Sonochemical synthesis and measurement of optical properties of zinc sulfide quantum dots

A facile sonochemical method has been developed to prepare very small zinc sulfide nanoparticles (ZnS NPs) of extremely small size about 1. nm in diameter using a set of ionic liquids based on the bis (trifluoromethylsulfonyl) imide anion and different cations of 1-alkyl-3-methyl-imidazolium. The structural features and optical properties of the NPs were determined in depth with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) analysis, and UV-vis absorption spectroscopy. The energy band gap measurements of ZnS NPs were calculated by UV-vis absorption spectroscopy. One of the interesting features of the present work is that the wide band gap semiconductor ZnS nanocrystals were prepared which are used in the fabrication of photonic devices.

The complex effects of the slow-releasing hydrogen sulfide donor GYY4137 in a model of acute joint inflammation and in human cartilage cells

The role of hydrogen sulfide (H2 S) in inflammation remains unclear with both pro- and anti-inflammatory actions of this gas described. We have now assessed the effect of GYY4137 (a slow-releasing H2 S donor) on lipopolysaccharide (LPS)-evoked release of inflammatory mediators from human synoviocytes (HFLS) and articular chondrocytes (HAC) in vitro. We have also examined the effect of GYY4137 in a complete Freund's adjuvant (CFA) model of acute joint inflammation in the mouse. GYY4137 (0.1-0.5 mM) decreased LPS-induced production of nitrite (NO2 (-) ), PGE2 , TNF-a and IL-6 from HFLS and HAC, reduced the levels and catalytic activity of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and reduced LPS-induced NF-?B activation in vitro. Using recombinant human enzymes, GYY4137 inhibited the activity of COX-2, iNOS and TNF-a converting enzyme (TACE). In the CFA-treated mouse, GYY4137 (50 mg/kg, i.p.) injected 1 hr prior to CFA increased knee joint swelling while an anti-inflammatory effect, as demonstrated by reduced synovial fluid myeloperoxidase (MPO) and N-acetyl-ß-D-glucosaminidase (NAG) activity and decreased TNF-a, IL-1ß, IL-6 and IL-8 concentration, was apparent when GYY4137 was injected 6 hrs after CFA. GYY4137 was also anti-inflammatory when given 18 hrs after CFA. Thus, although GYY4137 consistently reduced the generation of pro-inflammatory mediators from human joint cells in vitro, its effect on acute joint inflammation in vivo depended on the timing of administration.

Two-dimensional images of dissolved sulfide and metals in anoxic sediments by a novel diffusive gradients in thin film probe and optical scanning techniques

A novel diffusive gradients in thin film probe developed comprises diffusive gel layer of silver iodide (AgI) and a back-up Microchelex resin gel layer. 2D high-resolution images of sulfide and trace metals were determined respectively on the AgI gel by densitometric analysis and on the Microchelex resin layer with laser-ablation-inductively-coupled plasma mass spectrometry (LA-ICP-MS).We investigated the validity of the analytical procedures used for the determination of sulfide and trace metals. We found low relative standard deviations on replicate measurements, linear trace-metal calibration curves between the LA-ICP-MS signal and the true trace-metal concentration in the resin gel, and a good agreement of the sulfide results obtained with the AgI resin gel and with other analytical methods. The method was applied on anoxic sediment pore waters in an estuarine and marine system. Simultaneous remobilization of sulfide and trace metals was observed in the marine sediment.

Ionic liquids for efficient hydrogen sulfide and thiol scavenging

Functionalised pyridinium and ammonium ionic liquids bearing a Michael acceptor are shown to scavenge H₂S gas and various thiols, in most cases, without the aid of any added bases. Utilising the effective non-volatility of ionic liquids and ‘tagging’ malodourous substances to an ionic matrix renders them odourless.

Photoreduction of carbon dioxide on zinc sulfide to give four-carbon and two-carbon acids

Aqueous solutions of CO₂ containing tetramethylammonium chloride were photolysed with visible light in the presence of colloidal ZnS to yield tartaric acid, glyoxylic acid, oxalic acid, formic acid and formaldehyde.

