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Sample records for respiratory arsenate reductase

  1. Respiratory arsenate reductase as a bidirectional enzyme

    USGS Publications Warehouse

    Richey, C.; Chovanec, P.; Hoeft, S.E.; Oremland, R.S.; Basu, P.; Stolz, J.F.

    2009-01-01

    The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative respiratory arsenate reductase (Arr). Here we show that one homolog is expressed under chemolithoautotrophic conditions and exhibits both arsenite oxidase and arsenate reductase activity. We also demonstrate that Arr from two arsenate respiring bacteria, Alkaliphilus oremlandii and Shewanella sp. strain ANA-3, is also biochemically reversible. Thus Arr can function as a reductase or oxidase. Its physiological role in a specific organism, however, may depend on the electron potentials of the molybdenum center and [Fe–S] clusters, additional subunits, or constitution of the electron transfer chain. This versatility further underscores the ubiquity and antiquity of microbial arsenic metabolism.

  2. The respiratory arsenate reductase from Bacillus selenitireducens strain MLS10

    USGS Publications Warehouse

    Afkar, E.; Lisak, J.; Saltikov, C.; Basu, P.; Oremland, R.S.; Stolz, J.F.

    2003-01-01

    The respiratory arsenate reductase from the Gram-positive, haloalkaliphile, Bacillus selenitireducens strain MLS10 was purified and characterized. It is a membrane bound heterodimer (150 kDa) composed of two subunits ArrA (110 kDa) and ArrB (34 kDa), with an apparent Km for arsenate of 34 ??M and Vmax of 2.5 ??mol min-1 mg-1. Optimal activity occurred at pH 9.5 and 150 g l-1 of NaCl. Metal analysis (inductively coupled plasma mass spectrometry) of the holoenzyme and sequence analysis of the catalytic subunit (ArrA; the gene for which was cloned and sequenced) indicate it is a member of the DMSO reductase family of molybdoproteins. ?? 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

  3. Prokaryotic arsenate reductase enhances arsenate resistance in Mammalian cells.

    PubMed

    Wu, Dan; Tao, Xuanyu; Wu, Gaofeng; Li, Xiangkai; Liu, Pu

    2014-01-01

    Arsenic is a well-known heavy metal toxicant in the environment. Bioremediation of heavy metals has been proposed as a low-cost and eco-friendly method. This article described some of recent patents on transgenic plants with enhanced heavy metal resistance. Further, to test whether genetic modification of mammalian cells could render higher arsenic resistance, a prokaryotic arsenic reductase gene arsC was transfected into human liver cancer cell HepG2. In the stably transfected cells, the expression level of arsC gene was determined by quantitative real-time PCR. Results showed that arsC was expressed in HepG2 cells and the expression was upregulated by 3 folds upon arsenate induction. To further test whether arsC has function in HepG2 cells, the viability of HepG2-pCI-ArsC cells exposed to arsenite or arsenate was compared to that of HepG2-pCI cells without arsC gene. The results indicated that arsC increased the viability of HepG2 cells by 25% in arsenate, but not in arsenite. And the test of reducing ability of stably transfected cells revealed that the concentration of accumulated trivalent arsenic increased by 25% in HepG2-pCI-ArsC cells. To determine the intracellular localization of ArsC, a fusion vector with fluorescent marker pEGFP-N1-ArsC was constructed and transfected into.HepG2. Laser confocal microscopy showed that EGFP-ArsC fusion protein was distributed throughout the cells. Taken together, these results demonstrated that prokaryotic arsenic resistant gene arsC integrated successfully into HepG2 genome and enhanced arsenate resistance of HepG2, which brought new insights of arsenic detoxification in mammalian cells.

  4. Dissimilatory arsenate reductase activity and arsenate-respiring bacteria in bovine rumen fluid, hamster feces, and the termite hindgut

    USGS Publications Warehouse

    Herbel, M.J.; Switzer, Blum J.; Hoeft, S.E.; Cohen, S.M.; Arnold, L.L.; Lisak, J.; Stolz, J.F.; Oremland, R.S.

    2002-01-01

    Bovine rumen fluid and slurried hamster feces completely reduced millimolar levels of arsenate to arsenite upon incubation under anoxic conditions. This activity was strongly inhibited by autoclaving or aerobic conditions, and partially inhibited by tungstate or chloramphenicol. The rate of arsenate reduction was faster in feces from a population of arsenate-watered (100 ppm) hamsters compared to a control group watered without arsenate. Using radioisotope methods, arsenate reductase activity in hamster feces was also detected at very low concentrations of added arsenate (???10 ??M). Bacterial cultures were isolated from these materials, as well as from the termite hindgut, that grew using H2 as their electron donor, acetate as their carbon source, and arsenate as their respiratory electron acceptor. The three cultures aligned phylogenetically either with well-established enteric bacteria, or with an organism associated with feedlot fecal wastes. Because arsenite is transported across the gut epithelium more readily than arsenate, microbial dissimilatory reduction of arsenate in the gut may promote the body's absorption of arsenic and hence potentiate its toxicity. ?? 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

  5. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases

    PubMed Central

    Cesaro, Patrizia; Cattaneo, Chiara; Bona, Elisa; Berta, Graziella; Cavaletto, Maria

    2015-01-01

    Enzymatic reduction of arsenate to arsenite is the first known step in arsenate metabolism in all organisms. Although the presence of one mRNA arsenate reductase (PvACR2) has been characterized in gametophytes of P. vittata, no arsenate reductase protein has been directly observed in this arsenic hyperaccumulating fern, yet. In order to assess the possible presence of arsenate reductase in P. vittata, two recombinant proteins, ACR2-His6 and Trx-His6-S-Pv2.5–8 were prepared in Escherichia coli, purified and used to produce polyclonal antibodies. The presence of these two enzymes was evaluated by qRT-PCR, immunoblotting and direct MS analysis. Enzymatic activity was detected in crude extracts. For the first time we detected and identified two arsenate reductase proteins (PvACR2 and Pv2.5–8) in sporophytes and gametophytes of P. vittata. Despite an increase of the mRNA levels for both proteins in roots, no difference was observed at the protein level after arsenic treatment. Overall, our data demonstrate the constitutive protein expression of PvACR2 and Pv2.5–8 in P. vittata tissues and propose their specific role in the complex metabolic network of arsenic reduction. PMID:26412036

  6. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases.

    PubMed

    Cesaro, Patrizia; Cattaneo, Chiara; Bona, Elisa; Berta, Graziella; Cavaletto, Maria

    2015-09-28

    Enzymatic reduction of arsenate to arsenite is the first known step in arsenate metabolism in all organisms. Although the presence of one mRNA arsenate reductase (PvACR2) has been characterized in gametophytes of P. vittata, no arsenate reductase protein has been directly observed in this arsenic hyperaccumulating fern, yet. In order to assess the possible presence of arsenate reductase in P. vittata, two recombinant proteins, ACR2-His6 and Trx-His6-S-Pv2.5-8 were prepared in Escherichia coli, purified and used to produce polyclonal antibodies. The presence of these two enzymes was evaluated by qRT-PCR, immunoblotting and direct MS analysis. Enzymatic activity was detected in crude extracts. For the first time we detected and identified two arsenate reductase proteins (PvACR2 and Pv2.5-8) in sporophytes and gametophytes of P. vittata. Despite an increase of the mRNA levels for both proteins in roots, no difference was observed at the protein level after arsenic treatment. Overall, our data demonstrate the constitutive protein expression of PvACR2 and Pv2.5-8 in P. vittata tissues and propose their specific role in the complex metabolic network of arsenic reduction.

  7. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases

    NASA Astrophysics Data System (ADS)

    Cesaro, Patrizia; Cattaneo, Chiara; Bona, Elisa; Berta, Graziella; Cavaletto, Maria

    2015-09-01

    Enzymatic reduction of arsenate to arsenite is the first known step in arsenate metabolism in all organisms. Although the presence of one mRNA arsenate reductase (PvACR2) has been characterized in gametophytes of P. vittata, no arsenate reductase protein has been directly observed in this arsenic hyperaccumulating fern, yet. In order to assess the possible presence of arsenate reductase in P. vittata, two recombinant proteins, ACR2-His6 and Trx-His6-S-Pv2.5-8 were prepared in Escherichia coli, purified and used to produce polyclonal antibodies. The presence of these two enzymes was evaluated by qRT-PCR, immunoblotting and direct MS analysis. Enzymatic activity was detected in crude extracts. For the first time we detected and identified two arsenate reductase proteins (PvACR2 and Pv2.5-8) in sporophytes and gametophytes of P. vittata. Despite an increase of the mRNA levels for both proteins in roots, no difference was observed at the protein level after arsenic treatment. Overall, our data demonstrate the constitutive protein expression of PvACR2 and Pv2.5-8 in P. vittata tissues and propose their specific role in the complex metabolic network of arsenic reduction.

  8. Properties of the arsenate reductase of plasmid R773.

    PubMed

    Gladysheva, T B; Oden, K L; Rosen, B P

    1994-06-14

    Resistance to toxic oxyanions in Escherichia coli is conferred by the ars operon carried on plasmid R773. The gene products of this operon catalyze extrusion of antimonials and arsenicals from cells of E. coli, thus providing resistance to those toxic oxyanions. In addition, resistance to arsenate is conferred by the product of the arsC gene. In this report, purified ArsC protein was shown to catalyze reduction of arsenate to arsenite. The enzymatic activity of the ArsC protein required glutaredoxin as a source of reducing equivalents. Other reductants, including glutathione and thioredoxin, were not effective electron donors. A spectrophotometric assay was devised in which arsenate reduction was coupled to NADPH oxidation. The results obtained with the coupled assay corresponded to those found by direct reduction of radioactive arsenate to arsenite. The only substrate of the reaction was arsenate (Km = 8 mM); other oxyanions including phosphate, sulfate, and antimonate were not reduced. Phosphate and sulfate were weak inhibitors, while the product, arsenite, was a stronger inhibitor (Ki = 0.1 mM). Arsenate reductase activity exhibited a pH optimum of 6.3-6.8. These results indicate that the ArsC protein is a novel reductase, and elucidation of its enzymatic mechanism should be of interest.

  9. A Hybrid Mechanism for the Synechocystis Arsenate Reductase Revealed by Structural Snapshots during Arsenate Reduction*

    PubMed Central

    Hu, Cuiyun; Yu, Caifang; Liu, Yanhua; Hou, Xianhui; Liu, Xiaoyun; Hu, Yunfei; Jin, Changwen

    2015-01-01

    Evolution of enzymes plays a crucial role in obtaining new biological functions for all life forms. Arsenate reductases (ArsC) are several families of arsenic detoxification enzymes that reduce arsenate to arsenite, which can subsequently be extruded from cells by specific transporters. Among these, the Synechocystis ArsC (SynArsC) is structurally homologous to the well characterized thioredoxin (Trx)-coupled ArsC family but requires the glutaredoxin (Grx) system for its reactivation, therefore classified as a unique Trx/Grx-hybrid family. The detailed catalytic mechanism of SynArsC is unclear and how the “hybrid” mechanism evolved remains enigmatic. Herein, we report the molecular mechanism of SynArsC by biochemical and structural studies. Our work demonstrates that arsenate reduction is carried out via an intramolecular thiol-disulfide cascade similar to the Trx-coupled family, whereas the enzyme reactivation step is diverted to the coupling of the glutathione-Grx pathway due to the local structural difference. The current results support the hypothesis that SynArsC is likely a molecular fossil representing an intermediate stage during the evolution of the Trx-coupled ArsC family from the low molecular weight protein phosphotyrosine phosphatase (LMW-PTPase) family. PMID:26224634

  10. A novel arsenate reductase from the bacterium Thermus thermophilus HB27: its role in arsenic detoxification.

    PubMed

    Del Giudice, Immacolata; Limauro, Danila; Pedone, Emilia; Bartolucci, Simonetta; Fiorentino, Gabriella

    2013-10-01

    Microorganisms living in arsenic-rich geothermal environments act on arsenic with different biochemical strategies, but the molecular mechanisms responsible for the resistance to the harmful effects of the metalloid have only partially been examined. In this study, we investigated the mechanisms of arsenic resistance in the thermophilic bacterium Thermus thermophilus HB27. This strain, originally isolated from a Japanese hot spring, exhibited tolerance to concentrations of arsenate and arsenite up to 20mM and 15mM, respectively; it owns in its genome a putative chromosomal arsenate reductase (TtarsC) gene encoding a protein homologous to the one well characterized from the plasmid pI258 of the Gram+bacterium Staphylococcus aureus. Differently from the majority of microorganisms, TtarsC is part of an operon including genes not related to arsenic resistance; qRT-PCR showed that its expression was four-fold increased when arsenate was added to the growth medium. The gene cloning and expression in Escherichia coli, followed by purification of the recombinant protein, proved that TtArsC was indeed a thioredoxin-coupled arsenate reductase with a kcat/KM value of 1.2×10(4)M(-1)s(-1). It also exhibited weak phosphatase activity with a kcat/KM value of 2.7×10(-4)M(-1)s(-1). The catalytic role of the first cysteine (Cys7) was ascertained by site-directed mutagenesis. These results identify TtArsC as an important component in the arsenic resistance in T. thermophilus giving the first structural-functional characterization of a thermophilic arsenate reductase.

  11. Computational identification and analysis of arsenate reductase protein in Cronobacter sakazakii ATCC BAA-894 suggests potential microorganism for reducing arsenate.

    PubMed

    Chaturvedi, Navaneet; Singh, Vinay Kumar; Pandey, Paras Nath

    2013-06-01

    This study focuses a bioinformatics-based prediction of arsC gene product arsenate reductase (ArsC) protein in Cronobacter sakazakii BAA-894 strain. A protein structure-based study encloses three-dimensional structural modeling of target ArsC protein, was carried out by homology modeling method. Ultimately, the detection of active binding regions was carried out for characterization of functional sites in protein. The ten probable ligand binding sites were predicted for target protein structure and highlighted the common binding residues between target and template protein. It has been first time identified that modeled ArsC protein structure in C. sakazakii was structurally and functionally similar to well-characterized ArsC protein of Escherichia coli because of having same structural motifs and fold with similar protein topology and function. Investigation revealed that ArsC from C. sakazakii can play significant role during arsenic resistance and potential microorganism for bioremediation of arsenic toxicity.

  12. Adventitious Arsenate Reductase Activity of the Catalytic Domain of the Human Cdc25B and Cdc25C Phosphatases†

    PubMed Central

    Bhattacharjee, Hiranmoy; Sheng, Ju; Ajees, A. Abdul; Mukhopadhyay, Rita; Rosen, Barry P.

    2013-01-01

    A number of eukaryotic enzymes that function as arsenate reductases are homologues of the catalytic domain of the human Cdc25 phosphatase. For example, the Leishmania major enzyme LmACR2 is both a phosphatase and an arsenate reductase, and its structure bears similarity to the structure of the catalytic domain of human Cdc25 phosphatase. These reductases contain an active site C-X5-R signature motif, where C is the catalytic cysteine, the five X residues form a phosphate binding loop, and R is a highly conserved arginine, which is also present in human Cdc25 phosphatases. We therefore investigated the possibility that the three human Cdc25 isoforms might have adventitious arsenate reductase activity. The sequences for the catalytic domains of Cdc25A, -B, and -C were cloned individually into a prokaryotic expression vector, and their gene products were purified from a bacterial host using nickel affinity chromatography. While each of the three Cdc25 catalytic domains exhibited phosphatase activity, arsenate reductase activity was observed only with Cdc25B and -C. These two enzymes reduced inorganic arsenate but not methylated pentavalent arsenicals. Alteration of either the cysteine and arginine residues of the Cys-X5-Arg motif led to the loss of both reductase and phosphatase activities. Our observations suggest that Cdc25B and -C may adventitiously reduce arsenate to the more toxic arsenite and may also provide a framework for identifying other human protein tyrosine phosphatases containing the active site Cys-X5-Arg loop that might moonlight as arsenate reductases. PMID:20025242

  13. Genome-wide association mapping identifies a new arsenate reductase enzyme critical for limiting arsenic accumulation in plants.

    PubMed

    Chao, Dai-Yin; Chen, Yi; Chen, Jiugeng; Shi, Shulin; Chen, Ziru; Wang, Chengcheng; Danku, John M; Zhao, Fang-Jie; Salt, David E

    2014-12-01

    Inorganic arsenic is a carcinogen, and its ingestion through foods such as rice presents a significant risk to human health. Plants chemically reduce arsenate to arsenite. Using genome-wide association (GWA) mapping of loci controlling natural variation in arsenic accumulation in Arabidopsis thaliana allowed us to identify the arsenate reductase required for this reduction, which we named High Arsenic Content 1 (HAC1). Complementation verified the identity of HAC1, and expression in Escherichia coli lacking a functional arsenate reductase confirmed the arsenate reductase activity of HAC1. The HAC1 protein accumulates in the epidermis, the outer cell layer of the root, and also in the pericycle cells surrounding the central vascular tissue. Plants lacking HAC1 lose their ability to efflux arsenite from roots, leading to both increased transport of arsenic into the central vascular tissue and on into the shoot. HAC1 therefore functions to reduce arsenate to arsenite in the outer cell layer of the root, facilitating efflux of arsenic as arsenite back into the soil to limit both its accumulation in the root and transport to the shoot. Arsenate reduction by HAC1 in the pericycle may play a role in limiting arsenic loading into the xylem. Loss of HAC1-encoded arsenic reduction leads to a significant increase in arsenic accumulation in shoots, causing an increased sensitivity to arsenate toxicity. We also confirmed the previous observation that the ACR2 arsenate reductase in A. thaliana plays no detectable role in arsenic metabolism. Furthermore, ACR2 does not interact epistatically with HAC1, since arsenic metabolism in the acr2 hac1 double mutant is disrupted in an identical manner to that described for the hac1 single mutant. Our identification of HAC1 and its associated natural variation provides an important new resource for the development of low arsenic-containing food such as rice.

  14. Genome-wide Association Mapping Identifies a New Arsenate Reductase Enzyme Critical for Limiting Arsenic Accumulation in Plants

    PubMed Central

    Chao, Dai-Yin; Chen, Yi; Chen, Jiugeng; Shi, Shulin; Chen, Ziru; Wang, Chengcheng; Danku, John M.; Zhao, Fang-Jie; Salt, David E.

    2014-01-01

    Inorganic arsenic is a carcinogen, and its ingestion through foods such as rice presents a significant risk to human health. Plants chemically reduce arsenate to arsenite. Using genome-wide association (GWA) mapping of loci controlling natural variation in arsenic accumulation in Arabidopsis thaliana allowed us to identify the arsenate reductase required for this reduction, which we named High Arsenic Content 1 (HAC1). Complementation verified the identity of HAC1, and expression in Escherichia coli lacking a functional arsenate reductase confirmed the arsenate reductase activity of HAC1. The HAC1 protein accumulates in the epidermis, the outer cell layer of the root, and also in the pericycle cells surrounding the central vascular tissue. Plants lacking HAC1 lose their ability to efflux arsenite from roots, leading to both increased transport of arsenic into the central vascular tissue and on into the shoot. HAC1 therefore functions to reduce arsenate to arsenite in the outer cell layer of the root, facilitating efflux of arsenic as arsenite back into the soil to limit both its accumulation in the root and transport to the shoot. Arsenate reduction by HAC1 in the pericycle may play a role in limiting arsenic loading into the xylem. Loss of HAC1-encoded arsenic reduction leads to a significant increase in arsenic accumulation in shoots, causing an increased sensitivity to arsenate toxicity. We also confirmed the previous observation that the ACR2 arsenate reductase in A. thaliana plays no detectable role in arsenic metabolism. Furthermore, ACR2 does not interact epistatically with HAC1, since arsenic metabolism in the acr2 hac1 double mutant is disrupted in an identical manner to that described for the hac1 single mutant. Our identification of HAC1 and its associated natural variation provides an important new resource for the development of low arsenic-containing food such as rice. PMID:25464340

  15. Characterization of arsenate reductase in the extract of roots and fronds of Chinese brake fern, an arsenic hyperaccumulator.

    PubMed

    Duan, Gui-Lan; Zhu, Yong-Guan; Tong, Yi-Ping; Cai, Chao; Kneer, Ralf

    2005-05-01

    Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mM for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mM arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern.

  16. Characterization of Arsenate Reductase in the Extract of Roots and Fronds of Chinese Brake Fern, an Arsenic Hyperaccumulator1

    PubMed Central

    Duan, Gui-Lan; Zhu, Yong-Guan; Tong, Yi-Ping; Cai, Chao; Kneer, Ralf

    2005-01-01

    Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mm for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mm arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern. PMID:15834011

  17. An arsenate reductase homologue possessing phosphatase activity from sweet potato (Ipomoea batatas [L.] Lam): kinetic studies and characterization.

    PubMed

    Chan, Ya-Hui; Lin, Chao-Yi; Pai, Shou-Hsiung; Huang, Jenq-Kuen; Lin, Chi-Tsai

    2011-04-13

    A cDNA encoding a putative arsenate reductase homologue (IbArsR) was cloned from sweet potato (Ib). The deduced protein showed a high level of sequence homology (16-66%) with ArsRs from other organisms. A 3-D homology structure was created based on AtArsR (PDB code 1T3K ) from Arabidopsis thaliana. The putative active site of protein tyrosine phosphatase (HC(X)(5)R) is conserved in all reported ArsRs. IbArsR was overexpressed and purified. The monomeric nature of the enzyme was confirmed by 15% SDS-PAGE and molecular mass determination of the native enzyme via ESI Q-TOF. The IbArsR lacks arsenate reductase activity but possesses phosphatase activity. The Michaelis constant (K(M)) value for p-nitrophenyl phosphate (pNPP) was 11.11 mM. The phosphatase activity was inhibited by 0.5 mM sodium arsenate [As(V)]. The protein's half-life of deactivation at 25 °C was 6.1 min, and its inactivation rate constant K(d) was 1.1 × 10(-1) min(-1). The enzyme was active in a broad pH range from 4.0 to 11.0 with optimum activity at pH 10.0. Phosphatase would remove phosphate group from nucleic acid or dephosphorylation of other enzymes as regulation signaling.

  18. Genetic identification of arsenate reductase and arsenite oxidase in redox transformations carried out by arsenic metabolising prokaryotes - A comprehensive review.

    PubMed

    Kumari, Nisha; Jagadevan, Sheeja

    2016-11-01

    Arsenic (As) contamination in water is a cause of major concern to human population worldwide, especially in Bangladesh and West Bengal, India. Arsenite (As(III)) and arsenate (As(V)) are the two common forms in which arsenic exists in soil and groundwater, the former being more mobile and toxic. A large number of arsenic metabolising microorganisms play a crucial role in microbial transformation of arsenic between its different states, thus playing a key role in remediation of arsenic contaminated water. This review focuses on advances in biochemical, molecular and genomic developments in the field of arsenic metabolising bacteria - covering recent developments in the understanding of structure of arsenate reductase and arsenite oxidase enzymes, their gene and operon structures and their mechanism of action. The genetic and molecular studies of these microbes and their proteins may lead to evolution of successful strategies for effective implementation of bioremediation programs.

  19. OsHAC1;1 and OsHAC1;2 Function as Arsenate Reductases and Regulate Arsenic Accumulation.

    PubMed

    Shi, Shulin; Wang, Tao; Chen, Ziru; Tang, Zhong; Wu, Zhongchang; Salt, David E; Chao, Dai-Yin; Zhao, Fang-Jie

    2016-11-01

    Rice is a major dietary source of the toxic metalloid arsenic (As). Reducing its accumulation in rice (Oryza sativa) grain is of critical importance to food safety. Rice roots take up arsenate and arsenite depending on the prevailing soil conditions. The first step of arsenate detoxification is its reduction to arsenite, but the enzyme(s) catalyzing this reaction in rice remains unknown. Here, we identify OsHAC1;1 and OsHAC1;2 as arsenate reductases in rice. OsHAC1;1 and OsHAC1;2 are able to complement an Escherichia coli mutant lacking the endogenous arsenate reductase and to reduce arsenate to arsenite. OsHAC1:1 and OsHAC1;2 are predominantly expressed in roots, with OsHAC1;1 being abundant in the epidermis, root hairs, and pericycle cells while OsHAC1;2 is abundant in the epidermis, outer layers of cortex, and endodermis cells. Expression of the two genes was induced by arsenate exposure. Knocking out OsHAC1;1 or OsHAC1;2 decreased the reduction of arsenate to arsenite in roots, reducing arsenite efflux to the external medium. Loss of arsenite efflux was also associated with increased As accumulation in shoots. Greater effects were observed in a double mutant of the two genes. In contrast, overexpression of either OsHAC1;1 or OsHAC1;2 increased arsenite efflux, reduced As accumulation, and enhanced arsenate tolerance. When grown under aerobic soil conditions, overexpression of either OsHAC1;1 or OsHAC1;2 also decreased As accumulation in rice grain, whereas grain As increased in the knockout mutants. We conclude that OsHAC1;1 and OsHAC1;2 are arsenate reductases that play an important role in restricting As accumulation in rice shoots and grain.

  20. Development of a Molecular System for Studying Microbial Arsenate Respiration

    NASA Astrophysics Data System (ADS)

    Saltikov, C. W.; Newman, D. K.

    2002-12-01

    The toxic element arsenic is a major contaminant of many groundwaters and surface waters throughout the world. Arsenic enrichment is primarily of geological origin resulting from weathering processes and geothermal activity. Not surprisingly, microorganisms inhabiting anoxic arsenic-contaminated environments have evolved to exploit arsenate during respiration. Numerous bacteria have been isolated that use arsenate as a terminal electron acceptor for respiratory growth. The diversity of this metabolism appears to be widespread throughout the microbial tree of life, suggesting respiratory arsenate reduction is ancient in origin. Yet little is known about the molecular mechanisms for how these organisms respire arsenate. We have developed a model system in Shewanella trabarsenatis, strain ANA-3, a facultative anaerobe that respires arsenate and tolerates high concentrations of arsenite (10 mM). Through loss-of-function studies, we have identified genes involved in both arsenic resistance and arsenate respiration. The genes that confer resistance to arsenic are homologous to the well-characterized ars operon of E. coli. However, the respiratory arsenate reductase is predicted to encode a novel protein that shares homologous regions (~ 40 % similarity) to molybdopterin anaerobic reductases specific for DMSO, thiosulfate, nitrate, and polysulfide. I will discuss our emerging model for how strain ANA-3 respires arsenate and the relationship between arsenite resistance and arsenate respiration. I will also highlight the relevance of this type of analysis for biogeochemical studies.

  1. Solution structure of an arsenate reductase-related protein, YffB, from Brucella melitensis, the etiological agent responsible for brucellosis

    PubMed Central

    Buchko, Garry W.; Hewitt, Stephen N.; Napuli, Alberto J.; Van Voorhis, Wesley C.; Myler, Peter J.

    2011-01-01

    Brucella melitensis is the etiological agent responsible for brucellosis. Present in the B. melitensis genome is a 116-residue protein related to arsenate reductases (Bm-YffB; BR0369). Arsenate reductases (ArsC) convert arsenate ion (H2AsO4 −), a compound that is toxic to bacteria, to arsenite ion (AsO2 −), a product that may be efficiently exported out of the cell. Consequently, Bm-YffB is a potential drug target because if arsenate reduction is the protein’s major biological function then disabling the cell’s ability to reduce arsenate would make these cells more sensitive to the deleterious effects of arsenate. Size-exclusion chromatography and NMR spectroscopy indicate that Bm-YffB is a monomer in solution. The solution structure of Bm-YffB (PDB entry 2kok) shows that the protein consists of two domains: a four-stranded mixed β-sheet flanked by two α-helices on one side and an α-helical bundle. The α/β domain is characteristic of the fold of thioredoxin-like proteins and the overall structure is generally similar to those of known arsenate reductases despite the marginal sequence similarity. Chemical shift perturbation studies with 15N-labeled Bm-YffB show that the protein binds reduced glutathione at a site adjacent to a region similar to the HX 3CX 3R catalytic sequence motif that is important for arsenic detoxification activity in the classical arsenate-reductase family of proteins. The latter observation supports the hypothesis that the ArsC-YffB family of proteins may function as glutathione-dependent thiol reductases. However, comparison of the structure of Bm-YffB with the structures of proteins from the classical ArsC family suggest that the mechanism and possibly the function of Bm-YffB and other related proteins (ArsC-YffB) may differ from those of the ArsC family of proteins. PMID:21904062

  2. Solution structure of an arsenate reductase-related protein, YffB, from Brucella melitensis, the etiological agent responsible for brucellosis.

    PubMed

    Buchko, Garry W; Hewitt, Stephen N; Napuli, Alberto J; Van Voorhis, Wesley C; Myler, Peter J

    2011-09-01

    Brucella melitensis is the etiological agent responsible for brucellosis. Present in the B. melitensis genome is a 116-residue protein related to arsenate reductases (Bm-YffB; BR0369). Arsenate reductases (ArsC) convert arsenate ion (H(2)AsO(4)(-)), a compound that is toxic to bacteria, to arsenite ion (AsO(2)(-)), a product that may be efficiently exported out of the cell. Consequently, Bm-YffB is a potential drug target because if arsenate reduction is the protein's major biological function then disabling the cell's ability to reduce arsenate would make these cells more sensitive to the deleterious effects of arsenate. Size-exclusion chromatography and NMR spectroscopy indicate that Bm-YffB is a monomer in solution. The solution structure of Bm-YffB (PDB entry 2kok) shows that the protein consists of two domains: a four-stranded mixed β-sheet flanked by two α-helices on one side and an α-helical bundle. The α/β domain is characteristic of the fold of thioredoxin-like proteins and the overall structure is generally similar to those of known arsenate reductases despite the marginal sequence similarity. Chemical shift perturbation studies with (15)N-labeled Bm-YffB show that the protein binds reduced glutathione at a site adjacent to a region similar to the HX(3)CX(3)R catalytic sequence motif that is important for arsenic detoxification activity in the classical arsenate-reductase family of proteins. The latter observation supports the hypothesis that the ArsC-YffB family of proteins may function as glutathione-dependent thiol reductases. However, comparison of the structure of Bm-YffB with the structures of proteins from the classical ArsC family suggest that the mechanism and possibly the function of Bm-YffB and other related proteins (ArsC-YffB) may differ from those of the ArsC family of proteins.

  3. Hydrogen formation by an arsenate-reducing Pseudomonas putida, isolated from arsenic-contaminated groundwater in West Bengal, India.

    PubMed

    Freikowski, Dominik; Winter, Josef; Gallert, Claudia

    2010-12-01

    Anaerobic growth of a newly isolated Pseudomonas putida strain WB from an arsenic-contaminated soil in West Bengal, India on glucose, L: -lactate, and acetate required the presence of arsenate, which was reduced to arsenite. During aerobic growth in the presence of arsenite arsenate was formed. Anaerobic growth of P. putida WB on glucose was made possible presumably by the non-energy-conserving arsenate reductase ArsC with energy derived only from substrate level phosphorylation. Two moles of acetate were generated intermediarily and the reducing equivalents of glycolysis and pyruvate decarboxylation served for arsenate reduction or were released as H(2). Anaerobic growth on acetate and lactate was apparently made possible by arsenate reductase ArrA coupled to respiratory electron chain energy conservation. In the presence of arsenate, both substrates were totally oxidized to CO(2) and H(2) with part of the H(2) serving for respiratory arsenate reduction to deliver energy for growth. The growth yield for anaerobic glucose degradation to acetate was Y (Glucose) = 20 g/mol, leading to an energy coefficient of Y (ATP) = 10 g/mol adenosine-5'-triphosphate (ATP), if the Emden-Meyerhof-Parnas pathway with generation of 2 mol ATP/mol glucose was used. During growth on lactate and acetate no substrate chain phosphorylation was possible. The energy gain by reduction of arsenate was Y (Arsenate) = 6.9 g/mol, which would be little less than one ATP/mol of arsenate.

  4. Glutathione-S-transferase-omega [MMA(V) reductase] knockout mice: Enzyme and arsenic species concentrations in tissues after arsenate administration

    SciTech Connect

    Chowdhury, Uttam K.; Zakharyan, Robert A.; Hernandez, Alba; Avram, Mihaela D.; Kopplin, Michael J.; Aposhian, H. Vasken . E-mail: aposhian@u.arizona.edu

    2006-11-01

    Inorganic arsenic is a human carcinogen to which millions of people are exposed via their naturally contaminated drinking water. Its molecular mechanisms of carcinogenicity have remained an enigma, perhaps because arsenate is biochemically transformed to at least five other arsenic-containing metabolites. In the biotransformation of inorganic arsenic, GSTO1 catalyzes the reduction of arsenate, MMA(V), and DMA(V) to the more toxic + 3 arsenic species. MMA(V) reductase and human (hGSTO1-1) are identical proteins. The hypothesis that GST-Omega knockout mice biotransformed inorganic arsenic differently than wild-type mice has been tested. The livers of male knockout (KO) mice, in which 222 bp of Exon 3 of the GSTO1 gene were eliminated, were analyzed by PCR for mRNA. The level of transcripts of the GSTO1 gene in KO mice was 3.3-fold less than in DBA/1lacJ wild-type (WT) mice. The GSTO2 transcripts were about two-fold less in the KO mouse. When KO and WT mice were injected intramuscularly with Na arsenate (4.16 mg As/kg body weight); tissues removed at 0.5, 1, 2, 4, 8, and 12 h after arsenate injection; and the arsenic species measured by HPLC-ICP-MS, the results indicated that the highest concentration of the recently discovered and very toxic MMA(III), a key biotransformant, was in the kidneys of both KO and WT mice. The highest concentration of DMA(III) was in the urinary bladder tissue for both the KO and WT mice. The MMA(V) reducing activity of the liver cytosol of KO mice was only 20% of that found in wild-type mice. There appears to be another enzyme(s) other than GST-O able to reduce arsenic(V) species but to a lesser extent. This and other studies suggest that each step of the biotransformation of inorganic arsenic has an alternative enzyme to biotransform the arsenic substrate.

  5. Crystallization and preliminary crystallographic characterization of LmACR2, an arsenate/antimonate reductase from Leishmania major

    SciTech Connect

    Bisacchi, Davide; Zhou, Yao; Rosen, Barry P.; Mukhopadhyay, Rita; Bordo, Domenico

    2006-10-01

    LmACR2 from L. major is the first rhodanese-like enzyme directly involved in the reduction of arsenate and antimonate to be crystallized. Diffraction data have been collected to 1.99 Å resolution using synchrotron X-rays. Arsenic is present in the biosphere owing either to the presence of pesticides and herbicides used in agricultural and industrial activities or to leaching from geological formations. The health effects of prolonged exposure to arsenic can be devastating and may lead to various forms of cancer. Antimony(V), which is chemically very similar to arsenic, is used instead in the treatment of leishmaniasis, an infection caused by the protozoan parasite Leishmania sp.; the reduction of pentavalent antimony contained in the drug Pentostam to the active trivalent form arises from the presence in the Leishmania genome of a gene, LmACR2, coding for the protein LmACR2 (14.5 kDa, 127 amino acids) that displays weak but significant sequence similarity to the catalytic domain of Cdc25 phosphatase and to rhodanese enzymes. For structural characterization, LmACR2 was overexpressed, purified to homogeneity and crystallized in a trigonal space group (P321 or P3{sub 1}21/P3{sub 2}21). The protein crystallized in two distinct trigonal crystal forms, with unit-cell parameters a = b = 111.0, c = 86.1 Å and a = b = 111.0, c = 175.6 Å, respectively. At a synchrotron beamline, the diffraction pattern extended to a resolution limit of 1.99 Å.

  6. Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1.

    PubMed

    Ohtsuka, Toshihiko; Yamaguchi, Noriko; Makino, Tomoyuki; Sakurai, Kazuhiro; Kimura, Kenta; Kudo, Keitaro; Homma, Eri; Dong, Dian Tao; Amachi, Seigo

    2013-06-18

    Dissimilatory As(V) (arsenate)-reducing bacteria may play an important role in arsenic release from anoxic sediments in the form of As(III) (arsenite). Although respiratory arsenate reductase genes (arrA) closely related to Geobacter species have been frequently detected in arsenic-rich sediments, it is still unclear whether they directly participate in arsenic release, mainly due to lack of pure cultures capable of arsenate reduction. In this study, we isolated a novel dissimilatory arsenate-reducing bacterium, strain OR-1, from Japanese paddy soil, and found that it was phylogenetically closely related to Geobacter pelophilus. OR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, and fumarate as electron acceptors. OR-1 catalyzed dissolution of arsenic from arsenate-adsorbed ferrihydrite, while Geobacter metallireducens GS-15 did not. Furthermore, inoculation of washed cells of OR-1 into sterilized paddy soil successfully restored arsenic release. Arsenic K-edge X-ray absorption near-edge structure analysis revealed that strain OR-1 reduced arsenate directly on the soil solid phase. Analysis of putative ArrA sequences from paddy soils suggested that Geobacter-related bacteria, including those closely related to OR-1, play an important role in arsenic release from paddy soils. Our results provide direct evidence for arsenic dissolution by Geobacter species and support the hypothesis that Geobacter species play a significant role in reduction and mobilization of arsenic in flooded soils and anoxic sediments.

  7. Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1.

    PubMed

    Cuebas, Mariola; Villafane, Aramis; McBride, Michelle; Yee, Nathan; Bini, Elisabetta

    2011-07-01

    Geobacillus kaustophilus strain A1 was previously isolated from a geothermal environment for its ability to grow in the presence of high arsenate levels. In this study, the molecular mechanisms of arsenate resistance of the strain were investigated. As(V) was reduced to As(III), as shown by HPLC analysis. Consistent with the observation that the micro-organism is not capable of anaerobic growth, no respiratory arsenate reductases were identified. Using specific PCR primers based on the genome sequence of G. kaustophilus HTA426, three unlinked genes encoding detoxifying arsenate reductases were detected in strain A1. These genes were designated arsC1, arsC2 and arsC3. While arsC3 is a monocistronic locus, sequencing of the regions flanking arsC1 and arsC2 revealed the presence of additional genes encoding a putative arsenite transporter and an ArsR-like regulator upstream of each arsenate reductase, indicating the presence of sequences with putative roles in As(V) reduction, As(III) export and arsenic-responsive regulation. RT-PCR demonstrated that both sets of genes were co-transcribed. Furthermore, arsC1 and arsC2, monitored by quantitative real-time RT-PCR, were upregulated in response to As(V), while arsC3 was constitutively expressed at a low level. A mechanism for regulation of As(V) detoxification by Geobacillus that is both consistent with our findings and relevant to the biogeochemical cycle of arsenic and its mobility in the environment is proposed.

  8. Succinate-cytochrome c reductase: assessment of its value in the investigation of defects of the respiratory chain.

    PubMed

    Taylor, R W; Birch-Machin, M A; Bartlett, K; Turnbull, D M

    1993-06-19

    Defects of the respiratory chain are important causes of human disease and one of the most commonly used assays in the investigation of these patients is the measurement of succinate-cytochrome c reductase. However, this assay measures several components of the respiratory chain and the ability to detect a partial defect in one enzyme complex will depend on the amount of control exerted by that enzyme step on overall electron flux. We show that measurement of succinate-cytochrome c reductase activity may fail to detect partial defects of complex III and therefore is of limited diagnostic value in the identification of complex III defects. However, complex II is a major point of control of flux through succinate-cytochrome reductase and it is likely that measurement of the latter will detect defects of complex II.

  9. The evolution of respiratory O2/NO reductases: an out-of-the-phylogenetic-box perspective

    PubMed Central

    Ducluzeau, Anne-Lise; Schoepp-Cothenet, Barbara; van Lis, Robert; Baymann, Frauke; Russell, Michael J.; Nitschke, Wolfgang

    2014-01-01

    Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O2-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O2 in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O2-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O2-levels on life is the evolutionary history of the enzyme allowing organisms to tap into the redox power of molecular oxygen, i.e. the bioenergetic O2 reductases, alias the cytochrome and quinol oxidases. Consequently, molecular phylogenies reconstructed for this enzyme superfamily have been exploited over the last two decades in attempts to elucidate the interlocking between O2 levels in the environment and the evolution of respiratory bioenergetic processes. Although based on strictly identical datasets, these phylogenetic approaches have led to diametrically opposite scenarios with respect to the history of both the enzyme superfamily and molecular oxygen on the Earth. In an effort to overcome the deadlock of molecular phylogeny, we here review presently available structural, functional, palaeogeochemical and thermodynamic information pertinent to the evolution of the superfamily (which notably also encompasses the subfamily of nitric oxide reductases). The scenario which, in our eyes, most closely fits the ensemble of these non-phylogenetic data, sees the low O2-affinity SoxM- (or A-) type enzymes as the most recent evolutionary innovation and the high-affinity O2 reductases (SoxB or B and cbb3 or C) as arising independently from NO-reducing precursor enzymes. PMID:24968694

  10. Crystal structures of nitric oxide reductases provide key insights into functional conversion of respiratory enzymes.

    PubMed

    Tosha, Takehiko; Shiro, Yoshitsugu

    2013-03-01

    Respiration is an essential biological process to get bioenergy, ATP, for all kingdoms of life. Cytochrome c oxidase (COX) plays central role in aerobic respiration, catalyzing the reduction of O(2) coupled with pumping proton across the biological membrane. Nitric oxide reductase (NOR) involved in anaerobic nitrate respiration is suggested to be evolutionary related to COX and share the same progenitor with COX, on the basis of the amino acid sequence homology. Contrary to COX, NOR catalyzes the reduction of nitric oxide and shows no proton pumping ability. Thus, the respiratory enzyme acquires (or loses) proton pumping ability in addition to the conversion of the catalytic property along with the environmental change on earth. Recently, we solved the structures of two types of NORs, which provides novel insights into the functional conversion of the respiratory enzymes. In this review, we focus on the structural similarities and differences between COXs and NORs and discuss possible mechanism for the functional conversion of these enzymes during molecular evolution.

  11. Identification of anaerobic arsenite-oxidizing and arsenate-reducing bacteria associated with an alkaline saline lake in Khovsgol, Mongolia.

    PubMed

    Hamamura, Natsuko; Itai, Takaaki; Liu, Yitai; Reysenbach, Anna-Louise; Damdinsuren, Narantuya; Inskeep, William P

    2014-10-01

    Microbial arsenic transformation pathways associated with a saline lake located in northern Mongolia were examined using molecular biological and culturing approaches. Bacterial 16S rRNA gene sequences recovered from saline lake sediments and soils were affiliated with haloalkaliphiles, including Bacillus and Halomonas spp. Diverse sequences of arsenate respiratory reductase (arrA) and a new group of arsenite oxidase (arxA) genes were also identified. Pure cultures of arsenate-reducing Nitrincola strain and anaerobic arsenite-oxidizing Halomonas strain were isolated. The chemoorganotrophic Halomonas strain contains arxA gene similar to that of a chemoautotrophic arsenite-oxidizing Alkalilimnicola ehrlichii strain MLHE-1. These results revealed the diversity of arsenic transformation pathways associated with a geographically distinct saline system and the potential contribution of arx-dependent arsenite oxidation by heterotrophic bacteria.

  12. Role of Respiratory Nitrate Reductase in Ability of Pseudomonas fluorescens YT101 To Colonize the Rhizosphere of Maize

    PubMed Central

    Ghiglione, Jean-François; Gourbiere, François; Potier, Patrick; Philippot, Laurent; Lensi, Robert

    2000-01-01

    Selection of the denitrifying community by plant roots (i.e., increase in the denitrifier/total heterotroph ratio in the rhizosphere) has been reported by several authors. However, very few studies to evaluate the role of the denitrifying function itself in the selection of microorganisms in the rhizosphere have been performed. In the present study, we compared the rhizosphere survival of the denitrifying Pseudomonas fluorescens YT101 strain with that of its isogenic mutant deficient in the ability to synthesize the respiratory nitrate reductase, coinoculated in nonplanted or planted soil. We demonstrated that under nonlimiting nitrate conditions, the denitrifying wild-type strain had an advantage in the ability to colonize the rhizosphere of maize. Investigations of the effect of the inoculum characteristics (density of the total inoculum and relative proportions of mutant and wild-type strains) on the outcome of the selection demonstrated that the selective effect of the plant was expressed only during the phase of bacterial multiplication and that the intensity of selection was dependent on the magnitude of this phase. Moreover, application of the de Wit replacement series technique to our results suggests that the advantage of the wild-type strain was maximal when the ratio between the two strains in the inoculum was close to 1:1. This work constitutes the first direct demonstration that the presence of a functional structural gene encoding the respiratory nitrate reductase confers higher rhizosphere competence to a microorganism. PMID:10966422

  13. Part of respiratory nitrate reductase of Klebsiella aerogenes is intimately associated with the peptidoglycan.

    PubMed

    Abraham, P R; Wientjes, F B; Nanninga, N; Van't Riet, J

    1987-02-01

    Lysozyme digestion and sonication of sodium dodecyl sulfate (SDS)-purified Klebsiella aerogenes murein sacculi resulted in the quantitative release of both subunits of nitrate reductase, as well as a number of other cytoplasmic membrane polypeptides (5.2%, by weight, of the total membrane proteins). Similar results were obtained after lysozyme digestion of SDS-prepared peptidoglycan fragments, which excluded the phenomenon of simple trapping of the polypeptides by the surrounding peptidoglycan matrix. About 28% of membrane-bound nitrate reductase appears to be tightly associated with the peptidoglycan. Additional evidence for this association was demonstrated by positive immunogold labeling of SDS-murein sacculi and thin sections of plasmolyzed bacteria. Qualitative amino acid analysis of trypsin-treated sacculi, a tryptic product of holo-nitrate reductase, and amino- and carboxypeptidase digests of both nitrate reductase subunits indicated the possible existence of a terminal anchoring peptide containing the following amino acids: (Gly)n, Trp, Ser, Pro, Ile, Leu, Phe, Cys, Tyr, Asp, and Lys.

  14. Characterization of the nirK gene encoding the respiratory, Cu-containing nitrite reductase of Bradyrhizobium japonicum.

    PubMed

    Velasco, L; Mesa, S; Delgado, M J; Bedmar, E J

    2001-10-31

    The structural gene, nirK, for the respiratory Cu-containing nitrite reductase from Bradyrhizobium japonicum USDA110 has been isolated and sequenced. The deduced amino acid sequence exhibited a high degree of similarity to other Cu-containing nitrite reductases from various sources. The full-length protein included a signal peptide for protein export. Analysis of the sequence upstream from the structural nirK gene revealed the presence of an anaerobox located 83 base pairs from the putative translational start codon. Cells of strain GRK308, a nitrite reductase-deficient derivative of strain USDA110, were unable to grow when cultured under microaerobic conditions (1% O(2)) in the presence of either nitrate or nitrite. Maximal expression of a nirK-lacZ fusion in strain USDA110 required simultaneously both low level oxygen conditions and the presence of nitrate. Expression of beta-galactosidase activity was not detected in the B. japonicum fixL 7403, fixJ 7360 and fixK(2) 9043 mutants transformed with the nirK-lacZ fusion after incubation of the cells under oxygen-limiting conditions either with or without nitrate. Complementation of B. japonicum 9043 with the fixK(2) gene restored beta-galactosidase activity to levels similar to those found in the parental strain. These results suggest that nirK expression depends on the low-oxygen-responsive two-component regulatory system FixLJ and on the Fnr/FixK-like DNA binding protein FixK(2).

  15. Sulfide oxidation coupled to arsenate reduction by a diverse microbial community in a soda lake.

    PubMed

    Hollibaugh, James T; Budinoff, Charles; Hollibaugh, Ryan A; Ransom, Briana; Bano, Nasreen

    2006-03-01

    We characterized the arsenate-reducing, sulfide-oxidizing population of Mono Lake, California, by analyzing the distribution and diversity of rrnA, cbbL, and dissimilatory arsenate reductase (arrA) genes in environmental DNA, arsenate-plus sulfide-amended lake water, mixed cultures, and isolates. The arsenate-reducing community was diverse. An organism represented by an rrnA sequence previously retrieved from Mono Lake and affiliated with the Desulfobulbaceae (Deltaproteobacteria) appears to be an important member of the arsenate-reducing, sulfide-oxidizing community. Sulfide oxidation coupled with arsenate reduction appears to proceed via a two-electron transfer, resulting in the production of arsenite and an intermediate S compound that is subsequently disproportionated. A realgar-like As/S mineral was formed in some experiments.

  16. Substrate-dependent modulation of the enzymatic catalytic activity: reduction of nitrate, chlorate and perchlorate by respiratory nitrate reductase from Marinobacter hydrocarbonoclasticus 617.

    PubMed

    Marangon, Jacopo; Paes de Sousa, Patrícia M; Moura, Isabel; Brondino, Carlos D; Moura, José J G; González, Pablo J

    2012-07-01

    The respiratory nitrate reductase complex (NarGHI) from Marinobacter hydrocarbonoclasticus 617 (Mh, formerly Pseudomonas nautica 617) catalyzes the reduction of nitrate to nitrite. This reaction is the first step of the denitrification pathway and is coupled to the quinone pool oxidation and proton translocation to the periplasm, which generates the proton motive force needed for ATP synthesis. The Mh NarGH water-soluble heterodimer has been purified and the kinetic and redox properties have been studied through in-solution enzyme kinetics, protein film voltammetry and spectropotentiometric redox titration. The kinetic parameters of Mh NarGH toward substrates and inhibitors are consistent with those reported for other respiratory nitrate reductases. Protein film voltammetry showed that at least two catalytically distinct forms of the enzyme, which depend on the applied potential, are responsible for substrate reduction. These two forms are affected differentially by the oxidizing substrate, as well as by pH and inhibitors. A new model for the potential dependence of the catalytic efficiency of Nars is proposed.

  17. ArxA, a new clade of arsenite oxidase within the DMSO reductase family of molybdenum oxidoreductases

    USGS Publications Warehouse

    Zargar, Kamrun; Conrad, Alison; Bernick, David L.; Lowe, Todd M.; Stolc, Viktor; Hoeft, Shelley; Oremland, Ronald S.; Stolz, John; Saltikov, Chad W.

    2012-01-01

    Arsenotrophy, growth coupled to autotrophic arsenite oxidation or arsenate respiratory reduction, occurs only in the prokaryotic domain of life. The enzymes responsible for arsenotrophy belong to distinct clades within the DMSO reductase family of molybdenum-containing oxidoreductases: specifically arsenate respiratory reductase, ArrA, and arsenite oxidase, AioA (formerly referred to as AroA and AoxB). A new arsenite oxidase clade, ArxA, represented by the haloalkaliphilic bacterium Alkalilimnicola ehrlichii strain MLHE-1 was also identified in the photosynthetic purple sulfur bacterium Ectothiorhodospira sp. strain PHS-1. A draft genome sequence of PHS-1 was completed and an arx operon similar to MLHE-1 was identified. Gene expression studies showed that arxA was strongly induced with arsenite. Microbial ecology investigation led to the identification of additional arxA-like sequences in Mono Lake and Hot Creek sediments, both arsenic-rich environments in California. Phylogenetic analyses placed these sequences as distinct members of the ArxA clade of arsenite oxidases. ArxA-like sequences were also identified in metagenome sequences of several alkaline microbial mat environments of Yellowstone National Park hot springs. These results suggest that ArxA-type arsenite oxidases appear to be widely distributed in the environment presenting an opportunity for further investigations of the contribution of Arx-dependent arsenotrophy to the arsenic biogeochemical cycle.

  18. Redox-dependent open and closed forms of the active site of the bacterial respiratory nitric-oxide reductase revealed by cyanide binding studies.

    PubMed

    Grönberg, Karin L C; Watmough, Nicholas J; Thomson, Andrew J; Richardson, David J; Field, Sarah J

    2004-04-23

    The bacterial respiratory nitric-oxide reductase (NOR) catalyzes the respiratory detoxification of nitric oxide in bacteria and Archaea. It is a member of the well known super-family of heme-copper oxidases but has a [heme Fe-non-heme Fe] active site rather than the [heme Fe-Cu(B)] active site normally associated with oxygen reduction. Paracoccus denitrificans NOR is spectrally characterized by a ligand-to-metal charge transfer absorption band at 595 nm, which arises from the high spin ferric heme iron of a micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site. On reduction of the nonheme iron, the micro-oxo bridge is broken, and the ferric heme iron is hydroxylated or hydrated, depending on the pH. At present, the catalytic cycle of NOR is a matter of much debate, and it is not known to which redox state(s) of the enzyme nitric oxide can bind. This study has used cyanide to probe the nature of the active site in a number of different redox states. Our observations suggest that the micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site represents a closed or resting state of NOR that can be opened by reduction of the non-heme iron.

  19. Structures of reduced and ligand-bound nitric oxide reductase provide insights into functional differences in respiratory enzymes.

    PubMed

    Sato, Nozomi; Ishii, Shoko; Sugimoto, Hiroshi; Hino, Tomoya; Fukumori, Yoshihiro; Sako, Yoshihiko; Shiro, Yoshitsugu; Tosha, Takehiko

    2014-07-01

    Nitric oxide reductase (NOR) catalyzes the generation of nitrous oxide (N2O) via the reductive coupling of two nitric oxide (NO) molecules at a heme/non-heme Fe center. We report herein on the structures of the reduced and ligand-bound forms of cytochrome c-dependent NOR (cNOR) from Pseudomonas aeruginosa at a resolution of 2.3-2.7 Å, to elucidate structure-function relationships in NOR, and compare them to those of cytochrome c oxidase (CCO) that is evolutionarily related to NOR. Comprehensive crystallographic refinement of the CO-bound form of cNOR suggested that a total of four atoms can be accommodated at the binuclear center. Consistent with this, binding of bulky acetaldoxime (CH3-CH=N-OH) to the binuclear center of cNOR was confirmed by the structural analysis. Active site reduction and ligand binding in cNOR induced only ∼0.5 Å increase in the heme/non-heme Fe distance, but no significant structural change in the protein. The highly localized structural change is consistent with the lack of proton-pumping activity in cNOR, because redox-coupled conformational changes are thought to be crucial for proton pumping in CCO. It also permits the rapid decomposition of cytotoxic NO in denitrification. In addition, the shorter heme/non-heme Fe distance even in the bulky ligand-bound form of cNOR (∼4.5 Å) than the heme/Cu distance in CCO (∼5 Å) suggests the ability of NOR to maintain two NO molecules within a short distance in the confined space of the active site, thereby facilitating N-N coupling to produce a hyponitrite intermediate for the generation of N2O.

  20. ARSENATE REDUCTION BY ORGANIC COMPOUNDS

    EPA Science Inventory

    Arsenic is found in a variety of forms and oxidation states depending on soil pH and redox conditions. Under oxic conditions, arsenate is thermodynamically favored but arsenite, the more toxic and mobile form of arsenic, is favored under mildly reducing conditions. In many soil...

  1. Arsenate adsorption by unsaturated alluvial sediments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arsenate adsorption as a function of solution arsenic concentration and solution pH was investigated on five alluvial sediments from the Antelope Valley, Western Mojave Desert, California. Arsenate adsorption increased with increasing solution pH, exhibited a maximum around pH 4 to 5, and then decr...

  2. Nitrate and periplasmic nitrate reductases

    PubMed Central

    Sparacino-Watkins, Courtney; Stolz, John F.; Basu, Partha

    2014-01-01

    The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types – periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

  3. Definition of cytochrome c binding domains by chemical modification: Kinetics of reaction with beef mitochondrial reductase and functional organization of the respiratory chain*

    PubMed Central

    Speck, Samuel H.; Ferguson-Miller, Shelagh; Osheroff, Neil; Margoliash, E.

    1979-01-01

    An assay has been developed to study the steady-state kinetics of the reduction of cytochrome c by purified beef heart mitochondrial cytochrome c reductase (cytochrome bc1 complex, complex III). An analogue of coenzyme Q2 (2,3-dimethoxy-5-methyl-6-decylhydroquinone) was employed as an antimycin-sensitive reductant. The kinetics of reaction of ten different mono(4-carboxy-2,6-dinitrophenyl) derivatives of horse cytochrome c were determined. The modified proteins showed higher apparent Km values than the native protein and greater sensitivity to ionic strength, defining an interaction domain on cytochrome c for purified cytochrome c reductase. This interaction site is located on the front surface of the molecule (which contains the exposed heme edge) and surrounds the point at which the positive end of the dipole axis crosses the surface of the protein. The site is similar to that previously determined for mitochondrial cytochrome c oxidase and yeast cytochrome c peroxidase, suggesting that the primary interaction with redox partners is directed by the dipolar charge distribution on cytochrome c. The extensive overlapping of the interaction domains for the mitochondrial cytochrome c oxidase and reductase indicates that cytochrome c must be mobile in order to transfer electrons between them, depending on their relative positions in the membrane. Whether such mobility is necessary in intact mitochondria depends on whether the interactions with the complete membrane-bound system are the same as with the purified components. PMID:218193

  4. Biotransformation of the pesticide sodium arsenate.

    PubMed

    Shariatpanahi, M; Anderson, A C; Abdelghani, A A; Englande, A J; Hughes, J; Wilkinson, R F

    1981-01-01

    Biotransformation is an important parameter in assessing the environmental impact and fate of pesticides since metabolites produced may be either more or less toxic than the parent compound. Sodium arsenate (+5 inorganic), the wood preservative and insecticide, may be converted to both inorganic (+3) and organic compounds (-3) by microorganisms in soil, sediment and water bodies. Biotransformation of sodium arsenate was studied in pure cultures of 5 bacterial species using a mineral salt and limited carbon source medium. Arsenate concentrations were 10 microgram/ml and 100 microgram/ml of arsenic respectively. The rate of biodegradation of the parent compound was described by a first order composite exponential equation of the form Ct = C1e-k1t+C2e-k2t. Rates of production of metabolites (arsenite, monomethylarsine, dimethylarsine and trimethylarsine) were described by a first order exponential equation of the form Ct = Co (1-e-kt).

  5. Dissolution of Arsenic Minerals Mediated by Dissimilatory Arsenate Reducing Bacteria: Estimation of the Physiological Potential for Arsenic Mobilization

    PubMed Central

    Lukasz, Drewniak; Liwia, Rajpert; Aleksandra, Mantur; Aleksandra, Sklodowska

    2014-01-01

    The aim of this study was characterization of the isolated dissimilatory arsenate reducing bacteria in the context of their potential for arsenic removal from primary arsenic minerals through reductive dissolution. Four strains, Shewanella sp. OM1, Pseudomonas sp. OM2, Aeromonas sp. OM4, and Serratia sp. OM17, capable of anaerobic growth with As (V) reduction, were isolated from microbial mats from an ancient gold mine. All of the isolated strains: (i) produced siderophores that promote dissolution of minerals, (ii) were resistant to dissolved arsenic compounds, (iii) were able to use the dissolved arsenates as the terminal electron acceptor, and (iii) were able to use copper minerals containing arsenic minerals (e.g., enargite) as a respiratory substrate. Based on the results obtained in this study, we postulate that arsenic can be released from some As-bearing polymetallic minerals (such as copper ore concentrates or middlings) under reductive conditions by dissimilatory arsenate reducers in indirect processes. PMID:24724102

  6. Dissolution of arsenic minerals mediated by dissimilatory arsenate reducing bacteria: estimation of the physiological potential for arsenic mobilization.

    PubMed

    Lukasz, Drewniak; Liwia, Rajpert; Aleksandra, Mantur; Aleksandra, Sklodowska

    2014-01-01

    The aim of this study was characterization of the isolated dissimilatory arsenate reducing bacteria in the context of their potential for arsenic removal from primary arsenic minerals through reductive dissolution. Four strains, Shewanella sp. OM1, Pseudomonas sp. OM2, Aeromonas sp. OM4, and Serratia sp. OM17, capable of anaerobic growth with As (V) reduction, were isolated from microbial mats from an ancient gold mine. All of the isolated strains: (i) produced siderophores that promote dissolution of minerals, (ii) were resistant to dissolved arsenic compounds, (iii) were able to use the dissolved arsenates as the terminal electron acceptor, and (iii) were able to use copper minerals containing arsenic minerals (e.g., enargite) as a respiratory substrate. Based on the results obtained in this study, we postulate that arsenic can be released from some As-bearing polymetallic minerals (such as copper ore concentrates or middlings) under reductive conditions by dissimilatory arsenate reducers in indirect processes.

  7. Arsenate Resistance in the Unicellular Marine Diazotroph Crocosphaera watsonii.

    PubMed

    Dyhrman, Sonya T; Haley, Sheean T

    2011-01-01

    The toxic arsenate ion can behave as a phosphate analog, and this can result in arsenate toxicity especially in areas with elevated arsenate to phosphate ratios like the surface waters of the ocean gyres. In these systems, cellular arsenate resistance strategies would allow phytoplankton to ameliorate the effects of arsenate transport into the cell. Despite the potential coupling between arsenate and phosphate cycling in oligotrophic marine waters, relatively little is known about arsenate resistance in the nitrogen-fixing marine cyanobacteria that are key components of the microbial community in low nutrient systems. The unicellular diazotroph, Crocosphaera watsonii WH8501, was able to grow at reduced rates with arsenate additions up to 30 nM, and estimated arsenate to phosphate ratios of 6:1. The genome of strain WH8501 contains homologs for arsA, arsH, arsB, and arsC, allowing for the reduction of arsenate to arsenite and the pumping of arsenite out of the cell. The short-term addition of arsenate to the growth medium had no effect on nitrogen fixation. However, arsenate addition did result in the up-regulation of the arsB gene with increasing arsenate concentrations, indicating the induction of the arsenate detoxification response. The arsB gene was also up-regulated by phosphorus stress in concert with a gene encoding the high-affinity phosphate binding protein pstS. Both genes were down-regulated when phosphate was re-fed to phosphorus-stressed cells. A field survey of surface water from the low phosphate western North Atlantic detected expression of C. watsoniiarsB, suggestive of the potential importance of arsenate resistance strategies in this and perhaps other systems.

  8. Arsenolysis and Thiol-Dependent Arsenate Reduction

    EPA Science Inventory

    Conversion of arsenate to arsenite is a critical event in the pathway that leads from inorganic arsenic to a variety of methylated metabolites. The formation of methylated metabolites influences distribution and retention of arsenic and affects the reactivity and toxicity of thes...

  9. Thioredoxin reductase.

    PubMed Central

    Mustacich, D; Powis, G

    2000-01-01

    The mammalian thioredoxin reductases (TrxRs) are a family of selenium-containing pyridine nucleotide-disulphide oxidoreductases with mechanistic and sequence identity, including a conserved -Cys-Val-Asn-Val-Gly-Cys- redox catalytic site, to glutathione reductases. TrxRs catalyse the NADPH-dependent reduction of the redox protein thioredoxin (Trx), as well as of other endogenous and exogenous compounds. The broad substrate specificity of mammalian TrxRs is due to a second redox-active site, a C-terminal -Cys-SeCys- (where SeCys is selenocysteine), that is not found in glutathione reductase or Escherichia coli TrxR. There are currently two confirmed forms of mammalian TrxRs, TrxR1 and TrxR2, and it is possible that other forms will be identified. The availability of Se is a key factor determining TrxR activity both in cell culture and in vivo, and the mechanism(s) for the incorporation of Se into TrxRs, as well as the regulation of TrxR activity, have only recently begun to be investigated. The importance of Trx to many aspects of cell function make it likely that TrxRs also play a role in protection against oxidant injury, cell growth and transformation, and the recycling of ascorbate from its oxidized form. Since TrxRs are able to reduce a number of substrates other than Trx, it is likely that additional biological effects will be discovered for TrxR. Furthermore, inhibiting TrxR with drugs may lead to new treatments for human diseases such as cancer, AIDS and autoimmune diseases. PMID:10657232

  10. Functional roles of arcA, etrA, cyclic AMP (cAMP)-cAMP receptor protein, and cya in the arsenate respiration pathway in Shewanella sp. strain ANA-3.

    PubMed

    Murphy, Julie N; Durbin, K James; Saltikov, Chad W

    2009-02-01

    Microbial arsenate respiration can enhance arsenic release from arsenic-bearing minerals--a process that can cause arsenic contamination of water. In Shewanella sp. strain ANA-3, the arsenate respiration genes (arrAB) are induced under anaerobic conditions with arsenate and arsenite. Here we report how genes that encode anaerobic regulator (arcA and etrA [fnr homolog]) and carbon catabolite repression (crp and cya) proteins affect arsenate respiration in ANA-3. Transcription of arcA, etrA, and crp in ANA-3 was similar in cells grown on arsenate and cells grown under aerobic conditions. ANA-3 strains lacking arcA and etrA showed minor to moderate growth defects, respectively, with arsenate. However, crp was essential for growth on arsenate. In contrast to the wild-type strain, arrA was not induced in the crp mutant in cultures shifted from aerobic to anaerobic conditions containing arsenate. This indicated that cyclic AMP (cAMP)-cyclic AMP receptor (CRP) activates arr operon transcription. Computation analysis for genome-wide CRP binding motifs identified a putative binding motif within the arr promoter region. This was verified by electrophoretic mobility shift assays with cAMP-CRP and several DNA probes. Lastly, four putative adenylate cyclase (cya) genes were identified in the genome. One particular cya-like gene was differentially expressed under aerobic versus arsenate respiration conditions. Moreover, a double mutant lacking two of the cya-like genes could not grow with arsenate as a terminal electron acceptor; exogenous cAMP could complement growth of the double cya mutant. It is concluded that the components of the carbon catabolite repression system are essential to regulating arsenate respiratory reduction in Shewanella sp. strain ANA-3.

  11. Arsenate removal using a combination treatment of precipitation and nanofiltration.

    PubMed

    Chang, F F; Liu, W J

    2012-01-01

    A combination treatment of Ca-precipitation and nanofiltration membrane was studied to remove arsenate from water. The selected nanofiltration membrane was an amphoteric charged membrane, proved by the results of ATR-FTIR spectra and zeta potential. The arsenate and calcium removal efficiencies had the lowest values at the isoelectric point of the nanofiltration membrane, attributed to the loosest steric hindrance and the weakest electrostatic repulsion. Above the isoelectric point, arsenate precipitated with calcium ion to form the low solubility compound calcium arsenate, while steric hindrance was the main mechanism of arsenate removal. In contrast, below the isoelectric point, the nanofiltration membrane with positive charges rejected calcium ion by electrostatic repulsion. The high electrostatic shielding of calcium ion prevented arsenate from coming close to the NF membrane. Either high feed arsenate concentration or high calcium oxide dose improved the removal amount of arsenate during the nanofiltration membrane separation process. In addition, the arsenate removal efficiency approached the highest value at 200 μg/L of feed arsenate concentration. The optimal transmembrane pressure was in a range of 0.5-0.7 MPa to restrict the formation of fouling cake on the nanofiltration membrane surface.

  12. Dissimilatory arsenate and sulfate reduction in sediments of two hypersaline, arsenic-rich soda lakes: Mono and Searles Lakes, California.

    PubMed

    Kulp, T R; Hoeft, S E; Miller, L G; Saltikov, C; Murphy, J N; Han, S; Lanoil, B; Oremland, R S

    2006-10-01

    A radioisotope method was devised to study bacterial respiratory reduction of arsenate in sediments. The following two arsenic-rich soda lakes in California were chosen for comparison on the basis of their different salinities: Mono Lake (approximately 90 g/liter) and Searles Lake (approximately 340 g/liter). Profiles of arsenate reduction and sulfate reduction were constructed for both lakes. Reduction of [73As]arsenate occurred at all depth intervals in the cores from Mono Lake (rate constant [k] = 0.103 to 0.04 h(-1)) and Searles Lake (k = 0.012 to 0.002 h(-1)), and the highest activities occurred in the top sections of each core. In contrast, [35S]sulfate reduction was measurable in Mono Lake (k = 7.6 x10(4) to 3.2 x 10(-6) h(-1)) but not in Searles Lake. Sediment DNA was extracted, PCR amplified, and separated by denaturing gradient gel electrophoresis (DGGE) to obtain phylogenetic markers (i.e., 16S rRNA genes) and a partial functional gene for dissimilatory arsenate reduction (arrA). The amplified arrA gene product showed a similar trend in both lakes; the signal was strongest in surface sediments and decreased to undetectable levels deeper in the sediments. More arrA gene signal was observed in Mono Lake and was detectable at a greater depth, despite the higher arsenate reduction activity observed in Searles Lake. A partial sequence (about 900 bp) was obtained for a clone (SLAS-3) that matched the dominant DGGE band found in deeper parts of the Searles Lake sample (below 3 cm), and this clone was found to be closely related to SLAS-1, a novel extremophilic arsenate respirer previously cultivated from Searles Lake.

  13. Dissimilatory arsenate and sulfate reduction in sediments of two hypersaline, arsenic-rich soda lakes: Mono and Searles Lakes, California

    USGS Publications Warehouse

    Kulp, T.R.; Hoeft, S.E.; Miller, L.G.; Saltikov, C.; Murphy, J.N.; Han, S.; Lanoil, B.; Oremland, R.S.

    2006-01-01

    A radioisotope method was devised to study bacterial respiratory reduction of arsenate in sediments. The following two arsenic-rich soda lakes in California were chosen for comparison on the basis of their different salinities: Mono Lake (???90 g/liter) and Searles Lake (???340 g/liter). Profiles of arsenate reduction and sulfate reduction were constructed for both lakes. Reduction of [73As] arsenate occurred at all depth intervals in the cores from Mono Lake (rate constant [k] = 0.103 to 0.04 h-1) and Searles Lake (k = 0.012 to 0.002 h-1), and the highest activities occurred in the top sections of each core. In contrast, [35S] sulfate reduction was measurable in Mono Lake (k = 7.6 ?? 104 to 3.2 ?? 10-6 h-1) but not in Searles Lake. Sediment DNA was extracted, PCR amplified, and separated by denaturing gradient gel electrophoresis (DGGE) to obtain phylogenetic markers (i.e., 16S rRNA genes) and a partial functional gene for dissimilatory arsenate reduction (arrA). The amplified arrA gene product showed a similar trend in both lakes; the signal was strongest in surface sediments and decreased to undetectable levels deeper in the sediments. More arrA gene signal was observed in Mono Lake and was detectable at a greater depth, despite the higher arsenate reduction activity observed in Searles Lake. A partial sequence (about 900 bp) was obtained for a clone (SLAS-3) that matched the dominant DGGE band found in deeper parts of the Searles Lake sample (below 3 cm), and this clone was found to be closely related to SLAS-1, a novel extremophilic arsenate respirer previously cultivated from Searles Lake. Copyright ?? 2006, American Society for Microbiology. All Rights Reserved.

  14. Elucidating the Structures of the Low- and High-pH Mo(V) Species in Respiratory Nitrate Reductase: A Combined EPR, (14,15)N HYSCORE, and DFT Study.

    PubMed

    Rendon, Julia; Biaso, Frédéric; Ceccaldi, Pierre; Toci, René; Seduk, Farida; Magalon, Axel; Guigliarelli, Bruno; Grimaldi, Stéphane

    2017-03-31

    Respiratory nitrate reductases (Nars), members of the prokaryotic Mo/W-bis Pyranopterin Guanosine dinucleotide (Mo/W-bisPGD) enzyme superfamily, are key players in nitrate respiration, a major bioenergetic pathway widely used by microorganisms to cope with the absence of dioxygen. The two-electron reduction of nitrate to nitrite takes place at their active site, where the molybdenum ion cycles between Mo(VI) and Mo(IV) states via a Mo(V) intermediate. The active site shows two distinct pH-dependent Mo(V) electron paramagnetic resonance (EPR) signals whose structure and catalytic relevance have long been debated. In this study, we use EPR and HYSCORE techniques to probe their nuclear environment in Escherichia coli Nar (EcNar). By using samples prepared at different pH and through different enrichment strategies in (98)Mo and (15)N nuclei, we demonstrate that each of the two Mo(V) species is coupled to a single nitrogen nucleus with similar quadrupole characteristics. Structure-based density functional theory calculations allow us to propose a molecular model of the low-pH Mo(V) species consistent with EPR spectroscopic data. Our results show that the metal ion is coordinated by a monodentate aspartate ligand and permit the assignment of the coupled nitrogen nuclei to the Nδ of Asn52, a residue located ∼3.9 Å to the Mo atom in the crystal structures. This is confirmed by measurements on selectively (15)N-Asn labeled EcNar. Further, we propose a Mo-O(H)···HN structure to account for the transfer of spin density onto the interacting nitrogen nucleus deduced from HYSCORE analysis. This work provides a foundation for monitoring the structure of the molybdenum active site in the presence of various substrates or inhibitors in Nars and other molybdenum enzymes.

  15. Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate

    USGS Publications Warehouse

    Zobrist, J.; Dowdle, P.R.; Davis, J.A.; Oremland, R.S.

    2000-01-01

    Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite, a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was influenced by the method in which arsenate became associated with the mineral phases and may have been strongly coupled with arsenate desorption rates. The extent of release of arsenite into solution was governed by adsorption of arsenite onto the ferrihydrite or alumina phases. The results of these experiments have interpretive significance to the mobilization of arsenic in large alluvial aquifers, such as those of the Ganges in India and Bangladesh, and in the hyporheic zones of contaminated streams.Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was

  16. Investigation of biochemical responses of Bacopa monnieri L. upon exposure to arsenate.

    PubMed

    Mishra, Seema; Srivastava, Sudhakar; Dwivedi, Sanjay; Tripathi, Rudra Deo

    2013-08-01

    Widespread contamination of arsenic (As) is recognized as a global problem due to its well-known accumulation by edible and medicinal plants and associated health risks for the humans. In this study, phytotoxicity imposed upon exposure to arsenate [As(V); 0-250 μM for 1-7 days] and ensuing biochemical responses were investigated in a medicinal herb Bacopa monnieri L. vis-à-vis As accumulation. Plants accumulated substantial amount of As (total 768 μg g(-1) dw at 250 μM As(V) after 7 days) with the maximum As retention being in roots (60%) followed by stem (23%) and leaves (17%). The level of cysteine and total nonprotein thiols (NP-SH) increased significantly at all exposure concentrations and durations. Besides, the level of metalloid binding ligands viz., glutathione (GSH) and phytochelatins (PCs) increased significantly at the studied concentrations [50 and 250 μM As(V)] in both roots and leaves. The activities of various enzymes viz., arsenate reductase (AR), glutathione reductase (GR), superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and catalase (CAT) showed differential but coordinated stimulation in leaves and roots to help plants combat As toxicity up to moderate exposure concentrations (50 μM). However, beyond 50 μM, biomass production was found to decrease along with photosynthetic pigments and total soluble proteins, whereas lipid peroxidation increased. In conclusion, As accumulation potential of Bacopa may warrant its use as a phytoremediator but if Bacopa growing in contaminated areas is consumed by humans, it may prove to be toxic for health.

