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.

Mercury intracellular partitioning and chelation in a salt marsh plant, Halimione portulacoides (L.) Aellen: strategies underlying tolerance in environmental exposure.

PubMed

Válega, M; Lima, A I G; Figueira, E M A P; Pereira, E; Pardal, M A; Duarte, A C

2009-01-01

In the presence of metal stress, plants can resort to a series of tolerance mechanisms. Therefore field studies should be undertaken in order to evaluate the real role of these mechanisms in stress coping. The aim of this paper was to clarify the biochemical processes behind mercury tolerance in Halimione portulacoides (L.) Aellen (Caryophyllales: Chenopodiaceae) collected in a mercury contaminated salt marsh. Different fractions of mercury were separated: buffer-soluble (mainly cytosolic) and insoluble mercury (mainly associated with membranes and cell walls). The amounts in each fraction of metal were compared and related to metal distribution within plant organs. Protein-mercury complexes were isolated and analysed for their thiol content in order to assess wether the tolerance of this salt marsh plant was associated with the induction of metal chelation by phytochelatins. Overall, the mercury tolerance strategies of the plant are likely to involve root cell wall immobilization as a major mechanism of metal resistance, rather than metal chelation in the cytosolic fraction. Nevertheless, phytochelatins were demonstrated to chelate mercury under environmental exposure.

P/Q-type calcium channels activate neighboring calcium-dependent potassium channels in mouse motor nerve terminals.

PubMed

Protti, D A; Uchitel, O D

1997-08-01

The identity of the voltage-dependent calcium channels (VDCC), which trigger the Ca2+-gated K+ currents (IK(Ca)) in mammalian motor nerve terminals, was investigated by means of perineurial recordings. The effects of Ca2+ chelators with different binding kinetics on the activation of IK(Ca) were also examined. The calcium channel blockers of the P/Q family, omega-agatoxin IVA (omega-Aga-IVA) and funnel-web spider toxin (FTX), have been shown to exert a strong blocking effect on IK(Ca). In contrast, nitrendipine and omega-conotoxin GVIA (omega-CgTx) did not affect the Ca2+-activated K+ currents. The intracellular action of the fast Ca2+ buffers BAPTA and DM-BAPTA prevented the activation of the IK(Ca), while the slow Ca2+ buffer EGTA was ineffective at blocking it. These data indicate that P/Q-type VDCC mediate the Ca2+ influx which activates IK(Ca). The spatial association between Ca2+ and Ca2+-gated K+ channels is discussed, on the basis of the differential effects of the fast and slow Ca2+ chelators.

Novel double prodrugs of the iron chelator N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED): Synthesis, characterization, and investigation of activation by chemical hydrolysis and oxidation.

PubMed

Thiele, Nikki A; Abboud, Khalil A; Sloan, Kenneth B

2016-08-08

The development of iron chelators suitable for the chronic treatment of diseases where iron accumulation and subsequent oxidative stress are implicated in disease pathogenesis is an active area of research. The clinical use of the strong chelator N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) and its alkyl ester prodrugs has been hindered by poor oral bioavailability and lack of conversion to the parent chelator, respectively. Here, we present novel double prodrugs of HBED that have the carboxylate and phenolate donors of HBED masked with carboxylate esters and boronic acids/esters, respectively. These double prodrugs were successfully synthesized as free bases (7a-f) or as dimesylate salts (8a-c,e), and were characterized by (1)H, (13)C, and (11)B NMR; MP; MS; and elemental analysis. The crystal structure of 8a was solved. Three of the double prodrugs (8a-c) were selected for further investigation into their abilities to convert to HBED by stepwise hydrolysis and H2O2 oxidation. The serial hydrolysis of the pinacol and methyl esters of N,N'-bis(2-boronic acid pinacol ester benzyl)ethylenediamine-N,N'-diacetic acid methyl ester dimesylate (8a) was verified by LC-MS. The macro half-lives for the hydrolyses of 8a-c, measured by UV, ranged from 3.8 to 26.3 h at 37 °C in pH 7.5 phosphate buffer containing 50% MeOH. 9, the product of hydrolysis of 8a-c and the intermediate in the conversion pathway, showed little-to-no affinity for iron or copper in UV competition experiments. 9 underwent a serial oxidative deboronation by H2O2 in N-methylmorpholine buffer to generate HBED (k = 10.3 M(-1) min(-1)). The requirement of this second step, oxidation, before conversion to the active chelator is complete may confer site specificity when only localized iron chelation is needed. Overall, these results provide proof of principle for the activation of the double prodrugs by chemical hydrolysis and H2O2 oxidation, and merit further investigation into the protective capabilities of the prodrugs against H2O2-induced cell death. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

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

Winterbourn, C.C.; Sutton, H.C.

O2- was produced by gamma irradiation of formate solutions, by the action of xanthine oxidase on hypoxanthine and O2, and by the action of ferredoxin reductase on NADPH and paraquat in the presence of O2. Its reaction with H2O2 and various iron chelates was studied. Oxidation of deoxyribose to thiobarbituric acid-reactive products that was appropriately inhibited by OH. scavengers, or formate oxidation to CO2, was used to detect OH(.). With each source of O2-, and by these criteria, Fe(EDTA) efficiently catalyzed this (Haber-Weiss) reaction, but little catalysis was detectable with iron bound to DTPA, citrate, ADP, ATP, or pyrophosphate, ormore » without chelator in phosphate buffer. O2- produced from xanthine oxidase, but not from the other sources, underwent another iron-dependent reaction with H2O2, to produce an oxidant that did not behave as free OH(.). It was formed in phosphate or bicarbonate buffer, and caused deoxyribose oxidation that was readily inhibited by mannitol or Tris, but not by benzoate, formate, or dimethyl sulfoxide. It did not oxidize formate to CO2. Addition of EDTA changed the pattern of inhibition to that expected for a reaction of OH(.). The other chelators all inhibited deoxyribose oxidation, provided their concentrations were high enough. The results are compatible with iron bound to xanthine oxidase catalyzing production of a strong oxidant (which is not free OH.) from H2O2 and O2- produced by the enzyme.« less

DA-6034-induced mucin secretion via Ca2+-dependent pathways through P2Y receptor stimulation.

PubMed

Lee, Hun; Kim, Eung Kweon; Kim, Ji Yeon; Yang, Yu-Mi; Shin, Dong Min; Kang, Kyung Koo; Kim, Tae-im

2014-09-11

We evaluated whether DA-6034 is involved in mucin secretion via P2Y receptor activation and/or intracellular Ca2+ concentration ([Ca2+]i) change. Also, we investigated the effect of P2Y receptor inhibitors or Ca2+ chelators on the DA-6034-induced mucin secretion and [Ca2+]i increases. Effects of DA-6034 on mucin expression in primary, cultured, conjunctival epithelial cells was studied using RT-PCR, Western blot analysis, and periodic acid-schiff (PAS) staining. To evaluate thin film layer thickness generated by mucin and fluid secretion, cells were incubated in DA-6034 with/without P2Y antagonists or extracellular/intracellular Ca2+ chelators, and were imaged with confocal microscope using Texas Red-dextran dye. In addition, DA-6034-induced Ca2+-dependent Cl- channels opening was evaluated using perforated patch clamp. Fluo-4/AM was used to measure changes in [Ca2+]i induced by DA-6034 in Ca2+-free or Ca2+-containing buffered condition, as well as P2Y antagonists. DA-6034 induced the expression of mucin genes, production of mucin protein, and increase of number of mucin-secreting cells. P2Y antagonists inhibited DA-6034-induced mucin and fluid secretion, which was also affected by extracellular/intracellular Ca2+ chelators. DA-6034 stimulated Cl- channel opening and [Ca2+]i elevation. Further, [Ca2+]i increases induced by DA-6034 were lacking in either P2Y antagonists or Ca2+-free buffered condition, and diminished when endoplasmic reticulum Ca2+ was depleted by cyclopiazonic acid in Ca2+-free buffered condition. This study demonstrated that DA-6034 has a potential to induce mucin secretion via Ca2+-dependent pathways through P2Y receptors in multilayer, cultured, human conjunctival epithelial cells. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

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.

Novel Bifunctional Cyclic Chelator for 89Zr Labeling–Radiolabeling and Targeting Properties of RGD Conjugates

PubMed Central

2015-01-01

Within the last years 89Zr has attracted considerable attention as long-lived radionuclide for positron emission tomography (PET) applications. So far desferrioxamine B (DFO) has been mainly used as bifunctional chelating system. Fusarinine C (FSC), having complexing properties comparable to DFO, was expected to be an alternative with potentially higher stability due to its cyclic structure. In this study, as proof of principle, various FSC-RGD conjugates targeting αvß3 integrins were synthesized using different conjugation strategies and labeled with 89Zr. In vitro stability, biodistribution, and microPET/CT imaging were evaluated using [89Zr]FSC-RGD conjugates or [89Zr]triacetylfusarinine C (TAFC). Quantitative 89Zr labeling was achieved within 90 min at room temperature. The distribution coefficients of the different radioligands indicate hydrophilic character. Compared to [89Zr]DFO, [89Zr]FSC derivatives showed excellent in vitro stability and resistance against transchelation in phosphate buffered saline (PBS), ethylenediaminetetraacetic acid solution (EDTA), and human serum for up to 7 days. Cell binding studies and biodistribution as well as microPET/CT imaging experiments showed efficient receptor-specific targeting of [89Zr]FSC-RGD conjugates. No bone uptake was observed analyzing PET images indicating high in vivo stability. These findings indicate that FSC is a highly promising chelator for the development of 89Zr-based PET imaging agents. PMID:25941834

Binding of Soluble Natural Ligands to a Soluble Human T-Cell Receptor Fragment Produced in Escherichia coli

NASA Astrophysics Data System (ADS)

Hilyard, Katherine L.; Reyburn, Hugh; Chung, Shan; Bell, John I.; Strominger, Jack L.

1994-09-01

An Escherichia coli expression system has been developed to produce milligram quantities of the variable domains of a human T-cell receptor from a cytotoxic T cell that recognizes the HLA-A2-influenza matrix peptide complex as a single polypeptide chain. The recombinant protein was purified by metal-chelate chromatography and then refolded in a redox buffer system. The refolded protein was shown to directly bind both Staphylococcus aureus enterotoxin B and the major histocompatibility complex protein-peptide complex using a BIAcore biosensor. Thus this preparation of a single-chain, variable-domain, T-cell receptor fragment can bind both of its natural ligands and some of it is therefore a functional fragment of the receptor molecule.

Determination of Ultra-trace Rhodium in Water Samples by Graphite Furnace Atomic Absorption Spectrometry after Cloud Point Extraction Using 2-(5-Iodo-2-Pyridylazo)-5-Dimethylaminoaniline as a Chelating Agent.

PubMed

Han, Quan; Huo, Yanyan; Wu, Jiangyan; He, Yaping; Yang, Xiaohui; Yang, Longhu

2017-03-24

A highly sensitive method based on cloud point extraction (CPE) separation/preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection has been developed for the determination of ultra-trace amounts of rhodium in water samples. A new reagent, 2-(5-iodo-2-pyridylazo)-5-dimethylaminoaniline (5-I-PADMA), was used as the chelating agent and the nonionic surfactant TritonX-114 was chosen as extractant. In a HAc-NaAc buffer solution at pH 5.5, Rh(III) reacts with 5-I-PADMA to form a stable chelate by heating in a boiling water bath for 10 min. Subsequently, the chelate is extracted into the surfactant phase and separated from bulk water. The factors affecting CPE were investigated. Under the optimized conditions, the calibration graph was linear in the range of 0.1-6.0 ng/mL, the detection limit was 0.023 ng/mL for rhodium and relative standard deviation was 3.67% ( c = 1.0 ng/mL, n = 11)．The method has been applied to the determination of trace rhodium in water samples with satisfactory results.

LC-UV/MS methods for the analysis of prochelator - boronyl salicylaldehyde isonicotinoyl hydrazone (BSIH) and its active chelator salicylaldehyde isonicotinoyl hydrazone (SIH)

PubMed Central

Bureš, Jan; Jansová, Hana; Stariat, Ján; Filipský, Tomáš; Mladěnka, Přemysl; Šimůnek, Tomáš; Kučera, Radim; Klimeš, Jiří; Wang, Qin; Franz, Katherine J.; Kovaříková, Petra

2015-01-01

Salicylaldehyde isonicotinoyl hydrazone (SIH) is an intracellular iron chelator with well documented potential to protect against oxidative injury both in vitro and in vivo. However, it suffers from short biological half-life caused by fast hydrolysis of the hydrazone bond. Recently, a concept of boronate prochelators has been introduced as a strategy that might overcome these limitations. This study presents two complementary analytical methods for detecting the prochelator BSIH (boronyl salicylaldehyde isonicotinoyl hydrazone) along with its active metal-binding chelator SIH in different solution matrices and concentration ranges. An LC-UV method for determination of BSIH and SIH in buffer and cell culture medium was validated over concentrations of 7 – 115 and 4 – 115 μM, respectively, and applied to BSIH activation experiments in vitro. An LC-MS assay was validated for quantification of BSIH and SIH in plasma over the concentration range of 0.06 – 23 and 0.24 – 23 μM, respectively, and applied to stability studies in plasma in vitro as well as analysis of plasma taken after i.v. administration of BSIH to rats. A Zorbax-RP bonus column and mobile phases containing either phosphate buffer with EDTA or ammonium formate and methanol/acetonitrile mixture provided suitable conditions for the LC-UV and LC-MS analysis, respectively. Samples were diluted or precipitated with methanol prior to analysis. These separative analytical techniques establish the first validated protocols to investigate BSIH activation by hydrogen peroxide in multiple matrices, directly compare the stabilities of the prochelator and chelator in plasma, and provide the first basic pharmacokinetic data of this prochelator. Experiments reveal that BSIH is stable in all media tested and is partially converted to SIH by H2O2. The observed integrity of BSIH in plasma samples from the in vivo study suggest that the concept of prochelation might be a promising strategy for further development of aroylhydrazone cytoprotective agents. PMID:25527982

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.

Actinide and lanthanide separation process (ALSEP)

DOEpatents

Guelis, Artem V.

2013-01-15

The process of the invention is the separation of minor actinides from lanthanides in a fluid mixture comprising, fission products, lanthanides, minor actinides, rare earth elements, nitric acid and water by addition of an organic chelating aid to the fluid; extracting the fluid with a solvent comprising a first extractant, a second extractant and an organic diluent to form an organic extractant stream and an aqueous raffinate. Scrubbing the organic stream with a dicarboxylic acid and a chelating agent to form a scrubber discharge. The scrubber discharge is stripped with a simple buffering agent and a second chelating agent in the pH range of 2.5 to 6.1 to produce actinide and lanthanide streams and spent organic diluents. The first extractant is selected from bis(2-ethylhexyl)hydrogen phosphate (HDEHP) and mono(2-ethylhexyl)2-ethylhexyl phosphonate (HEH(EHP)) and the second extractant is selected from N,N,N,N-tetra-2-ethylhexyl diglycol amide (TEHDGA) and N,N,N',N'-tetraoctyl-3-oxapentanediamide (TODGA).

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.

Lack of Zn inhibition of Cd accumulation by rice (Oryza sativa L.) supports non-Zn transporter uptake of Cd

USDA-ARS?s Scientific Manuscript database

Rice (Oryza sativa L.) grown on Cd contaminated soils has been linked to health problems in subsistence rice farmers in Japan and China. For other crops, normal geogenic Zn inhibits the increased uptake of Cd on contaminated soils. A study was conducted using a multi-chelator buffered nutrient sol...

Using Chelator-Buffered Nutrient Solutions to Induce Ni-Deficiency in the Ni-Hyperaccumulator Alyssum murale

USDA-ARS?s Scientific Manuscript database

Ni is essential for all plants due to its role in urease. Many Alyssum species are known to hyperaccumulate Ni to over 20 g kg-1 dry weight (DW) while normal plants require only about 0.1 mg kg-1 DW. As part of our research on Ni hyperaccumulation by plants, we conducted experiments to measure the...

Synthesis and in vivo evaluation of 201Tl(III)-DOTA complexes for applications in SPECT imaging.

PubMed

Hijnen, Nicole M; de Vries, Anke; Blange, Roy; Burdinski, Dirk; Grüll, Holger

2011-05-01

The aim of this study was to assess the use of (201)thallium(3+) ((201)Tl(3+)) as a radiolabel for nuclear imaging tracers. Methods for labeling of 1,4,7,10-tetraazacyclododecane-N,N',N″,N'″ tetraacetic acid (DOTA) and diethylenetriaminepentaacetic acid (DTPA) chelators with (201)Tl(3+) were investigated, and the levels of stability of these chelates were tested in vitro and in vivo. (201)Tl(I)Cl was treated with hydrochloric acid and ozone to form (201)Tl(III)Cl(3). The procedure for labeling of DOTA and DTPA was optimized, testing different buffer solutions and pH values. The stability levels of (201)Tl(III)-DOTA and (201)Tl(III)-DTPA were assessed in buffer, mouse serum and human serum (1:1, v/v) at a temperature of 310 K for 48 h. Subsequently, in vivo stability studies with (201)Tl(III)-DOTA were performed, comparing the biodistribution of (201)Tl(III)-DOTA with that of (201)Tl(I)Cl in a single-isotope study and with that of (177)Lu(III)-DOTA in a dual-isotope single photon emission computed tomography study. (201)Tl(III)-DTPA, (201)Tl(III)-DOTA and (177)Lu(III)-DOTA were prepared with >95% radiochemical purity. While (201)Tl(III)-DOTA showed a prolonged level of stability in buffer and serum, (201)Tl was quickly released from DTPA in serum. Apart from some urinary excretion, the biodistribution of DOTA-chelated (201)Tl(3+) was similar to that of free (ionic) (201)Tl(+) and did not match the biodistribution of (177)Lu(III)-DOTA. This indicated a limited stability of (201)Tl(III)-DOTA complexes in vivo. Despite promising results on the labeling and in vitro stability of (201)Tl(III)-DOTA, our in vivo results indicate that the integrity of (201)Tl(III)-DOTA decreases to <20% during the time required for urinary excretion, thereby limiting the use of (201)Tl(3+) as a radiolabel for tracer imaging. Copyright © 2011 Elsevier Inc. All rights reserved.

Optimization of the cydex blue assay: A one-step colorimetric protein assay using cyclodextrins and compatible with detergents and reducers

PubMed Central

2018-01-01

Sodium dodecyl sulfate electrophoresis (SDS) is a protein separation technique widely used, for example, prior to immunoblotting. Samples are usually prepared in a buffer containing both high concentrations of reducers and high concentrations of SDS. This conjunction renders the samples incompatible with common protein assays. By chelating the SDS, cyclodextrins make the use of simple, dye-based colorimetric assays possible. In this paper, we describe the optimization of the assay, focussing on the cyclodextrin/SDS ratio and the use of commercial assay reagents. The adaptation of the assay to a microplate format and using other detergent-containing conventional extraction buffers is also described. PMID:29641569

Behavior of human immunoglobulin G adsorption onto immobilized Cu(II) affinity hollow-fiber membranes.

PubMed

Borsoi-Ribeiro, Mariana; Bresolin, Igor Tadeu Lazzarotto; Vijayalakshmi, Mookambeswaran; Bueno, Sônia Maria Alves

2013-10-01

Iminodiacetic acid (IDA) and tris(2-aminoethyl)amine (TREN) chelating ligands were immobilized on poly(ethylene vinyl alcohol) (PEVA) hollow-fiber membranes after activation with epichlorohydrin or butanediol diglycidyl ether (bisoxirane). The affinity membranes complexed with Cu(II) were evaluated for adsorption of human immunoglobulin G (IgG). The effects of matrix activation and buffer system on adsorption of IgG were studied. Isotherms of batch IgG adsorption onto finely cut membranes showed that neither of the chelates, IDA-Cu(II) or TREN-Cu(II), had a Langmuirean behavior with negative cooperativity for IgG binding. A comparison of equilibrium and dynamic maximum capacities showed that the dynamic capacity for a mini-cartridge in a cross-flow filtration mode (52.5 and 298.4 mg g(-1) dry weight for PEVA-TREN-Cu(II) and PEVA-IDA-Cu(II), respectively) was somewhat higher than the equilibrium capacity (9.2 and 73.3 mg g(-1) dry weight for PEVA-TREN-Cu(II) and PEVA-IDA-Cu(II), respectively). When mini-cartridges were used, the dynamic adsorption capacity of IDA-Cu(II) was the same for both mini-cartridge and agarose gel. Copyright © 2013 John Wiley & Sons, Ltd.

Deduction of a calcium ion circuit affecting rooster sperm in vitro.

PubMed

Froman, D P

2016-08-01

Four premises for rooster sperm preservation were outlined previously. Understanding mitochondrial Ca cycling in terms of whole-cell Ca flux was one premise. The present work tested the hypothesis that sperm mitochondria can be damaged by intracellular as well as extracellular Ca. Sperm were washed by centrifugation through 12% (wt/vol) Sperm were washed by centrifugation through 12%(at/vol) Accudenz to procure sperm at a physiological concentration within a chemically-defined suspension. Five solutions were tested. Each solution contained 30 m glucose, and had an osmolality of 320 mmol/kg and a pH of 7.4. Washed sperm were diluted to 2.0 × 10 sperm/mL. Each replicate sperm suspension was cooled to 10°C. Sperm mobility was measured after 1, 2, 4, 8, 12, and 24 h. Data were plotted as a function of time in each experiment. Function type was confirmed by lack of fit analysis. A parabola with a maximum at 3.7 h was observed when sperm were suspended in 205 m taurine buffered with 50 m-tris[hydroxyl-methyl]methyl-2-amino-ethanesulfonic acid (TES). This effect was attributed to a Ca flux from the nuclear envelope into mitochondria. An exponential decay was observed when TES-buffered taurine contained 2 m Ca. This effect was attributed to mitochondrial Ca overload induced by uptake of extracellular Ca. Exponential decay also was observed when TES-buffered taurine contained a Ca chelator. This effect was attributed to a Ca flux from the nuclear envelope through mitochondria and then into an extracellular Ca sink. This possibility was supported by the response of sperm to thapsigargin. Specifically, inhibition of sarcoendoplasmic reticulum Ca-ATPase compromised sperm mobility relative to a buffer control. Finally, a 60 m phosphate buffer containing 2 m citrate yielded a linear relationship in contrast to the TES-buffered solutions tested. Sperm mobility after 24 h of storage in the phosphate buffer was 92% of that observed for prewashed sperm. The linear response was attributed to weak chelators providing resistance within a Ca circuit and thereby preventing mitochondrial Ca overload. Fertility, however, was compromised when hens were inseminated with mobile sperm recovered after either 8 or 24 h of storage at 10°C. In conclusion, sperm cell Ca homeostasis was proven to be critical for maintaining sperm mobility in vitro, but mitochondrial Ca uptake is not the sole phenomenon that compromises sperm function during in vitro storage.

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.

Drawbacks of Dialysis Procedures for Removal of EDTA

PubMed Central

Mónico, Andreia; Martínez-Senra, Eva; Cañada, F. Javier; Zorrilla, Silvia

2017-01-01

Ethylenediaminetetraacetic acid (EDTA) is a chelating agent commonly used in protein purification, both to eliminate contaminating divalent cations and to inhibit protease activity. For a number of subsequent applications EDTA needs to be exhaustively removed. Most purification methods rely in extensive dialysis and/or gel filtration in order to exchange or remove protein buffer components, including metal chelators. We report here that dialysis protocols, even as extensive as those typically employed for protein refolding, may not effectively remove EDTA, which is reduced only by approximately two-fold and it also persists after spin-column gel filtration, as determined by NMR and by colorimetric methods. Remarkably, the most efficient removal was achieved by ultrafiltration, after which EDTA became virtually undetectable. These results highlight a potentially widespread source of experimental variability affecting free divalent cation concentrations in protein applications. PMID:28099451

Expanding the range of free calcium regulation in biological solutions.

PubMed

Dweck, David; Reyes-Alfonso, Avelino; Potter, James D

2005-12-15

Many biological systems use ethylene glycol bis (beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) to regulate the free calcium concentration ([Ca(2+)](free)) in the presence of physiological levels of free Mg(2+) ([Mg(2+)](free)). Frequently, it is necessary to work at [Ca(2+)](free) beyond EGTA's buffering capabilities. Therefore, we have developed methods to extend the buffering range by adding nitrilotriacetic acid (NTA) to solutions containing EGTA. This extension results from NTA having a lower K'(dCa) than EGTA. Such equilibria are solved by pCa Calculator, a computer program designed to aid in the study of Ca(2+)-dependent physiological processes while accounting for the effects of pH, temperature, and ionic strength. With multiple chelators and pH buffers from which to choose, pCa Calculator calculates the total concentration of each species required to achieve specified free concentrations of Ca(2+), ATP, and Mg(2+). The program is intuitive, user-friendly, and flexible enough to fix or vary the [Mg-ATP(2-)] and ionic strength. Moreover, it can account for increases in experimental volume from calcium addition. A comparative analysis is reported for testing solutions in the presence and absence of NTA by measuring the calcium binding affinity of fluorescent cardiac troponin C. These findings demonstrate that EGTA, when used in conjunction with NTA, improves and expands the regulation of free calcium in solution.

Method for regeneration of electroless nickel plating solution

DOEpatents

Eisenmann, Erhard T.

1997-01-01

An electroless nickel(EN)/hypophosphite plating bath is provided employing acetic acid/acetate as a buffer and which is, as a result, capable of perpetual regeneration while avoiding the production of hazardous waste. A regeneration process is provided to process the spent EN plating bath solution. A concentrated starter and replenishment solution is provided for ease of operation of the plating bath. The regeneration process employs a chelating ion exchange system to remove nickel cations from spent EN plating solution. Phosphites are then removed from the solution by precipitation. The nickel cations are removed from the ion exchange system by elution with hypophosphorous acid and the nickel concentration of the eluate adjusted by addition of nickel salt. The treated solution and adjusted eluate are combined, stabilizer added, and the volume of resulting solution reduced by evaporation to form the bath starter and replenishing solution.

Droplet Microfluidics for Compartmentalized Cell Lysis and Extension of DNA from Single-Cells

NASA Astrophysics Data System (ADS)

Zimny, Philip; Juncker, David; Reisner, Walter

Current single cell DNA analysis methods suffer from (i) bias introduced by the need for molecular amplification and (ii) limited ability to sequence repetitive elements, resulting in (iii) an inability to obtain information regarding long range genomic features. Recent efforts to circumvent these limitations rely on techniques for sensing single molecules of DNA extracted from single-cells. Here we demonstrate a droplet microfluidic approach for encapsulation and biochemical processing of single-cells inside alginate microparticles. In our approach, single-cells are first packaged inside the alginate microparticles followed by cell lysis, DNA purification, and labeling steps performed off-chip inside this microparticle system. The alginate microparticles are then introduced inside a micro/nanofluidic system where the alginate is broken down via a chelating buffer, releasing long DNA molecules which are then extended inside nanofluidic channels for analysis via standard mapping protocols.

Method for regeneration of electroless nickel plating solution

DOEpatents

Eisenmann, E.T.

1997-03-11

An electroless nickel(EN)/hypophosphite plating bath is provided employing acetic acid/acetate as a buffer and which is, as a result, capable of perpetual regeneration while avoiding the production of hazardous waste. A regeneration process is provided to process the spent EN plating bath solution. A concentrated starter and replenishment solution is provided for ease of operation of the plating bath. The regeneration process employs a chelating ion exchange system to remove nickel cations from spent EN plating solution. Phosphites are then removed from the solution by precipitation. The nickel cations are removed from the ion exchange system by elution with hypophosphorus acid and the nickel concentration of the eluate adjusted by addition of nickel salt. The treated solution and adjusted eluate are combined, stabilizer added, and the volume of resulting solution reduced by evaporation to form the bath starter and replenishing solution. 1 fig.

Automated cassette-based production of high specific activity [203/212Pb]peptide-based theranostic radiopharmaceuticals for image-guided radionuclide therapy for cancer.

PubMed

Li, Mengshi; Zhang, Xiuli; Quinn, Thomas P; Lee, Dongyoul; Liu, Dijie; Kunkel, Falk; Zimmerman, Brian E; McAlister, Daniel; Olewein, Keith; Menda, Yusuf; Mirzadeh, Saed; Copping, Roy; Johnson, Frances L; Schultz, Michael K

2017-09-01

A method for preparation of Pb-212 and Pb-203 labeled chelator-modified peptide-based radiopharmaceuticals for cancer imaging and radionuclide therapy has been developed and adapted for automated clinical production. Pre-concentration and isolation of radioactive Pb2+ from interfering metals in dilute hydrochloric acid was optimized using a commercially-available Pb-specific chromatography resin packed in disposable plastic columns. The pre-concentrated radioactive Pb2+ is eluted in NaOAc buffer directly to the reaction vessel containing chelator-modified peptides. Radiolabeling was found to proceed efficiently at 85°C (45min; pH 5.5). The specific activity of radiolabeled conjugates was optimized by separation of radiolabeled conjugates from unlabeled peptide via HPLC. Preservation of bioactivity was confirmed by in vivo biodistribution of Pb-203 and Pb-212 labeled peptides in melanoma-tumor-bearing mice. The approach has been found to be robustly adaptable to automation and a cassette-based fluid-handling system (Modular Lab Pharm Tracer) has been customized for clinical radiopharmaceutical production. Our findings demonstrate that the Pb-203/Pb-212 combination is a promising elementally-matched radionuclide pair for image-guided radionuclide therapy for melanoma, neuroendocrine tumors, and potentially other cancers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

DOE PAGES

Song, Na; Concepcion, Javier J.; Binstead, Robert A.; ...

2015-04-06

In aqueous solution above pH 2.4 with 4% (vol/vol) CH 3CN, the complex [Ru II(bda)(isoq) 2] (bda is 2,2'-bipyridine-6,6'-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [Ru II(CO 2-bpy-CO 2 $-$)(isoq) 2(NCCH 3)], as shown by 1H and 13C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO 4 3–, the calculated half-time for water oxidation is ~7 μs. In conclusion, the key to the rate accelerations with added bases is direct involvement of the buffer basemore » in either atom–proton transfer (APT) or concerted electron–proton transfer (EPT) pathways.« less

Determination of gallium at trace levels using a spectrofluorimetric method in synthetic U-Ga and Ga-As solutions.

PubMed

Kara, Derya; Fisher, Andrew; Foulkes, Mike; Hill, Steve J

2010-01-01

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of gallium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC) was synthesized and its fluorescence activity with gallium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of gallium in synthetically prepared Ga-U and Ga-As samples buffered at pH 4.0 using acetic acid-sodium acetate. The chelation reaction between Ga(III) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 30min at room temperature to complex completely. The limit of detection (LOD) (3sigma) for Ga(III) was 7.17 nM (0.50 microgL(-1)), determined from the analysis of 11 different solutions of 20 microg L(-1) Ga(III). Copyright 2009 Elsevier B.V. All rights reserved.

Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

PubMed Central

Song, Na; Concepcion, Javier J.; Binstead, Robert A.; Rudd, Jennifer A.; Vannucci, Aaron K.; Dares, Christopher J.; Coggins, Michael K.; Meyer, Thomas J.

2015-01-01

In aqueous solution above pH 2.4 with 4% (vol/vol) CH3CN, the complex [RuII(bda)(isoq)2] (bda is 2,2′-bipyridine-6,6′-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [RuII(CO2-bpy-CO2−)(isoq)2(NCCH3)], as shown by 1H and 13C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO43–, the calculated half-time for water oxidation is ∼7 μs. The key to the rate accelerations with added bases is direct involvement of the buffer base in either atom–proton transfer (APT) or concerted electron–proton transfer (EPT) pathways. PMID:25848035

New Chelators for Low Temperature Al(18)F-Labeling of Biomolecules.

PubMed

Cleeren, Frederik; Lecina, Joan; Billaud, Emilie M F; Ahamed, Muneer; Verbruggen, Alfons; Bormans, Guy M

2016-03-16

The Al(18)F labeling method is a relatively new approach that allows radiofluorination of biomolecules such as peptides and proteins in a one-step procedure and in aqueous solution. However, the chelation of the {Al(18)F}(2+) core with the macrocyclic chelators NOTA or NODA requires heating to 100-120 °C. Therefore, we have developed new polydentate ligands for the complexation of {Al(18)F}(2+) with good radiochemical yields at a temperature of 40 °C. The stability of the new Al(18)F-complexes was tested in phosphate buffered saline (PBS) at pH 7.4 and in rat serum. The stability of the Al(18)F-L3 complex was found to be comparable to that of the previously reported Al(18)F-NODA complex up to 60 min in rat serum. Moreover, the biodistribution of Al(18)F-L3 in healthy mice showed the absence of in vivo defluorination since no significant bone uptake was observed, whereas the major fraction of activity at 60 min p.i. was observed in liver and intestines, indicating hepatobiliary clearance of the radiolabeled ligand. The acyclic chelator H3L3 proved to be a good lead candidate for labeling of heat-sensitive biomolecules with fluorine-18. In order to obtain a better understanding of the different factors influencing the formation and stability of the complex, we carried out more in-depth experiments with ligand H3L3. As a proof of concept, we successfully conjugated the new AlF-chelator with the urea-based PSMA inhibitor Glu-NH-CO-NH-Lys to form Glu-NH-CO-NH-Lys(Ahx)L3, and a biodistribution study in healthy mice was performed with the Al(18)F-labeled construct. This new class of AlF-chelators may have a great impact on PET radiochemical space as it will stimulate the rapid development of new fluorine-18 labeled peptides and other heat-sensitive biomolecules.

Characterization of injury in isolated rat proximal tubules during cold incubation and rewarming.

PubMed

Bienholz, Anja; Walter, Björn; Pless-Petig, Gesine; Guberina, Hana; Kribben, Andreas; Witzke, Oliver; Rauen, Ursula

2017-01-01

Organ shortage leads to an increased utilization of marginal organs which are particularly sensitive to storage-associated damage. Cold incubation and rewarming-induced injury is iron-dependent in many cell types. In addition, a chloride-dependent component of injury has been described. This work examines the injury induced by cold incubation and rewarming in isolated rat renal proximal tubules. The tissue storage solution TiProtec® and a chloride-poor modification, each with and without iron chelators, were used for cold incubation. Incubation was performed 4°C for up to 168 h, followed by rewarming in an extracellular buffer (3 h at 37°C). After 48, 120 and 168 h of cold incubation LDH release was lower in solutions containing iron chelators. After rewarming, injury increased especially after cold incubation in chelator-free solutions. Without addition of iron chelators LDH release showed a tendency to be higher in chloride-poor solutions. Following rewarming after 48 h of cold incubation lipid peroxidation was significantly decreased and metabolic activity was tendentially better in tubules incubated with iron chelators. Morphological alterations included mitochondrial swelling and fragmentation being partially reversible during rewarming. ATP content was better preserved in chloride-rich solutions. During rewarming, there was a further decline of ATP content in the so far best conditions and minor alterations under the other conditions, while oxygen consumption was not significantly different compared to non-stored control tubules. Results show an iron-dependent component of preservation injury during cold incubation and rewarming in rat proximal renal tubules and reveal a benefit of chloride for the maintenance of tubular energy state during cold incubation.

Characterization of injury in isolated rat proximal tubules during cold incubation and rewarming

PubMed Central

Bienholz, Anja; Walter, Björn; Pless-Petig, Gesine; Guberina, Hana; Kribben, Andreas; Witzke, Oliver; Rauen, Ursula

2017-01-01

Organ shortage leads to an increased utilization of marginal organs which are particularly sensitive to storage-associated damage. Cold incubation and rewarming-induced injury is iron-dependent in many cell types. In addition, a chloride-dependent component of injury has been described. This work examines the injury induced by cold incubation and rewarming in isolated rat renal proximal tubules. The tissue storage solution TiProtec® and a chloride-poor modification, each with and without iron chelators, were used for cold incubation. Incubation was performed 4°C for up to 168 h, followed by rewarming in an extracellular buffer (3 h at 37°C). After 48, 120 and 168 h of cold incubation LDH release was lower in solutions containing iron chelators. After rewarming, injury increased especially after cold incubation in chelator-free solutions. Without addition of iron chelators LDH release showed a tendency to be higher in chloride-poor solutions. Following rewarming after 48 h of cold incubation lipid peroxidation was significantly decreased and metabolic activity was tendentially better in tubules incubated with iron chelators. Morphological alterations included mitochondrial swelling and fragmentation being partially reversible during rewarming. ATP content was better preserved in chloride-rich solutions. During rewarming, there was a further decline of ATP content in the so far best conditions and minor alterations under the other conditions, while oxygen consumption was not significantly different compared to non-stored control tubules. Results show an iron-dependent component of preservation injury during cold incubation and rewarming in rat proximal renal tubules and reveal a benefit of chloride for the maintenance of tubular energy state during cold incubation. PMID:28672023

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

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

A method to solubilise protein aggregates for immunoassay quantification which overcomes the neurofilament "hook" effect.

PubMed

Lu, Ching-Hua; Kalmar, Bernadett; Malaspina, Andrea; Greensmith, Linda; Petzold, Axel

2011-02-15

Neurofilament (Nf) aggregates are a common pathological feature of neurodegenerative disorders. Although Nf levels have been investigated as a potential disease biomarker, Nf aggregates may mask Nf epitopes, preventing accurate quantification by immunoassay. Using the SOD1(G93A) mouse model of amyotrophic lateral sclerosis, we developed a method to disrupt Nf aggregates, allowing optimal immunoassay performance. Phosphorylated (NfH(SMI35)) and hyperphosphorylated (NfH(SMI34)) Nf levels in plasma from 120-day SOD1(G93A) mice were quantified using an in-house ELISA modified for use with small volumes. Different pre-analytical methods were tested for their ability to solubilize Nf aggregates and immunoblotting was used for qualitative analysis. A 'hook effect' was observed for serially diluted plasma samples quantified using an ELISA originally developed for CSF samples. Immunoblotting confirmed the existence of high molecular-weight NfH aggregates in plasma and the resolving effect of timed urea on these aggregates. Thermostatic (pre-thawing) and chemical (calcium chelators, urea) pre-analytical processing of samples had variable success in disrupting NfH aggregates. Timed urea-calcium chelator incubation yielded the most consistent plasma NfH levels. A one hour sample pre-incubation with 0.5M urea in Barbitone-EDTA buffer at room temperature resolved the "hook effect" without compromising the ELISA. In SOD1(G93A) mice, median levels of NfH(SMI34) were over 10-fold and NfH(SMI35) levels 5-fold greater than controls. NfH aggregates can be solubilised and the "hook effect" abolished by a one-hour sample pre-incubation in a urea-calcium chelator-enriched buffer. This method is applicable for quantification of NfH phosphoforms in experimental and disease settings where Nf aggregate formation occurs. © 2010 Elsevier B.V. All rights reserved.

Large volume preconcentration and determination of nanomolar concentrations of iron in seawater using a renewable cellulose 8-hydroquinoline sorbent microcolumn and universal approach of post-column eluate utilization in a Lab-on-Valve system.

PubMed

Horstkotte, Burkhard; Chocholouš, Petr; Solich, Petr

2016-04-01

We report on a Lab-On-Valve (LOV) configuration for analyte preconcentration from milliliter sample volumes using confluent mixing in the holding coil for in-line addition of loading buffer. The system was applied to the spectrophotometric determination of iron(II) in acidified seawater using 1,10-phenanthroline as color reagent. A cellulose-based chelating sorbent containing 8-hydroxyquinoline was used for the first time in LOV and excellent retention behavior and loading capacity were found. The flow system employs a syringe pump for handling all solutions (sorbent suspension, loading buffer, water, eluent, and color reagent) and a peristaltic pump for sample propulsion and includes a fit-for-purpose 14 cm long detection glass flow cell and a bubble trap for in-line carrier degasification. Advantage was taken of the LOV flow-through port to keep the eluted analytes for re-aspiration for subsequent chromogenic reaction. In effect, a universal analyzer configuration and preconcentration procedure was developed, which is combinable with other analytes, sorbents, and reagents. Among the studied parameters were the compositions, pH, volumes, and flow rates of loading buffer, eluent, and color reagent, as well as the microcolumn size, repeatability, and system stability. Reproducibility of 4.1% RSD over the entire working range, a LOD of down to 5 nmol L(-1), sampling frequency of 12h(-1), and linearity up to 1 µmol L(-1) for 3.3 mL of sample were obtained and applicability to real samples was demonstrated. It was proven that both Fe(III) and Fe(II) were retained and yielded similar recovery and sensitivity values. The method was applied to coastal seawater samples and spiking experiments yielded recovery values close to 100%. Copyright © 2015 Elsevier B.V. All rights reserved.

Freeze-dried dog sperm: Dynamics of DNA integrity.

PubMed

Olaciregui, M; Luño, V; Gonzalez, N; De Blas, I; Gil, L

2015-10-01

Freeze-drying (FD) has been proposed as an alternative method to preserve spermatozoa. During the FD procedure, sperm DNA might become damaged by both freezing and drying stresses caused by the endonucleases, the oxidative stress and the storage conditions. We examined the DNA integrity of dog sperm freeze-dried with two kinds of chelating agents in FD buffers and storage at two different temperatures. Ejaculated sperm from four dogs were suspended in basic medium (10 mM Tris-HCl buffer+50 mM NaCl) supplemented with 50 mM EGTA or with 50 mM EDTA and then freeze-dried. Sperm samples were stored at 4°C as room temperature, and the analysis of DNA damage was performed after a month and 5 months of storage using a Sperm Chromatin Dispersion test. We found four different sperm populations according to the size of the halos around the sperm head: (1) absent halo, (2) <6 μm, (3) 6-10 μm, (4) >10 μm. All of them coexisted in each freeze-dried dog semen samples and differed significantly among different treatments. The highest percentage of spermatozoa with halo >10 μm was obtained when the semen samples were freeze-dried in EDTA medium and stored at room temperature for five months. Results suggested that both, the kind of chelating agent as well as storage temperature and period, influenced DNA integrity of freeze-dried dog sperm. Copyright © 2015 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.

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.

An online calculator for marine phytoplankton iron culturing experiments.

PubMed

Rivers, Adam R; Rose, Andrew L; Webb, Eric A

2013-10-01

Laboratory experiments with iron offer important insight into the physiology of marine phytoplankton and the biogeochemical cycles they influence. These experiments often rely on chelators to buffer the concentration of available iron, but the buffer can fail when cell density increases, causing the concentration of that iron to drop rapidly. To more easily determine the point when the iron concentration falls, we developed an online calculator to estimate the maximum phytoplankton density that a growth medium can support. The results of the calculator were compared to the numerical simulations of a Fe-limited culture of the diatom Thalassiosira weissflogii (Grunow) Fryxell and Hasle. Modeling reveals that the assumptions behind thermodynamic estimates of unchelated Fe concentration can fail before easily perceptible changes in growth rate, potentially causing physiological changes that could alter the conclusions of culture experiments. The calculator is available at http://www.marsci.uga.edu/fidoplankter. © 2013 Phycological Society of America.

Macrocyclic bifunctional chelating agents

DOEpatents

Meares, Claude F.; DeNardo, Sally J.; Cole, William C.; Mol, Min K.

1987-01-01

A copper chelate conjugate which is stable in human serum. The conjugate includes the copper chelate of a cyclic tetraaza di-, tri-, or tetra-acetic acid, a linker attached at one linker end to a ring carbon of the chelate, and a biomolecule joined at the other end of the linker. The conjugate, or the linker-copper chelate compound used in forming the conjugate, are designed for use in diagnostic and therapeutic applications which involve Cu(II) localization via the systemic route.

Biologics formulation factors affecting metal leachables from stainless steel.

PubMed

Zhou, Shuxia; Schöneich, Christian; Singh, Satish K

2011-03-01

An area of increasing concern and scientific scrutiny is the potential contamination of drug products by leachables entering the product during manufacturing and storage. These contaminants may either have a direct safety impact on the patients or act indirectly through the alteration of the physicochemical properties of the product. In the case of biotherapeutics, trace amounts of metal contaminants can arise from various sources, but mainly from contact with stainless steel (ss). The effect of the various factors, buffer species, solution fill volume per unit contact surface area, metal chelators, and pH, on metal leachables from contact with ss over time were investigated individually. Three major metal leachables, iron, chromium, and nickel, were monitored by inductively coupled plasma-mass spectrometry because they are the major components of 316L ss. Iron was primarily used to evaluate the effect of each factor since it is the most abundant. It was observed that each studied factor exhibited its own effect on metal leachables from contact with ss. The effect of buffer species and pH exhibited temperature dependence over the studied temperature range. The metal leachables decreased with the increased fill volume (mL) per unit contact ss surface area (cm(2)) but a plateau was achieved at approximately 3 mL/cm(2). Metal chelators produced the strongest effect in facilitating metal leaching. In order to minimize the metal leachables and optimize biological product stability, each formulation factor must be evaluated for its impact, to balance its risk and benefit in achieving the target drug product shelf life. © 2011 American Association of Pharmaceutical Scientists

Assessment of a gel-type chelating preparation containing 1-hydroxyethylidene-1, 1-bisphosphonate.

PubMed

Girard, S; Paqué, F; Badertscher, M; Sener, B; Zehnder, M

2005-11-01

To test an aqueous gel containing 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) regarding its interactions with sodium hypochlorite, its calcium binding capacity, and its potential in preventing the formation of a smear layer when used in conjunction with rotary root canal preparation. The experimental aqueous gel consisted of (w/v) 2% alginate, 3% aerosil, 10% Tween 80 and 18% HEBP. Interactions of gel components with hypochlorite were assessed using iodometric titration and monochromatic ultraviolet spectrometry. Two commercial paste-type chelators containing ethylenediaminetetraacetic acid (EDTA) and peroxide (RC-Prep and Glyde) served as controls. Calcium-binding capacities were measured in mixtures with a Ca2+ standard solution buffered at pH 10 using a calcium-selective measuring chain. Finally, root canals of 16 extracted single-rooted premolars per group were instrumented using ProFile instruments dipped in the experimental gel, RC-Prep, or nothing. Additionally, canals were rinsed with 10 mL of a 1% NaOCl solution during/after preparation. Smear scores in instrumented teeth were monitored using scanning electron microscopy. None of the experimental gel components showed short-term interactions with hypochlorite, whilst EDTA, peroxide, RC-Prep and Glyde immediately reduced the hypochlorite in solution. The experimental gel chelated 30 mg Ca2+ g-1, compared with 16 mg Ca2+ g-1 and 11 mg Ca2+ g-1 chelated by RC-Prep and Glyde respectively. Smear scores obtained with the experimental gel were significantly (P<0.05) lower than with RC-Prep in coronal and middle root thirds, whilst no differences were observed in apical root thirds. Under the conditions of this study, an HEBP gel appeared advantageous over currently available products.

A coumarin based Schiff base probe for selective fluorescence detection of Al3 + and its application in live cell imaging

NASA Astrophysics Data System (ADS)

Sen, Bhaskar; Sheet, Sanjoy Kumar; Thounaojam, Romita; Jamatia, Ramen; Pal, Amarta Kumar; Aguan, Kripamoy; Khatua, Snehadrinarayan

2017-02-01

A new coumarin based Schiff base compound, CSB-1 has been synthesized to detect metal ion based on the chelation enhanced fluorescence (CHEF). The cation binding properties of CSB-1 was thoroughly examined in UV-vis and fluorescence spectroscopy. In fluorescence spectroscopy the compound showed high selectivity toward Al3 + ion and the Al3 + can be quantified in mixed aqueous buffer solution (MeOH: 0.01 M HEPES Buffer; 9:1; v/v) at pH 7.4 as well as in BSA media. The fluorescence intensity of CSB-1 was enhanced by 24 fold after addition of only five equivalents of Al3 +. The fluorescence titration of CSB-1 with Al3 + in mixed aqueous buffer afforded a binding constant, Ka = (1.06 ± 0.2) × 104 M- 1. The colour change from light yellow to colourless and the appearance of blue fluorescence, which can be observed by the naked eye, provides a real-time method for Al3 + sensing. Further the live cell imaging study indicated that the detection of intracellular Al3 + ions are also readily possible in living cell.

An electrochemical study of natural and chemically controlled eumelanin

NASA Astrophysics Data System (ADS)

Xu, Ri; Prontera, Carmela Tania; Di Mauro, Eduardo; Pezzella, Alessandro; Soavi, Francesca; Santato, Clara

2017-12-01

Eumelanin is the most common form of the pigment melanin in the human body, with functions including antioxidant behavior, metal chelation, and free radical scavenging. This biopigment is of interest for biologically derived batteries and supercapacitors. In this work, we characterized the voltammetric properties of chemically controlled eumelanins produced from 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) building blocks, namely, DHI-melanin, DHICA-melanin, and natural eumelanin, extracted from the ink sac of cuttlefish, Sepia melanin. Eumelanin electrodes were studied for their cyclic voltammetric properties in acidic buffers including Na+, K+, NH4+, and Cu2+ ions.

Development of Iron-Chelating Poly(ethylene terephthalate) Packaging for Inhibiting Lipid Oxidation in Oil-in-Water Emulsions.

PubMed

Johnson, David R; Tian, Fang; Roman, Maxine J; Decker, Eric A; Goddard, Julie M

2015-05-27

Foods such as bulk oils, salad dressings, and nutritionally fortified beverages that are susceptible to oxidative degradation are often packaged in poly(ethylene terephthalate) (PET) bottles with metal chelators added to the food to maintain product quality. In the present work, a metal-chelating active packaging material is designed and characterized, in which poly(hydroxamic acid) (PHA) metal-chelating moieties were grafted from the surface of PET. Biomimetic PHA groups were grafted in a two-step UV-initiated process without the use of a photoinitiator. Surface characterization of the films by attenuated total reflective Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) suggested successful grafting and conversion of poly(hydroxyethyl acrylate) (PHEA) to PHA chelating moieties from the surface of PET. Colorimetric (ferrozine) and inductively coupled plasma mass spectroscopy (ICP-MS) assays demonstrated the ability of PET-g-PHA to chelate iron in a low-pH (3.0) environment containing a competitive metal chelator (citric acid). Lipid oxidation studies demonstrated the antioxidant activity of PET-g-PHA films in inhibiting iron-promoted oxidation in an acidified oil-in-water (O/W) emulsion model system (pH 3.0). Particle size and ζ-potential analysis indicated that the addition of PET-g-PHA films did not affect the physical stability of the emulsion system. This work suggests that biomimetic chelating moieties can be grafted from PET and effectively inhibit iron-promoted degradation reactions, enabling removal of metal-chelating additives from product formulations.

Selective digestion of Ba2+/Ca2+ alginate gel microdroplets for single-cell handling

NASA Astrophysics Data System (ADS)

Odaka, Masao; Hattori, Akihiro; Matsuura, Kenji; Yasuda, Kenji

2018-06-01

Cells encapsuled by polymer microdroplets are an effective platform for the identification and separation of individual cells for single-cell-based analysis. However, a key challenge is to maintain and release the captured cells in the microdroplets selectively, nondestructively, and noninvasively. We developed a simple method of encapsulating cells in alginate microdroplets having different digestion characteristics. Cells were diluted with an alginate polymer of sol state and encapsulated into microdroplets with Ba2+ and Ca2+ by a spray method. When a chelating buffer was applied, alginate gel microdroplets were digested according to the difference in chelating efficiency of linkage-divalent cations; hence, two types of alginate microdroplets were formed. Moreover, we examined the capability of the alginate gel to exchange linkage-divalent cations and found that both Ca2+ exchange in Ba-alginate microdroplets and Ba2+ exchange in Ca-alginate microdroplets occurred. These results indicate that the potential applications of a mixture of alginate microdroplets with different divalent cations control the selective digestion of microdroplets to improve the high-throughput, high-content microdroplet-based separation, analysis, or storage of single cells.

Purification method for recombinant proteins based on a fusion between the target protein and the C-terminus of calmodulin

NASA Technical Reports Server (NTRS)

Schauer-Vukasinovic, Vesna; Deo, Sapna K.; Daunert, Sylvia

2002-01-01

Calmodulin (CaM) was used as an affinity tail to facilitate the purification of the green fluorescent protein (GFP), which was used as a model target protein. The protein GFP was fused to the C-terminus of CaM, and a factor Xa cleavage site was introduced between the two proteins. A CaM-GFP fusion protein was expressed in E. coli and purified on a phenothiazine-derivatized silica column. CaM binds to the phenothiazine on the column in a Ca(2+)-dependent fashion and it was, therefore, used as an affinity tail for the purification of GFP. The fusion protein bound to the affinity column was then subjected to a proteolytic digestion with factor Xa. Pure GFP was eluted with a Ca(2+)-containing buffer, while CaM was eluted later with a buffer containing the Ca(2+)-chelating agent EGTA. The purity of the isolated GFP was verified by SDS-PAGE, and the fluorescence properties of the purified GFP were characterized.

Intramitochondrial Zn2+ accumulation via the Ca2+ uniporter contributes to acute ischemic neurodegeneration

PubMed Central

Medvedeva, Yuliya V.; Weiss, John H.

2014-01-01

Ca2+ and Zn2+ have both been implicated in the induction of acute ischemic neurodegeneration. We recently examined changes in intracellular Zn2+ and Ca2+ in CA1 pyramidal neurons subjected to oxygen glucose deprivation (OGD), and found that Zn2+ rises precede and contribute to the onset of terminal Ca2+ rises (“Ca2+ deregulation”), which are causatively linked to a lethal loss of membrane integrity. The present study seeks to examine the specific role of intramitochondrial Zn2+ accumulation in ischemic injury, using blockers of the mitochondrial Ca2+ uniporter (MCU), through which both Zn2+ and Ca2+ appear able to enter the mitochondrial matrix. In physiological extracellular Ca2+, treatment with the MCU blocker, Ruthenium Red (RR), accelerated the Ca2+ deregulation, most likely by disrupting mitochondrial Ca2+ buffering and thus accelerating the lethal cytosolic Ca2+ overload. However, when intracellular Ca2+ overload was slowed, either by adding blockers of major Ca2+ entry channels or by lowering the concentration of Ca2+ in the extracellular buffer, Ca2+ deregulation was delayed, and under these conditions either Zn2+ chelation or MCU blockade resulted in similar further delays of the Ca2+ deregulation. In parallel studies using the reactive oxygen species (ROS) indicator, hydroethidine, lowering Ca2+ surprisingly accelerated OGD induced ROS generation, and in these low Ca2+ conditions, either Zn2+ chelation or MCU block slowed the ROS generation. These studies suggest that, during acute ischemia, Zn2+ entry into mitochondria via the MCU induces mitochondrial dysfunction (including ROS generation) that occurs upstream of, and contributes to the terminal Ca2+ deregulation. PMID:24787898

Development and validation spectroscopic methods for the determination of lomefloxacin in bulk and pharmaceutical formulations

NASA Astrophysics Data System (ADS)

El-Didamony, A. M.; Hafeez, S. M.

2016-01-01

Four simple, sensitive spectrophotometric and spectrofluorimetric methods (A-D) for the determination of antibacterial drug lomefloxacin (LMFX) in pharmaceutical formulations have been developed. Method A is based on formation of ternary complex between Pd(II), eosin and LMFX in the presence of methyl cellulose as surfactant and acetate-HCl buffer pH 4.0. Spectrophotometrically, under the optimum conditions, the ternary complex showed absorption maximum at 530 nm. Methods B and C are based on redox reaction between LMFX and KMnO4 in acid and alkaline media. In indirect spectrophotometry method B the drug solution is treated with a known excess of KMnO4 in H2SO4 medium and subsequent determination of unreacted oxidant by reacting it with safronine O in the same medium at λmax = 520 nm. Direct spectrophotometry method C involves treating the alkaline solution of LMFX with KMnO4 and measuring the bluish green product at 604 nm. Method D is based on the chelation of LMFX with Zr(IV) to produce fluorescent chelate. At the optimum reaction conditions, the drug-metal chelate showed excitation maxima at 280 nm and emission maxima at 443 nm. The optimum experimental parameters for the reactions have been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drug in pharmaceutical preparations with good recoveries.

A model system for the evaluation of radioimmunoimaging of tumors

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

Koizumi, M.; Endo, K.; Sakahara, H.

1985-05-01

The authors have developed a simple model system that can be used to evaluate methods of radioimmunoimaging of tumors, using human chorionic gonadropin (hCG) as a model antigen, and a monoclonal antibody against hCG ..beta..-subunit as a model antibody. HCG was coated on a polystylene spherical bead with a quarter inch in diameter, and coated beads were washed extensively with phosphate buffered saline, and glycine acid buffer to remove the easily dissociable antigen. HCG-coated beads were put into the subcutaneous tissue on the back of mice. At 24 hr after the transplantation, when serum hCG was not detectable by themore » conventional RIA, radiolabeled antibodies were injected and its bio-distribution monitored. The %ID/g for the hCG coated beads increased to a maximum of 48 hr after the injection of radioiodinad antibody, whereas the %ID/g for most organs decreased with time. As a nonspecific antigen, beads coated with bovine serum albumin were transplanted and its uptake was as low as about one 50th of hCG-coated ones. The %ID/g of radioiodinated monoclonal antibody against human thyroglobulin (a nonspecific antibody) for hCG-coated beads was also negligible. Thus, the localization index (%ID of specific antibody / %ID of nonspecific antibody) reached to 15.0 at 24 hr, 35.5 at 48 hr and 57.8 at 96 hr after the injection. The biodistribution of In-111 labeled specific monoclonal antibody, prepared through the chelation with DTPA, demonstrated similar results with radioiodinated ones. This mouse model system that did not involve the use of tumors, yielded high localization index and reproducibilities and could be used to evaluate different methods for radiolabelng monoclonal antibodies.« less

Ligand-enhanced electrokinetic remediation of metal-contaminated marine sediments with high acid buffering capacity.

PubMed

Masi, Matteo; Iannelli, Renato; Losito, Gabriella

2016-06-01

The suitability of electrokinetic remediation for removing heavy metals from dredged marine sediments with high acid buffering capacity was investigated. Laboratory-scale electrokinetic remediation experiments were carried out by applying two different voltage gradients to the sediment (0.5 and 0.8 V/cm) while circulating water or two different chelating agents at the electrode compartments. Tap water, 0.1 M citric acid and 0.1 M ethylenediaminetetraacetic acid (EDTA) solutions were used respectively. The investigated metals were Zn, Pb, V, Ni and Cu. In the unenhanced experiment, the acid front could not propagate due to the high acid buffering capacity of the sediments; the production of OH(-) ions at the cathode resulted in a high-pH environment causing the precipitation of CaCO3 and metal hydroxides. The use of citric acid prevented the formation of precipitates, but solubilisation and mobilisation of metal species were not sufficiently achieved. Metal removal was relevant when EDTA was used as the conditioning agent, and the electric potential was raised up to 0.8 V/cm. EDTA led to the formation of negatively charged complexes with metals which migrated towards the anode compartment by electromigration. This result shows that metal removal from sediments with high acid buffering capacity may be achieved by enhancing the electrokinetic process by EDTA addition when the acidification of the medium is not economically and/or environmentally sustainable.

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.

Chelate effects in sulfate binding by amide/urea-based ligands.

PubMed

Jia, Chuandong; Wang, Qi-Qiang; Begum, Rowshan Ara; Day, Victor W; Bowman-James, Kristin

2015-07-07

The influence of chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands. Two of the urea-based hosts were selective for SO4(2-) in water-mixed DMSO-d6 systems. Results indicated that the mini-chelate effect provided by a single urea group with two NH binding sites appears to provide enhanced binding over two amide groups. Furthermore, additional urea binding sites incorporated into the host framework appeared to overcome to some extent competing hydration effects with increasing water content.

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.

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.

EDTA chelation effects on urinary losses of cadmium, calcium, chromium, cobalt, copper, lead, magnesium, and zinc.

PubMed

Waters, R S; Bryden, N A; Patterson, K Y; Veillon, C; Anderson, R A

2001-12-01

The efficacy of a chelating agent in binding a given metal in a biological system depends on the binding constants of the chelator for the particular metals in the system, the concentration of the metals, and the presence and concentrations of other ligands competing for the metals in question. In this study, we make a comparison of the in vitro binding constants for the chelator, ethylenediaminetetraacetic acid, with the quantitative urinary excretion of the metals measured before and after EDTA infusion in 16 patients. There were significant increases in lead, zinc, cadmium, and calcium, and these increases roughly corresponded to the expected relative increases predicted by the EDTA-metal-binding constants as measured in vitro. There were no significant increases in urinary cobalt, chromium, or copper as a result of EDTA infusion. The actual increase in cobalt could be entirely attributed to the cobalt content of the cyanocobalamin that was added to the infusion. Although copper did increase in the post-EDTA specimens, the increase was not statistically significant. In the case of magnesium, there was a net retention of approximately 85% following chelation. These data demonstrate that EDTA chelation therapy results in significantly increased urinary losses of lead, zinc, cadmium, and calcium following EDTA chelation therapy. There were no significant changes in cobalt, chromium, or copper and a retention of magnesium. These effects are likely to have significant effects on nutrient concentrations and interactions and partially explain the clinical improvements seen in patients undergoing EDTA chelation therapy.

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.

Influence of mixtures of calcium-chelating salts on the physicochemical properties of casein micelles.

PubMed

Kaliappan, S; Lucey, J A

2011-09-01

Calcium-chelating salts (CCS), such as phosphates and citrates, are often added to milk systems to modify physical properties like heat stability. The objective of this study was to investigate the effect of binary CCS mixtures on the properties of casein (CN) micelles including the distribution of Ca between the soluble and CN-bound states. Six binary CCS mixtures were prepared from 4 different types of CCS [i.e., trisodium citrate (TSC), disodium phosphate (DSP), tetrasodium pyrophosphate (TSPP), and sodium hexameta phosphate (SHMP)] by combining 2 CCS at a time in 5 different proportions (8.3:91.7, 29.2:70.8, 50:50, 70.8:29.2, and 91.7:8.3). Different concentrations of these mixtures (0, 0.1, 0.3, 0.5, and 0.7% wt/wt) were added to milk protein concentrate solutions (5% wt/wt) at pH 5.8. The ability of CCS to disperse CN particles and its interaction with Ca were assessed from turbidity measurements, acid-base titration behavior, and the quantity of CN-bound Ca and inorganic phosphate (Pi). Turbidity and the buffering peak at pH ∼5.0 during acid titration decreased with an increasing concentration of CCS. This was due to the chelation of Ca and the dispersion of CN micelles. The presence of TSC in mixtures decreased the amount of CN-bound Ca and Pi; however, the presence of TSPP in mixtures increased CN-bound Ca and Pi. When DSP was present at high proportions in mixtures of CCS, the CN-bound Ca and Pi slightly increased. When SHMP was used in mixtures of CCS, CN-bound Ca and Pi increased with the use of a low proportion of SHMP but decreased when SHMP was used at high proportions in the mixture. Combinations of DSP-TSPP used in the proportions 29.2:70.8, 50:50, and 70.8:29.2 resulted in the gelation of milk protein concentrates when the total CCS concentration was ≥0.3%. These results indicated that the type of CCS present in a mixture modified CN properties by various mechanisms, including chelation of Ca, dispersion of CN micelles, and formation of new types of Ca-CCS complexes. The type of interaction between the newly formed Ca-CCS complexes and the dispersed CN depended on the proportion, concentration, and type of CCS present in the mixtures. This information is useful in understanding how mixtures of CCS affect CN properties. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

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.

