Presence Of Ethylenediaminetetraacetic Acid Research Articles

Dual-responsive solvatochromic sensor for simultaneous detection and mechanism of Cr(III) and Co(II) cations by a new N2O4-donor tetrabenzodiaza-crown ether Macrocyclic ligand anchored to dipyridine moieties

The present study describes the chemosensing capability of an N2O4-donor tetrabenzodiaza-crown ether macrocyclic ligand derivatized by two pyridine side arms to afford the flexible macrocyclic ligand, 5,20-bis(pyridin-4-ylmethyl)-5,6,12,13,19,20,26,27octahydrotetrabenzo [e,i,o,s][1,4,11,14]tetraoxa[7,18]diazacycloicosine (PMHBOA). A selective colorimetric behavior of PMHBOA for the prompt detection of Cr(ΙΙΙ) and Co(ΙΙ) can be observed with naked eyes. The 1H, 13C{H} NMR, and infrared spectroscopy disclosed the ligand binding capability for selective metal ions, ascribed to a 1:1 complex formation with Cr(III) and Co(II) cations in isopropanol. The limit of detection (LOD) values were calculated as 580 and 850 nM for Cr(ΙΙΙ) and Co(ΙΙ), respectively, accompanied with suitable LOQs as 1.95 µM for Cr(III) and 2.85 µM for Co(II), respectively. The reusability was confirmed in the presence of ethylenediaminetetraacetic acid (EDTA). Moreover, a TLC-based fabricated paper strip successfully applied PMHBOA as a chemosensor for synchronous visible detection of Cr(III) and Co(II) in their alcoholic solution. Meanwhile, the observed color change along with the turn-off fluorescent of PMHBOA guaranteed a felicitous choice of candidate for Cr(III) in the presence of other library metal ions in isopropanol:H2O (9/1 v/v) solution. A fast separation test on the filter paper, impregnated with PMHBOA, was also employed to separate Cr(III) and Co(II) cations from aqueous solutions by recording UV–vis spectra. The 1H NMR spectroscopy supported the macrocycle ring and side arms as the parallel coordination site of PMHBOA with Cr(III) and Co(II).

Role of organic and inorganic amendments on physiological attributes of germinating pea seedlings under arsenic stress

There are scarce data regarding the effects of soil amendments on biophysicochemical responses of plants at the early stages of growth/germination. This study critically compares the effects of ethylene-diamine-tetra-acetic-acid (EDTA) and calcium (Ca) on biophysicochemical responses of germinating pea seedlings under varied arsenic levels (As, 25, 125, 250 µM). Arsenic alone enhanced hydrogen peroxide (H2O2) level in pea roots (176%) and shoot (89%), which significantly reduced seed germination percentage, pigment contents, and growth parameters. Presence of EDTA and Ca in growth culture minimized the toxic effects of As on pea seedlings, EDTA being more pertinent than Ca. Both the amendments decreased H2O2 levels in pea tissues (16% in shoot and 13% in roots by EDTA, and 7% by Ca in shoot), and maintained seed germination, pigment contents, and growth parameters of peas close to those of the control treatment. The effects of all As-treatments were more pronounced in the pea roots than in the shoot. The presence of organic and inorganic amendments can play a useful role in alleviating As toxicity at the early stages of pea growth. The scarcity of data demands comparing plant biophysicochemical responses at different stages of plant growth (germinating vs mature) in future studies.

A Julolidine Coupled Azine-based Reversible Chromo-fluorogenic Probe for Specific Detection of Cu2+Ions.

