Showing papers on "Zinc published in 1977"

Chemical Composition of Sewage Sludges and Analysis of Their Potential Use as Fertilizers

Abstract: Electron Spectroscopy for Chemical Analysis (ESCA) was used to provide information concerning the chemical bonding of zinc and copper present in the sludge obtained from the Dayton, Ohio sewage treatment plant. The binding energy of the Zn 2P/sub 3/2/ electron in sludge when placed under a vacuum of 10/sup -7/ Torr was 1023.8 +- 0.2 eV and the binding energy of the Cu 2p/sub 3/2/ electron in the sludge under similar conditions was 937.2 +- 0.3 eV. These energies are characteristic of both Zn and Cu being in the positive two oxidation state. The electronegativity of the ligand attached to either of these metals was found to be 3.5 +- 0.1 on the Pauling scale. This indicates that Zn and Cu exist in similar compounds, that the ligand binding site is oxygen, and that the possible compounds include carbonate, carboxylate, phosphate, nitrate, silicate, and/or oxide. ESCA, when used in conjunction with other methods, offers excellent potential for more specifically identifying the chemical form of metal in sludge or sludge mixtures.

Computer simulation of metal-ion equilibria in biofluids: models for the low-molecular-weight complex distribution of calcium(II), magnesium(II), manganese(II), iron(III), copper(II), zinc(II), and lead(II) ions in human blood plasma

Abstract: An investigation by computer simulation into the nature of the metal-ion binding to low-molecular-weight ligands in human blood plasma is described. Although the absolute concentrations of the metal-complex species are controlled by protein binding, the percentage distribution of transition-metal ions amongstthe low-molecular-weight ligands is not. Hence errors arising from the omission of protein–metal equilibria are successfully by-passed. The distribution of Ca2+, Mg2+, Mn2+, Fe3+, Cu2+, Zn2+, and Pb2+ amongst 5 000 complexes formed with 40 ligands has been computed. In order to cope with multicomponent systems of such a large size, a computer program has been developed. Ternary complexes account for the larger percentage of CuII and FeII species, all the former involving histidinate and all the latter, citrate. Binary complexes are favoured by CaII, MgII, and MnII. Zinc(II) and PbII form both binary and ternary complexes amongst the predominant species. In contrast with earlier work, ternary zinc citrate complexes are found to be important.

Carbon-13 nuclear magnetic resonance probe of active-site ionizations in human carbonic anhydrase B.

Abstract: Human carbonic anhydrase B (HCAB), prepared by a new affinity chromatography procedure, was carboxymethylated exclusively at NT of its active-site histidine-200 using 90% [1-13C]bromoacetate. The 13C nuclear magnetic resonance signal of the covalently attached carboxylate was easily detected over the natural abundance background due to the other carbonyl and carboxyl carbons of this 29 000 molecular weight zinc metalloenzyme. Its chemical shift proved very sensitive to the presence of inhibitors in the active site and to variations in pH. Two perturbing groups with pKa values of 6.0 and 9.2 were assigned to the modified histidine-200 itself and the zinc-bound water ligand, respectively, making use of 13C NMR titration data on Nr- and Nr-carboxymethyl-L-histidine model compounds. The results rule out histidine-200 as the critical group whose ionization controls the catalytic activity. They also strongly suggest an interaction of the carboxylate of the carboxymethyl group with either the zinc or its water ligand around pH 8, possibly explaining the basis for the major differences between HCAB and CmHCAB.

The Role of Malate, Oxalate, and Mustard Oil Glucosides in the Evolution of Zinc‐Resistance in Herbage Plants