Garlic's ability to prevent in vitro Cu2+-induced lipoprotein oxidation in human serum is preserved in heated garlic: effect unrelated to Cu2+-chelation

PubMed Central

Pedraza-Chaverrí, José; Gil-Ortiz, Mariana; Albarrán, Gabriela; Barbachano-Esparza, Laura; Menjívar, Marta; Medina-Campos, Omar N

2004-01-01

Background It has been shown that several extracts and compounds derived from garlic are able to inhibit Cu2+-induced low density lipoprotein oxidation. In this work we explored if the ability of aqueous garlic extract to prevent in vitro Cu2+-induced lipoprotein oxidation in human serum is affected by heating (a) aqueous garlic extracts or (b) garlic cloves. In the first case, aqueous extract of raw garlic and garlic powder were studied. In the second case, aqueous extract of boiled garlic cloves, microwave-treated garlic cloves, and pickled garlic were studied. It was also studied if the above mentioned preparations were able to chelate Cu2+. Methods Cu2+-induced lipoprotein oxidation in human serum was followed by the formation of conjugated dienes at 234 nm and 37°C by 240 min in a phosphate buffer 20 mM, pH 7.4. Blood serum and CuSO4 were added to a final concentration of 0.67% and 0.0125 mM, respectively. The lag time and the area under the curve from the oxidation curves were obtained. The Cu2+-chelating properties of garlic extracts were assessed using an approach based upon restoring the activity of xanthine oxidase inhibited in the presence of 0.050 mM Cu2+. The activity of xanthine oxidase was assessed by monitoring the production of superoxide anion at 560 nm and the formation of uric acid at 295 nm. Data were compared by parametric or non-parametric analysis of variance followed by a post hoc test. Results Extracts from garlic powder and raw garlic inhibited in a dose-dependent way Cu2+-induced lipoprotein oxidation. The heating of garlic extracts or garlic cloves was unable to alter significantly the increase in lag time and the decrease in the area under the curve observed with the unheated garlic extracts or raw garlic. In addition, it was found that the garlic extracts were unable to chelate Cu2+. Conclusions (a) the heating of aqueous extracts of raw garlic or garlic powder or the heating of garlic cloves by boiling, microwave or pickling do not affect garlic's ability to inhibit Cu2+-induced lipoprotein oxidation in human serum, and (b) this ability is not secondary to Cu2+-chelation. PMID:15341661

Guidelines on iron chelation therapy in patients with myelodysplastic syndromes and transfusional iron overload.

PubMed

Gattermann, Norbert

2007-12-01

Experts believe that iron overload is an important problem which could be avoided with suitable treatment. Guidelines on treating myelodysplastic syndromes (MDS) include sections on using iron chelation therapy to prevent or ameliorate transfusional iron overload. The proportion of MDS patients who may benefit from iron chelation therapy is 35-55%, depending on the length of survival necessary for iron to accumulate to a detrimental level. Candidates for iron chelation are mainly patients with dyserythropoietic and cytopenic subtypes of disease, which fall into the International Prognostic Scoring System (IPSS) Low-risk or Intermediate-1-risk categories, with median survival of 3-6 years.

[Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents

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

Not Available

1991-12-31

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

(Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents)

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

Not Available

1991-01-01

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

Chelating capture and magnetic removal of non-magnetic heavy metal substances from soil

PubMed Central

Fan, Liren; Song, Jiqing; Bai, Wenbo; Wang, Shengping; Zeng, Ming; Li, Xiaoming; Zhou, Yang; Li, Haifeng; Lu, Haiwei

2016-01-01

A soil remediation method based on magnetic beneficiation is reported. A new magnetic solid chelator powder, FS@IDA (core-shell Fe3O4@SiO2 nanoparticles coated with iminodiacetic acid chelators), was used as a reactive magnetic carrier to selectively capture non-magnetic heavy metals in soil by chelation and removal by magnetic separation. FS@IDA was prepared via inorganic-organic and organic synthesis reactions that generated chelating groups on the surface of magnetic, multi-core, core-shell Fe3O4@SiO2 (FS) nanoparticles. These reactions used a silane coupling agent and sodium chloroacetate. The results show that FS@IDA could chelate the heavy metal component of Cd, Zn, Pb, Cu and Ni carbonates, lead sulfate and lead chloride in water-insoluble salt systems. The resulting FS@IDA-Cd and FS@IDA-Pb chelates could be magnetically separated, resulting in removal rates of approximately 84.9% and 72.2% for Cd and Pb, respectively. FS@IDA could not remove the residual heavy metals and those bound to organic matter in the soil. FS@IDA did not significantly alter the chemical composition of the soil, and it allowed for fast chelating capture, simple magnetic separation and facilitated heavy metal elution. FS@IDA could also be easily prepared and reprocessed. PMID:26878770

Chelating capture and magnetic removal of non-magnetic heavy metal substances from soil.

PubMed

Fan, Liren; Song, Jiqing; Bai, Wenbo; Wang, Shengping; Zeng, Ming; Li, Xiaoming; Zhou, Yang; Li, Haifeng; Lu, Haiwei

2016-02-16

A soil remediation method based on magnetic beneficiation is reported. A new magnetic solid chelator powder, FS@IDA (core-shell Fe3O4@SiO2 nanoparticles coated with iminodiacetic acid chelators), was used as a reactive magnetic carrier to selectively capture non-magnetic heavy metals in soil by chelation and removal by magnetic separation. FS@IDA was prepared via inorganic-organic and organic synthesis reactions that generated chelating groups on the surface of magnetic, multi-core, core-shell Fe3O4@SiO2 (FS) nanoparticles. These reactions used a silane coupling agent and sodium chloroacetate. The results show that FS@IDA could chelate the heavy metal component of Cd, Zn, Pb, Cu and Ni carbonates, lead sulfate and lead chloride in water-insoluble salt systems. The resulting FS@IDA-Cd and FS@IDA-Pb chelates could be magnetically separated, resulting in removal rates of approximately 84.9% and 72.2% for Cd and Pb, respectively. FS@IDA could not remove the residual heavy metals and those bound to organic matter in the soil. FS@IDA did not significantly alter the chemical composition of the soil, and it allowed for fast chelating capture, simple magnetic separation and facilitated heavy metal elution. FS@IDA could also be easily prepared and reprocessed.

Chelating capture and magnetic removal of non-magnetic heavy metal substances from soil

NASA Astrophysics Data System (ADS)

Fan, Liren; Song, Jiqing; Bai, Wenbo; Wang, Shengping; Zeng, Ming; Li, Xiaoming; Zhou, Yang; Li, Haifeng; Lu, Haiwei

2016-02-01

A soil remediation method based on magnetic beneficiation is reported. A new magnetic solid chelator powder, FS@IDA (core-shell Fe3O4@SiO2 nanoparticles coated with iminodiacetic acid chelators), was used as a reactive magnetic carrier to selectively capture non-magnetic heavy metals in soil by chelation and removal by magnetic separation. FS@IDA was prepared via inorganic-organic and organic synthesis reactions that generated chelating groups on the surface of magnetic, multi-core, core-shell Fe3O4@SiO2 (FS) nanoparticles. These reactions used a silane coupling agent and sodium chloroacetate. The results show that FS@IDA could chelate the heavy metal component of Cd, Zn, Pb, Cu and Ni carbonates, lead sulfate and lead chloride in water-insoluble salt systems. The resulting FS@IDA-Cd and FS@IDA-Pb chelates could be magnetically separated, resulting in removal rates of approximately 84.9% and 72.2% for Cd and Pb, respectively. FS@IDA could not remove the residual heavy metals and those bound to organic matter in the soil. FS@IDA did not significantly alter the chemical composition of the soil, and it allowed for fast chelating capture, simple magnetic separation and facilitated heavy metal elution. FS@IDA could also be easily prepared and reprocessed.

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.

Determination of trace heavy metals in soil and sediments by atomic spectrometry following preconcentration with Schiff bases on Amberlite XAD-4.

PubMed

Kara, Derya; Fisher, Andrew; Hill, Steve J

2009-06-15

A matrix separation and analyte preconcentration system using Amberlite XAD copolymer resins functionalized by Schiff base reactions coupled with atomic spectrometry has been developed. Three different functionalized Amberlite XAD resins were synthesized using 4-phenylthiosemicarbazide, 2,3-dihydroxybenzaldehyde and 2-thiophenecarboxaldehyde as reagents. These resins could be used to preconcentrate transition and other trace heavy metal analytes from nitric acid digests of soil and sediment samples. Analyte retention was shown to work well at pH 6.0. After treatment of the digests with sodium fluoride and buffering to pH 6, samples that contain extremely large concentrations of iron were analysed for trace analytes without the excess iron overloading the capacity of the resin. The analytes Cd, Co, Cu, Ni and Pb were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with 0.1M HNO(3) directly to the detection system. Flame atomic absorption spectrometry was used as a means of detection during the studies. The efficiency of the chelating resin and the accuracy of the proposed method were evaluated by the analysis of soil (SO-2) and sediment (LGC 6157 and MESS-3) certified reference materials.

Photo-Curable Metal-Chelating Coatings Offer a Scalable Approach to Production of Antioxidant Active Packaging.

PubMed

Lin, Zhuangsheng; Goddard, Julie

2018-02-01

Synthetic metal chelators (for example, ethylenediaminetetraacetic acid, EDTA) are widely used as additives to control trace transition metal induced oxidation in consumer products. To enable removal of synthetic chelators in response to increasing consumer demand for clean label products, metal-chelating active food packaging technologies have been developed with demonstrated antioxidant efficacy in simulated food systems. However, prior work in fabrication of metal-chelating materials leveraged batch chemical reactions to tether metal-chelating ligands, a process with limited industrial translatability for large-scale fabrication. To improve the industrial translatability, we have designed a 2-step laminated photo-grafting process to introduce metal chelating functionality onto common polymeric packaging materials. Iminodiacetic acid (IDA) functionalized materials were fabricated by photo-grafting poly(acrylic acid) onto polypropylene (PP) films, followed by a second photo-grafting process to graft-polymerize an IDA functionalized vinyl monomer (GMA-IDA). The photo-grafting was conducted under atmospheric conditions and was completed in 2 min. The resulting IDA functionalized metal-chelating material was able to chelate iron and copper, and showed antioxidant efficacy against ascorbic acid degradation, supporting its potential to be used synergistically with natural antioxidants for preservation of food and beverage products. The 2-step photo-grafting process improves the throughput of active packaging coatings, enabling potential roll-to-roll fabrication of metal-chelating active packaging materials for antioxidant food packaging applications. To address consumer and retail demands for "clean label" foods and beverages without a corresponding loss in product quality and shelf life, producers are seeking next generation technologies such as active packaging. In this work, we will report the synthesis of metal-chelating active packaging films, which enable removal of the synthetic additive, ethylenediamine tetraacetic acid. The new synthesis technique improves the throughput of metal-chelating active packaging coatings, enabling potential roll-to-roll fabrication of the materials for antioxidant food packaging applications. © 2018 Institute of Food Technologists®.

Effect of the tether on the Mg(II), Ca(II), Cu(II) and Fe(III) stability constants and pM values of chelating agents related to EDDHA.

PubMed

Sierra, Miguel A; Gómez-Gallego, Mar; Alcázar, Roberto; Lucena, Juan J; Yunta, Felipe; García-Marco, Sonia

2004-11-07

The effect of the length and the structure of the tether on the chelating ability of EDDHA-like chelates have not been established. In this work, PDDHA (propylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid), BDDHA (butylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid) and XDDHA (p-xylylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid) have been obtained and their chemical behaviour has been studied and compared with that of EDDHA following our methodology. The purity of the chelating agents, and their protonation, Ca(II), Mg(II), Fe(III) and Cu(II) stability constants and pM values have been determined. The stability constants and pM values indicate that EDDHA forms the most stable chelates followed by PDDHA. However, the differences among the pFe values are small when a nutrient solution is used, and in these conditions the XDDHA/Fe(III) chelate is the most stable. The results obtained in this work indicate that all the chelating agents studied can be used as iron chlorosis correctors and they can be applied to soil/plant systems.

Evaluation of macrocyclic hydroxyisophthalamide ligands as chelators for zirconium-89

PubMed Central

Xu, Jide; Tatum, David; Magda, Darren

2017-01-01

The development of bifunctional chelators (BFCs) for zirconium-89 immuno-PET applications is an area of active research. Herein we report the synthesis and evaluation of octadentate hydroxyisophthalamide ligands (1 and 2) as zirconium-89 chelators. While both radiometal complexes could be prepared quantitatively and with excellent specific activity, preparation of 89Zr-1 required elevated temperature and an increased reaction time. 89Zr-1 was more stable than 89Zr-2 when challenged in vitro by excess DTPA or serum proteins and in vivo during acute biodistribution studies. Differences in radiometal complex stability arise from structural changes between the two ligand systems, and suggest further ligand optimization is necessary to enhance 89Zr chelation. PMID:28575044

Evaluation of macrocyclic hydroxyisophthalamide ligands as chelators for zirconium-89.

PubMed

Bhatt, Nikunj B; Pandya, Darpan N; Xu, Jide; Tatum, David; Magda, Darren; Wadas, Thaddeus J

2017-01-01

The development of bifunctional chelators (BFCs) for zirconium-89 immuno-PET applications is an area of active research. Herein we report the synthesis and evaluation of octadentate hydroxyisophthalamide ligands (1 and 2) as zirconium-89 chelators. While both radiometal complexes could be prepared quantitatively and with excellent specific activity, preparation of 89Zr-1 required elevated temperature and an increased reaction time. 89Zr-1 was more stable than 89Zr-2 when challenged in vitro by excess DTPA or serum proteins and in vivo during acute biodistribution studies. Differences in radiometal complex stability arise from structural changes between the two ligand systems, and suggest further ligand optimization is necessary to enhance 89Zr chelation.

Radiopharmaceutical stannic Sn-117m chelate compositions and methods of use

DOEpatents

Srivastava, Suresh C.; Meinken, George E.

2001-01-01

Radiopharmaceutical compositions including .sup.117m Sn labeled stannic (Sn.sup.4+) chelates are provided. The chelates are preferably polyhydroxycarboxylate, such as oxalates, tartrates, citrates, malonates, gluconates, glucoheptonates and the like. Methods of making .sup.117m Sn-labeled (Sn.sup.4+) polyhydroxycarboxylic chelates are also provided. The foregoing pharmaceutical compositions can be used in methods of preparing bone for scintigraphical analysis, for radiopharmaceutical skeletal imaging, treatment of pain resulting from metastatic bone involvement, treatment of primary bone cancer, treatment of cancer resulting from metastatic spread to bone from other primary cancers, treatment of pain resulting from rheumatoid arthritis, treatment of bone/joint disorders and to monitor radioactively the skeletal system.

Radiolabeling of DOTA-like conjugated peptides with generator-produced 68Ga and using NaCl-based cationic elution method

PubMed Central

Mueller, Dirk; Breeman, Wouter A P; Klette, Ingo; Gottschaldt, Michael; Odparlik, Andreas; Baehre, Manfred; Tworowska, Izabela; Schultz, Michael K

2017-01-01

Gallium-68 (68Ga) is a generator-produced radionuclide with a short half-life (t½ = 68 min) that is particularly well suited for molecular imaging by positron emission tomography (PET). Methods have been developed to synthesize 68Ga-labeled imaging agents possessing certain drawbacks, such as longer synthesis time because of a required final purification step, the use of organic solvents or concentrated hydrochloric acid (HCl). In our manuscript, we provide a detailed protocol for the use of an advantageous sodium chloride (NaCl)-based method for radiolabeling of chelator-modified peptides for molecular imaging. By working in a lead-shielded hot-cell system, 68Ga3+ of the generator eluate is trapped on a cation exchanger cartridge (100 mg, ∼8 mm long and 5 mm diameter) and then eluted with acidified 5 M NaCl solution directly into a sodium acetate-buffered solution containing a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) or DOTA-like chelator-modified peptide. The main advantages of this procedure are the high efficiency and the absence of organic solvents. It can be applied to a variety of peptides, which are stable in 1 M NaCl solution at a pH value of 3–4 during reaction. After labeling, neutralization, sterile filtration and quality control (instant thin-layer chromatography (iTLC), HPLC and pH), the radiopharmaceutical can be directly administered to patients, without determination of organic solvents, which reduces the overall synthesis-to-release time. This procedure has been adapted easily to automated synthesis modules, which leads to a rapid preparation of 68Ga radiopharmaceuticals (12–16 min). PMID:27172166

Radiolabeling of DOTA-like conjugated peptides with generator-produced (68)Ga and using NaCl-based cationic elution method.

PubMed

Mueller, Dirk; Breeman, Wouter A P; Klette, Ingo; Gottschaldt, Michael; Odparlik, Andreas; Baehre, Manfred; Tworowska, Izabela; Schultz, Michael K

2016-06-01

Gallium-68 ((68)Ga) is a generator-produced radionuclide with a short half-life (t½ = 68 min) that is particularly well suited for molecular imaging by positron emission tomography (PET). Methods have been developed to synthesize (68)Ga-labeled imaging agents possessing certain drawbacks, such as longer synthesis time because of a required final purification step, the use of organic solvents or concentrated hydrochloric acid (HCl). In our manuscript, we provide a detailed protocol for the use of an advantageous sodium chloride (NaCl)-based method for radiolabeling of chelator-modified peptides for molecular imaging. By working in a lead-shielded hot-cell system,(68)Ga(3+) of the generator eluate is trapped on a cation exchanger cartridge (100 mg, ∼8 mm long and 5 mm diameter) and then eluted with acidified 5 M NaCl solution directly into a sodium acetate-buffered solution containing a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) or DOTA-like chelator-modified peptide. The main advantages of this procedure are the high efficiency and the absence of organic solvents. It can be applied to a variety of peptides, which are stable in 1 M NaCl solution at a pH value of 3-4 during reaction. After labeling, neutralization, sterile filtration and quality control (instant thin-layer chromatography (iTLC), HPLC and pH), the radiopharmaceutical can be directly administered to patients, without determination of organic solvents, which reduces the overall synthesis-to-release time. This procedure has been adapted easily to automated synthesis modules, which leads to a rapid preparation of (68)Ga radiopharmaceuticals (12-16 min).

Gold(III) bis-thiosemicarbazonato complexes: synthesis, characterization, radiochemistry and X-ray crystal structure analysis.

PubMed

Bottenus, Brienne N; Kan, Para; Jenkins, Tyler; Ballard, Beau; Rold, Tammy L; Barnes, Charles; Cutler, Cathy; Hoffman, Timothy J; Green, Mark A; Jurisson, Silvia S

2010-01-01

A variety of (bis)thiosemicarbazone-based ligand systems have been investigated as chelating agents for Au(III) complexes with potential radiotherapeutic applications. Ligand systems containing an ethyl, propyl or butyl backbone between the two imine N donors have been synthesized to evaluate chelate ring size effects on the resultant Au(III) complex stability at the macroscopic and radiotracer levels. The Au(III) complexes were synthesized and characterized by NMR, electrospray ionization mass spectra, elemental analysis and X-ray crystallography. The (198)Au complexes were evaluated in vitro at the tracer level for stability in phosphate-buffered saline at pH 7.4 and 37 degrees C. One of these complexes [(198)Au(3,4-HxTSE)] showed high in vitro stability and was further evaluated in vivo in normal mice. [Au(ATSM)]AuCl(4).2CH(3)OH, (ATSM=diacetyl-bis(N(4)-methylthiosemicarbazone)) H(14)C(8)N(6)O(2)S(2)Cl(4)Au(2).2CH(3)OH, crystallized from methanol in the monoclinic space group P21/n with a=14.7293(13) A, b=7.7432(7) A, c=20.4363(18) A, beta=100.140(2) degrees, V=2294.4 (4) A(3), Z=4; [Au(3,4-HxTSE)]Cl.CH(3)CH(2)OH/AuCl(2), (3,4-HxTSE=3,4-hexanedione-bis(N(4)-ethylthiosemicarbazone)) H(26)C(13.6)N(6)O(0.8)S(2)Cl(1.2)Au(1.2), crystallized from ethanol in the monoclinic space group P21/c with a=10.1990(10) A, b=13.8833(14) A, c=15.1752(15) A, beta=99.353(2) degrees , V=2120.2 (4) A(3), Z=4. These studies revealed poor stability of the [(198)Au][Au(3,4-HxTSE)](+) complex; however, crystal structure data suggest potential alterations to the ligand backbone may increase stability. Copyright 2010 Elsevier Inc. All rights reserved.

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

Kinetic behavior of Fe(o,o-EDDHA)-humic substance mixtures in several soil components and in calcareous soils.

PubMed

Cerdán, Mar; Alcañiz, Sara; Juárez, Margarita; Jordá, Juana D; Bermúdez, Dolores

2007-10-31

Ferric ethylenediamine- N, N'-bis-(o-hydroxyphenylacetic)acid chelate (Fe(o, o-EDDHA)) is one of the most effective Fe fertilizers in calcareous soils. However, humic substances are occasionally combined with iron chelates in drip irrigation systems in order to lower costs. The reactivity of iron chelate-humic substance mixtures in several soil components and in calcareous soils was investigated through interaction tests, and their behavior was compared to the application of iron chelates and humic substances separately. Two commercial humic substances and two Fe(o, o-EDDHA) chelates (one synthesized in the laboratory and one commercial) were used to prepare iron chelate-humic substance mixtures at 50% (w/w). Various soil components (calcium carbonate, gibbsite, amorphous iron oxide, hematite, tenorite, zincite, amorphous Mn oxide, and peat) and three calcareous soils were shaken for 15 days with the mixtures and with iron chelate and humic substance solutions. The kinetic behavior of Fe(o, o-EDDHA) and Fe non-(o,o-EDDHA) (Fe bonded to (o,p-EDDHA) and other polycondensated ligands) and of the different nutrients solubilized after the interaction assay was determined. The results showed that the mixtures did not significantly reduce the retention of Fe(o, o-EDDHA) and Fe non-(o,o-EDDHA) in the soil components and the calcareous soils compared to the iron chelate solutions, but they did produce changes in the retention rate. Moreover, the competition between humic substances and synthetic chelating agents for complexing metal cations limited the effectiveness of the mixtures to mobilize nutrients from the substrates. The presence of Fe(o, p-EDDHA) and other byproducts in the commercial iron chelate had an important effect on the evolution of Fe(o, o-EDDHA) and the nutrient solubilization process.

Impact of iron chelators on short-term dissolution of basaltic glass

NASA Astrophysics Data System (ADS)

Perez, Anne; Rossano, Stéphanie; Trcera, Nicolas; Verney-Carron, Aurélie; Huguenot, David; van Hullebusch, Eric D.; Catillon, Gilles; Razafitianamaharavo, Angelina; Guyot, François

2015-08-01

Although microorganisms seem to play an important role in the alteration processes of basaltic glasses in solution, the elementary mechanisms involved remain unclear in particular with regard to the role of organic ligands excreted by the cells. Two glasses, one with Fe and one without Fe were synthesized to model basaltic glass compositions. Fe in the glass was mostly Fe(III) for enhancing interaction with siderophores, yet with small but significant amounts of Fe(II) (between 10% and 30% of iron). The prepared samples were submitted to abiotic alteration experiments in buffered (pH 6.4) diluted solutions of metal-specific ligands, namely oxalic acid (OA, 10 mM), desferrioxamine (DFA, 1 mM) or 2,2‧-bipyridyl (BPI, 1 mM). Element release from the glass into the solution after short term alteration (maximum 1 week) was measured by ICP-OES, and normalized mass losses and relative release ratios (with respect to Si) were evaluated for each element in each experimental condition. The presence of organic ligands had a significant effect on the dissolution of both glasses. Trivalent metals chelators (OA, DFA) impacted on the release of Fe3+ and Al3+, and thus on the global dissolution of both glasses, enhancing all release rates and dissolution stoichiometry (release rates were increased up to 7 times for Al or Fe). As expected, the mostly divalent metal chelator BPI interacted preferentially with Ca2+, Mg2+ and Fe2+. This study thus allows to highlight the central roles of iron and aluminium in interaction with some organic ligands in the alteration processes of basaltic glasses. It thus provides a step toward understanding the biological contribution of this fundamental geological process.

High Yield Production and Radiochemical Isolation of Isotopically Pure Arsenic-72 and Novel Radioarsenic Labeling Strategies for the Development of Theranostic Radiopharmaceuticals.

PubMed

Ellison, Paul A; Barnhart, Todd E; Chen, Feng; Hong, Hao; Zhang, Yin; Theuer, Charles P; Cai, Weibo; Nickles, Robert J; DeJesus, Onofre T

2016-01-20

Radioisotopes of arsenic are of considerable interest to the field of nuclear medicine with unique nuclear and chemical properties making them well-suited for use in novel theranostic radiopharmaceuticals. However, progress must still be made in the production of isotopically pure radioarsenic and in its stable conjugation to biological targeting vectors. This work presents the production and irradiation of isotopically enriched (72)Ge(m) discs in an irrigation-cooled target system allowing for the production of isotopically pure (72)As with capability on the order of 10 GBq. A radiochemical separation procedure isolated the reactive trivalent radioarsenic in a small volume buffered aqueous solution, while reclaiming (72)Ge target material. The direct thiol-labeling of a monoclonal antibody resulted in a conjugate exhibiting exceptionally poor in vivo stability in a mouse model. This prompted further investigations to alternative radioarsenic labeling strategies, including the labeling of the dithiol-containing chelator dihydrolipoic acid, and thiol-modified mesoporous silica nanoparticles (MSN-SH). Radioarsenic-labeled MSN-SH showed exceptional in vivo stability toward dearsenylation.

High Yield Production and Radiochemical Isolation of Isotopically Pure Arsenic-72 and Novel Radioarsenic Labeling Strategies for the Development of Theranostic Radiopharmaceuticals

PubMed Central

Ellison, Paul A.; Barnhart, Todd E.; Chen, Feng; Hong, Hao; Zhang, Yin; Theuer, Charles P.; Cai, Weibo; Nickles, Robert J.; DeJesus, Onofre T.

2016-01-01

Radioisotopes of arsenic are of considerable interest to the field of nuclear medicine with unique nuclear and chemical properties making them well-suited for use in novel theranostic radiopharmaceuticals. However, progress must still be made in the production of isotopically pure radioarsenic and in its stable conjugation to biological targeting vectors. This work presents the production and irradiation of isotopically enriched 72Ge(m) discs in an irrigation-cooled target system allowing for the production of isotopically pure 72As with capability on the order of 10 GBq. A radiochemical separation procedure isolated the reactive trivalent radioarsenic in a small volume buffered aqueous solution, while reclaiming 72Ge target material. The direct thiol-labeling of a monoclonal antibody resulted in a conjugate exhibiting exceptionally poor in vivo stability in a mouse model. This prompted further investigations to alternative radioarsenic labeling strategies, including the labeling of the dithiol-containing chelator dihydrolipoic acid, and thiol-modified mesoporous silica nanoparticles (MSN-SH). Radioarsenic-labeled MSN-SH showed exceptional in vivo stability toward dearsenylation. PMID:26646989

Plasmalemma Redox Activity and H+ Extrusion in Roots of Fe-Deficient Cucumber Plants 1

PubMed Central

Alcántara, Esteban; de la Guardia, Manuel D.; Romera, Francisco J.

1991-01-01

Cucumber plants (Cucumis sativus L.) with incipient Fe deficiency showed increased root capacity to reduce chelated Fe3+ compared to Fe-sufficient plants. When Fe-ethylenediaminete-traacetate was added to the root medium of the Fe-deficient plants, the reductase activity was associated with acidification of the medium and an increase in the net apparent K+ efflux. In the presence of the H+-ATPase inhibitor N,N′-dicyclohexylcarbodiimide the net apparent H+ efflux was completely suppressed, though some reductase activity was preserved, and the net apparent K+ efflux was significantly increased. The inhibition of the reductase activity by N,N′-dicyclohexylcarbodiimide was similar whether the pH of the medium was buffered or not. Anoxia and the protonophore carbonyl cyanide m-chlorophenyl hydrazone also caused a similar inhibition of the reductase activity. It is proposed that this redox system transports electrons only and that its activity is inhibited by plasmamembrane depolarization and anoxia. The H+ and K+ efflux associated with the reductase activity may be a result of the plasmamembrane depolarization it causes. PMID:16668294

The concept of "buffering" in systems and control theory: from metaphor to math.

PubMed

Schmitt, Bernhard M

2004-10-04

The paradigm of "buffering" is used increasingly for the description of diverse "systemic" phenomena encountered in evolutionary genetics, ecology, integrative physiology, and other areas. However, in this new context, the paradigm has not yet matured into a truly quantitative concept inasmuch as it lacks a corresponding quantitative measure of "systems-level buffering strength". Here, I develop such measures on the basis of a formal and general approach to the quantitation of buffering action. "Systems-level buffering" is shown to be synonymous with "disturbance rejection" in feedback-control systems, and can be quantitated by means of dimensionless proportions between partial flows in two-partitioned systems. The units allow either the time-independent, "static" buffering properties or the time-dependent, "dynamic" ones to be measured. Analogous to this "resistance to change", one can define and measure the "conductance to change"; this quantity corresponds to "set-point tracking" in feedback-control systems. Together, these units provide a systematic framework for the quantitation of buffering action in systems biology, and reveal the common principle behind systems-level buffering, classical acid-base buffering, and multiple other manifestations of buffering.

CONTROL OF CHELATOR-BASED UPSETS IN SURFACE FINISHING SHOP WASTE WATER TREATMENT SYSTEMS

EPA Science Inventory

Actual surface finishing shop examples are used to illustrate the use of process chemistry understanding and analyses to identify immediate, interim and permanent response options for industrial waste water treatment plant (IWTP) upset problems caused by chelating agents. There i...

Evaluation of macrocyclic hydroxyisophthalamide ligands as chelators for zirconium-89

DOE PAGES

Bhatt, Nikunj B.; Pandya, Darpan N.; Xu, Jide; ...

2017-06-02

The development of bifunctional chelators (BFCs) for zirconium-89 immuno-PET applications is an area of active research. We report the synthesis and evaluation of octadentate hydroxyisophthalamide ligands (1 and 2) as zirconium-89 chelators. And while both radiometal complexes could be prepared quantitatively and with excellent specific activity, preparation of 89Zr-1 required elevated temperature and an increased reaction time. 89Zr-1 was more stable than 89Zr-2 when challenged in vitro by excess DTPA or serum proteins and in vivo during acute biodistribution studies. The differences in radiometal complex stability arise from structural changes between the two ligand systems, and suggest further ligand optimizationmore » is necessary to enhance 89Zr chelation.« less

Evaluation of macrocyclic hydroxyisophthalamide ligands as chelators for zirconium-89

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

Bhatt, Nikunj B.; Pandya, Darpan N.; Xu, Jide

The development of bifunctional chelators (BFCs) for zirconium-89 immuno-PET applications is an area of active research. We report the synthesis and evaluation of octadentate hydroxyisophthalamide ligands (1 and 2) as zirconium-89 chelators. And while both radiometal complexes could be prepared quantitatively and with excellent specific activity, preparation of 89Zr-1 required elevated temperature and an increased reaction time. 89Zr-1 was more stable than 89Zr-2 when challenged in vitro by excess DTPA or serum proteins and in vivo during acute biodistribution studies. The differences in radiometal complex stability arise from structural changes between the two ligand systems, and suggest further ligand optimizationmore » is necessary to enhance 89Zr chelation.« less

Assessment and preliminary design of an energy buffer for regenerative braking in electric vehicles

NASA Technical Reports Server (NTRS)

Buchholz, R.; Mathur, A. K.

1979-01-01

Energy buffer systems, capable of storing the vehicle energy during braking and reusing this stored energy during acceleration, were examined. Some of these buffer systems when incorporated in an electric vehicle would result in an improvement in the performance and range under stop and go driving conditions. Buffer systems considered included flywheels, hydropneumatic, pneumatic, spring, and regenerative braking. Buffer ranking and rating criteria were established. Buffer systems were rated based on predicted range improvements, consumer acceptance, driveability, safety, reliability and durability, and initial and life cycle costs. A hydropneumatic buffer system was selected.

Extracellular chelation of zinc does not affect hippocampal excitability and seizure-induced cell death in rats

PubMed Central

Lavoie, Nathalie; Peralta, Modesto R; Chiasson, Marilou; Lafortune, Kathleen; Pellegrini, Luca; Seress, László; Tóth, Katalin

2007-01-01

In the nervous system, zinc can influence synaptic responses and at extreme concentrations contributes to epileptic and ischaemic neuronal injury. Zinc can originate from synaptic vesicles, the extracellular space and from intracellular stores. In this study, we aimed to determine which of these zinc pools is responsible for the increased hippocampal excitability observed in zinc-depleted animals or following zinc chelation. Also, we investigated the source of intracellularly accumulating zinc in vulnerable neurons. Our data show that membrane-permeable and membrane-impermeable zinc chelators had little or no effect on seizure activity in the CA3 region. Furthermore, extracellular zinc chelation could not prevent the accumulation of lethal concentrations of zinc in dying neurons following epileptic seizures. At the electron microscopic level, zinc staining significantly increased at the presynaptic membrane of mossy fibre terminals in kainic acid-treated animals. These data indicate that intracellular but not extracellular zinc chelators could influence neuronal excitability and seizure-induced zinc accumulation observed in the cytosol of vulnerable neurons. PMID:17095563

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.

Chemistry of carcinogenic metals.

PubMed Central

Martell, A E

1981-01-01

The periodic distribution of known and suspected carcinogenic metal ions is described, and the chemical behavior of various types of metal ions is explained in terms of the general theory of hard and soft acids and bases. The chelate effect is elucidated, and the relatively high stability of metal chelates in very dilute solutions is discussed. The concepts employed for the chelate effect are extended to explain the high stabilities of macrocyclic and cryptate complexes. Procedures for the use of equilibrium data to determine the speciation of metal ions and complexes under varying solution conditions are described. Methods for assessing the interferences by hydrogen ion, competing metal ions, hydrolysis, and precipitation are explained, and are applied to systems containing iron(III) chelates of fourteen chelating agents designed for effective binding of the ferric ion. The donor groups available for the building up of multidentate ligands are presented, and the ways in which they may be combined to achieve high affinity and selectivity for certain types of metal ions are explained. PMID:6791915

Plant-derived phenolic compounds prevent the DNA single-strand breakage and cytotoxicity induced by tert-butylhydroperoxide via an iron-chelating mechanism.

PubMed Central

Sestili, Piero; Diamantini, Giuseppe; Bedini, Annalida; Cerioni, Liana; Tommasini, Ilaria; Tarzia, Giorgio; Cantoni, Orazio

2002-01-01

The protective effects of selected members from a series of caffeic acid esters and flavonoids were tested in various toxicity paradigms using U937 cells, previously shown to be sensitive to either iron chelators or bona fide radical scavengers or to both classes of compounds. It was found that all the protective polyphenols were active at very low concentrations and that their effects were observed only under those conditions in which iron chelators also afforded protection. Consistently, active polyphenolic compounds, unlike the inactive ones, effectively chelated iron in an in vitro system. It follows that, at least under the experimental conditions utilized in the present study, the most prominent activity of these polyphenolic compounds resides in their ability to chelate iron. Further studies revealed that the protective effects afforded by the caffeic acid esters and flavonoids were largely mediated by the catechol moiety and that the relative biological potency of these compounds was a direct function of their lipophilicity. PMID:11988084

Hybrid data storage system in an HPC exascale environment

DOEpatents

Bent, John M.; Faibish, Sorin; Gupta, Uday K.; Tzelnic, Percy; Ting, Dennis P. J.

2015-08-18

A computer-executable method, system, and computer program product for managing I/O requests from a compute node in communication with a data storage system, including a first burst buffer node and a second burst buffer node, the computer-executable method, system, and computer program product comprising striping data on the first burst buffer node and the second burst buffer node, wherein a first portion of the data is communicated to the first burst buffer node and a second portion of the data is communicated to the second burst buffer node, processing the first portion of the data at the first burst buffer node, and processing the second portion of the data at the second burst buffer node.

Hydrogen peroxide-induced DNA damage is independent of nuclear calcium but dependent on redox-active ions.

PubMed Central

Jornot, L; Petersen, H; Junod, A F

1998-01-01

In cells undergoing oxidative stress, DNA damage may result from attack by .OH radicals produced by the Fenton reaction, and/or by nucleases activated by nuclear calcium. In the present study, the participation of these two mechanisms was investigated in HeLa cells. Nuclear-targeted aequorin was used for selectively monitoring Ca2+ concentrations within the nuclei ([Ca2+]n), in conjunction with the cell-permeant calcium chelator bis-(o-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid acetoxymethyl ester (BAPTA/AM), the lipid-soluble broad-spectrum metal chelator with low affinity for Ca2+ and Mg2+ N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and the high-affinity iron/copper chelator 1, 10-phenanthroline (PHE). In Ca2+-containing medium, H2O2 induced extensive DNA strand breaks and an increase in [Ca2+]n that was almost identical to that observed in the cytosol ([Ca2+]c). In cells bathed in Ca2+-free/EGTA medium, in which the increases in [Ca2+]n and [Ca2+]c due to H2O2 were significantly reduced, similar levels of DNA fragmentation also occurred. In cells preloaded with BAPTA/AM or TPEN, the small increase of [Ca2+]n normally elicited by H2O2 in Ca2+-free medium was completely buffered, and DNA damage was largely prevented. On the other hand, pretreatment with PHE did not affect the calcium response in the nuclei, but completely prevented DNA strand breakage induced by H2O2. Re-addition of 100 microM CuSO4 and 100 microM FeSO4 to TPEN- and PHE-treated cells prior to H2O2 challenge reversed the effect of TPEN and PHE, whereas 1 mM was necessary to negate the effect of BAPTA/AM. The levels of DNA strand breakage observed, however, did not correlate with the amounts of 8-hydroxy 2'-deoxyguanosine (8-OHdG): H2O2 did not produce 8-OHdG, whereas PHE alone slightly increased 8-OHdG levels. CuSO4 and FeSO4 enhanced the effects of PHE, particularly in the presence of H2O2. Exposure of cells to a mixture of CuSO4/FeSO4 also resulted in a significant increase in 8-OHdG levels, which was prevented in cells preloaded with BAPTA/AM. Similar results were obtained in a cell-free system using isolated calf thymus DNA exposed to CuSO4/FeSO4, regardless of whether H2O2 was present or not. These results suggest that BAPTA/AM prevents H2O2-induced DNA damage by acting as an iron/copper chelator. These data also indicate that caution must be exercised in using Ca2+ chelating agents as evidence for a role in cellular Ca2+ levels in experimental conditions in which transition-metal-ion-mediated oxidant production is also occurring. PMID:9742216

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

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

Subsurface Uranium Fate and Transport: Integrated Experiments and Modeling of Coupled Biogeochemical Mechanisms of Nanocrystalline Uraninite Oxidation by Fe(III)-(hydr)oxides - Project Final Report

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

Peyton, Brent M.; Timothy, Ginn R.; Sani, Rajesh K.

2013-08-14

Subsurface bacteria including sulfate reducing bacteria (SRB) reduce soluble U(VI) to insoluble U(IV) with subsequent precipitation of UO 2. We have shown that SRB reduce U(VI) to nanometer-sized UO 2 particles (1-5 nm) which are both intra- and extracellular, with UO 2 inside the cell likely physically shielded from subsequent oxidation processes. We evaluated the UO 2 nanoparticles produced by Desulfovibrio desulfuricans G20 under growth and non-growth conditions in the presence of lactate or pyruvate and sulfate, thiosulfate, or fumarate, using ultrafiltration and HR-TEM. Results showed that a significant mass fraction of bioreduced U (35-60%) existed as a mobile phasemore » when the initial concentration of U(VI) was 160 µM. Further experiments with different initial U(VI) concentrations (25 - 900 M) in MTM with PIPES or bicarbonate buffers indicated that aggregation of uraninite depended on the initial concentrations of U(VI) and type of buffer. It is known that under some conditions SRB-mediated UO 2 nanocrystals can be reoxidized (and thus remobilized) by Fe(III)-(hydr)oxides, common constituents of soils and sediments. To elucidate the mechanism of UO 2 reoxidation by Fe(III) (hydr)oxides, we studied the impact of Fe and U chelating compounds (citrate, NTA, and EDTA) on reoxidation rates. Experiments were conducted in anaerobic batch systems in PIPES buffer. Results showed EDTA significantly accelerated UO 2 reoxidation with an initial rate of 9.5 M day-1 for ferrihydrite. In all cases, bicarbonate increased the rate and extent of UO 2 reoxidation with ferrihydrite. The highest rate of UO 2 reoxidation occurred when the chelator promoted UO 2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO 2 dissolution did not occur, UO 2 reoxidation likely proceeded through an aqueous Fe(III) intermediate as observed for both NTA and citrate. To complement to these laboratory studies, we collected U-bearing samples from a surface seep at the Rifle field site and have measured elevated U concentrations in oxic iron-rich sediments. To translate experimental results into numerical analysis of U fate and transport, a reaction network was developed based on Sani et al. (2004) to simulate U(VI) bioreduction with concomitant UO 2 reoxidation in the presence of hematite or ferrihydrite. The reduction phase considers SRB reduction (using lactate) with the reductive dissolution of Fe(III) solids, which is set to be microbially mediated as well as abiotically driven by sulfide. Model results show the oxidation of HS– by Fe(III) directly competes with UO 2 reoxidation as Fe(III) oxidizes HS– preferentially over UO 2. The majority of Fe reduction is predicted to be abiotic, with ferrihydrite becoming fully consumed by reaction with sulfide. Predicted total dissolved carbonate concentrations from the degradation of lactate are elevated (log(pCO 2) ~ –1) and, in the hematite system, yield close to two orders-of-magnitude higher U(VI) concentrations than under initial carbonate concentrations of 3 mM. Modeling of U(VI) bioreduction with concomitant reoxidation of UO 2 in the presence of ferrihydrite was also extended to a two-dimensional field-scale groundwater flow and biogeochemically reactive transport model for the South Oyster site in eastern Virginia. This model was developed to simulate the field-scale immobilization and subsequent reoxidation of U by a biologically mediated reaction network.« less

An Ephemeral Burst-Buffer File System for Scientific Applications

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

Wang, Teng; Moody, Adam; Yu, Weikuan

BurstFS is a distributed file system for node-local burst buffers on high performance computing systems. BurstFS presents a shared file system space across the burst buffers so that applications that use shared files can access the highly-scalable burst buffers without changing their applications.

[Iron and invasive fungal infection].

PubMed

Álvarez, Florencio; Fernández-Ruiz, Mario; Aguado, José María

2013-01-01

Iron is an essential factor for both the growth and virulence of most of microorganisms. As a part of the innate (or nutritional) immune system, mammals have developed different mechanisms to store and transport this element in order to limit free iron bioavailability. To survive in this hostile environment, pathogenic fungi have specific uptake systems for host iron sources, one of the most important of which is based on the synthesis of siderophores-soluble, low-molecular-mass, high-affinity iron chelators. The increase in free iron that results from iron-overload conditions is a well-established risk factor for invasive fungal infection (IFI) such as mucormycosis or aspergillosis. Therefore, iron chelation may be an appealing therapeutic option for these infections. Nevertheless, deferoxamine -the first approved iron chelator- paradoxically increases the incidence of IFI, as it serves as a xeno-siderophore to Mucorales. On the contrary, the new oral iron chelators (deferiprone and deferasirox) have shown to exert a deleterious effect on fungal growth both in vitro and in animal models. The present review focuses on the role of iron metabolism in the pathogenesis of IFI and summarises the preclinical data, as well as the limited clinical experience so far, in the use of new iron chelators as treatment for mucormycosis and invasive aspergillosis. Copyright © 2012 Revista Iberoamericana de Micología. Published by Elsevier Espana. All rights reserved.

Phytoextraction of heavy metals from contaminated soil by co-cropping with chelator application and assessment of associated leaching risk.

PubMed

Wei, Z B; Guo, X F; Wu, Q T; Long, X X; Penn, C J

2011-08-01

Phytoextraction using hyperaccumulating plants is generally time-consuming and requires the cessation of agriculture. We coupled chelators and a co-cropping system to enhance phytoextraction rates, while allowing for agricultural production. An experiment on I m3 lysimeter beds was conducted with a co-cropping system consisting of the hyperaccumulator Sedum alfredii and low-accumulating corn (Zea Mays, cv. Huidan-4), with addition ofa mixture of chelators (MC), to assess the efficiency of chelator enhanced co-crop phytoextraction and the leaching risk caused by the chelator. The results showed that the addition of MC promoted the growth of S. alfredii in the first crop (spring-summer season) and significantly increased the metal phytoextraction. The DTPA-extractable and total metal concentrations in the topsoil were also reduced more significantly with the addition of MC compared with the control treatments. However, mono-cropped S. alfredii without MC was more suitable for maximizing S. alfredii growth and therefore phytoextraction of Zn and Cd during the autumn-winter seasons. No adverse impact to groundwater due to MC application was observed during the experiments with three crops and three MC applications. But elevated total Cd and Pb concentrations among subsoils compared to the initial subsoil concentrations were found for the co-crop + MC treatment after the third crop.

Molecular shuttle chelation: the use of ascorbate, desferrioxamine and Feralex-G in combination to remove nuclear bound aluminum.

PubMed

Kruck, Theo P; Cui, Jian-Guo; Percy, Maire E; Lukiw, Walter J

2004-06-01

1. Abundant data suggest that aluminum (Al(III)) exposure may be an environmental risk factor contributing to the development, progression and/or neuropathology of several human neurodegenerative disorders, including Alzheimer's disease (AD). 2. Nuclei appear to be one directed target for Al(III) binding, accumulation, and Al(III)-mediated dysfunction due in part to their high content of polyphosphorylated nucleic acids, nucleotides, and nucleoproteins. 3. The design of chelation therapies dealing with the removal of Al(III) from these genetic compartments therefore represents an attractive strategy to alleviate the development and/or progression of central nervous system dysfunction that may arise from excessive Al(III) exposure. 4. In this study we have investigated the potential application of 10 natural and synthetic Al(III) chelators, including ascorbate (AS), desferrioxamine (DF), and Feralex-G (FG), used either alone or in combination, to remove Al(III) preincubated with intact human brain cell nuclei. 5. Although nuclear bound Al(III) was found to be highly refractory to removal, the combination of AS+FG was found to be particularly effective in removing Al(III) from the nuclear matrix. 6. Our data suggest that chelators carrying cis-hydroxy ketone groups, such as FG, are particularly suited to the removal of Al(III) from complex biological systems. 7. We further suggest a mechanism whereby small chelating molecules may penetrate the nucleus, bind Al(III), diffuse to regions accessible by the larger DF or FG molecules and transfer their Al(III) to DF or FG. 8. The proposed mechanism, called molecular shuttle chelation may provide a useful pharmacotherapy in the potential treatment of Al(III) overload disease.

Optical property measurements of a novel type of upconverting reporter

NASA Astrophysics Data System (ADS)

Xiao, Xudong; Herring, Michael E.; Haushalter, Jeanne; Lee, Seonkyung; Kalogerakis, Kostas S.; Faris, Gregory W.

2003-07-01

We have recently developed a new type of reporter (upconverting chelate) for biomedical diagnostics. For this reporter, the light is absorbed and emitted by a lanthanide ion, rather than an organic molecule, as is the case for a typical fluorescent dye. These materials do not photobleach and have no autofluorescent background. We focus in this paper on neodymium ions complexed with the familiar chelating agents, EDTA, DPA, DTPA and DOTA. We have performed experimental measurements with one- and two-color laser light excitation for different chelate compounds. The samples are excited using two Nd:YAG-pumped dye laser systems that provide laser light near 587 nm and 800 nm. For one-color excitation, the emitted light depends quadratically on the incident laser power, as expected. Three strongly emitting lines are observed, located near 360 nm, 387 nm, and 417 nm. We observed more efficient upconversion in EDTA although the DPA chelates show comparable ground state absorbance. We have studied the influence of temporal delay between the two laser pulses and obtained the decay lifetime of the first intermediate state in the various chelated compounds.

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.

The fluorescence and resonance Rayleigh scattering spectra study on the interactions of palladium (II)-Nootropic chelate with Congo red and their analytical applications

NASA Astrophysics Data System (ADS)

Chen, Fang; Peng, Jingdong; Liu, Shaopu; Peng, Huanjun; Pan, Ziyu; Bu, Lingli; Xiao, Huan; Zhang, Ruiwen

2017-04-01

A highly sensitive detection approach of resonance Rayleigh scattering spectra (RRS) is firstly applied to analyzing nootropic drugs including piracetam (PIR) and oxiracetam (OXI). In HCl-NaAc buffer solution (pH = 3.0), the OXI chelated with palladium (II) to form the chelate cation [Pd2·OXI]2 +, and then reacted with Congo red (CGR) by virtue of electrostatic attraction and hydrophobic force to form binary complex [Pd2·OXI]. CGR2, which could result in the great enhancement of RRS. The resonance Rayleigh scattering signal was recorded at λex = λem = 375 nm. This mixture complex not only has higher RRS, but also makes contribution to significant increase of fluorescence, and the same phenomena also were discovered in PIR. The enhanced RRS intensity is in proportion to the PIR and OXI concentration in the range of 0.03-3.0 μg mL- 1, and the detection limit (DL) of RRS method for PIR and OXI is 2.3 ng mL- 1 and 9.7 ng mL- 1. In addition, the DL of fluorescence method for PIR and OXI is 8.4 μg mL- 1 and 19.5 μg mL- 1. Obviously, the RRS is the highly sensitive method, and the recoveries of the two kinds of nootropic drugs were range from 100.4% to 101.8.0% with RSD (n = 5) from 1.1% to 3.1% by RRS method. This paper not only investigated the optimum conditions for detecting nootropics with using RRS method, but also focused on the reasons for enhancing RRS intensity and the reaction mechanism, which in order to firm and contract the resultant. Finally, The RRS method has been applied to detect nootropic drugs in human urine samples with satisfactory results. Fig. S2. The effect of ionic strength: Pd (II)-CGR system (curve a); Pd (II)-OXI-CGR system (curve b); Pd (II)-PIR- CGR system (curve c). Pd (II): 2.0 × 10- 4 mol L- 1; CGR: 1.0 × 10- 5 mol L- 1; OXI: 1.5 μg mL- 1; PIR: 2 μg mL- 1; NaCl: 1 mol L- 1. Fig. S3. The effect of time: Pd (II)-OXI-CGR system (curve a); Pd (II)-PIR-CGR system (curve b). Pd (II): 2.0 × 10- 4 mol L- 1; CGR: 1.0 × 10- 5 mol L- 1; OXI: 1.5 μg mL- 1. Fig. S4 Absorption spectra for Pd (II)-Nootropic-CGR system. Measured using a water blank: (1) OXI; (2) GIR; (3) OXI-CGR; (4) Pd (II); (5) Pd(II)-OXI; (6) PIR-OXI-CGR, OXI: 1.0 μg mL- 1; Pd (II) concentration: 3.0 × 10- 4 mol L- 1; CGR concentration: 1.0 × 10- 5 mol L- 1; HCl-NaAc: pH 3.0.

Synthesis of zinc-crosslinked thiolated alginic acid beads and their in vitro evaluation as potential enteric delivery system with folic acid as model drug.

PubMed

Taha, M O; Aiedeh, K M; Al-Hiari, Y; Al-Khatib, H

2005-10-01

The aim of this study is to explore the potential of synthetic modifications of alginic acid as a method to enhance the stability of its complexes with divalent cations under physiological conditions. A fraction of algin's carboxylic acid moieties was substituted with thiol groups to different substitution degrees through conjugating alginate to cysteine to produce alginate-cysteine (AC) conjugates. Infrared spectrophotometry and iodometry were used to characterize the resulting polymeric conjugates in terms of structure and degree of substitution. Moreover, zinc ions were used to crosslink the resulting AC polymers. Folic acid loaded beads were prepared from Zinc-crosslinked AC polymers (AC-Zn) of different cysteine substitution degrees. The generated beads were then investigated in vitro for their capacity to modify folic acid release. AC-Zn polymeric beads resisted drug release under acidic conditions (pH 1.0). However, upon transfer to a phosphate buffer solution (pH 7.0) they released most of their contents almost immediately. This change in drug release behavior is most probably due to the sequestering of zinc cations by phosphate ions within the buffer solution to form insoluble chelates and, to a lesser extent, the ionization of the carboxylic acid and thiol moieties. Removal of zinc ions from the polymeric matrix seems to promote polymeric disintegration and subsequent drug release. A similar behavior is expected in vivo due to the presence of natural zinc sequestering agents in the intestinal fluids. AC-Zn polymers provided a novel approach for enteric drug delivery as drug release from these matrices complied with the USP specifications for enteric dosage forms.

The fast method of Cu-porphyrin complex synthesis for potential use in positron emission tomography imaging

NASA Astrophysics Data System (ADS)

Kilian, Krzysztof; Pęgier, Maria; Pyrzyńska, Krystyna

2016-04-01

Porphyrin based photosensitizers are useful agents for photodynamic therapy and fluorescence imaging of cancer. Additionally, porphyrins are excellent metal chelators, forming stable metalo-complexes and 64Cu isotope can serve as a positron emitter (t1/2 = 12.7 h). The other advantage of 64Cu is its decay characteristics that facilitates the use of 64Cu-porphyrin complex as a therapeutic agent. Thus, 64Cu chelation with porphyrin photosensitizer may become a simple and versatile labeling strategy for clinical positron emission tomography. The present study reports a convenient method for the synthesis of Cu complex with tetrakis(4-carboxyphenyl)porphyrin (TCPP). The experimental conditions for labeling, such as the metal-to-ligand molar ratio, pH and time of reaction were optimized to achieve a high complexation efficiency in a short period of time as possible. In order to accelerate the metallation, the use of substitution reactions of cadmium or lead porphyrin and the presence of reducing agent, such as ascorbic acid, hydroxylamine and flavonoid - morin, were evaluated. The optimum conditions for the synthesis of the copper complex were borate buffer at pH 9 with the addition of 10-fold molar excess, with respect to Cu2 + ions and TCPP and ascorbic acid which resulted in reduction of the reaction time from 30 min to below 1 min.

Partial Purification and Properties of an Alkaline α-Galactosidase from Mature Leaves of Cucurbita pepo1

PubMed Central

Gaudreault, Pierre-Richard; Webb, John A.

1983-01-01

A fourth molecular from of α-galactosidase, designated LIV, an alkaline α-galactosidase, was isolated from leaves of Cucurbita pepo and purified 165-fold. It was active over a narrow pH range with optimal hydrolysis of p-nitrophenyl-α-d-galactoside and stachyose at pH 7.5. The rate of stachyose hydrolysis was 10 times that of raffinose. Km determinations in McIlvaine buffer (200 millimolar Na2-phosphate, 100 millimolar citric acid, pH 7.5) for p-nitrophenyl-α-d-galactoside, stachyose, and raffinose were 1.40, 4.5, and 36.4 millimolar, respectively. LIV was partially inhibited by Ca2+, Mg2+, and Mn2+, more so by Ni2+, Zn2+, and Co2+, and highly so by Cu2+, Ag2+, Hg2+ and by p-chloromercuribenzoate. It was not inhibited by high concentrations of the substrate p-nitrophenyl-α-d-galactoside or by myo-inositol, but α-d-galactose was a strong inhibitor. As observed for most other forms of α-galactosidase, LIV only catalyzed the hydrolysis of glycosides possessing the α-d-galactose configuration at C1, C2, and C4, and did not hydrolyze p-nitrophenyl-α-d-fucoside (α-d-galactose substituted at C6). The enzyme was highly sensitive to buffers and chelating agents. Maximum hydrolytic activity for p-nitrophenyl-α-d-galactoside was obtained in McIlvaine buffer (pH 7.5). In 10 millimolar triethanolaminehydrochloride-NaOH (pH 7.5) or 10 millimolar Hepes-NaOH (pH 7.5), hydrolytic activity was virtually eliminated, but the addition of low concentrations of either ethylenediaminetetraacetate or citrate to these buffers restored activity almost completely. Partial restoration of activity was also observed, but at higher concentrations, with pyruvate and malate. Similar effects were found for stachyose hydrolysis, but in addition some inhibition of LIV in McIlvaine buffer, possibly due to the high phosphate concentration, was observed with this substrate. It is questionable whether the organic acid anions possess any regulatory control of LIVin vivo. It was possible that the results reflected the ability of these anions, and ethylene-diaminetetraacetate, to restore LIV activity through coordination with some toxic cation introduced as a buffer contaminant. Images Fig. 1 PMID:16662884

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.

Calorimetric studies of the interactions of metalloenzyme active site mimetics with zinc-binding inhibitors.

PubMed

Robinson, Sophia G; Burns, Philip T; Miceli, Amanda M; Grice, Kyle A; Karver, Caitlin E; Jin, Lihua

2016-07-19

The binding of drugs to metalloenzymes is an intricate process that involves several interactions, including binding of the drug to the enzyme active site metal, as well as multiple interactions between the drug and the enzyme residues. In order to determine the free energy contribution of Zn(2+) binding by known metalloenzyme inhibitors without the other interactions, valid active site zinc structural mimetics must be formed and binding studies need to be performed in biologically relevant conditions. The potential of each of five ligands to form a structural mimetic with Zn(2+) was investigated in buffer using Isothermal Titration Calorimetry (ITC). All five ligands formed strong 1 : 1 (ligand : Zn(2+)) binary complexes. The complexes were used in further ITC experiments to study their interaction with 8-hydroxyquinoline (8-HQ) and/or acetohydroxamic acid (AHA), two bidentate anionic zinc-chelating enzyme inhibitors. It was found that tetradentate ligands were not suitable for creating zinc structural mimetics for inhibitor binding in solution due to insufficient coordination sites remaining on Zn(2+). A stable binary complex, [Zn(BPA)](2+), which was formed by a tridentate ligand, bis(2-pyridylmethyl)amine (BPA), was found to bind one AHA in buffer or a methanol : buffer mixture (60 : 40 by volume) at pH 7.25 or one 8-HQ in the methanol : buffer mixture at pH 6.80, making it an effective structural mimetic for the active site of zinc metalloenzymes. These results are consistent with the observation that metalloenzyme active site zinc ions have three residues coordinated to them, leaving one or two sites open for inhibitors to bind. Our findings indicate that Zn(BPA)X2 can be used as an active site structural mimetic for zinc metalloenzymes for estimating the free energy contribution of zinc binding to the overall inhibitor active site interactions. Such use will help aid in the rational design of inhibitors to a variety of zinc metalloenzymes.

Distributed metadata in a high performance computing environment

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

Bent, John M.; Faibish, Sorin; Zhang, Zhenhua

A computer-executable method, system, and computer program product for managing meta-data in a distributed storage system, wherein the distributed storage system includes one or more burst buffers enabled to operate with a distributed key-value store, the co computer-executable method, system, and computer program product comprising receiving a request for meta-data associated with a block of data stored in a first burst buffer of the one or more burst buffers in the distributed storage system, wherein the meta data is associated with a key-value, determining which of the one or more burst buffers stores the requested metadata, and upon determination thatmore » a first burst buffer of the one or more burst buffers stores the requested metadata, locating the key-value in a portion of the distributed key-value store accessible from the first burst buffer.« less

Chelate-Modified Fenton Reaction for the Degradation of Trichloroethylene in Aqueous and Two-Phase Systems

PubMed Central

Lewis, Scott; Lynch, Andrew; Bachas, Leonidas; Hampson, Steve; Ormsbee, Lindell; Bhattacharyya, Dibakar

2009-01-01

Abstract The primary objective of this research was to model and understand the chelate-modified Fenton reaction for the destruction of trichloroethylene (TCE) present in both the aqueous and organic (in the form of droplets) phases. The addition of a nontoxic chelate (L), such as citrate or gluconic acid, allows for operation at near-neutral pH and controlled release of Fe(II)/Fe(III). For the standard Fenton reaction at low pH in two-phase systems, an optimum H2O2:Fe(II) molar ratio was found to be between 1:1 and 2:1. Experimentation proved the chelate-modified Fenton reaction effectively dechlorinated TCE in both the aqueous and organic phases at pH 6–7 using low H2O2:Fe(II) molar ratios (4:1 to 8:1). Increasing the L:Fe ratio was found to decrease the rate of H2O2 degradation in both Fe(II) and Fe(III) systems at near-neutral pH. Generalized models were developed to predict the concentration of TCE in the aqueous phase and TCE droplet radius as a function of time using literature-reported hydroxyl radical reaction kinetics and mass transfer relationships. Additional aspects of this work include the reusability of the Fe–citrate complex under repeated H2O2 injections in real water systems as well as packed column studies for simulated groundwater injection. PMID:20418966

Chelating effect of citric acid is negligible for development of enamel erosions.

PubMed

Azadi-Schossig, Parastu; Becker, Klaus; Attin, Thomas

2016-09-01

Citric acid (CA) is a component in beverages responsible for dental erosion. The aim of this study was to examine the influence of CA with different pH, titratable acid and buffer capacity (ß), and the impact of the chelating effect of CA on development of enamel erosions. In a superfusion model, hydroxy apatite (HAp) dissolution of bovine enamel was measured in four experiments (EXP 1-4) with 27 experimental groups (n = 8 per group). The samples were superfused with different CA variations and respective controls. EXP-1: Dilution series of HCl (pH 2.15-3.02). EXP-2: Dilution series of natural CA (56-1.75 mmol l(-1); pH 2.15-3.02). EXP-3: CA solutions (56 and 14 mmol l(-1), ß: 39.7 and 10.2 mmol l(-1) pH(-1), respectively) with different titratable acidity at equal pH values. EXP-4: CA concentrations (56-1.75 mmol l(-1)) neutralized to pH 7. CA led to higher HAp-dissolution than HCl. With higher pH, the difference in HAp-dissolution rate between the two acids became increasingly smaller. At equal pH, HAp-dissolution was higher for the CA with the higher amount of titratable acid. However, no clear correlation between erosion and titratable acid or ß could be found. Only minimal amounts of HAp were dissolved by neutralized CA compared to CA with natural pH. Under the chosen conditions chelating effects of CA do not have a relevant influence of HAp-dissolution of enamel. Moreover, amount of HAp-dissolution by CA is not attributed to a single factor alone. The interplay between the different parameters of CA seems to be responsible for its erosive potential. The erosive potential of solutions containing citric acid with unknown concentrations could not be predicted using a single parameter alone, and should at best determined in experimental set-ups.

Improved labelling of DTPA- and DOTA-conjugated peptides and antibodies with 111In in HEPES and MES buffer.

