EVALUATION OF METAL TOXICITY BY A MODIFIED METHOD BASED ON THE FUNGUS GERRONEMA VIRIDILUCENS BIOLUMINESCENCE IN AGAR MEDIUM

Metal cation toxicity to basidiomycete fungi is poorly understood, despite its well-known importance in terrestrial ecosystems. Moreover, there is no reported methodology for the routine evaluation of metal toxicity to basidiomycetes. In the present study, we describe the development of a procedure to assess the acute toxicity of metal cations (Na(+), K(+), Li(+), Ca(2+), Mg(2+), Co(2+), Zn(2+), Ni(2+), Mn(2+), Cd(2+), and Cu(2+)) to the bioluminescent basidiomycete fungus Gerronema viridilucens. The method is based on the decrease in the intensity of bioluminescence resulting from injuries sustained by the fungus mycelium exposed to either essential or nonessential metal toxicants. The assay described herein enables LIS to propose a metal toxicity series to Gerronenia viridilucens based on data obtained from the bioluminescence intensity (median effective concentration [EC50] values) versus metal concentration: Cd(2+) > Cu(2+) > Mn(2+) approximate to Ni(2+) approximate to Co(2+) > Zn(2+) > Mg(2+) > Li(+) > K(+) approximate to Na(+) > Ca(2+), and to shed some li-ht on the mechanism of toxic action of metal cations to basidiomycete fungi. Environ. Toxicol. Chem. 2010;29:320-326. (C) 2009 SETAC

Development of a heavy metal sorption system through the P=S functionalization of coconut (Cocos nucifera) fibers

Lignocellulosic residues are interesting materials for the production of heavy metal adsorbents for aquatic systems. Whole fibers taken from coconut (Cocos nucifera) husks were functionalized with the thiophosphoryl (P=S) group by means of the direct reaction with CI(3)P=S, (CH(3)O)(2)CIP=S or (CH(3)CH(2)O)(2)CIP=S in order to obtain an adsorptive system for `soft` metal ions, particularly Cd(2+). These functionalized fibers (FFs) were characterized by means of elemental analysis, infrared spectroscopy, thermal analysis and acid-base titration. Adsorption isotherms for Cd(2+) fitted the Langmuir model, with binding capacities of 0.2-5 mmol g(-1) of FF at 25 degrees C. (C) 2009 Elsevier Ltd. All rights reserved.

Group 11 (Cu, Ag, Au) promotion of 15%Co/Al(2)O(3) Fischer-Tropsch synthesis catalysts

Co/Al(2)O(3) Fischer-Tropsch synthesis catalysts promoted with different quantities of Group 11 metals (Cu, Ag, Au) were characterized and tested. The presence of relatively small quantities of such metals enhanced Co reducibility and, in the cases of Ag and Au, improved the surface Co metal active site densities. EXAFS experiments with the most loaded catalyst samples show that only Co-Co and Me-Me (Me = Cu, Ag and Au) coordination could be observed. This suggests that the greater fraction of the metals form different phases. However, the reduction promoting effect of the Group 11 metal is severely hampered once the catalyst receives a mild passivation treatment following primary reduction. An explanation in terms of promoter segregation during primary reduction is proposed. At lower promoter levels (0.83%Ag and 1.51%Au) and higher Ag levels (2.76%), significant gains in Co active site densities were achieved resulting in improved CO conversion levels relative to the unpromoted catalyst. Moreover, slight decreases in light product (e.g., CH(4)) selectivity and slight increases in C(5)+ selectivity were achieved. At high Au loading (5.05%), however, too much Au was loaded which, although significantly increasing the fraction of Co reduced, blocked Co surface sites and resulted in decreased Co conversion rates. While Cu facilitated Co reduction, the increased fraction of reduced Co did not translate to improved active site densities. It appears that a fraction of Cu tended to cover the rim of Co clusters, resulting in decreases in CO conversion rates and detrimental increases in light product selectivity. (C) 2009 Elsevier B.V. All rights reserved.

Can mass dissociation patterns of transition-metal complexes be predicted from electrochemical data?

The Cooks kinetic method has been very convenient to correlate the relative dissociation rates obtained by collision-induced fragmentation experiments with the energies of two related bonds in molecules and complexes in the gas phase. Reliable bond energy data are, however, not always available, particularly for polynuclear transition-metal complexes, such as the triruthenium acetate clusters of the general formula [Ru(3) (mu(3)-O)(mu-CH(3)COO)(6)(py)(2)(L)](+), where L = ring substituted N-heterocyclic ligands. Accordingly, their gas-phase collision-induced tandem mass spectrometry (CID MS/MS) dissociation patterns have been analyzed pursuing a relationship with the more easily accessible redox potentials (E(1/2)) and Lever`s E(L) parameters. In fact, excellent linear correlations of In(1/2A(L)/A(py)), where A(py) and A(L) are the abundance of the fragments retaining the pyridine (py) and L ligand, respectively, with E(1/2) and E(L) were found. This result shows that those electrochemical parameters are correlated with bond energies and can be used in the analysis of the dissociation data. Such modified Cooks method can be used, for example, to determine the electronic effects of substituents on the metal-ligand bonds for a series of transition-metal complexes. Copyright (C) 2008 John Wiley & Sons, Ltd.

