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PubMed2004

K2Ag6Sn3S10: a quaternary sulfide composed of silver sulfide layers pillared by zigzag chains 1infinity[SnS3]2-.

A novel framework K(2)Ag(6)Sn(3)S(10) was synthesized solvothermally and characterized by single-crystal diffraction. The framework comprises [Ag(6)SnS(4)](2+) cationic layers pillared by [SnS(3)](2)(-) zigzag chains formed by vertex-sharing SnS(4) tetrahedra, and potassium ions are located in 1D channels. This compound crystallizes in the orthorhombic Pbcn space group with a = 24.0201(2) A, b = 6.4017(3) A, c = 13.3056(4) A, Z = 4. Its thermal and optical properties are studied.

Journal Article↗
PubMed2005

Bis(di-2-pyridyl sulfide-kappa2N,N')(4-methylpyrimidin-2-yl 2-pyridylmethyl sulfide-kappa2N,S)ruthenium(II) bis(hexafluorophosphate) acetonitrile solvate.

The crystal structure of the title compound, [Ru(C10H8N2S)2(C11H11N3S)](PF6)2.C2H3N, is composed of a bivalent octahedral RuII complex, two PF6- anions and an acetonitrile solvent molecule. Two PF6- units are found on a crystallographic binary axis, therefore contributing just one half each to the asymmetric unit cell. The structure displays a peculiar stereochemistry of the cation. Three bidentate ligands around the Ru centre, together with the coordination of the non-symmetric S atom, mean that these two atoms are chiral. This would lead to four stereoisomers, but only an enantiomeric pair was found in the analyzed sample.

Journal Article↗
PubMed1995

Melanin production by a filamentous soil fungus in response to copper and localization of copper sulfide by sulfide-silver staining.

Gaeumannomyces graminis var. graminis, a filamentous soil ascomycete, exhibited enhanced cell wall melanin accumulation when exposed to as little as 0.01 mM CuSO(inf4) in minimal broth culture. Because its synthesis was inhibited by tricyclazole, the melanin produced in response to copper was dihydroxynaphthalene melanin. An additional hyphal cell wall layer was visualized by electron microscopy when hyphae were grown in the presence of copper and fixed by cryotechniques. This electron-dense layer was between the outer cell wall and the inner chitin layer and doubled the total wall thickness. In copper-grown cells that were also treated with tricyclazole, this electron-dense layer was absent. Atomic absorption spectroscopy demonstrated that up to 3.5 mg of Cu per g of fungal mycelium was adsorbed or taken up by hyphae grown in 0.06 mM CuSO(inf4). A method for silver enhancement was developed to determine the cellular location of CuS. CuS was present in cell walls and septa of copper-grown hyphae. Electron microscopy of silver-stained cells suggested that CuS was associated with the melanin layer of cell walls.

Journal Article↗
PubMed2000

Molecular addition compounds. 17. Borane and chloroborane adducts with organic sulfides for hydroboration

The following sulfides have been examined as borane carriers in comparison with dimethyl sulfide and 1,4-oxathiane: tert-butyl methyl sulfide, isoamyl methyl sulfide, ethyl isoamyl sulfide, tert-butyl isoamyl sulfide, diisoamyl sulfide, tetrahydrothiophene, tetrahydro-thiopyran, thioanisole, 3-ethylthiotetrahydrofuran, bis(3-tetrahydrofuryl) sulfide, and bis(2-methoxyethyl) sulfide. Their complexing ability toward borane increases in the following order: thioanisole < ether-sulfides < dialkyl sulfides < dimethyl sulfide. Borane adducts of the sulfides are liquids above 0 degrees C. The thioanisole adduct loses diborane at room temperature. The reactivity of the adducts toward 1-octene increases in the reversed order of the complexing ability of the sulfides. Diisoamyl sulfide has a mild, ethereal, agreeable aroma, its synthesis is economical and the borane adduct, 4.2 M in BH3, is stable over prolonged periods at room temperature. The sulfide can be recovered from hydroboration-oxidation products by distillation. Consequently, diisoamyl sulfide is a new promising borane carrier. Bis(2-methoxyethyl) sulfide, easily synthesized from the low cost thiodiethanol, is three times more soluble in water than 1,4-oxathiane. Its borane adduct is 6.0 M in BH3 and can substitute for more expensive borane-1,4-oxathiane in hydroboration reactions. Applications of these new borane adducts in the synthesis of mono- and dichloroborane adducts was also studied. The equilibrium ratios observed for the new chloroborane adducts were similar to that observed for dimethyl sulfide adducts. However, the hydroboration of 1-octene with these new chloroborane adducts are much faster than the corresponding adducts of dimethyl sulfide, which are currently used extensively.

