PcNRAMP1 Enhances Cadmium Uptake and Accumulation in Populus × canescens

Poplars are proposed for the phytoremediation of heavy metal (HM) polluted soil. Characterization of genes involved in HM uptake and accumulation in poplars is crucial for improving the phytoremediation efficiency. Here, Natural Resistance-Associated Macrophage Protein 1 (NRAMP1) encoding a transporter involved in cadmium (Cd) uptake and transport was functionally characterized in Populus × canescens. Eight putative PcNRAMPs were identified in the poplar genome and most of them were primarily expressed in the roots. The expression of PcNRAMP1 was induced in Cd-exposed roots and it encoded a plasma membrane-localized protein. PcNRAMP1 showed transport activity for Cd²⁺ when expressed in yeast. The PcNRAMP1-overexpressed poplars enhanced net Cd²⁺ influxes by 39–52% in the roots and Cd accumulation by 25–29% in aerial parts compared to the wildtype (WT). However, Cd-induced biomass decreases were similar between the transgenics and WT. Further analysis displayed that the two amino acid residues of PcNRAMP1, i.e., M236 and P405, play pivotal roles in regulating its transport activity for Cd²⁺. These results suggest that PcNRAMP1 is a plasma membrane-localized transporter involved in Cd uptake and transporting Cd from the roots to aerial tissues, and that the conserved residues in PcNRAMP1 are essential for its Cd transport activity in poplars.     

A Comparative Study on the Biosorption of Cd2+ onto Paecilomyces lilacinus XLA and Mucoromycote sp. XLC

The filamentous fungi XLA and XLC isolated from Cd-contaminated soil were identified morphologically and phylogenetically as Paecilomyces lilacinus and Mucoromycote sp., respectively. The minimum inhibitory concentrations (MICs) of Cd²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cr³⁺ and Cr⁶⁺ in minimum mineral (MM) medium agar plates were 29,786, 2945, 9425, 5080, 1785 and 204 mg·L⁻¹ for XLA and 11,240, 884, 9100, 2540, 3060 and 51 mg·L⁻¹ for XLC, respectively. Favorable biosorption conditions for adsorption of Cd²⁺ by the tested fungi were investigated. Efficient performances of the biosorbents were described using Langmuir isotherm model, and the predicted maximum biosorption capacities for Cd²⁺ were 77.61 mg·g⁻¹ of XLA and 79.67 mg·g⁻¹of XLC. Experiments on desorption potential of biosorbents validated their efficacy at a large scale. Results showed that XLA obtained a desorption rate of 84.7% by 2% EDTA and XLC gained a desorption rate of 78.9% by 0.1 M HCl. Analysis by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray photoelectron spectroscopy (XPS) suggested that groups of C–N, COO– for XLA and C–N, CH₂ and phosphate for XLC were the dominant binding sites for Cd²⁺ biosorption. Our results indicated that the fungus XLA, rather than XLC, could potentially be used as an inexpensive, eco-friendly and effective bioremediation agent for the removal of Cd²⁺ from wastewater.     

Pb Stress and Ectomycorrhizas: Strong Protective Proteomic Responses in Poplar Roots Inoculated with Paxillus involutus Isolate and Characterized by Low Root Colonization Intensity

The commonly observed increased heavy metal tolerance of ectomycorrhized plants is usually linked with the protective role of the fungal hyphae covering colonized plant root tips. However, the molecular tolerance mechanisms in heavy metal stressed low-colonized ectormyocrrhizal plants characterized by an ectomycorrhiza-triggered increases in growth are unknown. Here, we examined Populus × canescens microcuttings inoculated with the Paxillus involutus isolate, which triggered an increase in poplar growth despite successful colonization of only 1.9% ± 0.8 of root tips. The analyzed plants, lacking a mantle—a protective fungal biofilter—were grown for 6 weeks in agar medium enriched with 0.75 mM Pb(NO₃)₂. In minimally colonized ‘bare’ roots, the proteome response to Pb was similar to that in noninoculated plants (e.g., higher abundances of PM- and V-type H⁺ ATPases and lower abundance of ribosomal proteins). However, the more intensive activation of molecular processes leading to Pb sequestration or redirection of the root metabolic flux into amino acid and Pb chelate (phenolics and citrate) biosynthesis coexisted with lower Pb uptake compared to that in controls. The molecular Pb response of inoculated roots was more intense and effective than that of noninoculated roots in poplars.     

