic effects.

PubMed

Zavastin, Daniela Elena; Mircea, Cornelia; Aprotosoaie, Ana Clara; Gherman, Simona; Hancianu, Monica; Miron, Anca

2015-01-01

Armillaria mellea, known as honey mushroom, has been used both as food and medicine. In this work, the ethanolic and hydromethanolic extracts from Armillaria mellea fruiting bodies were investigated for their phenolic content, antioxidant and antihyperglycemic effects (in vitro studies). The total phenolics were quantified using Folin-Ciocalteu assay. The antioxidant activity was evaluated by testing the free radical scavenging capacity, reducing power and ferrous ion chelating ability; in addition, the capacity to inhibit 15-lipoxygenase was also assessed. The antihyperglycemic activity was investigated by α-glucosidase assay. Total phenolic contents of 21.68 ± 0.06 and 5.70 ± 0.28 mg/g were determined in the hydromethanolic and ethanolic extracts, respectively. The hydromethanolic extract showed higher free radical scavenging and reducing abilities (EC50 = 452.6 ± 2.7, 140.57 ± 1.45 and 129.45 ± 0.98 μg/mL in DPPH, ABTS and reducing power assays, respectively). The ethanolic extract proved to be more efficient in the ferrous ion chelation, 15-lipoxygenase and α-glucosidase inhibition assays (EC55 = 67.93 ± 0.35, 290.93 ± 2.05 and 8.54 ± 0.06 μg/mL, respectively). Armillaria mellea extracts showed antioxidant and antihyperglycemic potential in in vitro models and therefore they are promising candidates for the development of dietary supplements and pharmaceutical products.

New glycoside derivatives of carnosine and analogs resistant to carnosinase hydrolysis: synthesis and characterization of their copper(II) complexes.

PubMed

Lanza, Valeria; Bellia, Francesco; D'Agata, Roberta; Grasso, Giuseppe; Rizzarelli, Enrico; Vecchio, Graziella

2011-02-01

Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide widely and abundantly distributed in muscle and nervous tissues of several animal species. Many functions have been proposed for this compound, such as antioxidant and metal ion-chelator properties. However, the main limitation on therapeutic use of carnosine on pathologies related to increased oxidative stress and/or metal ion dishomeostasis is associated with the hydrolysis by the specific dipeptidase carnosinase. Several attempts have been made to overcome this limitation. On this basis, we functionalized carnosine and its amide derivative with small sugars such as glucose and lactose. The resistance of these derivatives to the carnosinase hydrolysis was tested and compared with that of carnosine. We found that the glycoconjugation protects the dipeptide moiety from carnosinase hydrolysis, thus potentially improving the availability of carnosine. The copper(II) binding properties of all the new synthesized compounds were investigated by spectroscopic (UV-Visible and circular dichroism) and ESI-MS studies. Particularly, the new family of amide derivatives that are not significantly hydrolyzed by carnosinase is a very promising class of carnosine derivatives. The sugar moiety can act as a recognition element. These new derivatives are potentially able to act as chelating agents in the development of clinical approaches for the regulation of metal homeostasis in the field of medicinal inorganic chemistry. Copyright © 2010 Elsevier Inc. All rights reserved.

Safety and Efficacy of Combined Chelation Therapy with Deferasirox and Deferoxamine in a Gerbil Model of Iron Overload

PubMed Central

Otto-Duessel, Maya; Brewer, Casey; Gonzalez, Ignacio; Nick, Hanspeter; Wood, John C.

2010-01-01

Introduction Combined therapy with deferoxamine (DFO) and deferasirox (DFX) may be performed empirically when DFX monotherapy fails. Given the lack of published data on this therapy, the study goal was to assess the safety and efficacy of combined DFO/DFX therapy in a gerbil model. Methods Thirty-two female Mongolian gerbils 8–10 weeks old were divided into 4 groups (sham chelated, DFO, DFX, DFO/DFX). Each received 10 weekly injections of 200 mg/kg iron dextran prior to initiation of 12 weeks of chelation. Experimental endpoints were heart and liver weights, iron concentration and histology. Results In the heart, there was no significant difference among the treatment groups for wet-to-dry ratio, iron concentration and iron content. DFX-treated animals exhibited lower organ weights relative to sham-chelated animals (less iron-mediated hypertrophy). DFO-treated organs did not differ from sham-chelated organs in any aspects. DFX significantly cleared hepatic iron. No additive effects were observed in the organs of DFO/DFX-treated animals. Conclusions Combined DFO/DFX therapy produced no detectable additive effect above DFX monotherapy in either the liver or heart, suggesting competition with spontaneous iron elimination mechanisms for chelatable iron. Combined therapy was well tolerated, but its efficacy could not be proven due to limitations in the animal model. PMID:19018129

Activated microporous materials through polymerization of microemulsion precursors

NASA Astrophysics Data System (ADS)

Venkatesan, Arunkumar

Microemulsions have been well studied for their unique characteristics. They are isotropic, thermodynamically stable and microstructured mixtures of oil and water stabilized by one or more surfactant species. They are formed spontaneously and are thermodynamically stable. Microemulsion precursors can be polymerized to make microporous solids with controlled pore structure and sizes. These polymeric solids have been studied extensively in the past. Although the fundamental properties of the microporous solids have been studied in depth, the development of specific applications that will utilize the unique properties of these solids has not been exhaustively researched. The current work establishes the feasibility of making activated microporous solids from microemulsion precursors, by the use of a ligand that chelates metals and also attaches itself to the polymer monolith. It also uses a novel 'in-situ' incorporation by combining the formulation and incorporation steps into one. The research objectives are, to formulate a microemulsion system that can yield useful microporous solids upon polymerization and activation, to characterize these solids using existing techniques available for analysis of similar microporous solids, to identify and understand the effect of the variables in the system and to study the influence of these variables on the performance characteristics of this material. Characterization techniques like Differential Scanning Calorimetry, Thermogravimetric Analysis and Scanning Electron Microscopy were used. A hydroxyethylmethylmethacrylate/methylmethacrylate/aqueous phase containing 10% SDS' system was chosen as the precursor microemulsion and the corresponding microporous solids were made. A metal chelating ligand, Congo Red, was incorporated onto the microporous polymer using NaOH as a binding agent. The ability of the resultant 'activated' microporous solid to remove metal ions from solution, was evaluated. The metal ion chosen was chromium and the influence of variables such as NaOH loading, Congo Red loading, Cross linker content etc. were studied. It was found that the microporous solids were effective in removing chromium from solution. They outperformed similar polymeric solids with ligands (reported in literature) in chromium removal. A removal of about 1500 micro moles of chromium ions per gram of dry polymer from a solution of 5 mMol/L initial concentration of chromium was observed. This is much more than the removal of 340 micro moles/gram of dry polymer reported in literature for comparable non-microporous systems.

Enhanced conjugation stability and blood circulation time of macromolecular gadolinium-DTPA contrast agent.

PubMed

Jenjob, Ratchapol; Kun, Na; Ghee, Jung Yeon; Shen, Zheyu; Wu, Xiaoxia; Cho, Steve K; Lee, Don Haeng; Yang, Su-Geun

2016-04-01

In this study, we prepared macromolecular MR T1 contrast agent: pullulan-conjugated Gd diethylene triamine pentaacetate (Gd-DTPA-Pullulan) and estimated residual free Gd(3+), chelation stability in competition with metal ions, plasma and tissue pharmacokinetics, and abdominal MR contrast on rats. Residual free Gd(3+) in Gd-DTPA-Pullulan was measured using colorimetric spectroscopy. The transmetalation of Gd(3+) incubated with Ca(2+) was performed by using a dialysis membrane (MWCO 100-500 Da) and investigated by ICP-OES. The plasma concentration profiles of Gd-DTPA-Pullulan were estimated after intravenous injection at a dose 0.1 mmol/kg of Gd. The coronal-plane abdominal images of normal rats were observed by MR imaging. The content of free Gd(3+), the toxic residual form, was less than 0.01%. Chelation stability of Gd-DTPA-Pullulan was estimated, and only 0.2% and 0.00045% of Gd(3+) were released from Gd-DTPA-Pullulan after 2h incubation with Ca(2+) and Fe(2+), respectively. Gd-DTPA-Pullulan displayed the extended plasma half-life (t1/2,α=0.43 h, t1/2,β=2.32 h), much longer than 0.11h and 0.79 h of Gd-EOB-DTPA. Abdominal MR imaging showed Gd-DTPA-Pullulan maintained initial MR contrast for 30 min. The extended plasma half-life of Gd-DTPA-Pullulan probably allows the prolonged MR acquisition time in clinic with enhanced MR contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

Assessment of Antioxidant and Phenolic Compound Concentrations as well as Xanthine Oxidase and Tyrosinase Inhibitory Properties of Different Extracts of Pleurotus citrinopileatus Fruiting Bodies

PubMed Central

Alam, Nuhu; Yoon, Ki Nam; Lee, Kyung Rim; Kim, Hye Young; Shin, Pyung Gyun; Cheong, Jong Chun; Yoo, Young Bok; Shim, Mi Ja; Lee, Min Woong

2011-01-01

Cellular damage caused by reactive oxygen species has been implicated in several diseases, thus establishing a significant role for antioxidants in maintaining human health. Acetone, methanol, and hot water extracts of Pleurotus citrinopileatus were evaluated for their antioxidant activities against β-carotene-linoleic acid and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, reducing power, ferrous ion-chelating abilities, and xanthine oxidase inhibitory activities. In addition, the tyrosinase inhibitory effects and phenolic compound contents of the extracts were also analyzed. Methanol and acetone extracts of P. citrinopileatus showed stronger inhibition of β-carotene-linoleic acid compared to the hot water extract. Methanol extract (8 mg/mL) showed a significantly high reducing power of 2.92 compared to the other extracts. The hot water extract was more effective than the acetone and methanole extracts for scavenging DPPH radicals. The strongest chelating effect (92.72%) was obtained with 1.0 mg/mL of acetone extract. High performance liquid chromatography analysis detected eight phenolic compounds, including gallic acid, protocatechuic acid, chlorogenic acid, ferulic acid, naringenin, hesperetin, formononetin, and biochanin-A, in an acetonitrile and hydrochloric acid (5 : 1) solvent extract. Xanthine oxidase and tyrosinase inhibitory activities of the acetone, methanol, and hot water extracts increased with increasing concentration. This study suggests that fruiting bodies of P. citrinopileatus can potentially be used as a readily accessible source of natural antioxidants. PMID:22783067