Ultrasensitive SERS nanoprobes for hazardous metal ions based on trimercaptotriazine-modified gold nanoparticles

Trimercaptotriazine-modified gold nanoparticles exhibit strong SERS effects,(1) yielding vibrational profiles very sensitive to the presence of heavy metal ions. Because of the contrasting response observed for selected vibrational bands in the SERS profiles, they provide useful nanoprobes for Hg2+ and Cd2+ ions, allowing direct quantitative assays by employing relative peak intensity ratios instead of using internal standards.

Metal transport parameters of a gneiss saprolitic silty soil for liner design

Diffusion coefficients and retardation factors of two metal cations (Cd2+ and Pb2+) were measured for a compacted Brazilian saprolitic soil derived from gneiss, aiming to assess its geoenvironmental performance as a liner for waste disposal sites. This soil occurs extensively all over the country in very thick layers, but has not been used in liners because of its hydraulic conductivity, higher than 10(-9) m/s when compacted at optimum water content of standard Proctor energy, but which can be reduced by means of appropriate compaction techniques or additives. Batch, column, and diffusion tests were carried out with monospecies synthetic solutions at pH 1, 3, and 5.5. Measured diffusion coefficients varied between 0.5 and 4 X 10(-10) m(2)/s. Retardation factors show that cadmium, a very mobile cation, is not adsorbed at pH I but is significantly retained at pH 3 and pH 5.5, whereas lead is retained at all tested pH values though slightly at pH 1. Estimated retardation factors from batch tests were 1.3-2.3 times those resulting from column tests and at its highest when obtained by diffusion tests; whereas batch tests allow a more complete exposure of the soil grains to the solution, time-dependent nonspecific adsorption may take longer to occur. The importance of contact time was observed and should be considered in further investigations. Its significant retention of metals suggests a promising utilization of this soil as a bottom liner for wastes landfills.

Antimicrobial Activity of Ethylenediaminedisuccinate Metal Complexes

It is shown that metal complexes of the biodegradable ligand ethylenediaminedisuccinic acid (edds) present antimicrobial activity towards fungi and bacteria. [Cd(edds)], in particular, is more toxic than free Cd2+ to Aspergillus niger, behaving as a `Trojan Horse` in the facilitated delivery of the toxic metal into the fungus.

Sensing hazardous metal ions using a fluoroionophore calix[4]arene species containing two 8-oxyquinoline groups

The interaction of a calix[4]arene-based species containing two 8-oxyquinoline chromophore pendants with hazardous metal ions has been investigated using optical absorption and fluorimetric techniques. In the presence of Hg(2+), Cd(2+), and Pb(2+) ions, there is only a small decrease of the calixarene absorption band at 283 nm. The main changes are associated with the absorption band of the 8-oxyquinoline group at 315 nm, undergoing a systematic bathochromic shift to above 350 nm. In addition, a systematic decrease of the oxyquinoline emission at lambda(em) = 392 nm (lambda(exc) = 315 nm) has been observed. These observations are consistent with the coordination of the metal ions to the quinoline groups attached to the calixarene ligand, providing a useful fluoroinophore species for analytical purposes.

New insights on surface-enhanced Raman scattering based on controlled aggregation and spectroscopic studies, DFT calculations and symmetry analysis for 3,6-bi-2-pyridyl-1,2,4,5-tetrazine adsorbed onto citrate-stabilized gold nanoparticles

Asystematic study on the surface-enhanced Raman scattering (SERS) for 3,6-bi-2-pyridyl-1,2,4,5-tetrazine (bptz) adsorbed onto citrate-modified gold nanoparticles (cit-AuNps) was carried out based on electronic and vibrational spectroscopy and density functional methods. The citrate/bptz exchange was carefully controlled by the stepwise addition of bptz to the cit-AuNps, inducing flocculation and leading to the rise of a characteristic plasmon coupling band in the visible region. Such stepwise procedure led to a uniform decrease of the citrate SERS signals and to the rise of characteristic peaks of bptz, consistent with surface binding via the N heterocyclic atoms. In contrast, single addition of a large amount of bptz promoted complete aggregation of the nanoparticles, leading to a strong enhancement of the SERS signals. In this case, from the distinct Raman profiles involved, the formation of a new SERS environment became apparent, conjugating the influence of the local hot spots and charge-transfer (CT) effects. The most strongly enhanced vibrations belong to a(1) and b(2) representations, and were interpreted in terms of the electromagnetic and the CT mechanisms: the latter involving significant contribution of vibronic coupling in the system. Copyright (C) 2010 John Wiley & Sons, Ltd.

Room Temperature, Metal-Free Synthesis of Diaryl Ethers with Use of Diaryliodonium Salts

A fast, high-yielding synthesis of diaryl ethers with use of mild and metal-free conditions has been developed. The scope includes bulky ortho-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives, and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the synthesis of complex molecules and in the pharmaceutical industry.

