Abstract  Human serum albumin (HSA) is the most abundant protein of blood serum, involved in the transport of metal ions, including Co(II). Using circular dichroism spectroscopic titrations we characterized three distinct Co(II) binding sites in HSA. Applying Cu(II), Ni(II) and Cd(II) ions as competitors we determined that these sites are identical with three binding sites known for other metal ions. We ordered these sites according to their binding affinities as cadmium site B (CdB)>multi-metal binding site (MBS)>N-terminal binding site (NTS). Using isothermal titration calorimetry (ITC) we confirmed the presence of these three binding sites and determined their conditional binding constants at pH 7.4 as 9+/-5, 1.1+/-0.5, and 0.9+/-0.3x10(4)M(-1), respectively. The impact of these results on the albumin cobalt binding (ACB) clinical assay for myocardial ischemia is discussed.

Abstract  We analysed the roles and distribution of metal ions in enzymatic catalysis using available public databases and our new resource Metal-MACiE (http://www.ebi.ac.uk/thornton-srv/databases/Metal_MACiE/home.html). In Metal-MACiE, a database of metal-based reaction mechanisms, 116 entries covering 21% of the metal-dependent enzymes and 70% of the types of enzyme-catalysed chemical transformations are annotated according to metal function. We used Metal-MACiE to assess the functions performed by metals in biological catalysis and the relative frequencies of different metals in different roles, which can be related to their individual chemical properties and availability in the environment. The overall picture emerging from the overview of Metal-MACiE is that redox-inert metal ions are used in enzymes to stabilize negative charges and to activate substrates by virtue of their Lewis acid properties, whereas redox-active metal ions can be used both as Lewis acids and as redox centres. Magnesium and zinc are by far the most common ions of the first type, while calcium is relatively less used. Magnesium, however, is most often bound to phosphate groups of substrates and interacts with the enzyme only transiently, whereas the other metals are stably bound to the enzyme. The most common metal of the second type is iron, which is prevalent in the catalysis of redox reactions, followed by manganese, cobalt, molybdenum, copper and nickel. The control of the reactivity of redox-active metal ions may involve their association with organic cofactors to form stable units. This occurs sometimes for iron and nickel, and quite often for cobalt and molybdenum.

Abstract  A new series of asymmetric salicyl-, furanyl-, thienyl- and pyrrolyl-derived ONNO, NNNO, ONNS & NNNS donor antibacterial and antifungal Schiff-bases and their copper(II) and zinc(II) metal complexes have been synthesized and characterized. IR spectra indicated the ligands to act as quartdentate towards divalent metal ions via two azomethine-N, deprotonated-O of salicyl, furanyl-O, thienyl-S and/or pyrrolyl-N. The magnetic moments and electronic spectral data suggest octahedral geometry for Cu(II) and Zn(II) complexes. NMR spectral data of the ligands and their diamagnetic zinc(II) complexes well-define their proposed structures/geometries. Elemental analyses data of the ligands and metal complexes agree with their proposed structures/geometries. The synthesized ligands, along with their metal complexes were screened for their antibacterial activity against B. cereus, C. diphtheriae, E. coli, K. pneumoniae, P. mirabilis, P. aeruginosa, S. typhi, S. dysenteriae and S. aureus strains and for in-vitro antifungal activity against T. schoenleinii, C. glabrata, P. boydii, C. albicans, A. niger, M. canis and T. mentagrophytes. The results of these studies show the metal complexes to be more antibacterial/antifungal against one or more species as compared to the uncomplexed ligands. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. Eight compounds, L(4), (1), (7), (8), (11), (17), (19) and (23) displayed potent cytotoxic activity with LD(50) = 1.445 x 10(- 3), 1.021 x 10(- 3), 7.478 x 10(- 4), 8.566 x 10(- 4), 1.028 x 10(- 3), 9.943 x 10(- 4), 8.730 x 10(- 4) and 1.124 x 10(- 3) M respectively, against Artemia salina.