DFT calculations, spectroscopy and antioxidant activity studies on (E)-2-nitro-4-[(phenylimino)methyl]phenol

NASA Astrophysics Data System (ADS)

Temel, Ersin; Alaşalvar, Can; Gökçe, Halil; Güder, Aytaç; Albayrak, Çiğdem; Alpaslan, Yelda Bingöl; Alpaslan, Gökhan; Dilek, Nefise

2015-02-01

We have reported synthesis and characterization of (E)-2-nitro-4-[(phenylimino)methyl]phenol by using X-ray crystallographic method, FT-IR and UV-vis spectroscopies and density functional theory (DFT). Optimized geometry and vibrational frequencies of the title compound in the ground state have been computed by using B3LYP with the 6-311G+(d,p) basis set. HOMO-LUMO energy gap, Non-linear optical properties and NBO analysis of the compound are performed at B3LYP/6-311G+(d,p) level. Additionally, as remarkable properties, antioxidant activity of the title compound (CMPD) has been determined by using different antioxidant test methods i.e. ferric reducing antioxidant power (FRAP), hydrogen peroxide scavenging (HPSA), free radical scavenging (FRSA) and ferrous ion chelating activities (FICA). When compared with standards (BHA, BHT, and α-tocopherol), we have concluded that CPMD has effective FRAP, HPSA, FRSA and FICA.

Theoretical, spectroscopic and antioxidant activity studies on (E)-2-[(2-fluorophenylimino)methyl]-4-hydroxyphenol and (E)-2-[(3-fluorophenylimino)methyl]-4-hydroxyphenol compounds

NASA Astrophysics Data System (ADS)

Alaşalvar, Can; Güder, Aytaç; Gökçe, Halil; Albayrak Kaştaş, Çiğdem; Çatak Çelik, Raziye

2017-04-01

We studied synthesis and characterization of the title compounds by using X-ray crystallographic technique, FT-IR spectroscopy, UV-Vis spectroscopy and Density functional method. Optimized geometry, vibrational frequencies and UV-Vis parameters of the title compounds in the ground state have been calculated by using B3LYP with the 6-311G+ (d,p) basis set. HOMO - LUMO energy gap, Non-linear optical properties are performed at B3LYP/6-311G+(d,p) level. For determination of antioxidant properties of the title compounds (CMPD1 and CMPD2) have been investigated by using different methods, i.e. ferric reducing antioxidant power (FRAP), hydrogen peroxide scavenging (HPSA), free radical scavenging (FRSA) and ferrous ion chelating activities (FICA). In comparison with standard antioxidants (BHA, BHT, and α-tocopherol), CPMD1 and CMPD2 have influential FRAP, HPSA, FRSA and FICA.

Method of removing oxides of sulfur and oxides of nitrogen from exhaust gases

DOEpatents

Walker, Richard J.

1986-01-01

A continuous method is presented for removing both oxides of sulfur and oxides of nitrogen from combustion or exhaust gases with the regeneration of the absorbent. Exhaust gas is cleaned of particulates and HCl by a water scrub prior to contact with a liquid absorbent that includes an aqueous solution of bisulfite and sulfite ions along with a metal chelate, such as, an iron or zinc aminopolycarboxylic acid. Following contact with the combustion gases the spent absorbent is subjected to electrodialysis to transfer bisulfite ions into a sulfuric acid solution while splitting water with hydroxide and hydrogen ion migration to equalize electrical charge. The electrodialysis stack includes alternate layers of anion selective and bipolar membranes. Oxides of nitrogen are removed from the liquid absorbent by air stripping at an elevated temperature and the regenerated liquid absorbent is returned to contact with exhaust gases for removal of sulfur oxides and nitrogen oxides.

Thermodynamics of Pb(ii) and Zn(ii) binding to MT-3, a neurologically important metallothionein.

PubMed

Carpenter, M C; Shami Shah, A; DeSilva, S; Gleaton, A; Su, A; Goundie, B; Croteau, M L; Stevenson, M J; Wilcox, D E; Austin, R N

2016-06-01

Isothermal titration calorimetry (ITC) was used to quantify the thermodynamics of Pb(2+) and Zn(2+) binding to metallothionein-3 (MT-3). Pb(2+) binds to zinc-replete Zn7MT-3 displacing each zinc ion with a similar change in free energy (ΔG) and enthalpy (ΔH). EDTA chelation measurements of Zn7MT-3 and Pb7MT-3 reveal that both metal ions are extracted in a tri-phasic process, indicating that they bind to the protein in three populations with different binding thermodynamics. Metal binding is entropically favoured, with an enthalpic penalty that reflects the enthalpic cost of cysteine deprotonation accompanying thiolate ligation of the metal ions. These data indicate that Pb(2+) binding to both apo MT-3 and Zn7MT-3 is thermodynamically favourable, and implicate MT-3 in neuronal lead biochemistry.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-01

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)—a chelating agent of copper II ions—was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

Tris{2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolate-κ2 O,O′}tris­(thio­cyanato-κN)europium(III)

PubMed Central

Liu, Jian-Feng; Liu, Jia-Lu; Zhao, Guo-Liang

2009-01-01

The metal center in the structure of the title compound, [Eu(NCS)3(C15H15NO2)3], is coordinated by three Schiff base 2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolate (L) ligands and three independent thio­cyanate ions. In the crystal structure, the acidic H atom is located on the Schiff base N atom and hydrogen bonded to the phenolate O atom. The coordination environment of the EuIII ion is nine-coordinate by three chelating methoxy­phenolate pairs of O atoms and three N-atom terminals of the thio­cyanate ions. The compound is isostructural with the CeIII analogue [Liu et al. (2009 ▶). Acta Cryst. E65, m650]. PMID:21578663

Anti-inflammatory drugs interacting with Zn(II), Cd(II) and Pt(II) metal ions.

PubMed

Dendrinou-Samara, C; Tsotsou, G; Ekateriniadou, L V; Kortsaris, A H; Raptopoulou, C P; Terzis, A; Kyriakidis, D A; Kessissoglou, D P

1998-09-01

Complexes of Zn(II), Cd(II) and Pt(II) metal ions with the anti-inflammatory drugs, 1-methyl-5-(p-toluoyl)-1H-pyrrole-2-acetic acid (Tolmetin), alpha-methyl-4-(2-methylpropyl)benzeneacetic acid (Ibuprofen), 6-methoxy-alpha-methylnaphthalene-2-acetic acid (Naproxen) and 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid (indomethacin) have been synthesized and characterized. In the structurally characterized Cd(naproxen)2 complex the anti-inflammatory drugs acts as bidentate chelate ligand coordinatively bound to metal ions through the deprotonated carboxylate group. Crystal data for 1: [C32H26O8Cd], orthorhombic, space group P22(1)2(1), a = 5.693(2) (A), b = 8.760(3) (A), c = 30.74(1) (A), V = 1533(1) A3, Z = 2. Antibacterial and growth inhibitory activity is higher than that of the parent ligands or the platinum(II) diamine compounds.

Method of producing catalytic material for fabricating nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seals, Roland D.; Menchhofer, Paul A.; Howe, Jane Y.

Methods of fabricating nano-catalysts are described. In some embodiments the nano-catalyst is formed from a powder-based substrate material and is some embodiments the nano-catalyst is formed from a solid-based substrate material. In some embodiments the substrate material may include metal, ceramic, or silicon or another metalloid. The nano-catalysts typically have metal nanoparticles disposed adjacent the surface of the substrate material. The methods typically include functionalizing the surface of the substrate material with a chelating agent, such as a chemical having dissociated carboxyl functional groups (--COO), that provides an enhanced affinity for metal ions. The functionalized substrate surface may then bemore » exposed to a chemical solution that contains metal ions. The metal ions are then bound to the substrate material and may then be reduced, such as by a stream of gas that includes hydrogen, to form metal nanoparticles adjacent the surface of the substrate.« less

NMR spectroscopy of Group 13 metal ions: biologically relevant aspects.

PubMed

André, J P; Mäcke, H R

2003-12-01

In spite of the fact that Group 13 metal ions (Al(3+), Ga(3+), In(3+) and Tl(+/3+)) show no main biological role, they are NMR-active nuclides which can be used in magnetic resonance spectroscopy of biologically relevant systems. The fact that these metal ions are quadrupolar (with the exception of thallium) means that they are particularly sensitive to ligand type and coordination geometry. The line width of the NMR signals of their complexes shows a strong dependence on the symmetry of coordination, which constitutes an effective tool in the elucidation of structures. Here we report published NMR studies of this family of elements, applied to systems of biological importance. Special emphasis is given to binding studies of these cations to biological molecules, such as proteins, and to chelating agents of radiopharmaceutical interest. The possibility of in vivo NMR studies is also stressed, with extension to (27)Al-based MRI (magnetic resonance imaging) experiments.

Method of producing catalytic materials for fabricating nanostructures

DOEpatents

Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

2013-02-19

Methods of fabricating nano-catalysts are described. In some embodiments the nano-catalyst is formed from a powder-based substrate material and is some embodiments the nano-catalyst is formed from a solid-based substrate material. In some embodiments the substrate material may include metal, ceramic, or silicon or another metalloid. The nano-catalysts typically have metal nanoparticles disposed adjacent the surface of the substrate material. The methods typically include functionalizing the surface of the substrate material with a chelating agent, such as a chemical having dissociated carboxyl functional groups (--COO), that provides an enhanced affinity for metal ions. The functionalized substrate surface may then be exposed to a chemical solution that contains metal ions. The metal ions are then bound to the substrate material and may then be reduced, such as by a stream of gas that includes hydrogen, to form metal nanoparticles adjacent the surface of the substrate.

