Ethylenediaminetriacetic Acid Research Articles

Effect of ligand on the redox reactions of thallium metal clusters

Pulse radiolysis of an aqueous solution of mono-valent thallium ion and mixed solutions of Tl+/Ag+ in the presence of various amino polycarboxylic acids such as trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and triethylenetetraminehexaacetic acid (TTHA) has been carried out. Abnormal valence states of Tl ions were generated. It is concluded that DCTA, DTPA, HEDTA and TTHA decrease the redox potential of Tl ions in aqueous solutions. It was observed that the electron transfer from complexed Tl2+ to Ag+ varied in the range 7.5 × 108 to 1.0 × 109, depending on the type of complexing ligand. Electron transfer from Tl2+ to Ag+ lead to the formation of silver atoms, which agglomerate further to form silver colloid.

Silver–zinc electrodeposition from a thiourea solution with added EDTA or HEDTA

This paper shows the study of silver–zinc electrodeposition from a thiourea solution with added (ethylenedinitrilo)tetraacetic acid (EDTA), disodium salt and N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), trisodium salt. Voltammetric results indicated that silver–zinc alloy can be obtained applying overpotential higher than 0.495 V, in Tu solution containing 1.0 × 10 −1 mol L −1 Zn(NO 3) 2 + 2.5 × 10 −2 mol L −1 AgNO 3. This was due to silver(I) ion complexation with thiourea, which shifted the silver deposition potential to more negative value and due to silver–zinc alloy deposition, which occurred at potentials more positive than the potential to zinc deposition alone. EDTA or HEDTA did not significantly affect the silver and zinc deposition potentials, but decreased the current density for silver–zinc deposition. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses of the silver–zinc deposits showed that the morphology and composition changed as a function of the conditions of deposition, viz, deposition potential ( E d), deposition charge density ( q d) and solution composition (silver, EDTA and HEDTA concentrations). EDS analysis of the deposits showed sulphur (S) incorporated into the silver–zinc deposit, while SEM images showed that this sulphur content seemed to improve the silver–zinc morphology, as did the presence of EDTA and HEDTA in the solution, which enhanced the sulphur incorporation into the silver–zinc deposit. X-ray diffraction (XRD) analysis of the silver–zinc deposit showed that it was amorphous, irrespective of its composition and morphology.

Multielemental Determination of GEOTRACES Key Trace Metals in Seawater by ICPMS after Preconcentration Using an Ethylenediaminetriacetic Acid Chelating Resin

GEOTRACES is an international research project on marine biogeochemical cycles of trace elements and their isotopes. GEOTRACES key trace metals in seawater are Al (8-1000 ng/kg), Mn (4-300 ng/kg), Fe (1-100 ng/kg), Cu (30-300 ng/kg), Zn (3-600 ng/kg), and Cd (0.1-100 ng/kg), of which global oceanic distribution will be determined on a number of research cruises. This work introduces a novel method of solid-phase extraction to determine Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater by adjusting the pH of the sample to 6 and carrying out a single preconcentration step. The trace metals were collected from approximately 120 mL of seawater using a column of a chelating resin containing the ethylenediaminetriacetic acid functional group and eluted with approximately 15 mL of 1 M HNO3. Mn and Fe in the eluate were measured by inductively coupled plasma mass spectrometry (ICPMS) using the dynamic reaction cell mode, and the other metals were measured using the standard mode. Using this procedure, the trace metals were collected quantitatively, while >99.9% of alkali and alkaline earth metals in seawater were removed. The procedural blank was <7% of the mean concentration in deep ocean waters, except 16% for Pb. The overall detection limit was <14% of the mean concentration in deep ocean waters. The RSD was <9%. Our values for the trace metals in the certified reference materials of seawater NASS-5 and nearshore seawater CASS-4 agreed with the certified values (except that there is no certified value for Al). This method was also successfully applied to the reference materials of open-ocean seawater produced by the SAFe program. Our Fe concentrations were 5.9 +/- 0.7 ng/kg for surface water (S1) and 50.4 +/- 2.9 ng/kg for deep water (D2), which are in agreement with the interlaboratory averages of 5.4 +/- 2.4 and 50.8 +/- 9.5 ng/L, respectively. The data for other metals were oceanographically consistent.