Journal Article↗
PubMed2005

Sulfide-oxidizing activity and bacterial community structure in a fluidized bed reactor from a zero-discharge mariculture system.

In the present work we describe a comprehensive analysis of sulfide oxidation in a fluidized bed reactor (FBR) from an environmentally sustainable, zero-discharge mariculture system. The FBR received oxygen-depleted effluent from a digestion basin (DB) that is responsible for gasification of organic matter and nitrogen. The FBR is a crucial component in this recirculating system because it safeguards the fish from the toxic sulfide produced in the DB. Microscale sulfide oxidation potential and bacterial community composition within FBR biofilms were correlated to biofilter performance by integrating bulk chemical, microsensor (O2, pH, and H2S), and molecular microbial community analyses. The FBR consistently oxidized sulfide during two years of continuous operation, with an estimated average sulfide removal rate of 1.3 g of sulfide-S L(FBR)(-1) d(-1). Maximum sulfide oxidation rates within the FBR biofilms were 0.36 and 0.21 mg of sulfide-S cm(-3) h(-1) in the oxic and anoxic layers, respectively, indicating that both oxygen and nitrate serve as electron acceptors for sulfide oxidation. The estimated anoxic sulfide removal rate, as extrapolated from bench scale, autotrophic, nitrate-amended experiments, was 0.7 g of sulfide-S L(FBR)(-1) d(-1), which is approximately 50% of the total estimated sulfide removal in the FBR. Community composition analyses using denaturing gradient gel electrophoresis (DGGE) of bacterial 16S rRNA gene fragments from FBR samples taken at six-month intervals revealed several sequences that were closely affiliated with sulfide-oxidizing bacteria. These included the denitrifying, sulfide-oxidizing bacteria Thiomicrospira denitrificans, members of the filamentous Thiothrix genus, and sulfide-oxidizing symbionts from the Gammaproteobacteria. In addition, marine Alphaproteobacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analyses showed significant shifts in the bacterial community composition between profiles over two years of sampling, indicating the presence of a diverse and dynamic microbial community within the functionally stable FBR. The FBR's combined capacity for both oxic and anoxic sulfide oxidation, as indicated by bulk chemical, microsensor, and molecular microbial analyses, gives it significant functional elasticity, which is crucial for proper performance in the dynamic environment of this mariculture system.

Aquaculture↗
PubMedDate not supplied

Strategies adopted by the mudskipper Boleophthalmus boddaerti to survive sulfide exposure in normoxia or hypoxia.