Among the various essential trace elements for living organisms, the copper (Cu2+) ions are the most important. However, Cu2+ ions are vital for the human body and are associated with necessary physiological processes; insufficient or excessiveness has many hazardous effects on our bodies. In the present contribution, strategically, we have introduced a julolidine-coupled azine-based, 9,9'-((1E,1'E)-hydrazine-1,2-diylidene bis(methanylylidene)) bis(1,2,3,5,6,7-hexahydropyrido [3,2,1-ij] quinolin-8-ol) (HDBQ) reversible chromo-fluorogenic probe for specific detection of Cu2+ ions. Probe HDBQ exhibits observable orange colorimetric change from yellow, which is visible to the naked eye in daylight. The highly green fluorescence HDBQ becomes a non-fluorescent one with the incorporation of Cu2+ ions. Interestingly, the colorimetric change and non-fluorescent HDBQ-Cu2+ complex reverse to the original HDBQ in the presence of ethylenediamine tetraacetic acid (EDTA). The detection and quantification limit of HDBQ towards the detection of Cu2+ ions is found to be in the µM range, which is much lower than the limit (31.5µM) recommended by WHO. We have also performed a colorimetric and fluorometric paper-based test strips-based experiment employing HDBQ for real-time on-site detection of Cu2+ ions. Using the reversibility characteristics of HDBQ for the consecutive addition of Cu2+ and EDTA, we have established the INHIBIT molecular logic gate. The present report brings a precise and sensitive probe for the detection of Cu2+ ions in real environmental and biological samples.

Synergistic effects of EDTA and lysozyme on the properties of hydroxypropyl starch nano antibacterial films

Hydroxypropyl starch (HPS) nano antibacterial films incorporating Ethylene Diamine Tetraacetic Acid (EDTA) and lysozyme (LY) were fabricated via solvent casting method. The synergistic effects of EDTA and LY on the microstructure, component interactions, color, optical, mechanical, barrier and antibacterial properties of HPS nano antibacterial films were evaluated. The results indicated that EDTA and LY were well dispersed in the matrix of the HPS nano antibacterial films, the film-forming substrates have good compatibility, resulting in a dense multi-layer structure of the HPS nano antibacterial films. The addition of EDTA and LY increased the color parameters (L*, a*, b* and △E*) of the HPS nano antibacterial films. The synergistic effects of EDTA and LY significantly decreased the light transmission of the HPS nano antibacterial films. The presence of EDTA and LY increased the tensile strength (TS) and the elongation at break (EAB) of the HPS nano antibacterial films. The TS and EAB of E2.5L1 reached the highest values of 6.329 MPa and 50.24 %, respectively. The incorporation of EDTA and LY had positive effects on the improvement of water vapor permeability (WVP) and oxygen permeability (OP). The WVP and OP of E2.5L1 reached the highest values of 0.9350 × 10−12 g cm/cm2•s•Pa and 0.297 × 10 −2 g m/m2 •d, respectively. In addition, EDTA and LY had significant synergistic effects on the antibacterial activity against S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria). E2.5L1 exhibited the highest antibacterial activity and the inhibition zone diameters of S. aureus and E. coli were 3.69 mm and 4.28 mm, respectively. The HPS nano antibacterial films incorporating EDTA and LY are potential functional packaging materials.

The enhanced flotation separation of magnesite and dolomite by introducing chelating reagent EDTA

In pulp environment, due to the migration and transformation of dissolved calcium ions, the surface properties of magnesite and dolomite tend to become similar, which in turn leads to difficulties in their flotation separation. In this paper, the chelating reagent EDTA is introduced to eliminate the adverse influence of calcium species and to restore the selectivity of magnesite-dolomite separation using sodium hexametaphosphate (SHMP) as depressant. Flotation experiments demonstrate that, in the presence of ethylenediaminetetraacetic acid (EDTA), the flotation recovery of magnesite increased by 22.14 % compared to using only the depressant SHMP. Zeta potential experiments combined with solution chemistry analysis indicate that the negatively charged hydrolysis species of EDTA can form soluble and stable chelates with positively charged Ca2+ and Ca(OH)+ species, effectively preventing the adsorption and transformation of calcium ions on the magnesite surface. Adsorption measurements directly confirm from a macroscopic perspective that the addition of EDTA reduces the adsorption of the depressant SHMP on the magnesite surface. X-ray photoelectron spectroscopy (XPS) measurements further confirm the phenomenon of calcium ion migration and transformation from the surface of magnesite to dolomite at the microscale, as well as the adsorption mechanisms of EDTA and SHMP on the surfaces of both minerals. Based on the experimental and analytical results, a flotation separation model of the system is established.