PubMed

Brom, Maarten; Joosten, Lieke; Oyen, Wim Jg; Gotthardt, Martin; Boerman, Otto C

2012-01-27

In single photon emission computed tomography [SPECT], high specific activity of 111In-labelled tracers will allow administration of low amounts of tracer to prevent receptor saturation and/or side effects. To increase the specific activity, we studied the effect of the buffer used during the labelling procedure: NaAc, NH4Ac, HEPES and MES buffer. The effect of the ageing of the 111InCl3 stock and cadmium contamination, the decay product of 111In, was also examined in these buffers. Escalating amounts of 111InCl3 were added to 1 μg of the diethylene triamine pentaacetic acid [DTPA]- and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid [DOTA]-conjugated compounds (exendin-3, octreotide and anti-carbonic anhydrase IX [CAIX] antibody). Five volumes of 2-(N-morpholino)ethanesulfonic acid [MES], 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid [HEPES], NH4Ac or NaAc (0.1 M, pH 5.5) were added. After 20 min at 20°C (DTPA-conjugated compounds), at 95°C (DOTA-exendin-3 and DOTA-octreotide) or at 45°C (DOTA-anti-CAIX antibody), the labelling efficiency was determined by instant thin layer chromatography. The effect of the ageing of the 111InCl3 stock on the labelling efficiency of DTPA-exendin-3 as well as the effect of increasing concentrations of Cd2+ (the decay product of 111In) were also examined. Specific activities obtained for DTPA-octreotide and DOTA-anti-CAIX antibody were five times higher in MES and HEPES buffer. Radiolabelling of DTPA-exendin-3, DOTA-exendin-3 and DTPA-anti-CAIX antibody in MES and HEPES buffer resulted in twofold higher specific activities than that in NaAc and NH4Ac. Labelling of DTPA-exendin-3 decreased with 66% and 73% for NaAc and NH4Ac, respectively, at day 11 after the production date of 111InCl3, while for MES and HEPES, the maximal decrease in the specific activity was 10% and 4% at day 11, respectively. The presence of 1 pM Cd2+ in the labelling mixture of DTPA-exendin-3 in NaAc and NH4Ac markedly reduced the labelling efficiency, whereas Cd2+ concentrations up to 0.1 nM did not affect the labelling efficiency in MES and HEPES buffer. We showed improved labelling of DTPA- and DOTA-conjugated compounds with 111In in HEPES and MES buffer. The enhanced labelling efficiency appears to be due to the reduced competitive chelation of cadmium. The enhanced labelling efficiency will allow more sensitive imaging of the biomarkers with SPECT.

Use of bicarbonate buffer systems for dissolution characterization of enteric-coated proton pump inhibitor tablets.

PubMed

Shibata, Hiroko; Yoshida, Hiroyuki; Izutsu, Ken-Ichi; Goda, Yukihiro

2016-04-01

The aim of this study was to assess the effects of buffer systems (bicarbonate or phosphate at different concentrations) on the in vitro dissolution profiles of commercially available enteric-coated tablets. In vitro dissolution tests were conducted using an USP apparatus II on 12 enteric-coated omeprazole and rabeprazole tablets, including innovator and generic formulations in phosphate buffers, bicarbonate buffers and a media modified Hanks (mHanks) buffer. Both omeprazole and rabeprazole tablets showed similar dissolution profiles among products in the compendial phosphate buffer system. However, there were large differences between products in dissolution lag time in mHanks buffer and bicarbonate buffers. All formulations showed longer dissolution lag times at lower concentrations of bicarbonate or phosphate buffers. The dissolution rank order of each formulation differed between mHanks buffer and bicarbonate buffers. A rabeprazole formulation coated with a methacrylic acid copolymer showed the shortest lag time in the high concentration bicarbonate buffer, suggesting varied responses depending on the coating layer and buffer components. Use of multiple dissolution media during in vitro testing, including high concentration bicarbonate buffer, would contribute to the efficient design of enteric-coated drug formulations. © 2016 Royal Pharmaceutical Society, Journal of Pharmacy and Pharmacology.

The quantitation of buffering action II. Applications of the formal & general approach.

PubMed

Schmitt, Bernhard M

2005-03-16

The paradigm of "buffering" originated in acid-base physiology, but was subsequently extended to other fields and is now used for a wide and diverse set of phenomena. In the preceding article, we have presented a formal and general approach to the quantitation of buffering action. Here, we use that buffering concept for a systematic treatment of selected classical and other buffering phenomena. H+ buffering by weak acids and "self-buffering" in pure water represent "conservative buffered systems" whose analysis reveals buffering properties that contrast in important aspects from classical textbook descriptions. The buffering of organ perfusion in the face of variable perfusion pressure (also termed "autoregulation") can be treated in terms of "non-conservative buffered systems", the general form of the concept. For the analysis of cytoplasmic Ca++ concentration transients (also termed "muffling"), we develop a related unit that is able to faithfully reflect the time-dependent quantitative aspect of buffering during the pre-steady state period. Steady-state buffering is shown to represent the limiting case of time-dependent muffling, namely for infinitely long time intervals and infinitely small perturbations. Finally, our buffering concept provides a stringent definition of "buffering" on the level of systems and control theory, resulting in four absolute ratio scales for control performance that are suited to measure disturbance rejection and setpoint tracking, and both their static and dynamic aspects. Our concept of buffering provides a powerful mathematical tool for the quantitation of buffering action in all its appearances.

Simple, mild, one-step labelling of proteins with gallium-68 using a tris(hydroxypyridinone) bifunctional chelator: a 68Ga-THP-scFv targeting the prostate-specific membrane antigen.

PubMed

Nawaz, Saima; Mullen, Gregory E D; Sunassee, Kavitha; Bordoloi, Jayanta; Blower, Philip J; Ballinger, James R

2017-10-25

Labelling proteins with gallium-68 using bifunctional chelators is often problematic because of unsuitably harsh labelling conditions such as low pH or high temperature and may entail post-labelling purification. To determine whether tris(hydroxypyridinone) (THP) bifunctional chelators offer a potential solution to this problem, we have evaluated the labelling and biodistribution of a THP conjugate with a new single-chain antibody against the prostate-specific membrane antigen (PSMA), an attractive target for staging prostate cancer (PCa). A single-chain variable fragment (scFv) of J591, a monoclonal antibody that recognises an external epitope of PSMA, was prepared in order to achieve biokinetics matched to the half-life of gallium-68. The scFv, J591c-scFv, was engineered with a C-terminal cysteine. J591c-scFv was produced in HEK293T cells and purified by size-exclusion chromatography. A maleimide THP derivative (THP-mal) was coupled site-specifically to the C-terminal cysteine residue. The THP-mal-J591c-scFv conjugate was labelled with ammonium acetate-buffered gallium-68 from a 68 Ge/ 68 Ga generator at room temperature and neutral pH. The labelled conjugate was evaluated in the PCa cell line DU145 and its PSMA-overexpressing variant in vitro and xenografted in SCID mice. J591c-scFv was produced in yields of 4-6 mg/l culture supernatant and efficiently coupled with the THP-mal bifunctional chelator. Labelling yields > 95% were achieved at room temperature following incubation of 5 μg conjugate with gallium-68 for 5 min without post-labelling purification. 68 Ga-THP-mal-J591c-scFv was stable in serum and showed selective binding to the DU145-PSMA cell line, allowing an IC50 value of 31.5 nM to be determined for unmodified J591c-scFv. Serial PET/CT imaging showed rapid, specific tumour uptake and clearance via renal elimination. Accumulation in DU145-PSMA xenografts at 90 min post-injection was 5.4 ± 0.5%ID/g compared with 0.5 ± 0.2%ID/g in DU145 tumours (n = 4). The bifunctional chelator THP-mal enabled simple, rapid, quantitative, one-step room temperature radiolabelling of a protein with gallium-68 at neutral pH without a need for post-labelling purification. The resultant gallium-68 complex shows high affinity for PSMA and favourable in vivo targeting properties in a xenograft model of PCa.

Petri net modelling of buffers in automated manufacturing systems.

PubMed

Zhou, M; Dicesare, F

1996-01-01

This paper presents Petri net models of buffers and a methodology by which buffers can be included in a system without introducing deadlocks or overflows. The context is automated manufacturing. The buffers and models are classified as random order or order preserved (first-in-first-out or last-in-first-out), single-input-single-output or multiple-input-multiple-output, part type and/or space distinguishable or indistinguishable, and bounded or safe. Theoretical results for the development of Petri net models which include buffer modules are developed. This theory provides the conditions under which the system properties of boundedness, liveness, and reversibility are preserved. The results are illustrated through two manufacturing system examples: a multiple machine and multiple buffer production line and an automatic storage and retrieval system in the context of flexible manufacturing.

Modern Chemistry Techniques Applied to Metal Behavior and Chelation in Medical and Environmental Systems ? Final Report

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

Sutton, M; Andresen, B; Burastero, S R

2005-02-03

This report details the research and findings generated over the course of a 3-year research project funded by Lawrence Livermore National Laboratory (LLNL) Laboratory Directed Research and Development (LDRD). Originally tasked with studying beryllium chemistry and chelation for the treatment of Chronic Beryllium Disease and environmental remediation of beryllium-contaminated environments, this work has yielded results in beryllium and uranium solubility and speciation associated with toxicology; specific and effective chelation agents for beryllium, capable of lowering beryllium tissue burden and increasing urinary excretion in mice, and dissolution of beryllium contamination at LLNL Site 300; {sup 9}Be NMR studies previously unstudied atmore » LLNL; secondary ionization mass spec (SIMS) imaging of beryllium in spleen and lung tissue; beryllium interactions with aerogel/GAC material for environmental cleanup. The results show that chelator development using modern chemical techniques such as chemical thermodynamic modeling, was successful in identifying and utilizing tried and tested beryllium chelators for use in medical and environmental scenarios. Additionally, a study of uranium speciation in simulated biological fluids identified uranium species present in urine, gastric juice, pancreatic fluid, airway surface fluid, simulated lung fluid, bile, saliva, plasma, interstitial fluid and intracellular fluid.« less

Social Buffering of Stress in Development: A Career Perspective

PubMed Central

Gunnar, Megan R.

2016-01-01

This review provides a broad overview of my research group's work on social buffering in human development in the context of the field. Much of the focus is on social buffering of the hypothalamic-pituitary-adrenocortical (HPA) system, one of the two major arms of the mammalian stress system. This focus reflects the centrality of the HPA system in research on social buffering in the fields of developmental psychobiology and developmental science. However, buffering of the cardiovascular and autonomic nervous system is also discussed. The central developmental question in this area derives from attachment theory which argues that the infant's experience of stress and arousal regulation in the context of her early attachment relationships is not an immature form of social buffering experienced in adulthood, but rather the foundation out of which individual differences in the capacity to gain stress relief from social partners emerge. The emergence of social buffering in infancy, changes in social buffering throughout childhood and adolescence, the influence of early experience on later individual differences in social buffering, and critical gaps in our knowledge are described. PMID:28544861

Bonding of wood fiber composites using a synthetic chelator-lignin activation system

Treesearch

D. Yelle; B. Goodell; D.J. Gardner; A. Amirbahman; P. Winistofer; S. Shaler

2004-01-01

Wood fibers, after thermo-mechanical pulping, have a high concentration of lignin on the outer surface of the fiber; the residual middle lamella of the woody cell wall. When wood fibers are oxidatively treated with a chelator produced by Gloeophyllum trabeum (a brown-rot fungus), in the presence of hydrogen peroxide (H2O2) and ferric iron (FeIII), free radicals are...

Analysis of Natural Buffer Systems and the Impact of Acid Rain

ERIC Educational Resources Information Center

Powers, David C.; Yoder, Claude H.; Higgs, Andrew T.; Obley, Matt L.; Hess, Kenneth R.; Leber, Phyllis A.

2005-01-01

The environmental significance of acid rain on water systems of different buffer capacities is discussed. The most prevalent natural buffer system is created by the equilibrium between carbonate ions and carbon dioxide.

Fluid extraction using carbon dioxide and organophosphorus chelating agents

DOEpatents

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

1998-11-24

Methods for extracting metalloid and metal species from a solid or liquid material by exposing the material to a fluid solvent, particularly supercritical CO{sub 2}, and a chelating agent are described. The chelating agent forms a chelate with the species, the chelate being soluble in the fluid to allow removal of the species from the material. In preferred embodiments the extraction solvent is supercritical CO{sub 2} and the chelating agent comprises an organophosphorous chelating agent, particularly sulfur-containing organophosphorous chelating agents, including mixtures of chelating agents. Examples of chelating agents include monothiophosphinic acid, di-thiophosphinic acid, phosphine sulfite, phosphorothioic acid, and mixtures thereof. The method provides an environmentally benign process for removing metal and metalloids from industrial waste solutions, particularly acidic solutions. Both the chelate and the supercritical fluid can be regenerated and the contaminant species recovered to provide an economic, efficient process. 1 fig.

Fluid extraction using carbon dioxide and organophosphorus chelating agents

DOEpatents

Smart, Neil G.; Wai, Chien M.; Lin, Yuehe; Kwang, Yak Hwa

1998-01-01

Methods for extracting metalloid and metal species from a solid or liquid material by exposing the material to a fluid solvent, particularly supercritical CO.sub.2, and a chelating agent are described. The chelating agent forms a chelate with the species, the chelate being soluble in the fluid to allow removal of the species from the material. In preferred embodiments the extraction solvent is supercritical CO.sub.2 and the chelating agent comprises an organophosphorous chelating agent, particularly sulfur-containing organophosphorous chelating agents, including mixtures of chelating agents. Examples of chelating agents include monothiophosphinic acid, di-thiophosphinic acid, phosphine sulfite, phosphorothioic acid, and mixtures thereof. The method provides an environmentally benign process for removing metal and metalloids from industrial waste solutions, particularly acidic solutions. Both the chelate and the supercritical fluid can be regenerated and the contaminant species recovered to provide an economic, efficient process.

Final Report for File System Support for Burst Buffers on HPC Systems

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

Yu, W.; Mohror, K.

Distributed burst buffers are a promising storage architecture for handling I/O workloads for exascale computing. As they are being deployed on more supercomputers, a file system that efficiently manages these burst buffers for fast I/O operations carries great consequence. Over the past year, FSU team has undertaken several efforts to design, prototype and evaluate distributed file systems for burst buffers on HPC systems. These include MetaKV: a Key-Value Store for Metadata Management of Distributed Burst Buffers, a user-level file system with multiple backends, and a specialized file system for large datasets of deep neural networks. Our progress for these respectivemore » efforts are elaborated further in this report.« less

Sodium ascorbate kills Candida albicans in vitro via iron-catalyzed Fenton reaction: importance of oxygenation and metabolism

PubMed Central

Avci, Pinar; Freire, Fernanda; Banvolgyi, Andras; Mylonakis, Eleftherios; Wikonkal, Norbert M; Hamblin, Michael R

2016-01-01

Aim: Ascorbate can inhibit growth and even decrease viability of various microbial species including Candida albicans. However the optimum conditions and the mechanism of action are unclear. Materials/methodology: Candida albicans shaken for 90 min in a buffered solution of ascorbate (90 mM) gave a 5-log reduction of cell viability, while there was no killing without shaking, in growth media with different carbon sources or at 4°C. Killing was inhibited by the iron chelator 2,2′-bipyridyl. Hydroxyphenyl fluorescein probe showed the intracellular generation of hydroxyl radicals. Results/conclusion: Ascorbate-mediated killing of C. albicans depends on oxygenation and metabolism, involves iron-catalyzed generation of hydroxyl radicals via Fenton reaction and depletion of intracellular NADH. Ascorbate could serve as a component of a topical antifungal therapy. PMID:27855492

Liposome encapsulation of chelating agents

DOEpatents

Rahman, Yueh Erh

1976-01-13

A method for transferring a chelating agent across a cellular membrane by encapsulating the charged chelating agent within liposomes and carrying the liposome-encapsulated chelating agent to the cellular membrane where the liposomes containing the chelating agent will be taken up by the cells, thereby transferring the chelating agent across the cellular membrane. A chelating agent can be introduced into the interior of a cell of a living organism wherein the liposomes will be decomposed, releasing the chelating agent to the interior of the cell. The released chelating agent will complex intracellularly deposited toxic heavy metals, permitting the more soluble metal complex to transfer across the cellular membrane from the cell and subsequently be removed from the living organism.

Iron chelating active packaging: Influence of competing ions and pH value on effectiveness of soluble and immobilized hydroxamate chelators.

PubMed

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

2016-04-01

Many packaged foods utilize synthetic chelators (e.g. ethylenediaminetetraacetic acid, EDTA) to inhibit iron-promoted oxidation or microbial growth which would result in quality loss. To address consumer demands for all natural products, we have previously developed a non-migratory iron chelating active packaging material by covalent immobilization of polyhydroxamate and demonstrated its efficacy in delaying lipid oxidation. Herein, we demonstrate the ability of this hydroxamate-functionalized iron chelating active packaging to retain iron chelating capacity; even in the presence of competing ions common in food. Both immobilized and soluble hydroxamate chelators retained iron chelating capacity in the presence of calcium, magnesium, and sodium competing ions, although at pH 5.0 the presence of calcium reduced immobilized hydroxamate iron chelation. A strong correlation was found between colorimetric and mass spectral analysis of iron chelation by the chelating packaging material. Such chelating active packaging may support reducing additive use in product formulations, while retaining quality and shelf life. Copyright © 2015 Elsevier Ltd. All rights reserved.

Bioinspired Interfacial Chelating-like Reinforcement Strategy toward Mechanically Enhanced Lamellar Materials.

PubMed

Chen, Ke; Zhang, Shuhao; Li, Anran; Tang, Xuke; Li, Lidong; Guo, Lin

2018-05-22

Many biological organisms usually derived from the ordered assembly of heterogeneous, hierarchical inorganic/organic constituents exhibit outstanding mechanical integration, but have proven to be difficult to produce the combination of excellent mechanical properties, such as strength, toughness, and light weight, by merely mimicking their component and structural characteristics. Herein, inspired by biologically strong chelating interactions of phytic acid (PA) or IP6 in many biomaterials, we present a biologically interfacial chelating-like reinforcement (BICR) strategy for fabrication of a highly dense ordered "brick-and-mortar" microstructure by incorporating tiny amounts of a natural chelating agent ( e. g., PA) into the interface or the interlamination of a material ( e. g., graphene oxide (GO)), which shows joint improvement in hardness (∼41.0%), strength (∼124.1%), maximum Young's modulus (∼134.7%), and toughness (∼118.5%) in the natural environment. Besides, for different composite matrix systems and artificial chelating agents, the BICR strategy has been proven successful for greatly enhancing their mechanical properties, which is superior to many previous reinforcing approaches. This point can be mainly attributed to the stronger noncovalent cross-linking interactions such as dense hydrogen bonds between the richer phosphate (hydroxyl) groups on its cyclohexanehexol ring and active sites of GO, giving rise to the larger energy dissipation at its hybrid interfaces. It is also simple and environmentally friendly for further scale-up fabrication and can be readily extended to other material systems, which opens an advanced reinforcement route to construct structural materials with high mechanical performance in an efficient way for practical applications.

The Multimission Image Processing Laboratory's virtual frame buffer interface

NASA Technical Reports Server (NTRS)

Wolfe, T.

1984-01-01

Large image processing systems use multiple frame buffers with differing architectures and vendor supplied interfaces. This variety of architectures and interfaces creates software development, maintenance and portability problems for application programs. Several machine-dependent graphics standards such as ANSI Core and GKS are available, but none of them are adequate for image processing. Therefore, the Multimission Image Processing laboratory project has implemented a programmer level virtual frame buffer interface. This interface makes all frame buffers appear as a generic frame buffer with a specified set of characteristics. This document defines the virtual frame uffer interface and provides information such as FORTRAN subroutine definitions, frame buffer characteristics, sample programs, etc. It is intended to be used by application programmers and system programmers who are adding new frame buffers to a system.

12 CFR 217.11 - Capital conservation buffer and countercyclical capital buffer amount.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 12 Banks and Banking 2 2014-01-01 2014-01-01 false Capital conservation buffer and countercyclical capital buffer amount. 217.11 Section 217.11 Banks and Banking FEDERAL RESERVE SYSTEM BOARD OF GOVERNORS... Requirements and Buffers § 217.11 Capital conservation buffer and countercyclical capital buffer amount. (a...

Control of lipid oxidation by nonmigratory active packaging films prepared by photoinitiated graft polymerization.

PubMed

Tian, Fang; Decker, Eric A; Goddard, Julie M

2012-08-08

Transition metal-promoted oxidation impacts the quality, shelf life, and nutrition of many packaged foods. Metal-chelating active packaging therefore offers a means to protect foods against oxidation. Herein, we report the development and characterization of nonmigratory metal-chelating active packaging. To prepare the films, carboxylic acids were grafted onto the surfaces of polypropylene films by photoinitiated graft polymerization of acrylic acid. Attenuated total reflectance/Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, and iron-chelating assay were used to characterize film properties. Graft polymerization yielded a carboxylic acid density of 68.67 ± 9.99 nmol per cm(2) film, with ferrous iron-chelating activity of 71.07 ± 12.95 nmol per cm(2). The functionalized films extended the lag phase of lipid oxidation in a soybean oil-in-water emulsion system from 2 to 9 days. The application of such nonmigratory active packaging films represents a promising approach to reduce additive use while maintaining food quality.

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.

A hexa-quinoline based C3-symmetric chemosensor for dual sensing of zinc(ii) and PPi in an aqueous medium via chelation induced "OFF-ON-OFF" emission.

PubMed

Sinha, Sanghamitra; Chowdhury, Bijit; Adarsh, Nayarassery N; Ghosh, Pradyut

2018-05-15

A quinoline-based C3-symmetric fluorescent probe (1), N,N',N''-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(1-(quinolin-2-yl)-N-(quinolin-2-ylmethyl)methanamine), has been developed which can selectively detect Zn2+ without the interference of Cd2+via significant enhancement in emission intensity (fluorescence "turn-ON") associated with distinct fluorescence colour changes and very low detection limits (35.60 × 10-9 M in acetonitrile and 29.45 × 10-8 M in 50% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile media). Importantly, this sensor is operative with a broad pH window (pH 4-10). The sensing phenomenon has been duly studied through UV-vis, steady-state, and time-resolved fluorescence spectroscopic methods indicating 1 : 3 stoichiometric binding between 1 and Zn2+ which is further corroborated by 1H NMR studies. Density functional theoretical (DFT) calculations provide the optimized molecular geometry and properties of the zinc complex, 1[Zn(ClO4)]33+, which is proposed to be formed in acetonitrile. The results are in line with the solution-state experimental findings. The single crystal X-ray study provides the solid state structure of the trinuclear Zn2+ complex showing solubility in an aqueous buffer (10 mM HEPES, pH = 7.4). Finally, the resulting trinuclear Zn2+ complex has been utilized as a fluorescence "turn-OFF" sensor for the selective detection of pyrophosphate in a 70% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile solvent with a nanomolar detection limit (45.37 × 10-9 M).

New tris(dopamine) derivative as an iron chelator. Synthesis, solution thermodynamic stability, and antioxidant research.

PubMed

Zhang, Qingchun; Jin, Bo; Shi, Zhaotao; Wang, Xiaofang; Lei, Shan; Tang, Xingyan; Liang, Hua; Liu, Qiangqiang; Gong, Mei; Peng, Rufang

2017-06-01

A new tris(dopamine) derivative, containing three dopamine chelate moieties which were attached to a trimesic acid molecular scaffold, has been prepared and fully characterized by NMR, FTIR and HRMS. The solution thermodynamic stability of the chelator with Fe(III), Mg(II), Zn(II) and Fe(II) ions was investigated. Results demonstrated that the chelator exhibited effective binding ability and improved selectivity to Fe(III) ion. The chelator possessed affinity similar to that of diethylenetriaminepentaacetic acid chelator for Fe(III) ion. The high affinity could be attributed to the favorable geometric arrangement between the chelator and Fe(III) ion coordination preference. The chelator also exhibited high antioxidant activity and nontoxicity to neuron-like rat pheochromocytoma cells. Hence, the chelator could be used as chelating agent for iron overload situations without depleting essential metal ions, such as Mg(II) and Zn(II) ions. Copyright © 2017. Published by Elsevier Inc.

Agarose electrophoresis of DNA in discontinuous buffers, using a horizontal slab apparatus and a buffer system with improved properties.

PubMed

Zsolnai, A; Orbán, L; Chrambach, A

1993-03-01

Using a horizontal slab apparatus with a buffer in the reservoirs at the level of the gel ("sea-level electrophoresis"), the retrograde discontinuous buffer system reported by Wiltfang et al. for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of proteins was applied to DNA electrophoresis. This application yielded the advantages of an increased displacement rate of the moving boundary front and a decrease in the concentration of the counterion base in the resolving phase, which yielded reduced relative mobility values at equivalent gel concentrations and practicable low buffer concentrations. The change of relative mobilities (Rf) with a variation of field strength is decreased compared to that of the migration rate in the continuous Tris-boric-acid-EDTA (TBE) buffer and thus the robustness of the system is improved, as well as the efficiency of separation. The system of Wiltfang et al. has in common with previously described discontinuous DNA system, that it is able to stack DNA from dilute samples and is insensitive to sample components with lower net mobilities than DNA, such as acetate. However, the variance of Rf at constant current density in the discontinuous buffer system is not improved over that of the migration rate at constant field strength in the continuous TBE buffer.

Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

NASA Astrophysics Data System (ADS)

Deshpande, Aniruddha S.; Khomane, Ramdas B.; Vaidya, Bhalchandra K.; Joshi, Renuka M.; Harle, Arti S.; Kulkarni, Bhaskar D.

2008-06-01

Sulfur nanoparticles were synthesized from hazardous H2S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe3+ malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 and n-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5 15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.

Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

PubMed Central

2008-01-01

Sulfur nanoparticles were synthesized from hazardous H2S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe3+–malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 andn-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5–15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.

SE-72/AS-72 generator system based on Se extraction/ As reextraction

DOEpatents

Fassbender, Michael Ernst; Ballard, Beau D

2013-09-10

The preparation of a .sup.72Se/.sup.72As radioisotope generator involves forming an acidic aqueous solution of an irradiated alkali bromide target such as a NaBr target, oxidizing soluble bromide in the solution to elemental bromine, removing the elemental bromine, evaporating the resulting solution to a residue, removing hydrogen chloride from the residue, forming an acidic aqueous solution of the residue, adding a chelator that selectively forms a chelation complex with selenium, and extracting the chelation complex from the acidic aqueous solution into an organic phase. As the .sup.72Se generates .sup.72As in the organic phase, the .sup.72As may be extracted repeatedly from the organic phase with an aqueous acid solution.

A dual-task design of corrosion-controlling and osteo-compatible hexamethylenediaminetetrakis- (methylene phosphonic acid) (HDTMPA) coating on magnesium for biodegradable bone implants application.

PubMed

Zhao, Sheng; Chen, Yingqi; Liu, Bo; Chen, Meiyun; Mao, Jinlong; He, Hairuo; Zhao, Yuancong; Huang, Nan; Wan, Guojiang

2015-05-01

Magnesium as well as its alloys appears increasingly as a revolutionary bio-metal for biodegradable implants application but the biggest challenges exist in its too fast bio-corrosion/degradation. Both corrosion-controllable and bio-compatible Mg-based bio-metal is highly desirable in clinic. In present work, hexamethylenediaminetetrakis (methylenephosphonic acid) [HDTMPA, (H2 O3 P-CH2 )2 -N-(CH2 )6 -N-(CH2 -PO3 H2 )2 ], as a natural and bioactive organic substance, was covalently immobilized and chelating-deposited onto Mg surface by means of chemical conversion process and dip-coating method, to fullfill dual-task performance of corrosion-protective and osteo-compatible functionalities. The chemical grafting of HDTMPA molecules, by participation of functional groups on pretreated Mg surface, ensured a firmly anchored base layer, and then sub-sequential chelating reactions of HDTMPA molecules guaranteed a homogenous and dense HDTMPA coating deposition on Mg substrate. Electrochemical corrosion and immersion degradation results reveal that the HDTMPA coated Mg provides a significantly better controlled bio-corrosion/degradation behavior in phosphate buffer saline solution as compared with untreated Mg from perspective of clinic requirement. Moreover, the HDTMPA coated Mg exhibits osteo-compatible in that it induces not only bioactivity of bone-like apatite precipitation but also promotes osteoblast cells adhesion and proliferation. Our well-controlled biodegradable and biocompatible HDTMPA modified Mg might bode well for next generation bone implant application. © 2014 Wiley Periodicals, Inc.

Method of encapsulating polyaminopolycarboxylic acid chelating agents in liposomes

DOEpatents

Rahman, Yueh Erh

1977-11-10

A method is provided for transferring a polyaminopolycarboxylic acid chelating agent across a cellular membrane by encapsulating the charged chelating agent within liposomes, which liposomes will be taken up by the cells, thereby transferring the chelating agent across the cellular membrane. The chelating agent is encapsulated within liposomes by drying a lipid mixture to form a thin film and wetting the lipid film with a solution containing the chelating agent. Mixing then results in the formation of a suspension of liposomes encapsulating the chelating agent, which liposomes can then be separated.

Molecular Innovations Towards Theranostics of Aggressive Prostate Cancer

DTIC Science & Technology

2013-09-01

14. ABSTRACT: In this project, we propose to develop a new drug delivery vehicle based on dendrimer nanotechnology for personalized medicine. This new...PI’s lab will make dendrimers bearing functional handles to conjugate with chelating agents provided by the Initiating PI’s lab for PET imaging and...has designed and synthesized the proposed bifunctional chelator scaffold system, CB-TE2A(tBu)2-N3 for the further construction of dendrimer -based

Thermophysical properties of carboxylic and amino acid buffers at subzero temperatures: relevance to frozen state stabilization.

PubMed

Sundaramurthi, Prakash; Suryanarayanan, Raj

2011-06-02

Macromolecules and other thermolabile biologicals are often buffered and stored in frozen or dried (freeze-dried) state. Crystallization of buffer components in frozen aqueous solutions and the consequent pH shifts were studied in carboxylic (succinic, malic, citric, tartaric acid) and amino acid (glycine, histidine) buffers. Aqueous buffer solutions were cooled from room temperature (RT) to -25 °C and the pH of the solution was measured as a function of temperature. The thermal behavior of frozen solutions was investigated by differential scanning calorimetry (DSC), and the crystallized phases were identified by X-ray diffractometry (XRD). Based on the solubility of the neutral species of each buffer system over a range of temperatures, it was possible to estimate its degree of supersaturation at the subambient temperature of interest. This enabled us to predict its crystallization propensity in frozen systems. The experimental and the predicted rank orderings were in excellent agreement. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartrate systems, at initial pH < pK(a)(2), only the most acidic buffer component (neutral form) crystallized on cooling, causing an increase in the freeze-concentrate pH. In glycine buffer solutions, when the initial pH was ∼3 units < isoelectric pH (pI = 5.9), β-glycine crystallization caused a small decrease in pH, while a similar effect but in the opposite direction was observed when the initial pH was ∼3 units > pI. In the histidine buffer system, depending on the initial pH, either histidine or histidine HCl crystallized.

Method for preparing radionuclide-labeled chelating agent-ligand complexes

DOEpatents

Meares, Claude F.; Li, Min; DeNardo, Sally J.

1999-01-01

Radionuclide-labeled chelating agent-ligand complexes that are useful in medical diagnosis or therapy are prepared by reacting a radionuclide, such as .sup.90 Y or .sup.111 In, with a polyfunctional chelating agent to form a radionuclide chelate that is electrically neutral; purifying the chelate by anion exchange chromatography; and reacting the purified chelate with a targeting molecule, such as a monoclonal antibody, to form the complex.

Concepts and goals in the management of transfusional iron overload.

PubMed

Porter, John B

2007-12-01

In this review, current concepts and goals of iron chelation therapy for thalassemias, sickle cell disease, and myelodysplastic syndromes are discussed. The primary goal of iron chelation therapy is to prevent the accumulation of iron reaching harmful levels by matching iron intake from blood transfusion, with iron excreted by iron chelation. Over 30 years of experience with deferoxamine has shown iron chelation to be an effective therapeutic modality. However, chelation efficiency is limited because most of the body's iron stores are not directly chelatable, and only a small fraction of body iron is chelatable at any moment. Once iron has been deposited in organs other than the liver, for example the heart, removal by chelation is slow and inefficient. Chelation efficiency can be improved by designing regimes where chelators are available 24 hr a day to bind labile iron pools in cells and plasma. Deferoxamine has a short plasma half-life and the parenteral infusions required to achieve steady plasma levels are demanding, with consequent variable adherence to therapy. Once-daily oral administration of deferasirox achieves continuous chelation with trough concentrations sufficient to decrease plasma labile iron species progressively, and achieves an efficiency of chelation not obtainable with deferiprone or deferoxamine monotherapy. 2007 Wiley-Liss, Inc

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.

Low oxygen tension reverses antineoplastic effect of iron chelator deferasirox in human glioblastoma cells.

PubMed

Legendre, Claire; Avril, Sylvie; Guillet, Catherine; Garcion, Emmanuel

2016-02-01

Overcoming resistance to treatment is an essential issue in many cancers including glioblastoma (GBM), the deadliest primary tumor of the central nervous system. As dependence on iron is a key feature of tumor cells, using chelators to reduce iron represents an opportunity to improve conventional GBM therapies. The aim of the present study was, therefore, to investigate the cytostatic and cytotoxic impact of the new iron chelator deferasirox (DFX) on human GBM cells in well-defined clinical situations represented by radiation therapy and mild-hypoxia. Under experimental normoxic condition (21% O2), deferasirox (DFX) used at 10 μM for 3 days reduced proliferation, led cell cycle arrest in S and G2-M phases and induced cytotoxicity and apoptosis in U251 and U87 GBM cells. The abolition of the antineoplastic DFX effects when cells were co-treated with ferric ammonium sulfate supports the hypothesis that its effects result from its ability to chelate iron. As radiotherapy is the main treatment for GBM, the combination of DFX and X-ray beam irradiation was also investigated. Irradiation at a dose of 16 Gy repressed proliferation, cytotoxicity and apoptosis, but only in U251 cells, while no synergy with DFX was observed in either cell line. Importantly, when the same experiment was conducted in mild-hypoxic conditions (3% O2), the antiproliferative and cytotoxic effects of DFX were abolished, and its ability to deplete iron was also impaired. Taken together, these in vitro results could raise the question of the benefit of using iron chelators in their native forms under the hypoxic conditions often encountered in solid tumors such as GBM. Developing new chemistry or a new drug delivery system that would keep DFX active in hypoxic cells may be the next step toward their application.

Grass buffers for playas in agricultural landscapes: A literature synthesis

USGS Publications Warehouse

Melcher, Cynthia P.; Skagen, Susan K.

2005-01-01

Future research should entail multiple-scale approaches at regional, wetland-complex, and individual watershed scales. Information needs include direct measures of buffer effectiveness in ‘real-world’ systems, refinement and field tests of buffer-effectiveness models, how buffers may affect floral and faunal communities of playas, and basic ecological information on playa function and playa wildlife ecology. Understanding how wildlife communities respond to patch size and habitat fragmentation is crucial for addressing questions regarding habitat quality of grass buffers in playa systems.

Hydrogeological constraints on riparian buffers for reduction of diffuse pollution: examples from the Bear Creek watershed in Iowa, USA.

PubMed

Simpkins, W W; Wineland, T R; Andress, R J; Johnston, D A; Caron, G C; Isenhart, T M; Schultz, R C

2002-01-01

Riparian Management Systems (RiMS) have been proposed to minimize the impacts of agricultural production and improve water quality in Iowa in the Midwestern USA. As part of RiMS, multispecies riparian buffers have been shown to decrease nutrient, pesticide, and sediment concentrations in runoff from adjacent crop fields. However, their effect on nutrients and pesticides moving in groundwater beneath buffers has been discussed only in limited and idealized hydrogeologic settings. Studies in the Bear Creek watershed of central Iowa show the variability inherent in hydrogeologic systems at the watershed scale, some of which may be favorable or unfavorable to future implementation of buffers. Buffers may be optimized by choosing hydrogeologic systems where a shallow groundwater flow system channels water directly through the riparian buffer at velocities that allow for processes such as denitrification to occur.

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

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.

Novel hexadentate and pentadentate chelators for 64Cu-based targeted PET imaging

PubMed Central

Sin, Inseok; Kang, Chisoo; Bandara, Nilantha; Sun, Xiang; Zhong, Yongliang; Rogers, Buck E.; Chong, Hyun-Soon

2014-01-01

A series of new hexadentate and pentadentate chelators were designed and synthesized as chelators of 64Cu. The new pentadentate and hexadentate chelators contain different types of donor groups and are expected to form neutral complexes with Cu(II). The new chelators were evaluated for complex kinetics and stability with 64Cu. The new chelators instantly bound to 64Cu with high labeling efficiency and maximum specific activity. All 64Cu-radiolabeled complexes in human serum remained intact for 2 days. The 64Cu-radiolabeled complexes were further challenged by EDTA in a 100-fold molar excess. Among the 64Cu-radiolabeled complexes evaluated, 64Cu-complex of the new chelator E was well tolerated with a minimal transfer of 64Cu to EDTA. 64Cu-radiolabeled complex of the new chelator E was further evaluated for biodistribution studies using mice and displayed rapid blood clearance and low organ uptake. 64Cu-chelator E produced a favorable in vitro and in vivo complex stability profiles comparable to 64Cu complex of the known hexadentate NOTA chelator. The in vitro and in vivo data highlight strong potential of the new chelator E for targeted PET imaging application. PMID:24657050

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.

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).

A technique for collection of exudate from pea seedlings

NASA Technical Reports Server (NTRS)

Hanson, S. D.; Cohen, J. D.; Bandurski, R. S. (Principal Investigator)

1985-01-01

Ethylenediaminetetraacetic acid (EDTA), at concentrations higher than 1.0 millimolar, is phytotoxic to etiolated seedlings of Pisum sativum. Substantial vascular exudation from pea epicotyls could be obtained without tissue damage at 0.5 millimolar EDTA if the solution was buffered at pH 7.5 with sodium N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid. Treated seedlings exuded 950 micrograms (leucine equivalents) of ninhydrin-positive material per day and 870 micrograms (glucose equivalents) of anthrone-positive material per day. Amino acid analysis showed the exudate to have glutamine as the major amido nitrogen containing compound and sucrose was shown to be the major sugar. Radiolabeled tryptophan and sucrose applied to cotyledons were transferred through the epicotyl and into the collection medium. The pH profile for exudation shows half maximal exudation at pH 7.2, indicating the promotion of exudation by EDTA is probably not due simply to Ca2+ chelation.

SODR Memory Control Buffer Control ASIC

NASA Technical Reports Server (NTRS)

Hodson, Robert F.

1994-01-01

The Spacecraft Optical Disk Recorder (SODR) is a state of the art mass storage system for future NASA missions requiring high transmission rates and a large capacity storage system. This report covers the design and development of an SODR memory buffer control applications specific integrated circuit (ASIC). The memory buffer control ASIC has two primary functions: (1) buffering data to prevent loss of data during disk access times, (2) converting data formats from a high performance parallel interface format to a small computer systems interface format. Ten 144 p in, 50 MHz CMOS ASIC's were designed, fabricated and tested to implement the memory buffer control function.

Targeting hypoxia in tumors using 2-nitroimidazoles with peptidic chelators for technetium-99m: effect of lipophilicity.

PubMed

Zhang, X; Su, Z F; Ballinger, J R; Rauth, A M; Pollak, A; Thornback, J R

2000-01-01

Tumor hypoxia is an important prognostic factor for response to therapy. Radiolabeled 2-nitroimidazoles have been used for imaging hypoxia, and the octanol/water partition coefficient (P) of these compounds appears to play a crucial role in their suitability for imaging. A series of 11 2-nitroimidazoles coupled to peptidic chelators for (99m)Tc with divergent P was developed and evaluated in an in vitro system. Two classes of N(3)S chelators were used: dialkyl-Gly-Ser-Cys-linker-2-nitroimidazole (Class I) and dialkyl-Gly-Lys(2-nitroimidazole)-Cys (Class II). The chelators were prepared by automated solid-phase peptide synthesis. Xanthine oxidase was able to reduce the 2-nitroimidiazole moiety on the ligands, but the rate of reduction varied 5-fold among the different chelators. The chelators were labeled by transchelation from [(99m)Tc]gluconate at temperatures between 22 and 100 degrees C. The reaction mixtures were analyzed by HPLC and their P values determined. The accumulation of each complex in suspension cultures of Chinese hamster ovary cells incubated under aerobic or extremely hypoxic conditions was determined. Radiochemical yields ranged from 5 to 80% for the 11 compounds. HPLC showed that some of the compounds formed two complexes with (99m)Tc, possibly syn and anti conformations with respect to the Tc=O bond. In general, the Class I chelators labeled more readily than the class II chelators. The P values of the (99m)Tc complexes varied from 0.0002 to 5 and were generally in accordance with predictions based on structure. There were also differences in P as a function of pH; the free acids had a lower P at pH 7.4 than at pH 2.0 due to ionization, whereas the amides did not show this effect. Accumulation levels in aerobic cells were related to P but varied over a narrow range. Four of the 11 compounds showed selective accumulation in hypoxic cells. The peptidic class of 2-nitroimidazoles, with flexible design and convenient solid-phase synthesis, deserves further study as agents for imaging hypoxia in tumors.

Photolysis of caged calcium in femtoliter volumes using two-photon excitation.

PubMed Central

Brown, E B; Shear, J B; Adams, S R; Tsien, R Y; Webb, W W

1999-01-01

A new technique for the determination of the two-photon uncaging action cross section (deltau) of photolyzable calcium cages is described. This technique is potentially applicable to other caged species that can be chelated by a fluorescent indicator dye, as well as caged fluorescent compounds. The two-photon action cross sections of three calcium cages, DM-nitrophen, NP-EGTA, and azid-1, are studied in the range of excitation wavelengths between 700 and 800 nm. Azid-1 has a maximum deltau of approximately 1.4 GM at 700 nm, DM-nitrophen has a maximum deltau of approximately 0.013 GM at 730 nm, and NP-EGTA has no measurable uncaging yield. The equations necessary to predict the amount of cage photolyzed and the temporal behavior of the liberated calcium distribution under a variety of conditions are derived. These equations predict that by using 700-nm light from a Ti:sapphire laser focused with a 1.3-NA objective, essentially all of the azid-1 within the two-photon focal volume would be photolyzed with a 10-micros pulse train of approximately 7 mW average power. The initially localized distributions of free calcium will dissipate rapidly because of diffusion of free calcium and uptake by buffers. In buffer-free cytoplasm, the elevation of the calcium concentration at the center of the focal volume is expected to last for approximately 165 micros. PMID:9876162

Aminothiol Receptors for Decorporation of Intravenously Administered 60Co in the Rat

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

Levitskaia, Tatiana G.; Morris, James E.; Creim, Jeffrey A.

2010-01-01

The reported investigation provides a comparison of the oral decorporation efficacy of L-glutathione (GSH), L-cysteine (Cys), and a liposomal GSH formulation (ReadiSorb) toward systemic cobalt-60 (60Co) to that observed following intravenous administration of GSH and Cys in F344 rats. L-histidine (His) was tested intravenously to compare in vivo efficacy of the aminothiol GSH and Cys chelators with that of aminoimidazole (His) chelator. 60Co was administered to animals by intravenous injection, followed by intravenous or oral gavage doses of a chelator repeated at 24 hour intervals for a total of 5 doses. The results suggest that GSH and Cys are potentmore » decorporation agents for 60Co in the rat model, although the efficacy of treatment depends largely on systemic availability of a chelator. The intravenous GSH or Cys were most effective in reducing tissue 60Co levels and in increasing excretion of radioactivity compared to control animals. Liposomal encapsulation was found to markedly enhance the oral bioavailability of GSH compared to non-formulated GSH. Oral administration of ReadiSorb reduced 60Co levels in nearly all tissues by 12-43% compared to that observed for non-formulated GSH. Efficacy of oral Cys was only slightly reduced in comparison with intravenous Cys. Further studies to optimize the dosing regimen in order to maximize decorporation efficiency are warranted.« less

In search of a viable reaction pathway in the chelation of a metallo-protein

NASA Astrophysics Data System (ADS)

Rose, Frisco; Hodak, Miroslav; Bernholc, Jerry

2010-03-01

Misfolded metallo-proteins are potential causal agents in the onset of neuro-degenerative diseases, such as Alzheimer's and Parkinson's Diseases (PD). Experimental results involving metal chelation have shown significant promise in symptom reduction and misfolding reversal. We explore, through atomistic simulations, potential reaction pathways for the chelation of Cu^2+ from the metal binding site in our representation of a partially misfolded α-synuclein, the protein implicated in PD. Our ab initio simulations use Density Functional Theory (DFT) and nudged elastic band to obtain the minimized energy coordinates of this reaction. Our simulations include ab initio water at the interaction site and in its first solvation shells, while the remainder is fully solvated with orbital-free DFT water representation [1]. Our ongoing studies of viable chelation agents include nicotine, caffeine and other potential reagents, we will review the best case agents in this presentation. [4pt] [1] Hodak M, Lu W, Bernholc J. Hybrid ab initio Kohn-Sham density functional theory/frozen-density orbital-free density functional theory simulation method suitable for biological systems. J. Chem. Phys. 2008 Jan;128(1):014101-9.

Diethylentriaminepenta acetic acid glucose conjugates as a cell permeable iron chelator.

PubMed

Mosayebnia, Mona; Shafiee-Ardestani, Mehdi; Pasalar, Parvin; Mashayekhi, Mojgan; Amanlou, Massoud

2014-01-01

To find out whether DTPA-DG complex can enhance clearance of intracellular free iron. Diethylenetriaminepentaacetic acid-D-deoxy-glucosamine (DTPA-DG) was synthesized and examined for its activity as a cell-permeable iron chelator in human hepatocellular carcinoma (HEPG2) cell line exposed to high concentration of iron sulfate and compared with deferoxamine (DFO), a prototype iron chelator. The effect of DTPA-DG on cell viability was monitored using the 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide MTT assay as well. There was a significant increase of iron level after iron overload induction in HEPG2 cell culture. DTPA-DG presented a remarkable capacity to iron burden reducing with estimated 50% inhibitory concentration value of 65.77 nM. In fact, glycosyl moiety was gained access of DTPA to intracellular iron deposits through glucose transporter systems. DTPA-DG, more potent than DFO to sequester deposits of free iron with no profound toxic effect. The results suggest the potential of DTPA-DG in chelating iron and permitting its excretion from primary organ storage.

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.

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

Effect of IDA and TREN chelating agents and buffer systems on the purification of human IgG with immobilized nickel affinity membranes.

PubMed

Ribeiro, Mariana Borsoi; Vijayalakshmi, Mookambesvaran; Todorova-Balvay, Daniele; Bueno, Sonia Maria Alves

2008-01-01

The purification of IgG from human plasma was studied by comparing two affinity membranes complexed with Ni(II), prepared by coupling iminodiacetic acid (IDA) and Tris(2-aminoethyl)amine (TREN) to poly(ethylenevinyl alcohol), PEVA, hollow fiber membranes. The Ni(II)-TREN-PEVA hollow fiber membrane had lower capacity for human IgG than the complex Ni(II)-IDA-PEVA, but with similar selectivity. The IgG in peak fractions eluted from the Ni(II)-IDA-PEVA with a stepwise concentration gradient of Tris-HCl pH 7.0 (100-700 mM) reached a purity of 98% (based on IgG, IgM, IgA, albumin, and transferrin nephelometric analysis). Adsorption IgG data at different temperatures (4-37 degrees C) were analyzed using Langmuir model resulting in a calculated maximum capacity at 25 degrees C of 204.6 mg of IgG/g of dry membrane. Decrease in Kd with increasing temperature (1.7x10(-5) to 5.3x10(-6) M) indicated an increase in affinity with increased temperature. The positive value of enthalpy change (26.2 kJ/mol) indicated that the adsorption of IgG in affinity membrane is endothermic. Therefore, lower temperature induces adsorption as verified experimentally.

Buffer-regulated biocorrosion of pure magnesium.

PubMed

Kirkland, Nicholas T; Waterman, Jay; Birbilis, Nick; Dias, George; Woodfield, Tim B F; Hartshorn, Richard M; Staiger, Mark P

2012-02-01

Magnesium (Mg) alloys are being actively investigated as potential load-bearing orthopaedic implant materials due to their biodegradability in vivo. With Mg biomaterials at an early stage in their development, the screening of alloy compositions for their biodegradation rate, and hence biocompatibility, is reliant on cost-effective in vitro methods. The use of a buffer to control pH during in vitro biodegradation is recognised as critically important as this seeks to mimic pH control as it occurs naturally in vivo. The two different types of in vitro buffer system available are based on either (i) zwitterionic organic compounds or (ii) carbonate buffers within a partial-CO(2) atmosphere. This study investigated the influence of the buffering system itself on the in vitro corrosion of Mg. It was found that the less realistic zwitterion-based buffer did not form the same corrosion layers as the carbonate buffer, and was potentially affecting the behaviour of the hydrated oxide layer that forms on Mg in all aqueous environments. Consequently it was recommended that Mg in vitro experiments use the more biorealistic carbonate buffering system when possible.

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.

Spectroscopic properties and Judd-Ofelt theory analysis of erbium chelates.

PubMed

Wang, Huaishan; Qian, Guodong; Wang, Zhiyu; Wang, Minquan

2005-11-01

Erbium chelates including tris(acetylacetonato) erbium(III) monohydrate, tris(acetylacetonato)(1,10-phenanthroline) erbium(III) and tris(trifluoroacetylacetonato)(1,10-phenanthroline) erbium(III) are synthesized. Judd-Ofelt theory is employed on basis of the UV-Vis-NIR absorption spectra of erbium chelates dissolved in methanol. Judd-Ofelt parameters of erbium chelates are determined by a least square fitting and dealt with the chemical structure of erbium chelates. Photoluminescence characteristics of erbium chelates are investigated upon excitation at 488 nm by an Ar(+) laser. The qualitative correlation of Judd-Ofelt parameters with photoluminescence properties for erbium chelates is also discussed. It is found that larger Omega(6) value for erbium chelate is and larger photoluminescence intensity at 1.54 microm is, and Omega(2) value should contribute to the photoluminescence full width at half maximum (FWHM) at 1.54 microm. The changes of Judd-Ofelt parameters result from the introduction of the second ligand phenathroline or the substitution of electron-drawing group CF(3) in beta-diketone for erbium chelates.

Development of a rapid biolistic assay to determine changes in relative levels of intracellular calcium in leaves following tetracycline uptake by pinto bean plants.

PubMed

Farkas, Michael H; Mojica, Elmer-Rico E; Patel, Minesh; Aga, Diana S; Berry, James O

2009-08-01

Tetracycline antibiotics, such as chlortetracycline (CTC) and tetracycline (TC), are introduced into agricultural lands through the application of manure as fertilizer. These compounds are phytotoxic to certain crop plants, including pinto beans (Phaseolus vulgaris), the species used for this investigation. While the mechanism of this toxicity is not yet understood, CTC is known to be a calcium chelator. We describe here a novel method to show that CTC is taken up by pinto bean plants and chelates calcium in leaves. Cameleon fusion proteins can provide qualitative and quantitative imaging of intracellular calcium levels, but current methodology requires stable transformation. Many plant species, including pinto beans, are not yet transformable using standard Agrobacterium-based protocols. To determine the role of calcium chelation in this plant, a rapid, biolistic method was developed to transiently express the cameleon protein. This method can easily be adapted to other plant systems. Our findings provide evidence that chelation of intracellular calcium by CTC is related to phytotoxic effects caused by this antibiotic in pinto beans. Root uptake of CTC and TC by pinto beans and their translocation to leaves were further verified by fluorescence spectroscopy and liquid chromatography/mass spectrometry, confirming results of the biolistic method that showed calcium chelation by tetracyclines in leaves.

Cost effectiveness of once-daily oral chelation therapy with deferasirox versus infusional deferoxamine in transfusion-dependent thalassaemia patients: US healthcare system perspective.

PubMed

Delea, Thomas E; Sofrygin, Oleg; Thomas, Simu K; Baladi, Jean-Francois; Phatak, Pradyumna D; Coates, Thomas D

2007-01-01

Deferasirox is a recently approved once-daily oral iron chelator that has been shown to reduce liver iron concentrations and serum ferritin levels to a similar extent as infusional deferoxamine. To determine the cost effectiveness of deferasirox versus deferoxamine in patients with beta-thalassaemia major from a US healthcare system perspective. A Markov model was used to estimate the total additional lifetime costs and QALYs gained with deferasirox versus deferoxamine in patients with beta-thalassaemia major and chronic iron overload from blood transfusions. Patients were assumed to be 3 years of age at initiation of chelation therapy and to receive prescribed dosages of deferasirox and deferoxamine that have been shown to be similarly effective in such patients. Compliance with chelation therapy and probabilities of iron overload-related cardiac disease and death by degree of compliance were estimated using data from published studies. Costs ($US, year 2006 values) of deferoxamine administration and iron overload-related cardiac disease were based on analyses of health insurance claims of transfusion-dependent thalassaemia patients. Utilities were based on a study of patient preferences for oral versus infusional chelation therapy, as well as published literature. Probabilistic and deterministic sensitivity analyses were employed to examine the robustness of the results to key assumptions. Deferasirox resulted in a gain of 4.5 QALYs per patient at an additional expected lifetime cost of $US126,018 per patient; the cost per QALY gained was $US28,255. The cost effectiveness of deferasirox versus deferoxamine was sensitive to the estimated costs of deferoxamine administration and the quality-of-life benefit associated with oral versus infusional therapy. Cost effectiveness was also relatively sensitive to the equivalent daily dose of deferasirox, and the unit costs of deferasirox and deferoxamine, and was more favourable in younger patients. Results of this analysis of the cost effectiveness of oral deferasirox versus infusional deferoxamine suggest that deferasirox is a cost effective iron chelator from a US healthcare perspective.

Assessment of potential aluminum chelators in an octanol/aqueous system and in the aluminum-loaded rabbit.

PubMed

Yokel, R A; Kostenbauder, H B

1987-11-01

Aluminum (Al) solubilization from Al borate and its distribution in an octanol/aqueous system (Do/w) were determined in the absence and presence of 12 potential Al chelators. Citrate, N,N'-bis-(2-hydroxybenzyl)ethylenediamine- N,N'-diacetic acid (HBED), cyclohexane-1,2-diaminotetraacetic acid (CDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), desferrioxamine, and ethylenediamine-N,N'-bis(2-dihydroxyphenylacetic acid) (EDDHA) were 55 to over 100% efficient in solubilizing equimolar amounts of Al. Tetracycline, EDTA, and 2,3-dihydroxybenzoic acid (DHBA) were less than 20% efficient. 1,4-Dioxane and fluoride were ineffective. The Do/w of Al averaged 0.005. The Do/w of the Al.chelator complex was generally less than that of Al, except for HBED and tetracycline (0.04 and 0.96, respectively). The Do/w of DHBA, desferrioxamine, EDDHA, and HBED were not influenced by Al, but tetracycline became more lipophilic. These compounds were tested for their ability to increase urinary Al excretion in Al-loaded rabbits. Chelators were given po weekly beginning 2 weeks after Al loading. Urine was obtained hourly from 3 hr prior to 6 hr after chelator administration and analyzed for Al. Fluoride and tetracycline (450 and 4500 mumol/kg) and citrate, NTA, EDTA, CDTA, DTPA, DHBA, HBED, and 1,4-dioxane (150 and 1500 mumol/kg) were ineffective. Following HBED administration, some of the Al-loaded rabbits died, presumably due to redistribution of Al within the rabbit. Following DTPA administration, some of the Al-loaded rabbits died, presumably due to DTPA. Oral EDDHA (1500 mumol/kg) significantly increased urinary Al excretion. EDDHA and desferrioxamine (150 mumol/kg) were administered by po, sc, and iv routes and were found to have comparable potency. The in vitro results may explain some of the in vivo findings. The in vitro methods may be useful to screen out compounds with no chelation potential. EDDHA-like compounds may have potential as alternatives to desferrioxamine in the prevention or treatment of Al accumulation and Al-induced toxicity.

System and Method for Network Bandwidth, Buffers and Timing Management Using Hybrid Scheduling of Traffic with Different Priorities and Guarantees

NASA Technical Reports Server (NTRS)

Bonk, Ted (Inventor); Hall, Brendan (Inventor); Smithgall, William Todd (Inventor); Varadarajan, Srivatsan (Inventor); DeLay, Benjamin F. (Inventor)

2017-01-01

Systems and methods for network bandwidth, buffers and timing management using hybrid scheduling of traffic with different priorities and guarantees are provided. In certain embodiments, a method of managing network scheduling and configuration comprises, for each transmitting end station, reserving one exclusive buffer for each virtual link to be transmitted from the transmitting end station; for each receiving end station, reserving exclusive buffers for each virtual link to be received at the receiving end station; and for each switch, reserving a exclusive buffer for each virtual link to be received at an input port of the switch. The method further comprises determining if each respective transmitting end station, receiving end station, and switch has sufficient capability to support the reserved buffers; and reporting buffer infeasibility if each respective transmitting end station, receiving end station, and switch does not have sufficient capability to support the reserved buffers.

Predicting the crystallization propensity of carboxylic acid buffers in frozen systems--relevance to freeze-drying.

PubMed

Sundaramurthi, Prakash; Suryanarayanan, Raj

2011-04-01

Selective crystallization of buffer components in frozen solutions is known to cause pronounced pH shifts. Our objective was to study the crystallization behavior and the consequent pH shift in frozen aqueous carboxylic acid buffers. Aqueous carboxylic acid buffers were cooled to -25°C and the pH of the solution was measured as a function of temperature. The thermal behavior of solutions during freezing and thawing was investigated by differential scanning calorimetry. The crystallized phases in frozen solution were identified by X-ray diffractometry. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartarate systems, at initial pH

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.

Pyclen Tri-n-butylphosphonate Ester as Potential Chelator for Targeted Radiotherapy: From Yttrium(III) Complexation to (90)Y Radiolabeling.

PubMed

Le Fur, Mariane; Beyler, Maryline; Lepareur, Nicolas; Fougère, Olivier; Platas-Iglesias, Carlos; Rousseaux, Olivier; Tripier, Raphaël

2016-08-15

The Y(3+) complex of PCTMB, the tri-n-butyl phosphonate ester of pyclen (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene), was synthesized as well as its Ho(3+) and Lu(3+) analogues. X-ray diffraction analyses revealed isomorphous dimeric M2(PCTMB)2·9H2O (M = Y, Ho, Lu) structures that crystallize in the centrosymmetric P1̅ triclinic space group. (1)H NMR and UV studies in aqueous solutions indicated that Y(3+) complexation is fast, being quantitative in 167 min at pH 3.8 and in 13 min at pH 5.5 (25 °C, acetate buffer, I = 0.150 M, [Y(3+)] = [PCTMB] = 0.2 mM). (1)H NMR DOSY and photon correlation spectroscopy experiments evidenced the formation of aggregates in chloroform with a bimodal distribution that changes slightly with concentration (11-24 and 240-258 nm). The behavior of the acid-assisted dissociation of the complex of Y(3+) with PCTMB was studied under pseudo-first-order conditions, and the half-life of the [Y(PCTMB)] complex in 0.5 M HCl at 25 °C was found to be 37 min, a value that decreases to 2.6 min in 5 M HCl. The Y(3+) complex of PCTMB is thermodynamically very stable, with a stability constant of log KY-PCTMB = 19.49 and pY = 16.7 measured by potentiometry. (90)Y complexation studies revealed fast radiolabeling kinetics; optimal radiolabeling conditions were obtained for (90)Y in acetate medium, PCTMB at 10(-4) to 10(-2) M in acetate buffer pH = 4.75, 15 min at 45-60 °C. In vitro stability studies in human serum showed that [(90)Y(PCTMB)] is quite stable, with about 90% of the activity still in the form of the radiotracer at 24 h and 80% from 48 h to 72 h. A comparison with other ligands such as PCTA, DOTA, and DTPA already used for in vivo application shows that [(90)Y(PCTMB)] is an interesting lipophilic and neutral analogue of these reference chelates for therapeutic applications in aqueous and nonaqueous media.

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.

Imaging of Ep-CAM Positive Metastatic Cancer in the Lymph System

DTIC Science & Technology

2011-01-01

bind Ep-CAM positive breast cancer cells in pH up to 8.3, which will be important for the chelating agent DOTA . The DOTA -NHS-ester is best conjugated...must be conjugated with the fluorophore (IRDye 800CW) and a chelating agent ( DOTA ), which sequesters the radio-metal completing the dual-label...done simultaneously, anti-Ep-CAM (9601) was conjugated with 5-fold excess IRDye, 5- fold excess DOTA or 500-fold excess DOTA overnight. After size

Protein Buffering in Model Systems and in Whole Human Saliva

PubMed Central

Lamanda, Andreas; Cheaib, Zeinab; Turgut, Melek Dilek; Lussi, Adrian

2007-01-01

The aim of this study was to quantify the buffer attributes (value, power, range and optimum) of two model systems for whole human resting saliva, the purified proteins from whole human resting saliva and single proteins. Two model systems, the first containing amyloglucosidase and lysozyme, and the second containing amyloglucosidase and α-amylase, were shown to provide, in combination with hydrogencarbonate and di-hydrogenphosphate, almost identical buffer attributes as whole human resting saliva. It was further demonstrated that changes in the protein concentration as small as 0.1% may change the buffer value of a buffer solution up to 15 times. Additionally, it was shown that there was a protein concentration change in the same range (0.16%) between saliva samples collected at the time periods of 13:00 and others collected at 9:00 am and 17:00. The mode of the protein expression changed between these samples corresponded to the change in basic buffer power and the change of the buffer value at pH 6.7. Finally, SDS Page and Ruthenium II tris (bathophenantroline disulfonate) staining unveiled a constant protein expression in all samples except for one 50 kDa protein band. As the change in the expression pattern of that 50 kDa protein band corresponded to the change in basic buffer power and the buffer value at pH 6.7, it was reasonable to conclude that this 50 kDa protein band may contain the protein(s) belonging to the protein buffer system of human saliva. PMID:17327922

Copper chelation by tetrathiomolybdate inhibits lipopolysaccharide-induced inflammatory responses in vivo

PubMed Central

Wei, Hao; Beckman, Joseph S.; Zhang, Wei-Jian

2011-01-01

Redox-active transition metal ions, such as iron and copper, may play an important role in vascular inflammation, which is an etiologic factor in atherosclerotic vascular diseases. In this study, we investigated whether tetrathiomolybdate (TTM), a highly specific copper chelator, can act as an anti-inflammatory agent, preventing lipopolysaccharide (LPS)-induced inflammatory responses in vivo. Female C57BL/6N mice were daily gavaged with TTM (30 mg/kg body wt) or vehicle control. After 3 wk, animals were injected intraperitoneally with 50 μg LPS or saline buffer and killed 3 h later. Treatment with TTM reduced serum ceruloplasmin activity by 43%, a surrogate marker of bioavailable copper, in the absence of detectable hepatotoxicity. The concentrations of both copper and molybdenum increased in various tissues, whereas the copper-to-molybdenum ratio decreased, consistent with reduced copper bioavailability. TTM treatment did not have a significant effect on superoxide dismutase activity in heart and liver. Furthermore, TTM significantly inhibited LPS-induced inflammatory gene transcription in aorta and heart, including vascular and intercellular adhesion molecule-1 (VCAM-1 and ICAM-1, respectively), monocyte chemotactic protein-1 (MCP-1), interleukin-6, and tumor necrosis factor (TNF)-α (ANOVA, P < 0.05); consistently, protein levels of VCAM-1, ICAM-1, and MCP-1 in heart were also significantly lower in TTM-treated animals. Similar inhibitory effects of TTM were observed on activation of nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) in heart and lungs. Finally, TTM significantly inhibited LPS-induced increases of serum levels of soluble ICAM-1, MCP-1, and TNF-α (ANOVA, P < 0.05). These data indicate that copper chelation with TTM inhibits LPS-induced inflammatory responses in aorta and other tissues of mice, most likely by inhibiting activation of the redox-sensitive transcription factors, NF-κB and AP-1. Therefore, copper appears to play an important role in vascular inflammation, and TTM may have value as an anti-inflammatory or anti-atherogenic agent. PMID:21724870

Luminescent lanthanide chelates and methods of use

DOEpatents

Selvin, Paul R.; Hearst, John

1997-01-01

The invention provides lanthanide chelates capable of intense luminescence. The celates comprise a lanthanide chelator covalently joined to a coumarin-like or quinolone-like sensitizer. Exemplary sensitzers include 2- or 4-quinolones, 2- or 4-coumarins, or derivatives thereof e.g. carbostyril 124 (7-amino-4-methyl-2-quinolone), coumarin 120 (7-amino-4-methyl-2-coumarin), coumarin 124 (7-amino-4-(trifluoromethyl)-2-coumarin), aminomethyltrimethylpsoralen, etc. The chelates form high affinity complexes with lanthanides, such as terbium or europium, through chelator groups, such as DTPA. The chelates may be coupled to a wide variety of compounds to create specific labels, probes, diagnostic and/or therapeutic reagents, etc. The chelates find particular use in resonance energy transfer between chelate-lanthanide complexes and another luminescent agent, often a fluorescent non-metal based resonance energy acceptor. The methods provide useful information about the structure, conformation, relative location and/or interactions of macromolecules.