The effects of sulfide on the energy metabolism of Boleophthalmus boddaerti in normoxia and hypoxia were examined. The 24-, 48-, and 96-h LC50 values of sulfide for B. boddaerti with body weight ranging from 11.6 to 14.2 g were 0.786, 0.567, and 0.467 mM, respectively. The tolerance of B. boddaerti to sulfide was not due to the presence of a sulfide-insensitive cytochrome c oxidase. There was no accumulation of lactate in the muscle and liver of specimens exposed to sulfide in normoxia. In addition, the levels of ATP, AMP, and energy charge in both the muscle and the liver were unaffected. These results indicate that B. boddaerti was able to sustain the energy supply required for its metabolic needs via mainly aerobic respiration when exposed to sulfide (up to 0.4 mM) in normoxia. Exposure of B. boddaerti simultaneously to hypoxia and 0.2 mM sulfide for 48 h resulted in decreases in the ATP levels in the muscle and liver. However, the energy charge in both tissues remained unchanged, and the level of lactate accumulated in the muscle was too low to have any major contribution to the energy budget of the fish. Our results reveal that B. boddaerti possesses inducible mechanisms to detoxify sulfide in an ample supply or a lack of O2. In normoxia, it detoxified sulfide to sulfate, sulfite, and thiosulfate. There were significant increases in the activities of sulfide oxidase in the muscle and liver of specimens exposed to sulfide, with that in the liver being >13-fold higher than that in the muscle. However, in hypoxia, sulfide oxidase activity in the liver was suppressed in response to environmental sulfide. In such conditions, there were significant increases in the activities of sulfane sulfur-forming enzyme(s) in the muscle and liver that were not observed in specimens exposed to sulfide in normoxia. Correspondingly, there were no changes in the levels of sulfate or sulfite in the muscle or liver. Instead, B. boddaerti detoxified sulfide mainly to sulfane sulfur in hypoxia. In conclusion, B. boddaerti was able to activate different mechanisms to detoxify sulfide, producing different types of detoxification products in normoxia and hypoxia.

Acclimatization↗
PubMed2000

Sulfide:quinone oxidoreductase in membranes of the hyperthermophilic bacterium Aquifex aeolicus (VF5).

The sulfide-dependent reduction of exogenous ubiquinone by membranes of the hyperthermophilic chemotrophic bacterium Aquifex aeolicus (VF5), the sulfide-dependent consumption of oxygen and the reduction of cytochromes by sulfide in membranes were studied. Sulfide reduced decyl-ubiquinone with a maximal rate of up to 3.5 micromol (mg protein)(-1) min(-1) at 20 degrees C. Rates of 220 nmol (mg protein)(-1) min(-1)] for the sulfide-dependent consumption of oxygen and 480 nmol (mg protein)(-1) min(-1) for the oxidation of sulfide at 20 C were estimated. The reactions were sensitive towards 2-n-nonyl-4-hydroxyquinoline-N-oxide, but insensitive towards cyanide. Both reduction of decyl-ubiquinone and consumption of oxygen by sulfide rapidly increased with increasing temperature. For the sulfide-dependent respiratory activity, a sulfide-to-oxygen ratio of 2.3+/-0.2 was measured. This indicates that sulfide was oxidized to the level of zero-valent sulfur. Reduction of cytochromes by sulfide was monitored with an LED-array spectrophotometer. Reduction of cytochrome b was stimulated by 2-n-nonyl-4-hydroxyquinoline-N-oxide in the presence of excess sulfide under oxic conditions. This "oxidant-induced reduction" of cytochrome b suggests that electron transport from sulfide to oxygen in A. aeolicus employs the cytochrome bc complex via the quinone pool. Comparison of the amino acid sequence with the sequence of the sulfide:quinone oxidoreductase from Rhodobacter capsulatus and of the flavocytochrome c from Allochromatium vinosum revealed that the sulfide:quinone oxidoreductase from A. aeolicus belongs to the glutathione reductase family of flavoproteins.

Amino Acid Sequence↗
PubMed2003

The loss of the hemoglobin H2S-binding function in annelids from sulfide-free habitats reveals molecular adaptation driven by Darwinian positive selection.