Detailed study of HEDTA’s chemodynamics upon gamma-radiolysis in a simulated, mixed waste

Gamma-radiolysis of the parent compound N-(2-hydroxyethyl)ethylenediamine-triacetic acid (HEDTA) in a simulant of a Hanford mixed waste, at γ-doses of 0–7.5·106±10% R, yielded extensive degradation. Two major degradation products, glyoxylate and N-(nitroso)iminodiacetic acid (NIDA), were identified, along with lower levels of malonate and oxalate. Comparison of HEDTA’s radiolysis with that of ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and citrate, from earlier studies, reveals several fundamental similarities, along with marked differences. Comparatively speaking, HEDTA’s radiolysis is not particularly diverse, but it is very dispersive.

Cadmium tolerance and accumulation of Althaea rosea Cav. and its potential as a hyperaccumulator under chemical enhancement

The role of ornamental plants has drawn much attention as the urban pollution levels exacerbate. Althaea rosea Cav. had showed its strong tolerance and accumulation ability of Cd in our previous work, thus, the effects of ethylenediamine triacetic acid (EDTA), ethylenegluatarotriacetic acid (EGTA) and sodium dodecyl sulfate (SDS) on its Cd phytoremediation capacity were further investigated in this work. It reconfirmed that the species had strong tolerance and accumulation ability of Cd. Particularly, the species can be regarded as a potential Cd-hyperaccumulator through applying chemical agents. However, different chelators and surfactants had great differences in affecting hyperaccumulating characteristics of the species. EGTA and SDS could not only increase the dry biomass of the plants, but also promote Cd accumulation in shoots and roots. On the contrary, EDTA was toxic to the species by restraining the growth of plants, although it could promote Cd accumulation in shoots and roots of the plants to a certain extent. Thus, EGTA and SDS were effective in enhancing phytoremediation with Althaea rosea Cav. for Cd contaminated soils, while EDTA is ineffective in this regard.

Stability and Anti-Oxidization of Aqueous MR Fluids Improved by Modifying Iron Particle Surface with Organic Molecule

N-glucose ethylenediamine triacetic acid (GED3A) was used to modify the surface of carbonyl iron (CI) particles for preparing composite magnetic particles (CMPs) and aqueous magnetorheologic (MR) fluids. The properties of the obtained CMPs, including morphology, magnetic property, and anti-oxidation ability, were characterized by scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The magnetorheologic properties of aqueous MR fluids were measured using a commercial rheometer equipped with a magnetic field supplier and controller. Meanwhile, the dispersion stability and the anti-oxidation ability of the prepared aqueous MR fluids were also analyzed via stability test, air oxidation test, and acid corrosion test, respectively. The results are shown in below. (i) The CMPs possess better soft magnetic properties (magnetic saturation (Ms): 182.2 emu·g-1, coercivity (Hc): 4.17 Oe, remanence (Mr): 0.1944 emu·g-1. (ii) Compared with the aqueous MR fluid based on CI particles, the dispersion stability, anti-oxidation ability, and magnetorheological effect of the aqueous MR fluid based on the CMPs were substantially improved. The sedimentation ratio dropped by about 24.4%; and in the range of 0.02-0.10 mol·L-1 of acids, the anti-oxidation ability increased by 92.6%-95.7% for HCl, and 86.1%-93.8% for HNO3.

Voltammetric and chronoamperometric studies of silver electrodeposition from a bath containing HEDTA

The electrodeposition of silver on platinum from ammonium-buffered solutions containing HEDTA (N-(2-hydroxyethyl)ethylenediaminetriacetic acid) at various concentrations was investigated. Potentiometric titration and voltammetric studies indicated that in the presence of 2.0 × 10−1 M HEDTA, the deposited silver was reduced from a mixture of [AgHEDTA]2− and [Ag(NH3)2]+ complexes, whereas at 2.0 × 10−2 M and 2.0 × 10−3 M HEDTA in the electrolyte, the silver was reduced from the [Ag(NH3)2]+ complexes alone. Hydrodynamic studies showed variation in the diffusion coefficient for the electroactive species in solution, depending on the HEDTA concentration. Chronoamperometric study in a solution containing 2.0 × 10−1 M HEDTA at low overpotential (0.000 V to –0.050 V) showed a transition from progressive to instantaneous nucleation in a single current transient, whereas, at −0.200 V only 3D-progressive nucleation controlled by mass transport was observed. Scanning electron microscope images showed that the silver films produced in silver baths with HEDTA were uniform, without cracks, and fine-grained, regardless of its concentration, while in the absence of HEDTA the morphology was rough and dendritic. X-ray diffraction analysis of the films obtained at various HEDTA concentrations revealed polycrystalline silver, similar to film obtained in cyanide and EDTA/ammonia baths.