  17. Uranyl and Arsenate Cosorption on Aluminum Oxide Surface

    SciTech Connect

    Tang, Y.; Reeder, R

    2009-01-01

    In this study, we examined the effects of simultaneous adsorption of aqueous arsenate and uranyl onto aluminum oxide over a range of pH and concentration conditions. Arsenate was used as a chemical analog for phosphate, and offers advantages for characterization via X-ray absorption spectroscopy. By combining batch experiments, speciation calculations, X-ray absorption spectroscopy, and X-ray diffraction, we investigated the uptake behavior of uranyl, as well as the local and long-range structure of the final sorption products. In the presence of arsenate, uranyl sorption was greatly enhanced in the acidic pH range, and the amount of enhancement is positively correlated to the initial arsenate and uranyl concentrations. At pH 4-6, U L{sub III-} and As K-edge EXAFS results suggest the formation of surface-sorbed uranyl and arsenate species as well as uranyl arsenate surface precipitate(s) that have a structure similar to tr{umlt o}gerite. Uranyl polymeric species or oxyhydroxide precipitate(s) become more important with increasing pH values. Our results provide the basis for predictive models of the uptake of uranyl by aluminum oxide in the presence of arsenate and (by analogy) phosphate, which can be especially important for understanding phosphate-based uranium remediation systems.

  18. WRKY6 Transcription Factor Restricts Arsenate Uptake and Transposon Activation in Arabidopsis[W

    PubMed Central

    Castrillo, Gabriel; Sánchez-Bermejo, Eduardo; de Lorenzo, Laura; Crevillén, Pedro; Fraile-Escanciano, Ana; TC, Mohan; Mouriz, Alfonso; Catarecha, Pablo; Sobrino-Plata, Juan; Olsson, Sanna; Leo del Puerto, Yolanda; Mateos, Isabel; Rojo, Enrique; Hernández, Luis E.; Jarillo, Jose A.; Piñeiro, Manuel; Paz-Ares, Javier; Leyva, Antonio

    2013-01-01

    Stress constantly challenges plant adaptation to the environment. Of all stress types, arsenic was a major threat during the early evolution of plants. The most prevalent chemical form of arsenic is arsenate, whose similarity to phosphate renders it easily incorporated into cells via the phosphate transporters. Here, we found that arsenate stress provokes a notable transposon burst in plants, in coordination with arsenate/phosphate transporter repression, which immediately restricts arsenate uptake. This repression was accompanied by delocalization of the phosphate transporter from the plasma membrane. When arsenate was removed, the system rapidly restored transcriptional expression and membrane localization of the transporter. We identify WRKY6 as an arsenate-responsive transcription factor that mediates arsenate/phosphate transporter gene expression and restricts arsenate-induced transposon activation. Plants therefore have a dual WRKY-dependent signaling mechanism that modulates arsenate uptake and transposon expression, providing a coordinated strategy for arsenate tolerance and transposon gene silencing. PMID:23922208

  19. Arsenate adsorption on ruthenium oxides: A spectroscopic and kinetic investigation

    SciTech Connect

    Luxton, Todd P.; Eick, Matthew J.; Scheckel, Kirk G.

    2008-12-08

    Arsenate adsorption on amorphous (RuO{sub 2} {center_dot} 1.1H{sub 2}O) and crystalline (RuO{sub 2}) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was used to determine the local coordination environment of adsorbed arsenate. Additionally, pressure-jump (p-jump) relaxation spectroscopy was used to investigate the kinetics of arsenate adsorption/desorption on ruthenium oxides. Chemical relaxations resulting from the induced pressure change were monitored via electrical conductivity detection. EXAFS data were collected for two initial arsenate solution concentrations, 3 and 33 mM at pH 5. The collected spectra indicated a similar coordination environment for arsenate adsorbed to RuO{sub 2} {center_dot} 1.1H{sub 2}O for both arsenate concentrations. In contrast the EXAFS spectra of RuO{sub 2} indicated differences in the local coordination environments for the crystalline material with increasing arsenate concentration. Data analysis indicated that both mono- and bidentate surfaces complexes were present on both RuO{sub 2} {center_dot} 1.1H{sub 2}O and RuO{sub 2}. Relaxation spectra from the pressure-jump experiments of both ruthenium oxides resulted in a double relaxation event. Based on the relaxation spectra, a two step reaction mechanism for arsenate adsorption is proposed resulting in the formation of a bidentate surface complex. Analysis of the kinetic and spectroscopic data suggested that while there were two relaxation events, arsenate adsorbed to ruthenium oxide surfaces through both mono- and bidentate surface complexes.

  20. Biotransformation of arsenic by bacterial strains mediated by oxido-reductase enzyme system.

    PubMed

    Vishnoi, N; Singh, D P

    2014-12-24

    The present study deals with the enzyme mediated biotransformation of arsenic in five arsenic tolerant strains (Bacillus subtilis, Bacillus megaterium, Bacillus pumilus, Paenibacillus macerans and Escherichia coli). Biotransformation ability of these isolates was evaluated by monitoring arsenite oxidase and arsenate reductase activity. Results showed that arsenic oxidase activity was exclusively present in P. macerans and B. pumilus while B. subtilis, B. megaterium and E. coli strains showed presence of Arsenic oxido-reductase enzyme. The reversible nature of arsenic oxido- reductase suggested that same enzyme can carry out oxidation and reduction of arsenic depending upon the relative concentration of arsenic species. Lineweaver-Burk plot of the arsenite oxidase activity in P. macerans showed highest Km value (Km- 200 μM) and lower Vmax (0.012 μmol mg-1 protein min-1) indicating lowest affinity of the enzyme for arsenite. On the contrary, E. coli showed the lower Km value ( Km- 38.46 μM) and higher Vmax (0.044 μmol mg-1 protein min-1) suggesting for higher affinity for the arsenite. Lineweaver-Burk plot of arsenate reductase activity showed the presence of this enzyme in B. subtilis, B. megaterium and E. coli which were in the range of 200-360 μM Km and Vmax value between 0.256- 0.129 mmol mg-1 protein min-1. These results suggested that affinity of the as reductase enzyme is lowest for arsenate than that for the arsenite. Thus, arsenite oxidase system appears to be a predominant mechanism of cellular defense in these bacterial strains.

  1. Effects of maternal restraint stress and sodium arsenate in mice.

    PubMed

    Rasco, J F; Hood, R D

    1994-01-01

    Either maternal restraint stress or sodium arsenate treatment during pregnancy can cause adverse effects on the mouse conceptus. The current study assessed the effects of both factors administered concurrently. Five treatment groups were used initially: (1) vehicle (H2O) control [C], (2) feed/water deprived [FWD], (3) sodium arsenate [SA], (4) restraint only [R], and (5) sodium arsenate plus restraint [SA+R]. A sixth group, arsenate plus feed/water deprived [SA+FWD], was added later, along with (7) a concurrent arsenate-only control [SAC]. Mated female CD-1 mice in Groups 3, 5, 6, and 7 were injected ip with sodium arsenate (20 mg/kg) on gestation day (GD) 9 (plug = day 1). Group 5 mice were restrained for 12 h beginning immediately after dosing. Groups 4 and 5 were restrained in the supine position from 9:00 a.m. to 9:00 p.m. on GD 9; FWD mice were deprived during that time. All females were killed on GD 18 and subjected to teratologic examination. Significantly increased exencephaly and decreased fetal weight were seen in SA+R Group fetuses. The incidence of supernumerary ribs was significantly higher in the SA+R Group than in the SA Group but did not differ from the R Group. These results add to the evidence that maternal stress combined with a chemical teratogen may have a greater effect on the conceptus than would exposure to either agent alone.

  2. Expression profiling of Crambe abyssinica under arsenate stress identifies genes and gene networks involved in arsenic metabolism and detoxification

    PubMed Central

    2010-01-01

    Background Arsenic contamination is widespread throughout the world and this toxic metalloid is known to cause cancers of organs such as liver, kidney, skin, and lung in human. In spite of a recent surge in arsenic related studies, we are still far from a comprehensive understanding of arsenic uptake, detoxification, and sequestration in plants. Crambe abyssinica, commonly known as 'abyssinian mustard', is a non-food, high biomass oil seed crop that is naturally tolerant to heavy metals. Moreover, it accumulates significantly higher levels of arsenic as compared to other species of the Brassicaceae family. Thus, C. abyssinica has great potential to be utilized as an ideal inedible crop for phytoremediation of heavy metals and metalloids. However, the mechanism of arsenic metabolism in higher plants, including C. abyssinica, remains elusive. Results To identify the differentially expressed transcripts and the pathways involved in arsenic metabolism and detoxification, C. abyssinica plants were subjected to arsenate stress and a PCR-Select Suppression Subtraction Hybridization (SSH) approach was employed. A total of 105 differentially expressed subtracted cDNAs were sequenced which were found to represent 38 genes. Those genes encode proteins functioning as antioxidants, metal transporters, reductases, enzymes involved in the protein degradation pathway, and several novel uncharacterized proteins. The transcripts corresponding to the subtracted cDNAs showed strong upregulation by arsenate stress as confirmed by the semi-quantitative RT-PCR. Conclusions Our study revealed novel insights into the plant defense mechanisms and the regulation of genes and gene networks in response to arsenate toxicity. The differential expression of transcripts encoding glutathione-S-transferases, antioxidants, sulfur metabolism, heat-shock proteins, metal transporters, and enzymes in the ubiquitination pathway of protein degradation as well as several unknown novel proteins serve as

  3. Structural characterization and vibrational spectroscopy of the arsenate mineral wendwilsonite.

    PubMed

    Frost, Ray L; Scholz, Ricardo; López, Andrés; Belotti, Fernanda Maria; Xi, Yunfei

    2014-01-24

    In this paper, we have investigated on the natural wendwilsonite mineral with the formulae Ca2(Mg,Co)(AsO4)2⋅2(H2O). Raman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of the wendwilsonite arsenate mineral. A comparison is made with the roselite mineral group with formula Ca2B(AsO4)2⋅2H2O (where B may be Co, Fe(2+), Mg, Mn, Ni, Zn). The Raman spectra of the arsenate related to tetrahedral arsenate clusters with stretching region shows strong differences between that of wendwilsonite and the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. The Raman arsenate (AsO4)(3-) stretching region shows strong differences between that of wendwilsonite and the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. In the infrared spectra complexity exists of multiple to tetrahedral (AsO4)(3-) clusters with antisymmetric stretching vibrations observed indicating a reduction of the tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong Raman bands around 450 cm(-1) are assigned to ν4 bending modes. Multiple bands in the 350-300 cm(-1) region assigned to ν2 bending modes provide evidence of symmetry reduction of the arsenate anion. Three broad bands for wendwilsonite found at 3332, 3119 and 3001 cm(-1) are assigned to OH stretching bands. By using a Libowitzky empirical equation, hydrogen bond distances of 2.65 and 2.75Å are estimated. Vibrational spectra enable the molecular structure of the wendwilsonite mineral to be determined and whilst similarities exist in the spectral patterns with the roselite mineral group, sufficient differences exist to be able to determine the identification of the minerals.

  4. ARSENATE CARRIER PRECIPITATION METHOD OF SEPARATING PLUTONIUM FROM NEUTRON IRRADIATED URANIUM AND RADIOACTIVE FISSION PRODUCTS

    DOEpatents

    Thompson, S.G.; Miller, D.R.; James, R.A.

    1961-06-20

    A process is described for precipitating Pu from an aqueous solution as the arsenate, either per se or on a bismuth arsenate carrier, whereby a separation from uranium and fission products, if present in solution, is accomplished.

  5. Shewanella sp. O23S as a Driving Agent of a System Utilizing Dissimilatory Arsenate-Reducing Bacteria Responsible for Self-Cleaning of Water Contaminated with Arsenic

    PubMed Central

    Drewniak, Lukasz; Stasiuk, Robert; Uhrynowski, Witold; Sklodowska, Aleksandra

    2015-01-01

    The purpose of this study was a detailed characterization of Shewanella sp. O23S, a strain involved in arsenic transformation in ancient gold mine waters contaminated with arsenic and other heavy metals. Physiological analysis of Shewanella sp. O23S showed that it is a facultative anaerobe, capable of growth using arsenate, thiosulfate, nitrate, iron or manganite as a terminal electron acceptor, and lactate or citrate as an electron donor. The strain can grow under anaerobic conditions and utilize arsenate in the respiratory process in a broad range of temperatures (10–37 °C), pH (4–8), salinity (0%–2%), and the presence of heavy metals (Cd, Co, Cr, Cu, Mn, Mo, Se, V and Zn). Under reductive conditions this strain can simultaneously use arsenate and thiosulfate as electron acceptors and produce yellow arsenic (III) sulfide (As2S3) precipitate. Simulation of As-removal from water containing arsenate (2.5 mM) and thiosulfate (5 mM) showed 82.5% efficiency after 21 days of incubation at room temperature. Based on the obtained results, we have proposed a model of a microbially mediated system for self-cleaning of mine waters contaminated with arsenic, in which Shewanella sp. O23S is the main driving agent. PMID:26121297

  6. Toxicity and bioaccumulation kinetics of arsenate in two freshwater green algae under different phosphate regimes.

    PubMed

    Wang, Ning-Xin; Li, Yan; Deng, Xi-Hai; Miao, Ai-Jun; Ji, Rong; Yang, Liu-Yan

    2013-05-01

    In the present study, the toxicity and bioaccumulation kinetics of arsenate in two green algae Chlamydomonas reinhardtii and Scenedesmus obliquus under phosphate-enriched (+P) and limited (-P) conditions were investigated. P-limitation was found to aggravate arsenate toxicity and S. obliquus was more tolerant than C. reinhardtii. Such phosphate-condition-dependent or algal-species-specific toxicity difference was narrowed when the relative inhibition of cell growth was plotted against intracellular arsenate content instead of its extracellular concentration. The discrepance was further reduced when the intracellular ratio of arsenic to phosphorus was applied. It suggests that both arsenate bioaccumulation and intracellular phosphorus played an important role in arsenate toxicity. On the other hand, arsenate uptake was induced by P-limitation and its variation with ambient arsenate concentration could be well fitted to the Michaelis-Menten model. Arsenate transporters of S. obliquus were found to have a higher affinity but lower capacity than those of C. reinhardtii, which explains its better regulation of arsenate accumulation than the latter species in the toxicity experiment. Further, arsenate depuration was facilitated and more was transformed to arsenite in C. reinhardtii or under -P condition. Intracellular proportion of arsenite was also increased after the algae were transferred from the long-term uptake media to a relatively clean solution in the efflux experiment. Both phenomena imply that algae especially the sensitive species could make physiological adjustments to alleviate the adverse effects of arsenate. Overall, our findings will facilitate the application of algae in arsenate remediation.

  7. Bridging arsenate surface complexes on the hematite (012) surface.

    SciTech Connect

    Catalano, J. G.; Zhang, Z.; Park, C.; Fenter, P.; Bedzyk, M. J.; Chemistry; Northwestern Univ.

    2007-04-15

    The fate of the oxoanion arsenate in diverse systems is strongly affected by its adsorption on the surfaces of iron (oxyhydr)oxide minerals. Predicting this behavior in the environment requires an understanding of the mechanisms of arsenate adsorption. In this study, the binding site and adsorption geometry of arsenate on the hematite (012) surface is investigated. The structure and termination of the hematite (012)-water interface were determined by high resolution X-ray reflectivity, revealing that two distinct terminations exist in a roughly 3:1 proportion. The occurrence of multiple terminations appears to be a result of sample preparation, and is not intrinsic to the hematite (012) surface. X-ray standing wave (XSW) measurements were used to determine the registry of adsorbed arsenate to the hematite structure, and thus the binding site and geometry of the resulting surface complex. Arsenate forms a bridging bidentate complex on two adjacent singly coordinated oxygen groups on each of the two distinct terminations present at the hematite surface. Although this geometry is consistent with that seen in past studies, the derived As-Fe distances are longer, the result of the topology of the FeO6 octahedra on the (012) surface. As EXAFS-derived As-Fe distances are often used to determine the adsorption mechanism in environmental samples (e.g., mine tailings, contaminated sediments), this demonstrates the importance of considering the possible sorbent surface structures and arrangements of adsorbates when interpreting such data. As multiple functional groups are present and multiple binding geometries are possible on the hematite (012) surface, the XSW data suggest that formation of bridging bidentate surface complexes on singly coordinated oxygen sites is the preferred adsorption mechanism on this and most other hematite surfaces (provided those surfaces contain adjacent singly coordinated oxygen groups). These measurements also constrain the likely reaction

  8. Quinone Reductase 2 Is a Catechol Quinone Reductase

    SciTech Connect

    Fu, Yue; Buryanovskyy, Leonid; Zhang, Zhongtao

    2008-09-05

    The functions of quinone reductase 2 have eluded researchers for decades even though a genetic polymorphism is associated with various neurological disorders. Employing enzymatic studies using adrenochrome as a substrate, we show that quinone reductase 2 is specific for the reduction of adrenochrome, whereas quinone reductase 1 shows no activity. We also solved the crystal structure of quinone reductase 2 in complexes with dopamine and adrenochrome, two compounds that are structurally related to catecholamine quinones. Detailed structural analyses delineate the mechanism of quinone reductase 2 specificity toward catechol quinones in comparison with quinone reductase 1; a side-chain rotational difference between quinone reductase 1 and quinone reductase 2 of a single residue, phenylalanine 106, determines the specificity of enzymatic activities. These results infer functional differences between two homologous enzymes and indicate that quinone reductase 2 could play important roles in the regulation of catecholamine oxidation processes that may be involved in the etiology of Parkinson disease.

  9. Dissimilatory arsenate reduction with sulfide as electron donor: experiments with mono lake water and Isolation of strain MLMS-1, a chemoautotrophic arsenate respirer.

    PubMed

    Hoeft, Shelley E; Kulp, Thomas R; Stolz, John F; Hollibaugh, James T; Oremland, Ronald S

    2004-05-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H(14)CO(3)(-) into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the delta-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  10. Dissimilatory arsenate reduction with sulfide as electron donor: Experiments with Mono Lake water and isolation of strain MLMS-1, a chemoautotrophic arsenate respirer

    USGS Publications Warehouse

    Hoeft, S.E.; Kulp, T.R.; Stolz, J.F.; Hollibaugh, J.T.; Oremland, R.S.

    2004-01-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H14CO3- into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the ??-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  11. Dissimilatory arsenate reduction with sulfide as the electron donor--Experiments with Mono Lake water and isolation of strain MLMS-1, a chemoautotrophic arsenate-respirer

    USGS Publications Warehouse

    Hoeft, Shelley E.; Kulp, Thomas R.; Stolz, John F.; Hollibaugh, James T.; Oremland, Ronald S.

    2004-01-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H14CO3− into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the δ-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  12. Rice-arsenate interactions in hydroponics: whole genome transcriptional analysis.

    PubMed

    Norton, Gareth J; Lou-Hing, Daniel E; Meharg, Andrew A; Price, Adam H

    2008-01-01

    Rice (Oryza sativa) varieties that are arsenate-tolerant (Bala) and -sensitive (Azucena) were used to conduct a transcriptome analysis of the response of rice seedlings to sodium arsenate (AsV) in hydroponic solution. RNA extracted from the roots of three replicate experiments of plants grown for 1 week in phosphate-free nutrient with or without 13.3 muM AsV was used to challenge the Affymetrix (52K) GeneChip Rice Genome array. A total of 576 probe sets were significantly up-regulated at least 2-fold in both varieties, whereas 622 were down-regulated. Ontological classification is presented. As expected, a large number of transcription factors, stress proteins, and transporters demonstrated differential expression. Striking is the lack of response of classic oxidative stress-responsive genes or phytochelatin synthases/synthatases. However, the large number of responses from genes involved in glutathione synthesis, metabolism, and transport suggests that glutathione conjugation and arsenate methylation may be important biochemical responses to arsenate challenge. In this report, no attempt is made to dissect differences in the response of the tolerant and sensitive variety, but analysis in a companion article will link gene expression to the known tolerance loci available in the BalaxAzucena mapping population.

  13. Arsenate adsorption onto iron oxide amended rice husk char.

    PubMed

    Cope, Christopher O; Webster, Damon S; Sabatini, David A

    2014-08-01

    In this study, rice husks were charred at 550 °C in a partially sealed ceramic vessel for 30minutes to create a high specific surface area (SSA) rice husk char (RHC). The RHC was then amended with iron oxides using dissolved ferric nitrate, Fe(NO3)3⋅9H2O, to provide a surface chemistry conducive to arsenic adsorption. The 550 °C iron oxide amended rice husk char's (550 IOA-RHC's) SSA was nearly 2.5 orders of magnitude higher and the arsenate adsorptive level was nearly 2 orders of magnitude higher than those reported for iron oxide amended sand, thus indicating a positive relationship between post-amendment SSA and arsenate adsorptive levels. Rice husks were then charred at temperatures ranging from 450 °C to 1050 °C to create an even higher SSA material, which might further increase arsenate adsorptive levels. The 950 °C RHC was chosen for amendment due to its high SSA and feasibility of being produced in the field. Once amended, the 950 °C iron oxide amended rice husk char (950 IOA-RHC) improved the arsenate adsorption capacity by thus confirming a positive relationship, though not a linear relationship, between post-amendment SSA and arsenic adsorptive capacity. Further study demonstrated that post-amendment mesoporous volume and mesoporous surface area appear to be better indicators of arsenic adsorptive capacity than SSA or iron content.

  14. Lowered dietary phosphate increases oral bioavailability of arsenate in mice

    EPA Science Inventory

    Arsenate (iAsv), an inorganic oxyanionic species, has physicochemical properties similar to inorganic phosphate (iP). There is evidence that iAsv competes with iP for transmembrane carriers that mediate iP uptake. Thus, it is possible that altered dietary intake of iP could modif...

  15. Arsenate Adsorption On Ruthenium Oxides: A Spectroscopic And Kinetic Investigation

    EPA Science Inventory

    Arsenate adsorption on amorphous (RuO2•1.1H2O) and crystalline (RuO2) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was ...

  16. Uptake, transport and transformation of arsenate in radishes (Raphanus sativus).

    PubMed

    Smith, Paula G; Koch, Iris; Reimer, Kenneth J

    2008-02-01

    The localization and identification of arsenic compounds in terrestrial plants are important for the understanding of arsenic uptake, transformation and translocation within these organisms, and contributes to our understanding of arsenic cycling in the environment. High performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS), and X-ray absorption near-edge structure (XANES) analysis identified arsenite, arsenate and arsenic(III)-sulphur compounds in leaf, stem and root sections of Rhaphanus sativus (radish) plants grown in both arsenic contaminated mine waste, and arsenic amended liquid cultures. The total arsenic distribution was similar between the plants grown in mine waste and those grown hydroponically. Arsenate was the predominant form of arsenic available in the growth mediums, and after it was taken up by roots, X-ray absorption spectroscopy (XAS) imaging indicated that some of the arsenate was transported to the shoots via the xylem. Additionally, arsenate was reduced by the plant and arsenic(III)-sulphur compound(s) accounted for the majority of arsenic in the leaf and stem of living plants. In this study the application of synchrotron techniques permitted the identification of arsenic(III)-sulphur species which were "invisible" to conventional HPLC-ICP-MS analysis.

  17. Dielectric and structural properties of ferroelectric betaine arsenate films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Yurko, E. I.; Svinarev, F. B.

    2014-12-01

    Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = T c is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from T c = 119 K in the films without deuterium to T c = 149 K, which corresponds to the degree of deuteration of approximately 60-70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

  18. Chromate Reduction by a Pseudomonad Isolated from a Site Contaminated with Chromated Copper Arsenate

    PubMed Central

    McLean, Jeff; Beveridge, Terry J.

    2001-01-01

    A pseudomonad (CRB5) isolated from a decommissioned wood preservation site reduced toxic chromate [Cr(VI)] to an insoluble Cr(III) precipitate under aerobic and anaerobic conditions. CRB5 tolerated up to 520 mg of Cr(VI) liter−1 and reduced chromate in the presence of copper and arsenate. Under anaerobic conditions it also reduced Co(III) and U(VI), partially internalizing each metal. Metal precipitates were also found on the surface of the outer membrane and (sometimes) on a capsule. The results showed that chromate reduction by CRB5 was mediated by a soluble enzyme that was largely contained in the cytoplasm but also found outside of the cells. The crude reductase activity in the soluble fraction showed a Km of 23 mg liter−1 (437 μM) and a Vmax of 0.98 mg of Cr h−1 mg of protein−1 (317 nmol min−1 mg of protein−1). Minor membrane-associated Cr(VI) reduction under anaerobiosis may account for anaerobic reduction of chromate under nongrowth conditions with an organic electron donor present. Chromate reduction under both aerobic and anaerobic conditions may be a detoxification strategy for the bacterium which could be exploited to bioremediate chromate-contaminated or other toxic heavy metal-contaminated environments. PMID:11229894

  19. Respiratory System

    MedlinePlus

    ... this page from the NHLBI on Twitter. The Respiratory System The respiratory system is made up of organs ... vessels, and the muscles that enable breathing. The Respiratory System Figure A shows the location of the respiratory ...

  20. Mobilization and re-adsorption of arsenate on ferrihydrite and hematite in the presence of oxalate.

    PubMed

    Yu, Bo; Jia, Shao-Yi; Liu, Yong; Wu, Song-Hai; Han, Xu

    2013-11-15

    In this study, mobilization and re-adsorption of arsenate on 2-line ferrihydrite and hematite in the presence of oxalate was investigated. Our results showed that arsenate could be mobilized during the dissolution of ferrihydrite and hematite. After reaching the maximum values, the released arsenate could re-adsorb on the residual ferrihydrite, whereas such an observation was not significant in hematite system. More reactive sites exposed during the dissolution of ferrihydrite could contribute to the re-adsorption of the released arsenate at pH 3.0, while the insignificant re-adsorption of arsenate on hematite could be explained by the inhibitory adsorption effect of oxalate on arsenate. Although dissolution rates of iron oxides decreased with the increase of arsenate on both ferrihydrite and hematite, dissolution rate was mainly determined by the reactivity of iron oxides, and ferrihydrite showed a higher reactivity than hematite in the presence of oxalate. Mathematic model proposed in our study further indicated that arsenate loading showed a more significant effect on arsenate mobilization in hematite system, while it was more effective in arsenate re-adsorption in ferrihydrite system.

  1. Use of drinking water treatment solids for arsenate removal from desalination concentrate.

    PubMed

    Xu, Xuesong; Lin, Lu; Papelis, Charalambos; Myint, Maung; Cath, Tzahi Y; Xu, Pei

    2015-05-01

    Desalination of impaired water can be hindered by the limited options for concentrate disposal. Selective removal of specific contaminants using inexpensive adsorbents is an attractive option to address the challenges of concentrate management. In this study, two types of ferric-based drinking water treatment solids (DWTS) were examined for arsenate removal from reverse osmosis concentrate during continuous-flow once-through column experiments. Arsenate sorption was investigated under different operating conditions including pH, arsenate concentration, hydraulic retention time, loading rate, temperature, and moisture content of the DWTS. Arsenate removal by the DWTS was affected primarily by surface complexation, electrostatic interactions, and arsenate speciation. Results indicated that arsenate sorption was highly dependent on initial pH and initial arsenate concentration. Acidic conditions enhanced arsenate sorption as a result of weaker electrostatic repulsion between predominantly monovalent H2AsO4(-) and negatively charged particles in the DWTS. High initial arsenate concentration increased the driving force for arsenate sorption to the DWTS surface. Tests revealed that the potential risks associated with the use of DWTS include the leaching of organic contaminants and ammonia, which can be alleviated by using wet DWTS or discarding the initially treated effluent that contains high organic concentration.

  2. Arsenate transport by sodium/phosphate cotransporter type IIb

    SciTech Connect

    Villa-Bellosta, Ricardo; Sorribas, Victor

    2010-08-15

    Arsenic is a metalloid that causes the dysfunction of critical enzymes, oxidative stress, and malignancies. In recent years several transporters of As{sup III} have been identified, including aquaglyceroporins (AQP) and multidrug resistance proteins (MRP). As{sup V} transport, however, has not been sufficiently studied because it has been assumed that arsenate is taken up by mammalian cells through inorganic phosphate (Pi) transporters. In this paper we have analyzed the role of Pi transporters in the uptake of arsenate by directly using {sup 73}As{sup V} as a radiotracer in phosphate transporter-expressing Xenopus laevis oocytes. The affinities of Pi transporters for H{sub 3}AsO{sub 4} were lower than the affinities for Pi. NaPiIIa, NaPiIIc, Pit1, and Pit2 showed a K{sub m} for arsenate that was > 1 mM (i.e., at least ten times lower than the affinities for Pi). The NaPiIIb isoform showed the highest affinity for As{sup V} in mouse (57 {mu}M), rat (51 {mu}M), and human (9.7 {mu}M), which are very similar to the affinities for Pi. Therefore, NaPiIIb can have a prominent role in the toxicokinetics of arsenic following oral exposure to freshwater or food contaminated with As{sup V}.

  3. The molecular basis of phosphate discrimination in arsenate-rich environments.

    PubMed

    Elias, Mikael; Wellner, Alon; Goldin-Azulay, Korina; Chabriere, Eric; Vorholt, Julia A; Erb, Tobias J; Tawfik, Dan S

    2012-11-01

    Arsenate and phosphate are abundant on Earth and have striking similarities: nearly identical pK(a) values, similarly charged oxygen atoms, and thermochemical radii that differ by only 4% (ref. 3). Phosphate is indispensable and arsenate is toxic, but this extensive similarity raises the question whether arsenate may substitute for phosphate in certain niches. However, whether it is used or excluded, discriminating phosphate from arsenate is a paramount challenge. Enzymes that utilize phosphate, for example, have the same binding mode and kinetic parameters as arsenate, and the latter's presence therefore decouples metabolism. Can proteins discriminate between these two anions, and how would they do so? In particular, cellular phosphate uptake systems face a challenge in arsenate-rich environments. Here we describe a molecular mechanism for this process. We examined the periplasmic phosphate-binding proteins (PBPs) of the ABC-type transport system that mediates phosphate uptake into bacterial cells, including two PBPs from the arsenate-rich Mono Lake Halomonas strain GFAJ-1. All PBPs tested are capable of discriminating phosphate over arsenate at least 500-fold. The exception is one of the PBPs of GFAJ-1 that shows roughly 4,500-fold discrimination and its gene is highly expressed under phosphate-limiting conditions. Sub-ångström-resolution structures of Pseudomonas fluorescens PBP with both arsenate and phosphate show a unique mode of binding that mediates discrimination. An extensive network of dipole-anion interactions, and of repulsive interactions, results in the 4% larger arsenate distorting a unique low-barrier hydrogen bond. These features enable the phosphate transport system to bind phosphate selectively over arsenate (at least 10(3) excess) even in highly arsenate-rich environments.

  4. Possible roles of plant sulfurtransferases in detoxification of cyanide, reactive oxygen species, selected heavy metals and arsenate.

    PubMed

    Most, Parvin; Papenbrock, Jutta

    2015-01-14

    Plants and animals have evolved various potential mechanisms to surmount the adverse effects of heavy metal toxicity. Plants possess low molecular weight compounds containing sulfhydryl groups (-SH) that actively react with toxic metals. For instance, glutathione (γ-Glu-Cys-Gly) is a sulfur-containing tripeptide thiol and a substrate of cysteine-rich phytochelatins (γ-Glu-Cys)2-11-Gly (PCs). Phytochelatins react with heavy metal ions by glutathione S-transferase in the cytosol and afterwards they are sequestered into the vacuole for degradation. Furthermore, heavy metals induce reactive oxygen species (ROS), which directly or indirectly influence metabolic processes. Reduced glutathione (GSH) attributes as an antioxidant and participates to control ROS during stress. Maintenance of the GSH/GSSG ratio is important for cellular redox balance, which is crucial for the survival of the plants. In this context, sulfurtransferases (Str), also called rhodaneses, comprise a group of enzymes widely distributed in all phyla, paving the way for the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors, at least in vitro. The best characterized in vitro reaction is the transfer of a sulfane sulfur atom from thiosulfate to cyanide, leading to the formation of sulfite and thiocyanate. Plants as well as other organisms have multi-protein families (MPF) of Str. Despite the presence of Str activities in many living organisms, their physiological role has not been clarified unambiguously. In mammals, these proteins are involved in the elimination of cyanide released from cyanogenic compounds. However, their ubiquity suggests additional physiological functions. Furthermore, it is speculated that a member of the Str family acts as arsenate reductase (AR) and is involved in arsenate detoxification. In summary, the role of Str in detoxification processes is still not well understood but seems to be a major function in the organism.

  5. Arsenate-induced maternal glucose intolerance and neural tube defects in a mouse model

    SciTech Connect

    Hill, Denise S.; Wlodarczyk, Bogdan J.; Mitchell, Laura E.; Finnell, Richard H.

    2009-08-15

    Background: Epidemiological studies have linked environmental arsenic (As) exposure to increased type 2 diabetes risk. Periconceptional hyperglycemia is a significant risk factor for neural tube defects (NTDs), the second most common structural birth defect. A suspected teratogen, arsenic (As) induces NTDs in laboratory animals. Objectives: We investigated whether maternal glucose homeostasis disruption was responsible for arsenate-induced NTDs in a well-established dosing regimen used in studies of arsenic's teratogenicity in early neurodevelopment. Methods: We evaluated maternal intraperitoneal (IP) exposure to As 9.6 mg/kg (as sodium arsenate) in LM/Bc/Fnn mice for teratogenicity and disruption of maternal plasma glucose and insulin levels. Selected compounds (insulin pellet, sodium selenate (SS), N-acetyl cysteine (NAC), L-methionine (L-Met), N-tert-Butyl-{alpha}-phenylnitrone (PBN)) were investigated for their potential to mitigate arsenate's effects. Results: Arsenate caused significant glucose elevation during an IP glucose tolerance test (IPGTT). Insulin levels were not different between arsenate and control dams before (arsenate, 0.55 ng/dl; control, 0.48 ng/dl) or after glucose challenge (arsenate, 1.09 ng/dl; control, 0.81 ng/dl). HOMA-IR index was higher for arsenate (3.9) vs control (2.5) dams (p = 0.0260). Arsenate caused NTDs (100%, p < 0.0001). Insulin pellet and NAC were the most successful rescue agents, reducing NTD rates to 45% and 35%. Conclusions: IPGTT, insulin assay, and HOMA-IR results suggest a modest failure of glucose stimulated insulin secretion and insulin resistance characteristic of glucose intolerance. Insulin's success in preventing arsenate-induced NTDs provides evidence that these arsenate-induced NTDs are secondary to elevated maternal glucose. The NAC rescue, which did not restore maternal glucose or insulin levels, suggests oxidative disruption plays a role.

  6. RATES OF HYDROUS FERRIC OXIDE CRYSTALLIZATION AND THE INFLUENCE ON COPRECIPITATED ARSENATE

    EPA Science Inventory

    Arsenate coprecipitated with hydrous ferric oxide (HFO) was stabilized against dissolution during transformation of HFO to more crystalline iron (hydr)oxides. The rate of arsenate stabilization approximately coincided with the rate of HFO transformation at pH 6 and 40 ?C. Compa...

  7. Arsenate immobilization associated with microbial oxidation of ferrous ion in complex acid sulfate water.

    PubMed

    Ma, Yingqun; Lin, Chuxia

    2012-05-30

    Chemical, XRD, SEM, RS, FTIR and XPS techniques were used to investigate arsenate immobilization associated with microbial Fe(2+) oxidation in a complex acid sulfate water system consisting of a modified 9 K solution (pH 2.0) plus As, Cu, Cd, Pb, Zn and Mn. At a 1:12.5:70 molar ratio of As:Fe:S, schweretmannite formation was impeded. This was in contrast with the predominant presence of schwertmannite when the heavy metals were absent, suggesting that a schwertmannite binding model is not valid for explaining arsenate immobilization in the complex system. In this study, arsenate was initially immobilized through co-precipitation with non-Fe metals and phosphate. Subsequently when sufficient Fe(3+) was produced from Fe(2+) oxidation, formation of a mixed iron, arsenate and phosphate phase predominated. The last stage involved surface complexation of arsenate species. Pb appeared to play an insignificant role in arsenate immobilization due to its strong affinity for sulfate to form anglesite. Phosphate strongly competed with arsenate for the available binding sites. However, As exhibited an increased capacity to compete with P and S for available binding sites from the co-precipitation to surface complexation stage. Adsorbed As tended to be in HAsO(4)(2-) form. The scavenged arsenate species was relatively stable after 2464-h aging.

  8. Arsenic Recovery by Stinging Nettle From Lead-Arsenate Contaminated Orchard Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil contamination with arsenic (As) is common in orchards with a history of lead-arsenate pesticide application. This problem is prevalent in the U.S. Northeast where lead-arsenate foliar sprays were used to control codling moth (Cydia pomonella) in apple orchards. Arsenic is not easily biodegrad...

  9. SORPTION OF ARSENITE AND ARSENATE ON A HIGH AFFINITY OXIDE: MACROSCOPIC AND MICROSCOPIC STUDIES

    EPA Science Inventory

    Sorption of arsenate and arsenite was examined on a Ru compound using macroscopic and microscopic techniques. Isotherms were constructed from batch studies at pH 4 through 8. Solution As was measured by ICAP. Samples of the Ru compound were equilibrated with arsenite and arsenate...

  10. Arsenate adsorption mechanisms at the allophane - Water interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2005-01-01

    We investigated arsenate (As(V)) reactivity and surface speciation on amorphous aluminosilicate mineral (synthetic allophane) surfaces using batch adsorption experiments, powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The adsorption isotherm experiments indicated that As(V) uptake increased with increasing [As(V)]0 from 50 to 1000 ??M (i.e., Langmuir type adsorption isotherm) and that the total As adsorption slightly decreased with increasing NaCl concentrations from 0.01 to 0.1 M. Arsenate adsorption was initially (0-10 h) rapid followed by a slow continuum uptake, and the adsorption processes reached the steady state after 720 h. X-ray absorption spectroscopic analyses suggest that As(V) predominantly forms bidentate binuclear surface species on aluminum octahedral structures, and these species are stable up to 11 months. Solubility calculations and powder XRD analyses indicate no evidence of crystalline AI-As(V) precipitates in the experimental systems. Overall, macroscopic and spectroscopic evidence suggest that the As(V) adsorption mechanisms at the allophane-water interface are attributable to ligand exchange reactions between As(V) and surface-coordinated water molecules and hydroxyl and silicate ions. The research findings imply that dissolved tetrahedral oxyanions (e.g., H2PO42- and H2AsO42-) are readily retained on amorphous aluminosilicate minerals in aquifer and soils at near neutral pH. The innersphere adsorption mechanisms might be important in controlling dissolved arsenate and phosphate in amorphous aluminosilicate-rich low-temperature geochemical environments. ?? 2005 American Chemical Society.

  11. Isolation of an arsenate-respiring bacterium from a redox front in an arsenic-polluted aquifer in West Bengal, Bengal Basin.

    PubMed

    Osborne, Thomas H; McArthur, John M; Sikdar, Pradip K; Santini, Joanne M

    2015-04-07

    Natural pollution of groundwater by arsenic adversely affects the health of tens of millions of people worldwide, with the deltaic aquifers of SE Asia being particularly polluted. The pollution is caused primarily by, or as a side reaction of, the microbial reduction of sedimentary Fe(III)-oxyhydroxides, but the organism(s) responsible for As release have not been isolated. Here we report the first isolation of a dissimilatory arsenate reducer from sediments of the Bengal Basin in West Bengal. The bacterium, here designated WB3, respires soluble arsenate and couples its reduction to the oxidation of acetate; WB3 is therefore implicated in the process of arsenic pollution of groundwater, which is largely by arsenite. The bacterium WB3 is also capable of reducing dissolved Fe(III) citrate, solid Fe(III)-oxyhydroxide, and elemental sulfur, using acetate as the electron donor. It is a member of the Desulfuromonas genus and possesses a dissimilatory arsenate reductase that was identified using degenerate polymerase chain reaction primers. The sediment from which WB3 was isolated was brown, Pleistocene sand at a depth of 35.2 m below ground level (mbgl). This level was some 3 cm below the boundary between the brown sands and overlying reduced, gray, Holocene aquifer sands. The color boundary is interpreted to be a reduction front that releases As for resorption downflow, yielding a high load of labile As sorbed to the sediment at a depth of 35.8 mbgl and concentrations of As in groundwater that reach >1000 μg/L.

  12. Understanding soluble arsenate removal kinetics by zerovalent iron media.

    PubMed

    Melitas, Nikos; Wang, Jianping; Conklin, Martha; O'Day, Peggy; Farrell, James

    2002-05-01

    Zerovalent iron filings have been proposed as a filter medium for removing arsenic compounds from potable water supplies. This research investigated the kinetics of arsenate removal from aqueous solutions by zerovalent iron media. Batch experiments were performed to determine the effect of the iron corrosion rate on the rate of As(V) removal. Tafel analyses were used to determine the effect of the As(V) concentration on the rate of iron corrosion in anaerobic solutions. As(V) removal in column reactors packed with iron filings was measured over a 1-year period of continuous operation. Comparison of As(V) removal by freely corroding and cathodically protected iron showed that rates of arsenate removal were dependent on the continuous generation of iron oxide adsorption sites. In addition to adsorption site availability, rates of arsenate removal were also limited by mass transfer associated with As(V) diffusion through iron corrosion products. Steady-state removal rates in the column reactor were up to 10 times faster between the inlet-end and the first sampling port than between the first sampling port and the effluent-end of the column. Faster removal near the influent-end of the column was due to a faster rate of iron oxidation in that region. The presence of 100 microg/L As(V) decreased the iron corrosion rate by up to a factor of 5 compared to a blank electrolyte solution. However, increasing the As(V) concentration from 100 to 20,000 microg/L resulted in no further decrease in the iron corrosion rate. The kinetics of arsenate removal ranged between zeroth- and first-order with respect to the aqueous As(V) concentration. The apparent reaction order was dependent on the availability of adsorption sites and on the aqueous As(V) concentration. X-ray absorption spectroscopy analyses showed the presence of iron metal, magnetite (Fe3O4), an Fe(III) oxide phase, and possibly an Fe(II,III) hydroxide phase in the reacted iron filings. These mixed valent oxide phases are

  13. Raman Investigations of Rare Earth Arsenate Single Crystals

    SciTech Connect

    Barros, G; Santos, C. C.; Ayala, A. P.; Guedes, I.; Boatner, Lynn A; Loong, C. K.

    2010-01-01

    Polarized Raman Spectroscopy was used to investigate the room-temperature phonon characteristics of a series of rare-earth arsenate (REAsO4, RE = Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu) single crystals. The Raman data were interpreted in a systematic manner based on the known tetragonal zircon structure of these compounds, and assignments and correlations were made for the observed bands. We found that the wavenumber of the internal modes of the AsO4 tetrahedron increased with increasing atomic number, and for three out of four lattice wavenumbers observed, this tendency was not nearly so marked as in the case of the internal mode wavenumber.

  14. Derived amino acid sequences of the nosZ gene (respiratory N2O reductase) from Alcaligenes eutrophus, Pseudomonas aeruginosa and Pseudomonas stutzeri reveal potential copper-binding residues. Implications for the CuA site of N2O reductase and cytochrome-c oxidase.

    PubMed

    Zumft, W G; Dreusch, A; Löchelt, S; Cuypers, H; Friedrich, B; Schneider, B

    1992-08-15

    The nosZ genes encoding the multicopper enzyme nitrous oxide reductase of Alcaligenes eutrophus H16 and the type strain of Pseudomonas aeruginosa were cloned and sequenced for structural comparison of their gene products with the homologous product of the nosZ gene from Pseudomonas stutzeri [Viebrock, A. & Zumft, W. G. (1988) J. Bacteriol. 170, 4658-4668] and the subunit II of cytochrome-c oxidase (COII). Both types of enzymes possess the CuA binding site. The nosZ genes were identified in cosmid libraries by hybridization with an internal 1.22-kb PstI fragment (NS220) of nosZ from P. stutzeri. The derived amino acid sequences indicate unprocessed gene products of 70084 Da (A. eutrophus) and 70695 Da (P. aeruginosa). The N-terminal sequences of the NosZ proteins have the characteristics of signal peptides for transport. A homologous domain, extending over at least 50 residues, is shared among the three derived NosZ sequences and the CuA binding region of 32 COII sequences. Only three out of nine cysteine residues of the NosZ protein (P. stutzeri) are invariant. Cys618 and Cys622 are assigned to a binuclear center, A, which is thought to represent the CuA site of NosZ and is located close to the C terminus. Two conserved histidines, one methionine, one aspartate, one valine and two aromatic residues are also part of the CuA consensus sequence, which is the domain homologous between the two enzymes. The CuA consensus sequence, however, lacks four strictly conserved residues present in all COII sequences. Cys165 is likely to be a ligand of a second binuclear center, Z, for which we assume mainly histidine coordination. Of 23 histidine residues in NosZ (P. stutzeri), 14 are invariant, 7 of which are in regions with a degree of conservation well above the 50% positional identity between the Alcaligenes and Pseudomonas sequences. Conserved tryptophan residues are located close to several potential copper ligands. Trp615 may contribute to the observed quenching of

  15. ARSENATE-INDUCED MATERNAL GLUCOSE INTOLERANCE AND NEURAL TUBE DEFECTS IN A MOUSE MODEL

    PubMed Central

    Hill, Denise S.; Wlodarczyk, Bogdan J.; Mitchell, Laura E.; Finnell, Richard H.

    2009-01-01

    Background Epidemiological studies have linked environmental arsenic (As) exposure to increased type 2 diabetes risk. Periconceptional hyperglycemia is a significant risk factor for neural tube defects (NTDs), the second most common structural birth defect. A suspected teratogen, arsenic (As) induces NTDs in laboratory animals. Objectives We investigated whether maternal glucose homeostasis disruption was responsible for arsenate-induced NTDs in a well-established dosing regimen used in studies of arsenic’s teratogenicity in early neurodevelopment. Methods We evaluated maternal intraperitoneal (I.P.) exposure to As 9.6 mg/kg (as sodium arsenate) in LM/Bc/Fnn mice for teratogenicity and disruption of maternal plasma glucose and insulin levels. Selected compounds (insulin pellet, sodium selenate (SS), N-acetyl cysteine (NAC), L-methionine (L-Met), N-tert-Butyl-α-phenylnitrone (PBN)) were investigated for their potential to mitigate arsenate’s effects. Results Arsenate caused significant glucose elevation during an I.P. glucose tolerance test (IPGTT). Insulin levels were not different between arsenate and control dams before (arsenate, 0.55 ng/dl; control, 0.48 ng/dl) or after glucose challenge (arsenate, 1.09 ng/dl; control, 0.81 ng/dl). HOMA-IR index was higher for arsenate (3.9) vs control (2.5) dams (p=0.0260). Arsenate caused NTDs (100%, p<0.0001). Insulin pellet and NAC were the most successful rescue agents, reducing NTD rates to 45% and 35%. Conclusions IPGTT, insulin assay, and HOMA-IR results suggest a modest failure of glucose stimulated insulin secretion and insulin resistance characteristic of glucose intolerance. Insulin’s success in preventing arsenate-induced NTDs provides evidence that these arsenate-induced NTDs are secondary to elevated maternal glucose. The NAC rescue, which did not restore maternal glucose or insulin levels, suggests oxidative disruption plays a role. PMID:19446573

  16. Respiratory acidosis

    MedlinePlus

    ... Names Ventilatory failure; Respiratory failure; Acidosis - respiratory Images Respiratory system References Effros RM, Swenson ER. Acid-base balance. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine . 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: ...

  17. Arsenate substitution in lead hydroxyl apatites: A Raman spectroscopic study.

    PubMed

    Giera, Alicja; Manecki, Maciej; Bajda, Tomasz; Rakovan, John; Kwaśniak-Kominek, Monika; Marchlewski, Tomasz

    2016-01-05

    A total of seven compounds of the hydroxylpyromorphite Pb10(PO4)6(OH)2 - hydroxylmimetite Pb10(AsO4)6(OH)2 (HPY-HMI) solid solution series were synthesized at 80°C from aqueous solutions and characterized using Raman spectroscopy. The positions of the bands in all spectra of the series depend on the content of arsenates and phosphates shifting to lower wavenumbers with substitution of (AsO4)(3-) for (PO4)(3-). This shift results from the decreasing bond strength of X-O (where X=P, As) and higher atomic mass of As than P. The position and intensity of major (PO4)(3-) and (AsO4)(3-) bands in Raman spectra exhibit linear correlation with As content, while the ratio of the intensities of these peaks shows exponential correlation. This results due to different polarizability of (PO4)(3-) and (AsO4)(3-) molecules. A small carbonate band develops with increasing As content indicating that hydroxyl lead apatites adopt the (CO3)(2-) ions, particularly at the arsenate end of the series.

  18. Arsenate removal from simulated groundwater with a Donnan dialyzer.

    PubMed

    Zhao, Bin; Zhao, Huazhang; Dockko, Seok; Ni, Jinren

    2012-05-15

    A simple point of use (POU) device based on the theory of Donnan dialysis was developed for the removal of arsenate (As(V)) in the present study. A commercial anion exchange membrane was used as a semipermeable barrier between the feed and stripping solution (As(V)-spiked groundwater and a 12gL(-1) table salt solution, respectively). The proposed POU device could be operated 26 times before replacing the stripping solution. In each batch, approximately 80% of the arsenate anions were transported across the membrane within 24h, and the arsenic concentration of the stripping solution was finally more than 180 times greater than that of the treated water. Cations were well preserved in treated water; however, a slight increase in the sodium ion concentration was observed due to electrolyte leakage. Alternatively, the chloride ion concentration significantly increased at the expense of a loss of sulfate and bicarbonate. The quality of treated water was in compliance with drinking water standards. Membrane fouling was investigated, and a reduction in the As(V) removal rates was not observed when the membrane was used repeatedly. Our results showed that the proposed Donnan dialysis POU device could effectively remove arsenic from drinking water in rural areas in a sustainable manner.

  19. Photoinduced Oxidation of Arsenite to Arsenate on Ferrihydrite

    SciTech Connect

    N Bhandari; R Reeder; D Strongin

    2011-12-31

    The photochemistry of an aqueous suspension of the iron oxyhydroxide, ferrihydrite, in the presence of arsenite has been investigated using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray absorption near edge structure (XANES), and solution phase analysis. Both ATR-FTIR and XANES show that the exposure of ferrihydrite to arsenite in the dark leads to no change in the As oxidation state, but the exposure of this arsenite-bearing surface, which is in contact with pH 5 water, to light leads to the conversion of the majority of the adsorbed arsenite to the As(V) bearing species, arsenate. Analysis of the solution phase shows that ferrous iron is released into solution during the oxidation of arsenite. The photochemical reaction, however, shows the characteristics of a self-terminating reaction in that there is a significant suppression of this redox chemistry before 10% of the total iron making up the ferrihydrite partitions into solution as ferrous iron. The self-terminating behavior exhibited by this photochemical arsenite/ferrihydrite system is likely due to the passivation of the ferrihydrite surface by the strongly bound arsenate product.

  20. Comparative proteomic analysis of rice shoots exposed to high arsenate.

    PubMed

    Liu, Yanli; Li, Ming; Han, Chao; Wu, Fengxia; Tu, Bingkun; Yang, Pingfang

    2013-10-01

    Consumption of arsenic contaminated water and cereals is a serious threat to humans all over the world. Rice (Oryza sativa "Nipponbare"), as a main cereal crop, can accumulate arsenic more than 10-fold that of in other cereals. To gain a comprehensive understanding of the response of rice subjected to 100 µM arsenate stress, a comparative proteomic analysis of rice shoots in combination with morphological and biochemical investigations have been performed in this study. The results demonstrated that arsenate suppressed the growth of rice seedlings, destroyed the cellular ultra-structure and changed the homeostasis of reactive oxygen species. Moreover, a total of 38 differentially displayed proteins, which were mainly involved in metabolism, redox and protein-metabolism, were identified. The data suggest the arsenic can inhibit rice growth through negatively affecting chloroplast structure and photosynthesis. In addition, upregulation of the proteins involved in redox and protein metabolism might help the rice to be resistant or tolerant to arsenic toxicity. In general, this study improves our understanding about the rice arsenic responsive mechanism.

  1. Graphene oxide/ferric hydroxide composites for efficient arsenate removal from drinking water.

    PubMed

    Zhang, Kai; Dwivedi, Vineet; Chi, Chunyan; Wu, Jishan

    2010-10-15

    A series of novel composites based on graphene oxide (GO) cross-linked with ferric hydroxide was developed for effective removal of arsenate from contaminated drinking water. GO, which was used as a supporting matrix here, was firstly treated with ferrous sulfate. Then, the ferrous compound cross-linked with GO was in situ oxidized to ferric compound by hydrogen peroxide, followed by treating with ammonium hydroxide. The morphology and composition of the composites were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The ferric hydroxide was found to be homogenously impregnated onto GO sheets in amorphous form. These composites were evaluated as absorbents for arsenate removal from contaminated drinking water. For the water with arsenate concentration at 51.14 ppm, more than 95% of arsenate was absorbed by composite GO-Fe-5 with an absorption capacity of 23.78 mg arsenate/g of composite. Effective arsenate removal occurred in a wide range of pH from 4 to 9. However, the efficiency of arsenate removal was decreased when pH was increased to higher than 8.

  2. Respiratory papillomas

    PubMed Central

    Alagusundaramoorthy, Sayee Sundar; Agrawal, Abhinav

    2016-01-01

    Papillomas are known to occur in the lower respiratory tract. They are however, rare compared to their occurrence in the upper respiratory tract. These are generally exophytic tumors in the more proximal upper airways however cases with more distal location with an inverted growth pattern have also been described in the literature. These can be solitary or multiple and multifocality associated with multiple papillomas in the upper respiratory/aerodigestive tract. The four major types of respiratory papillomas are (1) Recurrent respiratory papillomas, (2) solitary squamous papillomas, (3) solitary glandular papillomas, (4) mixed papillomas. We review the incidence, etiopathology, diagnosis, and possible treatment modalities and algorithms for these respiratory papillomas. PMID:27625447

  3. Respiratory Failure

    MedlinePlus

    Respiratory failure happens when not enough oxygen passes from your lungs into your blood. Your body's organs, ... brain, need oxygen-rich blood to work well. Respiratory failure also can happen if your lungs can' ...

  4. Respiratory system

    NASA Technical Reports Server (NTRS)

    Bartlett, R. G., Jr.

    1973-01-01

    The general anatomy and function of the human respiratory system is summarized. Breathing movements, control of breathing, lung volumes and capacities, mechanical relations, and factors relevant to respiratory support and equipment design are discussed.

  5. Respiratory alkalosis

    MedlinePlus

    ... shortness of breath. Alternative Names Alkalosis - respiratory Images Respiratory system References Effros RM, Swenson ER. Acid-base balance. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine . 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: ...

  6. Homology among arsenate resistance determinants of R factors in Escherichia coli.

    PubMed Central

    Mobley, H L; Silver, S; Porter, F D; Rosen, B P

    1984-01-01

    Escherichia coli bearing R factors R773 or R46 or hybrid recombinant plasmids carrying the arsenic resistance determinants derived from these plasmids synthesized inducible polypeptides of similar apparent molecular weights when exposed to arsenite salts (R773 derivative, 64,000 and 16,000; R46 derivative, 62,000, 16,500, and 13,500). In addition, both plasmids encoded energy-dependent arsenate efflux systems and demonstrated DNA sequence homology by filter blot hybridization. Human isolates of arsenate- and arsenite-resistant enterobacteria were tested for homology with the arsenate operon of R773 by colony blot hybridization. Approximately one-third of the isolates hybridized strongly, and two-thirds showed little or no evidence of homology, suggesting the presence of two or more genetically distinct arsenate resistant determinants. Images PMID:6370124

  7. Coprecipitation of arsenate with metal oxides: nature, mineralogy, and reactivity of aluminum precipitates.

    PubMed

    Violante, Antonio; Ricciardella, Mariarosaria; Del Gaudio, Stefania; Pigna, Massimo

    2006-08-15

    Arsenic mobilization in soils is mainly controlled by sorption/desorption processes, but arsenic also may be coprecipitated with aluminum and/or iron in natural environments. Although coprecipitation of arsenic with aluminum and iron oxides is an effective treatment process for arsenic removal from drinking water, the nature and reactivity of aluminum- or iron-arsenic coprecipitates has received little attention. We studied the mineralogy, chemical composition, and surface properties of aluminum-arsenate coprecipitates, as well as the sorption of phosphate on and the loss of arsenate from these precipitates. Aluminum-arsenate coprecipitates were synthesized at pH 4.0, 7.0, or 10.0 and As/Al molar ratio (R) of 0, 0.01, or 0.1 and were aged 30 or 210 d at 50 degrees C. In the absence of arsenate, gibbsite (pH 4.0 or 7.0) and bayerite (pH 10.0) formed, whereas in the presence of arsenate, very poorly crystalline precipitates formed. Short-range ordered materials (mainly poorly crystalline boehmite) formed at pH 4.0 (R = 0.01 and 0.1), 7.0, and 10.0 (R= 0.1) and did not transform into Al(OH)3 polymorphs even after prolonged aging. The surface properties and chemical composition of the aluminum precipitates were affected by the initial pH, R, and aging. Chemical dissolution of the samples by 6 mol L(-1) HCl and 0.2 mol L(-1) oxalic acid/ oxalate solution indicated that arsenate was present mainly in the short-range ordered precipitates. The sorption of phosphate onto the precipitates was influenced by the nature of the samples and the amounts of arsenate present in the precipitates. Large amounts of phosphate partially replaced arsenate only from the samples formed at R = 0.1. The quantities of arsenate desorbed from these coprecipitates by phosphate increased with increasing phosphate concentration, reaction time, and precipitate age butwere always lessthan 30% of the amounts of arsenate present in the materials and were particularly low (<4%) from the sample prepared

  8. Gas-bubbled nano zero-valent iron process for high concentration arsenate removal.

    PubMed

    Tanboonchuy, Visanu; Hsu, Jia-Chin; Grisdanurak, Nurak; Liao, Chih-Hsiang

    2011-02-28

    In this study, batch experiments were performed to investigate a novel process for high concentration arsenate removal in the presence of air and/or CO(2) bubbling. The pretreatment step, CO(2) bubbling at 300 mL/min for 5 min, was taken to adjust the solution pH to an acidic environment, followed by air bubbling at 300 mL/min for 10 min to increase dissolved oxygen in the solution. In the treatment period, the nano-scale zero-valent iron was applied to remove aqueous arsenate of 3000 μg/L, while the treatment system was continuously bubbled by 300 mL/min of air. Such a process resulted in outstanding performance in arsenate removal. Furthermore, in the field groundwater application, the arsenate removal rate for the proposed process was 5 times faster than the rate measured when the system was pretreated by acidic chemical species only.

  9. ASSESSING CHILDREN'S EXPOSURES TO THE WOOD PRESERVATIVE CCA (CHROMATED COPPER ARSENATE) ON TREATED PLAYSETS AND DECKS

    EPA Science Inventory

    Concerns have been raised regarding the safety of young children contacting arsenic and chromium residues while playing on and around Chromated Copper Arsenate (CCA) treated wood playground structures and decks. Although CCA registrants voluntarily canceled treated wood for re...

  10. Synthesis and phase transformations involving scorodite, ferric arsenate and arsenical ferrihydrite: Implications for arsenic mobility

    NASA Astrophysics Data System (ADS)

    Paktunc, Dogan; Dutrizac, John; Gertsman, Valery

    2008-06-01

    Scorodite, ferric arsenate and arsenical ferrihydrite are important arsenic carriers occurring in a wide range of environments and are also common precipitates used by metallurgical industries to control arsenic in effluents. Solubility and stability of these compounds are controversial because of the complexities in their identification and characterization in heterogeneous media. To provide insights into the formation of scorodite, ferric arsenate and ferrihydrite, series of synthesis experiments were carried out at 70 °C and pH 1, 2, 3 and 4.5 from 0.2 M Fe(SO 4) 1.5 solutions also containing 0.02-0.2 M Na 2HAsO 4. The precipitates were characterized by transmission electron microscopy, X-ray diffraction and X-ray absorption fine structure techniques. Ferric arsenate, characterized by two broad diffuse peaks on the XRD pattern and having the structural formula of FeAsO 4·4-7H 2O, is a precursor to scorodite formation. As defined by As XAFS and Fe XAFS, the local structure of ferric arsenate is profoundly different than that of scorodite. It is postulated that the ferric arsenate structure is made of single chains of corner-sharing Fe(O,OH) 6 octahedra with bridging arsenate tetrahedra alternating along the chains. Scorodite was precipitated from solutions with Fe/As molar ratios of 1 over the pH range of 1-4.5. The pH strongly controls the kinetics of scorodite formation and its transformation from ferric arsenate. The scorodite crystallite size increased from 7 to 33 nm by ripening and aggregation. Precipitates, resulting from continuous synthesis at pH 4.5 from solutions having Fe/As molar ratios ranging from 1 to 4 and resembling the compounds referred to as ferric arsenate, arsenical ferrihydrite and As-rich hydrous ferric oxide in the literature, represent variable mixtures of ferric arsenate and ferrihydrite. When the Fe/As ratio increases, the proportion of ferrihydrite increases at the expense of ferric arsenate. Arsenate adsorption appears to retard

  11. XAFS of Synthetic Iron(III)-Arsenate Co-Precipitates and Uranium Mill Neutralized Raffinate

    NASA Astrophysics Data System (ADS)

    Chen, N.; Jiang, D. T.; Cutler, J.; Demopoulos, G. P.; Rowson, J. W.

    2007-02-01

    XAFS studies were carried out for chemical speciation of arsenic species in uranium mill neutralized raffinate solids. To aid the structural characterization, synthetic iron(III)-arsenate co-precipitates were prepared to mimic the actual uranium mill tailings neutralization products. The principle components analysis method was used to validate the synthetic amorphous scorodite as a primary model compound for arsenate species in the raffinate samples under the specific precipitation conditions.

  12. XAFS of Synthetic Iron(III)-Arsenate Co-Precipitates and Uranium Mill Neutralized Raffinate

    SciTech Connect

    Chen, N.; Jiang, D. T.; Cutler, J.; Demopoulos, G. P.; Rowson, J. W.

    2007-02-02

    XAFS studies were carried out for chemical speciation of arsenic species in uranium mill neutralized raffinate solids. To aid the structural characterization, synthetic iron(III)-arsenate co-precipitates were prepared to mimic the actual uranium mill tailings neutralization products. The principle components analysis method was used to validate the synthetic amorphous scorodite as a primary model compound for arsenate species in the raffinate samples under the specific precipitation conditions.

  13. Concentration and chemical status of arsenic in the early placentas of arsenate-dosed hamsters

    SciTech Connect

    Hanlon, D.P.; Ferm, V.H.

    1987-04-01

    The authors determined the concentration and chemical status of arsenic in the placentas of hamsters following continuous exposure via the osmotic minipump to minimally and frankly teratogenic doses of arsenate. Close to 70% of the placental arsenic is bound to macromolecules, two-thirds of which is dialyzable. The remaining 30% of arsenic consists of low molecular weight species, predominantly inorganic arsenic. This mix is the same for minimally teratogenic and frankly teratogenic doses of arsenate.

  14. Characterization of microbial arsenate reduction in the anoxic bottom waters of Mono Lake, California

    USGS Publications Warehouse

    Hoeft, S.E.; Lucas, F.; Hollibaugh, J.T.; Oremland, R.S.

    2002-01-01

    Dissimilatory reduction of arsenate (DAsR) occurs in the arsenic-rich, anoxic water column of Mono Lake, California, yet the microorganisms responsible for this observed in situ activity have not been identified. To gain insight as to which microorganisms mediate this phenomenon, as well as to some of the biogeochemical constraints on this activity, we conducted incubations of arsenate-enriched bottom water coupled with inhibition/amendment studies and Denaturing Gradient Gel Electrophoresis (DGGE) characterization techniques. DAsR was totally inhibited by filter-sterilization and by nitrate, partially inhibited (~50%) by selenate, but only slightly (~25%) inhibited by oxyanions that block sulfate-reduction (molybdate and tungstate). The apparent inhibition by nitrate, however, was not due to action as a preferred electron acceptor to arsenate. Rather, nitrate addition caused a rapid, microbial re-oxidation of arsenite to arsenate, which gave the overall appearance of no arsenate loss. A similar microbial oxidation of As(III) was also found with Fe(III), a fact that has implications for the recycling of As(V) in Mono Lake's anoxic bottom waters. DAsR could be slightly (10%) stimulated by substrate amendments of lactate, succinate, malate, or glucose, but not by acetate, suggesting that the DAsR microflora is not electron donor limited. DGGE analysis of amplified 16S rDNA gene fragments from incubated arsenate-enriched bottom waters revealed the presence of two bands that were not present in controls without added arsenate. The resolved sequences of these excised bands indicated the presence of members of the epsilon (Sulfurospirillum) and delta (Desulfovibrio) subgroups of the Proteobacteria, both of which have representative species that are capable of anaerobic growth using arsenate as their electron acceptor.

  15. A cytochrome cd1-type nitrite reductase mediates the first step of denitrification in Alcaligenes eutrophus.

    PubMed

    Sann, R; Kostka, S; Friedrich, B

    1994-01-01

    Respiratory nitrite reductase (NIR) has been purified from the soluble extract of denitrifying cells of Alcaligenes eutrophus strain H16 to apparent electrophoretic homogeneity. The enzyme was induced under anoxic conditions in the presence of nitrite. Purified NIR showed typical features of a cytochrome cd1-type nitrite reductase. It appeared to be a dimer of kDa subunits, its activity was only weakly inhibited by the copper chelator diethyldithiocarbamate, and spectral analysis revealed absorption maxima which were characteristic for the presence of heme c and heme d1. The isoelectric point of 8.6 was considerably higher than the pI determined for cd1 nitrite reductases from pseudomonads. Eighteen amino acids at the N-terminus of the A. eutrophus NIR, obtained by protein sequencing, showed no significant homology to the N-terminal region of nitrite reductases from Pseudomonas stutzeri and Pseudomonas aeruginosa.

  16. Comparison of arsenate and cadmium toxicity in a freshwater amphipod (Gammarus pulex).

    PubMed

    Vellinger, Céline; Parant, Marc; Rousselle, Philippe; Immel, Françoise; Wagner, Philippe; Usseglio-Polatera, Philippe

    2012-01-01

    Cadmium is largely documented on freshwater organisms while arsenic, especially arsenate, is rarely studied. The kinetic of the LC50s values for both metals was realized on Gammarus pulex. Physiological [i.e. metal concentration in body tissues, bioconcentration factor (BCF)] effects and behavioural responses (via pleopods beats) were investigated after 240-h exposure. Arsenate LC50 value was 100 fold higher than Cd-LC50 value after 240-h exposure, while concentrations in gammarids were similar for both metals at their respective LC50s. BCF decreased with increasing cadmium concentration while BCF remained stable with increasing arsenate concentration. Moreover, BCF was between 148 and 344 times lower for arsenate than cadmium. A significant hypoventilation was observed for cadmium concentrations exceeding or close to the 240h-LC50(Cd), while gammarids hyperventilated for the lowest arsenate concentrations and hypoventilated for the highest arsenate concentrations. We discussed the relationships between potential action mechanisms of these two metals and observed results.

  17. Efficient removal of chromate and arsenate from individual and mixed system by malachite nanoparticles.

    PubMed

    Saikia, Jiban; Saha, Bedabrata; Das, Gopal

    2011-02-15

    Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an adsorbent for the removal of toxic arsenate and chromate. We report a high adsorption capacity for chromate and arsenate on malachite nanoparticle from both individual and mixed solution in pH ∼4-5. However, the adsorption efficiency decreases with the increase of solution pH. Batch studies revealed that initial pH, temperature, malachite nanoparticles dose and initial concentration of chromate and arsenate were important parameters for the adsorption process. Thermodynamic analysis showed that adsorption of chromate and arsenate on malachite nanoparticles is endothermic and spontaneous. The adsorption of these anions has also been investigated quantitatively with the help of adsorption kinetics, isotherm, and selectivity coefficient (K) analysis. The adsorption data for both chromate and arsenate were fitted well in Langmuir isotherm and preferentially followed the second order kinetics. The binding affinity of chromate is found to be slightly higher than arsenate in a competitive adsorption process which leads to the comparatively higher adsorption of chromate on malachite nanoparticles surface.

  18. Evidence for the aquatic binding of arsenate by natural organic matter-suspended Fe(III)

    USGS Publications Warehouse

    Ritter, K.; Aiken, G.R.; Ranville, J.F.; Bauer, M. E.; Macalady, D.L.

    2006-01-01

    Dialysis experiments with arsenate and three different NOM samples amended with Fe(III) showed evidence confirming the formation of aquatic arsenate-Fe(III)-NOM associations. A linear relationship was observed between the amount of complexed arsenate and the Fe(III) content of the NOM. The dialysis results were consistent with complex formation through ferric iron cations acting as bridges between the negatively charged arsenate and NOM functional groups and/or a more colloidal association, in which the arsenate is bound by suspended Fe(III)-NOM colloids. Sequential filtration experiments confirmed that a significant proportion of the iron present at all Fe/C ratios used in the dialysis experiments was colloidal in nature. These colloids may include larger NOM species that are coagulated by the presence of chelated Fe(III) and/or NOM-stabilized ferric (oxy)hydroxide colloids, and thus, the solution-phase arsenate-Fe(III)-NOM associations are at least partially colloidal in nature. ?? 2006 American Chemical Society.

  19. Respiratory alkalosis.

    PubMed

    Foster, G T; Vaziri, N D; Sassoon, C S

    2001-04-01

    Respiratory alkalosis is an extremely common and complicated problem affecting virtually every organ system in the body. This article reviews the various facets of this interesting problem. Respiratory alkalosis produces multiple metabolic abnormalities, from changes in potassium, phosphate, and calcium, to the development of a mild lactic acidosis. Renal handling of the above ions is also affected. The etiologies may be related to pulmonary or extrapulmonary disorders. Hyperventilation syndrome is a common etiology of respiratory alkalosis in the emergency department setting and is a diagnosis by exclusion. There are many cardiac effects of respiratory alkalosis, such as tachycardia, ventricular and atrial arrhythmias, and ischemic and nonischemic chest pain. In the lungs, vasodilation occurs, and in the gastrointestinal system there are changes in perfusion, motility, and electrolyte handling. Therapeutically, respiratory alkalosis is used for treatment of elevated intracranial pressure. Correction of a respiratory alkalosis is best performed by correcting the underlying etiology.

  20. Coprecipitation of arsenate with metal oxides. 2. Nature, mineralogy, and reactivity of iron(III) precipitates.

    PubMed

    Violante, Antonio; Del Gaudio, Stefania; Pigna, Massimo; Ricciardella, Mariarosaria; Banerjee, Dipanjan

    2007-12-15

    Coprecipitation of arsenic with iron or aluminum occurs in natural environments and is a remediation technology used to remove this toxic metalloid from drinking water and hydrometallurgical solutions. In this work, we studied the nature, mineralogy, and reactivity toward phosphate of iron-arsenate coprecipitates formed at As(V)/Fe(III) molar ratios (R) of 0, 0.01, or 0.1 and at pH 4.0, 7.0, and 10.0 aged for 30 or 210 days at 50 degrees C and studied the desorption of arsenate. At R = 0, goethite and hematite (with ferrihydrite at pH 4.0 and 7.0) crystallized, whereas at R = 0.01, the formation of ferrihydrite increased and hematite crystallization was favored over goethite. In some samples, the morphology of hematite changed from rounded platy crystals to ellipsoids. At R = 0.1, ferrihydrite formed in all the coprecipitates and remained unchanged even after 210 days of aging. The surface area and chemical composition of the precipitates were affected by pH, R, and aging. Chemical dissolution of the samples showed that arsenate was present mainly in ferrihydrite, but at R = 0.01, it was partially incorporated into the structures of crystalline Fe oxides. The sorption of phosphate on to the coprecipitates was affected not only by the mineralogy and surface area of the samples but also by the amounts of arsenate present in the oxides. The samples formed at pH 4.0 and 7.0 and at R = 0.1 sorbed lower amounts of phosphate than the precipitates obtained at R = 0 or 0.01, despite the former having a larger surface area and showing only a presence of short-range ordered materials. This is mainly due to the fact that in the coprecipitates at R = 0.1 arsenate occupied many sorption sites, thus preventing phosphate sorption. Less than 20% of the arsenate present in the coprecipitates formed at R = 0.1 was removed by phosphate and more from the samples synthesized at pH 7.0 or 10.0 than at pH 4.0. Moreover, we found that more arsenate was desorbed by phosphate from a

  1. The use of superporous p(3-acrylamidopropyl)trimethyl ammonium chloride cryogels for removal of toxic arsenate anions.

    PubMed

    Sahiner, Nurettin; Demirci, Sahin; Sahiner, Mehtap; Yilmaz, Selahattin; Al-Lohedan, Hamad

    2015-04-01

    Poly((3-Acrylamidopropyl)trimethylammonium chloride) (p(APTMACl)) cryogels were used as a superporous polymer network for the removal of toxic arsenate anions from an aqueous medium. The fast swelling in water, in about 7 s, was shown to be very useful leading to fast arsenate adsorption by p(APTMACl) cryogels within 30 min in comparison to 12 h for bulk common p(APTMACl) hydrogels. A maximum adsorption capacity of about 120 (mg/g) arsenate was obtained for p(APTMACl) cryogels. Both the Langmuir and Freundlich adsorption isotherms were applied for adsorption of arsenate anions by p(APTMACl) cryogels, and it was observed that the adsorption of arsenate anions by p(APTMACl) cryogels are represented better via Langmuir adsorption isotherm providing the R(2) value of 0.998. Furthermore, mag-p(APTMACl) cryogels were synthesized, and shown to be very useful in the fast removal of toxic arsenate anions. The mag-p(APTMACl) cryogels including the adsorbed arsenate were removed by an externally applied magnetic field, with some reduction in the arsenate ion adsorption capacity. It was also further demonstrated that p(APTMACl) cryogels can be reused in the adsorption of arsenate 5 times from aqueous environments without significant loss of adsorption capacity, from 113.47 ± 9 to 102.67 ± 6 mg/g.

