Sulfur Atoms Adsorbed on Cu(100) at Low Coverage: Characterization and Stability against Complexation

DOE PAGES

Walen, Holly; Liu, Da-Jiang; Oh, Junepyo; ...

2017-08-22

By using scanning tunneling microscopy, we characterize the size and bias-dependent shape of sulfur atoms on Cu(100) at low coverage (below 0.1 monolayers) and low temperature (quenched from 300 to 5 K). Sulfur atoms populate the Cu(100) terraces more heavily than steps at low coverage, but as coverage approaches 0.1 monolayers, close-packed step edges become fully populated, with sulfur atoms occupying sites on top of the step. Density functional theory (DFT) corroborates the preferential population of terraces at low coverage as well as the step adsorption site. In experiment, small regions with p(2 × 2)-like atomic arrangements emerge on themore » terraces as sulfur coverage approaches 0.1 monolayer. Using DFT, a lattice gas model has been developed, and Monte Carlo simulations based on this model have been compared with the observed terrace configurations. A model containing eight pairwise interaction energies, all repulsive, gives qualitative agreement. Experiment shows that atomic adsorbed sulfur is the only species on Cu(100) up to a coverage of 0.09 monolayers. There are no Cu–S complexes. Conversely, prior work has shown that a Cu 2S 3 complex forms on Cu(111) under comparable conditions. On the basis of DFT, this difference can be attributed mainly to stronger adsorption of sulfur on Cu(100) as compared with Cu(111).« less

Sulfur Atoms Adsorbed on Cu(100) at Low Coverage: Characterization and Stability against Complexation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walen, Holly; Liu, Da-Jiang; Oh, Junepyo

By using scanning tunneling microscopy, we characterize the size and bias-dependent shape of sulfur atoms on Cu(100) at low coverage (below 0.1 monolayers) and low temperature (quenched from 300 to 5 K). Sulfur atoms populate the Cu(100) terraces more heavily than steps at low coverage, but as coverage approaches 0.1 monolayers, close-packed step edges become fully populated, with sulfur atoms occupying sites on top of the step. Density functional theory (DFT) corroborates the preferential population of terraces at low coverage as well as the step adsorption site. In experiment, small regions with p(2 × 2)-like atomic arrangements emerge on themore » terraces as sulfur coverage approaches 0.1 monolayer. Using DFT, a lattice gas model has been developed, and Monte Carlo simulations based on this model have been compared with the observed terrace configurations. A model containing eight pairwise interaction energies, all repulsive, gives qualitative agreement. Experiment shows that atomic adsorbed sulfur is the only species on Cu(100) up to a coverage of 0.09 monolayers. There are no Cu–S complexes. Conversely, prior work has shown that a Cu 2S 3 complex forms on Cu(111) under comparable conditions. On the basis of DFT, this difference can be attributed mainly to stronger adsorption of sulfur on Cu(100) as compared with Cu(111).« less

Towards high-performance materials for road construction

NASA Astrophysics Data System (ADS)

Gladkikh, V.; Korolev, E.; Smirnov, V.

2017-10-01

Due to constant increase of traffic, modern road construction is in need of high-performance pavement materials. The operational performance of such materials can be characterized by many properties. Nevertheless, the most important ones are resistance to rutting and resistance to dynamical loads. It was proposed earlier to use sulfur extended asphalt concrete in road construction practice. To reduce the emission of sulfur dioxide and hydrogen sulfide during the concrete mix preparation and pavement production stages, it is beneficial to make such a concrete on the base of complex sulfur modifier. In the present work the influence of the complex modifier to mechanical properties of sulfur extended asphalt concrete was examined. It was shown that sulfur extended asphalt concrete is of high mechanical properties. It was also revealed that there as an anomalous negative correlations between strain capacity, fatigue life and fracture toughness.

Iron-sulfur Proteins Are the Major Source of Protein-bound Dinitrosyl Iron Complexes Formed in Escherichia coli Cells under Nitric Oxide Stress

PubMed Central

Landry, Aaron P.; Duan, Xuewu; Huang, Hao; Ding, Huangen

2011-01-01

Protein-bound dinitrosyl iron complexes (DNICs) have been observed in prokaryotic and eukaryotic cells under nitric oxide (NO) stress. The identity of proteins that bind DNICs, however, still remains elusive. Here we demonstrate that iron-sulfur proteins are the major source of protein-bound DNICs formed in Escherichia coli cells under NO stress. Expression of recombinant iron-sulfur proteins, but not the proteins without iron-sulfur clusters, almost doubles the amount of protein-bound DNICs formed in E. coli cells after NO exposure. Purification of recombinant proteins from the NO-exposed E. coli cells further confirms that iron-sulfur proteins, but not the proteins without iron-sulfur clusters, are modified forming protein-bound DINCs. Deletion of the iron-sulfur cluster assembly proteins IscA and SufA to block the [4Fe-4S] cluster biogenesis in E. coli cells largely eliminates the NO-mediated formation of protein-bound DNICs, suggesting that iron-sulfur clusters are mainly responsible for the NO-mediated formation of protein-bound DNICs in cells. Furthermore, depletion of “chelatable iron pool” in the wild-type E. coli cells effectively removes iron-sulfur clusters from proteins and concomitantly diminishes the NO-mediated formation of protein-bound DNICs, indicating that iron-sulfur clusters in proteins constitute at least part of “chelatable iron pool” in cells. PMID:21420489

Iron-Sulfur-Carbonyl and -Nitrosyl Complexes: A Laboratory Experiment.

ERIC Educational Resources Information Center

Glidewell, Christopher; And Others

1985-01-01

Background information, materials needed, procedures used, and typical results obtained, are provided for an experiment on iron-sulfur-carbonyl and -nitrosyl complexes. The experiment involved (1) use of inert atmospheric techniques and thin-layer and flexible-column chromatography and (2) interpretation of infrared, hydrogen and carbon-13 nuclear…

Engine Tests Using High-Sulfur Diesel Fuel

DTIC Science & Technology

1980-09-01

0.5 wt% sulfur because "too high a sulfur content results in excessive cylinder wear due to acid build-up in the lubricating oil" (Ref 1). Previous...that the addition of 0.3 vol% of an organo-zinc complex fuel additive (zinc naphthenate ) to high-sulfur diesel fuel was an effective means of...disulfide. Addition of 0.3 vol% zinc naphthenate to high- sulfur fuel increased the fuel ash to 0.035 wt% while the cetane number re- mained unchanged

Refining a complex nickel alloy to remove a sulfur impurity during vacuum induction melting: Part II

NASA Astrophysics Data System (ADS)

Sidorov, V. V.; Min, P. G.

2014-12-01

The results of studying the refining of complexly alloyed nickel melts from sulfur during melting in a vacuum induction furnace or with the use of an oxide calcium crucible, metallic calcium added to a melt, or rare-earth metals additions (which form thermodynamically stable refractory compounds with sulfur and, thus, eliminate the harmful effect of sulfur in the alloys) are reported.

Phylogenetic Evidence for the Existence of Novel Thermophilic Bacteria in Hot Spring Sulfur-Turf Microbial Mats in Japan

PubMed Central

Yamamoto, Hiroyuki; Hiraishi, Akira; Kato, Kenji; Chiura, Hiroshi X.; Maki, Yonosuke; Shimizu, Akira

1998-01-01

So-called sulfur-turf microbial mats, which are macroscopic white filaments or bundles consisting of large sausage-shaped bacteria and elemental sulfur particles, occur in sulfide-containing hot springs in Japan. However, no thermophiles from sulfur-turf mats have yet been isolated as cultivable strains. This study was undertaken to determine the phylogenetic positions of the sausage-shaped bacteria in sulfur-turf mats by direct cloning and sequencing of 16S rRNA genes amplified from the bulk DNAs of the mats. Common clones with 16S rDNA sequences with similarity levels of 94.8 to 99% were isolated from sulfur-turf mat samples from two geographically remote hot springs. Phylogenetic analysis showed that the phylotypes of the common clones formed a major cluster with members of the Aquifex-Hydrogenobacter complex, which represents the most deeply branching lineage of the domain bacteria. Furthermore, the bacteria of the sulfur-turf mat phylotypes formed a clade distinguishable from that of other members of the Aquifex-Hydrogenobacter complex at the order or subclass level. In situ hybridization with clone-specific probes for 16S rRNA revealed that the common phylotype of sulfur-turf mat bacteria is that of the predominant sausage-shaped bacteria. PMID:9572936

Using X-ray absorption to probe sulfur oxidation states in complex molecules

NASA Astrophysics Data System (ADS)

Vairavamurthy, A.

1998-10-01

X-ray absorption near-edge structure (XANES) spectroscopy offers an important non-destructive tool for determining oxidation states and for characterizing chemical speciation. The technique was used to experimentally verify the oxidation states of sulfur in different types of complex molecules because there are irregularities and uncertainties in assigning the values traditionally. The usual practice of determining oxidation states involves using a set of conventional rules. The oxidation state is an important control in the chemical speciation of sulfur, ranging from -2 to +6 in its different compounds. Experimental oxidation-state values for various types of sulfur compounds, using their XANES peak-energy positions, were assigned from a scale in which elemental sulfur and sulfate are designated as 0 and +6, respectively. Because these XANES-based values differed considerably from conventionally determined oxidation states for most sulfur compounds, a new term 'oxidation index' was coined to describe them. The experimental values were closer to those conventional values obtained by assigning shared electrons to the more electronegative atoms than to those based on other customary rules for assigning them. Because the oxidation index is distinct and characteristic for each different type of sulfur functionality, it becomes an important parameter for characterizing sulfur species, and for experimentally verifying uncertain oxidation states.

Characterization of Sulfur and Nanostructured Sulfur Battery Cathodes in Electron Microscopy Without Sublimation Artifacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levin, Barnaby D. A.; Zachman, Michael J.; Werner, Jörg G.

Abstract Lithium sulfur (Li–S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li–S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon–sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes. The resulting sublimation artifacts render characterization of sulfur in conventional electron microscopes problematic and unreliable. Here, we demonstratemore » two techniques, cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy in air (airSEM), that enable the reliable characterization of sulfur across multiple length scales by suppressing sulfur sublimation. We use cryo-TEM and airSEM to examine carbon–sulfur composites synthesized for use as Li–S battery cathodes, noting several cases where the commonly employed sulfur melt infusion method is highly inefficient at infiltrating sulfur into porous carbon hosts.« less

Supraglacial sulfur springs and associated biological activity in the Canadian high arctic - signs of life beneath the ice

USGS Publications Warehouse

Grasby, Stephen E.; Allen, Carlton C.; Longazo, Teresa G.; Lisle, John T.; Griffin, Dale W.; Beauchamp, Benoit

2003-01-01

Unique springs, discharging from the surface of an arctic glacier, release H2S and deposit native sulfur, gypsum, and calcite. The presence of sulfur in three oxidation states indicates a complex series of redox reactions. Physical and chemical conditions of the spring water and surrounding environment, as well as mineralogical and isotopic signatures, suggest biologically mediated reactions. Cell counts and DNA analyses confirm bacteria are present in the spring system, and a limited number of sequenced isolates suggests that complex communities of bacteria live within the glacial system.

Mitochondrial rhodanese: membrane-bound and complexed activity.

PubMed

Ogata, K; Volini, M

1990-05-15

We have proposed that phosphorylated and dephosphorylated forms of the mitochondrial sulfurtransferase, rhodanese, function as converter enzymes that interact with membrane-bound iron-sulfur centers of the electron transport chain to modulate the rate of mitochondrial respiration (Ogata, K., Dai, X., and Volini, M. (1989) J. Biol. Chem. 204, 2718-2725). In the present studies, we have explored some structural aspects of the mitochondrial rhodanese system. By sequential extraction of lysed mitochondria with phosphate buffer and phosphate buffer containing 20 mM cholate, we have shown that 30% of the rhodanese activity of bovine liver is membrane-bound. Resolution of cholate extracts on Sephadex G-100 indicates that part of the bound rhodanese is complexed with other mitochondrial proteins. Tests with the complex show that it forms iron-sulfur centers when incubated with the rhodanese sulfur-donor substrate thiosulfate, iron ions, and a reducing agent. Experiments on the rhodanese activity of rat liver mitochondria give similar results. Taken together, the findings indicate that liver rhodanese is in part bound to the mitochondrial membrane as a component of a multiprotein complex that forms iron-sulfur centers. The findings are consistent with the role we propose for rhodanese in the modulation of mitochondrial respiratory activity.

Binding of dinitrogen to an iron-sulfur-carbon site

NASA Astrophysics Data System (ADS)

Čorić, Ilija; Mercado, Brandon Q.; Bill, Eckhard; Vinyard, David J.; Holland, Patrick L.

2015-10-01

Nitrogenases are the enzymes by which certain microorganisms convert atmospheric dinitrogen (N2) to ammonia, thereby providing essential nitrogen atoms for higher organisms. The most common nitrogenases reduce atmospheric N2 at the FeMo cofactor, a sulfur-rich iron-molybdenum cluster (FeMoco). The central iron sites that are coordinated to sulfur and carbon atoms in FeMoco have been proposed to be the substrate binding sites, on the basis of kinetic and spectroscopic studies. In the resting state, the central iron sites each have bonds to three sulfur atoms and one carbon atom. Addition of electrons to the resting state causes the FeMoco to react with N2, but the geometry and bonding environment of N2-bound species remain unknown. Here we describe a synthetic complex with a sulfur-rich coordination sphere that, upon reduction, breaks an Fe-S bond and binds N2. The product is the first synthetic Fe-N2 complex in which iron has bonds to sulfur and carbon atoms, providing a model for N2 coordination in the FeMoco. Our results demonstrate that breaking an Fe-S bond is a chemically reasonable route to N2 binding in the FeMoco, and show structural and spectroscopic details for weakened N2 on a sulfur-rich iron site.

Sulfur K-edge XAS of WV=O vs. MoV=O Bis(dithiolene) Complexes: Contributions of Relativistic Effects to Electronic Structure and Reactivity of Tungsten Enzymes†

PubMed Central

Tenderholt, Adam L.; Szilagyi, Robert K.; Holm, Richard H.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.

2009-01-01

Molybdenum- or tungsten-containing enzymes catalyze oxygen atom transfer reactions involved in carbon, sulfur, or nitrogen metabolism. It has been observed that reduction potentials and oxygen atom transfer rates are different for W relative to Mo enzymes and the isostructural Mo/W complexes. Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations on [MoVO(bdt)2]− and [WVO(bdt)2]−, where bdt = benzene-1,2-dithiolate(2−), have been used to determine that the energies of the half-filled redox-active orbital, and thus the reduction potentials and M=O bond strengths, are different for these complexes due to relativistic effects in the W sites. PMID:17720249

Sulfur K-edge extended X-ray absorption fine structure spectroscopy of homoleptic thiolato complexes with Zn(II) and Cd(II).

PubMed

Matsunaga, Yuki; Fujisawa, Kiyoshi; Ibi, Naoko; Fujita, Mitsuharu; Ohashi, Tetuya; Amir, Nagina; Miyashita, Yoshitaro; Aika, Ken-Ichi; Izumi, Yasuo; Okamoto, Ken-Ichi

2006-02-01

The sulfur K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy is applied to homoleptic thiolato complexes with Zn(II) and Cd(II), (Et(4)N)[Zn(SAd)(3)] (1), (Et(4)N)(2)[{Zn(ScHex)(2)}(2)(mu-ScHex)(2)] (2), (Et(4)N)(2)[{Cd(ScHex)(2)}(2)(mu-ScHex)(2)] (3), (Et(4)N)(2)[{Cd(ScHex)}(4)(mu-ScHex)(6)] (4), [Zn(mu-SAd)(2)](n) (5), and [Cd(mu-SAd)(2)](n) (6) (HSAd=1-adamantanethiol, HScHex=cyclohexanethiol). The EXAFS results are consistent with the X-ray crystal data of 1-4. The structures of 5 and 6, which have not been determined by X-ray crystallography, are proposed to be polynuclear structures on the basis of the sulfur K-edge EXAFS, far-IR spectra, and elemental analysis. Clear evidences of the S...S interactions (between bridging atoms or neighboring sulfur atoms) and the S...C(far) interactions (in which C(far) atom is next to carbon atom directly bonded to sulfur atom) were observed in the EXAFS data for all complexes and thus lead to the reliable determination of the structures of 5 and 6 in combination with conventional zinc K-edge EXAFS analysis for 5. This new methodology, sulfur K-edge EXAFS, could be applied for the structural determination of in vivo metalloproteins as well as inorganic compounds.

The Alternative complex III: properties and possible mechanisms for electron transfer and energy conservation.

PubMed

Refojo, Patrícia N; Teixeira, Miguel; Pereira, Manuela M

2012-10-01

Alternative complexes III (ACIII) are recently identified membrane-bound enzymes that replace functionally the cytochrome bc(1/)b(6)f complexes. In general, ACIII are composed of four transmembrane proteins and three peripheral subunits that contain iron-sulfur centers and C-type hemes. ACIII are built by a combination of modules present in different enzyme families, namely the complex iron-sulfur molybdenum containing enzymes. In this article a historical perspective on the investigation of ACIII is presented, followed by an overview of the present knowledge on these enzymes. Electron transfer pathways within the protein are discussed taking into account possible different locations (cytoplasmatic or periplasmatic) of the iron-sulfur containing protein and their contribution to energy conservation. In this way several hypotheses for energy conservation modes are raised including linear and bifurcating electron transfer pathways. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). Copyright © 2012 Elsevier B.V. All rights reserved.

Fair performance comparison of different carbon blacks in lithium-sulfur batteries with practical mass loadings - Simple design competes with complex cathode architecture

NASA Astrophysics Data System (ADS)

Jozwiuk, Anna; Sommer, Heino; Janek, Jürgen; Brezesinski, Torsten

2015-11-01

The lithium-sulfur system is one of the most promising next generation battery systems, as elemental sulfur is cheap, abundant and has a high theoretical specific capacity. Although much research is conducted on complex sulfur/carbon composites and architectures, it is difficult to compare the performance of the cathodes to one another. Factors, such as different electrolyte composition and cell components strongly affect the cyclability of the battery. Here, we show the importance of optimizing ;standard; conditions to allow for fair performance comparison of different carbon blacks. Our optimal electrolyte-to-sulfur ratio is 11 μL mgsulfur-1 and high concentrations of LiNO3 (>0.6 M) are needed because nitrate is consumed continuously during cycling. Utilizing these standard conditions, we tested the cycling behavior of four types of cathodes with individual carbon blacks having different specific surface areas, namely Printex-A, Super C65, Printex XE-2 and Ketjenblack EC-600JD. Both the specific capacity and polysulfide adsorption capability clearly correlate with the surface area of the carbon being used. High specific capacities (>1000 mAh gsulfur-1 at C/5) are achieved with high surface area carbons. We also demonstrate that a simple cathode using Ketjenblack EC-600JD as the conductive matrix material can well compete with those having complex architectures or additives.

Multiple Sulfur Isotopes In The Molopo Farms Complex May Shed Light On Mechanisms Of Mineralization In The Bushveld Igneous Complex

NASA Astrophysics Data System (ADS)

Magalhaes, N.; Feineman, M. D.; Bybee, G. M.; Penniston-Dorland, S.; Farquhar, J.; Draper, C.; Escobar, E.; Gates, M.; Renusch, J.

2016-12-01

The 2.056 Ga Bushveld Igneous Complex (BIC) is host to the world's largest layered mafic-ultramafic intrusion, the Rustenburg Layered Suite (RLS), which has >80% of the world's known platinum group elements (PGEs) reserves. The BIC results from large-volume melt extraction from the mantle and may provide insight into the formation and compositional evolution of continental crust. Despite its scientific and economic importance, the total magma volume is poorly known. This is in part because the relationship between the BIC and nearby intrusive bodies of similar age remains uncertain. In this study, we present major element, trace element, and multiple sulfur isotope data for a suite of samples spanning the stratigraphy of the Molopo Farms Complex (MFC), a layered mafic intrusion located 200 km west of the Far Western Limb of the RLS. Similar to the RLS, the MFC contains an ultramafic lower zone, a mafic main zone, and an incompatible element enriched granophyric unit near the contact with the roof rocks. However, it has no Critical Zone, and an insignificant concentration of PGEs. Since the PGEs in the RLS are primarily hosted in sulfides, it has been inferred that the mineralization is closely linked to the source and behavior of sulfur. The RLS displays mass independent fractionation of sulfur (S-MIF; denoted by Δ33S), which suggests incorporation of surface-derived materials into the magma prior to or during emplacement. Multiple sulfur isotopes of MFC samples also show non-zero mean Δ33S (0.04±0.02‰, 1sd), although it is lower than the mean for the RLS (0.11±0.02‰, 1sd). Similarities in trace element ratios between the MFC mafic zone and RLS marginal zone suggest the same parental magma contributed to both intrusions. Taken together, these results suggest that both the RLS and the MFC started with similar magmatic compositions, and while both assimilated sulfur with an Archean surface-derived component, the RLS received more of this component in proportion to its volume. The lack of PGE mineralization in the MFC may reflect the lesser addition of Archean sedimentary sulfur.

A primer on sulfur for the planetary geologist

NASA Technical Reports Server (NTRS)

Theilig, E.

1982-01-01

Sulfur has been proposed as the dominant composition for the volcanic material on Io. Sulfur is a complex element which forms many intramolecular and intermolecular allotropes exhibiting a variety of physical properties. Cyclo-S8 sulfur is the most abundant and stable molecular form. The important molecular species within liquid sulfur change in concentration with temperature. Concentrations of the allotropes control the physical properties of the melt. Discontinuities in density, viscosity, and thermal properties reflect the polymerization process within liquid sulfur. Variations in the melting point are related to autodissociation of the liquid. Many solids forms of sulfur have been identified but only orthorhombic alpha and monoclinic beta sulfur, both composed of cyclo-S8 sulfur, are stable under terrestrial conditions. Physical properties of solid sulfur are dependent on the allotrope and, in some cases, the thermal history. Three natural terrestrial sulfur flows are described: (1) Siretoko-Iosan, Japan; (2) Volcan Azufre, Galapagos Islands; and (3) Mauna Loa, Hawaii. All of the flows are associated with fumarolic areas and are considered to have formed by the melting and mobilization of sulfur deposits. Surface textures of the flows indicate a behavior of molten sulfur similar to that of silicate lava. Channels, rivulets, and lobate edges were described for the flows. The solidification of man-made sulfur flows formed as part of the Frasch mining process by which sulfur is removed from the subsurface in a liquid state is described.

Incorporation of spheroidene and spheroidenone into light-harvesting complexes from purple sulfur bacteria.

PubMed

Ashikhmin, Aleksandr; Makhneva, Zoya; Bolshakov, Maksim; Moskalenko, Andrey

2017-05-01

Spheroidene and spheroidenone from the non-sulfur bacterium Rhodobacter (Rba.) sphaeroides were incorporated into diphenylamine (DPA) LH1-RC and LH2 complexes from sulfur bacteria Allochromatium (Alc.) minutissimum and Ectothiorhodospira (Ect.) haloalkaliphila in which carotenoid (Car) biosynthesis was inhibited by ~95%. A series of biochemical characteristics of the modified LH2 complexes was studied (electrophoretic mobility, absorption and CD spectra, Car composition, Car-to-BChl energy transfer and thermal stability). It was found that the electrophoretic mobility of the complexes with incorporated Cars did not change compared to that of the control and DPA-complexes, indicating the absence of any significant change in the structure of LH complexes upon DPA-treatment and subsequent incorporation of Cars. The analysis of fluorescence excitation spectra of the spheroidene-incorporated LH2 complex (LH2:sph) and the spheroidenone-incorporated LH2 complex (LH2:sph-ne) showed that spheroidene and spheroidenone exhibited relatively low efficiencies of energy transfer to BChl, when incorporated into the LH2 DPA-complexes from Alc. minutissimum and Ect. haloalkaliphila, although, they showed high efficiencies, being in their natural state in the LH2 complexes from Rba. sphaeroides. A significant increase in thermostability observed for the LH2:sph and LH2:sph-ne complexes with respect to the LH2 DPA-complexes indicated that the two incorporated Cars stabilized the structure of the LH2 complexes. Copyright © 2017 Elsevier B.V. All rights reserved.

XAFS studies of nickel and sulfur speciation in residual oil fly-ash particulate matters (ROFA PM).

PubMed

Pattanaik, Sidhartha; Huggins, Frank E; Huffman, Gerald P; Linak, William P; Miller, C Andrew

2007-02-15

XAFS spectroscopy has been employed to evaluate the effect of fuel compositions and combustion conditions on the amount, form, and distribution of sulfur and nickel in size-fractionated ROFA PM. Analysis of S K-edge XANES establish that sulfate is abundant in all PM. However, depending upon the combustion conditions, lesser amounts of thiophenic sulfur, metal sulfide, and elemental sulfur may also be observed. Least-squares fitting of Ni K-edge XANES reveals that most of the nickel in PM is present as bioavailable NiSO4.nH2O. The insoluble Ni mainly exists as a minor species, as nickel ferrite in PM2.5 (PM < 2.5 microm) and nickel sulfide, Ni(x)SY(y) in PM2.5+ (PM > 2.5 microm). The Ni K-edge XANES results are in agreement with the EXAFS data. Such detailed speciation of Ni and S in PM is needed for determining their mobility, bioavailability, and reactivity, and hence, their role in PM toxicity. This information is also important for understanding the mechanism of PM formation, developing effective remediation measures, and providing criteria for identification of potential emission sources. Transition metals complexing with sulfur is ubiquitous in nature. Therefore, this information on metal sulfur complex can be critical to a large body of environmental literature.

Microbial oxidative sulfur metabolism: biochemical evidence of the membrane-bound heterodisulfide reductase-like complex of the bacterium Aquifex aeolicus.

PubMed

Boughanemi, Souhela; Lyonnet, Jordan; Infossi, Pascale; Bauzan, Marielle; Kosta, Artémis; Lignon, Sabrina; Giudici-Orticoni, Marie-Thérèse; Guiral, Marianne

2016-08-01

The Hdr (heterodisulfide reductase)-like enzyme is predicted, from gene transcript profiling experiments previously published, to be essential in oxidative sulfur metabolism in a number of bacteria and archaea. Nevertheless, no biochemical and physicochemical data are available so far about this enzyme. Genes coding for it were identified in Aquifex aeolicus, a Gram-negative, hyperthermophilic, chemolithoautotrophic and microaerophilic bacterium that uses inorganic sulfur compounds as electron donor to grow. We provide biochemical evidence that this Hdr-like enzyme is present in this sulfur-oxidizing prokaryote (cultivated with thiosulfate or elemental sulfur). We demonstrate, by immunolocalization and cell fractionation, that Hdr-like enzyme is associated, presumably monotopically, with the membrane fraction. We show by co-immunoprecipitation assay or partial purification, that the Hdr proteins form a stable complex composed of at least five subunits, HdrA, HdrB1, HdrB2, HdrC1 and HdrC2, present in two forms of high molecular mass on native gel (∼240 and 450 kDa). These studies allow us to propose a revised model for dissimilatory sulfur oxidation pathways in A. aeolicus, with Hdr predicted to generate sulfite. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Using stable isotopes to monitor forms of sulfur during desulfurization processes: A quick screening method

USGS Publications Warehouse

Liu, Chao-Li; Hackley, Keith C.; Coleman, D.D.; Kruse, C.W.

1987-01-01

A method using stable isotope ratio analysis to monitor the reactivity of sulfur forms in coal during thermal and chemical desulfurization processes has been developed at the Illinois State Geological Survey. The method is based upon the fact that a significant difference exists in some coals between the 34S/32S ratios of the pyritic and organic sulfur. A screening method for determining the suitability of coal samples for use in isotope ratio analysis is described. Making these special coals available from coal sample programs would assist research groups in sorting out the complex sulfur chemistry which accompanies thermal and chemical processing of high sulfur coals. ?? 1987.

UV-light-driven prebiotic synthesis of iron-sulfur clusters

NASA Astrophysics Data System (ADS)

Bonfio, Claudia; Valer, Luca; Scintilla, Simone; Shah, Sachin; Evans, David J.; Jin, Lin; Szostak, Jack W.; Sasselov, Dimitar D.; Sutherland, John D.; Mansy, Sheref S.

2017-12-01

Iron-sulfur clusters are ancient cofactors that play a fundamental role in metabolism and may have impacted the prebiotic chemistry that led to life. However, it is unclear whether iron-sulfur clusters could have been synthesized on prebiotic Earth. Dissolved iron on early Earth was predominantly in the reduced ferrous state, but ferrous ions alone cannot form polynuclear iron-sulfur clusters. Similarly, free sulfide may not have been readily available. Here we show that UV light drives the synthesis of [2Fe-2S] and [4Fe-4S] clusters through the photooxidation of ferrous ions and the photolysis of organic thiols. Iron-sulfur clusters coordinate to and are stabilized by a wide range of cysteine-containing peptides and the assembly of iron-sulfur cluster-peptide complexes can take place within model protocells in a process that parallels extant pathways. Our experiments suggest that iron-sulfur clusters may have formed easily on early Earth, facilitating the emergence of an iron-sulfur-cluster-dependent metabolism.

A SERS characterization of the stability of polythionates at the gold-electrolyte interface

NASA Astrophysics Data System (ADS)

Mirza, Jeff; Smith, Scott R.; Baron, Janet Y.; Choi, Yeonuk; Lipkowski, Jacek

2015-01-01

A gold nanorod (AuNR) array electrode was employed to record SERS spectra as a function of immersion time in electrolyte solutions of tetrathionate, trithionate, the [Au(S2O3)2]3- complex, sulfide and thiosulfate. The generalized two-dimensional correlation spectroscopy was employed to deconvolute broad bands in the SERS spectra. The results show that the polythionates, tetrathionate and trithionate, sulfide, and the [Au(S2O3)2]3- complex decompose to form cyclo-S8, polymeric and monoatomic sulfur at the gold surface. The relative amount of these different forms of sulfur in the film formed at the surface depends on the nature of the electrolyte species. The decomposition of tetrathionate leads predominantly to the formation of cyclo-S8. Comparable amounts of all three forms of sulfur are formed in the solution of the [Au(S2O3)2]3- complex. Monoatomic sulfur is formed predominantly at the gold surface in solutions of trithionate and thiosulfate. In contrast to the previous suggestions, the results of this study demonstrate that polythionates are not present in the passive layer during gold leaching from thiosulfate solutions at a prolonged leaching times.

Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs

PubMed Central

2014-01-01

Background The paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling. Results Water samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L-1) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ34S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ34S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur–polysulfide – hydrogen sulfide system. Triple sulfur isotope (32S, 33S, 34S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆33S among species and between pools are observed. Conclusions The variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero–valent sulfur, as well as differences in ∆33S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways. PMID:24959098

Shared Sulfur Mobilization Routes for tRNA Thiolation and Molybdenum Cofactor Biosynthesis in Prokaryotes and Eukaryotes

PubMed Central

Leimkühler, Silke; Bühning, Martin; Beilschmidt, Lena

2017-01-01

Modifications of transfer RNA (tRNA) have been shown to play critical roles in the biogenesis, metabolism, structural stability and function of RNA molecules, and the specific modifications of nucleobases with sulfur atoms in tRNA are present in pro- and eukaryotes. Here, especially the thiomodifications xm5s2U at the wobble position 34 in tRNAs for Lys, Gln and Glu, were suggested to have an important role during the translation process by ensuring accurate deciphering of the genetic code and by stabilization of the tRNA structure. The trafficking and delivery of sulfur nucleosides is a complex process carried out by sulfur relay systems involving numerous proteins, which not only deliver sulfur to the specific tRNAs but also to other sulfur-containing molecules including iron–sulfur clusters, thiamin, biotin, lipoic acid and molybdopterin (MPT). Among the biosynthesis of these sulfur-containing molecules, the biosynthesis of the molybdenum cofactor (Moco) and the synthesis of thio-modified tRNAs in particular show a surprising link by sharing protein components for sulfur mobilization in pro- and eukaryotes. PMID:28098827

Sulfur activation at the Little Boy-Comet Critical Assembly: a replica of the Hiroshima bomb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerr, G.D.; Emery, J.F.; Pace, J.V. III

1985-04-01

Studies have been completed on the activation of sulfur by fast neutrons from the Little Boy-Comet Critical Assembly which replicates the general features of the Hiroshima bomb. The complex effects of the bomb's design and construction on leakage of sulfur-activation neutrons were investigated both experimentally and theoretically. Our sulfur activation studies were performed as part of a larger program to provide benchmark data for testing of methods used in recent source-term calculations for the Hiroshima bomb. Source neutrons capable of activating sulfur play an important role in determining neutron doses in Hiroshima at a kilometer or more from the pointmore » of explosion. 37 refs., 5 figs., 6 tabs.« less

Reactivity of pi-complexes of Ti, V, and Nb towards dithioacetic acid: Synthesis and structure of novel metal sulfur-containing complexes

NASA Technical Reports Server (NTRS)

Duraj, Stan A.; Andras, Maria T.; Hepp, Aloysius F.

1990-01-01

In order to use sulfur-containing resources economically and with minimal environmental damage, it is important to understand the desulfurization processes. Hydrodesulfurization, for example, is carried out on the surface of a heterogeneous metal sulfide catalyst. Studies of simple, soluble inorganic systems provide information regarding the structure and reactivity of sulfur-containing compounds with metal complexes. Further, consistent with recent trends in materials chemistry, many model compounds warrant further study as catalyst precursors. The reactivity of low-valent organometallic sandwich pi-complexes toward dithiocarboxylic acids is described. For example, treatment of bisbenzene vanadium with CH3CSSH affords a divanadium tetrakis(dithioacetate) complex. The crystallographically determined V-V bond distance, 2.800(2), is nearly the same as the V-V bond distance in a V(mu-nu squared-S2)2V' unit in the mineral patonite (VS4)n. The stability of the V2S4 core in the dimer is demonstrated by evidence of V2S4(+) in the mass spectrum (70 eV, solid probe) of the vanadium dimer. Several other systems relevant to HDS catalysis are also discussed.

Metallosulfoxides and -sulfones: Sulfur oxygenates of [1,5-Bis(2-mercaptoethyl)-1,5-diazacyclooctanato]palladium (II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuntulani, T.; Musie, G.; Reibenspies, J.H.

1995-12-06

Successive sulfur-site oxygenation of the dithiolate complex [1,5-bis(mercaptoethyl)-1,5 diazacyclooctanato]-palladium(II), Pd-1, using H{sub 2}O{sub 2} as an O atom source produced all but one member of the series of palladium(II) complexes containing sulfinate (metallosulfone) and sulfinate (metallosulfoxide) S-donor ligands: the monosulfoxide, PdS(=O)R or Pd-4; bis(sulfoxide), Pd(S(=O)R){sub 2} or Pd-5; sulfone/sulfoxide, Pd((SO{sub 2}R)S(=))R or Pd-6; and the bis(sulfone) Pd(SO{sub 2}R){sub 2} or Pd-3 complex. A unique site selectivity for the addition of a second O atom from H{sub 2}O{sub 2} to thiolate sulfur of Pd-4 producing the bis(sulfoxide), Pd-5, exclusively, precluded the preparation of the monosulfone complex, Pd(SO{sub 2}R)SR or Pd-2, viamore » that route. However, the dithiolate Pd-1 reacts with O{sub 2} photochemically in aprotic solvents, giving access to this last member of the series, Pd-2. Further reaction of Pd-2 with O{sub 2} under UV photolysis gives the bis(sulfone) complex, Pd-3. The oxygenates were characterized by various spectroscopies, electrochemistry, and X-ray crystallography. Mass spectrometry delineated a single O atom loss pathway for the sulfoxide species, while SO{sub 2} and O{sub 2} loss is found in sulfone cases. Electrochemical studies show that the addition of an O atom to a thiolate sulfur to create a sulfoxide S-donor results in a stabilization of the Pd{sup I} oxidation state in the range 50-70 mV, while the addition of an O atom to a sulfoxide sulfur to create a sulfone S-donor results in greater stabilization of the Pd{sup I} oxidation state in the range 190-220 mV.« less

Synthesis, structural characterization and conversion of dinuclear iron-sulfur clusters containing the disulfide ligand: [Cp*Fe(μ-η2:η2-bdt)(cis-μ-η1:η1-S2)FeCp*], [Cp*Fe(μ-S(C6H4S2))(cis-μ-η1:η1-S2)FeCp*], and [{Cp*Fe(bdt)}2(trans-μ-η1:η1-S2)].

PubMed

Ji, Xiaoxiao; Tong, Peng; Yang, Dawei; Wang, Baomin; Zhao, Jinfeng; Li, Yang; Qu, Jingping

2017-03-21

The treatment of [Cp*Fe(μ-η 2 :η 4 -bdt)FeCp*] (1, Cp* = η 5 -C 5 Me 5 , bdt = benzene-1,2-dithiolate) with 1/4 equiv. of elemental sulfur (S 8 ) gave a dinuclear iron-sulfur cluster [Cp*Fe(μ-η 2 :η 2 -bdt)(cis-μ-η 1 :η 1 -S 2 )FeCp*] (2), which contains a cis-1,2-disulfide ligand. When complex 2 further interacted with 1/8 equiv. of S 8 , another sulfur atom inserted into an Fe-S bond to give a rare product [Cp*Fe(μ-S(C 6 H 4 S 2 ))(cis-μ-η 1 :η 1 -S 2 )FeCp*] (3). Unexpectedly, a trans-1,2 disulfide-bridged diiron complex [{Cp*Fe(bdt)} 2 (trans-μ-η 1 :η 1 -S 2 )] (4) was isolated from the reaction of complex 1 with 1/2 equiv. of S 8 , which represents a structural isomer of [2Fe-2S] ferredoxin-type clusters. In addition, cis-1,2-disulfide-bridged complex 3 can slowly convert into trans-1,2-disulfide-bridged complex 4 and the complex [Cp*Fe(μ-η 2 :η 2 -S 2 )(cis-μ-η 1 :η 1 -S 2 )FeCp*] (5) by self-assembly reaction at ambient temperature, which is evidenced by time-dependent 1 H NMR spectroscopy.

Refining a complex nickel alloy to remove a sulfur impurity during vacuum induction melting: Part I

NASA Astrophysics Data System (ADS)

Sidorov, V. V.; Min, P. G.

2014-12-01

The peculiarities of refining a complexly alloyed nickel alloy from a sulfur impurity during melting of the alloy in a vacuum induction furnace are considered. The application of CaO-based slags is shown to allow the sulfur content in a metal to be decreased; however, in this case, the reduction of calcium, its transfer into the melt, and the degradation of the properties of the alloy take place.

The cytochrome complex SoxXA of Paracoccus pantotrophus is produced in Escherichia coli and functional in the reconstituted sulfur-oxidizing enzyme system.

PubMed

Rother, Dagmar; Friedrich, Cornelius G

2002-07-29

The heterodimeric c-type cytochrome complex SoxXA of Paracoccus pantotrophus was produced in Escherichia coli. The soxX and soxA genes, separated by two genes in the sox gene cluster of P. pantotrophus, were fused with ribosome binding sites optimal for E. coli and combined to give soxXA in pRD133.27. The cytochrome complex SoxXA was produced in E. coli M15 containing pRD133.27, pREP4 encoding the Lac repressor and plasmid pEC86, carrying essential cytochrome c maturation genes. SoxX and SoxA were formed in a ratio of about 2.5:1. SoxA appeared to be unstable when not complexed with SoxX. The cytochrome complex SoxXA, purified to homogeneity from periplasmic extracts of E. coli M15 (pRD133.27, pREP4, pEC86), exhibited identical biochemical and biophysical properties as compared to SoxXA of P. pantotrophus. Moreover, this cytochrome complex was shown to be equally catalytically active with respect to rates and reactivity with different sulfur substrates in the reconstituted sulfur-oxidizing enzyme system using homogeneous Sox-proteins of P. pantotrophus. Homogeneous SoxX was catalytically inactive.

RNA transcript sequencing reveals inorganic sulfur compound oxidation pathways in the acidophile Acidithiobacillus ferrivorans.

PubMed

Christel, Stephan; Fridlund, Jimmy; Buetti-Dinh, Antoine; Buck, Moritz; Watkin, Elizabeth L; Dopson, Mark

2016-04-01

Acidithiobacillus ferrivorans is an acidophile implicated in low-temperature biomining for the recovery of metals from sulfide minerals. Acidithiobacillus ferrivorans obtains its energy from the oxidation of inorganic sulfur compounds, and genes encoding several alternative pathways have been identified. Next-generation sequencing of At. ferrivorans RNA transcripts identified the genes coding for metabolic and electron transport proteins for energy conservation from tetrathionate as electron donor. RNA transcripts suggested that tetrathionate was hydrolyzed by the tetH1 gene product to form thiosulfate, elemental sulfur and sulfate. Despite two of the genes being truncated, RNA transcripts for the SoxXYZAB complex had higher levels than for thiosulfate quinone oxidoreductase (doxDAgenes). However, a lack of heme-binding sites in soxX suggested that DoxDA was responsible for thiosulfate metabolism. Higher RNA transcript counts also suggested that elemental sulfur was metabolized by heterodisulfide reductase (hdrgenes) rather than sulfur oxygenase reductase (sor). The sulfite produced as a product of heterodisulfide reductase was suggested to be oxidized by a pathway involving the sat gene product or abiotically react with elemental sulfur to form thiosulfate. Finally, several electron transport complexes were involved in energy conservation. This study has elucidated the previously unknown At. ferrivorans tetrathionate metabolic pathway that is important in biomining. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Acidithiobacillus caldus Sulfur Oxidation Model Based on Transcriptome Analysis between the Wild Type and Sulfur Oxygenase Reductase Defective Mutant

PubMed Central

Chen, Linxu; Ren, Yilin; Lin, Jianqun; Liu, Xiangmei; Pang, Xin; Lin, Jianqiang

2012-01-01

Background Acidithiobacillus caldus (A. caldus) is widely used in bio-leaching. It gains energy and electrons from oxidation of elemental sulfur and reduced inorganic sulfur compounds (RISCs) for carbon dioxide fixation and growth. Genomic analyses suggest that its sulfur oxidation system involves a truncated sulfur oxidation (Sox) system (omitting SoxCD), non-Sox sulfur oxidation system similar to the sulfur oxidation in A. ferrooxidans, and sulfur oxygenase reductase (SOR). The complexity of the sulfur oxidation system of A. caldus generates a big obstacle on the research of its sulfur oxidation mechanism. However, the development of genetic manipulation method for A. caldus in recent years provides powerful tools for constructing genetic mutants to study the sulfur oxidation system. Results An A. caldus mutant lacking the sulfur oxygenase reductase gene (sor) was created and its growth abilities were measured in media using elemental sulfur (S0) and tetrathionate (K2S4O6) as the substrates, respectively. Then, comparative transcriptome analysis (microarrays and real-time quantitative PCR) of the wild type and the Δsor mutant in S0 and K2S4O6 media were employed to detect the differentially expressed genes involved in sulfur oxidation. SOR was concluded to oxidize the cytoplasmic elemental sulfur, but could not couple the sulfur oxidation with the electron transfer chain or substrate-level phosphorylation. Other elemental sulfur oxidation pathways including sulfur diooxygenase (SDO) and heterodisulfide reductase (HDR), the truncated Sox pathway, and the S4I pathway for hydrolysis of tetrathionate and oxidation of thiosulfate in A. caldus are proposed according to expression patterns of sulfur oxidation genes and growth abilities of the wild type and the mutant in different substrates media. Conclusion An integrated sulfur oxidation model with various sulfur oxidation pathways of A. caldus is proposed and the features of this model are summarized. PMID:22984393

Synthesis and spectral characterization of mono- and binuclear copper(II) complexes derived from 2-benzoylpyridine-N4-methyl-3-thiosemicarbazone: Crystal structure of a novel sulfur bridged copper(II) box-dimer

NASA Astrophysics Data System (ADS)

Jayakumar, K.; Sithambaresan, M.; Aiswarya, N.; Kurup, M. R. Prathapachandra

2015-03-01

Mononuclear and binuclear copper(II) complexes of 2-benzoylpyridine-N4-methyl thiosemicarbazone (HL) were prepared and characterized by a variety of spectroscopic techniques. Structural evidence for the novel sulfur bridged copper(II) iodo binuclear complex is obtained by single crystal X-ray diffraction analysis. The complex [Cu2L2I2], a non-centrosymmetric box dimer, crystallizes in monoclinic C2/c space group and it was found to have distorted square pyramidal geometry (Addison parameter, τ = 0.238) with the square basal plane occupied by the thiosemicarbazone moiety and iodine atom whereas the sulfur atom from the other coordinated thiosemicarbazone moiety occupies the apical position. This is the first crystallographically studied system having non-centrosymmetrical entities bridged via thiolate S atoms with Cu(II)sbnd I bond. The tridentate thiosemicarbazone coordinates in mono deprotonated thionic tautomeric form in all complexes except in sulfato complex, [Cu(HL)(SO4)]·H2O (1) where it binds to the metal centre in neutral form. The magnetic moment values and the EPR spectral studies reflect the binuclearity of some of the complexes. The spin Hamiltonian and bonding parameters are calculated based on EPR studies. In all the complexes g|| > g⊥ > 2.0023 and the g values in frozen DMF are consistent with the dx2-y2 ground state. The thermal stabilities of some of the complexes were also determined.

Encapsulation of S/SWNT with PANI Web for Enhanced Rate and Cycle Performance in Lithium Sulfur Batteries

PubMed Central

Kim, Joo Hyun; Fu, Kun; Choi, Junghyun; Kil, Kichun; Kim, Jeonghyun; Han, Xiaogang; Hu, Liangbing; Paik, Ungyu

2015-01-01

Lithium-sulfur batteries show great potential to compete with lithium-ion batteries due to the fact that sulfur can deliver a high theoretical capacity of 1672 mAh/g and a high theoretical energy density of 2500 Wh/kg. But it has several problems to be solved in order to achieve high sulfur utilization with high Coulombic efficiency and long cycle life of Li-S batteries. These problems are mainly caused by the dissoluble polysulfide species, which are a series of complex reduced sulfur products, associating with shuttle effect between electrodes as well as side reactions on lithium metal anode. To alleviate these challenges, we developed a sulfur-carbon nanotube (S/SWNT) composite coated with polyaniline (PANI) polymer as polysulfide block to achieve high sulfur utilization, high Coulombic efficiency, and long cycle life. The PANI coated S/SWNT composite showed a superior specific capacity of 1011 mAh/g over 100 cycles and a good rate retention, demonstrating the synergic contribution of porous carbon and conducting polymer protection to address challenges underlying sulfur cathode. PMID:25752298

Influence of Sulfur on the Arsenic Phytoremediation Using Vallisneria natans (Lour.) Hara.

PubMed

Chen, Guoliang; Feng, Tao; Li, Zhixian; Chen, Zhang; Chen, Yuanqi; Wang, Haihua; Xiang, Yanci

2017-09-01

Influences of sulfur (S) on the accumulation and detoxification of arsenic (As) in Vallisneria natans (Lour.) Hara, an arsenic hyperaccumulating submerged aquatic plant, were investigated. At low sulfur levels (<20 mg/L), the thiols and As concentrations in the plant increased significantly with increasing sulfate nutrient supply. If sulfur levels were above 20 mg/L, the thiols and As concentrations in the plant did not increase further. There was a significant positive correlation between thiols and As in the plant. As(III) is the main form (>75%) present in the plant after exposure to As(V). Sulfur plays an important role in the arsenic translocation and detoxification, possibly through stimulating the synthesis of thiols and complexation of arsenite-phytochelatins. This suggests that addition of sulfur to the arsenic-contaminated water may provide a way to promote arsenic bioaccumulation in plants for phytoremediation of arsenic pollution.

New Proteins Involved in Sulfur Trafficking in the Cytoplasm of Allochromatium vinosum*

PubMed Central

Stockdreher, Yvonne; Sturm, Marga; Josten, Michaele; Sahl, Hans-Georg; Dobler, Nadine; Zigann, Renate; Dahl, Christiane

2014-01-01

The formation of periplasmic sulfur globules is an intermediate step during the oxidation of reduced sulfur compounds in various sulfur-oxidizing microorganisms. The mechanism of how this sulfur is activated and crosses the cytoplasmic membrane for further oxidation to sulfite by the dissimilatory reductase DsrAB is incompletely understood, but it has been well documented that the pathway involves sulfur trafficking mediated by sulfur-carrying proteins. So far sulfur transfer from DsrEFH to DsrC has been established. Persulfurated DsrC very probably serves as a direct substrate for DsrAB. Here, we introduce further important players in oxidative sulfur metabolism; the proteins Rhd_2599, TusA, and DsrE2 are strictly conserved in the Chromatiaceae, Chlorobiaceae, and Acidithiobacillaceae families of sulfur-oxidizing bacteria and are linked to genes encoding complexes involved in sulfur oxidation (Dsr or Hdr) in the latter two. Here we show via relative quantitative real-time PCR and microarray analysis an increase of mRNA levels under sulfur-oxidizing conditions for rhd_2599, tusA, and dsrE2 in Allochromatium vinosum. Transcriptomic patterns for the three genes match those of major genes for the sulfur-oxidizing machinery rather than those involved in biosynthesis of sulfur-containing biomolecules. TusA appears to be one of the major proteins in A. vinosum. A rhd_2599-tusA-dsrE2-deficient mutant strain, although not viable in liquid culture, was clearly sulfur oxidation negative upon growth on solid media containing sulfide. Rhd_2599, TusA, and DsrE2 bind sulfur atoms via conserved cysteine residues, and experimental evidence is provided for the transfer of sulfur between these proteins as well as to DsrEFH and DsrC. PMID:24648525

Influence of oxygenation on the reactivity of ruthenium-thiolato bonds in arene anticancer complexes: insights from XAS and DFT.

PubMed

Sriskandakumar, Thamayanthy; Petzold, Holm; Bruijnincx, Pieter C A; Habtemariam, Abraha; Sadler, Peter J; Kennepohl, Pierre

2009-09-23

Thiolate ligand oxygenation is believed to activate cytotoxic half-sandwich [(eta(6)-arene)Ru(en)(SR)](+) complexes toward DNA binding. We have made detailed comparisons of the nature of the Ru-S bond in the parent thiolato complexes and mono- (sulfenato) and bis- (sulfinato) oxygenated species including the influence of substituents on the sulfur and arene. Sulfur K-edge XAS indicates that S(3p) donation into the Ru(4d) manifold depends strongly on the oxidation state of the sulfur atom, whereas Ru K-edge data suggest little change at the metal center. DFT results are in agreement with the experimental data and allow a more detailed analysis of the electronic contributions to the Ru-S bond. Overall, the total ligand charge donation to the metal center remains essentially unchanged upon ligand oxygenation, but the origin of the donation differs markedly. In sulfenato complexes, the terminal oxo group makes a large contribution to charge donation and even small electronic changes in the thiolato complexes are amplified upon ligand oxygenation, an observation which carries direct implications for the biological activity of this family of complexes. Details of Ru-S bonding in the mono-oxygenated complexes suggest that these should be most susceptible to ligand exchange, yet only if protonation of the terminal oxo group can occur. The potential consequences of these results for biological activation are discussed.

The Reactive Sulfur Species Concept: 15 Years On.

PubMed

Giles, Gregory I; Nasim, Muhammad Jawad; Ali, Wesam; Jacob, Claus

2017-05-23

Fifteen years ago, in 2001, the concept of "Reactive Sulfur Species" or RSS was advocated as a working hypothesis. Since then various organic as well as inorganic RSS have attracted considerable interest and stimulated many new and often unexpected avenues in research and product development. During this time, it has become apparent that molecules with sulfur-containing functional groups are not just the passive "victims" of oxidative stress or simple conveyors of signals in cells, but can also be stressors in their own right, with pivotal roles in cellular function and homeostasis. Many "exotic" sulfur-based compounds, often of natural origin, have entered the fray in the context of nutrition, ageing, chemoprevention and therapy. In parallel, the field of inorganic RSS has come to the forefront of research, with short-lived yet metabolically important intermediates, such as various sulfur-nitrogen species and polysulfides (S x 2- ), playing important roles. Between 2003 and 2005 several breath-taking discoveries emerged characterising unusual sulfur redox states in biology, and since then the truly unique role of sulfur-dependent redox systems has become apparent. Following these discoveries, over the last decade a "hunt" and, more recently, mining for such modifications has begun-and still continues-often in conjunction with new, innovative and complex labelling and analytical methods to capture the (entire) sulfur "redoxome". A key distinction for RSS is that, unlike oxygen or nitrogen, sulfur not only forms a plethora of specific reactive species, but sulfur also targets itself, as sulfur containing molecules, i.e., peptides, proteins and enzymes, preferentially react with RSS. Not surprisingly, today this sulfur-centred redox signalling and control inside the living cell is a burning issue, which has moved on from the predominantly thiol/disulfide biochemistry of the past to a complex labyrinth of interacting signalling and control pathways which involve various sulfur oxidation states, sulfur species and reactions. RSS are omnipresent and, in some instances, are even considered as the true bearers of redox control, perhaps being more important than the Reactive Oxygen Species (ROS) or Reactive Nitrogen Species (RNS) which for decades have dominated the redox field. In other(s) words, in 2017, sulfur redox is "on the rise", and the idea of RSS resonates throughout the Life Sciences. Still, the RSS story isn't over yet. Many RSS are at the heart of "mistaken identities" which urgently require clarification and may even provide the foundations for further scientific revolutions in the years to come. In light of these developments, it is therefore the perfect time to revisit the original hypotheses, to select highlights in the field and to question and eventually update our concept of "Reactive Sulfur Species".

The Reactive Sulfur Species Concept: 15 Years On

PubMed Central

Giles, Gregory I.; Nasim, Muhammad Jawad; Ali, Wesam; Jacob, Claus

2017-01-01

Fifteen years ago, in 2001, the concept of “Reactive Sulfur Species” or RSS was advocated as a working hypothesis. Since then various organic as well as inorganic RSS have attracted considerable interest and stimulated many new and often unexpected avenues in research and product development. During this time, it has become apparent that molecules with sulfur-containing functional groups are not just the passive “victims” of oxidative stress or simple conveyors of signals in cells, but can also be stressors in their own right, with pivotal roles in cellular function and homeostasis. Many “exotic” sulfur-based compounds, often of natural origin, have entered the fray in the context of nutrition, ageing, chemoprevention and therapy. In parallel, the field of inorganic RSS has come to the forefront of research, with short-lived yet metabolically important intermediates, such as various sulfur-nitrogen species and polysulfides (Sx2−), playing important roles. Between 2003 and 2005 several breath-taking discoveries emerged characterising unusual sulfur redox states in biology, and since then the truly unique role of sulfur-dependent redox systems has become apparent. Following these discoveries, over the last decade a “hunt” and, more recently, mining for such modifications has begun—and still continues—often in conjunction with new, innovative and complex labelling and analytical methods to capture the (entire) sulfur “redoxome”. A key distinction for RSS is that, unlike oxygen or nitrogen, sulfur not only forms a plethora of specific reactive species, but sulfur also targets itself, as sulfur containing molecules, i.e., peptides, proteins and enzymes, preferentially react with RSS. Not surprisingly, today this sulfur-centred redox signalling and control inside the living cell is a burning issue, which has moved on from the predominantly thiol/disulfide biochemistry of the past to a complex labyrinth of interacting signalling and control pathways which involve various sulfur oxidation states, sulfur species and reactions. RSS are omnipresent and, in some instances, are even considered as the true bearers of redox control, perhaps being more important than the Reactive Oxygen Species (ROS) or Reactive Nitrogen Species (RNS) which for decades have dominated the redox field. In other(s) words, in 2017, sulfur redox is “on the rise”, and the idea of RSS resonates throughout the Life Sciences. Still, the RSS story isn’t over yet. Many RSS are at the heart of “mistaken identities” which urgently require clarification and may even provide the foundations for further scientific revolutions in the years to come. In light of these developments, it is therefore the perfect time to revisit the original hypotheses, to select highlights in the field and to question and eventually update our concept of “Reactive Sulfur Species”. PMID:28545257

Ruthenium chalcogenonitrosyl and bridged nitrido complexes containing chelating sulfur and oxygen ligands.

PubMed

Ng, Ho-Yuen; Cheung, Wai-Man; Kwan Huang, Enrique; Wong, Kang-Long; Sung, Herman H-Y; Williams, Ian D; Leung, Wa-Hung

2015-11-14

Ruthenium thio- and seleno-nitrosyl complexes containing chelating sulfur and oxygen ligands have been synthesised and their de-chalcogenation reactions have been studied. The reaction of mer-[Ru(N)Cl3(AsPh3)2] with elemental sulfur and selenium in tetrahydrofuran at reflux afforded the chalcogenonitrosyl complexes mer-[Ru(NX)Cl3(AsPh3)2] [X = S (1), Se (2)]. Treatment of 1 with KN(R2PS)2 afforded trans-[Ru(NS)Cl{N(R2PS)2}2] [R = Ph (3), Pr(i) (4), Bu(t) (5)]. Alternatively, the thionitrosyl complex 5 was obtained from [Bu(n)4N][Ru(N)Cl4] and KN(Bu(t)2PS)2, presumably via sulfur atom transfer from [N(Bu(t)2PS)2](-) to the nitride. Reactions of 1 and 2 with NaLOEt (LOEt(-) = [Co(η(5)-C5H5){P(O)(LOEt)2}3](-)) gave [Ru(NX)LOEtCl2] (X = S (8), Se (9)). Treatment of [Bu(n)4N][Ru(N)Cl4] with KN(R2PS)2 produced Ru(IV)-Ru(IV)μ-nitrido complexes [Ru2(μ-N){N(R2PS)2}4Cl] [R = Ph (6), Pr(i) (7)]. Reactions of 3 and 9 with PPh3 afforded 6 and [Ru(NPPh3)LOEtCl2], respectively. The desulfurisation of 5 with [Ni(cod)2] (cod = 1,5-cyclooctadiene) gave the mixed valance Ru(III)-Ru(IV)μ-nitrido complex [Ru2(μ-N){N(Bu(t)2PS)2}4] (10) that was oxidised by [Cp2Fe](PF6) to give the Ru(IV)-Ru(IV) complex [Ru2(μ-N){N(Bu(t)2PS)2}4](PF6) ([10]PF6). The crystal structures of 1, 2, 3, 7, 9 and 10 have been determined.

Sulfoquinovose in the biosphere: occurrence, metabolism and functions.

PubMed

Goddard-Borger, Ethan D; Williams, Spencer J

2017-02-20

The sulfonated carbohydrate sulfoquinovose (SQ) is produced in quantities estimated at some 10 billion tonnes annually and is thus a major participant in the global sulfur biocycle. SQ is produced by most photosynthetic organisms and incorporated into the sulfolipid sulfoquinovosyl diacylglycerol (SQDG), as well as within some archaea for incorporation into glycoprotein N-glycans. SQDG is found mainly within the thylakoid membranes of the chloroplast, where it appears to be important for membrane structure and function and for optimal activity of photosynthetic protein complexes. SQDG metabolism within the sulfur cycle involves complex biosynthetic and catabolic processes. SQDG biosynthesis is largely conserved within plants, algae and bacteria. On the other hand, two major sulfoglycolytic pathways have been discovered for SQDG degradation, the sulfo-Embden-Meyerhof-Parnas (sulfo-EMP) and sulfo-Entner-Doudoroff (sulfo-ED) pathways, which mirror the major steps in the glycolytic EMP and ED pathways. Sulfoglycolysis produces C3-sulfonates, which undergo biomineralization to inorganic sulfur species, completing the sulfur cycle. This review discusses the discovery and structural elucidation of SQDG and archaeal N-glycans, the occurrence, distribution, and speciation of SQDG, and metabolic pathways leading to the biosynthesis of SQDG and its catabolism through sulfoglycolytic and biomineralization pathways to inorganic sulfur. © 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.

Bacterial sulfur disproportionation constrains timing of neoproterozoic oxygenation

USGS Publications Warehouse

Kunzmann, Marcus; Bui, Thi Hao; Crockford, Peter W.; Halverson, Galen P.; Scott, Clinton T.; Lyons, Timothy W.; Wing, Boswell A.

2017-01-01

Various geochemical records suggest that atmospheric O2 increased in the Ediacaran (635–541 Ma), broadly coincident with the emergence and diversification of large animals and increasing marine ecosystem complexity. Furthermore, geochemical proxies indicate that seawater sulfate levels rose at this time too, which has been hypothesized to reflect increased sulfide oxidation in marine sediments caused by sediment mixing of the newly evolved macrofauna. However, the exact timing of oxygenation is not yet understood, and there are claims for significant oxygenation prior to the Ediacaran. Furthermore, recent evidence suggests that physical mixing of sediments did not become important until the late Silurian. Here we report a multiple sulfur isotope record from a ca. 835–630 Ma succession from Svalbard, further supported by data from Proterozoic strata in Canada, Australia, Russia, and the United States, in order to investigate the timing of oxygenation. We present isotopic evidence for onset of globally significant bacterial sulfur disproportionation and reoxidative sulfur cycling following the 635 Ma Marinoan glaciation. Widespread sulfide oxidation helps to explain the observed first-order increase in seawater sulfate concentration from the earliest Ediacaran to the Precambrian-Cambrian boundary by reducing the amount of sulfur buried as pyrite. Expansion of reoxidative sulfur cycling to a global scale also indicates increasing environmental O2 levels. Thus, our data suggest that increasing atmospheric O2 levels may have played a role in the emergence of the Ediacaran macrofauna and increasing marine ecosystem complexity.

Effect of pH and sulfur precursor concentration on electrochemically deposited CZTS thin films using glycine as the complexing agent

NASA Astrophysics Data System (ADS)

Paraye, Akanksha; Sani, Rabiya; Ramachandran, Manivannan; Selvam, Noyel Victoria

2018-03-01

Copper zinc tin sulfide (CZTS) a promising quaternary chalcogenide material was deposited using single step electrodeposition using glycine as the complexing agent. The deposition was studied at different sulfur concentrations and at different pH. The pH of the electrolyte was found to influence the stoichiometry of the deposits significantly. The deposits formed at pH 2.5 showed satisfactory stoichiometry. The thickness of the deposits was observed to decrease with increase in sulfur concentration and pH. The transmission electron spectroscopy analysis showed the formation of flower shaped core shell particles from the electrolyte that contained 80 mM sulfur precursor at pH 2.5. The band gap of the deposits was found to be in the range from 1.57 eV to 2.1 eV. X-ray diffraction analysis showed that the as synthesized particles were amorphous in nature, the crystallinity of which improved with annealing. The Mott Schottky analysis of the deposits in 0.1 M sodium perchlorate showed that the particles exhibited p-type conductivity.

Climate Change Impacts on Natural Sulfur Production: Ocean Acidification and Community Shifts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menzo, Zachary; Elliott, Scott; Hartin, Corinne

Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifying the possible effects climate change may have on dimethyl sulfide (DMS) emissions within the oceans. The investigation began with a review of the sulfur cycle in modern Earth system models. We then expanded the biogeochemical representation within Hector to include a natural ocean component while accounting for acidification and planktonic community shifts. The report presents results from both a latitudinal and a global perspective. This new approach highlights disparate outcomes which have been inadequately characterized via planetary averages in past publications. Our findings suggest that natural sulfur emissionsmore » (ESN) may exert a forcing up to 4 times that of the CO2 marine feedback, 0.62 and 0.15 Wm-2, respectively, and reverse the radiative forcing sign in low latitudes. Additionally, sensitivity tests were conducted to demonstrate the need for further examination of the DMS loop. Ultimately, the present work attempts to include dynamic ESN within reduced-complexity simulations of the sulfur cycle, illustrating its impact on the global radiative budget« less

Spectroscopic studies of two spectral variants of light-harvesting complex 2 (LH2) from the photosynthetic purple sulfur bacterium Allochromatium vinosum.

PubMed

Niedzwiedzki, Dariusz M; Bina, David; Picken, Nichola; Honkanen, Suvi; Blankenship, Robert E; Holten, Dewey; Cogdell, Richard J

2012-09-01

Two spectral forms of the peripheral light-harvesting complex (LH2) from the purple sulfur photosynthetic bacterium Allochromatium vinosum were purified and their photophysical properties characterized. The complexes contain bacteriochlorophyll a (BChl a) and multiple species of carotenoids. The composition of carotenoids depends on the light conditions applied during growth of the cultures. In addition, LH2 grown under high light has a noticeable split of the B800 absorption band. The influence of the change of carotenoid distribution as well as the spectral change of the excitonic absorption of the bacteriochlorophylls on the light-harvesting ability was studied using steady-state absorption, fluorescence and femtosecond time-resolved absorption at 77K. The results demonstrate that the change of the distribution of the carotenoids when cells were grown at low light adapts the absorptive properties of the complex to the light conditions and maintains maximum photon-capture performance. In addition, an explanation for the origin of the enigmatic split of the B800 absorption band is provided. This spectral splitting is also observed in LH2 complexes from other photosynthetic sulfur purple bacterial species. According to results obtained from transient absorption spectroscopy, the B800 band split originates from two spectral forms of the associated BChl a monomeric molecules bound within the same complex. Copyright © 2012 Elsevier B.V. All rights reserved.

Glutathione-complexed [2Fe-2S] clusters function in Fe-S cluster storage and trafficking.

PubMed

Fidai, Insiya; Wachnowsky, Christine; Cowan, J A

2016-10-01

Glutathione-coordinated [2Fe-2S] complex is a non-protein-bound [2Fe-2S] cluster that is capable of reconstituting the human iron-sulfur cluster scaffold protein IscU. This complex demonstrates physiologically relevant solution chemistry and is a viable substrate for iron-sulfur cluster transport by Atm1p exporter protein. Herein, we report on some of the possible functional and physiological roles for this novel [2Fe-2S](GS4) complex in iron-sulfur cluster biosynthesis and quantitatively characterize its role in the broader network of Fe-S cluster transfer reactions. UV-vis and circular dichroism spectroscopy have been used in kinetic studies to determine second-order rate constants for [2Fe-2S] cluster transfer from [2Fe-2S](GS4) complex to acceptor proteins, such as human IscU, Schizosaccharomyces pombe Isa1, human and yeast glutaredoxins (human Grx2 and Saccharomyces cerevisiae Grx3), and human ferredoxins. Second-order rate constants for cluster extraction from these holo proteins were also determined by varying the concentration of glutathione, and a likely common mechanism for cluster uptake was determined by kinetic analysis. The results indicate that the [2Fe-2S](GS4) complex is stable under physiological conditions, and demonstrates reversible cluster exchange with a wide range of Fe-S cluster proteins, thereby supporting a possible physiological role for such centers.

Synthesis and spectral characterization of mono- and binuclear copper(II) complexes derived from 2-benzoylpyridine-N⁴-methyl-3-thiosemicarbazone: crystal structure of a novel sulfur bridged copper(II) box-dimer.

PubMed

Jayakumar, K; Sithambaresan, M; Aiswarya, N; Kurup, M R Prathapachandra

2015-03-15

Mononuclear and binuclear copper(II) complexes of 2-benzoylpyridine-N(4)-methyl thiosemicarbazone (HL) were prepared and characterized by a variety of spectroscopic techniques. Structural evidence for the novel sulfur bridged copper(II) iodo binuclear complex is obtained by single crystal X-ray diffraction analysis. The complex [Cu2L2I2], a non-centrosymmetric box dimer, crystallizes in monoclinic C2/c space group and it was found to have distorted square pyramidal geometry (Addison parameter, τ=0.238) with the square basal plane occupied by the thiosemicarbazone moiety and iodine atom whereas the sulfur atom from the other coordinated thiosemicarbazone moiety occupies the apical position. This is the first crystallographically studied system having non-centrosymmetrical entities bridged via thiolate S atoms with Cu(II)I bond. The tridentate thiosemicarbazone coordinates in mono deprotonated thionic tautomeric form in all complexes except in sulfato complex, [Cu(HL)(SO4)]·H2O (1) where it binds to the metal centre in neutral form. The magnetic moment values and the EPR spectral studies reflect the binuclearity of some of the complexes. The spin Hamiltonian and bonding parameters are calculated based on EPR studies. In all the complexes g||>g⊥>2.0023 and the g values in frozen DMF are consistent with the d(x2-y2) ground state. The thermal stabilities of some of the complexes were also determined. Copyright © 2014 Elsevier B.V. All rights reserved.

Variable sulfur isotope composition of sulfides provide evidence for multiple sources of contamination in the Rustenburg Layered Suite, Bushveld Complex

NASA Astrophysics Data System (ADS)

Magalhães, Nivea; Penniston-Dorland, Sarah; Farquhar, James; Mathez, Edmond A.

2018-06-01

The Rustenburg Layered Suite (RLS) of the Bushveld Complex (BC) is famous for its platinum group element (PGE) ore, which is hosted in sulfides. The source of sulfur necessary to generate this type of mineralization is inferred to be the host rock of the intrusion. The RLS has a sulfur isotopic signature that indicates the presence of Archean surface-derived material (Δ33 S ≠ 0) in the magma. This signature, with an average value of Δ33 S = 0.112 ± 0.024 ‰, deviates from the expected Δ33 S value of the mantle of 0 ± 0.008 ‰. Previous work suggested that this signature is uniform throughout the RLS, which contrasts with radiogenic isotopes which vary throughout the igneous stratigraphy of the RLS. In this study, samples from key intervals within the igneous stratigraphy were analyzed, showing that Δ33 S values vary in the same stratigraphic levels as Sr and Nd isotopes. However, the variation is not consistent; in some levels there is a positive correlation and in others a negative correlation. This observation suggests that in some cases distinct magma pulses contained assimilated sulfur from different sources. Textural analysis shows no evidence for late addition of sulfur. These results also suggest that it is unlikely that large-scale assimilation and/or efficient mixing of host rock material in a single magma chamber occurred during emplacement. The data do not uniquely identify the source of sulfur in the different layers of the RLS, but the variation in sulfur isotope composition and its relationship to radiogenic isotope data calls for a reevaluation of the models for the formation and evolution of the RLS, which has the potential to impact the knowledge of how PGE deposits form.

Structural and Functional Analyses of the Proteins Involved in the Iron-Sulfur Cluster Biosynthesis

NASA Astrophysics Data System (ADS)

Wada, Kei

The iron-sulfur (Fe-S) clusters are ubiquitous prosthetic groups that are required to maintain such fundamental life processes as respiratory chain, photosynthesis and the regulation of gene expression. Assembly of intracellular Fe-S cluster requires the sophisticated biosynthetic systems called ISC and SUF machineries. To shed light on the molecular mechanism of Fe-S cluster assembly mediated by SUF machinery, several structures of the SUF components and their sub-complex were determined. The structural findings together with biochemical characterization of the core-complex (SufB-SufC-SufD complex) have led me to propose a working model for the cluster biosynthesis in the SUF machinery.

Heat conversion alternative petrochemical complexes efficiency

NASA Astrophysics Data System (ADS)

Mrakin, A. N.; Selivanov, A. A.; Morev, A. A.; Batrakov, P. A.; Kulbyakina, A. V.; Sotnikov, D. G.

2017-08-01

The paper presents the energy and economic efficiency calculation results of the petrochemical complexes based upon the sulfur oil shales processing by solid (ash) heat-carrier low-temperature carbonization plants by Galoter technology. The criterion for such enterprises fuel efficiency determining was developed on the base of the exergy methodology taking into account the recurrent publications consolidation. In this case, in supplying the consumers with paving bitumen, motor benzol, thiophene, toluene, 2-methylthiophene, xylene, gas sulfur, complex thermodynamic effectiveness was founded to amount to 53 %, and if ash residue realization is possible then it was founded to be to 70 %. The project economic attractiveness determining studies depending on the feedstock cost, its delivery way and investments amount changing were conducted.

Assessment of the stoichiometry and efficiency of CO2 fixation coupled to reduced sulfur oxidation

PubMed Central

Klatt, Judith M.; Polerecky, Lubos

2015-01-01

Chemolithoautotrophic sulfur oxidizing bacteria (SOB) couple the oxidation of reduced sulfur compounds to the production of biomass. Their role in the cycling of carbon, sulfur, oxygen, and nitrogen is, however, difficult to quantify due to the complexity of sulfur oxidation pathways. We describe a generic theoretical framework for linking the stoichiometry and energy conservation efficiency of autotrophic sulfur oxidation while accounting for the partitioning of the reduced sulfur pool between the energy generating and energy conserving steps as well as between the main possible products (sulfate vs. zero-valent sulfur). Using this framework, we show that the energy conservation efficiency varies widely among SOB with no apparent relationship to their phylogeny. Aerobic SOB equipped with reverse dissimilatory sulfite reductase tend to have higher efficiency than those relying on the complete Sox pathway, whereas for anaerobic SOB the presence of membrane-bound, as opposed to periplasmic, nitrate reductase systems appears to be linked to higher efficiency. We employ the framework to also show how limited rate measurements can be used to estimate the primary productivity of SOB without the knowledge of the sulfate-to-zero-valent-sulfur production ratio. Finally, we discuss how the framework can help researchers gain new insights into the activity of SOB and their niches. PMID:26052315

Inverse Vulcanization of Sulfur using Natural Dienes as Sustainable Materials for Lithium-Sulfur Batteries.

PubMed

Gomez, Iñaki; Leonet, Olatz; Blazquez, J Alberto; Mecerreyes, David

2016-12-20

Lithium-sulfur batteries are among the most promising next-generation battery systems due to the high capacity of sulfur as cathodic material. Beyond its interesting intrinsic properties, sulfur possesses a very low conductivity and complex electrochemistry, which involves the high solubility of the lithium sulfides in the electrolyte. These two characteristics are at the core of a series of limitations of its performance as active cathode material, which leads to batteries with low cyclability. Recently, inverse vulcanized sulfur was shown to retain capacity far better than elemental sulfur, leading to batteries with excellent cyclability. Nevertheless, the diene co-monomers used so far in the inverse vulcanization process are man-made molecules. Herein, a tentative work on exploring inverse vulcanization using two naturally available monomers, diallyl sulfide and myrcene, is presented. The inverse vulcanization of sulfur was successfully completed, and the resulting polymers were characterized by FTIR, NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Afterwards these polymers were tested as cathodic materials in lithium-sulfur cells. The sulfur-natural dienes materials exhibited high capacity at different C rates and high lifetime over 200 cycles with very high capacity retention at a moderate C rate of C/5. Altogether, these materials made from inexpensive and abundant chemicals are an excellent option as sustainable materials for electrochemical energy storage. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Materials for Lithium Sulfur Batteries-Ten Critical Questions.

PubMed

Borchardt, Lars; Oschatz, Martin; Kaskel, Stefan

2016-05-23

Lithium-sulfur batteries are among the most promising electrochemical energy storage devices of the near future. Especially the low price and abundant availability of sulfur as the cathode material and the high theoretical capacity in comparison to state-of-the art lithium-ion technologies are attractive features. Despite significant research achievements that have been made over the last years, fundamental (electro-) chemical questions still remain unanswered. This review addresses ten crucial questions associated with lithium-sulfur batteries and critically evaluates current research with respect to them. The sulfur-carbon composite cathode is a particular focus, but its complex interplay with other hardware components in the cell, such as the electrolyte and the anode, necessitates a critical discussion of other cell components. Modern in situ characterisation methods are ideally suited to illuminate the role of each component. This article does not pretend to summarise all recently published data, but instead is a critical overview over lithium-sulfur batteries based on recent research findings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Mammalian Proteins MMS19, MIP18, and ANT2 Are Involved in Cytoplasmic Iron-Sulfur Cluster Protein Assembly*

PubMed Central

van Wietmarschen, Niek; Moradian, Annie; Morin, Gregg B.; Lansdorp, Peter M.; Uringa, Evert-Jan

2012-01-01

Iron-sulfur (Fe-S) clusters are essential cofactors of proteins with a wide range of biological functions. A dedicated cytosolic Fe-S cluster assembly (CIA) system is required to assemble Fe-S clusters into cytosolic and nuclear proteins. Here, we show that the mammalian nucleotide excision repair protein homolog MMS19 can simultaneously bind probable cytosolic iron-sulfur protein assembly protein CIAO1 and Fe-S proteins, confirming that MMS19 is a central protein of the CIA machinery that brings Fe-S cluster donor proteins and the receiving apoproteins into proximity. In addition, we show that mitotic spindle-associated MMXD complex subunit MIP18 also interacts with both CIAO1 and Fe-S proteins. Specifically, it binds the Fe-S cluster coordinating regions in Fe-S proteins. Furthermore, we show that ADP/ATP translocase 2 (ANT2) interacts with Fe-S apoproteins and MMS19 in the CIA complex but not with the individual proteins. Together, these results elucidate the composition and interactions within the late CIA complex. PMID:23150669

Exploring the core level shift origin of sulfur and thiolates on Pd(111) surfaces.

PubMed

Salvarezza, Roberto Carlos; Carro, Pilar

2015-10-07

Thiol molecules on planar metal surfaces are widely used for building sensing and electronic devices and also as capping agents to protect and to control the size and shape of nanoparticles. In the case of Pd the thiol molecules exhibit a complex behavior because C-S bond scission is possible, resulting in a significant amount of co-adsorbed S. Therefore identification of these species on Pd is a key point for many applications, a task that is usually achieved by XPS. Here we show, from DFT calculations, that the core level shift (CLS) of the S 2p binding energy (BE) of thiol and sulfur on different thiol-Pd(111) surface models strongly depends on the adsorbed or subsurface state of sulfur atoms. Our results reflect the complexity of S 2p BE behavior and contribute to understanding and reanalyzing the experimental data of thiolated Pd surfaces.

Thiosulfate Transfer Mediated by DsrE/TusA Homologs from Acidothermophilic Sulfur-oxidizing Archaeon Metallosphaera cuprina*

PubMed Central

Liu, Li-Jun; Stockdreher, Yvonne; Koch, Tobias; Sun, Shu-Tao; Fan, Zheng; Josten, Michaele; Sahl, Hans-Georg; Wang, Qian; Luo, Yuan-Ming; Liu, Shuang-Jiang; Dahl, Christiane; Jiang, Cheng-Ying

2014-01-01

Conserved clusters of genes encoding DsrE and TusA homologs occur in many archaeal and bacterial sulfur oxidizers. TusA has a well documented function as a sulfurtransferase in tRNA modification and molybdenum cofactor biosynthesis in Escherichia coli, and DsrE is an active site subunit of the DsrEFH complex that is essential for sulfur trafficking in the phototrophic sulfur-oxidizing Allochromatium vinosum. In the acidothermophilic sulfur (S0)- and tetrathionate (S4O62−)-oxidizing Metallosphaera cuprina Ar-4, a dsrE3A-dsrE2B-tusA arrangement is situated immediately between genes encoding dihydrolipoamide dehydrogenase and a heterodisulfide reductase-like complex. In this study, the biochemical features and sulfur transferring abilities of the DsrE2B, DsrE3A, and TusA proteins were investigated. DsrE3A and TusA proved to react with tetrathionate but not with NaSH, glutathione persulfide, polysulfide, thiosulfate, or sulfite. The products were identified as protein-Cys-S-thiosulfonates. DsrE3A was also able to cleave the thiosulfate group from TusA-Cys18-S-thiosulfonate. DsrE2B did not react with any of the sulfur compounds tested. DsrE3A and TusA interacted physically with each other and formed a heterocomplex. The cysteine residue (Cys18) of TusA is crucial for this interaction. The single cysteine mutants DsrE3A-C93S and DsrE3A-C101S retained the ability to transfer the thiosulfonate group to TusA. TusA-C18S neither reacted with tetrathionate nor was it loaded with thiosulfate with DsrE3A-Cys-S-thiosulfonate as the donor. The transfer of thiosulfate, mediated by a DsrE-like protein and TusA, is unprecedented not only in M. cuprina but also in other sulfur-oxidizing prokaryotes. The results of this study provide new knowledge on oxidative microbial sulfur metabolism. PMID:25122768

In Situ NMR Observation of the Temporal Speciation of Lithium Sulfur Batteries during Electrochemical Cycling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hao; Sa, Niya; He, Meinan

The understanding of the reaction mechanism and temporal speciation of the lithium sulfur batteries is challenged by complex polysulfide disproportionation chemistry coupled with the precipitation and dissolution of species. In this report, for the first time, we present a comprehensive method to investigate lithium sulfur electrochemistry using in situ 7Li NMR spectroscopy, a technique that is capable of quantitatively capturing the evolution of the soluble and precipitated lithium (poly)sulfides during electrochemical cycling. Furthermore, through deconvolution and quantification, every lithium-bearing species was closely tracked and four-step soluble lithium polysulfide-mediated lithium sulfur electrochemistry was demonstrated in never before seen detail. Significant irreversiblemore » accumulation of Li 2S is observed on the Li metal anode after four cycles because of sulfur shuttling. We present the application of the method in order to study electrolyte/additive development and lithium protection research can be readily envisaged.« less

In Situ NMR Observation of the Temporal Speciation of Lithium Sulfur Batteries during Electrochemical Cycling

DOE PAGES

Wang, Hao; Sa, Niya; He, Meinan; ...