Abstract  Cobalt (II), copper (II), nickel (II) and zinc (II) complexes with 2-hydroxy-1-naphthaldehyde derived N-substituted sulfonamides have been synthesized and the nature of bonding and structure of compounds have been deduced from physical, analytical and spectral (IR, (1)H NMR, (13)C NMR, Mass and electronic) data. An octahedral geometry has been suggested for the complexes. Complexes along with the ligands were assessed for their antibacterial and antifungal activities on different species of pathogenic bacteria and fungi. The results revealed the ligands to possess moderate to significant antibacterial activity which was, in many cases, enhanced on chelation. Similar results were observed for antifungal activity. Brine shrimp bioassay was also carried out for in vitro cytotoxic properties against Artemia salina.

Abstract  A new Mannich base, [7-hydroxy-4-methyl-8-coumarinyl]glycine [MCGH(2)], has been prepared by the condensation of 7-hydroxy-4-methyl-coumarin with glycine and formaldehyde. Its conformational changes on complexation with transition metal ions [copper(II), cobalt(II), nickel(II), zinc(II) and cadmium(II)] have been studied on the basis of elemental analysis, conductivity measurements, spectral (infrared, (1)H NMR, electronic, EPR), magnetic and thermogravimetric studies. The infrared spectral studies of all the complexes reveal that the ligand has coordinated through -NH and two hydroxyl groups. The conductance data of the complexes suggest them to be non-electrolytes. Fluorescence property of the ligand and its metal complexes was studied and concluded that the ligand MCGH(2) can be a potential candidate for the determination of zinc(II) and cadmium(II) at room temperature by fluorimetric method. The antimicrobial activity of all the compounds was studied against Gram negative (Escherichia coli) and Gram positive (Bacillus cirroflagellosus) bacteria and fungi, Aspergillus niger and Candida albicans. It was observed that the coordination of metal ion has a pronounced effect on the microbial activities of the ligand. All the metal complexes have shown higher antimicrobial effect than the free ligand.

Abstract  The accurate modeling of metal coordination geometries plays an important role for structure-based drug design applied to metalloenzymes. For the development of a new metal interaction model, we perform a statistical analysis of metal interaction geometries that are relevant to protein-ligand complexes. A total of 43,061 metal sites of the Protein Data Bank (PDB), containing amongst others magnesium, calcium, zinc, iron, manganese, copper, cadmium, cobalt, and nickel, were evaluated according to their metal coordination geometry. Based on statistical analysis, we derived a model for the automatic calculation and definition of metal interaction geometries for the purpose of molecular docking analyses. It includes the identification of the metal-coordinating ligands, the calculation of the coordination geometry and the superposition of ideal polyhedra to identify the optimal positions for free coordination sites. The new interaction model was integrated in the docking software FlexX and evaluated on a data set of 103 metalloprotein-ligand complexes, which were extracted from the PDB. In a first step, the quality of the automatic calculation of the metal coordination geometry was analyzed. In 74% of the cases, the correct prediction of the coordination geometry could be determined on the basis of the protein structure alone. Secondly, the new metal interaction model was tested in terms of predicting protein-ligand complexes. In the majority of test cases, the new interaction model resulted in an improved docking accuracy of the top ranking placements.

Abstract  Complexes of the type [M(apabh)Cl] and [M(Hapabh)(H2O)SO4], where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hapabh = acetone p-amino acetophenone benzoylhydrazone have been synthesized and characterized. Electronic spectra and mu(eff) values suggest a square planar geometry for Co(II), Ni(II) and Cu(II) chloride complexes, whereas, octahedral geometry for the sulfato complexes. ESR data show isotropic spectra for [Cu(apabh)Cl] and axial spectra for [Cu(Hapabh)(H2O)SO4] and d(x2-y2) as the ground state for both Cu(II) complexes. The ligand acts as tridentate monobasic in all chloro complexes bonding through two >C=N- and a deprotonated enolate groups, whereas tridentate neutral in all sulfato complexes coordinating through two >C=N- and a>C=0 groups. Thermal analysis (TGA & DTA) of [Ni(apabh)Cl] complex shows a multi-step exothermic decomposition pattern. The complexes show a significant antifungal activity against Rizoctonia sp., Aspergillus sp. and Penicillium sp. and a considerably fair antibacterial activity against Pseudomonas sp. and Clostridium sp. The activity increases at higher concentration of the compound. (C) 2008 Elsevier Inc. All rights reserved.