  2. Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate

    USGS Publications Warehouse

    Waychunas, G.A.; Rea, B.A.; Fuller, C.C.; Davis, J.A.

    1993-01-01

    EXAFS spectra were collected on both the As and Fe K-edges from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages. Spectra also were collected for arsenate adsorbed on the surfaces of three FeOOH crystalline polymorphs, ?? (goethite), ?? (akaganeite), and ?? (lepidocrocite), and as a free ion in aqueous: solution. Analyses of the As EXAFS show clear evidence for inner sphere bidentate (bridging) arsenate complexes on the ferrihydrite surface and on the surfaces of the crystalline FeOOH polymorphs. The bridging arsenate is attached to adjacent apices of edge-sharing Fe oxyhydroxyl octahedra. The arsenic-iron distance at the interface (3.28 ??0.01 A ??) is close to that expected for this geometry on the FeOOH polymorph surfaces, but is slightly shorter on the ferrihydrite surfaces (3.25 ?? 0.02 A ??). Mono-dentate arsenate linkages (3.60 ?? 0.03 A ??) also occur on the ferrihydrite, but are not generally observed on the crystalline FeOOH polymorphs. The proportion of monodentate bonds appears largest for adsorption samples with the smallest As Fe molar ratio. In all cases the arsenate tetrahedral complex is relatively undistorted with As-O bonds of 1.66 ?? 0.01 A ??. Precipitation of arsenate or scorodite-like phases was not observed for any samples, all of which were prepared at a pH value of 8. The Fe EXAFS results confirm that the Fe-Fe correlations in the ferrihydrite are progressively disrupted in the CPT samples as the As Fe ratio is increased. Coherent crystallite size is probably no more than 10 A?? in diameter and no Fe oxyhydroxyl octahedra corner-sharing linkages (as would be present in FeOOH polymorphs) are observed at the largest As Fe ratios. Comparison of the number and type of Fe-Fe neighbors with the topological constraints imposed by the arsenate saturation limit in the CPT samples (about 0.7 As Fe) indicates ferrihydrite units consisting mainly

  3. Zeatin reductase in Phaseolus embryos

    SciTech Connect

    Martin, R.C.; Mok, David, W.S.; Mok, M.C. )

    1989-04-01

    Zeatin was converted to O-xylosylzeatin in embryos of Phaseolus vulgaris . O-xylosyldihydrozeatin was also identified as a zeatin metabolite. Incubation of embryo extracts with {sup 14}C-zeatin and {sup 14}C-O-xylosylzeatin revealed that reduction preceeds the O-xylosylation of zeatin. An enzyme responsible for reducing the N{sup 6}-side chain was isolated and partially purified using ammonium sulfate fractionation and affinity, gel filtration and anion exchange chromatography. The NADPH dependent reductase was zeatin specific and did not recognize cis-zeatin, ribosylzeatin, i{sup 6}Ade or i{sup 6}Ado. Two forms of the reductase could be separated by either gel filtration or anion exchange HPLC. The HMW isozyme (Mr. 55,000) eluted from the anion exchange column later than the LMW isozyme (Mr. 25,000). Interspecific differences in zeatin reductase activity were also detected.

  4. Isolated menthone reductase and nucleic acid molecules encoding same

    DOEpatents

    Croteau, Rodney B; Davis, Edward M; Ringer, Kerry L

    2013-04-23

    The present invention provides isolated menthone reductase proteins, isolated nucleic acid molecules encoding menthone reductase proteins, methods for expressing and isolating menthone reductase proteins, and transgenic plants expressing elevated levels of menthone reductase protein.

  5. The Pho4 transcription factor mediates the response to arsenate and arsenite in Candida albicans

    PubMed Central

    Urrialde, Verónica; Prieto, Daniel; Pla, Jesús; Alonso-Monge, Rebeca

    2015-01-01

    Arsenate (As (V)) is the dominant form of the toxic metalloid arsenic (As). Microorganisms have consequently developed mechanisms to detoxify and tolerate this kind of compounds. In the present work, we have explored the arsenate sensing and signaling mechanisms in the pathogenic fungus Candida albicans. Although mutants impaired in the Hog1 or Mkc1-mediated pathways did not show significant sensitivity to this compound, both Hog1 and Mkc1 became phosphorylated upon addition of sodium arsenate to growing cells. Hog1 phosphorylation upon arsenate challenge was shown to be Ssk1-dependent. A screening designed for the identification of transcription factors involved in the arsenate response identified Pho4, a transcription factor of the myc-family, as pho4 mutants were susceptible to As (V). The expression of PHO4 was shortly induced in the presence of sodium arsenate in a Hog1-independent manner. Pho4 level affects Hog1 phosphorylation upon As (V) challenge, suggesting an indirect relationship between Pho4 activity and signaling in C. albicans. Pho4 also mediates the response to arsenite as revealed by the fact that pho4 defective mutants are sensitive to arsenite and Pho4 becomes phosphorylated upon sodium arsenite addition. Arsenite also triggers Hog1 phosphorylation by a process that is, in this case, independent of the Ssk1 kinase. These results indicate that the HOG pathway mediates the response to arsenate and arsenite in C. albicans and that the Pho4 transcription factor can differentiate among As (III), As (V) and Pi, triggering presumably specific responses. PMID:25717325

  6. Characterization and adsorption of arsenate and selenite onto Kemiron.

    PubMed

    Oti, Douglas; Trotz, Maya

    2008-08-01

    Kemiron, a commercially available, porous iron oxide sorbent was evaluated in batch systems for arsenate (As(V)) and selenite (Se(IV)) removal from aqueous solutions as a function of pH, ionic strength, and particle size (< 38 micro m and between 250 and 425 micro m). BET surface area of Kemiron is 39.8 m(2)/g and Electron dispersive spectroscopy (EDS) studies found Kemiron to be 40.37% iron and 42.25% oxygen by mass. Langmuir isotherms best described the As(V) and Se(IV) removal at pH 7 with maximum adsorption capacity of 82 mg/g and 52 mg/g respectively. As(V) and Se(IV) sorption decreased as pH increased and both anions were unaffected by sodium nitrate (NaNO(3)) background electrolyte. As(V) sorption was not affected in surface water samples from the Hillsborough River. Batch kinetic models of the experimental data on the 250 to 425 micro m particle size yielded mass transfer coefficients of 0.0008 min(-1) and 0.009 min(-1) for As(V) and Se(IV) respectively.

  7. Effects of arsenate on growth and physiology in mallard ducklings

    USGS Publications Warehouse

    Camardese, M.B.; Hoffman, D.J.; LeCaptain, L.J.; Pendleton, G.W.

    1990-01-01

    Arsenic (As) has been found at elevated concentrations in irrigation drainwater and in aquatic plants utilized by waterfowl. Mallard (Anas platyrhynchos) duckings received an untreated diet (controls) or diets containing 30, 100 or 300 ppm As added as sodium arsenate. After 10 weeks blood and tissue samples were collected for biochemical and histological examination. Arsenic accumulated significantly in brain and liver of ducklings fed 100 or 300 ppm but did not result in histopathological lesions. The 300-ppm dietary As concentration decreased overall growth (weight gain) in males, whereas all concentrations of As decreased overall growth and rate of growth in females. Food consumption was less during the first three weeks in all 300-ppm group and during the second week for the 100-ppm compared to controls. Plasma sorbitol dehydrogenase activity and plasma glucose concentration were higher in the 300-ppm group compared to controls. Plasma triglyceride concentration increased in all As-treated groups. Brain ATP was lower in the 300-ppm group and sodium/potassium-dependent ATPase activity was higher in the 30- and 100-ppm groups. Hepatic glutathione peroxidase activity was lower in the 300-ppm group and malondialdehyde lower in all treatment groups. All treatment levels caused elevation in hepatic glutathione and ATP concentrations. These findings, in combination with altered duckling behavior (increased resting time) suggesting that concentrations of As that have been found in aquatic plants (up to 430 ppm dry weight) could adversely affect normal duckling development.

  8. Edaphic factors affecting the toxicity and accumulation of arsenate in the earthworm Lumbricus terrestris

    SciTech Connect

    Meharg, A.A.; Shore, R.F.; Broadgate, K.

    1998-06-01

    The toxicity and accumulation of arsenate was determined in the earthworm Lumbricus terrestris in soil from different layers of a forest profile. Toxicity increased fourfold between 2 and 10 d. Edaphic factors (pH, soil organic matter, and depth in soil profile) also affected toxicity with a three fold decrease in the concentration that causes 50% mortality with increasing depth in soil. In a 4-d exposure study, there was no evidence of arsenic bioconcentration in earthworm tissue, although bioaccumulation was occurring. There was a considerable difference in tissue residues between living and dead earthworms, with dead worms having higher concentrations. This difference was dependent on both soil arsenate concentration and on soil type. Over a wide range of soil arsenate concentrations, earthworm arsenic residues are homeostatically maintained in living worms, but this homeostasis breaks down during death. Alternatively, equilibration with soil residues may occur via accumulation after death. In long-term accumulation studies in soils dosed with a sublethal arsenate concentration, bioconcentration of arsenate did not occur until day 12, after which earthworm concentrations rose steadily above the soil concentration, with residues in worms three fold higher than soil concentrations by the termination of the study. This bioconcentration only occurred in depurated worms over the time period of the study. Initially, depurated worms had lower arsenic concentrations than undepurated until tissue concentrations were equivalent to the soil concentration. Once tissue concentration was greater than soil concentration, depurated worms had higher arsenic residues than undepurated.

  9. Evaluating the performance of iron nanoparticle resin in removing arsenate from water.

    PubMed

    Boldaji, Maryam Rahmani; Nabizadeh, Ramin; Dehghani, Mohammad Hadi; Nadafi, Kazem; Mahvi, Amir Hossein

    2010-01-01

    This research was undertaken to evaluate the effectiveness of a hybrid sorbent resin (Lewatit FO36) with goethite structure for removing arsenate from water. Column experiments (with constant flow rate of 8 mL/min, corresponding to 2 min empty bed contact time (EBCT)) were conducted to evaluate the adsorption capacity of resin before and after regeneration and effects of chloride, sulfate, bicarbonate and combined competing ions for arsenate removal from water. The adsorption capacity was approximately 3.229 mg/g that was reduced to 2.826 mg/g after regeneration with 12.48% decrease, which indicates to a successful regeneration procedure. Chloride and sulfate ions had no significant effects on arsenate removal but arsenic removal decreased in the presence of bicarbonate and combined ions. This reduction may be due to the ability of bicarbonate ions in extracting and mobilizing the arsenate ions from iron oxyhydroxides. Results of this study showed that Lewatit FO36 could be developed as a suitable sorbent for arsenate removal.

  10. Constant rate exposure of pregnant hamsters to arsenate during early gestation

    SciTech Connect

    Ferm, V.H.; Hanlon, D.P.

    1985-08-01

    The teratogenic and embryotoxic effects of constant-rate exposure of pregnant hamsters to arsenate have been examined by means of subcutaneous implants of osmotic minipumps. Different total exposure regimes were established by varying the duration of minipump implants and by varying the concentration of arsenate in the minipumps. Dams were killed on Day 13 pregnancy, 5 days after the critical stage of organogenesis. Numbers of resorptions, dead fetuses, and living fetuses were obtained. Fetal weights, crown-rump lengths, and the incidence of malformations were recorded. Control animals were treated identically with minipumps containing demineralized water. The percentage of malformations per litter, a direct measure of teratogenesis, was dependent only upon the concentration of arsenate in the minipumps. The minimum teratogenic response was achieved with a dose of 70 ..mu..mol/kg dam/24 hr during the critical stages of organogenesis. The embryotoxic (fetotoxic) indicators, fetal weight and crown-rump length, decreased with increases in exposure time and with increased concentrations of arsenate. The resorption rate also depended directly upon duration of exposure and concentration of arsenate in the mini-pump.

  11. Effects of pore size and dissolved organic matters on diffusion of arsenate in aqueous solution.

    PubMed

    Wang, Yulong; Wang, Shaofeng; Wang, Xin; Jia, Yongfeng

    2017-02-01

    Presented here is the influence of membrane pore size and dissolved organic matters on the diffusion coefficient (D) of aqueous arsenate, investigated by the diffusion cell method for the first time. The pH-dependent diffusion coefficient of arsenate was determined and compared with values from previous studies; the coefficient was found to decrease with increasing pH, showing the validity of our novel diffusion cell method. The D value increased dramatically as a function of membrane pore size at small pore sizes, and then increased slowly at pore sizes larger than 2.0μm. Using the ExpAssoc model, the maximum D value was determined to be 11.2565×10(-6)cm(2)/sec. The presence of dissolved organic matters led to a dramatic increase of the D of arsenate, which could be attributed to electrostatic effects and ionic effects of salts. These results improve the understanding of the diffusion behavior of arsenate, especially the important role of various environmental parameters in the study and prediction of the migration of arsenate in aquatic water systems.

  12. Differences in the immobilization of arsenite and arsenate by calcite

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yuka; Tanaka, Kazuya; Takahashi, Yoshio

    2012-08-01

    The sorption and coprecipitation experiments of arsenic (As) with calcite coupled with determinations of the chemical state of As both in the reaction fluid and in calcite were conducted to investigate the influence of the As oxidation state on its immobilization into calcite. The oxidation states of As in calcite and water were determined via As K-edge XANES and HPLC-ICP-MS analysis, respectively. The results of the sorption experiments at pH 8.2 show that only As(V) is distributed to calcite regardless of the As oxidation state in the solution. In coprecipitation experiments, As(V) is preferentially incorporated into calcite over a wide range of pH (7-12). On the other hand, the incorporation of As(III) into calcite is not observed at circumneutral pH. This difference between As(III) and As(V) is attributed to the fact that their dissolved species are neutral vs. negatively charged, respectively, at circumneutral pH (arsenite as H3AsO3; arsenate as H2AsO4- or HAsO42-). As the pH increases (>9), up to 33% of As(III)/Astotal ratio is partitioned into calcite or a precursor of calcite (metastable vaterite formed during the early stage of precipitation). The higher interaction of As with calcite at an alkaline pH compared with circumneutral pH is due to the negative charge of As(III) at alkaline pH. However, the As(III)/Astotal ratio decreases as time progresses and only As(V) can be found finally in calcite. The ratio of distribution coefficients of As(III) and As(V) into calcite (KAs(V)/KAs(III)) at pH ˜7 is larger than 2.1 × 103, suggesting that the oxidation state of As is a significant issue in considering the interaction between As and calcite in groundwater. Moreover, low KAs(III) shows that the sequestration of As via coprecipitation with calcite is not an important chemical process under reducing conditions, such as in the groundwaters in Bangladesh and other As-contaminated areas where As(III) is the dominant dissolved species of As. In the system spiked

  13. Impact of chromated copper arsenate (CCA) in wood mulch.

    PubMed

    Townsend, Timothy G; Solo-Gabriele, Helena; Tolaymat, Thabet; Stook, Kristin

    2003-06-20

    The production of landscape mulch is a major market for the recycling of yard trash and waste wood. When wood recovered from construction and demolition (C&D) debris is used as mulch, it sometimes contains chromated copper arsenate (CCA)-treated wood. The presence of CCA-treated wood may cause some potential environmental problems as a result of the chromium, copper, and arsenic present. Research was performed to examine the leachability of the three metals from a variety of processed wood mixtures in Florida. The mixtures tested included mixed wood from C&D debris recycling facilities and mulch purchased from retail outlets. The synthetic precipitation leaching procedure (SPLP) was performed to examine the leaching of chromium, copper and arsenic. Results were compared to Florida's groundwater cleanup target levels (GWCTLs). Eighteen of the 22 samples collected from C&D debris processing facilities leached arsenic at concentrations greater than Florida's GWCTL of 50 microg/l. The mean leachable arsenic concentration for the C&D debris samples was 153 microg/l with a maximum of 558 microg/l. One of the colored mulch samples purchased from a retail outlet leached arsenic above 50 microg/l, while purchased mulch samples derived from virgin materials did not leach detectable arsenic (<5 microg/l). A mass balance approach was used to compute the potential metal concentrations (mg/kg) that would result from CCA-treated wood being present in wood mulch. Less than 0.1% CCA-treated wood would cause a mulch to exceed Florida's residential clean soil guideline for arsenic (0.8 mg/kg).

  14. Combined Hydrous Ferric Oxide and Quaternary Ammonium Surfactant Tailoring of Granular Activated Carbon for Concurrent Arsenate and Perchlorate Removal

    SciTech Connect

    Jang, M.; Cannon, F; Parette, R; Yoon, S; Chen, W

    2009-01-01

    Activated carbon was tailored with both iron and quaternary ammonium surfactants so as to concurrently remove both arsenate and perchlorate from groundwater. The iron (hydr)oxide preferentially removed the arsenate oxyanion but not perchlorate; while the quaternary ammonium preferentially removed the perchlorate oxyanion, but not the arsenate. The co-sorption of two anionic oxyanions via distinct mechanisms has yielded intriguing phenomena. Rapid small-scale column tests (RSSCTs) with these dually prepared media employed synthetic waters that were concurrently spiked with arsenate and perchlorate; and these trial results showed that the quaternary ammonium surfactants enhanced arsenate removal bed life by 25-50% when compared to activated carbon media that had been preloaded merely with iron (hydr)oxide; and the surfactant also enhanced the diffusion rate of arsenate per the Donnan effect. The authors also employed natural groundwater from Rutland, MA which contained 60 microg/L As and traces of silica, and sulfate; and the authors spiked this with 40 microg/L perchlorate. When processing this water, activated carbon that had been tailored with iron and cationic surfactant could treat 12,500 bed volumes before 10 microg/L arsenic breakthrough, and 4500 bed volumes before 6 microg/L perchlorate breakthrough. Although the quaternary ammonium surfactants exhibited only a slight capacity for removing arsenate, these surfactants did facilitate a more favorably positively charged avenue for the arsenate to diffuse through the media to the iron sorption site (i.e. via the Donnan effect).

  15. Effect of flooding lead-arsenate contaminated orchard soil on growth, arsenic and lead accumulation in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lead-arsenate has been used as a pesticide in controlling codling moth (Cydia pomonella) in apple and plum orchards from 1900-1960. As a result, many old orchards contain high levels of arsenic. Flooding soils contaminated by lead-arsenate could increase plant arsenic and lead and become a human h...

  16. Ion chromatographic separation and determination of phosphate and arsenate in water and hair.

    PubMed

    Antony, P J; Karthikeyan, S; Iyer, C S P

    2002-02-15

    A simple and sensitive method for the sequential determination of phosphate and arsenate was developed based on initial ion chromatographic separation followed by detection as the ion-association complex formed by heteropolymolybdophosphate and arsenate with bismuth. With 200 microl sample injection and separation on a AS4A-SC column using an eluent of 3.5 mM sodium hydrogen carbonate-10.0 mM sodium hydroxide, the detection limits which are calculated as the concentration equivalent to twice the baseline noise, were found to be 0.8 microg/l and 4.2 microg/l for P and As, respectively. Spiked samples were analyzed and recoveries were found to be satisfactory in the range of 95-105% for phosphate and 90-105% for arsenate. Samples of water and hair were analyzed by the proposed method.

  17. Respiratory Therapists

    MedlinePlus

    ... programs typically include courses in human anatomy and physiology, chemistry, physics, microbiology, pharmacology, and math. Other courses ... and math skills. Respiratory therapists must understand anatomy, physiology, and other sciences and be able to calculate ...

  18. Effect of Aqueous Fe(II) on Arsenate Sorption on Goethite and Hematite

    SciTech Connect

    Catalano, Jeffrey G.; Luo, Yun; Otemuyiwa, Bamidele

    2011-11-17

    Biogeochemical iron cycling often generates systems where aqueous Fe(II) and solid Fe(III) oxides coexist. Reactions between these species result in iron oxide surface and phase transformations, iron isotope fractionation, and redox transformations of many contaminant species. Fe(II)-induced recrystallization of goethite and hematite has recently been shown to cause the repartitioning of Ni(II) at the mineral-water interface, with adsorbed Ni incorporating into the iron oxide structure and preincorporated Ni released back into aqueous solution. However, the effect of Fe(II) on the fate and speciation of redox inactive species incompatible with iron oxide structures is unclear. Arsenate sorption to hematite and goethite in the presence of aqueous Fe(II) was studied to determine whether Fe(II) causes substantial changes in the sorption mechanisms of such incompatible species. Sorption isotherms reveal that Fe(II) minimally alters macroscopic arsenate sorption behavior except at circumneutral pH in the presence of elevated concentrations (10{sup -3} M) of Fe(II) and at high arsenate loadings, where a clear signature of precipitation is observed. Powder X-ray diffraction demonstrates that the ferrous arsenate mineral symplesite precipitates under such conditions. Extended X-ray absorption fine structure spectroscopy shows that outside this precipitation regime arsenate surface complexation mechanisms are unaffected by Fe(II). In addition, arsenate was found to suppress Fe(II) sorption through competitive adsorption processes before the onset of symplesite precipitation. This study demonstrates that the sorption of species incompatible with iron oxide structure is not substantially affected by Fe(II) but that such species may potentially interfere with Fe(II)-iron oxide reactions via competitive adsorption.

  19. Adsorption of fluoride, phosphate, and arsenate ions on a new type of ion exchange fiber.

    PubMed

    Ruixia, Liu; Jinlong, Guo; Hongxiao, Tang

    2002-04-15

    A new type of ion exchange fiber for the removal of fluoride, phosphate, and arsenate ions has been developed. A batch adsorption technique for investigating adsorption kinetic and equilibrium parameters and determining pH adsorption edges is applied. It is shown that the adsorption properties of the ion exchange fiber for fluoride, phosphate, and arsenate ions depend on the pH value and anion concentration. The adsorption of arsenate on the sorbent reaches a maximum of 97.9% in the pH value range of 3.5 to 7.0. The adsorption percentage of phosphate is more than 99% in the pH range of 3.0 to 5.5. The adsorption of fluoride on the ion exchange fiber is found to be 90.4% at pH 3.0. The Freundlich model can describe the adsorption equilibrium data of fluoride, arsenate, and phosphate anions. The sorption of the three anions on the ion exchange fiber is a rapid process, and the adsorption kinetic data can be simulated very well by the pseudo-second-order rate equation. The column performance is carried out to assess the applicability of the ion exchange fiber for the removal of fluoride, phosphate, and arsenate ions from synthetic wastewaters with satisfactory removal efficiency. The desorption experiment shows that fluoride ion sorbed by the fiber column can be quantitatively desorbed with 5 mL of 0.50 mol/L NaOH at elution rate of 1 mL/min, and 30 mL of NaOH is necessary for the quantitative recovery of phosphate and arsenate ions.

  20. Arsenate removal by layered double hydroxides embedded into spherical polymer beads: Batch and column studies.

    PubMed

    Nhat Ha, Ho Nguyen; Kim Phuong, Nguyen Thi; Boi An, Tran; Mai Tho, Nguyen Thi; Ngoc Thang, Tran; Quang Minh, Bui; Van Du, Cao

    2016-01-01

    In this study, the performance of poly(layered double hydroxides) [poly(LDHs)] beads as an adsorbent for arsenate removal from aqueous solution was investigated. The poly(LDHs) beads were prepared by immobilizing LDHs into spherical alginate/polyvinyl alcohol (PVA)-glutaraldehyde beads (spherical polymer beads). Batch adsorption studies were conducted to assess the effect of contact time, solution pH, initial arsenate concentrations and co-existing anions on arsenate removal performance. The potential reuse of these poly(LDHs) beads was also investigated. Approximately 79.1 to 91.2% of arsenic was removed from an arsenate solution (50 mg As L(-1)) by poly(LDHs). The adsorption data were well described by the pseudo-second-order kinetics model and the Langmuir isotherm model, and the adsorption capacities of these poly(LDHs) beads at pH 8 were from 1.64 to 1.73 mg As g(-1), as calculated from the Langmuir adsorption isotherm. The adsorption ability of the poly(LDHs) beads decreased by approximately 5-6% after 5 adsorption-desorption cycles. Phosphates markedly decreased arsenate removal. The effect of co-existing anions on the adsorption capacity declined in the following order: HPO4 (2-) > HCO3 (-) > SO4 (2-) > Cl(-). A fixed-bed column study was conducted with real-life arsenic-containing water. The breakthrough time was found to be from 7 to 10 h. Under optimized conditions, the poly(LDHs) removed more than 82% of total arsenic. The results obtained in this study will be useful for further extending the adsorbents to the field scale or for designing pilot plants in future studies. From the viewpoint of environmental friendliness, the poly(LDHs) beads are a potential cost-effective adsorbent for arsenate removal in water treatment.

  1. [Respiratory distress].

    PubMed

    Galili, D; Garfunkel, A; Elad, S; Zusman, S P; Malamed, S F; Findler, M; Kaufman, E

    2002-01-01

    Dental treatment is usually conducted in the oral cavity and in very close proximity to the upper respiratory airway. The possibility of unintentionally compromising this airway is high in the dental environment. The accumulation of fluid (water or blood) near to the upper respiratory airway or the loosening of teeth fragmentations and fallen dental instruments can occur. Also, some of the drugs prescribed in the dental practice are central nervous system depressants and some are direct respiratory drive depressors. For this reason, awareness of the respiratory status of the dental patient is of paramount importance. This article focuses on several of the more common causes of respiratory distress, including airway obstruction, hyperventilation, asthma, bronchospasm, pulmonary edema, pulmonary embolism and cardiac insufficiency. The common denominator to all these conditions described here is that in most instances the patient is conscious. Therefore, on the one hand, valuable information can be retrieved from the patient making diagnosis easier than when the patient is unconscious. On the other hand, the conscious patient is under extreme apprehension and stress under such situations. Respiratory depression which occurs during conscious sedation or following narcotic analgesic medication will not be dealt with in this article. Advanced pain and anxiety control techniques such as conscious sedation and general anesthesia should be confined only to operators who undergo special extended training.

  2. Lead in tissue of cats fed pine voles from lead arsenate-treated orchards

    SciTech Connect

    Gilmartin, J.E.; Alo, D.K.; Richmond, M.E.; Bache, C.A.; Lisk, D.J.

    1985-02-01

    Lead arsenate has been used for many years for control of insects in apple orchards in the United States. In an earlier study, it was shown that such orchard soils may contain very high concentrations of lead and that orchards voles and mice inhibating such soils accumulate inordinately high levels of lead. It is of interest to learn the possible extent of deposition of lead in higher carnivores that may consume such orchard animals. In the work reported, cats were fed pine voles (Microtus pinetorum) captured in lead arsenate-treated orchards located in the vicinity of New Paltz, New York. Following sacrifice, the lead content of cat tissues was determined.

  3. Phosphate and arsenate removal efficiency by thermostable ferritin enzyme from Pyrococcus furiosus using radioisotopes.

    PubMed

    Sevcenco, Ana-Maria; Paravidino, Monica; Vrouwenvelder, Johannes S; Wolterbeek, Hubert Th; van Loosdrecht, Mark C M; Hagen, Wilfred R

    2015-06-01

    Oxo-anion binding properties of the thermostable enzyme ferritin from Pyrococcus furiosus were characterized with radiography. Radioisotopes (32)P and (76)As present as oxoanions were used to measure the extent and the rate of their absorption by the ferritin. Thermostable ferritin proved to be an excellent system for rapid phosphate and arsenate removal from aqueous solutions down to residual concentrations at the picomolar level. These very low concentrations make thermostable ferritin a potential tool to considerably mitigate industrial biofouling by phosphate limitation or to remove arsenate from drinking water.

  4. Formation of iron (hydr)oxides during the abiotic oxidation of Fe(II) in the presence of arsenate.

    PubMed

    Song, Jia; Jia, Shao-Yi; Yu, Bo; Wu, Song-Hai; Han, Xu

    2015-08-30

    Abiotic oxidation of Fe(II) is a common pathway in the formation of Fe (hydr)oxides under natural conditions, however, little is known regarding the presence of arsenate on this process. In hence, the effect of arsenate on the precipitation of Fe (hydr)oxides during the oxidation of Fe(II) is investigated. Formation of arsenic-containing Fe (hydr)oxides is constrained by pH and molar ratios of As:Fe during the oxidation Fe(II). At pH 6.0, arsenate inhibits the formation of lepidocrocite and goethite, while favors the formation of ferric arsenate with the increasing As:Fe ratio. At pH 7.0, arsenate promotes the formation of hollow-structured Fe (hydr)oxides containing arsenate, as the As:Fe ratio reaches 0.07. Arsenate effectively inhibits the formation of magnetite at pH 8.0 even at As:Fe ratio of 0.01, while favors the formation of lepidocrocite and green rust, which can be latterly degenerated and replaced by ferric arsenate with the increasing As:Fe ratio. This study indicates that arsenate and low pH value favor the slow growth of dense-structured Fe (hydr)oxides like spherical ferric arsenate. With the rapid oxidation rate of Fe(II) at high pH, ferric (hydr)oxides prefer to precipitate in the formation of loose-structured Fe (hydr)oxides like lepidocrocite and green rust.

  5. Nitrate reductase from Rhodopseudomonas sphaeroides.

    PubMed Central

    Kerber, N L; Cardenas, J

    1982-01-01

    The facultative phototroph Rhodopseudomonas sphaeroides DSM158 was incapable of either assimilating or dissimilating nitrate, although the organism could reduce it enzymatically to nitrite either anaerobically in the light or aerobically in the dark. Reduction of nitrate was mediated by a nitrate reductase bound to chromatophores that could be easily solubilized and functioned with chemically reduced viologens or photochemically reduced flavins as electron donors. The enzyme was solubilized, and some of its kinetic and molecular parameters were determined. It seemed to be nonadaptive, ammonia did not repress its synthesis, and its activity underwent a rapid decline when the cells entered the stationary growth phase. Studies with inhibitors and with metal antagonists indicated that molybdenum and possibly iron participate in the enzymatic reduction of nitrate. The conjectural significance of this nitrate reductase in phototrophic bacteria is discussed. PMID:6978883

  6. Subchronic dispositional and toxicological effects of arsenate administered in drinking water to mice.

    PubMed

    Hughes, M F; Thompson, D J

    1996-10-11

    Exposure to the drinking water contaminant arsenate is a daily occurrence and there are concerns that this exposure may lead to cancer. Although the acute dispositional effects of arsenate have been studied in detail, there is minimal information on the disposition and toxicological effects of it after continuous exposure. The objective of this study was to examine in mice the effect of a 4-wk treatment with arsenate administered in drinking water. Female B6C3F1 mice (3/cage) were housed in metabolism cages and given water and food ad libitum. Two groups (A, B) of mice were treated (4 cages/treatment/group) with distilled water (control, C) or water containing 0.025 mg/L (L) or 2.5 mg/L (H) arsenate. Group A was sacrificed on d 28 and plasma and urine samples were taken for determination of clinical chemistry parameters. Liver and kidney tissue samples were taken for histopathological analysis. The reduced nonprotein sulfhydryl (NPSH) content in several tissues was determined. Group B was gavaged with [73As]arsenate on d 28 and continued the arsenate drinking water exposure for 48 h. Excreta and tissues were collected and analyzed for 73As. Urine was further analyzed for arsenate and its metabolites. There were no effects on the mean daily amount of water and food consumed, whereas the mean daily urine volume excreted was significantly elevated by 10% in the H-treated animals compared to C and L. A dose-related hepatic vacuolar degeneration in the liver was observed, but no histological changes were evident in the kidney. Only clinical chemistry parameters in plasma were altered by the arsenate treatment. Glucose was significantly lower at the H dose compared to C and L, triglycerides were significantly greater in C than L and H, and creatinine was significantly greater in H than C. Hepatic NPSH content in the H animals was significantly lower than C and L animals, whereas no effects in lung and kidney were detected. The weights of liver, lung, and kidney, as well

  7. Non-linear optical titanyl arsenates: Crystal growth and properties

    NASA Astrophysics Data System (ADS)

    Nordborg, Jenni Eva Louise

    Crystals are appreciated not only for their appearance, but also for their unique physical properties which are utilized by the photonic industry in appliances that we come across every day. An important part of enabling the technical use of optical devices is the manufacture of crystals. This dissertation deals with a specific group of materials called the potassium titanyl phosphate (KIP) family, known for their non-linear optical and ferroelectric properties. The isomorphs vary in their linear optical and dielectric properties, which can be tuned to optimize device performance by forming solid solutions of the different materials. Titanyl arsenates have a wide range of near-infrared transmission which makes them useful for tunable infrared lasers. The isomorphs examined in the present work were primarily RbTiOASO4 (RTA) and CsTiOAsO4 (CTA) together with the mixtures RbxCs 1-xTiOAsO4 (RCTA). Large-scale crystals were grown by top seeding solution growth utilizing a three-zone furnace with excellent temperature control. Sufficiently slow cooling and constant upward lifting produced crystals with large volumes useable for technical applications. Optical quality RTA crystals up to 10 x 12 x 20 mm were grown. The greater difficulty in obtaining good crystals of CTA led to the use of mixed RCTA materials. The mixing of rubidium and cesium in RCTA is more favorable to crystal growth than the single components in pure RTA and CTA. Mixed crystals are rubidium-enriched and contain only 20-30% of the cesium concentration in the flux. The cesium atoms show a preference for the larger cation site. The network structure is very little affected by the cation substitution; consequently, the non-linear optical properties of the Rb-rich isomorphic mixtures of RTA and CTA can be expected to remain intact. Crystallographic methods utilizing conventional X-ray tubes, synchrotron radiation and neutron diffraction have been employed to investigate the properties of the atomic

  8. Denitrification by plant roots? New aspects of plant plasma membrane-bound nitrate reductase.

    PubMed

    Eick, Manuela; Stöhr, Christine

    2012-10-01

    A specific form of plasma membrane-bound nitrate reductase in plants is restricted to roots. Two peptides originated from plasma membrane integral proteins isolated from Hordeum vulgare have been assigned as homologues to the subunit NarH of respiratory nitrate reductase of Escherichia coli. Corresponding sequences have been detected for predicted proteins of Populus trichocarpa with high degree of identities for the subunits NarH (75%) and NarG (65%), however, with less accordance for the subunit NarI. These findings coincide with biochemical properties, particularly in regard to the electron donors menadione and succinate. Together with the root-specific and plasma membrane-bound nitrite/NO reductase, nitric oxide is produced under hypoxic conditions in the presence of nitrate. In this context, a possible function in nitrate respiration of plant roots and an involvement of plants in denitrification processes are discussed.

  9. Accumulation of lead and arsenic by carrots grown on four lead-arsenate contaminated orchard soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Concerns have been raised about possible human food chain transfer of contaminants resulting from crops grown on orchard soils with histories of lead arsenate use. The objective of this study was to determine the uptake of arsenic and lead by three cultivars of carrots. Carrots were grown on four ...

  10. Accumulation of lead and arsenic by lettuce grown on lead-arsenate contaminated orchard soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lead-arsenate was one of the preferred insecticides used as foliar spray to control codling moth (Cydia pomonella) in apple (Malus sylvestris Mill) orchards from the 1900's to the 1960’s. Lead and arsenic are generally immobile and remain in the surface soil. Some of these contaminated lands are now...

  11. COMPARATIVE METABOLISM OF ARSENIC IN MICE AFTER A SINGLE OR REPEATED ORAL ADMINISTRATION OF ARSENATE

    EPA Science Inventory

    COMPARATIVE METABOLISM OF ARSENIC IN MICE AFTER A SINGLE OR REPEATED ORAL ADMINISTRATION OF ARSENATE
    Michael F. Hughes*1, Elaina M. Kenyon1, Brenda C. Edwards1, Carol T. Mitchell1, Luz Maria Del Razo2 and David J. Thomas1
    1US EPA, ORD, NHEERL, ETD, PKB, Research Triangle Pa...

  12. [Removal of arsenate from drinking water by activated carbon supported nano zero-valent iron].

    PubMed

    Zhu, Hui-jie; Jia, Yong-feng; Yao, Shu-hu; Wu, Xing; Wang, Shu-ying

    2009-12-01

    A new adsorbent, activated carbon impregnated with nano zero-valent iron was prepared, which size of the needle-shaped iron particles in the pores of carbon was (30-500) nm x (1000-3000) nm and approximately 8.2% of iron was loaded onto it. The arsenate removal percentage was 99.5% by 1.5 g/L NZVI/AC in the 2 mg/L arsenic solution at pH 6.5 and (25 +/- 2) degrees C. The adsorption capacity was about 15.4 mg/g when equilibrium concentration was 1.0 mg/L. Kinetics revealed that uptake of arsenate ion by NZVI/AC was 91.4% in the first 12 h and equilibrium time was about 72 h. The intraparticle diffusion model was applied to study the mechanics of arsenate in the activated carbon. The presence of phosphate and silicate could significantly decrease arsenate removal while the effects of the other anions and cations on the arsenic removal were neglectable. NZVI/AC can be effectively regenerated when elution is done with 0.1 mol/L NaOH solution. Our results suggest that NZVI/AC is a suitable candidate for drinking water treatment due to its high reactivity.

  13. SORPTION OF ARSENATE AND ARSENITE ON A RUTHENIUM COMPOUND: A MACROSCOPIC AND MICROSCOPIC STUDY

    EPA Science Inventory

    Sorption of arsenate and arsenite was examined on a ruthenium compound using macroscopic and microscopic techniques. Batch sorption experiments at pH 4,5,6, 7 and 8 were employed to construct constant solid solution ratio isotherms (CSI). After equilibration at the appropriate pH...

  14. SORPTION OF ARSENATE AND ARSENITE ON RUO2.XH2O: A SPECTROSCOPIC AND MACROSCOPIC STUDY

    EPA Science Inventory

    The sorption of arsenate (As(V)) and arsenite (As(III)) on RuO2 xH2O was examined using macroscopic and microscopic techniques. Constant solid:solution ratio isotherms were constructed from batch sorption experiments to study the sorption of the inorganic arsenic species on RuO2...

  15. Bioaccumulation and oxidative stress in Daphnia magna exposed to arsenite and arsenate.

    PubMed

    Fan, Wenhong; Ren, Jinqian; Li, Xiaomin; Wei, Chaoyang; Xue, Feng; Zhang, Nan

    2015-11-01

    Arsenic pollution and its toxicity to aquatic organisms have attracted worldwide attention. The bioavailability and toxicity of arsenic are highly related to its speciation. The present study investigated the differences in bioaccumulation and oxidative stress responses in an aquatic organism, Daphnia magna, induced by 2 inorganic arsenic species (As(III) and As(V)). The bioaccumulation of arsenic, Na(+) /K(+) -adenosine triphosphatase (ATPase) activity, reactive oxygen species (ROS) content, total superoxide dismutase (SOD) activity, total antioxidative capability, and malondialdehyde content in D. magna were determined after exposure to 500 µg/L of arsenite and arsenate for 48 h. The results showed that the oxidative stress and antioxidative process in D. magna exposed to arsenite and arsenate could be divided into 3 phases, which were antioxidative response, oxidation inhibition, and antioxidative recovery. In addition, differences in bioaccumulation, Na(+) /K(+) -ATPase activity, and total SOD activity were also found in D. magna exposed to As(III) and As(V). These differences might have been the result of the high affinity of As(III) with sulfhydryl groups in enzymes and the structural similarity of As(V) to phosphate. Therefore, arsenate could be taken up by organisms through phosphate transporters, could substitute for phosphate in biochemical reactions, and could lead to a change in the bioaccumulation of arsenic and activity of enzymes. These characteristics were the possible reasons for the different toxicity mechanisms in the oxidative stress process of arsenite and arsenate.

  16. Genotoxic effects of sodium arsenite and sodium arsenate after chronic exposure of Drosophila melanogaster larvae

    SciTech Connect

    Ramos-Morales, P.; Ordaz, M.G.; Munoz, A.

    1995-11-01

    Two arsenic compounds, namely: NaAsO{sub 2} (Sodium Arsenite) and Na{sub 2}HAsO{sub 4} (Sodium Arsenate) were tested for its chronic effect in somatic cells of Drosophila melanogaster. In a previous study in Drosophila we found that both compounds induced SLRL mutations, but failed to induce sex chromosome loss. In the SMART, after acute exposure, only sodium arsenite was positive when cells of the wings were used; however, both were positives in cells of the eyes of Drosophila. The genotoxicity of both compounds localized mainly on somatic cells, in agreement with reports on the carcinogenicity potential of arsenical compounds. The Somatic mutation and recombination test (SMART) was run employing cells of the wing imaginal discs from flr{sup 3}/mwh larvae. First instar larvae (24 {plus_minus} 4 h) were treated during 96 hours with sodium arsenite [0.015-4.0 ppm], and sodium arsenate [0.2-10 ppm], negative control was treated with distilled water. The frequency of spots by wing induced by the two arsenic salts were compared with control according with Frei and Wuergler procedure. Data show that sodium arsenite tested negative at all concentrations, but sodium arsenate tested positive at 0.8, 2 and 10 ppm (P<0.05). This results were consistent with the co-mutagenic role of sodium arsenite, but show that sodium arsenate was mutagenic in Drosophila test system under chronic exposure.

  17. WASTE REDUCTION PRACTICES AT TWO CHROMATED COPPER ARSENATE WOOD-TREATING PLANTS

    EPA Science Inventory

    Two chromated copper arsenate (CCA) wood-treating plants were assessed for their waste reduction practices. The objectives of this study were to estimate the amount of hazardous wastes that a well-designed and well-main- tained CCA treatment facility would generate and to iden- t...

  18. Accumulation of lead and arsenic by potato grown on lead-arsenate contaminated orchard soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Concerns have been raised about the potential food chain transfer of metals in crops grown on historic orchard soils where lead arsenate pesticide was used. The objective of this study was to evaluate the uptake of lead and arsenic (As) by four potato (Solanum tuberosum L.) cultivars (Atlantic, Dar...

  19. Fatty acyl-CoA reductase

    SciTech Connect

    Reiser, Steven E.; Somerville, Chris R.

    1998-12-01

    The present invention relates to bacterial enzymes, in particular to an acyl-CoA reductase and a gene encoding an acyl-CoA reductase, the amino acid and nucleic acid sequences corresponding to the reductase polypeptide and gene, respectively, and to methods of obtaining such enzymes, amino acid sequences and nucleic acid sequences. The invention also relates to the use of such sequences to provide transgenic host cells capable of producing fatty alcohols and fatty aldehydes.

  20. Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC

    NASA Astrophysics Data System (ADS)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

    2012-09-01

    The competitive adsorption of arsenate and phosphate onto calcite was studied in batch experiments using calcite-equilibrated solutions. The solutions had circum-neutral pH (7-8.3) and covered a wide span in the activity of Ca2+ and CO32-. The results show that the adsorption of arsenate onto calcite is strongly reduced by the presence of phosphate, whereas phosphate adsorption is only slightly reduced by arsenate addition. Simultaneous and sequential addition (3 h apart) yields the same reduction in adsorption, underlining the high reversibility of the system. The reduction in adsorption of both arsenate and phosphate is most likely due to competition for the same sorption sites at the calcite surface, considering the similarity in sorption edges, pKa's and geometry of the two anions. The strong reduction in arsenate adsorption by competition with phosphate suggests that adsorption of arsenate onto calcite is of minor importance in most groundwater aquifers, as phosphate is often present at concentration levels sufficient to significantly reduce arsenate adsorption. The CD-MUSIC model for calcite was used successfully to model adsorption of arsenate and phosphate separately. By combining the models for single sorbate systems the competitive adsorption of phosphate and arsenate onto calcite in the binary system could be predicted. This is in contrast to the constant capacitance model (CCM) which under-predicted the competition when combining the models for single sorbate systems. This study clearly shows the importance of performing competitive adsorption studies for validation of multi-component models and for estimating the mobility of an ion in the environment.

  1. Selective removal of arsenate from drinking water using a polymeric ligand exchanger.

    PubMed

    An, Byungryul; Steinwinder, Thomas R; Zhao, Dongye

    2005-12-01

    The new maximum contaminant level (MCL) of 10 microg/L for arsenic in the US drinking water will take effect on January 22, 2006. The compliance cost is estimated to be approximately dollar 600 million per year using current treatment technologies. This research aims to develop an innovative ion exchange process that may help water utilities comply with the new MCL in a more cost-effective manner. A polymeric ligand exchanger (PLE) was prepared by loading Cu2+ to a commercially available chelating ion exchange resin. Results from batch and column experiments indicated that the PLE offered unusually high selectivity for arsenate over other ubiquitous anions such as sulfate, bicarbonate and chloride. The average binary arsenate/sulfate separation factor for the PLE was determined to be 12, which were over two orders of magnitude greater than that (0.1-0.2) for commercial strong-base anion (SBA) exchangers. Because of the enhanced arsenate selectivity, the PLE was able to treat approximately 10 times more bed volumes (BVs) of water than commonly used SBA resins. The PLE can operate optimally in the neutral pH range (6.0-8.0). The exhausted PLE can be regenerated highly efficiently. More than 95% arsenate capacity can be recovered using approximately 22 BVs of 4% (w/w) NaCl at pH 9.1, and the regenerated PLE can be reused without any capacity drop. Upon treatment using FeCl3, the spent brine was recovered and reused for regeneration, which may cut down the regenerant need and reduces the volume of process waste residuals. The PLE can be used as a highly selective and reusable sorbent for removal of arsenate from drinking water.

  2. The importance of glutathione and phytochelatins on the selenite and arsenate detoxification in Arabidopsis thaliana.

    PubMed

    Aborode, Fatai Adigun; Raab, Andrea; Voigt, Matthias; Costa, Leticia Malta; Krupp, Eva M; Feldmann, Joerg

    2016-11-01

    We investigated the role of glutathione (GSH) and phytochelatins (PCs) on the detoxification of selenite using Arabidopsis thaliana. The wild-type (WT) of Arabidopsis thaliana and its mutants (glutathione deficient Cad 2-1 and phytochelatins deficient Cad 1-3) were separately exposed to varying concentrations of selenite and arsenate and jointly to both toxicants to determine their sensitivities. The results of the study revealed that, the mutants were about 20-fold more sensitive to arsenate than the WT, an indication that the GSH and PCs affect arsenate detoxification. On the contrary, the WT and both mutants showed a similar level of sensitivity to selenite, an indication that the GSH and PCs do not significantly affect selenite detoxification. However, the WT is about 8 times more sensitive to selenite than to arsenate, and the mutants were more resistant to selenite than arsenate by a factor of 2. This could not be explained by the accumulation of both elements in roots and shoots in exposure experiments. The co-exposure of the WT indicates a synergistic effect with regards to toxicity since selenite did not induce PCs but arsenic and selenium compete in their PC binding as revealed by speciation analysis of the root extracts using HPLC-ICP-MS/ESI-MS. In the absence of PCs an antagonistic effect has been detected which might suggest indirectly that the formation of Se glutathione complex prevent the formation of detrimental selenopeptides. This study, therefore, revealed that PC and GSH have only a subordinate role in the detoxification of selenite.

  3. Preparative separation of arsenate from phosphate by IRA-400 (OH) for oxygen isotopic work.

    PubMed

    Tang, Xiaohui; Berner, Zsolt; Khelashvilli, Pirimze; Norra, Stefan

    2013-02-15

    The paper reports about a series of tests carried out to find out the optimal conditions for the preparative separation of arsenate and phosphate from natural waters, using the anion exchange resin Amberlite IRA-400 (OH). Freundlich isotherms have been constructed on basis of data obtained by stirring different amounts of resin (0.05-1.00 g) with solutions containing 1mg/L As and 10mg/L P in form of arsenate and phosphate and the effect of pH and P/As ratio on adsorption was investigated. It was found that at these concentrations 0.5 g of IRA-400 (OH) can adsorb quantitatively arsenate and phosphate within 1h. In a range of 3.6-11.1, pH seems to have no influence on the adsorption behavior of the resin, but at pH 1.5 the adsorption of both arsenate and phosphate drops to values close to zero. Experiments with solutions with P/As ratios in a range between 1 and 30 have shown that the concentration ratios have also little effect on adsorption. An efficient selective desorption of the anions could be achieved with 2 mol/L HNO3 or HCl, but the use of HCl is impracticable if the separation aims at precipitating arsenate for oxygen isotopic work. The reported adsorption/ desorption properties of the resin are supported also by data obtained by investigating the resin particles with a scanning electron microscope equipped with a fluorescence detection device.

  4. Effects of sodium arsenate exposure on liver fatty acid profiles and oxidative stress in rats.

    PubMed

    Kharroubi, Wafa; Dhibi, Madiha; Haouas, Zohra; Chreif, Imed; Neffati, Fadoua; Hammami, Mohamed; Sakly, Rachid

    2014-02-01

    The present study aimed to evaluate the effect of arsenic on liver fatty acids (FA) composition, hepatotoxicity and oxidative status markers in rats. Male rats were randomly devised to six groups (n=10 per group) and exposed to sodium arsenate at a dose of 1 and 10 mg/l for 45 and 90 days. Arsenate exposure is associated with significant changes in the FA composition in liver. A significant increase of saturated fatty acids (SFA) in all treated groups (p<0.01) and trans unsaturated fatty acids (trans UFA) in rats exposed both for short term for 10 mg/l (p<0.05) and long term for 1 and 10 mg/l (p<0.001) was observed. However, the cis UFA were significantly decreased in these groups (p<0.05). A markedly increase of indicator in cell membrane viscosity expressed as SFA/UFA was reported in the treated groups (p<0.001). A significant increase in the level of malondialdehyde by 38.3 % after 90 days of exposure at 10 mg/l was observed. Compared to control rats, significant liver damage was observed at 10 mg/l of arsenate by increasing plasma marker enzymes after 90 days. It is through the histological investigations in hepatic tissues of exposed rats that these damage effects of arsenate were confirmed. The antioxidant perturbations were observed to be more important at groups treated by the high dose (p<0.05). An increase in the level of protein carbonyls was observed in all treated groups (p<0.05). The present study provides evidence for a direct effect of arsenite on FA composition disturbance causing an increase of SFA and TFAs isomers, liver dysfunction and oxidative stress. Therefore, arsenate can lead to hepatic damage and propensity towards liver cancer.

  5. Coprecipitation of arsenate with metal oxides. 3. Nature, mineralogy, and reactivity of iron(III)-aluminum precipitates.

    PubMed

    Violante, Antonio; Pigna, Massimo; Del Gaudio, Stefania; Cozzolino, Vincenza; Banerjee, Dipanjan

    2009-03-01

    Coprecipitation involving arsenic with aluminum or iron has been studied because this technique is considered particularly efficient for removal of this toxic element from polluted waters. Coprecipitation of arsenic with mixed iron-aluminum solutions has received scant attention. In this work we studied (i)the mineralogy, surface properties, and chemical composition of mixed iron-aluminum oxides formed at initial Fe/Al molar ratio of 1.0 in the absence or presence of arsenate [As/ Fe+Al molar ratio (R) of 0, 0.01, or 0.1] and at pH 4.0, 7.0, and 10.0 and aged for 30 and 210 days at 50 degrees C and (ii) the removal of arsenate from the coprecipitates after addition of phosphate. The amounts of short-range ordered precipitates (ferrihydrite, aluminous ferrihydrite and/or poorly crystalline boehmite) were greater than those found in iron and aluminum systems (studied in previous works), due to the capacity of both aluminum and arsenate to retard or inhibitthe transformation of the initially formed precipitates into well-crystallized oxides (gibbsite, bayerite, and hematite). As a consequence, the surface areas of the iron-aluminum oxides formed in the absence or presence of arsenate were usually much larger than those of aluminum or iron oxides formed under the same conditions. Arsenate was found to be associated mainly into short-range ordered materials. Chemical composition of all samples was affected by pH, initial R, and aging. Phosphate sorption was facilitated by the presence of short-range ordered materials, mainly those richer in aluminum, but was inhibited by arsenate present in the samples. The quantities of arsenate replaced by phosphate, expressed as percentages of its total amount present in the samples, were particularly low, ranging from 10% to 26%. A comparison of the desorption of arsenate by phosphate from aluminum-arsenate and iron-arsenate (studied in previous works) and iron-aluminum-arsenate coprecipitates evidenced that phosphate has a greater

  6. Arabidopsis thaliana NIP7;1 is involved in tissue arsenic distribution and tolerance in response to arsenate.

    PubMed

    Lindsay, Emma R; Maathuis, Frans J M

    2016-03-01

    The Arabidopsis aquaglyceroporin NIP7;1 is involved in uptake and tolerance to the trivalent arsenic species arsenite. Here, we show that NIP7;1 is also involved in the response to pentavalent arsenate. Loss of function of NIP7;1 improved tolerance to arsenate and reduced arsenic levels in both the phloem and xylem, resulting in altered arsenic distribution between tissues. There was no clear correlation between growth and shoot arsenic concentration. This is the first report detailing the involvement of a NIP transporter in response to arsenate. The data suggest that these proteins are relevant targets for breeding and engineering arsenic tolerance in crops.

  7. Respiratory Home Health Care

    MedlinePlus

    ... Healthy Living > Living With Lung Disease > Respiratory Home Health Care Font: Aerosol Delivery Oxygen Resources Immunizations Pollution Nutrition ... Disease Articles written by Respiratory Experts Respiratory Home Health Care Respiratory care at home can contribute to improved ...

  8. Perinatal exposure to 50 ppb sodium arsenate induces Hypothalamic-Pituitary-Adrenal Axis dysregulation in male C57BL/6 mice

    PubMed Central

    Goggin, Samantha L.; Labrecque, Matthew T.; Allan, Andrea M.

    2012-01-01

    Over the past two decades, key advancements have been made in understanding the complex pathology that occurs following not only high levels of arsenic exposure (>1ppm) but also levels previously considered to be low (<100 ppb). Past studies have characterized the deleterious effects of arsenic on the various functions of cardiovascular, pulmonary, immunological, respiratory, endocrine and neurological systems. Other research has demonstrated an elevated risk of a multitude of cancers and increased rates of psychopathology, even at very low levels of arsenic exposure. The hypothalamic-pituitary-adrenal (HPA) axis represents a multisite integration center that regulates a wide scope of biological and physiological processes: breakdown within this system can generate an array of far-reaching effects, making it an intriguing candidate for arsenic-mediated damage. Using a mouse model, we examined the effects of perinatal exposure to 50 ppb sodium arsenate on the functioning of the HPA axis through the assessment of corticotrophin-releasing factor (CRF), proopiomelanocortin (Pomc) mRNA, adrenocorticotrophin hormone (ACTH), corticosterone (CORT), 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD 1), and glucocorticoid receptor (GR) protein and mRNA. Compared to controls, we observed that the perinatal arsenic-exposed offspring exhibit an increase in hypothalamic CRF, altered CORT secretion both at baseline and in response to a stressor, decreased hippocampal 11β-HSD 1 and altered subcellular GR distribution in the hypothalamus. These data indicate significant HPA axis impairment at post-natal day 35 resulting from perinatal exposure to 50 ppb sodium arsenate. Our findings suggest that the dysregulation of this critical regulatory axis could underlie important molecular and cognitive pathology observed following exposure to arsenic. PMID:22960421

  9. Microbial arsenic metabolism: New twists on an old poison

    USGS Publications Warehouse

    Stolz, J.F.; Basu, P.; Oremland, R.S.

    2010-01-01

    Phylogenetically diverse microorganisms metabolize arsenic despite its toxicity and are part of its robust iogeochemical cycle. Respiratory arsenate reductase is a reversible enzyme, functioning in some microbes as an arsenate reductase but in others as an arsenite oxidase. As(III) can serve as an electron donor for anoxygenic photolithoautotrophy and chemolithoautotrophy. Organoarsenicals, such as the feed additive roxarsone, can be used as a source of energy, releasing inorganic arsenic.

  10. Nitrate Reductase Regulates Expression of Nitrite Uptake and Nitrite Reductase Activities in Chlamydomonas reinhardtii 1

    PubMed Central

    Galván, Aurora; Cárdenas, Jacobo; Fernández, Emilio

    1992-01-01

    In Chlamydomonas reinhardtii mutants defective at the structural locus for nitrate reductase (nit-1) or at loci for biosynthesis of the molybdopterin cofactor (nit-3, nit-4, or nit-5 and nit-6), both nitrite uptake and nitrite reductase activities were repressed in ammonium-grown cells and expressed at high amounts in nitrogen-free media or in media containing nitrate or nitrite. In contrast, wild-type cells required nitrate induction for expression of high levels of both activities. In mutants defective at the regulatory locus for nitrate reductase (nit-2), very low levels of nitrite uptake and nitrite reductase activities were expressed even in the presence of nitrate or nitrite. Both restoration of nitrate reductase activity in mutants defective at nit-1, nit-3, and nit-4 by isolating diploid strains among them and transformation of a structural mutant upon integration of the wild-type nit-1 gene gave rise to the wild-type expression pattern for nitrite uptake and nitrite reductase activities. Conversely, inactivation of nitrate reductase by tungstate treatment in nitrate, nitrite, or nitrogen-free media made wild-type cells respond like nitrate reductase-deficient mutants with respect to the expression of nitrite uptake and nitrite reductase activities. Our results indicate that nit-2 is a regulatory locus for both the nitrite uptake system and nitrite reductase, and that the nitrate reductase enzyme plays an important role in the regulation of the expression of both enzyme activities. PMID:16668656

  11. Respiratory Distress

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The University of Miami School of Medicine asked the Research Triangle Institute for assistance in improvising the negative pressure technique to relieve respiratory distress in infants. Marshall Space Flight Center and Johnson Space Center engineers adapted this idea to the lower-body negative-pressure system seals used during the Skylab missions. Some 20,000 babies succumb to respiratory distress in the U.S. each year, a condition in which lungs progressively lose their ability to oxygenate blood. Both positive and negative pressure techniques have been used - the first to force air into lungs, the second to keep infant's lungs expanded. Negative pressure around chest helps the baby expand his lungs and maintain proper volume of air. If doctors can keep the infant alive for four days, the missing substance in the lungs will usually form in sufficient quantity to permit normal breathing. The Skylab chamber and its leakproof seals were adapted for medical use.

  12. Preabsorptive Metabolism of Sodium Arsenate by Anaerobic Microbiota of Mouse Cecum Forms a Variety of Methylated and Thiolated Arsenicals

    EPA Science Inventory

    The conventional scheme for arsenic methylation accounts for methylated oxyarsenical production but not for thioarsenical formation. Here, we report that in vitro anaerobic microbiota of mouse cecum converts arsenate into oxy- and thio- arsenicals. Besides methylarsonic acid (MMA...

  13. Mutational and gene expression analysis of mtrDEF, omcA and mtrCAB during arsenate and iron reduction in Shewanella sp. ANA-3.

    PubMed

    Reyes, Carolina; Murphy, Julie N; Saltikov, Chad W

    2010-07-01

    Arsenate respiration and Fe(III) reduction are important processes that influence the fate and transport of arsenic in the environment. The goal of this study was to investigate the impact of arsenate on Fe(III) reduction using arsenate and Fe(III) reduction deficient mutants of Shewanella sp. strain ANA-3. Ferrihydrite reduction in the absence of arsenate was similar for an arsenate reduction mutant (arrA and arsC deletion strain of ANA-3) compared with wild-type ANA-3. However, the presence of arsenate adsorbed onto ferrihydrite impeded Fe(III) reduction for the arsenate reduction mutant but not in the wild-type. In an Fe(III) reduction mutant (mtrDEF, omcA, mtrCAB null mutant of ANA-3), arsenate was reduced similarly to wild-type ANA-3 indicating the Fe(III) reduction pathway is not required for ferrihydrite-associated arsenate reduction. Expression analysis of the mtr/omc gene cluster of ANA-3 showed that omcA and mtrCAB were expressed under soluble Fe(III), ferrihydrite and arsenate growth conditions and not in aerobically grown cells. Expression of arrA was greater with ferrihydrite pre-adsorbed with arsenate relative to ferrihydrite only. Lastly, arrA and mtrA were simultaneously induced in cells shifted to anaerobic conditions and exposed to soluble Fe(III) and arsenate. These observations suggest that, unlike Fe(III), arsenate can co-induce operons (arr and mtr) implicated in arsenic mobilization.

  14. Regulation of sugar metabolism in rice (Oryza sativa L.) seedlings under arsenate toxicity and its improvement by phosphate.

    PubMed

    Choudhury, Bhaskar; Mitra, Souvik; Biswas, Asok K

    2010-01-01

    The effect of arsenate with or without phosphate on the growth and sugar metabolism in rice seedlings cv. MTU 1010 was studied. Arsenate was found to be more toxic for root growth than shoot growth and water content of the seedlings gradually decreased with increasing concentrations. Arsenate exposure at 20 μM and 100 μM resulted in an increase in reducing sugar content and decrease in non-reducing sugar content. There was a small increase in starch content, the activity of starch phosphorylase was increased but α-amylase activity was found to be decreased. Arsenate toxicity also affected the activities of different carbohydrate metabolizing enzymes. The activities of sucrose degrading enzymes viz., acid invertase and sucrose synthase were increased whereas, the activity of sucrose synthesizing enzyme, viz. sucrose phosphate synthase declined. The combined application of arsenate with phosphate exhibited significant alterations of all the parameters tested under the purview of arsenate treatment alone which was congenial to better growth and efficient sugar metabolism in rice seedlings. Thus, the use of phosphorus enriched fertilizers may serve to ensure the production of healthy rice plants in arsenic contaminated soils.

  15. Coprecipitated arsenate inhibits thermal transformation of 2-line ferrihydrite: implications for long-term stability of ferrihydrite.

    PubMed

    Wang, Zhaohui; Xiao, Dongxue; Bush, Richard T; Liu, Jianshe

    2015-03-01

    2-line ferrihydrite, a ubiquitous iron oxy-hydroxide found in natural and engineered systems, is an efficient sink for the toxic metalloids such as arsenic. While much is known of the excellent capacity of ferrihydrite to coprecipitate arsenate, there is little information concerning the long-term stability of arsenate-accumulated ferrihydrite. By thermal treatment methodology, the expedited transformation of ferrihydrite in the presence of coprecipitated arsenate was studied at varying As/Fe ratios (0-0.5) and different heating temperature (40, 300, 450, 600°C). Pure and transformed minerals were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Electron Spin Resonance (ESR), Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Fourier Transform Infrared Spectroscopy (FTIR). Arsenate was found to retard the thermal transformation of ferrihydrite. The extents of ferrihydrite transformation to hematite decreased with increasing As/Fe ratios, but increased at a higher heating temperature. It is predicted that the coprecipitated arsenate can stabilize the amorphous iron oxides against the transformation to more crystalline solids. Arsenate concentration appears to play an important role in this predicted long-term stability.

  16. Growth of Strain SES-3 with Arsenate and Other Diverse Electron Acceptors

    PubMed Central

    Laverman, A. M.; Blum, J. S.; Schaefer, J. K.; Phillips, E.; Lovley, D. R.; Oremland, R. S.

    1995-01-01

    The selenate-respiring bacterial strain SES-3 was able to use a variety of inorganic electron acceptors to sustain growth. SES-3 grew with the reduction of arsenate to arsenite, Fe(III) to Fe(II), or thiosulfate to sulfide. It also grew in medium in which elemental sulfur, Mn(IV), nitrite, trimethylamine N-oxide, or fumarate was provided as an electron acceptor. Growth on oxygen was microaerophilic. There was no growth with arsenite or chromate. Washed suspensions of cells grown on selenate or nitrate had a constitutive ability to reduce arsenate but were unable to reduce arsenite. These results suggest that strain SES-3 may occupy a niche as an environmental opportunist by being able to take advantage of a diversity of electron acceptors. PMID:16535143

  17. Effects of arsenate and arsenite on germination and some physiological attributes of barley Hordeum vulgare L.

    PubMed

    Sanal, Filiz; Seren, Gülay; Güner, Utku

    2014-04-01

    Arsenic (As) is toxic to plants and animals. We tested the effects of arsenite and arsenate (0-16 mg/L) on seed germination, and on relative root and shoot length, α-amylase activity, reducing sugars and soluble total protein contents, and malondialdehyde content in barley seedlings. We also measured As accumulation in barley stems and roots. The α-amylase activity, relative root and shoot length, and seed germination decreased with increasing concentrations of arsenate and arsenite. The reducing sugars content in barley seedlings increased after 4 days of growth on media containing As. In general, the protein content in roots and seedlings decreased with increasing doses of As. Arsenic in the tissues was quantified by hydride generation-atomic absorption spectrophotometry. To confirm the accuracy of the method, we analyzed the certified reference material WEPAL-IPE-168. The limit of detection was 1.2 μg/L and the relative standard deviation was <2.0 %.

  18. Neuroprotective role for carbonyl reductase?

    PubMed

    Maser, Edmund

    2006-02-24

    Oxidative stress is increasingly implicated in neurodegenerative disorders including Alzheimer's, Parkinson's, Huntington's, and Creutzfeld-Jakob diseases or amyotrophic lateral sclerosis. Reactive oxygen species seem to play a significant role in neuronal cell death in that they generate reactive aldehydes from membrane lipid peroxidation. Several neuronal diseases are associated with increased accumulation of abnormal protein adducts of reactive aldehydes, which mediate oxidative stress-linked pathological events, including cellular growth inhibition and apoptosis induction. Combining findings on neurodegeneration and oxidative stress in Drosophila with studies on the metabolic characteristics of the human enzyme carbonyl reductase (CR), it is clear now that CR has a potential physiological role for neuroprotection in humans. Several lines of evidence suggest that CR represents a significant pathway for the detoxification of reactive aldehydes derived from lipid peroxidation and that CR in humans is essential for neuronal cell survival and to confer protection against oxidative stress-induced brain degeneration.

  19. Arsenite-oxidizing and arsenate-reducing bacteria associated with arsenic-rich groundwater in Taiwan

    NASA Astrophysics Data System (ADS)

    Liao, Vivian Hsiu-Chuan; Chu, Yu-Ju; Su, Yu-Chen; Hsiao, Sung-Yun; Wei, Chia-Cheng; Liu, Chen-Wuing; Liao, Chung-Min; Shen, Wei-Chiang; Chang, Fi-John

    2011-04-01

    Drinking highly arsenic-contaminated groundwater is a likely cause of blackfoot disease in Taiwan, but microorganisms that potentially control arsenic mobility in the subsurface remain unstudied. The objective of this study was to investigate the relevant arsenite-oxidizing and arsenate-reducing microbial community that exists in highly arsenic-contaminated groundwater in Taiwan. We cultured and identified arsenic-transforming bacteria, analyzed arsenic resistance and transformation, and determined the presence of genetic markers for arsenic transformation. In total, 11 arsenic-transforming bacterial strains with different colony morphologies and varying arsenic transformation abilities were isolated, including 10 facultative anaerobic arsenate-reducing bacteria and one strictly aerobic arsenite-oxidizing bacterium. All of the isolates exhibited high levels of arsenic resistance with minimum inhibitory concentrations of arsenic ranging from 2 to 200 mM. Strain AR-11 was able to rapidly oxidize arsenite to arsenate at concentrations relevant to environmental groundwater samples without the addition of any electron donors or acceptors. We provide evidence that arsenic-reduction activity may be conferred by the ars operon(s) that were not amplified by the designed primers currently in use. The 16S rRNA sequence analysis grouped the isolates into the following genera: Pseudomonas, Bacillus, Psychrobacter, Vibrio, Citrobacter, Enterobacter, and Bosea. Among these genera, we present the first report of the genus Psychrobacter being involved in arsenic reduction. Our results further support the hypothesis that bacteria capable of either oxidizing arsenite or reducing arsenate coexist and are ubiquitous in arsenic-contaminated groundwater.

  20. Vanadium(V) oxide arsenate(V), VOAsO4

    PubMed Central

    Ezzine Yahmed, Safa; Zid, Mohamed Faouzi; Driss, Ahmed

    2011-01-01

    The vanadyl arsenate, VOAsO4, has been isolated by a solid-state reaction. The structure consists of distorted VO6 octa­hedra and AsO4 tetra­hedra sharing corners to build up VAsO7 layers parallel to ac linked by edge-sharing of VO6 octa­hedra, forming a three-dimensional framework. PMID:21522229

  1. An SEM-EDX and Raman spectroscopic study of the fibrous arsenate mineral liskeardite and in comparison with other arsenates kaňkite, scorodite and yvonite.

    PubMed

    Frost, Ray L; Scholz, Ricardo; Jirásek, Jakub; Belotti, Fernanda Maria

    2015-12-05

    The mineral liskeardite, an arsenate mineral with major cations of iron and aluminium, has been studied by a combination of scanning electron microscopy with energy dispersive spectroscopy and Raman spectroscopy. The mineral shows a fibrous nature. Semi-quantitative chemical analysis shows an Al and Fe arsenate phase with minor amounts of K, Cu, S and Si. Scanning electron microscopy shows a fibrous material. Intense Raman bands at 893, 867 and 843 cm(-1) are assigned to the ν1 and ν3 AsO4(3)(-) and HOAsO3(2)(-) symmetric and antisymmetric stretching vibrations. Raman bands are observed at 514, 499, 485 and 477 cm(-1) and are assigned to the ν4 out of plane bending modes of the AsO4(3)(-) and HOAsO3(2)(-) units. The series of bands at 373, 356 and 343 cm(-1) are assigned to the ν2 symmetric bending modes. Two groups of OH stretching bands are observed and assigned to OH unit and water stretching vibrations. A comparison of the Raman spectrum of liskeardite with scorodite, kaňkite and yvonite is made.

  2. UV and arsenate toxicity: a specific and sensitive yeast bioluminescence assay.

    PubMed

    Bakhrat, Anya; Eltzov, Evgeni; Finkelstein, Yishay; Marks, Robert S; Raveh, Dina

    2011-06-01

    We describe a Saccharomyces cerevisiae bioluminescence assay for UV and arsenate in which bacterial luciferase genes are regulated by the promoter of the yeast gene, UFO1. UFO1 encodes the F-box subunit of the Skp1–Cdc53–F-box protein ubiquitin ligase complex and is induced by DNA damage and by arsenate. We engineered the UFO1 promoter into an existing yeast bioreporter that employs human genes for detection of steroid hormone-disrupting compounds in water bodies. Our analysis indicates that use of an endogenous yeast promoter in different mutant backgrounds allows discrimination between different environmental signals. The UFO1-engineered yeast give a robust bioluminescence response to UVB and can be used for evaluating UV protective sunscreens. They are also effective in detecting extremely low concentrations of arsenate, particularly in pdr5Δ mutants that lack a mechanism to extrude toxic chemicals; however, they do not respond to cadmium or mercury. Combined use of endogenous yeast promoter elements and mutants of stress response pathways may facilitate development of high-specificity yeast bioreporters able to discriminate between closely related chemicals present together in the environment.

  3. Enhanced Arsenate Removal Performance in Aqueous Solution by Yttrium-Based Adsorbents

    PubMed Central

    Lee, Sang-Ho; Kim, Kyoung-Woong; Lee, Byung-Tae; Bang, Sunbaek; Kim, Hyunseok; Kang, Hyorang; Jang, Am

    2015-01-01

    Arsenic contamination in drinking water has become an increasingly important issue due to its high toxicity to humans. The present study focuses on the development of the yttrium-based adsorbents, with basic yttrium carbonate (BYC), Ti-loaded basic yttrium carbonate (Ti-loaded BYC) and yttrium hydroxide prepared using a co-precipitation method. The Langmuir isotherm results confirmed the maximum adsorption capacity of Ti-loaded BYC (348.5 mg/g) was 25% higher than either BYC (289.6 mg/g) or yttrium hydroxide (206.5 mg/g) due to its increased specific surface area (82 m2/g) and surface charge (PZC: 8.4). Pseudo first- and second-order kinetic models further confirmed that the arsenate removal rate of Ti-loaded BYC was faster than for BYC and yttrium hydroxide. It was subsequently posited that the dominant removal mechanism of BYC and Ti-loaded BYC was the carbonate-arsenate ion exchange process, whereas yttrium hydroxide was regarded to be a co-precipitation process. The Ti-loaded BYC also displayed the highest adsorption affinity for a wide pH range (3–11) and in the presence of coexisting anionic species such as phosphate, silicate, and bicarbonate. Therefore, it is expected that Ti-loaded BYC can be used as an effective and practical adsorbent for arsenate remediation in drinking water. PMID:26516879

  4. Enhanced Arsenate Removal Performance in Aqueous Solution by Yttrium-Based Adsorbents.

    PubMed

    Lee, Sang-Ho; Kim, Kyoung-Woong; Lee, Byung-Tae; Bang, Sunbaek; Kim, Hyunseok; Kang, Hyorang; Jang, Am

    2015-10-26

    Arsenic contamination in drinking water has become an increasingly important issue due to its high toxicity to humans. The present study focuses on the development of the yttrium-based adsorbents, with basic yttrium carbonate (BYC), Ti-loaded basic yttrium carbonate (Ti-loaded BYC) and yttrium hydroxide prepared using a co-precipitation method. The Langmuir isotherm results confirmed the maximum adsorption capacity of Ti-loaded BYC (348.5 mg/g) was 25% higher than either BYC (289.6 mg/g) or yttrium hydroxide (206.5 mg/g) due to its increased specific surface area (82 m²/g) and surface charge (PZC: 8.4). Pseudo first- and second-order kinetic models further confirmed that the arsenate removal rate of Ti-loaded BYC was faster than for BYC and yttrium hydroxide. It was subsequently posited that the dominant removal mechanism of BYC and Ti-loaded BYC was the carbonate-arsenate ion exchange process, whereas yttrium hydroxide was regarded to be a co-precipitation process. The Ti-loaded BYC also displayed the highest adsorption affinity for a wide pH range (3-11) and in the presence of coexisting anionic species such as phosphate, silicate, and bicarbonate. Therefore, it is expected that Ti-loaded BYC can be used as an effective and practical adsorbent for arsenate remediation in drinking water.

