Transport Of Cd2 Research Articles

Phytoremediation of soil contaminated with nickel, cadmium and cobalt

This pot experiment analyzed the use of Brassica napus, Elymus elongatus and Zea mays in the removal of Cd2+ Co2+ and Ni2+ from the soil. The utility of the plants under study for phytoremediation was analyzed based on the biomass of the aboveground parts and roots and the accumulation of metals, bioaccumulation, bioconcentration and translocation capability in the above-ground parts and roots. The effect of heavy metals on the soil enzyme activity and soil physicochemical properties was also determined. Among the species under study, only E. elongatus was found to be suitable for Cd2+ phytoextraction, whereas E. elongatus and Z. mays proved to be suitable for phytostabilisation of Cd2+ and Co2+ because the criterion of the accumulation of metals in the roots at a sufficient level was fulfilled. The index of bioaccumulation in roots was greater than one. Both plant species met the second condition which determined the utility for phytostabilisation, as since the transport of Cd2+ Co2+ and Ni2+ from the roots to the above-ground parts was limited.

The molecular mechanism underlying cadmium resistance in NHX1 transgenic Lemna turonifera was studied by comparative transcriptome analysis

Cadmium (Cd) is one of the most toxic heavy metals, which poses a serious threat to the environment. Our previous studies revealed that transgenic Lemna turonifera (hereafter mentioned as Transgenic) over expressing Na+/H+ Antiporter (AtNHX1) gene was more tolerant to Cd2+ stress than the Wild type plants (WT). To further explore the molecular mechanism underlying cadmium resistance, comprehensive transcriptome analysis and comparison were performed. For RNA-Seq, the trannsgenic and WT were treated with 50 μM CdCl2 for 24 h. In total, 2247 differentially expressed unigenes (DEGs) including 1195 upregulated and 1052 downregulated ones were discovered between Transgenic and WT samples. The downregulated genes associated with the adventitious root (AR), lateral root (LR) and root hair (RH) initiation might have prevented the root from abscission. Calcium signaling and ROS accumulation were regulated in response to cadmium stress. Moreover, the activation of genes involved in the production of trehalose and R-S glutathione increased the cadmium resistance of duckweed. Downregulation of genes involved in the transport of Cd2+ and upregulation of genes involved in vacuolar sequestration might have resulted in increased tolerance of Transgenic over WT. These findings might provide new ideas for improving plant cadmium resistance and phytoremediation. Comparative transcriptome analysis was applied to study the involvement of NHX1 in Cadmium detoxification. The genes associated with root, calcium signal and cadmium transports were regulated in transgenic duckweed.

Photo‐Electrodialysis Combination System for Cd2+ Removal Using Polymeric

The present work combines the solar energy with the environmental protection through the membrane selectivity for metallic ions. Firstly, we have elaborated new polymeric membranes for ions separation. The membrane is made up of cellulose acetate (CA) modified by polyelectrolytes (polyethylenimine (PEI), polyvinyl alcohol (PVA) and polyanetholsulfonic acid (PATSA) using glycerol as plasticizer. Different membranes are characterized by Fourier transform infrared spectroscopy (FTIR), X‐Ray diffraction (XRD), thermo‐gravimetric analysis (TGA) and scanning electron microscopy (SEM). In a second part, we have prepared two new photo‐electrodes, crystallizing in the brownmillerites structure: n‐Sr2Fe2O5 and p‐Sr2Co2O5 and their photo‐electrochemical characterizations are undertaken. As application, the transport of Cd2+ using the synthesized membranes coupled with the photo‐electrodes is studied. The photo‐catalytic results indicate that the combined hetero‐system n‐Sr2Fe2O5/p‐Sr2Co2O5 enhances considerably the electrons transfer. The diffusion flux of Cd2+ is considerably enhanced when the electrode is exposed to visible light illumination. The results show that the transport percentages of Cd2+ increases by 40% under solar energy and 25% under a tungsten lamp.

Synthesis of modified polymer inclusion membranes for photo-electrodeposition of cadmium using polarized electrodes

In this work, we have developed a novel class of polymeric inclusion membranes (PIMs) for the cations separation. The membrane is made up of cellulose triacetate modified by poly-electrolytes (poly-phosphoric acid, polyvinyl pyrolidone, polyacrylic acid, polyvinyl alcohol and poly-anetholsulfonic acid) using 2-hydroxy-5-dodecylbenzaldehyde incorporated into the polymer as carrier and tris ethyl hexyl phosphate or glycerine as plasticizers. Different PIMs are synthesized and characterized by the Fourier transform infrared, X-ray diffraction, thermal analysis and scanning electron microscopy. The influence of the membrane nature is studied using supports with different physical characteristics (porosity, thickness, hydrophobia). As application, the transport of Cd2+ using PIMs coupled with photo-electrodes is investigated.The photo-catalytic results indicate that the combined system p-CuFeO2/membrane/n-WO3 enhances considerably the electrons transfer toward the delafossite CuFeO2.The position of the conduction band of CuFeO2 is looked to be the key issue for the photo electrochemical Cd2+ reduction.

Effects of pH and soil texture on the adsorption and transport of Cd in soils

To better understand the adsorption and transport of Cd2+ in soils, column experiments were conducted with various soils and inflow solutions with different pH values. Breakthrough curves (BTCs) of the column tests were fitted using both the equilibrium and non-equilibrium models installed in the program of CXTFIT. Results showed that the equilibrium model fitted most of BTCs reasonably well. Values of the retardation factor (R) and the distribution coefficient (k d) for Cd2+ adsorption and transport increased with increasing pH values of the inflow solution and of the soil. However, the clay content was not a key factor to affect R and k d for Cd2+ adsorption and transport. The average dispersivity values and the variance values of dispersivity increased with increasing clay content of the soils.