Synthesis of Tetrahydrofurans by Cyclization of Homoallylic Alcohols with Iodine/Iodine(III)

Tetrahydrofuran derivatives can be obtained by cyclo-functionalization of homoallylic alcohols bearing a terminal double bound by using [hydroxy(tosyloxy)iodo]benzene (HTIB, Koser`s reagent) in the presence of a catalytic amount of 12 (20 mol %) in MeOH under mild conditions. This transformation is an overall 5-endo-trig cyclization, which occurs by two different pathways. The first is a 4-exo-trig cyclization followed by ring expansion, whereas the second is an electrophilic addition followed by a 5-endo-tet cyclization.

Trace-metal biogeochemistry in the Mediterranean Thau Lagoon, a shellfish farming area

The present study contributes to the knowledge of the biogeochemistry of Pb, Cd, Cu, and Ni in the Mediterranean Than Lagoon, southern France, which is an important shellfish farming system. The concentrations of the metals were determined in sediment cores and the overlying waters using inductively coupled plasma mass spectrometry. Particular attention was given to the determination of dissolved Cu species because of their dual role as essential nutrient and toxicant to planktonic organisms. Dissolved Cu speciation was determined using the diffusive gradient in thin-film technique (DGT) and competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV). Our data indicated a significant historical contamination of the sediments, which commenced in the second half of the 19th century, with trace metal inputs persisting until the end of the 20th century. In recent years a decrease in metal contamination has become apparent. The maxima observed for Pb, Cd, and Cu profiles probably indicate the occurence of anoxia crises. A strong complexation of the dissolved Cu species was observed in the waters of the Than Lagoon, which reduced the bioavailability of Cu. The dissolved Cu(2+) concentrations were probably too low to cause direct toxic effects on shellfish, but the highest concentration (5.29 pM) observed in this study can potentially influence phytoplankton communities. A comparison between the Cu speciation data indicates that up to 50% of the complexed Cu determined using CLE-ACSV was DGT labile.

Automated two-dimensional separation flow system with electrochemical preconcentration, stripping, capillary electrophoresis and contactless conductivity detection for trace metal ion analysis

This paper describes the automation of a fully electrochemical system for preconcentration, cleanup, separation and detection, comprising the hyphenation of a thin layer electrochemical flow cell with CE coupled with contactless conductivity detection (CE-C(4)D). Traces of heavy metal ions were extracted from the pulsed-flowing sample and accumulated on a glassy carbon working electrode by electroreduction for some minutes. Anodic stripping of the accumulated metals was synchronized with hydrodynamic injection into the capillary. The effect of the angle of the slant polished tip of the CE capillary and its orientation against the working electrode in the electrochemical preconcentration (EPC) flow cell and of the accumulation time were studied, aiming at maximum CE-C(4)D signal enhancement. After 6 min of EPC, enhancement factors close to 50 times were obtained for thallium, lead, cadmium and copper ions, and about 16 for zinc ions. Limits of detection below 25 nmol/L were estimated for all target analytes but zinc. A second separation dimension was added to the CE separation capabilities by staircase scanning of the potentiostatic deposition and/or stripping potentials of metal ions, as implemented with the EPC-CE-C(4)D flow system. A matrix exchange between the deposition and stripping steps, highly valuable for sample cleanup, can be straightforwardly programmed with the multi-pumping flow management system. The automated simultaneous determination of the traces of five accumulable heavy metals together with four non-accumulated alkaline and alkaline earth metals in a single run was demonstrated, to highlight the potentiality of the system.

Ultrasound promoted greener synthesis of 2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles

A rapid and cleaner procedure for the synthesis of a series of 2-(3,5-diaryl-45-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles under ultrasonic irradiation in ethanol is described. (C) 2010 Elsevier B.V. All rights reserved.

Removal of metal ions from aqueous solution by chelating polymeric hydrogel

Polysaccharide natural seed coat from the tree Magonia pubescens, in the form of hydrogel was used to remove metals in aqueous solution. Swelling tests indicate that seed coat presents hydrogel behavior, with maximum water absorption of 292 g water/g. Adsorption experiments performed using Na(+), Mg(2+), K(+), Ca(2+), Cr(3+), Fe(3+) and Zn(2+) demonstrated that the polysaccharide structure has a high capacity to extract these ions from the aqueous solution. Scanning electron microscopy revealed significant morphological changes of the material before and after water contact. Differential scanning calorimetry measurements indicate a signal shift of the water evaporation temperature in the material with adsorbed zinc. X-ray photoelectron spectroscopy analysis combined with theoretical studies by the density functional theory and on Hartree-Fock (HF) level evidence that the metallic ions were adsorbed through coordination with hydroxyl groups of polysaccharide. In the case of Zn(2+) the lowest HF energy was observed for the tetracoordination mode, where Zn(2+) is coordinated by two hydroxyl groups and two water molecules.