Obligatory reduction of ferric chelates in iron uptake by soybeans.

PubMed

Chaney, R L; Brown, J C; Tiffin, L O

1972-08-01

The contrasting Fe(2+) and Fe(3+) chelating properties of the synthetic chelators ethylenediaminedi (o-hydroxyphenylacetate) (EDDHA) and 4,7-di(4-phenylsulfonate)-1, 10-phenanthroline (bathophenanthrolinedisulfonate) (BPDS) were used to determine the valence form of Fe absorbed by soybean roots supplied with Fe(3+)-chelates. EDDHA binds Fe(3+) strongly, but Fe(2+) weakly; BPDS binds Fe(2+) strongly but Fe(3+) weakly. Addition of an excess of BPDS to nutrient solutions containing Fe(3+)-chelates inhibited soybean Fe uptake-translocation by 99+%; [Fe(II) (BPDS)(3)](4-) accumulated in the nutrient solution. The addition of EDDHA caused little or no inhibition. These results were observed with topped and intact soybeans. Thus, separation and absorption of Fe from Fe(3+)-chelates appear to require reduction of Fe(3+)-chelate to Fe(2+)-chelate at the root, with Fe(2+) being the principal form of Fe absorbed by soybean.

Internal Active Thermal Control System (IATCS) Sodium Bicarbonate/Carbonate Buffer in an Open Aqueous Carbon Dioxide System and Corollary Electrochemical/Chemical Reactions Relative to System pH Changes

NASA Technical Reports Server (NTRS)

Stegman, Thomas W.; Wilson, Mark E.; Glasscock, Brad; Holt, Mike

2014-01-01

The International Space Station (ISS) Internal Active Thermal Control System (IATCS) experienced a number of chemical changes driven by system absorption of CO2 which altered the coolant’s pH. The natural effects of the decrease in pH from approximately 9.2 to less than 8.4 had immediate consequences on system corrosion rates and corrosion product interactions with specified coolant constituents. The alkalinity of the system was increased through the development and implementation of a carbonate/bicarbonate buffer that would increase coolant pH to 9.0 – 10.0 and maintain pH above 9.0 in the presence of ISS cabin concentrations of CO2 up to twenty times higher than ground concentrations. This paper defines how a carbonate/bicarbonate buffer works in an open carbon dioxide system and summarizes the analyses performed on the buffer for safe and effective application in the on-orbit system. The importance of the relationship between the cabin environment and the IATCS is demonstrated as the dominant factor in understanding the system chemistry and pH trends before and after addition of the carbonate/bicarbonate buffer. The paper also documents the corollary electrochemical and chemical reactions the system has experienced and the rationale for remediation of these effects with the addition of the carbonate/bicarbonate buffer.

Preparation and preclinical evaluation of a 68Ga-labelled c(RGDfK) conjugate comprising the bifunctional chelator NODIA-Me.

PubMed

Läppchen, Tilman; Holland, Jason P; Kiefer, Yvonne; Bartholomä, Mark D

2018-01-01

We recently developed a chelating platform based on the macrocycle 1,4,7-triazacyclononane with up to three, five-membered azaheterocyclic arms for the development of 68 Ga- and 64 Cu-based radiopharmaceuticals. Here, a 68 Ga-labelled conjugate comprising the bifunctional chelator NODIA-Me in combination with the α v ß 3 -targeting peptide c(RGDfK) has been synthesized and characterized. The primary aim was to evaluate further the potential of our NODIA-Me chelating system for the development of 68 Ga-labelled radiotracers. The BFC NODIA-Me was conjugated to c(RGDfK) by standard peptide chemistry to obtain the final bioconjugate NODIA-Me-c(RGDfK) 3 in 72% yield. Labelling with [ 68 Ga]GaCl 3 was accomplished in a fully automated, cGMP compliant process to give [ 68 Ga]3 in high radiochemical yield (98%) and moderate specific activity (~ 8 MBq nmol- 1 ). Incorporation of the Ga-NODIA-Me chelate to c(RGDfK) 2 had only minimal influence on the affinity to integrin α v ß 3 (IC 50 values [ nat Ga]3 = 205.1 ± 1.4 nM, c(RGDfK) 2 = 159.5 ± 1.3 nM) as determined in competitive cell binding experiments in U-87 MG cell line. In small-animal PET imaging and ex vivo biodistribution studies, the radiotracer [ 68 Ga]3 showed low uptake in non-target organs and specific tumor uptake in U-87 MG tumors. The results suggest that the bifunctional chelator NODIA-Me is an interesting alternative to existing ligands for the development of 68 Ga-labelled radiopharmaceuticals.

Dynamic Buffer Capacity in Acid-Base Systems.

PubMed

Michałowska-Kaczmarczyk, Anna M; Michałowski, Tadeusz

The generalized concept of 'dynamic' buffer capacity β V is related to electrolytic systems of different complexity where acid-base equilibria are involved. The resulting formulas are presented in a uniform and consistent form. The detailed calculations are related to two Britton-Robinson buffers, taken as examples.

Tris-sucrose buffer system: a new specially designed medium for extracellular invertase production by immobilized cells of isolated yeast Cryptococcus laurentii MT-61.

PubMed

Aydogan, Mehmet Nuri; Taskin, Mesut; Canli, Ozden; Arslan, Nazli Pinar; Ortucu, Serkan

2014-01-01

The aims of the present study were to isolate new yeasts with high extracellular (exo) invertase activity and to investigate the usability of buffer systems as invertase production media by immobilized yeast cells. Among 70 yeast isolates, Cryptococcus laurentii MT-61 had the highest exo-invertase activity. Immobilization of yeast cells was performed using sodium alginate. Higher exo-invertase activity for immobilized cells was achieved in tris-sucrose buffer system (TSBS) compared to sodium acetate buffer system and potassium phosphate buffer system. TSBS was prepared by dissolving 30 g of sucrose in 1 L of tris buffer solution. The optimum pH, temperature, and incubation time for invertase production with immobilized cells were determined as 8.0, 35 °C and 36 h in TSBS, respectively. Under optimized conditions, maximum exo-invertase activity was found to be 28.4 U/mL in sterile and nonsterile TSBS. Immobilized cells could be reused in 14 and 12 successive cycles in sterile and nonsterile TSBS without any loss in the maximum invertase activity, respectively. This is the first report which showed that immobilized microbial cells could be used as a biocatalyst for exo-invertase production in buffer system. As an additional contribution, a new yeast strain with high invertase activity was isolated.

New calcium-selective smart contrast agents for magnetic resonance imaging.

PubMed

Verma, Kirti Dhingra; Forgács, Attila; Uh, Hyounsoo; Beyerlein, Michael; Maier, Martin E; Petoud, Stéphane; Botta, Mauro; Logothetis, Nikos K

2013-12-23

Calcium plays a vital role in the human body and especially in the central nervous system. Precise maintenance of Ca(2+) levels is very crucial for normal cell physiology and health. The deregulation of calcium homeostasis can lead to neuronal cell death and brain damage. To study this functional role played by Ca(2+) in the brain noninvasively by using magnetic resonance imaging, we have synthesized a new set of Ca(2+) -sensitive smart contrast agents (CAs). The agents were found to be highly selective to Ca(2+) in the presence of other competitive anions and cations in buffer and in physiological fluids. The structure of CAs comprises Gd(3+)-DO3A (DO3A=1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane) coupled to a Ca(2+) chelator o-amino phenol-N,N,O-triacetate (APTRA). The agents are designed to sense Ca(2+) present in extracellular fluid of the brain where its concentration is relatively high, that is, 1.2-0.8 mM. The determined dissociation constant of the CAs to Ca(2+) falls in the range required to sense and report changes in extracellular Ca(2+) levels followed by an increase in neural activity. In buffer, with the addition of Ca(2+) the increase in relaxivity ranged from 100-157%, the highest ever known for any T1-based Ca(2+)-sensitive smart CA. The CAs were analyzed extensively by the measurement of luminescence lifetime measurement on Tb(3+) analogues, nuclear magnetic relaxation dispersion (NMRD), and (17)O NMR transverse relaxation and shift experiments. The results obtained confirmed that the large relaxivity enhancement observed upon Ca(2+) addition is due to the increase of the hydration state of the complexes together with the slowing down of the molecular rotation and the retention of a significant contribution of the water molecules of the second sphere of hydration. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Susceptibility of enterococci to natural and synthetic iron chelators].

PubMed

Lisiecki, Paweł; Mikucki, Jerzy

2002-01-01

A total of 79 strains of enterococci belonging to 10 species were tested for susceptibility to natural and synthetic iron chelators. All strains produced siderophores. These enterococci were susceptible to three synthetic iron chelators only: 8-hydroxyquinoline, disodium versenate (EDTA) and o-phenanthroline. They were resistant to all other synthetic chelators: ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDHA), nitrilotriacetate, 2,2'-bipiridyl, salicylic acid, 8-hydroxy-5-sulphonic acid and to all natural chelators: ovotransferrine, human apotransferrine, horse apoferritine, desferrioxamine B, ferrichrome and rhodotorulic acid. The relations between susceptibility/resistance, iron assimilation and structure and stability constants of iron chelators were discussed.

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

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.

New concept to remove heavy metals from liquid waste based on electrochemical pH-switchable immobilized ligands

NASA Astrophysics Data System (ADS)

Pascal, Viel; Laetitia, Dubois; Joël, Lyskawa; Marc, Sallé; Serge, Palacin

2007-01-01

Absorption on resins is often used as secondary step in the treatment of water-based effluents, in order to reach very low concentrations. The separation of the trapped effluents from the resins and the regeneration of the resins for further use create wide volumes of secondary effluents coming from the washings of the resins with chemical reagents. We propose an alternative solution based on a "surface strategy" through adsorption phenomena and electrical control of the expulsion stage. The final goal is to limit or ideally to avoid the use of chemical reagents at the expulsion (or regeneration) stage of the depolluting process. Heavy metal ions were captured on active filters composed by a conducting surface covered by poly-4-vinylpyridine (P 4VP). Due to pyridine groups those polymer films have chelating properties for copper ions. Our strategy for electrical triggering of the copper expulsion in aqueous medium is based on pH sensitive chelating groups. Applying moderate electro-oxidizing conditions generates acidic conditions in the vicinity of the electrode, i.e. "inside" the polymer film. This allows a "switch-off" of the complexing properties of the film from the basic form of pyridine to pyridinium. Interestingly, no buffer washing is necessary to restore (or "switch-on") the complexing properties of the polymer film because the pH of the external medium is left unchanged by the electrochemical effect that affects only the vicinity of the electrode. Switch-on/switch-off cycles are followed and attested by IR spectroscopy and EQCM method.

A novel facile method of labeling octreotide with (18)F-fluorine.

PubMed

Laverman, Peter; McBride, William J; Sharkey, Robert M; Eek, Annemarie; Joosten, Lieke; Oyen, Wim J G; Goldenberg, David M; Boerman, Otto C

2010-03-01

Several methods have been developed to label peptides with (18)F. However, in general these are laborious and require a multistep synthesis. We present a facile method based on the chelation of (18)F-aluminum fluoride (Al(18)F) by 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). The method is characterized by the labeling of NOTA-octreotide (NOTA-d-Phe-cyclo[Cys-Phe-d-Trp-Lys-Thr-Cys]-Throl (MH(+) 1305) [IMP466]) with (18)F. Octreotide was conjugated with the NOTA chelate and labeled with (18)F in a 2-step, 1-pot method. The labeling procedure was optimized with regard to the labeling buffer, peptide, and aluminum concentration. Radiochemical yield, specific activity, in vitro stability, and receptor affinity were determined. Biodistribution of (18)F-IMP466 was studied in AR42J tumor-bearing mice and compared with that of (68)Ga-labeled IMP466. In addition, small-animal PET/CT images were acquired. IMP466 was labeled with Al(18)F in a single step with 50% yield. The labeled product was purified by high-performance liquid chromatography to remove unbound Al(18)F and unlabeled peptide. The radiolabeling, including purification, was performed in 45 min. The specific activity was 45,000 GBq/mmol, and the peptide was stable in serum for 4 h at 37 degrees C. Labeling was performed at pH 4.1 in sodium citrate, sodium acetate, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, and 2-(N-morpholino)ethanesulfonic acid buffer and was optimal in sodium acetate buffer. The apparent 50% inhibitory concentration of the (19)F-labeled IMP466 determined on AR42J cells was 3.6 nM. Biodistribution studies at 2 h after injection showed a high tumor uptake of (18)F-IMP466 (28.3 +/- 5.2 percentage injected dose per gram [%ID/g]; tumor-to-blood ratio, 300 +/- 90), which could be blocked by an excess of unlabeled peptide (8.6 +/- 0.7 %ID/g), indicating that the accumulation in the tumor was receptor-mediated. Biodistribution of (68)Ga-IMP466 was similar to that of (18)F-IMP466. (18)F-IMP466 was stable in vivo, because bone uptake was only 0.4 +/- 0.2 %ID/g, whereas free Al(18)F accumulated rapidly in the bone (36.9 +/- 5.0 %ID/g at 2 h after injection). Small-animal PET/CT scans showed excellent tumor delineation and high preferential accumulation in the tumor. NOTA-octreotide could be labeled rapidly and efficiently with (18)F using a 2-step, 1-pot method. The compound was stable in vivo and showed rapid accretion in somatostatin receptor subtype 2-expressing AR42J tumors in nude mice. This method can be used to label other NOTA-conjugated compounds with (18)F.

Characterization of the activity of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-be nzopyran-6-yl-hydrogen phosphate] potassium salt in hydroxyl radical elimination.

PubMed

Tomita, T; Kashima, M; Tsujimoto, Y

2000-03-01

The effect of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H -1-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-K1) on hydroxyl radical (*OH) elimination was studied using electron spin resonance (ESR) and spectrophotometric experiments. The addition of EPC-K, and *OH scavengers eliminated the *OH generated from Cu2+/H2O2, Fe2+/H2O2 and H2O2/UV-irradiation reaction systems. However, in competitive reactions using different concentrations of a spin-trap agent, the addition of the *OH scavenger altered the IC50 values, whereas the addition of EPC-K1 and a metal chelater did not change the value in the Cu2+/H2O2 and Fe2+/H2O2 reaction systems. The addition of EPC-K1 and metal chelater changed the ESR signal for free Cu2+. The spectrophotometric experiments confirmed that the addition of EPC-K1 and metal chelater altered the absorption spectra due to CuCl2 and FeSO4, whereas the *OH scavenger did not alter the spectra. Therefore, it was demonstrated that EPC-K, has the ability both to scavenge *OH directly and to inhibit the generation of *OH by the chelation of Cu2+ and Fe2+.

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.

The Potential Role of Systemic Buffers in Reducing Intratumoral Extracellular pH and Acid-Mediated Invasion

PubMed Central

Silva, Ariosto S.; Yunes, Jose A.; Gillies, Robert J.; Gatenby, Robert A.

2013-01-01

A number of studies have shown that the extracellular pH (pHe) in cancers is typically lower than that in normal tissue and that an acidic pHe promotes invasive tumor growth in primary and metastatic cancers. Here, we investigate the hypothesis that increased systemic concentrations of pH buffers reduce intratumoral and peritumoral acidosis and, as a result, inhibit malignant growth. Computer simulations are used to quantify the ability of systemic pH buffers to increase the acidic pHe of tumors in vivo and investigate the chemical specifications of an optimal buffer for such purpose. We show that increased serum concentrations of the sodium bicarbonate (NaHCO3) can be achieved by ingesting amounts that have been used in published clinical trials. Furthermore, we find that consequent reduction of tumor acid concentrations significantly reduces tumor growth and invasion without altering the pH of blood or normal tissues. The simulations also show that the critical parameter governing buffer effectiveness is its pKa. This indicates that NaHCO3, with a pKa of 6.1, is not an ideal intratumoral buffer and that greater intratumoral pHe changes could be obtained using a buffer with a pKa of ~7. The simulations support the hypothesis that systemic pH buffers can be used to increase the tumor pHe and inhibit tumor invasion. PMID:19276380

Stacking and determination of phenazine-1-carboxylic acid with low pKa in soil via moving reaction boundary formed by alkaline and double acidic buffers in capillary electrophoresis.

PubMed

Sun, Chong; Yang, Xiao-Di; Fan, Liu-Yin; Zhang, Wei; Xu, Yu-Quan; Cao, Cheng-Xi

2011-04-01

As shown herein, a normal moving reaction boundary (MRB) formed by an alkaline buffer and a single acidic buffer had poor stacking to the new important plant growth promoter of phenazine-1-carboxylic acid (PCA) in soil due to the leak induced by its low pK(a). To stack the PCA with low pK(a) efficiently, a novel stacking system of MRB was developed, which was formed by an alkaline buffer and double acidic buffers (viz., acidic sample and blank buffers). With the novel system, the PCA leaking into the blank buffer from the sample buffer could be well stacked by the prolonged MRB formed between the alkaline buffer and blank buffer. The relevant mechanism of stacking was discussed briefly. The stacking system, coupled with sample pretreatment, could achieve a 214-fold increase of PCA sensitivity under the optimal conditions (15 mM (pH 11.5) Gly-NaOH as the alkaline buffer, 15 mM (pH 3.0) Gly-HCl-acetonitrile (20%, v/v) as the acidic sample buffer, 15 mM (pH 3.0) Gly-HCl as the blank buffer, 3 min 13 mbar injection of double acidic buffers, benzoic acid as the internal standard, 75 μm i.d. × 53 cm (44 cm effective length) capillary, 25 kV and 248 nm). The limit of detection of PCA in soil was decreased to 17 ng/g, the intra-day and inter-day precision values (expressed as relative standard deviations) were 3.17-4.24% and 4.17-4.87%, respectively, and the recoveries of PCA at three concentration levels changed from 52.20% to 102.61%. The developed method could be used for the detection of PCA in soil at trace level.

Continuous processing of recombinant proteins: integration of refolding and purification using simulated moving bed size-exclusion chromatography with buffer recycling.

PubMed

Wellhoefer, Martin; Sprinzl, Wolfgang; Hahn, Rainer; Jungbauer, Alois

2014-04-11

Continuous processing of recombinant proteins was accomplished by combining continuous matrix-assisted refolding and purification by tandem simulated moving bed (SMB) size-exclusion chromatography (SEC). Recombinant proteins, N(pro) fusion proteins from inclusion bodies were dissolved with NaOH and refolded in the SMB system with a closed-loop set-up with refolding buffer as the desorbent buffer and buffer recycling of the refolding buffer of the raffinate by tangential flow filtration. For further purification of the refolded proteins, a second SMB operation also based on SEC was added. The whole system could be operated isocratically with refolding buffer as the desorbent buffer, and buffer recycling could also be applied in the purification step. Thus, a significant reduction in buffer consumption was achieved. The system was evaluated with two proteins, the N(pro) fusion pep6His and N(pro) fusion MCP-1. Refolding solution, which contained residual N(pro) fusion peptide, the cleaved autoprotease N(pro), and the cleaved target peptide was used as feed solution. Full separation of the cleaved target peptide from residual proteins was achieved at a purity and recovery in the raffinate and extract, respectively, of approximately 100%. In addition, more than 99% of the refolding buffer of the raffinate was recycled. A comparison of throughput, productivity, and buffer consumption of the integrated continuous process with two batch processes demonstrated that up to 60-fold higher throughput, up to 180-fold higher productivity, and at least 28-fold lower buffer consumption can be obtained by the integrated continuous process, which compensates for the higher complexity. Copyright © 2014 Elsevier B.V. All rights reserved.

Natural chelating agents for radionuclide decorporation

DOEpatents

Premuzic, E.T.

1985-06-11

This invention relates to the production of metal-binding compounds useful for the therapy of heavy metal poisoning, for biological mining and for decorporation of radionuclides. The present invention deals with an orderly and effective method of producing new therapeutically effective chelating agents. This method uses challenge biosynthesis for the production of chelating agents that are specific for a particular metal. In this approach, the desired chelating agents are prepared from microorganisms challenged by the metal that the chelating agent is designed to detoxify. This challenge induces the formation of specific or highly selective chelating agents. The present invention involves the use of the challenge biosynthetic method to produce new complexing/chelating agents that are therapeutically useful to detoxify uranium, plutonium, thorium and other toxic metals. The Pseudomonas aeruginosa family of organisms is the referred family of microorganisms to be used in the present invention to produce the new chelating agent because this family is known to elaborate strains resistant to toxic metals.

Function of the iron-binding chelator produced by Coriolus versicolor in lignin biodegradation.

PubMed

Wang, Lu; Yan, WenChao; Chen, JiaChuan; Huang, Feng; Gao, PeiJi

2008-03-01

An ultrafiltered low-molecular-weight preparation of chelating compounds was isolated from a wood-containing culture of the white-rot basidiomycete Coriolus versicolor. This preparation could chelate Fe3+ and reduce Fe3+ to Fe2+, demonstrating that the substance may serve as a ferric chelator, oxygen-reducing agent, and redox-cycling molecule, which would include functioning as the electron transport carrier in Fenton reaction. Lignin was treated with the iron-binding chelator and the changes in structure were investigated by 1H-NMR, 13C-NMR, difference spectrum caused by ionization under alkaline conditions and nitrobenzene oxidation. The results indicated that the iron-binding chelator could destroy the beta-O-4 bonds in etherified lignin units and insert phenolic hydroxyl groups. The low-molecular-weight chelator secreted by C. versicolor resulted in new phenolic substructures in the lignin polymer, making it susceptible to attack by laccase or manganese peroxidase. Thus, the synergic action of the iron-binding chelator and the lignocellulolytic enzymes made the substrate more accessible to degradation.

In vivo evaluation and small-animal PET/CT of a prostate cancer mouse model using 64Cu bombesin analogs: side-by-side comparison of the CB-TE2A and DOTA chelation systems.

PubMed

Garrison, Jered C; Rold, Tammy L; Sieckman, Gary L; Figueroa, Said Daibes; Volkert, Wynn A; Jurisson, Silvia S; Hoffman, Timothy J

2007-08-01

The BB2 receptor subtype, of the bombesin family of receptors, has been shown to be highly overexpressed in a variety of human tumors, including prostate cancer. Bombesin (BBN), a 14-amino acid peptide, has been shown to target the BB2 receptor with high affinity. 64Cu (half-life = 12.7 h, beta+: 18%, E(beta+ max) = 653 keV; beta-: 37%, E(beta- max) = 578 keV) is a radioisotope that has clinical potential for application in both diagnostic imaging and radionuclide therapy. Recently, new chelation systems such as 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4,11-diacetic acid (CB-TE2A) have been reported to significantly stabilize the 64Cu radiometal in vivo. The increased stability of the 64Cu-CB-TE2A chelate complex has been shown to significantly reduce nontarget retention compared with tetraazamacrocycles such as 1,4,7,10-tetraazacyclodoadecane-N,N',N'',N'''-tetraacetic acid (DOTA). The aim of this study was to determine whether the CB-TE2A chelation system could significantly improve the in vivo stability of 64Cu bombesin analogs. The study directly compares 64Cu bombesin analogs using the CB-TE2A and DOTA chelation systems in a prostate cancer xenograft SCID (severely compromised immunodeficient) mouse model. The CB-TE2A-8-AOC-BBN(7-14)NH2 and DOTA-8-AOC-BBN(7-14)NH2 conjugates were synthesized and radiolabeled with 64Cu. The receptor-binding affinity and internalization profile of each metallated conjugate was evaluated using PC-3 cells. Pharmacokinetic and small-animal PET/CT studies were performed using female SCID mice bearing PC-3 xenografts. In vivo BB2 receptor targeting was confirmed by tumor uptake values of 6.95 +/- 2.27 and 4.95 +/- 0.91 %ID/g (percentage injected dose per gram) at the 15-min time point for the 64Cu-CB-TE2A and 64Cu-DOTA radioconjugates, respectively. At the 24-h time point, liver uptake was substantially reduced for the 64Cu-CB-TE2A radioconjugate (0.21 +/- 0.06 %ID/g) compared with the 64Cu-DOTA radioconjugate (7.80 +/- 1.51 %ID/g). The 64Cu-CB-TE2A-8-AOC-BBN(7-14)NH2 radioconjugate demonstrated significant clearance, 98.60 +/- 0.28 %ID, from the mouse at 24 h after injection. In contrast, only 67.84 +/- 5.43 %ID of the 64Cu activity was excreted using the 64Cu-DOTA-8-AOC-BBN(7-14)NH2 radioconjugate because of nontarget retention. The pharmacokinetic and small-animal PET/CT studies demonstrate significantly improved nontarget tissue clearance for the 64Cu-CB-TE2A8-AOC-BBN(7-14)NH2. This is attributed to the improved in vivo stability of the 64Cu-CB-TE2A chelate complex as compared with the 64Cu-DOTA chelate complex.

On buffer overflow duration in a finite-capacity queueing system with multiple vacation policy

NASA Astrophysics Data System (ADS)

Kempa, Wojciech M.

2017-12-01

A finite-buffer queueing system with Poisson arrivals and generally distributed processing times, operating under multiple vacation policy, is considered. Each time when the system becomes empty, the service station takes successive independent and identically distributed vacation periods, until, at the completion epoch of one of them, at least one job waiting for service is detected in the buffer. Applying analytical approach based on the idea of embedded Markov chain, integral equations and linear algebra, the compact-form representation for the cumulative distribution function (CDF for short) of the first buffer overflow duration is found. Hence, the formula for the CDF of next such periods is obtained. Moreover, probability distributions of the number of job losses in successive buffer overflow periods are found. The considered queueing system can be efficienly applied in modelling energy saving mechanisms in wireless network communication.

How I treat transfusional iron overload.

PubMed

Hoffbrand, A Victor; Taher, Ali; Cappellini, Maria Domenica

2012-11-01

Patients with β-thalassemia major (TM) and other refractory anemias requiring regular blood transfusions accumulate iron that damages the liver, endocrine system, and most importantly the heart. The prognosis in TM has improved remarkably over the past 10 years. This improvement has resulted from the development of magnetic resonance imaging (MRI) techniques, especially T2*, to accurately measure cardiac and liver iron, and from the availability of 3 iron-chelating drugs. In this article we describe the use of MRI to determine which adult and pediatric patients need to begin iron chelation therapy and to monitor their progress. We summarize the properties of each of the 3 drugs, deferoxamine (DFO), deferiprone (DFP), and deferasirox (DFX), including their efficacy, patient acceptability, and side effects. We describe when to initiate or intensify therapy, switch to another drug, or use combined therapy. We also discuss the management of refractory anemias other than TM that may require multiple blood transfusions, including sickle cell anemia and myelodysplasia. The development of a potential fourth chelator FBS 0701 and the combined use of oral chelators may further improve the quality of life and survival in patients with TM and other transfusion-dependent patients.

Mercury removal in utility wet scrubber using a chelating agent

DOEpatents

Amrhein, Gerald T.

2001-01-01

A method for capturing and reducing the mercury content of an industrial flue gas such as that produced in the combustion of a fossil fuel or solid waste adds a chelating agent, such as ethylenediaminetetraacetic acid (EDTA) or other similar compounds like HEDTA, DTPA and/or NTA, to the flue gas being scrubbed in a wet scrubber used in the industrial process. The chelating agent prevents the reduction of oxidized mercury to elemental mercury, thereby increasing the mercury removal efficiency of the wet scrubber. Exemplary tests on inlet and outlet mercury concentration in an industrial flue gas were performed without and with EDTA addition. Without EDTA, mercury removal totaled 42%. With EDTA, mercury removal increased to 71%. The invention may be readily adapted to known wet scrubber systems and it specifically provides for the removal of unwanted mercury both by supplying S.sup.2- ions to convert Hg.sup.2+ ions into mercuric sulfide (HgS) and by supplying a chelating agent to sequester other ions, including but not limited to Fe.sup.2+ ions, which could otherwise induce the unwanted reduction of Hg.sup.2+ to the form, Hg.sup.0.

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.

Semiconductor films on flexible iridium substrates

DOEpatents

Goyal, Amit

2005-03-29

A laminate semiconductor article includes a flexible substrate, an optional biaxially textured oxide buffer system on the flexible substrate, a biaxially textured Ir-based buffer layer on the substrate or the buffer system, and an epitaxial layer of a semiconductor. Ir can serve as a substrate with an epitaxial layer of a semiconductor thereon.

INFLUENCE OF IRON CHELATION ON R1 AND R2 CALIBRATION CURVES IN GERBIL LIVER AND HEART

PubMed Central

Wood, John C.; Aguilar, Michelle; Otto-Duessel, Maya; Nick, Hanspeter; Nelson, Marvin D.; Moats, Rex

2008-01-01

MRI is gaining increasing importance for the noninvasive quantification of organ iron burden. Since transverse relaxation rates depend on iron distribution as well as iron concentration, physiologic and pharmacologic processes that alter iron distribution could change MRI calibration curves. This paper compares the effect of three iron chelators, deferoxamine, deferiprone, and deferasirox on R1 and R2 calibration curves according to two iron loading and chelation strategies. 33 Mongolian gerbils underwent iron loading (iron dextran 500 mg/kg/wk) for 3 weeks followed by 4 weeks of chelation. An additional 56 animals received less aggressive loading (200 mg/kg/week) for 10 weeks, followed by 12 weeks of chelation. R1 and R2 calibration curves were compared to results from 23 iron-loaded animals that had not received chelation. Acute iron loading and chelation biased R1 and R2 from the unchelated reference calibration curves but chelator-specific changes were not observed, suggesting physiologic rather than pharmacologic differences in iron distribution. Long term chelation deferiprone treatment increased liver R1 50% (p<0.01), while long term deferasirox lowered liver R2 30.9% (p<0.0001). The relationship between R1 and R2 and organ iron concentration may depend upon the acuity of iron loading and unloading as well as the iron chelator administered. PMID:18581418

Fe(III)-EDDHA and -EDDHMA sorption on Ca-montmorillonite, ferrihydrite, and peat.

PubMed

Hernández-Apaolaza, L; Lucena, J J

2001-11-01

The effectiveness of Fe chelates as Fe sources and carriers in soil can be severely limited by the adsorption of Fe chelates or chelating agents in the solid phase. To study this phenomenon, well-characterized peat, Ca-montmorillonite, and ferrihydrite were used as model compounds, and the adsorption of Fe-EDDHA and Fe-EDDHMA chelates were studied. Sorption isotherms for the meso and racemic isomers of these chelates on the soil materials are described. The variability of sorption with pH in peat and ferrihydrite was also determined because both have variable surface charge at different pH values. In montmorillonite, at low concentrations, the retention of Fe from the Fe-EDDHMA chelate is greater than the one of the Fe-EDDHA chelate. As well as the concentration increased, the inverse situation occurs. The behavior of both meso and racemic isomers of chelates in contact with Ca-montmorillonite is similar. The Fe-meso-EDDHA isomer was highly adsorbed on ferrihydrite, but the racemic isomer is not significantly retained by this oxide. For Fe-EDDHMA isomers, the racemic isomer was more retained by the oxide, but a small sorption of the racemic isomer was also observed. Results suggest that Fe-EDDHA chelates were more retained in peat than Fe-EDDHMA chelates. The most retained isomer of Fe-EDDHA was the meso isomer. For Fe-EDDHMA, the adsorption was very low for both racemic and meso isomers.

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

Neurotoxicity of dental amalgam is mediated by zinc.

PubMed

Lobner, D; Asrari, M

2003-03-01

The use of dental amalgam is controversial largely because it contains mercury. We tested whether amalgam caused toxicity in neuronal cultures and whether that toxicity was caused by mercury. In this study, we used cortical cell cultures to show for the first time that amalgam causes nerve cell toxicity in culture. However, the toxicity was not blocked by the mercury chelator, 2,3-dimercaptopropane-1-sulphonate (DMPS), but was blocked by the metal chelator, calcium disodium ethylenediaminetetraacetate (CaEDTA). DMPS was an effective mercury chelator in this system, since it blocked mercury toxicity. Of the components that comprise amalgam (mercury, zinc, tin, copper, and silver), only zinc neurotoxicity was blocked by CaEDTA. These results indicate that amalgam is toxic to nerve cells in culture by releasing zinc. While zinc is known to be neurotoxic, ingestion of zinc is not a major concern because zinc levels in the body are tightly regulated.

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

[68Ga]FSC-(RGD)3 a trimeric RGD peptide for imaging αvβ3 integrin expression based on a novel siderophore derived chelating scaffold—synthesis and evaluation

PubMed Central

Knetsch, Peter A.; Zhai, Chuangyan; Rangger, Christine; Blatzer, Michael; Haas, Hubertus; Kaeopookum, Piriya; Haubner, Roland; Decristoforo, Clemens

2015-01-01

Over the last years Gallium-68 (68Ga) has received tremendous attention for labeling of radiopharmaceuticals for positron emission tomography (PET). 68Ga labeling of biomolecules is currently based on bifunctional chelators containing aminocarboxylates (mainly DOTA and NOTA). We have recently shown that cyclic peptide siderophores have very good complexing properties for 68Ga resulting in high specific activities and excellent metabolic stabilities, in particular triacetylfusarinine-C (TAFC). We postulated, that, starting from its deacetylated form (Fusarinine-C (FSC)) trimeric bioconjugates are directly accessible to develop novel targeting peptide based 68Ga labeled radiopharmaceuticals. As proof of principle we report on the synthesis and 68Ga-radiolabeling of a trimeric FSC-RGD conjugate, [68Ga]FSC-(RGD)3, targeting αvβ3 integrin, which is highly expressed during tumor-induced angiogenesis. Synthesis of the RGD peptide was carried out applying solid phase peptide synthesis (SPPS), followed by the coupling to the siderophore [Fe]FSC via in situ activation using HATU/HOAt and DIPEA. Subsequent demetalation allowed radiolabeling of FSC-(RGD)3 with 68Ga. The radiolabeling procedure was optimized regarding peptide amount, reaction time, temperature as well buffer systems. For in vitro evaluation partition coefficient, protein binding, serum stability, αvβ3 integrin binding affinity, and tumor cell uptake were determined. For in vitro tests as well as for the biodistribution studies αvβ3 positive human melanoma M21 and αvβ3 negative M21-L cells were used. [68Ga]FSC-(RGD)3 was prepared with high radiochemical yield (> 98%). Distribution coefficient was − 3.6 revealing a hydrophilic character, and an IC50 value of 1.8 ± 0.6 nM was determined indicating a high binding affinity for αvβ3 integrin. [68Ga]FSC-(RGD)3 was stable in PBS (pH 7.4), FeCl3- and DTPA-solution as well as in fresh human serum at 37 °C for 2 hours. Biodistribution assay confirmed the receptor specific uptake found in vitro. Uptake in the αvβ3 positive tumor was 4.3% ID/g 60 min p.i. which was 3-fold higher than the monomeric [68Ga]NODAGA-RGD. Tumor to blood ratio of approx. 8 and tumor to muscle ratio of approx. 7 were observed. [68Ga]FSC-(RGD)3 serves as an example for the feasibility of a novel class of bifunctional chelators based on cyclic peptide siderophores and shows excellent targeting properties for αvβ3 integrin in vivo for imaging tumor-induced neovascularization. PMID:25459110

Free flow cell electrophoresis using zwitterionic buffer

NASA Technical Reports Server (NTRS)

Rodkey, R. Scott

1990-01-01

Studies of a zwitterionic buffer formulated for cell electrophoresis were done using the McDonnell-Douglas Continuous Flow Electrophoresis System. Standard buffers were analyzed for their stability in the electrical field and the results showed that both buffers tested were inherently unstable. Further, titration studies showed that the standards buffers buffered poorly at the pH employed for electrophoresis. The zwitterionic buffer buffered well at its nominal pH and was shown to be stable in the electrical field. Comparative studies of the buffer with standard cell separation buffers using formalin fixed rabbit and goose red blood cells showed that the zwitterionic buffer gave better resolution of the fixed cells. Studies with viable hybridoma cells showed that buffer Q supported cell viability equal to Hank's Balanced Salt Solution and that hybridoma cells in different stages of the growth cycle demonstrated reproducible differences in electrophoretic mobility.

Reduction and conversion of 2,4,6-trinitrotoluene (TNT) by sulfide under simulated anaerobic conditions.

PubMed

Qiao, Hua; Wang, He-ling; Feng, Hua-jun; Yao, Jun; Shen, Dong-sheng; Tang, Zhi-jian

2010-07-15

To account for the fast disappearance of TNT in anaerobic fermentative liquid, we investigated TNT (TNT(0)=50 mg/L) reduction by Na(2)S at 30+/-1 degrees C in two types of buffer systems, a phosphate buffer (PB, system A) and a CH(3)COOH-NaHCO(3) buffer (system B). The effects of pH, sulfide concentration and buffer system on the conversion and reaction rate of TNT were investigated. The effect of different variables on the conversion of TNT decreased in the following order: Na(2)S concentration>pH>buffer system. A kinetics study showed that TNT reduction by Na(2)S occurred in two stages separated by a change point. The observed rate constants of the first stage K(obs-1) were 1 order of magnitude lower than those of the second stage. The TNT conversion rate increased and the time to reach the change point became shorter with increasing Na(2)S concentration and pH. A 5-fold increase in Na(2)S concentration above the theoretical stoichiometric concentration was optimum. Observed rate constants of the first stage K(obs-1) were proportional to the hydrosulfide ion concentration and the conversion rate of TNT was greater and faster in buffer system B than in system A. 2010 Elsevier B.V. All rights reserved.

Chelators whose affinity for calcium is decreased by illumination

NASA Technical Reports Server (NTRS)

Tsien, Roger Y. (Inventor); Grynkiewicz, Grzegorz (Inventor); Minta, Akwasi (Inventor)

1987-01-01

The present invention discloses a group of calcium chelating compounds which have a descreased affinity for calcium following illumination. These new compounds contain a photolabile nitrobenzyl derivative coupled to a tetracarboxylate Ca.sup.2+ chelating parent compound having the octacoordinate chelating groups characteristic of EGTA or BAPTA. In a first form, the new compounds are comprised of a BAPTA-like chelator coupled to a single 2-nitrobenzyl derivative, which in turn is a photochemical precursor of a 2-nitrosobenzophenone. In a second form, the new compounds are comprised of a BAPTA-like chelator coupled to two 2-nitrobenzyl derivatives, themselves photochemical prcursors of the related 2-nitrosobenzophenones. The present invention also discloses a novel method for preparing 1-hydroxy- or 1-alkoxy-1-(2-nitroaryl)-1-aryl methanes. Methanes of this type are critical to the preparation of, or actually constitute, the photolabile Ca.sup.2+ chelating compounds disclosed and claimed herein.

Chelation therapy to treat atherosclerosis, particularly in diabetes: Is it time to reconsider?

PubMed Central

Lamas, Gervasio A; Ergui, Ian

2016-01-01

Summary Reports and case series have suggested a possible beneficial effect of chelation therapy in patients with atherosclerotic disease. Small randomized trials conducted in patients with angina or peripheral artery disease, however, were not sufficiently powered to provide conclusive evidence on clinical outcomes. The Trial to Assess Chelation Therapy (TACT) was the first randomized trial adequately powered to detect the effects of chelation therapy on clinical endpoints. Chelation reduced adverse cardiovascular events in a post myocardial infarction (MI) population. Patients with diabetes demonstrated even greater benefit, with a number needed to treat of 6.5 patients to prevent a cardiac event over 5 years. These results led to the revision of the ACC/AHA guideline recommendations for chelation therapy, changing its classification from class III to class IIb. TACT2, a replicative trial, will assess the effects of chelation therapy on cardiovascular outcomes in diabetic patients with a prior myocardial infarction. PMID:27149141

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

Chelation therapy after the Trial to Assess Chelation Therapy: results of a unique trial

PubMed Central

Avila, Maria D.; Escolar, Esteban; Lamas, Gervasio A.

2014-01-01

Purpose of review EDTA chelation therapy has been in off-label use for the treatment of atherosclerosis. We review the results of the first large-scale randomized trial of this treatment. Recent findings The trial to assess chelation therapy was a $30 million National Institutes of Health-funded study of the safety and efficacy of EDTA-based chelation infusions in 1708 post-myocardial infarction (MI) patients. The trial to assess chelation therapy demonstrated a significant (P = 0.035) 18% reduction in a combined primary endpoint of death, MI, stroke, coronary revascularization, or hospitalization for angina. In diabetic patients the benefit was more extreme, with a 41% relative reduction in risk (P = 0.0002) and a 43% reduction in total mortality (P = 0.011). Safety data were favorable. A reduction of oxidative stress by chelation of toxic metals has been proposed as a possible mechanism of action. Summary Recent research suggests that EDTA chelation may be a well-tolerated and effective treatment for post-MI patients. Future replication and mechanistic studies are important prior to implementation in all post-MI patients. PMID:25023079

Characterization of commercial iron chelates and their behavior in an alkaline and calcareous soil.

PubMed

Cantera, Rodrigo G; Zamarreño, Angel M; García-Mina, José M

2002-12-18

Iron deficiency is a common problem for many plants grown in alkaline and calcareous soils. To correct this problem, iron is supplied to plants as chelates. Several iron chelates are sold under diverse trademarks with different characteristics. This work evaluated 18 commercial products containing the most representative chelated iron sources used in agricultural practice in Spain when the study was done, namely the ferric chelates of EDDHA, EDDHMA, EDDCHA, EDDHSA, EDTA, and DTPA. The chelates were comprehensively characterized and quantitated by several techniques, including several chromatographic methods. Iron and chelate dynamics in soil were also studied in a model alkaline and calcareous soil. Results indicate that, in this model soil, among the different iron compounds studied only FeEDDHA and analogues have the capacity to maintain soluble iron in soil solution over time. These results are in agreement with general experience under field conditions. Furthermore, among the different ortho-ortho isomers of FeEDDHA's, FeEDDHSA and FeEDDCHA showed greater capacity than FeEDDHA and FeEDDHMA to maintain the chelated iron in soil solution over time.

Protocol to determine accurate absorption coefficients for iron containing transferrins

PubMed Central

James, Nicholas G.; Mason, Anne B.

2008-01-01

An accurate protein concentration is an essential component of most biochemical experiments. The simplest method to determine a protein concentration is by measuring the A280, using an absorption coefficient (ε), and applying the Beer-Lambert law. For some metalloproteins (including all transferrin family members) difficulties arise because metal binding contributes to the A280 in a non-linear manner. The Edelhoch method is based on the assumption that the ε of a denatured protein in 6 M guanidine-HCl can be calculated from the number of the tryptophan, tyrosine, and cystine residues. We extend this method to derive ε values for both apo- and iron-bound transferrins. The absorbance of an identical amount of iron containing protein is measured in: 1) 6 M guanidine-HCl (denatured, no iron); 2) pH 7.4 buffer (non-denatured with iron); and 3) pH 5.6 (or lower) buffer with a chelator (non-denatured without iron). Since the iron free apo-protein has an identical A280 under non-denaturing conditions, the difference between the reading at pH 7.4 and the lower pH directly reports the contribution of the iron. The method is fast and consumes ~1 mg of sample. The ability to determine accurate ε values for transferrin mutants that bind iron with a wide range of affinities has proven very useful; furthermore a similar approach could easily be followed to determine ε values for other metalloproteins in which metal binding contributes to the A280. PMID:18471984

Luminescent Properties of Eu(III) Chelates on Metal Nanorods

PubMed Central

Zhang, Jian; Fu, Yi; Ray, Krishanu; Wang, Yuan; Lakowicz, Joseph. R.

2013-01-01

In this article, we report the change of optical properties for europium chelates on silver nanorods by near-field interactions. The silver rods were fabricated in a seed-growth method followed by depositing thin layers of silica on the surfaces. The europium chelates were physically absorbed in the silica layers on the silver rods. The silver rods were observed to exhibit two plasmon absorption bands from longitudinal and transverse directions, respectively, centered at 394 and 675 nm, close to absorption and emission bands from the Eu(III) chelates. As a result, the immobilized Eu(III) chelates on the silver rods should have strong interactions with the silver nanorods and lead to greatly improved optical properties. The Eu–Ag rod complexes were observed to have enhanced emission intensity up to 240-fold in comparison with the Eu(III) chelates in the metal-free silica templates. This enhancement is much larger than the value for the Eu(III) chelates on the gold rods or silver spheres indicating the presence of stronger interactions for the Eu(III) chelates with the silver rods. The interactions of Eu(III) chelates with the silver rods were also proven by extremely reduced lifetime. Moreover, the Eu–Ag rod complexes exhibited a polarized emission, which was also due to strong interactions of the Eu(III) chelates with the silver rods. All of these features may promise that the Eu(III)–Ag rod complexes have great potential for use as fluorescence imaging agents in biological assays. PMID:24363816

Effect of Iron Chelation Therapy on Glucose Metabolism in Non-Transfusion-Dependent Thalassaemia.

PubMed

Chuansumrit, Ampaiwan; Pengpis, Pimprae; Mahachoklertwattana, Pat; Sirachainan, Nongnuch; Poomthavorn, Preamrudee; Sungkarat, Witaya; Kadegasem, Praguywan; Khlairit, Patcharin; Wongwerawattanakoon, Pakawan

2017-01-01

To compare insulin sensitivity, β-cell function and iron status biomarkers in non-transfusion-dependent thalassaemia (NTDT) with iron excess during pre- and post-iron chelation. Subjects with NTDT, aged older than 10 years, with serum ferritin >300 ng/ml, were included. Iron chelation with deferasirox (10 mg/kg/day) was prescribed daily for 6 months. Ten patients with a median age of 17.4 years were enrolled. The comparison between pre- and post-chelation demonstrated significantly lower iron load: median serum ferritin (551.4 vs. 486.2 ng/ml, p = 0.047), median TIBC (211.5 vs. 233.5 µg/dl, p = 0.009) and median non-transferrin binding iron (5.5 vs. 1.4 µM, p = 0.005). All patients had a normal oral glucose tolerance test (OGTT) both pre- and post-chelation. However, fasting plasma glucose was significantly reduced after iron chelation (85.0 vs.79.5 mg/dl, p = 0.047). MRI revealed no significant changes of iron accumulation in the heart and liver after chelation, but there was a significantly lower iron load in the pancreas, assessed by higher T2* at post-chelation compared with pre-chelation (41.9 vs. 36.7 ms, p = 0.047). No adverse events were detected. A trend towards improving insulin sensitivity and β-cell function as well as a reduced pancreatic iron load was observed following 6 months of iron chelation (TCTR20160523003). © 2016 S. Karger AG, Basel.

Nonthermal inactivation of Escherichia coli K12 in buffered peptone water using a pilot-plant scale supercritical carbon dioxide system with gas-liquid porous metal contractor

USDA-ARS?s Scientific Manuscript database

This study evaluated the effectiveness of a supercritical carbon dioxide (SCCO2) system, with a gas-liquid CO2 contactor, for reducing Escherichia coli K12 in diluted buffered peptone water. 0.1% (w/v) buffered peptone water inoculated with E. coli K12 was processed using the SCCO2 system at CO2 con...

Reducing interface recombination for Cu(In,Ga)Se{sub 2} by atomic layer deposited buffer layers

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

Hultqvist, Adam; Bent, Stacey F.; Li, Jian V.

2015-07-20

Partial CuInGaSe{sub 2} (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnO{sub x} buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystallinemore » II–VI systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.« less

Reducing interface recombination for Cu(In,Ga)Se 2 by atomic layer deposited buffer layers

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

Hultqvist, Adam; Li, Jian V.; Kuciauskas, Darius

2015-07-20

Partial CuInGaSe2 (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnOx buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystalline II-VImore » systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.« less

Reducing interface recombination for Cu(In,Ga)Se 2 by atomic layer deposited buffer layers

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

Hultqvist, Adam; Li, Jian V.; Kuciauskas, Darius

2015-07-20

Partial CuInGaSe2 (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnOx buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystalline II–VImore » systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.« less

Solution Preserves Nucleic Acids in Body-Fluid Specimens

NASA Technical Reports Server (NTRS)

Pierson, Duane L.; Stowe, Raymond P.

2004-01-01

A solution has been formulated to preserve deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in specimens of blood, saliva, and other bodily fluids. Specimens of this type are collected for diagnostic molecular pathology, which is becoming the method of choice for diagnosis of many diseases. The solution makes it possible to store such specimens at room temperature, without risk of decomposition, for subsequent analysis in a laboratory that could be remote from the sampling location. Thus, the solution could be a means to bring the benefits of diagnostic molecular pathology to geographic regions where refrigeration equipment and diagnostic laboratories are not available. The table lists the ingredients of the solution. The functions of the ingredients are the following: EDTA chelates divalent cations that are necessary cofactors for nuclease activity. In so doing, it functionally removes these cations and thereby retards the action of nucleases. EDTA also stabilizes the DNA helix. Tris serves as a buffering agent, which is needed because minor contaminants in an unbuffered solution can exert pronounced effects on pH and thereby cause spontaneous degradation of DNA. SDS is an ionic detergent that inhibits ribonuclease activity. SDS has been used in some lysis buffers and as a storage buffer for RNA after purification. The use of the solution is straightforward. For example, a sample of saliva is collected by placing a cotton roll around in the subject's mouth until it becomes saturated, then the cotton is placed in a collection tube. Next, 1.5 mL of the solution are injected directly into the cotton and the tube is capped for storage at room temperature. The effectiveness of the solution has been demonstrated in tests on specimens of saliva containing herpes simplex virus. In the tests, the viral DNA, as amplified by polymerase chain reaction, was detected even after storage for 120 days.

Experimental studies of the effects of buffered particle dampers attached to a multi-degree-of-freedom system under dynamic loads

NASA Astrophysics Data System (ADS)

Lu, Zheng; Lu, Xilin; Lu, Wensheng; Masri, Sami F.

2012-04-01

This paper presents a systematic experimental investigation of the effects of buffered particle dampers attached to a multi-degree-of-freedom (mdof) system under different dynamic loads (free vibration, random excitation as well as real onsite earthquake excitations), and analytical/computational study of such a system. A series of shaking table tests of a three-storey steel frame with the buffered particle damper system are carried out to evaluate the performance and to verify the analysis method. It is shown that buffered particle dampers have good performance in reducing the response of structures under dynamic loads, especially under random excitation case. It can effectively control the fundamental mode of the mdof primary system; however, the control effect for higher modes is variable. It is also shown that, for a specific container geometry, a certain mass ratio leads to more efficient momentum transfer from the primary system to the particles with a better vibration attenuation effect, and that buffered particle dampers have better control effect than the conventional rigid ones. An analytical solution based on the discrete element method is also presented. Comparison between the experimental and computational results shows that reasonably accurate estimates of the response of a primary system can be obtained. Properly designed buffered particle dampers can effectively reduce the response of lightly damped mdof primary system with a small weight penalty, under different dynamic loads.

Development of iron chelators for Cooley's anemia. Final report

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

Crosby, W.H.; Green, R.

Iron chelators were screened in an iron-loaded rat model using selective radioiron probes. In all experiments, chelators D and F, in that order, induced significant loss of radioiron compared with controls. However, use of chelator D was associated with side effects, and resulted in the death of some animals. There was some evidence that chelator A also caused iron loss significantly greater than controls. Chelators B, C and E were without apparent enhancing effect on radioiron excretion. This was a blind study and the compounds used were A - 2,3-Dihydroxybenzoic acid; B - N,N1-Dimethyladipohydroxamic acid; C - DL-Phenylalanine hydroxamic acid;more » D - Ethylenediamine-N,N1-bis(2-hydroxphenylacetic acid); E - Propionohydroxamic acid; and F - Deferrioxamine B.« less

Iron overload causes osteoporosis in thalassemia major patients through interaction with transient receptor potential vanilloid type 1 (TRPV1) channels

PubMed Central

Rossi, Francesca; Perrotta, Silverio; Bellini, Giulia; Luongo, Livio; Tortora, Chiara; Siniscalco, Dario; Francese, Matteo; Torella, Marco; Nobili, Bruno; Di Marzo, Vincenzo; Maione, Sabatino

2014-01-01

The pathogenesis of bone resorption in β-thalassemia major is multifactorial and our understanding of the underlying molecular and cellular mechanisms remains incomplete. Considering the emerging importance of the endocannabinoid/endovanilloid system in bone metabolism, it may be instructive to examine a potential role for this system in the development of osteoporosis in patients with β-thalassemia major and its relationship with iron overload and iron chelation therapy. This study demonstrates that, in thalassemic-derived osteoclasts, tartrate-resistant acid phosphatase expression inversely correlates with femoral and lumbar bone mineral density, and directly correlates with ferritin levels and liver iron concentration. The vanilloid agonist resiniferatoxin dramatically reduces cathepsin K levels and osteoclast numbers in vitro, without affecting tartrate-resistant acid phosphatase expression. The iron chelators deferoxamine, deferiprone and deferasirox decrease both tartrate-resistant acid phosphatase and cathepsin K expression, as well as osteoclast activity. Taken together, these data show that transient receptor potential vanilloid type 1 activation/desensitization influences tartrate-resistant acid phosphatase expression and activity, and this effect is dependent on iron, suggesting a pivotal role for iron overload in the dysregulation of bone metabolism in patients with thalassemia major. Our applied pharmacology provides evidence for the potential of iron chelators to abrogate these effects by reducing osteoclast activity. Whether iron chelation therapy is capable of restoring bone health in humans requires further study, but the potential to provide dual benefits for patients with β-thalassemia major –preventing iron-overload and alleviating associated osteoporotic changes – is exciting. PMID:25216685

A mathematical model of tumour and blood pHe regulation: The HCO3-/CO2 buffering system.

PubMed

Martin, Natasha K; Gaffney, Eamonn A; Gatenby, Robert A; Gillies, Robert J; Robey, Ian F; Maini, Philip K

2011-03-01

Malignant tumours are characterised by a low, acidic extracellular pH (pHe) which facilitates invasion and metastasis. Previous research has proposed the potential benefits of manipulating systemic pHe, and recent experiments have highlighted the potential for buffer therapy to raise tumour pHe, prevent metastases, and prolong survival in laboratory mice. To examine the physiological regulation of tumour buffering and investigate how perturbations of the buffering system (via metabolic/respiratory disorders or changes in parameters) can alter tumour and blood pHe, we develop a simple compartmentalised ordinary differential equation model of pHe regulation by the HCO3-/CO2 buffering system. An approximate analytical solution is constructed and used to carry out a sensitivity analysis, where we identify key parameters that regulate tumour pHe in both humans and mice. From this analysis, we suggest promising alternative and combination therapies, and identify specific patient groups which may show an enhanced response to buffer therapy. In addition, numerical simulations are performed, validating the model against well-known metabolic/respiratory disorders and predicting how these disorders could change tumour pHe. Copyright © 2010 Elsevier Inc. All rights reserved.

Modelling dimercaptosuccinic acid (DMSA) plasma kinetics in humans.

PubMed

van Eijkeren, Jan C H; Olie, J Daniël N; Bradberry, Sally M; Vale, J Allister; de Vries, Irma; Meulenbelt, Jan; Hunault, Claudine C

2016-11-01

No kinetic models presently exist which simulate the effect of chelation therapy on lead blood concentrations in lead poisoning. Our aim was to develop a kinetic model that describes the kinetics of dimercaptosuccinic acid (DMSA; succimer), a commonly used chelating agent, that could be used in developing a lead chelating model. This was a kinetic modelling study. We used a two-compartment model, with a non-systemic gastrointestinal compartment (gut lumen) and the whole body as one systemic compartment. The only data available from the literature were used to calibrate the unknown model parameters. The calibrated model was then validated by comparing its predictions with measured data from three different experimental human studies. The model predicted total DMSA plasma and urine concentrations measured in three healthy volunteers after ingestion of DMSA 10 mg/kg. The model was then validated by using data from three other published studies; it predicted concentrations within a factor of two, representing inter-human variability. A simple kinetic model simulating the kinetics of DMSA in humans has been developed and validated. The interest of this model lies in the future potential to use it to predict blood lead concentrations in lead-poisoned patients treated with DMSA.

Modelling of trace metal uptake by roots taking into account complexation by exogenous organic ligands

NASA Astrophysics Data System (ADS)

Jean-Marc, Custos; Christian, Moyne; Sterckeman, Thibault

2010-05-01

The context of this study is phytoextraction of soil trace metals such as Cd, Pb or Zn. Trace metal transfer from soil to plant depends on physical and chemical processes such as minerals alteration, transport, adsorption/desorption, reactions in solution and biological processes including the action of plant roots and of associated micro-flora. Complexation of metal ions by organic ligands is considered to play a role on the availability of trace metals for roots in particular in the event that synthetic ligands (EDTA, NTA, etc.) are added to the soil to increase the solubility of the contaminants. As this role is not clearly understood, we wanted to simulate it in order to quantify the effect of organic ligands on root uptake of trace metals and produce a tool which could help in optimizing the conditions of phytoextraction.We studied the effect of an aminocarboxilate ligand on the absorption of the metal ion by roots, both in hydroponic solution and in soil solution, for which we had to formalize the buffer power for the metal. We assumed that the hydrated metal ion is the only form which can be absorbed by the plants. Transport and reaction processes were modelled for a system made up of the metal M, a ligand L and the metal complex ML. The Tinker-Nye-Barber model was adapted to describe the transport of solutes M, L and ML in the soil and absorption of M by the roots. This allowed to represent the interactions between transport, chelating reactions, absorption of the solutes at the root surface, root growth with time, in order to simulate metal uptake by a whole root system.Several assumptions were tested such as i) absorption of the metal by an infinite sink and according to a Michaelis-Menten kinetics, solutes transport by diffusion with and without ii) mass flow and iii) soil buffer power for the ligand L. In hydroponic solution (without soil buffer power), ligands decreased the trace metal flux towards roots, as they reduced the concentration of hydrated metal ion. In soil, depending on the L/M ratio, the presence of metal complexes could increase the metal flux taken up by roots since the ligand desorbed the metal on soil solid phase while the complex dissociated and provided metal ions to the solution in the vicinity of the root.The model enabled to surround the conditions in which phytoextraction is thus optimized. In addition of complexation by organic ligands added to the soil, we expect to integrate complexation by roots organic exudates and by soil organic matter, as well as the competition of the metal ions with Ca2+ et H+.

The liver glucose-6-phosphatase of intact microsomes is inhibited and displays sigmoid kinetics in the presence of alpha-ketoglutarate-magnesium and oxaloacetate-magnesium chelates.

PubMed

Mithieux, G; Vega, F V; Riou, J P

1990-11-25

We have recently shown that the Ca.EGTA and Mg.EDTA complexes, but not free Ca2+ or Mg2+, inhibit the liver glucose-6-phosphatase (Mithieux, G., Vega, F. V., Beylot, M., and Riou, J. P. (1990) J. Biol. Chem. 265, 7257-7259). In this work, we report that, when complexed with Mg2+, two endogenous dicarboxylic keto acids (alpha-ketoglutarate (alpha-KG) and oxaloacetate (OAA] inhibit the glucose-6-phosphatase activity at low concentrations of substrate. This phenomenon is specific for complexes of Mg2+ with alpha-KG and OAA since 1) the complexes of Mg2+ with a number of other di- or tricarboxylic acids having high structural analogy with alpha-KG and OAA (oxalate, malate, succinate, citrate, aspartate, and glutamate) do not inhibit the glucose-6-phosphatase activity and 2) the Ca.alpha-KG and Ca.OAA chelates do not inhibit the glucose-6-phosphatase activity. In the presence of Mg.alpha-KG or Mg.OAA chelates, the enzyme displays sigmoid kinetics; the Hanes plots deviate from linearity, indicating the positive cooperative dependence of the velocity upon the substrate concentration. Hill coefficients (equal to 1 in the absence of the chelates) of 1.23 and 1.33 have been determined in the presence of Mg.alpha-KG and Mg.OAA complexes, respectively. The disruption of microsomal integrity by detergents abolishes the effect of Mg.alpha-KG and Mg.OAA, suggesting that the magnesium chelates inhibit the translocase component of the glucose-6-phosphatase system.