Solubility and Accumulation of Metals in Chinese Brake Fern, Vetiver and Rostrate Sesbania Using Chelating Agents

Greenhouse experiments were conducted to study the effects of chelating agents on the growth and metal accumulation of Chinese brake fern (Pteris vittata L.), vetiver (Vetiveria zizanioides L.), and rostrate sesbania (Sesbania rostrata L.) in soil contaminated with arsenic (As), Cu, Pb, and Zn. Among the five chelating agents used [ethylenediaminetriacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA), oxalic acid (OA), and phytic acid (PA)], OA was the best to mobilize As, EDTA to mobilize Cu and Pb, and HEDTA to mobilize Zn from soil, respectively. The biomass of vetiver was the highest, followed by rostrate sesbania. All chelating agents inhibited the growth of Chinese brake fern and rostrate sesbania, but HEDTA significantly increased the aboveground biomass of vetiver. Dry weights of both Chinese brake fern and rostrate sesbania decreased with increasing EDTA concentrations amended in the soil, especially in treatments with high EDTA concentrations. EDTA and HEDTA enhanced Cu, Zn, and Pb, but lowered As accumulation in all three plant species, except for As in vetiver, while OA significantly enhanced As accumulation in the aboveground part of vetiver. Concentrations of Cu, Zn, and Pb in the aboveground parts of plants increased significantly with the increase of EDTA concentrations and treatment time. In addition to As, Chinese brake fern also accumulated the highest Cu, Pb, and Zn in its aboveground parts among the three plant species grown in metal-contaminated soil with EDTA/HEDTA treatments. This species, therefore, can be used to simultaneously clean up As, Cu, Pb, and Zn from contaminated soils with the aid of EDTA or HEDTA.

Regulation of the Gating of BKCa Channel by Lipid Bilayer Thickness

Transmembrane segments of ion channels tend to match the hydrophobic thickness of lipid bilayers to minimize mismatch energy and to maintain their proper organization and function. To probe how ion channels respond to mismatch with lipid bilayers of different thicknesses, we examined the single channel activities of BK(Ca) (hSlo alpha-subunit) channels in planar bilayers of binary mixtures of DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) with phosphatidylcholines (PCs) of varying chain lengths, including PC 14:1, PC 18:1, PC 22:1, PC 24:1, and with porcine brain sphingomyelin. Bilayer thickness and structure was measured with small angle x-ray diffraction and atomic force microscopy. The open probability (P(o)) of the BK(Ca) channel was finely tuned by bilayer thickness, first decreasing with increases in bilayer thickness from PC 14:1 to PC 22:1 and then increasing from PC 22:1 to PC 24:1 and to porcine brain sphingomyelin. Single channel kinetic analyses revealed that the mean open time of the channel increased monotonically with bilayer thickness and, therefore, could not account for the biphasic changes in P(o). The mean closed time increased with bilayer thickness from PC 14:1 up to PC 22:1 and then decreased with further increases in bilayer thickness to PC 24:1 and sphingomyelin, correlating with changes in P(o). This is consistent with the proposition that bilayer thickness affects channel activity mainly through altering the stability of the closed state. We suggest a simple mechanical model that combines forces of lateral stress within the lipid bilayer with local hydrophobic mismatch between lipids and the protein to account for the biphasic modulation of BK(Ca) gating.

Organically modified sols as pseudostationary phases for microchip electrophoresis

We demonstrate that the selectivity of microchip electrophoresis separations is greatly improved by the presence of organically modified silica (Ormosil) sols in the run buffer. A negatively-charged N-(trimethoxysilylpropyl)ethylenediamine triacetic-acid (TETT)-based sol is used for improving the selectivity between nitroaromatic explosives and a methyltrimethoxysilane (MTMOS)-based sol is employed for enhancing the microchip separation of environmental pollutants, aminophenols. These sols are added to the run buffer and act as pseudostationary phases. Their presence in the run buffer changes the apparent mobility of studied solutes, and leads to a higher resolution. The observed mobilities changes reflect the interactions between the Ormosil sols and the solutes. Relevant experimental variables have been characterized and optimized. The diverse chemistry of Ormosil sols should be extremely useful for tailoring the selectivity of a wide range of electrophoresis microchip separations.

