Effect Of Chelating Ligands Research Articles

Effect of biodegradable chelating ligands on Fe uptake in and growth of marine microalgae

Iron (Fe) is an important nutrient for phytoplankton. The low solubility of Fe in oxic waters can be a growth-limiting factor for phytoplankton. Synthetic aminopolycarboxylates (APCs) such as ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) are widely used as Fe complexing agents for microalgae culture. However, the presence of these non-ready biodegradable APCS in aquatic systems may have serious environmental consequences. In the present study, the effects of biodegradable chelating ligands (hydroxyiminodisuccinic acid (HIDS), methylglycinediacetic acid (MGDA), and iminodisuccinate (IDS)) on Fe uptake in and growth of three coastal microalgae (Heterosigma akashiwo, Prymnesium parvum, and Skeletonema marinoi-dohrnii complex) were investigated, and the results were compared with those of non-ready biodegradable APCs (EDTA, ethylenediamine tetra-methylene phosphonic acid (EDTMP), and DTPA). The biodegradable chelating ligands did not have significant growth inhibition effect on the phytoplankton. Although the growth of the algae (except S. marinoi-dohrnii complex) was not affected substantially by 1.5 and 7.5 μM of DTPA, growth inhibition occurred by 7.5 μM of EDTMP and 150 μM of EDTA, DTPA, and EDTMP. The effect of chelating ligands on microalgal growth was likely to be associated with the intracellular Fe uptake influenced by the chelating ligands. On average, intracellular Fe concentrations for biodegradable chelating ligands were substantially higher than those for non-ready biodegradable APCs. Except H. akashiwo, the ratio of intra/extracellular Fe concentrations was highest for MGDA followed by IDS and HIDS. The results indicate that biodegradable chelating ligands are more efficient than non-ready biodegradable APCs in intracellular Fe uptake and algal growth.

Effect of chelating ligand, EDTA on the heat of sublimation of the triglycinylzinc(II) chloride – an NLO active single crystal

Triglycinylzinc(II) chloride, [(Gly)3Zn]Cl2 (TGZC) and 3 mol-% of EDTA doped Triglycinylzinc(II) chloride (E-TGZC) single crystals were grown from aqueous solution by slow cooling technique. Single crystal and powder XRD analyses confirmed that the crystal belongs to orthorhombic structure with non-centro symmetric space group Pbn21. Solid state kinetics was carried out by dynamic and thermal analysis (TG, DTA and DTG) at different heating rates of 5, 13, and 20 K. Kinetics of decomposition of single crystals was studied by means of model-free method, Arrhenius, Kissinger and Iso-conversional method. The values of activation energy (E) and the pre-exponential factor (ln A) of thermal decomposition at various linear heating rates were calculated. Thus the difference in activation energy of TGZC and E-TGZC calculated by Kissinger method suggested that the dopant EDTA lowers the activation energy of the TGZC crystal by 35–45 + 4 kJ/mol which is the main cause for the rapid growth of the doped crystal.

Interaction of histidine-tagged human proinsulin with immobilized nickel ion: Effect of chelating ligand and thermodynamics analysis

