Nitrolotriacetic Acid Research Articles

Toxicological risk assessment and prioritization of drinking water relevant contaminants of emerging concern

Toxicological risk assessment of contaminants of emerging concern (CEC) in (sources of) drinking water is required to identify potential health risks and prioritize chemicals for abatement or monitoring. In such assessments, concentrations of chemicals in drinking water or sources are compared to either (i) health-based (statutory) drinking water guideline values, (ii) provisional guideline values based on recent toxicity data in absence of drinking water guidelines, or (iii) generic drinking water target values in absence of toxicity data. Here, we performed a toxicological risk assessment for 163 CEC that were selected as relevant for drinking water. This relevance was based on their presence in drinking water and/or groundwater and surface water sources in downstream parts of the Rhine and Meuse, in combination with concentration levels and physicochemical properties. Statutory and provisional drinking water guideline values could be derived from publically available toxicological information for 142 of the CEC. Based on measured concentrations it was concluded that the majority of substances do not occur in concentrations which individually pose an appreciable human health risk. A health concern could however not be excluded for vinylchloride, trichloroethene, bromodichloromethane, aniline, phenol, 2-chlorobenzenamine, mevinphos, 1,4-dioxane, and nitrolotriacetic acid. For part of the selected substances, toxicological risk assessment for drinking water could not be performed since either toxicity data (hazard) or drinking water concentrations (exposure) were lacking. In absence of toxicity data, the Threshold of Toxicological Concern (TTC) approach can be applied for screening level risk assessment. The toxicological information on the selected substances was used to evaluate whether drinking water target values based on existing TTC levels are sufficiently protective for drinking water relevant CEC. Generic drinking water target levels of 37 μg/L for Cramer class I substances and 4 μg/L for Cramer class III substances in drinking water were derived based on these CEC. These levels are in line with previously reported generic drinking water target levels based on original TTC values and are shown to be protective for health effects of the majority of contaminants of emerging concern evaluated in the present study. Since the human health impact of many chemicals appearing in the water cycle has been studied insufficiently, generic drinking water target levels are useful for early warning and prioritization of CEC with unknown toxicity in drinking water and its sources for future monitoring.

Nitrolotriacetic acid assisted one step synthesis of highly stable silver nanoparticles in aqueous medium: Investigation of catalytic activity

Highly stable dispersion of nanosized silver nanoparticles have been synthesized using biodegradable nitrolotriacetic acid (NTA) as both stabilizing and reducing agent in aqueous medium without using any hazardous chemicals. Due to their readily accessible surface, the synthesized silver nanoparticles showed good catalytic activity in the industrially important catalytic reduction of 4-nitrophenol (4-NP) to the corresponding amines in the presence of NaBH4 and the results have been compared with that of polyvinylpyrrolidone (PVP) stabilized silver nanoparticles.

Atomic Force Microscopy‐Derived Nanoscale Chip for the Detection of Human Pathogenic Viruses

Native-protein nanolithography (NPNL) was used to fabricate stable bioactive arrays of viral receptor spots. The arrays were specific for the cognate virus and devoid of nonspecific protein and virus adsorption under physiologic conditions. The spot size ranged from 200 nm x 200 nm to 2 microm x 2 microm and up to 3 x 3 spots were arranged per array. With proper force adjustment in the patterning experiments, His(6)-tagged bovine serum albumin (BSA) molecules were selectively removed from the underlying self-assembled monolayer (SAM) while leaving the latter intact. Injection of His(6)-tagged very low density lipoprotein receptor (VLDLR-His(6)) constructs resulted in specific, oriented binding to the Ni(2+)-loaded bis-(nitrolotriacetic acid) (bis-NTA) groups to the re-exposed SAM areas. The arrays of viral receptors were used for the detection of human rhinovirus particles (serotype 2; HRV2) under native conditions by topographical imaging at high signal-to-noise ratio. The kinetic on-rate of the HRV2-VLDLR interaction was derived from the time-dependent binding of the virions to the VLDL receptor spots. No significant binding was observed for the major group virus HRV14 that uses the unrelated receptor ICAM-1.