Preparation and Adsorption Property of Imido-acetic Acid Type Chelating Nano-fibers by Electro-spinning Technique

NASA Astrophysics Data System (ADS)

Yang, Jiali; Lu, Lansi; Zhang, Zhu; Liao, Minhui; He, Huirong; Li, Lingxing; Chen, Jida; Chen, Shijin

2017-12-01

A novel nano-fibrous adsorbent from imino-acetic acid (IDA) and polyvinyl alcohol (PVA) mixture solution was prepared by electro-spinning technique. The nano-fibrous adsorbents with imino-acetic acid functional groups were characterized and demonstrated by fourier transform infrared spectrometry (FT-IR) and the scanning electron microscopy (SEM). The effect of the adsorbents to remove heavy metals such as lead (Pb) and copper (Cu) ions from the aqueous solution was studied. The maximum adsorption percentage (SP) of the metal ions can reach 93.08% for Cu (II) and 96.69% for Pb(II), respectively. Furthermore, it shows that the adsorption procedure of the adsorbents is spontaneous and endothermic, and adsorption rate fits well with pseudo-second-order kinetic model. Most importantly, the reusability of the nanofibers for removal of metal ions was also demonstrated to be used at least five times.

Methylene-bis[(aminomethyl)phosphinic acids]: synthesis, acid-base and coordination properties.

PubMed

David, Tomáš; Procházková, Soňa; Havlíčková, Jana; Kotek, Jan; Kubíček, Vojtěch; Hermann, Petr; Lukeš, Ivan

2013-02-21

Three symmetrical methylene-bis[(aminomethyl)phosphinic acids] bearing different substituents on the central carbon atom, (NH(2)CH(2))PO(2)H-C(R(1))(R(2))-PO(2)H(CH(2)NH(2)) where R(1) = OH, R(2) = Me (H(2)L(1)), R(1) = OH, R(2) = Ph (H(2)L(2)) and R(1),R(2) = H (H(2)L(3)), were synthesized. Acid-base and complexing properties of the ligands were studied in solution as well as in the solid state. The ligands show unusually high basicity of the nitrogen atoms (log K(1) = 9.5-10, log K(2) = 8.5-9) if compared with simple (aminomethyl)phosphinic acids and, consequently, high stability constants of the complexes with studied divalent metal ions. The study showed the important role of the hydroxo group attached to the central carbon atom of the geminal bis(phosphinate) moiety. Deprotonation of the hydroxo group yields the alcoholate anion which tends to play the role of a bridging ligand and induces formation of polynuclear complexes. Solid-state structures of complexes [H(2)N=C(NH(2))(2)][Cu(2)(H(-1)L(2))(2)]CO(3)·10H(2)O and Li(2)[Co(4)(H(-1)L(1))(3)(OH)]·17.5H(2)O were determined by X-ray diffraction. The complexes show unexpected geometries forming dinuclear and cubane-like structures, respectively. The dinuclear copper(II) complex contains a bridging μ(2)-alcoholate group with the (-)O-P(=O)-CH(2)-NH(2) fragments of each ligand molecule chelated to the different central ion. In the cubane cobalt(II) complex, one μ(3)-hydroxide and three μ(3)-alcoholate anions are located in the cube vertices and both phosphinate groups of one ligand molecule are chelating the same cobalt(II) ion while each of its amino groups are bound to different neighbouring metal ions. All such three metal ions are bridged by the alcoholate group of a given ligand.

Metal-dependent hydrolysis of myelin basic protein by IgGs from the sera of patients with multiple sclerosis.

PubMed

Polosukhina, Dar'ya I; Kanyshkova, Tat'yana G; Doronin, Boris M; Tyshkevich, Olga B; Buneva, Valentina N; Boiko, Alexey N; Gusev, Evgenii I; Nevinsky, Georgy A; Favorova, Olga O

2006-02-28

Homogeneous IgG fractions were obtained by chromatography of the sera of patients with multiple sclerosis (MS) on Protein G-Sepharose under conditions that remove non-specifically bound proteins. These IgGs contained several chelated metals, the relative amount of which decreases in the order: Fe>or=Ca>Cu>or=Zn>or=Mg>or=Mn>or=Pb>or=Co>or=Ni. In contrast to homogeneous IgGs of healthy individuals, Abs of MS patients effectively hydrolyzed human myelin basic protein (MBP). A minor metal-dependent fraction was obtained by chromatography of highly purified IgGs from MS patient on Chelex-100. This IgG fraction did not hydrolyze human MBP in the absence of Me(2+) ions but was activated after addition of Me(2+) ions: Mg(2+)>Mn(2+)>Cu(2+)>Ca(2+). Proteolytic activities of IgGs from other MS patients were also activated by other metal ions (Ni(2+), Fe(2+), Co(2+), Zn(2+), Pb(2+), and Co(2+)) and especially Ni(2+). Ni(2+)-activated IgGs were separated into distinct MBP-hydrolyzing fractions by chromatography on HiTraptrade mark Chelating Sepharose charged with Ni(2+). Detection of Mg(2+)-dependent proteolytic activity in the SDS-PAGE area corresponding only to IgG provided direct evidence that IgG from sera of MS patients possesses metal-dependent human MBP-hydrolyzing activity. Observed properties of MS abzymes distinguish them from other known mammalian metalloproteases and demonstrate their pronounced catalytic diversity. Metal-dependent IgGs from MS patients represent the first example of abzymes with metal-dependent proteolytic activity.

Equilibrium binding behavior of magnesium to wall teichoic acid.

PubMed

Thomas, Kieth J; Rice, Charles V

2015-10-01

Peptidoglycan and teichoic acids are the major cell wall components of Gram-positive bacteria that obtain and sequester metal ions required for biochemical processes. The delivery of metals to the cytoplasmic membrane is aided by anionic binding sites within the peptidoglycan and along the phosphodiester polymer of teichoic acid. The interaction with metals is a delicate balance between the need for attraction and ion diffusion to the membrane. Likewise, metal chelation from the extracellular fluid must initially have strong binding energetics that weaken within the cell wall to enable ion release. We employed atomic absorption and equilibrium dialysis to measure the metal binding capacity and metal binding affinity of wall teichoic acid and Mg2+. Data show that Mg2+ binds to WTA with a 1:2Mg2+ to phosphate ratio with a binding capacity of 1.27 μmol/mg. The affinity of Mg2+ to WTA was also found to be 41×10(3) M(-1) at low metal concentrations and 1.3×10(3) M(-1) at higher Mg2+ concentrations due to weakening electrostatic effects. These values are lower than the values describing Mg2+ interactions with peptidoglycan. However, the binding capacity of WTA is 4 times larger than peptidoglycan. External WTA initially binds metals with positive cooperativity, but metal binding switches to negative cooperativity, whereas interior WTA binds metals with only negative cooperativity. The relevance of this work is to describe changes in metal binding behavior depending on environment. When metals are sparse, chelation is strong to ensure survival yet the binding weakens when essential minerals are abundant. Copyright © 2015 Elsevier B.V. All rights reserved.

Impact of metal binding on the antitumor activity and cellular imaging of a metal chelator cationic imidazopyridine derivative.

PubMed

Roy, Mithun; Chakravarthi, Balabhadrapatruni V S K; Jayabaskaran, Chelliah; Karande, Anjali A; Chakravarty, Akhil R

2011-05-14

A new water soluble cationic imidazopyridine species, viz. (1E)-1-((pyridin-2-yl)methyleneamino)-3-(3-(pyridin-2-yl)imidazo[1,5-a]pyridin-2(3H)-yl)propan-2-ol (1), as a metal chelator is prepared as its PF(6) salt and characterized. Compound 1 shows fluorescence at 438 nm on excitation at 342 nm in Tris-HCl buffer giving a fluorescence quantum yield (φ) of 0.105 and a life-time of 5.4 ns. Compound 1, as an avid DNA minor groove binder, shows pUC19 DNA cleavage activity in UV-A light of 365 nm forming singlet oxygen species in a type-II pathway. The photonuclease potential of 1 gets enhanced in the presence of Fe(2+), Cu(2+) or Zn(2+). Compound 1 itself displays anticancer activity in HeLa, HepG2 and Jurkat cells with an enhancement on addition of the metal ions. Photodynamic effect of 1 at 365 nm also gets enhanced in the presence of Fe(2+) and Zn(2+). Fluorescence-based cell cycle analysis shows a significant dead cell population in the sub-G1 phase of the cell cycle suggesting apoptosis via ROS generation. A significant change in the nuclear morphology is observed from Hoechst 33258 and an acridine orange/ethidium bromide (AO/EB) dual nuclear staining suggesting apoptosis in cells when treated with 1 alone or in the presence of the metal ions. Apoptosis is found to be caspase-dependent. Fluorescence imaging to monitor the distribution of 1 in cells shows that 1 in the presence of metal ions accumulates predominantly in the cytoplasm. Enhanced uptake of 1 into the cells within 12 h is observed in the presence of Fe(2+) and Zn(2+).

Trace element uptake and distribution in plants.

PubMed

Graham, Robin D; Stangoulis, James C R

2003-05-01

There are similarities between mammals and plants in the absorption and transport of trace elements. The chemistry of trace element uptake from food sources in both cases is based on the thermodynamics of adsorption on charged solid surfaces embedded in a solution phase of charged ions and metal-binding ligands together with redox systems in the case of iron and some other elements. Constitutive absorption systems function in nutrient uptake during normal conditions, and inducible "turbo" systems increase the supply of a particular nutrient during deficiency. Iron uptake is the most studied of the micronutrients, and divides the plant kingdom into two groups: dicotyledonous plants have a turbo system that is an upregulated version of the constitutive system, which consists of a membrane-bound reductase and an ATP-driven hydrogen ion extrusion pump; and monocotyledonous plants have a constitutive system similar to that of the dicots, but with an inducible system remarkably different that uses the mugeneic acid class of phytosiderophores (PS). The PS system may in fact be an important port of entry for iron from an iron-rich but exceedingly iron-insoluble lithosphere into the iron-starved biosphere. Absorption of trace metals in these graminaceous plants is normally via divalent ion channels after reduction in the plasma membrane. Once absorbed, iron can be stored in plants as phytoferritin or transported to active sites by transport-specific ligands. The transport of iron and zinc into seeds is dominated by the phloem sap system, which has a high pH that requires chelation of heavy metals. Loading into grains involves three or four genes each that control chelation, membrane transport and deposition as phytate.