Abstract  Allergy contact dermatitis is a common occupational disease and the protective ointments are often used by the sensitized subjects. The efficacy of the chelation ability of the barrier creams containing Na2H2EDTA was evaluated. The in vitro test with the diffusion chamber and artificial membrane was performed. The effect of the Na2H2EDTA concentration (3, 5 or 10%), pH of the buffer for Na2H2EDTA dissolving and the vehicle of the ointment on the chelation of Ni2+ and Co2+ were assessed. The ointment with 10% Na2H2EDTA dissolved in the buffer of pH 7.0 or 7.4 buffer was found as optimal for the protection ability. There was no influence of the formula of the ointements on the efficiency of chelation.

Abstract  Materials used in osteosynthesis or artificial joint replacement are usually well tolerated. Complaints after such operations are mostly related to infection or mechanical problems but may also be caused by allergic reactions. The latter encompass skin changes, e.g., eczema, delayed wound/bone healing, recurrent effusion, pain, or implant loosening. In contrast to the high incidence of cutaneous metal contact allergy, allergies associated with implants are a rare condition. However, epidemiological data on the incidence of implant-related allergic reactions are still missing. Typical elicitors are nickel, chromium, cobalt, and constituents of bone cement (acrylates und additives such as gentamicin or benzoyl peroxide). After exclusion of the most common differential diagnoses, allergy diagnostic procedures are primarily based on patch tests including a metal and bone cement component series. Additional analysis of periimplant tissue is recommended. However, further studies are necessary to show the significance of the histologic findings and the role of the lymphocyte transformation test (LTT). Which combinations of factors will induce allergic sensitization to implants or trigger periimplant allergic reactions in the case of preexisting cutaneous metal allergy is still unknown. Titanium-based osteosynthesis materials are recommended for metal allergic patients. In elective hip replacements, a ceramic/polyethylene (PE) articulation should be used, and in knee replacements "alternative materials". If a regular, potentially applicable CoCr/PE articulation is preferred, the patient must be well informed and must give his/her written consent.

Abstract  This study compared the vertical misfit of 3-unit implant-supported nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloy and commercially pure titanium (cpTi) frameworks after casting as 1 piece, after sectioning and laser welding, and after simulated porcelain firings. The results on the tightened side showed no statistically significant differences. On the opposite side, statistically significant differences were found for Co-Cr alloy (118.64 mu m [SD: 91.48] to 39.90 mu m [SD: 27.13]) and cpTi (118.56 mu m [51.35] to 27.87 mu m [12.71]) when comparing 1-piece to laser-welded frameworks. With both sides tightened, only Co-Cr alloy showed statistically significant differences after laser welding. Ni-Cr alloy showed the lowest misfit values, though the differences were not statistically significantly different. Simulated porcelain firings revealed no significant differences.

Abstract  The physiological regulation of the red cell mass depends upon enhanced transcription of the erythropoietin (Epo) gene in response to hypoxia. Studies of Epo gene expression have been useful in investigating the mechanism by which cells and tissues sense hypoxia and respond with biologically appropriate alterations in gene expression. It is likely that oxygen sensing involves a heme protein in which cobalt and nickel can substitute for iron in the porphyrin ring. Indirect evidence suggests that the sensor is present in all cells and is a multi-subunit assembly containing an NAD(P)H oxidase capable of generating peroxide and reactive oxygen intermediates, which serve as signaling molecules. The up-regulation of Epo gene transcription by hypoxia is mediated by at least two known DNA-binding transcription factors, hypoxia-inducible factor 1 (HIF-1) and hepatic nuclear factor 4 (HNF-4), which bind to cognate response elements in a critical 3' enhancer approximately 50 bp in length. HIF-1 binding is induced by hypoxia as well as by cobalt. The activation of HIF-1 by hypoxia depends upon the selective protection of its alpha subunit from ubiquitin-dependent proteolysis by means of a mechanism that involves redox chemistry and perhaps phosphorylation. HNF-4 is an orphan nuclear receptor that is constitutively expressed in kidney and liver and which cooperates with HIF-1 to give maximal hypoxic induction. In hypoxic cells, p300 or a related family member forms a macromolecular assembly with HIF-1 and HNF-4, enabling transduction from the Epo 3' enhancer to the apparatus on the promoter responsible for the initiation of transcription.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. In this study, concentration of lead, cadmium, copper, cobalt, nickel, and manganese were measured in water, sediment, and fish (Cyprinus carpio and Barbus plebejus) samples at the upper Sakarya river basin in Sept. 1995-1996 period. Also, physical parameters of selected stations in the Sakarya river were measured. Mean concentrations of lead, cadmium, copper, nickel, and manganese differed between water, sediment, and fish samples by seasons. Mean concentrations of lead, cadmium, and cobalt increased in sediment samples in October and August. In water samples only cadmium and cobalt increased in October whereas lead and copper increased in August. Also, high levels of manganese concentrations were detected in water and sediment samples and fish tissue during the study.