Heavy Metal Complexation of Thiol-Containing Peptides from Soy Glycinin Hydrolysates

Many thiol-containing molecules show heavy metal complexation ability and are used as antidotes. In this study, the potential function associated with thiol-containing peptides (TCPs) from soy protein hydrolysates as natural detoxicants for heavy metals is reported. TCPs enriched by Thiopropyl-Sepharose 6B covalent chromatography had different molecular weight distributions as well as different numbers of proton dissociable groups, depending on the proteases and degree of hydrolysis. The major contribution of sulfhydryl groups was confirmed by the largest pH decrease between 8.0 and 8.5 of the pH titration curves. The complexation of TCPs with heavy metalswas evaluated by stability constants (β_n) of TCP-metal complexes whose stoichiometry was found to be 1:1 (ML) and 1:2 (ML₂). TCPs from degree of hydrolysis of 25% hydrolysates gave high affinities towards Hg²⁺, Cd²⁺, and Pb²⁺ (giving similar or even bigger lgβ values than that of glutathione). A significantly positive correlation was found between the logarithm of stability constants for ML₂ (lgβ₂) and the sulfhydryl group content. Molecular weight distribution of TCPs affected the complexation with Pb²⁺ notably more than Hg²⁺ and Cd²⁺. These results suggest that soy TCPs have the potential to be used in the formulation of functional foods to counteract heavy metal accumulation in humans.     

Deficiency of Thyroid Hormone Reduces Voltage-Gated Na+ Currents as Well as Expression of Na+/K+-ATPase in the Mouse Hippocampus

Mice lacking functional thyroid follicular cells, Pax8^−/− mice, die early postnatally, making them suitable models for extreme hypothyroidism. We have previously obtained evidence in postnatal rat neurons, that a down-regulation of Na⁺-current density could explain the reduced excitability of the nervous system in hypothyroidism. If such a mechanism underlies the development of coma and death in severe hypothyroidism, Pax8^−/− mice should show deficits in the expression of Na⁺ currents and potentially also in the expression of Na⁺/K⁺-ATPases, which are necessary to maintain low intracellular Na⁺ levels. We thus compared Na⁺ current densities in postnatal mice using the patch-clamp technique in the whole-cell configuration as well as the expression of three alpha and two beta-subunits of the Na⁺/K⁺-ATPase in wild type versus Pax8^−/− mice. Whereas the Na⁺ current density in hippocampal neurons from wild type mice was upregulated within the first postnatal week, the Na⁺ current density remained at a very low level in hippocampal neurons from Pax8^−/− mice. Pax8^−/− mice also showed significantly decreased protein expression levels of the catalytic α1 and α3 subunits of the Na⁺/K⁺-ATPase as well as decreased levels of the β2 isoform, with no changes in the α2 and β1 subunits.     

(R,R)-salen/salan-based polymer fluorescence sensors for Zn detection

(R,R)-salen-based polymer fluorescence sensor P-1 could be synthesized by the polymerization of 5,5′-(isoquinoline-5,8-diylbis(ethyne-2,1-diyl))-bis(3-tert-butyl-2-hydroxybenzaldehyde) (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition-elimination reaction, and (R,R)-salan-based polymer sensor P-2 could be obtained by the reduction reaction of P-1 with NaBH₄. The fluorescence response behaviors of two chiral polymers P-1 and P-2 on Zn²⁺ were investigated by fluorescence spectra. The fluorescence intensities of P-1 and P-2 can exhibit gradual enhancement upon addition of Zn²⁺. Compared with other cations, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Cd²⁺, Cr³⁺ and Pb²⁺, Zn²⁺ can lead to the pronounced fluorescence enhancement as high as 22.8-fold for P-1 and 3.75-fold for P-2, respectively. The results show that P-1 and P-2 incorporating (R,R)-salen/salan moieties as receptors in the polymer main chain backbone can exhibit high sensitivity and selectivity for Zn²⁺ detection.     