Cuprizone Intoxication Induces Cell Intrinsic Alterations in Oligodendrocyte Metabolism Independent of Copper Chelation.

PubMed

Taraboletti, Alexandra; Walker, Tia; Avila, Robin; Huang, He; Caporoso, Joel; Manandhar, Erendra; Leeper, Thomas C; Modarelli, David A; Medicetty, Satish; Shriver, Leah P

2017-03-14

Cuprizone intoxication is a common animal model used to test myelin regenerative therapies for the treatment of diseases such as multiple sclerosis. Mice fed this copper chelator develop reversible, region-specific oligodendrocyte loss and demyelination. While the cellular changes influencing the demyelinating process have been explored in this model, there is no consensus about the biochemical mechanisms of toxicity in oligodendrocytes and about whether this damage arises from the chelation of copper in vivo. Here we have identified an oligodendroglial cell line that displays sensitivity to cuprizone toxicity and performed global metabolomic profiling to determine biochemical pathways altered by this treatment. We link these changes with alterations in brain metabolism in mice fed cuprizone for 2 and 6 weeks. We find that cuprizone induces widespread changes in one-carbon and amino acid metabolism as well as alterations in small molecules that are important for energy generation. We used mass spectrometry to examine chemical interactions that are important for copper chelation and toxicity. Our results indicate that cuprizone induces global perturbations in cellular metabolism that may be independent of its copper chelating ability and potentially related to its interactions with pyridoxal 5'-phosphate, a coenzyme essential for amino acid metabolism.

Wound healing by topical application of antioxidant iron chelators: kojic acid and deferiprone.

PubMed

Mohammadpour, Mehrdad; Behjati, Mohaddeseh; Sadeghi, Amir; Fassihi, Afshin

2013-06-01

Kojic acid and deferiprone are iron chelators used for skin lightening and iron-overload treatment, respectively. As iron chelation and free radical scavenging are principal factors for wound healing, it was hypothesised that the local application of these compounds might accelerate wound healing in rats. Ointments of 3%, 6% and 9% of deferiprone and kojic acid were prepared and topical treatment was performed on in vivo wound models for 12 days twice in day for test and control groups. Topical treatment with 3%, 6% and 9% showed significant improvement in wound healing after 4 days (P < 0·001). Topical application of 3% and 6% deferiprone enhanced wound healing after 8 days (P < 0·026 and P < 0·001, respectively). Accelerated wound healing was seen using 3% and 6% deferiprone after 12 days (P = 0·003 and P < 0·001, respectively). DPPH scavenging assay was also performed to compare the antioxidant potencies of kojic acid and deferiprone. Deferiprone had more free radical scavenging power than kojic acid. Generally, deferiprone topical treatment, accelerated wound healing more than kojic acid because of its higher antioxidant and iron chelation abilities. © 2012 The Authors. International Wound Journal © 2012 John Wiley & Sons Ltd and Medicalhelplines.com Inc.

The ALMT Family of Organic Acid Transporters in Plants and Their Involvement in Detoxification and Nutrient Security.

PubMed

Sharma, Tripti; Dreyer, Ingo; Kochian, Leon; Piñeros, Miguel A

2016-01-01

About a decade ago, members of a new protein family of anion channels were discovered on the basis of their ability to confer on plants the tolerance toward toxic aluminum ions in the soil. The efflux of Al 3+ -chelating malate anions through these channels is stimulated by external Al 3+ ions. This feature of a few proteins determined the name of the entire protein family as Aluminum-activated Malate Transporters (ALMT). Meanwhile, after several years of research, it is known that the physiological roles of ALMTs go far beyond Al-detoxification. In this review article we summarize the current knowledge on this transporter family and assess their involvement in diverse physiological processes.

The ALMT Family of Organic Acid Transporters in Plants and Their Involvement in Detoxification and Nutrient Security

PubMed Central

Sharma, Tripti; Dreyer, Ingo; Kochian, Leon; Piñeros, Miguel A.

2016-01-01

About a decade ago, members of a new protein family of anion channels were discovered on the basis of their ability to confer on plants the tolerance toward toxic aluminum ions in the soil. The efflux of Al3+-chelating malate anions through these channels is stimulated by external Al3+ ions. This feature of a few proteins determined the name of the entire protein family as Aluminum-activated Malate Transporters (ALMT). Meanwhile, after several years of research, it is known that the physiological roles of ALMTs go far beyond Al-detoxification. In this review article we summarize the current knowledge on this transporter family and assess their involvement in diverse physiological processes. PMID:27757118

Physicochemical, antioxidant, DNA cleaving properties and antimicrobial activity of fisetin-copper chelates.

PubMed

Łodyga-Chruscińska, Elżbieta; Pilo, Maria; Zucca, Antonio; Garribba, Eugenio; Klewicka, Elżbieta; Rowińska-Żyrek, Magdalena; Symonowicz, Marzena; Chrusciński, Longin; Cheshchevik, Vitalij T

2018-03-01

Fisetin (3,3',4',7-tetrahydroxyflavone) metal chelates are of interest as this plant polyphenol has revealed broad prospects for its use as natural medicine in the treatment of various diseases. Metal interactions may change or enhance fisetin biological properties so understanding fisetin metal chelation is important for its application not only in medicine but also as a food additive in nutritional supplements. This work was aimed to determine and characterize copper complexes formed in different pH range at applying various metal/ligand ratios. Fisetin and Cu(II)-fisetin complexes were characterized by potentiometric titrations, UV-Vis (Ultraviolet-visible spectroscopy), EPR, ESI-MS, FTIR and cyclic voltammetry. Their effects on DNA were investigated by using circular dichroism, spectrofluorimetry and gel electrophoresis methods. The copper complex with the ratio of Cu(II)/fisetin 1/2 exhibited significant DNA cleavage activity, followed by complete degradation of DNA. The influence of copper(II) ions on antioxidant activity of fisetin in vitro has been studied using DPPH, ABTS and mitochondrial assays. The results have pointed out that fisetin or copper complexes can behave both as antioxidants or pro-oxidants. Antimicrobial activity of the compounds has been investigated towards several bacteria and fungi. The copper complex of Cu(II)/fisetin 1/2 ratio showed higher antagonistic activity against bacteria comparing to the ligand and it revealed a promising antifungal activity. Copyright © 2017 Elsevier Inc. All rights reserved.

Improvement of dexamethasone sensitivity by chelation of intracellular Ca2+ in pediatric acute lymphoblastic leukemia cells through the prosurvival kinase ERK1/2 deactivation.

PubMed

Abdoul-Azize, Souleymane; Dubus, Isabelle; Vannier, Jean-Pierre

2017-04-18

Previous studies have demonstrated that glucocorticoid hormones, including dexamethasone, induced alterations in intracellular calcium homeostasis in acute lymphoblastic leukemia (ALL) cells. However, the mechanism by which intracellular calcium homeostasis participates in dexamethasone sensitivity and resistance on ALL cells remains elusive. Here, we found that treatment of cells with dexamethasone resulted in increased intracellular calcium concentrations through store-operated calcium entry stimulation, which was curtailed by store-operated calcium channel blockers. We show that BAPTA-AM, an intracellular Ca2+ chelator, synergistically enhances dexamethasone lethality in two human ALL cell lines and in three primary specimens. This effect correlated with the inhibition of the prosurvival kinase ERK1/2 signaling pathway. Chelating intracellular calcium with Bapta-AM or inhibiting ERK1/2 with PD98059 significantly potentiated dexamethasone-induced mitochondrial membrane potential collapse, reactive oxygen species production, cytochrome c release, caspase-3 activity, and cell death. Moreover, we show that thapsigargin elevates intracellular free calcium ion level, and activates ERK1/2 signaling, resulting in the inhibition of dexamethasone-induced ALL cells apoptosis. Together, these results indicate that calcium-related ERK1/2 signaling pathway contributes to protect cells from dexamethasone sensitivity by limiting mitochondrial apoptotic pathway. This report provides a novel resistance pathway underlying the regulatory effect of dexamethasone on ALL cells.

Improvement of dexamethasone sensitivity by chelation of intracellular Ca2+ in pediatric acute lymphoblastic leukemia cells through the prosurvival kinase ERK1/2 deactivation

PubMed Central

Abdoul-Azize, Souleymane; Dubus, Isabelle; Vannier, Jean-Pierre

2017-01-01

Previous studies have demonstrated that glucocorticoid hormones, including dexamethasone, induced alterations in intracellular calcium homeostasis in acute lymphoblastic leukemia (ALL) cells. However, the mechanism by which intracellular calcium homeostasis participates in dexamethasone sensitivity and resistance on ALL cells remains elusive. Here, we found that treatment of cells with dexamethasone resulted in increased intracellular calcium concentrations through store-operated calcium entry stimulation, which was curtailed by store-operated calcium channel blockers. We show that BAPTA-AM, an intracellular Ca2+ chelator, synergistically enhances dexamethasone lethality in two human ALL cell lines and in three primary specimens. This effect correlated with the inhibition of the prosurvival kinase ERK1/2 signaling pathway. Chelating intracellular calcium with Bapta-AM or inhibiting ERK1/2 with PD98059 significantly potentiated dexamethasone-induced mitochondrial membrane potential collapse, reactive oxygen species production, cytochrome c release, caspase-3 activity, and cell death. Moreover, we show that thapsigargin elevates intracellular free calcium ion level, and activates ERK1/2 signaling, resulting in the inhibition of dexamethasone-induced ALL cells apoptosis. Together, these results indicate that calcium-related ERK1/2 signaling pathway contributes to protect cells from dexamethasone sensitivity by limiting mitochondrial apoptotic pathway. This report provides a novel resistance pathway underlying the regulatory effect of dexamethasone on ALL cells. PMID:28423696

Effect of Chelating Agents on the Stability of Nano-TiO2 Sol Particles for Sol-Gel Coating.