Selective Metal Binding to a Membrane-embedded Aspartate in the Escherichia coli Metal Transporter YiiP (FieF)

The cation diffusion facilitators (CDF) are a ubiquitous family of metal transporters that play important roles in homeostasis of a wide range of divalent metal cations. Molecular identities of substrate-binding sites and their metal selectivity in the CDF family are thus far unknown. By using isothermal titration calorimetry and stopped-flow spectrofluorometry, we directly examined metal binding to a highly conserved aspartate in the Escherichia coli CDF transporter YiiP (FieF). A D157A mutation abolished a Cd2+-binding site and impaired the corresponding Cd2+ transport. In contrast, substitution of Asp-157 with a cysteinyl coordination residue resulted in intact Cd2+ binding as well as full transport activity. A similar correlation was found for Zn2+ binding and transport, suggesting that Asp-157 is a metal coordination residue required for binding and transport of Cd2+ and Zn2+. The location of Asp-157 was mapped topologically to the hydrophobic core of transmembrane segment 5 (TM-5) where D157C was found partially accessible to thiol-specific labeling of maleimide polyethylene-oxide biotin. Binding of Zn2+ and Cd2+, but not Fe2+, Hg2+, Co2+, Ni2+, Mn2+, Ca2+, and Mg2+, protected D157C from maleimide polyethylene-oxide biotin labeling in a concentration-dependent manner. Furthermore, isothermal titration calorimetry analysis of YiiP(D157A) showed no detectable change in Fe2+ and Hg2+ calorimetric titrations, indicating that Asp-157 is not a coordination residue for Fe2+ and Hg2+ binding. Our results provided direct evidence for selective binding of Zn2+ and Cd2+ for to the highly conserved Asp-157 and defined its functional role in metal transport.

Thermodynamics of Re-Solvation of Cadmium Ions in Water-Acetone Solvents

On the basis of a method of differences of Volta-potentials at 298.15 K the real primary effect of an environment of cadmium ions and the real Gibbs energy for the transport of Cd2+ out of water into a water-acetone solvent (Me2CO) are determined. The surface potential at the nonaqueous solvent/gas phase interface \(\Delta \chi _{H_2 O}^S\) is obtained. This quantity is taken into account when calculating chemical thermodynamic characteristics for cadmium ions and the surface potential at the gas phase/acetone interface \(\Delta \chi ^{\operatorname{Me} _2 \operatorname{O} } = - 0.337\operatorname{V}\). Thermodynamic characteristics of the over-solvation of a II-I electrolyte with those for a I-I electrolyte are compared.

Cadmium uptake and subcellular compartmentation in the ectomycorrhizal fungus Paxillus involutus.

Cadmium uptake and subcellular compartmentation in the ectomycorrhizal fungus Paxillus involutus were investigated using radiotracer flux analyses. Concentration-dependent Cd2+-uptake kinetics were characterized by a smooth, non-saturating curve that could be dissected into linear and saturable components. The linear-uptake kinetic component was interpreted as representing binding of Cd to apoplastic components, whereas the remaining saturable component was the result of carrier-mediated transport across the plasma membrane. Cell-wall-bound Cd was almost completely removed during desorption from cell-wall preparations. Cd2+ desorption from intact mycelium was found to be a function of time involving three compartments corresponding in series to cell wall (50%), cytoplasm (30%) and vacuole (20%), when mycelia were exposed to a 0.05 microM Cd concentration. At 4 degrees C, most of the Cd recovered was due to the cell-wall-bound fraction, suggesting that transport across the plasma membrane is a metabolically mediated process. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) inhibited Cd accumulation in P. involutus mycelia by up to 28%, which indicates that transport of Cd2+ was partially dependent on the membrane potential. Cd2+ uptake into symplasm is linked to Ca2+ transport, as revealed by the inhibition of Cd accumulation by the Ca2+ ionophore A23187. The present work demonstrates the ability of the ectomycorrhizal fungus P. involutus to take up and further accumulate Cd in different compartments. Binding of Cd onto cell walls and accumulation of Cd in the vacuolar compartment may be regarded as two essential metal-detoxification mechanisms. These data represent a first step towards the understanding of metal-tolerance mechanisms in mycorrhizal fungi.

A Study of Cadmium Transport Pathways Using the Caco-2 Cell Model

The purpose of this study was to investigate the mechanism by which cadmium (Cd2+) crosses the intestinal epithelium using a Caco-2 cell model. Experimentation was designed to determine which of several possible pathways of transport are operative. These pathways include passive diffusion, transport via a calcium pathway, sulfhydryl-mediated transport, and carrier-mediated (active transport and/or facilitated diffusion) transport. To examine the diffusion pathway the effect of various apical cadmium concentrations on the amount of cadmium transported was tested. The effects of verapamil, calcium, and 1,25(OH)2vitamin D3(vit. D3) on Cd2+transport were examined to investigate the possible existence of a calcium transport pathway.N-Ethylmaleimide, a sulfhydryl group blocker, was used to determine whether Cd2+transport is sulfhydryl-mediated. Active transport was evaluated by examining the effect of 2,4-dinitrophenol, a metabolic inhibitor, on the transport of Cd2+. These studies indicated that: (1) a portion of the overall transport of Cd2+can be attributed to diffusion, (2) stimulation of calcium binding protein transcription by vit. D3enhances Cd2+transport, and (3) the transport process for Cd2+has both sulfhydryl-mediated and carrier-mediated components.