2017-03-03

The understanding of the reaction mechanism and temporal speciation of the lithium sulfur batteries is challenged by complex polysulfide disproportionation chemistry coupled with the precipitation and dissolution of species. In this report, for the first time, we present a comprehensive method to investigate lithium sulfur electrochemistry using in situ 7Li NMR spectroscopy, a technique that is capable of quantitatively capturing the evolution of the soluble and precipitated lithium (poly)sulfides during electrochemical cycling. Furthermore, through deconvolution and quantification, every lithium-bearing species was closely tracked and four-step soluble lithium polysulfide-mediated lithium sulfur electrochemistry was demonstrated in never before seen detail. Significant irreversiblemore » accumulation of Li 2S is observed on the Li metal anode after four cycles because of sulfur shuttling. We present the application of the method in order to study electrolyte/additive development and lithium protection research can be readily envisaged.« less

Crystalline sulfur dioxide: Crystal field splittings, absolute band intensities and complex refractive indices derived from infrared spectra

NASA Technical Reports Server (NTRS)

Khanna, R. K.; Zhao, Guizhi

1986-01-01

The infrared absorption spectra of thin crystalline films of sulfur dioxide at 90 K are reported in the 2700 to 450/cm region. The observed multiplicity of the spectral features in the regions of fundamentals is attributed to factor group splittings of the modes in a biaxial crystal lattice and the naturally present minor S-34, S-36, and O-18 isotopic species. Complex refractive indices determined by an iterative Kramers-Kronig analysis of the extinction data, and absolute band strengths derived from them, are also reported in this region.

Molecular orbital study of some eight-coordinate sulfur chelate complexes of molybdenum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perkins, P.G.; Schultz, F.A.

1983-03-30

A number of molybdenum complexes involving the formal oxidation states Mo(IV) and Mo(V) have been studied by a self-consistent-field molecular orbital technique. All the complexes were of dodecahedral geometry and had eight sulfurs chelated to the central metal atom. In all, a series of five tetrakis complexes was studied, including the ligands dithiocarbamate (dtc), thioxanthate (txn), 1,1-dicyano-2,2-ethylenedithiolate (i-mnt), 1-cyano-1-carbethoxy-2,2-ethylenedithiolate (ced), and 1,1-dicarbethoxy-2,2-ethylenedithiolate (ded). The 4d orbitals were included on molybdenum, and the empty 3d levels on all sulfur atoms. The results show that the highest occupied molecular orbital in each case has over 90% metal d/sub xy/ character. Further, themore » energy of this orbital is linearly related to the reversible half-wave potentials for Mo(IV) ..-->.. Mo(V) and Mo(V) ..-->.. Mo(VI) oxidations of the complexes. A further irreversible oxidation observed experimentally also is closely related to the calculated energy levels. Relationships between the calculated results and Mo 3d/sub 5///sub 2/ X-ray photoelectron binding energies, EPR parameters, and charge-transfer absorption energies are discussed. Electrochemical and spectroscopic properties of these MoS/sub 8/ complexes can be understood in terms of a manifold of orbital energies that retain approximately constant spacings between one another and that move up or down in absolute energy in response to the charge donated or withdrawn by the ligands.« less

Facts and fiction about sulfur metabolism in relation to plant-pathogen interactions.

PubMed

Bloem, E; Haneklaus, S; Salac, I; Wickenhäuser, P; Schnug, E

2007-09-01

Sulfur deficiency developed into a widespread nutrient disorder in the 1980s because of the drastic decrease of SO(2) emissions in western Europe after Clean Air Acts came into force. It was observed that not only the yield and quality of agricultural crops were negatively affected by sulfur deficiency but also their health status. Since the mid 1990s the physiological background of this latter phenomenon in the sulfur metabolism has been studied by different researchers. From 2001 until 2006, field trials with different varieties of oilseed rape were conducted in Germany, and also from 2001 until 2003 in Scotland, to investigate the underlying mechanisms of sulfur-induced resistance and to develop fertiliser strategies which increase the health status of crops and minimise the requirement for chemical fungicides. A comprehensive disease assessment was conducted and a range of different sulfur-containing metabolites and enzymes were analysed in relation to sulfur nutrition and fungal diseases. H2S emissions from field-grown crops under different sulfur nutritional status were studied for the first time and a positive relationship was observed. Besides S fertilisation, fungal infection increased H2S emissions, too. The studies deliver new insight into the complex of sulfur-induced resistance but many questions still remain open. This contribution will show different possible strategies to solve some of the open questions.

Impact of Seasonal Hypoxia on Activity and Community Structure of Chemolithoautotrophic Bacteria in a Coastal Sediment

PubMed Central

Lipsewers, Yvonne A.; Vasquez-Cardenas, Diana; Seitaj, Dorina; Schauer, Regina; Hidalgo-Martinez, Silvia; Meysman, Filip J. R.

2017-01-01

ABSTRACT Seasonal hypoxia in coastal systems drastically changes the availability of electron acceptors in bottom water, which alters the sedimentary reoxidation of reduced compounds. However, the effect of seasonal hypoxia on the chemolithoautotrophic community that catalyzes these reoxidation reactions is rarely studied. Here, we examine the changes in activity and structure of the sedimentary chemolithoautotrophic bacterial community of a seasonally hypoxic saline basin under oxic (spring) and hypoxic (summer) conditions. Combined 16S rRNA gene amplicon sequencing and analysis of phospholipid-derived fatty acids indicated a major temporal shift in community structure. Aerobic sulfur-oxidizing Gammaproteobacteria (Thiotrichales) and Epsilonproteobacteria (Campylobacterales) were prevalent during spring, whereas Deltaproteobacteria (Desulfobacterales) related to sulfate-reducing bacteria prevailed during summer hypoxia. Chemolithoautotrophy rates in the surface sediment were three times higher in spring than in summer. The depth distribution of chemolithoautotrophy was linked to the distinct sulfur oxidation mechanisms identified through microsensor profiling, i.e., canonical sulfur oxidation, electrogenic sulfur oxidation by cable bacteria, and sulfide oxidation coupled to nitrate reduction by Beggiatoaceae. The metabolic diversity of the sulfur-oxidizing bacterial community suggests a complex niche partitioning within the sediment, probably driven by the availability of reduced sulfur compounds (H2S, S0, and S2O32−) and electron acceptors (O2 and NO3−) regulated by seasonal hypoxia. IMPORTANCE Chemolithoautotrophic microbes in the seafloor are dependent on electron acceptors, like oxygen and nitrate, that diffuse from the overlying water. Seasonal hypoxia, however, drastically changes the availability of these electron acceptors in the bottom water; hence, one expects a strong impact of seasonal hypoxia on sedimentary chemolithoautotrophy. A multidisciplinary investigation of the sediments in a seasonally hypoxic coastal basin confirms this hypothesis. Our data show that bacterial community structure and chemolithoautotrophic activity varied with the seasonal depletion of oxygen. Unexpectedly, the dark carbon fixation was also dependent on the dominant microbial pathway of sulfur oxidation occurring in the sediment (i.e., canonical sulfur oxidation, electrogenic sulfur oxidation by cable bacteria, and sulfide oxidation coupled to nitrate reduction by Beggiatoaceae). These results suggest that a complex niche partitioning within the sulfur-oxidizing bacterial community additionally affects the chemolithoautotrophic community of seasonally hypoxic sediments. PMID:28314724

Impact of Seasonal Hypoxia on Activity and Community Structure of Chemolithoautotrophic Bacteria in a Coastal Sediment.

PubMed

Lipsewers, Yvonne A; Vasquez-Cardenas, Diana; Seitaj, Dorina; Schauer, Regina; Hidalgo-Martinez, Silvia; Sinninghe Damsté, Jaap S; Meysman, Filip J R; Villanueva, Laura; Boschker, Henricus T S

2017-05-15

Seasonal hypoxia in coastal systems drastically changes the availability of electron acceptors in bottom water, which alters the sedimentary reoxidation of reduced compounds. However, the effect of seasonal hypoxia on the chemolithoautotrophic community that catalyzes these reoxidation reactions is rarely studied. Here, we examine the changes in activity and structure of the sedimentary chemolithoautotrophic bacterial community of a seasonally hypoxic saline basin under oxic (spring) and hypoxic (summer) conditions. Combined 16S rRNA gene amplicon sequencing and analysis of phospholipid-derived fatty acids indicated a major temporal shift in community structure. Aerobic sulfur-oxidizing Gammaproteobacteria ( Thiotrichales ) and Epsilonproteobacteria ( Campylobacterales ) were prevalent during spring, whereas Deltaproteobacteria ( Desulfobacterales ) related to sulfate-reducing bacteria prevailed during summer hypoxia. Chemolithoautotrophy rates in the surface sediment were three times higher in spring than in summer. The depth distribution of chemolithoautotrophy was linked to the distinct sulfur oxidation mechanisms identified through microsensor profiling, i.e., canonical sulfur oxidation, electrogenic sulfur oxidation by cable bacteria, and sulfide oxidation coupled to nitrate reduction by Beggiatoaceae The metabolic diversity of the sulfur-oxidizing bacterial community suggests a complex niche partitioning within the sediment, probably driven by the availability of reduced sulfur compounds (H 2 S, S 0 , and S 2 O 3 2- ) and electron acceptors (O 2 and NO 3 - ) regulated by seasonal hypoxia. IMPORTANCE Chemolithoautotrophic microbes in the seafloor are dependent on electron acceptors, like oxygen and nitrate, that diffuse from the overlying water. Seasonal hypoxia, however, drastically changes the availability of these electron acceptors in the bottom water; hence, one expects a strong impact of seasonal hypoxia on sedimentary chemolithoautotrophy. A multidisciplinary investigation of the sediments in a seasonally hypoxic coastal basin confirms this hypothesis. Our data show that bacterial community structure and chemolithoautotrophic activity varied with the seasonal depletion of oxygen. Unexpectedly, the dark carbon fixation was also dependent on the dominant microbial pathway of sulfur oxidation occurring in the sediment (i.e., canonical sulfur oxidation, electrogenic sulfur oxidation by cable bacteria, and sulfide oxidation coupled to nitrate reduction by Beggiatoaceae ). These results suggest that a complex niche partitioning within the sulfur-oxidizing bacterial community additionally affects the chemolithoautotrophic community of seasonally hypoxic sediments. Copyright © 2017 American Society for Microbiology.

The coordination of sulfur in synthetic and biogenic Mg calcites: The red coral case

NASA Astrophysics Data System (ADS)

Perrin, J.; Rivard, C.; Vielzeuf, D.; Laporte, D.; Fonquernie, C.; Ricolleau, A.; Cotte, M.; Floquet, N.

2017-01-01

Sulfur has been recognized in biogenic calcites for a long time. However, its structural position is matter of debate. For some authors, sulfur is a marker of the organic matrix while it is part of the calcite structure itself for others. To better understand the place of sulfur in calcite, sulfated magnesian calcites (S-MgCalcite) have been synthetized at high pressure and temperature and studied by μ-XANES spectroscopy. S-MgCalcite XANES spectra show two different types of sulfur: sulfate (SO42-) as a predominant species and a small contribution of sulfite (SO32-), both substituting for carbonate ions in the calcite structure. To address the question of the position of sulfur in biogenic calcites, the oxidation states of sulfur in the skeleton and organic tissues of Corallium rubrum have been investigated by micro X-ray fluorescence (μ-XRF) and sulfur K-edge micro X-ray absorption near edge structure (μ-XANES) spectroscopy at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) on beamline ID21. In the skeleton, sulfur is mainly present as oxidized sulfur SO42- (+VI), plus a weak sulfite contribution. XANES spectra indicate that sulfur is inorganically incorporated as sulfur structurally substituted to carbonate ions (SSS). Although an organic matrix is present in the red coral skeleton, reduced organic sulfur could not be detected by μ-XANES spectroscopy in the skeleton probably due to low organic/inorganic sulfur ratio. In the organic tissues surrounding the skeleton, several sulfur oxidation states have been detected including disulfide (S-S), thioether (R-S-CH3), sulfoxide (SO2), sulfonate (SO2O-) and sulfate (SO42-). The unexpected occurrence of inorganic sulfate within the organic tissues suggests the presence of pre-organized organic/inorganic complexes in the circulatory system of the red coral, precursors to biomineralization ahead of the growth front.

Microbial community structure and sulfur biogeochemistry in mildly-acidic sulfidic geothermal springs in Yellowstone National Park.

PubMed

Macur, R E; Jay, Z J; Taylor, W P; Kozubal, M A; Kocar, B D; Inskeep, W P

2013-01-01

Geothermal and hydrothermal waters often contain high concentrations of dissolved sulfide, which reacts with oxygen (abiotically or biotically) to yield elemental sulfur and other sulfur species that may support microbial metabolism. The primary goal of this study was to elucidate predominant biogeochemical processes important in sulfur biogeochemistry by identifying predominant sulfur species and describing microbial community structure within high-temperature, hypoxic, sulfur sediments ranging in pH from 4.2 to 6.1. Detailed analysis of aqueous species and solid phases present in hypoxic sulfur sediments revealed unique habitats containing high concentrations of dissolved sulfide, thiosulfate, and arsenite, as well as rhombohedral and spherical elemental sulfur and/or sulfide phases such as orpiment, stibnite, and pyrite, as well as alunite and quartz. Results from 16S rRNA gene sequencing show that these sediments are dominated by Crenarchaeota of the orders Desulfurococcales and Thermoproteales. Numerous cultivated representatives of these lineages, as well as the Thermoproteales strain (WP30) isolated in this study, require complex sources of carbon and respire elemental sulfur. We describe a new archaeal isolate (strain WP30) belonging to the order Thermoproteales (phylum Crenarchaeota, 98% identity to Pyrobaculum/Thermoproteus spp. 16S rRNA genes), which was obtained from sulfur sediments using in situ geochemical composition to design cultivation medium. This isolate produces sulfide during growth, which further promotes the formation of sulfide phases including orpiment, stibnite, or pyrite, depending on solution conditions. Geochemical, molecular, and physiological data were integrated to suggest primary factors controlling microbial community structure and function in high-temperature sulfur sediments. © 2012 Blackwell Publishing Ltd.

Photochemical Formation of Aerosol in Planetary Atmospheres: Photon and Water Mediated Chemistry of SO_2

NASA Astrophysics Data System (ADS)

Kroll, Jay A.; Donaldson, D. J.; Vaida, Veronica

2016-06-01

Sulfur compounds have been observed in a number of planetary atmospheres throughout our solar system. Our current understanding of sulfur chemistry explains much of what we observe in Earth's atmosphere. However, several discrepancies between modeling and observations of the Venusian atmosphere show there are still problems in our fundamental understanding of sulfur chemistry. This is of particular concern due to the important role sulfur compounds play in the formation of aerosols, which have a direct impact on planetary climates, including Earth's. We investigate the role of water complexes in the hydration of sulfur oxides and dehydration of sulfur acids and will present spectroscopic studies to document such effects. I will present recent work investigating mixtures of SO_2 and water that generate large quantities of aerosol when irradiated with solar UV light, even in the absence of traditional OH chemistry. I will discuss a proposed mechanism for the formation of sulfurous acid (H_2SO_3) and present recent experimental work that supports this proposed mechanism. Additionally, the implications that photon-induced hydration of SO_2 has for aerosol formation in the atmosphere of earth as well as other planetary atmospheres will be discussed.

Sulfur mustard induces the formation of keratin aggregates in human epidermal keratinocytes.

PubMed

Dillman, James F; McGary, Kriston L; Schlager, John J

2003-12-01

The vesicant sulfur mustard is an alkylating agent that has the capacity to cross-link biological molecules. We are interested in identifying specific proteins that are altered upon sulfur mustard exposure. Keratins are particularly important for the structural integrity of skin, and several genetically inherited blistering diseases have been linked to mutations in keratin 5 and keratin 14. We examined whether sulfur mustard exposure alters keratin biochemistry in cultured human epidermal keratinocytes. Western blotting with specific monoclonal antibodies revealed the formation of stable high-molecular-weight "aggregates" containing keratin 14 and/or keratin 5. These aggregates begin to form within 15 min after sulfur mustard exposure. These aggregates display a complex gel electrophoresis pattern between approximately 100 and approximately 200 kDa. Purification and analysis of these aggregates by one- and two-dimensional gel electrophoresis and mass spectrometry confirmed the presence of keratin 14 and keratin 5 and indicate that at least some of the aggregates are composed of keratin 14-keratin 14, keratin 14-keratin 5, or keratin 5-keratin 5 dimers. These studies demonstrate that sulfur mustard induces keratin aggregation in keratinocytes and support further investigation into the role of keratin aggregation in sulfur mustard-induced vesication.

Advanced X-ray Spectroscopic Methods for Studying Iron-Sulfur-Containing Proteins and Model Complexes.

PubMed

DeBeer, Serena

2018-01-01

In this chapter, a brief overview of X-ray spectroscopic methods that may be utilized to obtain insight into the geometric and electronic structure of iron-sulfur proteins is provided. These methods include conventional methods, such as metal and ligand K-edge X-ray absorption, as well as more advanced methods including nonresonant and resonant X-ray emission. In each section, the basic information content of the spectra is highlighted and important experimental considerations are discussed. Throughout the chapter, recent applications to iron-sulfur-containing models and proteins are highlighted. © 2018 Elsevier Inc. All rights reserved.

Rapid and high-precision measurement of sulfur isotope and sulfur concentration in sediment pore water by multi-collector inductively coupled plasma mass spectrometry.

PubMed

Bian, Xiao-Peng; Yang, Tao; Lin, An-Jun; Jiang, Shao-Yong

2015-01-01

We have developed a technique for the rapid, precise and accurate determination of sulfur isotopes (δ(34)S) by MC-ICP-MS applicable to a range of sulfur-bearing solutions of different sulfur content. The 10 ppm Alfa-S solution (ammonium sulfate solution, working standard of the lab of the authors) was used to bracket other Alfa-S solutions of different concentrations and the measured δ(34)SV-CDT values of Alfa-S solutions deviate from the reference value to varying degrees (concentration effect). The stability of concentration effect has been verified and a correction curve has been constructed based on Alfa-S solutions to correct measured δ(34)SV-CDT values. The curve has been applied to AS solutions (dissolved ammonium sulfate from the lab of the authors) and pore water samples successfully, validating the reliability of our analytical method. This method also enables us to measure the sulfur concentration simultaneously when analyzing the sulfur isotope composition. There is a strong linear correlation (R(2)>0.999) between the sulfur concentrations and the intensity ratios of samples and the standard. We have constructed a regression curve based on Alfa-S solutions and this curve has been successfully used to determine sulfur concentrations of AS solutions and pore water samples. The analytical technique presented here enable rapid, precise and accurate S isotope measurement for a wide range of sulfur-bearing solutions - in particular for pore water samples with complex matrix and varying sulfur concentrations. Also, simultaneous measurement of sulfur concentrations is available. Copyright © 2014 Elsevier B.V. All rights reserved.

Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery: THE SUB-COMPLEX FORMED BY THE IRON DONOR, Yfh1 PROTEIN, AND THE SCAFFOLD, Isu1 PROTEIN.

PubMed

Ranatunga, Wasantha; Gakh, Oleksandr; Galeano, Belinda K; Smith, Douglas Y; Söderberg, Christopher A G; Al-Karadaghi, Salam; Thompson, James R; Isaya, Grazia

2016-05-06

The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24 Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery

PubMed Central

Ranatunga, Wasantha; Gakh, Oleksandr; Galeano, Belinda K.; Smith, Douglas Y.; Söderberg, Christopher A. G.; Al-Karadaghi, Salam; Thompson, James R.; Isaya, Grazia

2016-01-01

The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly. PMID:26941001

Mechanistic modeling of sulfur-deprived photosynthesis and hydrogen production in suspensions of Chlamydomonas reinhardtii

PubMed Central

Williams, C R; Bees, MA

2014-01-01

The ability of unicellular green algal species such as Chlamydomonas reinhardtii to produce hydrogen gas via iron-hydrogenase is well known. However, the oxygen-sensitive hydrogenase is closely linked to the photosynthetic chain in such a way that hydrogen and oxygen production need to be separated temporally for sustained photo-production. Under illumination, sulfur-deprivation has been shown to accommodate the production of hydrogen gas by partially-deactivating O2 evolution activity, leading to anaerobiosis in a sealed culture. As these facets are coupled, and the system complex, mathematical approaches potentially are of significant value since they may reveal improved or even optimal schemes for maximizing hydrogen production. Here, a mechanistic model of the system is constructed from consideration of the essential pathways and processes. The role of sulfur in photosynthesis (via PSII) and the storage and catabolism of endogenous substrate, and thus growth and decay of culture density, are explicitly modeled in order to describe and explore the complex interactions that lead to H2 production during sulfur-deprivation. As far as possible, functional forms and parameter values are determined or estimated from experimental data. The model is compared with published experimental studies and, encouragingly, qualitative agreement for trends in hydrogen yield and initiation time are found. It is then employed to probe optimal external sulfur and illumination conditions for hydrogen production, which are found to differ depending on whether a maximum yield of gas or initial production rate is required. The model constitutes a powerful theoretical tool for investigating novel sulfur cycling regimes that may ultimately be used to improve the commercial viability of hydrogen gas production from microorganisms. Biotechnol. Bioeng. 2014;111: 320–335. © 2013 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. PMID:24026984

Mechanistic modeling of sulfur-deprived photosynthesis and hydrogen production in suspensions of Chlamydomonas reinhardtii.

PubMed

Williams, C R; Bees, M A

2014-02-01

The ability of unicellular green algal species such as Chlamydomonas reinhardtii to produce hydrogen gas via iron-hydrogenase is well known. However, the oxygen-sensitive hydrogenase is closely linked to the photosynthetic chain in such a way that hydrogen and oxygen production need to be separated temporally for sustained photo-production. Under illumination, sulfur-deprivation has been shown to accommodate the production of hydrogen gas by partially-deactivating O2 evolution activity, leading to anaerobiosis in a sealed culture. As these facets are coupled, and the system complex, mathematical approaches potentially are of significant value since they may reveal improved or even optimal schemes for maximizing hydrogen production. Here, a mechanistic model of the system is constructed from consideration of the essential pathways and processes. The role of sulfur in photosynthesis (via PSII) and the storage and catabolism of endogenous substrate, and thus growth and decay of culture density, are explicitly modeled in order to describe and explore the complex interactions that lead to H2 production during sulfur-deprivation. As far as possible, functional forms and parameter values are determined or estimated from experimental data. The model is compared with published experimental studies and, encouragingly, qualitative agreement for trends in hydrogen yield and initiation time are found. It is then employed to probe optimal external sulfur and illumination conditions for hydrogen production, which are found to differ depending on whether a maximum yield of gas or initial production rate is required. The model constitutes a powerful theoretical tool for investigating novel sulfur cycling regimes that may ultimately be used to improve the commercial viability of hydrogen gas production from microorganisms. © 2013 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

Electrochemical hydrogenation of a homogeneous nickel complex to form a surface adsorbed hydrogen-evolving species

DOE PAGES

Martin, Daniel J.; McCarthy, Brian D.; Donley, Carrie L.; ...

2014-12-04

Here, a Ni(ii) complex with nitrogen and sulfur donor ligands degrades electrochemically in the presence of acid in acetonitrile to form an electrode adsorbed film that catalytically evolves hydrogen.

Hydration of AN Acid Anhydride: the Water Complex of Acetic Sulfuric Anhydride

NASA Astrophysics Data System (ADS)

Smith, CJ; Huff, Anna; Mackenzie, Becca; Leopold, Ken

2017-06-01

The water complex of acetic sulfuric anhydride (ASA, CH_{3}COOSO_{2}OH) has been observed by pulsed nozzle Fourier transform microwave spectroscopy. ASA is formed in situ in the supersonic jet via the reaction of SO_{3} and acetic acid and subsequently forms a complex with water during the expansion. Spectra of the parent and fully deuterated form, as well as those of the species derived from CH_{3}^{13}COOH, have been observed. The fitted internal rotation barrier of the methyl group is 219.599(21), \\wn indicating the complexation with water lowers the internal rotation barrier of the methyl group by 9% relative to that of free ASA. The observed species is one of several isomers identified theoretically in which the water inserts into the intramolecular hydrogen bond of the ASA. Aspects of the intermolecular potential energy surface are discussed.

Synthesis and structures of metal chalcogenide precursors

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

1990-01-01

The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

Identification of sulfur fumed Pinelliae Rhizoma using an electronic nose

PubMed Central

Zhou, Xia; Wan, Jun; Chu, Liang; Liu, Wengang; Jing, Yafeng; Wu, Chunjie

2014-01-01

Background: Pinelliae Rhizoma is a commonly used Chinese herb which will change brown during the natural drying process. However, sulfur fumed Pinelliae Rhizoma will get a better appearance than naturally dried one. Sulfur fumed Pinelliae Rhizoma is potentially toxical due to sulfur dioxide and sulfites formed during the fuming procedures. The odor components in sulfur fumed Pinelliae Rhizoma is complex. At present, there is no analytical method available to determine sulfur fumed Pinelliae Rhizoma simply and rapidly. To ensure medication safety, it is highly desirable to have an effective and simple method to identify sulfur fumed Pinelliae Rhizoma. Materials and Methods: This paper presents a novel approach using an electronic nose based on metal oxide sensors to identify whether Pinelliae Rhizoma was fumed with sulfur, and to predict the fuming degree of Pinelliae Rhizoma. Multivariate statistical methods such as principal components analysis (PCA), discriminant factorial analysis (DFA) and partial least squares (PLS) were used for data analyzing and identification. The use of the electronic nose to discriminate between different fuming degrees Pinelliae Rhizoma and naturally dried Pinelliae Rhizoma was demonstrated. Results: The electronic nose was also successfully applied to identify unknown samples including sulfur fumed samples and naturally dried samples, high recognition value was obtained. Quantitative analysis of fuming degree of Pinelliae Rhizoma was also demonstrated. The method developed is simple and fast, which provides a new quality control method of Chinese herbs from the aspect of odor. Conclusion: It has shown that this electronic nose based metal oxide sensor is sensitive to sulfur and sulfides. We suggest that it can serve as a supportive method to detect residual sulfur and sulfides. PMID:24914293

A Complex Between Biotin Synthase and The Iron-Sulfur Cluster Assembly Chaperone HscA That Enhances In Vivo Cluster Assembly†

PubMed Central

Reyda, Michael R.; Fugate, Corey J.; Jarrett, Joseph T.

2009-01-01

Biotin synthase (BioB) is an iron-sulfur enzyme that catalyzes the last step in biotin biosynthesis, the insertion of sulfur between the C6 and C9 carbons of dethiobiotin to complete the thiophane ring of biotin. Recent in vitro experiments suggest that the sulfur is derived from a [2Fe-2S]2+ cluster within BioB, and that the remnants of this cluster dissociate from the enzyme following each turnover. In order for BioB to catalyze multiple rounds of biotin synthesis, the [2Fe-2S]2+ cluster in BioB must be reassembled, a process that could be carried out in vivo by the ISC or SUF iron-sulfur cluster assembly systems. The bacterial ISC system includes HscA, an Hsp70-class molecular chaperone, whose yeast homolog has been shown to play an important but nonessential role in assembly of mitochondrial FeS clusters in S. cerevesiae. In the present work we show that in E. coli, HscA significantly improves the efficiency of the in vivo assembly of the [2Fe-2S]2+ cluster on BioB under conditions of low to moderate iron. In vitro, we show that HscA binds with increased affinity to BioB missing one or both FeS clusters, with a maximum of two HscA molecules per BioB dimer. BioB binds to HscA in an ATP/ADP-independent manner and a high affinity complex is also formed with a truncated form of HscA that lacks the nucleotide binding domain. Further, the BioB:HscA complex binds the FeS cluster scaffold protein IscU in a noncompetitive manner, generating a complex that contains all three proteins. We propose that HscA plays a role in facilitating the transfer of FeS clusters from IscU into the appropriate target apoproteins such as biotin synthase, perhaps by enhancing or prolonging the requisite protein:protein interaction. PMID:19821612

Biological iron-sulfur storage in a thioferrate-protein nanoparticle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaccaro, Brian J.; Clarkson, Sonya M.; Holden, James F.

Iron–sulfur clusters are ubiquitous in biology and function in electron transfer and catalysis. We assembled them from iron and cysteine sulfur on protein scaffolds. Iron is typically stored as iron oxyhydroxide, ferrihydrite, encapsulated in 12 nm shells of ferritin, which buffers cellular iron availability. We have characterized IssA, a protein that stores iron and sulfur as thioferrate, an inorganic anionic polymer previously unknown in biology. IssA forms nanoparticles reaching 300 nm in diameter and is the largest natural metalloprotein complex known. It is a member of a widely distributed protein family that includes nitrogenase maturation factors, NifB and NifX. IssAmore » nanoparticles are visible by electron microscopy as electron-dense bodies in the cytoplasm. Purified nanoparticles appear to be generated from 20 nm units containing B 6,400 Fe atoms and B 170 IssA monomers. In support of roles in both iron–sulfur storage and cluster biosynthesis, IssA reconstitutes the [4Fe-4S] cluster in ferredoxin in vitro.« less

Biological iron-sulfur storage in a thioferrate-protein nanoparticle

DOE PAGES

Vaccaro, Brian J.; Clarkson, Sonya M.; Holden, James F.; ...

2017-07-20

Iron–sulfur clusters are ubiquitous in biology and function in electron transfer and catalysis. We assembled them from iron and cysteine sulfur on protein scaffolds. Iron is typically stored as iron oxyhydroxide, ferrihydrite, encapsulated in 12 nm shells of ferritin, which buffers cellular iron availability. We have characterized IssA, a protein that stores iron and sulfur as thioferrate, an inorganic anionic polymer previously unknown in biology. IssA forms nanoparticles reaching 300 nm in diameter and is the largest natural metalloprotein complex known. It is a member of a widely distributed protein family that includes nitrogenase maturation factors, NifB and NifX. IssAmore » nanoparticles are visible by electron microscopy as electron-dense bodies in the cytoplasm. Purified nanoparticles appear to be generated from 20 nm units containing B 6,400 Fe atoms and B 170 IssA monomers. In support of roles in both iron–sulfur storage and cluster biosynthesis, IssA reconstitutes the [4Fe-4S] cluster in ferredoxin in vitro.« less

Archaea S-layer nanotube from a "black smoker" in complex with cyclo-octasulfur (S8 ) rings.

PubMed

McDougall, Matthew; Francisco, Olga; Harder-Viddal, Candice; Roshko, Roy; Meier, Markus; Stetefeld, Jörg

2017-12-01

Elemental sulfur exists primarily as an S80 ring and serves as terminal electron acceptor for a variety of sulfur-fermenting bacteria. Hyperthermophilic archaea from black smoker vents are an exciting research tool to advance our knowledge of sulfur respiration under extreme conditions. Here, we use a hybrid method approach to demonstrate that the proteinaceous cavities of the S-layer nanotube of the hyperthermophilic archaeon Staphylothermus marinus act as a storage reservoir for cyclo-octasulfur S8. Fully atomistic molecular dynamics (MD) simulations were performed and the method of multiconfigurational thermodynamic integration was employed to compute the absolute free energy for transferring a ring of elemental sulfur S8 from an aqueous bath into the largest hydrophobic cavity of a fragment of archaeal tetrabrachion. Comparisons with earlier MD studies of the free energy of hydration as a function of water occupancy in the same cavity of archaeal tetrabrachion show that the sulfur ring is energetically favored over water. © 2017 Wiley Periodicals, Inc.

Interfacial Mechanism in Lithium-Sulfur Batteries: How Salts Mediate the Structure Evolution and Dynamics.

PubMed

Lang, Shuang-Yan; Xiao, Rui-Juan; Gu, Lin; Guo, Yu-Guo; Wen, Rui; Wan, Li-Jun

2018-06-08

Lithium-sulfur batteries possess favorable potential for energy-storage applications due to their high specific capacity and the low cost of sulfur. Intensive understanding of the interfacial mechanism, especially the polysulfide formation and transformation under complex electrochemical environment, is crucial for the build-up of advanced batteries. Here we report the direct visualization of interfacial evolution and dynamic transformation of the sulfides mediated by the lithium salts via real-time atomic force microscopy monitoring inside a working battery. The observations indicate that the lithium salts influence the structures and processes of sulfide deposition/decomposition during discharge/charge. Moreover, the distinct ion interaction and diffusion in electrolytes manipulate the interfacial reactions determining the kinetics of the sulfide transformation. Our findings provide deep insights into surface dynamics of lithium-sulfur reactions revealing the salt-mediated mechanisms at nanoscale, which contribute to the profound understanding of the interfacial processes for the optimized design of lithium-sulfur batteries.

Performance study of magnesium-sulfur battery using a graphene based sulfur composite cathode electrode and a non-nucleophilic Mg electrolyte.

PubMed

Vinayan, B P; Zhao-Karger, Zhirong; Diemant, Thomas; Chakravadhanula, Venkata Sai Kiran; Schwarzburger, Nele I; Cambaz, Musa Ali; Behm, R Jürgen; Kübel, Christian; Fichtner, Maximilian

2016-02-14

Here we report for the first time the development of a Mg rechargeable battery using a graphene-sulfur nanocomposite as the cathode, a Mg-carbon composite as the anode and a non-nucleophilic Mg based complex in tetraglyme solvent as the electrolyte. The graphene-sulfur nanocomposites are prepared through a new pathway by the combination of thermal and chemical precipitation methods. The Mg/S cell delivers a higher reversible capacity (448 mA h g(-1)), a longer cyclability (236 mA h g(-1) at the end of the 50(th) cycle) and a better rate capability than previously described cells. The dissolution of Mg polysulfides to the anode side was studied by X-ray photoelectron spectroscopy. The use of a graphene-sulfur composite cathode electrode, with the properties of a high surface area, a porous morphology, a very good electronic conductivity and the presence of oxygen functional groups, along with a non-nucleophilic Mg electrolyte gives an improved battery performance.

Structure of human Fe-S assembly subcomplex reveals unexpected cysteine desulfurase architecture and acyl-ACP-ISD11 interactions.

PubMed

Cory, Seth A; Van Vranken, Jonathan G; Brignole, Edward J; Patra, Shachin; Winge, Dennis R; Drennan, Catherine L; Rutter, Jared; Barondeau, David P

2017-07-03

In eukaryotes, sulfur is mobilized for incorporation into multiple biosynthetic pathways by a cysteine desulfurase complex that consists of a catalytic subunit (NFS1), LYR protein (ISD11), and acyl carrier protein (ACP). This NFS1-ISD11-ACP (SDA) complex forms the core of the iron-sulfur (Fe-S) assembly complex and associates with assembly proteins ISCU2, frataxin (FXN), and ferredoxin to synthesize Fe-S clusters. Here we present crystallographic and electron microscopic structures of the SDA complex coupled to enzyme kinetic and cell-based studies to provide structure-function properties of a mitochondrial cysteine desulfurase. Unlike prokaryotic cysteine desulfurases, the SDA structure adopts an unexpected architecture in which a pair of ISD11 subunits form the dimeric core of the SDA complex, which clarifies the critical role of ISD11 in eukaryotic assemblies. The different quaternary structure results in an incompletely formed substrate channel and solvent-exposed pyridoxal 5'-phosphate cofactor and provides a rationale for the allosteric activator function of FXN in eukaryotic systems. The structure also reveals the 4'-phosphopantetheine-conjugated acyl-group of ACP occupies the hydrophobic core of ISD11, explaining the basis of ACP stabilization. The unexpected architecture for the SDA complex provides a framework for understanding interactions with acceptor proteins for sulfur-containing biosynthetic pathways, elucidating mechanistic details of eukaryotic Fe-S cluster biosynthesis, and clarifying how defects in Fe-S cluster assembly lead to diseases such as Friedreich's ataxia. Moreover, our results support a lock-and-key model in which LYR proteins associate with acyl-ACP as a mechanism for fatty acid biosynthesis to coordinate the expression, Fe-S cofactor maturation, and activity of the respiratory complexes.

A close-up look at Io from Galileo's near-infrared mapping spectrometer

USGS Publications Warehouse

Lopes-Gautier, R.; Doute, S.; Smythe, W.D.; Kamp, L.W.; Carlson, R.W.; Davies, A.G.; Leader, F.E.; McEwen, A.S.; Geissler, P.E.; Kieffer, S.W.; Keszthelyi, L.; Barbinis, E.; Mehlman, R.; Segura, M.; Shirley, J.; Soderblom, L.A.

2000-01-01

Infrared spectral images of Jupiter's volcanic moon Io, acquired during the October and November 1999 and February 2000 flybys of the Galileo spacecraft, were used to study the thermal structure and sulfur dioxide distribution of active volcanoes. Loki Patera, the solar system's most powerful known volcano, exhibits large expanses of dark, cooling lava on its caldera floor. Prometheus, the site of long-lived plume activity, has two major areas of thermal emission, which support ideas of plume migration. Sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought, indicating the presence of other sulfur compounds.

The role of iron-sulfides on cycling of organic carbon in the St Lawrence River system: Evidence of sulfur-promoted carbon sequestration?

NASA Astrophysics Data System (ADS)

Balind, K.; Barber, A.; Gélinas, Y.

2017-12-01

The biogeochemical cycle of sulfur is intimately linked with that of carbon, as well as with that of iron through the formation of iron-sulfur complexes. Iron-sulfide minerals such as mackinawite (FeS) and greigite (Fe3S4) form below the oxic/anoxic redox boundary in marine and lacustrine sediments and soils. Reactive iron species, abundant in surface sediments, can undergo reductive dissolution leading to the formation of soluble Fe(II) which can then precipitate in the form of iron sulfur species. While sedimentary iron-oxides have been thoroughly explored in terms of their ability to sorb and sequester organic carbon (OC) (Lalonde et al.; 2012), the role of FeS in the long-term preservation of OC remains undefined. In this study, we present depth profiles for carbon, iron, and sulfur in the aqueous-phase, along with data from sequential extractions of sulfur speciation in the solid-phase collected from sediment cores from the St Lawrence River and estuarine system, demonstrating the transition from fresh to saltwater sediments. Additionally, we present synthetic iron sulfur sorption experiments using both model and natural organic molecules in order to assess the importance of FeS in sedimentary carbon storage.

Hemilability of the 1,2-Bis(dimethylphosphino)ethane (dmpe) Ligand in Cp*Mo(NO)(κ2-dmpe).

PubMed

Holmes, Aaron S; Patrick, Brian O; Levesque, Taleah M; Legzdins, Peter

2017-09-18

Reaction of Cp*Mo(NO)Cl 2 with 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) in THF at ambient temperature forms [Cp*Mo(NO)(Cl)(κ 2 -dmpe)]Cl (1), which is isolable as an analytically pure yellow powder in 65% yield. Further addition of 2 equiv of Cp 2 Co to 1 in CH 2 Cl 2 affords dark red Cp*Mo(NO)(κ 2 -dmpe) (2), which was isolated in 36% yield by recrystallization from Et 2 O at -30 °C. Reaction of a benzene solution of 2 with an equimolar amount of elemental sulfur results in the immediate production of dark blue (μ-S)[Cp*Mo(NO)(κ 1 -dmpeS)] 2 (3), which is a rare example of a bimetallic transition-metal complex bridged by only a single sulfur atom and involving Mo═S═Mo bonding. In contrast, reaction of 2 with an excess of sulfur in benzene results in the formation of Cp*Mo(NO)(η 2 -S 2 )(κ 1 -dmpeS) (4). Complex 4 can also be formed by the addition of elemental sulfur to 3, thereby indicating that 3 is a precursor to 4. Cp*Mo(NO)(κ 2 -dmpe) (2) also undergoes interesting transformations when treated with organic bromides. For instance, reaction of 2 with 5 equiv benzyl bromide in THF produces the bimetallic complex (μ-dmpe)[Cp*Mo(NO)Br 2 ] 2 (5) and bibenzyl after 4 d at 70 °C probably via radical intermediates. In contrast to its reaction with benzyl bromide, complex 2 forms [Mo(NO)Br 2 (κ 2 -dmpe)] 2 (6), olefin, alkane, and Cp*H when treated with 5 equiv of 1-bromopropane or 1-bromooctane in THF at 70 °C for 72 h. Interestingly, complex 2 does not display any reactivity with bromobenzene or 1-bromoadamantane even after being heated for several days at 70 °C. All new complexes were characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them were established by single-crystal X-ray crystallographic analyses.

Importance of Extracellular Polymeric Substances from Thiobacillus ferrooxidans for Bioleaching

PubMed Central

Gehrke, Tilman; Telegdi, Judit; Thierry, Dominique; Sand, Wolfgang

1998-01-01

Leaching bacteria such as Thiobacillus ferrooxidans attach to pyrite or sulfur by means of extracellular polymeric substances (EPS) (lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrochemical interaction with the negatively charged pyrite surface. EPS from sulfur cells possess increased hydrophobic properties and do not attach to pyrite, indicating adaptability to the substrate or substratum. PMID:9647862

Kinetic and theoretical studies on the protonation of [Ni(2-SC6H4N){PhP(CH2CH2PPh2)2}]+: nitrogen versus sulfur as the protonation site.

PubMed

Petrou, Athinoula L; Koutselos, Andreas D; Wahab, Hilal S; Clegg, William; Harrington, Ross W; Henderson, Richard A

2011-02-07

The complexes [Ni(4-Spy)(triphos)]BPh(4) and [Ni(2-Spy)(triphos)]BPh(4) {triphos = PhP(CH(2)CH(2)PPh(2))(2), 4-Spy = 4-pyridinethiolate, 2-Spy = 2-pyridinethiolate} have been prepared and characterized both spectroscopically and using X-ray crystallography. In both complexes the triphos is a tridentate ligand. However, [Ni(4-Spy)(triphos)](+) comprises a 4-coordinate, square-planar nickel with the 4-Spy ligand bound to the nickel through the sulfur while [Ni(2-Spy)(triphos)](+) contains a 5-coordinate, trigonal-bipyramidal nickel with a bidentate 2-Spy ligand bound to the nickel through both sulfur and nitrogen. The kinetics of the reactions of [Ni(4-Spy)(triphos)](+) and [Ni(2-Spy)(triphos)](+) with lutH(+) (lut = 2,6-dimethylpyridine) in MeCN have been studied using stopped-flow spectrophotometry, and the two complexes show very different reactivities. The reaction of [Ni(4-Spy)(triphos)](+) with lutH(+) is complete within the deadtime of the stopped-flow apparatus (2 ms) and corresponds to protonation of the nitrogen. However, upon mixing [Ni(2-Spy)(triphos)](+) and lutH(+) a reaction is observed (on the seconds time scale) to produce an equilibrium mixture. The mechanistic interpretation of the rate law has been aided by the application of MSINDO semiempirical and ADF calculations. The kinetics and calculations are consistent with the reaction between [Ni(2-Spy)(triphos)](+) and lutH(+) involving initial protonation of the sulfur followed by dissociation of the nitrogen and subsequent transfer of the proton from sulfur to nitrogen. The factors affecting the position of protonation and the coupling of the coordination state of the 2-pyridinethiolate ligand to the site of protonation are discussed.

Comparison of environmental and isolate Sulfobacillus genomes reveals diverse carbon, sulfur, nitrogen, and hydrogen metabolisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Justice, Nicholas B.; Norman, Anders; Brown, Christopher T.

Bacteria of the genus Sulfobacillus are found worldwide as members of microbial communities that accelerate sulfide mineral dissolution in acid mine drainage environments (AMD), acid-rock drainage environments (ARD), as well as in industrial bioleaching operations. Despite their frequent identification in these environments, their role in biogeochemical cycling is poorly understood. Here we report draft genomes of five species of the Sulfobacillus genus (AMDSBA1-5) reconstructed by cultivation-independent sequencing of biofilms sampled from the Richmond Mine (Iron Mountain, CA). Three of these species (AMDSBA2, AMDSBA3, and AMDSBA4) have no cultured representatives while AMDSBA1 is a strain of S. benefaciens, and AMDSBA5 amore » strain of S. thermosulfidooxidans. We analyzed the diversity of energy conservation and central carbon metabolisms for these genomes and previously published Sulfobacillus genomes. Pathways of sulfur oxidation vary considerably across the genus, including the number and type of subunits of putative heterodisulfide reductase complexes likely involved in sulfur oxidation. The number and type of nickel-iron hydrogenase proteins varied across the genus, as does the presence of different central carbon pathways. Only the AMDSBA3 genome encodes a dissimilatory nitrate reducatase and only the AMDSBA5 and S. thermosulfidooxidans genomes encode assimilatory nitrate reductases. Lastly, within the genus, AMDSBA4 is unusual in that its electron transport chain includes a cytochrome bc type complex, a unique cytochrome c oxidase, and two distinct succinate dehydrogenase complexes. Overall, the results significantly expand our understanding of carbon, sulfur, nitrogen, and hydrogen metabolism within the Sulfobacillus genus.« less

Comparison of environmental and isolate Sulfobacillus genomes reveals diverse carbon, sulfur, nitrogen, and hydrogen metabolisms

DOE PAGES

Justice, Nicholas B.; Norman, Anders; Brown, Christopher T.; ...

2014-12-15

Bacteria of the genus Sulfobacillus are found worldwide as members of microbial communities that accelerate sulfide mineral dissolution in acid mine drainage environments (AMD), acid-rock drainage environments (ARD), as well as in industrial bioleaching operations. Despite their frequent identification in these environments, their role in biogeochemical cycling is poorly understood. Here we report draft genomes of five species of the Sulfobacillus genus (AMDSBA1-5) reconstructed by cultivation-independent sequencing of biofilms sampled from the Richmond Mine (Iron Mountain, CA). Three of these species (AMDSBA2, AMDSBA3, and AMDSBA4) have no cultured representatives while AMDSBA1 is a strain of S. benefaciens, and AMDSBA5 amore » strain of S. thermosulfidooxidans. We analyzed the diversity of energy conservation and central carbon metabolisms for these genomes and previously published Sulfobacillus genomes. Pathways of sulfur oxidation vary considerably across the genus, including the number and type of subunits of putative heterodisulfide reductase complexes likely involved in sulfur oxidation. The number and type of nickel-iron hydrogenase proteins varied across the genus, as does the presence of different central carbon pathways. Only the AMDSBA3 genome encodes a dissimilatory nitrate reducatase and only the AMDSBA5 and S. thermosulfidooxidans genomes encode assimilatory nitrate reductases. Lastly, within the genus, AMDSBA4 is unusual in that its electron transport chain includes a cytochrome bc type complex, a unique cytochrome c oxidase, and two distinct succinate dehydrogenase complexes. Overall, the results significantly expand our understanding of carbon, sulfur, nitrogen, and hydrogen metabolism within the Sulfobacillus genus.« less

Human frataxin activates Fe-S cluster biosynthesis by facilitating sulfur transfer chemistry.

PubMed

Bridwell-Rabb, Jennifer; Fox, Nicholas G; Tsai, Chi-Lin; Winn, Andrew M; Barondeau, David P

2014-08-05

Iron-sulfur clusters are ubiquitous protein cofactors with critical cellular functions. The mitochondrial Fe-S assembly complex, which consists of the cysteine desulfurase NFS1 and its accessory protein (ISD11), the Fe-S assembly protein (ISCU2), and frataxin (FXN), converts substrates l-cysteine, ferrous iron, and electrons into Fe-S clusters. The physiological function of FXN has received a tremendous amount of attention since the discovery that its loss is directly linked to the neurodegenerative disease Friedreich's ataxia. Previous in vitro results revealed a role for human FXN in activating the cysteine desulfurase and Fe-S cluster biosynthesis activities of the Fe-S assembly complex. Here we present radiolabeling experiments that indicate FXN accelerates the accumulation of sulfur on ISCU2 and that the resulting persulfide species is viable in the subsequent synthesis of Fe-S clusters. Additional mutagenesis, enzyme kinetic, UV-visible, and circular dichroism spectroscopic studies suggest conserved ISCU2 residue C104 is critical for FXN activation, whereas C35, C61, and C104 are all essential for Fe-S cluster formation on the assembly complex. These results cannot be fully explained by the hypothesis that FXN functions as an iron donor for Fe-S cluster biosynthesis, and further support an allosteric regulator role for FXN. Together, these results lead to an activation model in which FXN accelerates persulfide formation on NFS1 and favors a helix-to-coil interconversion on ISCU2 that facilitates the transfer of sulfur from NFS1 to ISCU2 as an initial step in Fe-S cluster biosynthesis.

Human Frataxin Activates Fe–S Cluster Biosynthesis by Facilitating Sulfur Transfer Chemistry

PubMed Central

2015-01-01

Iron–sulfur clusters are ubiquitous protein cofactors with critical cellular functions. The mitochondrial Fe–S assembly complex, which consists of the cysteine desulfurase NFS1 and its accessory protein (ISD11), the Fe–S assembly protein (ISCU2), and frataxin (FXN), converts substrates l-cysteine, ferrous iron, and electrons into Fe–S clusters. The physiological function of FXN has received a tremendous amount of attention since the discovery that its loss is directly linked to the neurodegenerative disease Friedreich’s ataxia. Previous in vitro results revealed a role for human FXN in activating the cysteine desulfurase and Fe–S cluster biosynthesis activities of the Fe–S assembly complex. Here we present radiolabeling experiments that indicate FXN accelerates the accumulation of sulfur on ISCU2 and that the resulting persulfide species is viable in the subsequent synthesis of Fe–S clusters. Additional mutagenesis, enzyme kinetic, UV–visible, and circular dichroism spectroscopic studies suggest conserved ISCU2 residue C104 is critical for FXN activation, whereas C35, C61, and C104 are all essential for Fe–S cluster formation on the assembly complex. These results cannot be fully explained by the hypothesis that FXN functions as an iron donor for Fe–S cluster biosynthesis, and further support an allosteric regulator role for FXN. Together, these results lead to an activation model in which FXN accelerates persulfide formation on NFS1 and favors a helix-to-coil interconversion on ISCU2 that facilitates the transfer of sulfur from NFS1 to ISCU2 as an initial step in Fe–S cluster biosynthesis. PMID:24971490

Conformation and recognition of DNA modified by a new antitumor dinuclear PtII complex resistant to decomposition by sulfur nucleophiles

PubMed Central

Zerzankova, Lenka; Suchankova, Tereza; Vrana, Oldrich; Farrell, Nicholas P.; Brabec, Viktor; Kasparkova, Jana

2011-01-01

Reported herein is a detailed biochemical and molecular biophysics study of the molecular mechanism of action of antitumor dinuclear PtII complex [{PtCl(DACH)}2-μ-Y]4+ [DACH = 1,2-diaminocyclohexane, Y =H2N(CH2)6NH2(CH2)2NH2(CH2)6NH2] (complex 1). This new, long-chain bifunctional dinuclear PtII complex is resistant to metabolic decomposition by sulfur-containing nucleophiles. The results show that DNA adducts of 1 can largely escape repair and yet inhibit very effectively transcription so that they should persist longer than those of conventional cisplatin. Hence, they could trigger a number of downstream cellular effects different from those triggered in cancer cells by DNA adducts of cisplatin. This might lead to the therapeutic effects that could radically improve chemotherapy by platinum complexes. In addition, the findings of the present work make new insights into mechanisms associated with antitumor effects of dinuclear/trinuclear PtII complexes possible. PMID:19682435

A Role for Iron-Sulfur Clusters in the Regulation of Transcription Factor Yap5-dependent High Iron Transcriptional Responses in Yeast*

PubMed Central

Li, Liangtao; Miao, Ren; Bertram, Sophie; Jia, Xuan; Ward, Diane M.; Kaplan, Jerry

2012-01-01

Yeast respond to increased cytosolic iron by activating the transcription factor Yap5 increasing transcription of CCC1, which encodes a vacuolar iron importer. Using a genetic screen to identify genes involved in Yap5 iron sensing, we discovered that a mutation in SSQ1, which encodes a mitochondrial chaperone involved in iron-sulfur cluster synthesis, prevented expression of Yap5 target genes. We demonstrated that mutation or reduced expression of other genes involved in mitochondrial iron-sulfur cluster synthesis (YFH1, ISU1) prevented induction of the Yap5 response. We took advantage of the iron-dependent catalytic activity of Pseudaminobacter salicylatoxidans gentisate 1,2-dioxygenase expressed in yeast to measure changes in cytosolic iron. We determined that reductions in iron-sulfur cluster synthesis did not affect the activity of cytosolic gentisate 1,2-dioxygenase. We show that loss of activity of the cytosolic iron-sulfur cluster assembly complex proteins or deletion of cytosolic glutaredoxins did not reduce expression of Yap5 target genes. These results suggest that the high iron transcriptional response, as well as the low iron transcriptional response, senses iron-sulfur clusters. PMID:22915593

DFT and TD-DFT study of the adsorption and detection of sulfur mustard chemical warfare agent by the C24, C12Si12, Al12N12, Al12P12, Be12O12, B12N12 and Mg12O12 nanocages

NASA Astrophysics Data System (ADS)

Jouypazadeh, Hamidreza; Farrokhpour, Hossein

2018-07-01

In the present research, the interaction of sulfur mustard, a chemical warfare agent, with the surface of C24, C12Si12, Al12N12, Al12P12, Be12O12, B12N12 and Mg12O12 nanocages was studied using the dispersion corrected density function theory (DFT-D3) method. The calculated adsorption energies of sulfur mustard on the surface of the nanocages showed that the Al12N12, C12Si12 and Mg12O12 are useful for the adsorption of the sulfur mustard. The quantum theory atom in molecule (QTAIM) analysis was used to study the nature of interactions of sulfur mustard with the surface of the selected nanocages. Based on QTAIM analysis, the majority of interactions of sulfur and chlorine atoms of sulfur mustard with the surface of the considered nanocages are covalent and quasi covalent whereas the interactions of hydrogen atoms of sulfur mustard with the surface of the nanocages are generally non-covalent. The charge transfer between sulfur mustard and the nanocages as well as chemical quantum descriptors of complexes were calculated using natural bond orbital (NBO) method. The most electron charge transfers from the sulfur mustard to B12N12 nanocage where the S atom of sulfur mustard donor a chemical bond to B atom of the nanocage. The ability of the considered nanocages for detecting sulfur mustard was studied using time-dependent density function theory (TD-DFT) and density of state (DOS) diagram. It is found that the C24, Al12P12, Be12O12 and B12N12 nanocages are useful sensors for this chemical agent.

Effect of amino acids on the interaction between cobalamin(II) and dehydroascorbic acid

NASA Astrophysics Data System (ADS)

Dereven'kov, I. A.; Thi, Thu Thuy Bui; Salnikov, D. S.; Makarov, S. V.

2016-03-01

The kinetics of the reaction between one-electron-reduced cobalamin (cobalamin(II), Cb(II)) and the two-electron-oxidized form of vitamin C (dehydroascorbic acid, DHA) with amino acids in an acidic medium is studied by conventional UV-Vis spectroscopy. It is shown that the oxidation of Cbl(II) by dehydroascorbic acid proceeds only in the presence of sulfur-containing amino acids (cysteine, acetylcysteine). A proposed reaction mechanism includes the step of amino acid coordination on the Co(II)-center through the sulfur atom, along with that of the interaction between this complex and DHA molecules, which results in the formation of ascorbyl radical and the corresponding Co(III) thiolate complex.

Syntheses, spectroscopic characterization, thermal study, molecular modeling, and biological evaluation of novel Schiff's base benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) with Ni(II), and Cu(II) metal complexes

NASA Astrophysics Data System (ADS)

Chandra, Sulekh; Gautam, Seema; Rajor, Hament Kumar; Bhatia, Rohit

2015-02-01

Novel Schiff's base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, 1H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen-sulfur donor (N2S2) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO3)2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO4)] complex may possessed square pyramidal geometry, [Ni(L)](NO3)2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand.

Links Between Ethylene and Sulfur Nutrition-A Regulatory Interplay or Just Metabolite Association?

PubMed

Wawrzynska, Anna; Moniuszko, Grzegorz; Sirko, Agnieszka

2015-01-01

Multiple reports demonstrate associations between ethylene and sulfur metabolisms, however the details of these links have not yet been fully characterized; the links might be at the metabolic and the regulatory levels. First, sulfur-containing metabolite, methionine, is a precursor of ethylene and is a rate limiting metabolite for ethylene synthesis; the methionine cycle contributes to both sulfur and ethylene metabolism. On the other hand, ethylene is involved in the complex response networks to various stresses and it is known that S deficiency leads to photosynthesis and C metabolism disturbances that might be responsible for oxidative stress. In several plant species, ethylene increases during sulfur starvation and might serve signaling purposes to initiate the process of metabolism reprogramming during adjustment to sulfur deficit. An elevated level of ethylene might result from increased activity of enzymes involved in its synthesis. It has been demonstrated that the alleviation of cadmium stress in plants by application of S seems to be mediated by ethylene formation. On the other hand, the ethylene-insensitive Nicotiana attenuata plants are impaired in sulfur uptake, reduction and metabolism, and they invest their already limited S into methionine needed for synthesis of ethylene constitutively emitted in large amounts to the atmosphere. Regulatory links of EIN3 and SLIM1 (both from the same family of transcriptional factors) involved in the regulation of ethylene and sulfur pathway, respectively, is also quite probable as well as the reciprocal modulation of both pathways on the enzyme activity levels.

HPLC-TOF-MS and HPLC-MS/MS combined with multivariate analysis for the characterization and discrimination of phenolic profiles in nonfumigated and sulfur-fumigated rhubarb.

PubMed

Yan, Yan; Zhang, Qianqian; Feng, Fang

2016-07-01

Sulfur fumigation has recently been used during the postharvest handling of rhubarb to reduce the drying duration and control pests. However, a few reports question the effect of sulfur fumigation on the bioactive components of rhubarb, which is crucial for the quality evaluation of the herbal medicine. The bottleneck limiting the study comes from the complex compounds that exist in herb samples with diverse structural features, wide concentration range and the difficulty to obtain all the reference standards. In this study, an integrated strategy based on the highly effective separation and analysis by liquid chromatography coupled with diode-array detection and time-of-flight/triple-quadruple tandem mass spectrometry combined with multivariate analysis was established. 68 phenolic compounds that exist in nonfumigated and sulfur-fumigated herb samples of rhubarb were tentatively assigned based on their retention behavior, UV spectra, accurate molecular weight, and mass spectral fragments. Qualitative and semiquantitative comparison revealed a serious reduction of the majority of phenolic compounds in sulfur-fumigated rhubarb. Furthermore, multivariate analysis was applied to holistically discriminate nonfumigated from sulfur-fumigated rhubarb and explore the characteristic chemical markers. The established approach was specific and rapid for characterizing and screening sulfur-fumigated rhubarb among commercial samples and could be applied for the quality assessment of other sulfur-fumigated herbs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assembly and Transfer of Iron–Sulfur Clusters in the Plastid

PubMed Central

Lu, Yan

2018-01-01

Iron-Sulfur (Fe-S) clusters and proteins are essential to many growth and developmental processes. In plants, they exist in the plastids, mitochondria, cytosol, and nucleus. Six types of Fe-S clusters are found in the plastid: classic 2Fe-2S, NEET-type 2Fe-2S, Rieske-type 2Fe-2S, 3Fe-4S, 4Fe-4S, and siroheme 4Fe-4S. Classic, NEET-type, and Rieske-type 2Fe-2S clusters have the same 2Fe-2S core; similarly, common and siroheme 4Fe-4S clusters have the same 4Fe-4S core. Plastidial Fe-S clusters are assembled by the sulfur mobilization (SUF) pathway, which contains cysteine desulfurase (EC 2.8.1.7), sulfur transferase (EC 2.8.1.3), Fe-S scaffold complex, and Fe-S carrier proteins. The plastidial cysteine desulfurase-sulfur transferase-Fe-S-scaffold complex system is responsible for de novo assembly of all plastidial Fe-S clusters. However, different types of Fe-S clusters are transferred to recipient proteins via respective Fe-S carrier proteins. This review focuses on recent discoveries on the molecular functions of different assembly and transfer factors involved in the plastidial SUF pathway. It also discusses potential points for regulation of the SUF pathway, relationships among the plastidial, mitochondrial, and cytosolic Fe-S assembly and transfer pathways, as well as several open questions about the carrier proteins for Rieske-type 2Fe-2S, NEET-type 2Fe-2S, and 3F-4S clusters. PMID:29662496

Complete Genome Sequence of Sulfuriferula sp. Strain AH1, a Sulfur-Oxidizing Autotroph Isolated from Weathered Mine Tailings from the Duluth Complex in Minnesota

PubMed Central

Roepke, Elizabeth W.; Hua, An An; Flood, Beverly E.; Bailey, Jake V.

2017-01-01

ABSTRACT We report the closed and annotated genome sequence of Sulfuriferula sp. strain AH1. Strain AH1 has a 2,877,007-bp chromosome that includes a partial Sox system for inorganic sulfur oxidation and a complete nitrogen fixation pathway. It also has a single 39,138-bp plasmid with genes for arsenic and mercury resistance. PMID:28798167

Idiosyncrasies of volcanic sulfur viscosity and the triggering of unheralded volcanic eruptions

NASA Astrophysics Data System (ADS)

Scolamacchia, Teresa; Cronin, Shane

2016-03-01

Unheralded "blue-sky" eruptions from dormant volcanoes cause serious fatalities, such as at Mt. Ontake (Japan) on 27 September 2014. Could these events result from magmatic gas being trapped within hydrothermal system aquifers by elemental sulfur (Se) clogging pores, due to sharp increases in its viscosity when heated above 159oC? This mechanism was thought to prime unheralded eruptions at Mt. Ruapehu in New Zealand. Impurities in sulfur (As, Te, Se) are known to modify S-viscosity and industry experiments showed that organic compounds, H2S, and halogens dramatically influence Se viscosity under typical hydrothermal heating/cooling rates and temperature thresholds. However, the effects of complex sulfur compositions are currently ignored at volcanoes, despite its near ubiquity in long-lived volcano-hydrothermal systems. Models of impure S behavior must be urgently formulated to detect pre-eruptive warning signs before the next "blue-sky" eruption

Frataxin Accelerates [2Fe-2S] Cluster Formation on the Human Fe–S Assembly Complex

PubMed Central

Fox, Nicholas G.; Das, Deepika; Chakrabarti, Mrinmoy; Lindahl, Paul A.; Barondeau, David P.

2015-01-01

Iron–sulfur (Fe–S) clusters function as protein cofactors for a wide variety of critical cellular reactions. In human mitochondria, a core Fe–S assembly complex [called SDUF and composed of NFS1, ISD11, ISCU2, and frataxin (FXN) proteins] synthesizes Fe–S clusters from iron, cysteine sulfur, and reducing equivalents and then transfers these intact clusters to target proteins. In vitro assays have relied on reducing the complexity of this complicated Fe–S assembly process by using surrogate electron donor molecules and monitoring simplified reactions. Recent studies have concluded that FXN promotes the synthesis of [4Fe-4S] clusters on the mammalian Fe–S assembly complex. Here the kinetics of Fe–S synthesis reactions were determined using different electron donation systems and by monitoring the products with circular dichroism and absorbance spectroscopies. We discovered that common surrogate electron donor molecules intercepted Fe–S cluster intermediates and formed high-molecular weight species (HMWS). The HMWS are associated with iron, sulfide, and thiol-containing proteins and have properties of a heterogeneous solubilized mineral with spectroscopic properties remarkably reminiscent of those of [4Fe-4S] clusters. In contrast, reactions using physiological reagents revealed that FXN accelerates the formation of [2Fe-2S] clusters rather than [4Fe-4S] clusters as previously reported. In the preceding paper [Fox, N. G., et al. (2015) Biochemistry 54, DOI: 10.1021/bi5014485], [2Fe-2S] intermediates on the SDUF complex were shown to readily transfer to uncomplexed ISCU2 or apo acceptor proteins, depending on the reaction conditions. Our results indicate that FXN accelerates a rate-limiting sulfur transfer step in the synthesis of [2Fe-2S] clusters on the human Fe–S assembly complex. PMID:26016518

Frataxin Accelerates [2Fe-2S] Cluster Formation on the Human Fe-S Assembly Complex.

PubMed

Fox, Nicholas G; Das, Deepika; Chakrabarti, Mrinmoy; Lindahl, Paul A; Barondeau, David P

2015-06-30

Iron-sulfur (Fe-S) clusters function as protein cofactors for a wide variety of critical cellular reactions. In human mitochondria, a core Fe-S assembly complex [called SDUF and composed of NFS1, ISD11, ISCU2, and frataxin (FXN) proteins] synthesizes Fe-S clusters from iron, cysteine sulfur, and reducing equivalents and then transfers these intact clusters to target proteins. In vitro assays have relied on reducing the complexity of this complicated Fe-S assembly process by using surrogate electron donor molecules and monitoring simplified reactions. Recent studies have concluded that FXN promotes the synthesis of [4Fe-4S] clusters on the mammalian Fe-S assembly complex. Here the kinetics of Fe-S synthesis reactions were determined using different electron donation systems and by monitoring the products with circular dichroism and absorbance spectroscopies. We discovered that common surrogate electron donor molecules intercepted Fe-S cluster intermediates and formed high-molecular weight species (HMWS). The HMWS are associated with iron, sulfide, and thiol-containing proteins and have properties of a heterogeneous solubilized mineral with spectroscopic properties remarkably reminiscent of those of [4Fe-4S] clusters. In contrast, reactions using physiological reagents revealed that FXN accelerates the formation of [2Fe-2S] clusters rather than [4Fe-4S] clusters as previously reported. In the preceding paper [Fox, N. G., et al. (2015) Biochemistry 54, DOI: 10.1021/bi5014485], [2Fe-2S] intermediates on the SDUF complex were shown to readily transfer to uncomplexed ISCU2 or apo acceptor proteins, depending on the reaction conditions. Our results indicate that FXN accelerates a rate-limiting sulfur transfer step in the synthesis of [2Fe-2S] clusters on the human Fe-S assembly complex.

Architecture of the Human Mitochondrial Iron-Sulfur Cluster Assembly Machinery.

PubMed

Gakh, Oleksandr; Ranatunga, Wasantha; Smith, Douglas Y; Ahlgren, Eva-Christina; Al-Karadaghi, Salam; Thompson, James R; Isaya, Grazia

2016-09-30

Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN 42-210 (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible fitting of protein structures docked into the EM map of the model revealed a [FXN 42-210 ] 24 ·[NFS1] 24 ·[ISD11] 24 ·[ISCU] 24 complex, consistent with the measured 1:1:1:1 stoichiometry of its four components. The complex structure fulfills distance constraints obtained from chemical cross-linking of the complex at multiple recurring interfaces, involving hydrogen bonds, salt bridges, or hydrophobic interactions between conserved residues. The complex consists of a central roughly cubic [FXN 42-210 ] 24 ·[ISCU] 24 sub-complex with one symmetric ISCU trimer bound on top of one symmetric FXN 42-210 trimer at each of its eight vertices. Binding of 12 [NFS1] 2 ·[ISD11] 2 sub-complexes to the surface results in a globular macromolecule with a diameter of ∼15 nm and creates 24 Fe-S cluster assembly centers. The organization of each center recapitulates a previously proposed conserved mechanism for sulfur donation from NFS1 to ISCU and reveals, for the first time, a path for iron donation from FXN 42-210 to ISCU. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Architecture of the Human Mitochondrial Iron-Sulfur Cluster Assembly Machinery*

PubMed Central

Gakh, Oleksandr; Ranatunga, Wasantha; Smith, Douglas Y.; Ahlgren, Eva-Christina; Al-Karadaghi, Salam; Thompson, James R.; Isaya, Grazia

2016-01-01

Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN42–210 (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible fitting of protein structures docked into the EM map of the model revealed a [FXN42–210]24·[NFS1]24·[ISD11]24·[ISCU]24 complex, consistent with the measured 1:1:1:1 stoichiometry of its four components. The complex structure fulfills distance constraints obtained from chemical cross-linking of the complex at multiple recurring interfaces, involving hydrogen bonds, salt bridges, or hydrophobic interactions between conserved residues. The complex consists of a central roughly cubic [FXN42–210]24·[ISCU]24 sub-complex with one symmetric ISCU trimer bound on top of one symmetric FXN42–210 trimer at each of its eight vertices. Binding of 12 [NFS1]2·[ISD11]2 sub-complexes to the surface results in a globular macromolecule with a diameter of ∼15 nm and creates 24 Fe-S cluster assembly centers. The organization of each center recapitulates a previously proposed conserved mechanism for sulfur donation from NFS1 to ISCU and reveals, for the first time, a path for iron donation from FXN42–210 to ISCU. PMID:27519411

Mechanism of ubiquinol oxidation by the bc(1) complex: role of the iron sulfur protein and its mobility.

PubMed

Crofts, A R; Guergova-Kuras, M; Huang, L; Kuras, R; Zhang, Z; Berry, E A

1999-11-30

Native structures of ubihydroquinone:cytochrome c oxidoreductase (bc(1) complex) from different sources, and structures with inhibitors in place, show a 16-22 A displacement of the [2Fe-2S] cluster and the position of the C-terminal extrinsic domain of the iron sulfur protein. None of the structures shows a static configuration that would allow catalysis of all partial reactions of quinol oxidation. We have suggested that the different conformations reflect a movement of the subunit necessary for catalysis. The displacement from an interface with cytochrome c(1) in native crystals to an interface with cytochrome b is induced by stigmatellin or 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole (UHDBT) and involves ligand formation between His-161 of the [2Fe-2S] binding cluster and the inhibitor. The movement is a rotational displacement, so that the same conserved docking surface on the iron sulfur protein interacts with cytochrome c(1) and with cytochrome b. The mobile extrinsic domain retains essentially the same tertiary structure, and the anchoring N-terminal tail remains in the same position. The movement occurs through an extension of a helical segment in the short linking span. We report details of the protein structure for the two main configurations in the chicken heart mitochondrial complex and discuss insights into mechanism provided by the structures and by mutant strains in which the docking at the cytochrome b interface is impaired. The movement of the iron sulfur protein represents a novel mechanism of electron transfer, in which a tethered mobile head allows electron transfer through a distance without the entropic loss from free diffusion.

Copper solubility in a basaltic melt and sulfide liquid/silicate melt partition coefficients of Cu and Fe

NASA Astrophysics Data System (ADS)

Ripley, Edward M.; Brophy, James G.; Li, Chusi

2002-09-01

The solubility of copper in a sulfur-saturated basaltic melt has been determined at 1245°C as a function of fO 2 and fS 2. Copper solubilities at log fO 2 values between -8 and -11 fall into two distinct populations as a function of fS 2. At log fS 2 values < -1.65, sulfide liquid that coexists with the basaltic glass quenches to sulfur-poor bornite solid solution. At log fS 2 values in excess of -1.65, the sulfide liquid quenches to a complex intergrowth of sulfur-rich bornite and intermediate solid solution. Copper solubilities in the low-fS 2 population range from 594 to 1550 ppm, whereas those in the high-fS 2 population range from 80 to 768 ppm. Sulfide liquid/silicate liquid partition coefficients (D) for Cu and Fe range from 480 to 1303 and 0.7 to 13.6, respectively. Metal-sulfur complexing in the silicate liquid is shown to be insignificant relative to metal-oxide complexing for Fe but permissible for Cu at high fS 2 values. On log D Fe (sulfide-silicate) and log D Cu (sulfide-silicate) vs. 1/2 (log fS 2 - log fO 2) diagrams, both fS 2 populations show distinct but parallel trends. The observation of two D values for any fS 2/fO 2 ratio indicates nonideal mixing of species involved in the exchange reaction. The two distinct trends observed for both Cu and Fe are thought to be due to variations in activity coefficient ratios (e.g., γ FeO/γ FeS and γ CuO 0.5/γ CuS 0.5). Results of the experiments suggest that accurate assessments of fS 2/fO 2 ratios are required for the successful numerical modeling of processes such as the partial melting of sulfide-bearing mantle and the crystallization of sulfide-bearing magmas, as well as the interpretation of sulfide mineralogical zoning. In addition, the experiments provide evidence for oxide or oxy-sulfide complexing for Cu in silicate magmas and suggest that the introduction of externally derived sulfur to mafic magma may be an important process for the formation of Cu-rich disseminated magmatic sulfide ore deposits.

Ru-OSO coordination photogenerated at 100 K in tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-camphorsulfonate.

PubMed

Phillips, Anthony E; Cole, Jacqueline M; d'Almeida, Thierry; Low, Kian Sing

2012-02-06

The photoinduced O-bound coordination mode in RuSO(2) complexes, previously observed only at 13 K, has been generated at 100 K in tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-camphorsulfonate. This coordination state, often denoted MS1, decays to the η(2)-bound MS2 state, with an estimated half-life of 3.4(8) h and a long-lived population of 2.9(4)% at 120 K.

Interaction of the iron–sulfur cluster assembly protein IscU with the Hsc66/Hsc20 molecular chaperone system of Escherichia coli

PubMed Central

Hoff, Kevin G.; Silberg, Jonathan J.; Vickery, Larry E.

2000-01-01

The iscU gene in bacteria is located in a gene cluster encoding proteins implicated in iron–sulfur cluster assembly and an hsc70-type (heat shock cognate) molecular chaperone system, iscSUA-hscBA. To investigate possible interactions between these systems, we have overproduced and purified the IscU protein from Escherichia coli and have studied its interactions with the hscA and hscB gene products Hsc66 and Hsc20. IscU and its iron–sulfur complex (IscU–Fe/S) stimulated the basal steady-state ATPase activity of Hsc66 weakly in the absence of Hsc20 but, in the presence of Hsc20, increased the ATPase activity up to 480-fold. Hsc20 also decreased the apparent Km for IscU stimulation of Hsc66 ATPase activity, and surface plasmon resonance studies revealed that Hsc20 enhances binding of IscU to Hsc66. Surface plasmon resonance and isothermal titration calorimetry further showed that IscU and Hsc20 form a complex, and Hsc20 may thereby aid in the targeting of IscU to Hsc66. These results establish a direct and specific role for the Hsc66/Hsc20 chaperone system in functioning with isc gene components for the assembly of iron–sulfur cluster proteins. PMID:10869428

Potential bronchoconstrictor stimuli in acid fog.

PubMed Central

Balmes, J R; Fine, J M; Gordon, T; Sheppard, D

1989-01-01

Acid fog is complex and contains multiple stimuli that may be capable of inducing bronchoconstriction. These stimuli include sulfuric and niric acids, the principal inorganic acids present; sulfites, formed in the atmosphere as a reaction product of sulfur dioxide and water droplets; fog water itself, a hypoosmolar aerosol; the organic acid hydroxymethanesulfonate, the bisulfite adduct of formaldehyde; and gaseous pollutants, e.g., sulfur dioxide, oxides of nitrogen, ozone. Given this complexity, evaluation of the respiratory health effects of naturally occurring acid fog requires assessment of the bronchoconstrictor potency of each component stimulus and possible interactions among these stimuli. We summarize the results of three studies that involve characterization of the bronchoconstrictor potency of acid fog stimuli and/or their interaction in subjects with asthma. The results of the first study indicate that titratable acidity appears to be a more important stimulus to bronchoconstriction than is pH. The results of the second study demonstrate that sulfite species are capable of inducing bronchoconstriction, especially when inhaled at acid pH. The results of the third study suggest that acidity can potentiate hypoosmolar fog-induced bronchoconstriction. PMID:2539989

Expression of Genes Involved in Iron and Sulfur Respiration in a Novel Thermophilic Crenarchaeon Isolated from Acid-Sulfate-Chloride Geothermal Systems

NASA Astrophysics Data System (ADS)

Kozubal, M.; Macur, R.; Inskeep, W. P.

2007-12-01

Acidic geothermal springs within Yellowstone National Park (YNP) provide an excellent opportunity to study microbial populations and their relationship with geochemical processes such as redox cycling and biomineralization of iron. Fourteen acid-sulfate-chloride (ASC) and acid-sulfate (AS) geothermal springs located in (YNP) have been extensively characterized for aqueous chemistry, solid phase mineral deposition and microbial diversity and distribution. The oxidation of Fe(II) with oxygen as an electron acceptor is exergonic under these conditions, consequently, Fe(II) may be an important electron donor driving primary production in ASC and AS habitats, and products of biomineralization (e.g. Fe[III]-oxides of varying crystallinity and structure, as well as jarosite in some cases) are common in the outflow channels of these environments. Recently, we isolated a novel Metallosphaera-like microorganism (Metallosphaera strain MK1) from an ASC spring in Norris Geyser Basin, YNP. Clone libraries (16S rRNA gene) from multiple sites suggest that microorganisms closely related to strain MK1 (between 98-100 percent similarity) dominate many spring locations between 55-80 C. The in situ abiotic oxidation rate of Fe(II) has been shown to be very slow in these systems and Metallosphaera strain MK1 has been directly implicated in biotic Fe(II) oxidation. Metallosphaera strain MK1 has been submitted for full genome sequencing and is yielding gene sequences related to the terminal oxidases SOXABC and SOXM super-complex. In addition, sequences from a recently characterized terminal oxidase FOX complex involved in Fe(II) and pyrite oxidation from Sulfolobus metallicus have been found in Metallosphaera strain MK1. A protein complex analogous to Metallosphaera sedula has been identified in strain MK1 and this complex has also been expressed in cells grown on pyrite and Fe(II). Other sequences identified in Metallosphaera strain MK1 that are involved in respiration are the TQO complex (thiosulfate:quinone oxidoreductase) related to the Acidianus ambivalens DOXAD complex and a sulfur reductase (SRE) complex related to one found in Sulfolobus solfataricus and Acidianus ambivalens. Here we report on the RNA expression of seven gene sequences from each of the above mentioned complexes for Metallosphaera strain MK1 grown aerobically on pyrite, sulfur, Fe(II)-ferrihydrite, and anaerobically with yeast extract and sulfur. In addition, expression studies are also compared to in situ samples collected from the geothermal Fe-mats.

Aromatic sulfonation with sulfur trioxide: mechanism and kinetic model.

PubMed

Moors, Samuel L C; Deraet, Xavier; Van Assche, Guy; Geerlings, Paul; De Proft, Frank

2017-01-01

Electrophilic aromatic sulfonation of benzene with sulfur trioxide is studied with ab initio molecular dynamics simulations in gas phase, and in explicit noncomplexing (CCl 3 F) and complexing (CH 3 NO 2 ) solvent models. We investigate different possible reaction pathways, the number of SO 3 molecules participating in the reaction, and the influence of the solvent. Our simulations confirm the existence of a low-energy concerted pathway with formation of a cyclic transition state with two SO 3 molecules. Based on the simulation results, we propose a sequence of elementary reaction steps and a kinetic model compatible with experimental data. Furthermore, a new alternative reaction pathway is proposed in complexing solvent, involving two SO 3 and one CH 3 NO 2 .

Surface Modification and Nanojunction Fabrication with Molecular Metal Wires

DTIC Science & Technology

2014-02-17

Title: Transition Metal Complexes of a Super Rigid Anthyridine Ligand: Structural, Magnetic and DFT Studies. Transition metal complexes of iron ( II ...Compounds with Masked Diazonium Capping Groups (J. Organomet. Chem. 2013, 745, 93). (3) New Diruthenium( II ,III) Compounds Bearing Terminal Olefin Groups...2012, 36, 2340). (2) Synthesis , Structure, Magnetism, and Single Molecular Conductance of Linear Trinickel String Complexes with Sulfur-Containing

Complex Hollow Nanostructures: Synthesis and Energy-Related Applications.

PubMed

Yu, Le; Hu, Han; Wu, Hao Bin; Lou, Xiong Wen David

2017-04-01

Hollow nanostructures offer promising potential for advanced energy storage and conversion applications. In the past decade, considerable research efforts have been devoted to the design and synthesis of hollow nanostructures with high complexity by manipulating their geometric morphology, chemical composition, and building block and interior architecture to boost their electrochemical performance, fulfilling the increasing global demand for renewable and sustainable energy sources. In this Review, we present a comprehensive overview of the synthesis and energy-related applications of complex hollow nanostructures. After a brief classification, the design and synthesis of complex hollow nanostructures are described in detail, which include hierarchical hollow spheres, hierarchical tubular structures, hollow polyhedra, and multi-shelled hollow structures, as well as their hybrids with nanocarbon materials. Thereafter, we discuss their niche applications as electrode materials for lithium-ion batteries and hybrid supercapacitors, sulfur hosts for lithium-sulfur batteries, and electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. The potential superiorities of complex hollow nanostructures for these applications are particularly highlighted. Finally, we conclude this Review with urgent challenges and further research directions of complex hollow nanostructures for energy-related applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Presence of Multiple Cellular Defects Associated with a Novel G50E Iron-Sulfur Cluster Scaffold Protein (ISCU) Mutation Leads to Development of Mitochondrial Myopathy*

PubMed Central

Saha, Prasenjit Prasad; Kumar, S. K. Praveen; Srivastava, Shubhi; Sinha, Devanjan; Pareek, Gautam; D'Silva, Patrick

2014-01-01

Iron-sulfur (Fe-S) clusters are versatile cofactors involved in regulating multiple physiological activities, including energy generation through cellular respiration. Initially, the Fe-S clusters are assembled on a conserved scaffold protein, iron-sulfur cluster scaffold protein (ISCU), in coordination with iron and sulfur donor proteins in human mitochondria. Loss of ISCU function leads to myopathy, characterized by muscle wasting and cardiac hypertrophy. In addition to the homozygous ISCU mutation (g.7044G→C), compound heterozygous patients with severe myopathy have been identified to carry the c.149G→A missense mutation converting the glycine 50 residue to glutamate. However, the physiological defects and molecular mechanism associated with G50E mutation have not been elucidated. In this report, we uncover mechanistic insights concerning how the G50E ISCU mutation in humans leads to the development of severe ISCU myopathy, using a human cell line and yeast as the model systems. The biochemical results highlight that the G50E mutation results in compromised interaction with the sulfur donor NFS1 and the J-protein HSCB, thus impairing the rate of Fe-S cluster synthesis. As a result, electron transport chain complexes show significant reduction in their redox properties, leading to loss of cellular respiration. Furthermore, the G50E mutant mitochondria display enhancement in iron level and reactive oxygen species, thereby causing oxidative stress leading to impairment in the mitochondrial functions. Thus, our findings provide compelling evidence that the respiration defect due to impaired biogenesis of Fe-S clusters in myopathy patients leads to manifestation of complex clinical symptoms. PMID:24573684

Syntheses, spectroscopic characterization, thermal study, molecular modeling, and biological evaluation of novel Schiff's base benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) with Ni(II), and Cu(II) metal complexes.