Antibacterial Synthetic Nanocelluloses Synergizing with a Metal-Chelating Agent.

Antibacterial materials composed of biodegradable and biocompatible constituents that are produced via eco-friendly synthetic strategies will become an attractive alternative to antibiotics to combat antibiotic-resistant bacteria. In this study, we demonstrated the antibacterial properties of nanosheet-shaped crystalline assemblies of enzymatically synthesized aminated cellulose oligomers (namely, surface-aminated synthetic nanocelluloses) and their synergy with a metal-chelating antibacterial agent, ethylenediaminetetraacetic acid (EDTA). Growth curves and colony counting assays revealed that the surface-aminated cellulose assemblies had an antibacterial effect against Gram-negative Escherichia coli (E. coli). The cationic assemblies appeared to destabilize the cell wall of E. coli through electrostatic interactions with anionic lipopolysaccharide (LPS) molecules on the outer membrane. The antibacterial properties were significantly enhanced by the concurrent use of EDTA, which potentially removed metal ions from LPS molecules, resulting in synergistic bactericidal effects. No antibacterial activity of the surface-aminated cellulose assemblies was observed against Gram-positive Staphylococcus aureus even in the presence of EDTA, further supporting the contribution of electrostatic interactions between the cationic assemblies and anionic LPS to the activity against Gram-negative bacteria. Analysis using quartz crystal microbalance with dissipation monitoring revealed the attractive interaction of the surface-aminated cellulose assembly with LPS Ra monolayers artificially produced on the device substrate.

Efficiency of cathodic arc-grown N-doped TiO2 films for the photocatalytic reduction of Cr(VI) under UV-Vis irradiation

The photocatalytic activity of undoped and N-doped TiO2 anatase films with different thicknesses prepared by cathodic arc deposition on glass substrates is reported. After TiO2 deposition, the doping of the films was carried out by plasma immersion ion implantation in a nitrogen environment. The composition of the films was studied by x-ray photoelectron spectroscopy, the surface morphology was analyzed by atomic force microscopy and the crystalline structure was examined by x-ray diffraction. The thickness was determined by observing the film cross section with scanning electron microscopy. The transmittance of the films in the UV-Vis range was studied as well. The photocatalytic activity of the films was evaluated through the efficiency in the reduction of Cr(VI) in the presence of ethylenediaminetetraacetic acid under UV-Vis irradiation. N-doped films presented a higher photocatalytic efficiency than undoped films: Cr(VI) reduction after 5 h irradiation augmented from 58% (pure TiO2) to 85% (N-doped TiO2) for films of 300 nm thickness, and from 69% to 85% for films with a thickness of 440 nm. On the other hand, pure TiO2 films of 790 nm thickness were more efficient (99% of Cr(VI) reduction) but the effect of doping on the photocatalytic activity was negligible.

Characterization of a Metallic-Ions-Independent L-Arabinose Isomerase from Endophytic Bacillus amyloliquefaciens for Production of D-Tagatose as a Functional Sweetener