Abstract: Malate, oxalate and mustard oils were analysed in zinc-resistant and zinc-sensitive ecotypes of Silene cucubalus Wib., Rumex acetosa L., Thlaspi alpestre L. and Agrostis tenuis Sibth. The effect of zinc on the activities of carbonic anhydrase and peroxidase in Siiene cucubalus was tested. Carbonic anhydrase of the zinc-resistant ecotypes was stimulated by addition in vivo of high amounts of zinc. The high activity of peroxidase in the non-zinc-resistant ecotypes after the addition of zinc documented a poisoning of the sensitive plants by zinc. The amount of oxalate differed greatly between ecotypes. There was, however, no direct correlation between zinc-resistance and oxalate. When applying zinc to the nutrient medium, the synthesis of oxalate was inhibited in zinc-sensitive, but stimulated in zinc-resistant ecotypes of Silene cucubalus and Rumex acetosa. In Thlaspi alpestre high concentrations of mustard oil glucosides were found. Zinc-resistant plants produced twice as much glucosides as sensitive ones. A possible role of mustard oils in zinc-resistance is discussed. In the content of malate there were great quantitative differences between zinc-resistant and zinc-sensitive plants. All zinc-resistant ecotypes of all the species contained much higher concentrations in their green organs than the sensitive ones. It is assumed that malate is a major factor in the evolution of zinc-resistance. Malate may act as a complexing agent for zinc within the plasma, whereas oxalate and mustard oils may function as “terminal acceptors” of large amounts of zinc. The role of malate may be extended by a special transport mechanism, by which zinc is eliminated from the plasma into the vacuole.

Non-Ohmic Properties of ZnO-Rare Earth Metal Oxide-Co 3 O 4 Ceramics

Abstract: Zinc oxide ceramics containing rare earth metal oxide and cobalt oxide which exhibit non-ohmic current-voltage characteristics were studied. The nonlinearity was similar to that of the zinc oxide varistor containing Bi2O3 and other additives. According to microstructural observations, the intergranular layer of the ceramics was found to be a rare earth metal oxide compound without Zn and Co atoms, and its thickness was expected to be less than 100 A. The nonlinear characteristics are attributed to the potential barrier due to the depletion layer formed in the interfacial region of the ZnO grainboundaries doped with Co atoms. Qualitative analysis of capacitance-voltage relations confirmed this model.

Cobalt(II) and zinc(II) complexes of the 'tripod' ligand tris(2-benzimidazylmethyl)amine. Some five-coordinate derivatives and some with mixed stereochemistries

Abstract: A series of cobalt(II) and zinc(II) complexes of the title ligand are reported which contain mixed stereochemistries, e.g., five-coordinate trigonal bipyramidal cations [M(ligand)X]+, and four-coor...

Zinc binding: a difference between human and bovine milk.

Abstract: Gel chromatography indicated that most of the zinc in cow9s milk was associated with high-molecular-weight fractions, whereas zinc in human milk was associated with low-molecular-weight fractions. A species difference in zinc-binding ligands may explain why symptoms of the genetic disorder of zinc metabolism, acrodermatitis enteropathica, can be alleviated by feeding human but not cow9s milk.

Effect of Acute Disease and ACTH on Serum Zinc Proteins

Abstract: The effect of acute disease and ACTH infusion on serum zinc proteins was studied in serums from 156 healthy and diseased subjects. The mean (±2 S.D.) zinc content of 20 normal serums was 96±20 μg per 100 ml. In 87 serums from acutely ill patients the zinc ranged from 92 to 40 μg per 100 ml. The mean values for nearly all categories of disease studied were lower than normal (P<0.001). Chromatography of normal serum on Sephadex G-100 separates two protein fractions, I and II, containing 37.8±8.8 and 76±10 μg of zinc per 100 ml, respectively. In serum from diseased patients the zinc in fraction I is unaltered where-as that in fraction II decreases to 29.8±7.5 μg per 100 ml (P<0.001). ACTH administration reduces serum zinc from 10 to 60 μg per 100 ml, the decrements being due to changes in the zinc content of fraction II. Thus, ACTH may have an important role in the reduction of zinc content associated with pathologic states. (N Engl J Med 296:1129–1134, 1977)

Zinc Deficiency in Crohn’s Disease

Abstract: Zinc nutriture has been studied in 30 patients with Crohn’s disease using plasma zinc, hair zinc, and taste acuity as indices. Significant reductions in plasma zinc concentrations and taste acuity wer