A primer for the Environmental Impact Assessment of mining at seafloor massive sulfide deposits

Seafloor massive sulfides (SMS) contain commercially viable quantities of high grade ores, making them attractive prospect sites for marine mining. SMS deposits may also contain hydrothermal vent ecosystems populated by high conservation value vent-endemic species. Responsible environmental management of these resources is best achieved by the adoption of a precautionary approach. Part of this precautionary approach involves the Environmental Impact Assessment (EIA) of exploration and exploitative activities at SMS deposits. The VentBase 2012 workshop provided a forum for stakeholders and scientists to discuss issues surrounding SMS exploration and exploitation. This forum recognised the requirement for a primer which would relate concepts underpinning EIA at SMS deposits. The purpose of this primer is to inform policy makers about EIA at SMS deposits in order to aid management decisions. The primer offers a basic introduction to SMS deposits and their associated ecology, and the basic requirements for EIA at SMS deposits; including initial data and information scoping, environmental survey, and ecological risk assessment. © 2013 Elsevier Ltd.

A primer for use of genetic tools in selecting and testing the suitability of set-aside sites protected from deep-sea seafloor massive sulfide mining activities

Seafloor massive sulfide (SMS) mining will likely occur at hydrothermal systems in the near future. Alongside their mineral wealth, SMS deposits also have considerable biological value. Active SMS deposits host endemic hydrothermal vent communities, whilst inactive deposits support communities of deep water corals and other suspension feeders. Mining activities are expected to remove all large organisms and suitable habitat in the immediate area, making vent endemic organisms particularly at risk from habitat loss and localised extinction. As part of environmental management strategies designed to mitigate the effects of mining, areas of seabed need to be protected to preserve biodiversity that is lost at the mine site and to preserve communities that support connectivity among populations of vent animals in the surrounding region. These "set-aside" areas need to be biologically similar to the mine site and be suitably connected, mostly by transport of larvae, to neighbouring sites to ensure exchange of genetic material among remaining populations. Establishing suitable set-asides can be a formidable task for environmental managers, however the application of genetic approaches can aid set-aside identification, suitability assessment and monitoring. There are many genetic tools available, including analysis of mitochondrial DNA (mtDNA) sequences (e.g. COI or other suitable mtDNA genes) and appropriate nuclear DNA markers (e.g. microsatellites, single nucleotide polymorphisms), environmental DNA (eDNA) techniques and microbial metagenomics. When used in concert with traditional biological survey techniques, these tools can help to identify species, assess the genetic connectivity among populations and assess the diversity of communities. How these techniques can be applied to set-aside decision making is discussed and recommendations are made for the genetic characteristics of set-aside sites. A checklist for environmental regulators forms a guide to aid decision making on the suitability of set-aside design and assessment using genetic tools. This non-technical primer document represents the views of participants in the VentBase 2014 workshop.

Pilot-scale evaluation of the application of low pH-inducible polyphosphate accumulation to the biological removal of phosphate from wastewaters.

To investigate the possible biotechnological application of the phenomenon of low pH-inducible phosphate uptake and polyphosphate accumulation, previously reported using pure microbial cultures and under laboratory conditions, a 2000 L activated sludge pilot plant was constructed at a municipal sewage treatment works. When operated as a single-stage reactor this removed more than 60% of influent phosphate from primary settled sewage at a pH of 6.0, as opposed to approximately 30% at the typical operational pH for the works of 7.0-7.3-yet without any deleterious effect on other treatment parameters. At these pH values the phosphorus content of the sludge was, respectively, 4.2% and 2.0%. At pH 6.0 some 33.9% of sludge microbial cells were observed to contain polyphosphate inclusions; the corresponding value at pH 7.0 was 18.7%. Such a process may serve as a prototype for the development of alternative biological and chemical options for phosphate removal from wastewaters.

Rational Attenuation of a Morbillivirus by Modulating the Activity of the RNA-Dependent RNA Polymerase

Negative-strand RNA viruses encode a single RNA-dependent RNA polymerase (RdRp) which transcribes and replicates the genome. The open reading frame encoding the RdRp from a virulent wild-type strain of rinderpest virus (RPV) was inserted into an expression plasmid. Sequences encoding enhanced green fluorescent protein (EGFP) were inserted into a variable hinge of the RdRp. The resulting polymerase was autofluorescent, and its activity in the replication/transcription of a synthetic minigenome was reduced. We investigated the potential of using this approach to rationally attenuate a virus by inserting the DNA sequences encoding the modified RdRp into a full-length anti-genome plasmid from which a virulent virus (rRPV(KO)) can be rescued. A recombinant virus, rRPV(KO)L-RRegfpR, which grew at an indistinguishable rate and to an identical titer as rRPV(KO) in vitro, was rescued. Fluorescently tagged polymerase was visible in large cytoplasmic inclusions and beneath the cell membrane. Subcutaneous injection of 10(4) TCID(50) of the rRPV(KO) parental recombinant virus into cattle leads to severe disease symptoms (leukopenia/diarrhea and pyrexia) and death by 9 days postinfection. Animals infected with rRPV(KO)L-RRegfpR exhibited transient leukopenia and mild pyrexia, and the only noticeable clinical signs were moderate reddening of one eye and a slight ocular-nasal discharge. Viruses that expressed the modified polymerase were isolated from peripheral blood lymphocytes and eye swabs. This demonstrates that a virulent morbillivirus can be attenuated in a single step solely by modulating RdRp activity and that there is not necessarily a correlation between virus growth in vitro and in vivo.