Regulatory Cell Populations in Relapsing-Remitting Multiple Sclerosis (RRMS) Patients: Effect of Disease Activity and Treatment Regimens

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) of autoimmune etiology that results from an imbalance between CNS-specific T effector cells and peripheral suppressive mechanisms mediated by regulatory cells (RC). In this research, we collected blood samples from 83 relapsing remitting MS (RRMS) patients and 45 healthy persons (HC), to assess the sizes of their RC populations, including CD4⁺CD25^highFoxp3⁺ (nTregs), CD3⁺CD4⁺HLA⁻G⁺, CD3⁺CD8⁺CD28⁻, CD3⁺CD56⁺, and CD56^bright cells, and how RC are affected by disease activity (acute phase or remission) and types of treatment (methylprednisolone, interferon, or natalizumab). In addition, we isolated peripheral blood mononuclear cells (PBMC) and cultured them with peptides mapping to myelin antigens, to determine RC responsiveness to autoantigens. The results showed decreased levels of nTregs in patients in the acute phase ± methylprednisolone and in remission + natalizumab, but HC levels in patients in remission or receiving interferon. Patients + interferon had the highest levels of CD3⁺CD4⁺HLA⁻G⁺ and CD3⁺CD8⁺CD28⁻ RC, and patients in the acute phase + methylprednisolone the lowest. Patients in remission had the highest levels of CD3⁺CD56⁺, and patients in remission + natalizumab the highest levels of CD56^bright cells. Only nTregs responded to autoantigens in culture, regardless of disease activity or treatment. The highest suppressive activity was exhibited by nTregs from patients in remission. In conclusion, in RRMS disease activity and type of treatment affect different RC populations. nTregs respond to myelin antigens, indicating that it is possible to restore immunological tolerance through nTreg induction.     

Fluoride ion reactions in the acetonitrile-10%(mole) water medium. pF scale and potential-pF diagrams relative to the silver, copper and hydrogen redox systems

Ag⁺, Cu⁺, Cu²⁺, Co²⁺, UO²⁺₂, La³⁺, Fe³⁺, Al³⁺ precipitation by fluoride ions and their reaction with H⁺ ion have been studied in the acetonitrile-10%(mole) water medium. The pF⁻ buffers are positioned on a pF⁻ scale extending over about 14 unities. The potential-pF⁻ diagrams relative to the silver, copper and hydrogen systems, established in the same medium, give evidence that in contrast with water, their redox properties depend largely on the fluoride ion concentration.     

Stability constants of metal ion complexes formed with N3-deprotonated uridine in aqueous solution

The acidity constant for the deprotonation of the (N3)H site of uridine (Urd) and the stability constants of the M(Urd–H)⁺ complexes with the metal ions M²⁺=Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺ or Cd²⁺ have been determined by potentiometric pH titrations in aqueous solution at 25 °C and I=0.1 M (NaNO₃). The stability constant of the Pb(Urd–H)⁺ complex could not be measured due to the hydrolysis of Pb(aq)²⁺. It is shown that previously determined and compiled stability constants are far too large; the reason being most likely the neglect of M(aq)²⁺ hydrolysis, at least in the cases of Mn²⁺, Zn²⁺ and Cd²⁺. Because of the low stability of the alkaline earth ion complexes, it is suggested that in these instances outersphere species are formed which most likely also involve the C2 and/or C4 carbonyl oxygens of the uracil residue.     