PubMed

Maeng, Wan Young; Yoo, Mi

2015-11-01

Agglomeration of sol particles in a titanium alkoxide (tetrabutyl orthotitanate (TBOT), > 97%) solution during the hydrolysis and condensation steps makes the sol solution difficult to use for synthesizing homogeneous sol-gel coating. Here, we have investigated the effect of stabilizing agents (acetic acid and ethyl acetoacetate (EAcAc)) on the agglomeration of Ti alkoxide particles during hydrolysis and condensation in order to determine the optimized conditions for controlling the precipitation of TiO2 particles. The study was conducted at R(AC) ([acetic acid]/[TBOT]) = 0.1-5 and R(EAcAc)([EAcAc]/[TBOT]) = 0.05-0.65. We also studied the effects of a basic catalyst ethanolamine (ETA), water, and HCl on sol stability. The chelating ligands in the precursor sol were analyzed with FT-IR. The coating properties were examined by focused ion beam. The stabilizing agents (acetic acid and EAcAc) significantly influenced the agglomeration and precipitation of TBOT precursor particles during hydrolysis. As R(AC) and R(EAcAc) increased, the agglomeration remarkably decreased. The stability of the sol with acetic acid and EAcAc arises from the coordination of the chelating ligand to TBOT that hinders hydrolysis and condensation. A uniform fine coating (thickness: 30 nm) on stainless steel was obtained by using an optimized sol with R(AC) = 0.5 and R(EAcAc) = 0.65.

Highly Efficient Interception and Precipitation of Uranium(VI) from Aqueous Solution by Iron-Electrocoagulation Combined with Cooperative Chelation by Organic Ligands.

PubMed

Li, Peng; Zhun, Bao; Wang, Xuegang; Liao, PingPing; Wang, Guanghui; Wang, Lizhang; Guo, Yadan; Zhang, Weimin

2017-12-19

A new strategy combining iron-electrocoagulation and organic ligands (OGLs) cooperative chelation was proposed to screen and precipitate low concentrations (0-18.52 μmol/L) of uranium contaminant in aqueous solution. We hypothesized that OGLs with amino, hydroxyl, and carboxyl groups hydrophobically/hydrophilically would realize precuring of uranyl ion at pH < 3.0, and the following iron-electrocoagulation would achieve faster and more efficient uranium precipitation. Experimentally, the strategy demonstrated highly efficient uranium(VI) precipitation efficiency, especially with hydrophilic macromolecular OGLs. The uranium removal efficiency at optimized experimental condition reached 99.65%. The decrease of zeta potential and the lattice enwrapping between U-OGLs chelates and flocculation precursor were ascribed to the enhanced uranium precipitation activity. Uranium was precipitated as oxides of U(VI) or higher valences that were easily captured in aggregated micelles under low operation current potential. The actual uranium tailing wastewater was treated, and a satisfied uranium removal efficiency of 99.02% was discovered. After elution of the precipitated flocs, a concentrated uranium solution (up to 106.52 μmol/L) with very few other metallic impurities was obtained. Therefore, the proposed strategy could remove uranium and concentrate it concurrently. This work could provide new insights into the purification and recovery of uranium from aqueous solutions in a cost-effective and environmentally friendly process.

Pharmacokinetics study of Zr-89-labeled melanin nanoparticle in iron-overload mice.

PubMed

Zhang, Pengjun; Yue, Yuanyuan; Pan, Donghui; Yang, Runlin; Xu, Yuping; Wang, Lizhen; Yan, Junjie; Li, Xiaotian; Yang, Min

2016-09-01

Melanin, a natural biological pigment present in many organisms, has been found to exhibit multiple functions. An important property of melanin is its ability to chelate metal ions strongly, which might be developed as an iron chelator for iron overload therapy. Herein, we prepared the ultrasmall water-soluble melanin nanoparticle (MP) and firstly evaluate the pharmacokinetics of MP in iron-overload mice to provide scientific basis for treating iron-overload. To study the circulation time and biodistribution, MP was labeled with (89)Zr, a long half-life (78.4h) positron-emitting metal which is suited for the labeling of nanoparticles and large bioactive molecule. MP was chelated with (89)Zr directly at pH5, resulting in non-decay-corrected yield of 89.6% and a radiochemical purity of more than 98%. The specific activity was at least190 MBq/μmol. The (89)Zr-MP was stable in human plasma and PBS for at least 48h. The half-life of (89)Zr-MP was about 15.70±1.74h in iron-overload mice. Biodistribution studies and MicroPET imaging showed that (89)Zr-MP mainly accumulated in liver and spleen, which are the target organ of iron-overload. The results indicate that the melanin nanoparticle is promising for further iron overload therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

Free metal ion depletion by "Good's" buffers. III. N-(2-acetamido)iminodiacetic acid, 2:1 complexes with zinc(II), cobalt(II), nickel(II), and copper(II); amide deprotonation by Zn(II), Co(II), and Cu(II).

PubMed

Lance, E A; Rhodes, C W; Nakon, R

1983-09-01

Potentiometric, visible, infrared, electron spin, and nuclear magnetic resonance studies of the complexation of N-(2-acetamido)iminodiacetic acid (H2ADA) by Ca(II), Mg(II), Mn(II), Zn(II), Co(II), Ni(II), and Cu(II) are reported. Ca(II) and Mg(II) were found not to form 2:1 ADA2- to M(II) complexes, while Mn(II), Cu(II), Ni(II), Zn(II), and Co(II) did form 2:1 metal chelates at or below physiological pH values. Co(II) and Zn(II), but not Cu(II), were found to induce stepwise deprotonation of the amide groups to form [M(H-1ADA)4-(2)]. Formation (affinity) constants for the various metal complexes are reported, and the probable structures of the various metal chelates in solution are discussed on the basis of various spectral data.

Structural diversity in Ni II cluster chemistry: Ni 5, Ni 6, and {NiNa 2} n complexes bearing the Schiff-base ligand N-naphthalidene-2-amino-5-chlorobenzoic acid

DOE PAGES

Perlepe, Panagiota S.; Cunha-Silva, Luis; Bekiari, Vlasoula; ...

2016-05-23

The employment of the fluorescent bridging and chelating ligand N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH 2) in Ni II cluster chemistry has led to a series of pentanuclear and hexanuclear compounds with different structural motifs, magnetic and optical properties, as well as an interesting 1-D coordination polymer. Synthetic parameters such as the inorganic anion present in the NiX 2 starting materials (X = ClO 4 - or Cl -), the reaction solvent and the nature of the organic base employed for the deprotonation of nacbH 2 were also proved to be structure-directing components. Undoubtedly, the reported results demonstrate the rich coordination chemistry ofmore » nacbH 2 in the presence of Ni II metal ions and the ability of this chelate to adopt a variety of different modes, thus fostering the formation of high-nuclearity molecules with many physical properties.« less

Two distinct modes of metal ion binding in the nuclease active site of a viral DNA-packaging terminase: insight into the two-metal-ion catalytic mechanism

PubMed Central

Zhao, Haiyan; Lin, Zihan; Lynn, Anna Y.; Varnado, Brittany; Beutler, John A.; Murelli, Ryan P.; Le Grice, Stuart F. J.; Tang, Liang

2015-01-01

Many dsDNA viruses encode DNA-packaging terminases, each containing a nuclease domain that resolves concatemeric DNA into genome-length units. Terminase nucleases resemble the RNase H-superfamily nucleotidyltransferases in folds, and share a two-metal-ion catalytic mechanism. Here we show that residue K428 of a bacteriophage terminase gp2 nuclease domain mediates binding of the metal cofactor Mg2+. A K428A mutation allows visualization, at high resolution, of a metal ion binding mode with a coupled-octahedral configuration at the active site, exhibiting an unusually short metal-metal distance of 2.42 Å. Such proximity of the two metal ions may play an essential role in catalysis by generating a highly positive electrostatic niche to enable formation of the negatively charged pentacovalent phosphate transition state, and provides the structural basis for distinguishing Mg2+ from Ca2+. Using a metal ion chelator β-thujaplicinol as a molecular probe, we observed a second mode of metal ion binding at the active site, mimicking the DNA binding state. Arrangement of the active site residues differs drastically from those in RNase H-like nucleases, suggesting a drifting of the active site configuration during evolution. The two distinct metal ion binding modes unveiled mechanistic details of the two-metal-ion catalysis at atomic resolution. PMID:26450964

[Influences of the mobile phase constitution, salt concentration and pH value on retention characters of proteins on the metal chelate column].

PubMed

Li, R; Di, Z M; Chen, G L

2001-09-01

The effects of the nature and concentration of salts, pH value and competitive eluent in the mobile phase on the protein retention have been systematically investigated. A mathematical expression describing the protein retention in metal chelate chromatography has been derived. It is proposed that the eluting power of the salt solution can be expressed by the eluent strength exponent epsilon. According to the retention characters of protein under different chromatographic conditions, the interaction between the various metal chelate ligands and proteins is discussed. The protein retention on the metal chelate column is a cooperative interactions of coordination, electrostatic and hydrophobic interaction. For the strong combined metal column with proteins such as IDA-Cu, the coordination is the most important, and the electrostatic interaction is secondary in chromatographic process. However, for the weak combined metal columns with proteins such as IDA-Ni, IDA-Co and IDA-Zn, the electrostatic interaction between the metal chelate ligands and proteins is the chief one, while the coordination is the next in importance. When the mobile phase contains high concentration of salt which can't form complex with the immobilized metal, the hydrophobic interaction between the protein and stationary phase will be increased. As the interaction between the metal chelate ligand and proteins relates to chromatographic operating conditions closely, different elution processes may be selected for different metal chelate columns. The gradient elution is generally performed by the low concentration of salt or different pH for weakly combined columns with proteins, however the competitive elution procedure is commonly utilized for strongly combined column. The experiment showed that NH3 is an excellent competitive eluent. It isn't only give the efficient separation of proteins, but also has the advantages of cheapness, less bleeding of the immobilized metals and ease of controlling NH3 concentration. The interaction between the metal chelate ligand and proteins and the selectivity of metal chelate chromatography can be changed through changing chromatographic conditions.

Exhaust gas clean up process

DOEpatents

Walker, Richard J.

1989-01-01

A method of cleaning an exhaust gas containing particulates, SO.sub.2 and NO.sub.x includes prescrubbing with water to remove HCl and most of the particulates, scrubbing with an aqueous absorbent containing a metal chelate and dissolved sulfite salt to remove NO.sub.x and SO.sub.2, and regenerating the absorbent solution by controlled heating, electrodialysis and carbonate salt addition. The NO.sub.x is removed as N.sub.2 or nitrogen-sulfonate ions and the oxides of sulfur are removed as a vaulable sulfate salt.