Measles virus superinfection immunity and receptor redistribution in persistently infected NT2 cells

A recombinant measles virus (MV) expressing red fluorescent protein (MVDsRed1) was used to produce a persistently infected cell line (piNT2-MVDsRed1) from human neural precursor (NT2) cells. A similar cell line (piNT2-MVeGFP) was generated using a virus that expresses enhanced green fluorescent protein. Intracytoplasmic inclusions containing the viral nucleocapsid protein were evident in all cells and viral glycoproteins were present at the cell surface. Nevertheless, the cells did not release infectious virus nor did they fuse to generate syncytia. Uninfected NT2 cells express the MV receptor CD46 uniformly over their surface, whereas CD46 was present in cell surface aggregates in the piNT2 cells. There was no decrease in the overall amount of CD46 in piNT2 compared to NT2 cells. Cell-to-cell fusion was observed when piNT2 cells were overlaid onto confluent monolayers of MV receptor-positive cells, indicating that the viral glycoproteins were correctly folded and processed. Infectious virus was released from the underlying cells, indicating that persistence was not due to gross mutations in the virus genome. Persistently infected cells were superinfected with MV or canine distemper virus and cytopathic effects were not observed. However, mumps virus could readily infect the cells, indicating that superinfection immunity is not caused by general soluble antiviral factors. As MVeGFP and MVDsRed1 are antigenically indistinguishable but phenotypically distinct it was possible to use them to measure the degree of superinfection immunity in the absence of any cytopathic effect. Only small numbers of non-fusing green fluorescent piNT2-MVDsRed1 cells (1 : 300 000) were identified in which superinfecting MVeGFP entered, replicated and expressed its genes.

Reactions of One-Electron-Oxidized Methionine with Oxygen: An ab initio study

A one-electron oxidation of a methionine residue is thought to be a key step in the neurotoxicity of the beta amyloid peptide of Alzheimer's disease. The chemistry of the radical cation of N-formylmethioninamide (11+) and two model systems, dimethyl sulfide (1+) and ethyl methyl sulfide (6+), in the presence of oxygen have been studied by B3LYP/6-31G(d) and CBS-RAD calculations. The stable form of 11+ has a three-electron bond between the sulfur radical cation and the carbonyl oxygen atom of the i - 1 residue. The radical cation may lose a proton from the methyl or methylene groups flanking the oxidized sulfur. Both 11+ and the resultant C-centered radicals may add oxygen to form peroxy radicals. The calculations indicate that unlike C-centered radicals the sulfur radical cation does not form a covalent bond to oxygen but rather forms a loose ion-induced dipole complex with an S-O separation of about 2.7 Å, and is bound by about 13 kJ mol-1 (on the basis of 1+ + O2). Direct intramolecular abstraction of an H atom from the C site is unlikely. It is endothermic by more than 20 kJ mol-1 and involves a high barrier (G = 79 kJ mol-1). The -to-S C-centered radicals will add oxygen to form peroxy radicals. The OH BDEs of the parent hydroperoxides are in the range of 352-355 kJ mol-1, similar to SH BDEs (360 kJ mol-1) and C-H BDEs (345-350 kJ mol-1). Thus, the peroxy radicals are oxidizing species comparable in strength to thiyl radicals and peptide backbone C-centered radicals. Each peroxy radical can abstract a hydrogen atom from the backbone C site of the Met residue to yield the corresponding C-centered radical/hydroperoxide in a weakly exothermic process with modest barriers in the range of 64-92 kJ mol-1.