D-Tagatose is a low-calorie sugar substitute that has gained increased attention as a functional sweetener owing to its nutraceutical and prebiotic properties. Traditionally, D-tagatose is produced via the enzymatic conversion of L-galactose to D-tagatose by L-arabinose isomerase (L-AI). Nonetheless, the most reported L-AI enzymes are ion-dependent enzymes requiring Mn2+ and/or Co2+ as cofactors for their reactions, which limits their application due to safety and health concerns. Herein, we addressed the facile bioconversion of L-galactose to D-tagatose using a novel recombinant metallic-ions-independent L-AI derived from endophytic Bacillus amyloliquefaciens CAAI isolated from cantaloupe fruits. The ORF (1500 bp) of the L-arabinose isomerase gene (araA) was cloned and over-expressed in Escherichia coli. The recombinant enzyme (BAAI) was purified to homogeneity using Ni-NTA affinity chromatography, yielding a single distinct band with an apparent molecular mass of approximately 59 kDa as deduced from SDS-PAGE analysis. The purified enzyme showed optimum activity at pH and temperature of 7.5 and 45 °C, respectively, with obvious enzymatic activity in the presence of ethylenediaminetetraacetic acid (EDTA), indicating the metallic-ions independence from BAAI. The Km values of BAAI for D-galactose and L-arabinose were 251.6 mM and 92.8 mM, respectively. The catalytic efficiency (kcat/Km) values for D-galactose and L-arabinose were found to be 2.34 and 46.85 mM–1 min–1, respectively. The results revealed the production of 47.2 g/L D-tagatose from D-galactose (100 g/L) with 47.2% bioconversion efficiency in a metallic-ions-free reaction system that could be implemented in safe-production of food-grade low-calorie sweetener, D-tagatose.

Metabolic Regulation of Copper Toxicity during Marine Mussel Embryogenesis.

The development of new tools for assessing the health of cultured shellfish larvae is crucial for aquaculture industries to develop and refine hatchery methodologies. We established a large-volume ecotoxicology/health stressor trial, exposing mussel (Perna canaliculus) embryos to copper in the presence of ethylenediaminetetraacetic acid (EDTA). GC/MS-based metabolomics was applied to identify potential biomarkers for monitoring embryonic/larval health and to characterise mechanisms of metal toxicity. Cellular viability, developmental abnormalities, larval behaviour, mortality, and a targeted analysis of proteins involved in the regulation of reactive oxygen species were simultaneously evaluated to provide a complementary framework for interpretative purposes and authenticate the metabolomics data. Trace metal analysis and speciation modelling verified EDTA as an effective copper chelator. Toxicity thresholds for P. canaliculus were low, with 10% developmental abnormalities in D-stage larvae being recorded upon exposure to 1.10 μg·L-1 bioavailable copper for 66 h. Sublethal levels of bioavailable copper (0.04 and 1.10 μg·L-1) caused coordinated fluctuations in metabolite profiles, which were dependent on development stage, treatment level, and exposure duration. Larvae appeared to successfully employ various mechanisms involving the biosynthesis of antioxidants and a restructuring of energy-related metabolism to alleviate the toxic effects of copper on cells and developing tissues. These results suggest that regulation of trace metal-induced toxicity is tightly linked with metabolism during the early ontogenic development of marine mussels. Lethal-level bioavailable copper (50.3 μg·L-1) caused severe metabolic dysregulation after 3 h of exposure, which worsened with time, substantially delayed embryonic development, induced critical oxidative damage, initiated the apoptotic pathway, and resulted in cell/organism death shortly after 18 h of exposure. Metabolite profiling is a useful approach to (1) assess the health status of marine invertebrate embryos and larvae, (2) detect early warning biomarkers for trace metal contamination, and (3) identify novel regulatory mechanisms of copper-induced toxicity.

Fabrication of branch-like Aph@LDH-MgO material through organic-inorganic hybrid conjugation for excellent anti-corrosion performance