High-level expression of 4-coumarate:coenzyme A ligase gene Pt4CL1 of Populus tomentosa in E. coli

In order to investigate the enzymatic properties of the 4CL1 of Populus tomentosa, the recombinant expression vector pQE31-4CL1 was constructed. The recombinant was identified by three restriction endonucleases, then the vector pQE31-4CL1 was transformed into expression host M15 (pREP4) and induced by isopropyl-α-D-thiogalactoside (IPTG) to express 60 kD fused protein Pt4CL1. The biologically active Pt4CL1, expressed as soluble protein, was achieved with 0.6 mmol·L−1 IPTG induction as the expression temperature declined from 37 to 28°C. The 6×His tag facilitates affinity binding to Ni2+-nitrolotriacetic acid (NTA) and enables one-step purification to acquire the molecular SDS-PAGE electrophoresis purity of the active 4CL1 protein by agarose coupled with Ni2+-NTA affinity chromatography. The optimal substrate for Pt4CL1 was 4-coumarate.

Anaerobic oxidation of arsenite in Mono Lake water and by a facultative, arsenite-oxidizing chemoautotroph, strain MLHE-1.

Arsenite [As(III)]-enriched anoxic bottom water from Mono Lake, California, produced arsenate [As(V)] during incubation with either nitrate or nitrite. No such oxidation occurred in killed controls or in live samples incubated without added nitrate or nitrite. A small amount of biological As(III) oxidation was observed in samples amended with Fe(III) chelated with nitrolotriacetic acid, although some chemical oxidation was also evident in killed controls. A pure culture, strain MLHE-1, that was capable of growth with As(III) as its electron donor and nitrate as its electron acceptor was isolated in a defined mineral salts medium. Cells were also able to grow in nitrate-mineral salts medium by using H(2) or sulfide as their electron donor in lieu of As(III). Arsenite-grown cells demonstrated dark (14)CO(2) fixation, and PCR was used to indicate the presence of a gene encoding ribulose-1,5-biphosphate carboxylase/oxygenase. Strain MLHE-1 is a facultative chemoautotroph, able to grow with these inorganic electron donors and nitrate as its electron acceptor, but heterotrophic growth on acetate was also observed under both aerobic and anaerobic (nitrate) conditions. Phylogenetic analysis of its 16S ribosomal DNA sequence placed strain MLHE-1 within the haloalkaliphilic Ectothiorhodospira of the gamma-PROTEOBACTERIA: Arsenite oxidation has never been reported for any members of this subgroup of the PROTEOBACTERIA:

Purification and Characterization of a GDP-fucose:Polypeptide Fucosyltransferase from Chinese Hamster Ovary Cells

A GDP-fucose:polypeptide fucosyltransferase was purified 5000-fold to homogeneity from Chinese hamster ovary cell extracts in the absence of detergent. The purification procedure included two affinity chromatographic steps using the acceptor substrate, a recombinant factor VII EGF-1 domain, and the donor substrate analog, GDP-hexanolamine, as ligands. The purified enzyme migrates as a single band of 44,000 daltons on SDS-polyacrylamide gel electrophoresis and is itself a glycoprotein with more than one high mannose type oligosaccharide chain with a total molecular weight of 4000. The Km values for factor VII EGF-1 domain and GDP-fucose are 15 and 6 microM, respectively. The Vmax is 2.5 micromol.min-1.mg-1. The presence of 50 mM Mn2+ increased the enzyme activity 17-fold, but Mn2+ was not absolutely required, since the enzyme exhibited some activity even in the presence of EDTA. The acceptor substrate specificity was studied using site-directed mutagenesis of human factor IX EGF domain. Only one of several differently folded species could serve as acceptor substrate, although they all had the same molecular weight as determined by liquid chromatography on-line with mass spectrometry. This indicates that the enzyme requires proper folding of the epidermal growth factor domain for its activity.