PubMed

Chandra, Sulekh; Gautam, Seema; Rajor, Hament Kumar; Bhatia, Rohit

2015-02-25

Novel Schiff's base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, (1)H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen-sulfur donor (N2S2) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO3)2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO4)] complex may possessed square pyramidal geometry, [Ni(L)](NO3)2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand. Copyright © 2014 Elsevier B.V. All rights reserved.

High Pressure Optical Studies of the Thallous Halides and of Charge-Transfer Complexes

NASA Astrophysics Data System (ADS)

Jurgensen, Charles Willard

High pressure was used to study the insulator -to-metal transition in sulfur and the thallous halides and to study the intermolecular interactions in charge -transfer complexes. The approach to the band overlap insulator -to-metal transition was studied in three thallous halides and sulfur by optical absorption measurements of the band gap as a function of pressure. The band gap of sulfur continuously decreases with pressure up to the insulator -to-metal transition which occurs between 450 and 485 kbars. The results on the thallous halides indicate that the indirect gap decreases more rapidly than the direct gap; the closing of the indirect gap is responsible for the observed insulator -to-metal transitions. High pressure electronic and vibrational spectroscopic measurements on the solid-state complexes of HMB-TCNE were used to study the intermolecular interactions of charge -transfer complexes. The vibrational frequency shifts indicate that the degree of charge transfer increases with pressure which is independently confirmed by an increase in the molar absorptivity of the electronic charge-transfer peak. Induction and dispersion forces contribute towards a red shift of the charge-transfer peak; however, charge-transfer resonance contributes toward a blue shift and this effect is dominant for the HMB-TCNE complexes. High pressure electronic spectra were used to study the effect of intermolecular interactions on the electronic states of TCNQ and its complexes. The red shifts with pressure of the electronic spectra of TCNQ and (TCNQ)(' -) in polymer media and of crystalline TCNQ can be understood in terms of Van der Waals interactions. None of the calculations which considered intradimer distance obtained the proper behavior for either the charge-transfer of the locally excited states of the complexes. The qualitative behavior of both states can be interpreted as the effect of increased mixing of the locally excited and charge transfer states.

A Glutaredoxin·BolA Complex Serves as an Iron-Sulfur Cluster Chaperone for the Cytosolic Cluster Assembly Machinery*♦

PubMed Central

Frey, Avery G.; Palenchar, Daniel J.; Wildemann, Justin D.; Philpott, Caroline C.

2016-01-01

Cells contain hundreds of proteins that require iron cofactors for activity. Iron cofactors are synthesized in the cell, but the pathways involved in distributing heme, iron-sulfur clusters, and ferrous/ferric ions to apoproteins remain incompletely defined. In particular, cytosolic monothiol glutaredoxins and BolA-like proteins have been identified as [2Fe-2S]-coordinating complexes in vitro and iron-regulatory proteins in fungi, but it is not clear how these proteins function in mammalian systems or how this complex might affect Fe-S proteins or the cytosolic Fe-S assembly machinery. To explore these questions, we use quantitative immunoprecipitation and live cell proximity-dependent biotinylation to monitor interactions between Glrx3, BolA2, and components of the cytosolic iron-sulfur cluster assembly system. We characterize cytosolic Glrx3·BolA2 as a [2Fe-2S] chaperone complex in human cells. Unlike complexes formed by fungal orthologs, human Glrx3-BolA2 interaction required the coordination of Fe-S clusters, whereas Glrx3 homodimer formation did not. Cellular Glrx3·BolA2 complexes increased 6–8-fold in response to increasing iron, forming a rapidly expandable pool of Fe-S clusters. Fe-S coordination by Glrx3·BolA2 did not depend on Ciapin1 or Ciao1, proteins that bind Glrx3 and are involved in cytosolic Fe-S cluster assembly and distribution. Instead, Glrx3 and BolA2 bound and facilitated Fe-S incorporation into Ciapin1, a [2Fe-2S] protein functioning early in the cytosolic Fe-S assembly pathway. Thus, Glrx3·BolA is a [2Fe-2S] chaperone complex capable of transferring [2Fe-2S] clusters to apoproteins in human cells. PMID:27519415

Substituting leucine for alanine-86 in the tether region of the iron-sulfur protein of the cytochrome bc1 complex affects the mobility of the [2Fe2S] domain.

PubMed

Ghosh, M; Wang, Y; Ebert, C E; Vadlamuri, S; Beattie, D S

2001-01-16

Mutating three conserved alanine residues in the tether region of the iron-sulfur protein of the yeast cytochrome bc(1) complex resulted in 22-56% decreases in enzymatic activity [Obungu et al. (2000) Biochim. Biophys. Acta 1457, 36-44]. The activity of the cytochrome bc(1) complex isolated from A86L was decreased 60% compared to the wild-type without loss of heme or protein and without changes in the 2Fe2S cluster or proton-pumping ability. The activity of the bc(1) complex from mutant A92R was identical to the wild-type, while loss of both heme and activity was observed in the bc(1) complex isolated from mutant A90I. Computer simulations indicated that neither mutation A86L nor mutation A92R affects the alpha-helical backbone in the tether region; however, the side chain of the leucine substituted for Ala-86 interacts with the side chain of Leu-89. The Arrhenius plot for mutant A86L was apparently biphasic with a transition observed at 17-19 degrees C and an activation energy of 279.9 kJ/mol below 17 degrees C and 125.1 kJ/mol above 17 degrees C. The initial rate of cytochrome c(1) reduction was lowered 33% in mutant A86L; however, the initial rate of cytochrome b reduction was unaffected, suggesting that movement of the tether region of the iron-sulfur protein is necessary for maximum rates of enzymatic activity. Substituting a leucine for Ala-86 impedes the unwinding of the alpha-helix and hence movement of the tether.

Theoretical studies of the marine sulfur cycle

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Kasting, James B.; Liu, May S.

1985-01-01

Several reduced sulfur compounds are produced by marine organisms and then enter the atmosphere, where they are oxidized and ultimately returned to the ocean or the land. The oceanic dimethyl sulfide (DMS) flux, in particular, represents a significant fraction of the annual global sulfur input to the atmosphere. In the atmosphere, this gas is converted to sulfur dioxide (SO2), methane sulfonic acid, and other organic acids which are relatively stable and about which little is known. SO2 is a short lived gas which, in turn, is converted to sulfuric acid and other sulfate compounds which contribute significantly to acid rain. Because of the complexity of the sulfur system, it is not well understood even in the unperturbed atmosphere. However, a number of new observations and experiments have led to a significant increase in the understanding of this system. A number of one dimensional model experiments were conducted on the gas phase part of the marine sulfur cycle. The results indicate the measured concentration of DMS and the amplitude of its diurnal cycle are in agreement with estimates of its global flux. It was also found that DMS can make a large contribution to the background SO2 concentration in the free troposphere. Estimates of CS2 concentrations in the atmosphere are inconsistent with estimated fluxes; however, measured reaction rates are consistent with the observed steep tropospheric gradient in CS2. Observations of CS2 are extremely sparse. Further study is planned.

Evaluation of comprehensive two-dimensional gas chromatography with flame photometric detection: potential application for sulfur speciation in shale oil.

PubMed

Mitrevski, Blagoj; Amer, Mohammad W; Chaffee, Alan L; Marriott, Philip J

2013-11-25

Flame photometric detection in the sulfur channel has been evaluated for sulfur speciation and quantification in comprehensive two-dimensional gas chromatography [GC × GC-FPD(S)] for S-compound speciation in shale extracts. Signal non-linearity and potential quenching effects were reportedly major limitations of this detector for analysis of sulfur in complex matrices. However, reliable linear relationships with correlation coefficient >0.99 can be obtained if the sum of the square root of each modulation slice in GC × GC is plotted vs. sulfur concentration. Furthermore, the quenching effects are reduced due to essentially complete separation of S-containing components from the hydrocarbon matrix. An increase of S/N of up to 150 times has been recorded for benzothiophene and dibenzothiophene in GC × GC-FPD when compared to GC-FPD due to the modulation process. As a consequence, 10 times lower detection limits were observed in the former mode. The applicability of the method was demonstrated using shale oil sample extracts. Three sulfur classes were completely separated and the target class (thiophenes) was successfully quantified after the rest of the sample was diverted to the second detector by using a heart-cut strategy. Based on the proposed method, 70% of the sulfur in the shale oil was assigned to the thiophenes, 24% to benzothiophenes, and 5% to dibenzothiophene compounds. Copyright © 2013 Elsevier B.V. All rights reserved.

Toxicity to and egg-laying avoidance of Drosophila suzukii (Diptera: Drosophilidae) caused by an old alternative inorganic insecticide preparation.

PubMed

Andreazza, Felipe; Vacacela Ajila, Henry E; Haddi, Khalid; Colares, Felipe; Pallini, Angelo; Oliveira, Eugênio E

2018-04-01

The application of synthetic insecticides remains the most used tool for the management of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). However, management of this pest in the organic production of soft-skinned fruits is a complex task due to the restricted number of registered products. Here, we assess the toxicity of lime sulfur and evaluate whether lime sulfur-treated strawberry plants affected the oviposition and development of D. suzukii. Lime sulfur exhibited adequate toxicity to D. suzukii (LC 50 = 26.6 mL L -1 ) without phytotoxicity to strawberry plants. When D. suzukii females were exposed to lime sulfur-treated plants in no-choice bioassays, oviposition was significantly (t-test, P < 0.05) reduced compared with that on untreated plants. In free-choice bioassays, D. suzukii females laid significantly (paired t-test, P < 0.05) more eggs on untreated plants. Furthermore, in the free-choice bioassays, immature development was slower for adults that originated from eggs laid on lime sulfur-treated plants than from those laid on untreated plants. Lime sulfur showed adequate control and, therefore, has potential for use as a management tool against D. suzukii infestations in organic production systems. This old, alternative insecticide preparation not only caused adult fly mortality, but also reduced the number of eggs laid on lime sulfur-treated plants. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Phosphoryl transfer reaction snapshots in crystals: Insights into the mechanism of protein kinase a catalytic subunit

DOE PAGES

Das, Amit; Gerlits, Oksana O.; Heller, William T.; ...

2015-06-19

To study the catalytic mechanism of phosphorylation catalyzed by cAMP-dependent protein kinase (PKA) a structure of the enzyme-substrate complex representing the Michaelis complex is of specific interest as it can shed light on the structure of the transition state. However, all previous crystal structures of the Michaelis complex mimics of the PKA catalytic subunit (PKAc) were obtained with either peptide inhibitors or ATP analogs. Here we utilized Ca 2+ ions and sulfur in place of the nucleophilic oxygen in a 20-residue pseudo-substrate peptide (CP20) and ATP to produce a close mimic of the Michaelis complex. In the ternary reactant complex,more » the thiol group of Cys-21 of the peptide is facing Asp-166 and the sulfur atom is positioned for an in-line phosphoryl transfer. Replacement of Ca 2+ cations with Mg 2+ ions resulted in a complex with trapped products of ATP hydrolysis: phosphate ion and ADP. As a result, the present structural results in combination with the previously reported structures of the transition state mimic and phosphorylated product complexes complete the snapshots of the phosphoryl transfer reaction by PKAc, providing us with the most thorough picture of the catalytic mechanism to date.« less

Function and Evolution of the Sox Multienzyme Complex in the Marine Gammaproteobacterium Congregibacter litoralis

PubMed Central

2014-01-01

Core sets of sox genes were detected in several genome sequenced members of the environmental important OM60/NOR5 clade of marine gammaproteobacteria. However, emendation of media with thiosulfate did not result in stimulation of growth in two of these strains and cultures of Congregibacter litoralis DSM 17192T did not oxidize thiosulfate to sulfate in concentrations of one mmol L−1 or above. On the other hand, a significant production of sulfate was detected upon growth with the organic sulfur compounds, cysteine and glutathione. It was found that degradation of glutathione resulted in the formation of submillimolar amounts of thiosulfate in the closely related sox-negative strain Chromatocurvus halotolerans DSM 23344T. It is proposed that the Sox multienzyme complex in Congregibacter litoralis and related members of the OM60/NOR5 clade is adapted to the oxidation of submillimolar amounts of thiosulfate and nonfunctional at higher concentrations of reduced inorganic sulfur compounds. Pelagic bacteria thriving in the oxic zones of marine environments may rarely encounter amounts of thiosulfate, which would allow its utilization as electron donor for lithoautotrophic or mixotrophic growth. Consequently, in evolution the Sox multienzyme complex in some of these bacteria may have been optimized for the effective utilization of trace amounts of thiosulfate generated from the degradation of organic sulfur compounds. PMID:25006520

Zim17/Tim15 links mitochondrial iron-sulfur cluster biosynthesis to nuclear genome stability.

PubMed

Díaz de la Loza, María Del Carmen; Gallardo, Mercedes; García-Rubio, María Luisa; Izquierdo, Alicia; Herrero, Enrique; Aguilera, Andrés; Wellinger, Ralf Erik

2011-08-01

Genomic instability is related to a wide-range of human diseases. Here, we show that mitochondrial iron-sulfur cluster biosynthesis is important for the maintenance of nuclear genome stability in Saccharomyces cerevisiae. Cells lacking the mitochondrial chaperone Zim17 (Tim15/Hep1), a component of the iron-sulfur biosynthesis machinery, have limited respiration activity, mimic the metabolic response to iron starvation and suffer a dramatic increase in nuclear genome recombination. Increased oxidative damage or deficient DNA repair do not account for the observed genomic hyperrecombination. Impaired cell-cycle progression and genetic interactions of ZIM17 with components of the RFC-like complex involved in mitotic checkpoints indicate that replicative stress causes hyperrecombination in zim17Δ mutants. Furthermore, nuclear accumulation of pre-ribosomal particles in zim17Δ mutants reinforces the importance of iron-sulfur clusters in normal ribosome biosynthesis. We propose that compromised ribosome biosynthesis and cell-cycle progression are interconnected, together contributing to replicative stress and nuclear genome instability in zim17Δ mutants.

MicroRNA-210 regulates mitochondrial free radical response to hypoxia and krebs cycle in cancer cells by targeting iron sulfur cluster protein ISCU.

PubMed

Favaro, Elena; Ramachandran, Anassuya; McCormick, Robert; Gee, Harriet; Blancher, Christine; Crosby, Meredith; Devlin, Cecilia; Blick, Christopher; Buffa, Francesca; Li, Ji-Liang; Vojnovic, Borivoj; Pires das Neves, Ricardo; Glazer, Peter; Iborra, Francisco; Ivan, Mircea; Ragoussis, Jiannis; Harris, Adrian L

2010-04-26

Hypoxia in cancers results in the upregulation of hypoxia inducible factor 1 (HIF-1) and a microRNA, hsa-miR-210 (miR-210) which is associated with a poor prognosis. In human cancer cell lines and tumours, we found that miR-210 targets the mitochondrial iron sulfur scaffold protein ISCU, required for assembly of iron-sulfur clusters, cofactors for key enzymes involved in the Krebs cycle, electron transport, and iron metabolism. Down regulation of ISCU was the major cause of induction of reactive oxygen species (ROS) in hypoxia. ISCU suppression reduced mitochondrial complex 1 activity and aconitase activity, caused a shift to glycolysis in normoxia and enhanced cell survival. Cancers with low ISCU had a worse prognosis. Induction of these major hallmarks of cancer show that a single microRNA, miR-210, mediates a new mechanism of adaptation to hypoxia, by regulating mitochondrial function via iron-sulfur cluster metabolism and free radical generation.

Structural principles for computational and de novo design of 4Fe-4S metalloproteins

PubMed Central

Nanda, Vikas; Senn, Stefan; Pike, Douglas H.; Rodriguez-Granillo, Agustina; Hansen, Will; Khare, Sagar D.; Noy, Dror

2017-01-01

Iron-sulfur centers in metalloproteins can access multiple oxidation states over a broad range of potentials, allowing them to participate in a variety of electron transfer reactions and serving as catalysts for high-energy redox processes. The nitrogenase FeMoCO cluster converts di-nitrogen to ammonia in an eight-electron transfer step. The 2(Fe4S4) containing bacterial ferredoxin is an evolutionarily ancient metalloprotein fold and is thought to be a primordial progenitor of extant oxidoreductases. Controlling chemical transformations mediated by iron-sulfur centers such as nitrogen fixation, hydrogen production as well as electron transfer reactions involved in photosynthesis are of tremendous importance for sustainable chemistry and energy production initiatives. As such, there is significant interest in the design of iron-sulfur proteins as minimal models to gain fundamental understanding of complex natural systems and as lead-molecules for industrial and energy applications. Herein, we discuss salient structural characteristics of natural iron-sulfur proteins and how they guide principles for design. Model structures of past designs are analyzed in the context of these principles and potential directions for enhanced designs are presented, and new areas of iron-sulfur protein design are proposed. PMID:26449207

Powering Lithium-Sulfur Battery Performance by Propelling Polysulfide Redox at Sulfiphilic Hosts.

PubMed

Yuan, Zhe; Peng, Hong-Jie; Hou, Ting-Zheng; Huang, Jia-Qi; Chen, Cheng-Meng; Wang, Dai-Wei; Cheng, Xin-Bing; Wei, Fei; Zhang, Qiang

2016-01-13

Lithium-sulfur (Li-S) battery system is endowed with tremendous energy density, resulting from the complex sulfur electrochemistry involving multielectron redox reactions and phase transformations. Originated from the slow redox kinetics of polysulfide intermediates, the flood of polysulfides in the batteries during cycling induced low sulfur utilization, severe polarization, low energy efficiency, deteriorated polysulfide shuttle, and short cycling life. Herein, sulfiphilic cobalt disulfide (CoS2) was incorporated into carbon/sulfur cathodes, introducing strong interaction between lithium polysulfides and CoS2 under working conditions. The interfaces between CoS2 and electrolyte served as strong adsorption and activation sites for polar polysulfides and therefore accelerated redox reactions of polysulfides. The high polysulfide reactivity not only guaranteed effective polarization mitigation and promoted energy efficiency by 10% but also promised high discharge capacity and stable cycling performance during 2000 cycles. A slow capacity decay rate of 0.034%/cycle at 2.0 C and a high initial capacity of 1368 mAh g(-1) at 0.5 C were achieved. Since the propelling redox reaction is not limited to Li-S system, we foresee the reported strategy herein can be applied in other high-power devices through the systems with controllable redox reactions.

Micronized coal-fired retrofit system for SO{sub x} reduction: Krakow Clean Fossil Fuels and Energy Efficiency Program. Technical progress report No. 3, October 1996--December 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

The PROJECT proposes to install a new TCS micronized coal-fired heating plant for the Produkcja I Hodowla Roslin Ogrodniczych (PHRO) Greenhouse Complex; Krzeszowice, Poland (about 20 miles west of Krakow). PHRO currently utilizes 14 heavy oil-fired boilers to produce heat for its greenhouse facilities and also home heating to several adjacent apartment housing complexes. The boilers currently burn a high-sulfur content heavy crude oil, called Mazute. For size orientation, the PHRO Greenhouse complex grows a variety of vegetables and flowers for the Southern Poland marketplace. The greenhouse area under glass is very large and equivalent to approximately 50 football fields.more » The new micronized coal fired boiler would: (1) provide a significant portion of the heat for PHRO and a portion of the adjacent apartment housing complexes, (2) dramatically reduce sulfur dioxide air pollution emissions, while satisfying new Polish air regulations, and (3) provide attractive savings to PHRO, based on the quantity of displaced oil. Currently, the Town of Krzeszowice is considering a district heating program that would replace some, or all, of the 40 existing small in-town heating boilers that presently burn high-sulfur content coal. Potentially the district heating system can be expanded and connected into the PHRO boiler network; so that, PHRO boilers can supply all, or a portion of, the Town`s heating demand. The new TCS micronized coal system could provide a portion of this demand.« less

Biogeochemical zonation of sulfur during the discharge of groundwater to lake in desert plateau (Dakebo Lake, NW China).

PubMed

Su, Xiaosi; Cui, Geng; Wang, Huang; Dai, Zhenxue; Woo, Nam-Chil; Yuan, Wenzhen

2018-06-01

As one of the important elements of controlling the redox system within the hyporheic and hypolentic zone, sulfur is involved in a series of complex biogeochemical processes such as carbon cycle, water acidification, formation of iron and manganese minerals, redox processes of trace metal elements and a series of important ecological processes. Previous studies on biogeochemistry of the hyporheic and hypolentic zones mostly concentrated on nutrients of nitrogen and phosphorus, heavy metals and other pollutants. Systematic study of biogeochemical behavior of sulfur and its main controlling factors within the lake hypolentic zone is very urgent and important. In this paper, a typical desert plateau lake, Dakebo Lake in northwestern China, was taken for example within which redox zonation and biogeochemical characteristics of sulfur affected by hydrodynamic conditions were studied based on not only traditional hydrochemical analysis, but also environmental isotope evidence. In the lake hypolentic zone of the study area, due to the different hydrodynamic conditions, vertical profile of sulfur species and environmental parameters differ at the two sites of the lake (western side and center). Reduction of sulfate, deposition and oxidation of sulfide, dissolution and precipitation of sulfur-bearing minerals occurred are responded well to Eh, dissolved oxygen, pH, organic carbon and microorganism according to which the lake hypolentic zone can be divided into reduced zone containing H 2 S, reduced zone containing no H 2 S, transition zone and oxidized zone. The results of this study provide valuable insights for understanding sulfur conversion processes and sulfur biogeochemical zonation within a lake hypolentic zone in an extreme plateau arid environment and for protecting the lake-wetland ecosystem in arid and semiarid regions.

Redox potentials and kinetics of the Ce 3+/Ce 4+ redox reaction and solubility of cerium sulfates in sulfuric acid solutions

NASA Astrophysics Data System (ADS)

Paulenova, A.; Creager, S. E.; Navratil, J. D.; Wei, Y.

Experimental work was performed with the aim of evaluating the Ce 4+/Ce 3+ redox couple in sulfuric acid electrolyte for use in redox flow battery (RFB) technology. The solubility of cerium sulfates in 0.1-4.0 M sulfuric acid at 20-60 °C was studied. A synergistic effect of both sulfuric acid concentration and temperature on the solubility of cerous sulfate was observed. The solubility of cerous sulfate significantly decreased with rising concentration of sulfuric acid and rising temperature, while the solubility of ceric sulfate goes through a significant maximum at 40 °C. Redox potentials and the kinetics of the cerous/ceric redox reaction were also studied under the same temperature-concentration conditions. The redox potentials were measured using the combined redox electrode (Pt-Ag/AgCl) in equimolar Ce 4+/Ce 3+ solutions (i.e.[Ce 3+]=[Ce 4+]) in sulfuric acid electrolyte. The Ce 3+/Ce 4+ redox potentials significantly decrease (i.e. shift to more negative values) with rising sulfuric acid concentration; a small maximum is observed at 40 °C. Cyclic voltammetric experiments confirmed slow electrochemical kinetics of the Ce 3+/Ce 4+ redox reaction on carbon glassy electrodes (CGEs) in sulfuric acid solutions. The observed dependencies of solubilities, the redox potentials and the kinetics of Ce 3+/Ce 4+ redox reaction on sulfuric acid concentration are thought to be the result of inequivalent complexation of the two redox species by sulfate anions: the ceric ion is much more strongly bound to sulfate than is the cerous ion. The best temperature-concentration conditions for the RFB electrolytes appear to be 40 °C and 1 M sulfuric acid, where the relatively good solubility of both cerium species, the maximum of redox potentials, and the more or less satisfying stability of CGE s were found. Even so, the relatively low solubility of cerium salts in sulfuric acid media and slow redox kinetics of the Ce 3+/Ce 4+ redox reaction at carbon indicate that the Ce 3+/Ce 4+ may not be well suited for use in RFB technology.

Sorbents based on asbestos with a layer of an hydroxyethylcyclam derivative of PVC containing aquacomplexes of sulfuric acid or sodium hydroxide with aza-crown groups

NASA Astrophysics Data System (ADS)

Tsivadze, A. Yu.; Fridman, A. Ya.; Morozova, E. M.; Sokolova, N. P.; Voloshchuk, A. M.; Petukhova, G. A.; Bardyshev, I. I.; Gorbunov, A. M.; Polyakova, I. Ya.; Titova, V. N.; Yavich, A. A.; Novikov, A. K.; Petrova, N. V.

2016-07-01

Aquacomplexes of sulfuric acid and sodium hydroxide with aza-crown groups are synthesized in cavities of a sorbent from the porous layer of a PVC cyclam-derivative grafted onto fibers of asbestos fabric. The structure of sorbents with complexes is studied and their adsorption characteristics are determined. It is shown that the affinity of the developed surface toward ethanol, benzene, and hexane depends on the nature of complexes in the pore walls, and the volume of cavities formed as a result of the pores on the developed asbestos surface being coated with networks of aza-crown groups is larger than that of cavities with walls of aza-crown groups in the layers of a PVC cyclam derivative. Indicators of H+- and OH--conductivity of sorbents with complexes as electrochemical bridges are determined. It is shown that the major part of H+- and OH--ions moves through complexes with aza-crown groups in the region of cavities formed of pores on the surface of asbestos.

Passivating the sulfur vacancy in monolayer MoS2

NASA Astrophysics Data System (ADS)

Lu, Haichang; Kummel, Andrew; Robertson, John

2018-06-01

Various methods to passivate the sulfur vacancy in 2D MoS2 are modeled using density functional theory (DFT) to understand the passivation mechanism at an atomic scale. First, the organic super acid, bis(trifluoromethane)sulfonimide (TFSI) is a strong protonating agent, and it is experimentally found to greatly increase the photoluminescence efficiency. DFT simulations find that the effectiveness of passivation depends critically on the charge state and number of hydrogens donated by TFSI since this determines the symmetry of the defect complex. A symmetrical complex is formed by three hydrogen atoms bonding to the defect in a -1 charge state, and this gives no bandgap states and a Fermi level in the midgap. However, a charge state of +1 gives a lower symmetry complex with one state in the gap. One or two hydrogens also give complexes with gap states. Second, passivation by O2 can provide partial passivation by forming a bridge bond across the S vacancy, but it leaves a defect state in the lower bandgap. On the other hand, substitutional additions do not shift the vacancy states out of the gap.

Improved selectivity for Pb(II) by sulfur, selenium and tellurium analogues of 1,8-anthraquinone-18-crown-5: synthesis, spectroscopy, X-ray crystallography and computational studies.

PubMed

Mariappan, Kadarkaraisamy; Alaparthi, Madhubabu; Hoffman, Mariah; Rama, Myriam Alcantar; Balasubramanian, Vinothini; John, Danielle M; Sykes, Andrew G

2015-07-14

We report here a series of heteroatom-substituted macrocycles containing an anthraquinone moiety as a fluorescent signaling unit and a cyclic polyheteroether chain as the receptor. Sulfur, selenium, and tellurium derivatives of 1,8-anthraquinone-18-crown-5 (1) were synthesized by reacting sodium sulfide (Na2S), sodium selenide (Na2Se) and sodium telluride (Na2Te) with 1,8-bis(2-bromoethylethyleneoxy)anthracene-9,10-dione in a 1 : 1 ratio. The optical properties of the new compounds are examined and the sulfur and selenium analogues produce an intense green emission enhancement upon association with Pb(II) in acetonitrile. Selectivity for Pb(II) is markedly improved as compared to the oxygen analogue 1 which was also competitive for Ca(II) ion. UV-Visible and luminescence titrations reveal that 2 and 3 form 1 : 1 complexes with Pb(II), confirmed by single-crystal X-ray studies where Pb(II) is complexed within the macrocycle through coordinate covalent bonds to neighboring carbonyl, ether and heteroether donor atoms. Cyclic voltammetry of 2-8 showed classical, irreversible oxidation potentials for sulfur, selenium and tellurium heteroethers in addition to two one-electron reductions for the anthraquinone carbonyl groups. DFT calculations were also conducted on 1, 2, 3, 6, 6 + Pb(II) and 6 + Mg(II) to determine the trend in energies of the HOMO and the LUMO levels along the series.

Effective Dual Polysulfide Rejection by a Tannic Acid/FeIII Complex-Coated Separator in Lithium-Sulfur Batteries.

PubMed

Zhang, Hong; Lin, Chuner; Hu, Xuanhe; Zhu, Baoku; Yu, Dingshan

2018-04-18

The solubility behaviour of polysulfides in electrolyte solutions is a major bottleneck prior to the practical application of the lithium-sulfur battery. To address this issue, we fabricate a tannic acid/Fe III complex-coated polypropylene (PP) separator (TA/Fe III -PP separator) via a simple, fast, and green method. Benefiting from dual-confinement effects based on Lewis acid-base interactions between Fe III and polysulfides as well as the dipole-dipole interactions between rich phenol groups and polysulfides, the migration of polysulfides is effectively suppressed. Meanwhile, the porous structure of the PP separator is not destroyed by an additional coating layer. Thus, the TA/Fe III -PP separator can retain rapid lithium ion transport, eventually leading to a significant improvement in both the discharge capacity and rate performance of the corresponding lithium-sulfur cells. The cell with the TA/Fe III -PP separator presents a low capacity fade of 0.06% per cycle over 1000 cycles at 2.0 C, along with a high Coulombic efficiency of >97% over 300 cycles at 0.5 C. With respect to the one with the bare PP separator, the cell with the TA/Fe III -PP separator exhibits a 1.7-fold increase in the discharge capacity at 3.0 C. The proposed simple and economical approach shows great potential in constructing advanced separators to retard the shuttle effect of polysulfides for lithium-sulfur batteries.

Iron-sulfur cluster biogenesis in mammalian cells: new insights into the molecular mechanisms of cluster delivery

PubMed Central

Maio, Nunziata; Rouault, Tracey. A.

2014-01-01

Iron-sulfur (Fe-S) clusters are ancient, ubiquitous cofactors composed of iron and inorganic sulfur. The combination of the chemical reactivity of iron and sulfur, together with many variations of cluster composition, oxidation states and protein environments, enables Fe-S clusters to participate in numerous biological processes. Fe-S clusters are essential to redox catalysis in nitrogen fixation, mitochondrial respiration and photosynthesis, to regulatory sensing in key metabolic pathways (i. e. cellular iron homeostasis and oxidative stress response), and to the replication and maintenance of the nuclear genome. Fe-S cluster biogenesis is a multistep process that involves a complex sequence of catalyzed protein- protein interactions and coupled conformational changes between the components of several dedicated multimeric complexes. Intensive studies of the assembly process have clarified key points in the biogenesis of Fe-S proteins. However several critical questions still remain, such as: what is the role of frataxin? Why do some defects of Fe-S cluster biogenesis cause mitochondrial iron overload? How are specific Fe-S recipient proteins recognized in the process of Fe-S transfer? This review focuses on the basic steps of Fe-S cluster biogenesis, drawing attention to recent advances achieved on the identification of molecular features that guide selection of specific subsets of nascent Fe-S recipients by the cochaperone HSC20. Additionally, it outlines the distinctive phenotypes of human diseases due to mutations in the components of the basic pathway. PMID:25245479

Global detection and analysis of volatile components from sun-dried and sulfur-fumigated herbal medicine by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry.

PubMed

Cao, Gang; Cai, Hao; Cong, Xiaodong; Liu, Xiao; Ma, Xiaoqing; Lou, Yajing; Qin, Kunming; Cai, Baochang

2012-08-21

The sulfur-fumigation process can induce changes in the contents of volatile compounds and the chemical transformation of herbal medicines. Although literature has reported many methods for analyzing volatile target compounds from herbal medicine, all of them are largely limited to target compounds and sun-dried samples. This study provides a comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOF/MS) method based on a chemical profiling approach to identify non-target and target volatile compounds from sun-dried and sulfur-fumigated herbal medicine. Using Chrysanthemum morifolium as a model herbal medicine, the combined power of this approach is illustrated by the identification of 209 and 111 volatile compounds with match quality >80% from sun-dried and sulfur-fumigated Chrysanthemum morifolium, respectively. The study has also shown that sulfur-fumigated samples showed a significant loss of the main active compounds and a more destructive fingerprint profile compared to the sun-dried ones. 50 volatile compounds were lost in the sulfur-fumigated Chrysanthemum morifolium sample. The approach and methodology reported in this paper would be useful for identifying complicated target and non-target components from various complex mixtures such as herbal medicine and its preparations, biological and environmental samples. Furthermore, it can be applied for the intrinsic quality control of herbal medicine and its preparations.

NMR- and GC/MS-based metabolomics of sulfur mustard exposed individuals: a pilot study.

PubMed

Nobakht, B Fatemeh; Aliannejad, Rasoul; Rezaei-Tavirani, Mostafa; Arefi Oskouie, Afsaneh; Naseri, Mohammad Taghi; Parastar, Hadi; Aliakbarzadeh, Ghazaleh; Fathi, Fariba; Taheri, Salman

2016-09-01

Sulfur mustard (SM) is a potent alkylating agent and its effects on cells and tissues are varied and complex. Due to limitations in the diagnostics of sulfur mustard exposed individuals (SMEIs) by noninvasive approaches, there is a great necessity to develop novel techniques and biomarkers for this condition. We present here the first nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC/MS) metabolic profiling of serum from and healthy controls to identify novel biomarkers in blood serum for better diagnostics. Of note, SMEIs were exposed to SM 30 years ago and that differences between two groups could still be found. Pathways in which differences between SMEIs and healthy controls are observed are related to lipid metabolism, ketogenesis, tricarboxylic acid (TCA) cycle and amino acid metabolism.

Hydrogen sulfide in plants: from dissipation of excess sulfur to signaling molecule.

PubMed

Calderwood, Alexander; Kopriva, Stanislav

2014-09-15

Sulfur is essential in all organisms for the synthesis of amino acids cysteine and methionine and as an active component of numerous co-factors and prosthetic groups. However, only plants, algae, fungi, and some prokaryotes are capable of using the abundant inorganic source of sulfur, sulfate. Plants take sulfate up, reduce it, and assimilate into organic compounds with cysteine being the first product of the pathway and a donor of reduced sulfur for synthesis of other S-containing compounds. Cysteine is formed in a reaction between sulfide, derived from reduction of sulfite and an activated amino acid acceptor, O-acetylserine. Sulfide is thus an important intermediate in sulfur metabolism, but numerous other functions in plants has been revealed. Hydrogen sulfide can serve as an alternative source of sulfur for plants, which may be significant in anaerobic conditions of waterlogged soils. On the other hand, emissions of hydrogen sulfide have been detected from many plant species. Since the amount of H2S discharged correlated with sulfate supply to the plants, the emissions were considered a mechanism for dissipation of excess sulfur. Significant hydrogen sulfide emissions were also observed in plants infected with pathogens, particularly with fungi. H2S thus seems to be part of the widely discussed sulfur-induced-resistance/sulfur-enhanced-defense. Recently, however, more evidence has emerged for a role for H2S in regulation and signaling. Sulfide stabilizes the cysteine synthase complex, increasing so the synthesis of its acceptor O-acetylserine. H2S has been implicating in regulation of plant stress response, particularly draught stress. There are more and more examples of processes regulated by H2S in plants being discovered, and hydrogen sulfide is emerging as an important signaling molecule, similar to its role in the animal and human world. How similar the functions, and homeostasis of H2S are in these diverse organisms, however, remains to be elucidated. Copyright © 2014 Elsevier Inc. All rights reserved.

Metatranscriptomic analysis of prokaryotic communities active in sulfur and arsenic cycling in Mono Lake, California, USA.

PubMed

Edwardson, Christian F; Hollibaugh, James T

2017-10-01

This study evaluates the transcriptionally active, dissimilatory sulfur- and arsenic-cycling components of the microbial community in alkaline, hypersaline Mono Lake, CA, USA. We sampled five depths spanning the redox gradient (10, 15, 18, 25 and 31 m) during maximum thermal stratification. We used custom databases to identify transcripts of genes encoding complex iron-sulfur molybdoenzyme (CISM) proteins, with a focus on arsenic (arrA, aioA and arxA) and sulfur cycling (dsrA, aprA and soxB), and assigned them to taxonomic bins. We also report on the distribution of transcripts related to the ars arsenic detoxification pathway. Transcripts from detoxification pathways were not abundant in oxic surface waters (10 m). Arsenic cycling in the suboxic and microaerophilic zones of the water column (15 and 18 m) was dominated by arsenite-oxidizing members of the Gammaproteobacteria most closely affiliated with Thioalkalivibrio and Halomonas, transcribing arxA. We observed a transition to arsenate-reducing bacteria belonging to the Deltaproteobacteria and Firmicutes transcribing arsenate reductase (arrA) in anoxic bottom waters of the lake (25 and 31 m). Sulfur cycling at 15 and 18 m was dominated by Gammaproteobacteria (Thioalkalivibrio and Thioalkalimicrobium) oxidizing reduced S species, with a transition to sulfate-reducing Deltaproteobacteria at 25 and 31 m. Genes related to arsenic and sulfur oxidation from Thioalkalivibrio were more highly transcribed at 15 m relative to other depths. Our data highlight the importance of Thioalkalivibrio to arsenic and sulfur biogeochemistry in Mono Lake and identify new taxa that appear capable of transforming arsenic.

Iron-sulfur protein in mitochondrial complexes of Spodoptera litura as potential site for ROS generation.

PubMed

Li, Liangde; Dong, Xiaolin; Shu, Benshui; Wang, Zheng; Hu, Qiongbo; Zhong, Guohua

2014-12-01

Mitochondrial complex I is the main source of reactive oxygen species (ROS) production, but the exact site of superoxide generation or their relative contribution is not clear. This study aims to determine the function of iron-sulfur clusters (ISCU) in the initiation of ROS generation. ISCU2 and ISCU8 were cloned from Spodoptera litura which shared the conserved amino acid sequence with other insects. The expressions of the two genes were ubiquitous throughout the whole development stages and tissues. Knockdown of ISCU2 and ISCU8 resulted in the decline of the ROS, whereas rotenone and azadirachtin treatment up-regulated ROS levels by increasing mRNA expression. Furthermore, antioxidant enzyme activity of SOD and POD were up-regulated by rotenone and azadirachtin treatment and then declined after ISCU was silenced. Our results suggest the possibility that the molecules of ISCU2 and ISCU8 in complex I may serve as potential sites in the initiation of ROS generation. Copyright © 2014 Elsevier Ltd. All rights reserved.

The insecticide target in the PSST subunit of complex I.

PubMed

Schuler, F; Casida, J E

2001-10-01

Current insecticides have been selected by sifting and winnowing hundreds of thousands of synthetic chemicals and natural products to obtain commercial preparations of optimal effectiveness and safety. This process has often ended up with compounds of high potency as inhibitors of the electron transport chain and more specifically of complex I (NADH:ubiquinone oxidoreductase). Many classes of chemicals are involved and the enzyme is one of the most complicated known, with 43 subunits catalyzing electron transfer from NADH to ubiquinone through flavin mononucleotide and up to eight iron-sulfur clusters. We used a potent photoaffinity ligand, (trifluoromethyl)diazirinyl[3H]pyridaben, to localize the insecticide target to a single high-affinity site in the PSST subunit that couples electron transfer from iron-sulfur cluster N2 to ubiquinone. Most importantly, all of the potent complex I-inhibiting pesticides, despite their great structural diversity, compete for this same specific binding domain in PSST. Finding their common mode of action and target provides insight into shared toxicological features and potential selection for resistant pests.

Vacancy clustering and its dissociation process in electroless deposited copper films studied by monoenergetic positron beams

NASA Astrophysics Data System (ADS)

Uedono, A.; Yamashita, Y.; Tsutsui, T.; Dordi, Y.; Li, S.; Oshima, N.; Suzuki, R.

2012-05-01

Positron annihilation was used to probe vacancy-type defects in electroless deposited copper films. For as-deposited films, two different types of vacancy-type defects were found to coexist; these were identified as vacancy aggregates (V3-V4) and larger vacancy clusters (˜V10). After annealing at about 200 °C, the defects started to diffuse toward the surface and aggregate. The same tendency has been observed for sulfur only, suggesting the formation of complexes between sulfur and vacancies. The defect concentration near the Cu/barrier-metal interface was high even after annealing above 600 °C, and this was attributed to an accumulation of vacancy-impurity complexes. The observed defect reactions were attributed to suppression of the vacancy diffusion to sinks through the formation of impurity-vacancy complexes. It was shown that electroless plating has a high potential to suppress the formation of voids/hillocks caused by defect migration.

Amphorous hydrated Fe(III) sulfate: metastable product and bio-geochemical marker of iron oxidizing thiobacilli

NASA Astrophysics Data System (ADS)

Lazaroff, Norman; Jollie, John; Dugan, Patrick R.

1998-07-01

Chemolithotrophic iron oxidation by Thiobacillus ferrooxidans and other iron oxidizing thiobacilli produce an Fe(III) sulfato complex that polymerizes as x-ray amorphous filaments approximately 40 nm in diameter. The precursor complex in solutionis seen by ATR-FTIR spectroscopy to have a sulfate spectrum resembling the v(subscript 3) and v(subscript 1) vibrational modes of the precipitated polymer. Chemically similar precipitates prepared by oxidation of acid ferrous sulfate with hydrogen peroxide have a different micromorphology, higher iron/sulfur ratio and acid solubility than the bacterial product. They possess coalescing globular microstructures composed of compacted micro-fibrils. Scanning electron microscopy and diffuse reflectance FTIR show the formation of iron polymer on the surface of immobilized cells of T. ferrooxidans, oxidizing iron during the corrosion of steel. Although spatially separated form the steel coupons by a membrane filter, the cell walls become covered with tufts of amorphous hydrated Fe(III) sulfate. The metastable polymer is converted to crystalline goethite, lepidocrocite, and magnetite in that order, as the pH rises due to proton reduction at cathodic sites on the steel. The instability of the iron polymer to changes in pH is also evidenced by the loss of sulfate when washed with lithium hydroxide solution at pH 8. Under those conditions there is little change in micromorphology, but restoration of sulfate with sulfuric acid at pH 2.5, fails to re-establish the original chemical structure. Adding sulfate salts of appropriate cations to solutions of the Fe(III) sulfato complex or suspensions of its precipitated polymer in dilute sulfuric acid, result in dissociation of the metastable complex followed by crystallization of ferric ions and sulfate in jarosites. Jarosites and other derivatives of iron precipitation by iron oxidizing thiobacilli, form conspicuous deposits in areas of natural pyrite leaching. The role of iron oxidizing thiobacilli in pyrite leaching, biohydrometallurgy, acid mine drainage, and the cycle of iron and sulfur in nature, has been studied for nearly 50 years. The manifestation of those activities, so widespread on Earth, can be a clue for seeking evidence of life elsewhere.

The Biogeochemistry of Sulfur in Hydrothermal Systems

NASA Technical Reports Server (NTRS)

Schulte, Mitchell; Rogers, K. L.; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. Understanding how sulfur became prevalent in biochemical processes and many biomolecules requires knowledge of the reaction properties of sulfur-bearing compounds. We have previously estimated thermodynamic data for thiols, the simplest organic sulfur compounds, at elevated temperatures and pressures. If life began in hydrothermal environments, it is especially important to understand reactions at elevated temperatures among sulfur-bearing compounds and other organic molecules essential for the origin and persistence of life. Here we examine reactions that may have formed amino acids with thiols as reaction intermediates in hypothetical early Earth hydrothermal environments. (There are two amino acids, cysteine and methionine, that contain sulfur.) Our calculations suggest that significant amounts of some amino acids were produced in early Earth hydrothermal fluids, given reasonable concentrations H2, NH3, H2S and CO. For example, preliminary results indicate that glycine activities as high as 1 mmol can be reached in these systems at 100 C. Alanine formation from propanethiol is also a favorable reaction. On the other hand, the calculated equilibrium log activities of cysteine and serine from propanethiol are -21 and -19, respectively, at 100 C. These results indicate that while amino acid formation with thiols as intermediates is favored in some cases, other mechanisms may have been necessary to produce significant amounts of other amino acids. Coupled with our previous results for thiols, these studies imply that sulfur may have been easily incorporated into the organic geochemistry of early Earth hydrothermal systems, leading to its widespread use in biomolecules. Formation of more complex biomolecules in hydrothermal systems may have required sulfur-bearing organic compounds as reaction intermediates.

Software User’s Manual for the RAILCAR4.1 Toxic Industrial Chemical Source Characterization Program

DTIC Science & Technology

2015-04-01

average cloud area during formation as half of the final cloud area of  Dc2/4.    Since the equations for these parameters can be quite  complex , the...hydrogen chloride  propane (LPG)  chlorine  hydrogen  cyanide  sulfur dioxide  chlorine dioxide  hydrogen fluoride  sulfuric acid  cyanogen chloride

IR spectroscopic study of the chemical composition of epiphytic lichens

NASA Astrophysics Data System (ADS)

Meysurova, A. F.; Khizhnyak, S. D.; Pakhomov, P. M.

2011-11-01

Changes in the chemical composition of lichens exposed to pollutants are investigated by means of FTIR spectroscopy. According to model experiments, alkyl nitrates, ammonium salts, amines, and sulfones develop in the lichen thallus through the action of ammonia and nitric and sulfuric acids. Spectroscopic data of modeling experiments enabled nitrogen- and sulfur-containing substances to be identified as the main air pollutants in the vicinity of a pig-breeding complex and information to be obtained on the content of the pollutants and their impact on the lichens.

TNF-alpha Expression Patterns as Potential Molecular Biomarker for Human Skin Cells Exposed to Vesicant Chemical Warfare Agents: Sulfur Mustard (HD) and Lewisite (L)

DTIC Science & Technology

2004-01-01

First World War. It was Sabourin et al., 2000). Skin injuries caused by called Hun Stoffe by the Allies and given the HD are complex and involve... Sabourin et al., 2000, Kan et al., 2003) sup- port the involvement of TNF-cx in animal models such as mouse skin and hairless guinea References pigs... Sabourin CLK. Petrali JP. Casillas RP. Alteration in inflamma- Pharmacol Toxicol. 2003:92:20 4 -13. tory cytokine gene expression in sulfur mustard exposed

Increase of chromium tolerance in Scenedesmus acutus after sulfur starvation: Chromium uptake and compartmentalization in two strains with different sensitivities to Cr(VI).

PubMed

Marieschi, M; Gorbi, G; Zanni, C; Sardella, A; Torelli, A

2015-10-01

In photosynthetic organisms sulfate constitutes the main sulfur source for the biosynthesis of GSH and its precursor Cys. Hence, sulfur availability can modulate the capacity to cope with environmental stresses, a phenomenon known as SIR/SED (Sulfur Induced Resistance or Sulfur Enhanced Defence). Since chromate may compete for sulfate transport into the cells, in this study chromium accumulation and tolerance were investigated in relation to sulfur availability in two strains of the unicellular green alga Scenedesmus acutus with different Cr-sensitivities. Paradoxically, sulfur deprivation has been demonstrated to induce a transient increase of Cr-tolerance in both strains. Sulfur deprivation is known to enhance the sulfate uptake/assimilation pathway leading to important consequences on Cr-tolerance: (i) reduced chromate uptake due to the induction of high affinity sulfate transporters (ii) higher production of cysteine and GSH which can play a role both through the formation of unsoluble complexes and their sequestration in inert compartments. To investigate the role of the above mentioned mechanisms, Cr accumulation in total cells and in different cell compartments (cell wall, membranes, soluble and miscellaneous fractions) was analyzed in both sulfur-starved and unstarved cells. Both strains mainly accumulated chromium in the soluble fraction, but the uptake was higher in the wild-type. In this type a short period of sulfur starvation before Cr(VI) treatment lowered chromium accumulation to the level observed in the unstarved Cr-tolerant strain, in which Cr uptake seems instead less influenced by S-starvation, since no significant decrease was observed. The increase in Cr-tolerance following S-starvation seems thus to rely on different mechanisms in the two strains, suggesting the induction of a mechanism constitutively active in the Cr-tolerant strain, maybe a high affinity sulfate transporter also in the wild-type. Changes observed in the cell wall and membrane fractions suggest a strong involvement of these compartments in Cr-tolerance increase following S-starvation. Copyright © 2015 Elsevier B.V. All rights reserved.

Oligoanilines as a suppressor of polysulfide shuttling in lithium–sulfur batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chi-Hao; Chung, Sheng-Heng; Han, Pauline

The migration of small polysulfide (LiPS) chains through the porous polymeric separators seriously jeopardizes the cycle life and energy density of lithium–sulfur (Li–S) batteries. Herein, we present a new concept in which an organic oligoaniline, amine-capped aniline trimer (ACAT), serves as an effective suppressor of the LiPS migration in Li–S cells. The strong interaction between LiPS and ACAT facilitates the formation of bulky ACAT–LiPS complexes (organoLiPS complexes), which are then size-selectively sieved by the porous polymeric separators employed in Li–S cells. Thus, the addition of ACAT significantly ameliorates the electrochemical performances of Li–S batteries due to suppressed LiPS migration. Thismore » new concept offers a viable strategy to achieve practically viable Li–S batteries.« less

Oligoanilines as a suppressor of polysulfide shuttling in lithium–sulfur batteries

DOE PAGES

Chang, Chi-Hao; Chung, Sheng-Heng; Han, Pauline; ...

2017-07-25

The migration of small polysulfide (LiPS) chains through the porous polymeric separators seriously jeopardizes the cycle life and energy density of lithium–sulfur (Li–S) batteries. Herein, we present a new concept in which an organic oligoaniline, amine-capped aniline trimer (ACAT), serves as an effective suppressor of the LiPS migration in Li–S cells. The strong interaction between LiPS and ACAT facilitates the formation of bulky ACAT–LiPS complexes (organoLiPS complexes), which are then size-selectively sieved by the porous polymeric separators employed in Li–S cells. Thus, the addition of ACAT significantly ameliorates the electrochemical performances of Li–S batteries due to suppressed LiPS migration. Thismore » new concept offers a viable strategy to achieve practically viable Li–S batteries.« less

Functional Analyses of NSF1 in Wine Yeast Using Interconnected Correlation Clustering and Molecular Analyses

PubMed Central

Bessonov, Kyrylo; Walkey, Christopher J.; Shelp, Barry J.; van Vuuren, Hennie J. J.; Chiu, David; van der Merwe, George

2013-01-01

Analyzing time-course expression data captured in microarray datasets is a complex undertaking as the vast and complex data space is represented by a relatively low number of samples as compared to thousands of available genes. Here, we developed the Interdependent Correlation Clustering (ICC) method to analyze relationships that exist among genes conditioned on the expression of a specific target gene in microarray data. Based on Correlation Clustering, the ICC method analyzes a large set of correlation values related to gene expression profiles extracted from given microarray datasets. ICC can be applied to any microarray dataset and any target gene. We applied this method to microarray data generated from wine fermentations and selected NSF1, which encodes a C2H2 zinc finger-type transcription factor, as the target gene. The validity of the method was verified by accurate identifications of the previously known functional roles of NSF1. In addition, we identified and verified potential new functions for this gene; specifically, NSF1 is a negative regulator for the expression of sulfur metabolism genes, the nuclear localization of Nsf1 protein (Nsf1p) is controlled in a sulfur-dependent manner, and the transcription of NSF1 is regulated by Met4p, an important transcriptional activator of sulfur metabolism genes. The inter-disciplinary approach adopted here highlighted the accuracy and relevancy of the ICC method in mining for novel gene functions using complex microarray datasets with a limited number of samples. PMID:24130853

S-induced modifications of the optoelectronic properties of ZnO mesoporous nanobelts

PubMed Central

Fabbri, Filippo; Nasi, Lucia; Fedeli, Paolo; Ferro, Patrizia; Salviati, Giancarlo; Mosca, Roberto; Calzolari, Arrigo; Catellani, Alessandra

2016-01-01

The synthesis of ZnO porous nanobelts with high surface-to-volume ratio is envisaged to enhance the zinc oxide sensing and photocatalytic properties. Yet, controlled stoichiometry, doping and compensation of as-grown n-type behavior remain open problems for this compound. Here, we demonstrate the effect of residual sulfur atoms on the optical properties of ZnO highly porous, albeit purely wurtzite, nanobelts synthesized by solvothermal decomposition of ZnS hybrids. By means of combined cathodoluminescence analyses and density functional theory calculations, we attribute a feature appearing at 2.36 eV in the optical emission spectra to sulfur related intra-gap states. A comparison of different sulfur configurations in the ZnO matrix demonstrates the complex compensating effect on the electronic properties of the system induced by S-inclusion. PMID:27301986

Structure of the Ergothioneine-Biosynthesis Amidohydrolase EgtC.

PubMed

Vit, Allegra; Mashabela, Gabriel T; Blankenfeldt, Wulf; Seebeck, Florian P

2015-07-06

The ubiquitous sulfur metabolite ergothioneine is biosynthesized by oxidative attachment of a sulfur atom to the imidazole ring of Nα-trimethylhistidine. Most actinobacteria, including Mycobacterium tuberculosis, use γ-glutamyl cysteine as a sulfur donor. In subsequent steps the carbon scaffold of γ-glutamyl cysteine is removed by the glutamine amidohydrolase EgtC and the β-lyase EgtE. We determined the crystal structure of EgtC from Mycobacterium smegmatis in complex with its physiological substrate. The set of active site residues that define substrate specificity in EgtC are highly conserved, even in homologues that are not involved in ergothioneine production. This conservation is compounded by the phylogenetic distribution of EgtC-like enzymes indicates that their last common ancestor might have emerged for a purpose other than ergothioneine production. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transport capabilities of environmental Pseudomonads for sulfur compounds

DOE PAGES

Zerbs, Sarah; Korajczyk, Peter J.; Noirot, Philippe H.; ...

2017-01-27

Sulfur is an essential element in plant rhizospheres and microbial activity plays a key role in increasing the biological availability of sulfur in soil environments. To better understand the mechanisms facilitating the exchange of sulfur-containing molecules in soil, we profiled the binding specificities of eight previously uncharacterized ABC transporter solute-binding proteins from plant-associated Pseudomonads. A high-throughput screening procedure indicated eighteen significant organosulfur binding ligands, with at least one high-quality screening hit for each protein target. Calorimetric and spectroscopic methods were used to validate the best ligand assignments and catalog the thermodynamic properties of the protein-ligand interactions. Two novel high-affinity ligandmore » binding activities were identified and quantified in this set of solute binding proteins. Bacteria were cultured in minimal media with screening library components supplied as the sole sulfur sources, demonstrating that these organosulfur compounds can be metabolized and confirming the relevance of ligand assignments. These results expand the set of experimentally validated ligands amenable to transport by this ABC transporter family and demonstrate the complex range of protein-ligand interactions that can be accomplished by solute-binding proteins. As a result, characterizing new nutrient import pathways provides insight into Pseudomonad metabolic capabilities which can be used to further interrogate bacterial survival and participation in soil and rhizosphere communities.« less

Pt(ii) coordination complexes as visible light photocatalysts for the oxidation of sulfides using batch and flow processes.

PubMed

Casado-Sánchez, Antonio; Gómez-Ballesteros, Rocío; Tato, Francisco; Soriano, Francisco J; Pascual-Coca, Gustavo; Cabrera, Silvia; Alemán, José

2016-07-12

A new catalytic system for the photooxidation of sulfides based on Pt(ii) complexes is presented. The catalyst is capable of oxidizing a large number of sulfides containing aryl, alkyl, allyl, benzyl, as well as more complex structures such as heterocycles and methionine amino acid, with complete chemoselectivity. In addition, the first sulfur oxidation in a continuous flow process has been developed.

X-ray Absorption and Emission Spectroscopic Studies of [L2Fe2S2]n Model Complexes: Implications for the Experimental Evaluation of Redox States in Iron–Sulfur Clusters

PubMed Central

2016-01-01

Herein, a systematic study of [L2Fe2S2]n model complexes (where L = bis(benzimidazolato) and n = 2-, 3-, 4-) has been carried out using iron and sulfur K-edge X-ray absorption (XAS) and iron Kβ and valence-to-core X-ray emission spectroscopies (XES). These data are used as a test set to evaluate the relative strengths and weaknesses of X-ray core level spectroscopies in assessing redox changes in iron–sulfur clusters. The results are correlated to density functional theory (DFT) calculations of the spectra in order to further support the quantitative information that can be extracted from the experimental data. It is demonstrated that due to canceling effects of covalency and spin state, the information that can be extracted from Fe Kβ XES mainlines is limited. However, a careful analysis of the Fe K-edge XAS data shows that localized valence vs delocalized valence species may be differentiated on the basis of the pre-edge and K-edge energies. These findings are then applied to existing literature Fe K-edge XAS data on the iron protein, P-cluster, and FeMoco sites of nitrogenase. The ability to assess the extent of delocalization in the iron protein vs the P-cluster is highlighted. In addition, possible charge states for FeMoco on the basis of Fe K-edge XAS data are discussed. This study provides an important reference for future X-ray spectroscopic studies of iron–sulfur clusters. PMID:27097289

Zinc and cadmium complexes of a plant metallothionein under radical stress: desulfurisation reactions associated with the formation of trans-lipids in model membranes.

PubMed

Torreggiani, Armida; Domènech, Jordi; Orihuela, Ruben; Ferreri, Carla; Atrian, Sílvia; Capdevila, Mercè; Chatgilialoglu, Chryssostomos

2009-06-08

Metallothioneins (MTs) are sulfur-rich proteins capable of binding metal ions to give metal clusters. The metal-MT aggregates used in this work were Zn- and Cd-QsMT, where QsMT is an MT from the plant Quercus suber. Reactions of reductive reactive species (H(*) atoms and e(aq)(-)), produced by gamma irradiation of water, with Zn- and Cd-QsMT were carried out in both aqueous solutions and vesicle suspensions, and were characterized by different approaches. By using a biomimetic model based on unsaturated lipid vesicle suspensions, the occurrence of tandem protein/lipid damage was shown. The reactions of reductive reactive species with methionine residues and/or sulfur-containing ligands afford diffusible sulfur-centred radicals, which migrate from the aqueous phase to the lipid bilayer and transform the cis double bond of the oleate moiety into the trans isomer. Tailored experiments allowed the reaction mechanism to be elucidated in some detail. The formation of sulfur-centred radicals is accompanied by the modification of the metal-QsMT complexes, which were monitored by various spectroscopic and spectrometric techniques (Raman, CD, and ESI-MS). Attack of the H(*) atom and e(aq)(-) on the metal-QsMT aggregates can induce significant structural changes such as partial deconstruction and/or rearrangement of the metal clusters and breaking of the protein backbone. Substantial differences were observed in the behaviour of the Zn- and Cd-QsMT aggregates towards the reactive species, depending on the different folding of the polypeptide in these two cases.

An active Mitochondrial Complex II Present in Mature Seeds Contains an Embryo-Specific Iron-Sulfur Subunit Regulated by ABA and bZIP53 and Is Involved in Germination and Seedling Establishment.

PubMed

Restovic, Franko; Espinoza-Corral, Roberto; Gómez, Isabel; Vicente-Carbajosa, Jesús; Jordana, Xavier

2017-01-01

Complex II (succinate dehydrogenase) is an essential mitochondrial enzyme involved in both the tricarboxylic acid cycle and the respiratory chain. In Arabidopsis thaliana , its iron-sulfur subunit (SDH2) is encoded by three genes, one of them ( SDH2.3 ) being specifically expressed during seed maturation in the embryo. Here we show that seed SDH2.3 expression is regulated by abscisic acid (ABA) and we define the promoter region (-114 to +49) possessing all the cis -elements necessary and sufficient for high expression in seeds. This region includes between -114 and -32 three ABRE (ABA-responsive) elements and one RY-enhancer like element, and we demonstrate that these elements, although necessary, are not sufficient for seed expression, our results supporting a role for the region encoding the 5' untranslated region (+1 to +49). The SDH2.3 promoter is activated in leaf protoplasts by heterodimers between the basic leucine zipper transcription factors bZIP53 (group S1) and bZIP10 (group C) acting through the ABRE elements, and by the B3 domain transcription factor ABA insensitive 3 (ABI3). The in vivo role of bZIP53 is further supported by decreased SDH2.3 expression in a knockdown bzip53 mutant. By using the protein synthesis inhibitor cycloheximide and sdh2 mutants we have been able to conclusively show that complex II is already present in mature embryos before imbibition, and contains mainly SDH2.3 as iron-sulfur subunit. This complex plays a role during seed germination sensu-stricto since we have previously shown that seeds lacking SDH2.3 show retarded germination and now we demonstrate that low concentrations of thenoyltrifluoroacetone, a complex II inhibitor, also delay germination. Furthermore, complex II inhibitors completely block hypocotyl elongation in the dark and seedling establishment in the light, highlighting an essential role of complex II in the acquisition of photosynthetic competence and the transition from heterotrophy to autotrophy.

Non-zero Δ33S preserved in rocks from the Basal Ultramafic Sequence indicate crustal contamination in the most primitive magma of the Rustenburg Layered Suite (Bushveld Complex, South Africa)

NASA Astrophysics Data System (ADS)

Magalhaes, N.; Wilson, A.; Penniston-Dorland, S.; Farquhar, J.

2017-12-01

The sulfur isotope composition of the Rustenburg Layered Suite (RLS) of the Bushveld Complex is different than expected from a magma sourced from the mantle (Δ33S=0), as measurements indicate the presence of an Archean surface-derived sulfur component. The Basal Ultramafic Sequence (BUS) is thought to be the most primitive magma of the RLS, as it is the lowest in the stratigraphy, has the highest Mg# (>0.92) for primary phases (olivine and orthopyroxene), and is in direct contact with the Magaliesberg quartzite of the Pretoria Group.We have measured the composition of sulfides in rocks from the Lower Zone, Marginal Zone, and the BUS, which were sampled in a 2300m drill core from the Clapham area, in the eastern Bushveld Complex. While the rocks of the Lower Zone have a relatively homogeneous non-zero Δ33S of 0.065‰, comparable to previous findings, there is an abrupt increase in the value of Δ33S (up to +0.301‰) in the Marginal Zone, which may be consistent with the observation in hand sample of assimilation of country rocks. The BUS also shows a surface-derived signal (average of 0.040‰), which is the lowest measured for any zone of the RLS.The non-zero Δ33S found in the Basal Ultramafic Sequence is evidence of the contamination of the magma with surface-derived material. In the upper parts of the intrusion, the Δ33S signature relates to whole-rock Sr and Nd isotopes, and their relationship suggests multiple sources of contamination. However, the relationship between sulfur and in-situ strontium isotope compositions (plagioclase) in this section of the RLS is not as clear as it is further up in the stratigraphy. This might reflect small-scale processes during the magmatic chamber stage, different compositions of local wall rock compared to deeper contaminants, or the presence of decoupled behavior between the isotope systems.These differences in the sulfur isotope composition between the different stratigraphic layers have been preserved regardless of any late magmatic processes that may have occurred, which further supports that the sulfur isotope composition of the RLS was not fully homogenized at a later stage by fluid migration.

Sulfur compounds in therapy: Radiation-protective agents, amphetamines, and mucopolysaccharide sulfation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foye, W.O.

1992-09-01

Sulfur-containing compounds have been used in the search for whole-body radiation-protective compounds, in the design of amphetamine derivatives that retain appetite-suppressive effects but lack most behavioral effects characteristic of amphetamines, and in the search for the cause of kidney stone formation in recurrently stoneforming patients. Organic synthetic procedures were used to prepare radiation-protective compounds having a variety of sulfur-containing functional groups, and to prepare amphetamine derivatives having electron-attracting sulfur functions. In the case of the kidney stone causation research, isolation of urinary mucopolysaccharides (MPS) from recurrently stoneforming patients was carried out and the extent of sulfation of the MPS wasmore » determined by electrophoresis. Whole-body radiation-protective agents with a high degree of protection against lethal doses of gamma-radiation in mice were found in a series of quinolinium and pyridinium bis(methylthio) and methylthio amino derivatives. Mechanism studies showed that the copper complexes of these agents mimicked the beneficial action of superoxide dismutase. Electron-attracting sulfur-containing functions on amphetamine nitrogen, as well as 4'-amino nitrogen provided amphetamine derivatives with good appetite-suppressant effects and few or no adverse behavioral effects. Higher than normal levels of sulfation of the urinary MPS of stone formers suggested a cause for recurrent kidney stone formation. A sulfation inhibitor was found to prevent recurrence of stone formation and inhibit growth of existing stones. The inclusion of various sulfur-containing functions in organic molecules yielded compounds having whole-body radiation protection from lethal doses of gamma-radiation in animals. The presence of electron-attracting sulfur functions in amphetamine gave derivatives that retained appetite-suppressant effects and eliminated most adverse behavioral effects.« less

A Saturn-Like Complex Composed of Macrocyclic Oligothiophene and C60 Fullerene: Structure, Stability, and Photophysical Properties in Solution and the Solid State.

PubMed

Shimizu, Hideyuki; Park, Kyu Hyung; Otani, Hiroyuki; Aoyagi, Shinobu; Nishinaga, Tohru; Aso, Yoshio; Kim, Dongho; Iyoda, Masahiko

2018-03-12

A Saturn-like 1:1 complex composed of macrocyclic oligothiophene E-8T7A and C 60 fullerene (C 60 ) was synthesized to investigate the interaction between macrocyclic oligothiophenes and C 60 in solution and the solid state. Because the Saturn-like 1:1 complex E-8T7A⋅C 60 is mainly stabilized by van der Waals interactions between C 60 and the sulfur atoms of the E-8T7A macrocycle, C 60 is rather weakly incorporated inside the macro-ring in solution. However, in the solid state the Saturn-like 1:1 complex preferentially formed single crystals or nanostructured polymorphs. Interestingly, X-ray analysis and theoretical calculations exhibited hindered rotation of C 60 in the Saturn-like complex due to interactions between C 60 and the sulfur atoms. Furthermore, the photoinduced charge transfer (CT) interaction between E-8T7A and C 60 in solution was investigated by using femtosecond transient absorption (TA) spectroscopy. The ultrafast TA spectral changes in the photoinduced absorption bands were attributed to the CT process in the Saturn-like structure. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrolytic cleavage of both CS2 carbon-sulfur bonds by multinuclear Pd(II) complexes at room temperature

NASA Astrophysics Data System (ADS)

Jiang, Xuan-Feng; Huang, Hui; Chai, Yun-Feng; Lohr, Tracy Lynn; Yu, Shu-Yan; Lai, Wenzhen; Pan, Yuan-Jiang; Delferro, Massimiliano; Marks, Tobin J.

2017-02-01

Developing homogeneous catalysts that convert CS2 and COS pollutants into environmentally benign products is important for both fundamental catalytic research and applied environmental science. Here we report a series of air-stable dimeric Pd complexes that mediate the facile hydrolytic cleavage of both CS2 carbon-sulfur bonds at 25 °C to produce CO2 and trimeric Pd complexes. Oxidation of the trimeric complexes with HNO3 regenerates the dimeric starting complexes with the release of SO2 and NO2. Isotopic labelling confirms that the carbon and oxygen atoms of CO2 originate from CS2 and H2O, respectively, and reaction intermediates were observed by gas-phase and electrospray ionization mass spectrometry, as well as by Fourier transform infrared spectroscopy. We also propose a plausible mechanistic scenario based on the experimentally observed intermediates. The mechanism involves intramolecular attack by a nucleophilic Pd-OH moiety on the carbon atom of coordinated µ-OCS2, which on deprotonation cleaves one C-S bond and simultaneously forms a C-O bond. Coupled C-S cleavage and CO2 release to yield [(bpy)3Pd3(µ3-S)2](NO3)2 (bpy, 2,2‧-bipyridine) provides the thermodynamic driving force for the reaction.

2D polymeric cadmium(II) complexes containing 1,3-imidazolidine-2-thione (Imt) ligand, [Cd(Imt)(H2O)2(SO4)]n and [Cd(Imt)2(N3)2]n

NASA Astrophysics Data System (ADS)

Mahmood, Rashid; Ahmad, Saeed; Fettouhi, Mohammed; Roisnel, Thierry; Gilani, Mazhar Amjad; Mehmood, Kashif; Murtaza, Ghulam; Isab, Anvarhusein A.

2018-03-01

The present study aims at preparing and carrying out the structural investigation of two polymeric cadmium(II) complexes of imidazolidine-2-thione (Imt) based on sulfate or azide ions, [Cd(Imt)(H2O)2(SO4)]n (1) and [Cd(Imt)2(N3)2]n (2). The structures of the complexes were determined by single crystal X-ray analysis. Both compounds, 1 and 2 crystallize in the form of 2D coordination polymers and the cadmium(II) ion is six-coordinate having a distorted octahedral geometry in each compound. In 1, the metal ion is bonded to one sulfur atom of Imt and five oxygen atoms with two from water and three of bridging sulfate ions. In 2, the cadmium coordination sphere is completed by two Imt molecules binding through the sulfur atoms and four nitrogen atoms of bridging azide ions. The crystal structures are stabilized by intra and intermolecular hydrogen bonding interactions. The complexes were also characterized by IR and NMR spectroscopy and the spectroscopic data is consistent with the binding of the ligands.

Synthetic Models for Nickel-Iron Hydrogenase Featuring Redox-Active Ligands.

PubMed

Schilter, David; Gray, Danielle L; Fuller, Amy L; Rauchfuss, Thomas B

2017-05-01

The nickel-iron hydrogenase enzymes efficiently and reversibly interconvert protons, electrons, and dihydrogen. These redox proteins feature iron-sulfur clusters that relay electrons to and from their active sites. Reported here are synthetic models for nickel-iron hydrogenase featuring redox-active auxiliaries that mimic the iron-sulfur cofactors. The complexes prepared are Ni II (μ-H)Fe II Fe II species of formula [(diphosphine)Ni(dithiolate)(μ-H)Fe(CO) 2 (ferrocenylphosphine)] + or Ni II Fe I Fe II complexes [(diphosphine)Ni(dithiolate)Fe(CO) 2 (ferrocenylphosphine)] + (diphosphine = Ph 2 P(CH 2 ) 2 PPh 2 or Cy 2 P(CH 2 ) 2 PCy 2 ; dithiolate = - S(CH 2 ) 3 S - ; ferrocenylphosphine = diphenylphosphinoferrocene, diphenylphosphinomethyl(nonamethylferrocene) or 1,1'-bis(diphenylphosphino)ferrocene). The hydride species is a catalyst for hydrogen evolution, while the latter hydride-free complexes can exist in four redox states - a feature made possible by the incorporation of the ferrocenyl groups. Mixed-valent complexes of 1,1'-bis(diphenylphosphino)ferrocene have one of the phosphine groups unbound, with these species representing advanced structural models with both a redox-active moiety (the ferrocene group) and a potential proton relay (the free phosphine) proximal to a nickel-iron dithiolate.

Synthetic Models for Nickel–Iron Hydrogenase Featuring Redox-Active Ligands*

PubMed Central

Schilter, David; Gray, Danielle L.; Fuller, Amy L.; Rauchfuss, Thomas B.

2017-01-01

The nickel–iron hydrogenase enzymes efficiently and reversibly interconvert protons, electrons, and dihydrogen. These redox proteins feature iron–sulfur clusters that relay electrons to and from their active sites. Reported here are synthetic models for nickel–iron hydrogenase featuring redox-active auxiliaries that mimic the iron–sulfur cofactors. The complexes prepared are NiII(μ-H)FeIIFeII species of formula [(diphosphine)Ni(dithiolate)(μ-H)Fe(CO)2(ferrocenylphosphine)]+ or NiIIFeIFeII complexes [(diphosphine)Ni(dithiolate)Fe(CO)2(ferrocenylphosphine)]+ (diphosphine = Ph2P(CH2)2PPh2 or Cy2P(CH2)2PCy2; dithiolate = −S(CH2)3S−; ferrocenylphosphine = diphenylphosphinoferrocene, diphenylphosphinomethyl(nonamethylferrocene) or 1,1′-bis(diphenylphosphino)ferrocene). The hydride species is a catalyst for hydrogen evolution, while the latter hydride-free complexes can exist in four redox states – a feature made possible by the incorporation of the ferrocenyl groups. Mixed-valent complexes of 1,1′-bis(diphenylphosphino)ferrocene have one of the phosphine groups unbound, with these species representing advanced structural models with both a redox-active moiety (the ferrocene group) and a potential proton relay (the free phosphine) proximal to a nickel–iron dithiolate. PMID:28819328

Kinetic modeling of electron transfer reactions in photosystem I complexes of various structures with substituted quinone acceptors.

PubMed

Milanovsky, Georgy E; Petrova, Anastasia A; Cherepanov, Dmitry A; Semenov, Alexey Yu

2017-09-01

The reduction kinetics of the photo-oxidized primary electron donor P 700 in photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 were analyzed within the kinetic model, which considers electron transfer (ET) reactions between P 700 , secondary quinone acceptor A 1 , iron-sulfur clusters and external electron donor and acceptors - methylviologen (MV), 2,3-dichloro-naphthoquinone (Cl 2 NQ) and oxygen. PS I complexes containing various quinones in the A 1 -binding site (phylloquinone PhQ, plastoquinone-9 PQ and Cl 2 NQ) as well as F X -core complexes, depleted of terminal iron-sulfur F A /F B clusters, were studied. The acceleration of charge recombination in F X -core complexes by PhQ/PQ substitution indicates that backward ET from the iron-sulfur clusters involves quinone in the A 1 -binding site. The kinetic parameters of ET reactions were obtained by global fitting of the P 700 + reduction with the kinetic model. The free energy gap ΔG 0 between F X and F A /F B clusters was estimated as -130 meV. The driving force of ET from A 1 to F X was determined as -50 and -220 meV for PhQ in the A and B cofactor branches, respectively. For PQ in A 1A -site, this reaction was found to be endergonic (ΔG 0  = +75 meV). The interaction of PS I with external acceptors was quantitatively described in terms of Michaelis-Menten kinetics. The second-order rate constants of ET from F A /F B , F X and Cl 2 NQ in the A 1 -site of PS I to external acceptors were estimated. The side production of superoxide radical in the A 1 -site by oxygen reduction via the Mehler reaction might comprise ≥0.3% of the total electron flow in PS I.

Theoretical estimation of equilibrium sulfur isotope fractionations among aqueous sulfite species: Implications for isotope models of microbial sulfate reduction

NASA Astrophysics Data System (ADS)

Eldridge, D. L.; Farquhar, J.; Guo, W.

2015-12-01

Sulfite (sensu lato), an intermediate in a variety sulfur redox processes, plays a particularly important role in microbial sulfate reduction. It exists intracellularly as multiple species between sets of enzymatic reactions that transform sulfate to sulfide, with the exact speciation depending on pH, T, and ionic strength. However, the complex speciation of sulfite is ignored in current isotope partitioning models of microbial sulfate reduction and simplified solely to the pyramidal SO32- (sulfite sensu stricto), due to a lack of appropriate constraints. We theoretically estimated the equilibrium sulfur isotope fractionations (33S/32S, 34S/32S, 36S/32S) among all documented sulfite species in aqueous solution, including sulfite (SO32-), bisulfite isomers and dimers ((HS)O3-, (HO)SO2-, S2O52-), and SO2(aq), through first principles quantum mechanical calculations. The calculations were performed at B3LYP/6-31+G(d,p) level using cluster models with 30-40 water molecules surrounding the solute. Our calculated equilibrium fractionation factors compare well to the available experimental constraints and suggest that the minor and often-ignored tetrahedral (HS)O3- isomer of bisulfite strongly influences isotope partitioning behavior in the sulfite system under most environmentally relevant conditions, particularly fractionation magnitudes and unusual temperature dependence. For example, we predict that sulfur isotope fractionation between sulfite and bulk bisulfite in solution should have an apparent inverse temperature dependence due to the influence of (HS)O3- and its increased stability at higher temperatures. Our findings highlight the need to appropriately account for speciation/isomerization of sulfur species in sulfur isotope studies. We will also present similar calculation results of other aqueous sulfur compounds (e.g., H2S/HS-, SO42-, S2O32-, S3O62-, and poorly documented SO22- species), and discuss the implication of our results for microbial sulfate reduction models and other sulfur-redox processes in nature.

Effect of variable hydrothermal conditions on sulfur speciation and isotopic compositions mediated by two Thiomicrospira strains

NASA Astrophysics Data System (ADS)

Houghton, J.; Wills, E.; Fike, D. A.

2012-12-01

Microbially mediated reactions involving elemental sulfur in low temperature hydrothermal environments are a critical component of the net hydrothermal flux of sulfur to the global oceans. We assess here the physiological impact on sulfur speciation and isotopic composition of two microbial strains at a range of pH conditions consistent with the sharp gradients found in seafloor hydrothermal environments. Thiomicrospira thermophila and T. crunogena, both isolated from hydrothermal vents at East Pacific Rise, were grown with thiosulfate as the electron donor under aerobic, closed system conditions at controlled pH and optimal temperature (35°C). T. thermophila at pH 8 produced sulfate at a 1:1 ratio with thiosulfate consumption during exponential growth, with the ratio decreasing as pH decreases. This stoichiometric ratio decreases more steeply as a function of pH during metabolism by T. crunogena. Sulfate:thiosulfate ratios less than one indicate the production of alternative oxidized sulfur compounds such as polythionates. The rate of sulfate production is comparable in both strains and is dependent on pH, decreasing from 0.8mM/hr at pH 8 to 0.2mM/hr at pH 5.6. Fractionation of 34S expressed as Δ34S between reactant and product range from 0‰ to 3‰ for both sulfate and elemental sulfur produced, with no difference between products in pH buffered experiments (pH 5.6 and 8.0). However, in unbuffered experiments during which growth causes pH to decrease from 7 to below 4.5, Δ34S(S2O3-SO4) is consistently larger than Δ34S(S2O3-S) in both strains by a factor of 2. The metabolic activity of these (and similar) strains indicate that complex and cryptic sulfur cycling may be occurring in the subsurface, associated with only minimal variation in the δ34S isotopic composition of sulfate and elemental sulfur.

Implications of mercury speciation in thiosulfate treated plants.

PubMed

Wang, Jianxu; Feng, Xinbin; Anderson, Christopher W N; Wang, Heng; Zheng, Lirong; Hu, Tiandou

2012-05-15

Mercury uptake was induced in two cultivars of Brassica juncea under field conditions using thiosulfate. Analysis was conducted to better understand the mechanism of uptake, speciation of mercury in plants, and redistribution of mercury in the soil. Plant mercury and sulfur concentrations were increased after thiosulfate treatment, and a linear correlation between mercury and sulfur was observed. Mercury may be absorbed and transported in plants as the Hg-thiosulfate complex. The majority of mercury in treated plant tissues (two cultivars) was bound to sulfur in a form similar to β-HgS (66-94%). Remaining mercury was present in forms similar to Hg-cysteine (1-10%) and Hg-dicysteine (8-28%). The formation of β-HgS may relate to the transport and assimilation of sulfate in plant tissues. Mercury-thiosulfate complex could decompose to mercuric and sulfate ions in the presence of free protons inside the plasma membrane, while sulfide ions would be produced by the assimilation of sulfate. The concomitant presence of mercuric ions and S(2-) would precipitate β-HgS. The mercury concentration in the rhizosphere decreased in the treated relative to the nontreated soil. The iron/manganese oxide and organic-bound fractions of soil mercury were transformed to more bioavailable forms (soluble and exchangeable and specifically sorbed) and taken up by plants.

Formation of mercury sulfide from Hg(II)−thiolate complexes in natural organic matter

USGS Publications Warehouse

Alain Manceau,; Cyprien Lemouchi,; Mironel Enescu,; Anne-Claire Gaillot,; Martine Lanson,; Valerie Magnin,; Pieter Glatzel,; Poulin, Brett; Ryan, Joseph N.; Aiken, George R.; Isabelle Gautier-Lunea,; Kathryn L. Nagy,

2015-01-01

Methylmercury is the environmental form of neurotoxic mercury that is biomagnified in the food chain. Methylation rates are reduced when the metal is sequestered in crystalline mercury sulfides or bound to thiol groups in macromolecular natural organic matter. Mercury sulfide minerals are known to nucleate in anoxic zones, by reaction of the thiol-bound mercury with biogenic sulfide, but not in oxic environments. We present experimental evidence that mercury sulfide forms from thiol-bound mercury alone in aqueous dark systems in contact with air. The maximum amount of nanoparticulate mercury sulfide relative to thiol-bound mercury obtained by reacting dissolved mercury and soil organic matter matches that detected in the organic horizon of a contaminated soil situated downstream from Oak Ridge, TN, in the United States. The nearly identical ratios of the two forms of mercury in field and experimental systems suggest a common reaction mechanism for nucleating the mineral. We identified a chemical reaction mechanism that is thermodynamically favorable in which thiol-bound mercury polymerizes to mercury–sulfur clusters. The clusters form by elimination of sulfur from the thiol complexes via breaking of mercury–sulfur bonds as in an alkylation reaction. Addition of sulfide is not required. This nucleation mechanism provides one explanation for how mercury may be immobilized, and eventually sequestered, in oxygenated surface environments.

Emerging targets for treating sulfur mustard-induced injuries.

PubMed

Ahmad, Shama; Ahmad, Aftab

2016-06-01

Sulfur mustard (SM; bis-(2-chlororethyl) sulfide) is a highly reactive, potent warfare agent that has recently reemerged as a major threat to military and civilians. Exposure to SM is often fatal, primarily due to pulmonary injuries and complications caused by its inhalation. Profound inflammation, hypercoagulation, and oxidative stress are the hallmarks that define SM-induced pulmonary toxicities. Despite advances, effective therapies are still limited. This current review focuses on inflammatory and coagulation pathways that influence the airway pathophysiology of SM poisoning and highlights the complexity of developing an effective therapeutic target. © 2016 New York Academy of Sciences.