Layered double hydroxides (LDH) frameworks have shown significant enhancement in stability and reusability, and their tailorable architecture brings new insight into the development of the next generation of hybrid materials, which attracted considerable attention in many fields over the years. One of the factors contributing to the widespread applicability of layered double hydroxides is their adaptable composition, which can accommodate a wide spectrum of potential anionic guests. This exceptional property makes the LDH system simple to adjust for various applications. However, most LDH systems are synthesized in situ in an autoclave at high temperatures and pressures that severely restrict the industrial use of such coating systems. In this study, LDH was directly synthesized on a magnesium alloy that had undergone plasma electrolytic oxidation (PEO) treatment in the presence of ethylenediaminetetraacetic acid, thereby avoiding the use of hydrothermal autoclave conditions. This LDH system was compared with a hybrid architecture consisting of organic-inorganic self-assembly. An organic layer was fabricated on top of the LDH film using 4-Aminophenol (Aph) compound, resulting in a smart hierarchical structure that can provide a robust Aph@LDH film with excellent anti-corrosion performance. At the molecular level, the conjugation characteristics and adsorption mechanism of Aph molecule were studied using two levels of theory as follows. First, Localized orbit locator (LOL)-π isosurface, electrostatic potential (ESP) distribution, and average local ionization energy (ALIE) on the molecular surface were used to highlight localization region, reveal the favorable electrophilic and nucleophilic attacks, and clearly explore the type of interactions that occurred around interesting regions. Second, first-principles based on density functional theory (DFT) was applied to study the hybrid mechanism of Aph on LDH system and elucidate their mutual interactions. The experimental and computational analyses suggest that the high π-electron density and delocalization characteristics of the functional groups and benzene ring in the Aph molecule played a leading role in the synergistic effects arising from the combination of organic and inorganic coatings. This work provides a promising approach to design advanced hybrid materials with exceptional electrochemical performance.

Ester Bonds for Modulation of the Mechanical Properties of Protein Hydrogels.

Hydrogels are soft materials constructed of physically or chemically crosslinked polymeric net-works with abundant water. The crosslinkers, as the mechanophores that bear and respond to mechanical forces, play a critical role in determining the mechanical properties of hydrogels. Here, we use a polyprotein as the crosslinker and mechanophore to form covalent polymer hydrogels in which the toughness and fatigue fracture are controlled by the mechanical unfolding of polyproteins. The protein Parvimonas sp. (ParV) is super stable and remains folded even at forces > 2 nN; however, it can unfold under loading forces of ~100 pN at basic pH values or low calcium concentrations due to destabilization of the protein structures. Through tuning the protein unfolding by pH and calcium concentrations, the hydrogel exhibits differences in modulus, strength, and anti-fatigue fracture. We found that due to the partially unfolding of ParV, the Young's modulus decreased at pH 9.0 or in the presence of EDTA (Ethylene Diamine Tetraacetic Acid), moreover, because partially unfolded ParV can be further completely unfolded due to the mechanically rupture of ester bond, leading to the observed hysteresis of the stretching and relaxation traces of the hydrogels, which is in line with single-molecule force spectroscopy experiments. These results display a new avenue for designing pH- or calcium-responsive hydrogels based on proteins and demonstrate the relationship between the mechanical properties of single molecules and macroscopic hydrogel networks.

Effects of EDTA on boron toxicity to the green algae Chlamydomonas reinhardtii, Chlorella sorokiniana, and Chlorella vulgaris

This study investigated whether the toxicity of boron to the green algal species Chlamydomonas reinhardtii, Chlorella sorokiniana, and Chlorella vulgaris was affected by the presence of ethylenediaminetetraacetic acid (EDTA). As EDTA exists widely in aquatic ecosystems, its effects must be considered when assessing metal toxicity. C. vulgaris was found to be the most insensitive among the three algae, as there was little change in the toxicity of boron for this species in the presence of EDTA when compared with that for the other species. In contrast, C. reinhardtii and C. sorokiniana were both highly sensitive to boron in the presence of EDTA. Based on Visual MINTEQ modeling results, we found that EDTA combined with micronutrients. This chelation reduced their availability for uptake by the algae; consequently, the algae were highly sensitive to boron. These results will be useful for future assessments of risk and management of boron in aquatic ecosystems.