Overexpression and Characterization of the Human Mitochondrial and Cytosolic Branched-chain Aminotransferases

We have developed overexpression systems for the human branched-chain aminotransferase isoenzymes. The enzymes function as dimers and have substrate specificity comparable with the rat enzymes. The human cytosolic enzyme appears to turn over 2-5 times faster than the mitochondrial enzyme, and there may be anion and cation effects on the kinetics of both enzymes. The two proteins demonstrate similar absorption profiles, and the far UV circular dichroism spectra show that no global structural changes occur when the proteins are converted from the pyridoxal to pyridoxamine form. On the other hand, the near UV circular dichroism spectra suggest differences in the local environment surrounding tyrosines within these proteins. Both enzymes require a reducing environment for maximal activity, but the mitochondrial enzyme can be inhibited by nickel ions in the presence of reducing agents, while the cytosolic enzyme is unaffected. Chemical denaturation profiles of the proteins show that there are differences in structural stability. Titration of -SH groups with 5,5'-dithiobis(2-nitrobenzoic acid) suggests that no disulfide bonds are present in the mitochondrial enzyme and that at least two disulfide bonds are present in the cytosolic enzyme. Two -SH groups are titrated in the native form of the mitochondrial enzyme, leading to complete inhibition of activity, while only one -SH group is titrated in the cytosolic enzyme with no effect on activity. Although these proteins share 58% identity in primary amino acid sequence, the local environment surrounding the active site appears unique for each isoenzyme.

Determination of nitrilotriacetic acid and ethylenediaminetetraacetic acid in environmental samples as their methyl ester derivatives by gas chromatography-mass spectrometry

A method for the determination of nitrolotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) in environmental samples such as river water and sediment is reported. An aqueous sample, after evaporation to dryness, was treated with a boron trifluoride-methanol mixture. The resulting methyl ester derivatives were determined by capillary GC-MS with selected-ion monitoring. NTA and EDTA could be determined in the ranges 4.1–12.2 and 3.9–11.8 ng/ml in water with relative standard deviations (R.S.D.s) of 3.1–7.8% and 11.0–19.7%, respectively. Their recoveries from river water and sediment were 74–92% with R.S.D. 1.5–6.8% and 51–60% with R.S.D. 14–16%, respectively.

The displacement of copper by iron at the specific binding sites of ovotransferrin

We have examined the kinetics and mechanism by which iron can displace copper at the specific metal-binding sites of ovotransferrin. Fe 2+ was added to Cu 2+-ovotransferrin-CO 3 2− in the presence of NaHCO 3 and ambient O 2. The reaction has been followed by standard and stopped-flow spectrophotometry, EPR spectroscopy and analysis of chromogen-reactive Fe 2+. The reaction is best described as triphasic. An initial jump in absorbance takes place in the first 2 s. In the next minute there is a further increase in absorbance and shift in the spectral maximum from 440 to 446 nm. The third phase is complex. The bulk of the spectrophotometric change, a decrease in absorbance with a shift to a maximum of 453 nm, lasts approx. 3 min. Minor spectral and EPR changes, however, take place over the next several hours. Chromogenic analysis of Fe 2+ indicates that approx. 1 min is reqired to oxidize the Fe 2+. EPR spectra reveal the formation of an Fe 3+-ovotransferrin complex within the first 20 s; however, this lacks the characteristic doublet of specific Fe 3+-ovotransferrin-CO 3 2−. The simultaneous presence of specific Cu 2+-ovotransferrin-CO 3 2− and Fe 3+-ovotransferrin-CO 3 2− s signals suggests a period in which the protein specifically binds both metal ions perhaps resulting from a differential reactivity of the two metal-binding sites. The addition of Cu(NO 3) 2 to Fe 3+-ovotransferrin-CO 3 2− resulted in a complex with specific Fe 3+ and non-specific Cu 2+. The EPR spectrum of this complex and the final product of our displacement reaction were virtually identical. Distinct parallels in reaction of Cu 2+-ovotransferrin-CO 3 2− with Fe(NH 4) 2(SO 4) 2, Fe(NO 3) 3 and Fe 3+-nitrolotriacetic acid were observed. A reaction sequence involving the binding and oxidation of non-specific Fe 2+ followed by Cu 2+ displacement by Fe 3+ at the specific sites and binding of non-specific Cu 2+ is suggested.