Synthesis, structure and reactivity of [Tm(Bu(t))]ZnH, a monomeric terminal zinc hydride compound in a sulfur-rich coordination environment: access to a heterobimetallic compound.

PubMed

Kreider-Mueller, Ava; Quinlivan, Patrick J; Rauch, Michael; Owen, Jonathan S; Parkin, Gerard

2016-02-07

The first terminal zinc hydride complex that features a sulfur-rich coordination environment, namely the tris(2-mercapto-1-tert-butylimidazolyl)hydroborato compound, [Tm(Bu(t))]ZnH, has been synthesized via the reaction of [Tm(Bu(t))]ZnOPh with PhSiH3. The Zn-H bond of [Tm(Bu(t))]ZnH is subject to insertion of CO2 and facile protolytic cleavage, of which the latter provides access to heterobimetallic [Tm(Bu(t))]ZnMo(CO)3Cp.

Acid rain impacts on calcium nutrition and forest health

Treesearch

Donald H. DeHayes; Paul G. Schaberg; Gary J. Hawley; G. Richard Strimbeck

1999-01-01

Forest ecosystems throughout the world are exposed to acid rain, a complex solution consisting largely of H+, SO42-, NH4+, and NO3- pollutant ions derived from sulfur and nitrogen oxides. Although the public in...

Human DNA polymerase ε is phosphorylated at serine-1940 after DNA damage and interacts with the iron-sulfur complex chaperones CIAO1 and MMS19

PubMed Central

Moiseeva, Tatiana; Gamper, Armin M.; Hood, Brian; Conrads, Thomas P.; Bakkenist, Christopher J.

2016-01-01

We describe a dynamic phosphorylation on serine-1940 of the catalytic subunit of human Pol ε, POLE1, following DNA damage. We also describe novel interactions between POLE1 and the iron-sulfur cluster assembly complex CIA proteins CIAO1 and MMS19. We show that serine-1940 is essential for the interaction between POLE1 and MMS19, but not POLE1 and CIAO1. No defect in either proliferation or survival was identified when POLE1 serine-1940 was mutated to alanine in human cells, even following treatment with DNA damaging agents. We conclude that serine-1940 phosphorylation and the interaction between serine-1940 and MMS19 are not essential functions in the C terminal domain of the catalytic subunit of DNA polymerase ε. PMID:27235625

Theoretical study of interactions between cysteine and perfluoropropanoic acid in gas and aqueous phase

NASA Astrophysics Data System (ADS)

Holmes, Tiffani M.; Doskocz, Jacek; Wright, Terrance; Hill, Glake A.

The interaction of perfluoropropanoic acid (PFPA) with the amino acid cysteine was investigated using density functional theory. Previous studies suggest that the peroxisome proliferator chemical, perfluorooctanoic acid, is circulated throughout the body by way of sulfur-containing amino acids. We present conformational analysis of the interactions of PFPA, a small model of perfluorooctanoic acid, with the sulfur-containing amino acid which occur by the process of hydrogen bonding, in which the hydrogen of the sulfhydryl group interacts with the carboxyl oxygen, and the amino nitrogen forms a hydrogen bond with the hydrogen of the bond OH group of the fluorinated alkyl. We also show in our structures a recently characterized weak nonbonded interaction between divalent sulfur and a main chain carboxyl oxygen in proteins. B3LYP calculated free energies and interaction energies predict low-energy, high-interaction conformations for complex systems of perfluorinated fatty acid interactions with cysteine.

Chiral Nickel(II) Complex Catalyzed Enantioselective Doyle-Kirmse Reaction of α-Diazo Pyrazoleamides.

PubMed

Lin, Xiaobin; Tang, Yu; Yang, Wei; Tan, Fei; Lin, Lili; Liu, Xiaohua; Feng, Xiaoming

2018-03-07

Although high enantioselectivity of [2,3]-sigmatropic rearrangement of sulfonium ylides (Doyle-Kirmse reaction) has proven surprisingly elusive using classic chiral Rh(II) and Cu(I) catalysts, in principle it is due to the difficulty in fine discrimination of the heterotopic lone pairs of sulfur and chirality inversion at sulfur of sulfonium ylides. Here, we show that the synergistic merger of new α-diazo pyrazoleamides and a chiral N, N'-dioxide-nickel(II) complex catalyst enables a highly enantioselective Doyle-Kirmse reaction. The pyrazoleamide substituent serves as both an activating and a directing group for the ready formation of a metal-carbene- and Lewis-acid-bonded ylide intermediate in the assistance of a dual-tasking nickel(II) complex. An alternative chiral Lewis-acid-bonded ylide pathway greatly improves the product enantiopurity even for the reaction of a symmetric diallylsulfane. The majority of transformations over a series of aryl- or vinyl-substituted α-diazo pyrazoleamindes and sulfides proceed rapidly (within 5-20 min in most cases) with excellent results (up to 99% yield and 96% ee), providing a breakthrough in enantioselective Doyle-Kirmse reaction.

Exome sequencing identifies NFS1 deficiency in a novel Fe-S cluster disease, infantile mitochondrial complex II/III deficiency.

PubMed

Farhan, Sali M K; Wang, Jian; Robinson, John F; Lahiry, Piya; Siu, Victoria M; Prasad, Chitra; Kronick, Jonathan B; Ramsay, David A; Rupar, C Anthony; Hegele, Robert A

2014-01-01

Iron-sulfur (Fe-S) clusters are a class of highly conserved and ubiquitous prosthetic groups with unique chemical properties that allow the proteins that contain them, Fe-S proteins, to assist in various key biochemical pathways. Mutations in Fe-S proteins often disrupt Fe-S cluster assembly leading to a spectrum of severe disorders such as Friedreich's ataxia or iron-sulfur cluster assembly enzyme (ISCU) myopathy. Herein, we describe infantile mitochondrial complex II/III deficiency, a novel autosomal recessive mitochondrial disease characterized by lactic acidemia, hypotonia, respiratory chain complex II and III deficiency, multisystem organ failure and abnormal mitochondria. Through autozygosity mapping, exome sequencing, in silico analyses, population studies and functional tests, we identified c.215G>A, p.Arg72Gln in NFS1 as the likely causative mutation. We describe the first disease in man likely caused by deficiency in NFS1, a cysteine desulfurase that is implicated in respiratory chain function and iron maintenance by initiating Fe-S cluster biosynthesis. Our results further demonstrate the importance of sufficient NFS1 expression in human physiology.

Versatile chelating behavior of benzil bis(thiosemicarbazone) in zinc, cadmium, and nickel complexes.

PubMed

López-Torres, Elena; Mendiola, Ma Antonia; Pastor, César J; Pérez, Beatriz Souto

2004-08-23

Reactions of benzil bis(thiosemicarbazone), LH(6), with M(NO(3))(2).nH(2)O (M = Zn, Cd, and Ni), in the presence of LiOH.H(2)O, show the versatile behavior of this molecule. The structure of the ligand, with the thiosemicarbazone moieties on opposite sides of the carbon backbone, changes to form complexes by acting as a chelating molecule. Complexes of these metal ions with empirical formula [MLH(4)] were obtained, although they show different molecular structures depending on their coordinating preferences. The zinc complex is the first example of a crystalline coordination polymer in which a bis(thiosemicarbazone) acts as bridging ligand, through a nitrogen atom, giving a 1D polymeric structure. The coordination sphere is formed by the imine nitrogen and sulfur atoms, and the remaining position, in a square-based pyramid, is occupied by an amine group of another ligand. The cadmium derivative shows the same geometry around the metal ion but consists of a dinuclear structure with sulfur atoms acting as a bridge between the metal ions. However, in the nickel complex LH(6) acts as a N(2)S(2) ligand yielding a planar structure for the nickel atom. The ligand and its complexes have been characterized by X-ray crystallography, microanalysis, mass spectrometry, IR, (1)H, and (13)C NMR spectroscopies and for the cadmium complex by (113)Cd NMR in solution and in the solid state.

Identification of a multi-protein reductive dehalogenase complex in Dehalococcoides mccartyi strain CBDB1 suggests a protein-dependent respiratory electron transport chain obviating quinone involvement.

PubMed

Kublik, Anja; Deobald, Darja; Hartwig, Stefanie; Schiffmann, Christian L; Andrades, Adarelys; von Bergen, Martin; Sawers, R Gary; Adrian, Lorenz

2016-09-01

Dehalococcoides mccartyi strain CBDB1 is an obligate organohalide-respiring bacterium using only hydrogen as electron donor and halogenated organics as electron acceptor. Here, we studied proteins involved in the respiratory chain under non-denaturing conditions. Using blue native gel electrophoresis (BN-PAGE), gel filtration and ultrafiltration an active dehalogenating protein complex with a molecular mass of 250-270 kDa was identified. The active subunit of reductive dehalogenase (RdhA) colocalised with a complex iron-sulfur molybdoenzyme (CISM) subunit (CbdbA195) and an iron-sulfur cluster containing subunit (CbdbA131) of the hydrogen uptake hydrogenase (Hup). No colocalisation between the catalytically active subunits of hydrogenase and reductive dehalogenase was found. By two-dimensional BN/SDS-PAGE the stability of the complex towards detergents was assessed, demonstrating stepwise disintegration with increasing detergent concentrations. Chemical cross-linking confirmed the presence of a higher molecular mass reductive dehalogenase protein complex composed of RdhA, CISM I and Hup hydrogenase and proved to be a potential tool for stabilising protein-protein interactions of the dehalogenating complex prior to membrane solubilisation. Taken together, the identification of the respiratory dehalogenase protein complex and the absence of indications for quinone participation in the respiration suggest a quinone-independent protein-based respiratory electron transfer chain in D. mccartyi. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Interfacial charge-transfer transitions in a TiO2-benzenedithiol complex with Ti-S-C linkages.

PubMed

Fujisawa, Jun-ichi; Muroga, Ryuki; Hanaya, Minoru

2015-11-28

Interfacial charge-transfer (ICT) transitions between organic materials and inorganic semiconductors are a new mechanism for light absorption at organic-semiconductor interfaces. ICT transitions cause one-step interfacial charge separation without loss of energy. This feature is potentially useful to realize efficient organic-inorganic hybrid solar cells. ICT transitions have been examined by employing titanium dioxide (TiO2) nanoparticles chemisorbed with π-conjugated molecules via Ti-O-C linkages. Here, we report ICT transitions in a TiO2 and 1,2-benzenedithiol (BDT) complex with Ti-S-C linkages. BDT adsorbs on TiO2 by the bridging bidentate coordination of the sulfur atoms to surface titanium atoms. The TiO2-BDT complex shows ICT transitions from the BDT moiety to the conduction band of TiO2 in the visible region. The ICT transitions occur by orbital overlaps between the d orbitals of the surface titanium atoms and the π orbitals of the benzene ring. Our density-functional-theory (DFT) analysis reveals that the 3p valence orbitals of the sulfur bridging atoms contribute to more than 50% of the highest occupied molecular orbital (HOMO) and the 3d-3p(sulfur)-π interaction via the Ti-S-C linkage enhances the electronic mixing between the titanium atoms and the benzene moiety as compared to the 3d-2p(oxygen)-πvia the Ti-O-C linkage. This result indicates the important role of the heavier-atom linkers for strong organic-inorganic electronic couplings.

SQUID-SIMS is a useful approach to uncover primary signals in the Archean sulfur cycle

NASA Astrophysics Data System (ADS)

Fischer, Woodward W.; Fike, David A.; Johnson, Jena E.; Raub, Timothy D.; Guan, Yunbin; Kirschvink, Joseph L.; Eiler, John M.

2014-04-01

Many aspects of Earth's early sulfur cycle, from the origin of mass-anomalous fractionations to the degree of biological participation, remain poorly understood-in part due to complications from postdepositional diagenetic and metamorphic processes. Using a combination of scanning high-resolution magnetic superconducting quantum interference device (SQUID) microscopy and secondary ion mass spectrometry (SIMS) of sulfur isotopes (32S, 33S, and 34S), we examined drill core samples from slope and basinal environments adjacent to a major Late Archean (∼2.6-2.5 Ga) marine carbonate platform from South Africa. Coupled with petrography, these techniques can untangle the complex history of mineralization in samples containing diverse sulfur-bearing phases. We focused on pyrite nodules, precipitated in shallow sediments. These textures record systematic spatial differences in both mass-dependent and mass-anomalous sulfur-isotopic composition over length scales of even a few hundred microns. Petrography and magnetic imaging demonstrate that mass-anomalous fractionations were acquired before burial and compaction, but also show evidence of postdepositional alteration 500 million y after deposition. Using magnetic imaging to screen for primary phases, we observed large spatial gradients in Δ33S (>4‰) in nodules, pointing to substantial environmental heterogeneity and dynamic mixing of sulfur pools on geologically rapid timescales. In other nodules, large systematic radial δ34S gradients (>20‰) were observed, from low values near their centers increasing to high values near their rims. These fractionations support hypotheses that microbial sulfate reduction was an important metabolism in organic-rich Archean environments-even in an Archean ocean basin dominated by iron chemistry.

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS.

PubMed

Lin, Zhiyong; Sun, Xiaoming; Peckmann, Jörn; Lu, Yang; Strauss, Harald; Xu, Li; Lu, Hongfeng; Teichert, Barbara M A

2017-08-31

Different sulfur isotope compositions of authigenic pyrite typically result from the sulfate-driven anaerobic oxidation of methane (SO4-AOM) and organiclastic sulfate reduction (OSR) in marine sediments. However, unravelling the complex pyritization sequence is a challenge because of the coexistence of different sequentially formed pyrite phases. This manuscript describes a sample preparation procedure that enables the use of secondary ion mass spectroscopy (SIMS) to obtain in situ δ 34 S values of various pyrite generations. This allows researchers to constrain how SO4-AOM affects pyritization in methane-bearing sediments. SIMS analysis revealed an extreme range in δ 34 S values, spanning from -41.6 to +114.8‰, which is much wider than the range of δ 34 S values obtained by the traditional bulk sulfur isotope analysis of the same samples. Pyrite in the shallow sediment mainly consists of 34 S-depleted framboids, suggesting early diagenetic formation by OSR. Deeper in the sediment, more pyrite occurs as overgrowths and euhedral crystals, which display much higher SIMS δ 34 S values than the framboids. Such 34 S-enriched pyrite is related to enhanced SO4-AOM at the sulfate-methane transition zone, postdating OSR. High-resolution in situ SIMS sulfur isotope analyses allow for the reconstruction of the pyritization processes, which cannot be resolved by bulk sulfur isotope analysis.

Advances in the measurement of sulfur isotopes by multi-collector ICP-MS (MC-ICP- MS)

NASA Astrophysics Data System (ADS)

Ridley, W. I.; Wilson, S. A.; Anthony, M. W.

2006-12-01

The demonstrated capability to measure 34S/32S by MC-ICP-MS with a precision (2ó) of ~0.2 per mil has many potential applications in geochemistry. However, a number of obstacles limit this potential. First, to achieve the precision indicated above requires sufficient mass resolution to separate isobaric interferences of 16O2 and 17O2 on 32S and 34S, respectively. These requirements for high resolution mean overall instrument sensitivity is reduced. Second, current methods preclude analysis of samples with complex matrices, a common characteristic of sulfur-bearing geologic materials. Here, we describe and discuss a method that provides both efficient removal of matrix constituents, and provides pre-concentration of S, thus overcoming these obstacles. The method involves the separation of sulfur from matrix constituents by high pressure (1000 psi) ion chromatography (HPIC), followed by isotope measurement using MC-ICP-MS. This combination allows for analysis of liquid samples with a wide range of S concentrations. A powerful advantage of this technique is the efficient separation of many sulfur species from matrix cations and anions (for instance in a seawater or acid mine drainage matrix), as well as the separation of sulfur species, e.g., sulfate, sulfite, thiosulfate, thiocynate, from each other for isotope analysis. The automated HPIC system uses a carbonate-bicarbonate eluent with eluent suppression, and has sufficient baseline separation to collect the various sulfur species as pure fractions. The individual fractions are collected over a specific time interval based upon a pre-determined elution profile and peak retention times. The addition of a second ion exchange column into the system allows pre-concentration of sulfur species by 2-3 orders of magnitude for samples that otherwise would have sulfur concentrations too low to provide precise isotopic ratios. The S isotope ratios are measured by MC-ICP-MS using a desolvating sample introduction system, a standard-sample bracketing method employing standards that are well characterized for sulfur isotope composition using stable isotope gas mass spectrometry. Data are collected in time-resolved mode, which reduces analytical time and allows for flexibility in data integration. Preliminary data indicates that sulfur species do not fractionate during the column chemistry.

Sulfur and iron geochemistry of the dynamic sedimentary system at the Costa Rica margin, IODP Expedition 344

NASA Astrophysics Data System (ADS)

Gott, C.; Riedinger, N.; Formolo, M.; Solomon, E. A.; Torres, M. E.; Bates, S. M.; Lyons, T. W.; 344 Scientific Party, I.

2013-12-01

One of the major targets of the CRISP (Costa Rica Seismogenesis Project) was to explore diagenetic processes, including fluid flow, related to the complex sedimentary and tectonic behavior of the Costa Rica margin system. Here we present preliminary results of the iron and sulfur geochemistry from sediments collected during the IODP Expedition 344 at Holes U1413B and U1414A. Our specific goal was to investigate the impact of this dynamic system on biogeochemical processes - especially regarding the sulfur cycle - and how minerals record these processes in the geologic record. The sediments at both investigated locations display non-steady state pore water conditions. Specifically, the deposits at Hole U1413B are characterized by a shallow sulfate-methane transition zone (SMTZ; approximately 15 mbsf), where released hydrogen sulfide reacts with reactive iron minerals to form iron sulfides. At Hole U1414A pore water sulfate is present at several hundreds of meters sediment depth, while the concentration of hydrogen sulfide is low (<4 μM). The measured concentrations of solid phase iron sulfides in the sediments indicate that pyrite is the main sulfur-bearing phase, reaching concentrations of 2 and 3 wt.%, in U1413B and U1414A, respectively. Sequential extractions of iron oxides reveal the presence of reactive iron phases, although in low concentrations (total iron oxides are below 1.1 wt.%), indicating ongoing alteration of iron oxides. The occurrence of these reactive iron minerals in the deeply buried sediments at Hole U1414A has implications for the deep biosphere - as those minerals can still be utilized by the microbial community. The non-steady state condition of the sedimentary system at both locations is also mirrored in the S-isotopic signal in the pore fluids as well as solid phase. The 34S-enriched sulfate (δ34S >+60 ‰) in the deeper sediment column is reflected in the δ34S profile of the in situ formed iron sulfides - the results can have implications for the interpretation of ancient rocks from similar active systems throughout Earth's history. Comparing the results of the investigated sediments at both sites, our data show variability, which may be caused by different sulfur sources and biogeochemical sulfur cycling driven by the tectonic and sedimentary complexity of the Costa Rica margin system.

Sulfur speciation and sulfide oxidation in the water column of the Black Sea

NASA Astrophysics Data System (ADS)

Luther, George W., III; Church, Thomas M.; Powell, David

We have applied sulfur speciation techniques to understand the chemistry and cycling of sulfur in Black Sea waters. The only reduced dissolved inorganic sulfur species detected (above the low minimum detection limits of the voltammetric methods employed) in the water column was hydrogen sulfide. The maximum concentration of sulfide (423 μM) is similar to previous reports. Using a cathodic stripping square wave voltammetry (CSSWV) method for nanomolar levels of sulfide, we determined the precise boundary between the "free" hydrogen sulfide (sulfidic) zone and the upper (oxic/suboxic) water column at the two stations studied. This boundary has apparently moved up by about 50 m in the past 20 years. Our results help demonstrate three chemically distinct zones of water in the central basin of the Black Sea: (1) the oxic [0-65 m], (2) the anoxic/nonsulfidic [65-100 m] and (3) the sulfidic [>100 m]. Sulfide bound to metals ("complexed" sulfide) is observed in both the oxic and anoxic/nonsulfidic zones of the water column. This supports previous studies on metal sulfide forms. From the electrochemical data, it is possible to estimate the strength of the complexation of sulfide to metals (log K = 10 to 11). Thiosulfate and sulfite were below our minimum detectable limit (MDL) of 50 nM using CSSWV. Elemental sulfur (MDL 5 nM) was detected below the onset of the hydrogen sulfide zone (90-100 m) with a maximum of 30-60 nM near 120 m. The sulfur speciation results for the Black Sea are lower by one order of magnitude or more than other marine systems such as the Cariaco Trench and salt marshes. New HPLC techniques were applied to detect thiols at submicromolar levels. The presence of thiols (2-mercaptoethylamine, 2-mercaptoethanol, N-acetylcysteine and glutathione) is correlated with the remineralization of organic matter at the oxic and anoxic/nonsulfidic interface. Water samples collected from the upper 50 m of the sulfidic zone showed significant sulfide oxidation on storage onboard ship even though they were filtered (0.2 μm) and handled to exclude oxygen contamination. Chemical additives such as formaldehyde, glutaraldehyde, hydroxylamine and ascorbic acid prevented or retarded the sulfide loss. Thiosulfate and azide did not inhibit sulfide loss. These studies suggest an anaerobic chemical oxidation of sulfide rather than a biological oxidation on stored and filtered samples.

Speciation And Uptake of Arsenic Accumulated By Corn Seedlings Using XAS And DRC-ICP-MS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, J.G.; Martinez-Martinez, A.; Peralta-Videa, J.R.

ICP-MS was used to investigate the uptake of As(III) and As(V) from hydroponics growth media by corn seedlings. It was found that arsenic uptake by the plant roots for the arsenic(V) and arsenic(III) treatments were 95 and 112 ppm, respectively. However, in the shoots of the arsenic (V) treatments had 18 ppm whereas arsenic(III) treatments had 12 ppm. XANES studies showed that As for both treatments arsenic was present as a mixture of an As(III) sulfur complex and an As(V) oxygen complex. The XANES data was corroborated by the EXAFS studies showing the presence of both oxygen and sulfur ligandsmore » coordinated to the arsenic. Iron concentrations were found to increase by 4 fold in the As(V) contaminated growth media and 7 fold in the As(III) treatment compared to the control iron concentration of 500 ppm. Whereas, the total iron concentration in the shoots was found to decrease by approximately the same amount for both treatments from 360 ppm in the control to approximately 125 ppm in both arsenic treatments. Phosphorus concentrations were found to decrease in both the roots and shoots compared to the control plants. The total sulfur in the roots was found to increase in the arsenic(III) and arsenic(V) treatments to 560 ppm and 800 ppm, respectively, compared to the control plants 358 ppm. In addition, the total sulfur in shoots of the plants was found to remain relatively constant at approximately 1080 ppm. The potassium concentrations in the plants were found to increase in the roots and decrease in the shoots.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourlier, Yoan; Cristini Robbe, Odile; Laboratoire de Physique des Lasers, Atomes et Molécules

Highlights: • CuIn{sub (1−x)}Ga{sub x}S{sub 2} thin films were prepared by sol–gel process. • Evolution of lattice parameters is characteristic of a solid solution. • Optical band gap was found to be linearly dependent on the gallium rate. - Abstract: In this paper, we report the elaboration of Cu(In,Ga)S{sub 2} chalcopyrite thin films via a sol–gel process. To reach this aim, solutions containing copper, indium and gallium complexes were prepared. These solutions were thereafter spin-coated onto the soda lime glass substrates and calcined, leading to metallic oxides thin films. Expected chalcopyrite films were finally obtained by sulfurization of oxides layersmore » using a sulfur atmosphere at 500 °C. The rate of gallium incorporation was studied both at the solutions synthesis step and at the thin films sulfurization process. Elemental and X-ray diffraction (XRD) analyses have shown the efficiency of monoethanolamine used as a complexing agent for the preparation of CuIn{sub (1−x)}Ga{sub x}S{sub 2} thin layers. Moreover, the replacement of diethanolamine by monoethanolamine has permitted the substitution of indium by isovalent gallium from x = 0 to x = 0.4 and prevented the precipitation of copper derivatives. XRD analyses of sulfurized thin films CuIn{sub (1−x)}Ga{sub x}S{sub 2,} clearly indicated that the increasing rate of gallium induced a shift of XRD peaks, revealing an evolution of the lattice parameter in the chalcopyrite structure. These results were confirmed by Raman analyses. Moreover, the optical band gap was also found to be linearly dependent upon the gallium rate incorporated within the thin films: it varies from 1.47 eV for x = 0 to 1.63 eV for x = 0.4.« less

Kinetic effects of sulfur oxidation on catalytic nitrile hydration: nitrile hydratase insights from bioinspired ruthenium(II) complexes.

PubMed

Kumar, Davinder; Nguyen, Tho N; Grapperhaus, Craig A

2014-12-01

Kinetic investigations inspired by the metalloenzyme nitrile hydratase were performed on a series of ruthenium(II) complexes to determine the effect of sulfur oxidation on catalytic nitrile hydration. The rate of benzonitrile hydration was quantified as a function of catalyst, nitrile, and water concentrations. Precatalysts L(n)RuPPh3 (n = 1-3; L(1) = 4,7-bis(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(2) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(3) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-sulfenato-propyl)-1-thia-4,7-diazacyclononane) were activated by substitution of triphenylphosphine with substrate in hot dimethylformamide solution. Rate measurements are consistent with a dynamic equilibrium between inactive aqua (L(n)Ru-OH2) and active nitrile (L(n)Ru-NCR) derivatives with K = 21 ± 1, 9 ± 0.9, and 23 ± 3 for L(1) to L(3), respectively. Subsequent hydration of the L(n)Ru-NCR intermediate yields the amide product with measured hydration rate constants (k's) of 0.37 ± 0.01, 0.82 ± 0.07, and 1.59 ± 0.12 M(-1) h(-1) for L(1) to L(3), respectively. Temperature dependent studies reveal that sulfur oxidation lowers the enthalpic barrier by 27 kJ/mol, but increases the entropic barrier by 65 J/(mol K). Density functional theory (DFT) calculations (B3LYP/LanL2DZ (Ru); 6-31G(d) (all other atoms)) support a nitrile bound catalytic cycle with lowering of the reaction barrier as a consequence of sulfur oxidation through enhanced nitrile binding and attack of the water nucleophile through a highly organized transition state.

Convenient, inexpensive quantification of elemental sulfur by simultaneous in situ reduction and colorimetric detection.

PubMed

Kwasniewski, Misha T; Allison, Rachel B; Wilcox, Wayne F; Sacks, Gavin L

2011-10-03

Rapid, inexpensive, and convenient methods for quantifying elemental sulfur (S(0)) with low or sub-μgg(-1) limits of detection would be useful for a range of applications where S(0) can act as a precursor for noxious off-aromas, e.g., S(0) in pesticide residues on winegrapes or as a contaminant in drywall. However, existing quantification methods rely on toxic reagents, expensive and cumbersome equipment, or demonstrate poor selectivity. We have developed and optimized an inexpensive, rapid method (∼15 min per sample) for quantifying S(0) in complex matrices. Following dispersion of the sample in PEG-400 and buffering, S(0) is quantitatively reduced to H(2)S in situ by dithiothreitol and simultaneously quantified by commercially available colorimetric H(2)S detection tubes. By employing multiple tubes, the method demonstrated linearity from 0.03 to 100 μg S(0) g(-1) for a 5 g sample (R(2)=0.994, mean CV=6.4%), and the methodological detection limit was 0.01 μg S(0) g(-1). Interferences from sulfite or sulfate were not observed. Mean recovery of an S(0) containing sulfur fungicide in grape macerate was 84.7% with a mean CV of 10.4%. Mean recovery of S(0) in a colloidal sulfur preparation from a drywall matrix was 106.6% with a mean CV of 6.9%. Comparable methodological detection limits, sensitivity, and recoveries were achieved in grape juice, grape macerate and with 1g drywall samples, indicating that the methodology should be robust across a range of complex matrices. Copyright © 2011 Elsevier B.V. All rights reserved.

Sulfur mobilization for Fe-S cluster assembly by the essential SUF pathway in the Plasmodium falciparum apicoplast and its inhibition.

PubMed

Charan, Manish; Singh, Nidhi; Kumar, Bijay; Srivastava, Kumkum; Siddiqi, Mohammad Imran; Habib, Saman

2014-06-01

The plastid of the malaria parasite, the apicoplast, is essential for parasite survival. It houses several pathways of bacterial origin that are considered attractive sites for drug intervention. Among these is the sulfur mobilization (SUF) pathway of Fe-S cluster biogenesis. Although the SUF pathway is essential for apicoplast maintenance and parasite survival, there has been limited biochemical investigation of its components and inhibitors of Plasmodium SUFs have not been identified. We report the characterization of two proteins, Plasmodium falciparum SufS (PfSufS) and PfSufE, that mobilize sulfur in the first step of Fe-S cluster assembly and confirm their exclusive localization to the apicoplast. The cysteine desulfurase activity of PfSufS is greatly enhanced by PfSufE, and the PfSufS-PfSufE complex is detected in vivo. Structural modeling of the complex reveals proximal positioning of conserved cysteine residues of the two proteins that would allow sulfide transfer from the PLP (pyridoxal phosphate) cofactor-bound active site of PfSufS. Sulfide release from the l-cysteine substrate catalyzed by PfSufS is inhibited by the PLP inhibitor d-cycloserine, which forms an adduct with PfSufS-bound PLP. d-Cycloserine is also inimical to parasite growth, with a 50% inhibitory concentration close to that reported for Mycobacterium tuberculosis, against which the drug is in clinical use. Our results establish the function of two proteins that mediate sulfur mobilization, the first step in the apicoplast SUF pathway, and provide a rationale for drug design based on inactivation of the PLP cofactor of PfSufS. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Supercritical carbon dioxide and sulfur in the Madison Limestone: A natural analog in southwest Wyoming for geologic carbon-sulfur co-sequestration

NASA Astrophysics Data System (ADS)

Kaszuba, John P.; Navarre-Sitchler, Alexis; Thyne, Geoffrey; Chopping, Curtis; Meuzelaar, Tom

2011-09-01

The Madison Limestone on the Moxa Arch, southwest Wyoming, USA contains large volumes (65-95%) of supercritical CO 2 that it has stored naturally for 50 million years. This reservoir also contains supercritical H 2S, aqueous sulfur complexes (SO 42- and HS -), and sulfur-bearing minerals (anhydrite and pyrite). Although SO 2 is not present, these sulfur-bearing phases are known products of SO 2 disproportionation in other water-rock systems. The natural co-occurrence of SO 42-, S 2-, supercritical CO 2 and brine affords the opportunity to evaluate the fate of a carbon-sulfur co-sequestration scenario. Mineralogic data was obtained from drill core and aqueous geochemical data from wells outside and within the current supercritical CO 2-sulfur-brine-rock system. In addition to dolomite, calcite, and accessory sulfur-bearing minerals, the Madison Limestone contains accessory quartz and the aluminum-bearing minerals feldspar, illite, and analcime. Dawsonite (NaAlCO 3(OH) 2), predicted as an important carbon sink in sequestration modeling studies, is not present. After confirming equilibrium conditions for the Madison Limestone system, reaction path models were constructed with initial conditions based on data from outside the reservoir. Addition of supercritical CO 2 to the Madison Limestone was simulated and the results compared to data from inside the reservoir. The model accurately predicts the observed mineralogy and captures the fundamental changes expected in a Madison Limestone-brine system into which CO 2 is added. pH decreases from 5.7 to 4.5 at 90 °C and to 4.0 at 110 °C, as expected from dissolution of supercritical CO 2, creation of carbonic acid, and buffering by the carbonate rock. The calculated redox potential increases by 0.1 V at 90 °C and 0.15 V at 110 °C due to equilibrium among CO 2, anhydrite, and pyrite. Final calculated Eh and pH match conditions for the co-existing sulfur phases present in produced waters and core from within the reservoir. Total dissolved solids increase with reaction progress, mostly due to dissolution of calcite with an accompanying increase in dissolved bicarbonate. The Madison Limestone is a natural example of the thermodynamic end point that similar fluid-rock systems will develop following emplacement of a supercritical CO 2-sulfur mixture and is a natural analog for geologic carbon-sulfur co-sequestration.

Silicon with an increased content of monoatomic sulfur centers: Sample fabrication and optical spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Astrov, Yu. A., E-mail: yuri.astrov@mail.ioffe.ru; Lynch, S. A.; Shuman, V. B.

2013-02-15

The effect of the high-temperature heating (at 1340 Degree-Sign C) of sulfur-doped silicon samples and their subsequent quenching is studied. The results of such a treatment are analyzed on the basis of Hall-effect data obtained in the temperature range T = 78-500 K. It is shown that the heating duration strongly affects the relative concentrations of different types of deep sulfur-related centers. At comparatively short heating durations of t = 2-10 min, the concentration of quasi-molecular S{sub 2} centers and S{sub X} complexes substantially decreases, whereas the density of monoatomic S{sub 1} centers grows. At the same time, the heatingmore » of a sample is accompanied by a monotonic decrease in the total concentration of electrically active sulfur over time. The results obtained make it possible to give recommendations concerning the optimal conditions for the fabrication of samples with a high concentration of S{sub 1} centers. The absorption spectra of the samples show that the method is promising for the observation of a number of quantum-optical effects involving deep S{sub 1} donors in silicon.« less

Inhibition of microbiological sulfide oxidation by methanethiol and dimethyl polysulfides at natron-alkaline conditions.

PubMed

van den Bosch, Pim L F; de Graaff, Marco; Fortuny-Picornell, Marc; van Leerdam, Robin C; Janssen, Albert J H

2009-06-01

To avoid problems related to the discharge of sulfidic spent caustics, a biotechnological process is developed for the treatment of gases containing both hydrogen sulfide and methanethiol. The process operates at natron-alkaline conditions (>1 mol L(-1) of sodium- and potassium carbonates and a pH of 8.5-10) to enable the treatment of gases with a high partial CO(2) pressure. In the process, methanethiol reacts with biologically produced sulfur particles to form a complex mixture predominantly consisting of inorganic polysulfides, dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS). The effect of these organic sulfur compounds on the biological oxidation of sulfide to elemental sulfur was studied with natron-alkaliphilic bacteria belonging to the genus Thioalkalivibrio. Biological oxidation rates were reduced by 50% at 0.05 mM methanethiol, while for DMDS and DMTS, this was estimated to occur at 1.5 and 1.0 mM, respectively. The inhibiting effect of methanethiol on biological sulfide oxidation diminished due to its reaction with biologically produced sulfur particles. This reaction increases the feasibility of biotechnological treatment of gases containing both hydrogen sulfide and methanethiol at natron-alkaline conditions.

Role of the Edge Properties in the Hydrogen Evolution Reaction on MoS2.

PubMed

Lazar, Petr; Otyepka, Michal

2017-04-06

Molybdenum disulfide, in particular its edges, has attracted considerable attention as possible substitute for platinum catalysts in the hydrogen evolution reaction (HER). The complex nature of the reaction complicates its detailed experimental investigations, which are mostly indirect and sample dependent. Therefore, density functional theory calculations were employed to study how the properties of the MoS 2 Mo-edge influence the thermodynamics of hydrogen adsorption onto the edge. The effect of the computational model (one-dimensional nanostripe), border symmetry imposed by its length, sulfur saturation of the edge, and dimensionality of the material are discussed. Hydrogen adsorption was found to depend critically on the coverage of extra sulfur at the Mo edge. The bare Mo-edge and fully sulfur-covered Mo-edge are catalytically inactive. The most favorable hydrogen binding towards HER was found for the Mo-edge covered by sulfur monomers. This edge provides hydrogen adsorption free energies positioned around -0.25 eV at up to 50 % hydrogen coverage, close to the experimental values of overpotential needed for the HER reaction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effects of organosulfur compounds upon the storage stability of Jet A fuel. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Heneman, F. C.

1981-01-01

This study examined the effect of sulfur-containing compounds on the storage stability of Jet A turbine fuel. It was found that alkyl sulfides and disulfides increased the fuel's stability while all thiols and thiophene derivatives tested decreased fuel stability (increased deposit formation) at temperatures and sulfur concentrations selected. Linear Arrhenius plots of sulfur-spiked fuel samples demonstrated that deposit formation decreased with increased slope for all alkyl sulfides, alkyl disulfides, thiols, and thiophene derivatives. A plot of insoluble deposit vs. concentration of added alkyl sulfide produces a negative slope. It appears that the inhibiting mechanism for alkyl sulfides is a result of the compound's reactivity with intermediate soluble precursors to deposit in the fuel. A method of approximating the relative basicity of weak organosulfur bases was developed via measurement of their resonance chemical shifts in proton NMR. Linear plots of log gm. deposit vs. change in chemical shift (shift differences between sulfur bases neat and complexed with I2) were found for alkyl sulfides and alkyl thiols. This suggests the possibility that increased deposit formation is due to base catalysis with these compound classes.

Asymmetric intramolecular Pauson-Khand reaction mediated by a remote sulfenyl or sulfinyl group.

PubMed

García Ruano, José Luis; Torrente, Esther; Parra, Alejandro; Alemán, José; Martín-Castro, Ana M

2012-08-03

In this work, we report the use of the asymmetric intramolecular Pauson-Khand reactions of 4-aryl-4-cyano-1,6-enynes for obtaining enantiomerically enriched bicyclo[3.3.0]octenones, and the influence of both the quaternary stereocenter and the sulfur functions located at ortho-position of the aryl group, on their stereoselectivity and reactivity. The sulfenyl derivatives bearing substituted or unsubstituted triple bonds and mono- and disubstituted alkene moieties afford bicyclo[3.3.0]octenones in high yields with complete diastereocontrol. These results are explained by assuming the association of the lone electron pair at sulfur to the Co-alkyne complexes.

Sulfur and Methylmercury in the Florida Everglades - the Biogeochemical Connection

NASA Astrophysics Data System (ADS)

Orem, W. H.; Gilmour, C. C.; Krabbenhoft, D. P.; Aiken, G.

2011-12-01

Methylmercury (MeHg) is a serious environmental problem in aquatic ecosystems worldwide because of its toxicity and tendency to bioaccumulate. The Everglades receives some of the highest levels of atmospheric mercury deposition and has some of the highest levels of MeHg in fish in the USA, posing a threat to pisciverous wildlife and people through fish consumption. USGS studies show that a combination of biogeochemical factors make the Everglades especially susceptible to MeHg production and bioaccumulation: (1) vast wetland area with anoxic soils supporting anaerobic microbial activity, (2) high rates of atmospheric mercury deposition, (3) high levels of dissolved organic carbon (DOC) that complexes and stabilizes mercury in solution for transport to sites of methylation, and (4) high sulfate loading in surface water that drives microbial sulfate reduction and mercury methylation. The high levels of sulfate in the Everglades represent an unnatural condition. Background sulfate levels are estimated to be <1 mg/L, but about 60% of the Everglades has surface water sulfate concentrations exceeding background. Highly sulfate-enriched marshes in the northern Everglades have average sulfate levels of 60 mg/L. Sulfate loading to the Everglades is principally a result of land and water management in south Florida. The highest concentrations of sulfate, averaging 60-70 mg/L, are in canal water in the Everglades Agricultural Area (EAA). Geochemical data and a preliminary sulfur mass balance for the EAA are consistent with sulfur currently used in agriculture, and sulfur released by oxidation of organic EAA soils (including legacy agricultural applications and natural sulfur) as the primary sources of sulfate enrichment to the canals and ecosystem. Sulfate loading increases microbial sulfate reduction and MeHg production in soils. The relationship between sulfate loading and MeHg production, however, is complex. Sulfate levels up to about 20-30 mg/L increase mercury methylation, but buildup of sulfide from microbial sulfate reduction begins to inhibit mercury methylation above this range. Sulfate from the EAA canals has primarily impacted the northern Everglades nearest the EAA, but recent evidence shows sulfate loading extending about 80 km further south into Everglades National Park. Current restoration plans to restore to deliver more water south to Everglades National Park may increase overall sulfur loads to the southern part of the ecosystem. A comprehensive Everglades restoration strategy should include reduction of sulfur loads as a goal because of the many detrimental impacts of sulfate on the ecosystem. Monitoring data show that the ecosystem response to changes in sulfate levels is rapid, and strategies for reducing sulfate loading may be effective in the near-term. A multifaceted approach employing best management practices for sulfur in agriculture, agricultural practices that minimize soil oxidation, and changes to stormwater treatment areas that increase sulfate retention, could help reduce sulfate loads to the Everglades, with resulting benefits.

Micronized coal-fired retrofit system for SO{sub x} reduction Krakow clean fossil fuels and energy efficiency program. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

This report describes results of a technical, financial and environmental assessment study for a project, which would have included a new TCS micronized coal-fired heating plant for the Produkcja I Hodowla Roslin Ogrodniczych (PHRO) Greenhouse Complex; Krzeszowice, Poland. Project site is about 20 miles west of Krakow, Poland. During the project study period, PHRO utilized 14 heavy oil-fired boilers to produce heat for its greenhouse facilities and also home heating to several adjacent apartment housing complexes. The boilers burn a high-sulfur content heavy crude oil, called mazute, The project study was conducted during a period extended from March 1996 throughmore » February 1997. For size orientation, the PHRO Greenhouse complex grows a variety of vegetables and flowers for the Southern Poland marketplace. The greenhouse area under glass is very large and equivalent to approximately 50 football fields, The new micronized coal fired boiler would have: (1) provided a significant portion of the heat for PHRO and a portion of the adjacent apartment housing complexes, (2) dramatically reduced sulfur dioxide air pollution emissions, while satisfying new Polish air regulations, and (3) provided attractive savings to PHRO, based on the quantity of displaced oil.« less

The deca-GX3 proteins Yae1-Lto1 function as adaptors recruiting the ABC protein Rli1 for iron-sulfur cluster insertion

PubMed Central

Paul, Viktoria Désirée; Mühlenhoff, Ulrich; Stümpfig, Martin; Seebacher, Jan; Kugler, Karl G; Renicke, Christian; Taxis, Christof; Gavin, Anne-Claude; Pierik, Antonio J; Lill, Roland

2015-01-01

Cytosolic and nuclear iron-sulfur (Fe-S) proteins are involved in many essential pathways including translation and DNA maintenance. Their maturation requires the cytosolic Fe-S protein assembly (CIA) machinery. To identify new CIA proteins we employed systematic protein interaction approaches and discovered the essential proteins Yae1 and Lto1 as binding partners of the CIA targeting complex. Depletion of Yae1 or Lto1 results in defective Fe-S maturation of the ribosome-associated ABC protein Rli1, but surprisingly no other tested targets. Yae1 and Lto1 facilitate Fe-S cluster assembly on Rli1 in a chain of binding events. Lto1 uses its conserved C-terminal tryptophan for binding the CIA targeting complex, the deca-GX3 motifs in both Yae1 and Lto1 facilitate their complex formation, and Yae1 recruits Rli1. Human YAE1D1 and the cancer-related ORAOV1 can replace their yeast counterparts demonstrating evolutionary conservation. Collectively, the Yae1-Lto1 complex functions as a target-specific adaptor that recruits apo-Rli1 to the generic CIA machinery. DOI: http://dx.doi.org/10.7554/eLife.08231.001 PMID:26182403

Pd(II) and Pt(II) complexes of α-keto stabilized sulfur ylide: Synthesis, structural, theoretical and catalytic activity studies

NASA Astrophysics Data System (ADS)

Sabounchei, Seyyed Javad; Hashemi, Ali; Sedghi, Asieh; Bayat, Mehdi; Akhlaghi Bagherjeri, Fateme; Gable, Robert W.

2017-05-01

Reaction of dimethyl sulfide with 2, 3‧-dibromoacetophenone led to formation of sulfonium salt [Me2SCH2C(O)C6H4-m-Br]Br (1). The resulted sulfonium salt was treated with NaOH and gave the α-keto stabilized sulfur ylide Me2SC(H)C(O)C6H4-m-Br (2). This ligand was reacted with [MCl2(cod)] (M = Pd, Pt; cod = 1,5-cyclooctadiene) to form the new cis- and trans-[MCl2(ylide)2] (M = Pd (cis- and trans-3), Pt (cis- and trans-4)) complexes. Characterization of the obtained compounds was performed by elemental analysis, IR, 1H and 13C NMR. Recrystallization of dichlorobis(ylide) palladium(II) and platinum(II) complexes from DMSO solution yielded the crystalline products, which X-ray diffraction data revealed that the both compounds were crystallized as cis-[MCl2(ylide)(DMSO)] (M = Pd (5), Pt (6)) complexes. Also, a theoretical study on structure and nature of the Msbnd C bonding between the Y ligand (ylide) and [MCl2·DMSO] fragments in [YMCl2·DMSO] (M = Pd, Pt) complexes has been reported via NBO and energy-decomposition analysis (EDA). Furthermore, the palladium catalyzed Suzuki-Miyaura reaction of various aryl chlorides with arylboronic acids was performed. The results showed that the Pd(II) complexes cis- and trans-3 catalyzed efficiently coupling reactions at low catalyst loading and short reaction time.

Effects of Calcium Ions on the Thermostability and Spectroscopic Properties of the LH1-RC Complex from a New Thermophilic Purple Bacterium Allochromatium tepidum.

PubMed

Kimura, Yukihiro; Lyu, Shuwen; Okoshi, Akira; Okazaki, Koudai; Nakamura, Natsuki; Ohashi, Akira; Ohno, Takashi; Kobayashi, Manami; Imanishi, Michie; Takaichi, Shinichi; Madigan, Michael T; Wang-Otomo, Zheng-Yu

2017-05-18

The light harvesting-reaction center (LH1-RC) complex from a new thermophilic purple sulfur bacterium Allochromatium (Alc.) tepidum was isolated and characterized by spectroscopic and thermodynamic analyses. The purified Alc. tepidum LH1-RC complex showed a high thermostability comparable to that of another thermophilic purple sulfur bacterium Thermochromatium tepidum, and spectroscopic characteristics similar to those of a mesophilic bacterium Alc. vinosum. Approximately 4-5 Ca 2+ per LH1-RC were detected by inductively coupled plasma atomic emission spectroscopy and isothermal titration calorimetry. Upon removal of Ca 2+ , the denaturing temperature of the Alc. tepidum LH1-RC complex dropped accompanied by a blue-shift of the LH1 Q y absorption band. The effect of Ca 2+ was also observed in the resonance Raman shift of the C3-acetyl νC═O band of bacteriochlorophyll-a, indicating changes in the hydrogen-bonding interactions between the pigment and LH1 polypeptides. Thermodynamic parameters for the Ca 2+ -binding to the Alc. tepidum LH1-RC complex indicated that this reaction is predominantly driven by the largely favorable electrostatic interactions that counteract the unfavorable negative entropy change. Our data support a hypothesis that Alc. tepidum may be a transitional organism between mesophilic and thermophilic purple bacteria and that Ca 2+ is one of the major keys to the thermostability of LH1-RC complexes in purple bacteria.

a Real-Time GIS Platform for High Sour Gas Leakage Simulation, Evaluation and Visualization

NASA Astrophysics Data System (ADS)

Li, M.; Liu, H.; Yang, C.

2015-07-01

The development of high-sulfur gas fields, also known as sour gas field, is faced with a series of safety control and emergency management problems. The GIS-based emergency response system is placed high expectations under the consideration of high pressure, high content, complex terrain and highly density population in Sichuan Basin, southwest China. The most researches on high hydrogen sulphide gas dispersion simulation and evaluation are used for environmental impact assessment (EIA) or emergency preparedness planning. This paper introduces a real-time GIS platform for high-sulfur gas emergency response. Combining with real-time data from the leak detection systems and the meteorological monitoring stations, GIS platform provides the functions of simulating, evaluating and displaying of the different spatial-temporal toxic gas distribution patterns and evaluation results. This paper firstly proposes the architecture of Emergency Response/Management System, secondly explains EPA's Gaussian dispersion model CALPUFF simulation workflow under high complex terrain and real-time data, thirdly explains the emergency workflow and spatial analysis functions of computing the accident influencing areas, population and the optimal evacuation routes. Finally, a well blow scenarios is used for verify the system. The study shows that GIS platform which integrates the real-time data and CALPUFF models will be one of the essential operational platforms for high-sulfur gas fields emergency management.

Sulfide-associated mineral assemblages in the Bushveld Complex, South Africa: platinum-group element enrichment by vapor refining by chloride-carbonate fluids

NASA Astrophysics Data System (ADS)

Kanitpanyacharoen, W.; Boudreau, A. E.

2013-02-01

The petrology of base metal sulfides and associated accessory minerals in rocks away from economically significant ore zones such as the Merensky Reef of the Bushveld Complex has previously received only scant attention, yet this information is critical in the evaluation of models for the formation of Bushveld-type platinum-group element (PGE) deposits. Trace sulfide minerals, primarily pyrite, pyrrhotite, pentlandite, and chalcopyrite are generally less than 100 microns in size, and occur as disseminated interstitial individual grains, as polyphase assemblages, and less commonly as inclusions in pyroxene, plagioclase, and olivine. Pyrite after pyrrhotite is commonly associated with low temperature greenschist alteration haloes around sulfide grains. Pyrrhotite hosted by Cr- and Ti-poor magnetite (Fe3O4) occurs in several samples from the Marginal to Lower Critical Zones below the platiniferous Merensky Reef. These grains occur with calcite that is in textural equilibrium with the igneous silicate minerals, occur with Cl-rich apatite, and are interpreted as resulting from high temperature sulfur loss during degassing of interstitial liquid. A quantitative model demonstrates how many of the first-order features of the Bushveld ore metal distribution could have developed by vapor refining of the crystal pile by chloride-carbonate-rich fluids during which sulfur and sulfide are continuously recycled, with sulfur moving from the interior of the crystal pile to the top during vapor degassing.

Fractionation of Sulfur Isotopes by Desulfovibrio vulgaris Mutants Lacking Periplasmic Hydrogenases or the Type I Tetraheme Cytochrome c3

NASA Astrophysics Data System (ADS)

Sim, M.; Ono, S.; Bosak, T.

2012-12-01

A large fraction of anaerobic mineralization of organic compounds relies on microbial sulfate reduction. Sulfur isotope fractionation by these microbes has been widely used to trace the biogeochemical cycling of sulfur and carbon, but intracellular mechanisms behind the wide range of fractionations observed in nature and cultures are not fully understood. In this study, we investigated the influence of electron transport chain components on the fractionation of sulfur isotopes by culturing Desulfovibrio vulgaris Hildenborough mutants lacking hydrogenases or type I tetraheme cytochrome c3 (Tp1-c3). The mutants were grown both in batch and continuous cultures. All tested mutants grew on lactate or pyruvate as the sole carbon and energy sources, generating sulfide. Mutants lacking cytoplasmic and periplasmic hydrogenases exhibited similar growth physiologies and sulfur isotope fractionations to their parent strains. On the other hand, a mutant lacking Tp1-c3 (ΔcycA) fractionated the 34S/32S ratio more than the wild type, evolving H2 in the headspace and exhibiting a lower specific respiration rate. In the presence of high concentrations of pyruvate, the growth of ΔcycA relied largely on fermentation rather than sulfate reduction, even when sulfate was abundant, producing the largest sulfur isotope effect observed in this study. Differences between sulfur isotope fractionation by ΔcycA and the wild type highlight the effect of electron transfer chains on the magnitude of sulfur isotope fractionation. Because Tp1-c3 is known to exclusively shuttle electrons from periplasmic hydrogenases to transmembrane complexes, electron transfers in the absence of Tp1-c3 should bypass the periplasmic hydrogen cycling, and the loss of reducing equivalents in the form of H2 can impair the flow of electrons from organic acids to sulfur, increasing isotope fractionation. Larger fractionation by ΔcycA can inform interpretations of sulfur isotope data at an environmental scale as well, because intracellular concentrations of electron transport components can be altered by environmental factors such as iron availability. Simultaneous sulfate reduction and fermentation, and their corresponding sulfur isotope effects, also generate a hypothesis that links sulfur isotope fractionation to the cellular energy budget. Theoretically, the largest fractionation during microbial sulfate reduction occurs when the backward fluxes equal the forward fluxes in sulfate reduction pathway. However, when the generation of ATP depends exclusively on sulfate respiration, a minimum respiration rate is required to fulfill the maintenance energy requirement. In contrast, when sulfate reduction occurs simultaneously with fermentation, the latter process may contribute toward maintenance energy, enabling slower and more reversible sulfate reduction, and leading to larger fractionation. Given that many sulfate-reducing microbes are also facultative fermenters, fermentation by sulfate reducing microbes in natural habitats and sulfur isotope signatures produced by such communities deserve further exploration.

Metal-Assisted Oxo Atom Addition to an Fe(III) Thiolate.

PubMed

Villar-Acevedo, Gloria; Lugo-Mas, Priscilla; Blakely, Maike N; Rees, Julian A; Ganas, Abbie S; Hanada, Erin M; Kaminsky, Werner; Kovacs, Julie A

2017-01-11

Cysteinate oxygenation is intimately tied to the function of both cysteine dioxygenases (CDOs) and nitrile hydratases (NHases), and yet the mechanisms by which sulfurs are oxidized by these enzymes are unknown, in part because intermediates have yet to be observed. Herein, we report a five-coordinate bis-thiolate ligated Fe(III) complex, [Fe III (S 2 Me2 N 3 (Pr,Pr))] + (2), that reacts with oxo atom donors (PhIO, IBX-ester, and H 2 O 2 ) to afford a rare example of a singly oxygenated sulfenate, [Fe III (η 2 -S Me2 O)(S Me2 )N 3 (Pr,Pr)] + (5), resembling both a proposed intermediate in the CDO catalytic cycle and the essential NHase Fe-S(O) Cys114 proposed to be intimately involved in nitrile hydrolysis. Comparison of the reactivity of 2 with that of a more electron-rich, crystallographically characterized derivative, [Fe III S 2 Me2 N Me N 2 amide (Pr,Pr)] - (8), shows that oxo atom donor reactivity correlates with the metal ion's ability to bind exogenous ligands. Density functional theory calculations suggest that the mechanism of S-oxygenation does not proceed via direct attack at the thiolate sulfurs; the average spin-density on the thiolate sulfurs is approximately the same for 2 and 8, and Mulliken charges on the sulfurs of 8 are roughly twice those of 2, implying that 8 should be more susceptible to sulfur oxidation. Carboxamide-ligated 8 is shown to be unreactive towards oxo atom donors, in contrast to imine-ligated 2. Azide (N 3 - ) is shown to inhibit sulfur oxidation with 2, and a green intermediate is observed, which then slowly converts to sulfenate-ligated 5. This suggests that the mechanism of sulfur oxidation involves initial coordination of the oxo atom donor to the metal ion. Whether the green intermediate is an oxo atom donor adduct, Fe-O═I-Ph, or an Fe(V)═O remains to be determined.

Unifying principles in homodimeric type I photosynthetic reaction centers: properties of PscB and the FA, FB and FX iron-sulfur clusters in green sulfur bacteria.

PubMed

Jagannathan, Bharat; Golbeck, John H

2008-12-01

The photosynthetic reaction center from the green sulfur bacterium Chlorobium tepidum (CbRC) was solubilized from membranes using Triton X-100 and isolated by sucrose density ultra-centrifugation. The CbRC complexes were subsequently treated with 0.5 M NaCl and ultrafiltered over a 100 kDa cutoff membrane. The resulting CbRC cores did not exhibit the low-temperature EPR resonances from FA- and FB- and were unable to reduce NADP+. SDS-PAGE and mass spectrometric analysis showed that the PscB subunit, which harbors the FA and FB clusters, had become dissociated, and was now present in the filtrate. Attempts to rebind PscB onto CbRC cores were unsuccessful. Mössbauer spectroscopy showed that recombinant PscB contains a heterogeneous mixture of [4Fe-4S]2+,1+ and other types of Fe/S clusters tentatively identified as [2Fe-2S]2+,1+ clusters and rubredoxin-like Fe3+,2+ centers, and that the [4Fe-4S]2+,1+ clusters which were present were degraded at high ionic strength. Quantitative analysis confirmed that the amount of iron and sulfide in the recombinant protein was sub-stoichiometric. A heme-staining assay indicated that cytochrome c551 remained firmly attached to the CbRC cores. Low-temperature EPR spectroscopy of photoaccumulated CbRC complexes and CbRC cores showed resonances between g=5.4 and 4.4 assigned to a S=3/2 ground spin state [4Fe-4S]1+ cluster and at g=1.77 assigned to a S=1/2 ground spin state [4Fe-4S]1+ cluster, both from FX-. These results unify the properties of the acceptor side of the Type I homodimeric reaction centers found in green sulfur bacteria and heliobacteria: in both, the FA and FB iron-sulfur clusters are present on a salt-dissociable subunit, and FX is present as an interpolypeptide [4Fe-4S]2+,1+ cluster with a significant population in a S=3/2 ground spin state.

SQUID–SIMS is a useful approach to uncover primary signals in the Archean sulfur cycle

PubMed Central

Fischer, Woodward W.; Fike, David A.; Johnson, Jena E.; Raub, Timothy D.; Guan, Yunbin; Kirschvink, Joseph L.; Eiler, John M.

2014-01-01

Many aspects of Earth’s early sulfur cycle, from the origin of mass-anomalous fractionations to the degree of biological participation, remain poorly understood—in part due to complications from postdepositional diagenetic and metamorphic processes. Using a combination of scanning high-resolution magnetic superconducting quantum interference device (SQUID) microscopy and secondary ion mass spectrometry (SIMS) of sulfur isotopes (32S, 33S, and 34S), we examined drill core samples from slope and basinal environments adjacent to a major Late Archean (∼2.6–2.5 Ga) marine carbonate platform from South Africa. Coupled with petrography, these techniques can untangle the complex history of mineralization in samples containing diverse sulfur-bearing phases. We focused on pyrite nodules, precipitated in shallow sediments. These textures record systematic spatial differences in both mass-dependent and mass-anomalous sulfur-isotopic composition over length scales of even a few hundred microns. Petrography and magnetic imaging demonstrate that mass-anomalous fractionations were acquired before burial and compaction, but also show evidence of postdepositional alteration 500 million y after deposition. Using magnetic imaging to screen for primary phases, we observed large spatial gradients in Δ33S (>4‰) in nodules, pointing to substantial environmental heterogeneity and dynamic mixing of sulfur pools on geologically rapid timescales. In other nodules, large systematic radial δ34S gradients (>20‰) were observed, from low values near their centers increasing to high values near their rims. These fractionations support hypotheses that microbial sulfate reduction was an important metabolism in organic-rich Archean environments—even in an Archean ocean basin dominated by iron chemistry. PMID:24706767

[The sources of inorganic sulfur in the process of cluster protein Fnr[4Fe-4S]2+ reconstruction in Escherichia coli cells cultivated with NO-donating agents].

PubMed

Vasil'eva, S V; Strel'tsova, D A; Vlaskina, A V; Mikoian, V D; Vanin, A F

2012-01-01

Dinitrosyl iron complexes (DNICs) with thiol ligands--binuclear and mononuclear--inhibited aidB gene expression in E. coli cells. This process is due to the nitrosylation of the active center in iron-sulfur protein Fnr [4Fe-4S]2+ by low-molecular DNICs. The next step is transformation of the above DNICs into the DNICs with the thiol groups in the apo-form of Fnr protein. These nitrosylated proteins are characterized by the EPR signal with g perpendicular = 2.04 and g parallel 1 = 2,014. An addition of sulfur containing L-Cys or N-A-L-Cys as well as Na2S to the cells lead to the increasing in the aidB gene expression simultaneously with an appearance of the EPR signal with g perpendicular = 2.04 and g parallel = 2.02 as the characteristics of the DNICs with persulfide (R-S-S-) ligands. We suppose that the recovery of the aidB gene activity was due to the accumulation of inorganic sulfur in the cells and reconstruction of the active center in Fnr[4Fe-4S]2+. It appears that the above process is the function of L-cysteine-desulfurase protein which repaired the active center of Fnr[4Fe-4S]2+ protein using the sulfur from L-Cys or N-A-L-Cys after its deacetylation. On the other side the ions of inorganic sulfur being reacted with SH-groups led to the transformation of DNIC with thiol ligands into the persulfides. Na2S was the most potent activator of the aidB gene expression in our experiments.

Copper thiobis(alkylphenols) and antioxidant compositions thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braid, M.

1980-09-30

Novel copper thiobis(alkylphenol-phenolate) complexes are effective antioxidant additives for various organic media such as oils of lubricating viscosity and plastics. Additionally these novel copper organo-sulfur compounds are highly useful as energy quenchers and antisludging agents in a variety of organic substrates.

Characterization of aromatic organosulfur model compounds relevant to fossil fuels by using atmospheric pressure chemical ionization with CS2 and high-resolution tandem mass spectrometry.

PubMed

Tang, Weijuan; Sheng, Huaming; Jin, Chunfen; Riedeman, James S; Kenttämaa, Hilkka I

2016-04-15

The chemistry of desulfurization involved in processing crude oil is greatly dependent on the forms of sulfur in the oil. Sulfur exists in different chemical bonding environments in fossil fuels, including those in thiophenes and benzothiophenes, thiols, sulfides, and disulfides. In this study, the fragmentation behavior of the molecular ions of 17 aromatic organosulfur compounds with various functionalities was systematically investigated by using high-resolution tandem mass spectrometry. Multiple-stage tandem mass spectrometric experiments were carried out using a linear quadrupole ion trap (LQIT) equipped with an atmospheric pressure chemical ionization (APCI) source. (+)APCI/CS2 was used to generate stable dominant molecular ions for all the compounds studied except for three sulfides that also showed abundant fragment ions. The LQIT coupled with an orbitrap mass spectrometer was used for elemental composition analysis, which facilitated the identification of the neutral molecules lost during fragmentation. The characteristic fragment ions generated in MS(2) and MS(3) experiments provide clues for the chemical bonding environment of sulfur atoms in the examined compounds. Upon collision-induced dissociation (CID), the molecular ions can lose the sulfur atom in a variety of ways, including as S (32 Da), HS(•) (33 Da), H2 S (34 Da), CS (44 Da), (•) CHS (45 Da) and CH2 S (46 Da). These neutral fragments are not only indicative of the presence of sulfur, but also of the type of sulfur present in the compound. Generally, losses of HS(•) and H2 S were found to be associated with compounds containing saturated sulfur functionalities, while losses of S, CS and (•) CHS were more common for heteroaromatic sulfur compounds. High-resolution tandem mass spectrometry with APCI/CS2 ionization is a viable approach to determining the types of organosulfur compounds. It can potentially be applied to analysis of complex mixtures, which is beneficial to improving the desulfurization process of fossil fuels. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Extracting metal ions with diphosphonic acid, or derivative thereof

DOEpatents

Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

1994-07-26

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulfur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

Identification of the iron-sulfur center of spinach ferredoxin-nitrite reductase as a tetranuclear center, and preliminary EPR studies of mechanism.

PubMed

Lancaster, J R; Vega, J M; Kamin, H; Orme-Johnson, N R; Orme-Johnson, W H; Krueger, R J; Siegel, L M

1979-02-25

EPR spectroscopic and chemical analyses of spinach nitrite reductase show that the enzyme contains one reducible iron-sulfur center, and one site for binding either cyanide or nitrite, per siroheme. The heme is nearly all in the high spin ferric state in the enzyme as isolated. The extinction coefficient of the enzyme has been revised to E386 = 7.6 X 10(4) cm-1 (M heme)-1. The iron-sulfur center is reduced with difficulty by agents such as reduced methyl viologen (equilibrated with 1 atm of H2 at pH 7.7 in the presence of hydrogenase) or dithionite. Complexation of the enzyme with CO (a known ligand for nitrite reductase heme) markedly increases the reducibility of the iron-sulfur center. New chemical analyses and reinterpretation of previous data show that the enzyme contains 6 mol of iron and 4 mol of acid-labile S2-/mol of siroheme. The EPR spectrum of reduced nitrite reductase in 80% dimethyl sulfoxide establishes clearly that the enzyme contains a tetranuclear iron-sulfur (Fe4S4) center. The ferriheme and Fe4S4 centers are reduced at similar rates (k = 3 to 4 s-1) by dithionite. The dithionite-reduced Fe4S4 center is rapidly (k = 100 s-1) reoxidized by nitrite. These results indicate a role for the Fe4S4 center in catalysis.

Near-Zero Emissions Oxy-Combustion Flue Gas Purification Task 2: SOx/Nox/Hg Removal for High Sulfur Coal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nick Degenstein; Minish Shah; Doughlas Louie

2012-05-01

The goal of this project is to develop a near-zero emissions flue gas purification technology for existing PC (pulverized coal) power plants that are retrofitted with oxy-combustion technology. The objective of Task 2 of this project was to evaluate an alternative method of SOx, NOx and Hg removal from flue gas produced by burning high sulfur coal in oxy-combustion power plants. The goal of the program was not only to investigate a new method of flue gas purification but also to produce useful acid byproduct streams as an alternative to using a traditional FGD and SCR for flue gas processing.more » During the project two main constraints were identified that limit the ability of the process to achieve project goals. 1) Due to boiler island corrosion issues >60% of the sulfur must be removed in the boiler island with the use of an FGD. 2) A suitable method could not be found to remove NOx from the concentrated sulfuric acid product, which limits sale-ability of the acid, as well as the NOx removal efficiency of the process. Given the complexity and safety issues inherent in the cycle it is concluded that the acid product would not be directly saleable and, in this case, other flue gas purification schemes are better suited for SOx/NOx/Hg control when burning high sulfur coal, e.g. this project's Task 3 process or a traditional FGD and SCR.« less

Recycling of water, carbon, and sulfur during subduction of serpentinites: A stable isotope study of Cerro del Almirez, Spain

NASA Astrophysics Data System (ADS)

Alt, Jeffrey C.; Garrido, Carlos J.; Shanks, W. C.; Turchyn, Alexandra; Padrón-Navarta, José Alberto; López Sánchez-Vizcaíno, Vicente; Gómez Pugnaire, María Teresa; Marchesi, Claudio

2012-04-01

We use the concentrations and isotope compositions of water, carbon, and sulfur in serpentinites and their dehydration products to trace the cycling of volatiles during subduction. Antigorite serpentinites from the Cerro del Almirez complex, Spain, contain 9-12 wt.% H2O and 910 ± 730 ppm sulfur, and have bulk δ18O values of 8.6 ± 0.4‰, δD = - 54 ± 5‰, and δ34S = 5.0‰, consistent with serpentinization at temperatures of ~ 200 °C by seawater hydrothermal fluids in a seafloor setting. The serpentinites were dehydrated to chlorite-harzburgite (olivine + orthopyroxene + chlorite) at 700 °C and 1.6-1.9 GPa during subduction metamorphism, resulting in loss of water, and sulfur. The chlorite-harzburgites contain 5.7 ± 1.9 wt.% H2O, and have bulk δ18O = 8.0 ± 0.9‰, and δD = - 77 ± 11‰. The rocks contain 650 ± 620 ppm sulfur having δ34S = 1.2‰. Dehydration of serpentinite resulted in loss of 5 wt.% H2O having δ18O = 8-10‰ and δD = - 27 to - 65‰, and loss of 260 ppm sulfur as sulfate, having δ34S = 14.5‰. The contents and δ13C of total carbon in the two rock types overlap, with a broad trend of decreasing carbon contents and δ13C from ~ 1300 to 200 ppm and - 9.6 to - 20.2‰. This reflects mixing between reduced carbon in the rocks (210 ppm, δ13C ≈ - 26‰) and seawater-derived carbonate (δ13C ≈ - 1‰). Our results indicate: 1) Serpentinized oceanic peridotites carry significant amounts of isotopically fractionated water, carbon and sulfur into subduction zones; 2) Subduction of serpentinites to high P and T results in loss of water, and sulfur, which can induce melting and contribute to 18O, D, and 34S enrichments and oxidation of the sub-arc mantle wedge; and 3) Isotopically fractionated water, carbon, and sulfur in serpentinite dehydration products are recycled deeper into the mantle where they can contribute to isotope heterogeneities and may be significant for volatile budgets of the deep Earth.

Recycling of water, carbon, and sulfur during subduction of serpentinites: A stable isotope study of Cerro del Almirez, Spain

USGS Publications Warehouse

Alt, Jeffrey C.; Garrido, Carlos J.; Shanks, Wayne C.; Turchyn, Alexandra; Padrón-Navarta, José Alberto; López Sánchez-Vizcaíno, Vicente; Gómez Pugnaire, María Teresa; Marchesi, Claudio

2012-01-01

We use the concentrations and isotope compositions of water, carbon, and sulfur in serpentinites and their dehydration products to trace the cycling of volatiles during subduction. Antigorite serpentinites from the Cerro del Almirez complex, Spain, contain 9–12 wt.% H2O and 910 ± 730 ppm sulfur, and have bulk δ18O values of 8.6 ± 0.4‰, δD = − 54 ± 5‰, and δ34S = 5.0‰, consistent with serpentinization at temperatures of ~ 200 °C by seawater hydrothermal fluids in a seafloor setting. The serpentinites were dehydrated to chlorite–harzburgite (olivine + orthopyroxene + chlorite) at 700 °C and 1.6–1.9 GPa during subduction metamorphism, resulting in loss of water, and sulfur. The chlorite–harzburgites contain 5.7 ± 1.9 wt.% H2O, and have bulk δ18O = 8.0 ± 0.9‰, and δD = − 77 ± 11‰. The rocks contain 650 ± 620 ppm sulfur having δ34S = 1.2‰. Dehydration of serpentinite resulted in loss of 5 wt.% H2O having δ18O = 8–10‰ and δD = − 27 to − 65‰, and loss of 260 ppm sulfur as sulfate, having δ34S = 14.5‰. The contents and δ13C of total carbon in the two rock types overlap, with a broad trend of decreasing carbon contents and δ13C from ~ 1300 to 200 ppm and − 9.6 to − 20.2‰. This reflects mixing between reduced carbon in the rocks (210 ppm, δ13C ≈ − 26‰) and seawater-derived carbonate (δ13C ≈ − 1‰). Our results indicate: 1) Serpentinized oceanic peridotites carry significant amounts of isotopically fractionated water, carbon and sulfur into subduction zones; 2) Subduction of serpentinites to high P and T results in loss of water, and sulfur, which can induce melting and contribute to 18O, D, and 34S enrichments and oxidation of the sub-arc mantle wedge; and 3) Isotopically fractionated water, carbon, and sulfur in serpentinite dehydration products are recycled deeper into the mantle where they can contribute to isotope heterogeneities and may be significant for volatile budgets of the deep Earth.

Therapeutic options to treat sulfur mustard poisoning--the road ahead.

PubMed

Smith, William J

2009-09-01

For the past 15 years the international research community has conducted a basic and applied research program aimed at identifying a medical countermeasure against chemical threat vesicant, or blistering, agents. The primary emphasis of this program has been the development of therapeutic protection against sulfur mustard and its cutaneous pathology-blister formation. In addition to the work on a medical countermeasures, significant research has been conducted on the development of topical skin protectants and medical strategies for wound healing. This review will focus on the pharmacological strategies investigated, novel therapeutic targets currently under investigation and therapeutic approaches being considered for transition to advanced development. Additionally, we will review the expansion of our understanding of the pathophysiological mechanisms of mustard injury that has come from this research. While great strides have been made through these investigations, the complexity of the mustard insult demands that further studies extend the inroads made and point the way toward better understanding of cellular and tissue disruptions caused by sulfur mustard.

Interpretation of the photoelectron spectra of FeS(2)(-) by a multiconfiguration computational approach.

PubMed

Clima, Sergiu; Hendrickx, Marc F A

2007-11-01

The ground states of FeS(2) and FeS(2)(-), and several low-lying excited electronic states of FeS(2) that are responsible for the FeS(2)(-) photoelectron spectrum, are calculated. At the B3LYP level an open, quasi-linear [SFeS](-) conformation is found as the most stable structure, which is confirmed at the ab initio CASPT2 computational level. Both the neutral and the anionic unsaturated complexes possess high-spin electronic ground states. For the first time a complete assignment of the photoelectron spectrum of FeS(2)(-) is proposed. The lowest energy band in this spectrum is ascribed to an electron detachment from the two highest-lying 3dpi antibonding orbitals (with respect to the iron-sulfur bonding) of iron. The next-lowest experimental band corresponds to an electron removal from nonbonding, nearly pure sulfur orbitals. The two highest bands in the spectra are assigned as electron detachments from pi and sigma bonding mainly sulfur orbitals.

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer.

PubMed

Frank, Patrick; Szilagyi, Robert K; Gramlich, Volker; Hsu, Hua-Fen; Hedman, Britt; Hodgson, Keith O

2017-02-06

Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M II (itao)(SO 4 )(H 2 O) 0,1 ] (M = Co, Ni, Cu) and [Cu(Me 6 tren)(SO 4 )] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO 4 )] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO 4 )] but not of [Cu(Me 6 tren)(SO 4 )] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M II (SO 4 )(H 2 O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin orbitals of the sulfate ligand, inducing negative spin density at the sulfate sulfur. Ground-state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand antibonding orbitals, producing measurable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS preedge features 0.5-2 eV below the rising sulfur K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the copper(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the sulfur and electron hole provides a new mechanism for the counterintuitive appearance of preedge transitions in the XAS spectra of transition-metal oxoanion ligands in the absence of any direct metal-absorber bond. The 2472.1 eV transition is evidence for further radicalization from copper(II), which extends across a hydrogen-bond bridge between sulfate and the itao ligand and involves orbitals at energies below the frontier set. This electronic structure feature provides a direct spectroscopic confirmation of the through-bond electron-transfer mechanism of redox-active metalloproteins.

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer

DOE PAGES

Frank, Patrick; Szilagyi, Robert K.; Gramlich, Volker; ...

2017-01-09

Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M II(itao)(SO 4)(H 2O) 0,1] (M = Co, Ni, Cu) and [Cu(Me 6tren)(SO 4)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal–sulfur bond, while the XAS preedge of [Zn(itao)(SO 4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO 4)] but not of [Cu(Me 6tren)(SO 4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M II(SO 4)(Hmore » 2O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin orbitals of the sulfate ligand, inducing negative spin density at the sulfate sulfur. Ground-state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand antibonding orbitals, producing measurable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS preedge features 0.5–2 eV below the rising sulfur K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the copper(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the sulfur and electron hole provides a new mechanism for the counterintuitive appearance of preedge transitions in the XAS spectra of transition-metal oxoanion ligands in the absence of any direct metal–absorber bond. The 2472.1 eV transition is evidence for further radicalization from copper(II), which extends across a hydrogen-bond bridge between sulfate and the itao ligand and involves orbitals at energies below the frontier set. In conclusion, this electronic structure feature provides a direct spectroscopic confirmation of the through-bond electron-transfer mechanism of redox-active metalloproteins.« less

EPA Research Highlights: Minimizing SO3 Emissions from Coal-Fired Power Plants

EPA Science Inventory

There have been substantial reductions in emissions of particulate matter, nitrogen oxides, and sulfur dioxide through the application of control technologies and strategies. The installation of control technologies has added to the complexity of coal-fired boilers and their ope...

Web-structured graphitic carbon fiber felt as an interlayer for rechargeable lithium-sulfur batteries with highly improved cycling performance

NASA Astrophysics Data System (ADS)

Lee, Dong Kyu; Ahn, Chi Won; Jeon, Hwan-Jin

2017-08-01

Graphitic carbon fiber felt (GCFF) with a crystalline graphitic carbon structure was facilely prepared by a combination of electrospinning and graphitization (2800 °C heat treatment) and was used as an interlayer between the cathode and separator in Li-S batteries. This GCFF interlayer trapped the polysulfides on the cathode side and increased the utilization of sulfur by suppressing the shuttle phenomenon. Also, the GCFF was shown to be able to act as an upper current collector to reduce the charge-transfer resistance owing to the high crystallinity of the graphitic carbon fibers. The sulfur cathode with the GCFF interlayer showed a high specific initial discharge capacity of 1280.14 mAh g-1 and excellent cycling stability (1004.62 mAh g-1 after 100 cycles) at 0.2 C. Also, an image of the glass fiber (GF) separator on the anode side confirmed the presence of an SEI after 200 cycles, which apparently resulted from stable Li deposition on the Li metal because of the low or medium concentration of sulfur in the electrolyte solution. Our observations should contribute to elucidating the key features of complex three-dimensional carbon fabrics with crystalline graphitic structures that allow them, when inserted as interlayers, to markedly improve the performance of rechargeable batteries.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zerbs, Sarah; Korajczyk, Peter J.; Noirot, Philippe H.

Sulfur is an essential element in plant rhizospheres and microbial activity plays a key role in increasing the biological availability of sulfur in soil environments. To better understand the mechanisms facilitating the exchange of sulfur-containing molecules in soil, we profiled the binding specificities of eight previously uncharacterized ABC transporter solute-binding proteins from plant-associated Pseudomonads. A high-throughput screening procedure indicated eighteen significant organosulfur binding ligands, with at least one high-quality screening hit for each protein target. Calorimetric and spectroscopic methods were used to validate the best ligand assignments and catalog the thermodynamic properties of the protein-ligand interactions. Two novel high-affinity ligandmore » binding activities were identified and quantified in this set of solute binding proteins. Bacteria were cultured in minimal media with screening library components supplied as the sole sulfur sources, demonstrating that these organosulfur compounds can be metabolized and confirming the relevance of ligand assignments. These results expand the set of experimentally validated ligands amenable to transport by this ABC transporter family and demonstrate the complex range of protein-ligand interactions that can be accomplished by solute-binding proteins. As a result, characterizing new nutrient import pathways provides insight into Pseudomonad metabolic capabilities which can be used to further interrogate bacterial survival and participation in soil and rhizosphere communities.« less

Polysulfide Speciation in the Bulk Electrolyte of a Lithium Sulfur Battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

McBrayer, Josefine D.; Beechem, Thomas E.; Perdue, Brian R.

In situ Raman microscopy was used to study polysulfide speciation in the bulk ether electrolyte during the discharge and charge of a Li-S electrochemical cell to assess the complex interplay between chemical and electrochemical reactions in solution. During discharge, long chain polysulfides and the S 3 - radical appear in the electrolyte at 2.4 V indicating a rapid equilibrium of the dissociation reaction to form S 3 -. When charging, however, an increase in the concentration of all polysulfide species was observed. This highlights the importance of the electrolyte to sulfur ratio and suggests a loss in the useful sulfurmore » inventory from the cathode to the electrolyte.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walden, William E.; Selezneva, Anna I.; Dupuy, Jérôme

Iron regulatory protein 1 (IRP1) binds iron-responsive elements (IREs) in messenger RNAs (mRNAs), to repress translation or degradation, or binds an iron-sulfur cluster, to become a cytosolic aconitase enzyme. The 2.8 angstrom resolution crystal structure of the IRP1:ferritin H IRE complex shows an open protein conformation compared with that of cytosolic aconitase. The extended, L-shaped IRP1 molecule embraces the IRE stem-loop through interactions at two sites separated by {approx}30 angstroms, each involving about a dozen protein:RNA bonds. Extensive conformational changes related to binding the IRE or an iron-sulfur cluster explain the alternate functions of IRP1 as an mRNA regulator ormore » enzyme.« less

Role of RIS/APC for manufacturing RFG/LSD. [Refinery Information Systems/Advanced Process Control, ReFormulated Gasoline/Low Sulfur Diesels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Latour, P.R.

Revolutionary changes in quality specifications (number, complexity, uncertainty, economic sensitivity) for reformulated gasolines (RFG) and low-sulfur diesels (LSD) are being addressed by powerful, new, computer-integrated manufacturing technology for Refinery Information Systems and Advanced Process Control (RIS/APC). This paper shows how the five active RIS/APC functions: performance measurement, optimization, scheduling, control and integration are used to manufacture new, clean fuels competitively. With current industry spending for this field averaging 2 to 3 cents/bbl crude, many refineries can capture 50 to 100 cents/bbl if the technology is properly employed and sustained throughout refining operations, organizations, and businesses.

Biogenesis and functions of mammalian iron-sulfur proteins in the regulation of iron homeostasis and pivotal metabolic pathways.

PubMed

Rouault, Tracey A; Maio, Nunziata

2017-08-04

Fe-S cofactors are composed of iron and inorganic sulfur in various stoichiometries. A complex assembly pathway conducts their initial synthesis and subsequent binding to recipient proteins. In this minireview, we discuss how discovery of the role of the mammalian cytosolic aconitase, known as iron regulatory protein 1 (IRP1), led to the characterization of the function of its Fe-S cluster in sensing and regulating cellular iron homeostasis. Moreover, we present an overview of recent studies that have provided insights into the mechanism of Fe-S cluster transfer to recipient Fe-S proteins. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Polysulfide Speciation in the Bulk Electrolyte of a Lithium Sulfur Battery

DOE PAGES

McBrayer, Josefine D.; Beechem, Thomas E.; Perdue, Brian R.; ...

2018-03-23

In situ Raman microscopy was used to study polysulfide speciation in the bulk ether electrolyte during the discharge and charge of a Li-S electrochemical cell to assess the complex interplay between chemical and electrochemical reactions in solution. During discharge, long chain polysulfides and the S 3 - radical appear in the electrolyte at 2.4 V indicating a rapid equilibrium of the dissociation reaction to form S 3 -. When charging, however, an increase in the concentration of all polysulfide species was observed. This highlights the importance of the electrolyte to sulfur ratio and suggests a loss in the useful sulfurmore » inventory from the cathode to the electrolyte.« less

THE GRAVIMETRIC DETERMINATION OF MOLYBDENUM IN URANIUM-MOLYBDENUM ALLOYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1959-03-01

The sample is dissolved in nitric and hydrochloric acids. After heating the solution with sulfuric acid, molybodenum is precipitated as the benzoin-oxime complex which is ignited to molybdic oxide. This is dissolved in ammonia, and the molybdenum is precipitated and weighed as lead molybdate. (auth)

A new hexanuclear iron-selenium nitrosyl cluster: primary exploration of the preparation methods, structure, and spectroscopic and electrochemical properties.