DNA sensing by a Eu-binding peptide containing a proflavine unit.

PubMed

Ancel, Laetitia; Gateau, Christelle; Lebrun, Colette; Delangle, Pascale

2013-01-18

Synthesis of a lanthanide-binding peptide (LBP) for the detection of double-stranded DNA is presented. A proflavine moiety was introduced into a high affinity LBP involving two unnatural chelating amino acids in the Ln ion coordination. The Eu(3+)-LBP complex is demonstrated to bind to ct-DNA and to sensitize Eu luminescence. The DNA binding process is effectively detected via the Eu-centered luminescence thanks to the intimate coupling between the LBP scaffold and DNA intercalating unit.

Tetraammine(carbonato-κ2 O,O′)cobalt(III) perchlorate

PubMed Central

Mohan, Singaravelu Chandra; Jenniefer, Samson Jegan; Muthiah, Packianathan Thomas; Jothivenkatachalam, Kandasamy

2013-01-01

In the title complex, [Co(CO3)(NH3)4]ClO4, both the cation and anion lie on a mirror plane. The CoIII ion is coordinated by two NH3 ligands and a chelating carbonato ligand in the equatorial sites and by two NH3 groups in the axial sites, forming a distorted octa­hedral geometry. In the crystal, N—H⋯O hydrogen bonds connect the anions and cations, forming a three-dimensional network. PMID:24109252

Preconcentration of Zn2+ and Cu2+ ions from food and vegetable samples using modified activated carbon.

PubMed

Ghaedi, M; Tavallali, H; Montazerozohori, M; Zahedi, E; Amirineko, M; Khodadoust, S; Karimipour, G

2012-11-01

In this work, two N/S-containing chelating agents 2-(4-methoxybenzylideneamino)thiophenol (2-4-MBAT) and 2-(4-chlorobenzylideneamino) benzenethiol (2-4-CBABT) were synthesized as new sorbents and were used for preconcentration of Zn(2+) and Cu(2+) ions in food and vegetable samples. In the proposed procedure, the trace amount of Zn(2+) and Cu(2+) ions from 250 mL of sample solution at pH = 5.0 was preconcentrated by 1 g of activated carbon (AC) loaded with 15 mg of 2-4-MBAT and 2-4-CBABT separately. The breakthrough volumes (maximum sample volume that their metal ions quantitatively can be enriched) for solid-phase extraction (SPE) procedure based on the AC modified with 2-4-MBAT and 2-4-CBABT were 800 and 750 mL, respectively. The sorbed Zn(2+) and Cu(2+) ions were efficiently eluted by 8 mL of 4 mol L(-1) HNO(3) and preconcentration factor of 112.5 and 93.7 and experimental enhancement factor of 30 and 35 ions were obtained for Zn(2+) and Cu(2+), respectively. The application of this enrichment procedure allowed the extraction of trace metal ions with recoveries exceeding of 90%.

Site-specific protein labeling with PRIME and chelation-assisted Click chemistry

PubMed Central

Uttamapinant, Chayasith; Sanchez, Mateo I.; Liu, Daniel S.; Yao, Jennifer Z.; White, Katharine A.; Grecian, Scott; Clarke, Scott; Gee, Kyle R.; Ting, Alice Y.

2016-01-01

This protocol describes an efficient method to site-specifically label cell-surface or purified proteins with chemical probes in two steps: PRobe Incorporation Mediated by Enzymes (PRIME) followed by chelation-assisted copper-catalyzed azide-alkyne cycloaddition (CuAAC). In the PRIME step, Escherichia coli lipoic acid ligase site-specifically attaches a picolyl azide derivative to a 13-amino acid recognition sequence that has been genetically fused onto the protein of interest. Proteins bearing picolyl azide are chemoselectively derivatized with an alkyne-probe conjugate by chelation-assisted CuAAC in the second step. We describe herein the optimized protocols to synthesize picolyl azide, perform PRIME labeling, and achieve CuAAC derivatization of picolyl azide on live cells, fixed cells, and purified proteins. Reagent preparations, including synthesis of picolyl azide probes and expression of lipoic acid ligase, take 12 d, while the procedure to perform site-specific picolyl azide ligation and CuAAC on cells or on purified proteins takes 40 min-3 h. PMID:23887180

Enhancing Potentially Plant-Available Lead Concentrations in Contaminated Residential Soils Using a Biodegradable Chelating Agent

NASA Astrophysics Data System (ADS)

Andra, S.; Datta, R.; Sarkar, D.; Saminathan, S.

2007-12-01

Chelation of heavy metals is an important factor in enhancing metal solubility and, hence, metal availability to plants to promote phytoremediation. In the present study, we compared the effects of application of a biodegradable chelating agent, namely, ethylenediaminedisuccinic acid (EDDS) on enhancing plant available form of lead (Pb) in Pb-based paint contaminated residential soils compared to that of a more commonly used, but non-biodegradable chelate, i.e., ethylenediaminetetraacetic acid (EDTA). Development of a successful phytoremediation model for metals such as Pb depends on a thorough understanding of the physical and chemical properties of the soil, along with the optimization of a chelate treatment to mobilize Pb from `unavailable' pools to potentially plant available fraction. In this context, we set out to perform batch incubation experiments to investigate the effectiveness of the two aforementioned chelates in enhancing plant available Pb at four different concentrations (0, 5, 10 and 15 mM/kg soil) and three treatment durations (0, 10 and 30 days). We selected 12 contaminated residential soils from two major metropolitan areas (San Antonio, TX and Baltimore, MD) with varying soil physico-chemical properties - the soils from San Antonio were primarily alkaline and those from Baltimore were typically acidic. Total soil Pb concentrations ranged between 256 mg/kg and 4,182 mg/kg. Our results show that both chelates increased the solubility of Pb, otherwise occluded in the complex soil matrix. For both EDTA and EDDS, the exchangeable concentrations of soil Pb also increased with increase in chelate concentration and incubation time. The most effective treatment was 15 mM chelate kg-1 soil incubated for 30 days, which caused many fold increase in potentially plant available Pb (a combination of the soluble and exchangeable fractions) relative to the unamended controls. Step wise multiple linear regression analysis using chelate-extractable Pb and soil properties showed that plant available Pb fraction could be assessed from the two inter-related soil parameters: soil organic matter and soil pH. Although EDTA was more effective in Pb solubilization than EDDS, the rapid kinetics of the Pb-EDTA complexation process and the prolonged persistence of EDTA in soils pose a potential groundwater contamination problem via metal leaching. In contrast to EDTA, EDDS addition caused relatively slow release of Pb from the soil matrix. The biodegradable nature (and short half life) of EDDS in soils makes it a promising chelating agent for use as soil amendment to enhance Pb solubilization and hence, potential plant uptake.

Production of polygalacturonase from Coriolus versicolor grown on tomato pomace and its chromatographic behaviour on immobilized metal chelates.

PubMed

do Rosário Freixo, Maria; Karmali, Amin; Arteiro, José Maria

2008-06-01

Tomato pomace and pectin were used as the sole carbon sources for the production of polygalacturonase from a strain of Coriolus versicolor in submerged culture. The culture of C. versicolor grown on tomato pomace exhibited a peak of polygalacturonase activity (1,427 U/l) on the third day of culture with a specific activity of 14.5 U/mg protein. The production of polygalacturonase by C. versicolor grown on pectin as a sole carbon source increased with the time of cultivation, reaching a maximum activity of 3,207 U/l of fermentation broth with a specific activity of 248 U/mg protein. The levels of different isoenzymes of polygalacturonase produced during the culture growth were analysed by native PAGE. Differential chromatographic behaviour of lignocellulosic enzymes produced by C. versicolor (i.e. polygalacturonase, xylanase and laccase) was studied on immobilized metal chelates. The effect of ligand concentration, pH, the length of spacer arm and the nature of metal ion were studied for enzyme adsorption on immobilized metal affinity chromatography (IMAC). The adsorption of these lignocellulosic enzymes onto immobilized metal chelates was pH-dependent since an increase in protein adsorption was observed as the pH was increased from 6.0 to 8.0. The adsorption of polygalacturonase as well as other enzymes to immobilized metal chelates was due to coordination of histidine residues which are available at the protein surface since the presence of imidazole in the equilibration buffer abolished the adsorption of the enzyme to immobilized metal chelates. A one-step purification of polygalacturonase from C. versicolor was devised by using a column of Sepharose 6B-EPI 30-IDA-Cu(II) and purified enzyme exhibited a specific activity of about 150 U/mg protein, final recovery of enzyme activity of 100% and a purification factor of about 10. The use of short spacer arm and the presence of imidazole in equilibration buffer exhibited a higher selectivity for purification of polygalacturonase on this column with a high purification factor. The purified enzyme preparation was analysed by SDS-PAGE as well as by "in situ" detection of enzyme activity.

Isolation and identification of calcium-chelating peptides from Pacific cod skin gelatin and their binding properties with calcium.

PubMed

Wu, Wenfei; Li, Bafang; Hou, Hu; Zhang, Hongwei; Zhao, Xue

2017-12-13

A calcium-chelating peptide is considered to have the ability to improve calcium absorption. In this study, Pacific cod skin gelatin hydrolysates treated with trypsin for 120 min exhibited higher calcium-chelating activity. Sequential chromatography, involving hydroxyapatite affinity chromatography and reversed phase high performance liquid chromatography, was used for the purification of calcium-chelating peptides. Two novel peptides with the typical characteristics of collagen were sequenced as GDKGESGEAGER and GEKGEGGHR based on LC-HRMS/MS, which showed a high affinity to calcium. Calcium-peptide complexation was further characterized by ESI-MS (MS and MS/MS) and FTIR spectroscopy. The results showed that the complexation of the two peptides with calcium was conducted mainly at the ratio of 1 : 1. The amino terminal group and the peptide bond of the peptide backbone as well as the amino group of the lysine side chain and the carboxylate of the glutamate side chain were the possible calcium binding sites for the two peptides. Meanwhile, several amino acid side chain groups, including the hydroxyl (Ser) and carboxylate (Asp) of GDKGESGEAGER and the imine (His) of GEKGEGGHR, were crucial in the complexation. The arginine residue in GEKGEGGHR also participated in the calcium coordination. Additionally, several active fragments with calcium-chelating activity were obtained using MS/MS spectra, including GDKGESGEAGE, GEAGER, GEK, EKG and KGE. This study suggests that gelatin-derived peptides have the potential to be used as a calcium-chelating ingredient to combat calcium deficiency.