Lack of induction of somatic aneuploidy in the mouse by nitrilotriacetic acid (NTA)

Nitrolotriacetic acid (NTA) was tested for the induction of aneuploidy in mouse bone marrow cells. Doses of 138 or 275 mg/kg of body weight were intraperitoneally injected 24 h after implantation of a bromodeoxyuridine tablet. Cell-replication kinetics was assessed by comparing the relative percentages of first, second and third metaphases in control and treated samples. The hyperploidy incidence was estimated in second metaphases only, together with the SCE/cell level. Mice injected with 1.8 mg/kg vinblastine (VBL) were used as positive controls. A slight delay of cell cycle was induced by NTA, as shown by regression analysis applied to average generation time values. No increase over the control level was observed for hyperploidy or SCE induction in NTA-treated mice. VBL induced both cell-cycle alteration and a highly significant ( P < 0.001) increase of the hyperploid cell frequency. On the basis of these and previous (Costa et al., 1988) observations it seems that the non-disjunctional activity of NTA in the mouse is confined to meiotic processes.

Determination of cobalt in plant digests by adsorption stripping voltammetry

The procedure involves adsorption of cobalt onto a static mercury drop as its dimethylgloximate complex (pH 9.3, adsorption potential −0.70 V, adsorption time 2 min), followed by a d.c. cathodic scan, effecting reduction at −1.15 V (SCE). Of the dominant electroactive trace elements in plants (Mn, Fe, Zn), only zinc interfered; it was masked by nitrolotriacetic acid (2 × 10 −4 M). The detection limit is 0.01 μg l −1 cobalt in the digest; the relative standard deviation is 2.5% at 0.75 μg l −1. Calibration is linear in the range 0–6.0 μg l −1 cobalt. Results obtained by the voltammetric method, by electrothermal atomic absorption spectrometry and neutron activation analysis are compared for seven pasture samples containing 0.1–0.2 mg kg −1 cobalt. The activation method provides validation for the same preparation and voltammetric results.

Application of amalgam electrodes in studies of heavy metals under natural water conditions

The application of amalgam electrodes for measuring the degree of complexation of metal ions is described with respect to natural water conditions. The amalgam electrodes are compared with the corresponding capabilities of ion-selective electrodes. A special cell is described for preparing the amalgam and for filling a hanging amalgam drop electrode. Factors affecting the reproducibility of the standard potentials and slopes, the response time and detection limits are discussed. Complexation measurements are described with lead and zinc amalgam electrodes. Triethylenetetramine, carbonate and nitrolotriacetic acid are used as ligands, to test the ability of these electrodes to measure correctly8 the degree of complexation even at low total-metal. concentrations (down to ca. 10 −7 M) and at very low concentrations of free metal ion (10 −15 M). Results obtained with well-characterized fulvinc compound and an algal culture medium (AAP) are also reported. The observed results are in compl;ete accordance with theoretical predictions (based on Nernstian behaviour), evven at the lowest concentrations of tltal and free metal ion used. An important limitation is that any oxidant in the solution can interfere by oxidizing the amalgma. Solutions must be carefully degassed to eliminate oxygen. It is shown that the interfering actin of oxidants can be corrected for by means of equations which are theoretically sound, even when the nature of the oxidant is unknown, provided that its content is not too high. Compared to ion-selective electrodes, amalgam electrodes are more reproducible, inexpensive and readily prepared for various metal ions which cannot be measured with ion-selective electrodes.