  5. Genetics Home Reference: 5-alpha reductase deficiency

    MedlinePlus

    ... About half of these individuals adopt a male gender role in adolescence or early adulthood. Related Information ... 1730-5. Citation on PubMed Cohen-Kettenis PT. Gender change in 46,XY persons with 5alpha-reductase- ...

  6. A dissimilatory nitrite reductase in Paracoccus halodenitrificans

    NASA Technical Reports Server (NTRS)

    Grant, M. A.; Hochstein, L. I.

    1984-01-01

    Paracoccus halodenitrificans produced a membrane-associated nitrite reductase. Spectrophotometric analysis showed it to be associated with a cd-cytochrome and located on the inner side of the cytoplasmic membrane. When supplied with nitrite, membrane preparations produced nitrous oxide and nitric oxide in different ratios depending on the electron donor employed. The nitrite reductase was maximally active at relatively low concentrations of sodium chloride and remained attached to the membranes at 100 mM sodium chloride.

  7. [Respiratory allergies].

    PubMed

    Chiriac, Anca Mirela; Demoly, Pascal

    2013-04-01

    Respiratory allergies represent a global and public health problem, due to their prevalence (still increasing), morbidity, impact on the quality of life and costs for the society. They mainly concern rhinitis (or rhinoconjunctivitis) and asthma. The diagnosis of allergy is dependent on a history of symptoms on exposure to an allergen together with the detection of allergen-specific IgE. Accurate diagnosis of allergies opens up therapeutic options that are otherwise not appropriate, such as allergen immunotherapy and allergen avoidance, that are prescribed following a stepwise approach. It has been a century since the first trial in specific immunotherapy was performed and this still remains the only disease modifying treatment for allergic individuals. In terms of route of administration, sublingual immunotherapy represents a good alternative to subcutaneous immunotherapy, considering its proven efficacy and better safety profile.

  8. Nitrate reduction in Haloferax alexandrinus: the case of assimilatory nitrate reductase.

    PubMed

    Kilic, Volkan; Kilic, Gözde Aydoğan; Kutlu, Hatice Mehtap; Martínez-Espinosa, Rosa María

    2017-03-21

    Haloferax alexandrinus Strain TM JCM 10717(T) = IFO 16590(T) is an extreme halophilic archaeon able to produce significant amounts of canthaxanthin. Its genome sequence has been analysed in this work using bioinformatics tools available at Expasy in order to look for genes encoding nitrate reductase-like proteins: respiratory nitrate reductase (Nar) and/or assimilatory nitrate reductase (Nas). The ability of the cells to reduce nitrate under aerobic conditions was tested. The enzyme in charge of nitrate reduction under aerobic conditions (Nas) has been purified and characterised. It is a monomeric enzyme (72 ± 1.8 kDa) that requires high salt concentration for stability and activity. The optimum pH value for activity was 9.5. Effectiveness of different substrates, electron donors, cofactors and inhibitors was also reported. High nitrite concentrations were detected within the culture media during aerobic/microaerobic cells growth. The main conclusion from the results is that this haloarchaeon reduces nitrate aerobically thanks to Nas and may induce denitrification under anaerobic/microaerobic conditions using nitrate as electron acceptor. The study sheds light on the role played by haloarchaea in the biogeochemical cycle of nitrogen, paying special attention to nitrate reduction processes. Besides, it provides useful information for future attempts on microecological and biotechnological implications of haloarchaeal nitrate reductases.

  9. Lungs and Respiratory System

    MedlinePlus

    ... Your 1- to 2-Year-Old Lungs and Respiratory System KidsHealth > For Parents > Lungs and Respiratory System Print ... ll have taken at least 600 million breaths. Respiratory System Basics All of this breathing couldn't happen ...

  10. Lungs and Respiratory System

    MedlinePlus

    ... Your 1- to 2-Year-Old Lungs and Respiratory System KidsHealth > For Parents > Lungs and Respiratory System A ... ll have taken at least 600 million breaths. Respiratory System Basics All of this breathing couldn't happen ...

  11. Characterization of thyroidal glutathione reductase

    SciTech Connect

    Raasch, R.J.

    1989-01-01

    Glutathione levels were determined in bovine and rat thyroid tissue by enzymatic conjugation with 1-chloro-2,4-dinitrobenzene using glutathione S-transferase. Bovine thyroid tissue contained 1.31 {+-} 0.04 mM reduced glutathione (GSH) and 0.14 {+-} 0.02 mM oxidized glutathione (GSSG). In the rat, the concentration of GSH was 2.50 {+-} 0.05 mM while GSSG was 0.21 {+-} 0.03 mM. Glutathione reductase (GR) was purified from bovine thyroid to electrophoretic homogeneity by ion exchange, affinity and molecular exclusion chromatography. A molecular weight range of 102-109 kDa and subunit size of 55 kDa were determined for GR. Thyroidal GR was shown to be a favoprotein with one FAD per subunit. The Michaelis constants of bovine thyroidal GR were determined to be 21.8 {mu}M for NADPH and 58.8 {mu}M for GSSG. The effect of thyroid stimulating hormone (TSH) and thyroxine (T{sub 4}) on in vivo levels of GR and glucose 6-phosphate dehydrogenase were determined in rat thyroid homogenates. Both enzymes were stimulated by TSH treatment and markedly reduced following T{sub 4} treatment. Lysosomal hydrolysis of ({sup 125}I)-labeled and unlabeled thyroglobulin was examined using size exclusion HPLC.

  12. Effect of silicic acid on arsenate and arsenite retention mechanisms on 6-L ferrihydrite: A spectroscopic and batch adsorption approach.

    PubMed

    Gao, Xiaodong; Root, Robert A; Farrell, James; Ela, Wendell; Chorover, Jon

    2013-11-01

    The competitive adsorption of arsenate and arsenite with silicic acid at the ferrihydrite-water interface was investigated over a wide pH range using batch sorption experiments, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) modeling. Batch sorption results indicate that the adsorption of arsenate and arsenite on the 6-L ferrihydrite surface exhibits a strong pH-dependence, and the effect of pH on arsenic sorption differs between arsenate and arsenite. Arsenate adsorption decreases consistently with increasing pH; whereas arsenite adsorption initially increases with pH to a sorption maximum at pH 7-9, where after sorption decreases with further increases in pH. Results indicate that competitive adsorption between silicic acid and arsenate is negligible under the experimental conditions; whereas strong competitive adsorption was observed between silicic acid and arsenite, particularly at low and high pH. In-situ, flow-through ATR-FTIR data reveal that in the absence of silicic acid, arsenate forms inner-sphere, binuclear bidentate, complexes at the ferrihydrite surface across the entire pH range. Silicic acid also forms inner-sphere complexes at ferrihydrite surfaces throughout the entire pH range probed by this study (pH 2.8 - 9.0). The ATR-FTIR data also reveal that silicic acid undergoes polymerization at the ferrihydrite surface under the environmentally-relevant concentrations studied (e.g., 1.0 mM). According to ATR-FTIR data, arsenate complexation mode was not affected by the presence of silicic acid. EXAFS analyses and DFT modeling confirmed that arsenate tetrahedra were bonded to Fe metal centers via binuclear bidentate complexation with average As(V)-Fe bond distance of 3.27 Å. The EXAFS data indicate that arsenite forms both mononuclear bidentate and binuclear bidentate complexes with 6-L ferrihydrite as indicated by two As

  13. Molecular characterization of nosRZDFYLX genes coding for denitrifying nitrous oxide reductase of Bradyrhizobium japonicum.

    PubMed

    Velasco, Leonardo; Mesa, Socorro; Xu, Chang-Ai; Delgado, María J; Bedmar, Eulogio J

    2004-04-01

    The nosRZDFYLX gene cluster for the respiratory nitrous oxide reductase from Bradyrhizobium japonicum strain USDA110 has been cloned and sequenced. Seven protein coding regions corresponding to nosR, nosZ, the structural gene, nosD, nosF, nosY, nosL, and nosX were detected. The deduced amino acid sequence exhibited a high degree of similarity to other nitrous oxide reductases from various sources. The NosZ protein included a signal peptide for protein export. Mutant strains carrying either a nosZ or a nosR mutation accumulated nitrous oxide when cultured microaerobically in the presence of nitrate. Maximal expression of a P nosZ-lacZ fusion in strain USDA110 required simultaneously both low level oxygen conditions and the presence of nitrate. Microaerobic activation of the fusion required FixLJ and FixK(2).

  14. The aldo-keto reductase superfamily homepage.

    PubMed

    Hyndman, David; Bauman, David R; Heredia, Vladi V; Penning, Trevor M

    2003-02-01

    The aldo-keto reductases (AKRs) are one of the three enzyme superfamilies that perform oxidoreduction on a wide variety of natural and foreign substrates. A systematic nomenclature for the AKR superfamily was adopted in 1996 and was updated in September 2000 (visit www.med.upenn.edu/akr). Investigators have been diligent in submitting sequences of functional proteins to the Web site. With the new additions, the superfamily contains 114 proteins expressed in prokaryotes and eukaryotes that are distributed over 14 families (AKR1-AKR14). The AKR1 family contains the aldose reductases, the aldehyde reductases, the hydroxysteroid dehydrogenases and steroid 5beta-reductases, and is the largest. Other families of interest include AKR6, which includes potassium channel beta-subunits, and AKR7 the aflatoxin aldehyde reductases. Two new families include AKR13 (yeast aldose reductase) and AKR14 (Escherichia coli aldehyde reductase). Crystal structures of many AKRs and their complexes with ligands are available in the PDB and accessible through the Web site. Each structure has the characteristic (alpha/beta)(8)-barrel motif of the superfamily, a conserved cofactor binding site and a catalytic tetrad, and variable loop structures that define substrate specificity. Although the majority of AKRs are monomeric proteins of about 320 amino acids in length, the AKR2, AKR6 and AKR7 family may form multimers. To expand the nomenclature to accommodate multimers, we recommend that the composition and stoichiometry be listed. For example, AKR7A1:AKR7A4 (1:3) would designate a tetramer of the composition indicated. The current nomenclature is recognized by the Human Genome Project (HUGO) and the Web site provides a link to genomic information including chromosomal localization, gene boundaries, human ESTs and SNPs and much more.

  15. Chicken muscle aldose reductase: purification, properties and relationship to other chicken aldo/keto reductases.

    PubMed

    Murphy, D G; Davidson, W S

    1986-01-01

    An enzyme that catalyzes the NADPH-dependent reduction of a wide range of aromatic and hydroxy-aliphatic aldehydes was purified from chicken breast muscle. This enzyme shares many properties with mammalian aldose reductases including molecular weight, relative substrate specificity, Michaelis constants, an inhibitor specificity. Therefore, it seems appropriate to call this enzyme an aldose reductase (EC 1.1.1.21). Chicken muscle aldose reductase appears to be kinetically identical to an aldose reductase that has been purified from chicken kidney (Hara et al., Eur. J. Biochem. 133, 207-214) and to hen muscle L-glycol dehydrogenase (Bernado et al., Biochim. biophys. Acta 659, 189-198). The association of this aldose reductase with muscular dystrophy in the chick is discussed.

  16. Arsenic-resistant proteobacterium from the phyllosphere of arsenic-hyperaccumulating fern (Pteris vittata L.) reduces arsenate to arsenite.

    PubMed

    Rathinasabapathi, Bala; Raman, Suresh Babu; Kertulis, Gina; Ma, Lena

    2006-07-01

    An arsenic-resistant bacterium, AsRB1, was isolated from the fronds of Pteris vittata grown in a site contaminated with copper chromium arsenate. The bacterium exhibited resistance to arsenate, arsenite, and antimony in the culture medium. AsRB1, like Pseudomonas putida, grew on MacConkey and xylose-lactose-desoxycholate agars and utilized citrate but, unlike P. putida, was positive for indole test and negative for oxidase test. A phylogenetic analysis of the 16S rRNA gene showed that AsRB1 is a proteobacterium of the beta subclass, related to Pseudomonas saccharophila and Variovorax paradoxus. Following an exogenous supply of arsenate, most arsenic occurred as arsenite in the medium and the cell extracts, suggesting reduction and extrusion of arsenic as the mechanism for arsenic resistance in AsRB1.

  17. Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH).

    PubMed

    Badruzzaman, Mohammad; Westerhoff, Paul; Knappe, Detlef R U

    2004-11-01

    Porous iron oxides are being evaluated and selected for arsenic removal in potable water systems. Granular ferric hydroxide, a typical porous iron adsorbent, is commercially available and frequently considered in evaluation of arsenic removal methods. GFH is a highly porous (micropore volume approximately 0.0394+/-0.0056 cm(3)g(-1), mesopore volume approximately 0.0995+/-0.0096 cm(3)g(-1)) adsorbent with a BET surface area of 235+/-8 m(2)g(-1). The purpose of this paper is to quantify arsenate adsorption kinetics on GFH and to determine if intraparticle diffusion is a rate-limiting step for arsenic removal in packed-bed treatment systems. Data from bottle-point isotherm and differential column batch reactor (DCBR) experiments were used to estimate Freundlich isotherm parameters (K and 1/n) as well as kinetic parameters describing mass transfer resistances due to film diffusion (k(f)) and intraparticle surface diffusion (D(s)). The pseudo-equilibrium (18 days of contact time) arsenate adsorption density at pH 7 was 8 microg As/mg dry GFH at a liquid phase arsenate concentration of 10 microg As/L. The homogeneous surface diffusion model (HSDM) was used to describe the DCBR data. A non-linear relationship (D(S)=3.0(-9) x R(p)(1.4)) was observed between D(s) and GFH particle radius (R(P)) with D(s) values ranging from 2.98 x 10(-12) cm(2)s(-1) for the smallest GFH mesh size (100 x 140) to 64 x 10(-11) cm(2)s(-1) for the largest GFH mesh size (10 x 30). The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorption by activated carbon despite differences in adsorption mechanisms (inner-sphere complexes for As versus hydrophobic interactions for organic contaminants). The findings are discussed in the context of intraparticle surface diffusion affecting packed-bed treatment system design and application of rapid small-scale column tests (RSSCTs) to simulate the performance of

  18. The tyrosyl free radical in ribonucleotide reductase.

    PubMed Central

    Gräslund, A; Sahlin, M; Sjöberg, B M

    1985-01-01

    The enzyme, ribonucleotide reductase, catalyses the formation of deoxyribonucleotides from ribonucleotides, a reaction essential for DNA synthesis in all living cells. The Escherichia coli ribonucleotide reductase, which is the prototype of all known eukaryotic and virus-coded enzymes, consists of two nonidentical subunits, proteins B1 and B2. The B2 subunit contains an antiferromagnetically coupled pair of ferric ions and a stable tyrosyl free radical. EPR studies show that the tyrosyl radical, formed by loss of ferric ions and a stable tyrosyl free radical. EPR studies show that the tyrosyl radical, formed by loss of an electron, has its unpaired spin density delocalized in the aromatic ring of tyrosine. Effects of iron-radical interaction indicate a relatively close proximity between the iron center and the radical. The EPR signal of the radical can be studied directly in frozen packed cells of E. coli or mammalian origin, if the cells are made to overproduce ribonucleotide reductase. The hypothetic role of the tyrosyl free radical in the enzymatic reaction is not yet elucidated, except in the reaction with the inhibiting substrate analogue 2'-azido-CDP. In this case, the normal tyrosyl radical is destroyed with concomitant appearance of a 2'-azido-CDP-localized radical intermediate. Attempts at spin trapping of radical reaction intermediates have turned out negative. In E. coli the activity of ribonucleotide reductase may be regulated by enzymatic activities that interconvert a nonradical containing form and the fully active protein B2. In synchronized mammalian cells, however, the cell cycle variation of ribonucleotide reductase, studied by EPR, was shown to be due to de novo protein synthesis. Inhibitors of ribonucleotide reductase are of medical interest because of their ability to control DNA synthesis. One example is hydroxyurea, used in cancer therapy, which selectively destroys the tyrosyl free radical. PMID:3007085

  19. Chemical Speciation and Bioaccessibility of Arsenic and Chromiumin Chromated Copper Arsenate-Treated Wood and Soils

    SciTech Connect

    Nico, Peter S.; Ruby, Michael V.; Lowney, Yvette W.; Holm,Stewart E.

    2005-10-12

    This research compares the As and Cr chemistry ofdislodgeable residues from Chromated Copper Arsenate (CCA)-treated woodcollected by two different techniques (directly from the board surfaceeither by rubbing with a soft bristle brush or from human hands aftercontact with CCA-treated wood), and demonstrates that these materials areequivalent in terms of the chemical form and bonding of As and Cr and interms of the As leaching behavior. This finding links the extensivechemical characterization and bioavailability testing that has been donepreviously on the brush-removed residue to a material that is derivedfrom human skin contact with CCA-treated wood. Additionally, thisresearch characterizes the arsenic present in biological fluids (sweatand simulated gastric fluid) following contact with these residues. Thedata demonstrate that in biological fluids, the arsenic is presentprimarily as free arsenate ions.Arsenic-containing soils were alsoextracted into human sweat to evaluate the potential for arsenicdissolution from soils at the skin surface. For soils from field sites,only a small fraction of the total arsenic is soluble in sweat. Based oncomparisons to reference materials that have been used in in vivo dermalabsorption studies, these findings suggest that the actual relativebioavailability via dermal absorption of As from CCA-residues and soilmay be well below the current default value of 3 percent used by U.S.EPA.

  20. Arsenate removal from water by an alumina-modified zeolite recovered from fly ash.

    PubMed

    Qiu, Wei; Zheng, Ying

    2007-09-30

    A cancrinite-type zeolite was synthesized from Class C fly ash by molten-salt method. The product (ZFA) was used as the adsorbent for the arsenate removal from water. The adsorption equilibriums of arsenate are investigated on various adsorbents. ZFA showed a higher adsorption capacity (5.1 mg g(-1)) than activated carbon (4.0 mg g(-1)), silica gel (0.46 mg g(-1)), zeolite NaY (1.4 mg g(-1)), and zeolite 5A (4.1 mg g(-1)). The relatively higher adsorption capacity of ZFA than zeolite NaY and 5A was attributed to the low Si/Al ratio and the mesoporous secondary pore structure of ZFA. However, it was found that the adsorption capacity of zeolites were generally lower than activated alumina (16.6 mg g(-1)), which is ascribed to the small pores in zeolite frameworks. The adsorption capacity of ZFA was significantly improved after loaded by alumina via a wet-impregnation method. The modified ZFA (ZFA-Al(50)) with the optimum alumina loading showed an adsorption capacity of 34.5 mg g(-1), which was 2.1 times higher than activated alumina. The Toxicity Characteristic Leaching Procedure (TCLP) leachability tests indicated that the spent ZFA and alumina-modified ZFA complied with the EPA regulations for safe disposal.

  1. Removing heavy metals in water: the interaction of cactus mucilage and arsenate (As (V)).

    PubMed

    Fox, Dawn I; Pichler, Thomas; Yeh, Daniel H; Alcantar, Norma A

    2012-04-17

    High concentrations of arsenic in groundwater continue to present health threats to millions of consumers worldwide. Particularly, affected communities in the developing world need accessible technologies for arsenic removal from drinking water. We explore the application of cactus mucilage, pectic polysaccharide extracts from Opuntia ficus-indica for arsenic removal. Synthetic arsenate (As (V)) solutions were treated with two extracts, a gelling extract (GE) and a nongelling extract (NE) in batch trials. The arsenic concentration at the air-water interface was measured after equilibration. The GE and NE treated solutions showed on average 14% and 9% increases in arsenic concentration at the air-water interface respectively indicating that the mucilage bonded and transported the arsenic to the air-water interface. FTIR studies showed that the -CO groups (carboxyl and carbonyl groups) and -OH (hydroxyl) functional groups of the mucilage were involved in the interaction with the arsenate. Mucilage activity was greater in weakly basic (pH 9) and weakly acidic (pH 5.5) pH. This interaction can be optimized and harnessed for the removal of arsenic from drinking water. This work breaks the ground for the application of natural pectic materials to the removal of anionic metallic species from water.

  2. Na₃Co₂(AsO₄)(As₂O₇): a new sodium cobalt arsenate.

    PubMed

    Guesmi, Abderrahmen; Driss, Ahmed

    2012-07-01

    In the title compound, tris-odium dicobalt arsenate diarsenate, Na₃Co₂AsO₄As₂O₇, the two Co atoms, one of the two As and three of the seven O atoms lie on special positions, with site symmetries 2 and m for the Co, m for the As, and 2 and twice m for the O atoms. The two Na atoms are disordered over two general and special positions [occupancies 0.72 (3):0.28 (3) and 0.940 (6):0.060 (6), respectively]. The main structural feature is the association of the CoO₆ octa-hedra in the ab plane, forming Co₄O₂₀ units, which are corner- and edge-connected via AsO₄ and As₂O₇ arsenate groups, giving rise to a complex polyhedral connectivity with small tunnels, such as those running along the b- and c-axis directions, in which the Na⁺ ions reside. The structural model is validated by both bond-valence-sum and charge-distribution methods, and the distortion of the coordination polyhedra is analyzed by means of the effective coordination number.

  3. Facile synthesis of highly active hydrated yttrium oxide towards arsenate adsorption.

    PubMed

    Yu, Yang; Yu, Ling; Sun, Min; Paul Chen, J

    2016-07-15

    A novel hydrated yttrium oxide adsorbent with high capacity towards the arsenate (As(V)) adsorption was fabricated by a one-step hydrothermal process. Structure analysis identified the hydrated yttrium oxide to be Y2O(OH)4·1.5H2O, which displayed as irregular rods in the range of tens to hundreds of nanometers. The adsorbent exhibited favorable As(V) adsorption efficiency in a wide pH range from 4.0 to 7.0, with the maximum adsorption capacity of 480.2mg-As/g obtained at pH 5.0. Both the kinetics and isotherm studies demonstrated that the adsorption of the As(V) was a monolayer chemical adsorption process, in which the ion exchange between the hydroxyl groups on the hydrated yttrium oxide and arsenate anions played a key role in the uptake of the As(V). During the adsorption, the As(V) anions were replaced the hydroxyl groups and bound to the hydrated yttrium oxide via the linkage of AsOY. The presence of fluoride and phosphate greatly hindered the As(V) uptake on the hydrated yttrium oxide, whereas the bicarbonate, sulfate and humic acid showed insignificant impacts on the removal.

  4. Evaluation of nitrate reductase activity in Rhizobium japonicum

    SciTech Connect

    Streeter, J.G.; DeVine, P.J.

    1983-08-01

    Nitrate reductase activity was evaluated by four approaches, using four strains of Rhizobium japonicum and 11 chlorate-resistant mutants of the four strains. It was concluded that in vitro assays with bacteria or bacteroids provide the most simple and reliable assessment of the presence or absence of nitrate reductase. Nitrite reductase activity with methyl viologen and dithionite was found, but the enzyme activity does not confound the assay of nitrate reductase. 18 references

  5. Isolation, sequence identification and tissue expression profile of two novel soybean (glycine max) genes-vestitone reductase and chalcone reductase.

    PubMed

    Liu, G Y

    2009-09-01

    The complete mRNA sequences of two soybean (glycine max) genes-vestitone reductase and chalcone reductase, were amplified using the rapid amplification of cDNA ends methods. The sequence analysis of these two genes revealed that soybean vestitone reductase gene encodes a protein of 327 amino acids which has high homology with the vestitone reductase of Medicago sativa (77%). The soybean chalcone reductase gene encodes a protein of 314 amino acids that has high homology with the chalcone reductase of kudzu vine (88%) and medicago sativa (83%). The expression profiles of the soybean vestitone reductase and chalcone reductase genes were studied and the results indicated that these two soybean genes were differentially expressed in detected soybean tissues including leaves, stems, roots, inflorescences, embryos and endosperm. Our experiment established the foundation for further research on these two soybean genes.

  6. Lead and Arsenic Uptake by Carrots Grown on Five Orchard Soils With History of Lead Arsenate Used

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lead arsenate was used to control codling moth in apple and plum orchards from 1900 to 1960. Consequently, many orchard soils are contaminated with lead (Pb) and arsenic (As). Some of these lands are being used for urban development and vegetable crop production. Both soil Pb and As have become i...

  7. Fate of arsenite and arsenate in flooded and not flooded soils of southwest Bangladesh irrigated with arsenic contaminated water.

    PubMed

    Martin, Maria; Violante, Antonio; Barberis, Elisabetta

    2007-10-01

    In Bangladesh and West Bengal, India, tons of arsenic are added every year to wide extensions of agricultural soils after irrigation with arsenic polluted groundwater, and the fate of the added arsenic in these water-soil environments is not yet clear. This work was aimed to investigate the accumulation and potential release of arsenite [As(III)] and arsenate [As(V)] in two adjacent soils of Bangladesh, irrigated with arsenic contaminated groundwater and cultivated under flooded or not flooded conditions. Both soils showed a scarce As accumulation, in spite of a good adsorption capacity, higher for As(III) than for As(V). The poorly ordered Fe oxides dominated As adsorption in the topsoil of the flooded soil, whereas the crystalline forms were more important in the well aerated soil. A high percentage of the native arsenic was exchangeable with phosphate and the freshly added arsenate or arsenite were even much more mobile. In our experimental conditions, the high As mobility was not dependent on the surface coverage, and, in the flooded soil, 60-70% of the freshly added arsenite or arsenate were desorbed with an infinite sink method, while in the not flooded soil arsenate was less desorbed than arsenite. Depending on their characteristics, some soils, in particular when cultivated under flooded conditions, can represent only a temporary sink for the added As, that can be easily released to waters and possibly enter the food chain from the water-soil system.

  8. Genome wide analysis of DNA methylation and gene expression changes in the mouse lung following subchronic arsenate exposure

    EPA Science Inventory

    Alterations in DNA methylation have been proposed as a mechanism for the complex toxicological effects of arsenic. In this study, whole genome DNA methylation and gene expression changes were evaluated in lungs from female mice exposed for 90 days to 50 ppm arsenate (As) in drink...

  9. Role of uniform pore structure and high positive charges in the arsenate adsorption performance of Al13-modified montmorillonite.

    PubMed

    Zhao, Shou; Feng, Chenghong; Huang, Xiangning; Li, Baohua; Niu, Junfeng; Shen, Zhenyao

    2012-02-15

    Four modified montmorillonite adsorbents with varied Al(13) contents (i.e., Na-Mont, AC-Mont, PAC(20)-Mont, and Al(13)-Mont) were synthesized and characterized by N(2) adsorption/desorption, X-ray diffraction, and Fourier-transform infrared analyses. The arsenate adsorption performance of the four adsorbents were also investigated to determine the role of intercalated Al(13), especially its high purity, high positive charge (+7), and special Keggin structure. With increased Al(13) content, the physicochemical properties (e.g., surface area, structural uniformity, basal spacing, and pore volume) and adsorption performance of the modified montmorillonites were significantly but disproportionately improved. The adsorption data well fitted the Freundlich and Redlich-Peterson isotherm model, whereas the kinetic data better correlated with the pseudo-second-order kinetic model. The arsenate sorption mechanism of the montmorillonites changed from physical to chemisorption after intercalation with Al(13). Increasing charges of the intercalated ions enhanced the arsenate adsorption kinetics, but had minimal effect on the structural changes of the montmorillonites. The uniform pore structure formed by intercalation with high-purity Al(13) greatly enhanced the pore diffusion and adsorption rate of arsenate, resulting in the high adsorption performance of Al(13)-Mont.

  10. Preconcentration of trace arsenite and arsenate with titanium dioxide nanoparticles and subsequent determination by silver diethyldithiocarbamate spectrophotometric method.

    PubMed

    Xiao, Yabing; Ling, Jie; Qian, Shahua; Lin, Anqing; Zheng, Wenjie; Xu, Weiya; Luo, Yuxuan; Zhang, Man

    2007-09-01

    A novel method of preconcentration of trace arsenite and arsenate by using titanium dioxide nanoparticles as adsorbent was described. The concentrations of preconcentrated arsenite and arsenate were determined by a silver diethyldithiocarbamate spectrophotometric method without desorption. Batch adsorption experiments were carried out as a function of the pH, contact time, amount of titanium dioxide nanoparticles, and solution volume. In the pH range 5 to 6, adsorption rates of arsenite and arsenate were higher than 98%. The calibration coefficient was 0.9991, and the linear range was 0 to 100 microg/L. The developed method was precise, with the relative standard deviation <5% at concentration level of 10 microg/L, with a detection limit (3sigma, n=6) of 0.44 microg/L. The accuracy of the method for total arsenic was validated by standard reference materials (SRM 3103a) (National Institute of Standards and Technology, Gaithersburg, Maryland). The method was also applied to the analysis of arsenite and arsenate in natural water samples to verify the accuracy. The recovery values remained in a narrow range, from 95 to 103%.

  11. Synergistic interaction of glyceraldehydes-3-phosphate dehydrogenase and ArsJ, a novel organoarsenical efflux permease, confers arsenate resistance.

    PubMed

    Chen, Jian; Yoshinaga, Masafumi; Garbinski, Luis D; Rosen, Barry P

    2016-06-01

    Microbial biotransformations are major contributors to the arsenic biogeocycle. In parallel with transformations of inorganic arsenic, organoarsenicals pathways have recently been recognized as important components of global cycling of arsenic. The well-characterized pathway of resistance to arsenate is reduction coupled to arsenite efflux. Here, we describe a new pathway of arsenate resistance involving biosynthesis and extrusion of an unusual pentavalent organoarsenical. A number of arsenic resistance (ars) operons have two genes of unknown function that are linked in these operons. One, gapdh, encodes the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase. The other, arsJ, encodes a major facilitator superfamily (MFS) protein. The two genes were cloned from the chromosome of Pseudomonas aeruginosa. When expressed together, but not alone, in Escherichia coli, gapdh and arsJ specifically conferred resistance to arsenate and decreased accumulation of As(V). Everted membrane vesicles from cells expressing arsJ accumulated As(V) in the presence of purified GAPDH, D-glceraldehylde 3-phosphate (G3P) and NAD(+) . GAPDH forms the unstable organoarsenical 1-arseno-3-phosphoglycerate (1As3PGA). We propose that ArsJ is an efflux permease that extrudes 1As3PGA from cells, where it rapidly dissociates into As(V) and 3-phosphoglycerate (3PGA), creating a novel pathway of arsenate resistance.

  12. Facile synthesis of size-tunable gold nanoparticles by pomegranate (Punica granatum) leaf extract: Applications in arsenate sensing

    SciTech Connect

    Rao, Ashit; Mahajan, Ketakee; Bankar, Ashok; Srikanth, Rapole; Kumar, Ameeta Ravi; Gosavi, Suresh; Zinjarde, Smita

    2013-03-15

    Highlights: ► Pomegranate leaf extracts mediated rapid gold nanoparticle (AuNP) synthesis. ► The phyto-inspired AuNPs were size-tuned and characterized. ► The reducing and capping agents in the extract were identified. ► The nanoparticles reacted specifically with arsenate (V) ions. - Abstract: When pomegranate leaf extracts were incubated with chloroauric acid (HAuCl{sub 4}), gold nanoparticles (AuNPs) were synthesized. These were characterized by a variety of techniques. With an increasing content of the leaf extract, a gradual decrease in size and an increase in monodispersity were observed. Transmission electron microscope (TEM) images showed that the phyto-fabricated AuNPs were surrounded by an amorphous layer. Gallic acid in the extract mediated the reduction and a natural decapeptide capped the nanostructures. Blocking of thiol groups in the decapeptide cysteine residues caused the nanoparticles to aggregate. On interaction with arsenate (V) ions, the UV–vis spectra of the nanoparticles showed a decrease in intensity and a red-shift. Energy dispersive spectra confirmed the presence of arsenate associated with the AuNPs. Thus, by using these AuNPs, a method for sensing the toxic arsenate ions could be developed.

  13. Tissue Distribution and Urinary Excretion of Dimethylated Arsenic and Its Metabolites in Dimethylarsinic acid- or Arsenate-treated Rats - MCEARD

    EPA Science Inventory

    Adult female Fisher 344 rats received drinking water containing 0, 4, 40, 100, or 200 parts per million of dimethylarsinic acid or 100 parts per million of arsenate for 14 days. Urine was collected during the last 24 h of exposure. Tissues were then taken for analysis of dimethy...

  14. Laccase Inhibition by Arsenite/Arsenate: Determination of Inhibition Mechanism and Preliminary Application to a Self-Powered Biosensor.

    PubMed

    Wang, Tao; Milton, Ross D; Abdellaoui, Sofiene; Hickey, David P; Minteer, Shelley D

    2016-03-15

    The reversible inhibition of laccase by arsenite (As(3+)) and arsenate (As(5+)) is reported for the first time. Oxygen-reducing laccase bioelectrodes were found to be inhibited by both arsenic species for direct electron-transfer bioelectrodes (using anthracene functionalities for enzymatic orientation) and for mediated electron-transfer bioelectrodes [using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as an electron mediator]. Both arsenic species were determined to behave via a mixed inhibition model (behaving closely to that of uncompetitive inhibitors) when evaluated spectrophotometrically using ABTS as the electron donor. Finally, laccase bioelectrodes were employed within an enzymatic fuel cell, yielding a self-powered biosensor for arsenite and arsenate. This conceptual self-powered arsenic biosensor demonstrated limits of detection (LODs) of 13 μM for arsenite and 132 μM for arsenate. Further, this device possessed sensitivities of 0.91 ± 0.07 mV/mM for arsenite and 0.98 ± 0.02 mV/mM for arsenate.

  15. Arsenate and Arsenite Sorption on Magnetite: Relations to Groundwater Arsenic Treatment Using Zerovalent Iron and Natural Attenuation

    EPA Science Inventory

    Magnetite (Fe3O4) is a zerovalent iron corrosion product; it is also formed in natural soil and sediment. Sorption of arsenate (As(V)) and arsenite (As(III)) on magnetite is an important process of arsenic removal from groundwater using zerovalent iron-based permeable reactive ba...

  16. Assessing Metal Contamination in Lead Arsenate Contaminated Orchard Soils Using Near and Mid-Infrared Diffuse Reflectance Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Historic use of lead-arsenate as pesticide in apple orchards left many soils contaminated with arsenic (As) and lead (Pb). Notorious health effects and their severe soil contamination are of primary concerns for major regulatory agencies, and community at large. Wet chemistry methods for soil anal...

  17. Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

    USGS Publications Warehouse

    Blum, Jodi Switzer; Kulp, Thomas R.; Han, Sukkyun; Lanoil, Brian; Saltikov, Chad W.; Stolz, John F.; Miller, Laurence G.; Oremland, Ronald S.

    2012-01-01

    A haloalkaliphilic sulfate-respiring bacterium, strain SLSR-1, was isolated from a lactate-fed stable enrichment culture originally obtained from the extreme environment of Searles Lake, California. The isolate proved capable of growth via sulfate-reduction over a broad range of salinities (125–330 g/L), although growth was slowest at salt-saturation. Strain SLSR-1 was also capable of growth via dissimilatory arsenate-reduction and displayed an even broader range of salinity tolerance (50–330 g/L) when grown under these conditions. Strain SLSR-1 could also grow via dissimilatory nitrate reduction to ammonia. Growth experiments in the presence of high borate concentrations indicated a greater sensitivity of sulfate-reduction than arsenate-respiration to this naturally abundant anion in Searles Lake. Strain SLSR-1 contained genes involved in both sulfate-reduction (dsrAB) and arsenate respiration (arrA). Amplicons of 16S rRNA gene sequences obtained from DNA extracted from Searles Lake sediment revealed the presence of close relatives of strain SLSR-1 as part of the flora of this ecosystem despite the fact that sulfate-reduction activity could not be detected in situ. We conclude that strain SLSR-1 can only achieve growth via arsenate-reduction under the current chemical conditions prevalent at Searles Lake. Strain SLSR-1 is a deltaproteobacterium in the family Desulfohalobiacea of anaerobic, haloalkaliphilic bacteria, for which we propose the name Desulfohalophilus alkaliarsenatis gen. nov., sp. nov.

  18. TISSUE DISTRIBUTION OF INORGANIC ARSENIC (AS) AND ITS METHYLATED METABOLITES IN MICE FOLLOWING ORAL ADMINISTRATION OF ARSENATE (ASV)

    EPA Science Inventory

    TISSUE DISTRIBUTION OF INORGANIC ARSENIC (iAs) AND ITS METHYLATED METABOLITES IN MICE FOLLOWING ORAL ADMINISTRATION OF ARSENATE (AsV). E M Kenyon1, L M Del Razo2, and M F Hughes1. 1NHEERL, ORD, US EPA, RTP, NC, USA; 2CINVESTAV-IPN, Mexico City, Mexico.

    The relationship o...

  19. Effects of meso-2,3-dimercaptosuccinic acid (DMSA) on the teratogenicity of sodium arsenate in mice

    SciTech Connect

    Bosque, M.A.; Domingo, J.L.; Llobet, J.M. ); Corbella, J. )

    1991-11-01

    Although the effects of arsenic on mammalian development are now well established, very few data on the protective activity of different chelators against embryotoxicity and teratogenicity of arsenic are available. Chelating agents may interact with teratogen metals to augment or ameliorate their actions. Researchers demonstrated that a single dose of 2,3-dimercaptopropanol (BAL) was capable of affording a degree of protection to arsenate exposed fetal mice. Subcutaneous treatment with 50 mg/kg of BAL 4 hr after arsenate reduced the frequency or severity of malformations compared with the effects of arsenate alone. However, BAL has several drawbacks. In recent years dimercaptosuccinic acid (DMSA) is receiving growing attention in the USA and Western Europe. Results of a number of different investigations in rodents have led to the conclusion that DMSA is much less toxic than BAL. Moreover, DMSA has been reported to be effective in inducing arsenic excretion. In the present study, the protective effects of DMSA in alleviating the embryotoxic and teratogenic effects of sodium arsenate were evaluated in mice.

  20. Post-translational Regulation of Nitrate Reductase

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate reductase (NR) catalyzes the reduction of nitrate to nitrite, which is the first step in the nitrate assimilation pathway, but can also reduce nitrite to nitric oxide (NO), an important signaling molecule that is thought to mediate a wide array of of developmental and physiological processes...

  1. Fumarate Reductase Activity of Streptococcus faecalis

    PubMed Central

    Aue, B. J.; Diebel, R. H.

    1967-01-01

    Some characteristics of a fumarate reductase from Streptococcus faecalis are described. The enzyme had a pH optimum of 7.4; optimal activity was observed when the ionic strength of the phosphate buffer was adjusted to 0.088. The Km value of the enzyme for reduced flavin mononucleotide was 2 × 10−4 m as determined with a 26-fold preparation. In addition to fumarate, the enzyme reduced maleate and mesaconate. No succinate dehydrogenase activity was detected, but succinate did act as an inhibitor of the fumarate reductase activity. Other inhibitors were malonate, citraconate, and trans-, trans-muconate. Metal-chelating agents did not inhibit the enzyme. A limited inhibition by sulfhydryl-binding agents was observed, and the preparations were sensitive to air oxidation and storage. Glycine, alanine, histidine, and possibly lysine stimulated fumarate reductase activity in the cell-free extracts. However, growth in media supplemented with glycine did not enhance fumarate reductase activity. The enzymatic activity appears to be constitutive. PMID:4960892

  2. Expression of denitrification enzymes in response to the dissolved oxygen level and respiratory substrate in continuous culture of Pseudomonas stutzeri.

    PubMed Central

    Körner, H; Zumft, W G

    1989-01-01

    The onset and cessation of the synthesis of denitrification enzymes of Pseudomonas stutzeri were investigated by using continuous culture and defined dissolved oxygen levels covering the full range of transition from air saturation to complete anaerobiosis. Expression of nitrate reductase, nitrite reductase (cytochrome cd1), and N2O reductase was controlled by discrete oxygen levels and by the nature of the nitrogenous oxide available for respiration. N2O reductase was synthesized constitutively at a low level; for enhanced expression, oxygen concentrations were required to decrease below 5 mg of O2 per liter. The threshold values for synthesis of nitrate reductase and cytochrome cd1 in the presence of nitrate were ca. 5 and ca. 2.5 mg of O2 per liter, respectively. With nitrous oxide as the respiratory substrate, nitrite reductase was again the most sensitive to oxygen concentration; however, thresholds for all denitrification enzymes shifted to lower oxygen levels. Whereas the presence of nitrate resulted in maximum expression and nearly uniform induction of all reductases, nitrite and nitrous oxide stimulated preferably the respective enzyme catalyzing reduction. In the absence of a nitrogenous oxide, anaerobiosis did not induce enzyme synthesis to any significant degree. The accumulation of nitrite seen during both the aerobic-anaerobic and anaerobic-aerobic transition phases was caused by the differences in onset or cessation of synthesis of nitrate and nitrite reductases and an inhibitory effect of nitrate on nitrite reduction. Images PMID:2764573

  3. Arsenate and Selenate Scavenging by Basaluminite: Insights into the Reactivity of Aluminum Phases in Acid Mine Drainage.

    PubMed

    Carrero, Sergio; Fernandez-Martinez, Alejandro; Pérez-López, Rafael; Poulain, Agnieszka; Salas-Colera, Eduardo; Nieto, José Miguel

    2017-01-03

    Basaluminite precipitation may play an important role in the behavior of trace elements in water and sediments affected by acid mine drainage and acid sulfate soils. In this study, the affinity of basaluminite and schwertmannite for arsenate and selenate is compared, and the coordination geometries of these oxyanions in both structures are reported. Batch isotherm experiments were conducted to examine the sorption capacity of synthetic schwertmannite and basaluminite and the potential competitive effect of sulfate. In addition, synchrotron-based techniques such as differential pair distribution function (d-PDF) analysis and extended X-ray absorption fine structure (EXAFS) were used to determine the local structure of As(V) and Se(VI) complexes. The results show that oxyanion exchange with structural sulfate was the main mechanism for removal of selenate, whereas arsenate was removed by a combination of surface complexes and oxyanion exchange. The arsenate adsorption capacity of basaluminite was 2 times higher than that of schwertmannite and 3 times higher than that of selenate in both phases. The sulfate:arsenate and sulfate:selenate exchange ratios were 1:2 and 1:1, respectively. High sulfate concentrations in the solutions did not show a competitive effect on arsenate sorption capacity but had a strong impact on selenate uptake, suggesting some kind of specific interaction for arsenate. Both d-PDF and EXAFS results indicated that the bidentate binuclear inner sphere was the most probable type of ligand for arsenate on both phases and for selenate on schwertmannite, whereas selenate forms outer-sphere complexes in the aluminum octahedral interlayer of basaluminite. Overall, these results show a strong affinity of poorly crystalline aluminum phases such as basaluminite for As(V) and Se(VI) oxyanions, with adsorption capacities on the same order of magnitude as those of iron oxides. The results obtained in this study are relevant to the understanding of trace

  4. Purification and characterization of the membrane-bound nitrate reductase isoenzymes of Bradyrhizobium japonicum.

    PubMed

    Fernández-López, M; Olivares, J; Bedmar, E J

    1996-08-19

    Two respiratory membrane-bound nitrate reductase (NR) isoenzymes, NRI and NRII, have been purified for the first time from one single microorganism. Triton X-100-solubilized NRs were purified by a three-step procedure of differential centrifugation, Q-Sepharose chromatography, and gel filtration on Sephacryl S-300. Both isoenzymes were purified to homogeneity by the criteria of NR activity staining in polyacrylamide gels run under non-denaturating conditions and coincident staining of the protein band by silver nitrate. NRI is composed of three subunits of 116 kDa, 68 kDa, and 56 kDa, whereas NRII is composed of four subunits of 116 kDa, 68 kDa, 59 kDa, and 56 kDa. The 116-kDa subunit of NRI and the 59-kDa subunit of NRII exhibited immunological cross-reactivity with the respiratory NR of Pseudomonas stutzeri strain ZoBell.

  5. Tissue distribution and urinary excretion of dimethylated arsenic and its metabolites in dimethylarsinic acid- or arsenate-treated rats

    SciTech Connect

    Adair, Blakely M.; Moore, Tanya; Conklin, Sean D.; Creed, John T.; Wolf, Douglas C.; Thomas, David J. . E-mail: thomas.david@epa.gov

    2007-07-15

    Adult female Fisher 344 rats received drinking water containing 0, 4, 40, 100, or 200 parts per million of dimethylarsinic acid or 100 parts per million of arsenate for 14 days. Urine was collected during the last 24 h of exposure. Tissues were then taken for analysis of dimethylated and trimethylated arsenicals; urines were analyzed for these arsenicals and their thiolated derivatives. In dimethylarsinic acid-treated rats, highest concentrations of dimethylated arsenic were found in blood. In lung, liver, and kidney, concentrations of dimethylated arsenic exceeded those of trimethylated species; in urinary bladder and urine, trimethylated arsenic predominated. Dimethylthioarsinic acid and trimethylarsine sulfide were present in urine of dimethylarsinic acid-treated rats. Concentrations of dimethylated arsenicals were similar in most tissues of dimethylarsinic acid- and arsenate-treated rats, including urinary bladder which is the target for dimethylarsinic acid-induced carcinogenesis in the rat. Mean concentration of dimethylated arsenic was significantly higher (P < 0.05) in urine of dimethylarsinic acid-treated rats than in arsenate-treated rats, suggesting a difference between treatment groups in the flux of dimethylated arsenic through urinary bladder. Concentrations of trimethylated arsenic concentrations were consistently higher in dimethylarsinic acid-treated rats than in arsenate-treated rats; these differences were significant (P < 0.05) in liver, urinary bladder, and urine. Concentrations of dimethylthioarsinic acid and trimethylarsine sulfide were higher in urine from dimethylarsinic acid-treated rats than from arsenate-treated rats. Dimethylarsinic acid is extensively metabolized in the rat, yielding significant concentrations of trimethylated species and of thiolated derivatives. One or more of these metabolites could be the species causing alterations of cellular function that lead to tumors in the urinary bladder.

  6. Upper respiratory tract (image)

    MedlinePlus

    The major passages and structures of the upper respiratory tract include the nose or nostrils, nasal cavity, mouth, throat (pharynx), and voice box (larynx). The respiratory system is lined with a mucous membrane that ...

  7. Avian respiratory system disorders

    USGS Publications Warehouse

    Olsen, G.H.

    1989-01-01

    Diagnosing and treating respiratory diseases in avian species requires a basic knowledge about the anatomy and physiology of this system in birds. Differences between mammalian and avian respiratory system function, diagnosis, and treatment are highlighted.

  8. MSFC Respiratory Protection Services

    NASA Technical Reports Server (NTRS)

    CoVan, James P.

    1999-01-01

    An overview of the Marshall Space Flight Center Respiratory Protection program is provided in this poster display. Respiratory protection personnel, building, facilities, equipment, customers, maintenance and operational activities, and Dynatech fit testing details are described and illustrated.

  9. Arsenate Uptake by Calcite: Macroscopic and Spectroscopic Characterization of Adsorption and Incorporation Mechanisms

    SciTech Connect

    Alexandratos,V.; Elzinga, E.; Reeder, R.

    2007-01-01

    Batch uptake experiments and X-ray element mapping and spectroscopic techniques were used to investigate As(V) (arsenate) uptake mechanisms by calcite, including adsorption and coprecipitation. Batch sorption experiments in calcite-equilibrated suspensions (pH 8.3; PCO{sub 2} = 10{sup -3.5} atm) reveal rapid initial sorption to calcite, with sorption rate gradually decreasing with time as available sorption sites decrease. An As(V)-calcite sorption isotherm determined after 24 h equilibration exhibits Langmuir-like behavior up to As concentrations of 300 {mu}M. Maximum distribution coefficient values (K{sub d}), derived from a best fit to a Langmuir model, are {approx}190 L kg{sup -1}. Calcite single crystals grown in the presence of As(V) show well-developed rhombohedral morphology with characteristic growth hillocks on (10{bar 1}4) surfaces at low As(V) concentrations ({<=}5 {mu}M), but habit modification is evident at As(V) concentrations {>=}30 {mu}M in the form of macrostep development preferentially on the - vicinal surfaces of growth hillocks. Micro-X-ray fluorescence element mapping of (10{bar 1}4) surfaces shows preferential incorporation of As in the - vicinal faces relative to + vicinals. EXAFS fit results for both adsorption and coprecipitation samples confirm that As occurs in the 5+ oxidation state in tetrahedral coordination with oxygen, i.e., as arsenate. For adsorption samples, As(V) forms inner-sphere surface complexes via corner-sharing with Ca octahedra. As(V) coprecipitated with calcite substitutes in carbonate sites but with As off-centered, as indicated by two Ca shells, and with likely disruption of local structure. The results indicate that As(V) interacts strongly with the calcite surface, similar to often-cited analog phosphate, and uptake can occur via both adsorption and coprecipitation reactions. Therefore, calcite may be effective for partial removal of dissolved arsenate from aquatic and soil systems.

  10. Atypical features of Thermus thermophilus succinate:quinone reductase.

    PubMed

    Kolaj-Robin, Olga; Noor, Mohamed R; O'Kane, Sarah R; Baymann, Frauke; Soulimane, Tewfik

    2013-01-01

    The Thermus thermophilus succinate:quinone reductase (SQR), serving as the respiratory complex II, has been homologously produced under the control of a constitutive promoter and subsequently purified. The detailed biochemical characterization of the resulting wild type (wt-rcII) and His-tagged (rcII-His(8)-SdhB and rcII-SdhB-His(6)) complex II variants showed the same properties as the native enzyme with respect to the subunit composition, redox cofactor content and sensitivity to the inhibitors malonate, oxaloacetate, 3-nitropropionic acid and nonyl-4-hydroxyquinoline-N-oxide (NQNO). The position of the His-tag determined whether the enzyme retained its native trimeric conformation or whether it was present in a monomeric form. Only the trimer exhibited positive cooperativity at high temperatures. The EPR signal of the [2Fe-2S] cluster was sensitive to the presence of substrate and showed an increased rhombicity in the presence of succinate in the native and in all recombinant forms of the enzyme. The detailed analysis of the shape of this signal as a function of pH, substrate concentration and in the presence of various inhibitors and quinones is presented, leading to a model for the molecular mechanism that underlies the influence of succinate on the rhombicity of the EPR signal of the proximal iron-sulfur cluster.

  11. Control of dihydrofolate reductase messenger ribonucleic acid production

    SciTech Connect

    Leys, E.J.; Kellems, R.E.

    1981-11-01

    The authors used methotrexate-resistant mouse cells in which dihydrofolate reductase levels are approximately 500 times normal to study the effect of growth stimulation on dihydrofolate reductase gene expression. As a result of growth stimulation, the relative rate of dihydrofolate reductase protein synthesis increased threefold, reaching a maximum between 25 and 30 h after stimulation. The relative rate of dihydrofolate reductase messenger ribonucleic acid production (i.e., the appearance of dihydrofolate reductase messenger ribonucleic acid in the cytoplasm) increased threefold after growth stimulation and was accompanied by a corresponding increase in the relative steady-state level of dihydrofolate reductase ribonucleic acid in the nucleus. However, the increase in the nuclear level of dihydrofolate reductase ribonucleic acid was not accompanied by a significant increase in the relative rate of transcription of the dihydrofolate reductase genes. These data indicated that the relative rate of appearance of dihydrofolate reductase messenger ribonucleic acid in the cytoplasm depends on the relative stability of the dihydrofolate reductase ribonucleic acid sequences in the nucleus and is not dependent on the relative rate of transcription of the dihydrofolate reductase genes.

  12. Augmentation of CFTR maturation by S-nitrosoglutathione reductase

    PubMed Central

    Sawczak, Victoria; Zaidi, Atiya; Butler, Maya; Bennett, Deric; Getsy, Paulina; Zeinomar, Maryam; Greenberg, Zivi; Forbes, Michael; Rehman, Shagufta; Jyothikumar, Vinod; DeRonde, Kim; Sattar, Abdus; Smith, Laura; Corey, Deborah; Straub, Adam; Sun, Fei; Palmer, Lisa; Periasamy, Ammasi; Randell, Scott; Kelley, Thomas J.; Lewis, Stephen J.

    2015-01-01

    S-nitrosoglutathione (GSNO) reductase regulates novel endogenous S-nitrosothiol signaling pathways, and mice deficient in GSNO reductase are protected from airways hyperreactivity. S-nitrosothiols are present in the airway, and patients with cystic fibrosis (CF) tend to have low S-nitrosothiol levels that may be attributed to upregulation of GSNO reductase activity. The present study demonstrates that 1) GSNO reductase activity is increased in the cystic fibrosis bronchial epithelial (CFBE41o−) cells expressing mutant F508del-cystic fibrosis transmembrane regulator (CFTR) compared with the wild-type CFBE41o− cells, 2) GSNO reductase expression level is increased in the primary human bronchial epithelial cells expressing mutant F508del-CFTR compared with the wild-type cells, 3) GSNO reductase colocalizes with cochaperone Hsp70/Hsp90 organizing protein (Hop; Stip1) in human airway epithelial cells, 4) GSNO reductase knockdown with siRNA increases the expression and maturation of CFTR and decreases Stip1 expression in human airway epithelial cells, 5) increased levels of GSNO reductase cause a decrease in maturation of CFTR, and 6) a GSNO reductase inhibitor effectively reverses the effects of GSNO reductase on CFTR maturation. These studies provide a novel approach to define the subcellular location of the interactions between Stip1 and GSNO reductase and the role of S-nitrosothiols in these interactions. PMID:26637637

  13. Respiratory Syncytial Virus

    MedlinePlus

    ... Your 1- to 2-Year-Old Respiratory Syncytial Virus KidsHealth > For Parents > Respiratory Syncytial Virus A A A What's in this article? About ... RSV When to Call the Doctor en español Virus respiratorio sincitial About RSV Respiratory syncytial (sin-SISH- ...

  14. Lungs and Respiratory System

    MedlinePlus

    ... A Week of Healthy Breakfasts Shyness Lungs and Respiratory System KidsHealth > For Teens > Lungs and Respiratory System Print ... didn't breathe, you couldn't live. Lungs & Respiratory System Basics Each day we breathe about 20,000 ...

  15. Lungs and Respiratory System

    MedlinePlus

    ... A Week of Healthy Breakfasts Shyness Lungs and Respiratory System KidsHealth > For Teens > Lungs and Respiratory System A ... didn't breathe, you couldn't live. Lungs & Respiratory System Basics Each day we breathe about 20,000 ...

  16. Rice-arsenate interactions in hydroponics: a three-gene model for tolerance.

    PubMed

    Norton, Gareth J; Nigar, Meher; Williams, Paul N; Dasgupta, Tapash; Meharg, Andrew A; Price, Adam H

    2008-01-01

    In this study, the genetic mapping of the tolerance of root growth to 13.3 muM arsenate [As(V)] using the BalaxAzucena population is improved, and candidate genes for further study are identified. A remarkable three-gene model of tolerance is advanced, which appears to involve epistatic interaction between three major genes, two on chromosome 6 and one on chromosome 10. Any combination of two of these genes inherited from the tolerant parent leads to the plant having tolerance. Lists of potential positional candidate genes are presented. These are then refined using whole genome transcriptomics data and bioinformatics. Physiological evidence is also provided that genes related to phosphate transport are unlikely to be behind the genetic loci conferring tolerance. These results offer testable hypotheses for genes related to As(V) tolerance that might offer strategies for mitigating arsenic (As) accumulation in consumed rice.

  17. Arsenite and arsenate removal from wastewater using cationic polymer-modified waste tyre rubber.

    PubMed

    Imyim, Apichat; Sirithaweesit, Thitayati; Ruangpornvisuti, Vithaya

    2016-01-15

    Waste tyre rubber (WTR) granulate was modified with a cationic polymer, poly(3-acrylamidopropyl)trimethylammonium chloride (p(APTMACl)). The resulting WTR/p(APTMACl) was utilized for the adsorption of arsenite, As(III) and arsenate, As(V) from aqueous medium in both batch and column methods. The level of adsorption increased gradually with increasing monomer concentration and contact time. The adsorption behavior obeyed the Freundlich model, and the rate of adsorption could be predicted by employing the pseudo-second order model. In the column method, As(V) could be adsorbed onto the sorbent more effectively than As(III). Remarkable desorption of As(III) and As(V) (99 and 92%, respectively) from the adsorbent was achieved using 0.10 M HCl as eluent. An approach of evaluation of adsorption capacity uncertainty is proposed.

  18. Chemistry and toxicology of building timbers pressure-treated with chromated copper arsenate: a review.

    PubMed

    Katz, Sidney A; Salem, Harry

    2005-01-01

    A recent agreement between the United States Environmental Protection Agency (USEPA) and the wood-treating industry will result in a phase-out of building timbers preserved with chromated copper arsenate (CCA). This agreement was motivated by a desire to reduce exposure to arsenic in the production, utilization and disposal of such material. The leaching of chromium, copper and arsenic from CCA-treated building timbers into water and soil and the subsequent environmental effects have been reviewed, as have the laboratory and epidemiological studies on the toxicology of CCA-treated building timbers. The benefits of the phase-out agreement are questionable because much arsenic will remain in the environment, and the alternatives to wood preservation with CCA are not without environmental consequences.

  19. Bacterial dissimilatory reduction of arsenate and sulfate in meromictic Mono Lake, California

    USGS Publications Warehouse

    Oremland, R.S.; Dowdle, P.R.; Hoeft, S.; Sharp, J.O.; Schaefer, J.K.; Miller, L.G.; Switzer, Blum J.; Smith, R.L.; Bloom, N.S.; Wallschlaeger, D.

    2000-01-01

    The stratified (meromictic) water column of alkaline and hypersaline Mono Lake, California, contains high concentrations of dissolved inorganic arsenic (~200 ??mol/L). Arsenic speciation changes from arsenate [As (V)] to arsenite [As (III)] with the transition from oxic surface waters (misolimnion) to anoxic bottom waters (monimolimnion). A radioassay was devised to measure the reduction of 73As (V) to 73As (III) and tested using cell suspensions of the As (V)-respiring Bacillus selenitireducens, which completely reduced the 73As (V). In field experiments, no significant activity was noted in the aerobic mixolimnion waters, but reduction of 73As (V) to 73As (III) was observed in all the monimolimnion samples. Rate constants ranged from 0.02 to 0.3/day, with the highest values in the samples from the deepest depths (24 and 28 m). The highest activities occurred between 18 and 21 m, where As (V) abundant (rate, ~5.9 ??mol/L per day). In contrast, sulfate reduction occurred at depths below 21 m, with the highest rates attained at 28 m (rate, ~2.3 ??mol/L per day). These results indicate that As (V) ranks second in importance, after sulfate, as an electron acceptor for anaerobic bacterial respiration in the water column. Annual arsenate respiration may mineralize as much as 14.2% of the pelagic photosynthetic carbon fixed during meromixis. When combined with sulfate-reduction data, anaerobic respiration in the water column can mineralize 32-55% of this primary production. As lakes of this type approach salt saturation, As (V) can become the most important electron acceptor for the biogeochemical cycling of carbon. Copyright (C) 2000 Elsevier Science Ltd.

  20. Can arsenates replace phosphates in natural biochemical processes? A computational study.

    PubMed

    Jissy, A K; Datta, Ayan

    2013-07-18

    A bacterial strain, GFAJ-1 was recently proposed to be substituting arsenic for phosphorus to sustain its growth. We have performed theoretical calculations for analyzing this controversial hypothesis by examining the addition of phosphate to ribose and glucose. Dispersion corrected Density Functional Theory (DFT) calculations in small molecules and QM/MM calculations on clusters derived from crystal structure are performed on structures involved in phosphorylation, considering both phosphates and arsenates. The exothermicity as well as the activation barriers for phosphate and arsenate transfer were examined. Quantum mechanical studies reveal that the relative stability of the products decrease marginally with successive substitution of P with As. However, simultaneously, the transition state barriers decrease with P replacement. This indicates that, kinetically, addition of As is more facile. Pseudorotation barriers for the pentavalent intermediates formed during the nucleophilic attack are also analyzed. A monotonic increase in barriers is observed for pseudorotation with the successive replacement of phosphorus with arsenic in methyl-DHP. A glucokinase crystal structure was chosen to construct a model system for QM/MM calculations. Free energy of the reaction (ΔG) reduces by less than 2.0 kcal/mol and the activation barrier (ΔG(‡)) decreases by ∼1 kcal/mol on arsenic incorporation. Thus, both DFT and QM/MM calculations show that arsenic can readily substitute phosphorus in key biomolecules. Secondary kinetic isotope effects for phosphorylation mechanism obtained by QM/MM calculations are also reported. The solvent kinetic isotopic effects (SKIE) for ATP and ATP (As) are calculated to be 5.81 and 4.73, respectively. A difference of ∼1.0 in SKIE suggests that it should be possible to experimentally determine the As-phosphorylation process.

  1. Bacterial dissimilatory reduction of arsenate and sulfate in meromictic Mono Lake, California

    NASA Astrophysics Data System (ADS)

    Oremland, Ronald S.; Dowdle, Philip R.; Hoeft, Shelly; Sharp, Jonathan O.; Schaefer, Jeffra K.; Miller, Laurence G.; Switzer Blum, Jodi; Smith, Richard L.; Bloom, Nicholas S.; Wallschlaeger, Dirk

    2000-09-01

    The stratified (meromictic) water column of alkaline and hypersaline Mono Lake, California, contains high concentrations of dissolved inorganic arsenic (˜200 μmol/L). Arsenic speciation changes from arsenate [As (V)] to arsenite [As (III)] with the transition from oxic surface waters (mixolimnion) to anoxic bottom waters (monimolimnion). A radioassay was devised to measure the reduction of 73As (V) to 73As (III) and tested using cell suspensions of the As (V)-respiring Bacillus selenitireducens, which completely reduced the 73As (V). In field experiments, no significant activity was noted in the aerobic mixolimnion waters, but reduction of 73As (V) to 73As (III) was observed in all the monimolimnion samples. Rate constants ranged from 0.02 to 0.3/day, with the highest values in the samples from the deepest depths (24 and 28 m). The highest activities occurred between 18 and 21 m, where As (V) was abundant (rate, ˜5.9 μmol/L per day). In contrast, sulfate reduction occurred at depths below 21 m, with the highest rates attained at 28 m (rate, ˜2.3 μmol/L per day). These results indicate that As (V) ranks second in importance, after sulfate, as an electron acceptor for anaerobic bacterial respiration in the water column. Annual arsenate respiration may mineralize as much as 14.2% of the pelagic photosynthetic carbon fixed during meromixis. When combined with sulfate-reduction data, anaerobic respiration in the water column can mineralize 32-55% of this primary production. As lakes of this type approach salt saturation, As (V) can become the most important electron acceptor for the biogeochemical cycling of carbon.

  2. Gallium Arsenate Dihydrate under Pressure: Elastic Properties, Compression Mechanism, and Hydrogen Bonding.

    PubMed

    Spencer, Elinor C; Soghomonian, Victoria; Ross, Nancy L

    2015-08-03

    Gallium arsenate dihydrate is a member of a class of isostructural compounds, with the general formula M(3+)AsO4·2H2O (M(3+) = Fe, Al, In, or Ga), which are being considered as potential solid-state storage media for the sequestration of toxic arsenic cations. We report the first high-pressure structural analysis of a metal arsenate dihydrate, namely, GaAsO4·2H2O. This compound crystallizes in the orthorhombic space group Pbca with Z = 8. Accurate unit cell parameters as a function of pressure were obtained by high-pressure single-crystal X-ray diffraction, and a bulk modulus of 51.1(3) GPa for GaAsO4·2H2O was determined from a third-order Birch-Murnaghan equation of state fit to the P-V data. Assessment of the pressure dependencies of the unit cell lengths showed that the compressibility of the structure along the axial directions increases in the order of [010] < [100] < [001]. This order was found to correlate well with the proposed compression mechanism for GaAsO4·2H2O, which involves deformation of the internal channel void spaces of the polyhedral helices that lie parallel to the [010] direction, and increased distortion of the GaO6 octahedra. The findings of the high-pressure diffraction experiment were further supported by the results from variable-pressure Raman analysis of GaAsO4·2H2O. Moreover, we propose a revised and more complex model for the hydrogen-bonding scheme in GaAsO4·2H2O, and on the basis of this revision, we reassigned the peaks in the OH stretching regions of previously published Raman spectra of this compound.

  3. Arsenate adsorption structures on aluminum oxide and phyllosilicate mineral surfaces in smelter-impacted soils.

    PubMed

    Beaulieu, Brett T; Savage, Kaye S

    2005-05-15

    A clearer understanding of arsenic (As) retention and transport in forest soils impacted by copper smelter emissions may reduce risks to human health and provide insight into As behavior in the vadose zone. On Vashon-Maury Island in Puget Sound, As is predominantly associated with the fine (< 63 microm) fraction of surficial soils. X-ray diffraction of oriented samples from the < 2 microm size fraction indicate that clinochlore isthe dominant phyllosilicate. X-ray absorption spectroscopy (XAS) was employed to examine As oxidation state and local coordination environment in impacted soil samples. Arsenic is present as As(V) in tetrahedral coordination with oxygen, associated with aluminum (Al) octahedra in bidentate binuclear (bridging) structures with As-Al distances of 3.15 - 3.16 angstroms. Including multiple scattering (MS) paths derived from the arsenate tetrahedron in esperanzaite significantly improved the match between XAS fine structure (EXAFS) data and models generated from theoretical phase and amplitude functions. The data are interpreted to indicate arsenate adsorption onto poorly crystalline aluminum oxyhydroxides and/or the edges of clinochlore interlayer hydroxyl sheets with constrained geometries causing MS to be important This implies that As initially released from the smelter as particulate As(III) and As(V) oxides was oxidized, dissolved, and adsorbed onto soil minerals and colloids; no evidence for relic arsenic oxide was observed. Physical transport of arsenic oxide particles and As adsorbed on soil colloids may account for limited downward migration of As within the soil column. The oxidizing and mildly acidic pH conditions in the upper vadose zone promote stable sorption complexes; barring substantial changes in soil chemistry, As is not expected to experience significant mobilization.

  4. Dissolved Calcium and Magnesium Carbonates Promote Arsenate Release From Ferrihydrite in Flow Systems

    NASA Astrophysics Data System (ADS)

    Saalfield, S. L.; Bostick, B. C.

    2007-12-01

    Field data from water systems around the world have shown that arsenic can reach toxic concentrations in dynamic groundwater systems. This is generally in contrast to analogous static systems at circumneutral pH, where arsenic is strongly retained by sorption to iron (hydr)oxides. Our research examines the effect of calcium and magnesium carbonates on As(V) mobility. In both dynamic flow and static experiments, arsenate was pre- sorbed to poorly crystalline iron hydroxides (1-10% sorption capacity), with varying aqueous compositions including calcium, magnesium, carbonate, sulfate, lactate, and other common groundwater species (pH 7.5-8). Thus we investigated how the dissolution of common carbonate minerals, specifically CaCO3 and MgCO3, affect arsenic behavior in the context of groundwater solutions. Under static (batch) conditions, no measurable arsenic (<10 μg/L) is released into solutions containing alkaline earth metals (AEMs) and carbonates. When elevated concentrations of AEMs and carbonate are introduced by dynamic flow, however, arsenic is mobilized at up to 500 μg/L, releasing significant proportions the total arsenic present. This is only the case when both of these species are present; with other common ion pairs, little to no arsenic is released. These results indicate that arsenate adsorption is kinetically controlled under flow conditions, resulting in very different mobility relative to otherwise equivalent static systems. Furthermore, the combination of alkaline earth metals and carbonates promotes As(V) mobility in column-based systems. We propose that these phenomena indicate a combination of physical and chemical effects by which diffusion limitation becomes dominant in limiting arsenic sorption in flow systems. Many carbonate-buffered aquifers, as well as those undergoing rapid mineralization of organic matter, could be affected by these processes of AEM-carbonate-limited sorption and increased arsenic mobility.

  5. [Music and respiratory pathology].

    PubMed

    Herer, B

    2001-04-01

    Musical performance, especially in singers and wind instrument players, depends on an effective pulmonary function. Performing artists may be seriously impaired by respiratory diseases that, comparatively, may produce only modest inconvenience for non-musicians. The report of two cases of respiratory diseases occurring in musicians herein provides an introduction to a review of the interactions between music and the human respiratory system. The following points are considered: epidemiological data; pulmonary function in musicians; favorable effects of music on the respiratory system; description of the main respiratory problems that may affect musicians.

  6. FRUCTOSE-6-PHOSPHATE REDUCTASE FROM SALMONELLA GALLINARUM

    PubMed Central

    Zancan, Glaci T.; Bacila, Metry

    1964-01-01

    Zancan, Glaci T. (Universidade do Paraná, Curitiba, Paraná, Brazil), and Metry Bacila. Fructose-6-phosphate reductase from Salmonella gallinarum. J. Bacteriol. 87:614–618. 1964.—A fructose-6-phosphate reductase present in cell-free extracts of Salmonella gallinarum was purified approximately 42 times. The optimal pH for this enzyme is 8.0. The enzyme is specific for fructose-6-phosphate and reduced nicotinamide adenine dinucleotide (NADH). The dissociation constants are 1.78 × 10−4m for fructose-6-phosphate and 8.3 × 10−5m for NADH. The Q10, reaction order, and equilibrium constant were determined. The enzyme is sensitive to p-chloromercuribenzoic acid, but not to o-iodosobenzoic acid nor to N-ethylmaleimide. PMID:14127579

  7. Electron transport to periplasmic nitrate reductase (NapA) of Wolinella succinogenes is independent of a NapC protein.

    PubMed

    Simon, Jörg; Sänger, Monica; Schuster, Stephan C; Gross, Roland

    2003-07-01

    The rumen bacterium Wolinella succinogenes grows by respiratory nitrate ammonification with formate as electron donor. Whereas the enzymology and coupling mechanism of nitrite respiration is well known, nitrate reduction to nitrite has not yet been examined. We report here that intact cells and cell fractions catalyse nitrate and chlorate reduction by reduced viologen dyes with high specific activities. A gene cluster encoding components of a putative periplasmic nitrate reductase system (napA, G, H, B, F, L, D) was sequenced. The napA gene was inactivated by inserting a kanamycin resistance gene cassette. The resulting mutant did not grow by nitrate respiration and did not reduce nitrate during growth by fumarate respiration, in contrast to the wild type. An antigen was detected in wild-type cells using an antiserum raised against the periplasmic nitrate reductase (NapA) from Paracoccus pantotrophus. This antigen was absent in the W. succinogenes napA mutant. It is concluded that the periplasmic nitrate reductase NapA is the only respiratory nitrate reductase in W. succinogenes, although a second nitrate-reducing enzyme is apparently induced in the napA mutant. The nap cluster of W. succinogenes lacks a napC gene whose product is thought to function in quinol oxidation and electron transfer to NapA in other bacteria. The W. succinogenes genome encodes two members of the NapC/NirT family, NrfH and FccC. Characterization of corresponding deletion mutants indicates that neither of these two proteins is required for nitrate respiration. A mutant lacking the genes encoding respiratory nitrite reductase (nrfHA) had wild-type properties with respect to nitrate respiration. A model of the electron transport chain of nitrate respiration is proposed in which one or more of the napF, G, H and L gene products mediate electron transport from menaquinol to the periplasmic NapAB complex. Inspection of the W. succinogenes genome sequence suggests that ammonia formation from

  8. The Distribution of Arsenate and Arsenite in Shoots and Roots of Holcus lanatus is Influenced by Arsenic Tolerance and Arsenate and Phosphate Supply

    PubMed Central

    Quaghebeur, Mieke; Rengel, Zdenko

    2003-01-01

    The recent discovery that phytochelatins are important for arsenic (As) detoxification in terrestrial plants results in the necessity to understand As speciation and metabolism in plant material. A hydroponic study was therefore conducted to examine the effects of different levels of phosphate and arsenate [As(V)] on As speciation and distribution in tolerant and non-tolerant clones of Holcus lanatus. Speciation of As in tissue (using high-performance liquid chromatography-inductively coupled plasma mass spectrometry) revealed that the predominant species present were the inorganic As species (As(V) and arsenite [As(III)]), although small levels (<1%) of organic As species (dimethylarsinic acid and monomethylarsonic acid) were detected in shoot material. In roots, the proportion of total As present as As(III) generally increased with increasing levels of As(V) in the nutrient solution, whereas in shoots, the proportion of total As present as As(III) generally decreased with increasing levels of As(V). H. lanatus plants growing in the high-phosphorus (P) (100 μm) solution contained a higher proportion of As(V) (with regard to total As) in both roots and shoots than plants supplied with low P (10 μm); in addition, tolerant clones generally contained a higher proportion of As(V) with regard to total As than non-tolerant clones. The study further revealed that As(V) can be reduced to As(III) in both roots and shoots. Although the reduction capacity was limited, the reduction was closely regulated by As influx for all treatments. The results therefore provide a new understanding about As metabolism in H. lanatus. PMID:12857839

  9. Cytochrome P450 3A, NADPH cytochrome P450 reductase and cytochrome b5 in the upper airways in horse.

    PubMed

    Tydén, E; Olsén, L; Tallkvist, J; Tjälve, H; Larsson, P

    2008-08-01

    Gene and protein expression as well as catalytic activity of cytochrome P450 (CYP) 3A were studied in the nasal olfactory and respiratory mucosa and the tracheal mucosa of the horse. We also examined the activity of NADPH cytochrome P450 reductase (NADPH P450 reductase), the amount of cytochrome b(5) and the total CYP content in these tissues. Comparative values for the above were obtained using liver as a control. The CYP3A related catalytic activity in the tissues of the upper airways was considerably higher than in the liver. The CYP3A gene and protein expression, on the other hand, was higher in the liver than in the upper airway tissues. Thus, the pattern of CYP3A metabolic activity does not correlate with the CYP3A gene and protein expression. Our results showed that the activity of NADPH P450 reductase and the level of cytochrome b(5) in the relation to the gene and protein expression of CYP3A were higher in the tissues of the upper airways than in the liver. It is concluded that CYP3A related metabolism in horse is not solely dependent on the expression of the enzyme but also on adequate levels of NADPH P450 reductase and cytochrome b(5).