Competitive Adsorption of Ag+, Pb2+, Ni2+, and Cd2+ Ions on Vermiculite

Competitive adsorption of Ag⁺, Pb²⁺, Ni²⁺, and Cd² ions on vermiuculite in a binary, ternary, and quaternary mixture was investigated in batch experiments. The effects of the presence of Ag⁺, Ni²⁺, and Cd²⁺ ions on the adsorption of Pb²⁺ ions were investigated in terms of the equilibrium isotherm. Experimental results indicated that Pb²⁺ ions always favorably adsorbed on vermiculite over Ag⁺, Ni²⁺, and Cd²⁺ ions. The adsorption equilibrium data of Pb²⁺ ions better fitted the Langmuir model than the Freundlich model. The results showed that the pseudo-second-order kinetics model was in good agreement with the experimental results for all metal ions, and the adsorption rate among the metal ions followed Ag⁺ > Pb²⁺ > Ni²⁺ > Cd²⁺. The desorption and regenration study indicated that vermiculite can be used repeatedly and be suitable for the design of a continuous process.     

A generalized model for the measurement of effective diffusion coefficients of heterovalent ions in ion exchangers by the zero-length column method

A generalized theoretical model for the measurement of effective diffusion coefficients of heterovalent ions in ion exchange resins by the zero-length column method was developed. The model included the resistance to mass transfer both in the particle and in the film and described ion fluxes with Nernst-Planck equations. Equilibria were described using a model based on the mass action law. The values of intraparticle diffusivity of Cu²⁺, Cd²⁺, Zn²⁺, and H⁺ on commercial Amberlite IR-120 were obtained by non-linear regression, these values agree fairly well with data reported previously in literature. The following trend was observed: D_Cu>D_Zn>D_Cd.     

Cd transfer across water/1,2-dichloroethane microinterfaces facilitated by complex formation with 1,10-Phenanthroline

The transfer of Cd²⁺ facilitated by 1,10-Phenanthroline (phen) was investigated at the microinterface of two immiscible electrolyte solutions, hosted by a 25 μm diameter orifice of a micropipette. Cyclic voltammetry (CV) was employed to examine the transfer in the conditions of the ligand (organic phase) in excess and Cd²⁺ (aqueous phase) in excess. In these conditions, asymmetric (peak-shaped in the forward scan and steady state in the backward scan), and reversible steady state (for the two scan directions) voltammograms were observed. The dependence of half-wave potential on the ligand concentration suggested that the equilibrium was effectively displaced towards a 1:3 (Cd²⁺:ligand) stoichiometry, with a formation constant, β₃ = 3.9 × 10²⁹. The diffusion coefficients of Cd²⁺ in the aqueous solution and those of phen, Cd(phen)₃²⁺ in organic phase were evaluated to be 6.5 × 10⁻⁶, 5.8 × 10⁻⁶, and 5.1 × 10⁻⁶ cm² s⁻¹ respectively, using CV.     

Highly Selective and Efficient Membrane Transport of Copper as Cu(SCN)2− 4 Ion Using K+-Dicyclohexyl-18-crown-6 as Carrier

Abstract

Potassium-Dicyclohexyl-18-Crown-6 Complex Was Used As A Highly Efficient Carrier For The Uphill Transport Of Copper As Cu(SCN)^2? ₄ Complex Ion Through A Chloroform Bulk Liquid Membrane. By Using Histidine As A Metal Ion Acceptor In The Receiving Phase At The Optimum Ph Of 7.4, The Amount Of Copper Transported Across The Liquid Membrane After 2 Hours Was 90.2 ± 1.0%. The Selectivity And Efficiency Of Copper Transport From Aqueous Solutions Containing Equimolar Mixtures Of Ag⁺, Cd²⁺, Zn²⁺, Ni²⁺, Fe²⁺, Co²⁺, Pb²⁺, Mn²⁺, Fe³⁺, Bi³⁺, And Cr³⁺ Ions Were Investigated. In The Presence Of Pyrophosphate As A Suitable Masking Agent In The Source Phase, The Interfering Effects Of Co²⁺, Zn²⁺, Pb²⁺, And Cd²⁺ Ions Were Completely Eliminated.     