Geophysical imaging of stimulated microbial biomineralization

Understanding how microorganisms influence the physical and chemical properties of the subsurface is hindered by our inability to observe microbial dynamics in real time and with high spatial resolution. Here, we investigate the use of noninvasive geophysical methods to monitor biomineralization at the laboratory scale during stimulated sulfate reduction under dynamic flow conditions. Alterations in sediment characteristics resulting from microbe-mediated sulfide mineral precipitation were concomitant with changes in complex resistivity and acoustic wave propagation signatures. The sequestration of zinc and iron in insoluble sulfides led to alterations in the ability of the pore fluid to conduct electrical charge and of the saturated sediments to dissipate acoustic energy. These changes resulted directly from the nucleation, growth, and development of nanoparticulate precipitates along grain surfaces and within the pore space. Scanning and transmission electron microscopy (SEM and TEM) confirmed the sulfides to be associated with cell surfaces, with precipitates ranging from aggregates of individual 3-5 nm nanocrystals to larger assemblages of up to 10-20 m in diameter. Anomalies in the geophysical data reflected the distribution of mineral precipitates and biomass over space and time, with temporal variations in the signals corresponding to changes in the aggregation state of the nanocrystalline sulfides. These results suggest the potential for using geophysical techniques to image certain subsurface biogeochemical processes, such as those accompanying the bioremediation of metal-contaminated aquifers.

Dioxygenase-catalysed oxidation of alkylaryl sulfides: sulfoxidation versus cis-dihydrodiol formation

Toluene- and naphthalene-dioxygenase-catalysed sulfoxidation of nine disubstituted methylphenyl sulfides, using whole cells of Pseudomonas putida, consistently gave the corresponding enantioenriched sulfoxides. Using the P. putida UV4 mutant strain, and these substrates, differing proportions of the corresponding cis-dihydrodiol sulfides were also isolated. Evidence was found for the concomitant dioxygenase-catalysed cis-dihydroxylation and sulfoxidation of methyl paratolyl sulfide. A simultaneous stereoselective reductase-catalysed deoxygenation of (S)-methyl para-tolyl sulfoxide, led to an increase in the proportion of the corresponding cis-dihydrodiol sulfide. The enantiopurity values and absolute configurations of the corresponding cis-dihydrodiol metabolites from methyl ortho-and para-substituted phenyl sulfides were determined by different methods, including chemoenzymatic syntheses from the cis-dihydrodiol metabolites of para-substituted iodobenzenes. Further evidence was provided to support the validity of an empirical model to predict, (i) the stereochemistry of cis-dihydroxylation of para-substituted benzene substrates, and (ii) the regiochemistry of cis-dihydroxylation reactions of ortho-substituted benzenes, each using toluene dioxygenase as biocatalyst.

Dioxygenase-catalysed mono-, di- and tri-oxygenation of dialkyl sulfides and thioacetals: chemoenzymatic synthesis of enantiopure cis-diol sulfoxides

Toluene dioxygenase (TDO)-catalysed monooxygenation of methylsulfanylmethyl phenyl sulfide 1 and methylsulfanylmethyl 2-pyridyl sulfide 4, using whole cells of Pseudomonas putida UV4, occurred exclusively at the alkyl aryl sulfur centre to yield the alkyl aryl sulfoxides 2 and 5 respectively. These sulfoxides, accompanied by the dialkyl sulfoxides 3 and 6, were also obtained from naphthalene dioxygenase (NDO)-catalysed sulfoxidation of thioacetals 1 and 4 using intact cells of P. putida NCIMB 8859. Enzymatic oxidation of methyl benzyl sulfide 7, 2-phenyl-1,3-dithiane 19, and 2-phenyl-1,3-dithiolane 23, using TDO, gave the corresponding dialkyl sulfoxides 8, 20 and 24 as minor bioproducts. TDO-catalysed dioxygenation of the alkyl benzyl sulfides 7, 15 and 17 and the thioacetals 19 and 23, with P. putida UV4, yielded the corresponding enantiopure cis-dihydrodiols 9, 16, 18, 21 and 25 as major metabolites and cis-dihydrodiol sulfoxides 14, 22 and 26 as minor metabolites, resulting from a tandem trioxygenation of substrates 7, 19 and 23 respectively. Chemical oxidation, of the enantiopure cis-dihydrodiol sulfides 9, 16, 18 and 21 with dimethyldioxirane (DMD), gave separable mixtures of the corresponding pairs of cis-dihydrodiol sulfoxide diastereoisomers 14 and 27, 28 and 29, 30 and 31, 22 and 32. While dialkyl sulfoxide bioproducts 3, 6, 20 and 24 were of variable enantiopurity (27-greater than or equal to 98% ee), alkyl aryl monosulfoxides 2 and 5, cis-dihydrodiols 9, 16, 18, 21 and 25 and cis-dihydrodiol sulfoxide bioproducts 14, 22 and 26 were all single enantiomers (greater than or equal to 98% ee). The absolute configurations of the products, obtained from enzyme-catalysed (TDO and NDO) and chemical (DMD) oxidation methods, were determined by stereochemical correlation, circular dichroism, and X-ray crystallographic methods.