  10. Characterization of erythrose reductases from filamentous fungi

    PubMed Central

    2013-01-01

    Proteins with putative erythrose reductase activity have been identified in the filamentous fungi Trichoderma reesei, Aspergillus niger, and Fusarium graminearum by in silico analysis. The proteins found in T. reesei and A. niger had earlier been characterized as glycerol dehydrogenase and aldehyde reductase, respectively. Corresponding genes from all three fungi were cloned, heterologously expressed in Escherichia coli, and purified. Subsequently, they were used to establish optimal enzyme assay conditions. All three enzymes strictly require NADPH as cofactor, whereas with NADH no activity could be observed. The enzymatic characterization of the three enzymes using ten substrates revealed high substrate specificity and activity with D-erythrose and D-threose. The enzymes from T. reesei and A. niger herein showed comparable activities, whereas the one from F. graminearum reached only about a tenth of it for all tested substrates. In order to proof in vivo the proposed enzyme function, we overexpressed the erythrose reductase-encoding gene in T. reesei. An increased production of erythritol by the recombinant strain compared to the parental strain could be detected. PMID:23924507

  11. Quantification of the effects of organic and carbonate buffers on arsenate and phosphate adsorption on a goethite-based granular porous adsorbent.

    PubMed

    Kanematsu, Masakazu; Young, Thomas M; Fukushi, Keisuke; Sverjensky, Dimitri A; Green, Peter G; Darby, Jeannie L

    2011-01-15

    Interest in the development of oxide-based materials for arsenate removal has led to a variety of experimental methods and conditions for determining arsenate adsorption isotherms, which hinders comparative evaluation of their adsorptive capacities. Here, we systematically investigate the effects of buffer (HEPES or carbonate), adsorbent dose, and solution pH on arsenate and phosphate adsorption isotherms for a previously well characterized goethite-based adsorbent (Bayoxide E33 (E33)). All adsorption isotherms obtained at different adsorbate/adsorbent concentrations were identical when 1 mM of HEPES (96 mg C/L) was used as a buffer. At low aqueous arsenate and phosphate concentration (∼1.3 μM), however, adsorption isotherms obtained using 10 mM of NaHCO(3) buffer, which is a reasonable carbonate concentration in groundwater, are significantly different from those obtained without buffer or with HEPES. The carbonate competitive effects were analyzed using the extended triple layer model (ETLM) with the adsorption equilibrium constant of carbonate calibrated using independent published carbonate adsorption data for pure goethite taking into consideration the different surface properties. The successful ETLM calculations of arsenate adsorption isotherms for E33 under various conditions allowed quantitative comparison of the arsenate adsorption capacity between E33 and other major adsorbents initially tested under varied experimental conditions in the literature.

  12. The removal of sulphate from mine water by precipitation as ettringite and the utilisation of the precipitate as a sorbent for arsenate removal.

    PubMed

    Tolonen, Emma-Tuulia; Hu, Tao; Rämö, Jaakko; Lassi, Ulla

    2016-10-01

    The aim of this research was to investigate sulphate removal from mine water by precipitation as ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and the utilisation of the precipitate as a sorbent for arsenate removal. The mine water sulphate concentration was reduced by 85-90% from the initial 1400 mg/L during ettringite precipitation depending on the treatment method. The precipitation conditions were also simulated with MINEQL + software, and the computational results were compared with the experimental results. The precipitated solids were characterised with X-ray diffraction and a scanning electron microscope. The precipitated solids were tested as sorbents for arsenate removal from the model solution. The arsenic(V) model solution concentration reduced 86-96% from the initial 1.5 mg/L with a 1 g/L sorbent dosage. The effect of initial arsenate concentration on the sorption of arsenate on the precipitate was studied and Langmuir, Freundlich, and Langmuir-Freundlich sorption isotherm models were fitted to the experimental data. The maximum arsenate sorption capacity (qm = 11.2 ± 4.7 mg/g) of the precipitate was obtained from the Langmuir-Freundlich isotherm. The results indicate that the precipitate produced during sulphate removal from mine water by precipitation as ettringite could be further used as a sorbent for arsenate removal.

  13. A Ferredoxin Disulfide Reductase Delivers Electrons to the Methanosarcina barkeri Class III Ribonucleotide Reductase

    PubMed Central

    2015-01-01

    Two subtypes of class III anaerobic ribonucleotide reductases (RNRs) studied so far couple the reduction of ribonucleotides to the oxidation of formate, or the oxidation of NADPH via thioredoxin and thioredoxin reductase. Certain methanogenic archaea contain a phylogenetically distinct third subtype of class III RNR, with distinct active-site residues. Here we report the cloning and recombinant expression of the Methanosarcina barkeri class III RNR and show that the electrons required for ribonucleotide reduction can be delivered by a [4Fe-4S] protein ferredoxin disulfide reductase, and a conserved thioredoxin-like protein NrdH present in the RNR operon. The diversity of class III RNRs reflects the diversity of electron carriers used in anaerobic metabolism. PMID:26536144

  14. Hydrogen sulfide alleviates toxic effects of arsenate in pea seedlings through up-regulation of the ascorbate-glutathione cycle: Possible involvement of nitric oxide.

    PubMed

    Singh, Vijay Pratap; Singh, Samiksha; Kumar, Jitendra; Prasad, Sheo Mohan

    2015-06-01

    In plants, hydrogen sulfide (H2S) is an emerging novel signaling molecule that is involved in growth regulation and abiotic stress responses. However, little is known about its role in the regulation of arsenate (As(V)) toxicity. Therefore, hydroponic experiments were conducted to investigate whether sodium hydrosulfide (NaHS; a source of H2S) is involved in the regulation of As(V) toxicity in pea seedlings. Results showed that As(V) caused decreases in growth, photosynthesis (measured as chlorophyll fluorescence) and nitrogen content, which was accompanied by the accumulation of As. As(V) treatment also reduced the activities of cysteine desulfhydrase and nitrate reductase, and contents of H2S and nitric oxide (NO). However, addition of NaHS ameliorated As(V) toxicity in pea seedlings, which coincided with the increased contents of H2S and NO. The cysteine level was higher under As(V) treatment in comparison to all other treatments (As-free; NaHS; As(V)+NaHS). The content of reactive oxygen species (ROS) and damage to lipids, proteins and membranes increased by As(V) while NaHS alleviated these effects. Enzymes of the ascorbate-glutathione cycle (AsA-GSH cycle) showed inhibition of their activities following As(V) treatment while their activities were increased by application of NaHS. The redox status of ascorbate and glutathione was disturbed by As(V) as indicated by a steep decline in their reduced/oxidized ratios. However, simultaneous NaHS application restored the redox status of the ascorbate and glutathione pools. The results of this study demonstrated that H2S and NO might both be involved in reducing the accumulation of As and triggering up-regulation of the AsA-GSH cycle to counterbalance ROS-mediated damage to macromolecules. Furthermore, the results suggest a crucial role of H2S in plant priming, and in particular for pea seedlings in mitigating As(V) stress.

  15. Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: Arsenate on hematite (0001) and (10-12)

    USGS Publications Warehouse

    Waychunas, G.; Trainor, T.; Eng, P.; Catalano, J.; Brown, G.; Davis, J.; Rogers, J.; Bargar, J.

    2005-01-01

    X-ray diffraction [crystal-truncation-rod (CTR)] studies of the surface structure of moisture-equilibrated hematite reveal sites for complexation not present on the bulk oxygen-terminated surface, and impose constraints on the types of inner-sphere sorption topologies. We have used this improved model of the hematite surface to analyze grazing-incidence EXAFS results for arsenate sorption on the c(0001) and r(10-12) surfaces measured in two electric vector polarizations. This work shows that the reconfiguration of the surface under moist conditions is responsible for an increased adsorption density of arsenate complexes on the (0001) surface relative to predicted ideal termination, and an abundance of "edge-sharing" bidentate complexes on both studied surfaces. We consider possible limitations on combining the methods due to differing surface sensitivities, and discuss further analysis possibilities using both methods. ?? Springer-Verlag 2005.

  16. Sulphate and arsenate minerals as environmental indicators in the weathering zones of selected ore deposits, Western Sudetes, Poland

    NASA Astrophysics Data System (ADS)

    Parafiniuk, Jan; Siuda, Rafał; Borkowski, Andrzej

    2016-09-01

    The results of a complex investigation of the sulphate and arsenate assemblages forming in the weathering zone of selected ore deposits in the Sudetes are presented. The development of the weathering zone has been characterised in the polymetallic ore deposits at Miedzianka-Ciechanowice and Radzimowice, and the pyrite deposit at Wieściszowice, which differ in the chemical compositions of the ore and barren minerals and the hydrological conditions. Secondary sulphate and arsenate mineral assemblages vary significantly among the ore deposits under study. Their crystallization is discussed, taking into consideration the stability of particular minerals and the paths of their transformation. It is shown that these minerals have great potential as indicators of weathering processes. A significant role for microorganisms in the formation of the weathering zone of the ore deposits under study is also proven.

  17. Methionine sulfoxide reductase contributes to meeting dietary methionine requirements

    PubMed Central

    Zhao, Hang; Kim, Geumsoo; Levine, Rodney L.

    2012-01-01

    Methionine sulfoxide reductases are present in all aerobic organisms. They contribute to antioxidant defenses by reducing methionine sulfoxide in proteins back to methionine. However, the actual in vivo roles of these reductases are not well defined. Since methionine is an essential amino acid in mammals, we hypothesized that methionine sulfoxide reductases may provide a portion of the dietary methionine requirement by recycling methionine sulfoxide. We used a classical bioassay, the growth of weanling mice fed diets varying in methionine, and applied it to mice genetically engineered to alter the levels of methionine sulfoxide reductase A or B1. Mice of all genotypes were growth retarded when raised on chow containing 0.10% methionine instead of the standard 0.45% methionine. Retardation was significantly greater in knockout mice lacking both reductases. We conclude that the methionine sulfoxide reductases can provide methionine for growth in mice with limited intake of methionine, such as may occur in the wild. PMID:22521563

  18. Different Arsenate and Phosphate Incorporation Effects on the Nucleation and Growth of Iron(III) (Hydr)oxides on Quartz

    SciTech Connect

    Neil, Chelsea W.; Lee, Byeongdu; Jun, Young-Shin

    2014-10-21

    Iron(III) (hydr)oxides play an important role in the geochemical cycling of contaminants in natural and engineered aquatic systems. The ability of iron(III) (hydr)oxides to immobilize contaminants can be related to whether the precipitates form heterogeneously (e.g., at mineral surfaces) or homogeneously in solution. Utilizing grazing incidence small-angle X-ray scattering (GISAXS), we studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions. For the iron(III) only system, the radius of gyration ( R g ) of heterogeneously formed precipitates grew from 1.5 to 2.5 ( ± 1.0) nm within 1 h. For the system containing 10-5 M arsenate, R g grew from 3.6 to 6.1 ( ± 0.5) nm, and for the system containing 10-5 M phosphate, R g grew from 2.0 to 4.0 ( ± 0.2) nm. While the systems containing these oxyanions had more growth, the system containing only iron(III) had the most nucleation events on substrates. Ex situ analyses of homogeneously and heterogeneously formed precipitates indicated that precipitates in the arsenate system had the highest water content and that oxyanions may bridge iron(III) hydroxide polymeric embryos to form a structure similar to ferric arsenate or ferric phosphate. These new fi ndings are important because di ff erences in nucleation and growth rates and particle sizes will impact the number of available reactive sites and the reactivity of newly formed particles toward aqueous contaminants.

  19. Structural Elucidation of Chalcone Reductase and Implications for Deoxychalcone Biosynthesis

    PubMed Central

    Bomati, Erin K.; Austin, Michael B.; Bowman, Marianne E.; Dixon, Richard A.; Noel, Joseph P.

    2010-01-01

    4,2′,4′,6′-tetrahydroxychalcone (chalcone) and 4,2′,4′-trihydroxychalcone (deoxychalcone) serve as precursors of ecologically important flavonoids and isoflavonoids. Deoxychalcone formation depends on chalcone synthase and chalcone reductase; however, the identity of the chalcone reductase substrate out of the possible substrates formed during the multistep reaction catalyzed by chalcone synthase remains experimentally elusive. We report here the three-dimensional structure of alfalfa chalcone reductase bound to the NADP+ cofactor and propose the identity and binding mode of its substrate, namely the non-aromatized coumaryl-trione intermediate of the chalcone synthase-catalyzed cyclization of the fully extended coumaryl-tetraketide thioester intermediate. In the absence of a ternary complex, the quality of the refined NADP+-bound chalcone reductase structure serves as a template for computer-assisted docking to evaluate the likelihood of possible substrates. Interestingly, chalcone reductase adopts the three-dimensional structure of the aldo/keto reductase superfamily. The aldo/keto reductase fold is structurally distinct from all known ketoreductases of fatty acid biosynthesis, which instead belong to the short-chain dehydrogenase/reductase superfamily. The results presented here provide structural support for convergent functional evolution of these two ketoreductases that share similar roles in the biosynthesis of fatty acids/polyketides. In addition, the chalcone reductase structure represents the first protein structure of a member of the aldo/ketoreductase 4 family. Therefore, the chalcone reductase structure serves as a template for the homology modeling of other aldo/ketoreductase 4 family members, including the reductase involved in morphine biosynthesis, namely codeinone reductase. PMID:15970585

  20. Early complications. Respiratory failure.

    PubMed

    Zwischenberger, J B; Alpard, S K; Bidani, A

    1999-08-01

    Pulmonary complications following thoracic surgery are common and associated with significant morbidity and mortality. Respiratory failure after pneumonectomy occurs in approximately 5% to 15% of cases and significantly increases patient mortality. Strategies for ventilator support are based on the nature of the underlying complication and the pathophysiology of respiratory failure. This article describes the cause and pathophysiology of respiratory failure and pulmonary embolus postpneumonectomy. Diagnosis, management, and innovative therapies are also reviewed.

  1. The human respiratory gate

    NASA Technical Reports Server (NTRS)

    Eckberg, Dwain L.

    2003-01-01

    Respiratory activity phasically alters membrane potentials of preganglionic vagal and sympathetic motoneurones and continuously modulates their responsiveness to stimulatory inputs. The most obvious manifestation of this 'respiratory gating' is respiratory sinus arrhythmia, the rhythmic fluctuations of electrocardiographic R-R intervals observed in healthy resting humans. Phasic autonomic motoneurone firing, reflecting the throughput of the system, depends importantly on the intensity of stimulatory inputs, such that when levels of stimulation are low (as with high arterial pressure and sympathetic activity, or low arterial pressure and vagal activity), respiratory fluctuations of sympathetic or vagal firing are also low. The respiratory gate has a finite capacity, and high levels of stimulation override the ability of respiration to gate autonomic responsiveness. Autonomic throughput also depends importantly on other factors, including especially, the frequency of breathing, the rate at which the gate opens and closes. Respiratory sinus arrhythmia is small at rapid, and large at slow breathing rates. The strong correlation between systolic pressure and R-R intervals at respiratory frequencies reflects the influence of respiration on these two measures, rather than arterial baroreflex physiology. A wide range of evidence suggests that respiratory activity gates the timing of autonomic motoneurone firing, but does not influence its tonic level. I propose that the most enduring significance of respiratory gating is its use as a precisely controlled experimental tool to tease out and better understand otherwise inaccessible human autonomic neurophysiological mechanisms.

  2. Effects of Phosphate on Arsenate Uptake and Translocation in Nonmetallicolous and Metallicolous Populations of Pteris Vittata L. Under Solution Culture.

    PubMed

    Wu, Fuyong; Wu, Shengchun; Deng, Dan; Wong, Ming Hung

    2015-01-01

    An arsenic hyperaccumulator, Pteris vittata L., is common in nature and could occur either on As-contaminated soils or on uncontaminated soils. However, it is not clear whether phosphate transporter play similar roles in As uptake and translocation in nonmetallicolous and metallicolous populations of P. vittata. Five populations were used to investigate effects of phosphate on arsenate uptake and translocation in the plants growing in 1.2 L 20% modified Hoagland's nutrient solution containing either 100 μM phosphate or no phosphate and 10 μM arsenate for 1, 2, 6, 12, 24 h, respectively. The results showed that the nonmetallicolous populations accumulated apparently more As in their fronds and roots than the metallicolous populations at both P supply levels. Phosphate significantly (P < 0.01) decreased frond and root concentrations of As during short time solution culture. In addition, the effects of phosphate on As translocation in P. vittata varied among different time-points during time-course hydroponics (1-24 h). The present results indicated that the inhibitory effect of phosphate on arsenate uptake was larger in the three nonmetallicolous populations than those in the two metallicolous populations of P. vittata.

  3. Arsenic mobility controlled by solid calcium arsenates: a case study in Mexico showcasing a potentially widespread environmental problem.

    PubMed

    Martínez-Villegas, Nadia; Briones-Gallardo, Roberto; Ramos-Leal, José A; Avalos-Borja, Miguel; Castañón-Sandoval, Alan D; Razo-Flores, Elías; Villalobos, Mario

    2013-05-01

    An As-contaminated perched aquifer under an urban area affected by mining was studied over a year to determine the contamination source species and the mechanism of As mobilization. Results show that the dissolution of calcium arsenates in residues disposed on an inactive smelter has caused high levels of As pollution in the adjoining downgradient 6-km perched aquifer, reaching up to 158 mg/L of dissolved As, and releasing a total of ca. 7.5 tons of As in a year. Furthermore, free calcium ion availability was found to control As mobility in the aquifer through the diagenetic precipitation of calcium arsenates (Ca5H2(AsO4)4·cH2O) preventing further mobilization of As. Results shown here represent a model for understanding a highly underreported mechanism of retention of arsenate species likely to dominate in calcium-rich environments, such as those in calcareous sediments and soils, where the commonly reported mechanism of adsorption to iron(III) oxyhydroxides is not the dominant process.

  4. [Ethanol-induced influence on the structure and arsenate adsorption of resin-based nano-hydrated ferric oxide].

    PubMed

    Wan, Qi; Li, Xu-Chun; Pan, Bing-Cai

    2013-08-01

    Here the role of ethanol in the synthesis of a new nanocomposite (D201-HFO) was evaluated in terms of its structure variation and arsenate adsorption. Results indicated that the ethanol-induced procedure improved the dispersion of HFO inside the polymer host D201 and increased the HFO sorption capacities towards arsenate by 20%. Also, the ethanol-induced procedure resulted in the increase of pore size, pore volume, and specific surface area of D201-HFO by 52%, 65% and 28%, respectively. Nevertheless, ethanol rinsing did not affect the mechanical strength of D201-HFO and the crystal type of the immobilized HFO. Little effects of the ethanol process was observed on the pH and co-anion dependent adsorption of arsenate. Furthermore, the ethanol step posed insignificant influence on the fix-bed adsorption and the repeated use of the adsorbent. The results showed that the ethanol procedure exerted little influence on the sorption properties of D201-HFO from the viewpoint of practical application and thus, it could not be included.

  5. Limited proteolysis of the nitrate reductase from spinach leaves.

    PubMed

    Kubo, Y; Ogura, N; Nakagawa, H

    1988-12-25

    The functional structure of assimilatory NADH-nitrate reductase from spinach leaves was studied by limited proteolysis experiments. After incubation of purified nitrate reductase with trypsin, two stable products of 59 and 45 kDa were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The fragment of 45 kDa was purified by Blue Sepharose chromatography. NADH-ferricyanide reductase and NADH-cytochrome c reductase activities were associated with this 45-kDa fragment which contains FAD, heme, and NADH binding fragment. After incubation of purified nitrate reductase with Staphylococcus aureus V8 protease, two major peaks were observed by high performance liquid chromatography size exclusion gel filtration. FMNH2-nitrate reductase and reduced methyl viologen-nitrate reductase activities were associated with the first peak of 170 kDa which consists of two noncovalently associated (75-90-kDa) fragments. NADH-ferricyanide reductase activity, however, was associated with the second peak which consisted of FAD and NADH binding sites. Incubation of the 45-kDa fragment with S. aureus V8 protease produced two major fragments of 28 and 14 kDa which contained FAD and heme, respectively. These results indicate that the molybdenum, heme, and FAD components of spinach nitrate reductase are contained in distinct domains which are covalently linked by exposed hinge regions. The molybdenum domain appears to be important in the maintenance of subunit interactions in the enzyme complex.

  6. Surface chemistry of ferrihydrite: Part 2. Kinetics of arsenate adsorption and coprecipitation

    USGS Publications Warehouse

    Fuller, C.C.; Dadis, J.A.; Waychunas, G.A.

    1993-01-01

    The kinetics of As(V) adsorption by ferrihydrite was investigated in coprecipitation and postsynthesis adsorption experiments conducted in the pH range 7.5-9.0. In coprecipitation experiments, As(V) was present in solution during the hydrolysis and precipitation of iron. In adsorption experiments, a period of rapid (<5 min) As(V) uptake from solution was followed by continued uptake for at least eight days, as As(V) diffused to adsorption sites on ferrihydrite surfaces within aggregates of colloidal particles. The time dependence of As(V) adsorption is well described by a general model for diffusion into a sphere if a subset of surface sites located near the exterior of aggregates is assumed to attain adsorptive equilibrium rapidly. The kinetics of As(V) desorption after an increase in pH were also consistent with diffusion as a rate-limiting process. Aging of pure ferrihydrite prior to As(V) adsorption caused a decrease in adsorption sites on the precipitate owing to crystallite growth. In coprecipitation experiments, the initial As(V) uptake was significantly greater than in post-synthesis adsorption experiments, and the rate of uptake was not diffusion limited because As(V) was coordinated by surface sites before crystallite growth and coagulation processes could proceed. After the initial adsorption, As(V) was slowly released from coprecipitates for at least one month, as crystallite growth caused desorption of As(V). Adsorption densities as high as 0.7 mole As(V) per mole of Fe were measured in coprecipitates, in comparison to 0.25 mole As(V) per mole of Fe in post-synthesis adsorption experiments. Despite the high Concentration of As(V) in the precipitates, EXAFS spectroscopy (Waychunas et al., 1993) showed that neither ferric arsenate nor any other As-bearing surface precipitate or solid solution was formed. The high adsorption densities are possible because the ferrihydrite particles are extremely small, approaching the size of small dioctahedral chains at

  7. Nitrite Reductase NirBD Is Induced and Plays an Important Role during In Vitro Dormancy of Mycobacterium tuberculosis

    PubMed Central

    Akhtar, Shamim; Khan, Arshad; Sohaskey, Charles D.; Jagannath, Chinnaswamy

    2013-01-01

    Mycobacterium tuberculosis is one of the strongest reducers of nitrate among all mycobacteria. Reduction of nitrate to nitrite, mediated by nitrate reductase (NarGHJI) of M. tuberculosis, is induced during the dormant stage, and the enzyme has a respiratory function in the absence of oxygen. Nitrite reductase (NirBD) is also functional during aerobic growth when nitrite is the sole nitrogen source. However, the role of NirBD-mediated nitrite reduction during the dormancy is not yet characterized. Here, we analyzed nitrite reduction during aerobic growth as well as in a hypoxic dormancy model of M. tuberculosis in vitro. When nitrite was used as the sole nitrogen source in the medium, the organism grew and the reduction of nitrite was evident in both hypoxic and aerobic cultures of M. tuberculosis. Remarkably, the hypoxic culture of M. tuberculosis, compared to the aerobic culture, showed 32- and 4-fold-increased expression of nitrite reductase (NirBD) at the transcription and protein levels, respectively. More importantly, a nirBD mutant of M. tuberculosis was unable to reduce nitrite and compared to the wild-type (WT) strain had a >2-log reduction in viability after 240 h in the Wayne model of hypoxic dormancy. Dependence of M. tuberculosis on nitrite reductase (NirBD) was also seen in a human macrophage-based dormancy model where the nirBD mutant was impaired for survival compared to the WT strain. Overall, the increased expression and essentiality of nitrite reductase in the in vitro dormancy models suggested that NirBD-mediated nitrite reduction could be critical during the persistent stage of M. tuberculosis. PMID:23935045

  8. Pyranopterin Coordination Controls Molybdenum Electrochemistry in Escherichia coli Nitrate Reductase.

    PubMed

    Wu, Sheng-Yi; Rothery, Richard A; Weiner, Joel H

    2015-10-09

    We test the hypothesis that pyranopterin (PPT) coordination plays a critical role in defining molybdenum active site redox chemistry and reactivity in the mononuclear molybdoenzymes. The molybdenum atom of Escherichia coli nitrate reductase A (NarGHI) is coordinated by two PPT-dithiolene chelates that are defined as proximal and distal based on their proximity to a [4Fe-4S] cluster known as FS0. We examined variants of two sets of residues involved in PPT coordination: (i) those interacting directly or indirectly with the pyran oxygen of the bicyclic distal PPT (NarG-Ser(719), NarG-His(1163), and NarG-His(1184)); and (ii) those involved in bridging the two PPTs and stabilizing the oxidation state of the proximal PPT (NarG-His(1092) and NarG-His(1098)). A S719A variant has essentially no effect on the overall Mo(VI/IV) reduction potential, whereas the H1163A and H1184A variants elicit large effects (ΔEm values of -88 and -36 mV, respectively). Ala variants of His(1092) and His(1098) also elicit large ΔEm values of -143 and -101 mV, respectively. An Arg variant of His(1092) elicits a small ΔEm of +18 mV on the Mo(VI/IV) reduction potential. There is a linear correlation between the molybdenum Em value and both enzyme activity and the ability to support anaerobic respiratory growth on nitrate. These data support a non-innocent role for the PPT moieties in controlling active site metal redox chemistry and catalysis.

  9. Living with Respiratory Failure

    MedlinePlus

    ... smoking. Emotional Issues and Support Living with respiratory failure may cause fear, anxiety, depression, and stress. Talk about how you feel with your health care team. Talking to a professional counselor also can ... to living with respiratory failure. You can see how other people who have ...

  10. Respiratory Care Therapist.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of respiratory care therapist, lists technical competencies and competency builders for 18 units pertinent to the health technologies cluster in general as well as those specific to the occupation of respiratory care therapist. The following…

  11. Tolerance, arsenic uptake, and oxidative stress in Acacia farnesiana under arsenate-stress.

    PubMed

    Alcantara-Martinez, Nemi; Guizar, Sandra; Rivera-Cabrera, Fernando; Anicacio-Acevedo, Blanca E; Buendia-Gonzalez, Leticia; Volke-Sepulveda, Tania

    2016-01-01

    Acacia farnesiana is a shrub widely distributed in soils heavily polluted with arsenic in Mexico. However, the mechanisms by which this species tolerates the phytotoxic effects of arsenic are unknown. This study aimed to investigate the tolerance and bioaccumulation of As by A. farnesiana seedlings exposed to high doses of arsenate (AsV) and the role of peroxidases (POX) and glutathione S-transferases (GST) in alleviating As-stress. For that, long-period tests were performed in vitro under different AsV treatments. A. farnesiana showed a remarkable tolerance to AsV, achieving a half-inhibitory concentration (IC50) of about 2.8 mM. Bioaccumulation reached about 940 and 4380 mg As·kg(-1) of dry weight in shoots and roots, respectively, exposed for 60 days to 0.58 mM AsV. Seedlings exposed to such conditions registered a growth delay during the first 15 days, when the fastest As uptake rate (117 mg kg(-1) day(-1)) occurred, coinciding with both the highest rate of lipid peroxidation and the strongest up-regulation of enzyme activities. GST activity showed a strong correlation with the As bioaccumulated, suggesting its role in imparting AsV tolerance. This study demonstrated that besides tolerance to AsV, A. farnesiana bioaccumulates considerable amounts of As, suggesting that it may be useful for phytostabilization purposes.

  12. Method to recover and reuse chromated copper arsenate wood preservative from spent treated wood

    SciTech Connect

    Kazi, Feroz Kabir M.; Cooper, Paul A. . E-mail: p.cooper@utoronto.ca

    2006-07-01

    The volume of chromated copper arsenate (CCA) treated wood products coming out of service is expected to increase dramatically during the next decade. There is a need for an alternative waste management approach to landfilling. This paper investigates the variables affecting extraction of CCA components from wood particles and the potential to oxidize and reuse the recovered chemicals. Most of the CCA components could be extracted by 10% H{sub 2}O{sub 2} at 50 deg. C in 6 h with an average extraction efficiency of 95% for Cr, 94% for Cu and 98% for As. The extract containing Cr{sup III}, Cu{sup II} and As{sup V} could be oxidized in several stages by aqueous 2.5% w/w H{sub 2}O{sub 2} in less than 2 h to a condition where it was compatible with CCA treating solutions and could be reused for treating new wood. When the recovered extract was mixed with fresh CCA solution in different ratios, the mixed CCA-C solutions had similar solution stability as freshly prepared CCA-C solution and treated wood had similar leaching properties as wood treated with fresh solution.

  13. Co-adsorption of Trichloroethylene and Arsenate by Iron-Impregnated Granular Activated Carbon.

    PubMed

    Deng, Baolin; Kim, Eun-Sik

    2016-05-01

    Co-adsorption of trichloroethylene (TCE) and arsenate [As(V)] was investigated using modified granular activated carbons (GAC): untreated, sodium hypochlorite-treated (NaClO-GAC), and NaClO with iron-treated GAC (NaClO/Fe-GAC). Batch experiments of single- [TCE or As(V)] and binary- [TCE and As(V)] components solutions are evaluated through Langmuir and Freundlich isotherm models and adsorption kinetic tests. In the single-component system, the adsorption capacity of As(V) was increased by the NaClO-GAC and the NaClO/Fe-GAC. The untreated GAC showed a low adsorption capacity for As(V). Adsorption of TCE by the NaClO/Fe-GAC was maximized, with an increased Freundlich constant. Removal of TCE in the binary-component system was decreased 15% by the untreated GAC, and NaClO- and NaClO/Fe-GAC showed similar efficiency to the single-component system because of the different chemical status of the GAC surfaces. Results of the adsorption isotherms of As(V) in the binary-component system were similar to adsorption isotherms of the single-component system. The adsorption affinities of single- and binary-component systems corresponded with electron transfer, competitive adsorption, and physicochemical properties.

  14. Interactive effects of arsenate, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings

    USGS Publications Warehouse

    Hoffman, D.J.; Sanderson, C.J.; LeCaptain, L.J.; Cromartie, E.; Pendleton, G.W.

    1992-01-01

    High concentrations of arsenic (As) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a maJor source of protein for wild ducklings, may vary in environments that are contaminated with selenium. Dayold mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm Se (as selenomethionine), 60 ppm Se, 200 ppm As (as sodium arsenate), 15 ppm Se with 200 ppm As, or 60 ppm Se with 200 ppm As. In a concurrent experiment, the same sequence was repeated with a proteinrestricted (7%) but isocaloric diet. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and livers had histopathological lesions. Arsenic alone caused some reduction in growth. Antagonistic interactive effects occurred between As and Se, including complete to partial alleviation of the following Se effects: mortality, impaired growth, hepatic lesions and lipid peroxidation, and altered glutathione and thiol status. With 7% protein, survival and growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and As (200 ppm) caused mortality, decreased growth, and liver histopathology. These findings suggest the potential for antagonistic effects of Se and As on duckling survival, growth, and physiology with adequate dietary protein but more severe toxicological effects when dietary protein is diminished.

  15. Effects of chronic exposure to arsenate on the cardiovascular function of rats.

    PubMed Central

    Carmignani, M; Boscolo, P; Iannaccone, A

    1983-01-01

    Cardiovascular function was studied in anaesthetised male rats which received 50 micrograms/ml of arsenic (as sodium arsenate) in deionised drinking water for 320 days. High urinary excretion of arsenic was found at the end of treatment and the metal accumulated considerably in the kidneys and liver, which both presented slight alterations. No histopathological modifications were evident in other organs. Base line blood pressure, cardiac inotropism, and chronotropism and cardiovascular reactivity to noradrenaline, acetylcholine, angiotensin II, bradykinin, histamine, and serotonin did not differ in exposed or in control animals. In the exposed group, however, there was potentiation of the effects of vascular beta-adrenoceptor stimulation and a reduction in the vascular responsiveness to angiotensin I. Chronic arsenic exposure did not affect the baroreflex sensitivity but was able to induce sympathetic hyperactivity or hypersensitivity, or both, possibly associated with an antivagal action. Our results might help to explain the cardiovascular alterations seen in people chronically exposed to high concentrations of arsenic. PMID:6871116

  16. Arsenic and chromium partitioning in a podzolic soil contaminated by chromated copper arsenate

    SciTech Connect

    Nico, Peter; Hopp, Luisa; Nico, Peter S.; Marcus, Matthew A.; Peiffer, Stefan

    2008-06-01

    This research combined the use of selective extractions and x-ray spectroscopy to examine the fate of As and Cr in a podzolic soil contaminated by chromated copper arsenate (CCA). Iron was enriched in the upper 30 cm due to a previous one-time treatment of the soil with Fe(II). High oxalate-soluble Al concentrations in the Bs horizon of the soil and micro-XRD data indicated the presence of short-range ordered aluminosilicates (i.e. proto-imogolite allophane, PIA). In the surface layers, Cr, as Cr(III), was partitioned between a mixed Fe(III)/Cr(III) solid phase that formed upon the Fe(II) application (25-50%) and a recalcitrant phase (50-75%) likely consisting of organic material such as residual CCA-treated wood. Deeper in the profile Cr appeared to be largely in the form of extractable (hydr)oxides. Throughout the soil, As was present as As(V). In the surface layers a considerable fraction of As was also associated with a recalcitrant phase, probably CCA-treated woody debris, and the remainder was associated with (hydr)oxide-like solid phases. In the Bs horizon, however, XAS and XRF findings strongly pointed to the presence of PIA acting as an effective adsorbent for As. This research shows for the first time the relevance of PIA for the adsorption of As in natural soils.

  17. Modeling oxyanion adsorption on ferralic soil, part 2: chromate, selenate, molybdate, and arsenate adsorption.

    PubMed

    Pérez, Claudio; Antelo, Juan; Fiol, Sarah; Arce, Florencio

    2014-10-01

    High levels of oxyanions are found in the soil environment, often as a result of human activity. At high concentrations, oxyanions can be harmful to both humans and wildlife. Information about the interactions between oxyanions and natural samples is essential for understanding the bioavailability, toxicity, and transport of these compounds in the environment. In the present study, the authors investigated the reactivity of different oxyanions (AsO4 , MoO4 , SeO4 , and CrO4 ) at different pH values in 2 horizons of a ferralic soil. By combining available microscopic data on iron oxides with the macroscopic data obtained, the authors were able to use the charge distribution model to accurately describe the adsorption of these 4 oxyanions and thus to determine the surface speciation. The charge distribution model was previously calibrated and evaluated using phosphate adsorption/desorption data. The adsorption behavior on ferralic soil is controlled mainly by the natural iron oxides present, and it is qualitatively analogous to that exhibited by synthetic iron oxides. The highest adsorption was found for arsenate ions, whereas the lowest was found for selenate, with chromate and molybdate ions showing an intermediate behavior.

  18. Nanoporous sorbent material as an oral phosphate binder and for aqueous phosphate, chromate, and arsenate removal

    PubMed Central

    Sangvanich, Thanapon; Ngamcherdtrakul, Worapol; Lee, Richard; Morry, Jingga; Castro, David; Fryxell, Glen E.; Yantasee, Wassana

    2014-01-01

    Phosphate removal is both biologically and environmentally important. Biologically, hyperphosphatemia is a critical condition in end-stage chronic kidney disease patients. Patients with hyperphosphatemia are treated long-term with oral phosphate binders to prevent phosphate absorption to the body by capturing phosphate in the gastrointestinal (GI) tract followed by fecal excretion. Environmentally, phosphate levels in natural water resources must be regulated according to limits set forth by the US Environmental Protection Agency. By utilizing nanotechnology and ligand design, we developed a new material to overcome limitations of traditional sorbent materials such as low phosphate binding capacity, slow binding kinetics, and negative interference by other anions. A phosphate binder based on iron-ethylenediamine on nanoporous silica (Fe-EDA-SAMMS) has been optimized for substrates and Fe(III) deposition methods. The Fe-EDA-SAMMS material had a 4-fold increase in phosphate binding capacity and a broader operating pH window compared to other reports. The material had a faster phosphate binding rate and was significantly less affected by other anions than Sevelamer HCl, the gold standard oral phosphate binder, and AG® 1-X8, a commercially available anion exchanger. It had less cytotoxicity to Caco-2 cells than lanthanum carbonate, another prescribed oral phosphate binder. The Fe-EDA-SAMMS also had high capacity for arsenate and chromate, two of the most toxic anions in natural water. PMID:25554735

  19. Arsenite and arsenate impact the oxidative status and antioxidant responses in Ocimum tenuiflorum L.

    PubMed

    Siddiqui, Fauzia; Tandon, P K; Srivastava, Sudhakar

    2015-07-01

    Biochemical responses of Ocimum tenuiflorum plants were studied upon exposure to arsenite (AsIII) and arsenate (AsV) for 1 to 10 d. Plants accumulated significant amounts of As in leaves (662 μg g(-1) dry weight; DW and 412 μg g(-1) DW in response to 100 μM AsIII and AsV exposure, respectively after 10 d). Consequently, fresh weight and growth of plants declined in a concentration dependent manner. Further, total chlorophyll and carotenoid contents also declined while oxidative stress markers increased, particularly on longer durations. Various antioxidant enzymes and thiols (cysteine and glutathione; GSH) showed significant and variable increases upon exposure to AsV and AsIII with the response being comparatively better in response to AsV. Proline increased significantly upon exposure to both AsIII and AsV. Plants thus tolerated high As concentrations through induced antioxidant machinery.

  20. Preparation and certification of arsenate [As(V)] reference material, NMIJ CRM 7912-a.

    PubMed

    Narukawa, Tomohiro; Kuroiwa, Takayoshi; Narushima, Izumi; Jimbo, Yasujiro; Suzuki, Toshihiro; Chiba, Koichi

    2010-05-01

    Arsenate [As(V)] solution reference material, National Metrology Institute of Japan (NMIJ) certified reference material (CRM) 7912-a, for speciation of arsenic species was developed and certified by NMIJ, the National Institute of Advanced Industrial Science and Technology. High-purity As(2)O(3) reagent powder was dissolved in 0.8 M HNO(3) solution and As(III) was oxidized to As(V) with HNO(3) to prepare 100 mg kg(-1) of As(V) candidate CRM solution. The solution was bottled in 400 bottles (50 mL each). The concentration of As(V) was determined by four independent analytical techniques-inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, graphite furnace atomic absorption spectrometry, and liquid chromatography inductively coupled plasma mass spectrometry-according to As(V) calibration solutions, which were prepared from the arsenic standard of the Japan Calibration Service system and whose species was guaranteed to be As(V) by NMIJ. The uncertainties of all the measurements and preparation procedures were evaluated. The certified value of As(V) in the CRM is (99.53 +/- 1.67) mg kg(-1) (k = 2).

  1. Impacts of amount of impregnated iron in granular activated carbon on arsenate adsorption capacities and kinetics.

    PubMed

    Chang, Qigang; Lin, Wei; Ying, Wei-Chi

    2012-06-01

    Iron-impregnated granular activated carbons (Fe-GAC) can remove arsenic effectively from water. In this study, Fe-GACs with iron content of 1.64 to 28.90% were synthesized using a new multi-step procedure for the investigation of effects of iron amount on arsenic adsorption capacities and kinetics. Langmuir model satisfactorily fit arsenic adsorption on Fe-GACs. The maximum arsenic adsorption capacity (q(m)) increased significantly with iron impregnation and reached 1,867 to 1,912 microg/g with iron content of 9.96 to 13.59%. Further increase of iron content (> 13.59%) caused gradual decrease of q(m). It was found that the amount of impregnated iron showed little impact on the affinity for arsenate. Kinetic study showed that the amount of impregnated iron affected the arsenic intraparticle diffusion rate greatly. The pseudo-second-order kinetic model fit arsenic adsorption kinetics on Fe-GACs better than the pseudo-first-order model. The arsenic adsorption rate increased with increasing of iron content from 1.64% to 13.59%, and then decreased with more impregnated iron (13.59 to 28.90%).

  2. Characterization of adsorption of aqueous arsenite and arsenate onto charred dolomite in microcolumn systems.

    PubMed

    Salameh, Yousef; Al-Muhtaseb, Ala'a H; Mousa, Hasan; Walker, Gavin M; Ahmad, Mohammad N M

    2014-01-01

    In this work, the removal of arsenite, As(III), and arsenate, As(V), from aqueous solutions onto thermally processed dolomite (charred dolomite) via microcolumn was evaluated. The effects of mass of adsorbent (0.5-2 g), initial arsenic concentration (50-2000 ppb) and particle size (<0.355-2 mm) on the adsorption capacity of charred dolomite in a microcolumn were investigated. It was found that the adsorption of As(V) and As(III) onto charred dolomite exhibited a characteristic 'S' shape. The adsorption capacity increased as the initial arsenic concentration increased. A slow decrease in the column adsorption capacity was noted as the particle size increased from>0.335 to 0.710-2.00 mm. For the binary system, the experimental data show that the adsorption of As(V) and As(III) was independent of both ions in solution. The experimental data obtained from the adsorption process were successfully correlated with the Thomas Model and Bed Depth Service Time Model.

  3. Enzyme toolbox: novel enantiocomplementary imine reductases.

    PubMed

    Scheller, Philipp N; Fademrecht, Silvia; Hofelzer, Sebastian; Pleiss, Jürgen; Leipold, Friedemann; Turner, Nicholas J; Nestl, Bettina M; Hauer, Bernhard

    2014-10-13

    Reducing reactions are among the most useful transformations for the generation of chiral compounds in the fine-chemical industry. Because of their exquisite selectivities, enzymatic approaches have emerged as the method of choice for the reduction of C=O and activated C=C bonds. However, stereoselective enzymatic reduction of C=N bonds is still in its infancy-it was only recently described after the discovery of enzymes capable of imine reduction. In our work, we increased the spectrum of imine-reducing enzymes by database analysis. By combining the currently available knowledge about the function of imine reductases with the experimentally uncharacterized diversity stored in protein sequence databases, three novel imine reductases with complementary enantiopreference were identified along with amino acids important for catalysis. Furthermore, their reducing capability was demonstrated by the reduction of the pharmaceutically relevant prochiral imine 2-methylpyrroline. These novel enzymes exhibited comparable to higher catalytic efficiencies than previously described enzymes, and their biosynthetic potential is highlighted by the full conversion of 2-methylpyrroline in whole cells with excellent selectivities.

  4. The role of Bradyrhizobium japonicum nitric oxide reductase in nitric oxide detoxification in soya bean root nodules.

    PubMed

    Meakin, G E; Jepson, B J N; Richardson, D J; Bedmar, E J; Delgado, M J

    2006-02-01

    The identification of nitric oxide-bound leghaemoglobin within soya bean nodules has led to the question of how Bradyrhizobium japonicum bacteroids overcome the toxicity of this nitric oxide. It has previously been shown that one candidate for nitric oxide detoxification, the respiratory nitric oxide reductase, is expressed in soya bean nodules from plants supplied with nitrate. In this paper, the role of this enzyme in nitric oxide detoxification is assessed and discussion is provided on other possible B. japonicum nitric oxide detoxification systems.

  5. Soluble ascorbate free radical reductase in the human lens.

    PubMed

    Bando, M; Obazawa, H

    1994-01-01

    A major and a minor ascorbate free radical (AFR) reductase were separated from the soluble fraction in the human lens cortex by DEAE-cellulose ion-exchange column chromatography. These AFR reductases also exhibited diaphorase activity using dichlorophenolindophenol and ferricyanide as electron acceptors. The major AFR reductase was partially purified by 5'AMP-Sepharose 4B affinity column chromatography. This partially purified AFR reductase showed a single band of diaphorase activity in native polyacrylamide disc gel electrophoresis. This activity band corresponded to the major protein observed in protein staining by Coomassie Brilliant Blue. However, the protein staining by Coomassie Brilliant Blue showed this activity band surrounded by diffused staining. Molecular weight of the partially purified AFR reductase was determined to be 32 kDa by gel filtration, and the apparent Km value for AFR was about 15 microM. This major lens AFR reductase could be distinguished from soluble Neurospora, Euglena and cucumber AFR reductases, and from two ubiquitous enzymes with reduction activity of AFR and/or foreign compounds, ie, NADH-cytochrome b5 reductase and DT-diaphorase, by their molecular weights, Km values and/or ion-exchange chromatographic behaviors.

  6. Functional and Phylogenetic Divergence of Fungal Adenylate-Forming Reductases

    PubMed Central

    Kalb, Daniel; Lackner, Gerald

    2014-01-01

    A key step in fungal l-lysine biosynthesis is catalyzed by adenylate-forming l-α-aminoadipic acid reductases, organized in domains for adenylation, thiolation, and the reduction step. However, the genomes of numerous ascomycetes and basidiomycetes contain an unexpectedly large number of additional genes encoding similar but functionally distinct enzymes. Here, we describe the functional in vitro characterization of four reductases which were heterologously produced in Escherichia coli. The Ceriporiopsis subvermispora serine reductase Nps1 features a terminal ferredoxin-NADP+ reductase (FNR) domain and thus belongs to a hitherto undescribed class of fungal multidomain enzymes. The second major class is characterized by the canonical terminal short-chain dehydrogenase/reductase domain and represented by Ceriporiopsis subvermispora Nps3 as the first biochemically characterized l-α-aminoadipic acid reductase of basidiomycete origin. Aspergillus flavus l-tyrosine reductases LnaA and LnbA are members of a distinct phylogenetic clade. Phylogenetic analysis supports the view that fungal adenylate-forming reductases are more diverse than previously recognized and belong to four distinct classes. PMID:25085485

  7. Other Community Respiratory Viruses.

    PubMed

    Wunderink, Richard G

    2017-03-01

    Polymerase chain reaction-based diagnosis has become the standard for viral pneumonia and other respiratory tract infections. Expansion of respiratory viral panels (RVPs) outside of influenza and, possibly, respiratory syncytial virus has led to the ability to diagnose viral infections for which no approved specific antiviral treatment exists. Careful clinical evaluation of the patient with a positive RVP is, therefore, critical given the limited repertoire of treatments. Generic treatments with intravenous immunoglobulin, ribavirin, and interferons may benefit select severe viral pneumonia patients, whereas cidofovir has activity for severe adenoviral pneumonia.

  8. Respiratory medicine of reptiles.

    PubMed

    Schumacher, Juergen

    2011-05-01

    Noninfectious and infectious causes have been implicated in the development of respiratory tract disease in reptiles. Treatment modalities in reptiles have to account for species differences in response to therapeutic agents as well as interpretation of diagnostic findings. Data on effective drugs and dosages for the treatment of respiratory diseases are often lacking in reptiles. Recently, advances have been made on the application of advanced imaging modalities, especially computed tomography for the diagnosis and treatment monitoring of reptiles. This article describes common infectious and noninfectious causes of respiratory disease in reptiles, including diagnostic and therapeutic regimen.

  9. Structure-activity relationship of pyrrole based S-nitrosoglutathione reductase inhibitors: carboxamide modification.

    PubMed

    Sun, Xicheng; Qiu, Jian; Strong, Sarah A; Green, Louis S; Wasley, Jan W F; Blonder, Joan P; Colagiovanni, Dorothy B; Stout, Adam M; Mutka, Sarah C; Richards, Jane P; Rosenthal, Gary J

    2012-03-15

    The enzyme S-nitrosoglutathione reductase (GSNOR) is a member of the alcohol dehydrogenase family (ADH) that regulates the levels of S-nitrosothiols (SNOs) through catabolism of S-nitrosoglutathione (GSNO). GSNO and SNOs are implicated in the pathogenesis of many diseases including those in respiratory, gastrointestinal, and cardiovascular systems. The pyrrole based N6022 was recently identified as a potent, selective, reversible, and efficacious GSNOR inhibitor which is currently in clinical development for acute asthma. We describe here the synthesis and structure-activity relationships (SAR) of novel pyrrole based analogs of N6022 focusing on carboxamide modifications on the pendant N-phenyl moiety. We have identified potent and novel GSNOR inhibitors that demonstrate efficacy in an ovalbumin (OVA) induced asthma model in mice.

  10. Discovery of potent and novel S-nitrosoglutathione reductase inhibitors devoid of cytochrome P450 activities.

    PubMed

    Sun, Xicheng; Qiu, Jian; Strong, Sarah A; Green, Louis S; Wasley, Jan W F; Blonder, Joan P; Colagiovanni, Dorothy B; Mutka, Sarah C; Stout, Adam M; Richards, Jane P; Rosenthal, Gary J

    2011-10-01

    The pyrrole based N6022 was recently identified as a potent, selective, reversible, and efficacious S-nitrosoglutathione reductase (GSNOR) inhibitor and is currently undergoing clinical development for the treatment of acute asthma. GSNOR is a member of the alcohol dehydrogenase family (ADH) and regulates the levels of S-nitrosothiols (SNOs) through catabolism of S-nitrosoglutathione (GSNO). Reduced levels of GSNO, as well as other nitrosothiols (SNOs), have been implicated in the pathogenesis of many diseases including those of the respiratory, cardiovascular, and gastrointestinal systems. Preservation of endogenous SNOs through GSNOR inhibition presents a novel therapeutic approach with broad applicability. We describe here the synthesis and structure-activity relationships (SAR) of novel pyrrole based analogues of N6022 focusing on removal of cytochrome P450 inhibition activities. We identified potent and novel GSNOR inhibitors having reduced CYP inhibition activities and demonstrated efficacy in a mouse ovalbumin (OVA) model of asthma.

  11. Physical, Chemical, and Biological Methods for the Removal of Arsenic Compounds

    PubMed Central

    Lim, K. T.; Shukor, M. Y.; Wasoh, H.

    2014-01-01

    Arsenic is a toxic metalloid which is widely distributed in nature. It is normally present as arsenate under oxic conditions while arsenite is predominant under reducing condition. The major discharges of arsenic in the environment are mainly due to natural sources such as aquifers and anthropogenic sources. It is known that arsenite salts are more toxic than arsenate as it binds with vicinal thiols in pyruvate dehydrogenase while arsenate inhibits the oxidative phosphorylation process. The common mechanisms for arsenic detoxification are uptaken by phosphate transporters, aquaglyceroporins, and active extrusion system and reduced by arsenate reductases via dissimilatory reduction mechanism. Some species of autotrophic and heterotrophic microorganisms use arsenic oxyanions for their regeneration of energy. Certain species of microorganisms are able to use arsenate as their nutrient in respiratory process. Detoxification operons are a common form of arsenic resistance in microorganisms. Hence, the use of bioremediation could be an effective and economic way to reduce this pollutant from the environment. PMID:24696853

  12. Transcripts of anthocyanidin reductase and leucoanthocyanidin reductase and measurement of catechin and epicatechin in tartary buckwheat.

    PubMed

    Kim, Yeon Bok; Thwe, Aye Aye; Kim, Yeji; Li, Xiaohua; Cho, Jin Woong; Park, Phun Bum; Valan Arasu, Mariadhas; Abdullah Al-Dhabi, Naif; Kim, Sun-Ju; Suzuki, Tastsuro; Hyun Jho, Kwang; Park, Sang Un

    2014-01-01

    Anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) play an important role in the monomeric units biosynthesis of proanthocyanidins (PAs) such as catechin and epicatechin in several plants. The aim of this study was to clone ANR and LAR genes involved in PAs biosynthesis and examine the expression of these two genes in different organs under different growth conditions in two tartary buckwheat cultivars, Hokkai T8 and T10. Gene expression was carried out by quantitative real-time RT-PCR, and catechin and epicatechin content was analyzed by high performance liquid chromatography. The expression pattern of ANR and LAR did not match the accumulation pattern of PAs in different organs of two cultivars. Epicatechin content was the highest in the flowers of both cultivars and it was affected by light in only Hokkai T8 sprouts. ANR and LAR levels in tartary buckwheat might be regulated by different mechanisms for catechin and epicatechin biosynthesis under light and dark conditions.

  13. Docking and molecular dynamics studies at trypanothione reductase and glutathione reductase active sites.

    PubMed

    Iribarne, Federico; Paulino, Margot; Aguilera, Sara; Murphy, Miguel; Tapia, Orlando

    2002-05-01

    A theoretical docking study on the active sites of trypanothione reductase (TR) and glutathione reductase (GR) with the corresponding natural substrates, trypanothione disulfide (T[S]2) and glutathione disulfide (GSSG), is reported. Molecular dynamics simulations were carried out in order to check the robustness of the docking results. The energetic results are in agreement with previous experimental findings and show the crossed complexes have lower stabilization energies than the natural ones. To test DOCK3.5, four nitro furanic compounds, previously designed as potentially active anti-chagasic molecules, were docked at the GR and TR active sites with the DOCK3.5 procedure. A good correlation was found between differential inhibitory activity and relative interaction energy (affinity). The results provide a validation test for the use of DOCK3.5 in connection with the design of anti-chagasic drugs.

  14. Transcripts of Anthocyanidin Reductase and Leucoanthocyanidin Reductase and Measurement of Catechin and Epicatechin in Tartary Buckwheat

    PubMed Central

    Kim, Yeon Bok; Thwe, Aye Aye; Kim, YeJi; Li, Xiaohua; Cho, Jin Woong; Park, Phun Bum; Valan Arasu, Mariadhas; Abdullah Al-Dhabi, Naif; Kim, Sun-Ju; Suzuki, Tastsuro; Hyun Jho, Kwang; Park, Sang Un

    2014-01-01

    Anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) play an important role in the monomeric units biosynthesis of proanthocyanidins (PAs) such as catechin and epicatechin in several plants. The aim of this study was to clone ANR and LAR genes involved in PAs biosynthesis and examine the expression of these two genes in different organs under different growth conditions in two tartary buckwheat cultivars, Hokkai T8 and T10. Gene expression was carried out by quantitative real-time RT-PCR, and catechin and epicatechin content was analyzed by high performance liquid chromatography. The expression pattern of ANR and LAR did not match the accumulation pattern of PAs in different organs of two cultivars. Epicatechin content was the highest in the flowers of both cultivars and it was affected by light in only Hokkai T8 sprouts. ANR and LAR levels in tartary buckwheat might be regulated by different mechanisms for catechin and epicatechin biosynthesis under light and dark conditions. PMID:24605062

  15. High-temperature, high-pressure hydrothermal synthesis, characterization, and structural relationships of layered uranyl arsenates.

    PubMed

    Liu, Hsin-Kuan; Ramachandran, Eswaran; Chen, Yi-Hsin; Chang, Wen-Jung; Lii, Kwang-Hwa

    2014-09-02

    Five new uranyl arsenates, Na14[(UO2)5(AsO4)8]·2H2O (1), K6[(UO2)5O5(AsO4)2] (2a), K4[(UO2)3O2(AsO4)2] (2b), Rb4[(UO2)3O2(AsO4)2] (3), and Cs6[(UO2)5O2(AsO4)4] (4), were synthesized by high-temperature, high-pressure hydrothermal reactions at about 560 °C and 1440 bar and were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and photoluminescence spectroscopy. Crystal data for compound 1: triclinic, P1, a = 7.0005(3) Å, b = 12.1324(4) Å, c = 13.7428(5) Å, α = 64.175(2)°, β = 89.092(2)°, γ = 85.548(2)°, V = 1047.26(7) Å(3), Z = 1, R1 = 0.0185; compound 2a: monoclinic, P2₁/c, a = 6.8615(3) Å, b = 24.702(1) Å, c = 7.1269(3) Å, β = 98.749(2)°, V = 1193.89(9) Å(3), Z = 2, R1 = 0.0225; compound 2b: monoclinic, P2₁/c, a = 6.7852(3) Å, b = 17.3640(8) Å, c = 7.1151(3) Å, β = 98.801(3)°, V = 828.42(6) Å(3), Z = 2, R1 = 0.0269; compound 3: monoclinic, P2₁/m, a = 6.9783(3) Å, b = 17.4513(8) Å, c = 7.0867(3) Å, β = 90.808(3)°, V = 862.94(7) Å(3), Z = 2, R1 = 0.0269; compound 4: triclinic, P1, a = 7.7628(3) Å, b = 9.3324(4) Å, c = 11.9336(4) Å, α = 75.611(2)°, β = 73.136(2)°, γ = 86.329(2)°, V = 801.37(5) Å(3), Z = 1, R1 = 0.0336. The five compounds have layer structures consisting of uranyl square, pentagonal, and hexagonal bipyramids as well as AsO4 tetrahedra. Compound 1 contains chains of discrete uranyl square and pentagonal bipyramids, 2a contains three-polyhedron-wide ribbons of edge- and corner-sharing uranyl square and pentagonal bipyramids, 2b and 3 contain dimers of edge-shairing pentagonal bipyramids that share edges with hexagonal bipyramids to form chains, and 4 contains one-polyhedron-wide zigzag chains of edge-sharing uranyl polyhedra. The double sheet structure of 1 is new, but the chain topology has been observed in an organically templated uranyl sulfate. Compound 2b is a new geometrical isomer of the phosphuranylite group. The sheet anion topologies of 2a and 4 can be obtained by

  16. The microbiota of the respiratory tract: gatekeeper to respiratory health.

    PubMed

    Man, Wing Ho; de Steenhuijsen Piters, Wouter A A; Bogaert, Debby

    2017-03-20

    The respiratory tract is a complex organ system that is responsible for the exchange of oxygen and carbon dioxide. The human respiratory tract spans from the nostrils to the lung alveoli and is inhabited by niche-specific communities of bacteria. The microbiota of the respiratory tract probably acts as a gatekeeper that provides resistance to colonization by respiratory pathogens. The respiratory microbiota might also be involved in the maturation and maintenance of homeostasis of respiratory physiology and immunity. The ecological and environmental factors that direct the development of microbial communities in the respiratory tract and how these communities affect respiratory health are the focus of current research. Concurrently, the functions of the microbiome of the upper and lower respiratory tract in the physiology of the human host are being studied in detail. In this Review, we will discuss the epidemiological, biological and functional evidence that support the physiological role of the respiratory microbiota in the maintenance of human health.

  17. Adsorption kinetics and isotherms of arsenite and arsenate on hematite nanoparticles and aggregates.

    PubMed

    Dickson, Dionne; Liu, Guangliang; Cai, Yong

    2017-01-15

    Iron (Fe) nanoparticles, e.g., zerovalent iron (ZVI) and iron oxide nanoparticles (IONP), have been used for remediation and environmental management of arsenic (As) contamination. These Fe nanoparticles, although originally nanosized, tend to form aggregates, in particular in the environment. The interactions of As with both nanoparticles and micron-sized aggregates should be considered when these Fe nanomaterials are used for mitigation of As issue. The objective of this study was to compare the adsorption kinetics and isotherm of arsenite (As(III)) and arsenate (As(V)) on bare hematite nanoparticles and aggregates and how this affects the fate of arsenic in the environment. The adsorption kinetic process was investigated with regards to the aggregation of the nanoparticles and the type of sorbed species. Kinetic data were best described by a pseudo second-order model. Both As species had similar rate constants, ranging from 3.82 to 6.45 × 10(-4) g/(μg·h), as rapid adsorption occurred within the first 8 h regardless of particle size. However, hematite nanoparticles and aggregates showed a higher affinity to adsorb larger amounts of As(V) (4122 ± 62.79 μg/g) than As(III) (2899 ± 71.09 μg/g) at equilibrium. We were able to show that aggregation and sedimentation of hematite nanoparticles occurs during the adsorption process and this might cause the immobilization and reduced bioavailability of arsenic. Isotherm studies were described by the Freundlich model and it confirmed that hematite nanoparticles have a significantly higher adsorption capacity for both As(V) and As(III) than hematite aggregates. This information is useful and can assist in predicting arsenic adsorption behavior and assessing the role of iron oxide nanoparticles in the biogeochemical cycling of arsenic.

  18. Residential arsenic and lead levels in an agricultural community with a history of lead arsenate use.

    PubMed

    Wolz, Sarah; Fenske, Richard A; Simcox, Nancy J; Palcisko, Gary; Kissel, John C

    2003-11-01

    Lead arsenate (PbHAsO4) was used as an insecticide in Washington fruit orchards from 1905 to 1947. We examined exposure potential for children living in an agricultural community with historic PbHAsO4 use. Soil and housedust samples were collected from 58 residences. Families were asked about land use history, age of home, and remodeling activities. Median concentrations of arsenic were higher in housedust than in soil (9.0 and 4.2 microg/g, respectively; P=0.05), as were lead concentrations (129 and 46 microg/g, respectively; P=0.0001). Significant associations were observed between indoor and outdoor levels of each metal, indicating track-in as an important exposure pathway. Homes on or near land use for pear or apple production between 1905 and 1947 had significantly higher soil (P=0.005) and housedust (P=0.004) lead, and soil arsenic (P=0.04) than did the other homes. Homes more than 30 years old had significantly higher soil and housedust lead than did newer homes (P=0.01). Homes remodeled within the past two years had significantly higher soil (P=0.01) and housedust (P=0.04) lead. Child doses extrapolated from these data indicate that 36% of homes had soil or dust arsenic levels above the minimum risk level estimated by the Agency for Toxic Substances and Disease Registry. None of the measured lead levels exceeded current US Environmental Protection Agency guidelines. Public health education programs focused on residential hygiene would be of value in areas of historic PbHAsO4 use.

  19. Biomineralization of Arsenate to Arsenic Sulfides is Greatly Enhanced at Mildly Acidic Conditions

    PubMed Central

    Rodriguez-Freire, Lucia; Sierra-Alvarez, Reyes; Root, Robert; Chorover, Jon; Field, James A.

    2014-01-01

    Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (AsV) and sulfate (SO42−). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system. A series of batch experiments was used to study the reduction of SO42− and AsV by an anaerobic biofilm mixed culture in a range of pH conditions (6.1–7.2), using ethanol as the electron donor. Total soluble concentrations and speciation of S and As were monitored. Solid phase speciation of arsenic was characterized by x-ray adsorption spectroscopy (XAS). A marked decrease of the total aqueous concentrations of As and S was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The amount of As removed was 2-fold higher and the rate of the As removal was up to 17-fold greater at pH 6.1 than at pH 7.2. Stoichiometric analysis and XAS results confirmed the precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results taken as a whole suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. PMID:25222328

  20. Arsenic Retention in Foliage and Soil after Monosodium Methyl Arsenate (MSMA) Application to Turfgrass.

    PubMed

    Matteson, Audrey R; Gannon, Travis W; Jeffries, Matthew D; Haines, Stephanie; Lewis, Dustin F; Polizzotto, Matthew L

    2014-01-01

    Monosodium methyl arsenate (MSMA) is a commonly used herbicide for weed control in turfgrass systems. There is concern that arsenic from applied MSMA could leach to groundwater or run off into surface water, thereby threatening human and ecosystem health. The USEPA has proposed a phase-out of the herbicide but is seeking additional research about the toxicity and environmental impacts of MSMA before establishing a final ruling. Little research has systematically investigated MSMA in field-based settings; instead, risks have been inferred from isolated field measurements or model-system studies. Accordingly, the overall goal of this study was to quantify the fate of arsenic after MSMA application to a managed turfgrass system. After MSMA application to turfgrass-covered and bareground lysimeters, the majority of arsenic was retained in turfgrass foliage and soils throughout year-long experiments, with 50 to 101% of the applied arsenic recovered in turfgrass systems and 55 to 66% recovered in bareground systems. Dissolved arsenic concentrations from 76.2-cm-depth pore water in the MSMA-treated soils were consistently <2 μg L, indistinguishable from background concentrations. As measured by adsorption isotherm experiments, MSMA retention by the sandy soil from our field site was markedly less than retention by a washed sand and a clay loam. Collectively, these results suggest that under aerobic conditions, minimal arsenic leaching to groundwater would occur after a typical application of MSMA to turfgrass. However, repeated MSMA application may pose environmental risks. Additional work is needed to examine arsenic cycling near the soil surface and to define arsenic speciation changes under different soil conditions.

  1. Functionalized chitosan electrospun nanofiber for effective removal of trace arsenate from water

    NASA Astrophysics Data System (ADS)

    Min, Ling-Li; Zhong, Lu-Bin; Zheng, Yu-Ming; Liu, Qing; Yuan, Zhi-Huan; Yang, Li-Ming

    2016-08-01

    An environment-friendly iron functionalized chitosan elctrospun nanofiber (ICS-ENF) was synthesized for trace arsenate removal from water. The ICS-ENF was fabricated by electrospinning a mixture of chitosan, PEO and Fe3+ followed by crosslinking with ammonia vapor. The physicochemical properties of ICS-ENF were characterized by FESEM, TEM-EDX and XRD. The ICS-ENF was found to be highly effective for As(V) adsorption at neutral pH. The As(V) adsorption occurred rapidly and achieved equilibrium within 100 min, which was well fitted by pseudo-second-order kinetics model. The As(V) adsorption decreased with increased ionic strength, suggesting an outer-sphere complexation of As(V) on ICS-ENF. Freundlich model well described the adsorption isotherm, and the maximum adsorption capacity was up to 11.2 mg/g at pH 7.2. Coexisting anions of chloride and sulfate showed negligible influence on As(V) removal, but phosphate and silicate significantly reduced As(V) adsorption by competing for adsorption sites. FTIR and XPS analysis demonstrated –NH, –OH and C–O were responsible for As(V) uptake. ICS-ENF was easily regenerated using 0.003 M NaOH, and the removal rate remained above 98% after ten successively adsorption-desorption recycles. This study extends the potential applicability of electrospun nanofibers for water purification and provides a promising approach for As(V) removal from water.

  2. Functionalized chitosan electrospun nanofiber for effective removal of trace arsenate from water

    PubMed Central

    Min, Ling-Li; Zhong, Lu-Bin; Zheng, Yu-Ming; Liu, Qing; Yuan, Zhi-Huan; Yang, Li-Ming

    2016-01-01

    An environment-friendly iron functionalized chitosan elctrospun nanofiber (ICS-ENF) was synthesized for trace arsenate removal from water. The ICS-ENF was fabricated by electrospinning a mixture of chitosan, PEO and Fe3+ followed by crosslinking with ammonia vapor. The physicochemical properties of ICS-ENF were characterized by FESEM, TEM-EDX and XRD. The ICS-ENF was found to be highly effective for As(V) adsorption at neutral pH. The As(V) adsorption occurred rapidly and achieved equilibrium within 100 min, which was well fitted by pseudo-second-order kinetics model. The As(V) adsorption decreased with increased ionic strength, suggesting an outer-sphere complexation of As(V) on ICS-ENF. Freundlich model well described the adsorption isotherm, and the maximum adsorption capacity was up to 11.2 mg/g at pH 7.2. Coexisting anions of chloride and sulfate showed negligible influence on As(V) removal, but phosphate and silicate significantly reduced As(V) adsorption by competing for adsorption sites. FTIR and XPS analysis demonstrated –NH, –OH and C–O were responsible for As(V) uptake. ICS-ENF was easily regenerated using 0.003 M NaOH, and the removal rate remained above 98% after ten successively adsorption-desorption recycles. This study extends the potential applicability of electrospun nanofibers for water purification and provides a promising approach for As(V) removal from water. PMID:27572634

  3. Glutathione-supported arsenate reduction coupled to arsenolysis catalyzed by ornithine carbamoyl transferase

    SciTech Connect

    Nemeti, Balazs; Gregus, Zoltan

    2009-09-01

    Three cytosolic phosphorolytic/arsenolytic enzymes, (purine nucleoside phosphorylase [PNP], glycogen phosphorylase, glyceraldehyde-3-phosphate dehydrogenase) have been shown to mediate reduction of arsenate (AsV) to the more toxic arsenite (AsIII) in a thiol-dependent manner. With unknown mechanism, hepatic mitochondria also reduce AsV. Mitochondria possess ornithine carbamoyl transferase (OCT), which catalyzes phosphorolytic or arsenolytic citrulline cleavage; therefore, we examined if mitochondrial OCT facilitated AsV reduction in presence of glutathione. Isolated rat liver mitochondria were incubated with AsV, and AsIII formed was quantified. Glutathione-supplemented permeabilized or solubilized mitochondria reduced AsV. Citrulline (substrate for OCT-catalyzed arsenolysis) increased AsV reduction. The citrulline-stimulated AsV reduction was abolished by ornithine (OCT substrate inhibiting citrulline cleavage), phosphate (OCT substrate competing with AsV), and the OCT inhibitor norvaline or PALO, indicating that AsV reduction is coupled to OCT-catalyzed arsenolysis of citrulline. Corroborating this conclusion, purified bacterial OCT mediated AsV reduction in presence of citrulline and glutathione with similar responsiveness to these agents. In contrast, AsIII formation by intact mitochondria was unaffected by PALO and slightly stimulated by citrulline, ornithine, and norvaline, suggesting minimal role for OCT in AsV reduction in intact mitochondria. In addition to OCT, mitochondrial PNP can also mediate AsIII formation; however, its role in AsV reduction appears severely limited by purine nucleoside supply. Collectively, mitochondrial and bacterial OCT promote glutathione-dependent AsV reduction with coupled arsenolysis of citrulline, supporting the hypothesis that AsV reduction is mediated by phosphorolytic/arsenolytic enzymes. Nevertheless, because citrulline cleavage is disfavored physiologically, OCT may have little role in AsV reduction in vivo.

  4. The role of phosphorus in the metabolism of arsenate by a freshwater green alga, Chlorella vulgaris.

    PubMed

    Baker, Josh; Wallschläger, Dirk

    2016-11-01

    A freshwater microalga, Chlorella vulgaris, was grown in the presence of varying phosphate concentrations (<10-500μg/L P) and environmentally realistic concentrations of arsenate (As(V)) (5-50μg/L As). Arsenic speciation in the culture medium and total cellular arsenic were measured using AEC-ICP-MS and ICP-DRC-MS, respectively, to determine arsenic biotransformation and uptake in the various phosphorus scenarios. At high phosphate concentration in the culture medium, >100μg/L P, the uptake and biotransformation of As(V) was minimal and dimethylarsonate (DMAs(V)) was the dominant metabolite excreted by C. vulgaris, albeit at relatively low concentrations. At common environmental P concentrations, 0-50μg/L P, the uptake and biotransformation of As(V) increased. At these higher As-uptake levels, arsenite (As(III)) was the predominant metabolite excreted from the cell. The concentrations of As(III) in these low P conditions were much higher than the concentrations of methylated arsenicals observed at the various P concentrations studied. The switchover threshold between the (small) methylation and (large) reduction of As(V) occurred around a cellular As concentration of 1fg/cell. The observed nearly quantitative conversion of As(V) to As(III) under low phosphate conditions indicates the importance of As(V) bio-reduction at common freshwater P concentrations. These findings on the influence of phosphorus on arsenic uptake, accumulation and excretion are discussed in relation to previously published research. The impact that the two scenarios of As(V) metabolism, As(III) excretion at high As(V)-uptake and methylarsenical excretion at low As(V)-uptake, have on freshwater arsenic speciation is discussed.

  5. Soil pollution assessment and identification of hyperaccumulating plants in chromated copper arsenate (CCA) contaminated sites, Korea.

    PubMed

    Usman, Adel R A; Lee, Sang Soo; Awad, Yasser M; Lim, Kyoung Jae; Yang, Jae E; Ok, Yong Sik

    2012-05-01

    In recent decades, heavy metal contamination in soil adjacent to chromated copper arsenate (CCA) treated wood has received increasing attention. This study was conducted to determine the pollution level (PL) based on the concentrations of Cr, Cu and As in soils and to evaluate the remediative capacity of native plant species grown in the CCA contaminated site, Gangwon Province, Korea. The pollution index (PI), integrated pollution index (IPI), bioaccumulation factors (BAF(shoots) and BAF(roots)) and translocation factor (TF) were determined to ensure soil contamination and phytoremediation availability. The 19 soil samples from 10 locations possibly contaminated with Cr, Cu and As were collected. The concentrations of Cr, Cu and As in the soil samples ranged from 50.56-94.13 mg kg(-1), 27.78-120.83 mg kg(-1), and 0.13-9.43 mg kg(-1), respectively. Generally, the metal concentrations decreased as the distance between the CCA-treated wood structure and sampling point increased. For investigating phytoremediative capacity, the 19 native plant species were also collected in the same area with soil samples. Our results showed that only one plant species of Iris ensata, which presented the highest accumulations of Cr (1120 mg kg(-1)) in its shoot, was identified as a hyperaccumulator. Moreover, the relatively higher values of BAF(shoot) (3.23-22.10) were observed for Typha orientalis, Iris ensata and Scirpus radicans Schk, suggesting that these plant species might be applicable for selective metal extraction from the soils. For phytostabilization, the 15 plant species with BAF(root) values>1 and TF values<1 were suitable; however, Typha orientalis was the best for Cr.

  6. Phytochelatin synthesis in Dunaliella salina induced by arsenite and arsenate under various phosphate regimes.

    PubMed

    Wang, Ya; Zhang, Chunhua; Zheng, Yanheng; Ge, Ying

    2017-02-01

    This study investigated the dynamic variations in thiol compounds, including cysteine (Cys), glutathione (GSH), and phytochelatins (PCs), in Dunaliella salina samples exposed to arsenite [As(III)] and arsenate [As(V)] under various phosphate (PO4(3-)) regimes. Our results showed that GSH was the major non-protein sulfhydryl compound in D. salina cells. As(III) and As(V) induced PC syntheses in D. salina. PC2, PC3, and PC4 were all found in algal cells; the PC concentrations decreased gradually while exposed to As for 3 d. The synthesis of PC2-3 was significantly affected by As(III) and As(V) concentrations in the cultures. More PCs were detected in the As(V)-treated algal cells compared with the As(III) treatment. PC levels increased with As(III)/As(V) amount in the medium, but remained stable after 112μgL(-1) As(V) exposure. In contrast, significant (p<0.001) positive correlations were observed between PC synthesis and intracellular As(III) content or As accumulation in As(III)-treated algal cells during the 72-h exposure. PO4(3-) had a significant influence on the PC synthesis in algal cells, irrespective of the As-treated species. Reductions in As uptake and subsequent PC synthesis by D. salina were observed as the PO4(3-) concentration in the growth medium increased. L-Buthionine sulfoximine (BSO) differentially influenced PC synthesis in As-treated D. salina under different extracellular PO4(3-) regimes. Overall, our data demonstrated that the production of GSH and PCs was affected by PO4(3-) and that these thiols played an important role in As detoxification by D. salina.

  7. Respiratory Syncytial Virus

    MedlinePlus

    ... respiratory syncytial virus (RSV) using indirect immunofluorescence technique. Biology & Genetics For more than 50 years, NIAID’s commitment ... Nucleotide Polymorphism Phylogenetics & Ontology Proteomics & Protein Analysis Systems Biology Data Portals Software Applications BCBB Mobyle Interface Designer ( ...

