The zntA gene of Escherichia coli encodes a Zn(II)-translocating P-type ATPase

The first Zn(II)-translocating P-type ATPase has been identified as the product of o732, a potential gene identified in the sequencing of the Escherichia coli genome. This gene, termed zntA, was disrupted by insertion of a kanamycin gene through homologous recombination. The mutant strain exhibited hypersensitivity to zinc and cadmium salts but not salts of other metals, suggesting a role in zinc homeostasis in E. coli. Everted membrane vesicles from a wild-type strain accumulated 65Zn(II) and 109Cd(II) by using ATP as an energy source. Transport was sensitive to vanadate, an inhibitor of P-type ATPases. Membrane vesicles from the zntA::kan strain did not accumulate those metal ions. Both the sensitive phenotype and transport defect of the mutant were complemented by expression of zntA on a plasmid.     

P-type ATPases mediate sodium and potassium effluxes in Schwanniomyces occidentalis

Two genes isolated from Schwanniomyces occidentalis, ENA1 and ENA2, encode P-type ATPases highly homologous to the Na-ATPases of Saccharomyces cerevisiae and complement the Na+ sensitivity of an S. cerevisiae mutant strain lacking its own Na-ATPases. The expression of both ENA1 and ENA2 was highly dependent on a high external pH, but whereas a high pH was sufficient for the expression of ENA2, the expression of ENA1 required a high pH and the presence of Na+. Disruption of ENA1 rendered the cells less tolerant to Na+ than the wild-type strain and decreased their capacity for Na+ extrusion. Disruption of ENA2 did not affect Na+ tolerance, but decreased both the growth at high pH and K+ efflux. We discuss these results and propose that fungal Na-ATPases should be considered alkali cation ATPases. By sequence comparison, we found that fungal Na-ATPases form a homogeneous group that can be distinguished from other cation-pumping P-type ATPases, except from the cta3 Ca-ATPase of Schizosaccharomyces pombe.     

P-type calcium ATPases in higher plants - biochemical, molecular and functional properties

Although structural aspects of cytosolic fatty acid binding proteins (FABPs) in mammalian tissues are now well understood, significant advances regarding the physiological function(s) of these proteins have been slow in forthcoming. Part of the difficulty lies in the complexity of the multigene FABP family with nearly twenty identified members. Furthermore, isoelectric focusing and ion exchange chromatography operationally resolve many of the mammalian native FABPs into putative isoforms. However, a more classical biochemical definition of an isoform, i.e. proteins differing by a single amino acid, suggests that the operational definition is too broad. Because at least one putative heart H-FABP isoform, the mammary derived growth inhibitor, was an artifact (Specht et al. (1996) J. Biol. Chem. 271: 1943-49), the ensuing skepticism and confusion cast doubt on the existence of FABP isoforms in general. Yet, increasing data suggest that several FABPs, e.g. human intestinal I-FABP, bovine and mouse heart H-FABP, rabbit myelin P2 protein and bovine liver L-FABP may exist as true isoforms. In contrast, the rat liver L-FABP putative isoforms may actually be due either to bound ligand, post-translational S-thiolation and/or structural conformers. In any case, almost nothing is known regarding possible functions of either the true or putative isoforms in vitro or in vivo. The objective of this article is to critically evaluate which FABPs form biochemically defined or true isoforms versus FABPs that form additional forms, operationally defined as isoforms. In addition, recent developments in the molecular basis for FABP true isoform formation, the processes leading to additional operationally defined putative isoforms and insights into potential function(s) of this unusual aspect of FABP heterogeneity will be examined.     

Stability constants of Zn(II), Pb(II), Cd(II) and Cu(II) complexes with hematoxylin

The composition and stability constants of the complexes of Zn(II), Pb(II), Cd(II) and Cu(II) with hematoxylin have been studied using direct current polarography and differential pulse polarography. The results showed the formation of 1:2 (M:L) complexes for Zn(II) and Pb(II), and a 1:6 (M:L) complex for Cd(II). However, the formation of copper-hematoxylin complex is irreversible. The values of the formation constants for the above complexes at 298, 308 and 318K were calculated as well as the relevant thermodynamic parameters.     