Abstract  The relationship between heme oxygenase (HO) activity and cytochrome-p-450 content associated with induced metallothionein (MT) was investigated in the liver of rats treated with various metals. Adult male Wistar-rats were injected intraperitoneally with cadmium-chloride (10108642), 3mg/kg; cobalt-chloride (7646799), 20mg/kg; zinc-acetate (557346), 33mg/kg; nickel-chloride (7718549), 40mg/kg; copper-sulfate (7758987), 15mg/kg; or manganous-acetate (638380), 45mg/kg and killed 24 or 72 hours later. Control rats were injected with 0.9% saline alone at the corresponding volumes per kilogram. The responses to treatments with metals of the A-series (cadmium, zinc, copper) that could bind to MT in-vivo and metals of the B-series (cobalt, nickel, manganese) that could not bind to MT in-vivo were compared. A single treatment with any metal in the A-series or B-series increased both hepatic HO activity and MT concentration. Repeated treatments with metals of the A-series, however, decreased HO activities more than a single injection despite appreciable increases in MT concentrations. Repeated treatments with metals of the B-series increased both HO activities and MT concentrations. Cytochrome-P-450 concentrations were depressed by single or repeated treatments with all metals tested. The authors conclude that the magnitude of hepatic HO activity is regulated by both the amount of zinc in the zinc-MT complex induced by the metal and by the ability of the metal to bind thionein. Additionally, some metals affect cytochrome-P-450 heme degradation regardless of the magnitude of HO activity.

Abstract  Few transition metal complexes of tetradentate N(2)O(2) donor Schiff base ligands containing 2-hydroxybenzylidene-4-aminoantipyrine and amino acids (alanine/valine) abbreviated to KHL(1)/KHL(2) have been synthesized. All the metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The Schiff bases KHL(1)/KHL(2) are found to act as tetradentate ligands using N(2)O(2) donor set of atoms leading to a square-planar geometry for the complexes around the metal ions. The binding behaviors of the complexes to calf thymus DNA have been investigated by absorption spectra, viscosity measurements and cyclic voltammetry. The DNA binding constants reveal that all these complexes interact with DNA through minor groove binding mode. The studies on mechanism of photocleavage reveal that singlet oxygen ((1)O(2)) and superoxide anion radical (O(2)(-)) may play an important role in the photocleavage. The Schiff bases and their metal complexes have been screened for their in vitro antibacterial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae and antifungal activities against Aspergillus niger, Fusarium solani, Culvularia lunata, Rhizoctonia bataicola and Candida albicans by MIC method.

Abstract  Hydrotalcite-like materials containing apart from magnesium and aluminum also copper, cobalt, nickel, and iron were prepared by a co-precipitation method. Thermal transformations of hydrotalcite-like materials were studied by thermal analysis methods as well as XRD, UV-vis-DRS, and XPS measurements of the samples calcined at various temperatures (600, 700, and 800 A degrees C). Calcined hydrotalcites, especially those containing cobalt and copper, were found to be active and selective catalysts of N2O decomposition. It was shown that an increase in the calcination temperature significantly activated the Co-containing catalysts. Promotion of the samples with potassium resulted in activation of the hydrotalcite-based catalysts.