  8. Respiratory Syncytial Virus Infections

    MedlinePlus

    Respiratory syncytial virus (RSV) causes mild, cold-like symptoms in adults and older healthy children. It can cause serious problems in ... tests can tell if your child has the virus. There is no specific treatment. You should give ...

  9. Respiratory muscle plasticity.

    PubMed

    Rowley, Katharine L; Mantilla, Carlos B; Sieck, Gary C

    2005-07-28

    Plasticity of respiratory muscles must be considered in the context of their unique physiological demands. The continuous rhythmic activation of respiratory muscles makes them among the most active in the body. Respiratory muscles, especially the diaphragm, are non-weight-bearing, and thus, in contrast to limb muscles, are not exposed to gravitational effects. Perturbations in normal activation and load known to induce plasticity in limb muscles may not cause similar adaptations in respiratory muscles. In this review, we explore the structural and functional properties of the diaphragm muscle and their response to alterations in load and activity. Overall, relatively modest changes in diaphragm structural and functional properties occur in response to perturbations in load or activity. However, disruptions in the normal influence of phrenic innervation by frank denervation, tetrodotoxin nerve block and spinal hemisection, induce profound changes in the diaphragm, indicating the substantial trophic influence of phrenic motoneurons on diaphragm muscle.

  10. Noninvasive respiratory monitoring

    SciTech Connect

    Nochomovitz, M.L.; Cherniack, N.S.

    1986-01-01

    This book contains 10 selections. Some of the titles are: Transcutaneous Monitoring of Respiratory Gases; Computed Tomography of the Chest; Measurement and Monitoring of Exhaled Carbon Dioxide; Oximetry; and Ultrasonic Evaluation of the Chest Wall and Pleura.

  11. What Causes Respiratory Failure?

    MedlinePlus

    ... Conditions Causing Respiratory Failure Figure A shows the location of the lungs, airways, diaphragm, rib cage, pulmonary arteries, brain, and spinal cord ... STATEMENT FOIA NO FEAR ACT OIG CONTACT US ...

  12. Methylenetetrahydrofolate reductase: biochemical characterization and medical significance.

    PubMed

    Trimmer, Elizabeth E

    2013-01-01

    Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylenetetrahydofolate (CH2-H4folate) to 5-methyltetrahydrofolate (CH3-H4folate). The enzyme employs a noncovalently-bound flavin adenine dinucleotide (FAD), which accepts reducing equivalents from NAD(P)H and transfers them to CH2-H4folate. The reaction provides the sole source of CH3-H4folate, which is utilized by methionine synthase in the synthesis of methionine from homocysteine. MTHFR plays a key role in folate metabolism and in the homeostasis of homocysteine; mutations in the enzyme lead to hyperhomocyst(e)inemia. A common C677T polymorphism in MTHFR has been associated with an increased risk for the development of cardiovascular disease, Alzheimer's disease, and depression in adults, and of neural tube defects in the fetus. The mutation also confers protection for certain types of cancers. This review presents the current knowledge of the enzyme, its biochemical characterization, and medical significance.

  13. Enhanced silver nanoparticle synthesis by optimization of nitrate reductase activity.

    PubMed

    Vaidyanathan, Ramanathan; Gopalram, Shubaash; Kalishwaralal, Kalimuthu; Deepak, Venkataraman; Pandian, Sureshbabu Ram Kumar; Gurunathan, Sangiliyandi

    2010-01-01

    Nanostructure materials are attracting a great deal of attention because of their potential for achieving specific processes and selectivity, especially in biological and pharmaceutical applications. The generation of silver nanoparticles using optimized nitrate reductase for the reduction of Ag(+) with the retention of enzymatic activity in the complex is being reported. This report involves the optimization of enzyme activity to bring about enhanced nanoparticle synthesis. Response surface methodology and central composite rotary design (CCRD) were employed to optimize a fermentation medium for the production of nitrate reductase by Bacillus licheniformis at pH 8. The four variables involved in the study of nitrate reductase were Glucose, Peptone, Yeast extract and KNO(3). Glucose had a significant effect on nitrate reductase production. The optimized medium containing (%) Glucose: 1.5, Peptone: 1, Yeast extract: 0.35 and KNO(3): 0.35 resulted in a nitrate reductase activity of 452.206 U/ml which is same as that of the central level. The medium A (showing least nitrate reductase activity) and the medium B (showing maximum nitrate reductase activity) were compared for the synthesis. Spectrophotometric analysis revealed that the particles exhibited a peak at 431 nm and the A(431) for the medium B was 2-fold greater than that of the medium A. The particles were also characterized using TEM. The particles synthesized using the optimized enzyme activity ranged from 10 to 80 nm and therefore can be extended to various medicinal applications.

  14. 2,4-Dienoyl-coenzyme A reductase deficiency: a possible new disorder of fatty acid oxidation.

    PubMed Central

    Roe, C R; Millington, D S; Norwood, D L; Kodo, N; Sprecher, H; Mohammed, B S; Nada, M; Schulz, H; McVie, R

    1990-01-01

    Several inherited disorders of fatty acid beta-oxidation have been described that relate mainly to saturated precursors. This study is the first report of an enzyme defect related only to unsaturated fatty acid oxidation and provides the first in vivo evidence that fat oxidation in humans proceeds by the reductase-dependent pathway. The patient was a black female, presenting in the neonatal period with persistent hypotonia. Biochemical studies revealed hyperlysinemia, hypocarnitinemia, normal organic acid profile, and an unusual acylcarnitine species in both urine and blood. The new metabolite was positively identified by mass spectrometry as 2-trans,4-cis-decadienoylcarnitine, derived from incomplete oxidation of linoleic acid. In spite of dietary therapy, the patient died of respiratory acidosis at four months of age. Samples of liver and muscle from the autopsy were assayed for 2,4-dienoyl-coenzyme A reductase activity. Using the substrate 2-trans,4-cis-decadienoylcoenzyme A, the reductase activity was 40% of the control value in liver and only 17% of that found in normal muscle. It is suggested that unsaturated substrates should be used for in vitro testing to cover the full range of potential beta-oxidation defects and that acylcarnitine species identification be used for in vivo detection of this disorder. PMID:2332510

  15. Selective adsorption of arsenate and the reversible structure transformation of the mesoporous metal-organic framework MIL-100(Fe).

    PubMed

    Cai, Jianhua; Wang, Xueyun; Zhou, Yue; Jiang, Li; Wang, Chunru

    2016-04-28

    Here we describe a highly porous metal-organic framework MIL-100(Fe), which is initially used as an arsenate adsorbent in water. An appropriate mesoporous size allows AsO4(3-) to enter unrestrained and then be captured successfully, furthermore resulting in the damage of long-range order of uniform mesopores. Moreover, the porous framework could also make AsO4(3-) be reversibly desorbed without structural changes and the long-range order of mesopores be recovered again.

  16. Treatment of synthetic arsenate wastewater with iron-air fuel cell electrocoagulation to supply drinking water and electricity in remote areas.

    PubMed

    Kim, Jung Hwan; Maitlo, Hubdar Ali; Park, Joo Yang

    2017-05-15

    Electrocoagulation with an iron-air fuel cell is an innovative arsenate removal system that can operate without an external electricity supply. Thus, this technology is advantageous for treating wastewater in remote regions where it is difficult to supply electricity. In this study, the possibility of real applications of this system for arsenate treatment with electricity production was verified through electrolyte effect investigations using a small-scale fuel cell and performance testing of a liter-scale fuel cell stack. The electrolyte species studied were NaCl, Na2SO4, and NaHCO3. NaCl was overall the most effective electrolyte for arsenate treatment, although Na2SO4 produced the greatest electrical current and power density. In addition, although the current density and power density were proportional to the concentrations of NaCl and Na2SO4, the use of concentrations above 20 mM of NaCl and Na2SO4 inhibited arsenate treatment due to competition effects between anions and arsenate in adsorption onto the iron hydroxide. The dominant iron hydroxide produced at the iron anode was found to be lepidocrocite by means of Raman spectroscopy. A liter-scale four-stack iron-air fuel cell with 10 mM NaCl electrolyte was found to be able to treat about 300 L of 1 ppm arsenate solution to below 10 ppb during 1 day, based on its 60-min treatment capacity, as well as produce the maximum power density of 250 mW/m(2).

  17. Raman spectroscopy of selected tsumcorite Pb(Zn,Fe3+)2(AsO4)2(OH,H2O) minerals--implications for arsenate accumulation.

    PubMed

    Frost, Ray L; Xi, Yunfei

    2012-02-01

    The presence of arsenic in the environment is a hazard. The accumulation of arsenate by a range of cations in the formation of minerals provides a mechanism for the accumulation of arsenate. The formation of the tsumcorite minerals is an example of a series of minerals which accumulate arsenate. There are about twelve examples in this mineral group. Raman spectroscopy offers a method for the analysis of these minerals. The structure of selected tsumcorite minerals with arsenate and sulphate anions were analysed by Raman spectroscopy. Isomorphic substitution of sulphate for arsenate is observed for gartrellite and thometzekite. A comparison is made with the sulphate bearing mineral natrochalcite. The position of the hydroxyl and water stretching vibrations are related to the strength of the hydrogen bond formed between the OH unit and the AsO(4)(3-) anion. Characteristic Raman spectra of the minerals enable the assignment of the bands to specific vibrational modes.

  18. No laughing matter: the unmaking of the greenhouse gas dinitrogen monoxide by nitrous oxide reductase.

    PubMed

    Schneider, Lisa K; Wüst, Anja; Pomowski, Anja; Zhang, Lin; Einsle, Oliver

    2014-01-01

    The gas nitrous oxide (N₂O) is generated in a variety of abiotic, biotic, and anthropogenic processes and it has recently been under scrutiny for its role as a greenhouse gas. A single enzyme, nitrous oxide reductase, is known to reduce N₂O to uncritical N₂, in a two-electron reduction process that is catalyzed at two unusual metal centers containing copper. Nitrous oxide reductase is a bacterial metalloprotein from the metabolic pathway of denitrification, and it forms a 130 kDa homodimer in which the two metal sites CuA and CuZ from opposing monomers are brought into close contact to form the active site of the enzyme. CuA is a binuclear, valence-delocalized cluster that accepts and transfers a single electron. The CuA site of nitrous oxide reductase is highly similar to that of respiratory heme-copper oxidases, but in the denitrification enzyme the site additionally undergoes a conformational change on a ligand that is suggested to function as a gate for electron transfer from an external donor protein. CuZ, the tetranuclear active center of nitrous oxide reductase, is isolated under mild and anoxic conditions as a unique [4Cu:2S] cluster. It is easily desulfurylated to yield a [4Cu:S] state termed CuZ (*) that is functionally distinct. The CuZ form of the cluster is catalytically active, while CuZ (*) is inactive as isolated in the [3Cu(1+):1Cu(2+)] state. However, only CuZ (*) can be reduced to an all-cuprous state by sodium dithionite, yielding a form that shows higher activities than CuZ. As the possibility of a similar reductive activation in the periplasm is unconfirmed, the mechanism and the actual functional state of the enzyme remain under debate. Using enzyme from anoxic preparations with CuZ in the [4Cu:2S] state, N2O was shown to bind between the CuA and CuZ sites, suggesting direct electron transfer from CuA to the substrate after its activation by CuZ.

  19. The structure of apo and holo forms of xylose reductase, a dimeric aldo-keto reductase from Candida tenuis.

    PubMed

    Kavanagh, Kathryn L; Klimacek, Mario; Nidetzky, Bernd; Wilson, David K

    2002-07-16

    Xylose reductase is a homodimeric oxidoreductase dependent on NADPH or NADH and belongs to the largely monomeric aldo-keto reductase superfamily of proteins. It catalyzes the first step in the assimilation of xylose, an aldose found to be a major constituent monosaccharide of renewable plant hemicellulosic material, into yeast metabolic pathways. It does this by reducing open chain xylose to xylitol, which is reoxidized to xylulose by xylitol dehydrogenase and metabolically integrated via the pentose phosphate pathway. No structure has yet been determined for a xylose reductase, a dimeric aldo-keto reductase or a family 2 aldo-keto reductase. The structures of the Candida tenuis xylose reductase apo- and holoenzyme, which crystallize in spacegroup C2 with different unit cells, have been determined to 2.2 A resolution and an R-factor of 17.9 and 20.8%, respectively. Residues responsible for mediating the novel dimeric interface include Asp-178, Arg-181, Lys-202, Phe-206, Trp-313, and Pro-319. Alignments with other superfamily members indicate that these interactions are conserved in other dimeric xylose reductases but not throughout the remainder of the oligomeric aldo-keto reductases, predicting alternate modes of oligomerization for other families. An arrangement of side chains in a catalytic triad shows that Tyr-52 has a conserved function as a general acid. The loop that folds over the NAD(P)H cosubstrate is disordered in the apo form but becomes ordered upon cosubstrate binding. A slow conformational isomerization of this loop probably accounts for the observed rate-limiting step involving release of cosubstrate. Xylose binding (K(m) = 87 mM) is mediated by interactions with a binding pocket that is more polar than a typical aldo-keto reductase. Modeling of xylose into the active site of the holoenzyme using ordered waters as a guide for sugar hydroxyls suggests a convincing mode of substrate binding.

  20. Solubilization and Resolution of the Membrane-Bound Nitrite Reductase from Paracoccus Halodenitrificans into Nitrite and Nitric Oxide Reductases

    NASA Technical Reports Server (NTRS)

    Grant, Michael A.; Cronin, Sonja E.; Hochstein, Lawrence I.

    1984-01-01

    Membranes prepared from Paracoccus halodenitrificans reduced nitrite or nitric oxide to nitrous oxide. Extraction of these membranes with the detergent CHAPSO [3-(3-Chlolamidoporopyldimethylammonio)-1-(2- hydroxy-1-propanesulfonate)], followed by ammonium sulfate fractionation of the solubilized proteins, resulted in the separation of nitrite and nitric oxide reductase activities. The fraction containing nitrite reductase activity spectrally resembled a cd-type cytochrome. Several cytochromes were detected in the nitric oxide reductase fraction. Which, if any, of these cytochromes is associated with the reduction of nitric oxide is not clear at this time.

  1. Enantioselective imine reduction catalyzed by imine reductases and artificial metalloenzymes.

    PubMed

    Gamenara, Daniela; Domínguez de María, Pablo

    2014-05-21

    Adding value to organic synthesis. Novel imine reductases enable the enantioselective reduction of imines to afford optically active amines. Likewise, novel bioinspired artificial metalloenzymes can perform the same reaction as well. Emerging proof-of-concepts are herein discussed.

  2. Exploration of Nitrate Reductase Metabolic Pathway in Corynebacterium pseudotuberculosis

    PubMed Central

    Abreu, Vinícius; Diniz, Carlos; Dorneles, Elaine M. S.; Barh, Debmalya

    2017-01-01

    Based on the ability of nitrate reductase synthesis, Corynebacterium pseudotuberculosis is classified into two biovars: Ovis and Equi. Due to the presence of nitrate reductase, the Equi biovar can survive in absence of oxygen. On the other hand, Ovis biovar that does not have nitrate reductase is able to adapt to various ecological niches and can grow on certain carbon sources. Apart from these two biovars, some other strains are also able to carry out the reduction of nitrate. The enzymes that are involved in electron transport chain are also identified by in silico methods. Findings about pathogen metabolism can contribute to the identification of relationship between nitrate reductase and the C. pseudotuberculosis pathogenicity, virulence factors, and discovery of drug targets. PMID:28316974

  3. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... activity of the enzyme glutathione reductase in serum, plasma, or erythrocytes by such techniques as fluorescence and photometry. The results of this assay are used in the diagnosis of liver disease,...

  4. Na3Co2(AsO4)(As2O7): a new sodium cobalt arsenate

    PubMed Central

    Guesmi, Abderrahmen; Driss, Ahmed

    2012-01-01

    In the title compound, tris­odium dicobalt arsenate diarsenate, Na3Co2AsO4As2O7, the two Co atoms, one of the two As and three of the seven O atoms lie on special positions, with site symmetries 2 and m for the Co, m for the As, and 2 and twice m for the O atoms. The two Na atoms are disordered over two general and special positions [occupancies 0.72 (3):0.28 (3) and 0.940 (6):0.060 (6), respectively]. The main structural feature is the association of the CoO6 octa­hedra in the ab plane, forming Co4O20 units, which are corner- and edge-connected via AsO4 and As2O7 arsenate groups, giving rise to a complex polyhedral connectivity with small tunnels, such as those running along the b- and c-axis directions, in which the Na+ ions reside. The structural model is validated by both bond-valence-sum and charge-distribution methods, and the distortion of the coordination polyhedra is analyzed by means of the effective coordination number. PMID:22807699

  5. Simultaneous reduction of arsenic(V) and uranium(VI) by mackinawite: role of uranyl arsenate precipitate formation.

    PubMed

    Troyer, Lyndsay D; Tang, Yuanzhi; Borch, Thomas

    2014-12-16

    Uranium (U) and arsenic (As) often occur together naturally and, as a result, can be co-contaminants at sites of uranium mining and processing, yet few studies have examined the simultaneous redox dynamics of U and As. This study examines the influence of arsenate (As(V)) on the reduction of uranyl (U(VI)) by the redox-active mineral mackinawite (FeS). As(V) was added to systems containing 47 or 470 μM U(VI) at concentrations ranging from 0 to 640 μM. In the absence of As(V), U was completely removed from solution and fully reduced to nano-uraninite (nano-UO2). While the addition of As(V) did not reduce U uptake, at As(V) concentrations above 320 μM, the reduction of U(VI) was limited due to the formation of a trögerite-like uranyl arsenate precipitate. The presence of U also significantly inhibited As(V) reduction. While less U(VI) reduction to nano-UO2 may take place in systems with high As(V) concentrations, formation of trögerite-like mineral phases may be an acceptable reclamation end point due to their high stability under oxic conditions.

  6. Rhizosphere colonization and arsenic translocation in sunflower (Helianthus annuus L.) by arsenate reducing Alcaligenes sp. strain Dhal-L.

    PubMed

    Cavalca, Lucia; Corsini, Anna; Bachate, Sachin Prabhakar; Andreoni, Vincenza

    2013-10-01

    In the present study, six arsenic-resistant strains previously isolated were tested for their plant growth promoting characteristics and heavy metal resistance, in order to choose one model strain as an inoculum for sunflower plants in pot experiments. The aim was to investigate the effect of arsenic-resistant strain on sunflower growth and on arsenic uptake from arsenic contaminated soil. Based on plant growth promoting characteristics and heavy metal resistance, Alcaligenes sp. strain Dhal-L was chosen as an inoculum. Beside the ability to reduce arsenate to arsenite via an Ars operon, the strain exhibited 1-amino-cyclopropane-1-carboxylic acid deaminase activity and it was also able to produce siderophore and indole acetic acid. Pot experiments were conducted with an agricultural soil contaminated with arsenic (214 mg kg⁻¹). A real time PCR method was set up based on the quantification of ACR3(2) type of arsenite efflux pump carried by Alcaligenes sp. strain Dhal-L, in order to monitor presence and colonisation of the strain in the bulk and rhizospheric soil. As a result of strain inoculation, arsenic uptake by plants was increased by 53 %, whereas ACR3(2) gene copy number in rhizospheric soil was 100 times higher in inoculated than in control pots, indicating the colonisation of strain. The results indicated that the presence of arsenate reducing strains in the rhizosphere of sunflower influences arsenic mobilization and promotes arsenic uptake by plant.

  7. Arsenate Reduction of Sediment is a Critical Step for Arsenic Release in Bangladesh Aquifers

    NASA Astrophysics Data System (ADS)

    Mailloux, B. J.; Silvern, R. F.; Kim, C.; Sun, J.; Ahmed, K.; van Geen, A.; Choudhury, I.; Bostick, B. C.

    2013-12-01

    Long-term exposure to trace levels of arsenic (As) in shallow groundwater puts millions of people at risk for chronic diseases in Bangladesh. Though the arsenic is naturally occurring in the shallow aquifers, the mobilization of arsenic from the sediment to the groundwater is predominantly driven by the coupling of microbial metabolism to the reduction of iron (Fe) oxides. However, it is unknown whether the reduction of arsenate, As(V), to arsenite, As(III), is a critical part of the mobilization process. The goal of this work was to determine the mineral phase speciation of arsenic in sediment across two arsenic gradients in shallow aquifers. Sediment cores were collected from two well-characterized sites in Araihazar, Bangladesh located about 25km east of the capital, Dhaka. Site B, a high arsenic, slow recharge, shallow aquifer, was located in the village of Baylakandi, and site F, a low arsenic, fast recharge, shallow aquifer, was located in the village of Lashkardi. Samples were collected from drill cuttings and cores taken every five feet from the surface to 60 feet at site B and 88 feet at site F and preserved in glycerol for analysis. The sediment was characterized for arsenic speciation using x-ray absorption near edge structure (XANES) on beamline 11-2 at the Stanford Synchrotron Radiation Lightsource which in bulk mode can determine As speciation on samples with less than 1 mg/kg As in the solid phase. Arsenic XANES linear combination fits were described by As(V), As(III) and As2S3 standards for each depth. At both sites, at depths with low concentrations of aqueous As the sediment was dominated by As(V). In contrast, at depths with elevated concentrations of aqueous As the sediment was dominated by As(III). These changes in solid phase As speciation cannot be accounted for by changes in aqueous As concentrations and indicate a bulk change occurs in the As speciation of the sediment in zones of elevated aqueous As concentrations. Therefore, reduction of

  8. Aerobic Reduction of Arsenate by a Bacterium Isolated From Activated Sludge

    NASA Astrophysics Data System (ADS)

    Kozai, N.; Ohnuki, T.; Hanada, S.; Nakamura, K.; Francis, A. J.

    2006-12-01

    Microlunatus phosphovorus strain NM-1 is a polyphosphate-accumulating bacterium isolated from activated sludge. This bacterium takes up a large amount of polyphosphate under aerobic conditions and release phosphate ions by hydrolysis of polyphosphate to orthophosphate under anaerobic conditions to derive energy for taking up substrates. To understand the nature of this strain, especially, influence of potential contaminants in sewage and wastewater on growth, we have been investigating behavior of this bacterium in media containing arsenic. The present paper mainly reports reduction of arsenate by this bacterium under aerobic conditions. The strain NM-1 (JCM 9379) was aerobically cultured at 30 °C in a nutrient medium containing 2.5 g/l peptone, 0.5 g/l glucose, 1.5 g/l yeast extract, and arsenic [Na2HAsO4 (As(V)) or Na3AsO3 (As(III))] at concentrations between 0 and 50 mM. The cells collected from arsenic-free media were dispersed in buffer solutions containing 2mM HEPES, 10mM NaCl, prescribed concentrations of As(V), and 0-0.2 percent glucose. Then, this cell suspension was kept at 20 °C under aerobic or anaerobic conditions. The speciation of arsenic was carried out by ion chromatography and ICP-MS. The growth of the strain under aerobic conditions was enhanced by the addition of As(V) at the concentration between 1 and 10 mM. The maximum optical density of the culture in the medium containing 5mM As(V) was 1.4 times greater than that of the control culture. Below the As(V) concentration of 10mM, most of the As(V) was reduced to As(III). The growth of the strain under anaerobic conditions has not been observed so far. The cells in the buffer solutions reduced As(V) under aerobic condition. The reduction was enhanced by the addition of glucose. However, the cell did not reduce As(V) under anaerobic conditions. The strain NM-1 showed high resistance to As(V) and As(III). The maximum optical density of the culture grown in a medium containing 50 mM As(V) was only

  9. Arsenate toxicity and metabolism in the halotolerant microalga Dunaliella salina under various phosphate regimes.

    PubMed

    Wang, Ya; Zheng, Yanheng; Liu, Cong; Xu, Pingping; Li, Hao; Lin, Qiaoyun; Zhang, Chunhua; Ge, Ying

    2016-06-15

    Microalgae play an important role in arsenic (As) biogeochemical cycles as they are capable of accumulating and metabolizing this metalloid efficiently. This study aimed to investigate the toxicity, accumulation and transformation of arsenate (As(v)) in Dunaliella salina, an exceptionally halotolerant microalga, under various phosphate (PO4(3-)) regimes. The results of the 72-h toxicity test showed that D. salina was tolerant to As(v). In addition, the toxicity of As(v) was mitigated by an increased PO4(3-) supply. D. salina resisted the adverse effects of As(v) through the suppression of As uptake, enhancement of As reduction, methylation in the cell and excretion from the cell. Our study revealed that D. salina reduced As(v) toxicity using different strategies, i.e., reduction of As uptake upon acute As stress (24 h) and increase of As efflux following chronic As exposure (9 day). Moreover, PO4(3-) strongly affected the adsorption, uptake and transformation of As(v) in D. salina. As(v) reduction, DMA production and As excretion were enhanced under P-limited conditions (0.112 mg L(-1)) or upon higher As(v) exposure (1120 μg L(-1)). Furthermore, PO4(3-) had a significant influence on the As removal ability of D. salina. A high As removal efficiency (>95.6%) was observed in the 5-day cultures at an initial As concentration of 11.2 μg L(-1) and PO4(3-) of 0.112 and 1.12 mg L(-1). However, only 10.9% of total As was removed under 11.2 mg L(-1) PO4(3-) after 9 days of incubation. The findings of this study illustrate the pivotal roles of extracellular PO4(3-) in As(v) toxicity and metabolism, and the results may be relevant for future research on the minimization of As contamination in algal products as well as on the enhancement of As removal from the environment.

  10. Anaerobic microbial mobilization and biotransformation of arsenate adsorbed onto activated alumina.

    PubMed

    Sierra-Alvarez, Reyes; Field, Jim A; Cortinas, Irail; Feijoo, Gumersindo; Teresa Moreira, Maria; Kopplin, Mike; Jay Gandolfi, A

    2005-01-01

    Due to the enactment of a stricter drinking water standard for arsenic in the United States, larger quantities of arsenic will be treated resulting in larger volumes of treatment residuals. The current United States Environmental Protection Agency recommendation is to dispose spent adsorbent residuals from arsenic treatment into non-hazardous municipal solid waste (MSW) landfills. The potential of microorganisms to alter the speciation affecting the mobility of arsenic in the disposal environment is therefore a concern. The purpose of this paper was to evaluate the potential of an anaerobic microbial consortium to biologically mobilize arsenate (As(V)) adsorbed onto activated alumina (AA), a common adsorbent used for treating arsenic in drinking water. Three anaerobic columns (0.27 l) packed with 100 g dry weight of AA containing 0.657 mg adsorbed As(V) (expressed as arsenic) per gram dry weight were continuously flushed with synthetic landfill leachate for 257 days. The fully biologically active column was inoculated with methanogenic anaerobic sludge (10 g volatile suspended solids l(-1) column) and was operated with a mixture of volatile fatty acids (VFA) in the feed (2.5 g chemical oxygen demand l(-1) feed). At the end of the experiment, 37% of the arsenic was removed from the column, of which 48% was accounted for by arsenical species identified in the column effluent. The most important form of arsenic eluted was arsenite (As(III)), accounting for nearly all of the identified arsenic in periods of high mobilization. Additionally, two methylated metabolites, methylarsonic acid and dimethylarsinic acid were observed. Mobilization of arsenic is attributed to the biological reduction of As(V) to As(III) since literature data indicates that As(III) is more weakly adsorbed to AA compared to As(V). Batch and continuous assays confirmed that VFA, present in landfill leachates, served as an electron donating substrate supporting enhanced rates of As(V) reduction to As

  11. Exogenous proline application ameliorates toxic effects of arsenate in Solanum melongena L. seedlings.

    PubMed

    Singh, Madhulika; Pratap Singh, Vijay; Dubey, Gunjan; Mohan Prasad, Sheo

    2015-07-01

    Hydroponic experiments were conducted to investigate an effect of exogenous application of proline (Pro; 25 µM) in alleviating arsenate (As(V); 5 and 25 µM) toxicity in Solanum melongena L. (eggplant) seedlings. Exposure of As(V) declined growth of eggplant, which was coincided with an enhanced accumulation of As. However, exogenous Pro application alleviated As(V) toxicity in eggplant seedlings by reducing the accumulation of As. The fluorescence characteristics (JIP-test): φP0, Ψ0, φE0, PIABS, ABS/RC, TR0/RC, ET0/RC, DI0/RC, NPQ and qP were also affected by As(V). However, the effects of As(V) were more prominent on PIABS DI0/RC and NPQ. In Pro treated seedlings, following parameters viz. φP0, Ψ0, φE0 and PIABS were stimulated, while, energy flux parameters (ABS/RC, TR0/RC, ET0/RC and DI0/RC) were inhibited. Toxic effects of As(V) on photochemistry of photosystem II (PS II) were ameliorated by an exogenous application of Pro. Oxidative stress markers: superoxide radical, hydrogen peroxide and malondialdehyde (lipid peroxidation) were enhanced by As(V) exposure, however, their levels were significantly diminished by an exogenous application of Pro. Treatment of As(V) stimulated the activities of superoxide dismutase, peroxidase and catalase except that of glutathione-S-transferase. Exogenous Pro application improved the activities of enzymatic antioxidants. The level of endogenous Pro was higher in As(V) treated as well as in Pro fed seedlings. The activity of a key enzyme of Pro biosynthesis: Δ(1)-pyrroline-5-carboxylate synthetase was higher in Pro fed seedlings. The activity of Pro dehydrogenase was inhibited under As(V) stress, and its activity was minimum in case of Pro+As(V) combination. These results indicate that Pro metabolism could play a key role in regulating the accumulation of As and levels of antioxidants, which concomitantly result into a better growth of eggplant seedlings when compared to the As(V) treatments alone.

  12. Purification and characterization of assimilatory nitrite reductase from Candida utilis.

    PubMed

    Sengupta, S; Shaila, M S; Rao, G R

    1996-07-01

    Nitrate assimilation in many plants, algae, yeasts and bacteria is mediated by two enzymes, nitrate reductase (EC 1.6.6.2) and nitrite reductase (EC 1.7.7.1). They catalyse the stepwise reduction of nitrate to nitrite and nitrite to ammonia respectively. The nitrite reductase from an industrially important yeast, Candida utilis, has been purified to homogeneity. Purified nitrite reductase is a heterodimer and the molecular masses of the two subunits are 58 and 66 kDa. The native enzyme exhibits a molecular mass of 126 kDa as analysed by gel filtration. The identify of the two subunits of nitrite reductase was confirmed by immunoblotting using antibody for Cucurbita pepo leaf nitrite reductase. The presence of two different sized transcripts coding for the two subunits was confirmed by (a) in vitro translation of mRNA from nitrate-induced C. utilis followed by immunoprecipitation of the in vitro translated products with heterologous nitrite reductase antibody and (b) Northern-blot analysis. The 66 kDa subunit is acidic in nature which is probably due to its phosphorylated status. The enzyme is stable over a range of temperatures. Both subunits can catalyse nitrite reduction, and the reconstituted enzyme, at a higher protein concentration, shows an activity similar to that of the purified enzyme. Each of these subunits has been shown to contain a few unique peptides in addition to a large number of common peptides. Reduced Methyl Viologen has been found to be as effective an electron donor as NADPH in the catalytic process, a phenomenon not commonly seen for nitrite reductases from other systems.

  13. Comparative anatomy of the aldo-keto reductase superfamily.

    PubMed

    Jez, J M; Bennett, M J; Schlegel, B P; Lewis, M; Penning, T M

    1997-09-15

    The aldo-keto reductases metabolize a wide range of substrates and are potential drug targets. This protein superfamily includes aldose reductases, aldehyde reductases, hydroxysteroid dehydrogenases and dihydrodiol dehydrogenases. By combining multiple sequence alignments with known three-dimensional structures and the results of site-directed mutagenesis studies, we have developed a structure/function analysis of this superfamily. Our studies suggest that the (alpha/beta)8-barrel fold provides a common scaffold for an NAD(P)(H)-dependent catalytic activity, with substrate specificity determined by variation of loops on the C-terminal side of the barrel. All the aldo-keto reductases are dependent on nicotinamide cofactors for catalysis and retain a similar cofactor binding site, even among proteins with less than 30% amino acid sequence identity. Likewise, the aldo-keto reductase active site is highly conserved. However, our alignments indicate that variation ofa single residue in the active site may alter the reaction mechanism from carbonyl oxidoreduction to carbon-carbon double-bond reduction, as in the 3-oxo-5beta-steroid 4-dehydrogenases (Delta4-3-ketosteroid 5beta-reductases) of the superfamily. Comparison of the proposed substrate binding pocket suggests residues 54 and 118, near the active site, as possible discriminators between sugar and steroid substrates. In addition, sequence alignment and subsequent homology modelling of mouse liver 17beta-hydroxysteroid dehydrogenase and rat ovary 20alpha-hydroxysteroid dehydrogenase indicate that three loops on the C-terminal side of the barrel play potential roles in determining the positional and stereo-specificity of the hydroxysteroid dehydrogenases. Finally, we propose that the aldo-keto reductase superfamily may represent an example of divergent evolution from an ancestral multifunctional oxidoreductase and an example of convergent evolution to the same active-site constellation as the short

  14. Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli.

    PubMed Central

    Iuchi, S; Lin, E C

    1987-01-01

    In Escherichia coli the presence of nitrate prevents the utilization of fumarate as an anaerobic electron acceptor. The induction of the narC operon encoding the nitrate reductase is coupled to the repression of the frd operon encoding the fumarate reductase. This coupling is mediated by nitrate as an effector and the narL product as the regulatory protein (S. Iuchi and E. C. C. Lin, Proc. Natl. Acad. Sci. USA 84:3901-3905, 1987). The protein-ligand complex appears to control narC positively but frd negatively. In the present study we found that a molybdenum coeffector acted synergistically with nitrate in the regulation of frd and narC. In chlD mutants believed to be impaired in molybdate transport (or processing), full repression of phi(frd-lac) and full induction of phi(narC-lac) by nitrate did not occur unless the growth medium was directly supplemented with molybdate (1 microM). This requirement was not clearly manifested in wild-type cells, apparently because it was met by the trace quantities of molybdate present as a contaminant in the mineral medium. In chlB mutants, which are known to accumulate the Mo cofactor because of its failure to be inserted as a prosthetic group into proteins such as nitrate reductase, nitrate repression of frd and induction of narC were also intensified by molybdate supplementation. In this case a deficiency of the molybdenum coeffector might have resulted from enhanced feedback inhibition of molybdate transport (or processing) by the elevated level of the unutilized Mo cofactor. In addition, mutations in chlE, which are known to block the synthesis of the organic moiety of the Mo cofactor, lowered the threshold concentration of nitrate (< 1 micromole) necessary for frd repression and narC induction. These changes could be explained simply by the higher intracellular nitrate attainable in cells lacking the ability to destroy the effector. PMID:3301812

  15. Distribution of Prx-linked hydroperoxide reductase activity among microorganisms.

    PubMed

    Takeda, Kouji; Nishiyama, Yoshitaka; Yoda, Koji; Watanabe, Toshihiro; Nimura-Matsune, Kaori; Mura, Kiyoshi; Tokue, Chiyoko; Katoh, Tetzuya; Kawasaki, Shinji; Niimura, Youichi

    2004-01-01

    Peroxiredoxin (Prx) constitutes a large family of enzymes found in microorganisms, animals, and plants, but the detection of the activities of Prx-linked hydroperoxide reductases (peroxiredoxin reductases) in cell extracts, and the purification based on peroxide reductase activity, have only been done in bacteria and Trypanosomatidae. A peroxiredoxin reductase (NADH oxidase) from a bacterium, Amphibacillus, displayed only poor activities in the presence of purified Prx from Saccharomyces or Synechocystis, while it is highly active in the presence of bacterial Prx. These results suggested that an enzyme system different from that in bacteria might exist for the reduction of Prx in yeast and cyanobacteria. Prx-linked hydroperoxide reductase activities were detected in cell extracts of Saccharomyces, Synechocystis, and Chlorella, and the enzyme activities of Saccharomyces and Chlorella were induced under vigorously aerated culture conditions and intensive light exposure conditions, respectively. Partial purification of Prx-linked peroxidase from the induced yeast cells indicated that the Prx-linked peroxidase system consists of two protein components, namely, thioredoxin and thioredoxin reductase. This finding is consistent with the previous report on its purification based on its protein protection activity against oxidation [Chae et al., J. Biol. Chem., 269, 27670-27678 (1994)]. In this study we have confirmed that Prx-linked peroxidase activity are widely distributed, not only in bacteria species and Trypanosomatidae, but also in yeast and photosynthetic microorganisms, and showed reconstitution of the activity from partially purified interspecies components.

  16. Carbon-carbon double-bond reductases in nature.

    PubMed

    Huang, Minmin; Hu, Haihong; Ma, Li; Zhou, Quan; Yu, Lushan; Zeng, Su

    2014-08-01

    Reduction of C = C bonds by reductases, found in a variety of microorganisms (e.g. yeasts, bacteria, and lower fungi), animals, and plants has applications in the production of metabolites that include pharmacologically active drugs and other chemicals. Therefore, the reductase enzymes that mediate this transformation have become important therapeutic targets and biotechnological tools. These reductases are broad-spectrum, in that, they can act on isolation/conjugation C = C-bond compounds, α,β-unsaturated carbonyl compounds, carboxylic acids, acid derivatives, and nitro compounds. In addition, several mutations in the reductase gene have been identified, some associated with diseases. Several of these reductases have been cloned and/or purified, and studies to further characterize them and determine their structure in order to identify potential industrial biocatalysts are still in progress. In this study, crucial reductases for bioreduction of C = C bonds have been reviewed with emphasis on their principal substrates and effective inhibitors, their distribution, genetic polymorphisms, and implications in human disease and treatment.

  17. Respiratory factors limiting exercise.

    PubMed

    Bye, P T; Farkas, G A; Roussos, C

    1983-01-01

    The question of respiratory factors limiting exercise has been examined in terms of possible limitations arising from the function of gas exchange, the respiratory mechanics, the energetics of the respiratory muscles, or the development of respiratory muscle fatigue. Exercise capacity is curtailed in the presence of marked hypoxia, and this is readily observed in patients with chronic airflow limitation and interstitial lung disease and in some athletes at high intensities of exercise. In patients with interstitial lung disease, gas exchange abnormality--partly the result of diffusion disequilibrium for oxygen transfer--occurs during exercise despite abnormally high ventilations. In contrast, in certain athletes arterial hypoxemia has been documented during heavy exercise, apparently as a result of relative hypoventilation. During strenuous exercise the maximum expiratory flow volume curves are attained both by patients with chronic airflow limitation and by normal subjects, in particular when they breathe dense gas, so that a mechanical constraint is imposed on further increases in ventilation. Similarly, the force velocity characteristics of the inspiratory muscles may also impose a constraint to further increases in inspiratory flows that affects the ability to increase ventilation. In addition, the oxygen cost of maintaining high ventilations is large. Analysis of results from blood flow experiments reveal a substantial increase in blood flow to the respiratory muscles during exercise, with the result that oxygen supply to the rest of the body may be lessened. Alternatively, high exercise ventilations may not be sustained indefinitely owing to the development of respiratory muscle fatigue that results in hypoventilation and reduced arterial oxygen tension.

  18. Microsecond subdomain folding in dihydrofolate reductase.

    PubMed

    Arai, Munehito; Iwakura, Masahiro; Matthews, C Robert; Bilsel, Osman

    2011-07-08

    The characterization of microsecond dynamics in the folding of multisubdomain proteins has been a major challenge in understanding their often complex folding mechanisms. Using a continuous-flow mixing device coupled with fluorescence lifetime detection, we report the microsecond folding dynamics of dihydrofolate reductase (DHFR), a two-subdomain α/β/α sandwich protein known to begin folding in this time range. The global dimensions of early intermediates were monitored by Förster resonance energy transfer, and the dynamic properties of the local Trp environments were monitored by fluorescence lifetime detection. We found that substantial collapse occurs in both the locally connected adenosine binding subdomain and the discontinuous loop subdomain within 35 μs of initiation of folding from the urea unfolded state. During the fastest observable ∼550 μs phase, the discontinuous loop subdomain further contracts, concomitant with the burial of Trp residue(s), as both subdomains achieve a similar degree of compactness. Taken together with previous studies in the millisecond time range, a hierarchical assembly of DHFR--in which each subdomain independently folds, subsequently docks, and then anneals into the native conformation after an initial heterogeneous global collapse--emerges. The progressive acquisition of structure, beginning with a continuously connected subdomain and spreading to distal regions, shows that chain entropy is a significant organizing principle in the folding of multisubdomain proteins and single-domain proteins. Subdomain folding also provides a rationale for the complex kinetics often observed.

  19. Active sites of thioredoxin reductases: why selenoproteins?

    PubMed

    Gromer, Stephan; Johansson, Linda; Bauer, Holger; Arscott, L David; Rauch, Susanne; Ballou, David P; Williams, Charles H; Schirmer, R Heiner; Arnér, Elias S J

    2003-10-28

    Selenium, an essential trace element for mammals, is incorporated into a selected class of selenoproteins as selenocysteine. All known isoenzymes of mammalian thioredoxin (Trx) reductases (TrxRs) employ selenium in the C-terminal redox center -Gly-Cys-Sec-Gly-COOH for reduction of Trx and other substrates, whereas the corresponding sequence in Drosophila melanogaster TrxR is -Ser-Cys-Cys-Ser-COOH. Surprisingly, the catalytic competence of these orthologous enzymes is similar, whereas direct Sec-to-Cys substitution of mammalian TrxR, or other selenoenzymes, yields almost inactive enzyme. TrxRs are therefore ideal for studying the biology of selenocysteine by comparative enzymology. Here we show that the serine residues flanking the C-terminal Cys residues of Drosophila TrxRs are responsible for activating the cysteines to match the catalytic efficiency of a selenocysteine-cysteine pair as in mammalian TrxR, obviating the need for selenium. This finding suggests that the occurrence of selenoenzymes, which implies that the organism is selenium-dependent, is not necessarily associated with improved enzyme efficiency. Our data suggest that the selective advantage of selenoenzymes is a broader range of substrates and a broader range of microenvironmental conditions in which enzyme activity is possible.

  20. INDUCTION OF CELL PROLIFERATION AND APOPTOSIS IN HL60 AND HACAT CELLS BY ARSENIC, ARSENATE, AND ARSENIC-CONTAMINATED DRINKING WATER

    EPA Science Inventory

    Induction of cell proliferation and apoptosis in HL-60 and HaCaT cells by arsenite, arsenate and arsenic-contaminated drinking water. T-C. Zhang, M. Schmitt, J. L. Mumford National Research Council, Washington DC and U.S. Environmental Protection Agency, NHEERL, Research Triangle...

  1. A PROBABILISTIC ARSENIC EXPOSURE ASSESSMENT FOR CHILDREN WHO CONTACT CHROMATED COPPER ARSENATE ( CAA )-TREATED PLAYSETS AND DECKS: PART 2 SENSITIVITY AND UNCERTAINTY ANALYSIS

    EPA Science Inventory

    A probabilistic model (SHEDS-Wood) was developed to examine children's exposure and dose to chromated copper arsenate (CCA)-treated wood, as described in Part 1 of this two part paper. This Part 2 paper discusses sensitivity and uncertainty analyses conducted to assess the key m...

  2. AN EVALUATION OF THE RELATIVE GENOTOXICITY OF ARSENITE, ARSENATE, AND FOUR METHYLATED METABOLITES IN VITRO USING THE ALKALINE SINGLE CELL GEL ASSAY

    EPA Science Inventory

    An Evaluation of the Relative Genotoxicity of Arsenite, Arsenate, and Four Methylated
    Metabolites In Vitro Using the Alkaline Single Cell Gel Assay (ASCG).

    Arsenic ( As) is a genotoxic and carcinogenic metal found in many drinking water systems throughout the world. ...

  3. Concentration-and time-dependent genomic changes in the mouse urinary bladder following exposure to arsenate in drinking water for up to twelve weeks

    EPA Science Inventory

    Inorganic arsenic (AsD is a known human bladder carcinogen. The objective of this study was to examine the concentration dependence of the genomic response to ASi in the urinary bladders of mice. C57BL/6J mice were exposed for 1 or 12 weeks to arsenate in drinking water at concen...

  4. Arsenic and phosphate rock impacted the abundance and diversity of bacterial arsenic oxidase and reductase genes in rhizosphere of As-hyperaccumulator Pteris vittata.

    PubMed

    Han, Yong-He; Fu, Jing-Wei; Xiang, Ping; Cao, Yue; Rathinasabapathi, Bala; Chen, Yanshan; Ma, Lena Q

    2017-01-05

    Microbially-mediated arsenic (As) transformation in soils affects As speciation and plant uptake. However, little is known about the impacts of As on bacterial communities and their functional genes in the rhizosphere of As-hyperaccumulator Pteris vittata. In this study, arsenite (AsIII) oxidase genes (aroA-like) and arsenate (AsV) reductase genes (arsC) were amplified from three soils, which were amended with 50mgkg(-1) As and/or 1.5% phosphate rock (PR) and grew P. vittata for 90 d. The aroA-like genes in the rhizosphere were 50 times more abundant than arsC genes, consistent with the dominance of AsV in soils. According to functional gene alignment, most bacteria belonged to α-, β- and γ-Proteobacteria. Moreover, aroA-like genes showed a higher biodiversity than arsC genes based on clone library analysis and could be grouped into nine clusters based on terminal restriction fragment length polymorphism (T-RFLP) analysis. Besides, AsV amendment elevated aroA-like gene diversity, but decreased arsC gene diversity. Redundancy analysis indicated that soil pH, available Ca and P, and AsV concentration were key factors driving diverse compositions in aroA-like gene community. This work identified new opportunities to screen for As-oxidizing and/or -reducing bacteria to aid phytoremediation of As-contaminated soils.

  5. [Respiratory complications after transfusion].

    PubMed

    Bernasinski, M; Mertes, P-M; Carlier, M; Dupont, H; Girard, M; Gette, S; Just, B; Malinovsky, J-M

    2014-05-01

    Respiratory complications of blood transfusion have several possible causes. Transfusion-Associated Circulatory Overload (TACO) is often the first mentioned. Transfusion-Related Acute Lung Injury (TRALI), better defined since the consensus conference of Toronto in 2004, is rarely mentioned. French incidence is low. Non-hemolytic febrile reactions, allergies, infections and pulmonary embolism are also reported. The objective of this work was to determine the statistical importance of the different respiratory complications of blood transfusion. This work was conducted retrospectively on transfusion accidents in six health centers in Champagne-Ardenne, reported to Hemovigilance between 2000 and 2009 and having respiratory symptoms. The analysis of data was conducted by an expert committee. Eighty-three cases of respiratory complications are found (316,864 blood products). We have counted 26 TACO, 12 TRALI (only 6 cases were identified in the original investigation of Hemovigilance), 18 non-hemolytic febrile reactions, 16 cases of allergies, 5 transfusions transmitted bacterial infections and 2 pulmonary embolisms. Six new TRALI were diagnosed previously labeled TACO for 2 of them, allergy and infection in 2 other cases and diagnosis considered unknown for the last 2. Our study found an incidence of TRALI 2 times higher than that reported previously. Interpretation of the data by a multidisciplinary committee amended 20% of diagnoses. This study shows the imperfections of our system for reporting accidents of blood transfusion when a single observer analyses the medical records.

  6. Obesity and respiratory diseases.

    PubMed

    Zammit, Christopher; Liddicoat, Helen; Moonsie, Ian; Makker, Himender

    2010-10-20

    The obesity epidemic is a global problem, which is set to increase over time. However, the effects of obesity on the respiratory system are often underappreciated. In this review, we will discuss the mechanical effects of obesity on lung physiology and the function of adipose tissue as an endocrine organ producing systemic inflammation and effecting central respiratory control. Obesity plays a key role in the development of obstructive sleep apnea and obesity hypoventilation syndrome. Asthma is more common and often harder to treat in the obese population, and in this study, we review the effects of obesity on airway inflammation and respiratory mechanics. We also discuss the compounding effects of obesity on chronic obstructive pulmonary disease (COPD) and the paradoxical interaction of body mass index and COPD severity. Many practical challenges exist in caring for obese patients, and we highlight the complications faced by patients undergoing surgical procedures, especially given the increased use of bariatric surgery. Ultimately, a greater understanding of the effects of obesity on the respiratory disease and the provision of adequate health care resources is vital in order to care for this increasingly important patient population.

  7. Obesity and respiratory diseases

    PubMed Central

    Zammit, Christopher; Liddicoat, Helen; Moonsie, Ian; Makker, Himender

    2010-01-01

    The obesity epidemic is a global problem, which is set to increase over time. However, the effects of obesity on the respiratory system are often underappreciated. In this review, we will discuss the mechanical effects of obesity on lung physiology and the function of adipose tissue as an endocrine organ producing systemic inflammation and effecting central respiratory control. Obesity plays a key role in the development of obstructive sleep apnea and obesity hypoventilation syndrome. Asthma is more common and often harder to treat in the obese population, and in this study, we review the effects of obesity on airway inflammation and respiratory mechanics. We also discuss the compounding effects of obesity on chronic obstructive pulmonary disease (COPD) and the paradoxical interaction of body mass index and COPD severity. Many practical challenges exist in caring for obese patients, and we highlight the complications faced by patients undergoing surgical procedures, especially given the increased use of bariatric surgery. Ultimately, a greater understanding of the effects of obesity on the respiratory disease and the provision of adequate health care resources is vital in order to care for this increasingly important patient population. PMID:21116339

  8. Textbook of respiratory medicine

    SciTech Connect

    Murray, J.F.; Nadel, J.

    1987-01-01

    This book presents a clinical reference of respiratory medicine. It also details basic science aspects of pulmonary physiology and describes recently developed, sophisticated diagnostic tools and therapeutic methods. It also covers anatomy, physiology, pharmacology, and pathology; microbiologic, radiologic, nuclear medicine, and biopsy methods for diagnosis.

  9. Respiratory muscle plasticity.

    PubMed

    Gransee, Heather M; Mantilla, Carlos B; Sieck, Gary C

    2012-04-01

    Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it. As such, respiratory muscle is in a constant state of remodeling, and the basis of muscle's plasticity is its ability to change protein expression and resultant protein balance in response to varying environmental conditions. Here, we will describe the changes of respiratory muscle imposed by extrinsic changes in mechanical load, activity, and innervation. Although there is a large body of literature on the structural and functional plasticity of respiratory muscles, we are only beginning to understand the molecular-scale protein changes that contribute to protein balance. We will give an overview of key mechanisms regulating protein synthesis and protein degradation, as well as the complex interactions between them. We suggest future application of a systems biology approach that would develop a mathematical model of protein balance and greatly improve treatments in a variety of clinical settings related to maintaining both muscle mass and optimal contractile function of respiratory muscles.

  10. Middle East respiratory syndrome.

    PubMed

    Zumla, Alimuddin; Hui, David S; Perlman, Stanley

    2015-09-05

    Middle East respiratory syndrome (MERS) is a highly lethal respiratory disease caused by a novel single-stranded, positive-sense RNA betacoronavirus (MERS-CoV). Dromedary camels, hosts for MERS-CoV, are implicated in direct or indirect transmission to human beings, although the exact mode of transmission is unknown. The virus was first isolated from a patient who died from a severe respiratory illness in June, 2012, in Jeddah, Saudi Arabia. As of May 31, 2015, 1180 laboratory-confirmed cases (483 deaths; 40% mortality) have been reported to WHO. Both community-acquired and hospital-acquired cases have been reported with little human-to-human transmission reported in the community. Although most cases of MERS have occurred in Saudi Arabia and the United Arab Emirates, cases have been reported in Europe, the USA, and Asia in people who travelled from the Middle East or their contacts. Clinical features of MERS range from asymptomatic or mild disease to acute respiratory distress syndrome and multiorgan failure resulting in death, especially in individuals with underlying comorbidities. No specific drug treatment exists for MERS and infection prevention and control measures are crucial to prevent spread in health-care facilities. MERS-CoV continues to be an endemic, low-level public health threat. However, the virus could mutate to have increased interhuman transmissibility, increasing its pandemic potential.

  11. Sulfite reductase protects plants against sulfite toxicity.

    PubMed

    Yarmolinsky, Dmitry; Brychkova, Galina; Fluhr, Robert; Sagi, Moshe

    2013-02-01

    Plant sulfite reductase (SiR; Enzyme Commission 1.8.7.1) catalyzes the reduction of sulfite to sulfide in the reductive sulfate assimilation pathway. Comparison of SiR expression in tomato (Solanum lycopersicum 'Rheinlands Ruhm') and Arabidopsis (Arabidopsis thaliana) plants revealed that SiR is expressed in a different tissue-dependent manner that likely reflects dissimilarity in sulfur metabolism between the plant species. Using Arabidopsis and tomato SiR mutants with modified SiR expression, we show here that resistance to ectopically applied sulfur dioxide/sulfite is a function of SiR expression levels and that plants with reduced SiR expression exhibit higher sensitivity than the wild type, as manifested in pronounced leaf necrosis and chlorophyll bleaching. The sulfite-sensitive mutants accumulate applied sulfite and show a decline in glutathione levels. In contrast, mutants that overexpress SiR are more tolerant to sulfite toxicity, exhibiting little or no damage. Resistance to high sulfite application is manifested by fast sulfite disappearance and an increase in glutathione levels. The notion that SiR plays a role in the protection of plants against sulfite is supported by the rapid up-regulation of SiR transcript and activity within 30 min of sulfite injection into Arabidopsis and tomato leaves. Peroxisomal sulfite oxidase transcripts and activity levels are likewise promoted by sulfite application as compared with water injection controls. These results indicate that, in addition to participating in the sulfate assimilation reductive pathway, SiR also plays a role in protecting leaves against the toxicity of sulfite accumulation.

  12. Limited Practice Respiratory Care Course.

    ERIC Educational Resources Information Center

    Anderson, Amy L.

    This 36-46 hour basic respiratory care course has been designed to enhance the skills of health professionals in providing limited respiratory care during those hours when a respiratory care practitioner is not available. Persons taking the course are assumed to have a basic knowledge of anatomy and physiology, administration of medications, and…

  13. Your Lungs and Respiratory System

    MedlinePlus

    ... dientes Video: Getting an X-ray Your Lungs & Respiratory System KidsHealth > For Kids > Your Lungs & Respiratory System Print A A A What's in this article? ... in your body, and they work with your respiratory system to allow you to take in fresh air, ...

  14. The role of succinate in the respiratory chain of Trypanosoma brucei procyclic trypomastigotes.

    PubMed

    Turrens, J F

    1989-04-15

    Trypanosoma brucei procyclic trypomastigotes were made permeable by using digitonin (0-70 micrograms/mg of protein). This procedure allowed exposure of coupled mitochondria to different substrates. Only succinate and glycerol phosphate (but not NADH-dependent substrates) were capable of stimulating oxygen consumption. Fluorescence studies on intact cells indicated that addition of succinate stimulates NAD(P)H oxidation, contrary to what happens in mammalian mitochondria. Addition of malonate, an inhibitor of succinate dehydrogenase, stimulated NAD(P)H reduction. Malonate also inhibited intact-cell respiration and motility, both of which were restored by further addition of succinate. Experiments carried out with isolated mitochondrial membranes showed that, although the electron transfer from succinate to cytochrome c was inhibitable by antimycin, NADH-cytochrome c reductase was antimycin-insensitive. We postulate that the NADH-ubiquinone segment of the respiratory chain is replaced by NADH-fumarate reductase, which reoxidizes the mitochondrial NADH and in turn generates succinate for the respiratory chain. This hypothesis is further supported by the inhibitory effect on cell growth and respiration of 3-methoxyphenylacetic acid, an inhibitor of the NADH-fumarate reductase of T. brucei.

  15. Effects of Dissolved Carbonate on Arsenate Adsorption and Surface Speciation at the Hematite-Water Interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2004-01-01

    Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [PCO2 = 10 -3.5 atm and ???0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L -1, [As(V)]0 = 1.5 mM and / = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L-1, [As(V)] 0 = 0.5 mM and / = 0.01 M NaCl], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (PCO2 = 10-3.5 atm)than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear (???2.8 A??) and bidentate binuclear (???3.3 A??) bonding at pH 4.5-8 and loading levels of 0.46-3.10 ??M m-2. Using the results of the pseudoequilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the PCO2 = 10-3.5 atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to

  16. Microdistribution of chromated copper arsenate preservative in rubberwood (Hevea brasiliensis Muell. Arg.)

    NASA Astrophysics Data System (ADS)

    Jusoh, Ismail Bin

    2000-08-01

    Rubberwood is popular for making indoor furniture since rubberwood is relatively abundant and sustainable. Currently more than 60% of the total annual rubberwood produced by rubber plantation is used as fuelwood. Rubberwood has the potential for both indoor and outdoor application. For exterior applications, preservative treatment is needed to extend the service life of rubberwood. The objectives of this study are to (1) assess treatability of rubberwood with chromated copper arsenate (CCA) preservative, (2) evaluate the natural decay resistance and efficacy of CCA on rubberwood, and (3) study the microdistribution of CCA components in rubberwood cells. The treatability of rubberwood was determined by measuring the penetration and retention of CCA type C preservative after a full-cell treatment. Natural decay resistance and efficacy of CCA treatment on rubberwood was estimated using a laboratory soilblock test according to AWPA E 10-91. The microdistribution of chromium, copper and arsenic in CCA-treated rubberwood was studied using scanning electron microscope in conjunction with energy dispersive X-ray analyzer (SEM-EDXA). As expected, longitudinal permeability was found to be better than the radial and the tangential permeability. The penetration and retention in the radial direction was about 3 times better than in the tangential direction. Longer pressure period increased penetration and retention of CCA type C in rubberwood. Complete penetration was achieved after 4 hours of pressure (1240 kPa) treatment. A pre-treatment steaming improved the treatability of rubberwood regardless of the anatomical direction. The average weight loss by white rot and brown rot was about 1.5 times higher than that of soft rot. A linear relationship was found between the weight loss and the incubation period for all the six test fungi. A CCA retention of 4.1 kg/m3 reduced weight loss to about 10% and retention of 14.5 kg/m3 reduced the weight loss of all test fungi at less than 2

  17. Climate change and respiratory disease: European Respiratory Society position statement.

    PubMed

    Ayres, J G; Forsberg, B; Annesi-Maesano, I; Dey, R; Ebi, K L; Helms, P J; Medina-Ramón, M; Windt, M; Forastiere, F

    2009-08-01

    Climate change will affect individuals with pre-existing respiratory disease, but the extent of the effect remains unclear. The present position statement was developed on behalf of the European Respiratory Society in order to identify areas of concern arising from climate change for individuals with respiratory disease, healthcare workers in the respiratory sector and policy makers. The statement was developed following a 2-day workshop held in Leuven (Belgium) in March 2008. Key areas of concern for the respiratory community arising from climate change are discussed and recommendations made to address gaps in knowledge. The most important recommendation was the development of more accurate predictive models for predicting the impact of climate change on respiratory health. Respiratory healthcare workers also have an advocatory role in persuading governments and the European Union to maintain awareness and appropriate actions with respect to climate change, and these areas are also discussed in the position statement.

  18. Uterine glutathione reductase activity: modulation by estrogens and progesterone.

    PubMed

    Díaz-Flores, M; Baiza-Gutman, L A; Pedrón, N N; Hicks, J J

    1999-10-29

    The aim of this study was to determine whether glutathione reductase activity in uterine tissue is regulated by sex hormones. In spayed rats uterine glutathione reductase was significantly increased by exogenous estrogen (P< 0.01), progesterone (P< 0.01) or estrogen plus progesterone (P<0.01). When enzyme activity is expressed per mg protein, daily administration of estrogen or progesterone induces a progressive increase of this enzyme between 24 to 48 h or 24 to 72 h of treatment, respectively. Whereas the combination of both steroids causes an earlier and higher increase in glutathione reductase activity at 24 h of treatment. Estradiol singly or in combination with progesterone induced the highest protein concentration in the uterus. Whereas uterine DNA concentration is only significantly affected by estradiol. Our results suggest that uterine glutathione reductase is regulated by estradiol and progesterone and may be involved in maintaining levels of reduced glutathione in the uterus. This compound may be required for control of the redox state of thiol groups and in detoxification reactions involving H2O2 and electrophylic substances. The antioxidant action of estrogens is partially due to the stimulation of glutathione reductase.

  19. HMG-CoA reductase guides migrating primordial germ cells.

    PubMed

    Van Doren, M; Broihier, H T; Moore, L A; Lehmann, R

    1998-12-03

    The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is best known for catalysing a rate-limiting step in cholesterol biosynthesis, but it also participates in the production of a wide variety of other compounds. Some clinical benefits attributed to inhibitors of HMG-CoA reductase are now thought to be independent of any serum cholesterol-lowering effect. Here we describe a new cholesterol-independent role for HMG-CoA reductase, in regulating a developmental process: primordial germ cell migration. We show that in Drosophila this enzyme is highly expressed in the somatic gonad and that it is necessary for primordial germ cells to migrate to this tissue. Misexpression of HMG-CoA reductase is sufficient to attract primordial germ cells to tissues other than the gonadal mesoderm. We conclude that the regulated expression of HMG-CoA reductase has a critical developmental function in providing spatial information to guide migrating primordial germ cells.

  20. Bacterial morphinone reductase is related to Old Yellow Enzyme.

    PubMed Central

    French, C E; Bruce, N C

    1995-01-01

    Morphinone reductase, produced by Pseudomonas putida M10, catalyses the NADH-dependent saturation of the carbon-carbon double bond of morphinone and codeinone, and is believed to be involved in the metabolism of morphine and codeine. The structural gene encoding morphinone reductase, designated morB, was cloned from Ps. putida M10 genomic DNA by the use of degenerate oligonucleotide probes based on elements of the amino acid sequence of the purified enzyme. Sequence analysis and structural characteristics indicated that morphinone reductase is related to the flavoprotein alpha/beta-barrel oxidoreductases, and is particularly similar to Old Yellow Enzyme of Saccharomyces spp. and the related oestrogen-binding protein of Candida albicans. Expressed sequence tags from several plant species show high homology to these enzymes, suggesting the presence of a family of enzymes conserved in plants and fungi. Although related bacterial proteins are known, morphinone reductase appears to be more similar to the eukaryotic proteins. Morphinone reductase was overexpressed in Escherichia coli, and has potential applications for the industrial preparation of semisynthetic opiates. Images Figure 1 Figure 5 PMID:8554504

  1. Purification and properties of proline reductase from Clostridium sticklandii.

    PubMed

    Seto, B; Stadtman, T C

    1976-04-25

    Proline reductase of Clostridium sticklandii is a membrane-bound protein and is released by treatment with detergents. The enzyme has been purified to homogeneity and is estimated by gel filtration and sedimentation equilibrium centrifugation to have a molecular weight of 298,000 to 327,000. A minimum molecular weight of 30,000 to 31,000 was calculated on the basis of sodium dodecyl sulfate-acrylamide gel electrophoresis and amino acid composition. Amino acid analysis showed a preponderance of acidic amino acids. No tryptophan was detected in the protein either spectrophotometrically or by amino acid analysis. A total of 20 sulfhydryl groups measured by titration of the reduced protein with 5,5'-dithiobis(2-nitrobenzoic acid) is in agreement with 20 cystic acid residues determined in hydrolysates of performic acid-oxidized protein. No molybdenum, iron, or selenium was found in the pure protein. Although NADH is the physiological electron donor for the proline reductase complex, the purified 300,000 molecular weight reductase component is inactive in the presence of NADH in vitro. Dithiothreitol, in contrast, can serve as electron donor both for unpurified (putative proline reductase complex) and purified proline reductase in vitro.

  2. Potential use of aldose reductase inhibitors to prevent diabetic complications.

    PubMed

    Zenon, G J; Abobo, C V; Carter, B L; Ball, D W

    1990-06-01

    Reviewed are (1) the biochemical basis and pathophysiology of diabetic complications and (2) the structure-activity relationships, pharmacology, pharmacokinetics, clinical trials, and adverse effects of aldose reductase inhibitors (ARIs). ARIs are a new class of drugs potentially useful in preventing diabetic complications, the most widely studied of which have been cataracts and neuropathy. ARIs inhibit aldose reductase, the first, rate-limiting enzyme in the polyol metabolic pathway. In nonphysiological hyperglycemia the activity of hexokinase becomes saturated while that of aldose reductase is enhanced, resulting in intracellular accumulation of sorbitol. Because sorbitol does not readily penetrate the cell membrane it can persist within cells, which may lead to diabetic complications. ARIs are a class of structurally dissimilar compounds that include carboxylic acid derivatives, flavonoids, and spirohydantoins. The major pharmacologic action of an ARI involves competitive binding to aldose reductase and consequent blocking of sorbitol production. ARIs delay cataract formation in animals, but the role of aldose reductase in cataract formation in human diabetics has not been established. The adverse effects of ARIs include hypersensitivity reactions. Although the polyol pathway may not be solely responsible for diabetic complications, studies suggest that therapy with ARIs could be beneficial. Further research is needed to determine the long-term impact and adverse effects of ARIs in the treatment of diabetic complications.

  3. Ferrate(VI)-induced arsenite and arsenate removal by in situ structural incorporation into magnetic iron(III) oxide nanoparticles.

    PubMed

    Prucek, Robert; Tuček, Jiří; Kolařík, Jan; Filip, Jan; Marušák, Zdeněk; Sharma, Virender K; Zbořil, Radek

    2013-04-02

    We report the first example of arsenite and arsenate removal from water by incorporation of arsenic into the structure of nanocrystalline iron(III) oxide. Specifically, we show the capability to trap arsenic into the crystal structure of γ-Fe2O3 nanoparticles that are in situ formed during treatment of arsenic-bearing water with ferrate(VI). In water, decomposition of potassium ferrate(VI) yields nanoparticles having core-shell nanoarchitecture with a γ-Fe2O3 core and a γ-FeOOH shell. High-resolution X-ray photoelectron spectroscopy and in-field (57)Fe Mössbauer spectroscopy give unambiguous evidence that a significant portion of arsenic is embedded in the tetrahedral sites of the γ-Fe2O3 spinel structure. Microscopic observations also demonstrate the principal effect of As doping on crystal growth as reflected by considerably reduced average particle size and narrower size distribution of the "in-situ" sample with the embedded arsenic compared to the "ex-situ" sample with arsenic exclusively sorbed on the iron oxide nanoparticle surface. Generally, presented results highlight ferrate(VI) as one of the most promising candidates for advanced technologies of arsenic treatment mainly due to its environmentally friendly character, in situ applicability for treatment of both arsenites and arsenates, and contrary to all known competitive technologies, firmly bound part of arsenic preventing its leaching back to the environment. Moreover, As-containing γ-Fe2O3 nanoparticles are strongly magnetic allowing their separation from the environment by application of an external magnet.

  4. The nitric-oxide reductase from Paracoccus denitrificans uses a single specific proton pathway.

    PubMed

    ter Beek, Josy; Krause, Nils; Reimann, Joachim; Lachmann, Peter; Ädelroth, Pia

    2013-10-18

    The NO reductase from Paracoccus denitrificans reduces NO to N2O (2NO + 2H(+) + 2e(-) → N2O + H2O) with electrons donated by periplasmic cytochrome c (cytochrome c-dependent NO reductase; cNOR). cNORs are members of the heme-copper oxidase superfamily of integral membrane proteins, comprising the O2-reducing, proton-pumping respiratory enzymes. In contrast, although NO reduction is as exergonic as O2 reduction, there are no protons pumped in cNOR, and in addition, protons needed for NO reduction are derived from the periplasmic solution (no contribution to the electrochemical gradient is made). cNOR thus only needs to transport protons from the periplasm into the active site without the requirement to control the timing of opening and closing (gating) of proton pathways as is needed in a proton pump. Based on the crystal structure of a closely related cNOR and molecular dynamics simulations, several proton transfer pathways were suggested, and in principle, these could all be functional. In this work, we show that residues in one of the suggested pathways (denoted pathway 1) are sensitive to site-directed mutation, whereas residues in the other proposed pathways (pathways 2 and 3) could be exchanged without severe effects on turnover activity with either NO or O2. We further show that electron transfer during single-turnover reduction of O2 is limited by proton transfer and can thus be used to study alterations in proton transfer rates. The exchange of residues along pathway 1 showed specific slowing of this proton-coupled electron transfer as well as changes in its pH dependence. Our results indicate that only pathway 1 is used to transfer protons in cNOR.

  5. Respiratory fluid mechanics

    NASA Astrophysics Data System (ADS)

    Grotberg, James B.

    2011-02-01

    This article covers several aspects of respiratory fluid mechanics that have been actively investigated by our group over the years. For the most part, the topics involve two-phase flows in the respiratory system with applications to normal and diseased lungs, as well as therapeutic interventions. Specifically, the topics include liquid plug flow in airways and at airway bifurcations as it relates to surfactant, drug, gene, or stem cell delivery into the lung; liquid plug rupture and its damaging effects on underlying airway epithelial cells as well as a source of crackling sounds in the lung; airway closure from "capillary-elastic instabilities," as well as nonlinear stabilization from oscillatory core flow which we call the "oscillating butter knife;" liquid film, and surfactant dynamics in an oscillating alveolus and the steady streaming, and surfactant spreading on thin viscous films including our discovery of the Grotberg-Borgas-Gaver shock.

  6. [Asbestos and respiratory diseases].

    PubMed

    Scherpereel, Arnaud

    2016-01-01

    Previous occupational asbestos exposure (more rarely environmental or domestic exposure) may induce various pleural and/or pulmonary, benign or malignant diseases, sometimes with a very long latency for malignant mesothelioma (MM). Asbestos has been widely extracted and used in Western countries and in emerging or developing countries, resulting in a peak of MM incidence in France around 2020 and likely in a world pandemic of asbestos-induced diseases. These patients have mostly benign respiratory diseases (pleural plugs) but may also be diagnosed with lung cancer or malignant pleural mesothelioma, and have a global poor outcome. New therapeutic tools (targeted therapies, immunotherapy…) with first promising results are developed. However, it is crucial to obtain a full ban of asbestos use worldwide, and to do a regular follow-up of asbestos-exposed subjects, mostly if they are already diagnosed with benign respiratory diseases. Finally, new cancers (larynx and ovary) were recently added to the list of asbestos-induced tumors.

  7. Respiratory fluid mechanics

    PubMed Central

    Grotberg, James B.

    2011-01-01

    This article covers several aspects of respiratory fluid mechanics that have been actively investigated by our group over the years. For the most part, the topics involve two-phase flows in the respiratory system with applications to normal and diseased lungs, as well as therapeutic interventions. Specifically, the topics include liquid plug flow in airways and at airway bifurcations as it relates to surfactant, drug, gene, or stem cell delivery into the lung; liquid plug rupture and its damaging effects on underlying airway epithelial cells as well as a source of crackling sounds in the lung; airway closure from “capillary-elastic instabilities,” as well as nonlinear stabilization from oscillatory core flow which we call the “oscillating butter knife;” liquid film, and surfactant dynamics in an oscillating alveolus and the steady streaming, and surfactant spreading on thin viscous films including our discovery of the Grotberg–Borgas–Gaver shock. PMID:21403768

  8. Respiratory fluid mechanics.

    PubMed

    Grotberg, James B

    2011-02-01

    This article covers several aspects of respiratory fluid mechanics that have been actively investigated by our group over the years. For the most part, the topics involve two-phase flows in the respiratory system with applications to normal and diseased lungs, as well as therapeutic interventions. Specifically, the topics include liquid plug flow in airways and at airway bifurcations as it relates to surfactant, drug, gene, or stem cell delivery into the lung; liquid plug rupture and its damaging effects on underlying airway epithelial cells as well as a source of crackling sounds in the lung; airway closure from "capillary-elastic instabilities," as well as nonlinear stabilization from oscillatory core flow which we call the "oscillating butter knife;" liquid film, and surfactant dynamics in an oscillating alveolus and the steady streaming, and surfactant spreading on thin viscous films including our discovery of the Grotberg-Borgas-Gaver shock.

  9. Ocular tropism of respiratory viruses.

    PubMed

    Belser, Jessica A; Rota, Paul A; Tumpey, Terrence M

    2013-03-01

    Respiratory viruses (including adenovirus, influenza virus, respiratory syncytial virus, coronavirus, and rhinovirus) cause a broad spectrum of disease in humans, ranging from mild influenza-like symptoms to acute respiratory failure. While species D adenoviruses and subtype H7 influenza viruses are known to possess an ocular tropism, documented human ocular disease has been reported following infection with all principal respiratory viruses. In this review, we describe the anatomical proximity and cellular receptor distribution between ocular and respiratory tissues. All major respiratory viruses and their association with human ocular disease are discussed. Research utilizing in vitro and in vivo models to study the ability of respiratory viruses to use the eye as a portal of entry as well as a primary site of virus replication is highlighted. Identification of shared receptor-binding preferences, host responses, and laboratory modeling protocols among these viruses provides a needed bridge between clinical and laboratory studies of virus tropism.

  10. Respiratory assessment in centronuclear myopathies

    PubMed Central

    Smith, Barbara K; Goddard, Melissa; Childers, Martin K.