Determinationof nitrolotriacetic acid in water by high-resolution gas chromatography

Nitrilotriacetic acid was determined in waters and waste-waters by high-resolution gas chromatography of the butylated acids isolated on an anion-exchange resin. The presented method is applicble to heavily loaded waste-waters and natural waters. A quantitation limit of 0.2 μg of the acid per litre of water was attained.

Effects of pH and chelating agents on iron binding by dietary fiber: implications for iron availability

Iron binding by isolated dietary fiber in the presence of iron ligands was measured. Iron-ligand solutions were mixed with isolated fiber and incubated. Bound and polymerized iron were estimated by centrifugation and ultrafiltration, respectively. Results showed that iron binding varied greatly with ligand used and with pH. Based on these studies, it was predicted that ligands would influence iron availability in the order ascorbate < citrate = nitrolotriacetic acid < EDTA. When added to a complex meal containing beef, bread, green beans, and milk, iron availability (measured by an in vitro method) was little affected by fiber, citrate, and ascorbate, but enhanced by nitrolotriacetic acid and EDTA. When added to a semisynthetic meal, fiber, ascorbate, citrate, nitrolotriacetic acid, and EDTA increased iron availability. It appears that the effect of dietary fiber on iron availability is greatly dependent on the ligands present in the meal.

Substitutes for phosphate containing washing products: Their toxicity and biodegradability in the aquatic environment

The toxicity of nitrolotriacetic acid (NTA), citrex-S-5, sodium alluminium silicate (NAS), carboxymethyloxysuccinate (CMOS), linear alkylbenzene sulfonate (LAS) and soap was examined using bacteria ( Pseudomonas fluorescens ), algae ( Chlorella vulgaris and Microcystis aeruginosa ), crustaceans ( Daphnia magna ), insects ( Aedes aegypti ), fishes ( Poecilia reticulata and Oryzias latipes ) and amphibians ( Xenopus laevis ). The biodegradability of NTA, citrex-S-5, CMOS and LAS was studied in the OECD-test. The acute toxicity of the compounds differed largely with the organisms tested (up to a factor 1,000). Based on the results of the short-term toxicity tests (with all test organisms) and the long-term toxicity tests (with Daphnia magna and in case of LAS also with Poecilia reticulata ) the following no-observed-effect concentrations (NOEC) could be derived: LAS 3.2 mg/1; NAS and soap 10 mg/1; CMOS 32 mg/1; NTA 100 mg/1 and citrex-S-5 320 mg/1. However, testing different samples of one test compound may result in marked differences in toxicity (e.g. NAS: a factor 32). All compounds tested showed to be biodegradable as the percentage DOC decreased more than 80% within four weeks. CMOS biodegraded quickly, whereas citrex-S-5 and LAS showed a somewhat slower rate of degradation. In contrast to the other compounds NTA required an adaptation period of 1 week.

Analysis of nitrolotriacetic acid in environmental wa

Analysis of nitrolotriacetic acid in environmental wa

A study of intracellular iron metabolism using pyridoxal isonicotinoyl hydrazone and other synthetic chelating agents