Enhanced transpiration by riparian buffer trees in response to advection in a humid temperate agricultural landscape

USGS Publications Warehouse

Hernandez-Santana, V.; Asbjornsen, H.; Sauer, T.; Isenhart, T.; Schilling, K.; Schultz, Ronald

2011-01-01

Riparian buffers are designed as management practices to increase infiltration and reduce surface runoff and transport of sediment and nonpoint source pollutants from crop fields to adjacent streams. Achieving these ecosystem service goals depends, in part, on their ability to remove water from the soil via transpiration. In these systems, edges between crop fields and trees of the buffer systems can create advection processes, which could influence water use by trees. We conducted a field study in a riparian buffer system established in 1994 under a humid temperate climate, located in the Corn Belt region of the Midwestern U.S. (Iowa). The goals were to estimate stand level transpiration by the riparian buffer, quantify the controls on water use by the buffer system, and determine to what extent advective energy and tree position within the buffer system influence individual tree transpiration rates. We primarily focused on the water use response (determined with the Heat Ratio Method) of one of the dominant species (Acer saccharinum) and a subdominant (Juglans nigra). A few individuals of three additional species (Quercus bicolor, Betula nigra, Platanus occidentalis) were monitored over a shorter time period to assess the generality of responses. Meteorological stations were installed along a transect across the riparian buffer to determine the microclimate conditions. The differences found among individuals were attributed to differences in species sap velocities and sapwood depths, location relative to the forest edge and prevailing winds and canopy exposure and dominance. Sapflow rates for A. saccharinum trees growing at the SE edge (prevailing winds) were 39% greater than SE interior trees and 30% and 69% greater than NW interior and edge trees, respectively. No transpiration enhancement due to edge effect was detected in the subdominant J. nigra. The results were interpreted as indicative of advection effects from the surrounding crops. Further, significant differences were document in sapflow rates between the five study species, suggesting that selection of species is important for enhancing specific riparian buffer functions. However, more information is needed on water use patterns among diverse species growing under different climatic and biophysical conditions to assist policy and management decisions regarding effective buffer design. ?? 2011.

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.

Concentration method for the spectrochemical determination of seventeen minor elements in natural water

USGS Publications Warehouse

Silvey, W.D.; Brennan, R.

1962-01-01

A method for the quantitative spectrochemical determination of microgram amounts of 17 minor elements in water is given. The chelating reagents 8-quinolinol, tannic acid, and thionalide are utilized to concentrate traces (1 to 500 ??g.) of aluminum, cobalt, chromium, copper, iron, gallium, germanium, manganese, nickel, titanium, vanadium, bismuth, lead, molybdenum, cadmium, zinc, and beryllium. Indium is added as a buffer, and palladium is used as an internal standard. The ashed oxides of these 17 metals are subsequently subjected to direct current arcing conditions during spectrum analysis. The method can be used to analyze waters with dissolved solids ranging from less than 100 to more than 100,000 p.p.m. There is no limiting concentration range for the determination of the heavy metals since any volume of sample can be used that will contain a heavy metal concentration within the analytical range of the method. Both the chemical and spectrographic procedures are described, and precision and accuracy data are given.

Effect of pH adjustment, homogenization and diafiltration on physicochemical, reconstitution, functional and rheological properties of medium protein milk protein concentrates (MPC70).

PubMed

Meena, Ganga Sahay; Singh, Ashish Kumar; Gupta, Vijay Kumar; Borad, Sanket; Arora, Sumit; Tomar, Sudhir Kumar

2018-04-01

Poor solubility is the major limiting factor in commercial applications of milk protein concentrates (MPC) powders. Retentate treatments such as pH adjustment using disodium phosphate (Na 2 HPO 4 ), also responsible for calcium chelation with homogenization and; its diafiltration with 150 mM NaCl solution were hypothesized to improve the functional properties of treated MPC70 powders. These treatments significantly improved the solubility, heat stability, water binding, dispersibility, bulk density, flowability, buffer index, foaming and emulsifying capacity of treated powders over control. Rheological behaviour of reconstituted MPC solutions was best explained by Herschel Bulkley model. Compared to rough, large globular structures with dents in control; majorly intact, separate, smaller particles of smooth surface, without any aggregation were observed in SEM micrograph of treated powders. Applied treatments are easy, cost-effective and capable to improve functional properties of treated powders that could replace control MPC70 powder in various food applications where protein functionality is of prime importance.

Influence of calcium on glucose biosensor response and on hydrogen peroxide detection.

PubMed

Labat-Allietta, N; Thévenot, D R

1998-01-01

Of small species capable of reaching a platinum working electrode from biological samples, calcium cations have been found to inhibit significantly glucose biosensor responses. The sensitivities to glucose of sensors immersed in carbonate buffer saline solutions decreased when 0.5 mM calcium chloride was added. The degree of inhibition was proportional to the glucose response in the absence of calcium (0-17% of the normalized current). Likewise, sensor sensitivities to hydrogen peroxide decreased, in the 5-90% range, in the presence of 0.5 mM calcium. Bare Pt-lr wires show a reversible inhibition of hydrogen peroxide sensitivity. This reversible inhibition is directly related to the decrease of hydrogen peroxide oxidation rate at the platinum anode: this has been evidenced, using rotating disk electrodes, by plotting Koutecky-Levich plots. Such inhibition has been found both for free and chelated calcium cations at levels below 1 mM. Several hypotheses for possible reactions between platinum, hydrogen peroxide and calcium are discussed.

Dual-mode fluorophore-doped nickel nitrilotriacetic acid-modified silica nanoparticles combine histidine-tagged protein purification with site-specific fluorophore labeling.

PubMed

Kim, Sung Hoon; Jeyakumar, M; Katzenellenbogen, John A

2007-10-31

We present the first example of a fluorophore-doped nickel chelate surface-modified silica nanoparticle that functions in a dual mode, combining histidine-tagged protein purification with site-specific fluorophore labeling. Tetramethylrhodamine (TMR)-doped silica nanoparticles, estimated to contain 700-900 TMRs per ca. 23 nm particle, were surface modified with nitrilotriacetic acid (NTA), producing TMR-SiO2-NTA-Ni2+. Silica-embedded TMR retains very high quantum yield, is resistant to quenching by buffer components, and is modestly quenched and only to a certain depth (ca. 2 nm) by surface-attached Ni2+. When exposed to a bacterial lysate containing estrogen receptor alpha ligand binding domain (ERalpha) as a minor component, these beads showed very high specificity binding, enabling protein purification in one step. The capacity and specificity of these beads for binding a his-tagged protein were characterized by electrophoresis, radiometric counting, and MALDI-TOF MS. ERalpha, bound to TMR-SiO2-NTA-Ni++ beads in a site-specific manner, exhibited good activity for ligand binding and for ligand-induced binding to coactivators in solution FRET experiments and protein microarray fluorometric and FRET assays. This dual-mode type TMR-SiO2-NTA-Ni2+ system represents a powerful combination of one-step histidine-tagged protein purification and site-specific labeling with multiple fluorophore species.

NMR measurements of Ca2+ and H+ transport mediated by A23187 and reconstituted plasma membrane Ca(2+)-ATPase.

PubMed

Waldeck, A R; Xu, A S; Roufogalis, B D; Kuchel, P W

1998-01-01

NMR-based assays for measuring the fluxes of Ca2+, H+, and ATP in liposomal systems are presented. The 19F NMR Ca(2+)-chelating molecule 5,5-difluoro-1,2-bis(o-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA) was trapped inside large unilamellar vesicles and used to monitor passive and A23187-mediated Ca2+ transport into them. The data were analyzed using progress curves of the transport reaction. They demonstrated the general applicability of 5FBAPTA as a 19F NMR probe of active Ca2+ transport. 31P NMR time-courses were used to monitor simultaneously the ATP hydrolysing activity of the reconstituted human erythrocyte Ca(2+)-ATPase and the concomitant acidification of the reaction medium in a suspension of small unilamellar vesicles. Using an estimate of the extraliposomal buffering capacity, the H+/ATP coupling stoichiometry, in the presence of A23187, was estimated from the NMR-derived data at steady state; it amounted to 1.4 +/- 0.3. This result is discussed with respect to the issue of molecular 'slip' in the context of a non-equilibrium thermodynamics model of the pump (accompanying paper in this issue). Importantly, NMR, in contrast to optical detection methods, can potentially register all fluxes and (electro)chemical gradients involved in the Ca(2+)-ATPase-mediated H+/Ca2+ counterport, in a single experiment.

Investigation of on-line chelant addition to PWR steam generators. Annual report, 1981

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

Tvedt, T.J.; Wallace, S.L.; Griffin, F. Jr.

1982-11-01

The thermostability of both ethylenediaminetetraacetic acid (EDTA) and hydroxyethylethylenediamininetriacetic acid (HEDTA) metal chelates in all volatile treatment water chemistry (AVT) was shown to be greater than or equal to thermostability of EDTA metal chelates in phosphate-sulfite water chemistry. HEDTA metal chelates were shown to have a much greater stability than EDTA metal chelates. Using samples taken from the EDTA metal chelate thermostability studies and samples from Commonwealth Research Corporation (CRC) model steam generators (MSG), EDTA decomposition products were determined. Active metal surfaces were shown to become passivated when exposed to EDTA and HEDTA concentrations as high as 0.1% w/w inmore » AVT. Trace amounts of iron in the water were found to increase the rate of passivation. Material balance and visual inspection data from CRC model steam generators showed that metal is being transported through and cleaning from the MSG's. EDTA metal chelates were removed from chelate solutions by passing the solutions over strong anion exchange resins.« less

Cu-free 1,3-dipolar cycloaddition click reactions to form isoxazole linkers in chelating ligands for fac-[M(I)(CO)3]+ centers (M = Re, 99mTc).

PubMed

Bottorff, Shalina C; Kasten, Benjamin B; Stojakovic, Jelena; Moore, Adam L; MacGillivray, Leonard R; Benny, Paul D

2014-02-17

Isoxazole ring formation was examined as a potential Cu-free alternative click reaction to Cu(I)-catalyzed alkyne/azide cycloaddition. The isoxazole reaction was explored at macroscopic and radiotracer concentrations with the fac-[M(I)(CO)3](+) (M = Re, (99m)Tc) core for use as a noncoordinating linker strategy between covalently linked molecules. Two click assembly methods (click, then chelate and chelate, then click) were examined to determine the feasibility of isoxazole ring formation with either alkyne-functionalized tridentate chelates or their respective fac-[M(I)(CO)3](+) complexes with a model nitrile oxide generator. Macroscale experiments, alkyne-functionalized chelates, or Re complexes indicate facile formation of the isoxazole ring. (99m)Tc experiments demonstrate efficient radiolabeling with click, then chelate; however, the chelate, then click approach led to faster product formation, but lower yields compared to the Re analogues.

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.

Targeting Iron Acquisition Blocks Infection with the Fungal Pathogens Aspergillus fumigatus and Fusarium oxysporum

PubMed Central

Leal, Sixto M.; Roy, Sanhita; Vareechon, Chairut; Carrion, Steven deJesus; Clark, Heather; Lopez-Berges, Manuel S.; diPietro, Antonio; Schrettl, Marcus; Beckmann, Nicola; Redl, Bernhard; Haas, Hubertus; Pearlman, Eric

2013-01-01

Filamentous fungi are an important cause of pulmonary and systemic morbidity and mortality, and also cause corneal blindness and visual impairment worldwide. Utilizing in vitro neutrophil killing assays and a model of fungal infection of the cornea, we demonstrated that Dectin-1 dependent IL-6 production regulates expression of iron chelators, heme and siderophore binding proteins and hepcidin in infected mice. In addition, we show that human neutrophils synthesize lipocalin-1, which sequesters fungal siderophores, and that topical lipocalin-1 or lactoferrin restricts fungal growth in vivo. Conversely, we show that exogenous iron or the xenosiderophore deferroxamine enhances fungal growth in infected mice. By examining mutant Aspergillus and Fusarium strains, we found that fungal transcriptional responses to low iron levels and extracellular siderophores are essential for fungal growth during infection. Further, we showed that targeting fungal iron acquisition or siderophore biosynthesis by topical application of iron chelators or statins reduces fungal growth in the cornea by 60% and that dual therapy with the iron chelator deferiprone and statins further restricts fungal growth by 75%. Together, these studies identify specific host iron-chelating and fungal iron-acquisition mediators that regulate fungal growth, and demonstrate that therapeutic inhibition of fungal iron acquisition can be utilized to treat topical fungal infections. PMID:23853581

Targeting iron acquisition blocks infection with the fungal pathogens Aspergillus fumigatus and Fusarium oxysporum.

PubMed

Leal, Sixto M; Roy, Sanhita; Vareechon, Chairut; Carrion, Steven deJesus; Clark, Heather; Lopez-Berges, Manuel S; Di Pietro, Antonio; diPietro, Antonio; Schrettl, Marcus; Beckmann, Nicola; Redl, Bernhard; Haas, Hubertus; Pearlman, Eric

2013-01-01

Filamentous fungi are an important cause of pulmonary and systemic morbidity and mortality, and also cause corneal blindness and visual impairment worldwide. Utilizing in vitro neutrophil killing assays and a model of fungal infection of the cornea, we demonstrated that Dectin-1 dependent IL-6 production regulates expression of iron chelators, heme and siderophore binding proteins and hepcidin in infected mice. In addition, we show that human neutrophils synthesize lipocalin-1, which sequesters fungal siderophores, and that topical lipocalin-1 or lactoferrin restricts fungal growth in vivo. Conversely, we show that exogenous iron or the xenosiderophore deferroxamine enhances fungal growth in infected mice. By examining mutant Aspergillus and Fusarium strains, we found that fungal transcriptional responses to low iron levels and extracellular siderophores are essential for fungal growth during infection. Further, we showed that targeting fungal iron acquisition or siderophore biosynthesis by topical application of iron chelators or statins reduces fungal growth in the cornea by 60% and that dual therapy with the iron chelator deferiprone and statins further restricts fungal growth by 75%. Together, these studies identify specific host iron-chelating and fungal iron-acquisition mediators that regulate fungal growth, and demonstrate that therapeutic inhibition of fungal iron acquisition can be utilized to treat topical fungal infections.

Labeling of monoclonal antibodies with a 67Ga-phenolic aminocarboxylic acid chelate. Part II. Comparison of immunoreactivity and biodistribution of monoclonal antibodies labeled with the 67Ga-chelate or with 131I.

PubMed

Matzku, S; Schuhmacher, J; Kirchgessner, H; Brüggen, J

1986-01-01

Coupling of the 67Ga-P-EDDHA chelate via carbodiimide to the anti-melanoma monoclonal antibody (Mab) M.2.9.4 resulted in a low degree of oligomerization, but a considerable degree of intra-molecular (inter-chain) cross-linking. However, this did not impair immunoreactivity, nor did the half-life in vivo differ substantially from that of 131I-M.2.9.4. Biodistribution analysis in normal mice showed Ga:I ratios near 1 in the blood and other tissues not involved in degradation and label excretion. In tissues of the reticulo-endothelial system (RES) and the kidneys, Ga:I ratios up to 2.51 were reached within 4 days of administration. In antigen-positive MeWo tumor tissue, retention of 67Ga also excreted that of 131I, so that tumor; organ ratios (except tumor:liver) were superior for the 67Ga-labeled MAb. It is concluded that the method of coupling pre-established 67Ga-P-EDDHA chelate to antibody results in a functionally intact tracer molecule, whose persistence in vivo is not significantly impaired. The major difference to I-labeled MAbs may be a prolonged retention of Ga in tissues (cells) physiologically involved in antibody catabolism.

Iron Chelation

MedlinePlus

... fortified cereals and eggs. What is Iron Chelation Therapy? Drugs called iron chelators remove extra iron from ... form that must be dissolved in juice or water and taken (by mouth) once a day. Most ...

Internet Teleoperation of a Robot with Streaming Buffer System under Varying Time Delays

NASA Astrophysics Data System (ADS)

Park, Jahng-Hyon; Shin, Wanjae

It is known that existence of irregular transmission time delay is a major bottleneck for application of advanced robot control schemes to internet telerobotic systems. In the internet teleoperation system, the irregular transmission time delay causes a critical problem, which includes instability and inaccuracy. This paper suggests a practical internet teleoperation system with streaming buffer system, which consists of a buffer, a buffer manager, and a control timer. The proposed system converts the irregular transmission time delay to a constant. So, the system effectively transmits the control input to a remote site to operate a robot stably and accurately. This feature enables short control input intervals. That means the entire system has a large control bandwidth. The validity of the proposed method is demonstrated by experiments of teleoperation from USC (University of Southern California in U. S.A.) to HYU (Hanyang Univ. in Korea) through the Internet. The proposed method is also demonstrated by experiments of teleoperation through the wireless internet.

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.

Zinc is released by cultured astrocytes as a gliotransmitter under hypoosmotic stress-loaded conditions and regulates microglial activity.

PubMed

Segawa, Shohei; Nishiura, Takeshi; Furuta, Takahiro; Ohsato, Yuki; Tani, Misaki; Nishida, Kentaro; Nagasawa, Kazuki

2014-01-17

Astrocytes contribute to the maintenance of brain homeostasis via the release of gliotransmitters such as ATP and glutamate. Here we examined whether zinc was released from astrocytes under stress-loaded conditions, and was involved in the regulation of microglial activity as a gliotransmitter. Hypoosmotic stress was loaded to astrocytes using balanced salt solution prepared to 214-314 mOsmol/L, and then intra- and extra-cellular zinc levels were assessed using Newport Green DCF diacetate (NG) and ICP-MS, respectively. Microglial activation by the astrocytic supernatant was assessed by their morphological changes and poly(ADP-ribose) (PAR) polymer accumulation. Exposure of astrocytes to hypoosmotic buffer, increased the extracellular ATP level in osmolarity-dependent manners, indicating a load of hypoosmotic stress. In hypoosmotic stress-loaded astrocytes, there were apparent increases in the intra- and extra-cellular zinc levels. Incubation of microglia in the astrocytic conditioned medium transformed them into the activated "amoeboid" form and induced PAR formation. Administration of an extracellular zinc chelator, CaEDTA, to the astrocytic conditioned medium almost completely prevented the microglial activation. Treatment of astrocytes with an intracellular zinc chelator, TPEN, suppressed the hypoosmotic stress-increased intracellular, but not the extracellular, zinc level, and the increase in the intracellular zinc level was blocked partially by a nitric oxide synthase inhibitor, but not by CaEDTA, indicating that the mechanisms underlying the increases in the intra- and extra-cellular zinc levels might be different. These findings suggest that under hypoosmotic stress-loaded conditions, zinc is released from astrocytes and then plays a primary role in microglial activation as a gliotransmitter. Copyright © 2013 Elsevier Inc. All rights reserved.

Antiglycation and Antioxidant Properties of Momordica charantia.

PubMed

Aljohi, Ali; Matou-Nasri, Sabine; Ahmed, Nessar

2016-01-01

The accumulation of advanced glycation endproducts (AGEs) and oxidative stress underlie the pathogenesis of diabetic complications. In many developing countries, diabetes treatment is unaffordable, and plants such as bitter gourd (or bitter melon; Momordica charantia) are used as traditional remedies because they exhibit hypoglycaemic properties. This study compared the antiglycation and antioxidant properties of aqueous extracts of M. charantia pulp (MCP), flesh (MCF) and charantin in vitro. Lysozyme was mixed with methylglyoxal and 0-15 mg/ml of M. charantia extracts in a pH 7.4 buffer and incubated at 37°C for 3 days. Crosslinked AGEs were assessed using gel electrophoresis, and the carboxymethyllysine (CML) content was analyzed by enzyme-linked immunosorbent assays. The antioxidant activities of the extracts were evaluated using assays to assess DPPH (1,1-diphenyl-2-picryl-hydrazyl) and hydroxyl radical scavenging activities, metal-chelating activity and reducing power of the extracts. The phenolic, flavonol and flavonoid content of the extracts were also determined. All extracts inhibited the formation of crosslinked AGEs and CML in a dose-dependent manner, with MCF being the most potent. The antioxidant activity of MCF was higher than that of MCP, but MCP showed the highest metal-chelating activity. MCF had the highest phenolic and flavonoid contents, whereas MCP had the highest flavonol content. M. charantia has hypoglycaemic effects, but this study shows that M. charantia extracts are also capable of preventing AGE formation in vitro. This activity may be due to the antioxidant properties, particularly the total phenolic content of the extracts. Thus, the use of M. charantia deserves more attention, as it may not only reduce hyperglycaemia but also protect against the build-up of tissue AGEs and reduce oxidative stress in patients with diabetes.

Antiglycation and Antioxidant Properties of Momordica charantia

PubMed Central

Aljohi, Ali; Matou-Nasri, Sabine; Ahmed, Nessar

2016-01-01

The accumulation of advanced glycation endproducts (AGEs) and oxidative stress underlie the pathogenesis of diabetic complications. In many developing countries, diabetes treatment is unaffordable, and plants such as bitter gourd (or bitter melon; Momordica charantia) are used as traditional remedies because they exhibit hypoglycaemic properties. This study compared the antiglycation and antioxidant properties of aqueous extracts of M. charantia pulp (MCP), flesh (MCF) and charantin in vitro. Lysozyme was mixed with methylglyoxal and 0–15 mg/ml of M. charantia extracts in a pH 7.4 buffer and incubated at 37°C for 3 days. Crosslinked AGEs were assessed using gel electrophoresis, and the carboxymethyllysine (CML) content was analyzed by enzyme-linked immunosorbent assays. The antioxidant activities of the extracts were evaluated using assays to assess DPPH (1,1-diphenyl-2-picryl-hydrazyl) and hydroxyl radical scavenging activities, metal-chelating activity and reducing power of the extracts. The phenolic, flavonol and flavonoid content of the extracts were also determined. All extracts inhibited the formation of crosslinked AGEs and CML in a dose-dependent manner, with MCF being the most potent. The antioxidant activity of MCF was higher than that of MCP, but MCP showed the highest metal-chelating activity. MCF had the highest phenolic and flavonoid contents, whereas MCP had the highest flavonol content. M. charantia has hypoglycaemic effects, but this study shows that M. charantia extracts are also capable of preventing AGE formation in vitro. This activity may be due to the antioxidant properties, particularly the total phenolic content of the extracts. Thus, the use of M. charantia deserves more attention, as it may not only reduce hyperglycaemia but also protect against the build-up of tissue AGEs and reduce oxidative stress in patients with diabetes. PMID:27513747

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+).

A novel method to label preformed liposomes with 64Cu for positron emission tomography (PET) imaging.

PubMed

Seo, Jai Woong; Zhang, Hua; Kukis, David L; Meares, Claude F; Ferrara, Katherine W

2008-12-01

Radiolabeling of liposomes with 64Cu (t(1/2)=12.7 h) is attractive for molecular imaging and monitoring drug delivery. A simple chelation procedure, performed at a low temperature and under mild conditions, is required to radiolabel preloaded liposomes without lipid hydrolysis or the release of the encapsulated contents. Here, we report a 64Cu postlabeling method for liposomes. A 64Cu-specific chelator, 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N',N'',N'''-tetraacetic acid (BAT), was conjugated with an artificial lipid to form a BAT-PEG-lipid. After incorporation of 0.5% (mol/mol) BAT-PEG-lipid during liposome formulation, liposomes were successfully labeled with 64Cu in 0.1 M NH4OAc pH 5 buffer at 35 degrees C for 30-40 min with an incorporation yield as high as 95%. After 48 h of incubation of 64Cu-liposomes in 50/50 serum/PBS solution, more than 88% of the 64Cu label was still associated with liposomes. After injection of liposomal 64Cu in a mouse model, 44+/-6.9, 21+/-2.7, 15+/-2.5, and 7.4+/-1.1 (n=4) % of the injected dose per cubic centimeter remained within the blood pool at 30 min, 18, 28, and 48 h, respectively. The biodistribution at 48 h after injection verified that 7.0+/-0.47 (n=4) and 1.4+/-0.58 (n=3) % of the injected dose per gram of liposomal 64Cu and free 64Cu remained in the blood pool, respectively. Our results suggest that this fast and easy 64Cu labeling of liposomes could be exploited in tracking liposomes in vivo for medical imaging and targeted delivery.

Self-assembled copper(II) metallacycles derived from asymmetric Schiff base ligands: efficient hosts for ADP/ATP in phosphate buffer.

PubMed

Kumar, Amit; Pandey, Rampal; Kumar, Ashish; Gupta, Rakesh Kumar; Dubey, Mrigendra; Mohammed, Akbar; Mobin, Shaikh M; Pandey, Daya Shankar

2015-10-21

Novel asymmetric Schiff base ligands 2-{[3-(3-hydroxy-1-methyl-but-2-enylideneamino)-2,4,6-trimethylphenylimino]-methyl}-phenol (H2L(1)) and 1-{[3-(3-hydroxy-1-methyl-but-2-enylideneamino)-2,4,6-trimethylphenylimino]-methyl}-naphthalen-2-ol (H2L(2)) possessing dissimilar N,O-chelating sites and copper(ii) metallacycles (CuL(1))4 (1) and (CuL(2))4 (2) based on these ligands have been described. The ligands and complexes have been thoroughly characterized by satisfactory elemental analyses, and spectral (IR, (1)H, (13)C NMR, ESI-MS, UV/vis) and electrochemical studies. Structures of H2L(2) and 1 have been unambiguously determined by X-ray single crystal analyses. The crystal structure of H2L(2) revealed the presence of two distinct N,O-chelating sites on dissimilar cores (naphthalene and β-ketoaminato groups) offering a diverse coordination environment. Metallacycles 1 and 2 having a cavity created by four Cu(ii) centres coordinated in a homo- and heteroleptic fashion with respective ligands act as efficient hosts for adenosine-5'-diphosphate (ADP) and adenosine-5'-triphosphate (ATP) respectively, over other nucleoside polyphosphates (NPPs). The disparate sensitivity of these metallacycles toward ADP and ATP has been attributed to the size of the ligands assuming diverse dimensions and spatial orientations. These are attuned for π-π stacking and electrostatic interactions suitable for different guest molecules under analogous conditions, metallacycle 1 offers better orientation for ADP, while 2 for ATP. The mechanism of the host-guest interaction has been investigated by spectral and electrochemical studies and supported by molecular docking studies.

Environmentally relevant concentrations of aminopolycarboxylate chelating agents mobilize Cd from humic acid.

PubMed

North, Ashley E; Sarpong-Kumankomah, Sophia; Bellavie, Andrew R; White, Wade M; Gailer, Jürgen

2017-07-01

Although Cd is a pollutant of public health relevance, many dietary sources from which it can be absorbed into human tissues remain unknown. While it is well established that the biogeochemical cycle of Cd involves its complexation with environment-derived ligands (e.g., humic acids, HAs) and anthropogenic ones (e.g., chelating agents, CAs), the interaction of Cd with both of these ligands is less well understood. To gain insight, a HA-Cd complex was injected on a size-exclusion chromatography (SEC) column coupled on-line with a flame atomic absorption spectrometer (FAAS) using 10mmol/L Tris buffer (pH8.0) as the mobile phase. This approach allowed us to observe the intact HA-Cd complex and the retention behavior of Cd as a function of 2-20μmol/L concentrations of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) or methylglycinediacetic acid (MGDA) that were added to the mobile phase. An increase of the retention time of Cd was indicative of a partial or complete abstraction of Cd from HA. Our results revealed that all CAs abstracted Cd from the HA-Cd complex at concentrations of 5μmol/L, while MGDA and DTPA were effective at 2μmol/L. The bioavailability of some of the on-column formed CA-Cd complexes explains the previously reported increased accumulation of Cd in periphyton in the ecosystem downstream of wastewater treatment plants. In addition, our results imply that the use of effluents which contain CAs and Cd for the irrigation of food crops can introduce Cd into the food supply and compromise food safety. Copyright © 2017. Published by Elsevier B.V.

Analysis of biogenic carbonates by inductively coupled plasma-mass spectrometry (ICP-MS). Flow injection on-line solid-phase preconcentration for trace element determination in fish otoliths.

PubMed

Arslan, Z; Paulson, A J

2002-04-01

The aragonite deposits within the ear bones (otoliths) of teleost fish retain a chemical signal reflecting the life history of fish (similar to rings of trees) and the nature of fish habitats. Otoliths dissolved in acid solutions contain high concentrations of calcium and a variety of proteins. Elimination of matrix salts and organic interferences during preconcentration is essential for accurate determination of trace elements in otolith solutions by inductively coupled plasma-quadrupole mass spectrometry. An iminodiacetate-based chelating resin (Toyopearl AF-Chelate 650 M) has been used for on-line preconcentration and matrix separation for the determination of 31 transition and rare elements. Successful preconcentration of the elements was achieved at pH 5 by on-line buffering, except Mn which required pH 8.8. Sample solutions were loaded on to the column for 1 min at 3.2 mL min(-1), and then eluted directly into the mass spectrometer with 4% v/v nitric acid. This procedure enabled up to 25-fold preconcentration with successful removal of the calcium matrix. The effect of heat-assisted oxidation with concentrated nitric acid was investigated to eliminate the organic matrix. It was found that heating to dryness after dissolution and further mineralization with the acid significantly improved the retention of the transition elements. The method was validated by analysis of a certified reference material produced from saggittal otoliths of emperor snapper ( Lutjanus sebae), and then applied to the determination of trace metal concentrations in juvenile bluefin tuna ( Thunnus thynnus) from the Western Pacific Ocean.

Phosphonate Pendant Armed Propylene Cross-Bridged Cyclam: Synthesis and Evaluation as a Chelator for Cu-64

PubMed Central

2015-01-01

A propylene cross-bridged macrocyclic chelator with two phosphonate pendant arms (PCB-TE2P) was synthesized from cyclam. Various properties of the synthesized chelator, including Cu-complexation, Cu-complex stability, 64Cu-radiolabeling, and in vivo behavior, were studied and compared with those of a previously reported propylene cross-bridged chelator (PCB-TE2A). PMID:26617972

Systems and methods for separating particles and/or substances from a sample fluid

DOEpatents

Mariella, Jr., Raymond P.; Dougherty, George M.; Dzenitis, John M.; Miles, Robin R.; Clague, David S.

2016-11-01

Systems and methods for separating particles and/or toxins from a sample fluid. A method according to one embodiment comprises simultaneously passing a sample fluid and a buffer fluid through a chamber such that a fluidic interface is formed between the sample fluid and the buffer fluid as the fluids pass through the chamber, the sample fluid having particles of interest therein; applying a force to the fluids for urging the particles of interest to pass through the interface into the buffer fluid; and substantially separating the buffer fluid from the sample fluid.

[Effects of long-term fertilization on pH buffer system of sandy loam calcareous fluvor-aquic soil].

PubMed

Wang, Ji-Dong; Qi, Bing-Jie; Zhang, Yong-Chun; Zhang, Ai-Jun; Ning, Yun-Wang; Xu, Xian-Ju; Zhang, Hui; Ma, Hong-Bo

2012-04-01

Soil samples (0-80 cm) were collected from a 30-year fertilization experimental site in Xuzhou, Jiangsu Province of East China to study the variations of the pH, calcium carbonate and active calcium carbonate contents, and pH buffer capacity of sandy loam calcareous fluvor-aquic soil under different fertilization treatments. Thirty-year continuous application of different fertilizers accelerated the acidification of topsoil (0-20 cm), with the soil pH decreased by 0.41-0.70. Under different fertilization, the soil pH buffer capacity (pHBC) varied from 15.82 to 21.96 cmol x kg(-1). As compared with no fertilization, single N fertilization decreased the pHBC significantly, but N fertilization combined with organic fertilization could significantly increase the pHBC. The soil pHBC had significant positive correlations with soil calcium carbonate and active calcium carbonate contents, but less correlation with soil organic matter content and soil cation exchange capacity, suggesting that after a long-term fertilization, the sandy loam calcareous fluvor-aquic soil was still of an elementary calcium carbonate buffer system, and soil organic matter and cation exchange capacity contributed little to the buffer system. The soil calcium carbonate and active calcium carbonate contents were greater in 0-40 cm than in 40-80 cm soil layer. Comparing with soil calcium carbonate, soil active calcium carbonate was more sensitive to reflect the changes of soil physical and chemical properties, suggesting that the calcium carbonate buffer system could be further classified as soil active calcium carbonate buffer system.

Data Elevator

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

BYNA, SUNRENDRA; DONG, BIN; WU, KESHENG

Data Elevator: Efficient Asynchronous Data Movement in Hierarchical Storage Systems Multi-layer storage subsystems, including SSD-based burst buffers and disk-based parallel file systems (PFS), are becoming part of HPC systems. However, software for this storage hierarchy is still in its infancy. Applications may have to explicitly move data among the storage layers. We propose Data Elevator for transparently and efficiently moving data between a burst buffer and a PFS. Users specify the final destination for their data, typically on PFS, Data Elevator intercepts the I/O calls, stages data on burst buffer, and then asynchronously transfers the data to their final destinationmore » in the background. This system allows extensive optimizations, such as overlapping read and write operations, choosing I/O modes, and aligning buffer boundaries. In tests with large-scale scientific applications, Data Elevator is as much as 4.2X faster than Cray DataWarp, the start-of-art software for burst buffer, and 4X faster than directly writing to PFS. The Data Elevator library uses HDF5's Virtual Object Layer (VOL) for intercepting parallel I/O calls that write data to PFS. The intercepted calls are redirected to the Data Elevator, which provides a handle to write the file in a faster and intermediate burst buffer system. Once the application finishes writing the data to the burst buffer, the Data Elevator job uses HDF5 to move the data to final destination in an asynchronous manner. Hence, using the Data Elevator library is currently useful for applications that call HDF5 for writing data files. Also, the Data Elevator depends on the HDF5 VOL functionality.« less

Chelation for Coronary Heart Disease

MedlinePlus

... also turn to chelation therapy using disodium EDTA (ethylene diamine tetra-acetic acid), a controversial complementary health ... and answers about two trials of an EDTA (ethylene diamine tetra-acetic acid) chelation therapy regimen for ...

Effective sulfur and energy recovery from hydrogen sulfide through incorporating an air-cathode fuel cell into chelated-iron process.

PubMed

Sun, Min; Song, Wei; Zhai, Lin-Feng; Cui, Yu-Zhi

2013-12-15

The chelated-iron process is among the most promising techniques for the hydrogen sulfide (H2S) removal due to its double advantage of waste minimization and resource recovery. However, this technology has encountered the problem of chelate degradation which made it difficult to ensure reliable and economical operation. This work aims to develop a novel fuel-cell-assisted chelated-iron process which employs an air-cathode fuel cell for the catalyst regeneration. By using such a process, sulfur and electricity were effectively recovered from H2S and the problem of chelate degradation was well controlled. Experiment on a synthetic sulfide solution showed the fuel-cell-assisted chelated-iron process could maintain high sulfur recovery efficiencies generally above 90.0%. The EDTA was preferable to NTA as the chelating agent for electricity generation, given the Coulombic efficiencies (CEs) of 17.8 ± 0.5% to 75.1 ± 0.5% for the EDTA-chelated process versus 9.6 ± 0.8% to 51.1 ± 2.7% for the NTA-chelated process in the pH range of 4.0-10.0. The Fe (III)/S(2-) ratio exhibited notable influence on the electricity generation, with the CEs improved by more than 25% as the Fe (III)/S(2-) molar ratio increased from 2.5:1 to 3.5:1. Application of this novel process in treating a H2S-containing biogas stream achieved 99% of H2S removal efficiency, 78% of sulfur recovery efficiency, and 78.6% of energy recovery efficiency, suggesting the fuel-cell-assisted chelated-iron process was effective to remove the H2S from gas streams with favorable sulfur and energy recovery efficiencies. Copyright © 2013 Elsevier B.V. All rights reserved.

CaNa2EDTA chelation attenuates cell damage in workers exposed to lead--a pilot study.

PubMed

Čabarkapa, A; Borozan, S; Živković, L; Stojanović, S; Milanović-Čabarkapa, M; Bajić, V; Spremo-Potparević, B

2015-12-05

Lead induced oxidative cellular damage and long-term persistence of associated adverse effects increases risk of late-onset diseases. CaNa2EDTA chelation is known to remove contaminating metals and to reduce free radical production. The objective was to investigate the impact of chelation therapy on modulation of lead induced cellular damage, restoration of altered enzyme activities and lipid homeostasis in peripheral blood of workers exposed to lead, by comparing the selected biomarkers obtained prior and after five-day CaNa2EDTA chelation intervention. The group of smelting factory workers diagnosed with lead intoxication and current lead exposure 5.8 ± 1.2 years were administered five-day CaNa2EDTA chelation. Elevated baseline activity of antioxidant enzymes Cu, Zn-SOD and CAT as well as depleted thiols and increased protein degradation products-carbonyl groups and nitrites, pointing to Pb induced oxidative damage, were restored toward normal values following the treatment. Lead showed inhibitor potency on both RBC AChE and BChE in exposed workers, and chelation re-established the activity of BChE, while RBC AChE remained unaffected. Also, genotoxic effect of lead detected in peripheral blood lymphocytes was significantly decreased after therapy, exhibiting 18.9% DNA damage reduction. Administration of chelation reversed the depressed activity of serum PON 1 and significantly decreased lipid peroxidation detected by the post-chelation reduction of MDA levels. Lactate dehydrogenase LDH1-5 isoenzymes levels showed evident but no significant trend of restoring toward normal control values following chelation. CaNa2EDTA chelation ameliorates the alterations linked with Pb mediated oxidative stress, indicating possible benefits in reducing health risks associated with increased oxidative damage in lead exposed populations. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

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

Signature-based store checking buffer

DOEpatents

Sridharan, Vilas; Gurumurthi, Sudhanva

2015-06-02

A system and method for optimizing redundant output verification, are provided. A hardware-based store fingerprint buffer receives multiple instances of output from multiple instances of computation. The store fingerprint buffer generates a signature from the content included in the multiple instances of output. When a barrier is reached, the store fingerprint buffer uses the signature to verify the content is error-free.

Questions and Answers on Unapproved Chelation Products

MedlinePlus

... OTC) to prevent or treat diseases. Companies are marketing unapproved OTC chelation therapy products to patients with ... 4. Why did FDA take this action? Companies marketing unapproved OTC chelation products with unsubstantiated treatment claims ...

Correction of anemia in a transfusion-dependent patient with primary myelofibrosis receiving iron chelation therapy with deferasirox (Exjade®, ICL670)

PubMed Central

Di Tucci, Anna Angela; Murru, Roberta; Alberti, Daniele; Rabault, Bertrand; Deplano, Simona; Angelucci, Emanuele

2007-01-01

Transfusional iron overload in patients with chronic anemias can result in multiple organ failure. Experience in the management of iron overload in patients with myelodysplastic syndromes is limited, as many do not receive chelation therapy due to short-life expectancy and the difficulties associated with the administration of the current reference standard chelator, deferoxamine. There have, however, been some reports of reduced transfusion requirement associated with chelation therapy in patients with myelodysplastic syndromes and myelofibrosis. Here, we discuss a patient with primary myelofibrosis and related transfusion-dependent anemia who received chelation therapy with the once-daily oral iron chelator, deferasirox. In addition to the reduced iron levels, the patient demonstrated an unexpected reduction in blood transfusion requirement, ultimately resulting in long-lasting transfusion-free survival. PMID:17391307

AN/SLQ-32 EW System Model: and Expandable, Object-Oriented, Process- Based Simulation

DTIC Science & Technology

1992-09-01

CONST threshold = 0.1; timetol = 0.01; orientol = 5.8; VAR rec, recLast :BufferBeamRecType; time,power : REAL; powerl,orientation : REAL; BEGIN NEW...PulseGroup); rec:-ASK BufferBeam Removed; time: =rec. time; orientation: =rec. orientation; OUTPUT ( "ORIENREFI, orientation); recLast :=ASK BufferBeam Last...TO Add(rec); IF (rec= recLast ) EXIT; END IF; rec :=ASK BufferBeam Remove o; ELSE ASK BufferBeam TO Add(rec); IF (rec = recLast ) EXIT; END IF; rec

On the delay analysis of a TDMA channel with finite buffer capacity

NASA Technical Reports Server (NTRS)

Yan, T.-Y.

1982-01-01

The throughput performance of a TDMA channel with finite buffer capacity for transmitting data messages is considered. Each station has limited message buffer capacity and has Poisson message arrivals. Message arrivals will be blocked if the buffers are congested. Using the embedded Markov chain model, the solution procedure for the limiting system-size probabilities is presented in a recursive fashion. Numerical examples are given to demonstrate the tradeoffs between the blocking probabilities and the buffer sizing strategy.

Dynamically-allocated multi-queue buffers for VLSI communication switches

NASA Technical Reports Server (NTRS)

Tamir, Yuval; Frazier, Gregory L.

1992-01-01

Several buffer structures are discussed and compared in terms of implementation complexity, interswitch handshaking requirements, and their ability to deal with variations in traffic patterns and message lengths. A new design of buffers is presented that provide non-FIFO message handling and efficient storage allocation for variable size packets using linked lists managed by a simple on-chip controller. The new buffer design is evaluated by comparing it to several alternative designs in the context of a multistage interconnection network. The present modeling and simulations show that the new buffer outperforms alternative buffers and can thus be used to improve the performance of a wide variety of systems currently using less efficient buffers.

Application of allflex conservation buffer in illumina genotyping.

PubMed

de Groot, M; Ras, T; van Haeringen, W A

2016-12-01

This experiment was designed to study if liquid conservation buffer used in the novel Tissue Sampling Technology (TST) from Allflex can be used for Illumina BeadChip genotyping. Ear punches were collected from 6 bovine samples, using both the Tissue Sampling Unit (TSU) as well as the Total Tagger Universal (TTU) collection system. The stability of the liquid conservation buffer was tested by genotyping samples on Illumina BeadChips, incubated at 0, 3, 15, 24, 48, 72, 168, 336, 720 h after sample collection. Additionally, a replenishment study was designed to test how often the liquid conservation buffer could be completely replenished before a significant call rate drop could be observed. Results from the stability study showed an average call rate of 0.993 for samples collected with the TSU system and 0.953 for samples collected with the TTU system, both exceeding the inclusion threshold call rate of 0.85. As an additional control, the identity of the individual animals was confirmed using the International Society of Animal Genetics (ISAG) recommended SNP panel. The replenishment study revealed a slight drop in the sample call rate after replenishing the conservation buffer for the fourth time for the TSU as well as the TTU samples. In routine analysis, this application allows for multiple experiments to be performed on the liquid conservation buffer, while maintaining the tissue samples for future use. The data collected in this study shows that the liquid conservation buffer used in the TST system can be used for Illumina BeadChip genotyping applications.

Natural chelates for radionuclide decorporation

DOEpatents

Premuzic, E.T.

1983-08-25

This invention relates to the method and resulting chelates of desorbing a radionuclide selected from thorium, uranium, and plutonium containing cultures in a bioavailable form involving pseudomonas or other microorganisms. A preferred microorganism is Pseudomonas aeruginosa which forms multiple chelates with thorium in the range of molecular weight 1000 to 1000 and also forms chelates with uranium of molecular weight in the area of 100 to 1000 and 1000 to 2000.

Di-macrocyclic terephthalamide ligands as chelators for the PET radionuclide zirconium-89

DOE PAGES

Pandya, Darpan N.; Pailloux, Sylvie; Tatum, David; ...

2014-12-18

The development of bifunctional chelators (BFCs) which can stably chelate zirconium-89 ((89)Zr) while being conjugated to targeting molecules is an area of active research. Herein we report the first octadentate terephthalamide ligands, which are easily radiolabeled with (89)Zr and are highly stable in vitro. Lastly, they represent a novel class of chelators, which are worthy of further development as BFCs for (89)Zr.

Synthetic and natural iron chelators: therapeutic potential and clinical use

PubMed Central

Hatcher, Heather C; Singh, Ravi N; Torti, Frank M; Torti, Suzy V

2013-01-01

Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade®) and deferiprone (Ferriprox®), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry. PMID:21425984

Transfusional iron overload and iron chelation therapy in thalassemia major and sickle cell disease.

PubMed

Marsella, Maria; Borgna-Pignatti, Caterina

2014-08-01

Iron overload is an inevitable consequence of blood transfusions and is often accompanied by increased iron absorption from the gut. Chelation therapy is necessary to prevent the consequences of hemosiderosis. Three chelators, deferoxamine, deferiprone, and deferasirox, are presently available and a fourth is undergoing clinical trials. The efficacy of all 3 available chelators has been demonstrated. Also, many studies have shown the efficacy of the combination of deferoxamine plus deferiprone as an intensive treatment of severe iron overload. Alternating chelators can reduce adverse effects and improve compliance. Adherence to therapy is crucial for good results. Copyright © 2014 Elsevier Inc. All rights reserved.

Supercritical fluid extraction

DOEpatents

Wai, Chien M.; Laintz, Kenneth

1994-01-01

A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated or lipophilic crown ether or fluorinated dithiocarbamate. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

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.

An improved synthesis and biological evaluation of a new cage-like bifunctional chelator, 4-((8-amino-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane-1-ylamino)methyl)benzoic acid, for 64Cu radiopharmaceuticals.

PubMed

Cai, Hancheng; Li, Zibo; Huang, Chiun-Wei; Park, Ryan; Shahinian, Anthony H; Conti, Peter S

2010-01-01

Stable attachment of (64)Cu(2+) to a targeting molecule usually requires the use of a bifunctional chelator (BFC). Sarcophagine (Sar) ligands rapidly coordinate (64)Cu(2+) within the multiple macrocyclic rings comprising the cage structure under mild conditions, providing high stability in vivo. Previously, we have designed a new versatile cage-like BFC Sar ligand, 4-((8-amino-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane-1-ylamino)methyl)benzoic acid (AmBaSar), for (64)Cu radiopharmaceuticals. Here we report the improved synthesis of AmBaSar, (64)Cu(2+) labeling conditions and its biological evaluation compared with the known BFC 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA). The AmBaSar was synthesized in four steps starting from (1,8-diamine-Sar) cobalt(III) pentachloride ([Co(DiAmSar)]Cl(5)) using an improved synthetic method. The AmBaSar was labeled with (64)Cu(2+) in pH 5.0 ammonium acetate buffer solution at room temperature, followed by analysis and purification with HPLC. The in vitro stability of (64)Cu-AmBaSar complex was evaluated in phosphate buffered saline (PBS), fetal bovine serum and mouse blood. The microPET imaging and biodistribution studies of (64)Cu-AmBaSar were performed in Balb/c mice, and the results were compared with (64)Cu-DOTA. The AmBaSar was readily prepared and characterized by MS and (1)H NMR. The radiochemical yield of (64)Cu-AmBaSar was >or=98% after 30 min of incubation at 25 degrees C. The (64)Cu-AmBaSar complex was analyzed and purified by HPLC with a retention time of 17.9 min. The radiochemical purity of (64)Cu-AmBaSar was more than 97% after 26 h of incubation in PBS or serum. The biological evaluation of (64)Cu-AmBaSar in normal mouse demonstrated renal clearance as the primary mode of excretion, with improved stability in vivo compared to (64)Cu-DOTA. The new cage-like BFC AmBaSar was prepared using a simplified synthetic method. The (64)Cu-AmBaSar complex could be obtained rapidly with high radiochemical yield (>/=98%) under mild conditions. In vitro and in vivo evaluation of AmBaSar demonstrated its promising potential for preparation of (64)Cu radiopharmaceuticals. Copyright 2010. Published by Elsevier Inc.

An efficient, cost effective, sensing behaviour liquid-liquid extraction and spectrophotometric determination of copper(II) incorporated with 4-(4‧-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole: Analysis of food samples, leafy vegetables, fertilizers and environmental samples

NASA Astrophysics Data System (ADS)

Barache, Umesh B.; Shaikh, Abdul B.; Lokhande, Tukaram N.; Kamble, Ganesh S.; Anuse, Mansing A.; Gaikwad, Shashikant H.

2018-01-01

The aim of the present work is to develop an efficient, simple and selective moreover cost-effective method for the extractive spectrophotometric determination of copper(II) by using the Schiff base 4-(4‧-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole [CBIMMT]. This chromogenic reagent forms a yellow coloured complex with copper(II) in acetate buffer at pH 4.2. The copper(II) complex with ligand is instantly extracted into chloroform and shows a maximum absorbance at 414 nm which remains stable for > 48 h. The composition of extracted complex is found to be 1:2 [copper(II): reagent] which was ascertained using Job's method of continuous variation, mole ratio method and slope ratio method. Under optimal conditions, the copper(II) complex in chloroform adheres to Beer's law up to 17.5 μg mL- 1 of copper(II). The optimum concentration range obtained from Ringbom's plot is from 5 μg mL- 1 to 17.5 μg mL- 1. The molar absorptivity, Sandell's sensitivity and enrichment factor of the extracted copper(II) chelate are 0.33813 × 104 L mol- 1 cm- 1, 0.01996 μg cm- 2 and 2.49 respectively. In the extraction of copper(II), several affecting factors including the solution pH, ligand concentration, equilibrium time, effect of foreign ions are optimized. The interfering effects of various cations and anions were also studied and use of masking agents enhances the selectivity of the method. The chromogenic sulphur containing reagent, 4-(4‧-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole has been synthesized in a single step with high purity and yield. The synthesized reagent has been successfully applied first time for determination of copper(II). The reagent forms stable chelate with copper(II) in buffer medium instantly and quantitatively extracted in chloroform within a minute. The method is successfully applied for the determination of copper(II) in various synthetic mixtures, complexes, fertilizers, environmental samples such as food samples, leafy vegetables, and water samples. The results are compared with those obtained with a reference procedure. Good agreement was attained. All the obtained results are indicative of a convenient, fast method for the extraction and quantification of micro levels of copper(II) from various environmental matrices without use of sophisticated instrumentation and procedure. The method showed a relative standard deviation of 0.42%.

An efficient, cost effective, sensing behaviour liquid-liquid extraction and spectrophotometric determination of copper(II) incorporated with 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole: Analysis of food samples, leafy vegetables, fertilizers and environmental samples.

PubMed

Barache, Umesh B; Shaikh, Abdul B; Lokhande, Tukaram N; Kamble, Ganesh S; Anuse, Mansing A; Gaikwad, Shashikant H

2018-01-15

The aim of the present work is to develop an efficient, simple and selective moreover cost-effective method for the extractive spectrophotometric determination of copper(II) by using the Schiff base 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole [CBIMMT]. This chromogenic reagent forms a yellow coloured complex with copper(II) in acetate buffer at pH4.2. The copper(II) complex with ligand is instantly extracted into chloroform and shows a maximum absorbance at 414nm which remains stable for >48h. The composition of extracted complex is found to be 1:2 [copper(II): reagent] which was ascertained using Job's method of continuous variation, mole ratio method and slope ratio method. Under optimal conditions, the copper(II) complex in chloroform adheres to Beer's law up to 17.5μgmL -1 of copper(II). The optimum concentration range obtained from Ringbom's plot is from 5μgmL -1 to 17.5μgmL -1 . The molar absorptivity, Sandell's sensitivity and enrichment factor of the extracted copper(II) chelate are 0.33813×10 4 Lmol -1 cm -1 , 0.01996μgcm -2 and 2.49 respectively. In the extraction of copper(II), several affecting factors including the solution pH, ligand concentration, equilibrium time, effect of foreign ions are optimized. The interfering effects of various cations and anions were also studied and use of masking agents enhances the selectivity of the method. The chromogenic sulphur containing reagent, 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole has been synthesized in a single step with high purity and yield. The synthesized reagent has been successfully applied first time for determination of copper(II). The reagent forms stable chelate with copper(II) in buffer medium instantly and quantitatively extracted in chloroform within a minute. The method is successfully applied for the determination of copper(II) in various synthetic mixtures, complexes, fertilizers, environmental samples such as food samples, leafy vegetables, and water samples. The results are compared with those obtained with a reference procedure. Good agreement was attained. All the obtained results are indicative of a convenient, fast method for the extraction and quantification of micro levels of copper(II) from various environmental matrices without use of sophisticated instrumentation and procedure. The method showed a relative standard deviation of 0.42%. Copyright © 2017 Elsevier B.V. All rights reserved.

Juxtaposition of chemical and mutation-induced developmental defects in zebrafish reveal a copper-chelating activity for kalihinol F.

PubMed

Sandoval, Imelda T; Manos, Elizabeth J; Van Wagoner, Ryan M; Delacruz, Richard Glenn C; Edes, Kornelia; Winge, Dennis R; Ireland, Chris M; Jones, David A

2013-06-20

A major hurdle in using complex systems for drug screening is the difficulty of defining the mechanistic targets of small molecules. The zebrafish provides an excellent model system for juxtaposing developmental phenotypes with mechanism discovery using organism genetics. We carried out a phenotype-based screen of uncharacterized small molecules in zebrafish that produced a variety of chemically induced phenotypes with potential genetic parallels. Specifically, kalihinol F caused an undulated notochord, defects in pigment formation, hematopoiesis, and neural development. These phenotypes were strikingly similar to the zebrafish mutant, calamity, an established model of copper deficiency. Further studies into the mechanism of action of kalihinol F revealed a copper-chelating activity. Our data support this mechanism of action for kalihinol F and the utility of zebrafish as an effective system for identifying therapeutic and target pathways. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluation of the antioxidant activity of four edible mushrooms from the Central Anatolia, Eskisehir - Turkey: Lactarius deterrimus, Suillus collitinus, Boletus edulis, Xerocomus chrysenteron.

PubMed

Sarikurkcu, Cengiz; Tepe, Bektas; Yamac, Mustafa

2008-09-01

The methanolic extracts of Lactarius deterrimus, Suillus collitinus, Boletus edulis, Xerocomus chrysenteron were analyzed for their antioxidant activities in different test systems namely beta-carotene/linoleic acid, DPPH free radical scavenging, reducing power and metal chelating activities in addition to their total phenolic and flavonoid contents. In beta-carotene/linoleic acid and DPPH systems, L. deterrimus and B. edulis showed the strongest activity patterns. Their activities were as strong as the positive controls. The reducing power of the species was excellent. Chelating capacity of the extracts was increased with the increasing concentration. On the other hand, B. edulis found to have the highest phenolic content. Total flavonoid content of S. collitinus found the superior to the other mushrooms.

Positron emission tomography based analysis of long-circulating cross-linked triblock polymeric micelles in a U87MG mouse xenograft model and comparison of DOTA and CB-TE2A as chelators of copper-64.

PubMed

Jensen, Andreas I; Binderup, Tina; Kumar EK, Pramod; Kjær, Andreas; Rasmussen, Palle H; Andresen, Thomas L

2014-05-12

Copolymers of ABC-type (PEG-PHEMA-PCMA) architecture were prepared by atom transfer radical polymerization and formulated as micelles with functionalizable primary alcohols in the shell-region (PHEMA-block) to which the metal-ion chelators DOTA or CB-TE2A were conjugated. Using this micelle system we compared the in vivo stabilities of DOTA and CB-TE2A as chelators of (64)Cu in micelle nanoparticles. The coumarin polymer (PCMA-block) micelle core was cross-linked by UV irradiation at 2 W/cm(2) for 30 min. The cross-linked micelles were labeled with (64)Cu at room temperature for 2 h (DOTA) or 80 °C for 3 h (CB-TE2A), giving labeling efficiencies of 60-76% (DOTA) and 40-47% (CB-TE2A). (64)Cu-micelles were injected into tumor-bearing mice (8 mg/kg) and PET/CT scans were carried out at 1, 22, and 46 h postinjection. The micelles showed good blood stability (T1/2: 20-26 h) and tumor uptake that was comparable with other nanoparticle systems. The DOTA micelles showed a biodistribution similar to the CB-TE2A micelles and the tumor uptake was comparable for both micelle types at 1 h (1.9% ID/g) and 22 h (3.9% ID/g) but diverged at 46 h with 3.6% ID/g (DOTA) and 4.9% ID/g (CB-TE2A). On the basis of our data, we conclude that cross-linked PEG-PHEMA-PCMA micelles have long circulating properties resulting in tumor accumulation and that DOTA and CB-TE2A (64)Cu-chelates show similar in vivo stability for the studied micelle system.

Diamidophosphines with six-membered chelates and their coordination chemistry with group 4 metals: development of a trimethylene-methane-tethered [PN2]-type "molecular claw".

PubMed

Batke, S; Kothe, T; Haas, M; Wadepohl, H; Ballmann, J

2016-02-28

The coordination chemistry of the phosphine-tethered diamidophosphine ligands PhP(CH2CH2CH2NHPh)2 (pr[NPN]H2) and PhP(1,2-CH2-C6H4-NHSiMe3)2 (bn[NPN]H2) featuring six-membered N–C3–P chelates was explored with group 4 metals, which allowed for the consecutive development of a new trimethylene-methane-tethered [PN2] scaffold. In the case of the propylene-linked system pr[NPN]H2, access to the sparingly soluble dibenzyl derivative pr[NPN]ZrBn2 (3-Zr) was gained, while thermally sensitive zirconium and hafnium diiodo complexes bn[NPN]MI2 (5-M, M = Zr, Hf) were isolated in the case of the benzylene-linked derivative bn[NPN]H2. Despite the related phosphine-tethered backbone architectures of both of these ligands, their group 4 complexes were found to exhibit either C1-symmetric (bn[NPN]MX2) or averaged CS-symmetric (pr[NPN]MX2) structures in solution. To restrain the overall flexibility of these systems and thereby control the properties of the resulting complexes without disrupting the six-membered chelates, the new trimethylene-methane-tethered N,N′-di-(tert-butyl)-substituted [PN2]H2 protioligand was designed. This tripodal ligand system was prepared on a gram scale and its CS-symmetric dichloro complexes [PN2]MCl2 (6-M, M = Ti, Zr, Hf) were isolated subsequently. The benzene-soluble dibenzyl derivative [PN2]ZrBn2 (7-Zr) was synthesised as well and characterised by X-ray diffraction. These results are discussed not only in conjunction with the known [NPN]-coordinated group 4 complexes incorporating five-membered chelates, but also in the context of “molecular claws” that are related to the new [PN2] tripod.

Chelation therapy to treat atherosclerosis, particularly in diabetes: is it time to reconsider?

PubMed

Lamas, Gervasio A; Ergui, Ian

2016-08-01

Case reports and case series have suggested a possible beneficial effect of chelation therapy in patients with atherosclerotic disease. Small randomized trials conducted in patients with angina or peripheral artery disease, however, were not sufficiently powered to provide conclusive evidence on clinical outcomes. The Trial to Assess Chelation Therapy (TACT) was the first randomized trial adequately powered to detect the effects of chelation therapy on clinical endpoints. We discuss results and future research. Expert commentary: Chelation reduced adverse cardiovascular events in a post myocardial infarction (MI) population. Patients with diabetes demonstrated even greater benefit, with a number needed to treat of 6.5 patients to prevent a cardiac event over 5 years, with a 41% relative reduction in risk of a cardiac event (p = 0.0002). These results led to the revision of the ACC/AHA guideline recommendations for chelation therapy, changing its classification from class III to class IIb. TACT2, a replicative trial, will assess the effects of chelation therapy on cardiovascular outcomes in diabetic patients with a prior myocardial infarction. We are seeking participating sites for TACT2.

Development of an iron chelating polyethylene film for active packaging applications.

PubMed

Tian, Fang; Decker, Eric A; Goddard, Julie M

2012-02-29

Metal-promoted oxidation reactions are a major cause of food quality deterioration. Active packaging offers novel approaches to controlling such oxidation for the purpose of extending shelf life. Herein, we report modification of the surface of polyethylene (PE) films to possess metal chelating activity. Metal chelating carboxylic acids were introduced to the film surface using cross-linking agents [polyethylenimine (PEI) or ethylenediamine (ED)] to increase the number of available carboxylic acids. ATR-FTIR, contact angle, dye assay, and iron chelating assay were used to characterize changes in surface chemistry after each functionalization step. The chelator poly(acrylic acid) (PAA) was attached to the surface at a density of 9.12 ± 0.71 nmol carboxyl groups/cm², and exhibited an iron chelating activity. The results indicate that PAA-modified PE films might have a higher affinity to Fe³⁺ than Fe²⁺ with the optimum binding pH at 5.0. Such inexpensive active packaging materials are promising in food industry for the preservation of liquid and semiliquid food products and have application in heavy metal chelation therapy for biomedical materials as well.

Networked buffering: a basic mechanism for distributed robustness in complex adaptive systems.

PubMed

Whitacre, James M; Bender, Axel

2010-06-15

A generic mechanism--networked buffering--is proposed for the generation of robust traits in complex systems. It requires two basic conditions to be satisfied: 1) agents are versatile enough to perform more than one single functional role within a system and 2) agents are degenerate, i.e. there exists partial overlap in the functional capabilities of agents. Given these prerequisites, degenerate systems can readily produce a distributed systemic response to local perturbations. Reciprocally, excess resources related to a single function can indirectly support multiple unrelated functions within a degenerate system. In models of genome:proteome mappings for which localized decision-making and modularity of genetic functions are assumed, we verify that such distributed compensatory effects cause enhanced robustness of system traits. The conditions needed for networked buffering to occur are neither demanding nor rare, supporting the conjecture that degeneracy may fundamentally underpin distributed robustness within several biotic and abiotic systems. For instance, networked buffering offers new insights into systems engineering and planning activities that occur under high uncertainty. It may also help explain recent developments in understanding the origins of resilience within complex ecosystems.

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.

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.

Extracting metals directly from metal oxides

DOEpatents

Wai, Chien M.; Smart, Neil G.; Phelps, Cindy

1997-01-01

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of .beta.-diketones, halogenated .beta.-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process.

Extracting metals directly from metal oxides

DOEpatents

Wai, C.M.; Smart, N.G.; Phelps, C.

1997-02-25

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of {beta}-diketones, halogenated {beta}-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process. 4 figs.

Method for separating metal chelates from other materials based on solubilities in supercritical fluids

DOEpatents

Wai, Chien M.; Smart, Neil G.; Phelps, Cindy

2001-01-01

A method for separating a desired metal or metalloi from impurities using a supercritical extraction process based on solubility differences between the components, as well as the ability to vary the solvent power of the supercritical fluid, is described. The use of adduct-forming agents, such as phosphorous-containing ligands, to separate metal or metalloid chelates in such processes is further disclosed. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of .beta.-diketones; phosphine oxides, such as trialkylphosphine oxides, triarylphosphine oxides and alkylarylphosphine oxides; phosphinic acids; carboxylic acids; phosphates, such as trialkylphosphates, triarylphosphates and alkylarylphosphates; crown ethers; dithiocarbamates; phosphine sulfides; phosphorothioic acids; thiophosphinic acids; halogenated analogs of these chelating agents; and mixtures of these chelating agents. In especially preferred embodiments, at least one of the chelating agents is fluorinated.

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.

Matching phosphate and maleate buffer systems for dissolution of weak acids: Equivalence in terms of buffer capacity of bulk solution or surface pH?

PubMed

Cristofoletti, Rodrigo; Dressman, Jennifer B

2016-06-01

The development of in vitro dissolution tests able to anticipate the in vivo fate of drug products has challenged pharmaceutical scientists over time, especially in the case of ionizable compounds. In the seminal model proposed by Mooney et al. thirty-five years ago, the pH at the solid-liquid interface (pH0) was identified as a key parameter in predicting dissolution rate. In the current work it is demonstrated that the in vitro dissolution of the weak acid ibuprofen in maleate and phosphate buffer systems is a function of the pH0, which in turn is affected by properties of the drug and the medium. The reported pH0 for ibuprofen dissolution in bicarbonate buffer, the predominant buffer species in the human small intestine under fasting conditions, can be achieved by reducing the phosphate buffer concentration to 5.0mM or the maleate buffer concentration to 2.2mM. Using this approach to identify the appropriate buffer/buffer capacity combination for in vitro experiments in FaSSIF-type media, it would be possible to increase the physiological relevance of this important biopharmaceutics tool. However, the necessity of monitoring and adjusting the bulk pH during the experiments carried out in 5.0mM phosphate or 2.2mM maleate buffers must also be taken into consideration. Copyright © 2016 Elsevier B.V. All rights reserved.