    2014-01-01

    The centronuclear myopathies (CNMs) are a group of inherited neuromuscular disorders classified as congenital myopathies. While several causative genes have been identified, some patients do not harbor any of the currently known mutations. These diverse disorders have common histological features, which include a high proportion of centrally-nucleated muscle fibers, and clinical attributes of muscle weakness and respiratory insufficiency. Respiratory problems in CNMs may manifest initially during sleep, but daytime symptoms, ineffective airway clearance, and hypoventilation predominate as more severe respiratory muscle dysfunction evolves. Respiratory muscle capacity can be evaluated using a variety of clinical tests selected with consideration for the age and baseline motor function of the patient. Similar clinical tests of respiratory function can also be incorporated into preclinical CNM canine models to offer insight for clinical trials. Since respiratory problems account for significant morbidity in patients, routine assessments of respiratory muscle function are discussed. PMID:24668768

  11. Middle East Respiratory Syndrome

    PubMed Central

    Zumla, Alimuddin; Hui, David S; Perlman, Stanley

    2016-01-01

    SUMMARY The Middle East Respiratory Syndrome (MERS) is a newly recognized highly lethal respiratory disease caused by a novel single stranded, positive sense RNA betacoronavirus (MERS-CoV). Dromedary camels, host species for MERS-CoV are implicated in the direct or indirect transmission to humans, although the exact mode of transmission remains unknown. First isolated from a patient who died from a severe respiratory illness in June 2012 in Jeddah, Saudi Arabia, as of 16 February 2015, 983 laboratory-confirmed cases of MERS-CoV (360 deaths; 36.6% mortality) were reported to the WHO. Cases have been acquired in both the community and hospitals with limited human-to-human transmission reported in the community. Whilst the majority of MERS cases have occurred in Saudi Arabia and the United Arab Emirates, cases have been reported from Europe, USA and Asia in people who traveled from the Middle East or their contacts. Clinical features of MERS range from asymptomatic or mild disease to acute respiratory distress syndrome and multi-organ failure resulting in death, especially in individuals with underlying co-morbidities. There is no specific drug treatment for MERS and infection prevention and control measures are crucial to prevent spread of MERS-CoV in health care facilities. MERS-CoV continues to be an endemic,low level public health threat. However, the concern remains that the virus could mutate to exhibit increased interhuman transmissibility, increasing pandemic potential. Our seminar presents an overview of current knowledge and perspectives on the epidemiology, virology, mode of transmission, pathogen-host responses, clinical features, diagnosis and development of new drugs and vaccines. PMID:26049252

  12. Sulfur Isotope Effects of Dissimilatory Sulfite Reductase

    PubMed Central

    Leavitt, William D.; Bradley, Alexander S.; Santos, André A.; Pereira, Inês A. C.; Johnston, David T.

    2015-01-01

    The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major (34S/32S) and minor (33S/32S, 36S/32S) sulfur isotope fractionations imparted by a central enzyme in the energy metabolism of sulfate reducers, dissimilatory sulfite reductase (DsrAB). Results from in vitro sulfite reduction experiments allow us to calculate the in vitro DsrAB isotope effect in 34S/32S (hereafter, 34εDsrAB) to be 15.3 ± 2‰, 2σ. The accompanying minor isotope effect in 33S, described as 33λDsrAB, is calculated to be 0.5150 ± 0.0012, 2σ. These observations facilitate a rigorous evaluation of the isotopic fractionation associated with the dissimilatory MSR pathway, as well as of the environmental variables that govern the overall magnitude of fractionation by natural communities of sulfate reducers. The isotope effect induced by DsrAB upon sulfite reduction is a factor of 0.3–0.6 times prior indirect estimates, which have ranged from 25 to 53‰ in 34εDsrAB. The minor isotope fractionation observed from DsrAB is consistent with a kinetic or equilibrium effect. Our in vitro constraints on the magnitude of 34εDsrAB is similar to the median value of experimental observations compiled from all known published work, where 34εr−p = 16.1‰ (r–p indicates reactant vs. product, n = 648). This value closely matches those of MSR operating at high sulfate reduction rates in both laboratory chemostat experiments (34εSO4−H2S =  17.3 ± 1.5‰, 2σ) and in modern marine sediments (34εSO4−H2S =  17.3 ± 3.8‰). Targeting the direct isotopic consequences of a specific enzymatic processes is a fundamental step toward a biochemical foundation for reinterpreting the biogeochemical and geobiological sulfur isotope records in

  13. Sulfur Isotope Effects of Dissimilatory Sulfite Reductase.

    PubMed

    Leavitt, William D; Bradley, Alexander S; Santos, André A; Pereira, Inês A C; Johnston, David T

    2015-01-01

    The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major ((34)S/(32)S) and minor ((33)S/(32)S, (36)S/(32)S) sulfur isotope fractionations imparted by a central enzyme in the energy metabolism of sulfate reducers, dissimilatory sulfite reductase (DsrAB). Results from in vitro sulfite reduction experiments allow us to calculate the in vitro DsrAB isotope effect in (34)S/(32)S (hereafter, [Formula: see text]) to be 15.3 ± 2‰, 2σ. The accompanying minor isotope effect in (33)S, described as [Formula: see text], is calculated to be 0.5150 ± 0.0012, 2σ. These observations facilitate a rigorous evaluation of the isotopic fractionation associated with the dissimilatory MSR pathway, as well as of the environmental variables that govern the overall magnitude of fractionation by natural communities of sulfate reducers. The isotope effect induced by DsrAB upon sulfite reduction is a factor of 0.3-0.6 times prior indirect estimates, which have ranged from 25 to 53‰ in (34)εDsrAB. The minor isotope fractionation observed from DsrAB is consistent with a kinetic or equilibrium effect. Our in vitro constraints on the magnitude of [Formula: see text] is similar to the median value of experimental observations compiled from all known published work, where (34)ε r-p = 16.1‰ (r-p indicates reactant vs. product, n = 648). This value closely matches those of MSR operating at high sulfate reduction rates in both laboratory chemostat experiments ([Formula: see text] 17.3 ± 1.5‰, 2σ) and in modern marine sediments ([Formula: see text] 17.3 ± 3.8‰). Targeting the direct isotopic consequences of a specific enzymatic processes is a fundamental step toward a biochemical foundation for reinterpreting the

  14. Selenium in thioredoxin reductase: a mechanistic perspective.

    PubMed

    Lacey, Brian M; Eckenroth, Brian E; Flemer, Stevenson; Hondal, Robert J

    2008-12-02

    Most high M(r) thioredoxin reductases (TRs) have the unusual feature of utilizing a vicinal disulfide bond (Cys(1)-Cys(2)) which forms an eight-membered ring during the catalytic cycle. Many eukaryotic TRs have replaced the Cys(2) position of the dyad with the rare amino acid selenocysteine (Sec). Here we demonstrate that Cys- and Sec-containing TRs are distinguished by the importance each class of enzymes places on the eight-membered ring structure in the catalytic cycle. This hypothesis was explored by studying the truncated enzyme missing the C-terminal ring structure in conjunction with oxidized peptide substrates to investigate the reduction and opening of this dyad. The peptide substrates were identical in sequence to the missing part of the enzyme, containing either a disulfide or selenylsulfide linkage, but were differentiated by the presence (cyclic) and absence (acyclic) of the ring structure. The ratio of these turnover rates informs that the ring is only of modest importance for the truncated mouse mitochondrial Sec-TR (ring/no ring = 32), while the ring structure is highly important for the truncated Cys-TRs from Drosophila melanogaster and Caenorhabditis elegans (ring/no ring > 1000). All three enzymes exhibit a similar dependence upon leaving group pK(a) as shown by the use of the acyclic peptides as substrates. These two factors can be reconciled for Cys-TRs if the ring functions to simultaneously allow for attack by a nearby thiolate while correctly positioning the leaving group sulfur atom to accept a proton from the enzymic general acid. For Sec-TRs the ring is unimportant because the lower pK(a) of the selenol relative to a thiol obviates its need to be protonated upon S-Se bond scission and permits physical separation of the selenol and the general acid. Further study of the biochemical properties of the truncated Cys and Sec TR enzymes demonstrates that the chemical advantage conferred on the eukaryotic enzyme by a selenol is the ability to

  15. Nanotechnology in respiratory medicine.

    PubMed

    Omlor, Albert Joachim; Nguyen, Juliane; Bals, Robert; Dinh, Quoc Thai

    2015-05-29

    Like two sides of the same coin, nanotechnology can be both boon and bane for respiratory medicine. Nanomaterials open new ways in diagnostics and treatment of lung diseases. Nanoparticle based drug delivery systems can help against diseases such as lung cancer, tuberculosis, and pulmonary fibrosis. Moreover, nanoparticles can be loaded with DNA and act as vectors for gene therapy in diseases like cystic fibrosis. Even lung diagnostics with computer tomography (CT) or magnetic resonance imaging (MRI) profits from new nanoparticle based contrast agents. However, the risks of nanotechnology also have to be taken into consideration as engineered nanomaterials resemble natural fine dusts and fibers, which are known to be harmful for the respiratory system in many cases. Recent studies have shown that nanoparticles in the respiratory tract can influence the immune system, can create oxidative stress and even cause genotoxicity. Another important aspect to assess the safety of nanotechnology based products is the absorption of nanoparticles. It was demonstrated that the amount of pulmonary nanoparticle uptake not only depends on physical and chemical nanoparticle characteristics but also on the health status of the organism. The huge diversity in nanotechnology could revolutionize medicine but makes safety assessment a challenging task.

  16. Electrode assemblies composed of redox cascades from microbial respiratory electron transfer chains

    SciTech Connect

    Gates, Andrew J.; Marritt, Sophie; Bradley, Justin; Shi, Liang; McMillan, Duncan G.; Jeuken, Lars J.; Richardson, David; Butt, Julea N.

    2013-10-01

    Respiratory and photosynthetic electron transfer chains are dependent on vectorial electron transfer through a series of redox proteins. Examples include electron transfer from NapC to NapAB nitrate reductase in Paracoccus denitrificans and from CymA to Fcc3 (flavocytochrome c3) fumarate reductase in Shewanella oneidensis MR-1. In the present article, we demonstrate that graphite electrodes can serve as surfaces for the stepwise adsorption of NapC and NapAB, and the stepwise adsorption of CymA and Fcc3. Aspects of the catalytic properties of these assemblies are different from those of NapAB and Fcc3 adsorbed in isolation. We propose that this is due to the formation of NapC-NapAB and of CymA-Fcc3 complexes that are capable of supporting vectorial electron transfer.

  17. Chemical-specific health consultation for chromated copper arsenate chemical mixture: port of Djibouti.

    PubMed

    Chou, Selene; Colman, Joan; Tylenda, Carolyn; De Rosa, Christopher

    2007-05-01

    The Agency for Toxic Substances and Disease Registry (ATSDR) prepared this health consultation to provide support for assessing the public health implications of hazardous chemical exposure, primarily through drinking water, related to releases of chromated copper arsenate (CCA) in the port of Djibouti. CCA from a shipment, apparently intended for treating electric poles, is leaking into the soil in the port area. CCA is a pesticide used to protect wood against decay-causing organisms. This mixture commonly contains chromium(VI) (hexavalent chromium) as chromic acid, arsenic(V) (pentavalent arsenic) as arsenic pentoxide and copper (II) (divalent copper) as cupric oxide, often in an aqueous solution or concentrate. Experimental studies of the fate of CCA in soil and monitoring studies of wood-preserving sites where CCA was spilled on the soil indicate that the chromium(VI), arsenic and copper components of CCA can leach from soil into groundwater and surface water. In addition, at CCA wood-preserving sites, substantial concentrations of chromium(VI), arsenic and copper remained in the soil and were leachable into water four years after the use of CCA was discontinued, suggesting prolonged persistence in soil, with continued potential for leaching. The degree of leaching depended on soil composition and the extent of soil contamination with CCA. In general, leaching was highest for chromium(VI), intermediate for arsenic and lowest for copper. Thus, the potential for contamination of sources of drinking water exists. Although arsenic that is leached from CCA-contaminated soil into surface water may accumulate in the tissues of fish and shellfish, most of the arsenic in these animals will be in a form (often called fish arsenic) that is less harmful. Copper, which leaches less readily than the other components, can accumulate in tissues of mussels and oysters. Chromium is not likely to accumulate in the tissues of fish and shellfish. Limited studies of air

  18. Cu(II)-reduction by Escherichia coli cells is dependent on respiratory chain components.

    PubMed

    Volentini, Sabrina I; Farías, Ricardo N; Rodríguez-Montelongo, Luisa; Rapisarda, Viviana A

    2011-10-01

    Copper is both an essential nutrient and a toxic element able to catalyze free radicals formation which damage lipids and proteins. Although the available copper redox species in aerobic environment is Cu(II), proteins that participate in metal homeostasis use Cu(I). With isolated Escherichia coli membranes, we have previously shown that electron flow through the respiratory chain promotes cupric ions reduction by NADH dehydrogenase-2 and quinones. Here, we determined Cu(II)-reductase activity by whole cells using strains deficient in these respiratory chain components. Measurements were done by the appearance of Cu(I) in the supernatants of cells exposed to sub-lethal Cu(II) concentrations. In the absence of quinones, the Cu(II)-reduction rate decreased ~70% in respect to the wild-type strain, while this diminution was about 85% in a strain lacking both NDH-2 and quinones. The decrease was ~10% in the absence of only NDH-2. In addition, we observed that quinone deficient strains failed to grow in media containing either excess or deficiency of copper, as we have described for NDH-2 deficient mutants. Thus, the Cu(II)-reduction by E. coli intact cells is mainly due to quinones and to a lesser extent to NDH-2, in a quinone-independent way. To our knowledge, this is the first in vivo demonstration of the involvement of E. coli respiratory components in the Cu(II)-reductase activity which contributes to the metal homeostasis.

  19. Recurrent respiratory papillomatosis.

    PubMed

    Venkatesan, Naren N; Pine, Harold S; Underbrink, Michael P

    2012-06-01

    Recurrent respiratory papillomatosis (RRP) is a rare, benign disease with no known cure. RRP is caused by infection of the upper aerodigestive tract with the human papillomavirus (HPV). Passage through the birth canal is thought to be the initial transmission event, but infection may occur in utero. HPV vaccines have helped to provide protection from cervical cancer; however, their role in the prevention of RRP is undetermined. Clinical presentation of initial symptoms of RRP may be subtle. RRP course varies, and current management focuses on surgical debulking of papillomatous lesions with or without concurrent adjuvant therapy.

  20. Acute respiratory distress syndrome.

    PubMed

    Gibbons, Cynthia

    2015-01-01

    Acute respiratory distress syndrome (ARDS) is a life-threatening condition with multiple causes and a high mortality rate. Approximately 150,000 cases are reported in the United States annually, making ARDS a public health concern. Management of the condition is complex because of its severity, and medical imaging is essential for both the diagnosis and management of ARDS. This article introduces common signs, symptoms, risk factors, and causes of ARDS. Diagnostic criteria, histopathology, treatment strategies, and prognostic information also are discussed. The article explains the value of medical imaging studies of ARDS, especially radiography, computed tomography, and ultrasonography.

  1. Adult respiratory distress syndrome.

    PubMed

    Cutts, S; Talboys, R; Paspula, C; Prempeh, E M; Fanous, R; Ail, D

    2017-01-01

    Adult respiratory distress syndrome (ARDS) has now been described as a sequela to such diverse conditions as burns, amniotic fluid embolism, acute pancreatitis, trauma, sepsis and damage as a result of elective surgery in general. Patients with ARDS require immediate intubation, with the average patient now being ventilated for between 8 and 11 days. While the acute management of ARDS is conducted by the critical care team, almost any surgical patient can be affected by the condition and we believe that it is important that a broader spectrum of hospital doctors gain an understanding of the nature of the pathology and its current treatment.

  2. Is the effect of silicon on rice uptake of arsenate (AsV) related to internal silicon concentrations, iron plaque and phosphate nutrition?

    PubMed

    Guo, W; Zhu, Y-G; Liu, W-J; Liang, Y-C; Geng, C-N; Wang, S-G

    2007-07-01

    Solution culture experiments were conducted to investigate the effects of silicon (Si) on arsenate (As(V)) uptake by rice. The addition of Si to the pretreatment or uptake solution significantly decreased shoot and root As concentrations (P<0.001 and P<0.05). The presence of Si in the pretreatment or uptake solution also significantly decreased shoot P concentrations (P<0.001). The data demonstrated that both internal and external Si inhibited the uptake of As and P. Results of As uptake kinetics showed that the mechanism of the effect of Si on arsenate uptake is not caused by direct competition for active sites of transporters with As. The effect of Si on As uptake was not entirely mediated through the effect of Si on P uptake. Although the addition of Si to pretreatment solutions still significantly decreased shoot and root As concentrations, the extent of reduction became smaller when rice roots were coated with iron plaque.

  3. K[AsW2O9], the first member of the arsenate-tungsten bronze family: Synthesis, structure, spectroscopic and non-linear optical properties

    NASA Astrophysics Data System (ADS)

    Alekseev, Evgeny V.; Felbinger, Olivier; Wu, Shijun; Malcherek, Thomas; Depmeier, Wulf; Modolo, Giuseppe; Gesing, Thorsten M.; Krivovichev, Sergey V.; Suleimanov, Evgeny V.; Gavrilova, Tatiana A.; Pokrovsky, Lev D.; Pugachev, Alexey M.; Surovtsev, Nikolay V.; Atuchin, Victor V.

    2013-08-01

    K[AsW2O9], prepared by high-temperature solid-state reaction, is the first member of the arsenate-tungsten bronze family. The structure of K[AsW2O9] is based on a 3-dimensional (3D) oxotungstate-arsenate framework with the non-centrosymmetric P212121 space group, a=4.9747(3) Å, b=9.1780(8) Å, c=16.681(2) Å. The material was characterized using X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Raman and infrared (IR) spectroscopic techniques. The results of DSC demonstrate that this phase is stable up to 1076 K. Second harmonic generation (SHG) measurements performed on a powder sample demonstrate noticeable (0.1 of LiIO3) non-linear optical (NLO) activity.

  4. Effect of glycine substitution on the ferroelectric phase of betaine arsenate [(CH 3) 3NCH 2COO·H 3AsO 4

    NASA Astrophysics Data System (ADS)

    Dekola, T.; Ribeiro, J. L.; Klöpperpieper, A.

    2011-09-01

    The present work reports an experimental investigation on the influence of glycine (NH 2CH 2COOH) substitution in the polar properties and the critical dynamics of the molecular ferroelectric betaine arsenate, (CH 3) 3NCH 2COO·H 3AsO 4. The dielectric dispersion (20 Hz<ν<3 MHz) and the thermally induced displacement currents are investigated in detail over the extended Curie region of the system (130 K< T<100 K). The results obtained for a single crystal with nominal glycine content of 20% are analyzed, compared with those obtained for pure betaine arsenate and discussed within the scope of a phenomenological Landau model previously used to describe a system with competing ferroelectric and structural instabilities.

  5. Structure-activity relationships of pyrrole based S-nitrosoglutathione reductase inhibitors: pyrrole regioisomers and propionic acid replacement.

    PubMed

    Sun, Xicheng; Qiu, Jian; Strong, Sarah A; Green, Louis S; Wasley, Jan W F; Colagiovanni, Dorothy B; Mutka, Sarah C; Blonder, Joan P; Stout, Adam M; Richards, Jane P; Chun, Lawrence; Rosenthal, Gary J

    2011-06-15

    S-Nitrosoglutathione reductase (GSNOR) is a member of the alcohol dehydrogenase family (ADH) that regulates the levels of S-nitrosothiols (SNOs) through catabolism of S-nitrosoglutathione (GSNO). GSNO and SNOs are implicated in the pathogenesis of many diseases including those in respiratory, cardiovascular, and gastrointestinal systems. The pyrrole based N6022 was recently identified as a potent, selective, reversible, and efficacious GSNOR inhibitor which is currently undergoing clinical development. We describe here the synthesis and structure-activity relationships (SAR) of novel pyrrole based analogues of N6022 focusing on scaffold modification and propionic acid replacement. We identified equally potent and novel GSNOR inhibitors having pyrrole regioisomers as scaffolds using a structure based approach.

  6. Diacetyl and related flavorant α-Diketones: Biotransformation, cellular interactions, and respiratory-tract toxicity.

    PubMed

    Anders, M W

    2017-02-05

    Exposure to diacetyl and related α-diketones causes respiratory-tract damage in humans and experimental animals. Chemical toxicity is often associated with covalent modification of cellular nucleophiles by electrophilic chemicals. Electrophilic α-diketones may covalently modify nucleophilic arginine residues in critical proteins and, thereby, produce the observed respiratory-tract pathology. The major pathway for the biotransformation of α-diketones is reduction to α-hydroxyketones (acyloins), which is catalyzed by NAD(P)H-dependent enzymes of the short-chain dehydrogenase/reductase (SDR) and the aldo-keto reductase (AKR) superfamilies. Reduction of α-diketones to the less electrophilic acyloins is a detoxication pathway for α-diketones. The pyruvate dehydrogenase complex may play a significant role in the biotransformation of diacetyl to CO2. The interaction of toxic electrophilic chemicals with cellular nucleophiles can be predicted by the hard and soft, acids and bases (HSAB) principle. Application of the HSAB principle to the interactions of electrophilic α-diketones with cellular nucleophiles shows that α-diketones react preferentially with arginine residues. Furthermore, the respiratory-tract toxicity and the quantum-chemical reactivity parameters of diacetyl and replacement flavorant α-diketones are similar. Hence, the identified replacement flavorant α-diketones may pose a risk of flavorant-induced respiratory-tract toxicity. The calculated indices for the reaction of α-diketones with arginine support the hypothesis that modification of protein-bound arginine residues is a critical event in α-diketone-induced respiratory-tract toxicity.

  7. A detoxifying oxygen reductase in the anaerobic protozoan Entamoeba histolytica.

    PubMed

    Vicente, João B; Tran, Vy; Pinto, Liliana; Teixeira, Miguel; Singh, Upinder

    2012-09-01

    We report the characterization of a bacterial-type oxygen reductase abundant in the cytoplasm of the anaerobic protozoan parasite Entamoeba histolytica. Upon host infection, E. histolytica is confronted with various oxygen tensions in the host intestine, as well as increased reactive oxygen and nitrogen species at the site of local tissue inflammation. Resistance to oxygen-derived stress thus plays an important role in the pathogenic potential of E. histolytica. The genome of E. histolytica has four genes that encode flavodiiron proteins, which are bacterial-type oxygen or nitric oxide reductases and were likely acquired by lateral gene transfer from prokaryotes. The EhFdp1 gene has higher expression in virulent than in nonvirulent Entamoeba strains and species, hinting that the response to oxidative stress may be one correlate of virulence potential. We demonstrate that EhFdp1 is abundantly expressed in the cytoplasm of E. histolytica and that the protein levels are markedly increased (up to ~5-fold) upon oxygen exposure. Additionally, we produced fully functional recombinant EhFdp1 and demonstrated that this enzyme is a specific and robust oxygen reductase but has poor nitric oxide reductase activity. This observation represents a new mechanism of oxygen resistance in the anaerobic protozoan pathogen E. histolytica.

  8. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  9. Thioredoxin and NADP-thioredoxin reductase from cultured carrot cells

    NASA Technical Reports Server (NTRS)

    Johnson, T. C.; Cao, R. Q.; Kung, J. E.; Buchanan, B. B.

    1987-01-01

    Dark-grown carrot (Daucus carota L.) tissue cultures were found to contain both protein components of the NADP/thioredoxin system--NADP-thioredoxin reductase and the thioredoxin characteristic of heterotrophic systems, thioredoxin h. Thioredoxin h was purified to apparent homogeneity and, like typical bacterial counterparts, was a 12-kdalton (kDa) acidic protein capable of activating chloroplast NADP-malate dehydrogenase (EC 1.1.1.82) more effectively than fructose-1,6-bisphosphatase (EC 3.1.3.11). NADP-thioredoxin reductase (EC 1.6.4.5) was partially purified and found to be an arsenite-sensitive enzyme composed of two 34-kDa subunits. Carrot NADP-thioredoxin reductase resembled more closely its counterpart from bacteria rather than animal cells in acceptor (thioredoxin) specificity. Upon greening of the cells, the content of NADP-thioredoxin-reductase activity, and, to a lesser extent, thioredoxin h decreased. The results confirm the presence of a heterotrophic-type thioredoxin system in plant cells and raise the question of its physiological function.

  10. Obtaining partial purified xylose reductase from Candida guilliermondii

    PubMed Central

    Tomotani, Ester Junko; de Arruda, Priscila Vaz; Vitolo, Michele; de Almeida Felipe, Maria das Graças

    2009-01-01

    The enzymatic bioconversion of xylose into xylitol by xylose reductase (XR) is an alternative for chemical and microbiological processes. The partial purified XR was obtained by using the following three procedures: an agarose column, a membrane reactor or an Amicon Ultra-15 50K Centrifugal Filter device at yields of 40%, 7% and 67%, respectively. PMID:24031408

  11. Dissimilatory Nitrite Reductase Genes from Autotrophic Ammonia-Oxidizing Bacteria

    PubMed Central

    Casciotti, Karen L.; Ward, Bess B.

    2001-01-01

    The presence of a copper-containing dissimilatory nitrite reductase gene (nirK) was discovered in several isolates of β-subdivision ammonia-oxidizing bacteria using PCR and DNA sequencing. PCR primers Cunir3 and Cunir4 were designed based on published nirK sequences from denitrifying bacteria and used to amplify a 540-bp fragment of the nirK gene from Nitrosomonas marina and five additional isolates of ammonia-oxidizing bacteria. Amplification products of the expected size were cloned and sequenced. Alignment of the nucleic acid and deduced amino acid (AA) sequences shows significant similarity (62 to 75% DNA, 58 to 76% AA) between nitrite reductases present in these nitrifiers and the copper-containing nitrite reductase found in classic heterotrophic denitrifiers. While the presence of a nitrite reductase in Nitrosomonas europaea is known from early biochemical work, preliminary sequence data from its genome indicate a rather low similarity to the denitrifier nirKs. Phylogenetic analysis of the partial nitrifier nirK sequences indicates that the topology of the nirK tree corresponds to the 16S rRNA and amoA trees. While the role of nitrite reduction in the metabolism of nitrifying bacteria is still uncertain, these data show that the nirK gene is present in closely related nitrifying isolates from many oceanographic regions and suggest that nirK sequences retrieved from the environment may include sequences from ammonia-oxidizing bacteria. PMID:11319103

  12. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  13. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  14. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  15. Dihydrofolate reductase: A potential drug target in trypanosomes and leishmania

    NASA Astrophysics Data System (ADS)

    Zuccotto, Fabio; Martin, Andrew C. R.; Laskowski, Roman A.; Thornton, Janet M.; Gilbert, Ian H.

    1998-05-01

    Dihydrofolate reductase has successfully been used as a drug target in the area of anti-cancer, anti-bacterial and anti-malarial chemotherapy. Little has been done to evaluate it as a drug target for treatment of the trypanosomiases and leishmaniasis. A crystal structure of Leishmania major dihydrofolate reductase has been published. In this paper, we describe the modelling of Trypanosoma cruzi and Trypanosoma brucei dihydrofolate reductases based on this crystal structure. These structures and models have been used in the comparison of protozoan, bacterial and human enzymes in order to highlight the different features that can be used in the design of selective anti-protozoan agents. Comparison has been made between residues present in the active site, the accessibility of these residues, charge distribution in the active site, and the shape and size of the active sites. Whilst there is a high degree of similarity between protozoan, human and bacterial dihydrofolate reductase active sites, there are differences that provide potential for selective drug design. In particular, we have identified a set of residues which may be important for selective drug design and identified a larger binding pocket in the protozoan than the human and bacterial enzymes.

  16. The Kinetics and Inhibition of the Enzyme Methemoglobin Reductase

    ERIC Educational Resources Information Center

    Splittgerber, A. G.; And Others

    1975-01-01

    Describes an undergraduate biochemistry experiment which involves the preparation and kinetics of an oxidation-reduction enzyme system, methemoglobin reductase. A crude enzyme extract is prepared and assayed spectrophotometrically. The enzyme system obeys Michaelis-Menton kinetics with respect to both substrate and the NADH cofactor. (MLH)

  17. [Malate oxidation by mitochondrial succinate:ubiquinone-reductase].

    PubMed

    Belikova, Iu O; Kotliar, A B

    1988-04-01

    Succinate:ubiquinone reductase was shown to catalyze the oxidation of L- and D-stereoisomers of malate by artificial electron acceptors and ubiquinone. The rate of malate oxidation by succinate:ubiquinone reductase is by two orders of magnitude lower than that for the natural substrate--succinate. The values of kinetic constants for the oxidation of D- and L-stereoisomers of malate are equal to: V infinity = 0.1 mumol/min/mg protein, Km = 2 mM and V infinity = 0.05 mumol/min/mg protein, Km = 2 mM, respectively. The malate dehydrogenase activity is fully inhibited by the inhibitors of the dicarboxylate-binding site of the enzyme, i.e., N-ethylmaleimide and malonate and is practically insensitive to carboxin, a specific inhibitor of the ubiquinone-binding center. The enol form of oxaloacetate was shown to be the product of malate oxidation by succinate:ubiquinone reductase. The kinetics of inhibition of the enzyme activity by the ketone and enol forms of oxaloacetate was studied. Both forms of oxaloacetate effectively inhibit the succinate:ubiquinone reductase reaction.

  18. [Inhibition of aldose reductase by Chinese herbal medicine].

    PubMed

    Mao, X M; Zhang, J Q

    1993-10-01

    Seven Chinese herbal drugs were screened for experimental inhibition of lens aldose reductase activity, among which quercetin exhibited potent enzyme-inhibitory activities in vitro. Its IC50 value was 3.44 x 10(-7) mol/L. It may be helpful in the prophylaxis and treatment of diabetic complications.

  19. Characterization of mitochondrial thioredoxin reductase from C. elegans

    SciTech Connect

    Lacey, Brian M.; Hondal, Robert J. . E-mail: Robert.Hondal@uvm.edu

    2006-08-04

    Thioredoxin reductase catalyzes the NADPH-dependent reduction of the catalytic disulfide bond of thioredoxin. In mammals and other higher eukaryotes, thioredoxin reductases contain the rare amino acid selenocysteine at the active site. The mitochondrial enzyme from Caenorhabditis elegans, however, contains a cysteine residue in place of selenocysteine. The mitochondrial C. elegans thioredoxin reductase was cloned from an expressed sequence tag and then produced in Escherichia coli as an intein-fusion protein. The purified recombinant enzyme has a k {sub cat} of 610 min{sup -1} and a K {sub m} of 610 {mu}M using E. coli thioredoxin as substrate. The reported k {sub cat} is 25% of the k {sub cat} of the mammalian enzyme and is 43-fold higher than a cysteine mutant of mammalian thioredoxin reductase. The enzyme would reduce selenocysteine, but not hydrogen peroxide or insulin. The flanking glycine residues of the GCCG motif were mutated to serine. The mutants improved substrate binding, but decreased the catalytic rate.

  20. The polymorphisms in methylenetetrahydrofolate reductase, methionine synthase, methionine synthase reductase, and the risk of colorectal cancer.

    PubMed

    Zhou, Daijun; Mei, Qiang; Luo, Han; Tang, Bo; Yu, Peiwu

    2012-01-01

    Polymorphisms in genes involved in folate metabolism may modulate the risk of colorectal cancer (CRC), but data from published studies are conflicting. The current meta-analysis was performed to address a more accurate estimation. A total of 41 (17,552 cases and 26,238 controls), 24(8,263 cases and 12,033 controls), 12(3,758 cases and 5,646 controls), and 13 (5,511 cases and 7,265 controls) studies were finally included for the association between methylenetetrahydrofolate reductase (MTHFR) C677T and A1289C, methione synthase reductase (MTRR) A66G, methionine synthase (MTR) A2756G polymorphisms and the risk of CRC, respectively. The data showed that the MTHFR 677T allele was significantly associated with reduced risk of CRC (OR = 0.93, 95%CI 0.90-0.96), while the MTRR 66G allele was significantly associated with increased risk of CRC (OR = 1.11, 95%CI 1.01-1.18). Sub-group analysis by ethnicity revealed that MTHFR C677T polymorphism was significantly associated with reduced risk of CRC in Asians (OR = 0.80, 95%CI 0.72-0.89) and Caucasians (OR = 0.84, 95%CI 0.76-0.93) in recessive genetic model, while the MTRR 66GG genotype was found to significantly increase the risk of CRC in Caucasians (GG vs. AA: OR = 1.18, 95%CI 1.03-1.36). No significant association was found between MTHFR A1298C and MTR A2756G polymorphisms and the risk of CRC. Cumulative meta-analysis showed no particular time trend existed in the summary estimate. Probability of publication bias was low across all comparisons illustrated by the funnel plots and Egger's test. Collectively, this meta-analysis suggested that MTHFR 677T allele might provide protection against CRC in worldwide populations, while MTRR 66G allele might increase the risk of CRC in Caucasians. Since potential confounders could not be ruled out completely, further studies were needed to confirm these results.

  1. The Polymorphisms in Methylenetetrahydrofolate Reductase, Methionine Synthase, Methionine Synthase Reductase, and the Risk of Colorectal Cancer

    PubMed Central

    Zhou, Daijun; Mei, Qiang; Luo, Han; Tang, Bo; Yu, Peiwu

    2012-01-01

    Polymorphisms in genes involved in folate metabolism may modulate the risk of colorectal cancer (CRC), but data from published studies are conflicting. The current meta-analysis was performed to address a more accurate estimation. A total of 41 (17,552 cases and 26,238 controls), 24(8,263 cases and 12,033 controls), 12(3,758 cases and 5,646 controls), and 13 (5,511 cases and 7,265 controls) studies were finally included for the association between methylenetetrahydrofolate reductase (MTHFR) C677T and A1289C, methione synthase reductase (MTRR) A66G, methionine synthase (MTR) A2756G polymorphisms and the risk of CRC, respectively. The data showed that the MTHFR 677T allele was significantly associated with reduced risk of CRC (OR = 0.93, 95%CI 0.90-0.96), while the MTRR 66G allele was significantly associated with increased risk of CRC (OR = 1.11, 95%CI 1.01-1.18). Sub-group analysis by ethnicity revealed that MTHFR C677T polymorphism was significantly associated with reduced risk of CRC in Asians (OR = 0.80, 95%CI 0.72-0.89) and Caucasians (OR = 0.84, 95%CI 0.76-0.93) in recessive genetic model, while the MTRR 66GG genotype was found to significantly increase the risk of CRC in Caucasians (GG vs. AA: OR = 1.18, 95%CI 1.03-1.36). No significant association was found between MTHFR A1298C and MTR A2756G polymorphisms and the risk of CRC. Cumulative meta-analysis showed no particular time trend existed in the summary estimate. Probability of publication bias was low across all comparisons illustrated by the funnel plots and Egger's test. Collectively, this meta-analysis suggested that MTHFR 677T allele might provide protection against CRC in worldwide populations, while MTRR 66G allele might increase the risk of CRC in Caucasians. Since potential confounders could not be ruled out completely, further studies were needed to confirm these results. PMID:22719222

  2. [Respiratory synchronization and breast radiotherapy].

    PubMed

    Mège, A; Ziouèche-Mottet, A; Bodez, V; Garcia, R; Arnaud, A; de Rauglaudre, G; Pourel, N; Chauvet, B

    2016-10-01

    Adjuvant radiation therapy following breast cancer surgery continues to improve locoregional control and overall survival. But the success of highly targeted-conformal radiotherapy such as intensity-modulated techniques, can be compromised by respiratory motion. The intrafraction motion can potentially result in significant under- or overdose, and also expose organs at risk. This article summarizes the respiratory motion and its effects on imaging, dose calculation and dose delivery by radiotherapy for breast cancer. We will review the methods of respiratory synchronization available for breast radiotherapy to minimize the respiratory impact and to spare organs such as heart and lung.

  3. Stability of arsenate-bearing Fe(III)/Al(III) co-precipitates in the presence of sulfide as reducing agent under anoxic conditions.

    PubMed

    Doerfelt, Christoph; Feldmann, Thomas; Roy, Ranjan; Demopoulos, George P

    2016-05-01

    Currently, the co-precipitation of arsenate with ferric iron at molar ratios Fe(III)/As(V) ≥ 3 by lime neutralization produces tailings solids that are stable under oxic conditions. However not much is known about the stability of these hazardous co-precipitates under anoxic conditions. These can develop in tailings storage sites by the action of co-discharged reactive sulfides, organic reagent residuals or bacterial activity. The ferric matrix can then undergo reductive dissolution reactions, which could release arsenic into the pore water. Co-ions like aluminum could provide a redox-immune sink to scavenge any mobilized arsenic as a result of reduction of ferric. As such, in this work Fe(III)/As(V) = 4 and aluminum substituted Fe(III)/Al(III)/As(V) = 2/2/1 co-precipitates were produced in a mini continuous co-precipitation process circuit and subjected to excess sulfide addition under inert gas to evaluate their stability. It was found that the ferric-arsenate co-precipitate could retain up to 99% (30 mg/L in solution) of its arsenic content despite the high pH (10.5) and extremely reducing (Eh < -200 mV) environment. There was no significant reduction of arsenate and only 45% of ferric iron was reduced. Partial aluminum substitution was found to cut the amount of mobilized arsenic by 50% (down to 15 mg/L) hence mixed Fe(III)/Al(III)-arsenate co-precipitates may offer better resistance to reductive destabilization over the long term than all iron co-precipitates.

  4. SORPTION OF ARSENATE AND ARSENITE ON RUO2 X H2O: ANALYSIS OF SORBED PHASE OXIDATION STATE BY XANES IN ADVANCED PHOTON SOURCE ACTIVITY REPORT 2002

    EPA Science Inventory

    The sorption reactions of arsenate (As(V)) and arsenite (As(III)) on RuO2 x H2O were examined by X-ray Absorption Near Edge Spectroscopy (XANES) to elucidate the solid state speciation of sorbed As. At all pH values studied (pH 4-8), RuO2 x H

  5. Towards a selective adsorbent for arsenate and selenite in the presence of phosphate: Assessment of adsorption efficiency, mechanism, and binary separation factors of the chitosan-copper complex.

    PubMed

    Yamani, Jamila S; Lounsbury, Amanda W; Zimmerman, Julie B

    2016-01-01

    The potential for a chitosan-copper polymer complex to select for the target contaminants in the presence of their respective competitive ions was evaluated by synthesizing chitosan-copper beads (CCB) for the treatment of (arsenate:phosphate), (selenite:phosphate), and (selenate:sulfate). Based on work by Rhazi et al., copper (II) binds to the amine moiety on the chitosan backbone as a monodentate complex (Type I) and as a bidentate complex crosslinking two polymer chains (Type II), depending on pH and copper loading. In general, the Type I complex exists alone; however, beyond threshold conditions of pH 5.5 during synthesis and a copper loading of 0.25 mol Cu(II)/mol chitosan monomer, the Type I and Type II complexes coexist. Subsequent chelation of this chitosan-copper ligand to oxyanions results in enhanced and selective adsorption of the target contaminants in complex matrices with high background ion concentrations. With differing affinities for arsenate, selenite, and phosphate, the Type I complex favors phosphate chelation while the Type II complex favors arsenate chelation due to electrostatic considerations and selenite chelation due to steric effects. No trend was exhibited for the selenate:sulfate system possibly due to the high Ksp of the corresponding copper salts. Binary separation factors, α12, were calculated for the arsenate-phosphate and selenite-phosphate systems, supporting the mechanistic hypothesis. While, further research is needed to develop a synthesis method for the independent formation of the Type II complexes to select for target contaminants in complex matrices, this work can provide initial steps in the development of a selective adsorbent.

  6. Draft Genome Sequence of Ochrobactrum pseudogrignonense Strain CDB2, a Highly Efficient Arsenate-Resistant Soil Bacterium from Arsenic-Contaminated Cattle Dip Sites.

    PubMed

    Yang, Yiren; Yu, Xuefei; Zhang, Ren

    2013-04-18

    We report the 4.97-Mb draft genome sequence of a highly efficient arsenate-resistant bacterium, Ochrobactrum sp. strain CDB2. It contains a novel arsenic resistance (ars) operon (arsR-arsC1-ACR3-arsC2-arsH-mfs) and two non-operon-associated ars genes, arsC3 and arsB. The genome information will aid in the understanding of the arsenic resistance mechanism of this and other bacterial species.

  7. Respiratory sounds compression.

    PubMed

    Yadollahi, Azadeh; Moussavi, Zahra

    2008-04-01

    Recently, with the advances in digital signal processing, compression of biomedical signals has received great attention for telemedicine applications. In this paper, an adaptive transform coding-based method for compression of respiratory and swallowing sounds is proposed. Using special characteristics of respiratory sounds, the recorded signals are divided into stationary and nonstationary portions, and two different bit allocation methods (BAMs) are designed for each portion. The method was applied to the data of 12 subjects and its performance in terms of overall signal-to-noise ratio (SNR) values was calculated at different bit rates. The performance of different quantizers was also considered and the sensitivity of the quantizers to initial conditions has been alleviated. In addition, the fuzzy clustering method was examined for classifying the signal into different numbers of clusters and investigating the performance of the adaptive BAM with increasing the number of classes. Furthermore, the effects of assigning different numbers of bits for encoding stationary and nonstationary portions of the signal were studied. The adaptive BAM with variable number of bits was found to improve the SNR values of the fixed BAM by 5 dB. Last, the possibility of removing the training part for finding the parameters of adaptive BAMs for each individual was investigated. The results indicate that it is possible to use a predefined set of BAMs for all subjects and remove the training part completely. Moreover, the method is fast enough to be implemented for real-time application.

  8. [Acute respiratory distress syndrome].

    PubMed

    Matĕjovic, M; Novák, I; Srámek, V; Rokyta, R; Hora, P; Nalos, M

    1999-04-26

    Acute respiratory distress syndrome (ARDS) is the general term used for severe acute respiratory failure of diverse aetiology. It is associated with a high morbidity, mortality (50-70%), and financial costs. Regardless of aetiology, the basic pathogenesis of ARDS is a systemic inflammatory response leading to a diffuse inflammatory process that involves both lungs, thus causing diffuse alveolar and endothelial damage with increased pulmonary capillary permeability and excessive extravascular lung water accumulation. ARDS is commonly associated with sepsis and multiple organ failure. The clinical picture involves progressive hypoxaemia, radiographic evidence of pulmonary oedema, decreased lung compliance and pulmonary hypertension. Despite the scientific and technological progress in critical care medicine, there is no specific ARDS therapy available at the moment and its management remains supportive. Therapeutic goals include resolution of underlying conditions, maintenance of acceptable gas exchange and tissue oxygenation and prevention of iatrogenic lung injury. Many new specific therapeutic strategies have been developed, however, most of them require further scientific evaluation. The paper reviews definition, basic pathogenesis and pathophysiology of ARDS and discusses current concepts of therapeutic possibilities of ARDS.

  9. Treatment of hirsutism with 5 alpha-reductase inhibitors.

    PubMed

    Brooks, J R

    1986-05-01

    Much os the evidence gathered from studies of 5 alpha-reductase activity levels and androgen metabolism in the skin of hirsute women and the excretion of androgen metabolites by hirsute women indicates that 5 alpha-reduced androgens are probably of primary importance in hirsutism. Unfortunately, until very recently, the lack of a suitable 5 alpha-reductase inhibitor made it very difficult to adequately test the hypothesis that such an inhibitor might be useful in the treatment of hirsutism and certain other androgen-related diseases. No substance was available which had good, unambiguous activity in vivo as a 5 alpha-reductase inhibitor. A number of 4-azasteroids have now been found to possess excellent 5 alpha-reductase inhibitory activity both in vitro and in vivo. Among other properties, several of these compounds show little or no affinity for the androgen receptor of rat prostate cytosol, they attenuate the growth promoting effect of T, but not DHT, on the ventral prostate of castrated male rats, they cause a marked reduction in prostatic DHT concentration in acutely treated rats and dogs and they bring about a significant decline in prostate size in chronically treated rats and dogs. It is expected that, in the near future, one or more of these highly active 5 alpha-reductase inhibitors will be tested in the clinic as a treatment for hirsutism. The results of those studies will be awaited with a great deal of interest since they should considerably advance our understanding of this disease and possibly contribute to its control.

  10. Assimilatory nitrate reductase from the green alga Ankistrodesmus braunii.

    PubMed

    De la Rosa, M A

    1983-01-01

    Assimilatory nitrate reductase (NAD(P)H-nitrate oxidoreductase, EC 1.6.6.2) from the green alga Ankistrodesmus braunii can be purified to homogeneity by dye-ligand chromatography on blue-Sepharose. The purified enzyme, whose turnover number is 623 s-1, presents an optimum pH of 7.5 and Km values of 13 microM, 23 microM and 0.15 mM for NADH, NADPH and nitrate, respectively. The NADH-nitrate reductase activity exhibits an iso ping pong bi bi kinetic mechanism. The molecular weight of the native nitrate reductase is 467 400, while that of its subunits is 58 750. These values suggest an octameric structure for the enzyme, which has been confirmed by electron microscopy. As deduced from spectrophotometric and fluorimetric studies, the enzyme contains FAD and cytochrome b-557 as prosthetic groups. FAD is not covalently bound to the protein and is easily dissociated in diluted solutions from the enzyme. Its apparent Km value is 4 nM, indicative of a high affinity of the enzyme for FAD. The results of the quantitative analyses of prosthetic groups indicate that nitrate reductase contains four molecules of flavin, four heme irons, and two atoms of molybdenum. The three components act sequentially transferring electrons from reduced pyridine nucleotides to nitrate, thus forming a short electron transport chain along the protein. A mechanism is proposed for the redox interconversion of the nitrate reductase activity. Inactivation seems to occur by formation of a stable complex of reduced enzyme with cyanide or superoxide, while reactivation is a consequence of reoxidation of the inactive enzyme. Both reactions imply the transfer of only one electron.

  11. Measurement of nitrous oxide reductase activity in aquatic sediments

    SciTech Connect

    Miller, L.G.; Oremland, R.S.; Paulsen, S.

    1986-01-01

    Denitrification in aquatic sediments was measured by an N/sub 2/O reductase assay. Sediments consumed small added quantities of N/sub 2/O over short periods (a few hours). In experiments with sediment slurries, N/sub 2/O reductase activity was inhibited by 0/sub 2/, C/sub 2/H/sub 2/, heat treatment, and by high levels of nitrate (1 mM) or sulfide (10 mM). However, ambient levels of nitrate (<100 ..mu..M) did not influence activity, and moderate levels (about 150 ..mu..M) induced only a short lag before reductase activity began. Moderate levels of sulfide (<1 mM) had no effect on N/sub 2/O reductase activity. Nitrous oxide reductase displayed Michaelis-Menten kinetics in sediments from freshwater, estuarine, and alkaline-saline environments. An in situ assay was devised in which a solution of N/sub 2/O was injected into sealed glass cores containing intact sediment. Two estimates of net rates of denitrification in San Francisco Bay under approximated in situ conditions were 0.009 and 0.041 mmol of N/sub 2/O per m/sup 2/ per h. Addition of chlorate to inhibit denitrification in these intact-core experiments (to estimate gross rates of N/sub 2/O consumption) resulted in approximately a 14% upward revision of estimates of net rates. These results were comparable to an in situ estimate of 0.022 mmol of N/sub 2/O per m/sup 2/ per h made with the acetylene block assay.

  12. Measurement of nitrous oxide reductase activity in aquatic sediments

    USGS Publications Warehouse

    Miller, L.G.; Oremland, R.S.; Paulsen, S.

    1986-01-01

    Denitrification in aquatic sediments was measured by an N2O reductase assay. Sediments consumed small added quantities of N2O over short periods (a few hours). In experiments with sediment slurries, N2O reductase activity was inhibited by O2, C2H2, heat treatment, and by high levels of nitrate (1 mM) or sulfide (10 mM). However, ambient levels of nitrate (<100 μM) did not influence activity, and moderate levels (about 150 μM) induced only a short lag before reductase activity began. Moderate levels of sulfide (<1 mM) had no effect on N2O reductase activity. Nitrous oxide reductase displayed Michaelis-Menten kinetics in sediments from freshwater (Km = 2.17 μM), estuarine (Km = 14.5 μM), and alkaline-saline (Km = 501 μM) environments. An in situ assay was devised in which a solution of N2O was injected into sealed glass cores containing intact sediment. Two estimates of net rates of denitrification in San Francisco Bay under approximated in situ conditions were 0.009 and 0.041 mmol of N2O per m2 per h. Addition of chlorate to inhibit denitrification in these intact-core experiments (to estimate gross rates of N2O consumption) resulted in approximately a 14% upward revision of estimates of net rates. These results were comparable to an in situ estimate of 0.022 mmol of N2O per m2 per h made with the acetylene block assay.

  13. Full-scale removal of arsenate and chromate from water using a limestone and ochreous sludge mixture as a low-cost sorbent material.

    PubMed

    Cederkvist, Karin; Holm, Peter E; Jensen, Marina B

    2010-05-01

    The oxyanions arsenate (AsO4(3-)) and chromate (CrO4(2-)) are major freshwater contaminants. Arsenate is a problematic contaminant in drinking water reservoirs, and chromate limits the use of urban stormwater runoff. High-capacity, low-cost, energy-efficient treatment technologies are required for the removal of these toxic anions from freshwater sources. Using a 50-m-long dual porosity filter, with limestone as filtering grains, treating stormwater runoff from Copenhagen, Denmark, we tested if addition of the waste product ochreous sludge can improve the removal of arsenate (As) and chromate (Cr) without compromising the calcite's removal affinity fowards metallic cations. Upon on-site embedding of the ochreous sludge, removal of arsenic and chromium was improved greatly, and copper (Cu) removal remained high. Steady-state effluent concentrations were reduced from 31 to 2 microg As/L, 127 to 1.5 microg Cr/L, and 18 to 9.6 microg Cu/L upon mixing with the ochreous sludge. Limestone-ochreous sludge represents a promising low-cost oxyanion and cation sorbent operating at neutral pH without pH control.

  14. Ultrasonic assisted arsenate adsorption on solvothermally synthesized calcite modified by goethite, α-MnO2 and goethite/α-MnO2.

    PubMed

    Markovski, Jasmina S; Đokić, Veljko; Milosavljević, Milutin; Mitrić, Miodrag; Perić-Grujić, Aleksandra A; Onjia, Antonije E; Marinković, Aleksandar D

    2014-03-01

    A highly porous calcium carbonate (calcite; sorbent 1) was used as a support for modification with α-FeOOH (calcite/goethite; sorbent 2), α-MnO2 (calcite/α-MnO2; sorbent 3) and α-FeOOH/α-MnO2 (calcite/goethite/α-MnO2; sorbent 4) in order to obtain a cheap hybrid materials for simple and effective arsenate removal from aqueous solutions. The adsorption ability of synthesized adsorbents was studied as a function of functionalization methods, pH, contact time, temperature and ultrasonic treatment. Comparison of the adsorptive effectiveness of synthesized adsorbents for arsenate removal, under ultrasound treatment and classical stirring method, has shown better performance of the former one reaching maximum adsorption capacities of 1.73, 21.00, 10.36 and 41.94 mg g(-1), for sorbents 1-4, respectively. Visual MINTEQ equilibrium speciation modeling was used for prediction of pH and interfering ion influences on arsenate adsorption.

  15. Identification and characterization of 2-naphthoyl-coenzyme A reductase, the prototype of a novel class of dearomatizing reductases.

    PubMed

    Eberlein, Christian; Estelmann, Sebastian; Seifert, Jana; von Bergen, Martin; Müller, Michael; Meckenstock, Rainer U; Boll, Matthias

    2013-06-01

    The enzymatic dearomatization of aromatic ring systems by reduction represents a highly challenging redox reaction in biology and plays a key role in the degradation of aromatic compounds under anoxic conditions. In anaerobic bacteria, most monocyclic aromatic growth substrates are converted to benzoyl-coenzyme A (CoA), which is then dearomatized to a conjugated dienoyl-CoA by ATP-dependent or -independent benzoyl-CoA reductases. It was unresolved whether or not related enzymes are involved in the anaerobic degradation of environmentally relevant polycyclic aromatic hydrocarbons (PAHs). In this work, a previously unknown dearomatizing 2-naphthoyl-CoA reductase was purified from extracts of the naphthalene-degrading, sulphidogenic enrichment culture N47. The oxygen-tolerant enzyme dearomatized the non-activated ring of 2-naphthoyl-CoA by a four-electron reduction to 5,6,7,8-tetrahydro-2-naphthoyl-CoA. The dimeric 150 kDa enzyme complex was composed of a 72 kDa subunit showing sequence similarity to members of the flavin-containing 'old yellow enzyme' family. NCR contained FAD, FMN, and an iron-sulphur cluster as cofactors. Extracts of Escherichia coli expressing the encoding gene catalysed 2-naphthoyl-CoA reduction. The identified NCR is a prototypical enzyme of a previously unknown class of dearomatizing arylcarboxyl-CoA reductases that are involved in anaerobic PAH degradation; it fundamentally differs from known benzoyl-CoA reductases.

  16. Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases

    NASA Technical Reports Server (NTRS)

    Min, Tongpil; Kasahara, Hiroyuki; Bedgar, Diana L.; Youn, Buhyun; Lawrence, Paulraj K.; Gang, David R.; Halls, Steven C.; Park, HaJeung; Hilsenbeck, Jacqueline L.; Davin, Laurence B.; Lewis, Norman G.; Kang, ChulHee

    2003-01-01

    Despite the importance of plant lignans and isoflavonoids in human health protection (e.g. for both treatment and prevention of onset of various cancers) as well as in plant biology (e.g. in defense functions and in heartwood development), systematic studies on the enzymes involved in their biosynthesis have only recently begun. In this investigation, three NADPH-dependent aromatic alcohol reductases were comprehensively studied, namely pinoresinol-lariciresinol reductase (PLR), phenylcoumaran benzylic ether reductase (PCBER), and isoflavone reductase (IFR), which are involved in central steps to the various important bioactive lignans and isoflavonoids. Of particular interest was in determining how differing regio- and enantiospecificities are achieved with the different enzymes, despite each apparently going through similar enone intermediates. Initially, the three-dimensional x-ray crystal structures of both PLR_Tp1 and PCBER_Pt1 were solved and refined to 2.5 and 2.2 A resolutions, respectively. Not only do they share high gene sequence similarity, but their structures are similar, having a continuous alpha/beta NADPH-binding domain and a smaller substrate-binding domain. IFR (whose crystal structure is not yet obtained) was also compared (modeled) with PLR and PCBER and was deduced to have the same overall basic structure. The basis for the distinct enantio-specific and regio-specific reactions of PCBER, PLR, and IFR, as well as the reaction mechanism and participating residues involved (as identified by site-directed mutagenesis), are discussed.

  17. Total X-ray scattering, EXAFS, and Mössbauer spectroscopy analyses of amorphous ferric arsenate and amorphous ferric phosphate

    NASA Astrophysics Data System (ADS)

    Mikutta, Christian; Schröder, Christian; Marc Michel, F.

    2014-09-01

    Amorphous ferric arsenate (AFA, FeAsO4·xH2O) is an important As precipitate in a range of oxic As-rich environments, especially acidic sulfide-bearing mine wastes. Its structure has been proposed to consist of small polymers of single corner-sharing FeO6 octahedra (rFe-Fe ∼3.6 Å) to which arsenate is attached as a monodentate binuclear 2C complex ('chain model'). Here, we analyzed the structure of AFA and analogously prepared amorphous ferric phosphates (AFP, FePO4·xH2O) by a combination of high-energy total X-ray scattering, Fe K-edge X-ray absorption spectroscopy, and 57Fe Mössbauer spectroscopy. Pair distribution function (PDF) analysis of total X-ray scattering data revealed that the coherently scattering domain size of AFA and AFP is about 8 Å. The PDFs of AFA lacked Fe-Fe pair correlations at r ∼3.6 Å indicative of single corner-sharing FeO6 octahedra, which strongly supports a local scorodite (FeAsO4·2H2O) structure. Likewise, the PDFs and Fe K-edge extended X-ray absorption fine structure data of AFP were consistent with a local strengite (FePO4·2H2O) structure of isolated FeO6 octahedra being corner-linked to PO4 tetrahedra (rFe-P = 3.25(1) Å). Mössbauer spectroscopy analyses of AFA and AFP indicated a strong superparamagnetism. While AFA only showed a weak onset of magnetic hyperfine splitting at 5 K, magnetic ordering of AFP was completely absent at this temperature. Mössbauer spectroscopy may thus offer a convenient way to identify and quantify AFA and AFP in mineral mixtures containing poorly crystalline Fe(III)-oxyhydroxides. In summary, our results imply a close structural relationship between AFA and AFP and suggest that these amorphous materials serve as templates for the formation of scorodite and strengite (phosphosiderite) in strongly acidic low-temperature environments.

  18. Respiratory effort from the photoplethysmogram.

    PubMed

    Addison, Paul S

    2017-03-01

    The potential for a simple, non-invasive measure of respiratory effort based on the pulse oximeter signal - the photoplethysmogram or 'pleth' - was investigated in a pilot study. Several parameters were developed based on a variety of manifestations of respiratory effort in the signal, including modulation changes in amplitude, baseline, frequency and pulse transit times, as well as distinct baseline signal shifts. Thirteen candidate parameters were investigated using data from healthy volunteers. Each volunteer underwent a series of controlled respiratory effort maneuvers at various set flow resistances and respiratory rates. Six oximeter probes were tested at various body sites. In all, over three thousand pleth-based effort-airway pressure (EP) curves were generated across the various airway constrictions, respiratory efforts, respiratory rates, subjects, probe sites, and the candidate parameters considered. Regression analysis was performed to determine the existence of positive monotonic relationships between the respiratory effort parameters and resulting airway pressures. Six of the candidate parameters investigated exhibited a distinct positive relationship (p<0.001 across all probes tested) with increasing upper airway pressure repeatable across the range of respiratory rates and flow constrictions studied. These were: the three fundamental modulations in amplitude (AM-Effort), baseline (BM-Effort) and respiratory sinus arrhythmia (RSA-Effort); two pulse transit time modulations - one using a pulse oximeter probe and an ECG (P2E-Effort) and the other using two pulse oximeter probes placed at different peripheral body sites (P2-Effort); and baseline shifts in heart rate, (BL-HR-Effort). In conclusion, a clear monotonic relationship was found between several pleth-based parameters and imposed respiratory loadings at the mouth across a range of respiratory rates and flow constrictions. The results suggest that the pleth may provide a measure of changing upper

  19. Immunological approach to the regulation of nitrate reductase in Monoraphidium braunii.

    PubMed

    Díez, J; López-Ruiz, A

    1989-02-01

    The effects of different culture conditions on nitrate reductase activity and nitrate reductase protein from Monoraphidium braunii have been studied, using two different immunological techniques, rocket immunoelectrophoresis and an enzyme-linked immunosorbent assay, to determine nitrate reductase protein. The nitrogen sources ammonium and glutamine repressed nitrate reductase synthesis, while nitrite, alanine, and glutamate acted as derepressors. There was a four- to eightfold increase of nitrate reductase activity and a twofold increase of nitrate reductase protein under conditions of nitrogen starvation versus growth on nitrate. Nitrate reductase synthesis was repressed in darkness. However, when Monoraphidium was grown under heterotrophic conditions with glucose as the carbon and energy source, the synthesis of nitrate reductase was maintained. With ammonium or darkness, changes in nitrate reductase activity correlated fairly well with changes in nitrate reductase protein, indicating that in both cases loss of activity was due to repression and not to inactivation of the enzyme. Experiments using methionine sulfoximine, to inhibit ammonium assimilation, showed that ammonium per se and not a product of its metabolism was the corepressor of the enzyme. The appearance of nitrate reductase activity after transferring the cells to induction media was prevented by cycloheximide and by 6-methylpurine, although in this latter case the effect was observed only in cells preincubated with the inhibitor for 1 h before the induction period.

  20. Recominant Pinoresino-Lariciresinol Reductase, Recombinant Dirigent Protein And Methods Of Use

    DOEpatents

    Lewis, Norman G.; Davin, Laurence B.; Dinkova-Kostova, Albena T.; Fujita, Masayuki , Gang; David R. , Sarkanen; Simo , Ford; Joshua D.

    2003-10-21

    Dirigent proteins and pinoresinol/lariciresinol reductases have been isolated, together with cDNAs encoding dirigent proteins and pinoresinol/lariciresinol reductases. Accordingly, isolated DNA sequences are provided from source species Forsythia intermedia, Thuja plicata, Tsuga heterophylla, Eucommia ulmoides, Linum usitatissimum, and Schisandra chinensis, which code for the expression of dirigent proteins and pinoresinol/lariciresinol reductases. In other aspects, replicable recombinant cloning vehicles are provided which code for dirigent proteins or pinoresinol/lariciresinol reductases or for a base sequence sufficiently complementary to at least a portion of dirigent protein or pinoresinol/lariciresinol reductase DNA or RNA to enable hybridization therewith. In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding dirigent protein or pinoresinol/lariciresinol reductase. Thus, systems and methods are provided for the recombinant expression of dirigent proteins and/or pinoresinol/lariciresinol reductases.

  1. Recombinant pinoresinol/lariciresinol reductase, recombinant dirigent protein, and methods of use

    DOEpatents

    Lewis, Norman G.; Davin, Laurence B.; Dinkova-Kostova, Albena T.; Fujita, Masayuki; Gang, David R.; Sarkanen, Simo; Ford, Joshua D.

    2001-04-03

    Dirigent proteins and pinoresinol/lariciresinol reductases have been isolated, together with cDNAs encoding dirigent proteins and pinoresinol/lariciresinol reductases. Accordingly, isolated DNA sequences are provided which code for the expression of dirigent proteins and pinoresinol/lariciresinol reductases. In other aspects, replicable recombinant cloning vehicles are provided which code for dirigent proteins or pinoresinol/lariciresinol reductases or for a base sequence sufficiently complementary to at least a portion of dirigent protein or pinoresinol/lariciresinol reductase DNA or RNA to enable hybridization therewith. In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding dirigent protein or pinoresinol/lariciresinol reductase. Thus, systems and methods are provided for the recombinant expression of dirigent proteins and/or pinoresinol/lariciresinol reductases.

  2. Respiratory Effects of Passive Smoking

    PubMed Central

    Shephard, Roy J.

    1991-01-01

    The acute and chronic respiratory effects of environmental cigarette smoke (other than lung cancer) are reviewed. Effects observed are not easily explained. There is strong evidence for an increased incidence of chronic respiratory disease in children of smokers and mounting evidence that occupational and domestic exposure increases the risk of chronic obstructive lung disease in adults. Imagesp962-a PMID:21229076

  3. Respiratory diseases of global consequence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Respiratory diseases are one of the two major categories of poultry diseases that cause the most severe economic losses globally (the other being enteric disease). The economic impact of respiratory disease is both direct, from the production losses caused by primary disease and indirect from preve...

  4. Porcine Reproductive and Respiratory Syndrome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Porcine reproductive and respiratory syndrome (PRRS) is the number one disease affecting US swine. It is caused by the PRRS virus (PRRSV) and is recognized as reproductive failure of sows and respiratory problems of piglets and growing pigs. This book chapter is part of the Office of International E...

  5. [Acute respiratory distress syndrome].

    PubMed

    Hecker, M; Weigand, M A; Mayer, K

    2012-05-01

    Acute respiratory distress syndrome (ARDS) is the clinical manifestation of an acute lung injury caused by a variety of direct and indirect injuries to the lung. The cardinal clinical feature of ARDS, refractory arterial hypoxemia, is the result of protein-rich alveolar edema with impaired surfactant function, due to vascular leakage and dysfunction with consequently impaired matching of ventilation to perfusion. Better understanding of the pathophysiology of ARDS has led to the development of novel therapies, pharmacological strategies, and advances in mechanical ventilation. However, protective ventilation is the only confirmed option in ARDS management improving survival, and few other therapies have translated into improved oxygenation or reduced ventilation time. The development of innovative therapy options, such as extracorporeal membrane oxygenation, have the potential to further improve survival of this devastating disease.

  6. Ventilation and respiratory mechanics.

    PubMed

    Sheel, Andrew William; Romer, Lee M

    2012-04-01

    During dynamic exercise, the healthy pulmonary system faces several major challenges, including decreases in mixed venous oxygen content and increases in mixed venous carbon dioxide. As such, the ventilatory demand is increased, while the rising cardiac output means that blood will have considerably less time in the pulmonary capillaries to accomplish gas exchange. Blood gas homeostasis must be accomplished by precise regulation of alveolar ventilation via medullary neural networks and sensory reflex mechanisms. It is equally important that cardiovascular and pulmonary system responses to exercise be precisely matched to the increase in metabolic requirements, and that the substantial gas transport needs of both respiratory and locomotor muscles be considered. Our article addresses each of these topics with emphasis on the healthy, young adult exercising in normoxia. We review recent evidence concerning how exercise hyperpnea influences sympathetic vasoconstrictor outflow and the effect this might have on the ability to perform muscular work. We also review sex-based differences in lung mechanics.

  7. Geometry of sorbed arsenate on ferrihydrite and crystalline FeOOH: Re-evaluation of EXAFS results and topological factors in predicting sorbate geometry, and evidence for monodentate complexes

    USGS Publications Warehouse

    Waychunas , Glenn A.; Davis, James A.; Fuller, Christopher C.

    1995-01-01

    Manceau's (1995) reinterpretation of some of our EXAFS results (Waychunas et al., 1993) has been analyzed using both old and newly collected data in an attempt to clarify the nature of proposed monodentate and edge-sharing bidentate arsenate complexes on the ferrihydrite surface. It is shown that EXAFS analysis utilizing data with sufficient k-range does indicate the presence of relatively short AsFe bonds, suggestive of an edge-sharing complex as indicated by Manceau (1995). However, a variety of data analysis factors and crystal chemical considerations create doubt in this assignment. Most significantly, X-ray scattering data collected on a sample of ferrihydrite with a large density of sorbed arsenate, which should show a substantial fraction of the edge-sharing complex, does not show any such correlation within fitting uncertainty. We also suggest that it is unnecessary to invoke the presence of edge-sharing bidentate arsenate to explain the surface growth poisoning of ferrihydrite with increasing sorbed arsenate, as Manceau (1995) claims.Further, we show that a model based on the topology of close packed oxygen ions offers a clear explanation why monodentate arsenate should appear on some surfaces and not on others, and why differing AsFe distances might be observed on a single surface with a single type of complex. This model also explains why bidentate sorbed arsenate can occupy positions with consistent “tilt” angles. Without such consistency, the sorbed arsenate would be highly positionally disordered, and difficult to detect accurately via EXAFS methods.

  8. Cardiolipin Supports Respiratory Enzymes in Plants in Different Ways

    PubMed Central

    Petereit, Jakob; Katayama, Kenta; Lorenz, Christin; Ewert, Linda; Schertl, Peter; Kitsche, Andreas; Wada, Hajime; Frentzen, Margrit; Braun, Hans-Peter; Eubel, Holger

    2017-01-01

    In eukaryotes the presence of the dimeric phospholipid cardiolipin (CL) is limited to the mitochondrial membranes. It resides predominantly in the inner membrane where it interacts with components of the mitochondrial electron transfer chain. CL deficiency has previously been shown to affect abundances of the plant NADH-dehydrogenase complex and its association with dimeric cyctochrome c reductase. Using an Arabidopsis thaliana knock-out mutant for the final enzyme of CL biosynthesis we here extend current knowledge on the dependence of plant respiration on CL. By correlating respiratory enzyme abundances with enzymatic capacities in mitochondria isolated from wild type, CL deficient and CL complemented heterotrophic cell culture lines a new picture of the participation of CL in plant respiration is emerging. Data indicate a loss of a general reduction of respiratory capacity in CL deficient mitochondria which cannot solely be attributed to decreased abundances or capacities of mitochondrial electron transfer protein complexes and supercomplexes. Instead, it most likely is the result of a loss of the mobile electron carrier cytochrome c. Furthermore, enzymes of the tricarboxylic acid cycle are found to have lower maximum activities in the mutant, including the succinate dehydrogenase complex. Interestingly, abundance of the latter is not altered, indicative of a direct impact of CL deficiency on the enzymatic capacity of this electron transfer chain protein complex. PMID:28228763

  9. Cardiolipin Supports Respiratory Enzymes in Plants in Different Ways.

    PubMed

    Petereit, Jakob; Katayama, Kenta; Lorenz, Christin; Ewert, Linda; Schertl, Peter; Kitsche, Andreas; Wada, Hajime; Frentzen, Margrit; Braun, Hans-Peter; Eubel, Holger

    2017-01-01

    In eukaryotes the presence of the dimeric phospholipid cardiolipin (CL) is limited to the mitochondrial membranes. It resides predominantly in the inner membrane where it interacts with components of the mitochondrial electron transfer chain. CL deficiency has previously been shown to affect abundances of the plant NADH-dehydrogenase complex and its association with dimeric cyctochrome c reductase. Using an Arabidopsis thaliana knock-out mutant for the final enzyme of CL biosynthesis we here extend current knowledge on the dependence of plant respiration on CL. By correlating respiratory enzyme abundances with enzymatic capacities in mitochondria isolated from wild type, CL deficient and CL complemented heterotrophic cell culture lines a new picture of the participation of CL in plant respiration is emerging. Data indicate a loss of a general reduction of respiratory capacity in CL deficient mitochondria which cannot solely be attributed to decreased abundances or capacities of mitochondrial electron transfer protein complexes and supercomplexes. Instead, it most likely is the result of a loss of the mobile electron carrier cytochrome c. Furthermore, enzymes of the tricarboxylic acid cycle are found to have lower maximum activities in the mutant, including the succinate dehydrogenase complex. Interestingly, abundance of the latter is not altered, indicative of a direct impact of CL deficiency on the enzymatic capacity of this electron transfer chain protein complex.

  10. Leaching of chromated copper arsenate (CCA)-treated wood in a simulated monofill and its potential impacts to landfill leachate.

    PubMed

    Jambeck, Jenna R; Townsend, Timothy; Solo-Gabriele, Helena

    2006-07-31

    The proper end-of-life management of chromated copper arsenate (CCA)-treated wood, which contains arsenic, copper, and chromium, is a concern to the solid waste management community. Landfills are often the final repository of this waste stream, and the impacts of CCA preservative metals on leachate quality are not well understood. Monofills are a type of landfill designed and operated to dispose a single waste type, such as ash, tires, mining waste, or wood. The feasibility of managing CCA-treated wood in monofills was examined using a simulated landfill (a leaching lysimeter) that contained a mix of new and weathered CCA-treated wood. The liquid to solid ratio (LS) reached in the experiment was 0.63:1. Arsenic, chromium, and copper leached from the lysimeter at average concentrations of 42 mg/L for arsenic, 9.4 mg/L for chromium, and 2.4 mg/L for copper. Complementary batch leaching studies using deionized water were performed on similar CCA-treated wood samples at LS of 5:1 and 10:1. When results from the lysimeter were compared to the batch test results, copper and chromium leachability appeared to be reduced in the lysimeter disposal environment. Of the three metals, arsenic leached to the greatest extent and was found to have the best correlation between the batch and the lysimeter experiments.

  11. Study on arsenate tolerant and sensitive cultivars of Zea mays L.: differential detoxification mechanism and effect on nutrients status.

    PubMed

    Mallick, Shekhar; Sinam, Geetgovind; Sinha, Sarita

    2011-07-01

    The study identifies sensitive and tolerant cultivars of Zea mays L. (cv. Azad kamal (AK) and Azad uttam (AU)) towards As(V) induced stress, based upon growth biochemical parameters and metal(loid) levels in a sand culture. As(V) (μgg⁻¹ dw) accumulation was lower in cv. AK (31 ± 1 and 107 ± 30) than cv. AU (34.5 ± 3.3 and 132.6) in leaves and roots, respectively, which correlated with lower levels of malondialdehyde and H₂O₂. No definite trend of Mn, Cu, Zn, Fe, Ca, K and Na accumulation signifies that As(V) has little influence on their uptake. Total chlorophyll and protein levels increased in cv. AK and decreased in cv. AU at 7d. Higher levels of SOD and GR in cv. AK and conversely higher levels of APX, GPX and CAT in cv. AU could be a possible differential detoxification mechanism between the cultivars. The results indicate that cv. AK seems to be arsenate tolerant than cv. AU. We assure that the undertaken study does not involve humans or experimental animals and were conducted in accordance with national and institutional guidelines for the protection of human subjects and animal welfare.

  12. Raman spectroscopic identification of arsenate minerals in situ at outcrops with handheld (532 nm, 785 nm) instruments

    NASA Astrophysics Data System (ADS)

    Culka, Adam; Kindlová, Helena; Drahota, Petr; Jehlička, Jan

    2016-02-01

    Minerals are traditionally identified under field conditions by experienced mineralogists observing the basic physical properties of the samples. Under laboratory conditions, a plethora of techniques are commonly used for identification of the geological phases based on their structural and spectroscopic parameters. In this area, Raman spectrometry has become a useful tool to complement the more widely applied XRD. Today, however, there is an acute need for a technique for unambiguous in situ identification of minerals, within the geological as well as planetary/exobiology realms. With the potential for miniaturization, Raman spectroscopy can be viewed as a practical technique to achieve these goals. Here, for the first time, the successful application of handheld Raman spectrometers is demonstrated to detect and discriminate arsenic phases in the form of earthy aggregates. The Raman spectroscopic analyses of arsenate minerals were performed in situ using two handheld instruments, using 532 and 785 nm excitation. Bukovskýite, kaňkite, parascorodite, and scorodite were identified from Kaňk near Kutná Hora, CZE; kaňkite, scorodite, and zýkaite were identified at the Lehnschafter gallery in an old silver mine at Mikulov near Teplice, Bohemian Massif, CZE.

  13. Natural variations in expression of regulatory and detoxification related genes under limiting phosphate and arsenate stress in Arabidopsis thaliana

    PubMed Central

    Shukla, Tapsi; Kumar, Smita; Khare, Ria; Tripathi, Rudra D.; Trivedi, Prabodh K.

    2015-01-01

    Abiotic stress including nutrient deficiency and heavy metal toxicity severely affects plant growth, development, and productivity. Genetic variations within and in between species are one of the important factors in establishing interactions and responses of plants with the environment. In the recent past, natural variations in Arabidopsis thaliana have been used to understand plant development and response toward different stresses at genetic level. Phosphorus deficiency negatively affects plant growth and metabolism and modulates expression of the genes involved in Pi homeostasis. Arsenate, As(V), a chemical analog of Pi, is taken up by the plants via phosphate transport system. Studies suggest that during Pi deficiency, enhanced As(V) uptake leads to increased toxicity in plants. Here, the natural variations in Arabidopsis have been utilized to study the As(V) stress response under limiting Pi condition. The primary root length was compared to identify differential response of three Arabidopsis accessions (Col-0, Sij-1, and Slavi-1) under limiting Pi and As(V) stress. To study the molecular mechanisms responsible for the differential response, comprehensive expression profiling of the genes involved in uptake, detoxification, and regulatory mechanisms was carried out. Analysis suggests genetic variation-dependent regulatory mechanisms may affect differential response of Arabidopsis natural variants toward As(V) stress under limiting Pi condition. Therefore, it is hypothesized that detailed analysis of the natural variations under multiple stress conditions might help in the better understanding of the biological processes involved in stress tolerance and adaptation. PMID:26557133

  14. Establishment and succession of an epibiotic community on chromated copper arsenate-treated wood in Mediterranean waters.