Iron chelation and multiple sclerosis

PubMed Central

Weigel, Kelsey J.; Lynch, Sharon G.; LeVine, Steven M.

2014-01-01

Histochemical and MRI studies have demonstrated that MS (multiple sclerosis) patients have abnormal deposition of iron in both gray and white matter structures. Data is emerging indicating that this iron could partake in pathogenesis by various mechanisms, e.g., promoting the production of reactive oxygen species and enhancing the production of proinflammatory cytokines. Iron chelation therapy could be a viable strategy to block iron-related pathological events or it can confer cellular protection by stabilizing hypoxia inducible factor 1α, a transcription factor that normally responds to hypoxic conditions. Iron chelation has been shown to protect against disease progression and/or limit iron accumulation in some neurological disorders or their experimental models. Data from studies that administered a chelator to animals with experimental autoimmune encephalomyelitis, a model of MS, support the rationale for examining this treatment approach in MS. Preliminary clinical studies have been performed in MS patients using deferoxamine. Although some side effects were observed, the large majority of patients were able to tolerate the arduous administration regimen, i.e., 6–8 h of subcutaneous infusion, and all side effects resolved upon discontinuation of treatment. Importantly, these preliminary studies did not identify a disqualifying event for this experimental approach. More recently developed chelators, deferasirox and deferiprone, are more desirable for possible use in MS given their oral administration, and importantly, deferiprone can cross the blood–brain barrier. However, experiences from other conditions indicate that the potential for adverse events during chelation therapy necessitates close patient monitoring and a carefully considered administration regimen. PMID:24397846

Cobalt, chromium and molybdenum ions kinetics in the human body: data gained from a total hip replacement with massive third body wear of the head and neuropathy by cobalt intoxication.

PubMed

Pazzaglia, U E; Apostoli, P; Congiu, T; Catalani, S; Marchese, M; Zarattini, G

2011-09-01

A patient with a total hip replacement developed optic, acoustic and peripheral neuropathy from metal ions intoxication, due to the wear products released from the prosthesis. Subsequently the kinetics of the metal ions was studied. Massive wear and acute intoxication allowed a study of the metal ions kinetics and of EDTA treatment. Plasma and other organic fluids were saturated by each of the metal ions released from the exposed surface according to the solubility of each ion; a larger fraction of Co ions was bound within red cells, while the plasmatic fraction appeared more movable. In a patient with a prosthesis subjected to wear, the ions released are from the prosthetic and from the debris surface (spread in the body). The latter is a function of the number and size of particles. Revision of the prosthesis from the point of view of the metal ions kinetics corresponded to a reduction of the releasing surface because of debris washed out by irrigation and tissue excision; however, the metal particles spread by lymphatic circulation continued to release ions even though the source of wear had been removed. Early diagnosis of high metal wear can be ascertained with mass spectrometry and after revision high levels of metal ions can only be reduced with repeated chelating treatment. It is preferable not to revise fractured ceramic components with a polyethylene-metal articulation.

Comparison of the octadentate bifunctional chelator DFO*-pPhe-NCS and the clinically used hexadentate bifunctional chelator DFO-pPhe-NCS for 89Zr-immuno-PET.

PubMed

Vugts, Danielle J; Klaver, Chris; Sewing, Claudia; Poot, Alex J; Adamzek, Kevin; Huegli, Seraina; Mari, Cristina; Visser, Gerard W M; Valverde, Ibai E; Gasser, Gilles; Mindt, Thomas L; van Dongen, Guus A M S

2017-02-01

All clinical 89 Zr-immuno-PET studies are currently performed with the chelator desferrioxamine (DFO). This chelator provides hexadentate coordination to zirconium, leaving two coordination sites available for coordination with, e.g., water molecules, which are relatively labile ligands. The unsaturated coordination of DFO to zirconium has been suggested to result in impaired stability of the complex in vivo and consequently in unwanted bone uptake of 89 Zr. Aiming at clinical improvements, we report here on a bifunctional isothiocyanate variant of the octadentate chelator DFO* and the in vitro and in vivo comparison of its 89 Zr-DFO*-mAb complex with 89 Zr-DFO-mAb. The bifunctional chelator DFO*-pPhe-NCS was prepared from previously reported DFO* and p-phenylenediisothiocyanate. Subsequently, trastuzumab was conjugated with either DFO*-pPhe-NCS or commercial DFO-pPhe-NCS and radiolabeled with Zr-89 according to published procedures. In vitro stability experiments were carried out in saline, a histidine/sucrose buffer, and blood serum. The in vivo performance of the chelators was compared in N87 tumor-bearing mice by biodistribution studies and PET imaging. In 0.9 % NaCl 89 Zr-DFO*-trastuzumab was more stable than 89 Zr-DFO-trastuzumab; after 72 h incubation at 2-8 °C 95 % and 58 % intact tracer were left, respectively, while in a histidine-sucrose buffer no difference was observed, both products were ≥ 92 % intact. In vivo uptake at 144 h post injection (p.i.) in tumors, blood, and most normal organs was similar for both conjugates, except for skin, liver, spleen, ileum, and bone. Tumor uptake was 32.59 ± 11.95 and 29.06 ± 8.66 % ID/g for 89 Zr-DFO*-trastuzumab and 89 Zr-DFO-trastuzumab, respectively. The bone uptake was significantly lower for 89 Zr-DFO*-trastuzumab compared to 89 Zr-DFO-trastuzumab. At 144 h p.i. for 89 Zr-DFO*-trastuzumab and 89 Zr-DFO-trastuzumab, the uptake in sternum was 0.92 ± 0.16 and 3.33 ± 0.32 % ID/g, in femur 0.78 ± 0.11 and 3.85, ± 0.80 and in knee 1.38 ± 0.23 and 8.20 ± 2.94 % ID/g, respectively. The uptake in bone decreased from 24 h to 144 h p.i. about two fold for the DFO* conjugate, while it increased about two fold for the DFO conjugate. Zr-DFO*-trastuzumab showed superior in vitro stability and in vivo performance when compared to 89 Zr-DFO-trastuzumab. This makes the new octadentate DFO* chelator a candidate successor of DFO for future clinical 89 Zr-immuno-PET.

Experimental Investigation on the Mechanism of Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

PubMed Central

Kuang, Gui-Chao; Guha, Pampa M.; Brotherton, Wendy S.; Simmons, J. Tyler; Stankee, Lisa A.; Nguyen, Brian T.; Clark, Ronald J.; Zhu, Lei

2011-01-01

A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in mediating a 2-picolylazide-involved AAC reaction than the fully reduced Cu(OAc)2. Finally, the discontinuous kinetic behavior that has been observed by us and others in copper(I/II)-mediated AAC reactions is explained by the likely catalyst disintegration during the course of a relatively slow reaction. Complementing the prior mechanistic conclusions drawn by other investigators which primarily focus on the copper(I)/alkyne interactions, we emphasize the kinetic significance of copper(I/II)/azide interaction. This work not only provides a mechanism accounting for the fast Cu(OAc)2-mediated AAC reactions involving chelating azides, which has apparent practical implications, but suggests the significance of mixed-valency dinuclear copper species in catalytic reactions where two copper centers carry different functions. PMID:21809811

Part 2. Comparison of emergency washing solutions in 70% hydrofluoric acid-burned human skin in an established ex vivo explants model

PubMed Central

Burgher, François; Mathieu, Laurence; Lati, Elian; Gasser, Philippe; Peno-Mazzarino, Laurent; Blomet, Joël; Hall, Alan H; Maibach, Howard I

2011-01-01

Background: Hydrofluoric acid (HF) is a small and partially dissociated acid (pKa 3.2), able to deeply penetrate into human skin in addition to the corrosiveness of the hydrogen ion (H+) and the toxicity of the fluoride ion (F-). However, there has been a lack of experimental studies to objectively characterize the results of human HF skin exposure decontamination. Methodology/principal findings: A previously established experimental method using a human skin explants ex vivo model (Part 1. Experimental 70% hydrofluoric acid (HF) burns: Histological observations in an established human skin explants ex vivo model) described the lesions that appeared following 70% HF penetration. Within 5min, 70% HF penetrates to the dermis. Using the same experimental conditions, a comparison study of two different washing protocols was performed: water + topical calcium gluconate (CaG) versus Hexafluorine®. In these conditions, washing for 15min with running tap water followed by topical CaG ointment only delayed burn onset, while severe tissue damage appeared later. In contrast, after washing with Hexafluorine® over 10 min, no histological lesions developed. These results are in accordance with the results of accidental human industrial case reports. Conclusion/significance: Amphoteric and hypertonic Hexafluorine® can deactivate H+ and chelate F- ions. Based on these results, it should be considered as a promising first-aid decontamination solution to prevent or minimize significant local and systemic consequences of concentrated HF skin exposures. PMID:21083510

TLc-A, the leading nanochelating-based nanochelator, reduces iron overload in vitro and in vivo.

PubMed

Kalanaky, Somayeh; Hafizi, Maryam; Safari, Sepideh; Mousavizadeh, Kazem; Kabiri, Mahboubeh; Farsinejad, Alireza; Fakharzadeh, Saideh; Nazaran, Mohammad Hassan

2016-03-01

Iron chelation therapy is an effective approach to the treatment of iron overload conditions, in which iron builds up to toxic levels in the body and may cause organ damage. Treatments using deferoxamine, deferasirox and deferiprone have been introduced and despite their disadvantages, they remain the first-line therapeutics in iron chelation therapy. Our study aimed to compare the effectiveness of the iron chelation agent TLc-A, a nano chelator synthetized based on the novel nanochelating technology, with deferoxamine. We found that TLc-A reduced iron overload in Caco2 cell line more efficiently than deferoxamine. In rats with iron overload, very low concentrations of TLc-A lowered serum iron level after only three injections of the nanochelator, while deferoxamine was unable to reduce iron level after the same number of injections. Compared with deferoxamine, TLc-A significantly increased urinary iron excretion and reduced hepatic iron content. The toxicity study showed that the intraperitoneal median lethal dose for TLc-A was at least two times higher than that for deferoxamine. In conclusion, our in vitro and in vivo studies indicate that the novel nano chelator compound, TLc-A, offers superior performance in iron reduction than the commercially available and widely used deferoxamine.