Study to optimize gellant polymer-water systems for the control of hypergolic spills and fires

NASA Technical Reports Server (NTRS)

Jennings, R. R.; Macwilliams, D. C.; Foshee, W. C.; Katzer, M. F.

1973-01-01

A system of buffered gelled water was developed to prevent and control fires from small spills of nitrogen tetroxide-(N2O4)-Aerozine 50-hypergolic fuel. Laboratory studies on various alkalis, buffers, and seavengers for the fuel components are described. Chilling and sodium acetate-acetic acid buffer was found to be the best additives to the gelled water. Field tests and a delivery system (airborne) for the extinguishant are described. A short movie showing the field testing is available upon request.

The Effects of pH on the Growth and Aspect Ratio of Chicken Egg White Lysozyme Crystals Prepared in Different Buffers

NASA Technical Reports Server (NTRS)

Gibson, U. J.; Horrell, E. E.; Kou, Y.; Pusey, Marc

2000-01-01

We have measured the nucleation and aspect ratio of CEWL crystals grown by vapor diffusion in acetate, butyrate, carbonate, succinate, and phosphate buffers in a range of pH spanning the pK(sub a) of these buffers. The nucleation numbers drop off significantly in the vicinity of pK(sub a) for each of the buffers except the phosphate system, in which we used only the pH range around the second titration point(pK2). There is a concomitant increase in the sizes of the crystals. Some typical nucleation number results are shown. These data support and extend other observations. In addition, we have examined changes in aspect ratio which accompany the suppression of nucleation within each buffer system. The length of the face in the [001] direction was measured, and compared to the width of the (110) face in the [110] type directions. We find that while the aspect ratio of the crystals is affected by pH, it is dominated by a correlation with the size of the crystals. Small crystals are longer in the [0011 direction than crystals that are larger (higher pH within a buffer system). This relationship is found to hold independent of the choice of buffer. These results are consistent with those of Judge et al, who used a batch process which resulted in uniform sizing of crystals at each pH. In these experiments, we specifically avoid agitating the protein/salt buffer mixture when combining the two. This permits the formation of a range of sizes at a given pH. The results for a .05 M acetate 5% NaCl buffer are also shown. We will discuss these results in light of a growth model.

ROBUST: The ROle of BUffering capacities in STabilising coastal lagoon ecosystems

NASA Astrophysics Data System (ADS)

de Wit, Rutger; Stal, Lucas J.; Lomstein, Bente Aa.; Herbert, Rodney A.; van Gemerden, Hans; Viaroli, Pierluigi; Cecherelli, Victor-Ugo; Rodríguez-Valera, Francisco; Bartoli, Marco; Giordani, Gianmarco; Azzoni, Roberta; Schaub, Bart; Welsh, David T.; Donnelly, Andrew; Cifuentes, Ana; Antón, Josefa; Finster, Kai; Nielsen, Lise B.; Pedersen, Anne-Grethe Underlien; Neubauer, Anne Turi; Colangelo, Marina A.; Heijs, Sander K.

2001-12-01

"Buffer capacities" has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that "buffering capacities" can be depleted progressively, and, therefore, we make a distinction between current and potential "buffering capacities". We have applied this concept to understand the limited "local stability" in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant-microbe interactions in the seagrass meadows.

Power impact of loop buffer schemes for biomedical wireless sensor nodes.

PubMed

Artes, Antonio; Ayala, Jose L; Catthoor, Francky

2012-11-06

Instruction memory organisations are pointed out as one of the major sources of energy consumption in embedded systems. As these systems are characterised by restrictive resources and a low-energy budget, any enhancement in this component allows not only to decrease the energy consumption but also to have a better distribution of the energy budget throughout the system. Loop buffering is an effective scheme to reduce energy consumption in instruction memory organisations. In this paper, the loop buffer concept is applied in real-life embedded applications that are widely used in biomedical Wireless Sensor Nodes, to show which scheme of loop buffer is more suitable for applications with certain behaviour. Post-layout simulations demonstrate that a trade-off exists between the complexity of the loop buffer architecture and the energy savings of utilising it. Therefore, the use of loop buffer architectures in order to optimise the instruction memory organisation from the energy efficiency point of view should be evaluated carefully, taking into account two factors: (1) the percentage of the execution time of the application that is related to the execution of the loops, and (2) the distribution of the execution time percentage over each one of the loops that form the application.

A review of pitfalls and progress in chelation treatment of metal poisonings.

PubMed

Andersen, Ole; Aaseth, Jan

2016-12-01

Most acute and chronic human metal poisonings are due to oral or inhalation exposure. Almost 80% of published animal experiments on chelation in metal poisoning used single or repeated intraperitoneal, intramuscular or intravenous administration of metal and chelator, impeding extrapolation to clinical settings. Intramuscular administration of dimercaptopropanol (BAL) has until now been used in acute arsenic, lead, and mercury poisonings, but repeated BAL administration increased the brain uptake of As, Pb and Hg in experimental animals. Also, diethyl dithiocarbamate (DDC) has been used as antidote in acute experimental animal parenteral Cd poisoning, and both DDC and tetraethylthiuram disulfide (TTD, disulfiram, Antabuse) have been used in nickel allergic patients. However, even one dose of DDC given immediately after oral Cd or Ni increased their brain uptake considerably. The calcium salt of ethylenediamminetetraacetic acid (CaEDTA) but not dimercaptosuccinic acid (DMSA) increased the brain uptake of Pb. In oral Cd or Hg poisoning, early oral administration of DMSA or dimercaptopropane sulfonate (DMPS) increased survival and reduced intestinal metal uptake. Oral administration of Prussian Blue or resins with fixed chelating groups that are not absorbed offer chelation approaches for decorporation after oral exposure to various metals. Diethylenetriaminepentaacetic acid (DTPA) nebulizers for pulmonary chelation after inhalation exposure need further development. Also, combined chelation with more than one compound may offer extensive advances. Solid knowledge on the chemistry of metal chelates together with relevant animal experiments should guide development of chelation procedures to alleviate and not aggravate the clinical status of poisoned patients. Copyright © 2016 Elsevier GmbH. All rights reserved.

Strategies for the preparation of bifunctional gadolinium(III) chelators

PubMed Central

Frullano, Luca; Caravan, Peter

2012-01-01

The development of gadolinium chelators that can be easily and readily linked to various substrates is of primary importance for the development high relaxation efficiency and/or targeted magnetic resonance imaging (MRI) contrast agents. Over the last 25 years a large number of bifunctional chelators have been prepared. For the most part, these compounds are based on ligands that are already used in clinically approved contrast agents. More recently, new bifunctional chelators have been reported based on complexes that show a more potent relaxation effect, faster complexation kinetics and in some cases simpler synthetic procedures. This review provides an overview of the synthetic strategies used for the preparation of bifunctional chelators for MRI applications. PMID:22375102

Hypersensitivity reaction with deferasirox

PubMed Central

Sharma, Atul; Arora, Ekta; Singh, Harmanjit

2015-01-01

Thalassemias comprise a group of hereditary blood disorders. Thalassemia major presents with anemia within the first 2 years of life requiring frequent blood transfusions for sustaining life. Regular blood transfusions lead to iron overload-related complications. Prognosis of thalassemia has improved because of the availability of iron-chelating agents. Oral iron chelators are the mainstay of chelation therapy. Deferasirox is a new-generation oral iron chelator for once daily usage. We herein describe a patient of beta thalassemia major who developed an allergic manifestation in the form of erythematous pruritic skin rashes to the oral iron chelator deferasirox. This is a rare adverse reaction reported with deferasirox that led to a therapeutic dilemma in this particular case. PMID:25969661

A MICROPROCESSOR ASCII CHARACTER BUFFERING SYSTEM

EPA Science Inventory

A microprocessor buffering system (MBS) was developed at the Environmental Monitoring and Support Laboratory -Cincinnati (EMSL-CI) to provide an efficient transfer for serial ASCII information between intelligent instrument systema and a Data General NOVA laboratory automation co...

Design of a Hole Trapping Ligand

DOE PAGES

La Croix, Andrew D.; O’Hara, Andrew; Reid, Kemar R.; ...

2017-01-18

A new ligand that covalently attaches to the surface of colloidal CdSe/ CdS nanorods and can simultaneously chelate a molecular metal center is described. The dithiocarbamate$-$bipyridine ligand system facilitates hole transfer through energetic overlap at the inorganic$-$organic interface and conjugation through the organic ligand to a chelated metal center. Density functional theory calculations show that the coordination of the free ligand to a CdS surface causes the formation of two hybridized molecular states that lie in the band gap of CdS. The further chelation of Fe(II) to the bipyridine moiety causes the presence of seven midgap states. Hole transfer frommore » the CdS valence band to the midgap states is dipole allowed and occurs at a faster rate than what is experimentally known for the CdSe/CdS band-edge radiative recombination. In the case of the ligand bound with iron, a two-step process emerges that places the hole on the iron, again at rates much faster than band gap recombination. The system was experimentally assembled and characterized via UV$-$vis absorbance spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence spectroscopy, and energy dispersive X-ray spectroscopy. Lastly, theoretically predicted red shifts in absorbance were observed experimentally, as well as the expected quench in photoluminescence and lifetimes in time-resolved photoluminescence« less

Phytoextraction of 55-year-old wastewater-irrigated soil in a Zn-Pb mine district: effect of plant species and chelators.

PubMed

Tai, YiPing; Yang, YuFen; Li, ZhiAn; Yang, Yang; Wang, JiaXi; Zhuang, Ping; Zou, Bi

2017-07-16

Untreated water from mining sites spreads heavy metal contamination. The present study assessed the phytoextraction performance of heavy metal-accumulating plants and the effects of chemical chelators on cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) removal from paddy fields that have been continuously irrigated with mining wastewater from mines for 55 years. Outdoor pot experiments showed that the total Pb, Zn, and Cd content was lower in the rhizosphere soil of Amaranthus hypochondriacus than in that of Sedum alfredii, Solanum nigrum, and Sorghum bicolor. The aboveground biomass (dry weight) and relative growth rate of A. hypochondriacus were significantly higher than that of the other three species (P < .05). However, the total metal accumulation was significantly higher in the A. hypochondriacus system than in the other plants' system (P < .05). The increase in shoot biomass of A. hypochondriacus depended mostly on the chelator type [ethylenediaminetetraacetic acid (EDTA), malate, oxalate, and citrate] and their application frequency. Single application of EDTA significantly increased the shoot biomass of A. hypochondriacus and total metal removal loading from soil (P < .05). In conclusion, A. hypochondriacus may be effective for in situ phytoremediation of heavy metal-contaminated farmland soil and EDTA can accelerate the phytoextraction effect.

Design of a Hole Trapping Ligand

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

La Croix, Andrew D.; O’Hara, Andrew; Reid, Kemar R.

A new ligand that covalently attaches to the surface of colloidal CdSe/ CdS nanorods and can simultaneously chelate a molecular metal center is described. The dithiocarbamate$-$bipyridine ligand system facilitates hole transfer through energetic overlap at the inorganic$-$organic interface and conjugation through the organic ligand to a chelated metal center. Density functional theory calculations show that the coordination of the free ligand to a CdS surface causes the formation of two hybridized molecular states that lie in the band gap of CdS. The further chelation of Fe(II) to the bipyridine moiety causes the presence of seven midgap states. Hole transfer frommore » the CdS valence band to the midgap states is dipole allowed and occurs at a faster rate than what is experimentally known for the CdSe/CdS band-edge radiative recombination. In the case of the ligand bound with iron, a two-step process emerges that places the hole on the iron, again at rates much faster than band gap recombination. The system was experimentally assembled and characterized via UV$-$vis absorbance spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence spectroscopy, and energy dispersive X-ray spectroscopy. Lastly, theoretically predicted red shifts in absorbance were observed experimentally, as well as the expected quench in photoluminescence and lifetimes in time-resolved photoluminescence« less

Evaluation of on-line chelant addition to PWR steam generators. Steam generator cleaning project

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

Tvedt, T.J.; Wallace, S.L.; Griffin, F. Jr.

1983-09-01

The investigation of chelating agents for continuous water treatment of secondary loops of PWR steam generators were conducted in two general areas: the study of the chemistry of chelating agents and the study of materials compatability with chelating agents. The thermostability of both EDTA and HEDTA metal chelates in All Volatile Treatment (AVT) water chemistry were shown to be greater than or equal to the thermostability of EDTA metal chelates in phosphate-sulfite water chemistry. HEDTA metal chelates were shown to have a much greater stability than EDTA metal chelates. Using samples taken from the EDTA metal chelate thermostability study andmore » from the Commonwealth Research Corporation (CRC) model steam generators (MSG), EDTA decomposition products were determined. Active metal surfaces were shown to become passivated when exposed to EDTA and HEDTA concentrations as high as 0.1% w/w in AVT. Trace amounts of iron in the water were found to increase the rate of passivation. Material balance and visual inspection data from CRC model steam generators showed that metal was transported through and cleaned from the MSG's. The Inconel 600 tubes of the salt water fouled model steam generators experienced pitting corrosion. Results of this study demonstrates the feasibility of EDTA as an on-line water treatment additive to maintain nuclear steam generators in a clean condition.« less

Glyphosate, a chelating agent-relevant for ecological risk assessment?

PubMed

Mertens, Martha; Höss, Sebastian; Neumann, Günter; Afzal, Joshua; Reichenbecher, Wolfram

2018-02-01

Glyphosate-based herbicides (GBHs), consisting of glyphosate and formulants, are the most frequently applied herbicides worldwide. The declared active ingredient glyphosate does not only inhibit the EPSPS but is also a chelating agent that binds macro- and micronutrients, essential for many plant processes and pathogen resistance. GBH treatment may thus impede uptake and availability of macro- and micronutrients in plants. The present study investigated whether this characteristic of glyphosate could contribute to adverse effects of GBH application in the environment and to human health. According to the results, it has not been fully elucidated whether the chelating activity of glyphosate contributes to the toxic effects on plants and potentially on plant-microorganism interactions, e.g., nitrogen fixation of leguminous plants. It is also still open whether the chelating property of glyphosate is involved in the toxic effects on organisms other than plants, described in many papers. By changing the availability of essential as well as toxic metals that are bound to soil particles, the herbicide might also impact soil life, although the occurrence of natural chelators with considerably higher chelating potentials makes an additional impact of glyphosate for most metals less likely. Further research should elucidate the role of glyphosate (and GBH) as a chelator, in particular, as this is a non-specific property potentially affecting many organisms and processes. In the process of reevaluation of glyphosate its chelating activity has hardly been discussed.

Timed non-transferrin bound iron determinations probe the origin of chelatable iron pools during deferiprone regimens and predict chelation response

PubMed Central

Aydinok, Yesim; Evans, Patricia; Manz, Chantal Y.; Porter, John B.

2012-01-01

Background Plasma non-transferrin bound iron refers to heterogeneous plasma iron species, not bound to transferrin, which appear in conditions of iron overload and ineffective erythropoiesis. The clinical utility of non-transferrin bound iron in predicting complications from iron overload, or response to chelation therapy remains unproven. We undertook carefully timed measurements of non-transferrin bound iron to explore the origin of chelatable iron and to predict clinical response to deferiprone. Design and Methods Non-transferrin bound iron levels were determined at baseline and after 1 week of chelation in 32 patients with thalassemia major receiving deferiprone alone, desferrioxamine alone, or a combination of the two chelators. Samples were taken at baseline, following a 2-week washout without chelation, and after 1 week of chelation, this last sample being taken 10 hours after the previous evening dose of deferiprone and, in those receiving desferrioxamine, 24 hours after cessation of the overnight subcutaneous infusion. Absolute or relative non-transferrin bound iron levels were related to transfusional iron loading rates, liver iron concentration, 24-hour urine iron and response to chelation therapy over the subsequent year. Results Changes in non-transferrin bound iron at week 1 were correlated positively with baseline liver iron, and inversely with transfusional iron loading rates, with deferiprone-containing regimens but not with desferrioxamine monotherapy. Changes in week 1 non-transferrin bound iron were also directly proportional to the plasma concentration of deferiprone-iron complexes and correlated significantly with urine iron excretion and with changes in liver iron concentration over the next 12 months. Conclusions The widely used assay chosen for this study detects both endogenous non-transferrin bound iron and the iron complexes of deferiprone. The week 1 increments reflect chelatable iron derived both from liver stores and from red cell catabolism. These increments correlate with urinary iron excretion and the change in liver iron concentration over the subsequent year thus predicting response to deferiprone-containing chelation regimes. This clinical study was registered at clinical.trials.gov with the number NCT00350662. PMID:22180427

AlGaSb Buffer Layers for Sb-Based Transistors

DTIC Science & Technology

2010-01-01

transistor ( HEMT ), molecular beam epitaxy (MBE), field-effect transistor (FET), buffer layer INTRODUCTION High-electron-mobility transistors ( HEMTs ) with InAs...monolayers/s. The use of thinner buffer layers reduces molecular beam epitaxial growth time and source consumption. The buffer layers also exhibit...source. In addition, some of the flux from an Sb cell in a molecular beam epitaxy (MBE) system will deposit near the mouth of the cell, eventually

Efficient sweep buffering in swept source optical coherence tomography using a fast optical switch

PubMed Central

Dhalla, Al-Hafeez; Shia, Kevin; Izatt, Joseph A.

2012-01-01

We describe a novel buffering technique for increasing the A-scan rate of swept source optical coherence tomography (SSOCT) systems employing low duty cycle swept source lasers. This technique differs from previously reported buffering techniques in that it employs a fast optical switch, capable of switching in 60 ns, instead of a fused fiber coupler at the end of the buffering stage, and is therefore appreciably more power efficient. The use of the switch also eliminates patient exposure to light that is not used for imaging that occurs at the end of the laser sweep, thereby increasing the system sensitivity. We also describe how careful management of polarization can remove undesirable artifacts due to polarization mode dispersion. In addition, we demonstrate how numerical compensation techniques can be used to modify the signal from a Mach-Zehnder interferometer (MZI) clock obtained from the original sweep to recalibrate the buffered sweep, thereby reducing the complexity of systems employing lasers with integrated MZI clocks. Combining these methods, we constructed an SSOCT system employing an Axsun technologies laser with a sweep rate of 100kHz and 6dB imaging range of 5.5mm. The sweep rate was doubled with sweep buffering to 200 kHz, and the imaging depth was extended to 9 mm using coherence revival. We demonstrated the feasibility of this system by acquiring images of the anterior segments and retinas of healthy human volunteers. PMID:23243559

Efficient sweep buffering in swept source optical coherence tomography using a fast optical switch.

PubMed

Dhalla, Al-Hafeez; Shia, Kevin; Izatt, Joseph A

2012-12-01

We describe a novel buffering technique for increasing the A-scan rate of swept source optical coherence tomography (SSOCT) systems employing low duty cycle swept source lasers. This technique differs from previously reported buffering techniques in that it employs a fast optical switch, capable of switching in 60 ns, instead of a fused fiber coupler at the end of the buffering stage, and is therefore appreciably more power efficient. The use of the switch also eliminates patient exposure to light that is not used for imaging that occurs at the end of the laser sweep, thereby increasing the system sensitivity. We also describe how careful management of polarization can remove undesirable artifacts due to polarization mode dispersion. In addition, we demonstrate how numerical compensation techniques can be used to modify the signal from a Mach-Zehnder interferometer (MZI) clock obtained from the original sweep to recalibrate the buffered sweep, thereby reducing the complexity of systems employing lasers with integrated MZI clocks. Combining these methods, we constructed an SSOCT system employing an Axsun technologies laser with a sweep rate of 100kHz and 6dB imaging range of 5.5mm. The sweep rate was doubled with sweep buffering to 200 kHz, and the imaging depth was extended to 9 mm using coherence revival. We demonstrated the feasibility of this system by acquiring images of the anterior segments and retinas of healthy human volunteers.

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.

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.

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

A rhodamine-based 'turn-on' Al³⁺ ion-selective reporter and the resultant complex as a secondary sensor for F⁻ ion are applicable to living cell staining.

PubMed

Sen, Buddhadeb; Mukherjee, Manjira; Banerjee, Samya; Pal, Siddhartha; Chattopadhyay, Pabitra

2015-05-14

A newly designed fluorescent aluminum(III) complex (L'-Al; 2) of a structurally characterized non-fluorescent rhodamine Schiff base (L) has been isolated in pure form and characterized using spectroscopic and physico-chemical methods with theoretical density functional theory (DFT) support. On addition of Al(III) ions to a solution of L in HEPES buffer (1 mM, pH 7.4; EtOH-water, 1 : 3 v/v) at 25 °C, the systematic increase in chelation-enhanced fluorescence (CHEF) enables the detection of Al(III) ions as low as 60 nM with high selectivity, unaffected by the presence of competitive ions. Interestingly, the Al(III) complex (L'-Al; 2) is specifically able to detect fluoride ions by quenching the fluorescence in the presence of large amounts of other anions in the HEPES buffer (1 mM, pH 7.4) at 25 °C. On the basis of our experimental and theoretical findings, the addition of Al(3+) ions to a solution of L helps to generate a new fluorescence peak at 590 nm, due to the selective binding of Al(3+) ions with L in a 1 : 1 ratio with a binding constant (K) of 8.13 × 10(4) M(-1). The Schiff base L shows no cytotoxic effect, and it can therefore be employed for determining the intracellular concentration of Al(3+) and F(-) ions by 2 in living cells using fluorescence microscopy.

Metal specificity of an iron-responsive element in Alzheimer's APP mRNA 5'untranslated region, tolerance of SH-SY5Y and H4 neural cells to desferrioxamine, clioquinol, VK-28, and a piperazine chelator.

PubMed

Bandyopadhyay, S; Huang, X; Cho, H; Greig, N H; Youdim, M B; Rogers, J T

2006-01-01

Iron closely regulates the expression of the Alzheimer's Amyloid Precursor Protein (APP) gene at the level of message translation by a pathway similar to iron control of the translation of the ferritin L- and H mRNAs by Iron-responsive Elements in their 5' untranslated regions (5'UTRs). Using transfection based assays in SH-SY5Y neuroblastoma cells we tested the relative efficiency by which iron, copper and zinc up-regulate IRE activity in the APP 5'UTR. Desferrioxamine (high affinity Fe3+ chelator), (ii) clioquinol (low affinity Fe/Cu/Zn chelator), (iii) piperazine-1 (oral Fe chelator), (iv) VK-28 (oral Fe chelator), were tested for their relative modulation of APP 5' UTR directed translation of a luciferase reporter gene. Iron chelation based therapeutic strategies for slowing the progression of Alzheimer's disease (and other neurological disorders that manifest iron imbalance) are discussed with regard to the relative neural toxic action of each chelator in SH-SY5Y cells and in H4 glioblastoma cells.

Extraction of metals using supercritical fluid and chelate forming legand

DOEpatents

Wai, Chien M.; Laintz, Kenneth E.

1998-01-01

A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated .beta.-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated .beta.-diketone and a trialkyl phosphate, or a fluorinated .beta.-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated .beta.-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

Extraction of metals using supercritical fluid and chelate forming ligand

DOEpatents

Wai, C.M.; Laintz, K.E.

1998-03-24

A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated {beta}-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated {beta}-diketone and a trialkyl phosphate, or a fluorinated {beta}-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated {beta}-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process. 7 figs.

Traveling waves in the discrete fast buffered bistable system.

PubMed

Tsai, Je-Chiang; Sneyd, James

2007-11-01

We study the existence and uniqueness of traveling wave solutions of the discrete buffered bistable equation. Buffered excitable systems are used to model, among other things, the propagation of waves of increased calcium concentration, and discrete models are often used to describe the propagation of such waves across multiple cells. We derive necessary conditions for the existence of waves, and, under some restrictive technical assumptions, we derive sufficient conditions. When the wave exists it is unique and stable.

Relationship among chelator adherence, change in chelators, and quality of life in thalassemia.

PubMed

Trachtenberg, Felicia L; Gerstenberger, Eric; Xu, Yan; Mednick, Lauren; Sobota, Amy; Ware, Hannah; Thompson, Alexis A; Neufeld, Ellis J; Yamashita, Robert

2014-10-01

Thalassemia, a chronic blood disease, necessitates life-long adherence to blood transfusions and chelation therapy to reduce iron overload. We examine stability of health-related quality of life (HRQOL) in thalassemia and adherence to chelation therapy over time, especially after changes in chelator choice. Thalassemia Longitudinal Cohort participants in the USA, UK, and Canada completed the SF-36v2 (ages 14+) and the PF-28 CHQ (parents of children <14 years). Chelation adherence was defined as self-reported percent of doses administered in the last 4 weeks. Two hundred and fifty-eight adults/adolescents (mean 29.7 years) and 133 children (mean 8.5 years) completed a mean of 2.8-years follow-up. Children made few chelator changes, whereas a mean of 2.2 changes was observed among the 37% of adults/adolescents who made chelator changes, mainly due to patient preference or medical necessity. Physical HRQOL improved among those with lower iron burden (better health status) at baseline who made a single change in chelator, but declined among participants with multiple changes and/or high iron burden (worse health status). Mental health improved among participants with lower iron burden, but iron overload was negatively associated with social functioning. Adherence did not significantly change over follow-up except for an increase after a change from deferoxamine (DFO) infusion to oral deferasirox (p = 0.03). Predictors of lower adherence for adults/adolescents at follow-up included side effects, smoking, younger age, problems preparing DFO, increased number of days per week DFO prescribed, and lower physical quality of life . Strategies to balance medical needs with family, work, and personal life may assist in adherence.

Chelation therapy and cardiovascular disease: connecting scientific silos to benefit cardiac patients.

PubMed

Peguero, Julio G; Arenas, Ivan; Lamas, Gervasio A

2014-08-01

Medical practitioners have treated atherosclerotic disease with chelation therapy for over 50 years. Lack of strong of evidence led conventional practitioners to abandon its use in the 1960s and 1970s. This relegated chelation therapy to complementary and alternative medicine practitioners, who reported good anecdotal results. Concurrently, the epidemiologic evidence linking xenobiotic metals with cardiovascular disease and mortality gradually accumulated, suggesting a plausible role for chelation therapy. On the basis of the continued use of chelation therapy without an evidence base, the National Institutes of Health released a Request for Applications for a definitive trial of chelation therapy. The Trial to Assess Chelation Therapy (TACT) was formulated as a 2 × 2 factorial randomized controlled trial of intravenous EDTA-based chelation vs. placebo and high-dose oral multivitamins and multiminerals vs. oral placebo. The composite primary endpoint was death, reinfarction, stroke, coronary revascularization, or hospitalization for angina. A total of 1708 post-MI patients who were 50 years or older with a creatinine of 2.0 or less were enrolled and received 55,222 infusions of disodium EDTA or placebo with a median follow-up of 55 months. Patients were on evidence-based post-MI medications including statins. EDTA proved to be safe. EDTA chelation therapy reduced cardiovascular events by 18%, with a 5-year number needed to treat (NNT) of 18. Prespecified subgroup analysis revealed a robust benefit in patients with diabetes mellitus with a 41% reduction in the primary endpoint (5-year NNT = 6.5), and a 43% 5-year relative risk reduction in all-cause mortality (5-year NNT = 12). The magnitude of benefit is such that it suggests urgency in replication and implementation, which could, due to the excellent safety record, occur simultaneously. Copyright © 2014 Elsevier Inc. All rights reserved.

Unexpected effect of dry olive leaf extract on the level of DNA damage in lymphocytes of lead intoxicated workers, before and after CaNa2EDTA chelation therapy.

PubMed

Čabarkapa, Andrea; Dekanski, Dragana; Živković, Lada; Milanović-Čabarkapa, Mirjana; Bajić, Vladan; Topalović, Dijana; Giampieri, Francesca; Gasparrini, Massimiliano; Battino, Maurizio; Spremo-Potparević, Biljana

2017-08-01

The CaNa 2 EDTA chelation therapy is often practiced with antioxidant supplementation. Dry olive leaf extract (DOLE) is natural product with antioxidant and DNA protective properties. The effects of DOLE on the levels of DNA damage were investigated ex vivo in peripheral blood lymphocytes (PBLs) of 19 workers occupationally exposed to lead (Pb), before and after CaNa 2 EDTA chelation therapy. DOLE demonstrated pronounced radical scavenging activity in concentrations ≥1 mg/mL, and showed no genotoxicity per se, in concentrations 0.125-1 mg/mL. The level of DNA damage in PBLs of workers before chelation therapy was elevated (24.21 ± 14.26) compared to controls (6.0 ± 3.37). The incubation of PBLs before chelation therapy with selected concentration of DOLE lead to a severe increase of DNA damage (64.03 ± 20.96), exhibiting prooxidant rather than antioxidant effect. After the five-day CaNa 2 EDTA chelation regimen, DNA damage in PBLs of workers decreased (8.26 ± 4.62) significantly compared to baseline. Treatment of PBLs with DOLE after chelation, again produced high level of damage (41.82 ± 23.17) and the acute prooxidant effects of DOLE remained, but, DNA damage was less severe than before chelation. The DOLE exhibits prooxidant effect in presence of Pb in lymphocytes of exposed workers, and its effect is less pronounced following the removal of Pb after standard chelation therapy. Copyright © 2016 Elsevier Ltd. 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.

46 CFR 58.25-45 - Buffers.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Buffers. 58.25-45 Section 58.25-45 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Steering Gear § 58.25-45 Buffers. For each vessel on an ocean, coastwise, or Great Lakes voyage...

46 CFR 58.25-45 - Buffers.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Buffers. 58.25-45 Section 58.25-45 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Steering Gear § 58.25-45 Buffers. For each vessel on an ocean, coastwise, or Great Lakes voyage...

46 CFR 58.25-45 - Buffers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Buffers. 58.25-45 Section 58.25-45 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Steering Gear § 58.25-45 Buffers. For each vessel on an ocean, coastwise, or Great Lakes voyage...

46 CFR 58.25-45 - Buffers.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Buffers. 58.25-45 Section 58.25-45 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Steering Gear § 58.25-45 Buffers. For each vessel on an ocean, coastwise, or Great Lakes voyage...

46 CFR 58.25-45 - Buffers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Buffers. 58.25-45 Section 58.25-45 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MAIN AND AUXILIARY MACHINERY AND RELATED SYSTEMS Steering Gear § 58.25-45 Buffers. For each vessel on an ocean, coastwise, or Great Lakes voyage...

Transglutaminase-mediated conjugation and nitride-technetium-99m labelling of a bis(thiosemicarbazone) bifunctional chelator.

PubMed

Salvarese, Nicola; Spolaore, Barbara; Marangoni, Selena; Pasin, Anna; Galenda, Alessandro; Tamburini, Sergio; Cicoria, Gianfranco; Refosco, Fiorenzo; Bolzati, Cristina

2018-06-01

An assessment study involving the use of the transglutaminase (TGase) conjugation method and the nitride-technetium-99m labelling on a bis(thiosemicarbazone) (BTS) bifunctional chelating agent is presented. The previously described chelator diacetyl-2-(N 4 -methyl-3-thiosemicarbazone)-3-(N 4 -amino-3-thiosemicarbazone), H 2 ATSM/A, has been functionalized with 6-aminohexanoic acid (ε-Ahx) to generate the bifunctional chelating agent diacetyl-2-(N 4 -methyl-3-thiosemicarbazone)-3-[N 4 -(amino)-(6-aminohexanoic acid)-3-thiosemicarbazone], H 2 ATSM/A-ε-Ahx (1), suitable for conjugation to glutamine (Gln) residues of bioactive molecules via TGase. The feasibility of the TGase reaction in the synthesis of a bioconjugate derivative was investigated using Substance P (SP) as model peptide. Compounds 1 and H 2 ATSM/A-ε-Ahx-SP (2) were labelled with nitride-technetium-99m, obtaining the complexes [ 99m Tc][Tc(N)(ATSM/A-ε-Ahx)] ( 99m Tc1) and [ 99m Tc][Tc(N)(ATSM/A-ε-Ahx-SP)] ( 99m Tc2). The chemical identity of 99m Tc1 and 99m Tc2 was confirmed by radio/UV-RP-HPLC combined with ESI-MS analysis on the respective carrier-added products 99g/99m Tc1 and 99g/99m Tc2. The stability of the radiolabelled complexes after incubation in various environments was investigated. All the results were compared with those obtained for the corresponding 64 Cu-analogues, 64 Cu1 and 64 Cu2. The TGase reaction allows the conjugation of 1 with the peptide, but it is not highly efficient due to instability of the chelator in the required conditions. The SP-conjugated complexes are unstable in mouse and human sera. However, indeed the BTS system can be exploited as nitride-technetium-99m chelator for highly efficient technetium labelling, thus making compound 1 worthy of further investigations for new targeted technetium and copper radiopharmaceuticals encompassing Single Photon Emission Computed Tomography and Positron Emission Tomography imaging. Copyright © 2018 Elsevier Inc. All rights reserved.

Reusable chelating resins concentrate metal ions from highly dilute solutions

NASA Technical Reports Server (NTRS)

Bauman, A. J.; Weetal, H. H.; Weliky, N.

1966-01-01

Column chromatographic method uses new metal chelating resins for recovering heavy-metal ions from highly dilute solutions. The absorbed heavy-metal cations may be removed from the chelating resins by acid or base washes. The resins are reusable after the washes are completed.

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.

Oxidation-Induced Degradable Nanogels for Iron Chelation

NASA Astrophysics Data System (ADS)

Liu, Zhi; Wang, Yan; Purro, Max; Xiong, May P.

2016-02-01

Iron overload can increase cellular oxidative stress levels due to formation of reactive oxygen species (ROS); untreated, it can be extremely destructive to organs and fatal to patients. Since elevated oxidative stress levels are inherent to the condition in such patients, oxidation-induced degradable nanogels for iron chelation were rationally designed by simultaneously polymerizing oxidation-sensitive host-guest crosslinkers between β-cyclodextrin (β-CD) and ferrocene (Fc) and iron chelating moieties composed of deferoxamine (DFO) into the final gel scaffold in reverse emulsion reaction chambers. UV-Vis absorption and atomic absorption spectroscopy (AAS) was used to verify iron chelating capability of nanogels. These materials can degrade into smaller chelating fragments at rates proportional to the level of oxidative stress present. Conjugating DFO reduces the cytotoxicity of the chelator in the macrophage cells. Importantly, the nanogel can effectively reduce cellular ferritin expression in iron overloaded cells and regulate intracellular iron levels at the same time, which is important for maintaining a homeostatic level of this critical metal in cells.

3-hydroxy-2(1H)-pyridinone chelating agents

DOEpatents

Raymond, K.N.; Xu, J.

1997-04-29

Disclosed is a series of improved metal chelating agents, which are highly effective upon both injection and oral administration; several of the most effective are of low toxicity. These chelating agents incorporate within their structure 1-hydroxy-2-pyridinone (1,2-HOPO) and 3-hydroxy-2-pyridinone (3,2-HOPO) moieties with a substituted carbamoyl group ortho to the hydroxy or oxo groups of the hydroxypyridinone ring. The electron-withdrawing carbamoyl group increases the acidity of the hydroxypyridinones. In the metal complexes of the chelating agents, the amide protons form very strong hydrogen bonds with its adjacent HOPO oxygen donor, making these complexes very stable at physiological conditions. The terminal N-substituents provides a certain degree of lipophilicity to the 3,2-HOPO, increasing oral activity. Also disclosed is a method of making the chelating agents and a method of producing a known compound, 3-hydroxy-1-alkyl-2(1H)pyridinone, used as a precursor to the chelating agent, safely and in large quantities. 2 figs.

3-hydroxy-2(1H)-pyridinone chelating agents

DOEpatents

Raymond, Kenneth N.; Xu, Jide

1997-01-01

Disclosed is a series of improved metal chelating agents, which are highly effective upon both injection and oral administration; several of the most effective are of low toxicity. These chelating agents incorporate within their structure 1-hydroxy-2-pyridinone (1,2-HOPO) and 3-hydroxy-2-pyridinone (3,2-HOPO) moieties with a substituted carbamoyl group ortho to the hydroxy or oxo groups of the hydroxypyridinone ring. The electron-withdrawing carbamoyl group increases the acidity of the hydroxypyridinones. In the metal complexes of said chelating agents, the amide protons form very strong hydrogen bonds with its adjacent HOPO oxygen donor, making these complexes very stable at physiological conditions. The terminal N-substituents provides a certain degree of lipophilicity to said 3,2-HOPO, increasing oral activity. Also disclosed is a method of making the chelating agents and a method of producing a known compound, 3-hydroxy-1-alkyl-2(1H)pyridinone, used as a precursor to the chelating agent, safely and in large quantities.

Synthesis and characterization of dihexyldithiocarbamate as a chelating agent in extraction of gold(III)

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

Fatimah, Soja Siti, E-mail: soja-sf@upi.edu; Department of Chemistry, Faculty of Mathematics and Natural Sciences, Padjadjaran University, Jl. Raya Bandung-Sumedang, Km. 21, Jatinangor; Bahti, Husein H.

2016-02-08

The use of dialkyldithiocarbamates as chelating agents of transition metals have been developing for decades. Many chelating agents have been synthesized and used in the extraction of the metals. Studies on particular aspects of extraction of the metals, such as the effect of increasing hydrophobicity of chelating agents on the effectiveness of the extraction, have been done. However, despite the many studies on the synthesis and applications of this type of chelating agents, interests in the aspect of molecular structure of the synthesized ligands and of their complexes, have been limited. This study aimed at synthesizing and characterizing dihexylthiocarbamate, andmore » using the ligand for the extraction of gold III). Characterization of the ligand and of its metal complex were done by using elemental analysis, DTG, and spectroscopic methods to include NMR, ({sup 1}H, and {sup 13}C), FTIR, and MS-ESI. Data on the synthesis, characterization, and the application of the ligand as a chelating agent are presented.« less

Synthesis and characterization of dihexyldithiocarbamate as a chelating agent in extraction of gold(III)

NASA Astrophysics Data System (ADS)

Fatimah, Soja Siti; Bahti, Husein H.; Hastiawan, Iwan; Permanasari, Anna

2016-02-01

The use of dialkyldithiocarbamates as chelating agents of transition metals have been developing for decades. Many chelating agents have been synthesized and used in the extraction of the metals. Studies on particular aspects of extraction of the metals, such as the effect of increasing hydrophobicity of chelating agents on the effectiveness of the extraction, have been done. However, despite the many studies on the synthesis and applications of this type of chelating agents, interests in the aspect of molecular structure of the synthesized ligands and of their complexes, have been limited. This study aimed at synthesizing and characterizing dihexylthiocarbamate, and using the ligand for the extraction of gold III). Characterization of the ligand and of its metal complex were done by using elemental analysis, DTG, and spectroscopic methods to include NMR, (1H, and 13C), FTIR, and MS-ESI. Data on the synthesis, characterization, and the application of the ligand as a chelating agent are presented.

Low noise buffer amplifiers and buffered phase comparators for precise time and frequency measurement and distribution

NASA Technical Reports Server (NTRS)

Eichinger, R. A.; Dachel, P.; Miller, W. H.; Ingold, J. S.

1982-01-01

Extremely low noise, high performance, wideband buffer amplifiers and buffered phase comparators were developed. These buffer amplifiers are designed to distribute reference frequencies from 30 KHz to 45 MHz from a hydrogen maser without degrading the hydrogen maser's performance. The buffered phase comparators are designed to intercompare the phase of state of the art hydrogen masers without adding any significant measurement system noise. These devices have a 27 femtosecond phase stability floor and are stable to better than one picosecond for long periods of time. Their temperature coefficient is less than one picosecond per degree C, and they have shown virtually no voltage coefficients.

Oxidation-Induced Degradable Nanogels for Iron Chelation

PubMed Central

Liu, Zhi; Wang, Yan; Purro, Max; Xiong, May P.

2016-01-01

Iron overload can increase cellular oxidative stress levels due to formation of reactive oxygen species (ROS); untreated, it can be extremely destructive to organs and fatal to patients. Since elevated oxidative stress levels are inherent to the condition in such patients, oxidation-induced degradable nanogels for iron chelation were rationally designed by simultaneously polymerizing oxidation-sensitive host-guest crosslinkers between β-cyclodextrin (β-CD) and ferrocene (Fc) and iron chelating moieties composed of deferoxamine (DFO) into the final gel scaffold in reverse emulsion reaction chambers. UV-Vis absorption and atomic absorption spectroscopy (AAS) was used to verify iron chelating capability of nanogels. These materials can degrade into smaller chelating fragments at rates proportional to the level of oxidative stress present. Conjugating DFO reduces the cytotoxicity of the chelator in the macrophage cells. Importantly, the nanogel can effectively reduce cellular ferritin expression in iron overloaded cells and regulate intracellular iron levels at the same time, which is important for maintaining a homeostatic level of this critical metal in cells. PMID:26868174

Spatial Characterization of Riparian Buffer Effects on Sediment Loads from Watershed Systems

EPA Science Inventory

Understanding all watershed systems and their interactions is a complex, but critical, undertaking when developing practices designed to reduce topsoil loss and chemical/nutrient transport from agricultural fields. The presence of riparian buffer vegetation in agricultural lands...

Methods for improved growth of group III nitride buffer layers

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

Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphologymore » of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).« less

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.

Inhibitory activity of chelating agent against bacteria associated with poultry processing

USDA-ARS?s Scientific Manuscript database

Ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-N, N’-disuccinic acid (EDDS) are chelating agents that can bind minerals that produce water hardness. By sequestering minerals in hard water, chelators reduce water hardness and increase the ability of cleansers to remove dirt and debris dur...

Power Impact of Loop Buffer Schemes for Biomedical Wireless Sensor Nodes

PubMed Central

Artes, Antonio; Ayala, Jose L.; Catthoor, Francky

2012-01-01

Instruction memory organisations are pointed out as one of the major sources of energy consumption in embedded systems. As these systems are characterised by restrictive resources and a low-energy budget, any enhancement in this component allows not only to decrease the energy consumption but also to have a better distribution of the energy budget throughout the system. Loop buffering is an effective scheme to reduce energy consumption in instruction memory organisations. In this paper, the loop buffer concept is applied in real-life embedded applications that are widely used in biomedical Wireless Sensor Nodes, to show which scheme of loop buffer is more suitable for applications with certain behaviour. Post-layout simulations demonstrate that a trade-off exists between the complexity of the loop buffer architecture and the energy savings of utilising it. Therefore, the use of loop buffer architectures in order to optimise the instruction memory organisation from the energy efficiency point of view should be evaluated carefully, taking into account two factors: (1) the percentage of the execution time of the application that is related to the execution of the loops, and (2) the distribution of the execution time percentage over each one of the loops that form the application. PMID:23202202

The chemical characteristics of organic iron sources and their relative bioavailabilities for broilers fed a conventional corn-soybean meal diet.

PubMed

Zhang, L Y; Lu, L; Zhang, L Y; Luo, X G

2016-06-01

Twenty-four organic Fe sources were evaluated by polarographic analysis and via solubility in buffers (pH 5 and 2) and deionized water. Organic Fe sources included 6 Fe-Met complexes (Fe-Met), 10 Fe-Gly complexes, 1 Fe-Lys complex, 4 Fe proteinates, and 3 Fe-AA complexes (Fe-AA). Sources varied considerably in chemical characteristics. Chelation strengths (quotient of formation [Q] values) ranged from weak (Q = 1.08) to extremely strong strength (Q = 8,590). A total of 1,170 1-d-old Arbor Acres male broilers were randomly allotted to 6 replicate cages (15 chicks/cage) for each of 13 treatments in a completely randomized design involving a 4 × 3 factorial arrangement of treatments (4 Fe sources × 3 added Fe levels) plus a control with no added Fe. Dietary treatments included a corn-soybean meal basal diet (control; 55.8 mg Fe/kg) and the basal diet supplemented with 20, 40, or 60 mg Fe/kg as iron sulfate (FeSO∙7HO); an Fe-Met with weak chelation strength (Fe-Met W; Q = 1.37; 14.7% Fe); an iron proteinate with moderate chelation strength (Fe-Prot M; Q = 43.6; 14.2% Fe); or an iron proteinate with extremely strong chelation strength (Fe-Prot ES; Q = 8,590; 10.2% Fe). The growth performance, Fe concentrations, hematological indices, and activities and gene expressions of 2 Fe-containing enzymes in tissues of broilers at 7, 14, and 21 d of age were determined in the present study. Transferrin saturation in plasma on 14 d; bone Fe on d 7 and 14; liver Fe on d 7, 14, and 21; kidney Fe on d 14; succinate dehydrogenase activities in the liver on d 21 and in the kidney on d 7 and 21; mRNA levels in the kidney and heart on d 14; and mRNA levels in the liver and kidney on d 21 linearly increased ( < 0.05) as added Fe levels increased. However, differences in bioavailabilities among Fe sources were detected ( < 0.05) only for the mRNA levels in the liver and kidney on d 21. Based on slope ratios from the multiple linear regression of mRNA level in the liver or kidney of broilers on d 21 on daily dietary analyzed Fe intake, the bioavailabilities of Fe-Met W, Fe-Prot M, and Fe-Prot ES relative to iron sulfate (100%) were 129 ( = 0.18), 164 ( < 0.003), and 174% ( < 0.001) or 102 ( = 0.95), 143 ( = 0.09), and 174% ( < 0.004), respectively. These results indicated that the relative bioavailabilities of organic Fe sources were closely related to their Q values and organic Fe sources with greater Q values showed higher Fe bioavailabilities.

Thermal buffering of receivers for parabolic dish solar thermal power plants

NASA Technical Reports Server (NTRS)

Manvi, R.; Fujita, T.; Gajanana, B. C.; Marcus, C. J.

1980-01-01

A parabolic dish solar thermal power plant comprises a field of parabolic dish power modules where each module is composed of a two-axis tracking parabolic dish concentrator which reflects sunlight (insolation) into the aperture of a cavity receiver at the focal point of the dish. The heat generated by the solar flux entering the receiver is removed by a heat transfer fluid. In the dish power module, this heat is used to drive a small heat engine/generator assembly which is directly connected to the cavity receiver at the focal point. A computer analysis is performed to assess the thermal buffering characteristics of receivers containing sensible and latent heat thermal energy storage. Parametric variations of the thermal inertia of the integrated receiver-buffer storage systems coupled with different fluid flow rate control strategies are carried out to delineate the effect of buffer storage, the transient response of the receiver-storage systems and corresponding fluid outlet temperature. It is concluded that addition of phase change buffer storage will substantially improve system operational characteristics during periods of rapidly fluctuating insolation due to cloud passage.

Buffer Gas Experiments in Mercury (Hg+) Ion Clock

NASA Technical Reports Server (NTRS)

Chung, Sang K.; Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

2004-01-01

We describe the results of the frequency shifts measured from various buffer gases that might be used as a buffer gas to increase the loading efficiency and cooling of ions trapped in a small mercury ion clock. The small mass, volume and power requirement of space clock precludes the use of turbo pumps. Hence, a hermetically sealed vacuum system, incorporating a suitable getter material with a fixed amount of inert buffer gas may be a practical alternative to the groundbased system. The collision shifts of 40,507,347.996xx Hz clock transition for helium, neon and argon buffer gases were measured in the ambient earth magnetic field. In addition to the above non-getterable inert gases we also measured the frequency shifts due to getterable, molecular hydrogen and nitrogen gases which may be used as buffer gases when incorporated with a miniature ion pump. We also examined the frequency shift due to the low methane gas partial pressure in a fixed higher pressure neon buffer gas environment. Methane gas interacted with mercury ions in a peculiar way as to preserve the ion number but to relax the population difference in the two hyperfine clock states and thereby reducing the clock resonance signal. The same population relaxation was also observed for other molecular buffer gases (N H,) but at much reduced rate.

Improvements in multimedia data buffering using master/slave architecture

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

Sheikh, S.; Ganesan, R.

1996-12-31

Advances in the networking technology and multimedia technology has necessitated a need for multimedia servers to be robust and reliable. Existing solutions have direct limitations such as I/O bottleneck and reliability of data retrieval. The system can store the stream of incoming data if enough buffer space is available or the mass storage is clearing the buffer data faster than queue input. A single buffer queue is not sufficient to handle the large frames. Queue sizes are normally several megabytes in length and thus in turn will introduce a state of overflow. The system should also keep track of themore » rewind, fast forwarding, and pause requests, otherwise queue management will become intricate. In this paper, we present a master/slave (server that is designated to monitor the workflow of the complete system. This server holds every other information of slaves by maintaining a dynamic table. It also controls the workload on each of the systems by redistributing request to others or handles the request by itself) approach which will overcome the limitations of today`s storage and also satisfy tomorrow`s storage needs. This approach will maintain the system reliability and yield faster response by using more storage units in parallel. A network of master/slave can handle many requests and synchronize them at all times. Using dedicated CPU and a common pool of queues we explain how queues can be controlled and buffer overflow can be avoided. We propose a layered approach to the buffering problem and provide a read-ahead solution to ensure continuous storage and retrieval of multimedia data.« less

A versatile electrophoresis system for the analysis of high- and low-molecular-weight proteins

PubMed Central

Tastet, Christophe; Lescuyer, Pierre; Diemer, Hélène; Luche, Sylvie; van Dorsselaer, Alain; Rabilloud, Thierry

2003-01-01

A new, versatile, multiphasic buffer system for high resolution sodium dodecyl sulfatepolyacrylamide gel electrophoresis of proteins in the relative molecular weight Mw range of 300,000-3000 Da is described. The system, based on the theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins in the above Mw range. The buffer system uses taurine and chloride as trailing and leading ion, respectively, and Tris, at a pH close to its pKa, as the buffering counter ion. Coupled with limited variation in the acrylamide concentration, this electrophoresis system allows to tailor the resolution in the 6–200 kDa Mw range, with minimal difficulties in the post electrophoretic identification processes. PMID:12783456

The Chelate Effect Redefined.

ERIC Educational Resources Information Center

da Silva, J. J. R. Frausto

1983-01-01

Discusses ambiguities of the accepted definition of the chelate effect, suggesting that it be defined in terms of experimental observation rather than mathematical abstraction. Indicates that the effect depends on free energy change in reaction, ligand basicity, pH of medium, type of chelates formed, and concentration of ligands in solution. (JN)

Literature Survey on Decorporation of Radionuclides from the Human Body

DTIC Science & Technology

2002-04-01

66 8. Adverse Health Effects Associated with... effects ........................................... 66 Table 11- Common foods with chelating effects ...Mn Tetracycline Fe, MR, Mn, Mo, Al, Ca Table 11- Common foods with chelating effects Foodstuff Chelate Cq hhPe 1314 99 M. 75’s Eggs 59Fe Soybean 65Zn

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.

PubMed

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol∕acetonitrile∕acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials.

In situ removal of contamination from soil

DOEpatents

Lindgren, Eric R.; Brady, Patrick V.

1997-01-01

A process of remediation of cationic heavy metal contamination from soil utilizes gas phase manipulation to inhibit biodegradation of a chelating agent that is used in an electrokinesis process to remove the contamination, and further gas phase manipulation to stimulate biodegradation of the chelating agent after the contamination has been removed. The process ensures that the chelating agent is not attacked by bioorganisms in the soil prior to removal of the contamination, and that the chelating agent does not remain as a new contaminant after the process is completed.

In situ removal of contamination from soil

DOEpatents

Lindgren, E.R.; Brady, P.V.

1997-10-14

A process of remediation of cationic heavy metal contamination from soil utilizes gas phase manipulation to inhibit biodegradation of a chelating agent that is used in an electrokinesis process to remove the contamination. The process also uses further gas phase manipulation to stimulate biodegradation of the chelating agent after the contamination has been removed. The process ensures that the chelating agent is not attacked by bioorganisms in the soil prior to removal of the contamination, and that the chelating agent does not remain as a new contaminant after the process is completed. 5 figs.

Iron chelation therapy for transfusional iron overload: a swift evolution.

PubMed

Musallam, Khaled M; Taher, Ali T

2011-01-01

Chronic transfusional iron overload leads to significant morbidity and mortality. While deferoxamine (DFO) is an effective iron chelator with over four decades of experience, it requires tedious subcutaneous infusions that reflect negatively on patient compliance. The novel oral iron chelators deferiprone (L1) and deferasirox (DFRA) opened new horizons for the management of transfusional siderosis. A large body of evidence is now available regarding their efficacy and safety in various populations and settings. Nevertheless, experience with both drugs witnessed some drawbacks, and the search for an ideal and cost-effective iron chelator continues.

SEPARATION PROCESS FOR TRANSURANIC ELEMENT AND COMPOUNDS THEREOF

DOEpatents

Magnusson, L.B.

1958-04-01

A process is described for the separation of neptunium, from aqueous solutions of neptunium, plutonium, uraniunn, and fission prcducts. This separation from an acidic aqueous solution of a tetravalent neptuniunn can be made by contacting the solution with a certain type of chelating,; agent, preferably dissolved in an organic solvent, to form a neptunium chelate compound. When the organic solvent is present, the neptunium chelate compound is extracted; otherwise, it precipitates from the aqueous solution and is separated by any suitable means. The chelating agent is a fluorinated BETA -diketone. such as trifluoroacetyl acetone.

3-hydroxy-2(1H)-pyridinone chelating agents

DOEpatents

Raymond, K.; Xu, J.

1999-04-06

Disclosed is a series of improved chelating agents and the chelates formed from these agents, which are highly effective upon both injection and oral administration. Several of the most effective are of low toxicity. These chelating agents incorporate within their structure 3-hydroxy-2-pyridinone (3,2-HOPO) moieties with a substituted carbamoyl group ortho to the hydroxy group of the hydroxypyridinone ring. The electron-withdrawing carbamoyl group increases the acidity, as well as the chemical stability towards oxidation and reduction, of the hydroxypyridinones. In the metal complexes of the chelating agents, the amide protons form very strong hydrogen bonds with the adjacent HOPO oxygen donor, making these complexes very stable at physiological conditions. The terminal N-substituents provide a certain degree of lipophilicity to the 3,2-HOPO, increasing oral activity. 2 figs.

3-hydroxy-2(1H)-pyridinone chelating agents

DOEpatents

Raymond, Kenneth; Xu, Jide

1999-01-01

Disclosed is a series of improved chelating agents and the chelates formed from these agents, which are highly effective upon both injection and oral administration. Several of the most effective are of low toxicity. These chelating agents incorporate within their structure 3-hydroxy-2-pyridinone (3,2-HOPO) moieties with a substituted carbamoyl group ortho to the hydroxy group of the hydroxypyridinone ring. The electron-withdrawing carbamoyl group increases the acidity, as well as the chemical stability towards oxidation and reduction, of the hydroxypyridinones. In the metal complexes of the chelating agents, the amide protons form very strong hydrogen bonds with the adjacent HOPO oxygen donor, making these complexes very stable at physiological conditions. The terminal N-substituents provide a certain degree of lipophilicity to the 3,2-HOPO, increasing oral activity.

Deaths associated with hypocalcemia from chelation therapy--Texas, Pennsylvania, and Oregon, 2003-2005.

PubMed

2006-03-03

Chelating agents bind lead in soft tissues and are used in the treatment of lead poisoning to enhance urinary and biliary excretion of lead, thus decreasing total lead levels in the body. During the past 30 years, environmental and dietary exposures to lead have decreased substantially, resulting in a considerable decrease in population blood lead levels (BLLs) and a corresponding decrease in the number of patients requiring chelation therapy. Chelating agents also increase excretion of other heavy metals and minerals, such as zinc and, in certain cases, calcium. This report describes three deaths associated with chelation-therapy--related hypocalcemia that resulted in cardiac arrest. Several drugs are used in the treatment of lead poisoning, including edetate disodium calcium (CaEDTA), dimercaperol (British anti-Lewisite), D-penicillamine, and meso-2,3-dimercaptosuccinic acid (succimer). Health-care providers who are unfamiliar with chelating agents and are considering this treatment for lead poisoning should consult an expert in the chemotherapy of lead poisoning. Hospital pharmacies should evaluate whether continued stocking of Na2EDTA is necessary, given the established risk for hypocalcemia, the availability of less toxic alternatives, and an ongoing safety review by the Food and Drug Administration (FDA). Health-care providers and pharmacists should ensure that Na2EDTA is not administered to children during chelation therapy.

Iron chelation therapy of transfusion-dependent β-thalassemia during pregnancy in the era of novel drugs: is deferasirox toxic?

PubMed

Diamantidis, Michael D; Neokleous, Nikolaos; Agapidou, Aleka; Vetsiou, Evaggelia; Manafas, Achilles; Fotiou, Paraskevi; Vlachaki, Efthymia

2016-05-01

The life expectancy of thalassemic patients has increased, and now approaches that of healthy individuals, thanks to improved treatment regimens. However, pregnancy in women with β-Thalassemia Μajor remains a challenging condition. Recent advances in managing this haemoglobinopathy offer the potential for safe pregnancies with favorable outcome. However, clinical data regarding the use of chelation therapy during pregnancy are limited, and it is unclear whether these agents impose any risk to the developing fetus. Successful pregnancies following unintentional treatment with deferoxamine or deferasirox have rarely been reported. Generally, chelators are not recommended during pregnancy. Regarding the new oral chelators, data on fetotoxicity are lacking. In the present study, we describe the evolution and successful outcome of nine pregnancies in six Greek thalassemic women who received deferasirox inadvertently during early pregnancy, and review the literature regarding fetal anomalies due to chelators. Use of chelation before embarking upon a non-programmed pregnancy remains a difficult and unresolved question. In our study, chelation treatment during pregnancy did not prevent the delivery of healthy children. Nonetheless, the use of deferasirox is contraindicated in pregnant women, based on the product label. Deferasirox should only be used during pregnancy if the potential benefit outweighs the potential fetal risk.

Oral chelators deferasirox and deferiprone for transfusional iron overload in thalassemia major: new data, new questions

PubMed Central

Neufeld, Ellis J.

2006-01-01

For nearly 30 years, patients with transfusional iron overload have depended on nightly deferoxamine infusions for iron chelation. Despite dramatic gains in life expectancy in the deferoxamine era for patients with transfusion-dependent anemias, the leading cause of death for young adults with thalassemia major and related disorders has been cardiac disease from myocardial iron deposition. Strategies to reduce cardiac disease by improving chelation regimens have been of the highest priority. These strategies have included development of novel oral iron chelators to improve compliance, improved assessment of cardiac iron status, and careful epidemiologic assessment of European outcomes with deferiprone, an oral alternative chelator available for about a decade. Each of these strategies is now bearing fruit. The novel oral chelator deferasirox was recently approved by the Food and Drug Administration (FDA); a randomized clinical trial demonstrates that deferasirox at 20 to 30 mg/kg/d can maintain or improve hepatic iron in thalassemia as well as deferoxamine. A randomized trial based on cardiac T2* magnetic resonance imaging (MRI) suggests that deferiprone can unload myocardial iron faster than deferoxamine. Retrospective epidemiologic data suggest dramatic reductions in cardiac events and mortality in Italian subjects exposed to deferiprone compared with deferoxamine. These developments herald a new era for iron chelation, but many unanswered questions remain. PMID:16627763

The Effect of Different Tea Varieties on Iron Chelation

NASA Astrophysics Data System (ADS)

Truong, S. K.; Karim, R.

2016-12-01

The chief objectives of this experiment are to distinguish which type of tea of four variants, pomegranate blackberry green, green, lemon chamomile (herbal), and earl grey (black), are capable of chelating the most iron (III) chloride (FeCl3) through titration. We hypothesized that if each tea variety chelates differing amounts of iron chloride, and if we conduct an experiment in which four different teas are mixed in the same amount of water, iron chloride, and iron chloride indicator EDTA, then the pomegranate blackberry green tea will bind to the most iron due to its large amount of fruit antioxidants. To summarize our methodology, we prepared three solutions of each tea, dissolved with 1 gram of FeCl3 to test three trials per tea variety. The chelation process took place overnight as teas cooled. Six drops of iron chloride indicator added to each solution began the titration. The necessary amount of 0.1M EDTA (ethylenediaminetetraacetic acid) drops required for each solution to turn to a universal amber color from its original dark tone indicates how many free iron molecules were left unbound by the tea solution. After careful analysis of the data, we discovered that blackberry pomegranate green tea possessed the best chelating abilities with 97.48% of FeCl3 adsorbed. Green tea followed with 96.67%. Herbal tea chelated 94.24% of the iron while earl grey absorbed the least amount at 93.43%. From our conclusion, we drew that since blackberry pomegranate green tea contained the highest amount of polyphenols and antioxidants as well as epigallocatechin gallate (EGCG) found in green teas, it was able to chelate the most amount of iron. The substances mentioned in blackberry pomegranate green tea possess the ability to form strong bonds with multiple heavy metals, such as iron (III) chloride atoms. Overall, each variety of tea contains different organic substances. Each of these substances possesses a unique chelating ability, determining how well the type of tea can bond to iron. Among the teas being tested in this experiment, blackberry pomegranate green tea absorbed the most iron, thus acting as the superior chelating agent. Our experiment opens up new opportunities for investigations in chelation therapy and heavy metal poisoning through the knowledge of biological chelating agents.

Effect of disodium EDTA chelation regimen on cardiovascular events in patients with previous myocardial infarction: the TACT randomized trial.

PubMed

Lamas, Gervasio A; Goertz, Christine; Boineau, Robin; Mark, Daniel B; Rozema, Theodore; Nahin, Richard L; Lindblad, Lauren; Lewis, Eldrin F; Drisko, Jeanne; Lee, Kerry L

2013-03-27

Chelation therapy with disodium EDTA has been used for more than 50 years to treat atherosclerosis without proof of efficacy. To determine if an EDTA-based chelation regimen reduces cardiovascular events. Double-blind, placebo-controlled, 2 × 2 factorial randomized trial enrolling 1708 patients aged 50 years or older who had experienced a myocardial infarction (MI) at least 6 weeks prior and had serum creatinine levels of 2.0 mg/dL or less. Participants were recruited at 134 US and Canadian sites. Enrollment began in September 2003 and follow-up took place until October 2011 (median, 55 months). Two hundred eighty-nine patients (17% of total; n=115 in the EDTA group and n=174 in the placebo group) withdrew consent during the trial. Patients were randomized to receive 40 infusions of a 500-mL chelation solution (3 g of disodium EDTA, 7 g of ascorbate, B vitamins, electrolytes, procaine, and heparin) (n=839) vs placebo (n=869) and an oral vitamin-mineral regimen vs an oral placebo. Infusions were administered weekly for 30 weeks, followed by 10 infusions 2 to 8 weeks apart. Fifteen percent discontinued infusions (n=38 [16%] in the chelation group and n=41 [15%] in the placebo group) because of adverse events. The prespecified primary end point was a composite of total mortality, recurrent MI, stroke, coronary revascularization, or hospitalization for angina. This report describes the intention-to-treat comparison of EDTA chelation vs placebo. To account for multiple interim analyses, the significance threshold required at the final analysis was P = .036. Qualifying previous MIs occurred a median of 4.6 years before enrollment. Median age was 65 years, 18% were female, 9% were nonwhite, and 31% were diabetic. The primary end point occurred in 222 (26%) of the chelation group and 261 (30%) of the placebo group (hazard ratio [HR], 0.82 [95% CI, 0.69-0.99]; P = .035). There was no effect on total mortality (chelation: 87 deaths [10%]; placebo, 93 deaths [11%]; HR, 0.93 [95% CI, 0.70-1.25]; P = .64), but the study was not powered for this comparison. The effect of EDTA chelation on the components of the primary end point other than death was of similar magnitude as its overall effect (MI: chelation, 6%; placebo, 8%; HR, 0.77 [95% CI, 0.54-1.11]; stroke: chelation, 1.2%; placebo, 1.5%; HR, 0.77 [95% CI, 0.34-1.76]; coronary revascularization: chelation, 15%; placebo, 18%; HR, 0.81 [95% CI, 0.64-1.02]; hospitalization for angina: chelation, 1.6%; placebo, 2.1%; HR, 0.72 [95% CI, 0.35-1.47]). Sensitivity analyses examining the effect of patient dropout and treatment adherence did not alter the results. Among stable patients with a history of MI, use of an intravenous chelation regimen with disodium EDTA, compared with placebo, modestly reduced the risk of adverse cardiovascular outcomes, many of which were revascularization procedures. These results provide evidence to guide further research but are not sufficient to support the routine use of chelation therapy for treatment of patients who have had an MI. clinicaltrials.gov Identifier: NCT00044213.