PubMed

Wang, Rongming; Xu, Wei; Zhang, Jian; Li, Lijuan

2010-06-07

A new hexanuclear iron-selenium nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)Se(6)(NO)(6)] (1), and a hexanuclear iron-sulfur nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)S(6)(NO)(6)] (2), were synthesized by the solvent-thermal reactions of [(n-Bu)(4)N][Fe(CO)(3)NO] with selenium or sulfur in methanol, while a tetranuclear iron-sulfur nitrosyl cluster, (Me(4)N)[Fe(4)S(3)(NO)(7)] (3), was also prepared by the solvent-thermal reaction of FeCl(2).4H(2)O with thiourea in the presence of (CH(3))(4)NCl, NaNO(2), and methanol. Complexes 1-3 were characterized by IR, UV-vis, (1)H NMR, electrochemistry, and single-crystal X-ray diffraction analysis. IR spectra of complexes 1 and 2 show the characteristic NO stretching frequencies at 1694 and 1698 cm(-1), respectively, while the absorptions of complex 3 appear at 1799, 1744, and 1710 cm(-1). The UV-vis spectra of complexes 1-3 show different bands in the range of 259-562 nm, which are assigned to the transitions between orbitals delocalized over the Fe-S cluster, the ligand-to-metal charge transfer, pi*(NO)-d(Fe), and the metal-to-ligand charge transfer, d(Fe)-pi*(NO). Single-crystal X-ray structural analysis reveals that complex 1 crystallizes in the monoclinic P2(1)/n space group with two molecules per unit cell. Two parallel "chair-shaped" structures, consisting of three iron and three selenium atoms, are connected by Fe-Se bonds with an average distance of 2.341 A; each iron center is bonded to three selenium atoms and a nitrogen atom from the nitrosyl ligand with a pseudotetrahedral center geometry. Cyclic voltammograms of complexes 1 and 2 display two cathodic and three anodic current peaks with an unusually strong cathodic peak. Further electrochemical investigations demonstrated that the intensity of the unusually strong peak is a result of at least three processes. One is the quasi-reversible reduction, and the other two are from an irreversible electrochemical process, in which the compound goes through a typical electron transfer and chemical reaction mechanism. Compound 3 shows three quasi-reversible reductions.

Stromatolitic structures associated with sulfur-bearing limestones from the Miocene (Badenian) of the Carpathian Foredeep (S Poland)

NASA Astrophysics Data System (ADS)

Siewicz, Andrzej Gä; Olchowy, Piotr

2010-05-01

The Middle Badenian (Miocene) evaporitic unit is widespread in the Miocene of the Carpathian Foredeep (South Poland). The unit is predominated by sulfates (gypsum + anhydrite) and locally in the northern marginal part of the foredeep contains carbonate complexes up to 45 m thick. The carbonate series are lithologically heterogenous and change from clayey and marl interlayers through marly to pure limestones and may be either sulfur-bearing or barren limestones locally intercalated by sulfate beds and layers. The bulk of the limestones consist of more or less calcareous, either non-bedded or bedded, laminated or streaky mudstones. The series is locally intercalated by breccia, rudstone (nodular) and gypsum-ghost facies. A characteristic feature of the carbonate mudstones lithofacies is the presence of variously developed sparse, thin and finely laminated layers and small (up to few centimeters in height) domal forms clearly resembling stromatolitic structures. The laminated layers usually are up to about 20 cm, discontinuous (up to a few tens meters long) and occur in various stratigraphic positions. The structures reveal wavy or flat, thin and subtle lamination consisting of intercalation of discontinuous native sulfur and calcareous laminae. They are lacking of gypsum selenite relics. There are two kinds of laminae: 1) thicker ones composed of finer to coarser crystalline calcite, sometimes with various clay admixtures and 2) thinner, commonly more or less discontinuous composed of subtle, fine crystalline and pure native sulfur. The calcite laminae are commonly barren with microfossils. The native sulfur laminae are commonly re-crystallized but often contain honey-comb like structures and local pockets with variously preserved sulfur microbial remains. The microfossils are poorly preserved and include coccoid and filamentous remains. The microbial structures are locally associated with irregular patches of structureless amorphous material resembling mucilage associated with many recent microorganisms. The calcite laminae are characterized by variable 18O values ranging in between -3.3 and -6.8‰ PDB and 13C ones from -31.7 to -57.2‰ PDB. The native sulfur forming laminae has positive 34S values changing from 4.6 to 17.2‰ CDT. Both the structural and isotopic data allow to interpret the stromatolitic structures as a result of microbial activity of syntropic sulfate-reducing and methanotrophic consortia + sulfide oxidizing bacteria. As it may be inferred from sedimentological and geochemical features of both the sulfur stromatolitic structures and associated sulfur-bearing limestones, the environment was generally shallow water, penesaline and euxinic, interrupted by meteoric influxes with precipitation of calcite and native sulfur, supply of both detrital and produced in situ organic matter. Such laminated structures have commonly been believed as a lithological equivalent of stromatolitic gypsum beds preserved due to massive replacement of solid gypsum by limestones and limestones + native sulfur. However, a more detailed comparison of geometry and distribution, sedimentological and petrologic features, as well as geochemical signatures accordingly exclude the native sulfur stromatolites as an analogue of the stromatolitic gypsum selenites. It argues against epigenetic replacement of solid sulfates and for syndepositional origin sulfur-bearing limestones.

Mercury Methylation by Desulfovibrio desulfuricans ND132 in the Presence of Polysulfides

PubMed Central

Jay, Jenny Ayla; Murray, Karen J.; Gilmour, Cynthia C.; Mason, Robert P.; Morel, François M. M.; Roberts, A. Lynn; Hemond, Harold F.

2002-01-01

The extracellular speciation of mercury may control bacterial uptake and methylation. Mercury-polysulfide complexes have recently been shown to be prevalent in sulfidic waters containing zero-valent sulfur. Despite substantial increases in total dissolved mercury concentration, methylation rates in cultures of Desulfovibrio desulfuricans ND132 equilibrated with cinnabar did not increase in the presence of polysulfides, as expected due to the large size and charged nature of most of the complexes. In natural waters not at saturation with cinnabar, mercury-polysulfide complexes would be expected to shift the speciation of mercury from HgS0(aq) toward charged complexes, thereby decreasing methylation rates. PMID:12406773

Lipoic acid metabolism and mitochondrial redox regulation.

PubMed

Solmonson, Ashley D; DeBerardinis, Ralph J

2017-11-30

Lipoic acid is an essential cofactor for mitochondrial metabolism and is synthesized de novo using intermediates from mitochondrial fatty acid synthesis type II, S-adenosylmethionine and iron-sulfur clusters. This cofactor is required for catalysis by multiple mitochondrial 2-ketoacid dehydrogenase complexes, including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Lipoic acid also plays a critical role in stabilizing and regulating these multi-enzyme complexes.  Many of these dehydrogenases are regulated by reactive oxygen species, mediated through the disulfide bond of the prosthetic lipoyl moiety.  Collectively, its functions explain why lipoic acid is required for cell growth, mitochondrial activity and coordination of fuel metabolism. Lipoic acid is an essential cofactor for mitochondrial metabolism and is synthesized de novo using intermediates from mitochondrial fatty acid synthesis type II, S-adenosylmethionine and iron-sulfur clusters. This cofactor is required for catalysis by multiple mitochondrial 2-ketoacid dehydrogenase complexes, including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Lipoic acid also plays a critical role in stabilizing and regulating these multi-enzyme complexes.  Many of these dehydrogenases are regulated by reactive oxygen species, mediated through the disulfide bond of the prosthetic lipoyl moiety.  Collectively, its functions explain why lipoic acid is required for cell growth, mitochondrial activity and coordination of fuel metabolism. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

Arsenic behavior in river sediments under redox gradient: a review.

PubMed

Gorny, Josselin; Billon, Gabriel; Lesven, Ludovic; Dumoulin, David; Madé, Benoît; Noiriel, Catherine

2015-02-01

The fate of arsenic - a redox sensitive metalloid - in surface sediments is closely linked to early diagenetic processes. The review presents the main redox mechanisms and final products of As that have been evidenced over the last years. Oxidation of organic matter and concomitant reduction of oxidants by bacterial activity result in redox transformations of As species. The evolution of the sediment reactivity will also induce secondary abiotic reactions like complexation/de-complexation, sorption, precipitation/dissolution and biotic reactions that could, for instance, lead to the detoxification of some As species. Overall, abiotic redox reactions that govern the speciation of As mostly involve manganese (hydr)-oxides and reduced sulfur species produced by the sulfate-reducing bacteria. Bacterial activity is also responsible for the inter-conversion between As(V) and As(III), as well as for the production of methylated arsenic species. In surficial sediments, sorption processes also control the fate of inorganic As(V), through the formation of inner sphere complexes with iron (hydr)-oxides, that are biologically reduced in buried sediment. Arsenic species can also be bound to organic matter, either directly to functional groups or indirectly through metal complexes. Finally, even if the role of reduced sulfur species in the cycling of arsenic in sediments has been evidenced, some of the transformations remain hypothetical and deserve further investigation. Copyright © 2014 Elsevier B.V. All rights reserved.

Endogenous generation of hydrogen sulfide and its regulation in Shewanella oneidensis

PubMed Central

Wu, Genfu; Li, Ning; Mao, Yinting; Zhou, Guangqi; Gao, Haichun

2015-01-01

Hydrogen sulfide (H2S) has been recognized as a physiological mediator with a variety of functions across all domains of life. In this study, mechanisms of endogenous H2S generation in Shewanella oneidensis were investigated. As a research model with highly diverse anaerobic respiratory pathways, the microorganism is able to produce H2S by respiring on a variety of sulfur-containing compounds with SirACD and PsrABC enzymatic complexes, as well as through cysteine degradation with three enzymes, MdeA, SO_1095, and SseA. We showed that the SirACD and PsrABC complexes, which are predominantly, if not exclusively, responsible for H2S generation via respiration of sulfur species, do not interplay with each other. Strikingly, a screen for regulators controlling endogenous H2S generation by transposon mutagenesis identified global regulator Crp to be essential to all H2S-generating processes. In contrast, Fnr and Arc, two other global regulators that have a role in respiration, are dispensable in regulating H2S generation via respiration of sulfur species. Interestingly, Arc is involved in the H2S generation through cysteine degradation by repressing expression of the mdeA gene. We further showed that expression of the sirA and psrABC operons is subjected to direct regulation of Crp, but the mechanisms underlying the requirement of Crp for H2S generation through cysteine degradation remain elusive. PMID:25972854

Sulfur Nanoparticles with Novel Morphologies Coupled with Brain-Targeting Peptides RVG as a New Type of Inhibitor Against Metal-Induced Aβ Aggregation.

PubMed

Sun, Jing; Xie, Wenjie; Zhu, Xufeng; Xu, Mengmeng; Liu, Jie

2018-04-18

Functionalized nanomaterials, which have been applied widely to inhibit amyloid-β protein (Aβ) aggregation, show enormous potential in the field of prevention and treatment of Alzheimer's disease (AD). A significant body of data has demonstrated that the morphology and size of nanomaterials have remarkable effects on their biological behaviors. In this work, we proposed and designed three kinds of brain-targeting sulfur nanoparticles (RVG@Met@SNPs) with novel morphologies (volute-like, tadpole-like, and sphere-like) and investigated the effect of different RVG@Met@SNPs on Aβ-Cu 2+ complex aggregation and their corresponding neurotoxicity. Among them, the sphere-like nanoparticles (RVG@Met@SS) exhibited the most effective inhibitory activity, due to their unique mini size effect, and they reduced 61.6% the Aβ-Cu 2+ complex aggregation and increased 92.4% SH-SY5Y cell viability in a dose of 10 μg/mL. In vitro and in vivo, the abilities of different morphologies of RVG@Met@SNPs to cross the blood-brain barrier (BBB) and target brain parenchymal cells were significantly different. Moreover, improvements in learning disability and cognitive loss were shown in the transgenic AD mice model using the Morris water maze test after multiple doses of RVG@Met@SNPs treatment. In general, the purpose of this research is to develop a biological application of sulfur nanoparticles and to provide a novel functionalized nanomaterial to treat AD.

Recalibrating the concentration of Precambrian seawater sulfate

NASA Astrophysics Data System (ADS)

Johnston, D. T.; Bradley, A. S.; Hoarfrost, A.; Girguis, P. R.

2010-12-01

The isotopic offset between sulfate sulfur and sulfide sulfur (δ34Ssulfate-sulfide) is widely used in the Precambrian as a paleo-indicator of seawater sulfate concentrations. Popularized by experimental work proposing an increase in seawater sulfate at the Archean - Proterozoic boundary, the concept of using a calibrated physiological process (dissimilatory sulfate reduction) to extract environmental information holds the potential to unlock numerous geological questions. To that end, the interpretability of sulfur isotope records relies on the degree to which strict quantitative constraints have been placed on the relationship between sulfate concentrations and sulfate reducing bacteria. Our work serves to extend those constraints. Here we present data from a series of replicate quasi-chemostat microbial reactors, inoculated with marine sediment from Monterey Bay and incubated with artificial seawater ([SO42-]< 5 mM). Our experimental design continuously removes sulfide and allows for systematic tracking of the dependence of δ34Ssulfate-sulfide on seawater sulfate concentration. In addition to expanding the existing δ34S context, we target high-precision multiple sulfur isotope data, which allows for a greater interpretability of both the overall result and its mapping onto environmental records. Further, we use natural abundance and δ18O spiked water within our experiments to assay rates of cellular re-oxidation (within the sulfate reduction pathway) and to constrain natural δ18O effects within these systems. Finally, we use modern molecular biological techniques to track community structure as a function of time and environmental conditions. Together, these data provide an integrated metric with which to interpret complex natural sulfur isotope records.

B. subtilis as a Model for Studying the Assembly of Fe-S Clusters in Gram-Positive Bacteria.

PubMed

Dos Santos, Patricia C

2017-01-01

Complexes of iron and sulfur (Fe-S clusters) are widely distributed in nature and participate in essential biochemical reactions. The biological formation of Fe-S clusters involves dedicated pathways responsible for the mobilization of sulfur, the assembly of Fe-S clusters, and the transfer of these clusters to target proteins. Genomic analysis of Bacillus subtilis and other Gram-positive bacteria indicated the presence of only one Fe-S cluster biosynthesis pathway, which is distinct in number of components and organization from previously studied systems. B. subtilis has been used as a model system for the characterization of cysteine desulfurases responsible for sulfur mobilization reactions in the biogenesis of Fe-S clusters and other sulfur-containing cofactors. Cysteine desulfurases catalyze the cleavage of the C-S bond from the amino acid cysteine and subsequent transfer of sulfur to acceptor molecules. These reactions can be monitored by the rate of alanine formation, the first product in the reaction, and sulfide formation, a byproduct of reactions performed under reducing conditions. The assembly of Fe-S clusters on protein scaffolds and the transfer of these clusters to target acceptors are determined through a combination of spectroscopic methods probing the rate of cluster assembly and transfer. This chapter provides a description of reactions promoting the assembly of Fe-S clusters in bacteria as well as methods used to study functions of each biosynthetic component and identify mechanistic differences employed by these enzymes across different pathways. © 2017 Elsevier Inc. All rights reserved.

HOMER CITY MULTISTREAM COAL CLEANING DEMONSTRATION: A PROGRESS REPORT

EPA Science Inventory

The report gives an overview of ongoing testing and evaluation of the Homer City Coal Cleaning Plant, built to enable the Homer City Power Complex to meet sulfur dioxide (SO2) emission levels mandated by the State of Pennsylvania and the U.S. Government. The plant was constructed...

Synthesis, characterization and reactivity of 3-mercaptopyruvic acid.

PubMed

Galardon, Erwan; Lec, Jean-Chrstophe

2018-05-20

A synthesis of the sulfur metabolic compound 3-mercaptopyruvic acid (3-MPH) is reported and allowed its isolation and characterization for the first time. Detailed kinetic, thermodynamic and spectroscopic studies of its complex behaviour in solution are discussed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A single exposure to photochemical smog causes airway irritation and cardiac dysrhythmia in mice

EPA Science Inventory

The data presented here shows that a single exposure to photochemical smog causes airway irritation and cardiac dysrhythmia in mice. Smog, which is a complex mixture of particulate matter and gaseous irritants (ozone, sulfur dioxide, reactive aldehydes), as well as components whi...

Adding to the Mercury Speciation Toolbox

NASA Astrophysics Data System (ADS)

Fitts, J. P.; Northrup, P. A.; Chidambaram, D.; Kalb, P. D.

2007-12-01

Mercury was used to separate lithium-6 isotope for weapons production at the Y-12 Plant in Oak Ridge, TN in the 1950s and 1960s. A large portion of the waste Hg entered the environment and continues to move throughout the sub-surface and surface waters in the area. Environmental management of Hg contamination within this complex hydrologic system, where Hg speciation and the mobile fraction have been found to vary widely, will require ongoing characterization and predictive modeling of Hg speciation. State-of-the-art spectroscopic tools that can directly probe Hg speciation in preserved aqueous and sediment samples with greater sensitivity, however, are required to determine rates and mechanisms of biogeochemical reactions. We will present the first results demonstrating the use of x-ray absorption spectroscopy (XAS) at the Hg M5 edge (2295 eV) to fingerprint Hg species. Heavy-metal M5 absorption edges can have very sharp features due to local electron transitions, and therefore, we are developing this edge as a tool for quantitative measurement of Hg species. In addition, sulfur speciation using the sulfur K absorption edge, which is at a similar energy (2472 eV), can be measured in the same scan as the Hg M5 edge. Potentially important organic and inorganic sulfur species (sulfide, disulfide, elemental sulfur, sulfite and sulfate) are readily differentiated, and thereby, provides an independent method for monitoring the redox state of the system along with changes in S-Hg bonding. We will also present x-ray microprobe 2-D concentration maps of Hg and other elements at the grain and pore scales to identify its microscopic distribution and chemical associations. When used in combination with established sequential extraction and direct spectroscopic methods, the addition of XAS at the Hg M5 edge should provide a significant advancement in the determination of Hg speciation in complex biogeochemical environments.

An Aerosol Condensation Model for Sulfur Trioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grant, K E

This document describes a model for condensation of sulfuric acid aerosol given an initial concentration and/or source of gaseous sulfur trioxide (e.g. fuming from oleum). The model includes the thermochemical effects on aerosol condensation and air parcel buoyancy. Condensation is assumed to occur heterogeneously onto a preexisting background aerosol distribution. The model development is both a revisiting of research initially presented at the Fall 2001 American Geophysical Union Meeting [1] and a further extension to provide new capabilities for current atmospheric dispersion modeling efforts [2]. Sulfuric acid is one of the most widely used of all industrial chemicals. In 1992,more » world consumption of sulfuric acid was 145 million metric tons, with 42.4 Mt (mega-tons) consumed in the United States [10]. In 2001, of 37.5 Mt consumed in the U.S., 74% went into producing phosphate fertilizers [11]. Another significant use is in mining industries. Lawuyi and Fingas [7] estimate that, in 1996, 68% of use was for fertilizers and 5.8% was for mining. They note that H{sub 2}SO{sub 4} use has been and should continue to be very stable. In the United States, the elimination of MTBE (methyl tertiary-butyl ether) and the use of ethanol for gasoline production are further increasing the demand for petroleum alkylate. Alkylate producers have a choice of either a hydrofluoric acid or sulfuric acid process. Both processes are widely used today. Concerns, however, over the safety or potential regulation of hydrofluoric acid are likely to result in most of the growth being for the sulfuric acid process, further increasing demand [11]. The implication of sulfuric acid being a pervasive industrial chemical is that transport is also pervasive. Often, this is in the form of oleum tankers, having around 30% free sulfur trioxide. Although sulfuric acid itself is not a volatile substance, fuming sulfuric acid (referred to as oleum) is [7], the volatile product being sulfur trioxide. Sulfate aerosols and mist may form in the atmosphere on tank rupture. From chemical spill data from 1990-1996, Lawuyi02 and Fingas [7] prioritize sulfuric acid as sixth most serious. During this period, they note 155 spills totaling 13 Mt, out of a supply volume of 3700 Mt. Lawuyi and Fingas [7] summarize information on three major sulfuric acid spills. On 12 February 1984, 93 tons of sulfuric acid were spilled when 14 railroad cars derailed near MacTier, Parry Sound, Ontario. On 13 December 1978, 51 railroad cars derailed near Springhill, Nova Scotia. One car, containing 93% sulfuric acid, ruptured, spilling nearly its entire contents. In July 1993, 20 to 50 tons of fuming sulfuric acid spilled at the General Chemical Corp. plant in Richmond, California, a major industrial center near San Francisco. The release occurred when oleum was being loaded into a nonfuming acid railroad tank car that contained only a rupture disk as a safety device. The tank car was overheated and this rupture disk blew. The resulting cloud of sulfuric acid drifted northeast with prevailing winds over a number of populated areas. More than 3,000 people subsequently sought medical attention for burning eyes, coughing, headaches, and nausea. Almost all were treated and released on the day of the spill. By the day after the release, another 5,000 people had sought medical attention. The spill forced the closure of five freeways in the region as well as some Bay Area Rapid Transit System stations. Apart from corrosive toxicity, there is the additional hazard that the reactions of sulfur trioxide and sulfuric acid vapors with water are extremely exothermic [10, 11]. While the vapors are intrinsically denser than air, there is thus the likelihood of strong, warming-induced buoyancy from reactions with ambient water vapor, water-containing aerosol droplets, and wet environmental surface. Nordin [12] relates just such an occurrence following the Richmond, CA spill, with the plume observed to rise to 300 m. For all practical purposes, sulfur trioxide was the constituent released from the heated tank car. The behavior of the resulting plume suggested that initially sulfur trioxide behaved as a dense gas, but the chemical reacted with air humidity, producing sulfuric acid and heat. The heat caused the plume to rise. Eventually the plume cooled, resulting in sulfuric acid descending towards people on the ground. This kind of behavior is not accounted for in the popular gas dispersion models. In the presence of complex terrain, such heat induced buoyancy could enable a sulfur trioxide cloud to leap local drainage boundaries with a single bound. Unless there were insufficient water/humidity to fully react with the SO{sub 3} and H{sub 2}SO{sub 4} on the first ascent, no secondary bounds would be expected, the cloud then behaving as a heavy tracer until sufficiently diluted.« less

Biogeochemical Modeling of the Second Rise of Oxygen

NASA Astrophysics Data System (ADS)

Smith, M. L.; Catling, D.; Claire, M.; Zahnle, K.

2014-03-01

The rise of atmospheric oxygen set the tempo for the evolution of complex life on Earth. Oxygen levels are thought to have increased in two broad steps: one step occurred in the Archean ~ 2.45 Ga (the Great Oxidation Event or GOE), and another step occured in the Neoproterozoic ~750-580 Ma (the Neoprotoerozoic Oxygenation Event or NOE). During the NOE, oxygen levels increased from ~1-10% of the present atmospheric level (PAL) (Holland, 2006), to ~15% PAL in the late Neoproterozoic, to ~100% PAL later in the Phanerozoic. Complex life requires O2, so this transition allowed complex life to evolve. We seek to understand what caused the NOE. To explore causes for the NOE, we build upon the biogeochemical model of Claire et al. (2006), which calculates the redox evolution of the atmosphere, ocean, biosphere, and crust in the Archean through to the early Proterozoic. In this model, the balance between oxygenconsuming and oyxgen-producing fluxes evolves over time such that at ~2.4 Ga, the rapidly acting sources of oxygen outweigh the rapidly-acting sinks. Or, in other words, at ~2.4 Ga, the flux of oxygen from organic carbon burial exceeds the sinks of oxygen from reaction with reduced volcanic and metamoprphic gases. The model is able to drive oxygen levels to 1-10% PAL in the Proterozoic; however, the evolving redox fluxes in the model cannot explain how oxygen levels pushed above 1-10% in the late Proterozoic. The authors suggest that perhaps another buffer, such as sulfur, is needed to describe Proterozoic and Phanerozoic redox evolution. Geologic proxies show that in the Proterozoic, up to 10% of the deep ocean may have been sulfidic. With this ocean chemistry, the global sulfur cycle would have worked differently than it does today. Because the sulfur and oxygen cycles interact, the oxygen concentration could have permanently changed due to an evolving sulfur cycle (in combination with evolving redox fluxes associated with other parts of the oxygen cycle and carbon cycles). To determine how fluxes of sulfur, carbon, and oxygen define oxygen levels before, during, and after the NOE, we add a sulfur cycle to the biogeochemical model of Claire et al. (2006). Understanding processes that impact the evolution of atmospheric oxygen on Earth is key to diagnosing the habitability of other planets because it is possible that other planets undergo a similar evolution. If a sulfidic deep ocean was instrumental in driving oxygen levels to modern values, then it would be valuable to remotely detect a sulfide-rich ocean on another planet. One such remotely-detectable signature could be the color of a sulfide-rich ocean. For example, Gallardo and Espinoza (2008) have hypothesized that a sulfidic ocean may be have been blacker in color. Even if a sulfidic ocean is not key to oxygenation, detecting a planet in transition--that is, a planet with intermediate levels of oxygen co-existing with higher levels of reduced gases - would be important for diagnosing habitability.

Determination of Total Sulfur, Sulfate, Sulfite, Thiosulfate, and Sulfolipids in Plants.

PubMed

Kurmanbayeva, Assylay; Brychkova, Galina; Bekturova, Aizat; Khozin, Inna; Standing, Dominic; Yarmolinsky, Dmitry; Sagi, Moshe

2017-01-01

In response to oxidative stress the biosynthesis of the ROS scavenger, glutathione is induced. This requires the induction of the sulfate reduction pathway for an adequate supply of cysteine, the precursor for glutathione. Cysteine also acts as the sulfur donor for the sulfuration of the molybdenum cofactor, crucial for the last step of ABA biosynthesis. Sulfate and sulfite are, respectively, the precursor and intermediate for cysteine biosynthesis and there is evidence for stress-induced sulfate uptake and further downstream, enhanced sulfite generation by 5'-phosphosulfate (APS) reductase (APR, EC 1.8.99.2) activity. Sulfite reductase (SiR, E.C.1.8.7.1) protects the chloroplast against toxic levels of sulfite by reducing it to sulfide. In case of sulfite accumulation as a result of air pollution or stress-induced premature senescence, such as in extended darkness, sulfite can be oxidized to sulfate by sulfite oxidase. Additionally sulfite can be catalyzed to thiosulfate by sulfurtransferases or to UDP-sulfoquinovose by SQD1, being the first step toward sulfolipid biosynthesis.Determination of total sulfur in plants can be accomplished using many techniques such as ICP-AES, high-frequency induction furnace, high performance ion chromatography, sulfur combustion analysis, and colorimetric titration. Here we describe a total sulfur detection method in plants by elemental analyzer (EA). The used EA method is simple, sensitive, and accurate, and can be applied for the determination of total S content in plants.Sulfate anions in the soil are the main source of sulfur, required for normal growth and development, of plants. Plants take up sulfate ions from the soil, which are then reduced and incorporated into organic matter. Plant sulfate content can be determined by ion chromatography with carbonate eluents.Sulfite is an intermediate in the reductive assimilation of sulfate to the essential amino acids cysteine and methionine, and is cytotoxic above a certain threshold if not rapidly metabolized and can wreak havoc at the cellular and whole plant levels. Plant sulfite content affects carbon and nitrogen homeostasis Therefore, methods capable of determining sulfite levels in plants are of major importance. Here we present two robust laboratory protocols which can be used for sulfite detection in plants.Thiosulfate is an essential sulfur intermediate less toxic than sulfite which is accumulating in plants in response to sulfite accumulation. The complexity of thiosulfate detection is linked to its chemical properties. Here we present a rapid, sensitive, and accurate colorimetric method based on the enzymatic conversion of thiosulfate to thiocyanate.The plant sulfolipid sulfoquinovosyldiacylglycerol (SQDG) accounts for a large fraction of organic sulfur in the biosphere. Aside from sulfur amino acids, SQDG represents a considerable sink for sulfate in plants and is the only sulfur-containing anionic glycerolipid that is found in the photosynthetic membranes of plastids. We present the separation of sulfolipids from other fatty acids in two simple ways: by one- and two-dimensional thin-layer chromatography.

Polymeric Cd(II), trinuclear and mononuclear Ni(II) complexes of 5-methyl-4-phenyl-1,2,4-triazole-3-thione: Synthesis, structural characterization, thermal behaviour, fluorescence properties and antibacterial activity

NASA Astrophysics Data System (ADS)

Bharty, M. K.; Paswan, S.; Dani, R. K.; Singh, N. K.; Sharma, V. K.; Kharwar, R. N.; Butcher, R. J.

2017-02-01

Syntheses of a polymeric Cd(II) complex, [Cd(mptt)2]n (1), a trinuclear Ni(II) complex, [Ni3(μ-mptt)4(μ-H2O)2(H2O)2(ttfa)2]·3H2O (2) and a mononuclear Ni(II) complex [Ni(mptt)2(en)2] (3) have been performed using the ligand 5-methyl-4-phenyl-1,2,4-triazole-3-thione (Hmptt) and nickel(II)/cadmium(II) salts {ttfa = thenoyltrifluroacetonate). The ligand and the complexes have been characterized by various physicochemical methods in addition to their single crystal X-ray structure. The Cd centre in complex 1 adopts a distorted tetrahedral geometry with one sulfur atom and two mptt ligands provide three nitrogen atoms from three triazole units. The sulfur atom of the ligand binds covalently and overall the ligand acts as uninigative N,S/N,N bidentate moiety. The polymeric structure of complex 1 results from the N atoms of the neighboring triazole units coordinating with the Cd(II) centre. The three Ni(II) centres in the trinuclear Ni(II) complex 2 form a linear arrangement and all have six coordinated arrangements. The middle Ni(II) binds with four deprotonated triazole ring nitrogens and two water molecules form two bridges. The terminal Ni(II) centres bind through two thenoyl oxygens, two triazole nitrogens and water molecules that formed bridges with the middle Ni centre. In complex 3, the nickel(II) centre is covalently bonded through two deprotonated triazole ring nitrogens from two ligand moieties and other four sites are occupied by four nitrogens from two bidentate en ligands. Thermogravimetric analyses (TGA) of the complexes indicated for NiO as the final residue. The bioefficacy of the ligand and complexes 2 and 3 have been examined against the growth of bacteria to evaluate their anti-microbial potential. Complex 2 showed high antibacterial activity as compared to the ligand and complex 3. Complexes 1, 2 and 3 are fluorescent materials with maximum emissions at 425, 421 and 396 nm at an excitation wavelength of 323, 348 and 322 nm, respectively.

Iron and Sulfur Geochemistry in Serpentinizing Groundwaters: Relationships to Microbiological Processes

NASA Astrophysics Data System (ADS)

Sabuda, M.; Kubo, M. D.; Cardace, D.; Hoehler, T. M.; McCollom, T. M.; Schrenk, M. O.

2016-12-01

Serpentinization of ultramafic rock in ophiolite complexes along continental margins leads to the mobilization of volatiles and reduced carbon compounds that can be used as sources of nutrients and energy by subsurface microbial communities. Simultaneously, the highly reducing character of serpentinite-associated fluids can lead to limitations in the availability of oxidants to support growth. The extent to which iron and sulfur compounds can serve as alternative electron acceptors in serpentinizing systems remains to be elucidated. Heterogeneous mineralogy, meteoric and groundwater source mixing, ancient marine sediment influence, and microbial metabolic activities likely contribute to variability in the identity and abundance of Fe and S compounds in serpentinite groundwater. At the Coast Range Ophiolite Microbial Observatory (CROMO) in northern California, the aqueous geochemistry of sulfur and iron in the alkaline groundwater was investigated at multiple time points taken from 12 wells located in two clusters, Core Shed and Quarry Valley, with individual boreholes sampling different depths. Colorimetric methods (HS-, ferrous and total iron), ion chromatography (SO42-), and ICP-MS (total Fe and S) were utilized and on average, both sulfate and sulfide are highest in the CSW wells (300 μM and 15 μM respectively), and lowest in the N08 wells (95 μM, 1.2 μM) within the Quarry Valley area. Ferrous iron measured <0.7 μM in all boreholes, likely due to the poor solubility of dissolved iron at high pH. Bioenergetic calculations were generated using CROMO geochemical data to investigate the favorability of various Fe and S red-ox reactions. Additionally, the presence of key genes in sulfur and iron metabolic pathways was examined in metagenomic assemblies from CROMO. Combined, these data reinforce the critical role that sulfur-associated metabolisms, in particular, play in serpentinite groundwater. Consequently, the sulfur biogeochemistry of such systems may influence geochemical cycles and ultimately be preserved in the rock record.

THE COLORIMETRIC DETERMINATION OF VANADIUM IN NIOBIUM-VANADIUM ALLOYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Articolo, O.J.

1959-06-26

A procedure is described for the analysis of vanadium in niobium-- vanadium alloys in the range >0.1% vanadium with an accuracy of better than 3%. The method was applied to the analysis of niobium alloys in which the nominal per cent vanadium varied between 0.3 to 4.6%. The sample is dissolved in a mixture of nitric and hydrofluoric acid and then evaporated to fumes with sulfuric acid. The niobium is hydrolyzed with sulfurous acid and separated from the vanadium by filtration. Hydrogen peroxide is added to the filtrate to form a reddish brown complex with the vanadium. The optical densitymore » of the resulting solution is obtained at 450 m mu on a model B Beckman spectrophotometer. (auth)« less

Friction and wear of iron in sulfuric acid

NASA Technical Reports Server (NTRS)

Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

1983-01-01

Elemental iron sliding on aluminum oxide in aerated sulfuric acid concentrations ranging from very dilute (0.000007 N; i.e., 4 ppm) to very concentrated (96 percent acid) was studied. Load and reciprocating sliding speeds were kept constant. With the most dilute acid of 0.7 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent, the high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid, and decreased somewhat at 50 percent in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It is apparent that the normal passivating film was being worn away and a galvanic cell established which rapidly attached to the wear area.

Coupling between anammox and autotrophic denitrification for simultaneous removal of ammonium and sulfide by enriched marine sediments.

PubMed

Rios-Del Toro, E Emilia; Cervantes, Francisco J

2016-06-01

In the present study, the capacity of enrichments derived from marine sediments collected from different sites of the Mexican littoral to perform anaerobic ammonium oxidation (anammox) coupled to sulfide-dependent denitrification for simultaneous removal of ammonium and sulfide linked to nitrite reduction was evaluated. Sulfide-dependent denitrification out-competed anammox during the simultaneous oxidation of sulfide and ammonium. Significant accumulation of elemental sulfur (ca. 14-30 % of added sulfide) occurred during the coupling between the two respiratory processes, while ammonium was partly oxidized (31-47 %) due to nitrite limitation imposed in sediment incubations. Nevertheless, mass balances revealed up to 38 % more oxidation of the electron donors available (ammonium and sulfide) than that expected from stoichiometry. Recycling of nitrite, from nitrate produced through anammox, is proposed to contribute to extra oxidation of sulfide, while additional ammonium oxidation is suggested by sulfate-reducing anammox (SR-anammox). The complex interaction between nitrogenous and sulfurous compounds occurring through the concomitant presence of autotrophic denitrification, conventional anammox and SR-anammox may significantly drive the nitrogen and sulfur fluxes in marine environments.

UV-Photochemistry of the Disulfide Bond: Evolution of Early Photoproducts from Picosecond X-ray Absorption Spectroscopy at the Sulfur K-Edge.

PubMed

Ochmann, Miguel; Hussain, Abid; von Ahnen, Inga; Cordones, Amy A; Hong, Kiryong; Lee, Jae Hyuk; Ma, Rory; Adamczyk, Katrin; Kim, Tae Kyu; Schoenlein, Robert W; Vendrell, Oriol; Huse, Nils

2018-05-30

We have investigated dimethyl disulfide as the basic moiety for understanding the photochemistry of disulfide bonds, which are central to a broad range of biochemical processes. Picosecond time-resolved X-ray absorption spectroscopy at the sulfur K-edge provides unique element-specific insight into the photochemistry of the disulfide bond initiated by 267 nm femtosecond pulses. We observe a broad but distinct transient induced absorption spectrum which recovers on at least two time scales in the nanosecond range. We employed RASSCF electronic structure calculations to simulate the sulfur-1s transitions of multiple possible chemical species, and identified the methylthiyl and methylperthiyl radicals as the primary reaction products. In addition, we identify disulfur and the CH 2 S thione as the secondary reaction products of the perthiyl radical that are most likely to explain the observed spectral and kinetic signatures of our experiment. Our study underscores the importance of elemental specificity and the potential of time-resolved X-ray spectroscopy to identify short-lived reaction products in complex reaction schemes that underlie the rich photochemistry of disulfide systems.

Laser fluorescence studies of the chemical interactions of sodium species with sulfur bearing fuels

NASA Technical Reports Server (NTRS)

Steinberg, M.; Schofield, K.

1983-01-01

By using a large matrix of fuel rich and fuel lean H2/O2/N2 and fuel rich C2H2/O2/N2 flames, the behavior of sodium and its interactions with sulfur at high temperatures was extensively characterized. OH concentrations were measured for each flame using the previously validated laser induced fluorescence technique. Sodium atomic concentrations were obtained by the saturated laser fluorescence method. Measurements were made in the absence and presence of up to 2% sulfur. In oxygen rich systems sodium is depleted by NaO2 and NaOH formation. The relative amounts of each are controlled by the degree of nonequilibration of the flame radicals and by the temperature. The bond strength of NaO2 was established. For the first time, a complete understanding of the complex behavior of sodium in fuel lean H2/O2 flames has emerged and computer modeling has permitted various rate constants of Na, NaO2 and NaOH reactions to be approximately fixed.

Ammonium Additives to Dissolve Lithium Sulfide through Hydrogen Binding for High-Energy Lithium-Sulfur Batteries.

PubMed

Pan, Huilin; Han, Kee Sung; Vijayakumar, M; Xiao, Jie; Cao, Ruiguo; Chen, Junzheng; Zhang, Jiguang; Mueller, Karl T; Shao, Yuyan; Liu, Jun

2017-02-08

In rechargeable Li-S batteries, the uncontrollable passivation of electrodes by highly insulating Li 2 S limits sulfur utilization, increases polarization, and decreases cycling stability. Dissolving Li 2 S in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of Li 2 S to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N-H groups plays a critical role in dissolving Li 2 S by forming complex ligands with S 2- anions coupled with the solvent's solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of Li 2 S, and therefore enable the direct use of Li 2 S as cathode material in Li-S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.

Preparation of nitrogen and sulfur co-doped ordered mesoporous carbon for enhanced microwave absorption performance

NASA Astrophysics Data System (ADS)

Yuan, Xiaoyan; Xue, Xingkun; Ma, Hailong; Guo, Shouwu; Cheng, Laifei

2017-09-01

Ordered mesoporous carbon nanomaterials (OMCs) co-doped with homogeneous nitrogen and sulfur heteroatoms were prepared by nanocasting with the pyrrole oligomer catalyzed by sulfuric acid as a precursor and ordered mesoporous silica SBA-15 as a hard-template. By multi-technique approach utilization, it was demonstrated that the N and S co-doped OMCs possessed high ordered mesoporous structures, large surface areas and homogeneous distribution of heteroatoms. As a microwave absorber, the as-prepared materials exhibited a minimum reflection loss (RL) of -32.5 dB at the thickness of 2.5 mm and an absorption bandwidth of 3.2 GHz (RL < -10 dB) in X-band (8.2-12.4 GHz). The good microwave absorption performance was mainly originated from the high electrical conductivity induced by the high surface activity and special structures. And microwave energy can be effectively attenuated through multiple reflections and absorptions in complex conductive network. The design strategy in this work would contribute to the production of a lightweight absorber, presenting a strong absorbency and a wide bandwidth in microwave frequency.

Sulfur radical species form gold deposits on Earth

PubMed Central

Pokrovski, Gleb S.; Kokh, Maria A.; Guillaume, Damien; Borisova, Anastassia Y.; Gisquet, Pascal; Hazemann, Jean-Louis; Lahera, Eric; Del Net, William; Proux, Olivier; Testemale, Denis; Haigis, Volker; Jonchière, Romain; Seitsonen, Ari P.; Ferlat, Guillaume; Vuilleumier, Rodolphe; Saitta, Antonino Marco; Boiron, Marie-Christine; Dubessy, Jean

2015-01-01

Current models of the formation and distribution of gold deposits on Earth are based on the long-standing paradigm that hydrogen sulfide and chloride are the ligands responsible for gold mobilization and precipitation by fluids across the lithosphere. Here we challenge this view by demonstrating, using in situ X-ray absorption spectroscopy and solubility measurements, coupled with molecular dynamics and thermodynamic simulations, that sulfur radical species, such as the trisulfur ion S3−, form very stable and soluble complexes with Au+ in aqueous solution at elevated temperatures (>250 °C) and pressures (>100 bar). These species enable extraction, transport, and focused precipitation of gold by sulfur-rich fluids 10–100 times more efficiently than sulfide and chloride only. As a result, S3− exerts an important control on the source, concentration, and distribution of gold in its major economic deposits from magmatic, hydrothermal, and metamorphic settings. The growth and decay of S3− during the fluid generation and evolution is one of the key factors that determine the fate of gold in the lithosphere. PMID:26460040

Suppressing Shuttle Effect Using Janus Cation Exchange Membrane for High-Performance Lithium-Sulfur Battery Separator.

PubMed

Li, Zhen; Han, Yu; Wei, Junhua; Wang, Wenqiang; Cao, Tiantian; Xu, Shengming; Xu, Zhenghe

2017-12-27

Suppressing the shuttle effect of polysulfide ions to obtain high durability and good electrochemical performance is of great concern in the field of lithium-sulfur batteries. To address this issue, a Janus membrane consisting of an ultrathin dense layer and a robust microporous layer is fabricated using cation exchange resin. Different from the composite membranes made from polyolefin membranes, the multiple layers of the Janus membrane in this study are synchronously generated by one step, getting rid of the additional complex coating processes. Excellent overall performance is obtained by the cooperation of multiple factors. The excellent ionic selectivity of cation exchange resin renders a great suppression of the shuttle effect, endowing the lithium-sulfur battery with high Coulombic efficiency of 92.0-99.0% (LiNO 3 -free electrolyte). The ultrathin property of a dense layer renders a low ionic resistance, resulting in 60% higher discharge capacity over the entire C-rates (versus the control sample with Celgard 2400 membrane). The robust macroporous layer supports the ultrathin layer to achieve a free-standing property, ensuring the usability of the Janus membrane.

Replacing Nitrogen by Sulfur: From Structurally Disordered Eumelanins to Regioregular Thiomelanin Polymers

PubMed Central

Iacomino, Mariagrazia; Mancebo-Aracil, Juan; Guardingo, Mireia; Martín, Raquel; Perfetti, Marco; Manini, Paola; Crescenzi, Orlando; Busqué, Félix; Sedó, Josep; Ruiz-Molina, Daniel

2017-01-01

The oxidative polymerization of 5,6-dihydroxybenzothiophene (DHBT), the sulfur analog of the key eumelanin building block 5,6-dihydroxyindole (DHI), was investigated to probe the role of nitrogen in eumelanin build-up and properties. Unlike DHI, which gives a typical black insoluble eumelanin polymer on oxidation, DHBT is converted to a grayish amorphous solid (referred to as thiomelanin) with visible absorption and electron paramagnetic resonance properties different from those of DHI melanin. Mass spectrometry experiments revealed gradational mixtures of oligomers up to the decamer level. Quite unexpectedly, nuclear magnetic resonance (NMR) analysis of the early oligomer fractions indicated linear, 4-, and 7-linked structures in marked contrast with DHI, which gives highly complex mixtures of partially degraded oligomers. Density functional theory (DFT) calculations supported the tendency of DHBT to couple via the 4- and 7-positions. These results uncover the role of nitrogen as a major determinant of the structural diversity generated by the polymerization of DHI, and point to replacement by sulfur as a viable entry to regioregular eumelanin-type materials for potential applications for surface functionalization by dip coating. PMID:29039817

Assessing acute toxicity of effluent from a textile industry and nearby river waters using sulfur-oxidizing bacteria in continuous mode.

PubMed

Gurung, Anup; Hassan, Sedky H A; Oh, Sang-Eun

2011-10-01

Bioassays are becoming an important tool for assessing the toxicity of complex mixtures of substances in aquatic environments in which Daphnia magna is routinely used as a test organism. Bioassays outweigh physicochemical analyses and are valuable in the decision-making process pertaining to the final discharge of effluents from wastewater treatment plants as they measure the total effect of the discharge which is ecologically relevant. In this study, the aquatic toxicity of a textile plant effluent and river water downstream from the plant were evaluated with sulfur-oxidizing bacterial biosensors in continuous mode. Collected samples were analysed for different physicochemical parameters and 1,4-dioxane was detected in the effluent. The effluent contained a relatively high chemical oxygen demand of 60 mg L(-1), which exceeded the limit set by the Korean government for industrial effluent discharges. Results showed that both the effluent and river waters were toxic to sulfur-oxidizing bacteria. These results show the importance of incorporating bioassays to detect toxicity in wastewater effluents for the sustainable management of water resources.

Ammonium Additives to Dissolve Lithium Sulfide through Hydrogen Binding for High-Energy Lithium–Sulfur Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Huilin; Han, Kee Sung; Vijayakumar, M.

In rechargeable Li-S batteries, the uncontrollable passivation of electrodes by highly insulating Li2S limits sulfur utilization, increases polarization and decreases cycling stability. Dissolving Li2S in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of Li2S to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N-H groups plays a critical role in dissolving Li2S by forming complex ligands with S2- anions coupled with themore » solvent’s solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of Li2S, therefore enables the direct use of Li2S as cathode material in Li-S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.« less

Simultaneous treatment of dimethyl disulfide and hydrogen sulfide in an alkaline biotrickling filter.

PubMed

Arellano-García, Luis; Le Borgne, Sylvie; Revah, Sergio

2018-01-01

Foul odors comprise generally a complex mixture of molecules, where reduced sulfur compounds play a key role due to their toxicity and low odor threshold. Previous reports on treating mixtures of sulfur compounds in single biofilters showed that hydrogen sulfide (H 2 S) interferes with the removal and degradation of other sulfur compounds. In this study, hydrogen sulfide (H 2 S) and dimethyl disulfide (DMDS) were fed to an alkaline biotrickling filter (ABTF) at pH 10, to evaluate the simultaneous removal of inorganic and organic sulfur compounds in a single, basic-pH system. The H 2 S-DMDS mixture was treated for more than 200 days, with a gas residence time of 40 s, attaining elimination capacities of 86 g DMDS m -3 h -1 and 17 g H2S m -3 h -1 and removal efficiencies close to 100%. Conversion of H 2 S and DMDS to sulfate was generally above 70%. Consumption of sulfide and formaldehyde was verified by respirometry, suggesting the coexistence of both methylotrophic and chemoautotrophic breakdown pathways by the immobilized alkaliphilic biomass. The molecular biology analysis showed that the long-term acclimation of the ABTF led to a great variety of bacteria, predominated by Thioalkalivibrio species, while fungal community was notoriously less diverse and dominated by Fusarium species. Copyright © 2017. Published by Elsevier Ltd.

Sulfur-oxidizing bacterial populations within cyanobacterial dominated coral disease lesions.

PubMed

Bourne, David G; van der Zee, Marc J J; Botté, Emmanuelle S; Sato, Yui

2013-08-01

This study investigated the diversity and quantitative shifts of sulfur-oxidizing bacteria (SOB) during the onset of black band disease (BBD) in corals using quantitative PCR (qPCR) and cloning approaches targeting the soxB gene, involved in sulfur oxidation. Four Montipora sp. coral colonies identified with lesions previously termed cyanobacterial patches (CP) (comprising microbial communities different from those of BBD lesions), was monitored in situ as CP developed into BBD. The overall abundance of SOB in both CP and BBD lesions were very low and near the detection limit of the qPCR assay, although consistently indicated that SOB populations decreased as the lesions transitioned from CP to BBD. Phylogenetic assessment of retrieved soxB genes showed that SOB in both CP and BBD lesions were dominated by one sequence type, representing > 70% of all soxB gene sequences and affiliated with members of the Rhodobacteraceae within the α-Proteobacteria. This study represents the first assessment targeting SOB within BBD lesions and clearly shows that SOB are not highly diverse or abundant in this complex microbial mat. The lack of oxidation of reduced sulfur compounds by SOB likely aids the accumulation of high levels of sulfide at the base of the BBD mat, a compound contributing to the pathogenicity of BBD lesions. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.

Discovery and Mechanistic Characterization of Selective Inhibitors of H2S-producing Enzyme: 3-Mercaptopyruvate Sulfurtransferase (3MST) Targeting Active-site Cysteine Persulfide

PubMed Central

Hanaoka, Kenjiro; Sasakura, Kiyoshi; Suwanai, Yusuke; Toma-Fukai, Sachiko; Shimamoto, Kazuhito; Takano, Yoko; Shibuya, Norihiro; Terai, Takuya; Komatsu, Toru; Ueno, Tasuku; Ogasawara, Yuki; Tsuchiya, Yukihiro; Watanabe, Yasuo; Kimura, Hideo; Wang, Chao; Uchiyama, Masanobu; Kojima, Hirotatsu; Okabe, Takayoshi; Urano, Yasuteru; Shimizu, Toshiyuki; Nagano, Tetsuo

2017-01-01

Very recent studies indicate that sulfur atoms with oxidation state 0 or −1, called sulfane sulfurs, are the actual mediators of some physiological processes previously considered to be regulated by hydrogen sulfide (H2S). 3-Mercaptopyruvate sulfurtransferase (3MST), one of three H2S-producing enzymes, was also recently shown to produce sulfane sulfur (H2Sn). Here, we report the discovery of several potent 3MST inhibitors by means of high-throughput screening (HTS) of a large chemical library (174,118 compounds) with our H2S-selective fluorescent probe, HSip-1. Most of the identified inhibitors had similar aromatic ring-carbonyl-S-pyrimidone structures. Among them, compound 3 showed very high selectivity for 3MST over other H2S/sulfane sulfur-producing enzymes and rhodanese. The X-ray crystal structures of 3MST complexes with two of the inhibitors revealed that their target is a persulfurated cysteine residue located in the active site of 3MST. Precise theoretical calculations indicated the presence of a strong long-range electrostatic interaction between the persulfur anion of the persulfurated cysteine residue and the positively charged carbonyl carbon of the pyrimidone moiety of the inhibitor. Our results also provide the experimental support for the idea that the 3MST-catalyzed reaction with 3-mercaptopyruvate proceeds via a ping-pong mechanism. PMID:28079151

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

NASA Astrophysics Data System (ADS)

Chelle-Michou, Cyril; Chiaradia, Massimo

2017-12-01

Chlorine and sulfur are of paramount importance for supporting the transport and deposition of ore metals at magmatic-hydrothermal systems such as the Coroccohuayco Fe-Cu-Au porphyry-skarn deposit, Peru. Here, we used recent partitioning models to determine the Cl and S concentration of the melts from the Coroccohuayco magmatic suite using apatite and amphibole chemical analyses. The pre-mineralization gabbrodiorite complex hosts S-poor apatite, while the syn- and post-ore dacitic porphyries host S-rich apatite. Our apatite data on the Coroccohuayco magmatic suite are consistent with an increasing oxygen fugacity (from the gabbrodiorite complex to the porphyries) causing the dominant sulfur species to shift from S2- to S6+ at upper crustal pressure where the magmas were emplaced. We suggest that this change in sulfur speciation could have favored S degassing, rather than its sequestration in magmatic sulfides. Using available partitioning models for apatite from the porphyries, pre-degassing S melt concentration was 20-200 ppm. Estimates of absolute magmatic Cl concentrations using amphibole and apatite gave highly contrasting results. Cl melt concentrations obtained from apatite (0.60 wt% for the gabbrodiorite complex; 0.2-0.3 wt% for the porphyries) seems much more reasonable than those obtained from amphibole which are very low (0.37 wt% for the gabbrodiorite complex; 0.10 wt% for the porphyries). In turn, relative variations of the Cl melt concentrations obtained from amphibole during magma cooling are compatible with previous petrological constraints on the Coroccohuayco magmatic suite. This confirms that the gabbrodioritic magma was initially fluid undersaturated upon emplacement, and that magmatic fluid exsolution of the gabbrodiorite and the pluton rooting the porphyry stocks and dikes were emplaced and degassed at 100-200 MPa. Finally, mass balance constraints on S, Cu and Cl were used to estimate the minimum volume of magma required to form the Coroccohuayco deposit. These three estimates are remarkably consistent among each other (ca. 100 km3) and suggest that the Cl melt concentration is at least as critical as that of Cu and S to form an economic mineralization.

Can we trust mass spectrometry for determination of arsenic peptides in plants: comparison of LC-ICP-MS and LC-ES-MS/ICP-MS with XANES/EXAFS in analysis of Thunbergia alata.

PubMed

Bluemlein, Katharina; Raab, Andrea; Meharg, Andrew A; Charnock, John M; Feldmann, Jörg

2008-04-01

The weakest step in the analytical procedure for speciation analysis is extraction from a biological material into an aqueous solution which undergoes HPLC separation and then simultaneous online detection by elemental and molecular mass spectrometry (ICP-MS/ES-MS). This paper describes a study to determine the speciation of arsenic and, in particular, the arsenite phytochelatin complexes in the root from an ornamental garden plant Thunbergia alata exposed to 1 mg As L(-1) as arsenate. The approach of formic acid extraction followed by HPLC-ES-MS/ICP-MS identified different As(III)-PC complexes in the extract of this plant and made their quantification via sulfur (m/z 32) and arsenic (m/z 75) possible. Although sulfur sensitivity could be significantly increased when xenon was used as collision gas in ICP-qMS, or when HR-ICP-MS was used in medium resolution, the As:S ratio gave misleading results in the identification of As(III)-PC complexes due to the relatively low resolution of the chromatography system in relation to the variety of As-peptides in plants. Hence only the parallel use of ES-MS/ICP-MS was able to prove the occurrence of such arsenite phytochelatin complexes. Between 55 and 64% of the arsenic was bound to the sulfur of peptides mainly as As(III)(PC(2))(2), As(III)(PC(3)) and As(III)(PC(4)). XANES (X-ray absorption near-edge spectroscopy) measurement, using the freshly exposed plant root directly, confirmed that most of the arsenic is trivalent and binds to S of peptides (53% As-S) while 38% occurred as arsenite and only 9% unchanged as arsenate. EXAFS data confirmed that As-S and As-O bonds occur in the plants. This study confirms, for the first time, that As-peptides can be extracted by formic acid and chromatographically separated on a reversed-phase column without significant decomposition or de-novo synthesis during the extraction step.

Installation Restoration Program Records Search for Des Moines Air National Guard Installation, Iowa

DTIC Science & Technology

1983-09-01

installation. Low-lying drainageways on the site are underlain by soils of the Gravity series and of the Wabash -Gravity-Nodaway complex. These soils...Shop The electric shop is located in Facility No. 100. Wastes generated from this area include nickel- -- ’ cadmium batteries (24/year) and sulfuric

78 FR 20868 - Approval and Promulgation of Implementation Plans; Designation of Areas for Air Quality Planning...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-08

... chemical reactions from precursor gases (e.g., secondary particles). Secondary particles, such as sulfates, nitrates, and complex carbon compounds, are formed from reactions with oxides of sulfur (SO X ), oxides of... nonattainment new source review (nonattainment NSR) permit programs; provisions for air pollution modeling; and...

Storage proteins of common bean identified with 2D-PAGE

USDA-ARS?s Scientific Manuscript database

The common bean is a significant source of protein, complex carbohydrates, fiber, and minerals. Seeds of most dry beans contain 15 to 25% protein and are rich in lysine but low in the sulfur containing amino acids cysteine and methionine. Knowledge of common bean proteins is important for research a...

Catalytic asymmetric synthesis of 2,2-disubstituted oxetanes from ketones by using a one-pot sequential addition of sulfur ylide.

PubMed

Sone, Toshihiko; Lu, Gang; Matsunaga, Shigeki; Shibasaki, Masakatsu

2009-01-01

Better the second time around: The title compounds were synthesized by using a one-pot double methylene transfer catalyzed by a heterobimetallic La/Li complex. Chiral amplification in the second step was the key to obtaining oxetanes in high enantiomeric excess (see scheme).

The LH2 complexes are assembled in the cells of purple sulfur bacterium Ectothiorhodospira haloalkaliphila with inhibition of carotenoid biosynthesis.

PubMed

Ashikhmin, Aleksandr; Makhneva, Zoya; Moskalenko, Andrey

2014-03-01

The effect of the inhibitor of carotenoid (Car) biosynthesis, diphenylamine (DPA), on the cells of the purple sulfur bacterium Ectothiorhodospira (Ect.) haloalkaliphila has been studied. There occurs an inhibition of the biosynthesis of colored Cars (≥99 %) at 71 μM DPA. Considering "empty" Car pockets (Moskalenko and Makhneva 2012) the content of Cars in the DPA-treated samples is first calculated more correctly. The total content of the colored Cars in the sample at 71 μM DPA does not exceed 1 % of the wild type. In the DPA-treated cells (membranes) a complete set of pigment-protein complexes is retained. The LH2 complex at 71 μM DPA is isolated, which is identical to the LH2 complex of the wild type in near IR absorption spectra. This suggests that the principles for assembling this LH2 complex in vivo in the absence of colored Cars remain the same. These results are in full agreement with the data obtained earlier for Allochromatium (Alc.) minutissimum (Moskalenko and Makhneva 2012). They are as follows: (1) DPA almost entirely inhibits the biosynthesis of the colored Cars in Ect. haloalkaliphila cells. (2) In the DPA-treated samples non-colored Cars are detected at 53.25 μM DPA (as traces) and at 71 μM DPA. (3) DPA may affect both phytoene synthase (at ≤71 μM DPA) and phytoene desaturase (at ≥53.25 μM DPA). (4) The assembly of LH2 complex does occur without any colored Cars.

Present-day Galactic Evolution: Low-metallicity, Warm, Ionized Gas Inflow Associated with High-velocity Cloud Complex A

NASA Astrophysics Data System (ADS)

Barger, K. A.; Haffner, L. M.; Wakker, B. P.; Hill, Alex. S.; Madsen, G. J.; Duncan, A. K.

2012-12-01

The high-velocity cloud Complex A is a probe of the physical conditions in the Galactic halo. The kinematics, morphology, distance, and metallicity of Complex A indicate that it represents new material that is accreting onto the Galaxy. We present Wisconsin Hα Mapper kinematically resolved observations of Complex A over the velocity range of -250 to -50 km s-1 in the local standard of rest reference frame. These observations include the first full Hα intensity map of Complex A across (\\mathit {l, b}) = (124{^\\circ }, 18{^\\circ }) to (171°, 53°) and deep targeted observations in Hα, [S II] λ6716, [N II] λ6584, and [O I] λ6300 toward regions with high H I column densities, background quasars, and stars. The Hα data imply that the masses of neutral and ionized material in the cloud are similar, both being greater than 106 M ⊙. We find that the Bland-Hawthorn & Maloney model for the intensity of the ionizing radiation near the Milky Way is consistent with the known distance of the high-latitude part of Complex A and an assumed cloud geometry that puts the lower-latitude parts of the cloud at a distance of 7-8 kpc. This compatibility implies a 5% ionizing photon escape fraction from the Galactic disk. We also provide the nitrogen and sulfur upper abundance solutions for a series of temperatures, metallicities, and cloud configurations for purely photoionized gas; these solutions are consistent with the sub-solar abundances found by previous studies, especially for temperatures above 104 K or for gas with a high fraction of singly ionized nitrogen and sulfur.

PRESENT-DAY GALACTIC EVOLUTION: LOW-METALLICITY, WARM, IONIZED GAS INFLOW ASSOCIATED WITH HIGH-VELOCITY CLOUD COMPLEX A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barger, K. A.; Haffner, L. M.; Wakker, B. P.

2012-12-20

The high-velocity cloud Complex A is a probe of the physical conditions in the Galactic halo. The kinematics, morphology, distance, and metallicity of Complex A indicate that it represents new material that is accreting onto the Galaxy. We present Wisconsin H{alpha} Mapper kinematically resolved observations of Complex A over the velocity range of -250 to -50 km s{sup -1} in the local standard of rest reference frame. These observations include the first full H{alpha} intensity map of Complex A across (l, b) = (124 Degree-Sign , 18 Degree-Sign ) to (171 Degree-Sign , 53 Degree-Sign ) and deep targeted observationsmore » in H{alpha}, [S II] {lambda}6716, [N II] {lambda}6584, and [O I] {lambda}6300 toward regions with high H I column densities, background quasars, and stars. The H{alpha} data imply that the masses of neutral and ionized material in the cloud are similar, both being greater than 10{sup 6} M{sub Sun }. We find that the Bland-Hawthorn and Maloney model for the intensity of the ionizing radiation near the Milky Way is consistent with the known distance of the high-latitude part of Complex A and an assumed cloud geometry that puts the lower-latitude parts of the cloud at a distance of 7-8 kpc. This compatibility implies a 5% ionizing photon escape fraction from the Galactic disk. We also provide the nitrogen and sulfur upper abundance solutions for a series of temperatures, metallicities, and cloud configurations for purely photoionized gas; these solutions are consistent with the sub-solar abundances found by previous studies, especially for temperatures above 10{sup 4} K or for gas with a high fraction of singly ionized nitrogen and sulfur.« less

An Fe-S cluster in the conserved Cys-rich region in the catalytic subunit of FAD-dependent dehydrogenase complexes.

PubMed

Shiota, Masaki; Yamazaki, Tomohiko; Yoshimatsu, Keiichi; Kojima, Katsuhiro; Tsugawa, Wakako; Ferri, Stefano; Sode, Koji

2016-12-01

Several bacterial flavin adenine dinucleotide (FAD)-harboring dehydrogenase complexes comprise three distinct subunits: a catalytic subunit with FAD, a cytochrome c subunit containing three hemes, and a small subunit. Owing to the cytochrome c subunit, these dehydrogenase complexes have the potential to transfer electrons directly to an electrode. Despite various electrochemical applications and engineering studies of FAD-dependent dehydrogenase complexes, the intra/inter-molecular electron transfer pathway has not yet been revealed. In this study, we focused on the conserved Cys-rich region in the catalytic subunits using the catalytic subunit of FAD dependent glucose dehydrogenase complex (FADGDH) as a model, and site-directed mutagenesis and electron paramagnetic resonance (EPR) were performed. By co-expressing a hitch-hiker protein (γ-subunit) and a catalytic subunit (α-subunit), FADGDH γα complexes were prepared, and the properties of the catalytic subunit of both wild type and mutant FADGDHs were investigated. Substitution of the conserved Cys residues with Ser resulted in the loss of dye-mediated glucose dehydrogenase activity. ICP-AEM and EPR analyses of the wild-type FADGDH catalytic subunit revealed the presence of a 3Fe-4S-type iron-sulfur cluster, whereas none of the Ser-substituted mutants showed the EPR spectrum characteristic for this cluster. The results suggested that three Cys residues in the Cys-rich region constitute an iron-sulfur cluster that may play an important role in the electron transfer from FAD (intra-molecular) to the multi-heme cytochrome c subunit (inter-molecular) electron transfer pathway. These features appear to be conserved in the other three-subunit dehydrogenases having an FAD cofactor. Copyright © 2016 Elsevier B.V. All rights reserved.

Computational studies of small neutral vanadium oxide clusters and their reactions with sulfur dioxide

NASA Astrophysics Data System (ADS)

Jakubikova, Elena; He, Sheng-Gui; Xie, Yan; Matsuda, Yoshiyuki; Bernstein, Elliot

2007-03-01

Vanadium oxide is a catalytic system that plays an important role in the conversion of SO2 to SO3. Density functional theory at the BPW91/LANL2DZ level is employed to obtain structures of VOy (y=1,,5), V2Oy (y=2,,7), V3Oy (y=4,,9), V4Oy (y=7,,12) and their complexes with SO2. BPW91/LANL2DZ is insufficient to describe properly relative V-O and S-O bond strengths of vanadium and sulfur oxides. Calibration of theoretical results with experimental data is necessary to compute enthalpies of reactions between VxOy and SO2. Theoretical results indicate SO2 to SO conversion occurs for oxygen-deficient clusters and SO2 to SO3 conversion occurs for oxygen-rich clusters. Subsequent experimental studies confirm the presence of SO in the molecular beam as well as the presence of VxOy complexes with SO2. Some possible mechanisms for SO3 formation and catalyst regeneration for solids are also suggested.

Hole Polaron Diffusion in the Final Discharge Product of Lithium–Sulfur Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhixiao; Balbuena, Perla B.; Mukherjee, Partha P.

Poor electronic conductivity of bulk lithium sulfide (Li 2S) is a critical challenge for the debilitating performance of the lithium–sulfur battery. In this study we focus on investigating the thermodynamic and kinetic properties of native defects in Li 2S based on a first-principles approach. It is found that the hole polaron p + can form in Li 2S by removing a 3p electron from an S 2– anion. The p + diffusion barrier is only 90 meV, which is much lower than the Li vacancy (V Li –) diffusion barrier. Hence p + has the potential to serve as amore » charge carrier in the discharge product. Once the vacancy–polaron complex (V Li -––2p +) forms, the charge transport will be hindered due to the relatively higher diffusion barrier of the complex. Heteroatom dopants, which can decrease the p + formation energy and increase V Li – formation energy, are expected to be introduced to the discharge product to improve the electronic conductivity.« less

Hole Polaron Diffusion in the Final Discharge Product of Lithium–Sulfur Batteries

DOE PAGES

Liu, Zhixiao; Balbuena, Perla B.; Mukherjee, Partha P.

2017-07-24

Poor electronic conductivity of bulk lithium sulfide (Li 2S) is a critical challenge for the debilitating performance of the lithium–sulfur battery. In this study we focus on investigating the thermodynamic and kinetic properties of native defects in Li 2S based on a first-principles approach. It is found that the hole polaron p + can form in Li 2S by removing a 3p electron from an S 2– anion. The p + diffusion barrier is only 90 meV, which is much lower than the Li vacancy (V Li –) diffusion barrier. Hence p + has the potential to serve as amore » charge carrier in the discharge product. Once the vacancy–polaron complex (V Li -––2p +) forms, the charge transport will be hindered due to the relatively higher diffusion barrier of the complex. Heteroatom dopants, which can decrease the p + formation energy and increase V Li – formation energy, are expected to be introduced to the discharge product to improve the electronic conductivity.« less

Zinc Bioavailability from Phytate-Rich Foods and Zinc Supplements. Modeling the Effects of Food Components with Oxygen, Nitrogen, and Sulfur Donor Ligands.

PubMed

Tang, Ning; Skibsted, Leif H

2017-10-04

Aqueous solubility of zinc phytate (K sp = (2.6 ± 0.2) × 10 -47 mol 7 /L 7 ), essential for zinc bioavailability from plant foods, was found to decrease with increasing temperature corresponding to ΔH dis of -301 ± 22 kJ/mol and ΔS dis of -1901 ± 72 J/(mol K). Binding of zinc to phytate was found to be exothermic for the stronger binding site and endothermic for the weaker binding site. The solubility of the slightly soluble zinc citrate and insoluble zinc phytate was found to be considerably enhanced by the food components with oxygen donor, nitrogen donor, and sulfur donor ligands. The driving force for the enhanced solubility is mainly due to the complex formation between zinc and the investigated food components rather than ligand exchange and ternary complex formation as revealed by quantum mechanical calculations and isothermal titration calorimetry. Histidine and citrate are promising ligands for improving zinc absorption from phytate-rich foods.

Mitochondrial iron-sulfur cluster biogenesis from molecular understanding to clinical disease

PubMed Central

Alfadhel, Majid; Nashabat, Marwan; Ali, Qais Abu; Hundallah, Khalid

2017-01-01

Iron–sulfur clusters (ISCs) are known to play a major role in various protein functions. Located in the mitochondria, cytosol, endoplasmic reticulum and nucleus, they contribute to various core cellular functions. Until recently, only a few human diseases related to mitochondrial ISC biogenesis defects have been described. Such diseases include Friedreich ataxia, combined oxidative phosphorylation deficiency 19, infantile complex II/III deficiency defect, hereditary myopathy with lactic acidosis and mitochondrial muscle myopathy, lipoic acid biosynthesis defects, multiple mitochondrial dysfunctions syndromes and non ketotic hyperglycinemia due to glutaredoxin 5 gene defect. Disorders of mitochondrial import, export and translation, including sideroblastic anemia with ataxia, EVEN-PLUS syndrome and mitochondrial complex I deficiency due to nucleotide-binding protein-like protein gene defect, have also been implicated in ISC biogenesis defects. With advances in next generation sequencing technologies, more disorders related to ISC biogenesis defects are expected to be elucidated. In this article, we aim to shed the light on mitochondrial ISC biogenesis, related proteins and their function, pathophysiology, clinical phenotypes of related disorders, diagnostic approach, and future implications. PMID:28064324

Distribution of rhodopin and spirilloxanthin between LH1 and LH2 complexes when incorporating carotenoid mixture into the membrane of purple sulfur bacterium Allochromatium minutissimum in vitro.

PubMed

Bolshakov, M A; Ashikhmin, A A; Makhneva, Z K; Moskalenko, A A

2016-11-01

Carotenoid mixture enriched by rhodopin and spirilloxanthin was incorporated in LH2 and LH1 complexes from Allochromatium (Alc.) minutissimum in vitro. The maximum incorporating level was ~95%. Rhodopin (56.4%) and spirilloxanthin (13.8%) were incorporated into the LH1 complex, in contrast to the control complex, which contained primarily spirilloxanthin (66.8%). After incorporating, the LH2 complex contained rhodopin (66.7%) and didehydrorhodopin (14.6%), which was close to their content in the control (67.4 and 20.5%, respectively). Thus, it was shown that carotenoids from the total pool are not selectively incorporated into LH2 and LH1 complexes in vitro in the proportion corresponding to the carotenoid content in the complexes in vivo.

The genome sequence of the metal-mobilizing, extremely thermoacidophilic archaeon Metallosphaera sedula provides insights into bioleaching-associated metabolism.

PubMed

Auernik, Kathryne S; Maezato, Yukari; Blum, Paul H; Kelly, Robert M

2008-02-01

Despite their taxonomic description, not all members of the order Sulfolobales are capable of oxidizing reduced sulfur species, which, in addition to iron oxidation, is a desirable trait of biomining microorganisms. However, the complete genome sequence of the extremely thermoacidophilic archaeon Metallosphaera sedula DSM 5348 (2.2 Mb, approximately 2,300 open reading frames [ORFs]) provides insights into biologically catalyzed metal sulfide oxidation. Comparative genomics was used to identify pathways and proteins involved (directly or indirectly) with bioleaching. As expected, the M. sedula genome contains genes related to autotrophic carbon fixation, metal tolerance, and adhesion. Also, terminal oxidase cluster organization indicates the presence of hybrid quinol-cytochrome oxidase complexes. Comparisons with the mesophilic biomining bacterium Acidithiobacillus ferrooxidans ATCC 23270 indicate that the M. sedula genome encodes at least one putative rusticyanin, involved in iron oxidation, and a putative tetrathionate hydrolase, implicated in sulfur oxidation. The fox gene cluster, involved in iron oxidation in the thermoacidophilic archaeon Sulfolobus metallicus, was also identified. These iron- and sulfur-oxidizing components are missing from genomes of nonleaching members of the Sulfolobales, such as Sulfolobus solfataricus P2 and Sulfolobus acidocaldarius DSM 639. Whole-genome transcriptional response analysis showed that 88 ORFs were up-regulated twofold or more in M. sedula upon addition of ferrous sulfate to yeast extract-based medium; these included genes for components of terminal oxidase clusters predicted to be involved with iron oxidation, as well as genes predicted to be involved with sulfur metabolism. Many hypothetical proteins were also differentially transcribed, indicating that aspects of the iron and sulfur metabolism of M. sedula remain to be identified and characterized.

The Genome Sequence of the Metal-Mobilizing, Extremely Thermoacidophilic Archaeon Metallosphaera sedula Provides Insights into Bioleaching-Associated Metabolism▿ †

PubMed Central

Auernik, Kathryne S.; Maezato, Yukari; Blum, Paul H.; Kelly, Robert M.

2008-01-01

Despite their taxonomic description, not all members of the order Sulfolobales are capable of oxidizing reduced sulfur species, which, in addition to iron oxidation, is a desirable trait of biomining microorganisms. However, the complete genome sequence of the extremely thermoacidophilic archaeon Metallosphaera sedula DSM 5348 (2.2 Mb, ∼2,300 open reading frames [ORFs]) provides insights into biologically catalyzed metal sulfide oxidation. Comparative genomics was used to identify pathways and proteins involved (directly or indirectly) with bioleaching. As expected, the M. sedula genome contains genes related to autotrophic carbon fixation, metal tolerance, and adhesion. Also, terminal oxidase cluster organization indicates the presence of hybrid quinol-cytochrome oxidase complexes. Comparisons with the mesophilic biomining bacterium Acidithiobacillus ferrooxidans ATCC 23270 indicate that the M. sedula genome encodes at least one putative rusticyanin, involved in iron oxidation, and a putative tetrathionate hydrolase, implicated in sulfur oxidation. The fox gene cluster, involved in iron oxidation in the thermoacidophilic archaeon Sulfolobus metallicus, was also identified. These iron- and sulfur-oxidizing components are missing from genomes of nonleaching members of the Sulfolobales, such as Sulfolobus solfataricus P2 and Sulfolobus acidocaldarius DSM 639. Whole-genome transcriptional response analysis showed that 88 ORFs were up-regulated twofold or more in M. sedula upon addition of ferrous sulfate to yeast extract-based medium; these included genes for components of terminal oxidase clusters predicted to be involved with iron oxidation, as well as genes predicted to be involved with sulfur metabolism. Many hypothetical proteins were also differentially transcribed, indicating that aspects of the iron and sulfur metabolism of M. sedula remain to be identified and characterized. PMID:18083856

Stratospheric Dynamical Response and Ozone Feedbacks in the Presence of SO2 Injections

NASA Astrophysics Data System (ADS)

Richter, Jadwiga H.; Tilmes, Simone; Mills, Michael J.; Tribbia, Joseph J.; Kravitz, Ben; MacMartin, Douglas G.; Vitt, Francis; Lamarque, Jean-Francois

2017-12-01

Injections of sulfur dioxide into the stratosphere are among several proposed methods of solar radiation management. Such injections could cool the Earth's climate. However, they would significantly alter the dynamics of the stratosphere. We explore here the stratospheric dynamical response to sulfur dioxide injections ˜5 km above the tropopause at multiple latitudes (equator, 15°S, 15°N, 30°S and 30°N) using a fully coupled Earth system model, Community Earth System Model, version 1, with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1(WACCM)). We find that in all simulations, the tropical lower stratosphere warms primarily between 30°S and 30°N, regardless of injection latitude. The quasi-biennial oscillation (QBO) of the tropical zonal wind is altered by the various sulfur dioxide injections. In a simulation with a 12 Tg yr-1 equatorial injection, and with fully interactive chemistry, the QBO period lengthens to ˜3.5 years but never completely disappears. However, in a simulation with specified (or noninteractive) chemical fields, including O3 and prescribed aerosols taken from the interactive simulation, the oscillation is virtually lost. In addition, we find that geoengineering does not always lengthen the QBO. We further demonstrate that the QBO period changes from 24 to 12-17 months in simulations with sulfur dioxide injections placed poleward of the equator. Our study points to the importance of understanding and verifying of the complex interactions between aerosols, atmospheric dynamics, and atmospheric chemistry as well as understanding the effects of sulfur dioxide injections placed away from the Equator on the QBO.

Mechanism of SO2 removal by carbon

USGS Publications Warehouse

Lizzio, Anthony A.; DeBarr, Joseph A.

1997-01-01

The reaction of SO2 with carbon (C) in the presence of O2 and H2O involves a series of reactions that leads to the formation of sulfuric acid as the final product. The rate-determining step in the overall process is the oxidation of SO2 to SO3. Three SO2 oxidation reactions are possible. Adsorbed SO2 (C−SO2) can react either with gas phase O2 or with adsorbed oxygen (C−O complex) to form sulfur trioxide (SO3), or gas phase SO2 can react directly with the C−O complex. In optimizing the SO2 removal capabilities of carbon, most studies only assume a given mechanism for SO2 adsorption and conversion to H2SO4 to be operable. The appropriate SO2 oxidation step and role of the C−O complex in this mechanism remain to be determined. The ultimate goal of this study was to prepare activated char from Illinois coal with optimal properties for low-temperature (80−150°C) removal of sulfur dioxide from coal combustion flue gas. The SO2 adsorption capacity of activated char was found to be inversely proportional to the amount of oxygen adsorbed on its surface. A temperature-programmed desorption technique was developed to titrate those sites responsible for adsorption of SO2 and conversion to H2SO4. On the basis of these results, a mechanism for SO2 removal by carbon was proposed. The derived rate expression showed SO2 adsorption to be dependent only on the fundamental rate constant and concentration of carbon atoms designated as free sites. Recent studies indicate a similar relationship exists between the rate of carbon gasification (in CO2 or H2O) and the number of reactive sites as determined by transient kinetics experiments. Utilizing the concept of active or free sites, it was possible to produce a char from Illinois coal having an SO2 adsorption capacity surpassing that of a commercial catalytic activated carbon.

Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity.

PubMed

Mena, Natalia P; Bulteau, Anne Laure; Salazar, Julio; Hirsch, Etienne C; Núñez, Marco T

2011-06-03

Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters are involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given that inhibition of complex I and iron accumulation are hallmarks of idiopathic Parkinson's disease, the findings reported here may have relevance for understanding the pathophysiology of this disease. Copyright © 2011 Elsevier Inc. All rights reserved.

Structure-Function of the Cytochrome b 6f Complex of Oxygenic Photosynthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cramer, W. A.; Yamashita, E.; Baniulis, D.

2014-03-20

Structure–function of the major integral membrane cytochrome b 6f complex that functions in cyanobacteria, algae, and green plants to transfer electrons between the two reaction center complexes in the electron transport chain of oxygenic photosynthesis is discussed in the context of recently obtained crystal structures of the complex and soluble domains of cytochrome f and the Rieske iron–sulfur protein. The energy-transducing function of the complex, generation of the proton trans-membrane electrochemical potential gradient, centers on the oxidation/reduction pathways of the plastoquinol/plastoquinone (QH 2/Q), the proton donor/acceptor within the complex. These redox reactions are carried out by five redox prosthetic groupsmore » embedded in each monomer, the high potential two iron–two sulfur cluster and the heme of cytochrome f on the electropositive side (p) of the complex, two noncovalently bound b-type hemes that cross the complex and the membrane, and a covalently bound c-type heme (c n) on the electronegative side (n). These five redox-active groups are organized in high- (cyt f/[2Fe–2S] and low-potential (hemes b p, b n, c n) electron transport pathways that oxidize and reduce the quinol and quinone on the p- and n-sides in a Q-cycle-type mechanism, while translocating as many as 2 H + to the p-side aqueous side for every electron transferred through the high potential chain to the photosystem I reaction center. The presence of heme c n and the connection of the n-side of the membrane and b 6f complex to the cyclic electron transport chain indicate that the Q cycle in the oxygenic photosynthetic electron transport chain differs from those connected to the bc 1 complex in the mitochondrial respiratory chain and the chain in photosynthetic bacteria. Inferences from the structure and C2 symmetry of the complex for the pathway of QH 2/Q transfer within the complex, problems posed by the presence of lipid in the inter-monomer cavity, and the narrow portal for QH2 passage through the p-side oxidation site proximal to the [2Fe–2S] cluster are discussed.« less

Biogenesis of iron-sulfur clusters in mammalian cells: new insights and relevance to human disease

PubMed Central

Rouault, Tracey A.

2012-01-01

Iron-sulfur (Fe-S) clusters are ubiquitous cofactors composed of iron and inorganic sulfur. They are required for the function of proteins involved in a wide range of activities, including electron transport in respiratory chain complexes, regulatory sensing, photosynthesis and DNA repair. The proteins involved in the biogenesis of Fe-S clusters are evolutionarily conserved from bacteria to humans, and many insights into the process of Fe-S cluster biogenesis have come from studies of model organisms, including bacteria, fungi and plants. It is now clear that several rare and seemingly dissimilar human diseases are attributable to defects in the basic process of Fe-S cluster biogenesis. Although these diseases –which include Friedreich’s ataxia (FRDA), ISCU myopathy, a rare form of sideroblastic anemia, an encephalomyopathy caused by dysfunction of respiratory chain complex I and multiple mitochondrial dysfunctions syndrome – affect different tissues, a feature common to many of them is that mitochondrial iron overload develops as a secondary consequence of a defect in Fe-S cluster biogenesis. This Commentary outlines the basic steps of Fe-S cluster biogenesis as they have been defined in model organisms. In addition, it draws attention to refinements of the process that might be specific to the subcellular compartmentalization of Fe-S cluster biogenesis proteins in some eukaryotes, including mammals. Finally, it outlines several important unresolved questions in the field that, once addressed, should offer important clues into how mitochondrial iron homeostasis is regulated, and how dysfunction in Fe-S cluster biogenesis can contribute to disease. PMID:22382365

EPR and ESE of CuS4 complex in Cu(dmit)2: g-Factor and hyperfine splitting correlation in tetrahedral Cu-sulfur complexes

NASA Astrophysics Data System (ADS)

Hoffmann, Stanisław K.; Goslar, Janina; Lijewski, Stefan; Zalewska, Alina

2013-11-01

Pseudotetrahedral CuS4 complexes of Cu(dmit)2 compound in DMF solution were studied by EPR, UV-Vis and electron spin echo methods. After rapid freezing at 77 K a good glassy state is formed and the CuS4 complex has a D2d symmetry of a compressed tetrahedron with xy ground state and spin-Hamiltonian parameters g|| = 2.089, g⊥ = 2.026, A|| = 146 × 10-4 cm-1 and A⊥ = 30 × 10-4 cm-1. The complex is not deformed in the glassy state and is very rigid as indicated by the echo detected spectrum and by electron spin relaxation which is governed by reorientations of methyl groups of surrounding DMF molecules as shown by electron spin echo envelope modulation (ESEEM) spectrum. The g|| and A|| of Cu(dmit)2 and other CuS4 complexes collected in Peisach-Blumberg correlation diagram were analyzed using extended Molecular Orbital theory. We explain why the correlation line for copper-sulfur complexes has larger slope compared to the CuO4 and CuN4 tetrahedra. Along the correlation line the delocalization of unpaired electron density onto ligand is constant and varies from β = 0.78-0.83 for g|| in the range 2.06-2.10 of correlation diagram. The slope of the line is determined by the product of MO-coefficients αc1, where α is a parameter characterizing delocalization of unpaired electron in x2-y2 and c1 < 1 is a mixing parameter decreasing when 4p contribution grows. We found, unexpectedly, that αc1≈0.7 for all CuS4 complexes suggesting a correlation between degree of tetrahedral deformation and MO-parameters. MO-coefficients for Cu(dmit)2 are α = 0.753, β = 0.752 and c1 = 0.930 confirming a strong delocalization of unpaired electron in xy and x2-y2 orbitals.