The nature of the chelating ligand is one of various factors affecting the performance of IMAC. In this work we studied the effect of three chelating ligands on the adsorption of recombinant human proinsulin with His-tag (proinsulin-(His) 6). The chelating ligands (complexed with Ni(II)) were two tetradentates (carboxymethylated aspartic acid, CM-Asp, and tris(2-aminoethyl)amine, TREN) and one pentadentate (tris (carboxymethyl) ethylenediamine, TED). Their performance were compared with the performance of one tridentate ligand (iminodiacetic acid, IDA) and the commercial adsorbent HisTrap both also complexed with Ni(II). Higher selectivities were achieved with Ni(II)-CM-Asp and Ni(II)-TED. The adsorption capacity decreased according to the order: TREN, HisTrap, IDA, CM-Asp, and TED (172.82, 167.98, 133.09, 110.18, and 69.22 mg of proinsulin/mL of gel, respectively, at 25 °C). Although TREN-agarose had the highest capacity, the ligand with the second highest capacity – HisTrap – showed better performance since proinsulin was eluted in a single, concentrated peak with imidazole, while for Ni(II)-TREN proinsulin was eluted with imidazole and EDTA, requiring an extra step to free the product from the EDTA. Therefore, the choice of an adsorbent for this separation depends on the priority: capacity (TREN or HisTrap for one step process) or selectivity (CM-Asp). Adsorption isotherms were determined for temperatures from 4 to 45 °C and the Langmuir model was fitted to the experimental data. The thermodynamics analysis showed positive Δ H° (from 18.83 to 86.05 kJ/mol), indicating that the adsorption of proinsuin-(His) 6 in all chelating ligands is an endothermic process. The negative change in Gibbs free energy (from −26.30 to −35.11 kJ/mol) indicated that the adsorption of the proinsulin-(His) 6 on all the adsorbents studied was a thermodynamically favorable process.

EFFECT OF BIODEGRADABLE CHELATING LIGAND ON IRON BIOAVAILABILITY AND RADISH GROWTH

The effect of chelating ligands on iron (Fe) uptake and growth of radish (Raphanus sativus L.) was investigated. The ethylenediaminetetraacetic acid (EDTA) increased 55Fe uptake in roots of radish though its subsequent translocation from roots to shoots and leaves did not increase. About 70%—80% of the total 55Fe was distributed in the roots while about 5%—15% and 11%—17% were in shoots and leaves, respectively. The EDTA increased iron uptake into the roots of radish, but not in the above ground parts of the plant. The growth of radish (Raphanus sativus L.) decreased drastically in alkaline condition (pH > 9), even though the concentration of iron was sufficient in the growth medium. The growth of radish was enhanced successfully by the addition of hydroxyiminodisuccinic acid (HIDS) and EDTA. This might be because HIDS and EDTA solubilize iron from its precipitation with hydroxides at higher pH, and increase iron bioavailability. The influence of EDTA and HIDS on radish growth was comparable. Increase of radish growth by ethylenediaminedisuccinic acid (EDDS) and methylglicinediacetic acid (MGDA) was less than those by EDTA and HIDS. Considering the reproducibility of the radish growth (biomass production) at pH 10, HIDS is supposed to be more effective compared to EDTA.

Effect of chelating ligands on Ni–Mo impregnation over wide-pore ZrO 2–TiO 2

Ethylenediamine tetraacetic acid (EDTA) and citric acid (CA) were used as organic chelating additives during preparation of NiMo catalysts with wide-pore ZrO 2–TiO 2 mixed oxides as carrier. A clear beneficial effect of using either chelator was evident when sulfided catalysts were tested in dibenzothiophene hydrodesulfurization (DBT HDS at 320 °C and 5.72 MPa, batch reactor) although the optimum concentration of EDTA and CA to obtain materials of maximized activity was different to each other (Ni/EDTA = 1 and Ni/CA = 1/2). These molar ratios seemed to correspond to total impregnated nickel chelation. Augmented chelator concentration resulted in catalysts of decreased hydrodesulfurizating properties probably due to delayed sulfidation of complexated molybdenum that could be formed by reaction of Mo 6+ containing species with organic additive excess. In a pseudo-first-order kinetic constant basis, the best catalyst prepared with EDTA had similar HDS activity to that of the optimized formulation with CA ( k HDS values of 7.8 × 10 −5 and 7.3 × 10 −5 m 3/kg cat s, respectively), both formulations being clearly superior to a NiMo/ZrO 2–TiO 2 catalyst prepared with no organic additive ( k HDS ∼ 4.7 × 10 −5 m 3/kg cat s). Characterization by thermal analyses (TGA, DTA) and infrared spectroscopy pointed out to delayed Ni 2+ sulfidation as the main cause of HDS activity improvement in catalysts prepared in presence of either organic chelator.