Effects of grazing management and buffer strips on metal runoff from pastures fertilized with poultry litter

USDA-ARS?s Scientific Manuscript database

Metal runoff from fields fertilized with poultry litter may pose a threat to aquatic systems. Buffer strips have been added to fields to reduce nutrients and solids runoff. However, scant information exists on the effects of buffer strips combined with grazing management strategies on metal runoff f...

Common data buffer

NASA Technical Reports Server (NTRS)

Byrne, F.

1981-01-01

Time-shared interface speeds data processing in distributed computer network. Two-level high-speed scanning approach routes information to buffer, portion of which is reserved for series of "first-in, first-out" memory stacks. Buffer address structure and memory are protected from noise or failed components by error correcting code. System is applicable to any computer or processing language.

Effects of riparian buffers on hydrology of northern seasonal ponds

Treesearch

Randall K. Kolka; Brian J. Palik; Daniel P. Tersteeg; James C. Bell

2011-01-01

Although seasonal ponds are common in northern, glaciated, forested landscapes, forest management guidelines are generally lacking for these systems. The objective of this study was to determine the effect of riparian buffer type on seasonal pond hydrology following harvest of the adjacent upland forest. A replicated block design consisting of four buffer treatments...

Where should buffers go? modeling riparian habitat connectivity in northeast Kansas

Treesearch

Gary Bentrup; Todd Kellerman

2004-01-01

Through many funding programs, riparian buffers are being created on agricultural lands to address significant water quality problems. Society and landowners are demanding many other environmental and social services (e.g., wildlife habitat and income diversification) from this practice. Resource planners therefore need to design riparian buffer systems in the right...

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

Jacks of metal/metalloid chelation trade in plants—an overview

PubMed Central

Anjum, Naser A.; Hasanuzzaman, Mirza; Hossain, Mohammad A.; Thangavel, Palaniswamy; Roychoudhury, Aryadeep; Gill, Sarvajeet S.; Rodrigo, Miguel A. Merlos; Adam, Vojtěch; Fujita, Masayuki; Kizek, Rene; Duarte, Armando C.; Pereira, Eduarda; Ahmad, Iqbal

2015-01-01

Varied environmental compartments including soils are being contaminated by a myriad toxic metal(loid)s (hereafter termed as “metal/s”) mainly through anthropogenic activities. These metals may contaminate food chain and bring irreparable consequences in human. Plant-based approach (phytoremediation) stands second to none among bioremediation technologies meant for sustainable cleanup of soils/sites with metal-contamination. In turn, the capacity of plants to tolerate potential consequences caused by the extracted/accumulated metals decides the effectiveness and success of phytoremediation system. Chelation is among the potential mechanisms that largely govern metal-tolerance in plant cells by maintaining low concentrations of free metals in cytoplasm. Metal-chelation can be performed by compounds of both thiol origin (such as GSH, glutathione; PCs, phytochelatins; MTs, metallothioneins) and non-thiol origin (such as histidine, nicotianamine, organic acids). This paper presents an appraisal of recent reports on both thiol and non-thiol compounds in an effort to shed light on the significance of these compounds in plant-metal tolerance, as well as to provide scientific clues for the advancement of metal-phytoextraction strategies. PMID:25883598

Lanthanide chelates of (bis)-hydroxymethyl-substituted DTTA with potential application as contrast agents in magnetic resonance imaging.

PubMed

Silvério, Sara; Torres, Susana; Martins, André F; Martins, José A; André, João P; Helm, Lothar; Prata, M Isabel M; Santos, Ana C; Geraldes, Carlos F G C

2009-06-28

A novel bis-hydroxymethyl-substituted DTTA chelator N'-Bz-C(4,4')-(CH(2)OH)(2)-DTTA () and its DTPA analogue C(4,4')-(CH(2)OH)(2)-DTPA () were synthesized and characterized. A variable-temperature (1)H NMR spectroscopy study of the solution dynamics of their diamagnetic (La) and paramagnetic (Sm, Eu) Ln(3+) complexes showed them to be rigid when compared with analogous Ln(3+)-DTTA and Ln(3+)-DTPA complexes, as a result of their C(4,4')-(CH(2)OH)(2) ligand backbone substitution. The parameters that govern the water (1)H relaxivity of the [Gd()(H(2)O)(2)](-) and [Gd()(H(2)O)](2-) complexes were obtained by (17)O and (1)H NMR relaxometry. While the relaxometric behaviour of the [Gd()(H(2)O)](2-) complex is very similar to the parent [Gd(DTPA)(H(2)O)](2-) system, the [Gd()(H(2)O)(2)](-) complex displays higher relaxivity, due to the presence of two inner sphere water molecules and an accelerated, near optimal water exchange rate. The [Gd()(H(2)O)(2)](-) complex interacts weakly with human serum albumin (HSA), and its fully bound relaxivity is limited by slow water exchange, as monitored by (1)H NMR relaxometry. This complex interacts weakly with phosphate, but does not form ternary complexes with bidentate bicarbonate and l-lactate anions, indicating that the two inner-sphere water molecules of the [Gd()(H(2)O)(2)](-) complex are not located in adjacent positions in the coordination sphere of the Gd(3+) ion. The transmetallation reaction rate of [Gd()(H(2)O)(2)](-) with Zn(2+) in phosphate buffer solution (pH 7.0) was measured to be similar to that of the backbone unsubstituted [Gd(DTTA-Me)(H(2)O)(2)](-), but twice faster than for [Gd(DTPA-BMA)(H(2)O)]. The in vivo biodistribution studies of the (153)Sm(3+)-labelled ligand () in Wistar rats reveal slow blood elimination and short term fixation in various organs, indicating some dissociation. The bis-hydroxymethyl-substituted DTTA skeleton can be seen as a new lead for the synthesis of high relaxivity contrast agents, although its low thermodynamic and kinetic stability will limit its use to in vitro and animal studies.

The effect of bicarbonate on menadione-induced redox cycling and cytotoxicity: potential involvement of the carbonate radical.

PubMed

Aljuhani, Naif; Michail, Karim; Karapetyan, Zubeida; Siraki, Arno G

2013-10-01

We have investigated the effect of NaHCO3 on menadione redox cycling and cytotoxicity. A cell-free system utilized menadione and ascorbic acid to catalyze a redox cycle, and we utilized murine hepatoma (Hepa 1c1c7) cells for in vitro experiments. Experiments were performed using low (2 mmol/L) and physiological (25 mmol/L) levels of NaHCO3 in buffer equilibrated to physiological pH. Using oximetry, ascorbic acid oxidation, and ascorbyl radical detection, we found that menadione redox cycling was enhanced by NaHCO3. Furthermore, Hepa 1c1c7 cells treated with menadione demonstrated cytotoxicity that was significantly increased with physiological concentrations of NaHCO3 in the media, compared with low levels of NaHCO3. Interestingly, the inhibition of superoxide dismutase (SOD) with 2 different metal chelators was associated with a protective effect against menadione cytotoxicity. Using isolated protein, we found a significant increase in protein carbonyls with menadione-ascorbate-SOD with physiological NaHCO3 levels; low NaHCO3 or SOD-free reactions produced lower levels of protein carbonyls. In conclusion, these findings suggest that the hydrogen peroxide generated by menadione redox cycling together with NaHCO3-CO2 are potential substrates for SOD peroxidase activity that can lead to carbonate-radical-enhanced cytotoxicity. These findings demonstrate the importance of NaHCO3 in menadione redox cycling and cytotoxicity.

Highly stabilized gadolinium chelates functionalized on metal nanoparticles as magnetic resonance imaging contrast agent

NASA Astrophysics Data System (ADS)

Siddiqui, Talha S.

Magnetic resonance imaging (MRI) is a non-invasive method for imaging and diagnosing tissue damage, organ function and the vascular system. Magnevist(TM) a complex of diethylenetriaminepentaacetic acid (DTPA) and Gd3+ is a clinically approved contrast agent for MRI. A derivative of DTPA was formed by the addition of two cysteine groups (DTPA-L-Cys) through amide linkage. The Gd complex of this ligand bonds with the silver surfaces through the cysteine thiols. GdDTPA-L-Cys was bound to ˜10nm diameter Ag nanoparticles for use as a multifunctional MRI contrast agent. The ligand and complex were characterized by 1H and 13C NMR, ESI-MS and IR spectroscopy. The silver construct was characterized by TEM, TGA and UV-Vis absorption spectra. The per metal complex r1 relaxivity of GdDTPA-L-Cys{Ag} greater than that of Magnavist(TM) with the same molarity for both compounds. The synthesis of a DTPA derivative is described that allows it to bind to silver or gold nanoparticles through a single thiol linkage (DTPASH). The resulting Gd complex, GdDTPASH, was bound to Ag nanoparticles to create a single monolayer on the surface. The construct was further stabilized in buffered solution with the addition of a thiolated PEG chain. The highly stabilized nanoparticle construct delivers a high payload of Gd compelex and is an effective T1 brightening agent. The production of this type of construct opens the way for engineered multimodal MRI contrast agents.

Transport of oxaliplatin species in water-saturated natural soil.

PubMed

Goykhman, Natalia; Dror, Ishai; Berkowitz, Brian

2018-06-05

This study reports the transport characteristics of the organometallic anticancer compound oxaliplatin and its derivatives in natural soil-water environments. Although pharmaceuticals and their derivatives have for many years been detected in water resources, and linked to toxicological impacts on ecological systems, their transport in soil and groundwater is not fully understood. Specifically, studies that describe transport of organometallic pharmaceuticals in porous media are rare, and the transport characteristics of platinum complexes have received little attention. Oxaliplatin transport was studied in sand, as a function of two added natural chelators (citrate and humic acid), and in soil, under four continuously monitored, environmentally-relevant redox conditions: oxic, nitrate reducing, iron reducing and methanogenic. In sand, oxaliplatin species retention was about 7%, and affected only mildly by added citrate, and by humic acid under buffered pH. Transport with unbuffered humic acid was affected significantly by pH variations, and exhibited strong retention at pH < 8. In soil, unexpectedly similar breakthrough patterns of oxaliplatin species were found for all redox conditions, exhibiting linear, reversible retention of 79-87%. The strongest retention was observed under iron reducing conditions, whereas the weakest retention was under oxic conditions. Increased cation activity appears to promote weaker sorption. The results indicate that soil composition is the leading factor affecting oxaliplatin species mobility and fate in the soil-water environment, followed by the weaker factors of redox conditions and cation activities. Copyright © 2018 Elsevier Ltd. All rights reserved.

Targeted Catalytic Inactivation of Angiotensin Converting Enzyme by Lisinopril-Coupled Transition Metal Chelates

PubMed Central

Joyner, Jeff C.; Hocharoen, Lalintip; Cowan, J. A.

2012-01-01

A series of compounds that target reactive transition metal chelates to somatic Angiotensin Converting Enzyme (sACE-1) have been synthesized. Half maximal inhibitory concentrations (IC50) and rate constants for both inactivation and cleavage of full length sACE-1 have been determined and evaluated in terms of metal-chelate size, charge, reduction potential, coordination unsaturation, and coreactant selectivity. Ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid (DOTA), and tripeptide GGH were linked to the lysine sidechain of lisinopril by EDC/NHS coupling. The resulting amide-linked chelate-lisinopril (EDTA-lisinopril, NTA-lisinopril, DOTA-lisinopril, and GGH-lisinopril) conjugates were used to form coordination complexes with iron, cobalt, nickel and copper, such that lisinopril could mediate localization of the reactive metal chelates to sACE-1. ACE activity was assayed by monitoring cleavage of the fluorogenic substrate Mca-RPPGFSAFK(Dnp)-OH, a derivative of bradykinin, following pre-incubation with metal-chelate-lisinopril compounds. Concentration-dependent inhibition of sACE-1 by metal-chelate-lisinopril complexes revealed IC50 values ranging from 44 nM to 4,500 nM for Ni-NTA-lisinopril and Ni-DOTA-lisinopril, respectively, versus 1.9 nM for lisinopril. Stronger inhibition was correlated with smaller size and lower negative charge of the attached metal chelates. Time-dependent inactivation of sACE-1 by metal-chelate-lisinopril complexes revealed a remarkable range of catalytic activities, with second order rate constants as high as 150,000 M−1min−1 (Cu-GGH-lisinopril), while catalyst-mediated cleavage of sACE-1 typically occurred at much lower rates, indicating that inactivation arose primary from sidechain modification. Optimal inactivation of sACE-1 was observed when the reduction potential for the metal center was poised near 1000 mV, reflecting the difficulty of protein oxidation. This class of metal-chelate-lisinopril complexes possesses a range of high-affinity binding to ACE, introduces the advantage of irreversible catalytic turnover, and marks an important step toward the development of multiple-turnover drugs for selective inactivation of sACE-1. PMID:22200082

Targeted catalytic inactivation of angiotensin converting enzyme by lisinopril-coupled transition-metal chelates.

PubMed

Joyner, Jeff C; Hocharoen, Lalintip; Cowan, J A

2012-02-22

A series of compounds that target reactive transition-metal chelates to somatic angiotensin converting enzyme (sACE-1) have been synthesized. Half-maximal inhibitory concentrations (IC(50)) and rate constants for both inactivation and cleavage of full-length sACE-1 have been determined and evaluated in terms of metal chelate size, charge, reduction potential, coordination unsaturation, and coreactant selectivity. Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), and tripeptide GGH were linked to the lysine side chain of lisinopril by 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride/N-hydroxysuccinimide coupling. The resulting amide-linked chelate-lisinopril (EDTA-lisinopril, NTA-lisinopril, DOTA-lisinopril, and GGH-lisinopril) conjugates were used to form coordination complexes with iron, cobalt, nickel, and copper, such that lisinopril could mediate localization of the reactive metal chelates to sACE-1. ACE activity was assayed by monitoring cleavage of the fluorogenic substrate Mca-RPPGFSAFK(Dnp)-OH, a derivative of bradykinin, following preincubation with metal chelate-lisinopril compounds. Concentration-dependent inhibition of sACE-1 by metal chelate-lisinopril complexes revealed IC(50) values ranging from 44 to 4500 nM for Ni-NTA-lisinopril and Ni-DOTA-lisinopril, respectively, versus 1.9 nM for lisinopril. Stronger inhibition was correlated with smaller size and lower negative charge of the attached metal chelates. Time-dependent inactivation of sACE-1 by metal chelate-lisinopril complexes revealed a remarkable range of catalytic activities, with second-order rate constants as high as 150,000 M(-1) min(-1) (Cu-GGH-lisinopril), while catalyst-mediated cleavage of sACE-1 typically occurred at much lower rates, indicating that inactivation arose primarily from side chain modification. Optimal inactivation of sACE-1 was observed when the reduction potential for the metal center was poised near 1000 mV, reflecting the difficulty of protein oxidation. This class of metal chelate-lisinopril complexes possesses a range of high-affinity binding to ACE, introduces the advantage of irreversible catalytic turnover, and marks an important step toward the development of multiple-turnover drugs for selective inactivation of sACE-1.

Promising Bifunctional Chelators for Copper 64-PET imaging: Practical 64Cu Radiolabeling and High In Vitro and In Vivo Complex Stability

PubMed Central

Wu, Ningjie; Kang, Chi Soo; Sin, Inseok; Ren, Siyuan; Liu, Dijie; Ruthengael, Varyanna C.; Lewis, Michael R.; Chong, Hyun-Soon

2016-01-01

Positron emission tomography (PET) using copper-64 is a sensitive and non-invasive imaging technique for diagnosis and staging of cancer. A bifunctional chelator that can present rapid radiolabeling kinetics and high complex stability with 64Cu is a critical component for targeted PET imaging. Bifunctional chelates 3p-C-NE3TA, 3p-C-NOTA, and 3p-C-DE4TA were evaluated for complexation kinetics and stability with 64Cu in vitro and in vivo. Hexadentate 3p-C-NOTA and heptadentate 3p-C-NE3TA possess a smaller TACN-based macrocyclic backbone, while nonadentate 3p-C-DE4TA is constructed on a larger CYCLEN-based ring. The frequently explored chelates of 64Cu, octadentate C-DOTA and hexadentate C-NOTA were also comparatively evaluated. Radiolabeling kinetics of bifunctional chelators with 64Cu was assessed under mild conditions. All bifunctional chelates instantly bound to 64Cu in excellent radiolabeling efficiency at room temperature. C-DOTA was less efficient in binding 64Cu than all other chelates. All 64Cu-radiolabeled bifunctional chelates remained stable in human serum without any loss of 64Cu for 2 days. When challenged by an excess amount of EDTA, 64Cu complexes of 3p-C-NE3TA and 3p-C-NOTA were shown to be more stable than 64Cu-C-DOTA and 64Cu-C-DE4TA. 3p-C-NE3TA and 3p-C-NOTA displayed comparable in vitro and in vivo complex stability to 64Cu-C-NOTA. In vivo biodistribution result indicates that the 64Cu-radiolabeled complexes of 3p-C-NOTA and 3p-C-NE3TA possess excellent in vivo complex stability, while 64Cu-3p-C-DE4TA was dissociated as evidenced by high renal and liver retention in mice. The results of in vitro and in vivo studies suggest that the bifunctional chelates 3p-C-NOTA and 3p-C-NE3TA offer excellent chelation chemistry with 64Cu for potential PET imaging applications. PMID:26666778

A Novel Nuclease Activity that is Activated by Ca2+ Chelated to EGTA

PubMed Central

Dominguez, Kenneth; Ward, W. Steven

2010-01-01

Most nucleases require a divalent cation as a cofactor, usually Mg2+ or Ca2+, and are inhibited by the chelators EDTA and EGTA. We report the existence of a novel nuclease activity, initially identified in the luminal fluids of the mouse male reproductive tract but subsequently found in other tissues, that requires EGTA chelated to calcium to digest DNA. We refer to this unique enzyme as CEAN (Chelated EGTA Activated Nuclease). Using a fraction of vas deferens luminal fluid, plasmid DNA was degraded in the presence of excess Ca2+ (Ca2+:EGTA = 16) or excess EGTA (Ca2+:EGTA = 0.25), but required the presence of both. Higher levels of EGTA (Ca2+:EGTA = 0.10) prevented activity, suggesting that unchelated EGTA may be a competitive inhibitor. The EGTA-Ca2+ activation of CEAN is reversible as removing EGTA-Ca2+ stops ongoing DNA degradation, but adding EGTA-Ca2+ again reactivates the enzyme. This suggests the possibility that CEAN binds directly to EGTA-Ca2+. CEAN has a greater specificity for the chelator than for the divalent cation. Two other chelators, BAPTA and sodium citrate, do not activate CEAN in the presence of cation, but chelated EDTA does. EGTA chelated to other divalent cations such as Mn2+, Zn2+, and Cu2+ activate CEAN, but not Mg2+. The activity is lost upon boiling suggesting that it is a protein. These data suggest that EGTA and EDTA may not always prevent DNA from nuclease damage. PMID:19938954

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.

Synergy and antagonism between iron chelators and antifungal drugs in Cryptococcus.

PubMed

Lai, Yu-Wen; Campbell, Leona T; Wilkins, Marc R; Pang, Chi Nam Ignatius; Chen, Sharon; Carter, Dee A

2016-10-01

Fungal infections remain very difficult to treat, and developing new antifungal drugs is difficult and expensive. Recent approaches therefore seek to augment existing antifungals with synergistic agents that can lower the therapeutic dose, increase efficacy and prevent resistance from developing. Iron limitation can inhibit microbial growth, and iron chelators have been employed to treat fungal infections. In this study, chequerboard testing was used to explore combinations of iron chelators with antifungal agents against pathogenic Cryptococcus spp. with the aim of determining how disruption to iron homeostasis affects antifungal susceptibility. The iron chelators ethylenediaminetetraacetic acid (EDTA), deferoxamine (DFO), deferiprone (DFP), deferasirox (DSX), ciclopirox olamine and lactoferrin (LF) were paired with the antifungal agents amphotericin B (AmB), fluconazole, itraconazole, voriconazole and caspofungin. All chelators except for DFO increased the efficacy of AmB, and significant synergy was seen between AmB and LF for all Cryptococcus strains. Addition of exogenous iron rescued cells from the antifungal effect of LF alone but could not prevent inhibition by AmB + LF, indicating that synergy was not due primarily to iron chelation but to other properties of LF that were potentiated in the presence of AmB. Significant synergy was not seen consistently for other antifungal-chelator combinations, and EDTA, DSX and DFP antagonised the activity of azole drugs in strains of Cryptococcus neoformans var. grubii. This study highlights the range of interactions that can be induced by chelators and indicates that most antifungal drugs are not enhanced by iron limitation in Cryptococcus. Copyright © 2016 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

Advanced Ultra-Violet (UV) Aircraft Fire Detection System. Volume 2. System Hardware Design, Software Design, and Test

DTIC Science & Technology

1982-08-01

REPORT SHT",, -ENGLAND A W*nson Match Company Saftey and Protion Division ISSUE " 3 (contd) HEADS 1 2 3 4 5 6 7 8 ,7 0 BITS iii ii The 832 tm inspection...input data buffering and output data buffering. 2.2.2.3.1. Power up, Reset Circuit To ensure correct system operation when power is first applied the...act in conjunction with R2, R3 and two buffer sections of IC2. When power is first applied , Cl is discharged, Via the pot chain divider of R2 and R3 the

Patents – Melvin Calvin

Science.gov Websites

plutonium from uranium and fission products in an aqueous acidic solution by use of a chelating agent. The concentration is adjusted to about 1 N bar. The aqueous solution is then contacted with a water-immiscible organic solvent solution and the chelating agent. The chelating agents covered by this invention comprise

Chelation Treatment for Autism Spectrum Disorders: A Systematic Review

ERIC Educational Resources Information Center

Davis, Tonya N.; O'Reilly, Mark; Kang, Soyeon; Lang, Russell; Rispoli, Mandy; Sigafoos, Jeff; Lancioni, Giulio; Copeland, Daelynn; Attai, Shanna; Mulloy, Austin

2013-01-01

Chelation treatment is used to eliminate specific metals from the body, such as mercury. It has been hypothesized that mercury poisoning may be a factor in autism and data suggest that perhaps 7% of individuals with autism spectrum disorder (ASD) have received chelation treatment. It would therefore seem timely to review studies investigating the…

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.

Hydroxypyridinone Derivatives: A Fascinating Class of Chelators with Therapeutic Applications - An Update.

PubMed

Chaves, Sílvia; Piemontese, Luca; Hiremathad, Asha; Santos, Maria A

2018-01-01

Hydroxypyridinones (HPs) are a family of N-heterocyclic metal chelators, which have been an attractive target in the development of a variety of new pharmaceutical drugs, due to their high metal chelating efficacy/specificity and easy derivatization to tune the desired biological properties. In fact, along the last decades, hydroxypyridinone derivatives, but mostly 3-hydroxy-4-pyridinone (3,4-HP), have been intensively used in drug design, following either a multitarget approach, in which one chelating unity is extrafunctionalized (hybridized) to enable the interaction with other important specific biological sites, or a polydenticity approach, in which more than one chelating moiety is conveniently attached to one scaffold, to increase the metal chelating efficacy. This review represents an update of the most recent publications (2014-2016) in mono-HP hybrids, namely as potential anti-Alzheimer's drugs, inhibitors of metalloenzymes and anti-microbials, and also polychelating compounds (poly- HP), in view of potential application, such as anti-microbial/biostatic agents, luminescent biosensors or diagnostic agents. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

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.

Fluid extraction

DOEpatents

Wai, Chien M.; Laintz, Kenneth E.

1999-01-01

A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated .beta.-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated .beta.-diketone and a trialkyl phosphate, or a fluorinated .beta.-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated .beta.-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

Comparison of synthetic chelators and low molecular weight organic acids in enhancing phytoextraction of heavy metals by two ecotypes of Sedum alfredii Hance.

PubMed

Liu, Dan; Islam, Ejazul; Li, Tingqiang; Yang, Xiaoe; Jin, Xiaofen; Mahmood, Qaisar

2008-05-01

Lab scale and pot experiments were conducted to compare the effects of synthetic chelators and low molecular weight organic acids (LMWOA) on the phytoextraction of multi-contaminated soils by two ecotypes of Sedum alfredii Hance. Through lab scale experiments, the treatment dosage of 5 and 10 mM for synthetic chelators and LMWOA, respectively, and the treatment time of 10 days were selected for pot experiment. In pot experiment, the hyperaccumulating ecotype (HE) was found more tolerant to the metal toxicity compared with the non-hyperaccumulating ecotype (NHE). EDTA for Pb, EDDS for Cu, and DTPA for Cu and Cd were found more effective to enhance heavy metal accumulation in the shoots of S. alfredii Hance. Compared with synthetic chelators, the phytoextraction ability of LMWOA was lesser. Considering the strong post-harvest effects of synthetic chelators, it is suggested that higher dosage of LMWOA could be practiced during phytoextraction, and some additional measures could also be taken to lower the potential environmental risks of synthetic chelators in the future studies.

Which psychosocial factors are related to chelation adherence in thalassemia? A systematic review.

PubMed

Evangeli, Michael; Mughal, Kulsoom; Porter, John B

2010-06-01

Good adherence to iron chelation therapy in thalassemia is crucial. Although there is evidence that adherence is related to regimen factors, there has been less emphasis on the relationship between psychosocial (psychological, demographic and social) factors and adherence. We present a systematic review of psychosocial correlates of chelation adherence in thalassemia. Nine studies met the inclusion criteria. Information was extracted regarding the study characteristics and the relationship between psychosocial factors and chelation adherence. Methodological quality was rated. The studies took place in a range of countries, were mostly cross sectional in design, and examined adherence to deferoxamine (DFO) only. Sample sizes ranged from 15 to 1573. A variety of psychosocial variables were examined. Definitions of adherence varied between studies and non adherence rates were also variable (9 to 66%). Older age was consistently associated with lower levels of chelation adherence. There were few other consistent findings. The methodological quality of studies was variable. There is a need for more methodologically sophisticated and theoretically informed studies on psychosocial correlates of chelation adherence. We offer specific suggestions.

In Vitro Inhibition of Leishmania Attachment to Sandfly Midguts and LL-5 Cells by Divalent Metal Chelators, Anti-gp63 and Phosphoglycans.

PubMed

Soares, Rodrigo Pedro; Altoé, Ellen Cristina Félix; Ennes-Vidal, Vítor; da Costa, Simone M; Rangel, Elizabeth Ferreira; de Souza, Nataly Araújo; da Silva, Vanderlei Campos; Volf, Petr; d'Avila-Levy, Claudia Masini

2017-07-01

Leishmania braziliensis and Leishmania infantum are the causative agents of cutaneous and visceral leishmaniasis, respectively. Several aspects of the vector-parasite interaction involving gp63 and phosphoglycans have been individually assayed in different studies. However, their role under the same experimental conditions was not studied yet. Here, the roles of divalent metal chelators, anti-gp63 antibodies and purified type I phosphoglycans (PGs) were evaluated during in vitro parasite attachment to the midgut of the vector. Parasites were treated with divalent metal chelators or anti-gp63 antibodies prior to the interaction with Lutzomyia longipalpis/Lutzomyia intermedia midguts or sand fly LL-5 cells. In vitro binding system was used to examine the role of PG and gp63 in parallel. Treatment with divalent metal chelators reduced Le. infantum adhesion to the Lu. longipalpis midguts. The most effective compound (Phen) inhibited the binding in both vectors. Similar results were observed in the interaction between both Leishmania species and the cell line LL-5. Finally, parallel experiments using anti-gp63-treated parasites and PG-incubated midguts demonstrated that both approaches substantially inhibited attachment in the natural parasite-vector pairs Le. infantum/Lu. longipalpis and Le. braziliensis/Lu. intermedia. Our results suggest that gp63 and/or PG are involved in parasite attachment to the midgut of these important vectors. Copyright © 2017 Elsevier GmbH. All rights reserved.

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.

Quilamine HQ1-44, an iron chelator vectorized toward tumor cells by the polyamine transport system, inhibits HCT116 tumor growth without adverse effect.

PubMed

Renaud, Stéphanie; Corcé, Vincent; Cannie, Isabelle; Ropert, Martine; Lepage, Sylvie; Loréal, Olivier; Deniaud, David; Gaboriau, François

2015-08-01

Tumor cell growth requires large iron quantities and the deprivation of this metal induced by synthetic metal chelators is therefore an attractive method for limiting the cancer cell proliferation. The antiproliferative effect of the Quilamine HQ1-44, a new iron chelator vectorized toward tumor cells by a polyamine chain, is related to its high selectivity for the Polyamine Transport System (PTS), allowing its preferential uptake by tumoral cells. The difference in PTS activation between healthy cells and tumor cells enables tumor cells to be targeted, whereas the strong dependence of these cells on iron ensures a secondary targeting. Here, we demonstrated in vitro that HQ1-44 inhibits DNA synthesis and cell proliferation of HCT116 cells by modulating the intracellular metabolism of both iron and polyamines. Moreover, in vivo, in xenografted athymic nude mice, we found that HQ1-44 was as effective as cis-platin in reducing HCT116 tumor growth, without its side effects. Furthermore, as suggested by in vitro data, the depletion in exogenous or endogenous polyamines, known to activate the PTS, dramatically enhanced the antitumor efficiency of HQ1-44. These data support the need for further studies to assess the value of HQ1-44 as an adjuvant treatment in cancer. Copyright © 2015 Elsevier Inc. All rights reserved.

Extraction of metals and/or metalloids from acidic media using supercritical fluids and salts

DOEpatents

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

1998-01-01

A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a fluid solvent, particularly supercritical carbon dioxide, containing a chelating agent is described. The chelating agent forms chelates that are soluble in the fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent comprises a trialkyl phosphate, a triaryl phosphate, a trialkylphosphine oxide, a triarylphosphine oxide, or mixtures thereof. The method provides an environmentally benign process for removing contaminants from industrial waste. The method is particularly useful for extracting actinides from acidic solutions, and the process can be aided by the addition of nitrate salts. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

Synthesis, iron binding and antimicrobial properties of hexadentate 3-hydroxypyridinones-terminated dendrimers.

PubMed

Zhou, Tao; Chen, Kai; Kong, Li-Min; Liu, Mu-Song; Ma, Yong-Min; Xie, Yuan-Yuan; Hider, Robert C

2018-05-30

Macromolecular chelators have potential applications in the medical area, for instance, in treatment of iron overload-related disorders and in the treatment of external infections. In this investigation, several novel iron(III)-selective hydroxypyridinone hexadentate-terminated first and second generation dendrimeric chelators were synthesized using a convergent strategy. Their iron chelating ability was demonstrated by UV/Visible spectrometry and high resolution mass spectrometry (HRMS). The iron binding affinities were also investigated by the competition with a fluorescent iron chelator CP691. The result indicated that these dendrimers possesses a high affinity for iron with a very high pFe 3+ value, which is close to that of an isolated hexadentate unit. These dendrimeric chelators were found to exhibit inhibitory effect on the growth of both Gram-positive and Gram-negative bacteria. Copyright © 2018 Elsevier Ltd. All rights reserved.

Chelation in root canal therapy reconsidered.

PubMed

Zehnder, Matthias; Schmidlin, Patrick; Sener, Beatrice; Waltimo, Tuomas

2005-11-01

The aim of this study was to assess interactions of EDTA and citric acid (CA) with sodium hypochlorite (NaOCl), the indispensable endodontic irrigant. Other chelators were simultaneously evaluated as possible alternatives: sodium triphosphate (STP), amino tris methylenephosphonic acid (ATMA), and 1- hydroxyethylidene-1, 1-bisphosphonate (HEBP). Available chlorine was titrated in chelator-NaOCl solutions. All chelators other than HEBP and STP caused an almost complete, immediate loss of available chlorine in solution. Atomic absorbtion spectrometry and SEM evaluation of root canal walls of instrumented teeth indicated that NaOCl had no negative effect on calcium-complexing ability of chelators. STP was too weak a complexing agent to warrant further studies. Finally, CA-, EDTA-, and HEBP-NaOCl mixtures were evaluated for their antimicrobial capacity. Again, EDTA and CA negatively interfered with NaOCl, while HEBP did not.

VORBrouter: A dynamic data routing system for Real-Time Seismic networks

NASA Astrophysics Data System (ADS)

Hansen, T.; Vernon, F.; Lindquist, K.; Orcutt, J.

2004-12-01

For anyone who has managed a moderately complex buffered real-time data transport system, the need for reliable adaptive data transport is clear. The ROADNet VORBrouter system, an extension to the ROADNet data catalog system [AGU-2003, Dynamic Dataflow Topology Monitoring for Real-time Seismic Networks], allows dynamic routing of real-time seismic data from sensor to end-user. Traditional networks consist of a series of data buffer computers with data transport interconnections configured by hand. This allows for arbitrarily complex data networks, which can often exceed full comprehension by network administrators, sometimes resulting in data loops or accidental data cutoff. In order to manage data transport systems in the event of a network failure, a network administrator must be called upon to change the data transport paths and to recover the missing data. Using VORBrouter, administrators can sleep at night while still providing 7/24 uninterupted data streams at realistic cost. This software package uses information from the ROADNet data catalog system to route packets around failed link outages and to new consumers in real-time. Dynamic data routing protocols operating on top of the Antelope Data buffering layer allow authorized users to request data sets from their local buffer and to have them delivered from anywhere within the network of buffers. The VORBrouter software also allows for dynamic routing around network outages, and the elimination of duplicate data paths within the network, while maintaining the nearly lossless data transport features exhibited by the underlying Antelope system. We present the design of the VORBrouter system, its features, limitations and some future research directions.

Arise, amphibians: stream buffers affect more than fish.

Treesearch

Sally Duncan

2003-01-01

Buffers along streams cover a tremendous proportion of the land base in the forested systems of the western Pacific Northwest. These buffers were designated primarily to conserve and restore habitat for salmon and trout, but conservation of habitat for a number of other organisms also has been implicit in their design. Recent research evaluated the importance of...

Tested Demonstrations: Buffer Capacity of Various Acetic Acid-Sodium Acetate Systems: A Lecture Experiment.

ERIC Educational Resources Information Center

Donahue, Craig J.; Panek, Mary G.

1985-01-01

Background information and procedures are provided for a lecture experiment which uses indicators to illustrate the concept of differing buffer capacities by titrating acetic acid/sodium acetate buffers with 1.0 molar hydrochloric acid and 1.0 molar sodium hydroxide. A table with data used to plot the titration curve is included. (JN)

Efficacy of buffer zones in disconnecting roads and streams in the coastal plain

Treesearch

J.M. III Grace; E. Davis

2010-01-01

Established forest BMPs rely heavily on the forest floor to disconnect upslope activities from stream systems. Optimizing the buffer length required to negate the storm runoff contribution of upslope activities has been a point of interest for soil scientist, hydrologist, and conservation professionals for the last century. Minimum buffer lengths have been recommended...

Modeling of the Modulation by Buffers of Ca2+ Release through Clusters of IP3 Receptors

PubMed Central

Zeller, S.; Rüdiger, S.; Engel, H.; Sneyd, J.; Warnecke, G.; Parker, I.; Falcke, M.

2009-01-01

Abstract Intracellular Ca2+ release is a versatile second messenger system. It is modeled here by reaction-diffusion equations for the free Ca2+ and Ca2+ buffers, with spatially discrete clusters of stochastic IP3 receptor channels (IP3Rs) controlling the release of Ca2+ from the endoplasmic reticulum. IP3Rs are activated by a small rise of the cytosolic Ca2+ concentration and inhibited by large concentrations. Buffering of cytosolic Ca2+ shapes global Ca2+ transients. Here we use a model to investigate the effect of buffers with slow and fast reaction rates on single release spikes. We find that, depending on their diffusion coefficient, fast buffers can either decouple clusters or delay inhibition. Slow buffers have little effect on Ca2+ release, but affect the time course of the signals from the fluorescent Ca2+ indicator mainly by competing for Ca2+. At low [IP3], fast buffers suppress fluorescence signals, slow buffers increase the contrast between bulk signals and signals at open clusters, and large concentrations of buffers, either fast or slow, decouple clusters. PMID:19686646

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).

Effect of thermal annealing treatment with titanium chelate on buffer layer in inverted polymer solar cells

NASA Astrophysics Data System (ADS)

Liu, Zhiyong; Wang, Ning; Fu, Yan

2016-12-01

The solution processable electron extraction layer (EEL) is crucial for polymer solar cells (PSCs). Here, we investigated titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as an EEL and fabricated inverted PSCs with a blend of poly(3-hexylthiophene) (P3HT) and indene-C60 bisadduct (ICBA) acting as the photoactive layer, with a structure of ITO/TIPD/P3HT:ICBA/MoO3/Ag. After thermal annealing treatment at 150 °C for 15 min, the PSC performances increased from 3.85% to 6.84% and they achieve stable power conversion efficiency (PCE), with a similar PCE compared with TiO2 as an EEL by the vacuum evaporated method. Fourier transform infrared spectroscopy (FTIR) and ultraviolet photoelectron spectroscopy (UPS) confirmed that the TIPD decomposed and formed the Tidbnd O bond, and the energy level of the lowest unoccupied molecular orbital and the highest occupied molecular orbital increased. The space charge limited current (SCLC) measurements further confirmed the improvement in electron collection and the transport ability using TIPD as the EEL and thermal annealing.

L-carnosine enhanced reproductive potential of the Saccharomyces cerevisiae yeast growing on medium containing glucose as a source of carbon.

PubMed

Kwolek-Mirek, Magdalena; Molon, Mateusz; Kaszycki, Pawel; Zadrag-Tecza, Renata

2016-08-01

Carnosine is an endogenous dipeptide composed of β-alanine and L-histidine, which occurs in vertebrates, including humans. It has a number of favorable properties including buffering, chelating, antioxidant, anti-glycation and anti-aging activities. In our study we used the Saccharomyces cerevisiae yeast as a model organism to examine the impact of L-carnosine on the cell lifespan. We demonstrated that L-carnosine slowed down the growth and decreased the metabolic activity of cells as well as prolonged their generation time. On the other hand, it allowed for enhancement of the yeast reproductive potential and extended its reproductive lifespan. These changes may be a result of the reduced mitochondrial membrane potential and decreased ATP content in the yeast cells. However, due to reduction of the post-reproductive lifespan, L-carnosine did not have an influence on the total lifespan of yeast. In conclusion, L-carnosine does not extend the total lifespan of S. cerevisiae but rather it increases the yeast's reproductive capacity by increasing the number of daughter cells produced.

Cu2+ triggers reversible aggregation of a disordered His-rich dehydrin MpDhn12 from Musa paradisiaca.

PubMed

Mu, Peiqiang; Feng, Dongru; Su, Jianbin; Zhang, Yang; Dai, Jinran; Jin, Honglei; Liu, Bing; He, Yanming; Qi, Kangbiao; Wang, Hongbin; Wang, Jinfa

2011-11-01

Copper is an essential nutrient, but it is toxic in excess. Here, we cloned and characterized a His-rich low molecular weight dehydrin from Musa paradisiaca, MpDhn12. Analysis by circular dichroism (CD) spectra and a thermal stability assay showed that MpDhn12 is an intrinsically disordered protein, and immobilized-metal affinity chromatography (IMAC) analysis revealed that MpDhn12 can bind Cu(2+) both in vitro and in vivo. Interestingly, MpDhn12 aggregated under excess Cu(2+) conditions, and the aggregation was reversible and impaired by histidine modification with diethylpyrocarbonate (DEPC), while the disordered structure of another dehydrin ERD14 (as a control) was not changed. Furthermore, MpDhn12 could complement the copper-sensitive phenotype of yeast mutant Δsod1. These results together suggested that MpDhn12 may take part in buffering copper levels through chelation and formation of aggregates in excess Cu(2+) conditions. To the best of our knowledge, it is the first report that a dehydrin interchanged between disordered and aggregated state triggered by copper.

Click chemistry improved wet adhesion strength of mussel-inspired citrate-based antimicrobial bioadhesives

PubMed Central

Guo, Jinshan; Kim, Gloria B.; Shan, Dingying; Kim, Jimin P.; Hu, Jianqing; Wang, Wei; Hamad, Fawzi G.; Qian, Guoying; Rizk, Elias B.; Yang, Jian

2016-01-01

For the first time, a convenient copper-catalyzed azide-alkyne cycloaddition (CuAAC, click chemistry) was successfully introduced into injectable citrate-based mussel-inspired bioadhesives (iCMBAs, iCs) to improve both cohesive and wet adhesive strengths and elongate the degradation time, providing numerous advantages in surgical applications. The major challenge to developing such an adhesive was the mutual inhibition effect between the oxidant used for crosslinking catechol groups and the Cu(II) reductant used for CuAAC, which was successfully minimized by adding a biocompatible buffering agent typically used in cell culture, 4-(2-hydroxyethyl) -1-piperazineethanesulfonic acid (HEPES), as a copper chelating agent. Among the investigated formulations, the highest adhesion strength achieved (223.11 ± 15.94 kPa) was around 13 times higher than that of a commercially available fibrin glue (15.4 ± 2.8 kPa). In addition, dual-crosslinked (i.e. click crosslinking and mussel-inspired crosslinking) iCMBAs still preserved considerable antibacterial and antifungal capabilities that are beneficial for the bioadhesives used as hemostatic adhesives or sealants for wound management. PMID:27770631

Determination of glutathione in human plasma using high-performance liquid chromatography with electrochemical detection with a carbon-epoxy resin composite electrode chemically modified with cobalt phthalocyanine.

PubMed

Wring, S A; Hart, J P; Birch, B J

1989-12-01

High-performance liquid chromatography with electrochemical detection (LCEC), incorporating a novel carbon-epoxy resin working electrode modified with cobalt phthalocyanine, has been employed for preliminary studies directed towards the determination of normal circulating levels of reduced glutathione (GSH) in human plasma. The mobile phase consisted of 0.05 M phosphate buffer (pH 3) containing 0.1% m/m ethylenediaminetetraacetic acid (EDTA); the calibration graph was linear in the range 0.24-30.7 ng of GSH injected. The mean recovery of GSH added to a control serum over the physiological concentration range (0.38-3.07 ng ml-1) was 99%; this was achieved following a simple sample pre-treatment method, prior to LCEC, involving chelation of divalent cations with EDTA and subsequent acidification with orthophosphoric acid. Using the LCEC method, the mean circulating level of GSH in plasma, found in three normal subjects, was 2.69 microM, GSH; this indicates that the method might be applicable to the determination of depressed circulating levels of GSH.

Inorganic polyphosphate in the microbial world. Emerging roles for a multifaceted biopolymer.

PubMed

Albi, Tomás; Serrano, Aurelio

2016-02-01

Inorganic polyphosphates (polyP) are linear polymers of tens to hundreds orthophosphate residues linked by phosphoanhydride bonds. These fairly abundant biopolymers occur in all extant forms of life, from prokaryotes to mammals, and could have played a relevant role in prebiotic evolution. Since the first identification of polyP deposits as metachromatic or volutin granules in yeasts in the nineteenth century, an increasing number of varied physiological functions have been reported. Due to their "high energy" bonds analogous to those in ATP and their properties as polyanions, polyP serve as microbial phosphagens for a variety of biochemical reactions, as a buffer against alkalis, as a storage of Ca(2+) and as a metal-chelating agent. In addition, recent studies have revealed polyP importance in signaling and regulatory processes, cell viability and proliferation, pathogen virulence, as a structural component and chemical chaperone, and as modulator of microbial stress response. This review summarizes the current status of knowledge and future perspectives of polyP functions and their related enzymes in the microbial world.

Rapid determination of trace copper in animal feed based on micro-plate colorimetric reaction and statistical partitioning correction.

PubMed

Niu, Yiming; Wang, Jiayi; Zhang, Chi; Chen, Yiqiang

2017-04-15

The objective of this study was to develop a micro-plate based colorimetric assay for rapid and high-throughput detection of copper in animal feed. Copper ion in animal feed was extracted by trichloroacetic acid solution and reduced to cuprous ion by hydroxylamine. The cuprous ion can chelate with 2,2'-bicinchoninic acid to form a Cu-BCA complex which was detected with high sensitivity by micro-plate reader at 354nm. The whole assay procedure can be completed within 20min. To eliminate matrix interference, a statistical partitioning correction approach was proposed, which makes the detection of copper in complex samples possible. The limit of detection was 0.035μg/mL and the detection range was 0.1-10μg/mL of copper in buffer solution. Actual sample analysis indicated that this colorimetric assay produced results consistent with atomic absorption spectrometry analysis. These results demonstrated that the developed assay can be used for rapid determination of copper in animal feed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Simultaneous determination of suspended particulate trace metals (Co, Ni, Cu, Zn, Cd and Pb) in seawater with small volume filtration assisted by microwave digestion and flow injection inductively coupled plasma mass spectrometer.

PubMed

Nakatsuka, Seiji; Okamura, Kei; Norisuye, Kazuhiro; Sohrin, Yoshiki

2007-06-26

A new technique for the determination of suspended particulate trace metals (P-metals >0.2 microm), such as Co, Ni, Cu, Zn, Cd and Pb, in open ocean seawater has been developed by using microwave digestion coupled with flow injection inductively coupled plasma mass spectrometry (FI-ICP-MS). Suspended particulate matter (SPM) was collected from 500 mL of seawater on a Nuclepore filter (0.2 microm) using a closed filtration system. Both the SPM and filter were completely dissolved by microwave digestion. Reagents for the digestion were evaporated using a clean evaporation system, and the metals were redissolved in 0.8 M HNO3. The solution was diluted with buffer solution to give pH 5.0 and the metals were determined by FI-ICP-MS using a chelating adsorbent of 8-hydroxyquinoline immobilized on fluorinated metal alkoxide glass (MAF-8HQ). The procedure blanks with a filter were found to be 0.048+/-0.008, 10.3+/-0.3, 0.27+/-0.05, 3.3+/-1.8, 0.02+/-0.03 and 0.85+/-0.09 ng L(-1) for Co, Ni, Cu, Zn, Cd and Pb, respectively (n=14). Detection limits defined as 3 times the standard deviation of the blanks were 0.023, 0.90, 0.14, 5.3, 0.078 and 0.28 ng L(-1) for Co, Ni, Cu, Zn, Cd and Pb, respectively. Accuracy was evaluated using certified reference materials of chlorella (NES CRM No. 3) and marine sediment (HISS-1). The method was applied to the determination of vertical distributions for P-Co, Ni, Cu, Zn, Cd and Pb in the Western North Pacific.

In situ magnetic separation of antibody fragments from Escherichia coli in complex media

PubMed Central

2013-01-01

Background In situ magnetic separation (ISMS) has emerged as a powerful tool to overcome process constraints such as product degradation or inhibition of target production. In the present work, an integrated ISMS process was established for the production of his-tagged single chain fragment variable (scFv) D1.3 antibodies (“D1.3”) produced by E. coli in complex media. This study investigates the impact of ISMS on the overall product yield as well as its biocompatibility with the bioprocess when metal-chelate and triazine-functionalized magnetic beads were used. Results Both particle systems are well suited for separation of D1.3 during cultivation. While the triazine beads did not negatively impact the bioprocess, the application of metal-chelate particles caused leakage of divalent copper ions in the medium. After the ISMS step, elevated copper concentrations above 120 mg/L in the medium negatively influenced D1.3 production. Due to the stable nature of the model protein scFv D1.3 in the biosuspension, the application of ISMS could not increase the overall D1.3 yield as was shown by simulation and experiments. Conclusions We could demonstrate that triazine-functionalized beads are a suitable low-cost alternative to selectively adsorb D1.3 fragments, and measured maximum loads of 0.08 g D1.3 per g of beads. Although copper-loaded metal-chelate beads did adsorb his-tagged D1.3 well during cultivation, this particle system must be optimized by minimizing metal leakage from the beads in order to avoid negative inhibitory effects on growth of the microorganisms and target production. Hereby, other types of metal chelate complexes should be tested to demonstrate biocompatibility. Such optimized particle systems can be regarded as ISMS platform technology, especially for the production of antibodies and their fragments with low stability in the medium. The proposed model can be applied to design future ISMS experiments in order to maximize the overall product yield while the amount of particles being used is minimized as well as the number of required ISMS steps. PMID:23688064

Spacecraft optical disk recorder memory buffer control

NASA Technical Reports Server (NTRS)

Hodson, Robert F.

1993-01-01

This paper discusses the research completed under the NASA-ASEE summer faculty fellowship program. The project involves development of an Application Specific Integrated Circuit (ASIC) to be used as a Memory Buffer Controller (MBC) in the Spacecraft Optical Disk System (SODR). The SODR system has demanding capacity and data rate specifications requiring specialized electronics to meet processing demands. The system is being designed to support Gigabit transfer rates with Terabit storage capability. The complete SODR system is designed to exceed the capability of all existing mass storage systems today. The ASIC development for SODR consist of developing a 144 pin CMOS device to perform format conversion and data buffering. The final simulations of the MBC were completed during this summer's NASA-ASEE fellowship along with design preparations for fabrication to be performed by an ASIC manufacturer.

Impact of educational programme regarding chelation therapy on the quality of life for B-thalassemia major children.

PubMed

Abu Samra, Omayma; Auda, Wafaa; Kamhawy, Heba; Al-Tonbary, Youssef

2015-06-01

Objectives Thalassemia is the most common genetic disorder in Egypt, with an estimated carrier rate of 9-10%. It is a genetic blood disorder which can be fatal if proper chelation is not received. The introduction of chelating agents capable of removing excessive iron from the body has dramatically increased life expectancy and improved the overall quality of life. The aim of this study was to assess the impact of educational programmes regarding chelation therapy on the quality of life of thalassemic children. Methods The study was carried out at the Mansoura University Children's Hospital in the period between March 2010 and May 2011. It included 173 B-thalassemia children (84 boys and 89 girls) with age ranging between 8-18 years. The researcher used a predesigned interviewing questionnaire to collect data regarding children's knowledge about thalassemia and its management, especially regarding chelation therapy. The paediatric quality-of-life inventory tool (Peds QL 4.0 generic core) was also used to assess the studied children's quality of life. Results There was a significant statistical difference of the studied children's knowledge regarding chelation therapy and their quality of life. Conclusion There was a positive effect of the educational programme in improving children's knowledge score and their quality of life. Application of educational programmes for thalassemic children and their nurses regarding chelation therapy and its importance in preventing thalassemia complications is established.

A 128K-bit CCD buffer memory system

NASA Technical Reports Server (NTRS)

Siemens, K. H.; Wallace, R. W.; Robinson, C. R.

1976-01-01

A prototype system was implemented to demonstrate that CCD's can be applied advantageously to the problem of low power digital storage and particularly to the problem of interfacing widely varying data rates. 8K-bit CCD shift register memories were used to construct a feasibility model 128K-bit buffer memory system. Peak power dissipation during a data transfer is less than 7 W., while idle power is approximately 5.4 W. The system features automatic data input synchronization with the recirculating CCD memory block start address. Descriptions are provided of both the buffer memory system and a custom tester that was used to exercise the memory. The testing procedures and testing results are discussed. Suggestions are provided for further development with regards to the utilization of advanced versions of CCD memory devices to both simplified and expanded memory system applications.

Estimation of Separation Buffers for Wind-Prediction Error in an Airborne Separation Assistance System

NASA Technical Reports Server (NTRS)

Consiglio, Maria C.; Hoadley, Sherwood T.; Allen, B. Danette

2009-01-01

Wind prediction errors are known to affect the performance of automated air traffic management tools that rely on aircraft trajectory predictions. In particular, automated separation assurance tools, planned as part of the NextGen concept of operations, must be designed to account and compensate for the impact of wind prediction errors and other system uncertainties. In this paper we describe a high fidelity batch simulation study designed to estimate the separation distance required to compensate for the effects of wind-prediction errors throughout increasing traffic density on an airborne separation assistance system. These experimental runs are part of the Safety Performance of Airborne Separation experiment suite that examines the safety implications of prediction errors and system uncertainties on airborne separation assurance systems. In this experiment, wind-prediction errors were varied between zero and forty knots while traffic density was increased several times current traffic levels. In order to accurately measure the full unmitigated impact of wind-prediction errors, no uncertainty buffers were added to the separation minima. The goal of the study was to measure the impact of wind-prediction errors in order to estimate the additional separation buffers necessary to preserve separation and to provide a baseline for future analyses. Buffer estimations from this study will be used and verified in upcoming safety evaluation experiments under similar simulation conditions. Results suggest that the strategic airborne separation functions exercised in this experiment can sustain wind prediction errors up to 40kts at current day air traffic density with no additional separation distance buffer and at eight times the current day with no more than a 60% increase in separation distance buffer.

VIRTUAL FRAME BUFFER INTERFACE

NASA Technical Reports Server (NTRS)

Wolfe, T. L.

1994-01-01

Large image processing systems use multiple frame buffers with differing architectures and vendor supplied user interfaces. This variety of architectures and interfaces creates software development, maintenance, and portability problems for application programs. The Virtual Frame Buffer Interface program makes all frame buffers appear as a generic frame buffer with a specified set of characteristics, allowing programmers to write code which will run unmodified on all supported hardware. The Virtual Frame Buffer Interface converts generic commands to actual device commands. The virtual frame buffer consists of a definition of capabilities and FORTRAN subroutines that are called by application programs. The virtual frame buffer routines may be treated as subroutines, logical functions, or integer functions by the application program. Routines are included that allocate and manage hardware resources such as frame buffers, monitors, video switches, trackballs, tablets and joysticks; access image memory planes; and perform alphanumeric font or text generation. The subroutines for the various "real" frame buffers are in separate VAX/VMS shared libraries allowing modification, correction or enhancement of the virtual interface without affecting application programs. The Virtual Frame Buffer Interface program was developed in FORTRAN 77 for a DEC VAX 11/780 or a DEC VAX 11/750 under VMS 4.X. It supports ADAGE IK3000, DEANZA IP8500, Low Resolution RAMTEK 9460, and High Resolution RAMTEK 9460 Frame Buffers. It has a central memory requirement of approximately 150K. This program was developed in 1985.

The effects of biological buffers TRIS, TAPS, TES on the stability of lysozyme.

PubMed

Pannuru, Pavani; Rani, Anjeeta; Venkatesu, Pannuru; Lee, Ming-Jer

2018-06-01

To explore the mechanism of lysozyme stabilization in buffer system, we have investigated the interactions between lysozyme and the biological buffers (TRIS, TAPS, and TES) using spectroscopic techniques, including ultraviolet-visible (UV-Vis), fluorescence, thermal fluorescence, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) spectroscopy. From the series of spectroscopic studies, it is found that the native structure of the protein remains intact in the different concentrations (0.05, 0.1, 0.25, 0.5, and 1.0M) of the biological buffer aqueous solutions at pH7.0. Moreover, all these three investigated buffers are able to protect lysozyme against thermal denaturation, particularly in high concentration (1.0M) of the buffer aqueous solutions. Copyright © 2018 Elsevier B.V. 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.

Mitigation of Cd accumulation in paddy rice (Oryza sativa L.) by Fe fertilization.

PubMed

Chen, Zhe; Tang, Ye-Tao; Yao, Ai-Jun; Cao, Jian; Wu, Zhuo-Hao; Peng, Zhe-Ran; Wang, Shi-Zhong; Xiao, Shi; Baker, Alan J M; Qiu, Rong-Liang

2017-12-01

Cadmium uptake in rice is believed to be mediated by the Fe transport system. Phyto-available Cd can be changed by Fe fertilization of substrates. This work investigated whether and how Fe fertilization affects mitigation of Cd accumulation in paddy rice. A 90-d soil column experiment was conducted to study the change of Cd and Fe availability in soil after Fe fertilization (ionic and chelated Fe). A low-Cd accumulating cultivar (TY116) and a high-Cd accumulating cultivar (JY841) were grown in two Cd-polluted paddy soils amended with chelated Fe fertilizers. Additionally, both cultivars were grown in hydroponics to compare Fe-related gene expression in EDDHAFe-deficient and EDDHAFe-sufficient roots. The column experiment showed that EDTANa 2 Fe(II) and EDDHAFe(III) fertilization had a better mitigation effect on soil Cd availability compared to FeSO 4 ·7H 2 O. Moreover, the field experiment demonstrated that these two chelated fertilizations could reduce Cd concentrations in brown rice by up to 80%. Iron concentrations in the brown rice were elevated by Fe chelates. Compared to EDDHAFe(III), EDTANa 2 Fe(II) fertilization had a stronger mitigation effect by generating more EDTANa 2 Cd(II) in the soil solution to decrease phyto-available Cd in the soil. While EDDHAFe(III) fertilization could increase soil pH and decrease soil Eh which contributed to decreasing phyto-available Cd in a contaminated soil. In the hydroponic experiment, Fe sufficiency significantly reduced Cd concentrations in above-ground organs. In some cases, the expression of OsIRT1, OsNRAMP1 and OsNRAMP5 was inhibited under Fe sufficiency relative to Fe deficiency conditions. These results suggest that mitigation of rice Cd by Fe chelate fertilization results from a decrease in available Cd in substrates and the inhibition of the expression of several Fe-related genes in the IRT and NRAMP families. Copyright © 2017 Elsevier Ltd. All rights reserved.

Superstatistical Energy Distributions of an Ion in an Ultracold Buffer Gas

NASA Astrophysics Data System (ADS)

Rouse, I.; Willitsch, S.

2017-04-01

An ion in a radio frequency ion trap interacting with a buffer gas of ultracold neutral atoms is a driven dynamical system which has been found to develop a nonthermal energy distribution with a power law tail. The exact analytical form of this distribution is unknown, but has often been represented empirically by q -exponential (Tsallis) functions. Based on the concepts of superstatistics, we introduce a framework for the statistical mechanics of an ion trapped in an rf field subject to collisions with a buffer gas. We derive analytic ion secular energy distributions from first principles both neglecting and including the effects of the thermal energy of the buffer gas. For a buffer gas with a finite temperature, we prove that Tsallis statistics emerges from the combination of a constant heating term and multiplicative energy fluctuations. We show that the resulting distributions essentially depend on experimentally controllable parameters paving the way for an accurate control of the statistical properties of ion-atom hybrid systems.

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.

Dynamic Modeling of ALS Systems

NASA Technical Reports Server (NTRS)

Jones, Harry

2002-01-01

The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design. All life support systems exhibit behavior that varies over time. ALS systems must respond to equipment operating cycles, repair schedules, and occasional off-nominal behavior or malfunctions. Biological components, such as bioreactors, composters, and food plant growth chambers, usually have operating cycles or other complex time behavior. Buffer sizes, material stocks, and resupply rates determine dynamic system behavior and directly affect system mass and cost. Dynamic simulation is needed to avoid the extremes of costly over-design of buffers and material reserves or system failure due to insufficient buffers and lack of stored material.

Quality of life, clinical effectiveness, and satisfaction in patients with beta thalassemia major and sickle cell anemia receiving deferasirox chelation therapy.

PubMed

Senol, Sefika Pinar; Tiftik, Eyup Naci; Unal, Selma; Akdeniz, Aydan; Tasdelen, Bahar; Tunctan, Bahar

2016-03-01

There is a need to remove excess iron with iron chelation therapy (ICT) to avoid the serious clinical sequelae associated with iron overload in patients with beta thalassemia major (BTM) and sickle cell anemia (SCA). Due to the effects of the diseases and their treatments, ICT is still a major reason for unsatisfactory compliance. The aim of this single-center observational study was to evaluate the quality of life, clinical effectiveness, and satisfaction in pediatric and adult patients with BTM and SCA receiving deferasirox (DFX) chelation therapy. In this study, 37 pediatric and 35 adult patients with BTM or SCA receiving DFX for at least 6 months participated. Upon receipt of Informed Consent Form, Case Report Form, Demographic Data Collection Form, Child Health Questionnaire-Parent Form, Life Quality Survey Short Form-36, and ICT Satisfaction Survey were used to obtain data for the effectiveness of ICT and parameters that may affect compliance to treatment and life quality of the participants. As a main index for the effectiveness of DFX chelation therapy, serum ferritin levels were higher than the normal values in the patients receiving DFX. The increased ferritin levels were also associated with hematological and biochemical abnormalities. Our findings regarding quality of life and satisfaction with DFX chelation therapy indicated that the patients with BTM or SCA had lower scores. Overall, problems with treatment regimen and side effects appeared to be common causes of poor compliance to DFX chelation therapy. Our findings suggest that health care providers should be aware of the importance of monitoring iron load with timely initiation of DFX chelation therapy and ongoing adjustments to chelation regimens and/or transfusion methods to decrease hospitalizations and improve compliance to ICT of the patients with BTM and SCA.

Chelate assisted phytoextraction of heavy metals from soil. Effect, mechanism, toxicity, and fate of chelating agents.

PubMed

Evangelou, Michael W H; Ebel, Mathias; Schaeffer, Andreas

2007-06-01

The low-cost, plant-based phytoextraction technique has often been described as a promising technique to remediate heavy metal contaminated agricultural land. The application of chelating agents has shown positive effects in increasing the solubility of heavy metals in soil and therefore in enhancing phytoextraction. This paper gives an overview of the chelating agents applied in recent studies. Various synthetic aminopolycarboxylic acids, such as ethylene diamine tetraacetic acid, and natural ones such as, ethylene diamine disuccinate and nitrilotriacetic acid, are described. Additionally, results of the application of natural low molecular weight organic acids, such as citric and tartaric acid are given. The effectiveness of these different chelating agents varies according to the plant and the heavy metals used. Furthermore, a focus is laid on the chelating agents fate after application and on its toxicity to plants and soil microorganisms, as well as it degradation. The rate of degradation is of great importance for the future of chelate assisted phytoextraction as it has a direct impact on the leaching probability. An effective prevention of leaching will be crucial for the acceptance and the economic breakthrough of enhanced phytoextraction, but a satisfactory solution to this key issue has so far not been found. Possibly further experiments in the field of enhanced phytoextraction will be able to solve this major problem, but over decades various greenhouse experiments and recently field experiments have resulted in different observations. Therefore, it is questionable if further research in this direction will lead to a promising solution. Phytoextraction has possibly reached a turning point in which it should distance itself from chelate assisted phytoextraction and focus on alternative options.