Release of metal elements from clays during elution with EDTA: Insights into the side effects of washing contaminated sites

Ethylenediaminetetraacetic acid (EDTA) is frequently used to wash heavy metal contaminated fields, especially low-permeability zones which are rich in clays and have strong adsorption. However, the release kinetics of cations from clayey sediments during EDTA elution and the potential mechanisms controlling the cation release remain open questions. This study implemented heavy metal invasion and EDTA flushing experiments in a sandbox with clay-containing low-permeability layers, and batch kinetic experiments of cation release from clays in the presence of EDTA. Relatively small amounts of interlayer cations (i.e., Ca, Na, and K) and almost no structural cations (i.e., Al, Mg, Fe) were released due to ion exchange during the invasion of heavy metals. EDTA elution greatly enhanced the release of cations from clays; more interlayer cations were brought out via the complexation, and structural cations were released from clays because metal‑oxygen bonds in octahedral sheets were broken by EDTA. The first-order release rate constants of structural cations were around 0.008 min−1 and almost one order of magnitude smaller than those of interlayer cations (around 0.05 min−1), that is, mineral dissolution was slower. Additionally, when EDTA was injected into groundwater systems together with heavy metals from pollutant source zones, EDTA was mostly chelated with heavy metals and few cations were released from sediments. By adjusting the timing of EDTA injection, the complexation between EDTA and heavy metals became preferred, and little free EDTA remained and affected clays. This provides new insights into the side effects of washing heavy metal contaminated sites with chelating agents.

Inhibition of Strontium Adsorption and Desorption by Ethylenediaminetetraacetic Acid at the Barite (001)–Water Interface

Understanding the sorption behavior of ions at the mineral–water interface is important to determine the fate of elements in the environment. Here, we used barite to understand metal and organic molecule interactions with ionic crystals as organic molecules are used to remove scale that can form during oil recovery in sulfate-rich settings. The sorption behavior of strontium (Sr) on the (001) surface in the presence of ethylenediaminetetraacetic acid (EDTA) was measured using in situ specular X-ray reflectivity (XR) and resonant anomalous X-ray reflectivity (RAXR). Based on the XR results, the presence of EDTA disrupts the barite surface structure, particularly that of the top two monolayers. A maximum of 0.7 (±0.2) EDTA molecules per surface unit cell are adsorbed, though the exact amount cannot be distinguished from that of other adsorbed species, such as Ba2+ and H2O. Based on the RAXR results, the presence of EDTA inhibits Sr incorporation into the barite surface and binds with Sr in solution to limit the amount of Sr2+ in solution. The Sr-EDTA2– complex then binds with barium ions at the barite surface, presumably in a bi-nuclear, bi-dentate state. Desorption of the Sr was also measured in the presence of EDTA. The desorption experiments show that ∼75% of the sorbed strontium was removed following extended reactions with EDTA and deionized water. There were minimal changes in the surface structure following desorption measurements implying that changes following Sr sorption in the presence of EDTA may be irreversible.

NMR-Relaxometric Investigation of Mn(II)-Doped Polyoxometalates in Aqueous Solutions.

Solution behavior of K;5[(Mn(H2O))PW11O39]·7H2O (1), Na3.66(NH4)4.74H3.1[(MnII(H2O))2.75(WO(H2O))0.25(α-B-SbW9O33)2]·27H2O (2), and Na4.6H3.4[(MnII(H2O)3)2(WO2)2(β-B-TeW9O33)2]·19H2O (3) was studied with NMR-relaxometry and HPLC-ICP-AES (High Performance Liquid Chromatography coupled with Inductively Coupled Plasma Atomic Emission Spectroscopy). According to the data, the [(Mn(H2O))PW11O39]5- Keggin-type anion is the most stable in water among the tested complexes, even in the presence of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). Aqueous solutions of 2 and 3 anions are less stable and contain other species resulting from dissociation of Mn2+. Quantum chemical calculations show the change in Mn2+ electronic state between [Mn(H2O)6]2+ and [(Mn(H2O))PW11O39]5-.