Abstract  Micro electrochemical machining (ECM) of tungsten carbide with cobalt binder (WC-Co) was studied using ultrashort pulses. In ECM, the machining characteristics were investigated according to machining conditions such as electrolyte, workpiece potential, and applied voltage pulse. Using a mixture of sulfuric acid and nitric acid, microstructures with a sharp edge and good surface quality were machined on tungsten carbide alloy. The potentials of workpiece electrode and tool electrode were determined by considering the machining rate, machining stability, and surface quality of products. With the negative potential of the workpiece electrode, oxide formation was successfully prevented and shape with good surface quality in the range from R-a 0.069 mu m to 0.075 mu m were obtained by electrochemical machining. Moreover, the performance of ECM, which includes machining gap, tapering, surface roughness, and machining time, without tool wear was compared with that of electrical discharge machining (EDM). Microstructures of WC-Co with a sharp edge and good surface quality were obtained by electrochemical milling and electrochemical drilling. Micro electrochemical turning was also introduced to fabricate micro shafts. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  Batch adsorption technique was used to study the adsorption of cobalt on NiO. The aim of this work was to examine the effect of pH, concentration and temperature on the ion exchange removal of Co2+ from aqueous solution by the NiO surface. We used Langmuir model to interpret the adsorption data. The Kurbatov-type plots were tested to determine the adsorption mechanism. The kinetics of Co2+ adsorption on NiO was best described by film diffusion model. A well-known thermodynamic equation was used to assess the enthalpy and entropy of the system. The thermodynamic data were indicative of the spontaneous nature of the endothermic sorption process of Co2+ onto the NiO.

Abstract  Dietary exposure to 11  elements was assessed by the Total Diet Study (TDS) method. Sixty-four pooled samples representing 96.5% of the diet in Yaoundé, Cameroon, were prepared as consumed before analysis. Consumption data were sourced from a household budget survey. Dietary exposures were compared with nutritional or health-based guidance values (HBGV) and to worldwide TDS results. Elevated prevalence of inadequate intake was estimated for calcium (71.6%), iron (89.7%), magnesium (31.8%), zinc (46.9%) and selenium (87.3%). The percentage of the study population exceeding the tolerable upper intake levels was estimated as <3.2% for calcium, iron, magnesium, zinc and cobalt; 19.1% of the population exceeded the HBGV for sodium. No exceedance of the HBGV for inorganic mercury was predicted in the population. The margin of exposure ranged from 0.91 to 25.0 for inorganic arsenic depending on the reference point. The "Fish" food group was the highest contributor to intake for calcium (65%), cobalt (32%) and selenium (96%). This group was the highest contributor to the exposure to total arsenic (71%) and organic mercury (96%). The "Cereals and cereal products" highly contributed to iron (26%), zinc (26%) and chromium (25%) intakes. The "Tubers and starches" highly contributed to magnesium (39%) and potassium (52%) intakes. This study highlights the dietary deficiency of some essential elements and a low dietary exposure to toxic elements in Yaoundé.

Abstract  Synthesis of a novel surfactant with an oligo- -alanine hydrophilic headgroup was achieved via the carbonylative oligomerization of aziridine followed by coupling with n-octylamine in one pot. The chemical structure of the surfactant was confirmed by NMR and MALDI MS. Preliminary studies on its surface properties, including surface tension measurement and its adsorption on polystyrene latex particles, are reported.

Abstract  The modern methods of preparation of nanoparticles of metals (cobalt and iron) and their oxides are described. The results of Fischer-Tropsch synthesis in a three-phase (gas-liquid-solid) system over iron and cobalt nanocatalysts are discussed. It is noted that in most cases, nanocatalysts exhibit a higher activity in comparison with conventional catalysts that are used for the liquid-phase synthesis. Under certain conditions, the efficiency of a nanocatalyst can achieve 5 kg/(kg cat h), which is an order of magnitude higher than that of conventional catalyst systems.

Abstract  Mesostructured Co3O4/C composites of high surface area have been synthesized via a one-step replica route by co-nanocasting cobalt and carbon precursors into mesoporous silica, in which the Co3O4 nanoparticles are homogeneously dispersed in the mesoporous structure of carbon substrates. The mesostructured composites showed relatively high catalytic activities for oxygen reduction reaction (ORR), and that with a Co loading content of 4.3 at% exhibited the best electrochemical performance for ORR. The relatively high catalytic activity is attributed to the effects of the redox couples (Co(3+)/Co(2+)) together with the contribution from the conductive mesoporous carbon substrate.