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.

Charge-Neutral Constant pH Molecular Dynamics Simulations Using a Parsimonious Proton Buffer.

PubMed

Donnini, Serena; Ullmann, R Thomas; Groenhof, Gerrit; Grubmüller, Helmut

2016-03-08

In constant pH molecular dynamics simulations, the protonation states of titratable sites can respond to changes of the pH and of their electrostatic environment. Consequently, the number of protons bound to the biomolecule, and therefore the overall charge of the system, fluctuates during the simulation. To avoid artifacts associated with a non-neutral simulation system, we introduce an approach to maintain neutrality of the simulation box in constant pH molecular dynamics simulations, while maintaining an accurate description of all protonation fluctuations. Specifically, we introduce a proton buffer that, like a buffer in experiment, can exchange protons with the biomolecule enabling its charge to fluctuate. To keep the total charge of the system constant, the uptake and release of protons by the buffer are coupled to the titration of the biomolecule with a constraint. We find that, because the fluctuation of the total charge (number of protons) of a typical biomolecule is much smaller than the number of titratable sites of the biomolecule, the number of buffer sites required to maintain overall charge neutrality without compromising the charge fluctuations of the biomolecule, is typically much smaller than the number of titratable sites, implying markedly enhanced simulation and sampling efficiency.

Quasi-aromatic Möbius Metal Chelates.

PubMed

Mahmoudi, Ghodrat; Afkhami, Farhad A; Castiñeiras, Alfonso; García-Santos, Isabel; Gurbanov, Atash; Zubkov, Fedor I; Mitoraj, Mariusz P; Kukułka, Mercedes; Sagan, Filip; Szczepanik, Dariusz W; Konyaeva, Irina A; Safin, Damir A

2018-04-16

We report the design as well as structural and spectroscopic characterizations of two new coordination compounds obtained from Cd(NO 3 ) 2 ·4H 2 O and polydentate ligands, benzilbis(pyridin-2-yl)methylidenehydrazone (L I ) and benzilbis(acetylpyridin-2-yl)methylidenehydrazone (L II ), in a mixture with two equivalents of NH 4 NCS in MeOH, namely [Cd(SCN)(NCS)(L I )(MeOH)] (1) and [Cd(NCS) 2 (L II )(MeOH)] (2). Both L I and L II are bound via two pyridyl-imine units yielding a tetradentate coordination mode giving rise to the 12 π electron chelate ring. It has been determined for the first time (qualitatively and quantitatively), using the EDDB electron population-based method, the HOMA index, and the ETS-NOCV charge and energy decomposition scheme, that the chelate ring containing Cd II can be classified as a quasi-aromatic Möbius motif. Notably, using the methyl-containing ligand L II controls the exclusive presence of the NCS - connected with the Cd II atom (structure 2), while applying L I allows us to simultaneously coordinate NCS - and SCN - ligands (structure 1). Both systems are stabilized mostly by hydrogen bonding, C-H···π interactions, aromatic π···π stacking, and dihydrogen C-H···H-C bonds. The optical properties have been investigated by diffused reflectance spectroscopy as well as molecular and periodic DFT/TD-DFT calculations. The DFT-based ETS-NOCV analysis as well as periodic calculations led us to conclude that the monomers which constitute the obtained chelates are extremely strongly bonded to each other, and the calculated interaction energies are found to be in the regime of strong covalent connections. Intramolecular van der Waals dispersion forces, due to the large size of L I and L II , appeared to significantly stabilize these systems as well as amplify the aromaticity phenomenon.

Computer simulation of two electrophoretic columns coupled for isoelectric focusing in simple buffers

NASA Technical Reports Server (NTRS)

Tsai, Amos; Mosher, Richard A.; Bier, Milan

1986-01-01

Computer simulation is used to analyze a system of two electrophoretic columns coupled by mixing the anolyte of one with the catholyte of the other. A mathematical model is presented which is used to predict the pH gradients formed by monovalent buffers in this system, when the currents in the columns are unequal. In the column with the higher current a pH gradient is created which increases from anode to cathode and is potentially useful for isoelectric focusing. The breadth of this gradient is dependent upon the ratio of the currents. The function of the second column is the compensation of buffer migration which occurs in the first column, thereby maintaining constant electrolyte composition. The effects of buffer pKs and mobilities are evaluated.

Retinal abnormalities in β-thalassemia major.

PubMed

Bhoiwala, Devang L; Dunaief, Joshua L

2016-01-01

Patients with beta (β)-thalassemia (β-TM: β-thalassemia major, β-TI: β-thalassemia intermedia) have a variety of complications that may affect all organs, including the eye. Ocular abnormalities include retinal pigment epithelial degeneration, angioid streaks, venous tortuosity, night blindness, visual field defects, decreased visual acuity, color vision abnormalities, and acute visual loss. Patients with β-thalassemia major are transfusion dependent and require iron chelation therapy to survive. Retinal degeneration may result from either retinal iron accumulation from transfusion-induced iron overload or retinal toxicity induced by iron chelation therapy. Some who were never treated with iron chelation therapy exhibited retinopathy, and others receiving iron chelation therapy had chelator-induced retinopathy. We will focus on retinal abnormalities present in individuals with β-thalassemia major viewed in light of new findings on the mechanisms and manifestations of retinal iron toxicity. Copyright © 2016 Elsevier Inc. All rights reserved.

Extraction of metals and/or metalloids from acidic media using supercritical fluids and salts

DOEpatents

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

1998-06-23

A method is described for extracting metalloid and metal species from a solid or liquid material by exposing the material to a fluid solvent, particularly supercritical carbon dioxide, containing a chelating agent. The chelating agent forms chelates that are soluble in the fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent comprises a trialkyl phosphate, a triaryl phosphate, a trialkylphosphine oxide, a triarylphosphine oxide, or mixtures thereof. The method provides an environmentally benign process for removing contaminants from industrial waste. The method is particularly useful for extracting actinides from acidic solutions, and the process can be aided by the addition of nitrate salts. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process. 7 figs.

Bifunctional chelating agent for the design and development of site specific radiopharmaceuticals and biomolecule conjugation strategy

DOEpatents

Katti, Kattesh V.; Prabhu, Kandikere R.; Gali, Hariprasad; Pillarsetty, Nagavara Kishore; Volkert, Wynn A.

2003-10-21

There is provided a method of labeling a biomolecule with a transition metal or radiometal in a site specific manner to produce a diagnostic or therapeutic pharmaceutical compound by synthesizing a P.sub.2 N.sub.2 -bifunctional chelating agent intermediate, complexing the intermediate with a radio metal or a transition metal, and covalently linking the resulting metal-complexed bifunctional chelating agent with a biomolecule in a site specific manner. Also provided is a method of synthesizing the --PR.sub.2 containing biomolecules by synthesizing a P.sub.2 N.sub.2 -bifunctional chelating agent intermediate, complexing the intermediate with a radiometal or a transition metal, and covalently linking the resulting radio metal-complexed bifunctional chelating agent with a biomolecule in a site specific manner. There is provided a therapeutic or diagnostic agent comprising a --PR.sub.2 containing biomolecule.

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.

Combination of a Copper-Ion Selective Electrode and Fluorometric Titration for the Determination of Copper(II) Ion Conditional Stability Constants of Humic Substances.

PubMed

Chen, Juan; Chen, Hao; Zhang, Xing-wen; Lei, Kun; Kenny, Jonathan E

2015-11-01

A fluorescence quenching model using copper(II) ion (Cu(2+)) ion selective electrode (Cu-ISE) is developed. It uses parallel factor analysis (PARAFAC) to model fluorescence excitation-emission matrices (EEMs) of humic acid (HA) samples titrated with Cu(2+) to resolve fluorescence response of fluorescent components to Cu(2+) titration. Meanwhile, Cu-ISE is employed to monitor free Cu(2+) concentration ([Cu]) at each titration step. The fluorescence response of each component is fit individually to a nonlinear function of [Cu] to find the Cu(2+) conditional stability constant for that component. This approach differs from other fluorescence quenching models, including the most up-to-date multi-response model that has a problematic assumption on Cu(2+) speciation, i.e., an assumption that total Cu(2+) present in samples is a sum of [Cu] and those bound by fluorescent components without taking into consideration the contribution of non-fluorescent organic ligands and inorganic ligands to speciation of Cu(2+). This paper employs the new approach to investigate Cu(2+) binding by Pahokee peat HA (PPHA) at pH values of 6.0, 7.0, and 8.0 buffered by phosphate or without buffer. Two fluorescent components (C1 and C2) were identified by PARAFAC. For the new quenching model, the conditional stability constants (logK1 and logK2) of the two components all increased with increasing pH. In buffered solutions, the new quenching model reported logK1 = 7.11, 7.89, 8.04 for C1 and logK2 = 7.04, 7.64, 8.11 for C2 at pH 6.0, 7.0, and 8.0, respectively, nearly two log units higher than the results of the multi-response model. Without buffer, logK1 and logK2 decreased but were still high (>7) at pH 8.0 (logK1 = 7.54, logK2 = 7.95), and all the values were at least 0.5 log unit higher than those (4.83 ~ 5.55) of the multi-response model. These observations indicate that the new quenching model is more intrinsically sensitive than the multi-response model in revealing strong fluorescent binding sites of PPHA in different experimental conditions. The new model was validated by testing it with a mixture of two fluorescing Cu(2+) chelating organic compounds, i.e., l-tryptophan and salicylic acid mixed with one non-fluorescent binding compound oxalic acid titrated with Cu(2+) at pH 5.0.

Stability of buffer-free freeze-dried formulations: A feasibility study of a monoclonal antibody at high protein concentrations.

PubMed

Garidel, Patrick; Pevestorf, Benjamin; Bahrenburg, Sven

2015-11-01

We studied the stability of freeze-dried therapeutic protein formulations over a range of initial concentrations (from 40 to 160 mg/mL) and employed a variety of formulation strategies (including buffer-free freeze dried formulations, or BF-FDF). Highly concentrated, buffer-free liquid formulations of therapeutic monoclonal antibodies (mAbs) have been shown to be a viable alternative to conventionally buffered preparations. We considered whether it is feasible to use the buffer-free strategy in freeze-dried formulations, as an answer to some of the known drawbacks of conventional buffers. We therefore conducted an accelerated stability study (24 weeks at 40 °C) to assess the feasibility of stabilizing freeze-dried formulations without "classical" buffer components. Factors monitored included pH stability, protein integrity, and protein aggregation. Because the protein solutions are inherently self-buffering, and the system's buffer capacity scales with protein concentration, we included highly concentrated buffer-free freeze-dried formulations in the study. The tested formulations ranged from "fully formulated" (containing both conventional buffer and disaccharide stabilizers) to "buffer-free" (including formulations with only disaccharide lyoprotectant stabilizers) to "excipient-free" (with neither added buffers nor stabilizers). We evaluated the impacts of varying concentrations, buffering schemes, pHs, and lyoprotectant additives. At the end of 24 weeks, no change in pH was observed in any of the buffer-free formulations. Unbuffered formulations were found to have shorter reconstitution times and lower opalescence than buffered formulations. Protein stability was assessed by visual inspection, sub-visible particle analysis, protein monomer content, charge variants analysis, and hydrophobic interaction chromatography. All of these measures found the stability of buffer-free formulations that included a disaccharide stabilizer comparable to buffer-based formulations, especially at protein concentrations up to and including 115 mg/mL. Copyright © 2015 Elsevier B.V. All rights reserved.

The effect of extracellular weak acids and bases on the intracellular buffering power of snail neurones.

PubMed Central

Szatkowski, M S

1989-01-01

1. Intracellular pH (pHi) was measured in snail neurones using pH-sensitive glass microelectrodes. The influence of externally applied weak acids and bases on the total intracellular buffering power (beta T) was investigated by monitoring the pHi changes caused by the intracellular ionophoretic injection of HCl. 2. In the absence of weak acids or bases a reduction in the extracellular HEPES concentration had no effect on pHi or on beta T. It did, however, reduce slightly the rate of pHi recovery following HCl injection. 3. The presence of CO2 greatly increased beta T. However, as predicted for an open buffer system, the contributions to intracellular buffering by CO2 (beta CO2) decreased as pHi decreased. 4. When added to the superfusate, procaine, 4-aminopyridine, trimethylamine and NH4Cl (1-10 mM) all increased steady-state pHi. Procaine was fastest at increasing pHi and 4-aminopyridine the slowest. All four of these weak bases increased beta T. 5. The intracellular buffering action by these weak bases varied. HCl injection in the presence of procaine usually resulted in steady-state pHi changes with no pHi transients. In the presence of the other three weak bases HCl injections resulted in intracellular acidifications which were followed by pHi recovery-like transients. However, these were not blocked by SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid) or by CaCl2 and I thus conclude that these transients were as a result of slow or incomplete intracellular buffering by the weak bases. 6. In many cells there was a good correlation between the measured contributions to intracellular buffering by the weak bases (beta base) and those predicted assuming a simple two-compartment open system. In all cases, as predicted, beta base increased as pHi decreased. 7. I found a clear relationship between the concentration of external buffer (HEPES) and the rate at which weak bases, applied to the superfusate, were able to increase pHi. The greater the extracellular buffer concentration the greater was the speed of intracellular alkalinization. 8. Lowering the extracellular buffer concentration reduced the efficiency of intracellular buffering by weak bases in response to an intracellular acid load. HCl injection in the presence of weak base caused a larger initial intracellular acidification if the extracellular HEPES concentration was reduced. 9. In conclusion, both weak acids and weak bases can make very large, pHi-dependent contributions to intracellular buffering by way of open buffer systems.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2555474

Complexation of buffer constituents with neutral complexation agents: part I. Impact on common buffer properties.

PubMed

Riesová, Martina; Svobodová, Jana; Tošner, Zdeněk; Beneš, Martin; Tesařová, Eva; Gaš, Bohuslav

2013-09-17

The complexation of buffer constituents with the complexation agent present in the solution can very significantly influence the buffer properties, such as pH, ionic strength, or conductivity. These parameters are often crucial for selection of the separation conditions in capillary electrophoresis or high-pressure liquid chromatography (HPLC) and can significantly affect results of separation, particularly for capillary electrophoresis as shown in Part II of this paper series (Beneš, M.; Riesová, M.; Svobodová, J.; Tesařová, E.; Dubský, P.; Gaš, B. Anal. Chem. 2013, DOI: 10.1021/ac401381d). In this paper, the impact of complexation of buffer constituents with a neutral complexation agent is demonstrated theoretically as well as experimentally for the model buffer system composed of benzoic acid/LiOH or common buffers (e.g., CHES/LiOH, TAPS/LiOH, Tricine/LiOH, MOPS/LiOH, MES/LiOH, and acetic acid/LiOH). Cyclodextrins as common chiral selectors were used as model complexation agents. We were not only able to demonstrate substantial changes of pH but also to predict the general complexation characteristics of selected compounds. Because of the zwitterion character of the common buffer constituents, their charged forms complex stronger with cyclodextrins than the neutral ones do. This was fully proven by NMR measurements. Additionally complexation constants of both forms of selected compounds were determined by NMR and affinity capillary electrophoresis with a very good agreement of obtained values. These data were advantageously used for the theoretical descriptions of variations in pH, depending on the composition and concentration of the buffer. Theoretical predictions were shown to be a useful tool for deriving some general rules and laws for complexing systems.

Parallel processor-based raster graphics system architecture

DOEpatents

Littlefield, Richard J.

1990-01-01

An apparatus for generating raster graphics images from the graphics command stream includes a plurality of graphics processors connected in parallel, each adapted to receive any part of the graphics command stream for processing the command stream part into pixel data. The apparatus also includes a frame buffer for mapping the pixel data to pixel locations and an interconnection network for interconnecting the graphics processors to the frame buffer. Through the interconnection network, each graphics processor may access any part of the frame buffer concurrently with another graphics processor accessing any other part of the frame buffer. The plurality of graphics processors can thereby transmit concurrently pixel data to pixel locations in the frame buffer.

21 CFR 176.150 - Chelating agents used in the manufacture of paper and paperboard.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Chelating agents used in the manufacture of paper... Chelating agents used in the manufacture of paper and paperboard. The substances named in paragraph (a) of this section may be safely used in the manufacture of paper and paperboard, in accordance with the...

Use of Magnetic Resonance Imaging to Monitor Iron Overload

PubMed Central

Wood, John C.

2014-01-01

SYNOPSIS Treatment of iron overload requires robust estimates of total body iron burden and its response to iron chelation therapy. Compliance with chelation therapy varies considerably among patients and individual reporting is notoriously unreliable. Even with perfect compliance, intersubject variability in chelator effectiveness is extremely high, necessitating reliable iron estimates to guide dose titration. In addition, each chelator has a unique profile with respect to clearing iron stores from different organs. This chapter will present the tools available to clinicians monitoring their patients, focusing on non-invasive magnetic resonance imaging methods because they have become the de-facto standard of care. PMID:25064711

Combined chelation based on glycosyl-mono- and bis-hydroxypyridinones for aluminium mobilization: solution and biodistribution studies.

PubMed

Chaves, Sílvia; Dron, Paul I; Danalache, Florina A; Sacoto, Diana; Gano, Lurdes; Santos, M Amélia

2009-11-01

Taking into account the recognized interest of a poly-pharmacological strategy in chelation therapy, a study of aluminium combined chelation based on 3-hydroxy-4-pyridinone (3,4-HP) compounds with complementary properties, associated to different denticity, size and extrafunctionality, is presented herein. In particular, Al-chelation has been explored, using a tetradentate IDA bis-(3,4-HP) ligand, L, and two N-glycosyl mono-(3,4-HP) derivatives (A or B). Combined complexation studies with the tetradentate and the most promising bidentate ligand (A) evidenced the formation of ternary complexes with high thermodynamic stability (Al-L-A) being the predominant species at physiological pH. In vivo studies on the ability for radiotracer ((67)Ga) removal from loaded mice, as a model of aluminium accumulation in body, have shown that the simultaneous administration to (67)Ga-loaded mice of a mono- and a bis-(3,4-HP) chelator (e.g. A and L) leads to a rapid metal elimination from main organs and whole animal model. This may be rationalized by coadjuvation and eventual synergistic effects, due to complementary accessibility of the chelators to different cellular compartments.

Chelation: A Fundamental Mechanism of Action of AGE Inhibitors, AGE Breakers, and Other Inhibitors of Diabetes Complications

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

Nagai, Rhoji; Murray, David B.; Metz, Thomas O.

2012-03-01

Advanced glycation or glycoxidation end-products (AGE) increase in tissue proteins with age, and their rate of accumulation is increased in diabetes, nephropathy and inflammatory diseases. AGE inhibitors include a range of compounds that are proposed to act by trapping carbonyl and dicarbonyl intermediates in AGE formation. However, some among the newer generation of AGE inhibitors lack reactive functional groups that would trap reaction intermediates, indicating an alternative mechanism of action. We propose that AGE inhibitors function primarily as chelators, inhibiting metal-catalyzed oxidation reactions. The AGE-inhibitory activity of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers is also consistent with their chelatingmore » activity. Finally, compounds described as AGE breakers, or their hydrolysis products, also have strong chelating activity, suggesting that these compounds also act through their chelating activity. We conclude that chelation is the common, and perhaps the primary, mechanism of action of AGE inhibitors and breakers, and that chronic, mild chelation therapy should prove useful in treatment of diabetes and age-related diseases characterized by oxidative stress, inflammation and increased chemical modification of tissue proteins by advanced glycoxidation and lipoxidation end-products.« less

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

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.

Synthesis of Two New Group 13 Benzoato-Chloro Complexes: A Structural Study of Gallium and Indium Chelating Carboxylates

NASA Technical Reports Server (NTRS)

Duraj, Stan A.; Hepp, Aloysius F.; Woloszynek, Robert; Protasiewicz, John D.; Dequeant, Michael; Ren, Tong

2010-01-01

Two new heteroleptic chelated-benzoato gallium (III) and indium (III) complexes have been prepared and structurally characterized. The molecular structures of [GaCl2(4-Mepy)2(O2CPh)]4-Mepy (1) and [InCl(4-Mepy)2(O2CPh)2]4-Mepy (2) have been determined by single-crystal x-ray diffraction. The gallium compound (1) is a distorted octahedron with cis-chloride ligands co-planar with the chelating benzoate and the 4-methylpyridines trans to each other. This is the first example of a Ga(III) structure with a chelating benzoate. The indium compound (2) is a distorted pentagonal bipyramid with two chelating benzoates, one 4-methylpyridine in the plane and a chloride trans to the other 4-methylpyridine. The indium bis-benzoate is an unusual example of a seven-coordinate structure with classical ligands. Both complexes, which due to the chelates, could also be described as pseudo-trigonal bipyramidal, include a three-bladed motif with three roughly parallel aromatic rings that along with a solvent of crystallization and electron-withdrawing chloride ligand(s) stabilize the solid-state structures.

Nanogels from Metal-Chelating Crosslinkers as Versatile Platforms Applied to Copper-64 PET Imaging of Tumors and Metastases

DOE PAGES

Lux, Jacques; White, Alexander G.; Chan, Minnie; ...

2015-01-01

Metals are essential in medicine for both therapy and diagnosis. We recently created the first metal-chelating nanogel imaging agent, which employed versatile, reproducible chemistry that maximizes chelation stability. Here we demonstrate that our metal chelating crosslinked nanogel technology is a powerful platform by incorporating 64Cu to obtain PET radiotracers. Polyacrylamide-based nanogels were crosslinked with three different polydentate ligands (DTPA, DOTA, NOTA). NOTA-based nanogels stably retained 64Cu in mouse serum and accumulated in tumors in vivo as detected by PET/CT imaging. Measurement of radioactivity in major organs ex vivo confirmed this pattern, revealing a high accumulation (12.3% ID/g and 16.6% ID/g)more » in tumors at 24 and 48 h following administration, with lower accumulation in the liver (8.5% ID/g at 24 h) and spleen (5.5% ID/g). Nanogels accumulated even more efficiently in metastases (29.9% and 30.4% ID/g at 24 and 48 h). These metal-chelating nanogels hold great promise for future application as bimodal PET/MRI agents; chelation of β-emitting radionuclides could enable radiation therapy.« less

Chelation therapy to prevent diabetes-associated cardiovascular events.

PubMed

Diaz, Denisse; Fonseca, Vivian; Aude, Yamil W; Lamas, Gervasio A

2018-05-24

For over 60 years, chelation therapy with disodium ethylene diamine tetraacetic acid (EDTA, edetate) had been used for the treatment of cardiovascular disease (CVD) despite lack of scientific evidence for efficacy and safety. The Trial to Assess Chelation Therapy (TACT) was developed and received funding from the National Institutes of Health (NIH) to ascertain the safety and efficacy of chelation therapy in patients with CVD. This pivotal trial demonstrated an improvement in outcomes in postmyocardial infarction (MI) patients. Interestingly, it also showed a particularly large reduction in CVD events and all-cause mortality in the prespecified subgroup of patients with diabetes. The TACT results may support the concept of metal chelation to reduce metal-catalyzed oxidation reactions that promote the formation of advanced glycation end products, a precursor of diabetic atherosclerosis. In this review, we summarize the epidemiological and basic evidence linking toxic metal accumulation and diabetes-related CVD, supported by the salutary effects of chelation in TACT. If the ongoing NIH-funded TACT2, in diabetic post-MI patients, proves positive, this unique therapy will enter the armamentarium of endocrinologists and cardiologists seeking to reduce the atherosclerotic risk of their diabetic patients.

In vitro and in vivo evaluation of potential aluminum chelators.

PubMed

Graff, L; Muller, G; Burnel, D

1995-10-01

The potential for aluminium (Al) chelation by different compounds was determined using 2 in vitro techniques. The formation of stable complexes with Al in an aqueous solution was evaluated using pulse polarography. This technique allowed the influence of temperature and calcium (Ca) to be studied for each compound. Certain compounds (EDDHA, HAES, citric acid and HBED) showed great chelation in the absence of Ca2+ at a temperature of 37 +/- 1 C. An ultrafiltration technique combined with Al determination by atomic emission spectroscopy allowed the efficiency of different substances to complex Al that were previously bound to serum proteins to be estimated. The kinetics of chelation and minimum efficient concentration have been determined for all products studied. EDDHA had chelation potential similar to DFO. The real efficacies of the compounds were studied in vivo to compare the effectiveness of repeated administrations of the best chelating agents (EDDHA, DFO, HAES and tartaric acid) on the distribution and excretion of Al after repeated i.p. administrations to rats. Intraperitoneal EDDHA significantly increased urinary metal (Al, Ca, Cu, Fe and Zn) excretion. These excretions may be correlated to a renal toxic potential property.

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.

64Cu-Labeled Repebody Molecules for Imaging of Epidermal Growth Factor Receptor-Expressing Tumors.

PubMed

Pyo, Ayoung; Yun, Misun; Kim, Hyeon Sik; Kim, Tae-Yoon; Lee, Joong-Jae; Kim, Jung Young; Lee, Sunwoo; Kwon, Seong Young; Bom, Hee-Seung; Kim, Hak-Sung; Kim, Dong-Yeon; Min, Jung-Joon

2018-02-01

The epidermal growth factor receptor (EGFR) is a member of the erbB family of receptors and is overexpressed in many tumor types. A repebody is a newly designed nonantibody protein scaffold for tumor targeting that contains leucine-rich repeat modules. In this study, 3 64 Cu-labeled anti-EGFR repebodies with different chelators were synthesized, and their biologic characteristics were assessed in cultured cells and tumor-bearing mice. Methods: Repebodies were synthesized with the chelators 2-( p -isothiocyanatobenzyl)-1,4,7-triazacyclononane- N,N',N,″- triacetic acid trihydrochloride ([ p -SCN-Bn]-NOTA), 2,2',2″-(10-(2-(2,5-dioxopyrrolidin-1-yloxy)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (DOTA- N -hydroxysuccinimide ester), or 1-( p -isothiocyanatobenzyl)diethylenetriamine pentaacetic acid trihydrochloride ([ p -SCN-Bn]-DTPA) in 1.0 M NaHCO 3 buffer (pH 9.2) for 24 h. Purified NOTA-, DOTA-, and DTPA-conjugated repebody were radiolabeled with 64 Cu in 0.1 M NH 4 OAc buffer (pH 5.5). To compare the EGFR-binding affinities of the repebodies, cellular uptake studies were performed with the human non-small cell lung cancer cell line H1650 (high expression of EGFR) and the human colon adenocarcinoma cell line SW620 (low expression of EGFR). Biodistribution and small-animal PET imaging studies were performed using H1650 tumor-bearing mice. Results: Radiochemical yields of the 64 Cu-labeled repebodies were approximately 70%-80%. Cellular uptake of the NOTA-, DOTA-, and DTPA-repebodies was over 4-fold higher in H1650 cells than in SW620 cells at 1 h. The 3 repebodies had accumulated specifically in H1650 tumor-bearing nude mice by 1 h after intravenous injection and were retained for over 24 h, as measured by the percentage injected dose per gram of tissue (%ID/g). Tumor uptake of all repebodies increased from 1 to 6 h (at 1 h, 6.28, 8.46, and 6.91 %ID/g for NOTA-, DOTA-, and DTPA-repebody, respectively; at 6 h, 9.4, 8.28, and 10.1 %ID/g, respectively). H1650 tumors were clearly visible after injection of each repebody, with high tumor-to-background ratios (at 1 h, 3.43, 4.89, and 2.38 for NOTA-, DOTA-, and DTPA-repebody, respectively; at 6 h, 3.05, 4.36, and 2.08; at 24 h, 3.81, 4.58, and 2.86). Conclusion: The 3 64 Cu-repebody complexes demonstrated specific and rapid uptake in EGFR-expressing tumors within 1 h and may have potential as novel EGFR imaging agents for PET. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Development of an On-Demand, Generic, Drug-Delivery System

DTIC Science & Technology

1985-08-06

systems Two systems were evaluated for CO2 evolution. The first of these was an enzymatic system based on urea and urease . The second system was based...PHM 84 Research pH Meter was used te monitor pH. Solutions of various buffer concen- trations and pHs were prepared for each buffer system. One urease ...Measurement of carbon dio~ide production was accomplished using the apparatus shown in Figure 2. Carbon dioxide was generated by putting a urease tablet in the

'Trophic whales' as biotic buffers: weak interactions stabilize ecosystems against nutrient enrichment.

PubMed

Schwarzmüller, Florian; Eisenhauer, Nico; Brose, Ulrich

2015-05-01

Human activities may compromise biodiversity if external stressors such as nutrient enrichment endanger overall network stability by inducing unstable dynamics. However, some ecosystems maintain relatively high diversity levels despite experiencing continuing disturbances. This indicates that some intrinsic properties prevent unstable dynamics and resulting extinctions. Identifying these 'ecosystem buffers' is crucial for our understanding of the stability of ecosystems and an important tool for environmental and conservation biologists. In this vein, weak interactions have been suggested as stabilizing elements of complex systems, but their relevance has rarely been tested experimentally. Here, using network and allometric theory, we present a novel concept for a priori identification of species that buffer against externally induced instability of increased population oscillations via weak interactions. We tested our model in a microcosm experiment using a soil food-web motif. Our results show that large-bodied species feeding at the food web's base, so called 'trophic whales', can buffer ecosystems against unstable dynamics induced by nutrient enrichment. Similar to the functionality of chemical or mechanical buffers, they serve as 'biotic buffers' that take up stressor effects and thus protect fragile systems from instability. We discuss trophic whales as common functional building blocks across ecosystems. Considering increasing stressor effects under anthropogenic global change, conservation of these network-intrinsic biotic buffers may help maintain the stability and diversity of natural ecosystems. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

Biophysical stability of hyFc fusion protein with regards to buffers and various excipients.

PubMed

Lim, Jun Yeul; Kim, Nam Ah; Lim, Dae Gon; Eun, Chang-yong; Choi, Donghoon; Jeong, Seong Hoon

2016-05-01

A novel non-cytolytic hybrid Fc (hyFc) with an intact Ig structure without any mutation in the hyFc region, was developed to construct a long-acting agonistic protein. The stability of interleukin-7 (IL-7) fused with the hyFc (GXN-04) was evaluated to develop early formulations. Various biophysical methods were utilized and three different buffer systems with various pH ranges were investigated including histidine-acetate, sodium citrate, and tris buffers. Various excipients were incorporated into the systems to obtain optimum protein stability. Two evident thermal transitions were observed with the unfolding of IL-7 and hyFc. The Tm and ΔH increased with pH, suggesting increased conformational stability. Increased Z-average size with PDI and decreased zeta potential with pH increase, with the exception of tris buffer, showed aggregation issues. Moreover, tris buffer at higher pH showed aggregation peaks from DLS. Non-ionic surfactants were effective against agitation by outcompeting protein molecules for hydrophobic surfaces. Sucrose and sorbitol accelerated protein aggregation during agitation, but exhibited a protective effect against oxidation, with preferential exclusion favoring the compact states of GXN-04. The stability of GXN-04 was varied by basal buffers and excipients, hence the buffers and excipients need to be evaluated carefully to achieve the maximum stability of proteins. Copyright © 2016 Elsevier B.V. All rights reserved.

Ironing out the role of the cyclin-dependent kinase inhibitor, p21 in cancer: Novel iron chelating agents to target p21 expression and activity.

PubMed

Moussa, Rayan S; Park, Kyung Chan; Kovacevic, Zaklina; Richardson, Des R

2018-03-20

Iron (Fe) has become an important target for the development of anti-cancer therapeutics with a number of Fe chelators entering human clinical trials for advanced and resistant cancer. An important aspect of the activity of these compounds is their multiple molecular targets, including those that play roles in arresting the cell cycle, such as the cyclin-dependent kinase inhibitor, p21. At present, the exact mechanism by which Fe chelators regulate p21 expression remains unclear. However, recent studies indicate the ability of chelators to up-regulate p21 at the mRNA level was dependent on the chelator and cell-type investigated. Analysis of the p21 promoter identified that the Sp1-3-binding site played a significant role in the activation of p21 transcription by Fe chelators. Furthermore, there was increased Sp1/ER-α and Sp1/c-Jun complex formation in melanoma cells, suggesting these complexes were involved in p21 promoter activation. Elucidating the mechanisms involved in the regulation of p21 expression in response to Fe chelator treatment in neoplastic cells will further clarify how these agents achieve their anti-tumor activity. It will also enhance our understanding of the complex roles p21 may play in neoplastic cells and lead to the development of more effective and specific anti-cancer therapies. Copyright © 2018 Elsevier Inc. All rights reserved.

Combinational chelation therapy abrogates lead-induced neurodegeneration in rats.

PubMed

Pachauri, Vidhu; Saxena, Geetu; Mehta, Ashish; Mishra, Deepshikha; Flora, Swaran J S

2009-10-15

Lead, a ubiquitous and potent neurotoxicant causes oxidative stress which leads to numerous neurobehavioral and physiological alterations. The ability of lead to bind sulfhydryl groups or compete with calcium could be one of the reasons for its debilitating effects. In the present study, we addressed: i) if chelation therapy could circumvent the altered oxidative stress and prevent neuronal apoptosis in chronic lead-intoxicated rats, ii) whether chelation therapy could reverse biochemical and behavioral changes, and iii) if mono or combinational therapy with captopril (an antioxidant) and thiol chelating agents (DMSA/MiADMSA) is more effective than individual thiol chelator in lead-exposed rats. Results indicated that lead caused a significant increase in reactive oxygen species, nitric oxide, and intracellular free calcium levels along with altered behavioral abnormalities in locomotor activity, exploratory behavior, learning, and memory that were supported by changes in neurotransmitter levels. A fall in membrane potential, release of cytochrome c, and DNA damage indicated mitochondrial-dependent apoptosis. Most of these alterations showed significant recovery following combined therapy with captopril with MiADMSA and to a smaller extend with captopril+DMSA over monotherapy with these chelators. It could be concluded from our present results that co-administration of a potent antioxidant (like captopril) might be a better treatment protocol than monotherapy to counter lead-induced oxidative stress. The major highlight of the work is an interesting experimental evidence of the efficacy of combinational therapy using an antioxidant with a thiol chelator in reversing neurological dystrophy caused due to chronic lead exposure in rats.

Preparation by enzymolysis and bioactivity of iron complex of fish protein hydrolysate (Fe-FPH) from low value fish

NASA Astrophysics Data System (ADS)

Deng, Shanggui; Huo, Jiancong; Xie, Chao

2008-08-01

Preparation of Fe2+ chelate of fish protein hydrolysate (Fe-FPH) obtained from low value fish proteins was introduced and its bioactivity was studied by compound enzymolysis. The optimum conditions for hydrolysate chelating Fe2+ are DH (degree of hydrolysis) at 5%, pH 7.0, 20°C and 15 min chelating time for FM (material not being defatted). Four types of Fe-FPH including CA (deposit after chelating), CB (deposit in 50% of absolute ethanol solution), CC (suspended deposit in 80% of absolute ethanol solution), and CD (bottom deposit in 80% of absolute ethanol solution) were fractionated with absolute ethanol from FM. Structural analysis through infra-red spectrum revealed that Fe2+ was combined strongly with amino-group and carboxyl-group in each chelate and each Fe2+ could form two five-member ring structures. All of the four chelates were shown more significant antioxidative activity and can be used as natural hydrophobic and hydrophilic antioxidant. Among all the chelates, the CB possesses the most effective antioxidative activity at 92% as high as that of a-tocopherol. Among all Fe-FPHs, only CD showed the most effective antibacterial activity against Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Bacillus subtilis and can be used as natural antibacterial. It provides a more effective way for utilization of low value fish proteins and key information of Fe-FPH as additive in food industry.

Recommendations for provoked challenge urine testing.

PubMed

Ruha, Anne-Michelle

2013-12-01

"Urine mobilization test," "challenge test," and "provoked urine test" are all terms used to describe the administration of a chelating agent to a person prior to collection of their urine to test for metals. There is no standard, validated challenge test. Despite recommendations by professional and government organizations against the use of provoked urine testing, the tests are still commonly used and recommended by some practitioners. Challenge testing utilizes a variety of chelating agents, including dimercaptosuccinic acid (DMSA), dimercaptopropanesulfonate (DMPS), and ethylenediaminetetraacetic acid (EDTA). The agents are given by a variety of routes of administration, doses used are inconsistent, and urine collection procedures vary. Additional problems with challenge tests include comparison of results to inappropriate reference ranges and creatinine correction of urine obtained within hours of chelator administration. Human volunteer studies demonstrate that mercury is detected in the urine of most people even in the absence of known exposure or chelator administration, and that urinary mercury excretion rises after administration of a chelator, regardless of exposure history and in an unpredictable fashion. Studies also demonstrate that challenge testing fails to reveal a "body burden" of mercury due to remote exposure. Chelating agents have been associated with adverse reactions. Current evidence does not support the use of DMPS, DMSA, or other chelation challenge tests for the diagnosis of metal toxicity. Since there are no established reference ranges for provoked urine samples in healthy subjects, no reliable evidence to support a diagnostic value for the tests, and potential harm, these tests should not be utilized.

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.

Genetic variability, individuality and the evolution of the mammalian brain.

PubMed

Lipp, H P

1995-12-01

The neo-Darwinian theory of evolution has difficulty in explaining the rapid evolution of mammalian brain and behavior. I shall argue that the plasticity mechanisms of the brain (i.e., system homeostasis, developmental reorganization, structural adult plasticity, and cognition and learning) have evolved primarily as genetic buffer systems which protect subtle mutations influencing brain structures from natural selection. These buffer systems permit accumulation of genetic variation in the higher system levels of the brain (simply defined as structures with late differentiation), while low-level systems are kept constant by natural selection. The organization of this intrinsic genetic buffering system provides several features facilitating neo-Darwinian evolution: In conclusion, the evolutionary appearance of cognition and intelligence is an ordinary biological mechanism compensating evolutionary drags such as long lifespans and fewer offspring. The concept has heuristic value for identifying gene-brain-behavior relationships and for explaining behavioral consequences of artifical gene deletions.

Basal buffer systems for a newly glycosylated recombinant human interferon-β with biophysical stability and DoE approaches.

PubMed

Kim, Nam Ah; Song, Kyoung; Lim, Dae Gon; Hada, Shavron; Shin, Young Kee; Shin, Sangmun; Jeong, Seong Hoon

2015-10-12

The purpose of this study was to develop a basal buffer system for a biobetter version of recombinant human interferon-β 1a (rhIFN-β 1a), termed R27T, to optimize its biophysical stability. The protein was pre-screened in solution as a function of pH (2-11) using differential scanning calorimetry (DSC) and dynamic light scattering (DLS). According to the result, its experimental pI and optimal pH range were 5.8 and 3.6-4.4, respectively. Design of experiment (DoE) approach was developed as a practical tool to aid formulation studies as a function of pH (2.9-5.7), buffer (phosphate, acetate, citrate, and histidine), and buffer concentration (20 mM and 50 mM). This method employed a weight-based procedure to interpret complex data sets and to investigate critical key factors representing protein stability. The factors used were Tm, enthalpy, and relative helix contents which were obtained by DSC and Fourier Transform Infrared spectroscopy (FT-IR). Although the weights changed by three responses, objective functions from a set of experimental designs based on four buffers were highest in 20 mM acetate buffer at pH 3.6 among all 19 scenarios tested. Size exclusion chromatography (SEC) was adopted to investigate accelerated storage stability in order to optimize the pH value with susceptible stability since the low pH was not patient-compliant. Interestingly, relative helix contents and storage stability (monomer remaining) increased with pH and was the highest at pH 4.0. On the other hand, relative helix contents and thermodynamic stability decreased at pH 4.2 and 4.4, suggesting protein aggregation issues. Therefore, the optimized basal buffer system for the novel biobetter was proposed to be 20 mM acetate buffer at pH 3.8±0.2. Copyright © 2015 Elsevier B.V. All rights reserved.

A dynamic system for the simulation of fasting luminal pH-gradients using hydrogen carbonate buffers for dissolution testing of ionisable compounds.

PubMed

Garbacz, Grzegorz; Kołodziej, Bartosz; Koziolek, Mirko; Weitschies, Werner; Klein, Sandra

2014-01-23

The hydrogen carbonate buffer is considered as the most biorelevant buffer system for the simulation of intestinal conditions and covers the physiological pH range of the luminal fluids from pH 5.5 to about pH 8.4. The pH value of a hydrogen carbonate buffer is the result of a complex and dynamic interplay of the concentration of hydrogen carbonate ions, carbonic acid, the concentration of dissolved and solvated carbon dioxide and its partial pressure above the solution. The complex equilibrium between the different ions results in a thermodynamic instability of hydrogen carbonate solutions. In order to use hydrogen carbonate buffers with pH gradients in the physiological range and with the dynamics observed in vivo without changing the ionic strength of the solution, we developed a device (pHysio-grad®) that provides both acidification of the dissolution medium by microcomputer controlled carbon dioxide influx and alkalisation by degassing. This enables a continuous pH control and adjustment during dissolution of ionisable compounds. The results of the pH adjustment indicate that the system can compensate even rapid pH changes after addition of a basic or acidic moiety in amounts corresponding up to 90% of the overall buffer capacity. The results of the dissolution tests performed for a model formulation containing ionizable compounds (Nexium 20mg mups) indicate that both the simulated fasting intraluminal pH-profiles and the buffer species can significantly affect the dissolution process by changing the lag time prior to initial drug release and the release rate of the model compound. A prediction of the in vivo release behaviour of this formulation is thus most likely strongly related to the test conditions such as pH and buffer species. Copyright © 2013 Elsevier B.V. All rights reserved.

Buffer Gas Acquisition and Storage

NASA Technical Reports Server (NTRS)

Parrish, Clyde F.; Lueck, Dale E.; Jennings, Paul A.; Callahan, Richard A.; Delgado, H. (Technical Monitor)

2001-01-01

The acquisition and storage of buffer gases (primarily argon and nitrogen) from the Mars atmosphere provides a valuable resource for blanketing and pressurizing fuel tanks and as a buffer gas for breathing air for manned missions. During the acquisition of carbon dioxide (CO2), whether by sorption bed or cryo-freezer, the accompanying buffer gases build up in the carbon dioxide acquisition system, reduce the flow of CO2 to the bed, and lower system efficiency. It is this build up of buffer gases that provide a convenient source, which must be removed, for efficient capture Of CO2 Removal of this buffer gas barrier greatly improves the charging rate of the CO2 acquisition bed and, thereby, maintains the fuel production rates required for a successful mission. Consequently, the acquisition, purification, and storage of these buffer gases are important goals of ISRU plans. Purity of the buffer gases is a concern e.g., if the CO, freezer operates at 140 K, the composition of the inert gas would be approximately 21 percent CO2, 50 percent nitrogen, and 29 percent argon. Although there are several approaches that could be used, this effort focused on a hollow-fiber membrane (HFM) separation method. This study measured the permeation rates of CO2, nitrogen (ND, and argon (Ar) through a multiple-membrane system and the individual membranes from room temperature to 193K and 10 kpa to 300 kPa. Concentrations were measured with a gas chromatograph that used a thermoconductivity (TCD) detector with helium (He) as the carrier gas. The general trend as the temperature was lowered was for the membranes to become more selective, In addition, the relative permeation rates between the three gases changed with temperature. The end result was to provide design parameters that could be used to separate CO2 from N2 and Ar.

Accelerating Science with the NERSC Burst Buffer Early User Program

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

Bhimji, Wahid; Bard, Debbie; Romanus, Melissa

NVRAM-based Burst Buffers are an important part of the emerging HPC storage landscape. The National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory recently installed one of the first Burst Buffer systems as part of its new Cori supercomputer, collaborating with Cray on the development of the DataWarp software. NERSC has a diverse user base comprised of over 6500 users in 700 different projects spanning a wide variety of scientific computing applications. The use-cases of the Burst Buffer at NERSC are therefore also considerable and diverse. We describe here performance measurements and lessons learned from the Burstmore » Buffer Early User Program at NERSC, which selected a number of research projects to gain early access to the Burst Buffer and exercise its capability to enable new scientific advancements. To the best of our knowledge this is the first time a Burst Buffer has been stressed at scale by diverse, real user workloads and therefore these lessons will be of considerable benefit to shaping the developing use of Burst Buffers at HPC centers.« less

The role of social buffering on chronic disruptions in quality of care: evidence from caregiver-based interventions in foster children.

PubMed

Flannery, Jessica E; Beauchamp, Kathryn G; Fisher, Philip A

2017-02-01

There is growing evidence that social support can buffer the physiological stress response, specifically cortisol reactivity. We use a developmental framework to review the importance of social buffering in early childhood, a period of heightened plasticity for programming of the hypothalamic-pituitary-adrenal (HPA) axis. The social environment, in which parents play the largest role in early life, is a critical agent in the developmental trajectory of the HPA axis. A prevailing model of social buffering primarily focuses on the role of social support in the context of acute stressors and cortisol response. This review expands this model to provide evidence of the mechanism of social buffering, or lack thereof, across periods of chronic stress by applying the social buffer model to children involved in the child welfare system. We also highlight current interventions that capitalize on the mechanism of social buffering to modify HPA axis functioning across childhood. Last, we synthesize our findings using the social buffering framework to inform future targeted interventions.

Joint optimization of maintenance, buffers and machines in manufacturing lines

NASA Astrophysics Data System (ADS)

Nahas, Nabil; Nourelfath, Mustapha

2018-01-01

This article considers a series manufacturing line composed of several machines separated by intermediate buffers of finite capacity. The goal is to find the optimal number of preventive maintenance actions performed on each machine, the optimal selection of machines and the optimal buffer allocation plan that minimize the total system cost, while providing the desired system throughput level. The mean times between failures of all machines are assumed to increase when applying periodic preventive maintenance. To estimate the production line throughput, a decomposition method is used. The decision variables in the formulated optimal design problem are buffer levels, types of machines and times between preventive maintenance actions. Three heuristic approaches are developed to solve the formulated combinatorial optimization problem. The first heuristic consists of a genetic algorithm, the second is based on the nonlinear threshold accepting metaheuristic and the third is an ant colony system. The proposed heuristics are compared and their efficiency is shown through several numerical examples. It is found that the nonlinear threshold accepting algorithm outperforms the genetic algorithm and ant colony system, while the genetic algorithm provides better results than the ant colony system for longer manufacturing lines.

Good’s buffers as a basis for developing self-buffering and biocompatible ionic liquids for biological research†

PubMed Central

Taha, Mohamed; e Silva, Francisca A.; Quental, Maria V.; Ventura, Sónia P. M.; Freire, Mara G.; Coutinho, João A. P.

2014-01-01

This work reports a promising approach to the development of novel self-buffering and biocompatible ionic liquids for biological research in which the anions are derived from biological buffers (Good’s buffers, GB). Five Good’s buffers (Tricine, TES, CHES, HEPES, and MES) were neutralized with four suitable hydroxide bases (1-ethyl-3-methylimidazolium, tetramethylammonium, tetraethylammonium, and tetrabutylammonium) producing 20 Good’s buffer ionic liquids (GB-ILs). The presence of the buffering action of the synthesized GB-ILs was ascertained by measuring their pH-profiles in water. Moreover, a series of mixed GB-ILs with wide buffering ranges were formulated as universal buffers. The impact of GB-ILs on bovine serum albumin (BSA), here used as a model protein, is discussed and compared with more conventional ILs using spectroscopic techniques, such as infrared and dynamic light scattering. They appear to display, in general, a greater stabilizing effect on the protein secondary structure than conventional ILs. A molecular docking study was also carried out to investigate on the binding sites of GB-IL ions to BSA. We further used the QSAR-human serum albumin binding model, log K(HSA), to calculate the binding affinity of some conventional ILs/GB-ILs to HSA. The toxicity of the GB and GB-ILs was additionally evaluated revealing that they are non-toxic against Vitro fischeri. Finally, the GB-ILs were also shown to be able to form aqueous biphasic systems when combined with aqueous solutions of inorganic or organic salts, and we tested their extraction capability for BSA. These systems were able to extract BSA with an outstanding extraction efficiency of 100% in a single step for the GB-IL-rich phase, and, as a result, the use of GB-IL-based ABS for the separation and extraction of other added-value biomolecules is highly encouraging and worthy of further investigation. PMID:25729325

Using fluorescent dyes as proxies to study herbicide removal by sorption in buffer zones.

PubMed

Dollinger, Jeanne; Dagès, Cécile; Voltz, Marc

2017-04-01

The performance of buffer zones for removing pesticides from runoff water varies greatly according to landscape settings, hydraulic regime, and system design. Evaluating the performance of buffers for a range of pesticides and environmental conditions can be very expensive. Recent studies suggested that the fluorescent dyes uranine and sulforhodamine B could be used as cost-effective surrogates of herbicides to evaluate buffer performance. However, while transformation mechanisms in buffers have been extensively documented, sorption processes of both dyes have rarely been investigated. In this study, we measured the adsorption, desorption, and kinetic sorption coefficients of uranine and sulforhodamine B for a diverse range of buffer zone materials (soils, litters, plants) and compared the adsorption coefficients (Kd) to those of selected herbicides. We also compared the global sorption capacity of 6 ditches, characterized by varying proportions of the aforementioned materials, between both dyes and a set of four herbicides using the sorption-induced pesticide retention indicator (SPRI). We found that both the individual Kd of uranine for the diverse buffer materials and the global sorption capacity of the ditches are equivalent to those of the herbicides diuron, isoproturon, and metolachlor. The Kd of sulforhodamine B on plants and soils are equivalent to those of glyphosate, and the global sorption capacities of the ditches are equivalent for both molecules. Hence, we demonstrate for the first time that uranine can be used as a proxy of moderately hydrophobic herbicides to evaluate the performance of buffer systems, whereas sulforhodamine B can serve as a proxy for more strongly sorbing herbicides.

Two Dimensional Heat Transfer around Penetrations in Multilayer Insulation

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.; Kelly, Andrew O.; Jumper, Kevin M.

2012-01-01

The objective of this task was to quantify thermal losses involving integrating MLI into real life situations. Testing specifically focused on the effects of penetrations (including structural attachments, electrical conduit/feedthroughs, and fluid lines) through MLI. While there have been attempts at quantifying these losses both analytically and experimentally, none have included a thorough investigation of the methods and materials that could be used in such applications. To attempt to quantify the excess heat load coming into the system due to the integration losses, a calorimeter was designed to study two dimensional heat transfer through penetrated MLI. The test matrix was designed to take as many variables into account as was possible with the limited test duration and system size. The parameters varied were the attachment mechanism, the buffer material (for buffer attachment mechanisms only), the thickness of the buffer, and the penetration material. The work done under this task is an attempt to measure the parasitic heat loads and affected insulation areas produced by system integration, to model the parasitic loads, and from the model produce engineering equations to allow for the determination of parasitic heat loads in future applications. The methods of integration investigated were no integration, using a buffer to thermally isolate the strut from the MLI, and temperature matching the MLI on the strut. Several materials were investigated as a buffer material including aerogel blankets, aerogel bead packages, cryolite, and even an evacuated vacuum space (in essence a no buffer condition).

Influence of hydrological and geochemical processes on the transport of chelated metals and chromate in fractured shale bedrock

NASA Astrophysics Data System (ADS)

Jardine, P. M.; Mehlhorn, T. L.; Larsen, I. L.; Bailey, W. B.; Brooks, S. C.; Roh, Y.; Gwo, J. P.

2002-03-01

Field-scale processes governing the transport of chelated radionuclides in groundwater remain conceptually unclear for highly structured, heterogeneous environments. The objectives of this research were to provide an improved understanding and predictive capability of the hydrological and geochemical mechanisms that control the transport behavior of chelated radionuclides and metals in anoxic subsurface environments that are complicated by fracture flow and matrix diffusion. Our approach involved a long-term, steady-state natural gradient field experiment where nonreactive Br - and reactive 57Co(II)EDTA 2-, 109CdEDTA 2-, and 51Cr(VI) were injected into a fracture zone of a contaminated fractured shale bedrock. The spatial and temporal distribution of the tracer and solutes was monitored for 500 days using an array of groundwater sampling wells instrumented within the fast-flowing fracture regime and a slower flowing matrix regime. The tracers were preferentially transported along strike-parallel fractures coupled with the slow diffusion of significant tracer mass into the bedrock matrix. The chelated radionuclides and metals were significantly retarded by the solid phase with the mechanisms of retardation largely due to redox reactions and sorption coupled with mineral-induced chelate-radionuclide dissociation. The formation of significant Fe(III)EDTA - byproduct that accompanied the dissociation of the radionuclide-chelate complexes was believed to be the result of surface interactions with biotite which was the only Fe(III)-bearing mineral phase present in these Fe-reducing environments. These results counter current conceptual models that suggest chelated contaminants move conservatively through Fe-reducing environments since they are devoid of Fe-oxyhydroxides that are known to aggressively compete for chelates in oxic regimes. Modeling results further demonstrated that chelate-radionuclide dissociation reactions were most prevalent along fractures where accelerated weathering processes are expected to expose more primary minerals than the surrounding rock matrix. The findings of this study suggest that physical retardation mechanisms (i.e. diffusion) are dominant within the matrix regime, whereas geochemical retardation mechanisms are dominant within the fracture regime.

[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.

Polyaminoquinoline iron chelators for vectorization of antiproliferative agents: design, synthesis, and validation.

PubMed

Corcé, Vincent; Morin, Emmanuelle; Guihéneuf, Solène; Renault, Eric; Renaud, Stéphanie; Cannie, Isabelle; Tripier, Raphaël; Lima, Luís M P; Julienne, Karine; Gouin, Sébastien G; Loréal, Olivier; Deniaud, David; Gaboriau, François

2012-09-19

Iron chelation in tumoral cells has been reported as potentially useful during antitumoral treatment. Our aim was to develop new polyaminoquinoline iron chelators targeting tumoral cells. For this purpose, we designed, synthesized, and evaluated the biological activity of a new generation of iron chelators, which we named Quilamines, based on an 8-hydroxyquinoline (8-HQ) scaffold linked to linear polyamine vectors. These were designed to target tumor cells expressing an overactive polyamine transport system (PTS). A set of Quilamines bearing variable polyamine chains was designed and assessed for their ability to interact with iron. Quilamines were also screened for their cytostatic/cytotoxic effects and their selective uptake by the PTS in the CHO cell line. Our results show that both the 8-HQ moiety and the polyamine part participate in the iron coordination. HQ1-44, the most promising Quilamine identified, presents a homospermidine moiety and was shown to be highly taken up by the PTS and to display an efficient antiproliferative activity that occurred in the micromolar range. In addition, cytotoxicity was only observed at concentrations higher than 100 μM. We also demonstrated the high complexation capacity of HQ1-44 with iron while much weaker complexes were formed with other cations, indicative of a high selectivity. We applied the density functional theory to study the binding energy and the electronic structure of prototypical iron(III)-Quilamine complexes. On the basis of these calculations, Quilamine HQ1-44 is a strong tridentate ligand for iron(III) especially in the form of a 1:2 complex.

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.

Efficiency of a new strategy involving a new class of natural hetero-ligand iron(III) chelates (Fe(III)-NHL) to improve fruit tree growth in alkaline/calcareous soils.

PubMed

Fuentes, Marta; Ortuño, María F; Pérez-Sarmiento, Francisco; Bacaicoa, Eva; Baigorri, Roberto; Conejero, Wenceslao; Torrecillas, Arturo; García-Mina, José M

2012-12-01

Iron (Fe) chlorosis is a serious problem affecting the yield and quality of numerous crops and fruit trees cultivated in alkaline/calcareous soils. This paper describes the efficiency of a new class of natural hetero-ligand Fe(III) chelates (Fe-NHL) to provide available Fe for chlorotic lemon trees grown in alkaline/calcareous soils. These chelates involve the participation in the reaction system of a partially humified lignin-based natural polymer and citric acid. First results showed that Fe-NHL was adsorbed on the soil matrix while maintaining available Fe for plants in alkaline/calcareous solution. The effects of using three different sources as Fe fertilisers were also compared: two Fe-NHL formulations (NHL1, containing 100% of Fe as Fe-NHL, and NHL2, containing 80% of Fe as Fe-NHL and 20% of Fe as Fe-ethylenediamine-N,N'-bis-(o-hydroxyphenylacetic) acid (Fe-EDDHA)) and Fe-EDDHA. Both Fe-NHL formulations increased fruit yield without negative effects on fruit quality in comparison with Fe-EDDHA. In the absence of the Fe-starter fraction (NHL1), trees seemed to optimise Fe assimilation and translocation from Fe-NHL, directing it to those parts of the plant more involved in development. The field assays confirmed that Fe-NHL-based fertilisers are able to provide Fe to chlorotic trees, with results comparable to Fe-EDDHA. Besides, this would imply a more sustainable and less expensive remediation than synthetic chelates. Copyright © 2012 Society of Chemical Industry.

Continuous chelation irrigation improves the adhesion of epoxy resin-based root canal sealer to root dentine.

PubMed

Neelakantan, P; Varughese, A A; Sharma, S; Subbarao, C V; Zehnder, M; De-Deus, G

2012-12-01

To test the impact of continuous chelation by NaOCl+ etidronic acid (HEBP) during instrumentation, and a final rinse of EDTA or NaOCl + HEBP on the dentine bond strength of an epoxy resin sealer (AH Plus). Single-rooted teeth (n = 100) were divided into five groups (n = 20) based on the irrigation protocol and their root canals instrumented using a rotary Ni-Ti system: 2.5% NaOCl during instrumentation followed by bi-distilled water (G1) or 17% EDTA (G2) as final rinse; 1 : 1 mixture of 5% NaOCl and 18% HEBP during instrumentation, and the same mixture (G3), 17% EDTA (G4) or bi-distilled water (G5) as final rinse. Canals were filled with AH Plus. Roots were sectioned, and push-out tests were performed in coronal, middle and apical root thirds. Results were analysed using analysis of variance (anova) and Bonferroni test for multiple comparisons. The alpha-type error was set at 0.05 for all the analyses. Push-out bond strength was highest in coronal and lowest in apical root thirds (P < 0.05). Groups that used NaOCl + HEBP irrigation during instrumentation had significantly higher bond strengths than groups following the NaOCl-EDTA irrigation in all root thirds (P < 0.05). The use of a strong chelator as final flush further increased bond strengths (G4, P < 0.05). The continuous chelation irrigation protocol optimizes the bond strength of an epoxy resin sealer to dentine. © 2012 International Endodontic Journal.

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.

Antioxidant activity of oregano, parsley, and olive mill wastewaters in bulk oils and oil-in-water emulsions enriched in fish oil.

PubMed

Jimenez-Alvarez, D; Giuffrida, F; Golay, P A; Cotting, C; Lardeau, A; Keely, Brendan J

2008-08-27

The antioxidant activity of oregano, parsley, olive mill wastewaters (OMWW), Trolox, and ethylenediaminetetraacetic acid (EDTA) was evaluated in bulk oils and oil-in-water (o/w) emulsions enriched with 5% tuna oil by monitoring the formation of hydroperoxides, hexanal, and t-t-2,4-heptadienal in samples stored at 37 degrees C for 14 days. In bulk oil, the order of antioxidant activity was, in decreasing order (p < 0.05), OMWW > oregano > parsley > EDTA > Trolox. The antioxidant activity in o/w emulsion followed the same order except that EDTA was as efficient an antioxidant as OMWW. In addition, the total phenolic content, the radical scavenging properties, the reducing capacity, and the iron chelating activity of OMWW, parsley, and oregano extracts were determined by the Folin-Ciocalteau, oxygen radical absorbance capacity, ferric reducing antioxidant power, and iron(II) chelating activity assays, respectively. The antioxidant activity of OMWW, parsley, and oregano in food systems was related to their total phenolic content and radical scavenging capacity but not to their ability to chelate iron in vitro. OMWW was identified as a promising source of antioxidants to retard lipid oxidation in fish oil-enriched food products.

Removal of heavy metal species from industrial sludge with the aid of biodegradable iminodisuccinic acid as the chelating ligand.

PubMed

Wu, Qing; Duan, Gaoqi; Cui, Yanrui; Sun, Jianhui

2015-01-01

High level of heavy metals in industrial sludge was the obstacle of sludge disposal and resource recycling. In this study, iminodisuccinic acid (IDS), a biodegradable chelating ligand, was used to remove heavy metals from industrial sludge generated from battery industry. The extraction of cadmium, copper, nickel, and zinc from battery sludge with aqueous solution of IDS was studied under various conditions. It was found that removal efficiency greatly depends on pH, chelating agent's concentration, as well as species distribution of metals. The results showed that mildly acidic and neutral systems were not beneficial to remove cadmium. About 68 % of cadmium in the sample was extracted at the molar ratio of IDS to heavy metals 7:1 without pH adjustment (pH 11.5). Copper of 91.3 % and nickel of 90.7 % could be removed by IDS (molar ratio, IDS: metals = 1:1) with 1.2 % phosphoric acid effectively. Removal efficiency of zinc was very low throughout the experiment. Based on the experimental results, IDS could be a potentially useful chelant for heavy metal removal from battery industry sludge.

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.

The quantitation of buffering action I. A formal & general approach.

PubMed

Schmitt, Bernhard M

2005-03-15

Although "buffering" as a homeostatic mechanism is a universal phenomenon, the quantitation of buffering action remains controversial and problematic. Major shortcomings are: lack of a buffering strength unit for some buffering phenomena, multiple and mutually incommensurable units for others, and lack of a genuine ratio scale for buffering strength. Here, I present a concept of buffering that overcomes these shortcomings. Briefly, when, for instance, some "free" H+ ions are added to a solution (e.g. in the form of strong acid), buffering is said to be present when not all H+ ions remain "free" (i.e., bound to H2O), but some become "bound" (i.e., bound to molecules other than H2O). The greater the number of H+ ions that become "bound" in this process, the greater the buffering action. This number can be expressed in two ways: 1) With respect to the number of total free ions added as "buffering coefficient b", defined in differential form as b = d(bound)/d(total). This measure expresses buffering action from nil to complete by a dimensionless number between 0 and 1, analogous to probabilites. 2) With respect to the complementary number of added ions that remain free as "buffering ratio B", defined as the differential B = d(bound)/d(free). The buffering ratio B provides an absolute ratio scale, where buffering action from nil to perfect corresponds to dimensionless numbers between 0 and infinity, and where equal differences of buffering action result in equal intervals on the scale. Formulated in purely mathematical, axiomatic form, the concept reveals striking overlap with the mathematical concept of probability. However, the concept also allows one to devise simple physical models capable of visualizing buffered systems and their behavior in an exact yet intuitive way. These two measures of buffering action can be generalized easily to any arbitrary quantity that partitions into two compartments or states, and are thus suited to serve as standard units for buffering action. Some exemplary treatments of classical and non-classical buffering phenomena are presented in the accompanying paper.