Zinc Correction of Defective Chemotaxis in Acrodermatitis Enteropathica

Abstract: • Three patients with acrodermatitis enteropathica (AE), a disorder of zinc metabolism, demonstrated a zinc-responsive defect in chemotaxis of neutrophils and monocytes. Monocyte chemotaxis was depressed during a controlled period of zinc deficiency and increased to normal values after administration of oral zinc sulfate supplements that was sufficient to restore normal plasma zinc levels. In the only patient in whom neutrophils were also studied, a similar defect in chemotaxis of neutrophils was corrected by administration of zinc sulfate supplements. Preincubation of defective cells in vitro with zinc sulfate increased chemotaxis in an almost linear dose-response relationship. These findings suggest an important role for zinc in neutrophil and monocyte chemotaxis and demonstrate a correctable immune defect in AE. ( Arch Dermatol 113:422-425, 1977)

The uptake of lead, zinc, cadmium, and copper by the pulmonate mollusc, Helix aspersa muller, and its relevance to the monitoring of heavy metal contamination of the environment

Abstract: The occurrence of lead, zinc, cadmium, and copper in individuals of Helix aspersa from two sites of varying degrees of contamination was studied. Zinc, cadmium, and copper were shown to increase in a linear fashion with animal weight. The rate of uptake for zinc and cadmium in particular was significantly greater at the more contaminated site. Statistical analysis of the data, using correlation and regression techniques provided information on apparent intermetallic effects. It is concluded that because metal uptake and body weight show a positive linear relationship only the use of animals of similar weight and/or size can be used for monitoring purposes. Even then, different patterns of uptake into different organs and interactions between metal uptakes are such as to seriously question the use of Helix, and other molluscs, for monitoring purposes unless specific organs from comparably sized and/or aged animals are used.

Release of Particles Containing Metals from Vegetation into the Atmosphere

Abstract: Studies with radioisotopes indicate that in the laboratory pea plants and pine tree seedlings release zinc and lead into the atmosphere. Field studies carried out on radiolabeled plots vegetated with a variety of grasses and small herbaceous plants also show that these elements are released into the atmosphere. The metals, associated with particles of various sizes, are released from the plant surfaces, and the loss mechanism is influenced by growth conditions, the concentrations of the elements in the leaves, and meteorological factors. For plants whose leaves have about equal concentrations of zinc and lead, the amount of zinc released is usually two orders of magnitude greater than the amount of lead. The significance of the process is discussed in terms of the overall trace metal composition of atmospheric particulates.

Zinc adsorption by goethite in the absence and presence of phosphate

Abstract: Zinc adsorption by goethite in the presence of 0.1M sodium chloride was found to occur at pH values well below the isoelectric point of the goethite when the surface was positive and the zinc in a cationic form. This confirms data already presented by Forbes et al. (1976). The presence of phosphate or zinc on the goethite surface was found to increase slightly the adsorption of zinc and phosphate respectively. Depending on the pH value, the total adsorption could be larger than for either ion in the absence of the other and the capacity of the surface for each of the ions. As suggested by Stanton and Burger, a surface complex may be formed.

Permeation of manganese, cadmium, zinc, and beryllium through calcium channels of an insect muscle membrane.

Abstract: Larval muscle fibers of a beetle, Xylotrupes dichotomus, produce calcium spikes that are maintained when the fibers are bathed in saline solutions containing manganese, cadmium, zinc, or beryllium instead of calcium. This indicates that these cations permeate the calcium channels of the muscle fiber. By contrast, cobalt, nickel, and magnesium are nonpermeating and behave as competitive inhibitors of the permeation of the other divalent cations. Some of the permeating cations suppress delayed rectification.

“Copper” granules in the barnacle Balanus balanoides

Abstract: Balanus balanoides (L.) collected from an area with high heavy-metal run-off contained two different types of granule within the parenchyma cells of the prosoma. X-ray microprobe analysis shows one to be the familiar “zinc” granule made up of concentric layers and giving major peaks for phosphorus and zinc, and the other to be homogeneous and giving peaks for sulphur and copper. This latter granule is designated the “copper” granule. Whilst “zinc” granules are known to be composed of inorganic phosphate, various tests on “copper” granules in sections and in a granule-rich pellet have shown that the copper is probably complexed with organic matter. The tests also demonstrated the relatively, insoluble (inert) nature of these granules. Although “zinc” and “copper” granules were present together in the prosoma, atomic absorption analyses of whole bodies (prosoma+thorax) have shown the level of zinc (50.28 μg/mg dry weight) to be much higher than that of copper (3.75 μg/mg dry weight).