Oxidation of Aqueous EDTA and Associated Organics and Coprecipitation of Inorganics by Ambient Iron-Mediated Aeration

Cationic metal and radionuclide contaminants can be extracted from soils to groundwater with sequestering agents such as EDTA. However, EDTA must then be removed fromthe groundwater, by advanced oxidation or specialized biological treatment. In this work, aqueous individual metal-EDTA solutions were aerated with steel wool for 25 h, at ambient pH, temperature, and pressure. Removal of approximately 99% of EDTA (0.09-1.78 mM); glyoxylic acid (0.153 mM); chelated Cd2+ (0.94 and 0.0952 mM), Pb2+ (0.0502 mM), and Hg2+ (0.0419 mM); and free chromate and vanadate was shown. EDTA was oxidized to glyoxylic acid and formaldehyde, and metals/metalloids were coprecipitated together with iron oxyhydroxide floc. Free arsenite and arsenate were each removed at 99.97%. Free Sr2+, and chelated Ni2+ were removed at 92% and 63%, respectively. Similar removals were obtained from mixtures, including 99.996+/-0.004% removal of total arsenic (95% confidence). Traces of iminodiacetic acid, nitrilotriacetic acid, and ethylenediaminetriacetic acid were detected after 25 h. Results are consistent with first-order, solution-phase oxidation of EDTA and glyoxylic acid by ferryl ion and H202, respectively, with inhibition due to sludge accumulation, and equilibrium metal coprecipitation. This ambient process, to our knowledge previously unknown, agrees with recently reported findings and shows promise for remediation of metals, metalloids, and radionuclides in wastewater, soil, and sediment.

Selection of appropriate organic additives for enhancing Zn and Cd phytoextraction by hyperaccumulators

Chelant-enhanced phytoextraction is one of the most promising technologies to remove heavy metals from soil. The key of the technology is to choose suitable additives in combination with a suitable plant. In the present study, laboratory batch experiment of metal solubilization, cress seeds germination were undertaken to investigate the metal-mobilizing capability and the phytotoxicity of organic additives, including ethylene diamine triacetic acid (EDTA), citric acid, acetic acid, oxalic acid, glutamine and monosodium glutamate waste liquid (MGWL) from food industry. Experiments in pots were carried out to study the effects of the additives on Zn and Cd phytoextraction. Furthermore, a leaching experiment with lysimeter was performed to evaluate the environmental risks of additive-induced leaching to underground water. The results showed that EDTA had a strong mobilizing ability for Zn and Cd, followed by mixed reagent (MR) and MGWL. MGWL and acetic acid at 5 mmol equivalent per liter resulted in seed germination index less than 2%. Experiments in pots verified the phytotoxicity of acetic acid and MGWL. Addition of the mixed reagent at 6–10 mmol/kg significantly increased Zn phytoextraction by Thlaspi caerulescens. The same for EDTA and the mixed reagent at 10 mmol/kg by Sedum alfredii. But only mixed reagents could significantly increase Cd phytoextraction by the studied hyperaccumulators. This suggested that the strong chelant was not always the good agent to enhance phytoextraction. S. alfredii combined with 2–10 mmol/kg soil MR was preferred for phytoremediation of Cd/Zn contaminated soils in southern China, this could result in high phytoextraction of Cd/Zn and reduce the leaching risk to underground water than EDTA assisted phytoextration.

Hybrid Electrochemical Treatment for Persistent Metal Complex at Conductive Diamond Electrodes and Clarification of Its Reaction Route

The hybrid electrochemical treatment for persistent organometallic complexes [Cu–ethylenediaminetetraacetic acid (EDTA)] that was a combination of the reduction recovery of the center metal as nanoparticles and the oxidative decomposition of the organic ligand was attempted using the potential cycling at the oxygen-terminated boron-doped diamond (BDD) electrode. In the step of the recovery of the center metal of the organo-metal complex in the potential cycling from the reduction potential for , by stepping up the anodic potential limit to the potential region for oxygen evolution reaction, the reionization of electrodeposited Cu could be suppressed in the presence of the dissolved oxygen. Moreover, separation of the electrodeposited Cu as nanoparticles from the electrode surface could be achieved by introducing the oxygen-containing functional groups on the diamond surface. The oxidation of the particle surface by the dissolved oxygen might induce the formation of the insulating layer and accelerate the separation by the electrostatic repulsive force between the oxygen-terminated surface and the insulating layer on the Cu particles. The reaction pathway of the treatment was analyzed using the long-term potential cycling at the potential region between the reduction potential of Cu and the oxidation potential of the EDTA. In flow injection analysis with the UV detector, the formation of the Cu particles by the reduction reaction of the ion from was clarified to mainly occur in the initial stage of the electrolysis. Moreover, in high-performance liquid chromatography analysis with the electrogenerated chemiluminescence detector for the treated solution, ethylenediaminetriacetic acid (ED3A) and ethylenediaminediacetic acid (EDDA) were observed. Therefore, it was confirmed that the liberated EDTA was oxidized to ED3A and EDDA through sequential removal of the acetate groups. An unidentified product (supposed to be the small size of a hydrocarbon) appeared after during the electrolysis. Although the concentration of this unidentified product was not decreased in the electrolysis with anodic potential limit of , the concentration decay for this product was observed for the potential cycling up to , suggesting that for the full oxidation of EDTA to , it might be effective for the electrochemical oxidation by the radical available over at BDD.