Cadmium-sulfide crystallites in Cd-. gamma. -glutamyl peptide complexes from Lycopersicon and Daucus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reese, R.N.; Winge, D.R.

1989-04-01

Hydroponically-grown tomato plants (Lycopersicon esculentum P. Mill. cv stone) and suspension-cultured carrot cells (Daucus carota L.) exposed to 100 {mu}M cadmium salts produced metal-{gamma}-glutamyl peptide complexes containing acid labile sulfur. The properties of the complexes resemble the Cd-{gamma}-glutamyl complexes from Schizosaccharomyces pombe and Candida glabrata, known to contain a CdS crystallite core. The crystallite core is stabilized by a coating of peptides of the general structure ({gamma}-Glu-Cys){sub n}-Gly. The Cd-peptide complexes contain predominantly peptides of n{sub 2}, n{sub 3}, n{sub 4} and n{sub 3}desGly. Zn-peptide complexes were also isolated from carrot cultures grown in MS medium supplemented with 2 mMmore » Zn and cysteine. Results of preliminary characterization of these complexes are consistent with the presence of a colloidal particle similar to that of the Cd-complexes.« less

Crystal structure of mitochondrial respiratory membrane protein complex II.

PubMed

Sun, Fei; Huo, Xia; Zhai, Yujia; Wang, Aojin; Xu, Jianxing; Su, Dan; Bartlam, Mark; Rao, Zihe

2005-07-01

The mitochondrial respiratory Complex II or succinate:ubiquinone oxidoreductase (SQR) is an integral membrane protein complex in both the tricarboxylic acid cycle and aerobic respiration. Here we report the first crystal structure of Complex II from porcine heart at 2.4 A resolution and its complex structure with inhibitors 3-nitropropionate and 2-thenoyltrifluoroacetone (TTFA) at 3.5 A resolution. Complex II is comprised of two hydrophilic proteins, flavoprotein (Fp) and iron-sulfur protein (Ip), and two transmembrane proteins (CybL and CybS), as well as prosthetic groups required for electron transfer from succinate to ubiquinone. The structure correlates the protein environments around prosthetic groups with their unique midpoint redox potentials. Two ubiquinone binding sites are discussed and elucidated by TTFA binding. The Complex II structure provides a bona fide model for study of the mitochondrial respiratory system and human mitochondrial diseases related to mutations in this complex.

Exhaustive oxidation of a nickel dithiolate complex: some mechanistic insights en route to sulfate formation.

PubMed

Hosler, Erik R; Herbst, Robert W; Maroney, Michael J; Chohan, Balwant S

2012-01-21

A study of the step-wise oxidation of a Ni(II) diaminodithiolate complex through the formation of sulfate, the ultimate sulfur oxygenate, is reported. Controlled oxygenations or peroxidations of a neutral, planar, tetracoordinate, low-spin Ni(II) complex of a N(2)S(2)-donor ligand, (N,N'-dimethyl-N-N'-bis(2-mecaptoethyl)-1,3-propanediaminato) nickel(ii) (1), led to a series of sulfur oxygenates that have been isolated and characterized by ESI-MS and single-crystal X-ray diffraction. A monosulfenate complex (2) was detected by ESI-MS as a product of oxidation with one equivalent of H(2)O(2). However, this complex proved too unstable to isolate. Reaction of the dithiolate (1) with two equivalents of H(2)O(2) or one O(2) molecule leads to the formation of a monosulfinate complex (3), which was isolated and fully characterized by crystallography. The oxidation product of the monosulfinate (3) produced with either O(2) or H(2)O(2) is an interesting dimeric complex containing both sulfonate and thiolate ligands (4), this complex was fully characterized by crystallography, details of which were reported earlier by us. A disulfonate complex (7) is produced by reaction of 1 in the presence of O(2) or by reaction with exactly six equivalents of H(2)O(2). This complex was isolated and also fully characterized by crystallography. Possible intermediates in the conversion of the monosulfinate complex (3) to the disulfonate complex (7) include complexes with mixed sulfonate/sulfenate (5) or sulfonate/sulfinate (6) ligands. Complex 5, a four-oxygen adduct of 1, was not detected, but the sulfonate/sulfinate complex (6) was isolated and characterized. The oxidation chemistry of 1 is very different from that reported for other planar cis-N(2)S(2) Ni(ii) complexes including N,N'-dimethyl-N-N'-bis(2-mecaptoethyl)-1,3-ethylenediaminato) nickel(II), (8), and N,N'-bis(mercaptoethyl)-1,5-diazacyclooctane nickel(II). To address the structural aspects of the reactivity differences, the crystal structure of 8 was also determined. A comparison of the structures of planar Ni(II) complexes containing cis-dithiolate ligands, strongly suggests that the differences in reactivity are determined in part by the degree of flexibility that is allowed by the NN' chelate ring.

Carbon Disulfide Cosolvent Electrolytes for High-Performance Lithium Sulfur Batteries.

PubMed

Gu, Sui; Wen, Zhaoyin; Qian, Rong; Jin, Jun; Wang, Qingsong; Wu, Meifen; Zhuo, Shangjun

2016-12-21

Development of lithium sulfur (Li-S) batteries with high Coulombic efficiency and long cycle stability remains challenging due to the dissolution and shuttle of polysulfides in electrolyte. Here, a novel additive, carbon disulfide (CS 2 ), to the organic electrolyte is reported to improve the cycling performance of Li-S batteries. The cells with the CS 2 -additive electrolyte exhibit high Coulombic efficiency and long cycle stability, showing average Coulombic efficiency >99% and a capacity retention of 88% over the entire 300 cycles. The function of the CS 2 additive is 2-fold: (1) it inhibits the migration of long-chain polysulfides to the anode by forming complexes with polysulfides and (2) it passivates electrode surfaces by inducing the protective coatings on both the anode and the cathode.

Cadmium-sulfide crystallites in Cd-(. gamma. EC) sub n G peptide complexes from tomato. [Lycopersicon esculentum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reese, R.N.; White, C.A.; Winge, D.R.

Hydroponically grown tomato plants (Lycopersicon esculentum P. Mill cv Golden Boy) exposed to 100 micromolar cadmium sulfate produced metal-({gamma}EC){sub n}G peptide complexes containing acid-labile sulfur. The properties of the complexes resemble those of the cadmium-({gamma}EC){sub n}G peptide complexes from Schizo-saccharomyces pombe and Candida glabrata known to contain a cadmium sulfide crystallite core. The crystallite is stabilized by a sheath of peptides of general structure ({gamma}Glu-Cys){sub n}-Gly. The cadmium-peptide complexes of tomato contained predominantly peptides of n{sub 3}, n{sub 4}, and n{sub 5}. Spectroscopic analyses indicated that the tomato cadmium-sulfide-peptide complex contained CdS crystallite core particles smaller than 2.0 nanometers inmore » diameter.« less

ELUTION OF URANIUM VALUES FROM ION EXCHANGE RESINS

DOEpatents

Kennedy, R.H.

1959-11-24

A process is described for eluting complex uranium ions absorbed on ion exchange resins. The resin is subjected to the action of an aqueous eluting solution contuining sulfuric acid and an alkali metal, ammonium, or magnesium chloride or nitrate, the elution being carried out until the desired amount of the uranium is removed from the resin.

Application of Microbeam Techniques to Identifying and Assessing Comagmatic Mixing Between Summit and Rift Eruptions at Kilauea Volcano (Invited)

NASA Astrophysics Data System (ADS)

Thornber, C. R.; Rowe, M. C.; Adams, D. T.; Orr, T. R.

2010-12-01

Near-continuous eruption of Kilauea Volcano since 1983 has yielded an extensive record of glass, phenocryst and melt-inclusion chemistry from well-quenched lava that can be correlated with geophysical and geological monitoring data. Eruption temperatures are determined using glass thermometry. Microbeam evaluation of phenocryst mineralogy, morphology, texture, zoning and melt inclusions helps to constrain magma storage and transport within the edifice and to track the evolution of shallow magmatic plumbing during this prolonged eruptive era. For most of this eruption up to April 2001, east rift lava was olivine-phyric and olivine-liquid relations indicated equilibrium crystallization during summit-to-rift magma transport. From 2001 to present, most lava erupted from vents near Pu`u O`o has been a relatively low-temperature “hybrid”, characterized by a disequilibrium low-pressure phenocryst assemblage. Olivine (Fo81.5-80.5) coexists with phenocrysts of lower temperature clinopyroxene (±plagioclase, ±Fe-rich olivine). Mixing between hotter and cooler magma is texturally documented by complex pyroxene zoning and resorption and olivine overgrowths on resorbed pyroxene. The co-magmatic mixing is not apparent in bulk lava analyses, since both components are fractionates of parent magmas with indistinguishable trace-element signatures. Post-2001 rift-zone lava indicates perpetual flushing of stored magma by hotter recharge magma rising from the mantle source. Geophysical and gas monitoring data confirm an increase in magma supply to Kilauea Volcano between 2001 and 2008, which we have interpreted as increasing the efficiency of the flushing process. Since March 2008, the petrology of the new summit lava lake and contemporaneously erupted rift zone lava provides new perspective on complexities of magma degassing, crystallization and mixing prior to rift eruption. Bulk lava chemistry, SIMS and LA-ICPMS analyses of matrix glasses and olivine melt-inclusions in both rift zone lava and summit tephra reveal identical trace-element concentrations, thus confirming that both eruption sites share a common magma source. Because Kilauea magma degasses all of its primary sulfur (~1200 to 1500 ppm) at pressures less than 100 bars, shallow summit-to-rift magma mixing and crystallization is quantified by study of relative sulfur concentrations in melt inclusions. For higher temperature magma at the summit, olivine (Fo82.0-83.5) contains melt inclusions with 600-1400 ppm S. A small population of rift zone phenocrysts have similar sulfur contents, while typical rift zone olivine inclusions contain 300-700 ppm S. Complex zoned pyroxene phenocrysts with multiple inclusions have trapped melts of low to high sulfur concentrations ranging from100 to 1000 ppm. Collectively, these microbeam observations provide evidence for dynamic pre-eruptive comingling between hotter, sulfur-rich magma rising beneath the summit with a denser, cooler and degassed pyroxene-bearing magma mush, prior to eruption on the east rift.

Sulfuric acid on Europa and the radiolytic sulfur cycle.

PubMed

Carlson, R W; Johnson, R E; Anderson, M S

1999-10-01

A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

Control of copper resistance and inorganic sulfur metabolism by paralogous regulators in Staphylococcus aureus.

PubMed

Grossoehme, Nicholas; Kehl-Fie, Thomas E; Ma, Zhen; Adams, Keith W; Cowart, Darin M; Scott, Robert A; Skaar, Eric P; Giedroc, David P

2011-04-15

All strains of Staphylococcus aureus encode a putative copper-sensitive operon repressor (CsoR) and one other CsoR-like protein of unknown function. We show here that NWMN_1991 encodes a bona fide Cu(I)-inducible CsoR of a genetically unlinked copA-copZ copper resistance operon in S. aureus strain Newman. In contrast, an unannotated open reading frame found between NWMN_0027 and NWMN_0026 (denoted NWMN_0026.5) encodes a CsoR-like regulator that represses expression of adjacent genes by binding specifically to a pair of canonical operator sites positioned in the NWMN_0027-0026.5 intergenic region. Inspection of these regulated genes suggests a role in assimilation of inorganic sulfur from thiosulfate and vectorial sulfur transfer, and we designate NWMN_0026.5 as CstR (CsoR-like sulfur transferase repressor). Expression analysis demonstrates that CsoR and CstR control their respective regulons in response to distinct stimuli with no overlap in vivo. Unlike CsoR, CstR does not form a stable complex with Cu(I); operator binding is instead inhibited by oxidation of the intersubunit cysteine pair to a mixture of disulfide and trisulfide linkages by a likely metabolite of thiosulfate assimilation, sulfite. CsoR is unreactive toward sulfite under the same conditions. We conclude that CsoR and CstR are paralogs in S. aureus that function in the same cytoplasm to control distinct physiological processes.

Control of Copper Resistance and Inorganic Sulfur Metabolism by Paralogous Regulators in Staphylococcus aureus*

PubMed Central

Grossoehme, Nicholas; Kehl-Fie, Thomas E.; Ma, Zhen; Adams, Keith W.; Cowart, Darin M.; Scott, Robert A.; Skaar, Eric P.; Giedroc, David P.

2011-01-01

All strains of Staphylococcus aureus encode a putative copper-sensitive operon repressor (CsoR) and one other CsoR-like protein of unknown function. We show here that NWMN_1991 encodes a bona fide Cu(I)-inducible CsoR of a genetically unlinked copA-copZ copper resistance operon in S. aureus strain Newman. In contrast, an unannotated open reading frame found between NWMN_0027 and NWMN_0026 (denoted NWMN_0026.5) encodes a CsoR-like regulator that represses expression of adjacent genes by binding specifically to a pair of canonical operator sites positioned in the NWMN_0027–0026.5 intergenic region. Inspection of these regulated genes suggests a role in assimilation of inorganic sulfur from thiosulfate and vectorial sulfur transfer, and we designate NWMN_0026.5 as CstR (CsoR-like sulfur transferase repressor). Expression analysis demonstrates that CsoR and CstR control their respective regulons in response to distinct stimuli with no overlap in vivo. Unlike CsoR, CstR does not form a stable complex with Cu(I); operator binding is instead inhibited by oxidation of the intersubunit cysteine pair to a mixture of disulfide and trisulfide linkages by a likely metabolite of thiosulfate assimilation, sulfite. CsoR is unreactive toward sulfite under the same conditions. We conclude that CsoR and CstR are paralogs in S. aureus that function in the same cytoplasm to control distinct physiological processes. PMID:21339296

One step electrodeposition of Cu2ZnSnS4 thin films in a novel bath with sulfurization free annealing

NASA Astrophysics Data System (ADS)

Tang, Aiyue; Li, Zhilin; Wang, Feng; Dou, Meiling; Pan, Youya; Guan, Jingyu

2017-04-01

Cu2ZnSnS4 (CZTS) is a quaternary kesterite compound with suitable band gap for thin film solar cells. In most electrodeposition-anneal routes, sulfurization is inevitable because the as-deposited film is lack of S. In this work, a novel green electrolyte was designed for synthesizing CZTS thin films with high S content. In the one-step electrodeposition, K4P2O7 and C7H6O6S were added to form complex with metallic ions in the electrolyte, which could attribute to co-deposition. The as-deposited film obtained high S content satisfying stoichiometry. After a sulfurization free annealing, the continuous and uniform CZTS thin film was obtained, which had pure kesterite structure and a suitable band gap of 1.53 eV. Electrodeposition mechanism investigation revealed that the K4P2O7 prevented the excessive deposition of Cu2+ and Sn2+. The C7H6O6S promoted the reduction of Zn2+. So the additives narrowed the co-deposition potentials of the metallic elements through a synergetic effect. They also promoted the reduction of S2O32- to ensure the co-deposition of the four elements and the stoichiometry. The sulfurization free annealing process can promote the commercialization of CZTS films and the successful design principle of environmental friendly electrolytes could be applied in other electrodeposition systems.

Inorganic Reactive Sulfur-Nitrogen Species: Intricate Release Mechanisms or Cacophony in Yellow, Blue and Red?

PubMed Central

Grman, Marian; Nasim, Muhammad Jawad; Leontiev, Roman; Misak, Anton; Jakusova, Veronika; Ondrias, Karol; Jacob, Claus

2017-01-01

Since the heydays of Reactive Sulfur Species (RSS) research during the first decade of the Millennium, numerous sulfur species involved in cellular regulation and signalling have been discovered. Yet despite the general predominance of organic species in organisms, recent years have also seen the emergence of inorganic reactive sulfur species, ranging from inorganic polysulfides (HSx−/Sx2−) to thionitrous acid (HSNO) and nitrosopersulfide (SSNO−). These inorganic species engage in a complex interplay of reactions in vitro and possibly also in vivo. Employing a combination of spectrophotometry and sulfide assays, we have investigated the role of polysulfanes from garlic during the release of nitric oxide (•NO) from S-nitrosoglutathione (GSNO) in the absence and presence of thiol reducing agents. Our studies reveal a distinct enhancement of GSNO decomposition by compounds such as diallyltrisulfane, which is most pronounced in the presence of cysteine and glutathione and presumably proceeds via the initial release of an inorganic mono- or polysulfides, i.e., hydrogen sulfide (H2S) or HSx−, from the organic polysulfane. Albeit being of a preliminary nature, our spectrophotometric data also reveals a complicated underlying mechanism which appears to involve transient species such as SSNO−. Eventually, more in depth studies are required to further explore the underlying chemistry and wider biological and nutritional implications of this interplay between edible garlic compounds, reductive activation, inorganic polysulfides and their interplay with •NO storage and release. PMID:28212297

TusA (YhhP) and IscS are required for molybdenum cofactor-dependent base-analog detoxification

PubMed Central

Kozmin, Stanislav G; Stepchenkova, Elena I; Schaaper, Roel M

2013-01-01

Lack of molybdenum cofactor (Moco) in Escherichia coli leads to hypersensitivity to the mutagenic and toxic effects of N-hydroxylated base analogs, such as 6-N-hydroxylaminopurine (HAP). This phenotype is due to the loss of two Moco-dependent activities, YcbX and YiiM, that are capable of reducing HAP to adenine. Here, we describe two novel HAP-sensitive mutants containing a defect in iscS or tusA (yhhP) gene. IscS is a major L-cysteine desulfurase involved in iron–sulfur cluster synthesis, thiamine synthesis, and tRNA thiomodification. TusA is a small sulfur-carrier protein that interacts with IscS. We show that both IscS and TusA operate within the Moco-dependent pathway. Like other Moco-deficient strains, tusA and iscS mutants are HAP sensitive and resistant to chlorate under anaerobic conditions. The base-analog sensitivity of iscS or tusA strains could be suppressed by supplying exogenous L-cysteine or sulfide or by an increase in endogenous sulfur donors (cysB constitutive mutant). The data suggest that iscS and tusA mutants have a defect in the mobilization of sulfur required for active YcbX/YiiM proteins as well as nitrate reductase, presumably due to lack of functional Moco. Overall, our data imply a novel and indispensable role of the IscS/TusA complex in the activity of several molybdoenzymes. PMID:23894086

Iron clad wetlands: Soil iron-sulfur buffering determines coastal wetland response to salt water incursion

NASA Astrophysics Data System (ADS)

Schoepfer, Valerie A.; Bernhardt, Emily S.; Burgin, Amy J.

2014-12-01

Coastal freshwater wetland chemistry is rapidly changing due to increased frequency of salt water incursion, a consequence of global change. Seasonal salt water incursion introduces sulfate, which microbially reduces to sulfide. Sulfide binds with reduced iron, producing iron sulfide (FeS), recognizable in wetland soils by its characteristic black color. The objective of this study is to document iron and sulfate reduction rates, as well as product formation (acid volatile sulfide (AVS) and chromium reducible sulfide (CRS)) in a coastal freshwater wetland undergoing seasonal salt water incursion. Understanding iron and sulfur cycling, as well as their reduction products, allows us to calculate the degree of sulfidization (DOS), from which we can estimate how long soil iron will buffer against chemical effects of sea level rise. We show that soil chloride, a direct indicator of the degree of incursion, best predicted iron and sulfate reduction rates. Correlations between soil chloride and iron or sulfur reduction rates were strongest in the surface layer (0-3 cm), indicative of surface water incursion, rather than groundwater intrusion at our site. The interaction between soil moisture and extractable chloride was significantly related to increased AVS, whereas increased soil chloride was a stronger predictor of CRS. The current DOS in this coastal plains wetland is very low, resulting from high soil iron content and relatively small degree of salt water incursion. However, with time and continuous salt water exposure, iron will bind with incoming sulfur, creating FeS complexes, and DOS will increase.

Sulfur biogeochemistry of cold seeps in the Green Canyon region of the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Formolo, Michael J.; Lyons, Timothy W.

2013-10-01

Cold seeps in the Gulf of Mexico provide a natural laboratory to study biogeochemical cycling of sulfur, carbon, and oxygen at hydrate- and hydrocarbon-rich deep marine settings with obvious additional relevance to studies of diverse modern and ancient seeps. Of particular interest are the sulfur isotope signatures of microbial sulfate reduction coupled to anaerobic oxidation of methane and other non-methane liquid and gaseous hydrocarbons. Whereas most of the published sulfur isotope data from cold seep systems pertain to pore-water species, our study integrates both solid and dissolved sulfur: acid-volatile sulfides (SAVS), pyrite (Spy), elemental sulfur (S°), dissolved sulfate and ΣH2S. Modeled and 35SO42- reduction rates and δ13C and δ18O data for authigenic carbonates are integrated within this sulfur framework. Our results indicate extreme variability over narrow spatial and temporal scales within short distances (meters) from active seeps. High rates of microbial sulfate reduction can lead to complete consumption of the sulfate within the upper few centimeters of burial, while meters away the sulfate profile shows little depletion. Such small-scale variability must reflect the structure and temporal dynamics of hydrocarbon migration in the presence of low amounts of background organic matter. Our past work demonstrated that electron donors other than methane drive significant levels of microbial activity at these seeps, and very recent work has demonstrated that oxidation of higher chain volatile hydrocarbons can contribute to the high levels of microbial activity. These findings are consistent with our new results. Elevated concentrations of pyrite and diagenetic carbonate relative to background sediments are diagnostic of active seepage, yet the S isotopes tell more complex stories. Low levels of the transient, 'instantaneous' products of S cycling-AVS and S°-show high δ34S values that increase with depth. Most of the pyrite formation, however, seems to be very early as limited by the availability of reactive Fe phases. As such, δ34S values for pyrite at ancient seeps can show consistently low δ34S values that undersell the full intensity of microbial sulfate reduction. Low sedimentation rates, and the resulting low detrital iron fluxes, may in fact limit our ability to recognize seeps in the geologic record using only δ34S compositions for pyrite.

Electrochemical and spectroscopic effects of mixed substituents in bis(phenolate)–copper(II) galactose oxidase model complexes

PubMed Central

Pratt, Russell C.; Lyons, Christopher T.; Wasinger, Erik C.; Stack, T. Daniel. P.

2012-01-01

Non-symmetric substitution of salen (1R1,R2) and reduced salen (2R1,R2) CuII-phenoxyl complexes with a combination of -tBu, -SiPr, and -OMe substituents leads to dramatic differences in their redox and spectroscopic properties, providing insight into the influence of the cysteine-modified tyrosine cofactor in the enzyme galactose oxidase (GO). Using a modified Marcus-Hush analysis, the oxidized copper complexes are characterized as Class II mixed-valent due to the electronic differentiation between the two substituted phenolates. Sulfur K-edge X-ray absorption spectroscopy (XAS) assesses the degree of radical delocalization onto the single sulfur atom of non-symmetric [1tBu,SMe]+ at 7%, consistent with other spectroscopic and electrochemical results that suggest preferential oxidation of the -SMe bearing phenolate. Estimates of the thermodynamic free-energy difference between the two localized states (ΔG∘) and reorganizational energies (λR1R2) of [1R1,R2]+ and [2R1,R2]+ leads to accurate predictions of the spectroscopically observed IVCT transition energies. Application of the modified Marcus-Hush analysis to GO using parameters determined for [2R1,R2]+ predicts a νmax of ~ 13600 cm−1, well within the energy range of the broad Vis-NIR band displayed by the enzyme. PMID:22471355

Interactions of iron-bound frataxin with ISCU and ferredoxin on the cysteine desulfurase complex leading to Fe-S cluster assembly.

PubMed

Cai, Kai; Frederick, Ronnie O; Tonelli, Marco; Markley, John L

2018-06-01

Frataxin (FXN) is involved in mitochondrial iron‑sulfur (Fe-S) cluster biogenesis and serves to accelerate Fe-S cluster formation. FXN deficiency is associated with Friedreich ataxia, a neurodegenerative disease. We have used a combination of isothermal titration calorimetry and multinuclear NMR spectroscopy to investigate interactions among the components of the biological machine that carries out the assembly of iron‑sulfur clusters in human mitochondria. Our results show that FXN tightly binds a single Fe 2+ but not Fe 3+ . While FXN (with or without bound Fe 2+ ) does not bind the scaffold protein ISCU directly, the two proteins interact mutually when each is bound to the cysteine desulfurase complex ([NFS1] 2 :[ISD11] 2 :[Acp] 2 ), abbreviated as (NIA) 2 , where "N" represents the cysteine desulfurase (NFS1), "I" represents the accessory protein (ISD11), and "A" represents acyl carrier protein (Acp). FXN binds (NIA) 2 weakly in the absence of ISCU but more strongly in its presence. Fe 2+ -FXN binds to the (NIA) 2 -ISCU 2 complex without release of iron. However, upon the addition of both l-cysteine and a reductant (either reduced FDX2 or DTT), Fe 2+ is released from FXN as consistent with Fe 2+ -FXN being the proximal source of iron for Fe-S cluster assembly. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Do constructed wetlands remove metals or increase metal bioavailability?

PubMed

Xu, Xiaoyu; Mills, Gary L

2018-07-15

The H-02 wetland was constructed to treat building process water and storm runoff water from the Tritium Processing Facility on the Department of Energy's Savannah River Site (Aiken, SC). Monthly monitoring of copper (Cu) and zinc (Zn) concentrations and water quality parameters in surface waters continued from 2014 to 2016. Metal speciation was modeled at each sampling occasion. Total Cu and Zn concentrations released to the effluent stream were below the NPDES limit, and the average removal efficiency was 65.9% for Cu and 71.1% for Zn. The metal-removal processes were found out to be seasonally regulated by sulfur cycling indicated by laboratory and model results. High temperature, adequate labile organic matter, and anaerobic conditions during the warm months (February to August) favored sulfate reduction that produced sulfide minerals to significantly remove metals. However, the dominant reaction in sulfur cycling shifted to sulfide oxidation during the cool months (September to next March). High concentrations of metal-organic complexes were observed, especially colloidal complexes of metal and fulvic acid (FA), demonstrating adsorption to organic matter became the primary process for metal removal. Meanwhile, the accumulation of metal-FA complexes in the wetland system will cause negative effects to the surrounding environment as they are biologically reactive, highly bioavailable, and can be easily taken up and transferred to ecosystems by trophic exchange. Copyright © 2018 Elsevier Ltd. All rights reserved.

Friedreich's Ataxia Variants I154F and W155R Diminish Frataxin-Based Activation of the Iron-Sulfur Cluster Assembly Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Chi-Lin; Bridwell-Rabb, Jennifer; Barondeau, David P

2011-11-07

Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease that has been linked to defects in the protein frataxin (Fxn). Most FRDA patients have a GAA expansion in the first intron of their Fxn gene that decreases protein expression. Some FRDA patients have a GAA expansion on one allele and a missense mutation on the other allele. Few functional details are known for the ~15 different missense mutations identified in FRDA patients. Here in vitro evidence is presented that indicates the FRDA I154F and W155R variants bind more weakly to the complex of Nfs1, Isd11, and Isu2 and thereby are defectivemore » in forming the four-component SDUF complex that constitutes the core of the Fe-S cluster assembly machine. The binding affinities follow the trend Fxn ~ I154F > W155F > W155A ~ W155R. The Fxn variants also have diminished ability to function as part of the SDUF complex to stimulate the cysteine desulfurase reaction and facilitate Fe-S cluster assembly. Four crystal structures, including the first for a FRDA variant, reveal specific rearrangements associated with the loss of function and lead to a model for Fxn-based activation of the Fe-S cluster assembly complex. Importantly, the weaker binding and lower activity for FRDA variants correlate with the severity of disease progression. Together, these results suggest that Fxn facilitates sulfur transfer from Nfs1 to Isu2 and that these in vitro assays are sensitive and appropriate for deciphering functional defects and mechanistic details for human Fe-S cluster biosynthesis.« less

NADP-Specific Electron-Bifurcating [FeFe]-Hydrogenase in a Functional Complex with Formate Dehydrogenase in Clostridium autoethanogenum Grown on CO

PubMed Central

Wang, Shuning; Huang, Haiyan; Kahnt, Jörg; Mueller, Alexander P.; Köpke, Michael

2013-01-01

Flavin-based electron bifurcation is a recently discovered mechanism of coupling endergonic to exergonic redox reactions in the cytoplasm of anaerobic bacteria and archaea. Among the five electron-bifurcating enzyme complexes characterized to date, one is a heteromeric ferredoxin- and NAD-dependent [FeFe]-hydrogenase. We report here a novel electron-bifurcating [FeFe]-hydrogenase that is NADP rather than NAD specific and forms a complex with a formate dehydrogenase. The complex was found in high concentrations (6% of the cytoplasmic proteins) in the acetogenic Clostridium autoethanogenum autotrophically grown on CO, which was fermented to acetate, ethanol, and 2,3-butanediol. The purified complex was composed of seven different subunits. As predicted from the sequence of the encoding clustered genes (fdhA/hytA-E) and from chemical analyses, the 78.8-kDa subunit (FdhA) is a selenocysteine- and tungsten-containing formate dehydrogenase, the 65.5-kDa subunit (HytB) is an iron-sulfur flavin mononucleotide protein harboring the NADP binding site, the 51.4-kDa subunit (HytA) is the [FeFe]-hydrogenase proper, and the 18.1-kDa (HytC), 28.6-kDa (HytD), 19.9-kDa (HytE1), and 20.1-kDa (HytE2) subunits are iron-sulfur proteins. The complex catalyzed both the reversible coupled reduction of ferredoxin and NADP+ with H2 or formate and the reversible formation of H2 and CO2 from formate. We propose the complex to have two functions in vivo, namely, to normally catalyze CO2 reduction to formate with NADPH and reduced ferredoxin in the Wood-Ljungdahl pathway and to catalyze H2 formation from NADPH and reduced ferredoxin when these redox mediators get too reduced during unbalanced growth of C. autoethanogenum on CO (E0′ = −520 mV). PMID:23893107

NADP-specific electron-bifurcating [FeFe]-hydrogenase in a functional complex with formate dehydrogenase in Clostridium autoethanogenum grown on CO.

PubMed

Wang, Shuning; Huang, Haiyan; Kahnt, Jörg; Mueller, Alexander P; Köpke, Michael; Thauer, Rudolf K

2013-10-01

Flavin-based electron bifurcation is a recently discovered mechanism of coupling endergonic to exergonic redox reactions in the cytoplasm of anaerobic bacteria and archaea. Among the five electron-bifurcating enzyme complexes characterized to date, one is a heteromeric ferredoxin- and NAD-dependent [FeFe]-hydrogenase. We report here a novel electron-bifurcating [FeFe]-hydrogenase that is NADP rather than NAD specific and forms a complex with a formate dehydrogenase. The complex was found in high concentrations (6% of the cytoplasmic proteins) in the acetogenic Clostridium autoethanogenum autotrophically grown on CO, which was fermented to acetate, ethanol, and 2,3-butanediol. The purified complex was composed of seven different subunits. As predicted from the sequence of the encoding clustered genes (fdhA/hytA-E) and from chemical analyses, the 78.8-kDa subunit (FdhA) is a selenocysteine- and tungsten-containing formate dehydrogenase, the 65.5-kDa subunit (HytB) is an iron-sulfur flavin mononucleotide protein harboring the NADP binding site, the 51.4-kDa subunit (HytA) is the [FeFe]-hydrogenase proper, and the 18.1-kDa (HytC), 28.6-kDa (HytD), 19.9-kDa (HytE1), and 20.1-kDa (HytE2) subunits are iron-sulfur proteins. The complex catalyzed both the reversible coupled reduction of ferredoxin and NADP(+) with H2 or formate and the reversible formation of H2 and CO2 from formate. We propose the complex to have two functions in vivo, namely, to normally catalyze CO2 reduction to formate with NADPH and reduced ferredoxin in the Wood-Ljungdahl pathway and to catalyze H2 formation from NADPH and reduced ferredoxin when these redox mediators get too reduced during unbalanced growth of C. autoethanogenum on CO (E0' = -520 mV).

Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mena, Natalia P.; Millennium Institute of Cell Dynamics and Biotechnology, Santiago; Bulteau, Anne Laure

2011-06-03

Highlights: {yields} Mitochondrial complex I inhibition resulted in decreased activity of Fe-S containing enzymes mitochondrial aconitase and cytoplasmic aconitase and xanthine oxidase. {yields} Complex I inhibition resulted in the loss of Fe-S clusters in cytoplasmic aconitase and of glutamine phosphoribosyl pyrophosphate amidotransferase. {yields} Consistent with loss of cytoplasmic aconitase activity, an increase in iron regulatory protein 1 activity was found. {yields} Complex I inhibition resulted in an increase in the labile cytoplasmic iron pool. -- Abstract: Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters aremore » involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given that inhibition of complex I and iron accumulation are hallmarks of idiopathic Parkinson's disease, the findings reported here may have relevance for understanding the pathophysiology of this disease.« less

A rapid and high-precision method for sulfur isotope δ(34)S determination with a multiple-collector inductively coupled plasma mass spectrometer: matrix effect correction and applications for water samples without chemical purification.

PubMed

Lin, An-Jun; Yang, Tao; Jiang, Shao-Yong

2014-04-15

Previous studies have indicated that prior chemical purification of samples, although complex and time-consuming, is essential in obtaining precise and accurate results for sulfur isotope ratios using multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). In this study, we introduce a new, rapid and precise MC-ICP-MS method for sulfur isotope determination from water samples without chemical purification. The analytical work was performed on an MC-ICP-MS instrument with medium mass resolution (m/Δm ~ 3000). Standard-sample bracketing (SSB) was used to correct samples throughout the analytical sessions. Reference materials included an Alfa-S (ammonium sulfate) standard solution, ammonium sulfate provided by the lab of the authors and fresh seawater from the South China Sea. A range of matrix-matched Alfa-S standard solutions and ammonium sulfate solutions was used to investigate the matrix (salinity) effect (matrix was added in the form of NaCl). A seawater sample was used to confirm the reliability of the method. Using matrix-matched (salinity-matched) Alfa-S as the working standard, the measured δ(34)S value of AS (-6.73 ± 0.09‰) was consistent with the reference value (-6.78 ± 0.07‰) within the uncertainty, suggesting that this method could be recommended for the measurement of water samples without prior chemical purification. The δ(34)S value determination for the unpurified seawater also yielded excellent results (21.03 ± 0.18‰) that are consistent with the reference value (20.99‰), thus confirming the feasibility of the technique. The data and the results indicate that it is feasible to use MC-ICP-MS and matrix-matched working standards to measure the sulfur isotopic compositions of water samples directly without chemical purification. In comparison with the existing MC-ICP-MS techniques, the new method is better for directly measuring δ(34)S values in water samples with complex matrices; therefore, it can significantly accelerate analytical turnover. Copyright © 2014 John Wiley & Sons, Ltd.

Hardgrove grindability study of Powder River Basin and Appalachian coal components in the blend to a midwestern power station

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padgett, P.L.; Hower, J.C.

1996-12-31

Five coals representing four distinct coal sources blended at a midwestern power station were subjected to detailed analysis of their Hardgrove grindability. The coals are: a low-sulfur, high volatile A bituminous Upper Elkhorn No. 3 coal (Pike County, KY); a medium-sulfur, high volatile A bituminous Pittsburgh coal (southwestern PA); a low-sulfur, subbituminous Wyodak coal from two mines in the eastern Powder River Basin (Campbell County, WY). The feed and all samples processed in the Hardgrove grindability test procedure were analyzed for their maceral and microlithotype content. The high-vitrinite Pittsburgh coal and the relatively more petrographically complex Upper Elkhorn No. 3more » coal exhibit differing behavior in grindability. The Pittsburgh raw feed, 16x30 mesh fraction (HGI test fraction), and the {minus}30 mesh fraction (HGI reject) are relatively similar petrographically, suggesting that the HGI test fraction is reasonably representative of the whole feed. The eastern Kentucky coal is not as representative of the whole feed, the HGI test fraction having lower vitrinite than the rejected {minus}30 mesh fraction. The Powder River Basin coals are high vitrinite and show behavior similar to the Pittsburgh coal.« less

Soft Cysteine Signaling Network: The Functional Significance of Cysteine in Protein Function and the Soft Acids/Bases Thiol Chemistry That Facilitates Cysteine Modification.

PubMed

Wible, Ryan S; Sutter, Thomas R

2017-03-20

The unique biophysical and electronic properties of cysteine make this molecule one of the most biologically critical amino acids in the proteome. The defining sulfur atom in cysteine is much larger than the oxygen and nitrogen atoms more commonly found in the other amino acids. As a result of its size, the valence electrons of sulfur are highly polarizable. Unique protein microenvironments favor the polarization of sulfur, thus increasing the overt reactivity of cysteine. Here, we provide a brief overview of the endogenous generation of reactive oxygen and electrophilic species and specific examples of enzymes and transcription factors in which the oxidation or covalent modification of cysteine in those proteins modulates their function. The perspective concludes with a discussion of cysteine chemistry and biophysics, the hard and soft acids and bases model, and the proposal of the Soft Cysteine Signaling Network: a hypothesis proposing the existence of a complex signaling network governed by layered chemical reactivity and cross-talk in which the chemical modification of reactive cysteine in biological networks triggers the reorganization of intracellular biochemistry to mitigate spikes in endogenous or exogenous oxidative or electrophilic stress.

Iron dissolution of dust source materials during simulated acidic processing: the effect of sulfuric, acetic, and oxalic acids.

PubMed

Chen, Haihan; Grassian, Vicki H

2013-09-17

Atmospheric organic acids potentially display different capacities in iron (Fe) mobilization from atmospheric dust compared with inorganic acids, but few measurements have been made on this comparison. We report here a laboratory investigation of Fe mobilization of coal fly ash, a representative Fe-containing anthropogenic aerosol, and Arizona test dust, a reference source material for mineral dust, in pH 2 sulfuric acid, acetic acid, and oxalic acid, respectively. The effects of pH and solar radiation on Fe dissolution have also been explored. The relative capacities of these three acids in Fe dissolution are in the order of oxalic acid > sulfuric acid > acetic acid. Oxalate forms mononuclear bidentate ligand with surface Fe and promotes Fe dissolution to the greatest extent. Photolysis of Fe-oxalate complexes further enhances Fe dissolution with the concomitant degradation of oxalate. These results suggest that ligand-promoted dissolution of Fe may play a more significant role in mobilizing Fe from atmospheric dust compared with proton-assisted processing. The role of atmospheric organic acids should be taken into account in global-biogeochemical modeling to better access dissolved atmospheric Fe deposition flux at the ocean surface.

40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2011 CFR

2011-07-01

... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference method...

40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2012 CFR

2012-07-01

... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference method...

40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2013 CFR

2013-07-01

... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference method...

40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2014 CFR

2014-07-01

... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level...). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference method...

In-situ measurement of sulfur isotopic ratios in zoned apatite crystals via SIMS: a new tool for interpreting dynamic sulfur behavior in magmas

NASA Astrophysics Data System (ADS)

Economos, R. C.; Boehnke, P.; Burgisser, A.

2017-12-01

Sulfur is an important element in igneous systems due to its impact on magma redox, its role in the formation of economically valuable ore deposits, and the influence of catastrophic volcanogenic sulfur degassing on global climate. The mobility and geochemical behavior of sulfur in magmas is complex due to its multi-valent (from S2- to S6+) and multi-phase (solid, immiscible liquid, gaseous, dissolved ions) nature. Sulfur behavior is closely linked with the evolution of oxygen fugacity (fO2) in magmas; the record of fO2 evolution is often difficult to extract from rock records, particularly for intrusive systems that undergo cyclical magmatic processes and crystallize to the solidus. We apply a novel method of measuring S isotopic ratios via secondary ion mass spectrometry (SIMS) in zoned apatite crystals that we interpret as a record of open-system magmatic processes. We analyzed the S concentration and isotopic variations preserved in multiple apatite crystals from single hand specimens from the Cadiz Valley Batholith, CA via electron microprobe and ion microprobe at UCLA. A single, isotopically homogeneous crystal of Durango apatite was characterized for absolute isotopic ratio for this study (UCLA-D1). Isotopic variations in single apatite crystals ranged from 0 to 3.8‰ δ34S and total variation within a single hand sample was 6.1‰ δ34S. High S concentration cores yielded high isotopic ratios while low S concentration rims yielded low isotopic ratios. We favor an explanation of a combination of magma mixing and open-system, ascent-driven degassing under moderately reduced conditions: fO2 at or below NNO +1, although the synchronous crystallization of apatite and anhydrite is also a viable scenario. These findings have implications for the coupled S and fO2 evolution of granitic plutons and suggest that in-situ apatite S isotopic measurements could be a powerful new tool for evaluating redox and S systematics in magmatic systems.

The Effects of Redox Reactions on Sulfur Isotopes in Sulfide Melts at 1200 °C: Implications for 34S Enrichment in Magmas

NASA Astrophysics Data System (ADS)

Sanderson, A. M.; Frank, M. R.; Dodd, J. P.; Walker, J. A.

2017-12-01

δ34S values of mantle derived melts in subduction zones can differ from mantle values. This is often attributed to assimilation of country rock or interaction with another S-bearing reservoir. We hypothesized that variations in oxygen fugacity, f(O2), and in sulfur's valence state, may impact a change in the measured δ34S value of sulfide melts. Two synthetic sulfide melts (SM5 & SM7) with a composition of the mono-sulfide solution (MSS; Fe51S37Ni5Cu7) were homogenized for 30, 60 and 90 minutes at an oxygen fugacity between the quartz-fayalite-magnetite (QFM) and iron-wüstite (IW) buffers. Samples were separated into aliquots and subjected to varying fO2 (atmospheric O2, nickel-nickel oxide (NNO), QFM, and IW) at 1200 °C. Equilibrium was established through reversals and as a function of time. The δ34S value of the starting material was measured to be +7.3 to 7.9 ‰ (VCDT). δ34S values from experiments are displayed here relative to the starting material used for that experiment (δ34Ssample - δ34Sstarting). Experiments conducted at log f(O2) of -11.74 (IW), -10.02, -8.3 (QFM), and -7.6 (NNO) were found to be +0.1, +0.6, +1.7, and +1.8 ‰, respectively. The measured average δ34S values were found to vary directly with the imposed oxygen fugacity. The enrichment in 34S relative to 32S is most likely related to changes in the sulfur redox state (from S2-) or sulfur volatilization. Our results suggest that volatilization or variations in a magma's oxidation state can produce measurable changes in δ34S and that those changes must be considered when using δ34S to evaluate possible external sulfur contributions. These results will likely inform discussions on the source of metals and sulfur in layered mafic intrusions (e.g. Bushveld Complex).

Sulfur and carbon geochemistry of the Santa Elena peridotites: Comparing oceanic and continental processes during peridotite alteration

NASA Astrophysics Data System (ADS)

Schwarzenbach, Esther M.; Gill, Benjamin C.; Gazel, Esteban; Madrigal, Pilar

2016-05-01

Ultramafic rocks exposed on the continent serve as a window into oceanic and continental processes of water-peridotite interaction, so called serpentinization. In both environments there are active carbon and sulfur cycles that contain abiogenic and biogenic processes, which are eventually imprinted in the geochemical signatures of the basement rocks and the calcite and magnesite deposits associated with fluids that issue from these systems. Here, we present the carbon and sulfur geochemistry of ultramafic rocks and carbonate deposits from the Santa Elena ophiolite in Costa Rica. The aim of this study is to leverage the geochemistry of the ultramafic sequence and associated deposits to distinguish between processes that were dominant during ocean floor alteration and those dominant during low-temperature, continental water-peridotite interaction. The peridotites are variably serpentinized with total sulfur concentrations up to 877 ppm that is typically dominated by sulfide over sulfate. With the exception of one sample the ultramafic rocks are characterized by positive δ34Ssulfide (up to + 23.1‰) and δ34Ssulfate values (up to + 35.0‰). Carbon contents in the peridotites are low and are isotopically distinct from typical oceanic serpentinites. In particular, δ13C of the inorganic carbon suggests that the carbon is not derived from seawater, but rather the product of the interaction of meteoric water with the ultramafic rocks. In contrast, the sulfur isotope data from sulfide minerals in the peridotites preserve evidence for interaction with a hydrothermal fluid. Specifically, they indicate closed system abiogenic sulfate reduction suggesting that oceanic serpentinization occurred with limited input of seawater. Overall, the geochemical signatures preserve evidence for both oceanic and continental water-rock interaction with the majority of carbon (and possibly sulfate) being incorporated during continental water-rock interaction. Furthermore, there is evidence for microbial activity that was possibly stimulated by carbon sourced from water-rock interaction with adjacent sediments or fluid inclusions. This study provides detailed insight into the complex hydrothermal history of continental serpentinization systems and adds to our understanding of the carbon and sulfur cycling within peridotite-hosted hydrothermal systems.

Sulfur we breathe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawyer, J.W.

1978-03-01

The standards set to control the level of SO/sub 2/ in the atmosphere may not be having a proportionate effect on the formation of air-borne sulfates and sulfites and thus may not be protecting us from their harmful effects. The relationship of SO/sub 2/ levels to sulfate and sulfite concentrations is a much more complex issue than is recognized by existing regulations.

Installation Restoration Program Records Search for 132 Tactical Fighter Wing, Iowa Air National Guard, Des Moines Municipal Airport.

DTIC Science & Technology

1983-09-01

underlain by soils of the Gravity series and " of the Wabash -Gravity-Nodaway complex. These soils, primarily silty clay loams, are formed in fine...Electric Shop The electric shop is located in Facility No. 100. Wastes generated from this area include nickel- S cadmium batteries (24/year) and sulfuric

Isolation, Characterization, and Ecology of Sulfur-Respiring Crenarchaea Inhabiting Acid-Sulfate-Chloride-Containing Geothermal Springs in Yellowstone National Park▿ †

PubMed Central

Boyd, Eric S.; Jackson, Robert A.; Encarnacion, Gem; Zahn, James A.; Beard, Trevor; Leavitt, William D.; Pi, Yundan; Zhang, Chuanlun L.; Pearson, Ann; Geesey, Gill G.

2007-01-01

Elemental sulfur (S0) is associated with many geochemically diverse hot springs, yet little is known about the phylogeny, physiology, and ecology of the organisms involved in its cycling. Here we report the isolation, characterization, and ecology of two novel, S0-reducing Crenarchaea from an acid geothermal spring referred to as Dragon Spring. Isolate 18U65 grows optimally at 70 to 72°C and at pH 2.5 to 3.0, while isolate 18D70 grows optimally at 81°C and pH 3.0. Both isolates are chemoorganotrophs, dependent on complex peptide-containing carbon sources, S0, and anaerobic conditions for respiration-dependent growth. Glycerol dialkyl glycerol tetraethers (GDGTs) containing four to six cyclopentyl rings were present in the lipid fraction of isolates 18U65 and 18D70. Physiological characterization suggests that the isolates are adapted to the physicochemical conditions of Dragon Spring and can utilize the natural organic matter in the spring as a carbon and energy source. Quantitative PCR analysis of 16S rRNA genes associated with the S0 flocs recovered from several acid geothermal springs using isolate-specific primers indicates that these two populations together represent 17 to 37% of the floc-associated DNA. The physiological characteristics of isolates 18U65 and 18D70 are consistent with their potential widespread distribution and putative role in the cycling of sulfur in acid geothermal springs throughout the Yellowstone National Park geothermal complex. Based on phenotypic and genetic characterization, the designations Caldisphaera draconis sp. nov. and Acidilobus sulfurireducens sp. nov. are proposed for isolates 18U65 and 18D70, respectively. PMID:17720836

Formic acid catalyzed hydrolysis of SO3 in the gas phase: a barrierless mechanism for sulfuric acid production of potential atmospheric importance.

PubMed

Hazra, Montu K; Sinha, Amitabha

2011-11-02

Computational studies at the B3LYP/6-311++G(3df,3pd) and MP2/6-311++G(3df,3pd) levels are performed to explore the changes in reaction barrier height for the gas phase hydrolysis of SO(3) to form H(2)SO(4) in the presence of a single formic acid (FA) molecule. For comparison, we have also performed calculations for the reference reaction involving water assisted hydrolysis of SO(3) at the same level. Our results show that the FA assisted hydrolysis of SO(3) to form H(2)SO(4) is effectively a barrierless process. The barrier heights for the isomerization of the SO(3)···H(2)O···FA prereactive collision complex, which is the rate limiting step in the FA assisted hydrolysis, are found to be respectively 0.59 and 0.08 kcal/mol at the B3LYP/6-311++G(3df,3pd) and MP2/6-311++G(3df,3pd) levels. This is substantially lower than the ~7 kcal/mol barrier for the corresponding step in the hydrolysis of SO(3) by two water molecules--which is currently the accepted mechanism for atmospheric sulfuric acid production. Simple kinetic analysis of the relative rates suggests that the reduction in barrier height facilitated by FA, combined with the greater stability of the prereactive SO(3)···H(2)O···FA collision complex compared to SO(3)···H(2)O···H(2)O and the rather plentiful atmospheric abundance of FA, makes the formic acid mediated hydrolysis reaction a potentially important pathway for atmospheric sulfuric acid production.

Tissue factor pathway inhibitor prevents airway obstruction, respiratory failure and death due to sulfur mustard analog inhalation.

PubMed

Rancourt, Raymond C; Veress, Livia A; Ahmad, Aftab; Hendry-Hofer, Tara B; Rioux, Jacqueline S; Garlick, Rhonda B; White, Carl W

2013-10-01

Sulfur mustard (SM) inhalation causes airway injury, with enhanced vascular permeability, coagulation, and airway obstruction. The objective of this study was to determine whether recombinant tissue factor pathway inhibitor (TFPI) could inhibit this pathogenic sequence. Rats were exposed to the SM analog 2-chloroethyl ethyl sulfide (CEES) via nose-only aerosol inhalation. One hour later, TFPI (1.5mg/kg) in vehicle, or vehicle alone, was instilled into the trachea. Arterial O2 saturation was monitored using pulse oximetry. Twelve hours after exposure, animals were euthanized and bronchoalveolar lavage fluid (BALF) and plasma were analyzed for prothrombin, thrombin-antithrombin complex (TAT), active plasminogen activator inhibitor-1 (PAI-1) levels, and fluid fibrinolytic capacity. Lung steady-state PAI-1 mRNA was measured by RT-PCR analysis. Airway-capillary leak was estimated by BALF protein and IgM, and by pleural fluid measurement. In additional animals, airway cast formation was assessed by microdissection and immunohistochemical detection of airway fibrin. Airway obstruction in the form of fibrin-containing casts was evident in central conducting airways of rats receiving CEES. TFPI decreased cast formation, and limited severe hypoxemia. Findings of reduced prothrombin consumption, and lower TAT complexes in BALF, demonstrated that TFPI acted to limit thrombin activation in airways. TFPI, however, did not appreciably affect CEES-induced airway protein leak, PAI-1 mRNA induction, or inhibition of the fibrinolytic activity present in airway surface liquid. Intratracheal administration of TFPI limits airway obstruction, improves gas exchange, and prevents mortality in rats with sulfur mustard-analog-induced acute lung injury. Copyright © 2013 Elsevier Inc. All rights reserved.

Analysis of Ecological Distribution and Genomic Content from a Clade of Bacteroidetes Endemic to Sulfidic Environments

NASA Astrophysics Data System (ADS)

Zhou, K.; Sylvan, J. B.; Hallam, S. J.

2017-12-01

The Bacteroidetes are a ubiquitous phylum of bacteria found in a wide variety of habitats. Marine Bacteroidetes are known to utilize complex carbohydrates and have a potentially important role in the global carbon cycle through processing these compounds, which are not digestible by many other microbes. Some members of the phylum are known to perform denitrification and are facultative anaerobes, but Bacteroidetes are not known to participate in sulfur redox cycling. Recently, it was shown that a clade of uncultured Bacteroidetes, including the VC2.1_Bac22 group, appears to be endemic to sulfidic environments, including hydrothermal vent sulfide chimneys, sediments and marine water column oxygen minimum zones (OMZs). This clade, dubbed the Sulfiphilic Bacteroidetes, is not detected in 16S rRNA amplicon studies from non-sulfidic environments. To test the hypothesis that the Sulphiphilic Bacteroidetes are involved in sulfur redox chemistry, we updated our meta-analysis of the clade using 16s rRNA sequences from public databases and employed single-cell genomics to survey their genomic potential using 19 single amplified genomes (SAGs) isolated from the seasonally anoxic Saanich Inlet, a seasonally hypoxic basin in British Columbia. Initial analysis of these SAGs indicates the Sulphiphilic Bacteroidetes may perform sulfur redox reactions using a three gene psrABC operon encoding the polysulfide reductase enzyme complex with a thiosulfate sulfurtransferase (rhodanese), which putatively uses cyanide to convert thiosulfate to sulfite, just upstream. Interestingly, this is the same configuration as discovered recently in some Marine Group A bacteria. Further aspects of the Sulphiphilic Bacteroidetes' genomic potential will be presented in light of their presence in sulfidic environments.

Malfunctioning of the iron-sulfur cluster assembly machinery in Saccharomyces cerevisiae produces oxidative stress via an iron-dependent mechanism, causing dysfunction in respiratory complexes.

PubMed

Gomez, Mauricio; Pérez-Gallardo, Rocío V; Sánchez, Luis A; Díaz-Pérez, Alma L; Cortés-Rojo, Christian; Meza Carmen, Victor; Saavedra-Molina, Alfredo; Lara-Romero, Javier; Jiménez-Sandoval, Sergio; Rodríguez, Francisco; Rodríguez-Zavala, José S; Campos-García, Jesús

2014-01-01

Biogenesis and recycling of iron-sulfur (Fe-S) clusters play important roles in the iron homeostasis mechanisms involved in mitochondrial function. In Saccharomyces cerevisiae, the Fe-S clusters are assembled into apoproteins by the iron-sulfur cluster machinery (ISC). The aim of the present study was to determine the effects of ISC gene deletion and consequent iron release under oxidative stress conditions on mitochondrial functionality in S. cerevisiae. Reactive oxygen species (ROS) generation, caused by H2O2, menadione, or ethanol, was associated with a loss of iron homeostasis and exacerbated by ISC system dysfunction. ISC mutants showed increased free Fe2+ content, exacerbated by ROS-inducers, causing an increase in ROS, which was decreased by the addition of an iron chelator. Our study suggests that the increment in free Fe2+ associated with ROS generation may have originated from mitochondria, probably Fe-S cluster proteins, under both normal and oxidative stress conditions, suggesting that Fe-S cluster anabolism is affected. Raman spectroscopy analysis and immunoblotting indicated that in mitochondria from SSQ1 and ISA1 mutants, the content of [Fe-S] centers was decreased, as was formation of Rieske protein-dependent supercomplex III2IV2, but this was not observed in the iron-deficient ATX1 and MRS4 mutants. In addition, the activity of complexes II and IV from the electron transport chain (ETC) was impaired or totally abolished in SSQ1 and ISA1 mutants. These results confirm that the ISC system plays important roles in iron homeostasis, ROS stress, and in assembly of supercomplexes III2IV2 and III2IV1, thus affecting the functionality of the respiratory chain.

40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2014 CFR

2014-07-01

... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as sulfur...

40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2013 CFR

2013-07-01

... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as sulfur...

40 CFR 50.5 - National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2012 CFR

2012-07-01

... standard for sulfur oxides (sulfur dioxide). 50.5 Section 50.5 Protection of Environment ENVIRONMENTAL....5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level... than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as sulfur...

Method of removing and recovering elemental sulfur from highly reducing gas streams containing sulfur gases

DOEpatents

Gangwal, Santosh K.; Nikolopoulos, Apostolos A.; Dorchak, Thomas P.; Dorchak, Mary Anne

2005-11-08

A method is provided for removal of sulfur gases and recovery of elemental sulfur from sulfur gas containing supply streams, such as syngas or coal gas, by contacting the supply stream with a catalyst, that is either an activated carbon or an oxide based catalyst, and an oxidant, such as sulfur dioxide, in a reaction medium such as molten sulfur, to convert the sulfur gases in the supply stream to elemental sulfur, and recovering the elemental sulfur by separation from the reaction medium.

Method of preparing graphene-sulfur nanocomposites for rechargeable lithium-sulfur battery electrodes

DOEpatents

Liu, Jun; Lemmon, John P; Yang, Zhenguo; Cao, Yuliang; Li, Xiaolin

2015-04-07

A method of preparing a graphene-sulfur nanocomposite for a cathode in a rechargeable lithium-sulfur battery comprising thermally expanding graphite oxide to yield graphene layers, mixing the graphene layers with a first solution comprising sulfur and carbon disulfide, evaporating the carbon disulfide to yield a solid nanocomposite, and grinding the solid nanocomposite to yield the graphene-sulfur nanocomposite. Rechargeable-lithium-sulfur batteries having a cathode that includes a graphene-sulfur nanocomposite can exhibit improved characteristics. The graphene-sulfur nanocomposite can be characterized by graphene sheets with particles of sulfur adsorbed to the graphene sheets. The sulfur particles have an average diameter of less than 50 nm.

Hydrolysis and coordination behavior of ferrocenyl-phosphonodithiolate: Synthesis and structure of Cu 4[FcP(OCH 3)( μ-S)( μ3-S)] 4 [Fc = Fe( η5-C 5H 4)( η5-C 5H 5)

NASA Astrophysics Data System (ADS)

Liu, Shu-Lei; Wang, Xi-Ying; Duan, Taike; Leung, Wa-Hung; Zhang, Qian-Feng

2010-02-01

Treatment of the dimeric [FcP(S)( μ-S)] 2 [Fc = Fe( η5-C 5H 4)( η5-C 5H 5)] with the organic base Et 3N in methylene chloride solution resulted in the isolation of a multi-component compound [Et 3NH] 2[(FcPO 2S) 2CH 2][FcPS(OH) 2] 2·CH 2Cl 2 ( 1·CH 2Cl 2). The formation of the [(FcPO 2S) 2CH 2] 2- anion was due to the dechlorination of methylene chloride, it consists of two [FcPO 2S] 2- units bridging by a methylene group. Reaction of Na[FcP(OCH 3)S 2] with equal equivalent of [Cu(MeCN) 4][ClO 4] in methanol afforded a sole tetranuclear copper(I) complex Cu 4[FcP(OCH 3)( μ-S)( μ3-S)] 4 ( 2). The neutral complex 2 consists of a crystallographically centrosymmetric tetramer containing four CuS 3 arrays each of which has one μ-sulfur and two μ3-sulfur bridges.

Inclusion bodies of aggregated hemosiderins in liver macrophages.

PubMed

Hayashi, Hisao; Tatsumi, Yasuaki; Wakusawa, Shinya; Shigemasa, Ryota; Koide, Ryoji; Tsuchida, Ken-Ichi; Morotomi, Natsuko; Yamashita, Tetsuji; Kumagai, Kotaro; Ono, Yukiya; Hayashi, Kazuhiko; Ishigami, Masatoshi; Goto, Hidemi; Kato, Ayako; Kato, Koichi

2017-12-01

Hemosiderin formation is a structural indication of iron overload. We investigated further adaptations of the liver to excess iron. Five patients with livers showing iron-rich inclusions larger than 2 µm were selected from our database. The clinical features of patients and structures of the inclusions were compared with those of 2 controls with mild iron overload. All patients had severe iron overload with more than 5000 ng/mL of serum ferritin. Etiologies were variable, from hemochromatosis to iatrogenic iron overload. Their histological stages were either portal fibrosis or cirrhosis. Inclusion bodies were ultra-structurally visualized as aggregated hemosiderins in the periportal macrophages. X-ray analysis always identified, in addition to a large amount of iron complexes including oxygen and phosphorus, a small amount of copper and sulfur in the mosaic matrixes of inclusions. There were no inclusions in the control livers. Inclusion bodies, when the liver is loaded with excess iron, may appear in the macrophages as isolated organella of aggregated hemosiderins. Trace amounts of copper-sulfur complexes were always identified in the mosaic matrices of the inclusions, suggesting cuproprotein induction against excess iron. In conclusion, inclusion formation in macrophages may be an adaptation of the liver loaded with excess iron.

Manipulating the Surface Chemistry of Quantum Dots for Sensitive Ratiometric Fluorescence Detection of Sulfur Dioxide.

PubMed

Li, Huihui; Zhu, Houjuan; Sun, Mingtai; Yan, Yehan; Zhang, Kui; Huang, Dejian; Wang, Suhua

2015-08-11

Herein, we report a novel approach to the rapid visual detection of gaseous sulfur dioxide (SO2) by manipulating the surface chemistry of 3-aminopropyltriethoxysilane (APTS)-modified quantum dots (QDs) using fluorescent coumarin-3-carboxylic acid (CCA) for specific reaction with SO2. The CCA molecules are attached to the surface amino groups of the QDs through electrostatic attraction, thus the fluorescence of CCA is greatly suppressed because of the formation of an ion-pair complex between the ATPS-modified QDs and CCA. Such an interaction is vulnerable to SO2 because SO2 can readily react with surface amino groups to form strong charge-transfer complexes and subsequently release the strongly fluorescent CCA molecules. The mechanism has been carefully verified through a series of control experiments. Upon exposure to different amounts of SO2, the fluorescent color of the nanoparticle-based sensor displays continuously changes from red to blue. Most importantly, the approach owns high selectivity for SO2 and a tolerance of interference, which enables the sensor to detect SO2 in a practical application. Using this fluorescence-based sensing method, we have achieved a visual detection limit of 6 ppb for gaseous SO2.

Coordination behavior of ligand based on NNS and NNO donors with ruthenium(III) complexes and their catalytic and DNA interaction studies

NASA Astrophysics Data System (ADS)

Manikandan, R.; Viswnathamurthi, P.

2012-11-01

Reactions of 2-acetylpyridine-thiosemicarbazone HL1, 2-acetylpyridine-4-methyl-thiosemicarbazone HL2, 2-acetylpyridine-4-phenyl-thiosemicarbazone HL3 and 2-acetylpyridine-semicarbazone HL4 with ruthenium(III) precursor complexes were studied and the products were characterized by analytical and spectral (FT-IR, electronic, EPR and EI-MS) methods. The ligands coordinated with the ruthenium(III) ion via pyridine nitrogen, azomethine nitrogen and thiolate sulfur/enolate oxygen. An octahedral geometry has been proposed for all the complexes based on the studies. All the complexes are redox active and display an irreversible and quasireversible metal centered redox processes. Further, the catalytic activity of the new complexes has been investigated for the transfer hydrogenation of ketones in the presence of isopropanol/KOH and the Kumada-Corriu coupling of aryl halides with aryl Grignard reagents. The DNA cleavage efficiency of new complexes has also been tested.

Liquid and Emulsified Sulfur in Submarine Solfatara Fields of two Northern Mariana Arc Volcanoes.

NASA Astrophysics Data System (ADS)

Nakamura, K.; Embley, R. W.; Chadwick, W. W.; Butterfield, D. A.; Takano, B.; Resing, J. A.; de Ronde, C. E.; Lilley, M. D.; Lupton, J. E.; Merle, S. G.; Inagaki, F.

2006-12-01

Because elemental sulfur melting point is ca 100 deg C (depend on allotropes and heating rate, S8 triple point temperature: 115 deg C), the evidence of liquid sulfur has been known for many subaerial crater lakes and small ponds in geothermal regions throughout the world. But the milky nature of water (sulfur-in- water emulsion in limited water mass) prohibited the direct observation of on-going processes at the bottom of these subaerial lakes. In the passive degassing environment at the summit craters of Daikoku and Nikko Seamounts of the northern Mariana Arc, the continuous flushing of sulfur emulsion by seawater allowed us to observe on- going submarine solfatara processes and associated chemistry through dives with ROVs during the NT05-18 cruise (JAMSTEC R/V Natsushima and ROV hyper-Dolphin) and the Submarine Ring of Fire 2006 cruise (R/V Melville and ROV JASON II). A higher viscosity for liquid elemental sulfur relative to that of seawater, as well as a limited stability of sulfur emulsion (aqueous sulfur sol) at high temperatures in electrolyte solution (seawater), ensures limited mobility of liquid sulfur in the conduits of hydrothermal vents. The subseafloor boiling depth of hydrothermal fluid limits the locus of any liquid sulfur reservoir. It was observed in an exposed liquid sulfur pond that the penetration of gas bubbles (mostly CO2) created sulfur emulsion while collapsing liquid sulfur film between seawater and gas bubbles. Liquid sulfur pits, encrusted sulfur, liquid sulfur fountain structure, sulfur stalactites and stalagmites, mini-pillow lava-like sulfur flows, accretionary sulfur lapilli and sulfur deltas were also observed at the summits of two volcanoes. Note: Solfatara: Italian. A type of fumarole, the gases of which are characteristically sulfurous. In 'Glossary of geology.'

[Determination of polyphenolic complex in wines by electrochemical methods and using the enzymes tyrosinase and laccase].

PubMed

Shleev, S V; Chekanova, S A; Koroleva, O V; Stepanova, E V; Telegin, Iu A; Sen'kina, Z E

2004-01-01

Several red wines were studied to find a correlation between physicochemical parameters characterizing the antioxidant status of wine and total content of phenols in samples. The content of dissolved oxygen (its value varied from 0.75 to 3.28 mg/ml), pH (3.10-3.63), redox potential (-186 to -106 mV), mass concentration of free and total sulfur dioxide (10-30 and 36-200 mg/dm3, respectively), absorption spectra, and total phenol content were determined. The wines fell into two main groups-with a relatively low (1850-2050 mg/dm3) and high (2300-2900 mg/dm3) contents of polyphenols. It was demonstrated that physicochemical parameters (except for the content of sulfur dioxide) correlate with the total phenol content in the wines studied.

Light element geochemistry of the Apollo 16 site

NASA Technical Reports Server (NTRS)

Kerridge, J. F.; Kaplan, I. R.; Petrowski, C.; Chang, S.

1975-01-01

The abundance and isotopic composition of carbon, sulfur, and nitrogen, the abundance of helium and hydrogen, and the content of metallic iron are reported for lunar surface samples from the Apollo 16 landing site at Cayley-Descartes. The light elements show marked interstation variability at the site. The abundances in soils of C, N, He, and H are apparently controlled mainly by exposure to the solar wind, through implantation or stripping processes. Carbon abundances (but not observed isotopic distributions) are compatible with a model in which equilibrium is established after 10,000-100,000 yr between solar wind input and loss by proton stripping. Sulfur abundances in soils are apparently controlled by abundances in local country rocks, but the lunar S cycle is quite complex. A metallic iron component may have originated by solar wind reduction of lunar Fe(2+).

Morphological Features of Diamond Crystals Dissolved in Fe0.7S0.3 Melt at 4 GPa and 1400°C

NASA Astrophysics Data System (ADS)

Sonin, V. M.; Zhimulev, E. I.; Pomazanskiy, B. S.; Zemnuhov, A. L.; Chepurov, A. A.; Afanasiev, V. P.; Chepurov, A. I.

2018-01-01

An experimental study of the dissolution of natural and synthetic diamonds in a sulfur-bearing iron melt (Fe0.7S0.3) with high P-T parameters (4 GPa, 1400°C) was performed. The results demonstrated that under these conditions, octahedral crystals with flat faces and rounded tetrahexahedral diamond crystals are transformed into rounded octahedroids, which have morphological characteristics similar to those of natural diamonds from kimberlite. It was suggested that, taking into account the complex history of individual natural diamond crystals, including the dissolution stages, sulfur-bearing metal melts up to sulfide melts were not only diamond-forming media during the early evolution of the Earth, but also natural solvents of diamond in the mantle environment before the formation of kimberlitic melts.

Rhodanese Functions as Sulfur Supplier for Key Enzymes in Sulfur Energy Metabolism

PubMed Central

Aussignargues, Clément; Giuliani, Marie-Cécile; Infossi, Pascale; Lojou, Elisabeth; Guiral, Marianne; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

2012-01-01

How microorganisms obtain energy is a challenging topic, and there have been numerous studies on the mechanisms involved. Here, we focus on the energy substrate traffic in the hyperthermophilic bacterium Aquifex aeolicus. This bacterium can use insoluble sulfur as an energy substrate and has an intricate sulfur energy metabolism involving several sulfur-reducing and -oxidizing supercomplexes and enzymes. We demonstrate that the cytoplasmic rhodanese SbdP participates in this sulfur energy metabolism. Rhodaneses are a widespread family of proteins known to transfer sulfur atoms. We show that SbdP has also some unusual characteristics compared with other rhodaneses; it can load a long sulfur chain, and it can interact with more than one partner. Its partners (sulfur reductase and sulfur oxygenase reductase) are key enzymes of the sulfur energy metabolism of A. aeolicus and share the capacity to use long sulfur chains as substrate. We demonstrate a positive effect of SbdP, once loaded with sulfur chains, on sulfur reductase activity, most likely by optimizing substrate uptake. Taken together, these results lead us to propose a physiological role for SbdP as a carrier and sulfur chain donor to these key enzymes, therefore enabling channeling of sulfur substrate in the cell as well as greater efficiency of the sulfur energy metabolism of A. aeolicus. PMID:22496367

Graphene-sulfur nanocomposites for rechargeable lithium-sulfur battery electrodes

DOEpatents

Liu, Jun; Lemmon, John P; Yang, Zhenguo; Cao, Yuiliang; Li, Xiaolin

2014-06-17

Rechargeable lithium-sulfur batteries having a cathode that includes a graphene-sulfur nanocomposite can exhibit improved characteristics. The graphene-sulfur nanocomposite can be characterized by graphene sheets with particles of sulfur adsorbed to the graphene sheets. The sulfur particles have an average diameter less than 50 nm..

Limits to sulfur accumulation in transgenic lupin seeds expressing a foreign sulfur-rich protein.

PubMed

Tabe, Linda M; Droux, Michel

2002-03-01

The low sulfur amino acid content of legume seeds restricts their nutritive value for animals. We have investigated the limitations to the accumulation of sulfur amino acids in the storage proteins of narrow leaf lupin (Lupinus angustifolius) seeds. Variation in sulfur supply to lupin plants affected the sulfur amino acid accumulation in the mature seed. However, when sulfur was in abundant supply, it accumulated to a large extent in oxidized form, rather than reduced form, in the seeds. At all but severely limiting sulfur supply, addition of a transgenic (Tg) sink for organic sulfur resulted in an increase in seed sulfur amino acid content. We hypothesize that demand, or sink strength for organic sulfur, which is itself responsive to environmental sulfur supply, was the first limit to the methionine (Met) and cysteine (Cys) content of wild-type lupin seed protein under most growing conditions. In Tg, soil-grown seeds expressing a foreign Met- and Cys-rich protein, decreased pools of free Met, free Cys, and glutathione indicated that the rate of synthesis of sulfur amino acids in the cotyledon had become limiting. Homeostatic mechanisms similar to those mediating the responses of plants to environmental sulfur stress resulted in an adjustment of endogenous protein composition in Tg seeds, even when grown at adequate sulfur supply. Uptake of sulfur by lupin cotyledons, as indicated by total seed sulfur at maturity, responded positively to increased sulfur supply, but not to increased demand in the Tg seeds.

Limits to Sulfur Accumulation in Transgenic Lupin Seeds Expressing a Foreign Sulfur-Rich Protein

PubMed Central

Tabe, Linda M.; Droux, Michel

2002-01-01

The low sulfur amino acid content of legume seeds restricts their nutritive value for animals. We have investigated the limitations to the accumulation of sulfur amino acids in the storage proteins of narrow leaf lupin (Lupinus angustifolius) seeds. Variation in sulfur supply to lupin plants affected the sulfur amino acid accumulation in the mature seed. However, when sulfur was in abundant supply, it accumulated to a large extent in oxidized form, rather than reduced form, in the seeds. At all but severely limiting sulfur supply, addition of a transgenic (Tg) sink for organic sulfur resulted in an increase in seed sulfur amino acid content. We hypothesize that demand, or sink strength for organic sulfur, which is itself responsive to environmental sulfur supply, was the first limit to the methionine (Met) and cysteine (Cys) content of wild-type lupin seed protein under most growing conditions. In Tg, soil-grown seeds expressing a foreign Met- and Cys-rich protein, decreased pools of free Met, free Cys, and glutathione indicated that the rate of synthesis of sulfur amino acids in the cotyledon had become limiting. Homeostatic mechanisms similar to those mediating the responses of plants to environmental sulfur stress resulted in an adjustment of endogenous protein composition in Tg seeds, even when grown at adequate sulfur supply. Uptake of sulfur by lupin cotyledons, as indicated by total seed sulfur at maturity, responded positively to increased sulfur supply, but not to increased demand in the Tg seeds. PMID:11891268

Sulfur Assimilation in Developing Lupin Cotyledons Could Contribute Significantly to the Accumulation of Organic Sulfur Reserves in the Seed

PubMed Central

Tabe, Linda Marie; Droux, Michel

2001-01-01

It is currently assumed that the assimilation of sulfur into reduced forms occurs predominantly in the leaves of plants. However, developing seeds have a strong requirement for sulfur amino acids for storage protein synthesis. We have assessed the capacity of developing seeds of narrow-leaf lupin (Lupinus angustifolius) for sulfur assimilation. Cotyledons of developing lupin seeds were able to transfer the sulfur atom from 35S-labeled sulfate into seed proteins in vitro, demonstrating the ability of the developing cotyledons to perform all the steps of sulfur reduction and sulfur amino acid biosynthesis. Oxidized sulfur constituted approximately 30% of the sulfur in mature seeds of lupins grown in the field and almost all of the sulfur detected in phloem exuded from developing pods. The activities of three enzymes of the sulfur amino acid biosynthetic pathway were found in developing cotyledons in quantities theoretically sufficient to account for all of the sulfur amino acids that accumulate in the protein of mature lupin seeds. We conclude that sulfur assimilation by developing cotyledons is likely to be an important source of sulfur amino acids for the synthesis of storage proteins during lupin seed maturation. PMID:11351081

Sulfur assimilation in developing lupin cotyledons could contribute significantly to the accumulation of organic sulfur reserves in the seed.

PubMed

Tabe, L M; Droux, M

2001-05-01

It is currently assumed that the assimilation of sulfur into reduced forms occurs predominantly in the leaves of plants. However, developing seeds have a strong requirement for sulfur amino acids for storage protein synthesis. We have assessed the capacity of developing seeds of narrow-leaf lupin (Lupinus angustifolius) for sulfur assimilation. Cotyledons of developing lupin seeds were able to transfer the sulfur atom from 35S-labeled sulfate into seed proteins in vitro, demonstrating the ability of the developing cotyledons to perform all the steps of sulfur reduction and sulfur amino acid biosynthesis. Oxidized sulfur constituted approximately 30% of the sulfur in mature seeds of lupins grown in the field and almost all of the sulfur detected in phloem exuded from developing pods. The activities of three enzymes of the sulfur amino acid biosynthetic pathway were found in developing cotyledons in quantities theoretically sufficient to account for all of the sulfur amino acids that accumulate in the protein of mature lupin seeds. We conclude that sulfur assimilation by developing cotyledons is likely to be an important source of sulfur amino acids for the synthesis of storage proteins during lupin seed maturation.

Effect of sulfur content in a sulfur-activated carbon composite on the electrochemical properties of a lithium/sulfur battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jin-Woo; Kim, Changhyeon; Ryu, Ho-Suk

2015-09-15

Highlights: • The content of sulfur in activated carbon was controlled by solution process. • The sulfur electrode with low sulfur content shows the best performance. • The Li/S battery has capacity of 1360 mAh/g at 1 C and 702 mAh/g at 10 C. - Abstract: The content of sulfur in sulfur/activated carbon composite is controlled from 32.37 wt.% to 55.33 wt.% by a one-step solution-based process. When the sulfur content is limited to 41.21 wt.%, it can be loaded into the pores of an activated carbon matrix in a highly dispersed state. On the contrary, when the sulfur contentmore » is 55.33 wt.%, crystalline sulfur can be detected on the surface of the activated carbon matrix. The best electrochemical performance can be obtained for a sulfur electrode with the lowest sulfur content. The sulfur/activated carbon composite with 32.37 wt.% sulfur afforded the highest first discharge capacity of 1360 mAh g{sup −1} at 1 C rate and a large reversible capacity of 702 mAh g{sup −1} at 10 C (16.75 A/g)« less

Properties of Sulfur Concrete.

DTIC Science & Technology

1979-07-06

36 Thermal Contraction . . . . . . . . . . . 37 Summary of Sulfur Concrete (unmodified) . . . 39 Modified Sulfur Concrete............ 40...Compressive strength of PCPD- modified sulfur concrete 47 20 Functional connection between reaction time and temperature in making DCPD- modified sulfur concrete...39 MODIFIED SULFUR CONCRETE In the previous section it was shown that sulfur concrete exhibits several undesirable properties, such as 1 poor

40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2011 CFR

2011-07-01

... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts...

40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2012 CFR

2012-07-01

... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts...

40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2010 CFR

2010-07-01

... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts...

40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2013 CFR

2013-07-01

... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts...

40 CFR 50.17 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2014 CFR

2014-07-01

... standards for sulfur oxides (sulfur dioxide). 50.17 Section 50.17 Protection of Environment ENVIRONMENTAL....17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts...

Sulfuric acid-sulfur heat storage cycle

DOEpatents

Norman, John H.

1983-12-20

A method of storing heat is provided utilizing a chemical cycle which interconverts sulfuric acid and sulfur. The method can be used to levelize the energy obtained from intermittent heat sources, such as solar collectors. Dilute sulfuric acid is concentrated by evaporation of water, and the concentrated sulfuric acid is boiled and decomposed using intense heat from the heat source, forming sulfur dioxide and oxygen. The sulfur dioxide is reacted with water in a disproportionation reaction yielding dilute sulfuric acid, which is recycled, and elemental sulfur. The sulfur has substantial potential chemical energy and represents the storage of a significant portion of the energy obtained from the heat source. The sulfur is burned whenever required to release the stored energy. A particularly advantageous use of the heat storage method is in conjunction with a solar-powered facility which uses the Bunsen reaction in a water-splitting process. The energy storage method is used to levelize the availability of solar energy while some of the sulfur dioxide produced in the heat storage reactions is converted to sulfuric acid in the Bunsen reaction.

Influence of Sulfur Fertilization on the Antioxidant Activities of Onion Juices Prepared by Thermal Treatment

PubMed Central

Koh, Eunmi; Surh, Jeonghee

2016-01-01

Two onions (Sulfur-1 and Sulfur-4) cultivated with different sulfur applications were thermally processed to elucidate the effects of heat treatment on browning index and antioxidant activity. Sulfur-4 onion had higher sulfur content compared with the Sulfur-1 onion. After thermal processing, browning intensity was different between the two onions juices, with lower values observed for Sulfur-4 onion juice. This suggests that sulfur inhibits the Maillard browning reaction. The total reducing capacity of the juices increased at higher thermal processing temperatures; however, it was also lower in the Sulfur-4 onion juice. This suggests that the heat treatment of onions enhanced their antioxidant activity, but the effect was offset in the Sulfur-4 onion juice presumably due to higher sulfur content. This study indicates that sulfur, a core element for the functionality of onions, can decrease the antioxidant activity of thermally processed onions because of its potential as a Maillard reaction inhibitor. PMID:27390734

Transcriptional and Proteomic Profiling of Aspergillus flavipes in Response to Sulfur Starvation.

PubMed

El-Sayed, Ashraf S A; Yassin, Marwa A; Ali, Gul Shad

2015-01-01

Aspergillus flavipes has received considerable interest due to its potential to produce therapeutic enzymes involved in sulfur amino acid metabolism. In natural habitats, A. flavipes survives under sulfur limitations by mobilizing endogenous and exogenous sulfur to operate diverse cellular processes. Sulfur limitation affects virulence and pathogenicity, and modulates proteome of sulfur assimilating enzymes of several fungi. However, there are no previous reports aimed at exploring effects of sulfur limitation on the regulation of A. flavipes sulfur metabolism enzymes at the transcriptional, post-transcriptional and proteomic levels. In this report, we show that sulfur limitation affects morphological and physiological responses of A. flavipes. Transcription and enzymatic activities of several key sulfur metabolism genes, ATP-sulfurylase, sulfite reductase, methionine permease, cysteine synthase, cystathionine β- and γ-lyase, glutathione reductase and glutathione peroxidase were increased under sulfur starvation conditions. A 50 kDa protein band was strongly induced by sulfur starvation, and the proteomic analyses of this protein band using LC-MS/MS revealed similarity to many proteins involved in the sulfur metabolism pathway.