Ion imprinted polymeric nanoparticles for selective separation and sensitive determination of zinc ions in different matrices

NASA Astrophysics Data System (ADS)

Shamsipur, Mojtaba; Rajabi, Hamid Reza; Pourmortazavi, Seied Mahdi; Roushani, Mahmoud

2014-01-01

Preparation of Zn2+ ion-imprinted polymer (Zn-IIP) nanoparticles is presented in this report. The Zn-IIP nanoparticles are prepared by dissolving stoichiometric amounts of zinc nitrate and selected chelating ligand, 3,5,7,20,40-pentahydroxyflavone, in 15 mL ethanol-acetonitrile (2:1; v/v) mixture as a porogen solvent in the presence of ethylene glycol-dimethacrylate (EGDMA) as cross-linking, methacrylic acid (MAA) as functional monomer, and 2,2-azobisisobutyronitrile (AIBN) as initiator. After polymerization, Cavities in the polymer particles corresponding to the Zn2+ ions were created by leaching the polymer in HCl aqueous solution. The synthesized IIPs were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal analysis techniques. Also, the pH range for rebinding of Zn2+ ion on the IIP and equilibrium binding time were optimized, using flame atomic absorption spectrometry. In selectivity study, it was found that imprinting results increased affinity of the material toward Zn2+ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for six times without any significant decrease in polymer binding affinities. Finally, the prepared sorbent was successfully applied to the selective recognition and determination of zinc ion in different real samples.

Inorganic-organic Ag-rhodamine 6G hybrid nanorods: "turn on" fluorescent sensors for highly selective detection of Pb2+ ions in aqueous solution.

PubMed

Tyagi, A K; Ramkumar, Jayshree; Jayakumar, O D

2012-02-07

Lead metal ions are of great concern and the monitoring of their concentration in the environment has become extremely important. In the present study, a new inorganic-organic hybrid assay of Ag nanorods (AgNR)-Rhodamine 6G (R6G) was developed for the sensitive and selective determination of Pb(2+) ions in aqueous solutions. To the best of our knowledge there is almost no literature on the use of silver nanorod sensors for determination of lead ions in aqueous solutions. The sensor is developed by the coating of R6G on the surface of AgNRs. The sensing is based on the photoluminescence of R6G. The sensor was rapid as the measurements were carried out within 3 min of addition of the test solution to the AgNR-R6G hybrid. Moreover, the system showed excellent stability at tested concentration levels of Pb(2+) ions. The naked eye detection of the colour was possible with 1 mg L(-1) of Pb(2+) ions. The present method has a detection limit of 50 μg L(-1) of Pb(2+) (for a signal/noise (S/N) ratio > 3). The selectivity toward Pb(2+) ions against other metal ions was improved using chelating agents. The proposed method was validated by analysis using different techniques.

Design of Internalizing PSMA-specific Glu-ureido-based Radiotherapeuticals

PubMed Central

Wüstemann, Till; Bauder-Wüst, Ulrike; Schäfer, Martin; Eder, Matthias; Benesova, Martina; Leotta, Karin; Kratochwil, Clemens; Haberkorn, Uwe; Kopka, Klaus; Mier, Walter

2016-01-01

Despite the progress in diagnosis and treatment, prostate cancer (PCa) is one of the main causes for cancer-associated deaths among men. Recently, prostate-specific membrane antigen (PSMA) binding tracers have revolutionized the molecular imaging of this disease. The translation of these tracers into therapeutic applications is challenging because of high PSMA-associated kidney uptake. While both the tumor uptake and the uptake in the kidneys are PSMA-specific, the kidneys show a more rapid clearance than tumor lesions. Consequently, the potential of endoradiotherapeutic drugs targeting PSMA is highly dependent on a sustained retention in the tumor - ideally achieved by predominant internalization of the respective tracer. Previously, we were able to show that the pharmacokinetics of the tracers containing the Glu-urea-based binding motif can be further enhanced with a specifically designed linker. Here, we evaluate an eventual influence of the chelator moiety on the pharmacokinetics, including the tumor internalization. A series of tracers modified by different chelators were synthesized using solid phase chemistry. The conjugates were radiolabeled to evaluate the influence on the receptor binding affinity, the ligand-induced internalization and the biodistribution behavior. Competitive binding and internalization assays were performed on PSMA positive LNCaP cells and the biodistribution of the most promising compound was evaluated by positron emission tomography (PET) in LNCaP-tumor-bearing mice. Interestingly, conjugation of the different chelators did not cause significant differences: all compounds showed nanomolar binding affinities with only minor differences. PET imaging of the 68Ga-labeled CHX-A''-DTPA conjugate revealed that the chelator moiety does not impair the specificity of tumor uptake when compared to the gold standard PSMA-617. However, strong differences of the internalization ratios caused by the chelator moiety were observed: differences in internalization between 15% and 65% were observed, with the CHX-A''-DTPA conjugate displaying the highest internalization ratio. A first-in-man PET/CT study proved the high tumor uptake of this 68Ga-labeled PSMA-targeting compound. These data indicate that hydrophobic entities at the chelator mediate the internalization efficacy. Based on its specific tumor uptake in combination with its very high internalization ratio, the clinical performance of the chelator-conjugated Glu-urea-based PSMA inhibitors will be further elucidated. PMID:27279903

Monitoring underlying epoxy-coated St-37 corrosion via 8-hydroxyquinoline as a fluorescent indicator

NASA Astrophysics Data System (ADS)

Roshan, Shamim; Sarabi Dariani, Ali Asghar; Mokhtari, Javad

2018-05-01

In the present study, successful performance of 8-hydroxyquinoline (8-HQ) as a ferric ion sensitive indicator is described. 8-HQ was used in epoxy coating because of its desirable properties. It doesn't exhibit premature fluorescence when mixed with coating precursors. Additionally it shows fluorescence turn-on mechanism upon chelate formation with Fe2+/Fe3+ ions produced during anodic reaction. The effect of different concentrations of 8-HQ (0.05, 0.1, 0.5 and 1 wt.%) incorporated in the epoxy coating on corrosion detection as well as optical and electrochemical behavior of the applied coating were studied. The fluorescence property of 8-HQ/Fe3+ solutions was evaluated by using fluorometer. The UV-Visible spectroscopy was used to investigate the effect of 8-HQ presence in the coating on transparency of the free films of the samples. The corrosion detection was performed by fluorescence microscope and the anti-corrosion performance of coated samples containing different concentrations of 8-HQ was studied using salt spray standard test and electrochemical impedance spectroscopy (EIS). The results of UV-Visible spectroscopy demonstrated that increasing 8-HQ concentration causes a slight decrease in coating transparency. According to the results of electrochemical impedance spectroscopy (EIS) measurements, the polarization resistance of the coated St-37 sample containing 0.1 wt.% 8-HQ was about 109 Ohm cm2 after 6 weeks immersion in corrosive electrolyte, while St-37 plates coated with other 8-HQ concentrations showed decreased resistance levels of about 106 Ohm cm2, during the same immersion period. Based on fluorescence microscopic investigation, as a result of incorporating 8-HQ into the epoxy matrix, fluorescence could be observed in regions where Fe2+/Fe3+ ions were produced through anodic reactions. This method is capable of detecting corrosion in situ at early stages before the metal surface suffers serious damages.

A theoretical study on the electronic structures and equilibrium constants evaluation of Deferasirox iron complexes.

PubMed

Salehi, Samie; Saljooghi, Amir Shokooh; Izadyar, Mohammad

2016-10-01

Elemental iron is essential for cellular growth and homeostasis but it is potentially toxic to the cells and tissues. Excess iron can contribute in tumor initiation and tumor growth. Obviously, in iron overload issues using an iron chelator in order to reduce iron concentration seems to be vital. This study presents the density functional theory calculations of the electronic structure and equilibrium constant for iron-deferasirox (Fe-DFX) complexes in the gas phase, water and DMSO. A comprehensive study was performed to investigate the Deferasirox-iron complexes in chelation therapy. Calculation was performed in CAMB3LYP/6-31G(d,p) to get the optimized structures for iron complexes in high and low spin states. Natural bond orbital and quantum theory of atoms in molecules analyses was carried out with B3LYP/6-311G(d,p) to understand the nature of complex bond character and electronic transition in complexes. Electrostatic potential effects on the complexes were evaluated using the CHelpG calculations. The results indicated that higher affinity for Fe(III) is not strictly a function of bond length but also the degree of Fe-X (X=O,N) covalent bonding. Based on the quantum reactivity parameters which have been investigated here, it is possible reasonable design of the new chelators to improve the chelator abilities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis and Use of [Cd(Detu)2(OOCCH3)2]·H2O as Single Molecule Precursor for Cds Nanoparticles

PubMed Central

Ajibade, Peter A.

2013-01-01

Substituted thiourea ligands are of interest because they possess various donor sites for metal ions and their application in separation of metal ions and as antimicrobial agents. The coordination of the sulfur donor atom led to interest in them as precursor for semiconductor nanoparticles. In this study, cadmium(II) complex of diethylthiourea was synthesized and characterized by elemental analysis, FTIR, and X-ray crystallography. Single crystal X-ray structure of the complex showed that the octahedral geometry around the Cd ion consists of two molecules of diethylthiourea acting as monodentate ligands and two chelating acetate ions. The thermal decomposition of the compound showed that it decomposed to give CdS. The compound was thermolysed in hexadecylamine (HDA) to prepare HDA-capped CdS nanoparticles. The absorption spectrum showed blue shifts in its absorption band edges which clearly indicated quantum confinement effect, and the emission spectrum showed characteristic band edge luminescence. The broad diffraction peaks of the XRD pattern showed the materials to be of the nanometric size. PMID:24294141