Unnatural multidentate metal ligating α-amino acids

A family of penta- and hexadentate metal ligating α-amino acids, suitably protected for Fmoc solid-phase chemistry, has been prepared. These residues incorporate the mono-amides of ethanolaminetriacetic acid, ethylenediaminetriacetic acid, and ethylenediaminetetraacetic acid as side chains. Side chains are tethered varying distances ( n) from the Cα-carbon to allow metal binding events to occur at distinct distances from the peptide backbone. These residues are designed to allow the facile installation of metal chelates along a peptide backbone.

Iron-Mediated Aeration: Evaluation of Energy-Assisted Enhancement for In Situ Subsurface Remediation

Laboratory tests using ultraviolet radiation and sonocation energy were found to kinetically enhance an iron-mediated aeration (IMA) process under development to remove chelated metals and radionuclides and associated organics, from groundwater and soils. A model inorganic contaminant ( Cd2+ ) chelated with ethylenediamine tetraacetic acid (EDTA) was used. The IMA process breaks the complex, releasing the target metal for removal. Overall experimental results indicate that the EDTA degradation mechanism can be accelerated compared to nonenergized IMA, by a factor of 2 using sonocation energy and by a factor of 3–4 using photochemical energy at circumneutral pH. No differences in the by-products were indicated in chemical analyses. For both sonocation and photochemical tests, the major breakdown products detected were glyoxylic acid and formaldehyde. Only minor amounts of larger molecular weight species (iminodiacetic acid, nitrilotriacetic acid, and ethylenediamine triacetic acid) were detected.

Speciation of Chromium(III) and Cobalt(III) (Amino)carboxylate Complexes Using Capillary Electrophoresis

Capillary electrophoresis (CE) can very efficiently resolve different dissolved metal ion species as long as rates of ligand exchange are slow relative to time scales required for electromigration. Here, we detail the separation of several Cr(III) and Co(III) complexes with the multidentate chelating agents iminodiacetic acid, nitrilotriacetic acid, trans-1,2-cyclohexanediaminetetracetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, trimethylenediaminetetraacetic acid, and ethylenediaminetetraacetic acid. Successes in speciating some Ni(II) and Co(II) complexes are also reported. For Cr(III) and Co(III), subtle differences in metal ion-chelating agent stereochemistry, chelating agent denticity, and number of bridging ligands are discernible due to the high resolving power of CE. New peaks and heightened baselines were encountered when a pH buffer with strong complexing properties (orthophosphate) was employed in the background electrolyte. For this reason, we recommend using pH buffers with very weak or negligible complex properties (e.g., MES and MOPS).

Synthesis and properties of N-hexadecyl ethylenediamine triacetic acid.

A new kind of surfactant named N-hexadecyl ethylenediamine triacetic acid (HED3A) was synthesized from anhydrous ethylenediamine, 1-bromohexadecane, and chloroacetic acid. Testing showed stability of HED3A in hard water, wetting power, dispersing power, and surface tension increased along with pH value. Stability in hard water of trisodium N-hexadecyl ethylenediamine triacetate (3NaHED3A) was at level 4, which was better than that of sodium dodecylsulfate (SDS) and sodium dodecylbenzene sulfonate (LAS). Other properties of 3NaHED3A including wetting power, dispersing power, emulsifying power, and surface tension had intermediate value between SDS, LAS, AES, peregal-O, and cetyltrimethylammonium chloride (CTAC). The ethylenediamine triacetic acid (ED3A) group in 3NaHED3A can chelate many kinds of metal ions, which indicates a promising application prospect in many fields including metal anticorrosion, corrosion control agent, additives in electroplating solution, and ore selection and solid surface treatment.