The Hydrothermal Chemistry of Gold, Arsenic, Antimony, Mercury and Silver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bessinger, Brad; Apps, John A.

2003-03-23

A comprehensive thermodynamic database based on the Helgeson-Kirkham-Flowers (HKF) equation of state was developed for metal complexes in hydrothermal systems. Because this equation of state has been shown to accurately predict standard partial molal thermodynamic properties of aqueous species at elevated temperatures and pressures, this study provides the necessary foundation for future exploration into transport and depositional processes in polymetallic ore deposits. The HKF equation of state parameters for gold, arsenic, antimony, mercury, and silver sulfide and hydroxide complexes were derived from experimental equilibrium constants using nonlinear regression calculations. In order to ensure that the resulting parameters were internally consistent,more » those experiments utilizing incompatible thermodynamic data were re-speciated prior to regression. Because new experimental studies were used to revise the HKF parameters for H2S0 and HS-1, those metal complexes for which HKF parameters had been previously derived were also updated. It was found that predicted thermodynamic properties of metal complexes are consistent with linear correlations between standard partial molal thermodynamic properties. This result allowed assessment of several complexes for which experimental data necessary to perform regression calculations was limited. Oxygen fugacity-temperature diagrams were calculated to illustrate how thermodynamic data improves our understanding of depositional processes. Predicted thermodynamic properties were used to investigate metal transport in Carlin-type gold deposits. Assuming a linear relationship between temperature and pressure, metals are predicted to predominantly be transported as sulfide complexes at a total aqueous sulfur concentration of 0.05 m. Also, the presence of arsenic and antimony mineral phases in the deposits are shown to restrict mineralization within a limited range of chemical conditions. Finally, at a lesser aqueous sulfur concentration of 0.01 m, host rock sulfidation can explain the origin of arsenic and antimony minerals within the paragenetic sequence.« less

Secondary benzylation with benzyl alcohols catalyzed by a high-valent heterobimetallic Ir-Sn complex.

PubMed

Podder, Susmita; Choudhury, Joyanta; Roy, Sujit

2007-04-13

A highly efficient secondary benzylation procedure has been demonstrated using a high-valent heterobimetallic complex [Ir2(COD)2(SnCl3)2(Cl)2(mu-Cl)2] 1 as the catalyst in 1,2-dichloroethane to afford the corresponding benzylated products in moderate to excellent yields. The reaction was performed not only with carbon nucleophiles (arenes and heteroarenes) but also with oxygen (alcohol), nitrogen (amide and sulfonamide), and sulfur (thiol) nucleophiles. Mechanistic investigation showed the intermediacy of the ether in this reaction. An electrophilic mechanism is proposed from Hammett correlation.

SHRIMP-SI Multiple Sulfur Isotope Analysis of Sulfides from Brazilian Deposits: Analytical Capability to Resolve Single Grain Textural Complexities and Distinct Sulfur Sources

NASA Astrophysics Data System (ADS)

Ireland, T. R.; Teles, G. D. S.; Chemale, F., Jr.; Avila, J.

2016-12-01

The Archean atmosphere is thought to be several times more reducing than the present day atmosphere, and the occurrence of Mass Independent Fractionation of Sulfur isotopes (MIF-S) in sulfides of sedimentary and volcanogenic rocks older than 2.45 Ga reinforces it. The most accepted mechanism to generate MIF-S requires photochemical reactions with volcanogenic SO2 in an anoxic atmosphere (O2 levels <10-5 PAL). The identification of MIF-S, noted as Δ33S and Δ36S, requires precise measurements of less abundant 33S and 36S isotopes, which were first attained by bulk isotope analyses. However, in-situ analysis has become essential, as many of ancient sulfide samples have suffered post-depositional processes, and their primary isotopic signature from the atmosphere are now overprinted by mass-dependent fractionation processes. High-precision and resolution in situ measurements of 32S, 33S, 34S and 36S in sulfides can be achieved by SHRIMP-SI, which allows isotopic determinations with internal errors better than 0.05‰ for Δ33S and 0.2‰ for Δ36S (2SE), and reproducibility about 0.1‰ for Δ33S and better than 0.5‰ for Δ36S (2SD). Examples of the SHRIMP-SI capability are provided by multiple sulfur isotope analysis of samples from Brazil, the Au-(U) and pyrite deposits of Jacobina Basin and the massive sulfide deposits of the 3.3 Ga Mundo Novo Greenstone Belt. The level of precision and spatial resolution achievable with SHRIMP-SI allowed the isotopic distinction between sedimentary and post-depositional pyrites in Jacobina Basin, as well as the identification of different sulfur sources in the Mundo Novo Greenstone Belt VMS deposits.

Single-cell sequencing of Thiomargarita reveals genomic flexibility for adaptation to dynamic redox conditions

DOE PAGES

Winkel, Matthias; Salman-Carvalho, Verena; Woyke, Tanja; ...

2016-06-21

Large, colorless sulfur-oxidizing bacteria (LSB) of the family Beggiatoaceae form thick mats at sulfidic sediment surfaces, where they efficiently detoxify sulfide before it enters the water column. The genus Thiomargarita harbors the largest known free-living bacteria with cell sizes of up to 750 μm in diameter. In addition to their ability to oxidize reduced sulfur compounds, some Thiornargarita spp. are known to store large amounts of nitrate, phosphate and elemental sulfur internally. To date little is known about their energy yielding metabolic pathways, and how these pathways compare to other Beggiatoaceae. Here, we present a draft single-cell genome of amore » chain-forming " Candidatus Thiomargarita nelsonii Thio36", and conduct a comparative analysis to five draft and one full genome of other members of the Beggiatoaceae. " Ca. T. nelsonii Thio36" is able to respire nitrate to both ammonium and dinitrogen, which allows them to flexibly respond to environmental changes. Genes for sulfur oxidation and inorganic carbon fixation confirmed that " Ca. T. nelsonii Thio36" can function as a chemolithoautotroph. Carbon can be fixed via the Calvin-Benson-Bassham cycle, which is common among the Beggiatoaceae. In addition we found key genes of the reductive tricarboxylic acid cycle that point toward an alternative CO 2 fixation pathway. Surprisingly, " Ca. T. nelsonii Thio36" also encodes key genes of the C2-cycle that convert 2-phosphoglycolate to 3-phosphoglycerate during photorespiration in higher plants and cyanobacteria. Moreover, we identified a novel trait of a flavin-based energy bifurcation pathway coupled to a Na +-translocating membrane complex (Rnf). The coupling of these pathways may be key to surviving long periods of anoxia. As other Beggiatoaceae " Ca. T. nelsonii Thio36" encodes many genes similar to those of (filamentous) cyanobacteria. In conclusion, the genome of " Ca. T. nelsonii Thio36" provides additional insight into the ecology of giant sulfur-oxidizing bacteria, and reveals unique genomic features for the Thiomargarita lineage within the Beggiatoaceae.« less

Probing Ligand Effects on the Redox Energies of [4Fe-4S] Clusters Using Broken-Symmetry Density Functional Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niu, Shuqiang; Ichiye, Toshiko

A central issue in understanding redox properties of iron-sulfur proteins is determining the factors that tune the reduction potentials of the Fe-S clusters. Recently, Solomon and coworkers have shown that the Fe-S bond covalency of protein analogs measured by %L, the percent ligand character of the Fe 3d orbitals, from ligand K-edge X-ray absorption spectroscopy (XAS) correlates with the electrochemical redox potentials. Also, Wang and coworkers have measured electron detachment energies for iron-sulfur clusters without environmental perturbations by gas-phase photoelectron spectroscopy (PES). Here the correlations of the ligand character with redox energy and %L character are examined in [Fe₄S₄L₄]2⁻ clustersmore » with different ligands by broken symmetry density functional theory (BS-DFT) calculations using the B3LYP functional together with PES and XAS experimental results. These gas-phase studies assess ligand effects independently of environmental perturbations and thus provide essential information for computational studies of iron-sulfur proteins. The B3LYP oxidation energies agree well with PES data, and the %L character obtained from natural bond orbital analysis correlates with XAS values, although it systematically underestimates them because of basis set effects. The results show that stronger electron-donating terminal ligands increase %Lt, the percent ligand character from terminal ligands, but decrease %Sb, the percent ligand character from the bridging sulfurs. Because the oxidized orbital has significant Fe-Lt antibonding character, the oxidation energy correlates well with %Lt. However, because the reduced orbital has varying contributions of both Fe-Lt and Fe-Sb antibonding character, the reduction energy does not correlate with either %Lt or %Sb. Overall, BSDFT calculations together with XAS and PES experiments can unravel the complex underlying factors in the redox energy and chemical bonding of the [4Fe-4S] clusters in iron-sulfur proteins.« less

Sulfur mustard induced nuclear translocation of glyceraldehyde-3-phosphate-dehydrogenase (GAPDH).

PubMed

Steinritz, Dirk; Weber, Jana; Balszuweit, Frank; Thiermann, Horst; Schmidt, Annette

2013-12-05

Sulfur Mustard (SM) is a vesicant chemical warfare agent, which is acutely toxic to a variety of organ systems including skin, eyes, respiratory system and bone marrow. The underlying molecular pathomechanism was mainly attributed to the alkylating properties of SM. However, recent studies have revealed that cellular responses to SM exposure are of more complex nature and include increased protein expression and protein modifications that can be used as biomarkers. In order to confirm already known biomarkers, to detect potential new ones and to further elucidate the pathomechanism of SM, we conducted large-scale proteomic experiments based on a human keratinocyte cell line (HaCaT) exposed to SM. Surprisingly, our analysis identified glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) as one of the up-regulated proteins after exposure of HaCaT cells to SM. In this paper we demonstrate the sulfur mustard induced nuclear translocation of GAPDH in HaCaT cells by 2D gel-electrophoresis (2D GE), immunocytochemistry (ICC), Western Blot (WB) and a combination thereof. 2D GE in combination with MALDI-TOF MS/MS analysis identified GAPDH as an up-regulated protein after SM exposure. Immunocytochemistry revealed a distinct nuclear translocation of GAPDH after exposure to 300μM SM. This finding was confirmed by fractionated WB analysis. 2D GE and subsequent immunoblot staining of GAPDH demonstrated two different spot locations of GAPH (pI 7.0 and pI 8.5) that are related to cytosolic or nuclear GAPDH respectively. After exposure to 300μM SM a significant increase of nuclear GAPDH at pI 8.5 occurred. Nuclear GAPDH has been associated with apoptosis, detection of structural DNA alterations, DNA repair and regulation of genomic integrity and telomere structure. The results of our study add new aspects to the pathophysiology of sulfur mustard toxicity, yet further studies will be necessary to reveal the specific function of nuclear GAPDH in the pathomechanism of sulfur mustard. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winkel, Matthias; Salman-Carvalho, Verena; Woyke, Tanja

Large, colorless sulfur-oxidizing bacteria (LSB) of the family Beggiatoaceae form thick mats at sulfidic sediment surfaces, where they efficiently detoxify sulfide before it enters the water column. The genus Thiomargarita harbors the largest known free-living bacteria with cell sizes of up to 750 μm in diameter. In addition to their ability to oxidize reduced sulfur compounds, some Thiornargarita spp. are known to store large amounts of nitrate, phosphate and elemental sulfur internally. To date little is known about their energy yielding metabolic pathways, and how these pathways compare to other Beggiatoaceae. Here, we present a draft single-cell genome of amore » chain-forming " Candidatus Thiomargarita nelsonii Thio36", and conduct a comparative analysis to five draft and one full genome of other members of the Beggiatoaceae. " Ca. T. nelsonii Thio36" is able to respire nitrate to both ammonium and dinitrogen, which allows them to flexibly respond to environmental changes. Genes for sulfur oxidation and inorganic carbon fixation confirmed that " Ca. T. nelsonii Thio36" can function as a chemolithoautotroph. Carbon can be fixed via the Calvin-Benson-Bassham cycle, which is common among the Beggiatoaceae. In addition we found key genes of the reductive tricarboxylic acid cycle that point toward an alternative CO 2 fixation pathway. Surprisingly, " Ca. T. nelsonii Thio36" also encodes key genes of the C2-cycle that convert 2-phosphoglycolate to 3-phosphoglycerate during photorespiration in higher plants and cyanobacteria. Moreover, we identified a novel trait of a flavin-based energy bifurcation pathway coupled to a Na +-translocating membrane complex (Rnf). The coupling of these pathways may be key to surviving long periods of anoxia. As other Beggiatoaceae " Ca. T. nelsonii Thio36" encodes many genes similar to those of (filamentous) cyanobacteria. In conclusion, the genome of " Ca. T. nelsonii Thio36" provides additional insight into the ecology of giant sulfur-oxidizing bacteria, and reveals unique genomic features for the Thiomargarita lineage within the Beggiatoaceae.« less

THE ANTIBACTERIAL PROPERTIES OF SULFUR

PubMed Central

Weld, Julia T.; Gunther, Anne

1947-01-01

1. Saturated solutions of sulfur in alcohol (alcohol-sulfur) when diluted with broth are inhibitory to the growth of various Gram-positive bacteria and to C. hominis. By an arbitrary method of unitage with S. aureus as the test organism, our alcohol-sulfur contains 1,600 to 2,000 units per cc. and one unit contains between 0.24 and 0.34 gamma sulfur. The activity of a preparation is in general directly proportional to its sulfur content. 2. Solutions of sulfur in carbowax (carbowax-sulfur) when diluted with broth are likewise inhibitory to the growth of various Gram-positive bacteria and to C. hominis. When S. aureus is used as test organism, 1 unit contains between 0.1 and 0.2 gamma sulfur. The activity of these preparations is also in general directly proportional to their sulfur content. 3. Carbowax-sulfur when incorporated in agar in 1–500 to 1–2,000 dilution inhibits the growth of various Gram-positive aerobic and anaerobic bacteria, C. hominis, and certain dermatophytes. 4. Our experiments appear to show that both alcohol-sulfur and carbowax-sulfur owe their inhibitory properties to the sulfur particles that are dispersed throughout the medium when these sulfur preparations are diluted with broth. The inhibitory effect of these particles may or may not be due to a combination of the sulfur particles with substances in the medium in which they are suspended. 5. Evidence suggests that the activity of both alcohol-sulfur and carbowax-sulfur is due to sulfur in the same form. The inhibitory effect is characterized by prolonged bacteriostasis with similar activity over a wide range of dilutions. There is no evidence of true bactericidal action even with the highest concentrations used. PMID:19871634

Niche specialization of novel Thaumarchaeota to oxic and hypoxic acidic geothermal springs of Yellowstone National Park

PubMed Central

Beam, Jacob P; Jay, Zackary J; Kozubal, Mark A; Inskeep, William P

2014-01-01

Novel lineages of the phylum Thaumarchaeota are endemic to thermal habitats, and may exhibit physiological capabilities that are not yet observed in members of this phylum. The primary goals of this study were to conduct detailed phylogenetic and functional analyses of metagenome sequence assemblies of two different thaumarchaeal populations found in high-temperature (65–72 °C), acidic (pH∼3) iron oxide and sulfur sediment environments of Yellowstone National Park (YNP). Metabolic reconstruction was coupled with detailed geochemical measurements of each geothermal habitat and reverse-transcriptase PCR to confirm the in situ activity of these populations. Phylogenetic analyses of ribosomal and housekeeping proteins place these archaea near the root of the thaumarchaeal branch. Metabolic reconstruction suggests that these populations are chemoorganotrophic and couple growth with the reduction of oxygen or nitrate in iron oxide habitats, or sulfur in hypoxic sulfur sediments. The iron oxide population has the potential for growth via the oxidation of sulfide to sulfate using a novel reverse sulfate reduction pathway. Possible carbon sources include aromatic compounds (for example, 4-hydroxyphenylacetate), complex carbohydrates (for example, starch), oligopeptides and amino acids. Both populations contain a type III ribulose bisphosphate carboxylase/oxygenase used for carbon dioxide fixation or adenosine monophosphate salvage. No evidence for the oxidation of ammonia was obtained from de novo sequence assemblies. Our results show that thermoacidophilic Thaumarchaeota from oxic iron mats and hypoxic sulfur sediments exhibit different respiratory machinery depending on the presence of oxygen versus sulfide, represent deeply rooted lineages within the phylum Thaumarchaeota and are endemic to numerous sites in YNP. PMID:24196321

Modeling hydrologic controls on sulfur processes in sulfate-impacted wetland and stream sediments

NASA Astrophysics Data System (ADS)

Ng, G.-H. C.; Yourd, A. R.; Johnson, N. W.; Myrbo, A. E.

2017-09-01

Recent studies show sulfur redox processes in terrestrial settings are more important than previously considered, but much remains uncertain about how these processes respond to dynamic hydrologic conditions in natural field settings. We used field observations from a sulfate-impacted wetland and stream in the mining region of Minnesota (USA) to calibrate a reactive transport model and evaluate sulfur and coupled geochemical processes under contrasting hydrogeochemical scenarios. Simulations of different hydrological conditions showed that flux and chemistry differences between surface water and deeper groundwater strongly control hyporheic zone geochemical profiles. However, model results for the stream channel versus wetlands indicate sediment organic carbon content to be the more important driver of sulfate reduction rates. A complex nonlinear relationship between sulfate reduction rates and geochemical conditions is apparent from the model's higher sensitivity to sulfate concentrations in settings with higher organic content. Across all scenarios, simulated e- balance results unexpectedly showed that sulfate reduction dominates iron reduction, which is contrary to the traditional thermodynamic ladder but corroborates recent experimental findings by Hansel et al. (2015) that "cryptic" sulfur cycling could drive sulfate reduction in preference over iron reduction. Following the thermodynamic ladder, our models shows that high surface water sulfate slows methanogenesis in shallow sediments, but field observations suggest that sulfate reduction may not entirely suppress methane. Overall, our results show that sulfate reduction may serve as a major component making up and influencing terrestrial redox processes, with dynamic hyporheic fluxes controlling sulfate concentrations and reaction rates, especially in high organic content settings.

Anaerobic Sulfur Metabolism Coupled to Dissimilatory Iron Reduction in the Extremophile Acidithiobacillus ferrooxidans

PubMed Central

Osorio, Héctor; Mangold, Stefanie; Denis, Yann; Ñancucheo, Ivan; Esparza, Mario; Johnson, D. Barrie; Bonnefoy, Violaine; Dopson, Mark

2013-01-01

Gene transcription (microarrays) and protein levels (proteomics) were compared in cultures of the acidophilic chemolithotroph Acidithiobacillus ferrooxidans grown on elemental sulfur as the electron donor under aerobic and anaerobic conditions, using either molecular oxygen or ferric iron as the electron acceptor, respectively. No evidence supporting the role of either tetrathionate hydrolase or arsenic reductase in mediating the transfer of electrons to ferric iron (as suggested by previous studies) was obtained. In addition, no novel ferric iron reductase was identified. However, data suggested that sulfur was disproportionated under anaerobic conditions, forming hydrogen sulfide via sulfur reductase and sulfate via heterodisulfide reductase and ATP sulfurylase. Supporting physiological evidence for H2S production came from the observation that soluble Cu2+ included in anaerobically incubated cultures was precipitated (seemingly as CuS). Since H2S reduces ferric iron to ferrous in acidic medium, its production under anaerobic conditions indicates that anaerobic iron reduction is mediated, at least in part, by an indirect mechanism. Evidence was obtained for an alternative model implicating the transfer of electrons from S0 to Fe3+ via a respiratory chain that includes a bc1 complex and a cytochrome c. Central carbon pathways were upregulated under aerobic conditions, correlating with higher growth rates, while many Calvin-Benson-Bassham cycle components were upregulated during anaerobic growth, probably as a result of more limited access to carbon dioxide. These results are important for understanding the role of A. ferrooxidans in environmental biogeochemical metal cycling and in industrial bioleaching operations. PMID:23354702

Method for Hot Real-Time Sampling of Gasification Products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pomeroy, Marc D

The Thermochemical Process Development Unit (TCPDU) at the National Renewable Energy Laboratory (NREL) is a highly instrumented half-ton/day pilot scale plant capable of demonstrating industrially relevant thermochemical technologies from lignocellulosic biomass conversion, including gasification. Gasification creates primarily Syngas (a mixture of Hydrogen and Carbon Monoxide) that can be utilized with synthesis catalysts to form transportation fuels and other valuable chemicals. Biomass derived gasification products are a very complex mixture of chemical components that typically contain Sulfur and Nitrogen species that can act as catalysis poisons for tar reforming and synthesis catalysts. Real-time hot online sampling techniques, such as Molecular Beammore » Mass Spectrometry (MBMS), and Gas Chromatographs with Sulfur and Nitrogen specific detectors can provide real-time analysis providing operational indicators for performance. Sampling typically requires coated sampling lines to minimize trace sulfur interactions with steel surfaces. Other materials used inline have also shown conversion of sulfur species into new components and must be minimized. Sample line Residence time within the sampling lines must also be kept to a minimum to reduce further reaction chemistries. Solids from ash and char contribute to plugging and must be filtered at temperature. Experience at NREL has shown several key factors to consider when designing and installing an analytical sampling system for biomass gasification products. They include minimizing sampling distance, effective filtering as close to source as possible, proper line sizing, proper line materials or coatings, even heating of all components, minimizing pressure drops, and additional filtering or traps after pressure drops.« less

NIF-type iron-sulfur cluster assembly system is duplicated and distributed in the mitochondria and cytosol of Mastigamoeba balamuthi.

PubMed

Nývltová, Eva; Šuták, Robert; Harant, Karel; Šedinová, Miroslava; Hrdy, Ivan; Paces, Jan; Vlček, Čestmír; Tachezy, Jan

2013-04-30

In most eukaryotes, the mitochondrion is the main organelle for the formation of iron-sulfur (FeS) clusters. This function is mediated through the iron-sulfur cluster assembly machinery, which was inherited from the α-proteobacterial ancestor of mitochondria. In Archamoebae, including pathogenic Entamoeba histolytica and free-living Mastigamoeba balamuthi, the complex iron-sulfur cluster machinery has been replaced by an ε-proteobacterial nitrogen fixation (NIF) system consisting of two components: NifS (cysteine desulfurase) and NifU (scaffold protein). However, the cellular localization of the NIF system and the involvement of mitochondria in archamoebal FeS assembly are controversial. Here, we show that the genes for both NIF components are duplicated within the M. balamuthi genome. One paralog of each protein contains an amino-terminal extension that targets proteins to mitochondria (NifS-M and NifU-M), and the second paralog lacks a targeting signal, thereby reflecting the cytosolic form of the NIF machinery (NifS-C and NifU-C). The dual localization of the NIF system corresponds to the presence of FeS proteins in both cellular compartments, including detectable hydrogenase activity in Mastigamoeba cytosol and mitochondria. In contrast, E. histolytica possesses only single genes encoding NifS and NifU, respectively, and there is no evidence for the presence of the NIF machinery in its reduced mitochondria. Thus, M. balamuthi is unique among eukaryotes in that its FeS cluster formation is mediated through two most likely independent NIF machineries present in two cellular compartments.

NIF-type iron-sulfur cluster assembly system is duplicated and distributed in the mitochondria and cytosol of Mastigamoeba balamuthi

PubMed Central

Nývltová, Eva; Šuták, Robert; Harant, Karel; Šedinová, Miroslava; Hrdý, Ivan; Pačes, Jan; Vlček, Čestmír; Tachezy, Jan

2013-01-01

In most eukaryotes, the mitochondrion is the main organelle for the formation of iron-sulfur (FeS) clusters. This function is mediated through the iron-sulfur cluster assembly machinery, which was inherited from the α-proteobacterial ancestor of mitochondria. In Archamoebae, including pathogenic Entamoeba histolytica and free-living Mastigamoeba balamuthi, the complex iron-sulfur cluster machinery has been replaced by an ε-proteobacterial nitrogen fixation (NIF) system consisting of two components: NifS (cysteine desulfurase) and NifU (scaffold protein). However, the cellular localization of the NIF system and the involvement of mitochondria in archamoebal FeS assembly are controversial. Here, we show that the genes for both NIF components are duplicated within the M. balamuthi genome. One paralog of each protein contains an amino-terminal extension that targets proteins to mitochondria (NifS-M and NifU-M), and the second paralog lacks a targeting signal, thereby reflecting the cytosolic form of the NIF machinery (NifS-C and NifU-C). The dual localization of the NIF system corresponds to the presence of FeS proteins in both cellular compartments, including detectable hydrogenase activity in Mastigamoeba cytosol and mitochondria. In contrast, E. histolytica possesses only single genes encoding NifS and NifU, respectively, and there is no evidence for the presence of the NIF machinery in its reduced mitochondria. Thus, M. balamuthi is unique among eukaryotes in that its FeS cluster formation is mediated through two most likely independent NIF machineries present in two cellular compartments. PMID:23589868

Transport of sulfur dioxide from the Asian Pacific Rim to the North Pacific troposphere

NASA Astrophysics Data System (ADS)

Thornton, Donald C.; Bandy, Alan R.; Blomquist, Byron W.; Talbot, Robert W.; Dibb, Jack E.

1997-12-01

The NASA Pacific Exploratory Mission over the Western Pacific Ocean (PEM-West B) field experiment provided an opportunity to study sulfur dioxide (SO2) in the troposphere over the western Pacific Ocean from the tropics to 60°N during February-March 1993. The large suite of chemical and physical measurements yielded a complex matrix in which to understand the distribution of sulfur dioxide over the western Pacific region. In contrast to the late summer period of Pacific Exploratory Mission-West A (PEM-West A) (1991) over this same area, SO2 showed little increase with altitude, and concentrations were much lower in the free troposphere than during the PEM-West B period. Volcanic impacts on the upper troposphere were again found as a result of deep convection in the tropics. Extensive emission of SO2 from the Pacific Rim land masses were primarily observed in the lower well-mixed part of the boundary layer but also in the upper part of the boundary layer. Analyses of the SO2 data with aerosol sulfate, beryllium-7, and lead-210 indicated that SO2 contributed to half or more of the observed total oxidized sulfur (SO2 plus aerosol sulfate) in free tropospheric air. The combined data set suggests that SO2 above 8.5 km is transported from the surface but with aerosol sulfate being removed more effectively than SO2. Cloud processing and rain appeared to be responsible for lower SO2 levels between 3 and 8.5 km than above or below this region.

A spectroscopic method for observing the domain movement of the Rieske iron–sulfur protein

PubMed Central

Brugna, Myriam; Rodgers, Simon; Schricker, Anna; Montoya, Guillermo; Kazmeier, Michael; Nitschke, Wolfgang; Sinning, Irmgard

2000-01-01

The g-tensor orientation of the chemically reduced Rieske cluster in cytochrome bc1 complex from Rhodovulum sulfidophilum with respect to the membrane was determined in the presence and absence of inhibitors and in the presence of oxidized and reduced quinone in the quinol-oxidizing-site (Qo-site) by EPR on two-dimensionally ordered samples. Almost identical orientations were observed when oxidized or reduced quinone, stigmatellin, or 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole was present. Occupancy of the Qo-site by myxothiazole induced appearance of a minority population with a substantially differing conformation and presence of E-β-methoxyacrylate-stilbene significantly reduced the contribution of the major conformation observed in the other cases. Furthermore, when the oxidized iron–sulfur cluster was reduced at cryogenic temperatures by the products of radiolysis, the orientation of its magnetic axes was found to differ significantly from that of the chemically reduced center. The “irradiation-induced” conformation converts to that of the chemically reduced center after thawing of the sample. These results confirm the effects of Qo-site inhibitors on the equilibrium conformation of the Rieske iron–sulfur protein and provide evidence for a reversible redox-influenced interconversion between conformational states. Moreover, the data obtained with the iron—sulfur protein demonstrate that the conformation of “EPR-inaccessible” reduction states of redox centers can be studied by inducing changes of redox state at cryogenic temperatures. This technique appears applicable to a wide range of comparable electron transfer systems performing redox-induced conformational changes. PMID:10681446

Pervaporation and sorption behavior of zeolite-filled polyethylene glycol hybrid membranes for the removal of thiophene species.

PubMed

Lin, Ligang; Zhang, Yuzhong; Li, Hong

2010-10-01

Polyethylene glycol (PEG)-CuY zeolite hybrid membranes were prepared for sulfur removal from gasoline feed. The sorption and diffusion behavior of typical gasoline components through the hybrid membranes has been investigated by systematic studies of dynamic sorption curves. Influencing factors including feed temperature, permeate pressure, and zeolite content in the membranes on membrane performance have been evaluated. Immersion experiments results showed the preferential sorption of thiophene, which is key in fulfilling the separation of thiophene/hydrocarbon mixtures. The sorption, diffusion, and permeation coefficients of gasoline components in filled membranes are higher than those in unfilled membranes. Pervaporation (PV) and gas chromatography (GC) experiments results corresponded to the discussions on dynamic sorption curves. PV experiments showed that lower permeate pressure meant higher separation performance. The optimum temperature occurred at 383K, and an Arrhenius relationship existed between permeation flux and operating temperature. The CuY zeolite filling led to a significant increase of flux since the porous zeolite provides for more diffusion for small molecules in mixed matrix membranes. The sulfur enrichment factor increased first and then decreased with the increasing zeolite content, which was attributed to the combined influence of complexation force between CuY and thiophenes as well as the trade-off phenomenon between flux and selectivity. At 9 wt% CuY content, a higher permeation flux (3.19 kg/(m(2) h)) and sulfur enrichment factor (2.95) were obtained with 1190 microg/g sulfur content level in gasoline feed. Copyright 2010 Elsevier Inc. All rights reserved.

Method for removing sulfur oxide from waste gases and recovering elemental sulfur

DOEpatents

Moore, Raymond H.

1977-01-01

A continuous catalytic fused salt extraction process is described for removing sulfur oxides from gaseous streams. The gaseous stream is contacted with a molten potassium sulfate salt mixture having a dissolved catalyst to oxidize sulfur dioxide to sulfur trioxide and molten potassium normal sulfate to solvate the sulfur trioxide to remove the sulfur trioxide from the gaseous stream. A portion of the sulfur trioxide loaded salt mixture is then dissociated to produce sulfur trioxide gas and thereby regenerate potassium normal sulfate. The evolved sulfur trioxide is reacted with hydrogen sulfide as in a Claus reactor to produce elemental sulfur. The process may be advantageously used to clean waste stack gas from industrial plants, such as copper smelters, where a supply of hydrogen sulfide is readily available.

Formation of Multilayer Graphene Domains with Strong Sulfur-Carbon Interaction and Enhanced Sulfur Reduction Zones for Lithium-Sulfur Battery Cathodes.

PubMed

Perez Beltran, Saul; Balbuena, Perla B

2018-02-12

A newly designed sulfur/graphene computational model emulates the electrochemical behavior of a Li-S battery cathode, promoting the S-C interaction through the edges of graphene sheets. A random mixture of eight-membered sulfur rings mixed with small graphene sheets is simulated at 64 wt %sulfur loading. Structural stabilization and sulfur reduction calculations are performed with classical reactive molecular dynamics. This methodology allowed the collective behavior of the sulfur and graphene structures to be accounted for. The sulfur encapsulation induces ring opening and the sulfur phase evolves into a distribution of small chain-like structures interacting with C through the graphene edges. This new arrangement of the sulfur phase not only leads to a less pronounced volume expansion during sulfur reduction but also to a different discharge voltage profile, in qualitative agreement with earlier reports on sulfur encapsulation in microporous carbon structures. The Li 2 S phase grows around ensembles of parallel graphene nanosheets during sulfur reduction. No diffusion of sulfur or lithium between graphene nanosheets is observed, and extended Li 2 S domains bridging the space between carbon ensembles are suppressed. The results emphasize the importance of morphology on the electrochemical performance of the composite material. The sulfur/graphene model outlined here provides new understanding of the graphene effects on the sulfur reduction behavior and the role that van der Waals interactions may play in promoting formation of multilayer graphene ensembles and small Li 2 S domains during sulfur reduction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

40 CFR 50.4 - National primary ambient air quality standards for sulfur oxides (sulfur dioxide).

Code of Federal Regulations, 2010 CFR

2010-07-01

... standards for sulfur oxides (sulfur dioxide). 50.4 Section 50.4 Protection of Environment ENVIRONMENTAL....4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). Link to an... to or greater than 0.005 ppm shall be rounded up). (c) Sulfur oxides shall be measured in the ambient...

Naval Research Reviews, Volume 32, Number 4

DTIC Science & Technology

1980-01-01

iron while (e.g., carbon, chlorine, phosphorous, sulfur, zinc other areas are still covered by an oxide . An XPS and boron). An example of the chemical...picture. Metallic bearing components, for ex- major impact on tribology. The first is the develop- ample, usually have complex oxide films on their...the composition or thickncs. IThe optical image is m,.chanisms responsible for ion beam degradation of rotated slightly withrespecttoelectronimages

Wet Chemistry Synthesis of Multidimensional Nanocarbon-Sulfur Hybrid Materials with Ultrahigh Sulfur Loading for Lithium-Sulfur Batteries.

PubMed

Du, Wen-Cheng; Yin, Ya-Xia; Zeng, Xian-Xiang; Shi, Ji-Lei; Zhang, Shuai-Feng; Wan, Li-Jun; Guo, Yu-Guo

2016-02-17

An optimized nanocarbon-sulfur cathode material with ultrahigh sulfur loading of up to 90 wt % is realized in the form of sulfur nanolayer-coated three-dimensional (3D) conducting network. This 3D nanocarbon-sulfur network combines three different nanocarbons, as follows: zero-dimensional carbon nanoparticle, one-dimensional carbon nanotube, and two-dimensional graphene. This 3D nanocarbon-sulfur network is synthesized by using a method based on soluble chemistry of elemental sulfur and three types of nanocarbons in well-chosen solvents. The resultant sulfur-carbon material shows a high specific capacity of 1115 mA h g(-1) at 0.02C and good rate performance of 551 mA h g(-1) at 1C based on the mass of sulfur-carbon composite. Good battery performance can be attributed to the homogeneous compositing of sulfur with the 3D hierarchical hybrid nanocarbon networks at nanometer scale, which provides efficient multidimensional transport pathways for electrons and ions. Wet chemical method developed here provides an easy and cost-effective way to prepare sulfur-carbon cathode materials with high sulfur loading for application in high-energy Li-S batteries.

Effect of solvents on the electrochemical properties of binder-free sulfur cathode films in lithium–sulfur batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryu, Ho-Suk; Kim, Byeong-Wook; Park, Jin-Woo

Highlights: • The binder-free sulfur electrode with high sulfur contents of 75 wt.% was fabricated. • The binder-free sulfur electrode using NMP solvents showed 784 mAh g{sup −1} after 40 cycles. • The solvent affect the electrochemical properties of binder-free sulfur electrode films. - Abstract: The effects of solvents on the preparation of sulfur cathodes were investigated by fabricating binder-free sulfur electrode films using three different solvents: 1-methyl-2-pyrrolidinone (NMP), acetonitrile, and deionized water. These solvents are commonly employed to dissolve binders used to prepare sulfur cathodes for lithium–sulfur batteries. The sulfur electrode fabricated with NMP had a higher discharge capacitymore » and longer cycle life than the ones fabricated with acetonitrile and deionized water. Better adhesion between the current collector and the sulfur electrode accounted for the improved capacity and cycle life of the battery. In addition, the stability of the electrode in the electrolyte was a result of the solubility of sulfur in the solvent. We thus concluded that the solvents used in the fabrication of sulfur electrodes had a positive influence on the electrochemical properties of Li–S batteries.« less

Speciation of sulfur from filamentous microbial mats from sulfidic cave springs using X-ray absorption near-edge spectroscopy.

PubMed

Engel, Annette Summers; Lichtenberg, Henning; Prange, Alexander; Hormes, Josef

2007-04-01

Most transformations within the sulfur cycle are controlled by the biosphere, and deciphering the abiotic and biotic nature and turnover of sulfur is critical to understand the geochemical and ecological changes that have occurred throughout the Earth's history. Here, synchrotron radiation-based sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy is used to examine sulfur speciation in natural microbial mats from two aphotic (cave) settings. Habitat geochemistry, microbial community compositions, and sulfur isotope systematics were also evaluated. Microorganisms associated with sulfur metabolism dominated the mats, including members of the Epsilonproteobacteria and Gammaproteobacteria. These groups have not been examined previously by sulfur K-edge XANES. All of the mats consisted of elemental sulfur, with greater contributions of cyclo-octasulfur (S8) compared with polymeric sulfur (Smicro). While this could be a biological fingerprint for some bacteria, the signature may also indicate preferential oxidation of Smicro and S8 accumulation. Higher sulfate content correlated to less S8 in the presence of Epsilonproteobacteria. Sulfur isotope compositions confirmed that sulfur content and sulfur speciation may not correlate to microbial metabolic processes in natural samples, thereby complicating the interpretation of modern and ancient sulfur records.

Sulfur-impregnated disordered carbon nanotubes cathode for lithium-sulfur batteries.

PubMed

Guo, Juchen; Xu, Yunhua; Wang, Chunsheng

2011-10-12

The commercialization of lithium-sulfur batteries is hindered by low cycle stability and low efficiency, which are induced by sulfur active material loss and polysulfide shuttle reaction through dissolution into electrolyte. In this study, sulfur-impregnated disordered carbon nanotubes are synthesized as cathode material for the lithium-sulfur battery. The obtained sulfur-carbon tube cathodes demonstrate superior cyclability and Coulombic efficiency. More importantly, the electrochemical characterization indicates a new stabilization mechanism of sulfur in carbon induced by heat treatment.

Transcriptional and Proteomic Profiling of Aspergillus flavipes in Response to Sulfur Starvation

PubMed Central

El-Sayed, Ashraf S. A.; Yassin, Marwa A.; Ali, Gul Shad

2015-01-01

Aspergillus flavipes has received considerable interest due to its potential to produce therapeutic enzymes involved in sulfur amino acid metabolism. In natural habitats, A. flavipes survives under sulfur limitations by mobilizing endogenous and exogenous sulfur to operate diverse cellular processes. Sulfur limitation affects virulence and pathogenicity, and modulates proteome of sulfur assimilating enzymes of several fungi. However, there are no previous reports aimed at exploring effects of sulfur limitation on the regulation of A. flavipes sulfur metabolism enzymes at the transcriptional, post-transcriptional and proteomic levels. In this report, we show that sulfur limitation affects morphological and physiological responses of A. flavipes. Transcription and enzymatic activities of several key sulfur metabolism genes, ATP-sulfurylase, sulfite reductase, methionine permease, cysteine synthase, cystathionine β- and γ-lyase, glutathione reductase and glutathione peroxidase were increased under sulfur starvation conditions. A 50 kDa protein band was strongly induced by sulfur starvation, and the proteomic analyses of this protein band using LC-MS/MS revealed similarity to many proteins involved in the sulfur metabolism pathway. PMID:26633307

On the nature of carbon-hydrogen bond activation at rhodium and related reactions.

PubMed

Jones, William D

2005-06-27

Over the past 20 years, substantial progress has been made in the understanding of the activation of C-H and other strong bonds by reactive metal complexes in low oxidation states. This paper will present an overview of the use of pentamethylcyclopentadienyl and trispyrazolylborate rhodium complexes for the activation of arene and alkane C-H bonds. Insights into bond strengths, kinetic and thermodynamic selectivities, and the nature of the intermediates involved will be reviewed. The role of eta-2 arene complexes will be shown to be critical to the C-H activation reactions. Some information about the fleeting alkane sigma-complexes will also be presented. In addition, use of these complexes with thiophenes has shown the ability to cleave C-S bonds. Mechanistic information has been obtained indicating coordination through sulfur prior to cleavage. Relevant examples of nickel-based C-S cleavage will also be given.

Synthesis, structures and properties of three copper complexes with dibutyldithiocarbamate ligand

NASA Astrophysics Data System (ADS)

Wang, Chen; Niu, Jiao; Li, Jun; Ma, Xiaoxun

2017-05-01

Three copper complexes constructed with sulfur-containing dibutyldithiocarbamate ligand (DDTC), [(Et2NCS2)4Cu2] (1), [(Et2NCS2)(EtO)Cu]2 (2) and [(Et2NCS2)6Cu13I10]n (3) have been synthesized through the reaction of CuI with different mole ratios of DDTC under solution-diffusion conditions. The single crystal X-ray diffraction revealed that divalent Cu cations in complexes 1 and 2 imply that the reactant, Cu(I), was involved in the redox process. They formed binuclear complexes according to bridging S from DDTC ligands and O atoms from ethanol molecules respectively. The mixed valence Cu cations had two types of coordination environments in complex 3 and formed a two-dimensional layered coordination polymer by bridging the five-core Cu(I) clusters and Cu(II). The powder X-ray diffraction, luminescent, thermogravimetric analysis, etc. were also studied in this paper.

Molecular details of the yeast frataxin-Isu1 interaction during mitochondrial Fe-S cluster assembly

PubMed Central

Cook, Jeremy D.; Kondapalli, Kalyan C.; Rawat, Swati; Childs, William C.; Murugesan, Yogapriya; Dancis, Andrew; Stemmler, Timothy L.

2010-01-01

Frataxin, a conserved nuclear encoded mitochondrial protein, plays a direct role in iron-sulfur cluster biosynthesis within the ISC assembly pathway. Humans with frataxin deficiency have Friedreich’s ataxia, a neurodegenerative disorder characterized by mitochondrial iron overload and disruption in Fe-S cluster synthesis. Biochemical and genetic studies have shown frataxin interacts with the iron-sulfur cluster assembly scaffold protein (in yeast, there are two: Isu1 and Isu2), indicating frataxin plays a direct role in cluster assembly, possibly by serving as an iron chaperone n the assembly pathway. Here we provide molecular details of how yeast frataxin (Yfh1) interacts with Isu1 as a structural module to better understand the multiprotein complex assembly that completes Fe-S cluster assembly; this complex also includes the cysteine desulfurase (Nfs1 in yeast) and the accessory protein (Isd11), together in the mitochondria. Thermodynamic binding parameters for protein partner and iron binding were measured for the yeast orthologs using isothermal titration calorimetry (ITC). Nuclear magnetic resonance spectroscopy was used to provide the molecular details to understand how Yfh1 interacts with Isu1. X-ray absorption studies were used to electronically and structurally characterize how iron is transferred to Isu1 and then incorporated into a Fe-S cluster. These results were combined with previously published data to generate a structural model for how the Fe-S cluster protein assembly complex can come together to accomplish Fe-S cluster assembly. PMID:20815377

Redox Chemistry of Gold(I) Phosphine Thiolates: Sulfur-Based Oxidation

PubMed Central

Jiang, Tong; Wei, Gang; Turmel, Cristopher; Bruce, Alice E.

1994-01-01

The redox chemistry of mononuclear and dinuclear gold(I) phosphine arylthiolate complexes was recently investigated by using electrochemical, chemical, and photochemical techniques. We now report the redox chemistry of dinuclear gold(I) phosphine complexes containing aliphatic dithiolate ligands. These molecules differ from previously studied gold(I) phosphine thiolate complexes in that they are cyclic and contain aliphatic thiolates. Cyclic voltammetry experiments of Au2 (LL)(pdt) [pdt = propanedithiol; LL = 1,2-bis(diphenylphosphino)-ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb), 1,5-bis(diphenylphosphino)pentane (dpppn)] in 0.1 M TBAH/CH3CN or CH2Cl2 solutions at 50 to 500 mV/sec using glassy carbon or platinum electrodes, show two irreversible anodic processes at ca. +0.6 and +1.1 V (vs. SCE). Bulk electrolyses at +0.9 V and +1.4 V result in n values of 0.95 and 3.7, respectively. Chemical oxidation of Au2(dppp)(pdt) using one equivalent of Br2 (2 oxidizing equivalents) yields 1,2-dithiolane and Au2(dppp)Br2. The reactivity seen upon mild oxidation ≤ +1.0 V is consistent with formal oxidation of a thiolate ligand, followed by a fast chemical reaction that results in cleavage of a second gold-sulfur bond. Oxidation at higher potentials (≥ +1.3 V) is consistent with oxidation of gold(I) to gold(III). Structural and electrochemical differences between gold(I) aromatic and aliphatic thiolate oxidation processes are discussed. PMID:18476260

Molecular Details of the Yeast Frataxin-Isu1 Interaction during Mitochondrial Fe-S Cluster Assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, J.; Kondapalli, K; Rawat, S

2010-01-01

Frataxin, a conserved nuclear-encoded mitochondrial protein, plays a direct role in iron-sulfur cluster biosynthesis within the ISC assembly pathway. Humans with frataxin deficiency have Friedreich's ataxia, a neurodegenerative disorder characterized by mitochondrial iron overload and disruption in Fe-S cluster synthesis. Biochemical and genetic studies have shown frataxin interacts with the iron-sulfur cluster assembly scaffold protein (in yeast, there are two, Isu1 and Isu2), indicating frataxin plays a direct role in cluster assembly, possibly by serving as an iron chaperone in the assembly pathway. Here we provide molecular details of how yeast frataxin (Yfh1) interacts with Isu1 as a structural modulemore » to improve our understanding of the multiprotein complex assembly that completes Fe-S cluster assembly; this complex also includes the cysteine desulfurase (Nfs1 in yeast) and the accessory protein (Isd11), together in the mitochondria. Thermodynamic binding parameters for protein partner and iron binding were measured for the yeast orthologs using isothermal titration calorimetry. Nuclear magnetic resonance spectroscopy was used to provide the molecular details to understand how Yfh1 interacts with Isu1. X-ray absorption studies were used to electronically and structurally characterize how iron is transferred to Isu1 and then incorporated into an Fe-S cluster. These results were combined with previously published data to generate a structural model for how the Fe-S cluster protein assembly complex can come together to accomplish Fe-S cluster assembly.« less

Molecular details of the yeast frataxin-Isu1 interaction during mitochondrial Fe-S cluster assembly.

PubMed

Cook, Jeremy D; Kondapalli, Kalyan C; Rawat, Swati; Childs, William C; Murugesan, Yogapriya; Dancis, Andrew; Stemmler, Timothy L

2010-10-12

Frataxin, a conserved nuclear-encoded mitochondrial protein, plays a direct role in iron-sulfur cluster biosynthesis within the ISC assembly pathway. Humans with frataxin deficiency have Friedreich's ataxia, a neurodegenerative disorder characterized by mitochondrial iron overload and disruption in Fe-S cluster synthesis. Biochemical and genetic studies have shown frataxin interacts with the iron-sulfur cluster assembly scaffold protein (in yeast, there are two, Isu1 and Isu2), indicating frataxin plays a direct role in cluster assembly, possibly by serving as an iron chaperone in the assembly pathway. Here we provide molecular details of how yeast frataxin (Yfh1) interacts with Isu1 as a structural module to improve our understanding of the multiprotein complex assembly that completes Fe-S cluster assembly; this complex also includes the cysteine desulfurase (Nfs1 in yeast) and the accessory protein (Isd11), together in the mitochondria. Thermodynamic binding parameters for protein partner and iron binding were measured for the yeast orthologs using isothermal titration calorimetry. Nuclear magnetic resonance spectroscopy was used to provide the molecular details to understand how Yfh1 interacts with Isu1. X-ray absorption studies were used to electronically and structurally characterize how iron is transferred to Isu1 and then incorporated into an Fe-S cluster. These results were combined with previously published data to generate a structural model for how the Fe-S cluster protein assembly complex can come together to accomplish Fe-S cluster assembly.

Keep your Sox on: Community genomics-directed isolation and microscopic characterization of the dominant subsurface sulfur-oxidizing bacterium in a sediment aquifer

NASA Astrophysics Data System (ADS)

Mullin, S. W.; Wrighton, K. C.; Luef, B.; Wilkins, M. J.; Handley, K. M.; Williams, K. H.; Banfield, J. F.

2012-12-01

Community genomics and proteomics (proteogenomics) can be used to predict the metabolic potential of complex microbial communities and provide insight into microbial activity and nutrient cycling in situ. Inferences regarding the physiology of specific organisms then can guide isolation efforts, which, if successful, can yield strains that can be metabolically and structurally characterized to further test metagenomic predictions. Here we used proteogenomic data from an acetate-stimulated, sulfidic sediment column deployed in a groundwater well in Rifle, CO to direct laboratory amendment experiments to isolate a bacterial strain potentially involved in sulfur oxidation for physiological and microscopic characterization (Handley et al, submitted 2012). Field strains of Sulfurovum (genome r9c2) were predicted to be capable of CO2 fixation via the reverse TCA cycle and sulfur oxidation (Sox and SQR) coupled to either nitrate reduction (Nap, Nir, Nos) in anaerobic environments or oxygen reduction in microaerobic (cbb3 and bd oxidases) environments; however, key genes for sulfur oxidation (soxXAB) were not identified. Sulfidic groundwater and sediment from the Rifle site were used to inoculate cultures that contained various sulfur species, with and without nitrate and oxygen. We isolated a bacterium, Sulfurovum sp. OBA, whose 16S rRNA gene shares 99.8 % identity to the gene of the dominant genomically characterized strain (genome r9c2) in the Rifle sediment column. The 16S rRNA gene of the isolate most closely matches (95 % sequence identity) the gene of Sulfurovum sp. NBC37-1, a genome-sequenced deep-sea sulfur oxidizer. Strain OBA grew via polysulfide, colloidal sulfur, and tetrathionate oxidation coupled to nitrate reduction under autotrophic and mixotrophic conditions. Strain OBA also grew heterotrophically, oxidizing glucose, fructose, mannose, and maltose with nitrate as an electron acceptor. Over the range of oxygen concentrations tested, strain OBA was not capable of aerobic growth, but it could tolerate low oxygen conditions in the polysulfide/nitrate growth medium, suggesting that oxidases identified by genomics may play a role in detoxification rather than energy generation. Cryo-TEM imaging showed that strain OBA cells are rod-shaped and ~0.4 wide and 1.0 μm in length, and confirmed metagenomics-based predictions of a Gram-negative cell envelope, pili and polyphosphate body production. Our results show the value of integrating metagenomics, culturing, and microscopic imaging to discern the physiology of bacteria involved in biogeochemical transformations in the subsurface.

Multiple sulfur isotopes monitor fluid evolution of an Archean orogenic gold deposit

NASA Astrophysics Data System (ADS)

LaFlamme, Crystal; Sugiono, Dennis; Thébaud, Nicolas; Caruso, Stefano; Fiorentini, Marco; Selvaraja, Vikraman; Jeon, Heejin; Voute, François; Martin, Laure

2018-02-01

The evolution of a gold-bearing hydrothermal fluid from its source to the locus of gold deposition is complex as it experiences rapid changes in thermochemical conditions during ascent through the crust. Although it is well established that orogenic gold deposits are generated during time periods of abundant crustal growth and/or reworking, the source of fluid and the thermochemical processes that control gold precipitation remain poorly understood. In situ analyses of multiple sulfur isotopes offer a new window into the relationship between source reservoirs of Au-bearing fluids and the thermochemical processes that occur along their pathway to the final site of mineralisation. Whereas δ34S is able to track changes in the evolution of the thermodynamic conditions of ore-forming fluids, Δ33S is virtually indelible and can uniquely fingerprint an Archean sedimentary reservoir that has undergone mass independent fractionation of sulfur (MIF-S). We combine these two tracers (δ34S and Δ33S) to characterise a gold-bearing laminated quartz breccia ore zone and its sulfide-bearing alteration halo in the (+6 Moz Au) structurally-controlled Archean Waroonga deposit located in the Eastern Goldfields Superterrane of the Yilgarn Craton, Western Australia. Over 250 analyses of gold-associated sulfides yield a δ34S shift from what is interpreted as an early pre-mineralisation phase, with chalcopyrite-pyrrhotite (δ34S = +0.7‰ to +2.9‰) and arsenopyrite cores (δ34S = ∼-0.5‰), to a syn-mineralisation stage, reflected in Au-bearing arsenopyrite rims (δ34S = -7.6‰ to +1.5‰). This shift coincides with an unchanging Δ33S value (Δ33S = +0.3‰), both temporally throughout the Au-hosting hydrothermal sulfide paragenesis and spatially across the Au ore zone. These results indicate that sulfur is at least partially recycled from MIF-S-bearing Archean sediments. Further, the invariant nature of the observed MIF-S signature demonstrates that sulfur is derived from a homogeneous MIF-S-bearing fluid reservoir at depth, rather than being locally sourced at the site of Au precipitation. Finally, by constraining the MIF-S-bearing sulfur source to a fixed reservoir, we are able to display the thermochemical evolution of the ore fluid in δ34S space and capture the abrupt change in oxidation state that causes Au precipitation. Our results highlight the importance of constraining multiple sulfur isotopes in space and time in order to elucidate the source and evolution of any given Au-bearing fluid.

40 CFR 80.580 - What are the sampling and testing methods for sulfur?

Code of Federal Regulations, 2010 CFR

2010-07-01

...,000 ppm sulfur standard of § 80.510(k), sulfur content may be determined using ASTM D2622... the 500 ppm sulfur standard of § 80.510(a)(1), sulfur content may be determined using ASTM D2622... to the 1,000 ppm sulfur standard of § 80.510(k), sulfur content may be determined using ASTM D4294...

Swept Away: Resuspension of Bacterial Mats Regulates Benthic-Pelagic Exchange of Sulfur

NASA Astrophysics Data System (ADS)

Grant, Jonathan; Bathmann, Ulrich V.

1987-06-01

Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.

Metagenomic analyses of the late Pleistocene permafrost - additional tools for reconstruction of environmental conditions

NASA Astrophysics Data System (ADS)

Rivkina, Elizaveta; Petrovskaya, Lada; Vishnivetskaya, Tatiana; Krivushin, Kirill; Shmakova, Lyubov; Tutukina, Maria; Meyers, Arthur; Kondrashov, Fyodor

2016-04-01

A comparative analysis of the metagenomes from two 30 000-year-old permafrost samples, one of lake-alluvial origin and the other from late Pleistocene Ice Complex sediments, revealed significant differences within microbial communities. The late Pleistocene Ice Complex sediments (which have been characterized by the absence of methane with lower values of redox potential and Fe2+ content) showed a low abundance of methanogenic archaea and enzymes from both the carbon and nitrogen cycles, but a higher abundance of enzymes associated with the sulfur cycle. The metagenomic and geochemical analyses described in the paper provide evidence that the formation of the sampled late Pleistocene Ice Complex sediments likely took place under much more aerobic conditions than lake-alluvial sediments.

Refiners Switch to RFG Complex Model

EIA Publications

1998-01-01

On January 1, 1998, domestic and foreign refineries and importers must stop using the "simple" model and begin using the "complex" model to calculate emissions of volatile organic compounds (VOC), toxic air pollutants (TAP), and nitrogen oxides (NOx) from motor gasoline. The primary differences between application of the two models is that some refineries may have to meet stricter standards for the sulfur and olefin content of the reformulated gasoline (RFG) they produce and all refineries will now be held accountable for NOx emissions. Requirements for calculating emissions from conventional gasoline under the anti-dumping rule similarly change for exhaust TAP and NOx. However, the change to the complex model is not expected to result in an increase in the price premium for RFG or constrain supplies.

Hydrogen bonding assemblies in host guest complexes with 18-crown-6

NASA Astrophysics Data System (ADS)

Fonari, M. S.; Simonov, Yu. A.; Kravtsov, V. Ch.; Lipkowski, J.; Ganin, E. V.; Yavolovskii, A. A.

2003-02-01

Recent X-ray crystal structural data for two novel 1:2 host-guest complexes of 18-crown-6 with neutral organic molecules, thiaamide hydrazide of 2-aminobenzoic acid and thiaamide hydrazide of 4-amino-1,2,5-thiadiazole-3-carbonic acid are reported. The supramolecular structures of these two and five relative complexes are discussed from the point of view of participation of donor groups in coordination with the crown ether, and donor and acceptor groups in the self-assembly of the guest molecules. Guest molecules have incorporated amine and hydrazine moieties as proton donors and carbonyl oxygen and sulfur (in thiadiazole and in thiaamine moieties) as proton acceptors. The guest-guest interactions appeared to be crucial in the final architecture.

End-Functionalized Palladium SCS Pincer Polymers via Controlled Radical Polymerizations.

PubMed

Lye, Diane S; Cohen, Aaron E; Wong, Madeleine Z; Weck, Marcus

2017-07-01

A direct and facile route toward semitelechelic polymers, end-functionalized with palladated sulfur-carbon-sulfur pincer (Pd II -pincer) complexes is reported that avoids any post-polymerization step. Key to our methodology is the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization with functionalized chain-transfer agents. This strategy yields Pd end-group-functionalized materials with monomodal molar mass dispersities (Đ) of 1.18-1.44. The RAFT polymerization is investigated using a Pd II -pincer chain-transfer agent for three classes of monomers: styrene, tert-butyl acrylate, and N-isopropylacrylamide. The ensuing Pd II -pincer end-functionalized polymers are analyzed using 1 H NMR spectroscopy, gel-permeation chromatography, and elemental analysis. The RAFT polymerization methodology provides a direct pathway for the fabrication of Pd II -pincer functionalized polymers with complete end-group functionalization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Interaction of Global Biochemical Cycles

NASA Technical Reports Server (NTRS)

Moore, B., III; Dastoor, M. N.

1984-01-01

The global biosphere in an exceedingly complex system. To gain an understanding of its structure and dynamic features, it is necessary not only to increase the knowledge about the detailed processes but also to develop models of how global interactions take place. Attempts to analyze the detailed physical, chemical and biological processes in this context need to be guided by an advancement of understanding of the latter. It is necessary to develop a strategy of data gathering that severs both these purposes simultaneously. The following papers deal with critical aspects in the global cycles of carbon, nitrogen, phosphorus and sulfur in details as well as the cycle of water and the flow of energy in the Earth's environment. The objective is to set partly the foundation for the development of mathematical models that allow exploration of the coupled dynamics of the global cycles of carbon, nitrogen, phosphorus, sulfur, as well as energy and water flux.

Zinc Pyrithione Inhibits Yeast Growth through Copper Influx and Inactivation of Iron-Sulfur Proteins▿†

PubMed Central

Reeder, Nancy L.; Kaplan, Jerry; Xu, Jun; Youngquist, R. Scott; Wallace, Jared; Hu, Ping; Juhlin, Kenton D.; Schwartz, James R.; Grant, Raymond A.; Fieno, Angela; Nemeth, Suzanne; Reichling, Tim; Tiesman, Jay P.; Mills, Tim; Steinke, Mark; Wang, Shuo L.; Saunders, Charles W.

2011-01-01

Zinc pyrithione (ZPT) is an antimicrobial material with widespread use in antidandruff shampoos and antifouling paints. Despite decades of commercial use, there is little understanding of its antimicrobial mechanism of action. We used a combination of genome-wide approaches (yeast deletion mutants and microarrays) and traditional methods (gene constructs and atomic emission) to characterize the activity of ZPT against a model yeast, Saccharomyces cerevisiae. ZPT acts through an increase in cellular copper levels that leads to loss of activity of iron-sulfur cluster-containing proteins. ZPT was also found to mediate growth inhibition through an increase in copper in the scalp fungus Malassezia globosa. A model is presented in which pyrithione acts as a copper ionophore, enabling copper to enter cells and distribute across intracellular membranes. This is the first report of a metal-ligand complex that inhibits fungal growth by increasing the cellular level of a different metal. PMID:21947398

Long-term evaluation of the fate of sulfur mustard on dry and humid soils, asphalt, and concrete.

PubMed

Mizrahi, Dana M; Goldvaser, Michael; Columbus, Ishay

2011-04-15

The long-term fate of the blister agent sulfur mustard (HD, bis(2-chloroethyl)sulfide) was determined in a variety of commercial and natural matrices. HD was found to be extremely stable in dry matrices for over a year. The addition of 5% water to the matrices induced slow degradation of HD, which lasted several months. The major degradation product in sands and asphalt was found to be a sulfonium salt, S[CH(2)CH(2)S(+)(CH(2)CH(2)OH)(2)](2) (H-2TG). Red loam soil, which has not been examined before, exhibited strong interaction with HD, both in dry form and in the presence of water. Humid red loam soil gave rise to unique oxidative degradation products. On humid concrete HD degraded to a complex mixture of products, including vinyls. This may be attributed to the basic sites incorporated in concrete.

Zinc isotope evidence for sulfate-rich fluid transfer across subduction zones.

PubMed

Pons, Marie-Laure; Debret, Baptiste; Bouilhol, Pierre; Delacour, Adélie; Williams, Helen

2016-12-16

Subduction zones modulate the chemical evolution of the Earth's mantle. Water and volatile elements in the slab are released as fluids into the mantle wedge and this process is widely considered to result in the oxidation of the sub-arc mantle. However, the chemical composition and speciation of these fluids, which is critical for the mobility of economically important elements, remain poorly constrained. Sulfur has the potential to act both as oxidizing agent and transport medium. Here we use zinc stable isotopes (δ 66 Zn) in subducted Alpine serpentinites to decipher the chemical properties of slab-derived fluids. We show that the progressive decrease in δ 66 Zn with metamorphic grade is correlated with a decrease in sulfur content. As existing theoretical work predicts that Zn-SO 4 2- complexes preferentially incorporate heavy δ 66 Zn, our results provide strong evidence for the release of oxidized, sulfate-rich, slab serpentinite-derived fluids to the mantle wedge.

Think Yellow and Keep Green—Role of Sulfanes from Garlic in Agriculture

PubMed Central

Anwar, Awais; Gould, Emma; Tinson, Ryan; Groom, Murree; Hamilton, Chris J.

2016-01-01

Reactive sulfur species from garlic have long been renowned for their health benefits and antimicrobial properties. In agriculture the subject matter is now gathering momentum in the search for new bio-pesticides to addressing emerging environmental concerns and tighter restrictions on the use of many conventional chemical pesticides. Although the precise modes of action of these garlic-derived bioactives is complex, recent research has provided a number of new insights that deepen our understanding of garlic-derived products, such as garlic extracts and oils. Herein, their activity against various crop-damaging pests is reviewed. In many cases, there seems to be a broad range of activity associated with the sulfur-containing compounds derived from Allium species, which manifests itself in diverse insecticidal, antifungal, and nematicidal activities. These activities open a new understanding to develop this natural chemistry as a “green pesticide”. PMID:28042817

Think Yellow and Keep Green-Role of Sulfanes from Garlic in Agriculture.

PubMed

Anwar, Awais; Gould, Emma; Tinson, Ryan; Groom, Murree; Hamilton, Chris J

2016-12-30

Reactive sulfur species from garlic have long been renowned for their health benefits and antimicrobial properties. In agriculture the subject matter is now gathering momentum in the search for new bio-pesticides to addressing emerging environmental concerns and tighter restrictions on the use of many conventional chemical pesticides. Although the precise modes of action of these garlic-derived bioactives is complex, recent research has provided a number of new insights that deepen our understanding of garlic-derived products, such as garlic extracts and oils. Herein, their activity against various crop-damaging pests is reviewed. In many cases, there seems to be a broad range of activity associated with the sulfur-containing compounds derived from Allium species, which manifests itself in diverse insecticidal, antifungal, and nematicidal activities. These activities open a new understanding to develop this natural chemistry as a "green pesticide".

Uses of lunar sulfur

NASA Technical Reports Server (NTRS)

Vaniman, D.; Pettit, D.; Heiken, G.

1992-01-01

Sulfur and sulfur compounds have a wide range of applications for their fluid, electrical, chemical, and biochemical properties. Although known abundances on the Moon are limited (approximately 0.1 percent in mare soils), sulfur is relatively extractable by heating. Coproduction of sulfur during oxygen extraction from ilmenite-rich mare soils could yield sulfur in masses up to 10 percent of the mass of oxygen produced. Sulfur deserves serious consideration as a lunar resource.

Cytochromes and iron sulfur proteins in sulfur metabolism of phototrophic bacteria

NASA Technical Reports Server (NTRS)

Fischer, U.

1985-01-01

Dissimilatory sulfur metabolism in phototrophic sulfur bacteria provides the bacteria with electrons for photosynthetic electron transport chain and, with energy. Assimilatory sulfate reduction is necessary for the biosynthesis of sulfur-containing cell components. Sulfide, thiosulfate, and elemental sulfur are the sulfur compounds most commonly used by phototrophic bacteria as electron donors for anoxygenic photosynthesis. Cytochromes or other electron transfer proteins, like high-potential-iron-sulfur protein (HIPIP) function as electron acceptors or donors for most enzymatic steps during the oxidation pathways of sulfide or thiosulfate. Yet, heme- or siroheme-containing proteins themselves undergo enzymatic activities in sulfur metabolism. Sirohemes comprise a porphyrin-like prosthetic group of sulfate reductase. eenzymatic reactions involve electron transfer. Electron donors or acceptors are necessary for each reaction. Cytochromes and iron sulfur problems, are able to transfer electrons.

Luminescence of defects in the structural transformation of layered tin dichalcogenides

NASA Astrophysics Data System (ADS)

Sutter, P.; Komsa, H.-P.; Krasheninnikov, A. V.; Huang, Y.; Sutter, E.

2017-12-01

Layered tin sulfide semiconductors are both of fundamental interest and attractive for energy conversion applications. Sn sulfides crystallize in several stable bulk phases with different Sn:S ratios (SnS2, Sn2S3, and SnS), which can transform into phases with a lower sulfur concentration by introduction of sulfur vacancies (VS). How this complex behavior affects the optoelectronic properties remains largely unknown but is of key importance for understanding light-matter interactions in this family of layered materials. Here, we use the capability to induce VS and drive a transformation between few-layer SnS2 and SnS by electron beam irradiation, combined with in-situ cathodoluminescence spectroscopy and ab-initio calculations to probe the role of defects in the luminescence of these materials. In addition to the characteristic band-edge emission of the endpoint structures, our results show emerging luminescence features accompanying the SnS2 to SnS transformation. Comparison with calculations indicates that the most prominent emission in SnS2 with sulfur vacancies is not due to luminescence from a defect level but involves recombination of excitons bound to neutral VS in SnS2. These findings provide insight into the intrinsic and defect-related optoelectronic properties of Sn chalcogenide semiconductors.

Interaction of sulfuric acid corrosion and mechanical wear of iron

NASA Technical Reports Server (NTRS)

Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

1986-01-01

Friction and wear experiment were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

Interaction of sulfuric acid corrosion and mechanical wear of iron

NASA Technical Reports Server (NTRS)

Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

1984-01-01

Friction and wear experiments were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

Progression in sulfur isotopic compositions from coal to fly ash: Examples from single-source combustion in Indiana

USGS Publications Warehouse

Yaofa, Jiang; Elswick, E.R.; Mastalerz, Maria

2008-01-01

Sulfur occurs in multiple mineral forms in coals, and its fate in coal combustion is still not well understood. The sulfur isotopic composition of coal from two coal mines in Indiana and fly ash from two power plants that use these coals were studied using geological and geochemical methods. The two coal beds are Middle Pennsylvanian in age; one seam is the low-sulfur ( 5%) Springfield Coal Member of the Petersburg Formation. Both seams have ash contents of approximately 11%. Fly-ash samples were collected at various points in the ash-collection system in the two plants. The results show notable difference in ??34S for sulfur species within and between the low-sulfur and high-sulfur coal. The ??34S values for all sulfur species are exclusively positive in the low-sulfur Danville coal, whereas the ??34S values for sulfate, pyritic, and organic sulfur are both positive and negative in the high-sulfur Springfield coal. Each coal exhibits a distinct pattern of stratigraphic variation in sulfur isotopic composition. Overall, the ??34S for sulfur species values increase up the section in the low-sulfur Danville coal, whereas they show a decrease up the vertical section in the high-sulfur Springfield coal. Based on the evolution of ??34S for sulfur species, it is suggested that there was influence of seawater on peat swamp, with two marine incursions occurring during peat accumulation of the high-sulfur Springfield coal. Therefore, bacterial sulfate reduction played a key role in converting sulfate into hydrogen sulfide, sulfide minerals, and elemental sulfur. The differences in ??34S between sulfate sulfur and pyritic sulfur is very small between individual benches of both coals, implying that some oxidation occurred during deposition or postdeposition. The ??34S values for fly ash from the high-sulfur Springfield coal (averaging 9.7???) are greatly enriched in 34S relative to those in the parent coal (averaging 2.2???). This indicates a fractionation of sulfur isotopes during high-sulfur coal combustion. By contrast, the ??34S values for fly-ash samples from the low-sulfur Danville coal average 10.2???, only slightly enriched in 34S relative to those from the parent coal (average 7.5???). The ??34S values for bulk S determined directly from the fly-ash samples show close correspondence with the ??34S values for SO4- 2 leached from the fly ash in the low-sulfur coal, suggesting that the transition from pyrite to sulfate occurred via high-temperature oxidation during coal combustion. ?? 2007 Elsevier B.V. All rights reserved.

Improving the reliability of road materials based on micronized sulfur composites

NASA Astrophysics Data System (ADS)

Abdrakhmanova, K. K.

2015-01-01

The work contains the results of a nano-structural modification of sulfur that prevents polymorphic transformations from influencing the properties of sulfur composites where sulfur is present in a thermodynamic stable condition that precludes destruction when operated. It has been established that the properties of sulfur-based composite materials can be significantly improved by modifying sulfur and structuring sulfur binder by nano-dispersed fiber particles and ultra-dispersed state filler. The paper shows the possibility of modifying Tengiz sulfur by its fragmenting which ensures that the structured sulfur is structurally changed and stabilized through reinforcement by ultra-dispersed fiber particles allowing the phase contact area to be multiplied. Interaction between nano-dispersed fibers of chrysotile asbestos and sulfur ensures the implementation of the mechanical properties of chrysotile asbestos tubes in reinforced composite and its integrity provided that the surface of chrysotile asbestos tubes are highly moistened with molten sulfur and there is high adhesion between the tubes and the matrix that, in addition to sulfur, contains limestone microparticles. Ability to apply materials in severe operation conditions and possibility of exposure in both aggressive medium and mechanical loads makes produced sulfur composites required by the road construction industry.

Sulfur Speciation in Peat: a Time-zero Signature for the " Spruce and Peatland Responses Under Climate and Environmental Change" Experiment

NASA Astrophysics Data System (ADS)

Furman, O.; Toner, B. M.; Sebestyen, S. D.; Kolka, R. K.; Nater, E. A.

2014-12-01

As part of the "Spruce and Peatland Responses Under Climate and Environmental Change" (SPRUCE) experiment, we made initial measurements of sulfur speciation in peat. These observations represent a "time-zero" relative to the intended soil warming experiment which begins in 2015. Total sulfur and sulfur speciation were measured in peat cores (solid phase) from nine plots (hollows and hummocks) to a depth of 2 m. Peat samples were packed under nitrogen and frozen in the field immediately after collection. All subsequent sample storage, handling, and processing were conducted under inert gas. Sulfur speciation was measured using bulk sulfur 1s X-ray absorption near edge structure (XANES) spectroscopy at the SXRMB instrument at the Canadian Light Source, Saskatoon, SK, Canada and at the 9-BM instrument, Advanced Photon Source, Argonne National Laboratory, IL, USA. Total sulfur concentrations ranged from 968 to 4077 mg sulfur / kg dry peat. Sulfur content increased with depth from 2 g sulfur / m2 in the 0-10 cm increment to a maximum value of 38 g sulfur / m2 in the 50-60 cm increment. These sulfur loadings produced high quality XANES spectra. The nine cores exhibited reproducible trends with depth in both total sulfur and specific sulfur species; however, variability in sulfur speciation was greatest in the top 40 cm. All sulfur detected within the peat solids was in an organic form. The most abundant sulfur species group was composed of organic mono-sulfide and thiol forms, representing approximately half of the total sulfur at all depths. Sulfonate and ester-sulfate species were 10-15 mol% of sulfur and exhibited low variability with depth. A subsurface maximum in organic di-sulfide was observed in the 20-30 cm depth increment, which is the transition zone between transiently oxidized acrotelm and permanently saturated anaerobic catotelm. Quantification of major sulfur pools is important for the SPRUCE experiment as they are likely to be indicators of changes in the oxidation-reduction (redox) status, and mercury methylation potential, of the peat in response to warming and enhanced carbon dioxide.

Microbial Desulfurization of a Crude Oil Middle-Distillate Fraction: Analysis of the Extent of Sulfur Removal and the Effect of Removal on Remaining Sulfur

PubMed Central

Grossman, M. J.; Lee, M. K.; Prince, R. C.; Garrett, K. K.; George, G. N.; Pickering, I. J.

1999-01-01

Rhodococcus sp. strain ECRD-1 was evaluated for its ability to desulfurize a 232 to 343°C middle-distillate (diesel range) fraction of Oregon basin (OB) crude oil. OB oil was provided as the sole source of sulfur in batch cultures, and the extent of desulfurization and the chemical fate of the residual sulfur in the oil after treatment were determined. Gas chromatography (GC), flame ionization detection, and GC sulfur chemiluminesce detection analysis were used to qualitatively evaluate the effect of Rhodococcus sp. strain ECRD-1 treatment on the hydrocarbon and sulfur content of the oil, respectively. Total sulfur was determined by combustion of samples and measurement of released sulfur dioxide by infrared absorption. Up to 30% of the total sulfur in the middle distillate cut was removed, and compounds across the entire boiling range of the oil were affected. Sulfur K-edge X-ray absorption-edge spectroscopy was used to examine the chemical state of the sulfur remaining in the treated OB oil. Approximately equal amounts of thiophenic and sulfidic sulfur compounds were removed by ECRD-1 treatment, and over 50% of the sulfur remaining after treatment was in an oxidized form. The presence of partially oxidized sulfur compounds indicates that these compounds were en route to desulfurization. Overall, more than two-thirds of the sulfur had been removed or oxidized by the microbial treatment. PMID:9872778

Crystal structures of copper(II) chloride, copper(II) bromide, and copper(II) nitrate complexes with pyridine-2-carbaldehyde thiosemicarbazone

NASA Astrophysics Data System (ADS)

Chumakov, Yu. M.; Tsapkov, V. I.; Jeanneau, E.; Bairac, N. N.; Bocelli, G.; Poirier, D.; Roy, J.; Gulea, A. P.

2008-09-01

The crystal structures of chloro-(2-formylpyridinethiosemicarbazono)copper dimethyl sulfoxide solvate ( I), bromo-(2-formylpyridinethiosemicarbazono)copper ( II), and (2-formylpyridinethiosemicarbazono)copper(II) nitrate dimethyl sulfoxide solvate ( III) are determined using X-ray diffraction. In the crystals, complexes I and II form centrosymmetric dimers in which the thiosemicarbazone sulfur atom serves as a bridge and occupies the fifth coordination site of the copper atom of the neighboring complex related to the initial complex through the center of symmetry. In both cases, the coordination polyhedron of the complexing ion is a distorted tetragonal bipyramid. Complex III in the crystal structure forms polymer chains in which the copper atom of one complex forms the coordination bond with the thicarbamide nitrogen atom of the neighboring complex. In this structure, the coordination polyhedron of the central atom is an elongated tetragonal bipyramid. It is established that complexes I III at a concentration of 10-5 mol/l selectively inhibit the growth of 60 to 90 percent of the cancer tumor cells of the human myeloid leukemia (HL-60).

Incorporating Sulfur Inside the Pores of Carbons for Advanced Lithium-Sulfur Batteries: An Electrolysis Approach.

PubMed

He, Bin; Li, Wen-Cui; Yang, Chao; Wang, Si-Qiong; Lu, An-Hui

2016-01-26

We have developed an electrolysis approach that allows effective and uniform incorporation of sulfur inside the micropores of carbon nanosheets for advanced lithium-sulfur batteries. The sulfur-carbon hybrid can be prepared with a 70 wt % sulfur loading, in which no nonconductive sulfur agglomerations are formed. Because the incorporated sulfur is electrically connected to the carbon matrix in nature, the hybrid cathode shows excellent electrochemical performance, including a high reversible capacity, good rate capability, and good cycling stability, as compared to one prepared using the popular melt-diffusion method.

Mesoporous hollow carbon spheres for lithium–sulfur batteries: distribution of sulfur and electrochemical performance

PubMed Central

Juhl, Anika C; Schneider, Artur; Ufer, Boris; Brezesinski, Torsten

2016-01-01

Summary Hollow carbon spheres (HCS) with a nanoporous shell are promising for the use in lithium–sulfur batteries because of the large internal void offering space for sulfur and polysulfide storage and confinement. However, there is an ongoing discussion whether the cavity is accessible for sulfur. Yet no valid proof of cavity filling has been presented, mostly due to application of unsuitable high-vacuum methods for the analysis of sulfur distribution. Here we describe the distribution of sulfur in hollow carbon spheres by powder X-ray diffraction and Raman spectroscopy along with results from scanning electron microscopy and nitrogen physisorption. The results of these methods lead to the conclusion that the cavity is not accessible for sulfur infiltration. Nevertheless, HCS/sulfur composite cathodes with areal sulfur loadings of 2.0 mg·cm−2 were investigated electrochemically, showing stable cycling performance with specific capacities of about 500 mAh·g−1 based on the mass of sulfur over 500 cycles. PMID:27826497

Determination of total sulfur content via sulfur-specific chemiluminescence detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubala, S.W.; Campbell, D.N.; DiSanzo, F.P.

A specially designed system, based upon sulfur-specific chemiluminescence detection (SSCD), was developed to permit the determination of total sulfur content in a variety of samples. This type of detection system possesses several advantages such as excellent linearity and selectivity, low minimum detectable levels, and an equimolar response to various sulfur compounds. This paper will focus on the design and application of a sulfur-specific chemiluminescence detection system for use in determining total sulfur content in gasoline.

Solubility of gold in oxidized, sulfur-bearing fluids at 500-850 °C and 200-230 MPa: A synthetic fluid inclusion study

NASA Astrophysics Data System (ADS)

Guo, Haihao; Audétat, Andreas; Dolejš, David

2018-02-01

Although Au solubility in magmatic-hydrothermal fluids has been investigated by numerous previous studies, there is a dearth of data on oxidized (log fO2 > FMQ+2.5; FMQ - fayalite-magnetite-quartz buffer), sulfur-bearing fluids such as those that formed porphyry Cu-Au (-Mo) deposits. We performed experiments to constrain the effects of fluid salinity, HCl content, sulfur content, fO2 and temperature on Au solubility in such oxidized, sulfur-bearing fluids. For this purpose, small aliquots of fluids equilibrated with Au metal were trapped at high pressure and temperature in the form of synthetic fluid inclusions in quartz and were subsequently analyzed by LA-ICP-MS. Additionally, Raman spectra were collected from quartz-hosted fluid inclusions at up to 600 °C to help to identify the nature of dissolved gold and sulfur species. Gold solubility was found to be affected most strongly by the HCl content of the fluid, followed by fO2, fluid salinity and temperature. Compared to these factors the sulfur content of the fluid has relatively little influence. At 600 °C and 100 MPa, fluids with geologically realistic HCl contents (∼1.1 wt%) and salinities (7-50 wt% NaClequiv) dissolve ∼1000-3000 ppm Au at oxygen fugacities controlled by the magnetite-hematite buffer. At even more oxidized conditions (three log units above the hematite-magnetite fO2 buffer), HCl-, NaCl- and H2SO4-rich fluids can dissolve up to 5 wt% Au at 800 °C and 200 MPa. The observed Au solubility trends are controlled by HCl0 species in the Na-H-Cl-SO4 fluid and are quantitatively reproduced by existing thermodynamic data for Au-Cl complexes. In all experiments, AuCl0 and AuCl2- species are predicted to occur in comparable although variable concentrations, and account for more than 95% of Au solutes. Natural, high-temperature (>500 °C) brine inclusions from porphyry Cu-Au (-Mo) deposits contain significantly less Au than gold-saturated brines that were synthesized experimentally, implying that the natural brines were Au-undersaturated. Consequently, gold grades in Au-rich porphyries were not controlled by the precipitation of native Au, but rather by factors that caused the precipitation of Au-bearing hydrothermal sulfides such as bornite.

Partitioning of mercury in aqueous biphasic systems and on ABEC resins.

PubMed

Rogers, R D; Griffin, S T

1998-06-26

Poly(ethylene glycol)-based aqueous biphasic systems (PEG-ABS) can be utilized to separate and recover metal ions in environmental and hydrometallurgical applications. A concurrent study was conducted comparing the partitioning of mercury between aqueous layers in an ABS [Me-PEG-5000/(NH4)2SO4] and partitioning of mercury from aqueous solutions to aqueous biphasic extraction chromatographic (ABEC-5000) resins. In ammonium sulfate solutions, mercury partitions to the salt-rich phase in ABS, but by using halide ion extractants, mercury will partition to the PEG-rich phase after formation of a chloro, bromo or iodo complex. The efficacy of the extractant increases in the order Cl-

Spectroscopic and structural investigation of interaction of 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione potassium salt with molecular iodine

NASA Astrophysics Data System (ADS)

Ivolgina, Victoria A.; Chernov'yants, Margarita S.

2018-06-01

The interest in the study of heteroaromatic thioamides which are known to exhibit antithyroid activity is stimulated by the variety and an unusual structure their complexes with molecular iodine. The directions of dithiones investigation are diversity enough, however a few works are devoted to the study them as the potential thyreostatics. The ability of 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thion potassium salt to form the outer-sphere charge-transfer complex in dilute chloroform solution, coordinating 2 iodine molecules has been studied by UV-vis spectroscopy (lgβ = 7.91). The compound of the 5,5‧-disulfanediylbis(3-phenyl-1,3,4-thiadiazole-2(3H)-thione) - product of irreversible oxidation of 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione potassium salt has been isolated and characterized by X-ray diffraction. Intermolecular interactions between sulfur atoms are observed with very short interatomic distance, shorter than sum of van der Waals radii. The contact between heterocyclic sulfur and heterocyclic nitrogen is also slightly short - 3.169 Å (0.053 Å less than vdW radii sum). This investigation constitutes a starting point for study of novel antithyroid drugs in future.