Determination of Ethylenediaminetetraacetic acid (EDTA) levels in surface waters by high performance liquid chromatography (HPLC)-Ultraviolet/Visible (UV/VIS) detector

Ethylenediaminetetraacetic acid (EDTA) is a chemical that is harmful to human health with its high solubility in water, which is used as a metal chelating agent in industries such as medicine, food, personal care product, agriculture. Thus, it is necessary to should be monitored in surface waters taken from dams supplying drinking and utility water. This work presents the applicability of the HPLC-UV/VIS system for the quantification of EDTA in surface waters based on the limit values of national and international legislation such as the Turkish Regulation on the Management of Surface Water Quality. The applicability of EDTA quantification in surface water was checked with validation study. The method validation consisted of selectivity, calibration curve linearity, limit of detection (LOD) and limit of quantification (LOQ), accuracy (recovery), and precision. In selectivity study, no peaks belonging to interfering compounds that would cause false-positive results were found in the chromatograms at the retention time of EDTA (5.773 min.). The linearity of EDTA was obtained ranging from 10 µg/L to 200 µg/L concentrations with the correlation coefficient of 0.9985 and the calibration curve equation of y=4659.4x-50223. The LOD and LOQ values of EDTA was 2.85 µg/L and 9.51 µg/L with the RSD of 5.36. In accuracy, the mean recovery of EDTA in surface water has been determined as 87.51 percent with an RSD of 6.11. The repeatability (RSD, %) varied from 5.44 % to 7.02 % with concentrations of 35.19 ± 1.91 μg/L and 17.11 ± 1.20 μg/L, whereas the reproducibility (RSD, %) was obtained at 3.45 % with the concentration of 34.13 ± 1.18 μg/L. In this study, the presence of EDTA was investigated in approximately 300 surface water samples and EDTA was found as positive in the concentration range of 11.17 µg/L to 52.14 µg/L in eleven real samples.

Effect of Different Additives on the Structure and Activity of β-Galactosidase Immobilized on a Concanavalin A–Modified Silica-Coated Titanium Dioxide Nanocomposite

Interpreting the relationship between the activity and structure of β-galactosidase is necessary to perceive the impact of the enzyme’s conformation on its catalysis. The current study thoroughly explains the effects of additives such as ethylenediaminetetraacetic acid (EDTA), sodium dodecyl sulfate (SDS), dithiothreitol (DTT), and urea on β-galactosidase activity and structure. β-Galactosidase activity was determined at various ionic strengths and temperatures as a function of time. Structural studies evaluating changes in the secondary and tertiary structures of the enzyme in the presence of the additives were conducted using ultraviolet (UV)-visible and intrinsic fluorescence spectroscopy. The immobilized enzyme showed enhanced stability under different environmental conditions. Activity assays demonstrated concentration-dependent inactivation of β-galactosidase in the presence of SDS and urea, which suggests that hydrophobic and charged residues are present near the active site. In the presence of EDTA, loss in activity was noted, which confirms that β-galactosidase is a metalloenzyme. Enhancement in enzyme activity in the presence of DTT suggests the presence of a cysteine residue near the catalytic center. In UV-visible and intrinsic fluorescence spectroscopy studies, the native enzyme showed significant conformational transitions in the presence of DTT, SDS, and urea and very few changes in the presence of EDTA. However, the immobilized enzyme could resist significant structural changes. In conclusion, this study provides a detailed description of the association between the activity and conformational stability of β-galactosidase.

Candidate primary reference measurement procedure for the amount-of-substance content of a complexing agent expressed as EDTA based on the coulometric titration with electrogenerated Hg ions

The primary reference measurement procedure is a method to realize the definition of the quantity without relation to a reference standard of the same quantity. This paper presents a candidate primary reference measurement procedure for the measurement of the amount-of-substance of a complexing agent expressed as ethylenediaminetetraacetic acid (EDTA) based on coulometric titration. Herein, mercury (Hg) was used as the anode because it does not undergo spontaneous oxidation. Furthermore, a 1:1 complex is formed between the electrogenerated Hg2+ ions and EDTA (in the form of Y4−). Although the electrochemical oxidation of Hg may generate Hg2 2+ ion, Hg2 2+ undergoes disproportionation in the presence of EDTA, thereby forming the desired Hg2+ species. The equivalence point occurs at the maximum of the derivative of the theoretical titration curve. As such, the measurement results were obtained by assuming that the maximum of the derivative of the experimental titration curve was the end point. The developed procedure was employed for the measurement of the amount-of-substance content of the complexing agent in EDTA reference material certified at the Slovak Institute of Metrology. The experimental measurements agreed well with the certified value for the reference material within the measurement uncertainty. The candidate procedure will be useful in certifying EDTA reference material and establishing international equivalence of amount content of the complexing agent.