Functional expression of the menkes disease protein reveals common biochemical mechanisms among the copper-transporting P-type ATPases

Menkes disease is a fatal neurodegenerative disorder of childhood caused by the absence or dysfunction of a putative P-type ATPase encoded on the X chromosome. To elucidate the function of the Menkes disease protein, a plasmid containing the open reading frame of the human Menkes disease gene was constructed and used to transform a strain of Saccharomyces cerevisiae deficient in CCC2, the yeast Menkes/Wilson disease gene homologue. ccc2Delta yeast are deficient in copper transport into the secretory pathway, and expression of a wild type human Menkes cDNA complemented this defect, as evidenced by the restoration of copper incorporation into the multicopper oxidase Fet3p. Site-directed mutagenesis demonstrated the essential role of four specific amino acids in this process, including a conserved histidine, which is the site of the most common disease mutation in the homologous Wilson disease protein. The expression of Menkes cDNAs with successive mutations of the conserved cysteine residues in the six amino-terminal MXCXXC metal binding domains confirmed the essential role of these cysteine residues in copper transport but revealed that each of these domains is not functionally equivalent. These data demonstrate that the Menkes disease protein functions to deliver copper into the secretory pathway of the cell and that this process involves biochemical mechanisms common to previously characterized members of this P-type ATPase family.     

Sorption Behavior and Mechanism of Pb(II) on Chinese Loess

Lead pollution is common in Western China and has caused serious public health problems recently. The treatment of wastewater containing Pb(II) is stringent for the sustainable development of local economics. The Chinese loess proved effective to remove Pb(II) from aqueous solution and applicable in the treatment of wastewater from lead–zinc ore mining sites. The adsorption capacity of Chinese loess about Pb(II) is determined as high as 270.26?mg?g?1 in this study. Factors affecting the adsorption of Pb(II) include slurry concentration, solution pH, temperature, and equilibrating duration. The optimum conditions for Pb(II) adsorption include sorbent dosage ≥ 0.05?g/50?mL, pHi ≥ pHzpc, temperature = 55°C, and equilibration duration ≥ 30?min. The isotherms and kinetic data are well fitted with Langmuir model and pseudo-first order kinetics, respectively. The thermodynamic behavior reveals the exothermic and spontaneous nature of the adsorption. The adsorption of Pb(II) on loess involves chemical reaction with calcite and surface complexation with clay minerals and hydrolysis of quartz; the former is considered as the dominant mechanism. X-ray diffraction and Fourier transform infrared patterns confirmed these speculations.     

Preconcentration of Pb(II), Cd(II), Cu(II) and Hg(II) with 2-mercapto-5-phenylamino-1,3,4-thiadiazole impregnated on silica gel

Silica gel modified by the addition of 2-mercapto-5-phenylamino-1,3,4-thiadiazole (MPATD) was developed for the preconcentration of Pb(II), Cd(II), Cu(II) and Hg(II) at trace levels. A "series" experimental procedure permitted the determination of the optimal working conditions (time and pH) and an "on-column" experimental method permitted the determination of the quantity of MPATD retained on silica gel, the uptake capacity, the most suitable eluent and the minimum volume of eluent for which the maximum quantity of metal cations is recovered. The maximal retention capacity on the impregnated silica gel columns was obtained at pH 7.5-8 and was 1500 micrograms g-1 for Pb(II) and about 1000 micrograms g-1 for Cd(II), Cu(II) and Hg(II). The effect of preconcentration is relevant; on passing 1 l of solution containing 1 microgram ml-1 of cation through a column containing 5 g of impregnated silicagel, after elution with 30-50 ml of the appropriate eluent the cation concentration increased about 15-20-fold. The determination of cations by flame AAS was statistically evaluated and showed recoveries higher than 96% for Pb(II), 98.5% for Cd(II) and 97.95% for Cu(II) after elution with 4 M HNO3 and about 99.15% for Hg(II) after elution with thiourea.     