Spectroscopic and structural investigation of interaction of 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione potassium salt with molecular iodine.

PubMed

Ivolgina, Victoria A; Chernov'yants, Margarita S

2018-06-15

The interest in the study of heteroaromatic thioamides which are known to exhibit antithyroid activity is stimulated by the variety and an unusual structure their complexes with molecular iodine. The directions of dithiones investigation are diversity enough, however a few works are devoted to the study them as the potential thyreostatics. The ability of 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thion potassium salt to form the outer-sphere charge-transfer complex in dilute chloroform solution, coordinating 2 iodine molecules has been studied by UV-vis spectroscopy (lgβ=7.91). The compound of the 5,5'-disulfanediylbis(3-phenyl-1,3,4-thiadiazole-2(3H)-thione) - product of irreversible oxidation of 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione potassium salt has been isolated and characterized by X-ray diffraction. Intermolecular interactions between sulfur atoms are observed with very short interatomic distance, shorter than sum of van der Waals radii. The contact between heterocyclic sulfur and heterocyclic nitrogen is also slightly short - 3.169Å (0.053Å less than vdW radii sum). This investigation constitutes a starting point for study of novel antithyroid drugs in future. Copyright © 2018 Elsevier B.V. All rights reserved.

Polymersomes containing iron sulfide (FeS) as primordial cell model : for the investigation of energy providing redox reactions.

PubMed

Alpermann, Theodor; Rüdel, Kristin; Rüger, Ronny; Steiniger, Frank; Nietzsche, Sandor; Filiz, Volkan; Förster, Stephan; Fahr, Alfred; Weigand, Wolfgang

2011-04-01

According to Wächtershäuser's "Iron-Sulfur-World" one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on external energy sources, the "Iron-Sulfur-World" is based on the catalytic and energy reproducing redox system FeS+H2S-->FeS2+H2. The energy release out of this redox reaction (∆RG°=-38 kJ/mol, pH 0) could be the cause for the subsequent synthesis of complex organic molecules and the precondition for the development of more complex units similar to cells known today. Here we show the possibility for precipitating iron sulfide inside vesicles composed of amphiphilic block-copolymers as a model system for a first prebiotic unit. Our findings could be an indication for a chemoautotrophic FeS based origin of life.

Completing the Heterocubane Family [Cp*AlE]4 (E = O, S, Se, and Te) by Selective Oxygenation and Sulfuration of [Cp*Al]4: Density Functional Theory Calculations of [Cp*AlE]4 and Reactivity of [Cp*AlO]4 toward Hydrolysis.

PubMed

Stelzer, Adrian C; Hrobárik, Peter; Braun, Thomas; Kaupp, Martin; Braun-Cula, Beatrice

2016-05-16

The subvalent aluminum compound [Cp*Al]4 (1) reacts with dioxygen, N2O, or sulfur to yield the heterocubane complexes [Cp*AlX]4 [X = O (2) and S (3)]. Treatment of [Cp*AlO]4 (2) with (tBuO)3SiOH gave [(tBuO)3SiOAlO]4 (6) and Cp*H. The structures and spectroscopic data of the Al clusters are supported by density functional theory (DFT) calculations, which also demonstrate the importance of noncovalent interactions (NCI) in oligomeric Al(I) complexes as well as in [Cp*AlS]4 and the heavier homologues of Se and Te. The computed (27)Al NMR shifts indicate a deshielding at the Al centers with increasing electronegativity of the chalcogen atom as well as significant spin-orbit shielding effects within the heavier heterocubane [Al4E4] cores. Further hydrolysis of 6 with an additional amount of silanol in the presence of water resulted in the formation of [Al4(OH)6(OH2)2(OSiOtBu3)6] (7), which shows a structural motif found in boehmite and diaspore.

Kinetic mechanism of the dimeric ATP sulfurylase from plants

PubMed Central

Ravilious, Geoffrey E.; Herrmann, Jonathan; Goo Lee, Soon; Westfall, Corey S.; Jez, Joseph M.

2013-01-01

In plants, sulfur must be obtained from the environment and assimilated into usable forms for metabolism. ATP sulfurylase catalyses the thermodynamically unfavourable formation of a mixed phosphosulfate anhydride in APS (adenosine 5′-phosphosulfate) from ATP and sulfate as the first committed step of sulfur assimilation in plants. In contrast to the multi-functional, allosterically regulated ATP sulfurylases from bacteria, fungi and mammals, the plant enzyme functions as a mono-functional, non-allosteric homodimer. Owing to these differences, here we examine the kinetic mechanism of soybean ATP sulfurylase [GmATPS1 (Glycine max (soybean) ATP sulfurylase isoform 1)]. For the forward reaction (APS synthesis), initial velocity methods indicate a single-displacement mechanism. Dead-end inhibition studies with chlorate showed competitive inhibition versus sulfate and non-competitive inhibition versus APS. Initial velocity studies of the reverse reaction (ATP synthesis) demonstrate a sequential mechanism with global fitting analysis suggesting an ordered binding of substrates. ITC (isothermal titration calorimetry) showed tight binding of APS to GmATPS1. In contrast, binding of PPi (pyrophosphate) to GmATPS1 was not detected, although titration of the E•APS complex with PPi in the absence of magnesium displayed ternary complex formation. These results suggest a kinetic mechanism in which ATP and APS are the first substrates bound in the forward and reverse reactions, respectively. PMID:23789618

SufD and SufC ATPase activity are required for iron acquisition during in vivo Fe-S cluster formation on SufB.

PubMed

Saini, Avneesh; Mapolelo, Daphne T; Chahal, Harsimranjit K; Johnson, Michael K; Outten, F Wayne

2010-11-02

In vivo biogenesis of Fe-S cluster cofactors requires complex biosynthetic machinery to limit release of iron and sulfide, to protect the Fe-S cluster from oxidation, and to target the Fe-S cluster to the correct apoenzyme. The SufABCDSE pathway for Fe-S cluster assembly in Escherichia coli accomplishes these tasks under iron starvation and oxidative stress conditions that disrupt Fe-S cluster metabolism. Although SufB, SufC, and SufD are all required for in vivo Suf function, their exact roles are unclear. Here we show that SufB, SufC, and SufD, coexpressed with the SufS-SufE sulfur transfer pair, purify as two distinct complexes (SufBC(2)D and SufB(2)C(2)) that contain Fe-S clusters and FADH(2). These studies also show that SufC and SufD are required for in vivo Fe-S cluster formation on SufB. Furthermore, while SufD is dispensable for in vivo sulfur transfer, it is absolutely required for in vivo iron acquisition. Finally, we demonstrate for the first time that the ATPase activity of SufC is necessary for in vivo iron acquisition during Fe-S cluster assembly.

Adsorptive Desulfurization of Model Gasoline by Using Different Zn Sources Exchanged NaY Zeolites.

PubMed

Rui, Jingwei; Liu, Fei; Wang, Rijie; Lu, Yanfei; Yang, Xiaoxia

2017-02-17

A series of Zn-modified NaY zeolites were prepared by the liquid-phase ion-exchange method with different Zn sources, including Zn(NO₃)₂, Zn(Ac)₂ and ZnSO₄. The samples were tested as adsorbents for removing an organic sulfur compound from a model gasoline fuel containing 1000 ppmw sulfur. Zn(Ac)₂-Y exhibited the best performance for the desulfurization of gasoline at ambient conditions. Combined with the adsorbents' characterization results, the higher adsorption capacity of Zn(Ac)₂-Y is associated with a higher ion-exchange degree. Further, the results demonstrated that the addition of 5 wt % toluene or 1-hexene to the diluted thiophene (TP) solution in cyclohexane caused a large decrease in the removal of TP from the model gasoline fuel. This provides evidence about the competition through the π-complexation between TP and toluene for adsorption on the active sites. The acid-catalyzed alkylation by 1-hexene of TP and the generated complex mixture of bulky alkylthiophenes would adsorb on the surface active sites of the adsorbent and block the pores. The regenerated Zn(Ac)₂-Y adsorbent afforded 84.42% and 66.10% of the initial adsorption capacity after the first two regeneration cycles.

40 CFR 80.213 - What alternative sulfur standards and requirements apply to transmix processors and transmix...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 16 2011-07-01 2011-07-01 false What alternative sulfur standards and... ADDITIVES Gasoline Sulfur Gasoline Sulfur Standards § 80.213 What alternative sulfur standards and... TGP meets the applicable sulfur standards under § 80.210 or § 80.220, prior to the TGP leaving the...

40 CFR 80.213 - What alternative sulfur standards and requirements apply to transmix processors and transmix...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 16 2010-07-01 2010-07-01 false What alternative sulfur standards and... ADDITIVES Gasoline Sulfur Gasoline Sulfur Standards § 80.213 What alternative sulfur standards and... TGP meets the applicable sulfur standards under § 80.210 or § 80.220, prior to the TGP leaving the...

40 CFR 80.213 - What alternative sulfur standards and requirements apply to transmix processors and transmix...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 17 2014-07-01 2014-07-01 false What alternative sulfur standards and... ADDITIVES Gasoline Sulfur Gasoline Sulfur Standards § 80.213 What alternative sulfur standards and... TGP meets the applicable sulfur standards under § 80.210 or § 80.220, prior to the TGP leaving the...

40 CFR 80.213 - What alternative sulfur standards and requirements apply to transmix processors and transmix...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 17 2013-07-01 2013-07-01 false What alternative sulfur standards and... ADDITIVES Gasoline Sulfur Gasoline Sulfur Standards § 80.213 What alternative sulfur standards and... TGP meets the applicable sulfur standards under § 80.210 or § 80.220, prior to the TGP leaving the...

Molecular and biochemical characterization of two tungsten- and selenium-containing formate dehydrogenases from Eubacterium acidaminophilum that are associated with components of an iron-only hydrogenase.

PubMed

Graentzdoerffer, Andrea; Rauh, David; Pich, Andreas; Andreesen, Jan R

2003-01-01

Two gene clusters encoding similar formate dehydrogenases (FDH) were identified in Eubacterium acidaminophilum. Each cluster is composed of one gene coding for a catalytic subunit ( fdhA-I, fdhA-II) and one for an electron-transferring subunit ( fdhB-I, fdhB-II). Both fdhA genes contain a TGA codon for selenocysteine incorporation and the encoded proteins harbor five putative iron-sulfur clusters in their N-terminal region. Both FdhB subunits resemble the N-terminal region of FdhA on the amino acid level and contain five putative iron-sulfur clusters. Four genes thought to encode the subunits of an iron-only hydrogenase are located upstream of the FDH gene cluster I. By sequence comparison, HymA and HymB are predicted to contain one and four iron-sulfur clusters, respectively, the latter protein also binding sites for FMN and NAD(P). Thus, HymA and HymB seem to represent electron-transferring subunits, and HymC the putative catalytic subunit containing motifs for four iron-sulfur clusters and one H-cluster specific for Fe-only hydrogenases. HymD has six predicted transmembrane helices and might be an integral membrane protein. Viologen-dependent FDH activity was purified from serine-grown cells of E. acidaminophilum and the purified protein complex contained four subunits, FdhA and FdhB, encoded by FDH gene cluster II, and HymA and HymB, identified after determination of their N-terminal sequences. Thus, this complex might represent the most simple type of a formate hydrogen lyase. The purified formate dehydrogenase fraction contained iron, tungsten, a pterin cofactor, and zinc, but no molybdenum. FDH-II had a two-fold higher K(m) for formate (0.37 mM) than FDH-I and also catalyzed CO(2) reduction to formate. Reverse transcription (RT)-PCR pointed to increased expression of FDH-II in serine-grown cells, supporting the isolation of this FDH isoform. The fdhA-I gene was expressed as inactive protein in Escherichia coli. The in-frame UGA codon for selenocysteine incorporation was read in the heterologous system only as stop codon, although its potential SECIS element exhibited a quite high similarity to that of E. coli FDH.

Derivatives of cysteine related to the thiosulfate metabolism of sulfur bacteria by the multi-enzyme complex "Sox"-studied by B3LYP-PCM and G3X(MP2) calculations.

PubMed

Steudel, Ralf; Steudel, Yana

2010-01-21

Certain sulfur bacteria oxidize thiosulfate enzymatically to sulfate, and derivatives of the amino acid cysteine play an important role as intermediates in this process. Since some of the proposed intermediates have so far been of hypothetical nature, we have investigated the structures and thermodynamic properties of more than 60 related derivatives of cysteine (CysH) by high-level quantum chemical calculations both in the gas phase and in a polarizable continuum using the PCM method to simulate an aqueous solution. Most of these molecules and anions were studied for the first time. Especially for the smaller species several conformational isomers of similar energy were identified; their relative stabilities are mainly determined by intramolecular hydrogen bonds. In contrast to the thiolate ion [Cys](-), the gaseous anions [CysS](-), [CysSO(2)](-), [CysSO(3)](-) and [CysSSO(3)](-) are most stable as zwitterions containing an NH(3) rather than an NH(2) group. This result also holds for the polarizable continuum. On the other hand, the related neutral molecules CysH, CysSH and CysSO(2)H are predicted to exist as NH(2) derivatives rather than zwitterions in the gas phase and this connectivity is predicted for CysH and CysSH also in the polarizable continuum. A model molecule of composition C(4)H(7)N(2)O(2)SH (abbreviated as RSH) simulating the structural environment of a cysteine residue within the peptide chain near the corresponding reaction center of the thiosulfate oxidizing enzyme complex "Sox" was used to elucidate the geometry of the proposed reaction intermediates as well as their thermodynamic properties. In the polarizable phase, the S-sulfonate ions [CysSO(3)](-) and [RSSO(3)](-) are predicted to react exothermically with water to the corresponding thiol and hydrogensulfate ions. These results support the proposed mechanism for enzymatic thiosulfate metabolism. Sulfur dioxide and hydrogensulfite anions are predicted to react exothermically and exergonically with thiolate and persulfide anions to give the corresponding S-sulfinate species [RSSO(2)](-) and [RSSSO(2)](-), respectively. The latter ions help to explain the inhibition of certain thiolate based enzymes by aqueous sulfite, disulfite and dithionite anions in sulfur oxidizing microorganisms.

The role of crystallization-driven exsolution on the sulfur mass balance in volcanic arc magmas

USGS Publications Warehouse

Su, Yanqing; Huber, Christian; Bachmann, Olivier; Zajacz, Zoltán; Wright, Heather M.; Vazquez, Jorge A.

2016-01-01

The release of large amounts of sulfur to the stratosphere during explosive eruptions affects the radiative balance in the atmosphere and consequentially impacts climate for up to several years after the event. Quantitative estimations of the processes that control the mass balance of sulfur between melt, crystals, and vapor bubbles is needed to better understand the potential sulfur yield of individual eruption events and the conditions that favor large sulfur outputs to the atmosphere. The processes that control sulfur partitioning in magmas are (1) exsolution of volatiles (dominantly H2O) during decompression (first boiling) and during isobaric crystallization (second boiling), (2) the crystallization and breakdown of sulfide or sulfate phases in the magma, and (3) the transport of sulfur-rich vapor (gas influx) from deeper unerupted regions of the magma reservoir. Vapor exsolution and the formation/breakdown of sulfur-rich phases can all be considered as closed-system processes where mass balance arguments are generally easier to constrain, whereas the contribution of sulfur by vapor transport (open system process) is more difficult to quantify. The ubiquitous “excess sulfur” problem, which refers to the much higher sulfur mass released during eruptions than what can be accounted for by amount of sulfur originally dissolved in erupted melt, as estimated from melt inclusion sulfur concentrations (the “petrologic estimate”), reflects the challenges in closing the sulfur mass balance between crystals, melt, and vapor before and during a volcanic eruption. In this work, we try to quantify the relative importance of closed- and open-system processes for silicic arc volcanoes using kinetic models of sulfur partitioning during exsolution. Our calculations show that crystallization-induced exsolution (second boiling) can generate a significant fraction of the excess sulfur observed in crystal-rich arc magmas. This result does not negate the important role of vapor migration in sulfur mass balance but rather points out that second boiling (in situ exsolution) can provide the necessary yield to drive the excess sulfur to the levels observed for crystal-rich systems. In contrast, in crystal-poor systems, magma recharge that releases sulfur-rich bubbles is necessary and most likely the primary contributor to sulfur mass balance. Finally, we apply our model to account for the effect of sulfur partitioning during second boiling and its impact on sulfur released during the Cerro Galan supereruption in Argentina (2.08 Ma) and show the potential importance of second boiling in releasing a large amount of sulfur to the atmosphere during the eruption of large crystal-rich ignimbrites.

Iron L2,3-Edge X-ray Absorption and X-ray Magnetic Circular Dichroism Studies of Molecular Iron Complexes with Relevance to the FeMoco and FeVco Active Sites of Nitrogenase

PubMed Central

2017-01-01

Herein, a systematic study of a series of molecular iron model complexes has been carried out using Fe L2,3-edge X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopies. This series spans iron complexes of increasing complexity, starting from ferric and ferrous tetrachlorides ([FeCl4]−/2–), to ferric and ferrous tetrathiolates ([Fe(SR)4]−/2–), to diferric and mixed-valent iron–sulfur complexes [Fe2S2R4]2–/3–. This test set of compounds is used to evaluate the sensitivity of both Fe L2,3-edge XAS and XMCD spectroscopy to oxidation state and ligation changes. It is demonstrated that the energy shift and intensity of the L2,3-edge XAS spectra depends on both the oxidation state and covalency of the system; however, the quantitative information that can be extracted from these data is limited. On the other hand, analysis of the Fe XMCD shows distinct changes in the intensity at both L3 and L2 edges, depending on the oxidation state of the system. It is also demonstrated that the XMCD intensity is modulated by the covalency of the system. For mononuclear systems, the experimental data are correlated with atomic multiplet calculations in order to provide insights into the experimental observations. Finally, XMCD is applied to the tetranuclear heterometal–iron–sulfur clusters [MFe3S4]3+/2+ (M = Mo, V), which serve as structural analogues of the FeMoco and FeVco active sites of nitrogenase. It is demonstrated that the XMCD data can be utilized to obtain information on the oxidation state distribution in complex clusters that is not readily accessible for the Fe L2,3-edge XAS data alone. The advantages of XMCD relative to standard K-edge and L2,3-edge XAS are highlighted. This study provides an important foundation for future XMCD studies on complex (bio)inorganic systems. PMID:28653855

Effects of sulfur impregnation temperature on the properties and mercury adsorption capacities of activated carbon fibers (ACFs)

USGS Publications Warehouse

Hsi, H.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

2001-01-01

Laboratory studies were conducted to determine the role of sulfur functional groups and micropore surface area of carbon-based adsorbents on the adsorption of Hg0 from simulated coal combustion flue gases. In this study, raw activated carbon fibers that are microporous (ACF-20) were impregnated with elemental sulfur between 250 and 650 ??C. The resulting samples were saturated with respect to sulfur content. Total sulfur content of the sulfur impregnated ACF samples decreased with increasing impregnation temperatures from 250 and 500 ??C and then remained constant to 650 ??C. Results from sulfur K-edge X-ray absorption near-edge structure (S-XANES) spectroscopy showed that sulfur impregnated on the ACF samples was in both elemental and organic forms. As sulfur impregnation temperature increased, however, the relative amounts of elemental sulfur decreased with a concomitant increase in the amount of organic sulfur. Thermal analyses and mass spectrometry revealed that sulfur functional groups formed at higher impregnation temperatures were more thermally stable. In general, sulfur impregnation decreased surface area and increased equilibrium Hg0 adsorption capacity when compared to the raw ACF sample. The ACF sample treated with sulfur at 400 ??C had a surface area of only 94 m2/g compared to the raw ACF sample's surface area of 1971 m2/g, but at least 86% of this sample's surface area existed as micropores and it had the largest equilibrium Hg0adsorption capacities (2211-11343 ??g/g). Such a result indicates that 400 ??C is potentially an optimal sulfur impregnation temperature for this ACF. Sulfur impregnated on the ACF that was treated at 400 ??C was in both elemental and organic forms. Thermal analyses and CS2extraction tests suggested that elemental sulfur was the main form of sulfur affecting the Hg0 adsorption capacity. These findings indicate that both the presence of elemental sulfur on the adsorbent and a microporous structure are important properties for improving the performance of carbon-based adsorbents for the removal of Hg0 from coal combustion flue gases.

Sulfur species in source rock bitumen before and after hydrous pyrolysis determined by X-ray absorption near-edge structure

USGS Publications Warehouse

Bolin, Trudy B.; Birdwell, Justin E.; Lewan, Michael; Hill, Ronald J.; Grayson, Michael B.; Mitra-Kirtley, Sudipa; Bake, Kyle D.; Craddock, Paul R.; Abdallah, Wael; Pomerantz, Andrew E.

2016-01-01

The sulfur speciation of source rock bitumen (chloroform-extractable organic matter in sedimentary rocks) was examined using sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy for a suite of 11 source rocks from around the world. Sulfur speciation was determined for both the native bitumen in thermally immature rocks and the bitumen produced by thermal maturation of kerogen via hydrous pyrolysis (360 °C for 72 h) and retained within the rock matrix. In this study, the immature bitumens had higher sulfur concentrations than those extracted from samples after hydrous pyrolysis. In addition, dramatic and systematic evolution of the bitumen sulfur moiety distributions following artificial thermal maturation was observed consistently for all samples. Specifically, sulfoxide sulfur (sulfur double bonded to oxygen) is abundant in all immature bitumen samples but decreases substantially following hydrous pyrolysis. The loss in sulfoxide sulfur is associated with a relative increase in the fraction of thiophene sulfur (sulfur bonded to aromatic carbon) to the extent that thiophene is the dominant sulfur form in all post-pyrolysis bitumen samples. This suggests that sulfur moiety distributions might be used for estimating thermal maturity in source rocks based on the character of the extractable organic matter.

Advanced Sulfur Cathode Enabled by Highly Crumpled Nitrogen-Doped Graphene Sheets for High-Energy-Density Lithium-Sulfur Batteries.

PubMed

Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail L; Wang, Donghai

2016-02-10

Herein, we report a synthesis of highly crumpled nitrogen-doped graphene sheets with ultrahigh pore volume (5.4 cm(3)/g) via a simple thermally induced expansion strategy in absence of any templates. The wrinkled graphene sheets are interwoven rather than stacked, enabling rich nitrogen-containing active sites. Benefiting from the unique pore structure and nitrogen-doping induced strong polysulfide adsorption ability, lithium-sulfur battery cells using these wrinkled graphene sheets as both sulfur host and interlayer achieved a high capacity of ∼1000 mAh/g and exceptional cycling stability even at high sulfur content (≥80 wt %) and sulfur loading (5 mg sulfur/cm(2)). The high specific capacity together with the high sulfur loading push the areal capacity of sulfur cathodes to ∼5 mAh/cm(2), which is outstanding compared to other recently developed sulfur cathodes and ideal for practical applications.

Accumulation of atmospheric sulfur in some Costa Rican soils

USGS Publications Warehouse

Bern, Carleton R.; Townsend, Alan R.

2013-01-01

Sulfur is one of the macronutrient elements whose sources to terrestrial ecosystems should shift from dominance by rock-weathering to atmospheric deposition as soils and underlying substrate undergo progressive weathering and leaching. However, the nature and timing of this transition is not well known. We investigated sources of sulfur to tropical rain forests growing on basalt-derived soils in the Osa Peninsula region of Costa Rica. Sulfur sources were examined using stable isotope ratios (δ34S) and compared to chemical indices of soil development. The most weathered soils, and the forests they supported, are dominated by atmospheric sulfur, while a less weathered soil type contains both rock-derived and atmospheric sulfur. Patterns of increasing δ34S with increasing soil sulfur concentration across the landscape suggest atmospheric sulfur is accumulating, and little rock-derived sulfur has been retained. Soil sulfur, minus adsorbed sulfate, is correlated with carbon and nitrogen, implying that sulfur accumulation occurs as plants and microbes incorporate sulfur into organic matter. Only the lower depth increments of the more weathered soils contained significant adsorbed sulfate. The evidence suggests a pattern of soil development in which sulfur-bearing minerals in rock, such as sulfides, weather early relative to other minerals, and the released sulfate is leached away. Sulfur added via atmospheric deposition is retained as organic matter accumulates in the soil profile. Adsorbed sulfate accumulates later, driven by changes in soil chemistry and mineralogy. These aspects of sulfur behavior during pedogenesis in this environment may hasten the transition to dominance by atmospheric sources.

Aerobic sulfur-oxidizing bacteria: Environmental selection and diversification

NASA Technical Reports Server (NTRS)

Caldwell, D.

1985-01-01

Sulfur-oxidizing bacteria oxidize reduced inorganic compounds to sulfuric acid. Lithotrophic sulfur oxidizer use the energy obtained from oxidation for microbial growth. Heterotrophic sulfur oxidizers obtain energy from the oxidation of organic compounds. In sulfur-oxidizing mixotrophs energy are derived either from the oxidation of inorganic or organic compounds. Sulfur-oxidizing bacteria are usually located within the sulfide/oxygen interfaces of springs, sediments, soil microenvironments, and the hypolimnion. Colonization of the interface is necessary since sulfide auto-oxidizes and because both oxygen and sulfide are needed for growth. The environmental stresses associated with the colonization of these interfaces resulted in the evolution of morphologically diverse and unique aerobic sulfur oxidizers.

High sulfur loading cathodes fabricated using peapodlike, large pore volume mesoporous carbon for lithium-sulfur battery.

PubMed

Li, Duo; Han, Fei; Wang, Shuai; Cheng, Fei; Sun, Qiang; Li, Wen-Cui

2013-03-01

Porous carbon materials with large pore volume are crucial in loading insulated sulfur with the purpose of achieving high performance for lithium-sulfur batteries. In our study, peapodlike mesoporous carbon with interconnected pore channels and large pore volume (4.69 cm(3) g(-1)) was synthesized and used as the matrix to fabricate carbon/sulfur (C/S) composite which served as attractive cathodes for lithium-sulfur batteries. Systematic investigation of the C/S composite reveals that the carbon matrix can hold a high but suitable sulfur loading of 84 wt %, which is beneficial for improving the bulk density in practical application. Such controllable sulfur-filling also effectively allows the volume expansion of active sulfur during Li(+) insertion. Moreover, the thin carbon walls (3-4 nm) of carbon matrix not only are able to shorten the pathway of Li(+) transfer and conduct electron to overcome the poor kinetics of sulfur cathode, but also are flexible to warrant structure stability. Importantly, the peapodlike carbon shell is beneficial to increase the electrical contact for improving electronic conductivity of active sulfur. Meanwhile, polymer modification with polypyrrole coating layer further restrains polysulfides dissolution and improves the cycle stability of carbon/sulfur composites.

Effect of Carbon and Binder on High Sulfur Loading Electrode for Li-S Battery Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Ke; Cama, Christina A.; Huang, Jian

For the Lithium-Sulfur (Li-S) battery to be competitive in commercialization, it is requested that the sulfur electrode must have deliverable areal capacity > 8 mAh cm -2, which corresponds to a sulfur loading > 6 mg cm -2. At this relatively high sulfur loading, we evaluated the impact of binder and carbon type on the mechanical integrity and the electrochemical properties of sulfur electrodes. We identified hydroxypropyl cellulose (HPC) as a new binder for the sulfur electrode because it offers better adhesion between the electrode and the aluminum current collector than the commonly used polyvinylidene fluoride (PVDF) binder. In combinationmore » with the binder study, multiple types of carbon with high specific surface area were evaluated as sulfur hosts for high loading sulfur electrodes. A commercial microporous carbon derived from wood with high pore volume showed the best performance. An electrode with sulfur loading up to 10 mg cm -2 was achieved with the optimized recipe. Based on systematic electrochemical studies, the soluble polysulfide to insoluble Li 2S 2/Li 2S conversion was identified to be the major barrier for high loading sulfur electrodes to achieve high sulfur utilization.« less

Effect of Carbon and Binder on High Sulfur Loading Electrode for Li-S Battery Technology

DOE PAGES

Sun, Ke; Cama, Christina A.; Huang, Jian; ...

2017-03-10

For the Lithium-Sulfur (Li-S) battery to be competitive in commercialization, it is requested that the sulfur electrode must have deliverable areal capacity > 8 mAh cm -2, which corresponds to a sulfur loading > 6 mg cm -2. At this relatively high sulfur loading, we evaluated the impact of binder and carbon type on the mechanical integrity and the electrochemical properties of sulfur electrodes. We identified hydroxypropyl cellulose (HPC) as a new binder for the sulfur electrode because it offers better adhesion between the electrode and the aluminum current collector than the commonly used polyvinylidene fluoride (PVDF) binder. In combinationmore » with the binder study, multiple types of carbon with high specific surface area were evaluated as sulfur hosts for high loading sulfur electrodes. A commercial microporous carbon derived from wood with high pore volume showed the best performance. An electrode with sulfur loading up to 10 mg cm -2 was achieved with the optimized recipe. Based on systematic electrochemical studies, the soluble polysulfide to insoluble Li 2S 2/Li 2S conversion was identified to be the major barrier for high loading sulfur electrodes to achieve high sulfur utilization.« less

Oxidation of a [Cu2S] complex by N2O and CO2: insights into a role of tetranuclearity in the CuZ site of nitrous oxide reductase.

PubMed

Bagherzadeh, Sharareh; Mankad, Neal P

2018-01-25

Oxidation of a [Cu 2 (μ-S)] complex by N 2 O or CO 2 generated a [Cu 2 (μ-SO 4 )] product. In the presence of a sulfur trap, a [Cu 2 (μ-O)] species also formed from N 2 O. A [Cu 2 (μ-CS 3 )] species derived from CS 2 modeled initial reaction intermediates. These observations indicate that one role of tetranuclearity in the Cu Z catalytic site of nitrous oxide reductase is to protect the crucial S 2- ligand from oxidation.

Concentration-Discharge Relationships, Nested Reaction Fronts, and the Balance of Oxidative and Acid-Base Weathering Fluxes in an Alpine Catchment, East River, Colorado

NASA Astrophysics Data System (ADS)

Winnick, M.; Carroll, R. W. H.; Williams, K. H.; Maxwell, R. M.; Maher, K.

2016-12-01

Although important for solute production and transport, the varied interactions between biogeochemical processes and subsurface hydrology remain poorly characterized. We investigate these couplings in the headwaters of the East River, CO, a high-elevation shale-dominated catchment system in the Rocky Mountains, using concentration-discharge (C-Q) relationships for major cations, anions, and organic carbon. Dissolved organic carbon (DOC) displays a positive C-Q relationship with well-defined clockwise hysteresis, indicating the mobilization and depletion of DOC in the upper soil horizons and highlighting the importance of shallow flowpaths through the snowmelt period. Cation and anion concentrations demonstrate that carbonate weathering, which dominates solute fluxes, is promoted by both carbonic acid and sulfuric acid derived from oxidation of pyrite in the shale bedrock. Sulfuric acid weathering in the deep subsurface dominates during base flow conditions when waters have infiltrated below the hypothesized pyrite oxidation front, whereas carbonic acid weathering plays a dominant role during the snowmelt period as a result of shallow flowpaths. Differential C-Q relationships between solutes suggest that infiltrating waters approach calcite saturation before reaching the pyrite oxidation front, after which sulfuric acid reduces carbonate alkalinity. This increase in CO2(aq) at the expense of HCO3- results in outgassing of CO2 when waters equilibrate to surface conditions, and reduces the export of carbon and alkalinity from the East River by roughly 33% annually. Future changes in snowmelt dynamics that control the balance of carbonic and sulfuric acid weathering therefore have the capacity to substantially alter the cycling of carbon in the East River catchment. Ultimately, we demonstrate that differential C-Q relationships between major solutes can provide unique insights into the complex subsurface flow and biogeochemical dynamics that operate at catchment scales.

Fragmentation analysis of water-soluble atmospheric organic matter using ultrahigh-resolution FT-ICR mass spectrometry.

PubMed

Leclair, Jeffrey P; Collett, Jeffrey L; Mazzoleni, Lynn R

2012-04-17

Isolated water-soluble atmospheric organic matter (AOM) analytes extracted from radiation fogwater samples were analyzed using collision induced dissociation with ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Tandem mass analysis was performed on several mass ranges between 100 and 400 Da to characterize the functional groups of AOM species. Compounds containing nitrogen and/or sulfur were targeted because of the high number of oxygen atoms contained in their molecular formulas. Due to the large number of isobaric ions in the precursor isolation ranges, large numbers of product ions resulted from collision induced dissociation. Common neutral losses were assigned by matching the molecular formulas of the expected product ions with the detected product ions within the appropriate mass spectra. Since polar functional groups are expected to affect the hygroscopic properties of aerosols, the losses of H(2)O, CO(2), CH(3)OH, HNO(3), CH(3)NO(3), SO(3), SO(4) and combinations of these were specifically targeted. Among the 421 compounds studied, the most frequently observed neutral losses were CO(2) (54%), H(2)O (43%) and CH(3)OH (40%). HNO(3) losses were observed for 63% of the studied nitrogen containing compounds and 33% of the studied compounds containing both nitrogen and sulfur. SO(3) losses were observed for 85% of the studied sulfur containing compounds and 42% of studied compounds containing both nitrogen and sulfur. A number of molecular formulas matching those of monoterpene ozonolysis SOA were observed; they include organonitrates, organosulfates, and nitroxy-organosulfates. Overall, the results of fragmentation analysis of 400+ individual molecular precursors elucidate the complexity and multifunctional nature of the isolated water-soluble AOM.

Role of the HSPA9/HSC20 chaperone pair in promoting directional human iron-sulfur cluster exchange involving monothiol glutaredoxin 5.

PubMed

Olive, Joshua A; Cowan, J A

2018-07-01

Iron‑sulfur clusters are essential cofactors found across all domains of life. Their assembly and transfer are accomplished by highly conserved protein complexes and partners. In eukaryotes a [2Fe-2S] cluster is first assembled in the mitochondria on the iron‑sulfur cluster scaffold protein ISCU in tandem with iron, sulfide, and electron donors. Current models suggest that a chaperone pair interacts with a cluster-bound ISCU to facilitate cluster transfer to a monothiol glutaredoxin. In humans this protein is glutaredoxin 5 (GLRX5) and the cluster can then be exchanged with a variety of target apo proteins. By use of circular dichroism spectroscopy, the kinetics of cluster exchange reactivity has been evaluated for human GLRX5 with a variety of cluster donor and acceptor partners, and the role of chaperones determined for several of these. In contrast to the prokaryotic model, where heat-shock type chaperone proteins HscA and HscB are required for successful and efficient transfer of a [2Fe-2S] cluster from the ISCU scaffold to a monothiol glutaredoxin. However, in the human system the chaperone homologs, HSPA9 and HSC20, are not necessary for human ISCU to promote cluster transfer to GLRX5, and appear to promote the reverse transfer. Cluster exchange with the human iron‑sulfur cluster carrier protein NFU1 and ferredoxins (FDX's), and the role of chaperones, has also been evaluated, demonstrating in certain cases control over the directionality of cluster transfer. In contrast to other prokaryotic and eukaryotic organisms, NFU1 is identified as a more likely physiological donor of [2Fe-2S] cluster to human GLRX5 than ISCU. Copyright © 2018 Elsevier Inc. All rights reserved.

Snowmelt controls on concentration-discharge relationships and the balance of oxidative and acid-base weathering fluxes in an alpine catchment, East River, Colorado: ACID-BASE VERSUS OXIDATIVE WEATHERING FLUXES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winnick, Matthew J.; Carroll, Rosemary W. H.; Williams, Kenneth H.

Although important for riverine solute and nutrient fluxes, the connections between biogeochemical processes and subsurface hydrology remain poorly characterized. We investigate these couplings in the East River, CO, a high-elevation shale-dominated catchment in the Rocky Mountains, using concentration-discharge (C-Q) relationships for major cations, anions, and organic carbon. Dissolved organic carbon (DOC) displays a positive C-Q relationship with clockwise hysteresis, indicating mobilization and depletion of DOC in the upper soil horizons and emphasizing the importance of shallow flowpaths during snowmelt. Cation and anion concentrations demonstrate that carbonate weathering, which dominates solute fluxes, is promoted by both sulfuric acid derived from pyritemore » oxidation in the shale bedrock and carbonic acid derived from subsurface respiration. Sulfuric acid weathering dominates during baseflow conditions when waters infiltrate below the inferred pyrite oxidation front, whereas carbonic acid weathering plays a dominant role during snowmelt as a result of shallow flowpaths. Differential C-Q relationships between solutes suggest that infiltrating waters approach calcite saturation before reaching the pyrite oxidation front, after which sulfuric acid reduces carbonate alkalinity. This reduction in alkalinity results in CO 2 outgassing when waters equilibrate to surface conditions, and reduces the riverine export of carbon and alkalinity by roughly 33% annually. In conclusion, future changes in snowmelt dynamics that control the balance of carbonic and sulfuric acid weathering may substantially alter carbon cycling in the East River. Ultimately, we demonstrate that differential C-Q relationships between major solutes can provide unique insights into the complex subsurface flow and biogeochemical dynamics that operate at catchment scales.« less

From lithium to sodium: cell chemistry of room temperature sodium–air and sodium–sulfur batteries

PubMed Central

Hartmann, Pascal; Bender, Conrad L; Busche, Martin; Eufinger, Christine

2015-01-01

Summary Research devoted to room temperature lithium–sulfur (Li/S8) and lithium–oxygen (Li/O2) batteries has significantly increased over the past ten years. The race to develop such cell systems is mainly motivated by the very high theoretical energy density and the abundance of sulfur and oxygen. The cell chemistry, however, is complex, and progress toward practical device development remains hampered by some fundamental key issues, which are currently being tackled by numerous approaches. Quite surprisingly, not much is known about the analogous sodium-based battery systems, although the already commercialized, high-temperature Na/S8 and Na/NiCl2 batteries suggest that a rechargeable battery based on sodium is feasible on a large scale. Moreover, the natural abundance of sodium is an attractive benefit for the development of batteries based on low cost components. This review provides a summary of the state-of-the-art knowledge on lithium–sulfur and lithium–oxygen batteries and a direct comparison with the analogous sodium systems. The general properties, major benefits and challenges, recent strategies for performance improvements and general guidelines for further development are summarized and critically discussed. In general, the substitution of lithium for sodium has a strong impact on the overall properties of the cell reaction and differences in ion transport, phase stability, electrode potential, energy density, etc. can be thus expected. Whether these differences will benefit a more reversible cell chemistry is still an open question, but some of the first reports on room temperature Na/S8 and Na/O2 cells already show some exciting differences as compared to the established Li/S8 and Li/O2 systems. PMID:25977873

From lithium to sodium: cell chemistry of room temperature sodium-air and sodium-sulfur batteries.

PubMed

Adelhelm, Philipp; Hartmann, Pascal; Bender, Conrad L; Busche, Martin; Eufinger, Christine; Janek, Juergen

2015-01-01

Research devoted to room temperature lithium-sulfur (Li/S8) and lithium-oxygen (Li/O2) batteries has significantly increased over the past ten years. The race to develop such cell systems is mainly motivated by the very high theoretical energy density and the abundance of sulfur and oxygen. The cell chemistry, however, is complex, and progress toward practical device development remains hampered by some fundamental key issues, which are currently being tackled by numerous approaches. Quite surprisingly, not much is known about the analogous sodium-based battery systems, although the already commercialized, high-temperature Na/S8 and Na/NiCl2 batteries suggest that a rechargeable battery based on sodium is feasible on a large scale. Moreover, the natural abundance of sodium is an attractive benefit for the development of batteries based on low cost components. This review provides a summary of the state-of-the-art knowledge on lithium-sulfur and lithium-oxygen batteries and a direct comparison with the analogous sodium systems. The general properties, major benefits and challenges, recent strategies for performance improvements and general guidelines for further development are summarized and critically discussed. In general, the substitution of lithium for sodium has a strong impact on the overall properties of the cell reaction and differences in ion transport, phase stability, electrode potential, energy density, etc. can be thus expected. Whether these differences will benefit a more reversible cell chemistry is still an open question, but some of the first reports on room temperature Na/S8 and Na/O2 cells already show some exciting differences as compared to the established Li/S8 and Li/O2 systems.

Effects of cattle slurry acidification on ammonia and methane evolution during storage.

PubMed

Petersen, Søren O; Andersen, Astrid J; Eriksen, Jørgen

2012-01-01

Slurry acidification before storage is known to reduce NH(3) emissions, but recent observations have indicated that CH(4) emissions are also reduced. We investigated the evolution of CH(4) from fresh and aged cattle slurry during 3 mo of storage as influenced by pH adjustment to 5.5 with sulfuric acid. In a third storage experiment, cattle slurry acidified with commercial equipment on two farms was incubated. In the manipulation experiments, effects of acid and sulfate were distinguished by adding hydrochloric acid and potassium sulfate separately or in combination, rather than sulfuric acid. In one experiment sulfur was also added to slurry as the amino acid methionine in separate treatments. In each treatment 20-kg portions of slurry (n = 4) were stored for 95 d. All samples were subsampled nine to 10 times for determination of NH(3) and CH(4) evolution rates using a 2-L flow-through system. In all experiments, the pH of acidified cattle slurry increased gradually to between 6.5 and 7. Acidification of slurry reduced the evolution of CH(4) by 67 to 87%. The greatest reduction was observed with aged cattle slurry, which had a much higher potential for CH(4) production than fresh slurry. Sulfate and methionine amendment to cattle slurry without pH adjustment also significantly inhibited methanogenesis, probably as a result of sulfide production. The study suggests that complex microbial interactions involving sulfur transformations and pH determine the potential for CH(4) emission during storage of cattle slurry, and that slurry acidification may be a cost-effective greenhouse gas mitigation option. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Laboratory measurements and astronomical search for the HSO radical★★

PubMed Central

Cazzoli, Gabriele; Lattanzi, Valerio; Kirsch, Till; Gauss, Jürgen; Tercero, Belén; Cernicharo, José; Puzzarini, Cristina

2016-01-01

Context Despite the fact that many sulfur-bearing molecules, ranging from simple diatomic species up to astronomical complex molecules, have been detected in the interstellar medium, the sulfur chemistry in space is largely unknown and a depletion in the abundance of S-containing species has been observed in the cold, dense interstellar medium (ISM). The chemical form of the missing sulfur has yet to be identified. Aims For these reasons, in view of the fact that there is a large abundance of triatomic species harbouring sulfur, oxygen, and hydrogen, we decided to investigate the HSO radical in the laboratory to try its astronomical detection. Methods High-resolution measurements of the rotational spectrum of the HSO radical were carried out within a frequency range well up into the THz region. Subsequently, a rigorous search for HSO in the two most studied high-mass star-forming regions, Orion KL and Sagittarius (Sgr) B2, and in the cold dark cloud Barnard 1 (B1-b) was performed. Results The frequency coverage and the spectral resolution of our measurements allowed us to improve and extend the existing dataset of spectroscopic parameters, thus enabling accurate frequency predictions up to the THz range. These were used to derive the synthetic spectrum of HSO, by means of the MADEX code, according to the physical parameters of the astronomical source under consideration. For all sources investigated, the lack of HSO lines above the confusion limit of the data is evident. Conclusions The derived upper limit to the abundance of HSO clearly indicates that this molecule does not achieve significant abundances in either the gas phase or in the ice mantles of dust grains. PMID:27721513

Improved photobio-H2 production regulated by artificial miRNA targeting psbA in green microalga Chlamydomonas reinhardtii.

PubMed

Li, Hui; Liu, Yanmei; Wang, Yuting; Chen, Meirong; Zhuang, Xiaoshan; Wang, Chaogang; Wang, Jiangxin; Hu, Zhangli

2018-01-01

Sulfur-deprived cultivation of Chlamydomonas reinhardtii , referred as "two-stage culture" transferring the cells from regular algal medium to sulfur-deplete one, has been extensively studied to improve photobio-H 2 production in this green microalga. During sulfur-deprivation treatment, the synthesis of a key component of photosystem II complex, D1 protein, was inhibited and improved photobio-H 2 production could be established in C. reinhardtii . However, separation of algal cells from a regular liquid culture medium to a sulfur-deprived one is not only a discontinuous process, but also a cost- and time-consuming operation. More applicable and economic alternatives for sustained H 2 production by C. reinhardtii are still highly required. In the present study, a significant improvement in photobio-H 2 production was observed in the transgenic green microalga C. reinhardtii , which employed a newly designed strategy based on a heat-inducible artificial miRNA (amiRNA) expression system targeting D1-encoded gene, psbA . A transgenic algal strain referred as "amiRNA-D1" has been successfully obtained by transforming the expression vector containing a heat-inducible promoter. After heat shock conducted in the same algal cultures, the expression of amiRNA-D1 was detected increased 15-fold accompanied with a 73% decrease of target gene psbA . More interestingly, this transgenic alga accumulated about 60% more H 2 content than the wild-type strain CC-849 at the end of 7-day cultivation. The photobio-H 2 production in the engineered transgenic alga was significantly improved. Without imposing any nutrient-deprived stress, this novel strategy provided a convenient and efficient way for regulation of photobio-H 2 production in green microalga by simply "turn on" the expression of a designed amiRNA.

Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador

NASA Astrophysics Data System (ADS)

Makowski Giannoni, S.; Rollenbeck, R.; Trachte, K.; Bendix, J.

2014-10-01

Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have been roughly identified in only a few lowland tropical forests. Even scarcer are studies of this type in tropical mountain forests, many of them mega-diversity hotspots and especially vulnerable to acidic deposition. In these places, the topographic complexity and related streamflow conditions affect the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass burning, no source emission data has been used for determining the contribution of each source to the deposition. The main goal of the current study is to evaluate sulfate (SO4- deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back-trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state-of-the-art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological station and to rain-deposited sulfate at the upriver mountain pass El Tiro meteorological station.

Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador

NASA Astrophysics Data System (ADS)

Makowski Giannoni, S.; Rollenbeck, R.; Trachte, K.; Bendix, J.

2014-05-01

Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have being roughly identified in only a few lowland tropical forests. Even scarcer are these type of studies in tropical mountain forests, many of them megadiversity hotspots and especially vulnerable to acidic deposition. Here, the topographic complexity and related streamflow condition the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass-burning, no source-emission data has been used for determining the contribution of each of them to the deposition. The main goal of the current study is to evaluate sulfate (SO4-) deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state of the art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological station and to rain-deposited sulfate at the upriver mountain-pass El Tiro meteorological station.

Snowmelt controls on concentration-discharge relationships and the balance of oxidative and acid-base weathering fluxes in an alpine catchment, East River, Colorado: ACID-BASE VERSUS OXIDATIVE WEATHERING FLUXES

DOE PAGES

Winnick, Matthew J.; Carroll, Rosemary W. H.; Williams, Kenneth H.; ...

2017-03-01

Although important for riverine solute and nutrient fluxes, the connections between biogeochemical processes and subsurface hydrology remain poorly characterized. We investigate these couplings in the East River, CO, a high-elevation shale-dominated catchment in the Rocky Mountains, using concentration-discharge (C-Q) relationships for major cations, anions, and organic carbon. Dissolved organic carbon (DOC) displays a positive C-Q relationship with clockwise hysteresis, indicating mobilization and depletion of DOC in the upper soil horizons and emphasizing the importance of shallow flowpaths during snowmelt. Cation and anion concentrations demonstrate that carbonate weathering, which dominates solute fluxes, is promoted by both sulfuric acid derived from pyritemore » oxidation in the shale bedrock and carbonic acid derived from subsurface respiration. Sulfuric acid weathering dominates during baseflow conditions when waters infiltrate below the inferred pyrite oxidation front, whereas carbonic acid weathering plays a dominant role during snowmelt as a result of shallow flowpaths. Differential C-Q relationships between solutes suggest that infiltrating waters approach calcite saturation before reaching the pyrite oxidation front, after which sulfuric acid reduces carbonate alkalinity. This reduction in alkalinity results in CO 2 outgassing when waters equilibrate to surface conditions, and reduces the riverine export of carbon and alkalinity by roughly 33% annually. In conclusion, future changes in snowmelt dynamics that control the balance of carbonic and sulfuric acid weathering may substantially alter carbon cycling in the East River. Ultimately, we demonstrate that differential C-Q relationships between major solutes can provide unique insights into the complex subsurface flow and biogeochemical dynamics that operate at catchment scales.« less

Biogenesis of Mercury-Sulfur Nanoparticles in Plant Leaves from Atmospheric Gaseous Mercury.

PubMed

Manceau, Alain; Wang, Jianxu; Rovezzi, Mauro; Glatzel, Pieter; Feng, Xinbin

2018-04-03

Plant leaves serve both as a sink for gaseous elemental mercury (Hg) from the atmosphere and a source of toxic mercury to terrestrial ecosystems. Litterfall is the primary deposition pathway of atmospheric Hg to vegetated soils, yet the chemical form of this major Hg input remains elusive. We report the first observation of in vivo formation of mercury sulfur nanoparticles in intact leaves of 22 native plants from six different species across two sampling areas from China. The plants grew naturally in soils from a mercury sulfide mining and retorting region at ambient-air gaseous-Hg concentrations ranging from 131 ± 19 to 636 ± 186 ng m -3 and had foliar Hg concentration between 1.9 and 31.1 ng Hg mg -1 dry weight (ppm). High energy resolution X-ray absorption near-edge structure (HR-XANES) spectroscopy shows that up to 57% of the acquired Hg is nanoparticulate, and the remainder speciated as a bis-thiolate complex (Hg(SR) 2 ). The fractional amount of nanoparticulate Hg is not correlated with Hg concentration. Variation likely depends on leaf age, plant physiology, and natural variability. Nanoparticulate Hg atoms are bonded to four sulfide or thiolate sulfur atoms arranged in a metacinnabar-type (β-HgS) coordination environment. The nanometer dimension of the mercury-sulfur clusters outmatches the known binding capacity of plant metalloproteins. These findings give rise to challenging questions on their exact nature, how they form, and their biogeochemical reactivity and fate in litterfall, whether this mercury pool is recycled or stored in soils. This study provides new evidence that metacinnabar-type nanoparticles are widespread in oxygenated environments.

Nonprotective Alumina Growth in Sulfur-Doped NiAl(Zr)

NASA Technical Reports Server (NTRS)

Smialek, James L.

2000-01-01

The 1200 C oxidation behavior of NiAl was examined at various levels of sulfur and zirconium dopants to test the possibility of a critical S/Zr ratio required for adhesion. Cyclic furnace testing for 200 1 -hr cycles and interrupted testing for 500 hr were used as screening tests. Pure NiAl and NiAl(Zr) with 0. 14 at.% Zr were chosen as model base compositions; they exhibited normal, slow-growing scales (3 Mg/sq cm) with excellent adhesion for the Zr-doped alloys. NiAl with about 120 ppma S exhibited a substantial weight loss (-20 Mg/sq cm) in cyclic tests and a very large weight gain (+60 Mg/sq cm) in interrupted tests. The major surface phase remained as alpha -Al2O3. Sulfur doping the NiAl(Zr) alloy caused massive weight gains of 80 - 100 Mg/sq cm, swelling, cracking, and nearly complete conversion into NiAl2O4, and alpha- Al2O3. The initial objective of determining critical S/Zr ratios for adhesion was therefore unattainable. Initiation of the catastrophic attack was examined after a 10 hr exposure, revealing a few sites of broad, raised, and cracked ridges. In cross-section, the ridges appeared as modular intrusions, with a complex, fractal, oxide-metal interface. They were primarily alumina (with occasional entrapped islands of NiAl2O4 or pure Ni metal). They possessed a unique microstructure consisting of 0.3 microns lamellae, separated by 0.1 microns open channels. This allowed for rapid growth controlled by gaseous diffusion. The microstructure is discussed in terms of SO2 evolution and a sulfur-driven de-passivation process.

Sulfur Removal by Adding Iron During the Digestion Process of High-sulfur Bauxite

NASA Astrophysics Data System (ADS)

Zhanwei, Liu; Hengwei, Yan; Wenhui, Ma; Keqiang, Xie; Dunyong, Li; Licong, Zheng; Pengfei, Li

2018-04-01

This paper proposes a novel approach to sulfur removal by adding iron during the digestion process. Iron can react with high-valence sulfur (S2O3 2-, SO3 2-, SO4 2-) to generate S2- at digestion temperature, and then S2- enter red mud in the form of Na3FeS3 to be removed. As iron dosage increases, high-valence sulfur concentration decreases, but the concentration of S2- increases; sulfur digestion rate decreases while sulfur content in red mud markedly increases; the alumina digestion rate, conversely, remains fairly stable. So sulfur can be removed completely by adding iron in digestion process, which provide a theoretical basis for the effective removal of sulfur in alumina production process.

Three-dimensional porous carbon composites containing high sulfur nanoparticle content for high-performance lithium–sulfur batteries

PubMed Central

Li, Guoxing; Sun, Jinhua; Hou, Wenpeng; Jiang, Shidong; Huang, Yong; Geng, Jianxin

2016-01-01

Sulfur is a promising cathode material for lithium–sulfur batteries because of its high theoretical capacity (1,675 mA h g−1); however, its low electrical conductivity and the instability of sulfur-based electrodes limit its practical application. Here we report a facile in situ method for preparing three-dimensional porous graphitic carbon composites containing sulfur nanoparticles (3D S@PGC). With this strategy, the sulfur content of the composites can be tuned to a high level (up to 90 wt%). Because of the high sulfur content, the nanoscale distribution of the sulfur particles, and the covalent bonding between the sulfur and the PGC, the developed 3D S@PGC cathodes exhibit excellent performance, with a high sulfur utilization, high specific capacity (1,382, 1,242 and 1,115 mA h g−1 at 0.5, 1 and 2 C, respectively), long cycling life (small capacity decay of 0.039% per cycle over 1,000 cycles at 2 C) and excellent rate capability at a high charge/discharge current. PMID:26830732

Cytoplasmic Sulfurtransferases in the Purple Sulfur Bacterium Allochromatium vinosum: Evidence for Sulfur Transfer from DsrEFH to DsrC

PubMed Central

Stockdreher, Yvonne; Venceslau, Sofia S.; Josten, Michaele; Sahl, Hans-Georg; Pereira, Inês A. C.; Dahl, Christiane

2012-01-01

While the importance of sulfur transfer reactions is well established for a number of biosynthetic pathways, evidence has only started to emerge that sulfurtransferases may also be major players in sulfur-based microbial energy metabolism. Among the first organisms studied in this regard is the phototrophic purple sulfur bacterium Allochromatium vinosum. During the oxidation of reduced sulfur species to sulfate this Gammaproteobacterium accumulates sulfur globules. Low molecular weight organic persulfides have been proposed as carrier molecules transferring sulfur from the periplasmic sulfur globules into the cytoplasm where it is further oxidized via the “Dsr” (dissimilatory sulfite reductase) proteins. We have suggested earlier that the heterohexameric protein DsrEFH is the direct or indirect acceptor for persulfidic sulfur imported into the cytoplasm. This proposal originated from the structural similarity of DsrEFH with the established sulfurtransferase TusBCD from E. coli. As part of a system for tRNA modification TusBCD transfers sulfur to TusE, a homolog of another crucial component of the A. vinosum Dsr system, namely DsrC. Here we show that neither DsrEFH nor DsrC have the ability to mobilize sulfane sulfur directly from low molecular weight thiols like thiosulfate or glutathione persulfide. However, we demonstrate that DsrEFH binds sulfur specifically to the conserved cysteine residue DsrE-Cys78 in vitro. Sulfur atoms bound to cysteines in DsrH and DsrF were not detected. DsrC was exclusively persulfurated at DsrC-Cys111 in the penultimate position of the protein. Most importantly, we show that persulfurated DsrEFH indeed serves as an effective sulfur donor for DsrC in vitro. The active site cysteines Cys78 of DsrE and Cys20 of DsrH furthermore proved to be essential for sulfur oxidation in vivo supporting the notion that DsrEFH and DsrC are part of a sulfur relay system that transfers sulfur from a persulfurated carrier molecule to the dissimilatory sulfite reductase DsrAB. PMID:22815818

Tetrathionate and Elemental Sulfur Shape the Isotope Composition of Sulfate in Acid Mine Drainage

PubMed Central

Balci, Nurgul; Brunner, Benjamin; Turchyn, Alexandra V.

2017-01-01

Sulfur compounds in intermediate valence states, for example elemental sulfur, thiosulfate, and tetrathionate, are important players in the biogeochemical sulfur cycle. However, key understanding about the pathways of oxidation involving mixed-valance state sulfur species is still missing. Here we report the sulfur and oxygen isotope fractionation effects during the oxidation of tetrathionate (S4O62−) and elemental sulfur (S°) to sulfate in bacterial cultures in acidic conditions. Oxidation of tetrathionate by Acidithiobacillus thiooxidans produced thiosulfate, elemental sulfur and sulfate. Up to 34% of the tetrathionate consumed by the bacteria could not be accounted for in sulfate or other intermediate-valence state sulfur species over the experiments. The oxidation of tetrathionate yielded sulfate that was initially enriched in 34S (ε34SSO4−S4O6) by +7.9‰, followed by a decrease to +1.4‰ over the experiment duration, with an average ε34SSO4−S4O6 of +3.5 ± 0.2‰ after a month of incubation. We attribute this significant sulfur isotope fractionation to enzymatic disproportionation reactions occurring during tetrathionate decomposition, and to the incomplete transformation of tetrathionate into sulfate. The oxygen isotope composition of sulfate (δ18OSO4) from the tetrathionate oxidation experiments indicate that 62% of the oxygen in the formed sulfate was derived from water. The remaining 38% of the oxygen was either inherited from the supplied tetrathionate, or supplied from dissolved atmospheric oxygen (O2). During the oxidation of elemental sulfur, the product sulfate became depleted in 34S between −1.8 and 0‰ relative to the elemental sulfur with an average for ε34SSO4−S0 of −0.9 ± 0.2‰ and all the oxygen atoms in the sulfate derived from water with an average normal oxygen isotope fractionation (ε18OSO4−H2O) of −4.4‰. The differences observed in δ18OSO4 and the sulfur isotope composition of sulfate (δ34SSO4), acid production, and mixed valence state sulfur species generated by the oxidation of the two different substrates suggests a metabolic flexibility in response to sulfur substrate availability. Our results demonstrate that microbial processing of mixed-valence-state sulfur species generates a significant sulfur isotope fractionation in acidic environments and oxidation of mixed-valence state sulfur species may produce sulfate with characteristic sulfur and oxygen isotope signatures. Elemental sulfur and tetrathionate are not only intermediate-valence state sulfur compounds that play a central role in sulfur oxidation pathways, but also key factors in shaping these isotope patterns. PMID:28861071

Sulfur recirculation for increased electricity production in Waste-to-Energy plants.

PubMed

Andersson, Sven; Blomqvist, Evalena W; Bäfver, Linda; Jones, Frida; Davidsson, Kent; Froitzheim, Jan; Karlsson, Martin; Larsson, Erik; Liske, Jesper

2014-01-01

Sulfur recirculation is a new technology for reducing boiler corrosion and dioxin formation. It was demonstrated in full-scale tests at a Waste to Energy plant in Göteborg (Sweden) during nearly two months of operation. Sulfur was recirculated as sulfuric acid from the flue gas cleaning back to the boiler, thus creating a sulfur loop. The new technology was evaluated by extensive measurement campaigns during operation under normal conditions (reference case) and operation with sulfur recirculation. The chlorine content of both fly ash and boiler ash decreased and the sulfur content increased during the sulfur recirculation tests. The deposit growth and the particle concentration decreased with sulfur recirculation and the dioxin concentration (I-TEQ) of the flue gas was reduced by approximately 25%. Sulfuric acid dew point measurements showed that the sulfuric acid dosage did not lead to elevated SO3 concentrations, which may otherwise induce low temperature corrosion. In the sulfur recirculation corrosion probe exposures, the corrosion rate decreased for all tested materials (16Mo3, Sanicro 28 and Inconel 625) and material temperatures (450 °C and 525 °C) compared to the reference exposure. The corrosion rates were reduced by 60-90%. Sulfur recirculation prevented the formation of transition metal chlorides at the metal/oxide interface, formation of chromate and reduced the presence of zinc in the corrosion products. Furthermore, measured corrosion rates at 525 °C with sulfur recirculation in operation were similar or lower compared to those measured at 450 °C material temperature in reference conditions, which corresponds to normal operation at normal steam temperatures. This implies that sulfur recirculation allows for higher steam data and electricity production without increasing corrosion. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Experiments on δ34S mixing between organic and inorganic sulfur species during thermal maturation

USGS Publications Warehouse

Amrani, Alon; Said-Ahamed, Ward; Lewan, Michael D.; Aizenshtat, Zeev

2006-01-01

Reduced sulfur species were studied to constrain isotopic exchange-mixing with synthetic polysulfide cross-linked macromolecules (PCLM), model sulfur containing molecules and natural sulfur-rich kerogen, asphalt and oil of the Dead Sea area. PCLM represents protokerogens that are rich in sulfur and thermally unstable. Mixing rates of PCLM with HS-(aq) (added as (NH4)2S(aq)) at low to moderate temperatures (50–200 °C) are rapid. Elemental sulfur and H2S(gas) fully mix isotopes with PCLM during pyrolysis conditions at 200 °C. During these reactions significant structural changes of the PCLM occur to form polysulfide dimers, thiolanes and thiophenes. As pyrolysis temperatures or reaction times increase, the PCLM thermal products are transformed to more aromatic sulfur compounds. Isotopic mixing rates increase with increasing pyrolysis temperature and time. Polysulfide bonds (S–S) in the PCLM are responsible for most of these structural and isotopic changes because of their low stability. Conversely, sulfur isotope mixing does not occur between dibenzothiophene (aromatic S) or hexadecanthiol (C–SH) and HS-(aq) at 200 °C after 48 h. This shows that rates of sulfur isotope mixing are strongly dependent on the functionality of the sulfur in the organic matter. The order of isotopic mixing rates for organic matter is kerogen > asphalt > oil, which is inverse to their sulfur thermal stability. Asphalt and oil with more refractory sulfur show significantly lower isotopes mixing rates than the kerogen with more labile sulfur. Based on the findings of the present study we suggest that sulfur isotopes mixing can occur from early diagenesis into catagenesis and result in isotopic homogenization of the inorganic and organic reduced sulfur pools.

Sulfur variability and petrology of the Lower Block Coal Member (Pennsylvanian) in Southwest Indiana

USGS Publications Warehouse

Padgett, P.L.; Rimmer, S.M.; Ferm, J.C.; Hower, J.C.; Eble, C.F.; Mastalerz, Maria

1999-01-01

The Lower Block Coal Member (Pennsylvanian-Atokan, Westphalian C) is an economic low-to medium-sulfur, low-ash coal resource in the Illinois Basin. Sulfur content is generally low (averaging 1.0%) in the study area, but varies over short distances. Higher sulfur areas occur as isolated pods and epigenetic pyrite increases significantly in the upper third of the selected columns in higher sulfur areas. Sulfur variations cannot be predicted by typical geologic characteristics such as roof lithology, seam thickness, or seam elevation. Petrographic analysis shows that pyrite is generally associated with brighter microlithotypes, except in higher sulfur areas where infilling pyrite forms are associated with inertite. Higher sulfur areas reflect the water chemistry of the paleomire during and shortly after peat accumulation. Locally, abundant pyrofusinite provided additional pore space for pyrite precipitation.The Lower Block Coal Member (Pennsylvanian-Atokan, Westphalian C) is an economic low- to medium-sulfur, low-ash coal resource in the Illinois Basin. Sulfur content is generally low (averaging 1.0%) in the study area, but varies over short distances. Higher sulfur areas occur as isolated pods and epigenetic pyrite increases significantly in the upper third of the selected columns in higher sulfur areas. Sulfur variations cannot be predicted by typical geologic characteristics such as roof lithology, seam thickness, or seam elevation. Petrographic analysis shows that pyrite is generally associated with brighter microlithotypes, except in higher sulfur areas where infilling pyrite forms are associated with inertite. Higher sulfur areas reflect the water chemistry of the paleomire during and shortly after peat accumulation. Locally, abundant pyrofusinite provided additional pore space for pyrite precipitation.

Sulfur speciation and bioaccumulation in camphor tree leaves as atmospheric sulfur indicator analyzed by synchrotron radiation XRF and XANES.

PubMed

Zeng, Jianrong; Zhang, Guilin; Bao, Liangman; Long, Shilei; Tan, Mingguang; Li, Yan; Ma, Chenyan; Zhao, Yidong

2013-03-01

Analyzing and understanding the effects of ambient pollution on plants is getting more and more attention as a topic of environmental biology. A method based on synchrotron radiation X-ray fluorescence and X-ray absorption near edge structure spectroscopy was established to analyze the sulfur concentration and speciation in mature camphor tree leaves (CTLs), which were sampled from 5 local fields in Shanghai, China. Annual SO2 concentration, SO4(2-) concentration in atmospheric particulate, SO4(2-) and sulfur concentration in soil were also analyzed to explore the relationship between ambient sulfur sources and the sulfur nutrient cycling in CTLs. Total sulfur concentration in mature camphor tree leaves was 766-1704 mg/kg. The mainly detected sulfur states and their corresponding compounds were +6 (sulfate, include inorganic sulfate and organic sulfate), +5.2 (sulfonate), +2.2 (suloxides), +0.6 (thiols and thiothers), +0.2 (organic sulfides). Total sulfur concentration was strongly correlated with sulfate proportion with a linear correlation coefficient up to 0.977, which suggested that sulfur accumulated in CTLs as sulfate form. Reduced sulfur compounds (organic sulfides, thiols, thioethers, sulfoxide and sulfonate) assimilation was sufficed to meet the nutrient requirement for growth at a balanced level around 526 mg/kg. The sulfate accumulation mainly caused by atmospheric sulfur pollution such as SO2 and airborne sulfate particulate instead of soil contamination. From urban to suburb place, sulfate in mature CTLs decreased as the atmospheric sulfur pollution reduced, but a dramatic increase presented near the seashore, where the marine sulfate emission and maritime activity pollution were significant. The sulfur concentration and speciation in mature CTLs effectively represented the long-term biological accumulation of atmospheric sulfur pollution in local environment.

Successful sulfur recovery in low sulfurate compounds obtained from the zinc industry: Evaporation-condensation method.

PubMed

Suárez-Gómez, Sergio Luis; Sánchez, Maria Luisa; Blanco, Francisco; Ayala, Julia; de Cos Juez, Francisco Javier

2017-08-15

The improvement of an evaporation-condensation method allows for successful recovery of elemental sulfur from sulfide concentrates from the zinc industry. Elemental sulfur can be obtained with this method in samples with a low (60%) sulfur content. The effects of heating temperature between 150°C and 250°C and heating time up to 120min on the recovery of sulfur are also studied. Elemental sulfur obtained in this way is of high purity and therefore, there is no need for further purification. The treatment of these industrial residues would help removing sulfur from the environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Graphene oxide as a sulfur immobilizer in high performance lithium/sulfur cells

DOEpatents

Zhang, Yuegang; Cairns, Elton J.; Ji, Liwen; Rao, Mumin

2017-06-06

The loss of sulfur cathode material as a result of polysulfide dissolution causes significant capacity fading in rechargeable lithium/sulfur cells. Embodiments of the invention use a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide. This approach obtains a uniform and thin (.about.tens of nanometers) sulfur coating on graphene oxide sheets by a chemical reaction-deposition strategy and a subsequent low temperature thermal treatment process. Strong interaction between graphene oxide and sulfur or polysulfides demonstrate lithium/sulfur cells with a high reversible capacity of 950-1400 mAh g.sup.-1, and stable cycling for more than 50 deep cycles at 0.1 C.

System for adding sulfur to a fuel cell stack system for improved fuel cell stability

DOEpatents

Mukerjee, Subhasish; Haltiner, Jr., Karl J; Weissman, Jeffrey G

2013-08-13

A system for adding sulfur to a reformate stream feeding a fuel cell stack, having a sulfur source for providing sulfur to the reformate stream and a metering device in fluid connection with the sulfur source and the reformate stream. The metering device injects sulfur from the sulfur source to the reformate stream at a predetermined rate, thereby providing a conditioned reformate stream to the fuel cell stack. The system provides a conditioned reformate stream having a predetermined sulfur concentration that gives an acceptable balance of minimal drop in initial power with the desired maximum stability of operation over prolonged periods for the fuel cell stack.

Sulfur in vacuum - Sublimation effects on frozen melts, and applications to Io's surface and torus

NASA Technical Reports Server (NTRS)

Nash, Douglas B.

1987-01-01

Vacuum sublimation effects on solid sulfur yield a form of the element that is white at room temperature, is fluffy in texture, and forms on frozen sulfur in vacuum through differential evaporation of molecular species in the solid. This vacuum sulfur should exist in large quantity on Io, if the solid free sulfur there has solidified from a melt; a sulfur volcanism model for Io is accordingly developed on this basis which implies that the color and spectra of different sulfur regions of Io could indicate their relative crystallization ages and cooling histories. The flux of sublimating hotspot sulfur appears consistent with estimated turnover rates of the Io surface.

System for adding sulfur to a fuel cell stack system for improved fuel cell stability

DOEpatents

Mukerjee, Subhasish [Pittsford, NY; Haltiner, Jr., Karl J; Weissman, Jeffrey G [West Henrietta, NY

2012-03-06

A system for adding sulfur to a fuel cell stack, having a reformer adapted to reform a hydrocarbon fuel stream containing sulfur contaminants, thereby providing a reformate stream having sulfur; a sulfur trap fluidly coupled downstream of the reformer for removing sulfur from the reformate stream, thereby providing a desulfurized reformate stream; and a metering device in fluid communication with the reformate stream upstream of the sulfur trap and with the desulfurized reformate stream downstream of the sulfur trap. The metering device is adapted to bypass a portion of the reformate stream to mix with the desulfurized reformate stream, thereby producing a conditioned reformate stream having a predetermined sulfur concentration that gives an acceptable balance of minimal drop in initial power with the desired maximum stability of operation over prolonged periods for the fuel cell stack.

Method for the desulfurization of hot product gases from coal gasifier

DOEpatents

Grindley, Thomas

1988-01-01

The gasification of sulfur-bearing coal produces a synthesis gas which contains a considerable concentration of sulfur compounds especially hydrogen sulfide that renders the synthesis gas environmentally unacceptable unless the concentration of the sulfur compounds is significantly reduced. To provide for such a reduction in the sulfur compounds a calcium compound is added to the gasifier with the coal to provide some sulfur absorption. The synthesis gas from the gasifier contains sulfur compounds and is passed through an external bed of a regenerable solid absorbent, preferably zinc ferrite, for essentially completed desulfurizing the hot synthesis gas. This absorbent is, in turn, periodically or continuously regenerated by passing a mixture of steam and air or oxygen through the bed for converting absorbed hydrogen sulfide to sulfur dioxide. The resulting tail gas containing sulfur dioxide and steam is injected into the gasifier where the sulfur dioxide is converted by the calcium compound into a stable form of sulfur such as calcium sulfate.

PROCEEDINGS ON SYNCHROTRON RADIATION: Transfer characterization of sulfur from coal-burning emission to plant leaves by PIXE and XANES

NASA Astrophysics Data System (ADS)

Bao, Liang-Man; Zhang, Gui-Lin; Zhang, Yuan-Xim; Li, Yan; Lin, Jun; Liu, Wei; Cao, Qing-Chen; Zhao, Yi-Dong; Ma, Chen-Yan; Han, Yong

2009-11-01

The impact of coal-burning emission on sulfur in camphor leaves was investigated using Proton Induced X-ray Emission (PIXE) and synchrotron radiation technique X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The PIXE results show that the sulfur concentrations in the leaves collected at the polluted site are significantly higher than those in controls. The Sulfur XANES spectra show the presence of organic (disulfides, thiols, thioethers, sulfonates and sulfoxides) and inorganic sulfur (sulfates) in the leaves. The inorganic sulfur in the leaves of camphor tree polluted by coal combustion is 15% more than that of the control site. The results suggest that the long-term coal-burning pollution resulted in an enhanced content of the total sulfur and sulfate in the leaves, and the uptake of sulfur by leaves had exceeded the metabolic requirement of plants and the excess of sulfur was stored as SO2-4. It can monitor the sulfur pollution in atmosphere.

Decoupling of Neoarchean sulfur sources recorded in Algoma-type banded iron formation

NASA Astrophysics Data System (ADS)

Diekrup, David; Hannington, Mark D.; Strauss, Harald; Ginley, Stephen J.

2018-05-01

Neoarchean Algoma-type banded iron formations (BIFs) are widely viewed as direct chemical precipitates from proximal volcanic-hydrothermal vents. However, a systematic multiple sulfur isotope study of oxide-facies BIF from a type locality in the ca. 2.74 Ga Temagami greenstone belt reveals mainly bacterial turnover of atmospheric elemental sulfur in the host basin rather than deposition of hydrothermally cycled seawater sulfate or sulfur from direct volcanic input. Trace amounts of chromium reducible sulfur that were extracted for quadruple sulfur isotope (32S-33S-34S-36S) analysis record the previously known mass-independent fractionation of volcanic SO2 in the Archean atmosphere (S-MIF) and biological sulfur cycling but only minor contributions from juvenile sulfur, despite the proximity of volcanic sources. We show that the dominant bacterial metabolisms were iron reduction and sulfur disproportionation, and not sulfate reduction, consistent with limited availability of organic matter and the abundant ferric iron deposited as Fe(OH)3. That sulfur contained in the BIF was not a direct volcanic-hydrothermal input, as expected, changes the view of an important archive of the Neoarchean sulfur cycle in which the available sulfur pools were strongly decoupled and only species produced photochemically under anoxic atmospheric conditions were deposited in the BIF-forming environment.

Investigating Arsenic Mobilization Mechanisms as well as Complexation Between Arsenic and Polysulfides Associated With a Bangladeshi Rice Paddy

NASA Astrophysics Data System (ADS)

Lin, T.; Kampalath, R.; Jay, J.

2009-12-01

The presence of arsenic in the groundwater has led to the largest environmental poisoning in history. Although it is a worldwide issue that affects numerous countries, including Taiwan, Bangladesh, India, China, Mexico, Peru, Australia, and the United States, the issue is of greatest concern in the West Bengal region. In the Ganges Delta, as many as 2 million people are diagnosed with arsenicosis each year. The World Health Organization (WHO) estimates 200,000 to 270,000 arsenic-induced cancer-related deaths in Bangladesh alone. More than 100 million people in the country consume groundwater that exceeds the WHO limit as 50% of the 8 million wells contain groundwater with more than 10 μg/L. Despite the tragic public health implications of this problem, we do not yet have a complete answer to the question of why dissolved arsenic concentrations are so high in the groundwater of the Ganges Delta. Since 1999, we have been intensively studying a field site in Munshiganj, Bangladesh with extremely high levels of arsenic in groundwater (up to 1.2 mg/L). Sediment cores were collected from two locations at the field site: 1) the rice paddy and 2) edge of a nearby irrigation pond. Recharge from irrigation ponds have recently been hypothesized to be an important site of arsenic mobilization. Recent work has proposed mineral dissolution under phosphorus-limited conditions as an important mechanism for arsenic mobilization. Using microcosms with paddy and pond sediment, we are comparing arsenic release via this mechanism with that resulting from reduction of iron hydroxides at our site. Concurrently, we are looking at enhanced solubility of As in the presence of polysulfides as the effects of elemental sulfur on As solubility have not been well researched. We hypothesize that the presence of elemental sulfur, and consequent formation of polysulfides, will substantially increase the solubility of orpiment in sulfidic water and that sorption of these complexes will significantly affect the mobility of these species of As in groundwater. We have shown substantial (order of magnitude) increases in metal solubility in bottle in the presence of elemental sulfur and sulfide compared to bottles in the presence of the same concentration of sulfide alone. This is presumably attributable to metal-polysulfide complexation. Further experiments measuring solubility over a range of pH and sulfide levels are necessary to model the data and determine complexation constants. By elucidating As mobilization mechanisms at an experimental rice paddy, this work could ultimately lead to solutions that minimize As exposure in critical populations.

Understanding the role of different conductive polymers in improving the nanostructured sulfur cathode performance.

PubMed

Li, Weiyang; Zhang, Qianfan; Zheng, Guangyuan; Seh, Zhi Wei; Yao, Hongbin; Cui, Yi

2013-01-01

Lithium sulfur batteries have brought significant advancement to the current state-of-art battery technologies because of their high theoretical specific energy, but their wide-scale implementation has been impeded by a series of challenges, especially the dissolution of intermediate polysulfides species into the electrolyte. Conductive polymers in combination with nanostructured sulfur have attracted great interest as promising matrices for the confinement of lithium polysulfides. However, the roles of different conductive polymers on the electrochemical performances of sulfur electrode remain elusive and poorly understood due to the vastly different structural configurations of conductive polymer-sulfur composites employed in previous studies. In this work, we systematically investigate the influence of different conductive polymers on the sulfur cathode based on conductive polymer-coated hollow sulfur nanospheres with high uniformity. Three of the most well-known conductive polymers, polyaniline (PANI), polypyrrole (PPY), and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated, respectively, onto monodisperse hollow sulfur nanopsheres through a facile, versatile, and scalable polymerization process. The sulfur cathodes made from these well-defined sulfur nanoparticles act as ideal platforms to study and compare how coating thickness, chemical bonding, and the conductivity of the polymers affected the sulfur cathode performances from both experimental observations and theoretical simulations. We found that the capability of these three polymers in improving long-term cycling stability and high-rate performance of the sulfur cathode decreased in the order of PEDOT > PPY > PANI. High specific capacities and excellent cycle life were demonstrated for sulfur cathodes made from these conductive polymer-coated hollow sulfur nanospheres.

Sulfur poisoning of CeO[subscript 2]-Al[subscript 2]O[subscript 3]-supported mono- and bi-metallic Ni and Rh catalysts in steam reforming of liquid hydrocarbons at low and high temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Chao; Chen, Yongsheng; Li, Yan

2010-12-01

In order to develop a better understanding on sulfur poisoning of reforming catalysts in fuel processing for hydrogen production, steam reforming of liquid hydrocarbons was performed over CeO{sub 2}-Al{sub 2}O{sub 3} supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 C. XANES was used to identify the sulfur species in the used catalysts and to study their impacts on the metal surface properties probed by XPS. It was found that both monometallic catalysts rapidly deactivated at 550 C, and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 C dramaticallymore » improved the sulfur tolerance of the Rh catalyst. XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The presence of sulfur induced severe carbon deposition on the Ni catalyst at 800 C. The superior sulfur tolerance of the Rh catalyst at 800 C may be associated with its capability in sulfur oxidation. It is likely that the formation of the oxygen-shielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh by inhibiting direct rhodium-sulfur interaction. Moreover, XPS indicated that the metal surface properties of the Rh catalysts after the reaction without and with sulfur at 800 C are similar, suggesting that sulfur poisoning on Rh was mitigated under the high-temperature condition. Although the Rh-Ni catalyst exhibited better sulfur tolerance than the monometallic catalysts at 550 C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800 C probably due to the severe carbon deposition on the bimetallic catalyst.« less

Structural basis for energy transduction by respiratory alternative complex III.

PubMed

Sousa, Joana S; Calisto, Filipa; Langer, Julian D; Mills, Deryck J; Refojo, Patrícia N; Teixeira, Miguel; Kühlbrandt, Werner; Vonck, Janet; Pereira, Manuela M

2018-04-30

Electron transfer in respiratory chains generates the electrochemical potential that serves as energy source for the cell. Prokaryotes can use a wide range of electron donors and acceptors and may have alternative complexes performing the same catalytic reactions as the mitochondrial complexes. This is the case for the alternative complex III (ACIII), a quinol:cytochrome c/HiPIP oxidoreductase. In order to understand the catalytic mechanism of this respiratory enzyme, we determined the structure of ACIII from Rhodothermus marinus at 3.9 Å resolution by single-particle cryo-electron microscopy. ACIII presents a so-far unique structure, for which we establish the arrangement of the cofactors (four iron-sulfur clusters and six c-type hemes) and propose the location of the quinol-binding site and the presence of two putative proton pathways in the membrane. Altogether, this structure provides insights into a mechanism for energy transduction and introduces ACIII as a redox-driven proton pump.

Luminescence, electrochemistry and host-guest properties of dinuclear platinum(ii) terpyridyl complexes of sulfur-containing bridging ligands.

PubMed

Tang, Rowena Pui-Ling; Wong, Keith Man-Chung; Zhu, Nianyong; Yam, Vivian Wing-Wah

2009-05-28

A series of dinuclear platinum(ii) terpyridyl and terpyridyl-crown complexes with 2,2-dicyano-1,1-ethylenedithiolate (i-mnt), 1,3-benzenedithiolate (SC(6)H(4)S-1,3) and N,N-diethyldithiocarbamate (dtc) bridging ligands have been synthesized and characterized. Their photophysical and electrochemical properties, together with that of the related mononuclear platinum(ii) terpyridyl-crown complex and its crown-free analogue, have been studied. The ion-binding properties of the terpyridyl-crown complexes have been determined by electronic absorption spectroscopy and ESI-mass spectrometry. The X-ray crystal structures of [Pt(trpyC[triple bond, length as m-dash]C-benzo-15-crown-5)Cl]PF(6), [{Pt(trpy)}(2)(micro-SC(6)H(4)S-1,3)](PF(6))(2) and [{Pt(trpy)}(2){micro-(i-mnt)}](PF(6))(2) have also been determined.