Kinetics and mechanism of rhenium-ethylenediaminetetraacetic acid (Re(IV)-EDTA) complex degradation; For 99Tc-EDTA degradation in the natural environment

Mechanism and kinetics of Rhenium complexes as a surrogate of Technetium-99 ( 99 Tc) is worthy of study from radioactive waste safe disposal perspective. Re(IV)-EDTA was synthesized via the reduction of Re(VII) with Sn(II) in the presence of Ethylenediaminetetraacetic acid (EDTA). The Re(IV)-EDTA was then degraded by H 2 O 2 (7%–30%) at pH of 3–11 in ionic strength I = 0–2 M solution. The Re-EDTA was observed to degrade more rapidly at pH of ≤ 3–4 than one of ≥ 10–11 and remained stable at pH = 7–9. The Re-EDTA was degraded in accordance with the H + addition mechanism in the acidic range and ligand charge transfer in the alkaline region. Complex degradation followed the zero-order rate kinetics for the H + and Re-EDTA parameters, apart from a pH of 3, for which degradation was a better fit to first order kinetics. A higher Re(IV)-EDTA stability at a pH of 7–9 demonstrated that Re(IV)-EDTA (or 99 Tc(IV)-EDTA) tends to be more persistent in natural environments similar to the pH range of 7–9. • Re-EDTA and [ReO-Cl 5 ] 2- complexes were degraded by H 2 O 2 . • Re-EDTA degradation followed exponential model in pH ≤ 4. • Re-EDTA degradation followed a linear model in pH ≥ 10. • Re-EDTA was stable at pH 7–7.5 because H 2 O 2 undergoes self-degradation. • 99 Tc-EDTA complex may follow the same Re-EDTA degradation model.

Photocatalytic and mechanical properties of immobilized nanotubular TiO2 photocatalysts obtained by anodic oxidation: a novel combined analysis.

The photocatalytic and mechanical performance of TiO2 nanotubular coatings obtained by anodic oxidation of commercial titanium, using an NH4F and 3.5% v/v water in ethylene glycol solution as electrolyte was investigated.After the anodization, the coatings were thermally treated at 450°C for 2h. The effects of the anodizing voltage (40-80V) and NH4F concentration (0.06, 0.15, 0.27M) on the formation of the nanotube arrays were evaluated. Nanotube diameters (57 to 114nm), wall thicknesses (4 to 13nm), and lengths (5 to 17µm) increased with the anodizing voltage and the NH4F concentration. The photocatalysts were characterized by scanning electron microscopy, glancing incidence X-ray diffraction, and UV-Vis diffuse reflectance spectroscopy. The mechanical properties of the photocatalysts were determined: adhesion using the tape test (ASTM D3359) and erosion resistance through a 3h accelerated test. The photocatalytic activity of the nanotubes under UV irradiation was evaluated using hexavalent chromium (Cr(VI)) in the presence of ethylenediaminetetraacetic acid (EDTA), using a 1.25 EDTA/Cr(VI) molar ratio solution at pH 2. A complete Cr(VI) transformation after 3h of irradiation was obtained for all samples, with a better performance than that of an immobilized P25 sample. The photocatalyst obtained with 0.27M NH4F at 40V presented a good behavior in adherence and erosion resistance, together with a very good photocatalytic activity. This novel analysis, combining photocatalytic and mechanical tests, proved that the new TiO2 nanotubular coatings could be successfully used as immobilized photocatalysts in photoreactors for water treatment.