Phenylalanine-Derived β-Lactam TRPM8 Modulators. Configuration Effect on the Antagonist Activity

Transient receptor potential cation channel subfamily M member 8 (TRPM8) is a Ca²⁺ non-selective ion channel implicated in a variety of pathological conditions, including cancer, inflammatory and neuropathic pain. In previous works we identified a family of chiral, highly hydrophobic β–lactam derivatives, and began to intuit a possible effect of the stereogenic centers on the antagonist activity. To investigate the influence of configuration on the TRPM8 antagonist properties, here we prepare and characterize four possible diastereoisomeric derivatives of 4-benzyl-1-[(3′-phenyl-2′-dibenzylamino)prop-1′-yl]-4-benzyloxycarbonyl-3-methyl-2-oxoazetidine. In microfluorography assays, all isomers were able to reduce the menthol-induced cell Ca²⁺ entry to larger or lesser extent. Potency follows the order 3R,4R,2′R > 3S,4S,2′R ≅ 3R,4R,2′S > 3S,4S,2′S, with the most potent diastereoisomer showing a half inhibitory concentration (IC₅₀) in the low nanomolar range, confirmed by Patch-Clamp electrophysiology experiments. All four compounds display high receptor selectivity against other members of the TRP family. Furthermore, in primary cultures of rat dorsal root ganglion (DRG) neurons, the most potent diastereoisomers do not produce any alteration in neuronal excitability, indicating their high specificity for TRPM8 channels. Docking studies positioned these β-lactams at different subsites by the pore zone, suggesting a different mechanism than the known N-(3-aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)-benzamide (AMTB) antagonist.     

Contribution a l'etude des complexes du cation cadmium (II) avec l'acide laćtique et l'acide malonique en milieu Na+(ClO−4)3M A 25°C

The potentiometric study of neutralisation at 25°C, in Na⁺ (ClO^?₄)3M medium, with NaOH as titrant, of solutions: Cd²⁺ cation-lactic acid (between neutralisation rate values 0 to 1); and of Cd²⁺ cation-malonic acid (between neutralisation rate values 1–2), allows consideration of the formation of mononuclear complexes with lactic acid, and mononuclear and polynuclear complexes with malonic acid.The interpretation of experimental data ph = f(x)_R induces one to suppose the existence of the following species: lactic acid: Cd(Lact)⁺, Cd(Lact)₂; malonic acid; Cd(Mal); Cd(Mal)^2?₂; Cd(Mal)^4?₃; Cd₂(Mal)₂; Cd₂(Mal)^2?₃.The constants of formation of those complexes have been determined by non-linear regression.     

Poly(2‐acrylamido glycolic acid‐co‐2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid): Synthesis,characterization, and retention properties for environmentally impacting metal ions

Poly(2‐acrylamido glycolic acid‐co‐2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) [P(AGA‐co‐APSA)] was synthesized by radical polymerization in an aqueous solution. The water‐soluble polymer, containing secondary amide, hydroxyl, carboxylic, and sulfonic acid groups, was investigated, in view of their metal‐ion‐binding properties, as a polychelatogen with the liquid‐phase polymer‐based retention technique under different experimental conditions. The investigated metal ions were Ag⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Cr³⁺, and these were studied at pHs 3, 5, and 7. P(AGA‐co‐APSA) showed efficient retention of all metal ions at the pHs studied, with a minimum of 60% for Co(II) at pH 3 and a maximum close to 100% at pH 7 for all metal ions. The maximum retention capacity (n metal ion/n polymer) ranged from 0.22 for Cd²⁺ to 0.34 for Ag⁺. The antibacterial activity of Ag⁺, Cu²⁺, Zn²⁺, and Cd²⁺ polymer–metal complexes was studied, and P(AGA‐co‐APSA)–Cd²⁺ presented selective antibacterial activity for Staphylococcus aureus with a minimum inhibitory concentration of 2 μg/mL. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ligating behavior and metal uptake of N‐sulphonylpolyamine chelating resins anchored on polystyrene‐divinylbenzene beads