Abstract  The Keggin type heteropolyacids of tungsten and molybdenum (HPW and HPMo) and heteropolyacid salts of cobalt with changing stoichiometry H(3-2x) Co (x) PM(12)O(40) where M = Mo or W, x = A1/2, 1, 1A1/2 were synthesized and immobilized on chitosan. The complexes were characterized by X-ray diffraction and for first time by zeta potential measurements. These complexes were employed as catalysts in the cyclooctane oxidation with molecular oxygen. The introduction of cobalt into HPW structure shows a substantial influence on the catalytic activity of heteropolyacid salts in the oxidation of cyclooctane while the incorporation of cobalt atoms into HPMo only to some extent improves its catalytic properties. The cobalt molybdophosphates supported on chitosan show a similar catalytic activity as unsupported catalysts while the catalytic activity of cobalt tungstophosphate upon immobilization decreases.

Abstract  Occupational and environmental lung diseases are a group of pulmonary disorders caused by inhalation of harmful particles, mists, vapors or gases. Mineralogical analysis is not generally required in the diagnosis of most cases of these diseases. Apart from minerals that are encountered rarely or only in specific occupations, small quantities of mineral dusts are present in the healthy lung. As such when mineralogical analysis is required, quantitative or semi-quantitative methods must be employed. An electron probe microanalyzer with wavelength dispersive spectrometer (EPMA-WDS) enables analysis of human lung tissue for deposits of elements by both qualitative and semi-quantitative methods. Since 1993, we have analyzed 162 cases of suspected occupational and environmental lung diseases using an EPMA-WDS. Our institute has been accepting online requests for elemental analysis of lung tissue samples by EPMA-WDS since January 2011. Hard metal lung disease is an occupational interstitial lung disease that primarily affects workers exposed to the dust of tungsten carbide. The characteristic pathological findings of the disease are giant cell interstitial pneumonia (GIP) with centrilobular fibrosis, surrounded by mild alveolitis with giant cells within the alveolar space. EPMA-WDS analysis of biopsied lung tissue from patients with GIP has demonstrated that tungsten and/or cobalt is distributed in the giant cells and centrilobular fibrosing lesion in GIP. Pneumoconiosis, caused by amorphous silica, and acute interstitial pneumonia, associated with the giant tsunami, were also elementally analyzed by EPMA-WDS. The results suggest that commonly found elements, such as silicon, aluminum, and iron, may cause occupational and environmental lung diseases.

Abstract  The precipitation of natrojarosite from iron sodium sulfate solutions has been investigated at temperatures close to the atmospheric boiling point, in batch and semi-batch conditions. Semi-batch conditions make it possible to maintain a weaker iron concentration in the stirred reactor, leading to lower supersaturations, closer to those in continuous and possibly seeded MSMPRs or tanks-in series units. In these reactors, primary and secondary nucleations are few, allowing the growth of pure monocrystalline particles of controlled size and size dispersion. Both modi operandi lead to agglomerates made of crystals of cubic habit. The surface of cauliflower-like particles from the batch modus operandi displays overlaying crystals, of size between 100 and 400 nm. The particles from the semi-batch mode, with moderate iron addition, are rougher and show bigger intergrown constitutive crystals of size up to a few microns, which denotes lesser secondary nucleation and more growth. A model is developed to characterize iron(III) and sulfate speciation with non-ideal behavior in the mother solution. It is used to compare the variations of supersaturation in the reactor between the batch and the semi-batch conditions. During the first 500 min, the supersaturation resulting from a moderate addition of iron is 10,000-10 times lower than during batch kinetics, which agrees with the reduction of secondary nucleation suggested by scanning electron micrographs. The semi-batch technique, which can be combined with the addition of support particles, is worth further work, aiming to reduce secondary nucleation and to determine the crystallite growth rate expression of natrojarosite as a function of supersaturation, using the model of solution developed in this work. (c) 2011 Elsevier B.V. All rights reserved.