The hemoglobin of the deep-sea hydrothermal vent vestimentiferan Riftia pachyptila (annelid) is able to bind toxic hydrogen sulfide (H(2)S) to free cysteine residues and to transport it to fuel endosymbiotic sulfide-oxidising bacteria. The cysteine residues are conserved key amino acids in annelid globins living in sulfide-rich environments, but are absent in annelid globins from sulfide-free environments. Synonymous and nonsynonymous substitution analysis from two different sets of orthologous annelid globin genes from sulfide rich and sulfide free environments have been performed to understand how the sulfide-binding function of hemoglobin appeared and has been maintained during the course of evolution. This study reveals that the sites occupied by free-cysteine residues in annelids living in sulfide-rich environments and occupied by other amino acids in annelids from sulfide-free environments, have undergone positive selection in annelids from sulfide-free environments. We assumed that the high reactivity of cysteine residues became a disadvantage when H(2)S disappeared because free cysteines without their natural ligand had the capacity to interact with other blood components, disturb homeostasis, reduce fitness and thus could have been counterselected. To our knowledge, we pointed out for the first time a case of function loss driven by molecular adaptation rather than genetic drift. If constraint relaxation (H(2)S disappearance) led to the loss of the sulfide-binding function in modern annelids from sulfide-free environments, our work suggests that adaptation to sulfide-rich environments is a plesiomorphic feature, and thus that the annelid ancestor could have emerged in a sulfide-rich environment.

Amino Acid Sequence↗
PubMed2005

Sulfide-iron interactions in domestic wastewater from a gravity sewer.

Interactions between iron and sulfide in domestic wastewater from a gravity sewer were investigated with particular emphasis on redox cycling of iron and iron sulfide formation. The concentration ranges of iron and total sulfide in the experiments were 0.4-5.4mgFeL(-1) and 0-5.1mgSL(-1), respectively. During anaerobic conditions, iron reduction kinetics were investigated and reduction rates amounted on average to 1.32mgFeL(-1)d(-1). Despite the very low solubility of iron sulfide, the reduced iron reacted only partly with sulfide to produce iron sulfide, even when dissolved sulfide was in excess. When a ferric chloride solution was added to sulfide containing anaerobic wastewater, the ferric iron was quickly reduced to ferrous forms by oxidation of dissolved sulfide and the ferrous iron precipitated almost completely as iron sulfide. During aerobic conditions, iron sulfide was oxidized with a half-life period of 11.7h. The oxidation rate of iron sulfide was significantly lower than that reported for the oxidation of dissolved sulfide.

Bioreactors↗
PubMed2003

Relationship between periodontal pocket sulfide levels and subgingival species.

BACKGROUND: Many species implicated in the pathogenesis of periodontal disease produce volatile sulfur compounds (VSC). This investigation examined the relationship between levels of sulfide and subgingival bacterial species in the same periodontal pockets. MATERIAL AND METHODS: Twenty chronic periodontitis subjects were measured clinically at six sites per tooth for plaque, gingivitis, bleeding on probing, suppuration, pocket depth and attachment level. Subgingival plaque samples, taken from the mesial aspect of each tooth, were individually analyzed for their content of 40 bacterial species using checkerboard DNA-DNA hybridization. Sulfide levels were measured at the same sites using a Diamond Probe/Perio 2000 system. Clinical and microbiological data were averaged for sulfide-positive and -negative sites separately in each subject and then averaged across subjects. Significance differences in clinical and microbial parameters between sulfide-positive and -negative sites were sought using the Wilcoxon signed ranks test. RESULTS: Mean total DNA probe counts (x10(5), +/-SEM) at sulfide-negative and -positive sites were 44.0 +/- 9.9 and 65.0 +/- 13.3, respectively (p < 0.01). Seventeen species were found at significantly higher levels in sulfide-positive than -negative sites. These included abundant producers of VSC such as members of the genera Fusobacterium, Campylobacter, Prevotella, Treponema and Eubacterium, and Bacteriodes forsythus, Selenomonas noxia and Propionibacterium acnes. Prevotella intermedia, Bacteriodes forsythus, Prevotella nigrescens, Fusobacterium nucleatum ss vincentii and Treponema denticola exhibited the greatest difference in mean counts between sulfide-negative and -positive sites. Orange and red complex species were at higher counts at shallow (< 4 mm) sulfide-positive than shallow sulfide-negative sites. Although not statistically significant, mean clinical parameters were somewhat higher at sulfide-positive than sulfide-negative sites. CONCLUSIONS: Intra-pocket sulfide levels reflect the levels of sulfide-producing species and may provide useful diagnostic information.

Adult↗