磁性壳聚糖/氧化石墨烯吸附材料的制备及其对Pb(II)的吸附

以壳聚糖(CS)和改进的hummers法制备的氧化石墨烯(GO)为原料,采用化学交联法合成出CS-GO复合材料,再通过化学共沉淀法制备出磁性壳聚糖/氧化石墨烯(MCSGO)复合吸附材料。采用X射线衍射仪(XRD)和傅里叶变换红外光谱仪(FT-IR)对MCSGO的结构和官能团进行表征,并研究了MCSGO吸附水体中Pb(II)的吸附性能和吸附机理。结果表明,GO和CS以NH-CO键交联,通过负载Fe₃O₄成功赋予CS-GO磁性;室温下,当Pb(II)初始质量浓度为50mg/L、吸附剂用量为0.04g、pH值为5时,吸附90min达平衡,平衡吸附量为60.99mg/g,拟二级动力学模型和Langmuir等温吸附模型可以用来描述MCSGO对Pb(II)的吸附行为,说明该吸附过程属于均匀表面的单分子层化学吸附。在外加磁场下对MCSGO进行磁分离,表明MCSGO具有很好的磁分离性能。以盐酸作为解吸剂对MCSGO进行再生,MCSGO吸附材料循环再生使用6次后,吸附量仅下降16.72%,说明MCSGO具有优异的循环再生吸附性。     

Study on the extraction mechanism and thermodynamics of Pb(II) with a o-phenylendiamine tetraacetic acid

The extraction mechanism and thermodynamics of Pb(II) with a novel o-phenylendiamine tetraacetic acid (H₄PDTA) were studied by high performance liquid chromatography with UV detector. The effects of extraction time, reciprocating oscillation frequency, Pb(II) concentration, H₄PDTA concentration and Pb(II) solution acidity on Pb(II) extraction were investigated. The results showed that the extraction ratio of Pb(II) increased with an increase of pH and H₄PEDTA concentration with a reciprocating oscillation frequency of 120 CPM (cycles per minute). The composition of the extraction complex was determined by slope methods and UV spectral analysis. The extraction mechanism of Pb(II) was proved to be a chelate extraction reaction and the values of thermodynamic function at 25°C were determined: \(\overline {K_{ex} } = 2.18 \times 10^3\), ΔG _r = –19.05 kJ mol^–1, ΔH _r = –9.965 kJ mol^–1 and ΔS _r = 30.47 J mol^–1 K^–1.     

Removal of Cd (II) and Pb (II) from aqueous environment using Moringa Oleifera seeds as biosorbent: A low cost and ecofriendly technique for water purification

Ever-growing list of chemical contaminants released into the environment through excessive industrialization on a large scale includes numerous chemical pollutants more prominently heavy metals. The discharge of heavy metals in aqueous system and their removal have been a challenging task for environmentalists for last one decade. Keeping these views in mind, the present study highlights the efficacy of shelled Moringa oleifera seeds (SMOS) in decontaminating Cd (II) and Pb (II) ions from aqueous environment both present as single metal and as binary metal solution. The extent of adsorption capacity for Cd (II) and Pb (II) on Moringa oleifera seeds for binary metal ions [76.59% and 81.10%] was found to be low as compared to single metal ions [85.10% and 96.10%]. Morphological changes observed in Scanning Electron Micrographs of native and treated SMOS indicates the existence of biosorption phenomenon. Fourier Transform Infrared Spectrometry of the exhausted seed biomass highlights amino acids-metal interaction responsible for sorption phenomenon. The sorption capacity of regenerated biomass remained almost constant after three cycle of sorption suggesting that the lifetime cycle was sufficient for continuous application.     

Anti-inflammatory drugs interacting with Zn(II), Cd(II) and Pt(II) metal ions

Complexes of Zn(II), Cd(II) and Pt(II) metal ions with the anti-inflammatory drugs, 1-methyl-5-(p-toluoyl)-1H-pyrrole-2-acetic acid (Tolmetin), alpha-methyl-4-(2-methylpropyl)benzeneacetic acid (Ibuprofen), 6-methoxy-alpha-methylnaphthalene-2-acetic acid (Naproxen) and 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid (indomethacin) have been synthesized and characterized. In the structurally characterized Cd(naproxen)2 complex the anti-inflammatory drugs acts as bidentate chelate ligand coordinatively bound to metal ions through the deprotonated carboxylate group. Crystal data for 1: [C32H26O8Cd], orthorhombic, space group P22(1)2(1), a = 5.693(2) (A), b = 8.760(3) (A), c = 30.74(1) (A), V = 1533(1) A3, Z = 2. Antibacterial and growth inhibitory activity is higher than that of the parent ligands or the platinum(II) diamine compounds.