Biological and photochemical degradation rates of diethylenetriaminepentaacetic acid (DTPA) in the presence and absence of Fe(III)

The environmental fate of ethylenediaminetetraacetic acid (EDTA) has been extensively studied, while much less is known about the environmental behaviour of diethylenetriaminepentaacetic acid (DTPA). In this study, it was confirmed that DTPA is persistent toward biodegradation. The biodegradability of DTPA was investigated in the absence and in the presence of Fe(III) by using CO 2 evolution test and Manometric respirometry test. The CO 2 evolution and oxygen uptake of iron-free (DTPA was added as free acid) and Fe(III)DTPA were less than in inoculum blank. Possible inhibitor effect was analysed by testing biodegradation of sodium benzoate with and without iron-free or Fe(III)DTPA in the Manometric respirometry test. Only slight inhibition was observed when DTPA was added as free acid. Photodegradation of iron-free DTPA and Fe(III)–DTPA complex was studied by using sunlight and UV radiation at the range 315–400 nm emitted by black light lamps. The results indicate that DTPA added as free acid degrades photochemically in humic lake water. Fe(III)DTPA was shown to be very photolabile in humic lake water in the summer; the photochemical half-life was below one hour. Photodegradation products were identified by the mass spectrometric technique (GC–MS). It was shown that photodegradation of Fe(III)DTPA does not result in total mineralization of the compound. Diethylenetriaminetetraacetic acid, diethylenetriaminetriacetic acid, ethylenediaminetriacetic acid, N, N ′- and/or N, N-ethylenediaminediacetic acid, iminodiacetate, ethylenediaminemonoacetic acid and glycine were identified as photodegradation products of Fe(III)DTPA. Based on these observations, we propose a photodegradation pathway for Fe(III)DTPA.

Inactivation of human glutamate dehydrogenase by aluminum.

Aluminum inactivated glutamate dehydrogenase (GDH) by a pseudo-first-order reaction at micromolar concentrations. A double-reciprocal plot gave a straight line with a k(inact) of 2.7 min(-1) and indicated the presence of a binding step prior to inactivation. The inactivation was strictly pH dependent and a marked increase in sensitivity to aluminum was observed as the pH decreased. At a pH higher than 8.5, no inactivation was observed. The completely inactivated GDH contained 2 mol of aluminum per mole of enzyme subunit monomer. When preincubated with enzyme, several chelators such as citrate, NaF, N-(2-hydroxyethyl) ethylenediaminetriacetic acid or ethylenediaminetriacetic acid efficiently protected the enzyme against the aluminum inactivation. In a related experiment, only citrate and NaF released the aluminum from the completely inactivated aluminum-enzyme complex and fully recovered the enzyme activity. Ferritin, NADP+, or nerve growth factor did not show any effects on the recovery of the aluminum-inactivated GDH activity. The dissociation constant for the aluminum-enzyme complex was calculated to be 5.3 microM. Although aluminum has been known to form a complex with nucleotides, no such effects were observed in the inactivation of GDH by aluminum as determined using GDHs mutated at the ADP-binding site, NAD+-binding site or GTP-binding site. Circular dichroism studies showed that the binding of aluminum to the enzyme induced a decrease in alpha helices and beta sheets and an increase in random coil. Therefore, inactivation of GDH by aluminum is suggested to be due to the conformational change induced by aluminum binding. These results suggest a possibility that aluminum-induced alterations in enzymes of the glutamate system may be one of the causes of aluminum-induced neurotoxicity.

The Deposition Characteristics of Accelerated Nonformaldehyde Electroless Copper Plating

The deposition process of an electroless copper plating solution using sodium citrate as the main complexing agent and sodium hypophosphite as the reducing agent has been investigated. The deposit composition, structure, and catalytic activity for the oxidation of hypophosphite during the process have been investigated. Formamidine disulfide (fd) has been shown to accelerate the deposition rate of the electroless plating just as it does with electroless plating solutions using N-(2-hydroxyethyl)ethylenediaminetriacetic acid trisodium salt hydrate (HEDTA) as the complexing agent. For solutions with the mole ratio of 42, the deposition rate decreased with time and terminated after 90 min plating because the surface catalytic activity of the deposit had decreased with thickness. A copper deposit with total thickness of 6.48-6.59 μm was obtained after 90 min plating. The decrease in the deposition rate with time was mitigated by decreasing the mole ratio, holding the concentration of copper ions constant. An optimized electroless copper plating process with sustained deposition rate with time and high metal conductivity was developed. The bath was used in a fully additive high density wiring process. © 2003 The Electrochemical Society. All rights reserved.