Effect of magnesium on the properties of zinc alkaline phosphatase

Abstract: Alkaline phosphatase of Escherichia coli, isolated by procedures which do not alter its intrinsic metal content, contains 4.0 +/- 0.3 g-atoms of tightly bound zinc per mole (Kd less than 1 muM) and 1.3 +/- 0.2 g-atoms of magnesium per mole (Bosron, W.F., Kennedy, F.S., and Vallee, B.L. (1975), Biochemistry 14, 2275-2282). Importantly, the binding of magnesium is dependent both upon pH and zinc content. Hence, the failure to assign the maximal magnesium stoichiometry to enzyme isolated by conventional procedures may be considered a consequence of the conditions chosen for optimal bacterial growth and purification of the enzyme which are not the conditions for optimal binding of magnesium to alkaline phosphatase. Under the conditions employed for the present experimental studies, a maximum of six metal sites are available to bind zinc and magnesium, i.e., four for zinc and two for magnesium. Magnesium alone does not activate the apoenzyme, but it regulates the nature of the zinc-dependent restoration of catalytic activity to apophosphatase, increasing the activity of enzyme containing 2-g-atoms of zinc five-fold and that of enzyme containing 4-g-atoms of zinc 1.4-fold. Moreover, hydrogen-tritium exchange reveals the stabilizing effects of magnesium on the structural properties of phosphatase. However, neither the KM for substrate nor the phosphate binding stoichiometry and Ki are significantly altered by magnesium. Hence, magnesium, which is specificially bound to the enzyme, both stabilizes the dynamic protein structure and regulates the expression of catalytic activity by zinc in alkaline phosphatase.

Semiconductor electrodes. 13. Characterization and behavior of n-type zinc oxide, cadmium sulfide, and gallium phosphide electrodes in acetonitrile solutions