Amberlite XAD‐2 has been functionalized by coupling through –SO₂‐with ethylenediamine, propylenediamine, and diethylenetriamine to give the corresponding polyamine chelating resins I–III. The solid metallopolymer complexes of the synthesized chelating resins with Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ were synthesized. The polyamine derivatives and their metal complexes were characterized by elemental analysis, spectral (IR, UV/V, and ESR), and magnetic studies. The batch equilibrium method was utilized for using the chelating polyamines for the removal of Cu⁺², Zn⁺², Cd⁺², and Pb⁺² ions from aqueous solutions at different pH values and different shaking times at room temperature. The selective extraction of Cu⁺² from a mixture of the four metal ions and the metal capacities of the chelating resins were evaluated using atomic absorption spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1839–1846, 2005     

C,N‐Pyridylpyrazole‐Based Ligands: Synthesis and Preliminary Use in Metal Ion Extraction

Abstract

The synthesis of new N‐donor pyridylpyrazole ligands with a functionalized arm is described. The complexation capabilities of these compounds towards bivalent metal ions (Hg²⁺, Cd²⁺, Pb²⁺, Cu²⁺, and Zn²⁺) and alkali metal ions (K⁺, Na⁺, and Li⁺) were investigated using the liquid‐liquid extraction process. The percentage limits of extraction were determined by atomic absorption measurements.     

Characterization in Inhibitory Effectiveness of Carbamazepine in Voltage-Gated Na+ and Erg-Mediated K+ Currents in a Mouse Neural Crest-Derived (Neuro-2a) Cell Line

Carbamazepine (CBZ, Tegretol^®) is an anticonvulsant used in the treatment of epilepsy and neuropathic pain; however, several unwanted effects of this drug have been noticed. Therefore, the regulatory actions of CBZ on ionic currents in electrically excitable cells need to be reappraised, although its efficacy in suppressing voltage-gated Na⁺ current (I_Na) has been disclosed. This study was undertaken to explore the modifications produced by CBZ on ionic currents (e.g., I_Na and erg-mediated K⁺ current [I_K(erg)]) measured from Neuro-2a (N2a) cells. In these cells, we found that this drug differentially suppressed the peak (transient, I_Na(T)) and sustained (late, I_Na(L)) components of I_Na in a concentration-dependent manner with effective IC₅₀ of 56 and 18 μM, respectively. The overall current–voltage relationship of I_Na(T) with or without the addition of CBZ remained unchanged; however, the strength (i.e., ∆area) in the window component of I_Na (I_Na(W)) evoked by the short ascending ramp pulse (V_ramp) was overly lessened in the CBZ presence. Tefluthrin (Tef), a synthetic pyrethroid, known to stimulate I_Na, augmented the strength of the voltage-dependent hysteresis (Hys_(V)) of persistent I_Na (I_Na(P)) in response to the isosceles-triangular V_ramp; moreover, further application of CBZ attenuated Tef-mediated accentuation of I_Na(P)’s Hys_(V). With a two-step voltage protocol, the recovery of I_Na(T) inactivation seen in Neuro-2a cells became progressively slowed by adding CBZ; however, the cumulative inhibition of I_Na(T) evoked by pulse train stimulation was enhanced during exposure to this drug. Neuro-2a-cell exposure to CBZ (100 μM), the magnitude of erg-mediated K⁺ current measured throughout the entire voltage-clamp steps applied was mildly inhibited. The docking results regarding the interaction of CBZ and voltage-gate Na⁺ (Na_V) channel predicted the ability of CBZ to bind to some amino-acid residues in Na_V due to the existence of a hydrogen bond or hydrophobic contact. It is conceivable from the current investigations that the I_Na (I_Na(T), I_Na(L), I_Na(W), and I_Na(P)) residing in Neuro-2a cells are susceptible to being suppressed by CBZ, and that its block on I_Na(L) is larger than that on I_Na(T). Collectively, the magnitude and gating of Na_V channels produced by the CBZ presence might have an impact on its anticonvulsant and analgesic effects occurring in vivo.