1. 1. Rabbit reticulocytes with a high level of non-heme radioiron induced by preincubation with isonicotinic acid hydrazide and transferrin-bound 59Fe, were reincubated with various synthetic chelating agents and the amount of radioiron released from the cells was determined. Some substances, especially derivatives of pyridoxal or 2-hydroxybenzaldehyde and isonicotinic acid hydrazide or benzhydrazide, were found to mobilize significantly iron from 59Fe-labeled reticulocytes. The effectiveness of the compounds tested decreases in the following order: pyridoxal isonicotinoyl hydrazone, pyridoxal benzoyl hydrazone, 2-hydroxybenzal isonicotinoyl hydrazone, 2-hydroxybenzal benzoyl hydrazone, pyridoxal-valine Schiff base, pyridoxal. The efficiency of these compounds exceeded the ability of common chelators such as desferrioxamine, 2,2′-bipyridine, nitrolotriacetic acid, etc., to mobilize iron from reticulocytes. 2. 2. Iron mobilization from reticulocytes by pyridoxal isonicotinoyl hydrazone requires ATP to be produced by cells and is completely blocked by low temperature (4°C). Although the effect of desferrioxamine is also prevented by low temperature, modest iron mobilization due to this chelator seems to occur independently of ATP production in reticulocytes. 3. 3. Pyridoxal isonicotinoyl hydrazone mobilizes iron mainly from mitochondria and in part also from ferritin. Although 2,2′-bipyridine seems to enter reticulocyte mitochondria and bind iron there, this chelator is not able to release iron either from mitochondria or from the cells. 4. 4. Reticulocytes with a high level of non-heme radioiron are envisaged as a useful system for testing biological effectiveness of various iron chelators. 5. 5. Pyridoxal isonicotinoyl hydrazone was shown to be an effective in vivo chelator since its administration to mice decreased 59Fe radioactivity in liver, spleen and kidney.

Equilibrium studies of metal-ion complexes of interest to natural waters—VIII

Abstract A pH-titration study is reported at 25·0 ± 0·1°C and μ = 0·1 M (NaClO 4 ) of the equilibria and distribution of complexes in the 2-ligand systems, relevant to soils, (i) M 2+ -fulvate-NTA, (ii) M 2+ -fulvate-phosphate and (iii) M 2+ -NTA-phosphate, where M 2+ = Pb, Cd or Zn, NTA = nitrolotriacetic acid and phosphate = H n PO 4 . Equilibria in the Pb and Cd systems were confirmed using metal-ion-selective electrodes. In (i), M (NTA) and (NTA) M (fulvate) predominate in weakly acidic or neutral solution. In systems (ii) and (iii), (phosphate) M ′(fulvate) and (phosphate) M ′(NTA) predominate, where M ′ = Cd 2+ or Zn 2+ . However, Pb(fulvate) and (phosphate)Pb(fulvate) complexes are insoluble, which could account for the low mobility of Pb in soils and the low uptake of Pb by plants. The role of mixed-ligand complexes in soil chemistry is discussed.

Potentiometric studies on stepwise mixed ligand complex formation Cu(II), Ni(II) or Zn(II)-nitrilotriacetic acid-hydroxy acid

Potentiometric studies of the interaction between copper(II), nickel(II) and zinc(II) nitrilotriacetates with certain bidentate ligands, such as salicylic acid(SA),5-sulphosalicylic acid (SSA) and 1,2-dihydroxy benzene-3,5-disulphonic acid (Tiron) are reported. Ternary complexes having a 1 : 1 : 1 molar ratio of metal ion to nitrolotriacetic acid (NTA) to be secondary ligand are formed. Their formation constants (Log K MAB) are reported and the probable reaction mechanism is discussed. The order of stability in terms of metal ion has been found to be Cu(II) > Zn(II) > Ni(II) and in terms of secondary ligand as Tiron > SA > SSA.

Complexes of 2,6-dicarboxypiperidineacetic acid with some divalent metal ions

The preparation of a new quadridentate ligand related to nitrolotriacetic acid, 2,6-dicarboxypiperidineacetic acid, ▪ has been carried out and the solution stabilities of some complexes which are formed by it with divalent metal ions have been measured (25°C, μ = 0·1). The piperidine ring introduces some steric effects into this ligand and the ways in which these are reflected in the stability constants are described. On the basis of the linear relationship between pk N and log K found previously for ligands related to nitrilotriacetic acid, it is shown that the magnesium chelate has been markedly stabilized. This is in contrast with the results obtained for related ligands. The copper(II) complex is particularly stable and a possible explanation for this enhanced stability in terms of the shape of the chelating cavity is discussed.