Abstract: The photoelectrochemical behavior of n-ZnO, n-CdS, and n-GaP single crystal semiconductor electrodes was investigated in acetonitrile which contained various electroactive compounds whose standard redox potential varied by over 3.2 V. The cyclic voltammograms of the n-type semiconductors in the dark and illuminated were compared to the Nernstian behavior at a Pt disk electrode. The photodissolution of the semiconductor electrodes did not occur until the electrode potential was well positive of the flat band potential. An underpotential was developed for the photooxidation of solution species at each semiconductor. A model for electron transfer at the semiconductor-solution interface is proposed which incorporates a surface state or intermediate level which can mediate electron transfer and surface recombination. The model is used to discuss previous work with semiconductors, electron transfer, and stabilization of the semiconductor surface. Key factors in the utilization of semiconductor electrodes in electrochemical cells and devices, including those for solar energy conversion, are knowledge of the relative locations of the energy levels in the semiconductor and solution and an understanding of the role that surface states or intermediate levels in the band gap region may play in the charge transfer processes. This information has been obtained by studying the electrochemical properties of the semiconductor electrode in solutions containing different redox couples and assuming that the model of Gerischer' can be used to rationalize the observed current-potential (i-V) behavior. This model basically requires that charge transfer occur isoenergetically from the conduction or valence bands of the semiconductor to solution species. A number of such studies of different semiconductors in aqueous solutions2-I0 have shown that while this model is useful in locating the band positions, it is necessary to invoke intermediate levels or surface states within the band gap region to explain the i -V and spectroscopic behavior. W e have previously' I s i 2 discussed the advantages of using a nonaqueous solvent, such as acetonitrile (ACN), in studying the behavior of the semiconductors Ti02 and Si. These include a much wider potential range (Le., effective solvent band gap) for investigating the semiconductor behavior and the availability of a large number of well-characterized couples which undergo reversible one-electron transfer reactions at potentials throughout this range. Thus the studies on the n-Ti02/ACN interface demonstrated the occurrence of reductions and oxidations of species whose standard potentials were located above the flat-band potential (V,) via the conduction band, and reduction of species, via an intermediate level or surface states, a t potentials positive of Vfi. We should also mention the work of Landsberg et al.13 which was primarily concerned with reductions a t n-GaP in A C N a t potentials negative of Vfi. The work reported here deals with a study of the behavior of n-type ZnO, CdS, and G a P with A C N solutions. The location of the bands, the determination of V,, and the mapping of the band gap region is described and the behavior of these materials (which photodecompose in aqueous solutions) under irradiation is discussed. Finally a model which relates the interfacial charge transfer rate to competitive rates involving the conduction and valence bands and surface states is proposed. Experimental Section Low-resistivity single crystal semiconductors about 1 m m thick and polished with 0.5 1 alumina were used. The n-GaP and n-ZnO were obtained from Atomergic Chemicals (Long Island, N.Y.) and the n-CdS from National Lead. The (OOl), (OOl), and (1 11) faces were used for the n-ZnO, n-CdS, and n-Gap, respectively. Two ohmic contacts were made on each by electrodepositing indium from a 0.1 M InC13 solution on the back of the crystal. The n-GaP was heated in a hydrogen atmosphere for about 1 h following the In deposition at 400 \"C to make the contact ohmic. In each case the current measured between the two contacts was directly proportional to the applied voltage and independent of polarity. A copper wire was connected to the ohmic contacts with conducting silver epoxy cement (Allied Products Corp., New Haven, Conn.). The back and sides of the crystal were then covered with insulating 5-min epoxy (Devcon Corp., Danvers, Mass.) and mounted on a small glass disk connected to a glass tube with silicone adhesive (Dow Corning, Midland, Mich.). The glass tube provided an insulated internal path for the wire from the electrode. There was no apparent chemical attack on the silicone adhesive from either the A C N or the etching solutions. The n-ZnO was first etched in H3P04 and then in concentrated HC1, each for 15 s.14 The n-CdS and n-GaP were etched in 11 M HCl for 1 min. Most of the compounds used in this study were obtained from commercial sources. The Ru(TPTZ)*(C104)3 (TPTZ = 2,4,6-tripyridyl-s-triazene) and Ru(bpy)3(C104)2 were prepared as described previ0us1y.l~ Most of the compounds were recrystallized several times from an appropriate solvent and all have been previously characterized in this laboratory. Controlled potential coulometry was used with some compounds to transform them to the desired oxidation state. Polarographic grade tetra-n-butylammonium perchlorate (TBAP), which was dried for 3 days under vacuum, was used as the supporting electrolyte. The ACN was dried and purified as previously described.I6 A cyclic voltammogram was obtained a t a platinum disk electrode a t the beginning of each experiment to ensure the purity of the solutions and to locate the standard potential with respect to the reference electrode. A three-compartment cell, similar to the previous design, I was used for the electrochemical measurements. The reference electrode was either a silver pseudoreference electrode, consisting of a silver wire in the supporting electrolyte solution and separated from the test solution by a medium porosity fritted-glass disk or a silver wire in a 0.1 M A g N 0 3 solution separated from the main compartment by a porous Vycor glass junction. All values a re reported vs. the aqueous SCE. The counter electrode for voltammetric measurements was a coiled platinum wire separated from the main compartment by a Kohl, Bard / n-Type ZnO, CdS, and GaP Electrodes

Zinc deposit structures obtained from high purity synthetic and industrial acid sulphate electrolytes with and without antimony and glue additions

Abstract: A characteristic morphology and crystal orientation; namely (112) (114) (102), has been obtained for zinc deposits electrowon from high purity synthetic and industrial acid sulphate electrolytes. These deposit characteristics persisted over a wide range of experimental conditions which included variations in the applied current density and changes in the anode materials and cathode pretreatments. The addition of either antimony or glue to the electrolyte produced deposit morphologies and orientations which were distinctly different from those obtained for addition-free electrolytes. When both antimony and glue additions were made to the electrolyte, however, the deposit morphologies and crystal orientations were similar to those obtained from addition-free solutions. The various deposit morphologies and orientations obtained were shown to correlate with changes occurring in the zinc deposition overvoltage.