    PubMed

    Karayanni, Hera; Kormas, Konstantinos Ar; Cragg, Simon; Nicolaidou, Artemis

    2010-01-01

    Colonization and succession of an epibiotic animal community on chromated copper arsenate (CCA)-treated wood were studied for 18 months in the eastern Mediterranean (Saronikos Gulf, Aegean Sea). Pine wood panels, 200 x 100 x 25 mm, impregnated with CCA at retentions of 0, 12, 24, and 48 kg m(-3) were used. The abundance or surface coverage of the most characteristic taxa (polychaetes, mollusca, crustacea bryozoa, sponges, ascidians) was measured in situ, while 12 months after submersion two panels of each retention were removed and examined in the laboratory. A total of 26 taxa were identified, among which polychaetes of the family Serpulidae dominated. The controls carried the largest number of species (17) but the lowest number of individuals. On panels with CCA retentions of 12 and 24 kg m(-3), 14 and 16 species were observed, respectively, while at 48 kg m(-3), only 9 species were found. Only the controls were affected by boring bivalves of the family Teredinidae and started to break up within 3 months of submersion. Statistically significant differences in barnacle and polychaete abundance were found between treated and untreated panels. There were no significant differences among panels treated at the three CCA loadings. Ordination by nonmetric multidimensional scaling showed a seasonal effect on the colonization of the treated panels, with the highest recruitment during the warmer months of the study.

  15. Arsenate and arsenite exposure modulate antioxidants and amino acids in contrasting arsenic accumulating rice (Oryza sativa L.) genotypes.

    PubMed

    Dave, Richa; Tripathi, Rudra Deo; Dwivedi, Sanjay; Tripathi, Preeti; Dixit, Garima; Sharma, Yogesh Kumar; Trivedi, Prabodh Kumar; Corpas, Francisco J; Barroso, Juan B; Chakrabarty, Debasis

    2013-11-15

    Carcinogenic arsenic (As) concentrations are found in rice due to irrigation with contaminated groundwater in South-East Asia. The present study evaluates comparative antioxidant property and specific amino acid accumulation in contrasting rice genotypes corresponding to differential As accumulation during arsenate (As(V)) and arsenite (As(III)) exposures. The study was conducted on two contrasting As accumulating rice genotypes selected from 303 genotype accessions, in hydroponic conditions. Maximum As accumulation was up to 1181 μg g(-1) dw in the roots of high As accumulating genotype (HARG), and 89 μg g(-1) dw in low As accumulating genotype (LARG) under As(III) exposures. The inorganic As was correlated more significantly upon exposures to As(III) than As(V). In the presence of As(V) various antioxidant enzymes guiacol peroxidase (GPX), ascorbate peroxidase (APX) and superoxide dismutase (SOD) were highly stimulated in HARG. The stress responsive amino acids proline, cysteine, glycine, glutamic acid and methionine showed higher accumulation in HARG than LARG. A clear correlation was found between stress responsive amino acids, As accumulation and antioxidative response. The comparisons between the contrasting genotypes helped to determine the significance of antioxidants and specific amino acid response to As stress.

  16. Arsenate Impact on the Metabolite Profile, Production, and Arsenic Loading of Xylem Sap in Cucumbers (Cucumis sativus L.).

    PubMed

    Uroic, M Kalle; Salaün, Pascal; Raab, Andrea; Feldmann, Jörg

    2012-01-01

    Arsenic uptake and translocation studies on xylem sap focus generally on the concentration and speciation of arsenic in the xylem. Arsenic impact on the xylem sap metabolite profile and its production during short term exposure has not been reported in detail. To investigate this, cucumbers were grown hydroponically and arsenate (As(V)) and DMA were used for plant treatment for 24 h. Total arsenic and arsenic speciation in xylem sap was analyzed including a metabolite profiling under As(V) stress. Produced xylem sap was quantified and absolute arsenic transported was determined. As(V) exposure had a significant impact on the metabolite profile of xylem sap. Four m/z values corresponding to four compounds were up-regulated, one compound down-regulated by As(V) exposure. The compound down-regulated was identified to be isoleucine. Furthermore, As(V) exposure had a significant influence on sap production, leading to a reduction of up to 96% sap production when plants were exposed to 1000 μg kg(-1) As(V). No difference to control plants was observed when plants were exposed to 1000 μg kg(-1) DMA. Absolute arsenic amount in xylem sap was the lowest at high As(V) exposure. These results show that As(V) has a significant impact on the production and metabolite profile of xylem sap. The physiological importance of isoleucine needs further attention.

  17. Evaluating the potential for environmental pollution from chromated copper arsenate (CCA)-treated wood waste: a new mass balance approach.

    PubMed

    Mercer, T G; Frostick, L E

    2014-07-15

    The potential for pollution from arsenic, chromium and copper in chromated copper arsenate (CCA) treated wood waste was assessed using two lysimeter studies. The first utilised lysimeters containing soil and CCA wood waste mulch exposed to natural conditions over a five month period. The second study used the same lysimeter setup in a regulated greenhouse setting with a manual watering regime. Woodchip, soil and leachate samples were evaluated for arsenic, chromium and copper concentrations. Resultant concentration data were used to produce mass balances, an approach thus far unused in such studies. This novel analysis revealed new patterns of mobility and distribution of the elements in the system. The results suggest that CCA wood waste tends to leach on initial exposure to a leachant and during weathering of the wood. When in contact with soil, metal(loid) transport is reduced due to complexation reactions. With higher water application or where the adsorption capacity of the soil is exceeded, the metal(loid)s are transported through the soil column as leachate. Overall, there was an unexplained loss of metal(loid)s from the system that might be attributed to volatilisation of arsenic and plant uptake. This suggests a hitherto unidentified risk to both the environment and human health.

  18. Evaluating landfill disposal of chromated copper arsenate (CCA) treated wood and potential effects on groundwater: evidence from Florida.

    PubMed

    Saxe, Jennifer K; Wannamaker, Eric J; Conklin, Scott W; Shupe, Todd F; Beck, Barbara D

    2007-01-01

    Chromated copper arsenate (CCA) treated wood has been used for more than 50 years. Recent attention has been focused on appropriate disposal of CCA-treated wood when its service life ends. Groups in the US and Europe concerned with the possibility of arsenic migration to groundwater from disposed CCA-treated wood have proposed that consumers be required to dispose of the wood as a hazardous waste, in the most protective of landfills. We examined available data for evidence of arsenic migration from unlined construction and demolition (C&D) debris landfills in Florida, where CCA-treated wood is disposed. Florida was chosen because soil, groundwater, landfill design, weather, and levels of CCA-treated wood use make the state a uniquely sensitive indicator for observing arsenic migration from CCA-treated wood disposal sites, should it occur. We developed and quality-checked a CCA-treated wood disposal model to estimate the amount of wood and associated arsenic disposed. By 2000, an estimated 13 million kg of arsenic in CCA-treated wood was disposed in Florida; however, groundwater monitoring data do not indicate that arsenic is migrating from unlined C&D landfills. Our results provide evidence that highly stringent regulation of CCA-treated wood disposal, such as treatment as a hazardous waste, is unnecessary.

  19. The X-ray crystal structure of APR-B, an atypical adenosine 5'-phosphosulfate reductase from Physcomitrella patens.

    PubMed

    Stevenson, Clare E M; Hughes, Richard K; McManus, Michael T; Lawson, David M; Kopriva, Stanislav

    2013-11-15

    Sulfonucleotide reductases catalyse the first reductive step of sulfate assimilation. Their substrate specificities generally correlate with the requirement for a [Fe4S4] cluster, where adenosine 5'-phosphosulfate (APS) reductases possess a cluster and 3'-phosphoadenosine 5'-phosphosulfate reductases do not. The exception is the APR-B isoform of APS reductase from the moss Physcomitrella patens, which lacks a cluster. The crystal structure of APR-B, the first for a plant sulfonucleotide reductase, is consistent with a preference for APS. Structural conservation with bacterial APS reductase rules out a structural role for the cluster, but supports the contention that it enhances the activity of conventional APS reductases.

  20. Dysrhythmias of the respiratory oscillator

    NASA Astrophysics Data System (ADS)

    Paydarfar, David; Buerkel, Daniel M.

    1995-03-01

    Breathing is regulated by a central neural oscillator that produces rhythmic output to the respiratory muscles. Pathological disturbances in rhythm (dysrhythmias) are observed in the breathing pattern of children and adults with neurological and cardiopulmonary diseases. The mechanisms responsible for genesis of respiratory dysrhythmias are poorly understood. The present studies take a novel approach to this problem. The basic postulate is that the rhythm of the respiratory oscillator can be altered by a variety of stimuli. When the oscillator recovers its rhythm after such perturbations, its phase may be reset relative to the original rhythm. The amount of phase resetting is dependent upon stimulus parameters and the level of respiratory drive. The long-range hypothesis is that respiratory dysrhythmias can be induced by stimuli that impinge upon or arise within the respiratory oscillator with certain combinations of strength and timing relative to the respiratory cycle. Animal studies were performed in anesthetized or decerebrate preparations. Neural respiratory rhythmicity is represented by phrenic nerve activity, allowing use of open-loop experimental conditions which avoid negative chemical feedback associated with changes in ventilation. In animal experiments, respiratory dysrhythmias can be induced by stimuli having specific combinations of strength and timing. Newborn animals readily exhibit spontaneous dysrhythmias which become more prominent at lower respiratory drives. In human subjects, swallowing was studied as a physiological perturbation of respiratory rhythm, causing a pattern of phase resetting that is characterized topologically as type 0. Computational studies of the Bonhoeffer-van der Pol (BvP) equations, whose qualitative behavior is representative of many excitable systems, supports a unified interpretation of these experimental findings. Rhythmicity is observed when the BvP model exhibits recurrent periods of excitation alternating with

  1. Pyrroline-5-Carboxylate Reductase in Soybean Nodules 1

    PubMed Central

    Chilson, Oscar P.; Kelly-Chilson, Anne E.; Schneider, Julie D.

    1992-01-01

    Characteristics of pyrroline-5-carboxylate reductase (P5CR) from Bradyrhizobium japonicum bacteroids and cultured rhizobia were compared with those of the enzyme in soybean nodule host cytosol. Reductase from host cytosol differed from that in bacteroids in: (a) the effect of pH on enzymic activity, (b) the capacity to catalyze both reduction of pyrroline-5-carboxylic acid and NAD+-dependent proline oxidation, (c) apparent affinities for pyrroline-5-carboxylic acid, and (d) sensitivities to inhibition by NADP+ and proline. The K1 for proline inhibition of P5CR in bacteroid cytosol was 1.8 millimolar. The properties of P5CR in B. japonicum and bacteroid cytosol were similar. The specific activities of P5CR in the cytosolic fractions of the nodule host and the bacteroid compartment were also comparable. PMID:16668837

  2. Characterization of 12-Oxo-Phytodienoic Acid Reductase in Corn

    PubMed Central

    Vick, Brady A.; Zimmerman, Don C.

    1986-01-01

    12-Oxo-phytodienoic acid reductase, an enzyme of the biosynthetic pathway that converts linolenic acid to jasmonic acid, has been characterized from the kernel and seedlings of corn (Zea mays L.). The molecular weight of the enzyme, estimated by gel filtration, was 54,000. Optimum enzyme activity was observed over a broad pH range, from pH 6.8 to 9.0. The enzyme had a Km of 190 micromolar for its substrate, 12-oxo-phytodienoic acid. The preferred reductant was NADPH, for which the enzyme exhibited a Km of 13 micromolar, compared with 4.2 millimolar for NADH. Reductase activity was low in the corn kernel but increased five-fold by the fifth day after germination and then gradually declined. PMID:16664582

  3. Respiratory function in handicapped children.

    PubMed

    Ishida, C; Fujita, M; Umemoto, H; Taneda, M; Sanae, N; Tazaki, T

    1990-01-01

    The aim of this study was to evaluate respiratory function of severely handicapped children. Tidal volumes and respiratory rates were determined in a total of 130 children with different clinical motor abilities. Tidal volume of non-sitters (n = 39) was significantly lower than ambulators (n = 49) or sitters (n = 42) (p less than 0.01). There was no difference in respiratory rate among the three groups. Among 45 children whose vital capacity could be determined, the tidal volumes showed a significant correlation with vital capacity (r = 0.56, p less than 0.001). Among four children whose tidal volume was less than 200 ml and respiratory rate was more than 30 cpm, blood gas analysis revealed hypoxia in three of them. The tidal volumes, therefore, would be a useful guide to estimate respiratory functions. It was concluded that the respiratory function in a non-sitter with reduced tidal volume is impaired, and that preventive measures must be taken against respiratory infection.

  4. [Properties of a nitrite reductase inhibitor protein from Pseudomonas aeruginosa].

    PubMed

    Karapetian, A V; Nalbandian, R M

    1993-08-01

    The amino acid composition and major physico-chemical properties of the "nonblue" copper protein isolated earlier from Pseudomonas aeruginosa have been determined. It has been found that the azurin oxidase, cytochrome c551 oxidase and superoxide dismutase activities of the enzyme are inhibited by this protein. The inhibition seems to be due to the protein interaction with the electron-accepting center of nitrite reductase.

  5. Stress and acute respiratory infection

    SciTech Connect

    Graham, N.M.; Douglas, R.M.; Ryan, P.

    1986-09-01

    To examine the relationship between stress and upper respiratory tract infection, 235 adults aged 14-57 years, from 94 families affiliated with three suburban family physicians in Adelaide, South Australia, participated in a six-month prospective study. High and low stress groups were identified by median splits of data collected from the Life Events Inventory, the Daily Hassles Scale, and the General Health Questionnaire, which were administered both before and during the six months of respiratory diary data collection. Using intra-study stress data, the high stress group experienced significantly more episodes (mean of 2.71 vs. 1.56, p less than 0.0005) and symptom days (mean of 29.43 vs. 15.42, p = 0.005) of respiratory illness. The two groups were almost identical with respect to age, sex, occupational status, smoking, passive smoking, exposure to air pollution, family size, and proneness to acute respiratory infection in childhood. In a multivariate model with total respiratory episodes as the dependent variable, 21% of the variance was explained, and two stress variables accounted for 9% of the explained variance. Significant, but less strong relationships were also identified between intra-study stress variables and clinically definite episodes and symptom days in both clinically definite and total respiratory episodes. Pre-study measures of stress emphasized chronic stresses and were less strongly related to measures of respiratory illness than those collected during the study. However, significantly more episodes (mean of 2.50 vs. 1.75, p less than 0.02) and symptom days (mean of 28.00 vs. 17.06, p less than 0.03) were experienced in the high stress group. In the multivariate analyses, pre-study stress remained significantly associated with total respiratory episodes nd symptom days in total and ''definite'' respiratory episodes.

  6. Aldose and aldehyde reductases : structure-function studies on the coenzyme and inhibitor-binding sites.

    SciTech Connect

    El-Kabbani, O.; Old, S. E.; Ginell, S. L.; Carper, D. A.; Biosciences Division; Monash Univ.; NIH

    1999-09-03

    PURPOSE: To identify the structural features responsible for the differences in coenzyme and inhibitor specificities of aldose and aldehyde reductases. METHODS: The crystal structure of porcine aldehyde reductase in complex with NADPH and the aldose reductase inhibitor sorbinil was determined. The contribution of each amino acid lining the coenzyme-binding site to the binding of NADPH was calculated using the Discover package. In human aldose reductase, the role of the non-conserved Pro 216 (Ser in aldehyde reductase) in the binding of coenzyme was examined by site-directed mutagenesis. RESULTS: Sorbinil binds to the active site of aldehyde reductase and is hydrogen-bonded to Trp 22, Tyr 50, His 113, and the non-conserved Arg 312. Unlike tolrestat, the binding of sorbinil does not induce a change in the side chain conformation of Arg 312. Mutation of Pro 216 to Ser in aldose reductase makes the binding of coenzyme more similar to that of aldehyde reductase. CONCLUSIONS: The participation of non-conserved active site residues in the binding of inhibitors and the differences in the structural changes required for the binding to occur are responsible for the differences in the potency of inhibition of aldose and aldehyde reductases. We report that the non-conserved Pro 216 in aldose reductase contributes to the tight binding of NADPH.

  7. Early diagnosis and management of 5 alpha-reductase deficiency.

    PubMed Central

    Odame, I; Donaldson, M D; Wallace, A M; Cochran, W; Smith, P J

    1992-01-01

    Two siblings of Pakistani origin, karyotype 46 XY, were born with predominantly female external genitalia with minute phallus, bifid scrotum, urogenital sinus, and palpable gonads. The older sibling at the age of 8 days showed an adequate testosterone response to human chorionic gonadotrophin (hCG) stimulation. The diagnosis of 5 alpha-reductase deficiency was made at age 6 years when no 5 alpha-reduced glucocorticoid metabolites were detectable in urine even after tetracosactrin (Synacthen) stimulation. In the younger sibling the diagnosis of 5 alpha-reductase deficiency was provisionally made at the early age of 3 days on the basis of high urinary tetrahydrocortisol (THF)/allotetrahydrocortisol (5 alpha-THF) ratio and this ratio increased with age confirming the diagnosis. Plasma testosterone: dihydrotestosterone (DHT) ratio before and after hCG stimulation was within normal limits at age 3 days but was raised at age 9 months. Topical DHT cream application to the external genitalia promoted significant phallic growth in both siblings and in the older sibling corrective surgery was facilitated. In prepubertal male pseudohermaphrodites with normal or raised testosterone concentrations, phallic growth in response to DHT cream treatment could be an indirect confirmation of 5 alpha-reductase deficiency. Images Figure 1 PMID:1626992

  8. Cloning and Sequence Analysis of Two Pseudomonas Flavoprotein Xenobiotic Reductases

    PubMed Central

    Blehert, David S.; Fox, Brian G.; Chambliss, Glenn H.

    1999-01-01

    The genes encoding flavin mononucleotide-containing oxidoreductases, designated xenobiotic reductases, from Pseudomonas putida II-B and P. fluorescens I-C that removed nitrite from nitroglycerin (NG) by cleavage of the nitroester bond were cloned, sequenced, and characterized. The P. putida gene, xenA, encodes a 39,702-Da monomeric, NAD(P)H-dependent flavoprotein that removes either the terminal or central nitro groups from NG and that reduces 2-cyclohexen-1-one but did not readily reduce 2,4,6-trinitrotoluene (TNT). The P. fluorescens gene, xenB, encodes a 37,441-Da monomeric, NAD(P)H-dependent flavoprotein that exhibits fivefold regioselectivity for removal of the central nitro group from NG and that transforms TNT but did not readily react with 2-cyclohexen-1-one. Heterologous expression of xenA and xenB was demonstrated in Escherichia coli DH5α. The transcription initiation sites of both xenA and xenB were identified by primer extension analysis. BLAST analyses conducted with the P. putida xenA and the P. fluorescens xenB sequences demonstrated that these genes are similar to several other bacterial genes that encode broad-specificity flavoprotein reductases. The prokaryotic flavoprotein reductases described herein likely shared a common ancestor with old yellow enzyme of yeast, a broad-specificity enzyme which may serve a detoxification role in antioxidant defense systems. PMID:10515912

  9. The existence and significance of a mitochondrial nitrite reductase.

    PubMed

    Nohl, Hans; Staniek, Katrin; Kozlov, Andrey V

    2005-01-01

    The physiological functions of nitric oxide (NO) are well established. The finding that the endothelium-derived relaxing factor (EDRF) is NO was totally unexpected. It was shown that NO is a reaction product of an enzymatically catalyzed, overall, 5-electron oxidation of guanidinium nitrogen from L-arginine followed by the release of the free radical species NO. NO is synthesized by a single protein complex supported by cofactors, coenzymes (such as tetrahydrobiopterin) and cytochrome P450. The latter can uncouple from substrate oxidation producing O2*- radicals. The research groups of Richter [Ghafourifar P, Richter C. Nitric oxide synthase activity in mitochondria. FEBS Lett 1997; 418: 291-296.] and Boveris [Giulivi C, Poderoso JJ, Boveris A. Production of nitric oxide by mitochondria. J Biol Chem 1998; 273: 11038-11043.] identified a mitochondrial NO synthase (NOS). There are, however, increasing reports demonstrating that mitochondrial NO is derived from cytosolic NOS belonging to the Ca2+-dependent enzymes. NO was thought to control cytochrome oxidase. This assumption is controversial due to the life-time of NO in biological systems (millisecond range). We found a nitrite reductase in mitochondria which is of major interest. Any increase of nitrite in the tissue which is the first oxidation product of NO, for instance following NO donors, will stimulate NO-recycling via mitochondrial nitrite reductase. In this paper, we describe the identity and the function of mitochondrial nitrite reductase and the consequences of NO-recycling in the metabolic compartment of mitochondria.

  10. Phosphoglycerate kinase acts in tumour angiogenesis as a disulphide reductase

    NASA Astrophysics Data System (ADS)

    Lay, Angelina J.; Jiang, Xing-Mai; Kisker, Oliver; Flynn, Evelyn; Underwood, Anne; Condron, Rosemary; Hogg, Philip J.

    2000-12-01

    Disulphide bonds in secreted proteins are considered to be inert because of the oxidizing nature of the extracellular milieu. An exception to this rule is a reductase secreted by tumour cells that reduces disulphide bonds in the serine proteinase plasmin. Reduction of plasmin initiates proteolytic cleavage in the kringle 5 domain and release of the tumour blood vessel inhibitor angiostatin. New blood vessel formation or angiogenesis is critical for tumour expansion and metastasis. Here we show that the plasmin reductase isolated from conditioned medium of fibrosarcoma cells is the glycolytic enzyme phosphoglycerate kinase. Recombinant phosphoglycerate kinase had the same specific activity as the fibrosarcoma-derived protein. Plasma of mice bearing fibrosarcoma tumours contained several-fold more phosphoglycerate kinase, as compared with mice without tumours. Administration of phosphoglycerate kinase to tumour-bearing mice caused an increase in plasma levels of angiostatin, and a decrease in tumour vascularity and rate of tumour growth. Our findings indicate that phosphoglycerate kinase not only functions in glycolysis but is secreted by tumour cells and participates in the angiogenic process as a disulphide reductase.

  11. The effect of quercetin and galangin on glutathione reductase.

    PubMed

    Paulíková, Helena; Berczeliová, Elena

    2005-12-01

    Quercetin and galangin can change the activity of glutathione reductase. Quercetin (a catechol structure in the B-ring) and galangin (any hydroxyl group in the B-ring) have different biological activities but, both possess high antioxidant abilities. Quercetin during the antioxidative action, is converted into an oxidized products (o-semiquinone and o-quinone), and subsequently glutathionyl adducts may be formed or SH-enzyme can be inhibited. We have tried to see whether inhibition of glutathione reductase (GR) can be influenced by preincubation of enzyme with NADPH (a creation of reduced form of enzyme, GRH(2)) and whether diaphorase activity of the enzyme is decreased by these flavonoids. The results confirmed that quercetin inhibits GRH(2) and inhibition is reduced by addition of EDTA or N-acetylcysteine. Both of flavonoids have no effect on diaphorase activity of glutathione reductase and this enzyme could increase the production of free radicals by catalysis of reduction of o-quinone during action of quercetin in vivo.

  12. Auscultation of the respiratory system

    PubMed Central

    Sarkar, Malay; Madabhavi, Irappa; Niranjan, Narasimhalu; Dogra, Megha

    2015-01-01

    Auscultation of the lung is an important part of the respiratory examination and is helpful in diagnosing various respiratory disorders. Auscultation assesses airflow through the trachea-bronchial tree. It is important to distinguish normal respiratory sounds from abnormal ones for example crackles, wheezes, and pleural rub in order to make correct diagnosis. It is necessary to understand the underlying pathophysiology of various lung sounds generation for better understanding of disease processes. Bedside teaching should be strengthened in order to avoid erosion in this age old procedure in the era of technological explosion. PMID:26229557

  13. [Travel and chronic respiratory insufficiency].

    PubMed

    Bonnet, D; Marotel, C; Miltgen, J; N'Guyen, G; Cuguilliere, A; L'Her, P

    1997-01-01

    Changes in climate, altitude and lifestyle during travel confronts patients presenting chronic respiratory insufficiency with special problems. A major challenge is related to high altitude during air travel. To limit risks, a preflight examination is necessary to ascertain respiratory status. Patients requiring oxygen therapy must ensure availability both during the flight and at the destination. Patients with asthma or chronic bronchitis must bring along a sufficient supply of usual inhalers. All patients should carry a doctor's letter describing their condition and listing medications. Using these elementary precautions, patients with chronic respiratory insufficiency can safely enjoy sightseeing and outdoor leisure activities.

  14. Assessing Respiratory System Mechanical Function.

    PubMed

    Restrepo, Ruben D; Serrato, Diana M; Adasme, Rodrigo

    2016-12-01

    The main goals of assessing respiratory system mechanical function are to evaluate the lung function through a variety of methods and to detect early signs of abnormalities that could affect the patient's outcomes. In ventilated patients, it has become increasingly important to recognize whether respiratory function has improved or deteriorated, whether the ventilator settings match the patient's demand, and whether the selection of ventilator parameters follows a lung-protective strategy. Ventilator graphics, esophageal pressure, intra-abdominal pressure, and electric impedance tomography are some of the best-known monitoring tools to obtain measurements and adequately evaluate the respiratory system mechanical function.

  15. Multiplex detection of respiratory pathogens

    DOEpatents

    McBride, Mary [Brentwood, CA; Slezak, Thomas [Livermore, CA; Birch, James M [Albany, CA

    2012-07-31

    Described are kits and methods useful for detection of respiratory pathogens (influenza A (including subtyping capability for H1, H3, H5 and H7 subtypes) influenza B, parainfluenza (type 2), respiratory syncytial virus, and adenovirus) in a sample. Genomic sequence information from the respiratory pathogens was analyzed to identify signature sequences, e.g., polynucleotide sequences useful for confirming the presence or absence of a pathogen in a sample. Primer and probe sets were designed and optimized for use in a PCR based, multiplexed Luminex assay to successfully identify the presence or absence of pathogens in a sample.

  16. The Chilliwack Respiratory Survey, 1963

    PubMed Central

    Anderson, Donald O.; Ferris, Benjamin G.; Davis, T. W.

    1965-01-01

    In order to ascertain the prevalence of chronic respiratory disease in residents of a rural town and to determine the relative importance of tobacco smoking and air pollution, a survey was conducted of 726 persons living at Chilliwack, British Columbia, in May and June, 1963. Over 95% of a random sample of adults was interviewed and performed simple tests of respiratory function. The sample was selected from a commercial census. An analysis of the demographic characteristics of the sample indicated that the group, aged 25 to 74 years, was reasonably representative for detailed study of chronic respiratory disease. PMID:14289136

  17. Catalytic mechanism and substrate selectivity of aldo-keto reductases: insights from structure-function studies of Candida tenuis xylose reductase.

    PubMed

    Kratzer, Regina; Wilson, David K; Nidetzky, Bernd

    2006-09-01

    Aldo-keto reductases (AKRs) constitute a large protein superfamily of mainly NAD(P)-dependent oxidoreductases involved in carbonyl metabolism. Catalysis is promoted by a conserved tetrad of active site residues (Tyr, Lys, Asp and His). Recent results of structure-function relationship studies for xylose reductase (AKR2B5) require an update of the proposed catalytic mechanism. Electrostatic stabilization by the epsilon-NH3+ group of Lys is a key source of catalytic power of xylose reductase. A molecular-level analysis of the substrate binding pocket of xylose reductase provides a case of how a very broadly specific AKR achieves the requisite selectivity for its physiological substrate and could serve as the basis for the design of novel reductases with improved specificities for biocatalytic applications.

  18. Respiratory chain proteins.

    PubMed

    Kadenbach, B; Schneyder, B; Mell, O; Stroh, S; Reimann, A

    1991-01-01

    Mammalian mitochondrial DNA codes for 13 proteins, which are all components of energy transducing enzyme complexes of the respiratory chain, i.e. the complexes which translocate protons across the inner mitochondrial membrane. The number of subunits of these enzyme complexes increase with increasing evolutionary stage of the organism. The additional nuclear coded subunits of the enzyme complexes from higher organisms are involved in the regulation of respiration, as demonstrated by the influence of intraliposomal ATP and ADP on the reconstituted cytochrome c oxidase (COX) from bovine heart. This regulation is not found with the reconstituted enzyme from P. denitrificans, which lacks the nuclear coded subunits. Some of the nuclear coded subunits occur in tissue-specific isoforms, as reported for COX and NADH dehydrogenase. Tissue-specific regulation of COX activity is also demonstrated by the differential effects of intraliposomal ADP on the kinetics of reconstituted COX from bovine liver and heart, which differ in subunits VIa, VIIa and VIII. At least 3 different COX isozymes occur in bovine liver, heart or skeletal muscle and smooth muscle. An evolutionary relationship between COX subunits VIa and VIc and between VIIa and VIIb is suggested based on the crossreactivity of monoclonal antibodies, amino acid sequence homology and hybridization at low stringency of PCR-amplified cDNAs for subunits VIa-1, VIa-h and VIc from the rat.

  19. Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans.

    PubMed

    ter Beek, Josy; Krause, Nils; Ädelroth, Pia

    2016-01-01

    Variant nomenclature: the variants were made in the NorB subunit if not indicated by the superscript c, which are variants in the NorC subunit (e.g. E122A = exchange of Glu-122 in NorB for an Ala, E71cD; exchange of Glu-71 in NorC for an Asp). Bacterial NO reductases (NORs) are integral membrane proteins from the heme-copper oxidase superfamily. Most heme-copper oxidases are proton-pumping enzymes that reduce O2 as the last step in the respiratory chain. With electrons from cytochrome c, NO reductase (cNOR) from Paracoccus (P.) denitrificans reduces NO to N2O via the following reaction: 2NO+2e-+2H+→N2O+H2O. Although this reaction is as exergonic as O2-reduction, cNOR does not contribute to the electrochemical gradient over the membrane. This means that cNOR does not pump protons and that the protons needed for the reaction are taken from the periplasmic side of the membrane (since the electrons are donated from this side). We previously showed that the P. denitrificans cNOR uses a single defined proton pathway with residues Glu-58 and Lys-54 from the NorC subunit at the entrance. Here we further strengthened the evidence in support of this pathway. Our further aim was to define the continuation of the pathway and the immediate proton donor for the active site. To this end, we investigated the region around the calcium-binding site and both propionates of heme b3 by site directed mutagenesis. Changing single amino acids in these areas often had severe effects on cNOR function, with many variants having a perturbed active site, making detailed analysis of proton transfer properties difficult. Our data does however indicate that the calcium ligation sphere and the region around the heme b3 propionates are important for proton transfer and presumably contain the proton donor. The possible evolutionary link between the area for the immediate donor in cNOR and the proton loading site (PLS) for pumped protons in oxygen-reducing heme-copper oxidases is discussed.

  20. Biochemical and biophysical characterization of succinate: quinone reductase from Thermus thermophilus.

    PubMed

    Kolaj-Robin, Olga; O'Kane, Sarah R; Nitschke, Wolfgang; Léger, Christophe; Baymann, Frauke; Soulimane, Tewfik

    2011-01-01

    Enzymes serving as respiratory complex II belong to the succinate:quinone oxidoreductases superfamily that comprises succinate:quinone reductases (SQRs) and quinol:fumarate reductases. The SQR from the extreme thermophile Thermus thermophilus has been isolated, identified and purified to homogeneity. It consists of four polypeptides with apparent molecular masses of 64, 27, 14 and 15kDa, corresponding to SdhA (flavoprotein), SdhB (iron-sulfur protein), SdhC and SdhD (membrane anchor proteins), respectively. The existence of [2Fe-2S], [4Fe-4S] and [3Fe-4S] iron-sulfur clusters within the purified protein was confirmed by electron paramagnetic resonance spectroscopy which also revealed a previously unnoticed influence of the substrate on the signal corresponding to the [2Fe-2S] cluster. The enzyme contains two heme b cofactors of reduction midpoint potentials of -20mV and -160mV for b(H) and b(L), respectively. Circular dichroism and blue-native polyacrylamide gel electrophoresis revealed that the enzyme forms a trimer with a predominantly helical fold. The optimum temperature for succinate dehydrogenase activity is 70°C, which is in agreement with the optimum growth temperature of T. thermophilus. Inhibition studies confirmed sensitivity of the enzyme to the classical inhibitors of the active site, as there are sodium malonate, sodium diethyl oxaloacetate and 3-nitropropionic acid. Activity measurements in the presence of the semiquinone analog, nonyl-4-hydroxyquinoline-N-oxide (NQNO) showed that the membrane part of the enzyme is functionally connected to the active site. Steady-state kinetic measurements showed that the enzyme displays standard Michaelis-Menten kinetics at a low temperature (30°C) with a K(M) for succinate of 0.21mM but exhibits deviation from it at a higher temperature (70°C). This is the first example of complex II with such a kinetic behavior suggesting positive cooperativity with k' of 0.39mM and Hill coefficient of 2.105. While the crystal

  1. Methionine Sulfoxide Reductases Are Essential for Virulence of Salmonella Typhimurium

    PubMed Central

    Rouf, Syed Fazle; Kitowski, Vera; Böhm, Oliver M.; Rhen, Mikael; Jäger, Timo; Bange, Franz-Christoph

    2011-01-01

    Production of reactive oxygen species represents a fundamental innate defense against microbes in a diversity of host organisms. Oxidative stress, amongst others, converts peptidyl and free methionine to a mixture of methionine-S- (Met-S-SO) and methionine-R-sulfoxides (Met-R-SO). To cope with such oxidative damage, methionine sulfoxide reductases MsrA and MsrB are known to reduce MetSOs, the former being specific for the S-form and the latter being specific for the R-form. However, at present the role of methionine sulfoxide reductases in the pathogenesis of intracellular bacterial pathogens has not been fully detailed. Here we show that deletion of msrA in the facultative intracellular pathogen Salmonella (S.) enterica serovar Typhimurium increased susceptibility to exogenous H2O2, and reduced bacterial replication inside activated macrophages, and in mice. In contrast, a ΔmsrB mutant showed the wild type phenotype. Recombinant MsrA was active against free and peptidyl Met-S-SO, whereas recombinant MsrB was only weakly active and specific for peptidyl Met-R-SO. This raised the question of whether an additional Met-R-SO reductase could play a role in the oxidative stress response of S. Typhimurium. MsrC is a methionine sulfoxide reductase previously shown to be specific for free Met-R-SO in Escherichia (E.) coli. We tested a ΔmsrC single mutant and a ΔmsrBΔmsrC double mutant under various stress conditions, and found that MsrC is essential for survival of S. Typhimurium following exposure to H2O2, as well as for growth in macrophages, and in mice. Hence, this study demonstrates that all three methionine sulfoxide reductases, MsrA, MsrB and MsrC, facilitate growth of a canonical intracellular pathogen during infection. Interestingly MsrC is specific for the repair of free methionine sulfoxide, pointing to an important role of this pathway in the oxidative stress response of Salmonella Typhimurium. PMID:22073230

  2. Kinetic characteristics of ZENECA ZD5522, a potent inhibitor of human and bovine lens aldose reductase.

    PubMed

    Cook, P N; Ward, W H; Petrash, J M; Mirrlees, D J; Sennitt, C M; Carey, F; Preston, J; Brittain, D R; Tuffin, D P; Howe, R

    1995-04-18

    Aldose reductase (aldehyde reductase 2) catalyses the conversion of glucose to sorbitol, and methylglyoxal to acetol. Treatment with aldose reductase inhibitors (ARIs) is a potential approach to decrease the development of diabetic complications. The sulphonylnitromethanes are a recently discovered class of aldose reductase inhibitors, first exemplified by ICI215918. We now describe enzyme kinetic characterization of a second sulphonylnitromethane, 3',5'-dimethyl-4'-nitromethylsulphonyl-2-(2-tolyl)acetanilide (ZD5522), which is at least 10-fold more potent against bovine lens aldose reductase in vitro and which also has a greater efficacy for reduction of rat nerve sorbitol levels in vivo (ED95 = 2.8 mg kg-1 for ZD5522 and 20 mg kg-1 for ICI 215918). ZD5522 follows pure noncompetitive kinetics against bovine lens aldose reductase when either glucose or methylglyoxal is varied (K(is) = K(ii) = 7.2 and 4.3 nM, respectively). This contrasts with ICI 215918 which is an uncompetitive inhibitor (K(ii) = 100 nM) of bovine lens aldose reductase when glucose is varied. Against human recombinant aldose reductase, ZD5522 displays mixed noncompetitive kinetics with respect to both substrates (K(is) = 41 nM, K(ii) = 8 nM with glucose and K(is) = 52 nM, K(ii) = 3.8 nM with methylglyoxal). This is the first report of the effects of a sulphonylnitromethane on either human aldose reductase or utilization of methylglyoxal. These results are discussed with reference to a Di Iso Ordered Bi Bi mechanism for aldose reductase, where the inhibitors compete with binding of both the aldehyde substrate and alcohol product. This model may explain why aldose reductase inhibitors follow noncompetitive or uncompetitive kinetics with respect to aldehyde substrates, and X-ray crystallography paradoxically locates an ARI within the substrate binding site. Aldehyde reductase (aldehyde reductase 1) is closely related to aldose reductase. Inhibition of bovine kidney aldehyde reductase by ZD5522

  3. Middle East Respiratory Syndrome (MERS)

    MedlinePlus

    ... also been found in camels and in one bat. While it is believed to come from animals, ... Prevention. Middle East Respiratory Syndrome (MERS): Frequently Asked Questions and Answers. Updated December 2, 2015. www.cdc. ...

  4. How Is Respiratory Failure Treated?

    MedlinePlus

    ... to treat the underlying cause of the condition. Oxygen Therapy and Ventilator Support If you have respiratory ... mask that fits over your nose and mouth. Oxygen Therapy The image shows how a nasal cannula ...

  5. Adsorption and desorption of arsenate on sandy sediments from contaminated and uncontaminated saturated zones: Kinetic and equilibrium modeling.

    PubMed

    Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Dunne, Aislinn; Tran, Tiffany; Yang, Chao; Lam, Jacquelyn R; Reynolds, Matthew D; Davis, James A; Jay, Jennifer A

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites.

  6. Behavioural and Physiological Responses of Gammarus pulex Exposed to Cadmium and Arsenate at Three Temperatures: Individual and Combined Effects

    PubMed Central

    Vellinger, Céline; Felten, Vincent; Sornom, Pascal; Rousselle, Philippe; Beisel, Jean-Nicolas; Usseglio-Polatera, Philippe

    2012-01-01

    This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and15°C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na+] and [Cl−] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na+] and [Cl−] while AsV alone had a weak impact only on [Cl−]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as ‘additive’ for all the tested binary mixtures and temperatures (except for the lowest combination at 10°C considered as “antagonistic”). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl−] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na+] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity

  7. Arsenic (+ 3 oxidation state) methyltransferase genotype affects steady-state distribution and clearance of arsenic in arsenate-treated mice

    SciTech Connect

    Hughes, Michael F.; Edwards, Brenda C.; Herbin-Davis, Karen M.; Saunders, Jesse; Styblo, Miroslav; Thomas, David J.

    2010-12-15

    Arsenic (+ 3 oxidation state) methyltransferase (As3mt) catalyzes formation of mono-, di-, and tri-methylated metabolites of inorganic arsenic. Distribution and retention of arsenic were compared in adult female As3mt knockout mice and wild-type C57BL/6 mice using a regimen in which mice received daily oral doses of 0.5 mg of arsenic as arsenate per kilogram of body weight. Regardless of genotype, arsenic body burdens attained steady state after 10 daily doses. At steady state, arsenic body burdens in As3mt knockout mice were 16 to 20 times greater than in wild-type mice. During the post dosing clearance period, arsenic body burdens declined in As3mt knockout mice to {approx} 35% and in wild-type mice to {approx} 10% of steady-state levels. Urinary concentration of arsenic was significantly lower in As3mt knockout mice than in wild-type mice. At steady state, As3mt knockout mice had significantly higher fractions of the body burden of arsenic in liver, kidney, and urinary bladder than did wild-type mice. These organs and lung had significantly higher arsenic concentrations than did corresponding organs from wild-type mice. Inorganic arsenic was the predominant species in tissues of As3mt knockout mice; tissues from wild-type mice contained mixtures of inorganic arsenic and its methylated metabolites. Diminished capacity for arsenic methylation in As3mt knockout mice prolongs retention of inorganic arsenic in tissues and affects whole body clearance of arsenic. Altered retention and tissue tropism of arsenic in As3mt knockout mice could affect the toxic or carcinogenic effects associated with exposure to this metalloid or its methylated metabolites.

  8. Development of a set of simple bacterial biosensors for quantitative and rapid measurements of arsenite and arsenate in potable water.

    PubMed

    Stocker, Judith; Balluch, Denisa; Gsell, Monika; Harms, Hauke; Feliciano, Jessika; Daunert, Sylvia; Malik, Khurseed A; van der Meer, Jan Roelof

    2003-10-15

    Testing for arsenic pollution is commonly performed with chemical test kits of unsatisfying accuracy. Bacterial biosensors are an interesting alternative as they are easily produced, simple, and highly accurate devices. Here, we describe the development of a set of bacterial biosensors based on a nonpathogenic laboratory strain of Escherichia coli, the natural resistance mechanism of E. coli against arsenite and arsenate, and three reporter proteins: bacterial luciferase, beta-galactosidase and Green Fluorescent Protein (GFP). The biosensors were genetically optimized to reduce background expression in the absence of arsenic. In calibration experiments with the biosensors and arsenite-amended potable water, arsenite concentrations at 4 microg of As/L (0.05 microM) were routinely and accurately measured. The currently most quantitative system expressed the bacterial luciferase as reporter protein, responding proportional with a concentration range between 8 and 80 microg of As/L. Sensor cells could be stored as frozen batches, resuspended in plain media, and exposed to the aqueous test sample, and light emission was measured after 30-min incubation. Field testing for arsenite was achieved with a system that contained beta-galactosidase, producing a visible blue color at arsenite concentrations above 8 microg/L. For this sensor, a protocol was developed in which the sensor cells were dried on a paper strip and placed in the aqueous test solution for 30 min after which time color development was allowed to take place. The GFP sensor showed good potential for continuous rather than end point measurements. In all cases, growth of the biosensors and production of the strip test was achieved by very simple means with common growth media, and quality control of the sensors was performed by isolating the respective plasmids with the genetic constructs according to simple standard genetic technologies. Therefore, the biosensor cells and protocols may offer a realistic

  9. Assessing the current and future impacts of the disposal of chromated copper arsenate-treated wood in unlined landfills.

    PubMed

    Hawley, Elisabeth L; Kresic, Neven; Wright, Alexandra P; Kavanaugh, Michael C

    2009-03-01

    Several states have recently considered altering disposal requirements for chromated copper arsenate (CCA)-treated wood waste, particularly Florida, where CCA-treated wood waste is disposed in unlined construction and demolition (C&D) debris and Class III municipal solid waste (MSW) landfills. The primary concern is the potential for CCA-treated wood waste to elevate arsenic levels in groundwater downgradient of the disposal sites. To address this concern, we evaluated the impact of past disposal practices of these wastes in unlined Florida C&D and Class III landfills by conducting a statistical analysis of two sets of groundwater data compiled by the Florida Department of Environmental Protection (FDEP). The databases contain water quality data from C&D and Class III landfills in Florida covering 15 yr of record from February 1992 through February 2007 and together provide the most complete datasets to evaluate this issue. Comparative statistics of the different population groups in the databases showed that the arithmetic mean concentrations of total arsenic were in most cases higher in background wells than in wells downgradient of the landfills. The statistical analysis indicates that past disposal of CCA-treated wood in C&D and Class III landfills in Florida has not increased arsenic levels downgradient of the landfills. Policy decisions regarding the continued disposal of CCA-treated wood waste as a nonhazardous waste in unlined landfills must therefore be based on a scientifically sound assessment of potential future impacts. Quantitative predictions of future impacts are difficult and pose several scientific challenges. Therefore, future management decisions should be based on a more accurate and comprehensive risk analysis that assesses the risks and benefits of different alternatives and takes into account the natural attenuation capacity of soils and aquifer solids for arsenic and the practical limitations of managing this waste stream as a hazardous

  10. Chromium on the Hands of Children After Playing in Playgrounds Built from Chromated Copper Arsenate (CCA)–Treated Wood

    PubMed Central

    Hamula, Camille; Wang, Zhongwen; Zhang, Hongquan; Kwon, Elena; Li, Xing-Fang; Gabos, Stephan; Le, X. Chris

    2006-01-01

    Children’s exposure to arsenic and chromium from playground equipment constructed with chromated copper arsenate (CCA)–treated wood is a potential concern because of children’s hand-to-mouth activity. However, there exists no direct measure of Cr levels on the hands of children after playing in such playgrounds. In this study we measured both soluble and total Cr on the hands of 139 children playing in playgrounds, eight of which were constructed with CCA-treated wood and eight of which were not. Children’s age and duration of play were recorded. The hands of each child were washed after play with 150 mL deionized water, which was collected in a bag and subsequently underwent analysis of Cr and 20 other elements, using inductively coupled plasma mass spectrometry. Total average Cr on the hands of 63 children who played in CCA playgrounds was 1,112 ± 1,089 ng (median, 688; range 78–5,875). Total average Cr on the hands of 64 children who played in non-CCA playgrounds was 652 ± 586 ng (median, 492; range 61–3,377). The difference between the two groups is statistically significant (p < 0.01). Cr levels were highly correlated to both Cu (r = 0.672) and As (r = 0.736) levels in CCA playgrounds (p ≤ 0.01), but not non-CCA playgrounds (r = 0.252 and 0.486 for Cu and As, respectively). Principal-component analysis indicates that Cr, Cu, and As are more closely grouped together in CCA than in non-CCA playgrounds. These results suggest that the elevated levels of Cr and As on children’s hands are due to direct contact with CCA wood. PMID:16507472

  11. Chromium on the hands of children after playing in playgrounds built from chromated copper arsenate (CCA)-treated wood.

    PubMed

    Hamula, Camille; Wang, Zhongwen; Zhang, Hongquan; Kwon, Elena; Li, Xing-Fang; Gabos, Stephan; Le, X Chris

    2006-03-01

    Children's exposure to arsenic and chromium from playground equipment constructed with chromated copper arsenate (CCA)-treated wood is a potential concern because of children's hand-to-mouth activity. However, there exists no direct measure of Cr levels on the hands of children after playing in such playgrounds. In this study we measured both soluble and total Cr on the hands of 139 children playing in playgrounds, eight of which were constructed with CCA-treated wood and eight of which were not. Children's age and duration of play were recorded. The hands of each child were washed after play with 150 mL deionized water, which was collected in a bag and subsequently underwent analysis of Cr and 20 other elements, using inductively coupled plasma mass spectrometry. Total average Cr on the hands of 63 children who played in CCA playgrounds was 1,112 +/- 1,089 ng (median, 688; range 78-5,875). Total average Cr on the hands of 64 children who played in non-CCA playgrounds was 652 +/- 586 ng (median, 492; range 61-3,377). The difference between the two groups is statistically significant (p < 0.01). Cr levels were highly correlated to both Cu (r = 0.672) and As (r = 0.736) levels in CCA playgrounds (p < or = 0.01), but not non-CCA playgrounds (r = 0.252 and 0.486 for Cu and As, respectively). Principal-component analysis indicates that Cr, Cu, and As are more closely grouped together in CCA than in non-CCA playgrounds. These results suggest that the elevated levels of Cr and As on children's hands are due to direct contact with CCA wood.

  12. Dissimilatory Arsenate Reduction and In Situ Microbial Activities and Diversity in Arsenic-rich Groundwater of Chianan Plain, Southwestern Taiwan.

    PubMed

    Das, Suvendu; Liu, Chia-Chuan; Jean, Jiin-Shuh; Liu, Tsunglin

    2016-02-01

    Although dissimilatory arsenic reduction (DAsR) has been recognized as an important process for groundwater arsenic (As) enrichment, its characterization and association with in situ microbial activities and diversity in As-rich groundwater is barely studied. In this work, we collected As-rich groundwater at depths of 23, 300, and 313 m, respectively, from Yenshui-3, Budai-Shinwen, and Budai-4 of Chianan plain, southwestern Taiwan, and conducted incubation experiments using different electron donors, acceptors, and sulfate-reducing bacterial inhibitor (tungstate) to characterize DAsR. Moreover, bacterial diversity was evaluated using 454-pyrosequencing targeting bacterial 16S rRNAs. MPN technique was used to enumerate microorganisms with different in situ metabolic functions. The results revealed that DAsR in groundwater of Chianan plain was a biotic phenomenon (as DAsR was totally inhibited by filter sterilization), enhanced by the type of electron donor (in this case, lactate enhanced DAsR but acetate and succinate did not), and limited by the availability of arsenate. In addition to oxidative recycling of As(III), dissolution of As(V)-saturated manganese and iron minerals by indigenous dissimilatory Mn(IV)- and Fe(III)-reducing bacteria, and abiotic oxidation of As(III) with Mn(IV) regenerated As(V) in the groundwater. Sulfate-respiring bacteria contributed 7.4 and 28.2 % to the observed DAsR in groundwater of Yinshui-3 and Budai-Shinwen, respectively, whereas their contribution was negligible in groundwater of Budai-4. A noticeable variation in dominant genera Acinetobacter and Bacillus was observed within the groundwater. Firmicutes dominated in highly As-rich groundwater of Yenshui-3, whereas Proteobacteria dominated in comparatively less As-rich groundwater of Budai-Shinwen and Budai 4.

  13. Climate Change and Respiratory Infections.

    PubMed

    Mirsaeidi, Mehdi; Motahari, Hooman; Taghizadeh Khamesi, Mojdeh; Sharifi, Arash; Campos, Michael; Schraufnagel, Dean E

    2016-08-01

    The rate of global warming has accelerated over the past 50 years. Increasing surface temperature is melting glaciers and raising the sea level. More flooding, droughts, hurricanes, and heat waves are being reported. Accelerated changes in climate are already affecting human health, in part by altering the epidemiology of climate-sensitive pathogens. In particular, climate change may alter the incidence and severity of respiratory infections by affecting vectors and host immune responses. Certain respiratory infections, such as avian influenza and coccidioidomycosis, are occurring in locations previously unaffected, apparently because of global warming. Young children and older adults appear to be particularly vulnerable to rapid fluctuations in ambient temperature. For example, an increase in the incidence in childhood pneumonia in Australia has been associated with sharp temperature drops from one day to the next. Extreme weather events, such as heat waves, floods, major storms, drought, and wildfires, are also believed to change the incidence of respiratory infections. An outbreak of aspergillosis among Japanese survivors of the 2011 tsunami is one such well-documented example. Changes in temperature, precipitation, relative humidity, and air pollution influence viral activity and transmission. For example, in early 2000, an outbreak of Hantavirus respiratory disease was linked to a local increase in the rodent population, which in turn was attributed to a two- to threefold increase in rainfall before the outbreak. Climate-sensitive respiratory pathogens present challenges to respiratory health that may be far greater in the foreseeable future.

  14. Surveillance for emerging respiratory viruses.

    PubMed

    Al-Tawfiq, Jaffar A; Zumla, Alimuddin; Gautret, Philippe; Gray, Gregory C; Hui, David S; Al-Rabeeah, Abdullah A; Memish, Ziad A

    2014-10-01

    Several new viral respiratory tract infectious diseases with epidemic potential that threaten global health security have emerged in the past 15 years. In 2003, WHO issued a worldwide alert for an unknown emerging illness, later named severe acute respiratory syndrome (SARS). The disease caused by a novel coronavirus (SARS-CoV) rapidly spread worldwide, causing more than 8000 cases and 800 deaths in more than 30 countries with a substantial economic impact. Since then, we have witnessed the emergence of several other viral respiratory pathogens including influenza viruses (avian influenza H5N1, H7N9, and H10N8; variant influenza A H3N2 virus), human adenovirus-14, and Middle East respiratory syndrome coronavirus (MERS-CoV). In response, various surveillance systems have been developed to monitor the emergence of respiratory-tract infections. These include systems based on identification of syndromes, web-based systems, systems that gather health data from health facilities (such as emergency departments and family doctors), and systems that rely on self-reporting by patients. More effective national, regional, and international surveillance systems are required to enable rapid identification of emerging respiratory epidemics, diseases with epidemic potential, their specific microbial cause, origin, mode of acquisition, and transmission dynamics.

  15. Respiratory manifestations in endocrine diseases

    PubMed Central

    LENCU, CODRUŢA; ALEXESCU, TEODORA; PETRULEA, MIRELA; LENCU, MONICA

    2016-01-01

    The control mechanisms of respiration as a vital function are complex: voluntary – cortical, and involuntary – metabolic, neural, emotional and endocrine. Hormones and hypothalamic neuropeptides (that act as neurotrasmitters and neuromodulators in the central nervous system) play a role in the regulation of respiration and in bronchopulmonary morphology. This article presents respiratory manifestations in adult endocrine diseases that evolve with hormone deficit or hypersecretion. In hyperthyroidism, patients develop ventilation disorders, obstructive and central sleep apnea, and pleural collection. The respiratory abnormalities in hyperthyroidism as a result of the hypermetabolic action of thyroid hormones are hyperventilation, myopathy and cardiovascular involvement; recent studies have reported pulmonary arterial hypertension in Graves’ disease, as a result of the association of several mechanisms. Thyroid hypertrophy can induce through compression of the upper airways dyspnea, stridor, wheezing and cough. The respiratory disorders in acromegaly are ventilatory dysfunction and sleep apnea, which contribute to an unfavorable evolution of the disease. Respiratory changes in parathyroid, adrenal and reproductive system diseases have been described. Respiratory disorders should be recognized, investigated and monitored by medical practitioners of various specialties (family physicians, internists, endocrinologists, pneumologists, cardiologists). They are frequently severe, causing an unfavorable evolution of the associated endocrine and respiratory disease. PMID:27857512

  16. Structural characterization of poorly-crystalline scorodite, iron(III)-arsenate co-precipitates and uranium mill neutralized raffinate solids using X-ray absorption fine structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, N.; Jiang, D. T.; Cutler, J.; Kotzer, T.; Jia, Y. F.; Demopoulos, G. P.; Rowson, J. W.

    2009-06-01

    X-ray absorption fine structure (XAFS) is used to characterize the mineralogy of the iron(III)-arsenate(V) precipitates produced during the raffinate (aqueous effluent) neutralization process at the McClean Lake uranium mill in northern Saskatchewan, Canada. To facilitate the structural characterization of the precipitated solids derived from the neutralized raffinate, a set of reference compounds were synthesized and analyzed. The reference compounds include crystalline scorodite, poorly-crystalline scorodite, iron(III)-arsenate co-precipitates obtained under different pH conditions, and arsenate-adsorbed on goethite. The poorly-crystalline scorodite (prepared at pH 4 with Fe/As = 1) has similar As local structure as that of crystalline scorodite. Both As and Fe K-edge XAFS of poorly-crystalline scorodite yield consistent results on As-Fe (or Fe-As) shell. From As K-edge analysis the As-Fe shell has an inter-atomic distance of 3.33 ± 0.02 Å and coordination number of 3.2; while from Fe K-edge analysis the Fe-As distance and coordination number are 3.31 ± 0.02 Å and 3.8, respectively. These are in contrast with the typical arsenate adsorption on bidentate binuclear sites on goethite surfaces, where the As-Fe distance is 3.26 ± 0.03 Å and coordination number is close to 2. A similar local structure identified in the poorly-crystalline scorodite is also found in co-precipitation solids (Fe(III)/As(V) = 3) when precipitated at the same pH (pH = 4): As-Fe distance 3.30 ± 0.03 Å and coordination number 3.9; while at pH = 8 the co-precipitate has As-Fe distance of 3.27 ± 0.03 Å and coordination number about 2, resembling more closely the adsorption case. The As local structure in the two neutralized raffinate solid series (precipitated at pH values up to 7) closely resembles that in the poorly-crystalline scorodite. All of the raffinate solids have the same As-Fe inter-atomic distance as that in the poorly-crystalline scorodite, and a systematic decrease in the

  17. Regulation of Nitrate Reductase Activity in Corn (Zea mays L.) Seedlings by Endogenous Metabolites 1

    PubMed Central

    Schrader, L. E.; Hageman, R. H.

    1967-01-01

    Primary and secondary metabolites of inorganic nitrogen metabolism were evaluated as inhibitors of nitrate reductase (EC 1.6.6.1) induction in green leaf tissue of corn seedlings. Nitrite, nitropropionic acid, ammonium ions, and amino acids were not effective as inhibitors of nitrate reductase activity or synthesis. Increasing α-amino nitrogen and protein content of intact corn seedlings by culture techniques significantly enhanced rather than decreased the potential for induction of nitrate reductase activity in excised seedlings. Secondary metabolites, derived from phenylalanine and tyrosine, were tested as inhibitors of induction of nitrate reductase. Of the 9 different phenylpropanoid compounds tested, only coumarin, trans-cinnamic and trans-o-hydroxycinnamic acids inhibited induction of nitrate reductase. While coumarin alone exhibited a relatively greater inhibitory effect on enzyme induction than on general protein synthesis (the latter measured by incorporation of labeled amino acids), this differential effect may have been dependent upon unequal rates of synthesis and accumulation with respect to the initial levels of nitrate reductase and general proteins. Because of the short half-life of nitrate reductase, inhibitors of protein synthesis in general could still achieve differential regulation of nitrogen metabolism. Coumarin did not inhibit nitrate reductase activity when added directly to the assay mixture at 5 mm. Carbamyl phosphate and its chemical derivative, cyanate, were found to be competitive (with nitrate) inhibitors of nitrate reductase. The data suggest that cyanate is the active inhibitor in the carbamyl phosphate preparations. PMID:16656715

  18. A flavone from Manilkara indica as a specific inhibitor against aldose reductase in vitro.

    PubMed

    Haraguchi, Hiroyuki; Hayashi, Ryosuke; Ishizu, Takashi; Yagi, Akira

    2003-09-01

    Isoaffinetin (5,7,3',4',5'-pentahydroxyflavone-6-C-glucoside) was isolated from Manilkara indica as a potent inhibitor of lens aldose reductase by bioassay-directed fractionation. This C-glucosyl flavone showed specific inhibition against aldose reductases (rat lens, porcine lens and recombinant human) with no inhibition against aldehyde reductase and NADH oxidase. Kinetic analysis showed that isoaffinetin exhibited uncompetitive inhibition against both dl-glyceraldehyde and NADPH. A structure-activity relationship study revealed that the increasing number of hydroxy groups in the B-ring contributes to the increase in aldose reductase inhibition by C-glucosyl flavones.

  19. Ammonification in Bacillus subtilis Utilizing Dissimilatory Nitrite Reductase Is Dependent on resDE

    PubMed Central

    Hoffmann, Tamara; Frankenberg, Nicole; Marino, Marco; Jahn, Dieter

    1998-01-01

    During anaerobic nitrate respiration Bacillus subtilis reduces nitrate via nitrite to ammonia. No denitrification products were observed. B. subtilis wild-type cells and a nitrate reductase mutant grew anaerobically with nitrite as an electron acceptor. Oxygen-sensitive dissimilatory nitrite reductase activity was demonstrated in cell extracts prepared from both strains with benzyl viologen as an electron donor and nitrite as an electron acceptor. The anaerobic expression of the discovered nitrite reductase activity was dependent on the regulatory system encoded by resDE. Mutation of the gene encoding the regulatory Fnr had no negative effect on dissimilatory nitrite reductase formation. PMID:9422613

  20. Structure of the Molybdenum Site of EEcherichia Coli Trimethylamine N-Oxide Reductase

    SciTech Connect

    Zhang, L.; Nelson, K.Johnson; Rajagopalan, K.V.; George, G.N.

    2009-05-28

    We report a structural characterization of the molybdenum site of recombinant Escherichia coli trimethylamine N-oxide (TMAO) reductase using X-ray absorption spectroscopy. The enzyme active site shows considerable similarity to that of dimethyl sulfoxide (DMSO) reductase, in that, like DMSO reductase, the TMAO reductase active site can exist in multiple forms. Examination of the published crystal structure of TMAO oxidase from Shewanella massilia indicates that the postulated Mo coordination structure is chemically impossible. The presence of multiple active site structures provides a potential explanation for the anomalous features reported from the crystal structure.

  1. Components of glycine reductase from Eubacterium acidaminophilum. Cloning, sequencing and identification of the genes for thioredoxin reductase, thioredoxin and selenoprotein PA.

    PubMed

    Lübbers, M; Andreesen, J R

    1993-10-15

    The genes encoding thioredoxin reductase (trxB), thioredoxin (trxA), protein PA of glycine reductase (grdA) and the first 23 amino acids of the large subunit of protein PC of glycine reductase (grdC) belonging to the reductive deamination systems present in Eubacterium acidaminophilum were cloned and sequenced. The proteins were products of closely linked genes with 314 codons (thioredoxin reductase), 110 codons (thioredoxin), and 158 codons (protein PA). The protein previously called 'atypically small lipoamide dehydrogenase' or 'electron transferring flavoprotein' could now conclusively be identified as a thioredoxin reductase (subunit mass of 34781 Da) by the alignment with the enzyme of Escherichia coli showing the same typical order of the corresponding domains. The thioredoxin (molecular mass of 11742 Da) deviated considerably from the known consensus sequence, even in the most strongly conserved redox-active segment WCGPC that was now GCVPC. The selenocysteine of protein PA (molecular mass of 16609 Da) was encoded by TGA. The protein was highly similar to those of Clostridium purinolyticum and Clostridium sticklandii involved in glycine reductase. Thioredoxin reductase and thioredoxin of E. acidaminophilum could be successfully expressed in E. coli.

  2. Burden of respiratory viruses in patients with acute respiratory failure.

    PubMed

    Schnell, David; Gits-Muselli, Maud; Canet, Emmanuel; Lemiale, Virginie; Schlemmer, Benoît; Simon, François; Azoulay, Elie; Legoff, Jérôme

    2014-07-01

    Respiratory viruses (RVs) are ubiquitous pathogens that represent a major cause of community-acquired pneumonia and chronic pulmonary diseases exacerbations. However, their contribution to acute respiratory failure events requiring intensive care unit admission in the era of rapid multiplex molecular assay deserves further evaluation. This study investigated the burden of viral infections in non immunocompromised patients admitted to the intensive care unit for acute respiratory failure using a multiplex molecular assay. Patients were investigated for RVs using immunofluoresence testing and a commercial multiplex molecular assay, and for bacteria using conventional culture. Half the patients (34/70, 49%) had a documented RVs infection. No other pathogen was found in 24 (71%) patients. Viral infection was detected more frequently in patients with obstructive respiratory diseases (64% vs. 29%; P = 0.0075). Multiplex molecular assay should be considered as an usefull diagnostic tool in patients admitted to the intensive care unit with acute respiratory failure, especially those with acute exacerbations of chronic obstructive pulmonary disease and asthma.

  3. [Respiratory problems in severe scoliosis].

    PubMed

    Barois, A

    1999-01-01

    In kyphoscoliosis restrictive ventilatory defect occurs. In idiopathic scoliosis vital capacity failure is significantly correlated with Cobb angle, vertebral rotation, and thoracic lordosis. Maximum voluntary ventilation is the most affected measurement. Forced expiratory volume in 1 second is reduced. Residual volume remains longtime normal. Hypoxemia due to decrease of diffusing capacity occurs, with initially reflex hyperventilation hypocapnia, and secondary hypercapnia. Pulmonary hypertension and cor pulmonale is related to hypoventilation and hypoxia. The lung situated on the concave side of the scoliosis curve shows a more functional derangement. Ventilatory pattern consists of low tidal volume and high respiratory rate with increase of ventilatory work. Scoliosis that appears in the earlier stage of the life has the worst respiratory prognosis (before 5 years of age) with impairement of lung and thoracic growth. To stimulate pulmonary and thoracic growth, intermittent ventilatory assistance by pressure preset ventilator should be performed as soon as possible and pursued up to 8 years of age, at least, more if necessity. In over 60 degrees angle idiopathic scoliosis, respiratory failure appears after 40 to 50 years of age. Non invasive ventilatory assistance with preset pressure ventilator by oral way in moderate cases and nocturnal nasal ventilation by volume ventilator or inspiratory assistance ventilator, in the most severe cases are efficient. In very severe and acute respiratory insufficiency (scoliosis over 90 degrees) ventilation by intubation then tractheostomy may be required. Earlier orthopedic management and surgical procedure to correct and stabilize spinal deformities is the best to prevent respiratory insufficiency. For scoliosis below 60 degrees, post operative pulmonary complications are very low, with no requirement of post operative ventilatory support. In very severe respiratory insufficiency treatment of respiratory failure precedes, and

  4. Probiotics in respiratory virus infections.

    PubMed

    Lehtoranta, L; Pitkäranta, A; Korpela, R

    2014-08-01

    Viral respiratory infections are the most common diseases in humans. A large range of etiologic agents challenge the development of efficient therapies. Research suggests that probiotics are able to decrease the risk or duration of respiratory infection symptoms. However, the antiviral mechanisms of probiotics are unclear. The purpose of this paper is to review the current knowledge on the effects of probiotics on respiratory virus infections and to provide insights on the possible antiviral mechanisms of probiotics. A PubMed and Scopus database search was performed up to January 2014 using appropriate search terms on probiotic and respiratory virus infections in cell models, in animal models, and in humans, and reviewed for their relevance. Altogether, thirty-three clinical trials were reviewed. The studies varied highly in study design, outcome measures, probiotics, dose, and matrices used. Twenty-eight trials reported that probiotics had beneficial effects in the outcome of respiratory tract infections (RTIs) and five showed no clear benefit. Only eight studies reported investigating viral etiology from the respiratory tract, and one of these reported a significant decrease in viral load. Based on experimental studies, probiotics may exert antiviral effects directly in probiotic-virus interaction or via stimulation of the immune system. Although probiotics seem to be beneficial in respiratory illnesses, the role of probiotics on specific viruses has not been investigated sufficiently. Due to the lack of confirmatory studies and varied data available, more randomized, double-blind, and placebo-controlled trials in different age populations investigating probiotic dose response, comparing probiotic strains/genera, and elucidating the antiviral effect mechanisms are necessary.

  5. Respiratory care management information systems.

    PubMed

    Ford, Richard M

    2004-04-01

    Hospital-wide computerized information systems evolved from the need to capture patient information and perform billing and other financial functions. These systems, however, have fallen short of meeting the needs of respiratory care departments regarding work load assessment, productivity management, and the level of outcome reporting required to support programs such as patient-driven protocols. The respiratory care management information systems (RCMIS) of today offer many advantages over paper-based systems and hospital-wide computer systems. RCMIS are designed to facilitate functions specific to respiratory care, including assessing work demand, assigning and tracking resources, charting, billing, and reporting results. RCMIS incorporate mobile, point-of-care charting and are highly configurable to meet the specific needs of individual respiratory care departments. Important and substantial benefits can be realized with an RCMIS and mobile, wireless charting devices. The initial and ongoing costs of an RCMIS are justified by increased charge capture and reduced costs, by way of improved productivity and efficiency. It is not unusual to recover the total cost of an RCMIS within the first year of its operation. In addition, such systems can facilitate and monitor patient-care protocols and help to efficiently manage the vast amounts of information encountered during the practitioner's workday. Respiratory care departments that invest in RCMIS have an advantage in the provision of quality care and in reducing expenses. A centralized respiratory therapy department with an RCMIS is the most efficient and cost-effective way to monitor work demand and manage the hospital-wide allocation of respiratory care services.

  6. Structural and Biochemical Characterization of Cinnamoyl-CoA Reductases.

    PubMed

    Sattler, Steven A; Walker, Alexander M; Vermerris, Wilfred; Sattler, Scott E; Kang, ChulHee

    2017-02-01

    Cinnamoyl-coenzyme A reductase (CCR) catalyzes the reduction of hydroxycinnamoyl-coenzyme A (CoA) esters using NADPH to produce hydroxycinnamyl aldehyde precursors in lignin synthesis. The catalytic mechanism and substrate specificity of cinnamoyl-CoA reductases from sorghum (Sorghum bicolor), a strategic plant for bioenergy production, were deduced from crystal structures, site-directed mutagenesis, and kinetic and thermodynamic analyses. Although SbCCR1 displayed higher affinity for caffeoyl-CoA or p-coumaroyl-CoA than for feruloyl-CoA, the enzyme showed significantly higher activity for the latter substrate. Through molecular docking and comparisons between the crystal structures of the Vitis vinifera dihydroflavonol reductase and SbCCR1, residues threonine-154 and tyrosine-310 were pinpointed as being involved in binding CoA-conjugated phenylpropanoids. Threonine-154 of SbCCR1 and other CCRs likely confers strong substrate specificity for feruloyl-CoA over other cinnamoyl-CoA thioesters, and the T154Y mutation in SbCCR1 led to broader substrate specificity and faster turnover. Through data mining using our structural and biochemical information, four additional putative CCR genes were discovered from sorghum genomic data. One of these, SbCCR2, displayed greater activity toward p-coumaroyl-CoA than did SbCCR1, which could imply a role in the synthesis of defense-related lignin. Taken together, these findings provide knowledge about critical residues and substrate preference among CCRs and provide, to our knowledge, the first three-dimensional structure information for a CCR from a monocot species.

  7. Thioredoxin Glutathione Reductase-Dependent Redox Networks in Platyhelminth Parasites

    PubMed Central

    Bonilla, Mariana; Gladyshev, Vadim N.

    2013-01-01

    Abstract Significance: Platyhelminth parasites cause chronic infections that are a major cause of disability, mortality, and economic losses in developing countries. Maintaining redox homeostasis is a major adaptive problem faced by parasites and its disruption can shift the biochemical balance toward the host. Platyhelminth parasites possess a streamlined thiol-based redox system in which a single enzyme, thioredoxin glutathione reductase (TGR), a fusion of a glutaredoxin (Grx) domain to canonical thioredoxin reductase (TR) domains, supplies electrons to oxidized glutathione (GSSG) and thioredoxin (Trx). TGR has been validated as a drug target for schistosomiasis. Recent Advances: In addition to glutathione (GSH) and Trx reduction, TGR supports GSH-independent deglutathionylation conferring an additional advantage to the TGR redox array. Biochemical and structural studies have shown that the TR activity does not require the Grx domain, while the glutathione reductase and deglutathionylase activities depend on the Grx domain, which receives electrons from the TR domains. The search for TGR inhibitors has identified promising drug leads, notably oxadiazole N-oxides. Critical Issues: A conspicuous feature of platyhelminth TGRs is that their Grx-dependent activities are temporarily inhibited at high GSSG concentrations. The mechanism underlying the phenomenon and its biological relevance are not completely understood. Future Directions: The functional diversity of Trxs and Grxs encoded in platyhelminth genomes remains to be further assessed to thoroughly understand the TGR-dependent redox network. Optimization of TGR inhibitors and identification of compounds targeting other parasite redox enzymes are good options to clinically develop relevant drugs for these neglected, but important diseases. Antioxid. Redox Signal. 19, 735–745. PMID:22909029

  8. Middle East respiratory syndrome and severe acute respiratory syndrome.

    PubMed

    Vijay, Rahul; Perlman, Stanley

    2016-02-01

    The recent emergence of the Middle East respiratory syndrome (MERS)-CoV, a close relative of the Severe Acute respiratory syndrome (SARS)-CoV, both of which caused a lethal respiratory infection in humans, reinforces the need for further understanding of coronavirus pathogenesis and the host immune response. These viruses have evolved diverse strategies to evade and block host immune responses, facilitating infection and transmission. Pathogenesis following infection with these viruses is characterized by a marked delay in the induction of Type I interferon (IFN I) and, subsequently, by a poor adaptive immune response. Therapies that expedite IFN I induction as well as interventions that antagonize immunoevasive virus proteins are thus promising candidates for immune modulation.

  9. Methylenetetrahydrofolate Reductase C677T: Hypoplastic Left Heart and Thrombosis.

    PubMed

    Spronk, Kimberly J; Olivero, Anthony D; Haw, Marcus P; Vettukattil, Joseph J

    2015-10-01

    The incidence of congenital heart defects is higher in infants with mutation of methylenetetrahydrofolate reductase (MTHFR) gene. The MTHFR C677T gene decreases the bioavailability of folate and increases plasma homocysteine, a risk factor for thrombosis. There have been no reported cases in the literature on the clinical implications of this procoagulable state in the setting of cyanotic heart disease, which itself has prothrombotic predisposition. Two patients with hypoplastic left heart syndrome developed postoperative thrombotic complications, both were homozygous for MTHFR C677T. We present these cases and highlight the implications of MTHFR mutation in the management of complex congenital heart disease.

  10. Terpenoids from Diplophyllum taxifolium with quinone reductase-inducing activity.

    PubMed

    Wang, Xiao; Zhang, Jiao-Zhen; Zhou, Jin-Chuan; Shen, Tao; Lou, Hong-Xiang

    2016-03-01

    Two new ent-prenylaromadendrane-type diterpenoids, diplotaxifols A (1) and B (2), a new ent-eudesmol, ent-eudesma-4(15),11(13)-dien-6α,12-diol (3), eight new eudesmanolides enantiomers (4-11) of the corresponding compounds from higher plants along with four known ent-eudesmanolides (12-15) were isolated from the 95% EtOH extract of Chinese liverwort Diplophyllum taxifolium. Their structures were elucidated on the basis of MS, NMR and IR spectral data, and confirmed by single-crystal X-ray diffraction analysis. The quinone reductase-inducing activity of the compounds was evaluated.

  11. Applications of Carboxylic Acid Reductases in Oleaginous Microbes

    SciTech Connect

    Resch, Michael G.; Linger, Jeffrey; McGeehan, John; Tyo, Keith; Beckham, Gregg

    2016-04-24

    Carboxylic acid reductases (CARs) are recently emerging reductive enzymes for the direct production of aldehydes from biologically-produced carboxylic acids. Recent work has demonstrated that these powerful enzymes are able to reduce a very broad range of volatile- to long-chain fatty acids as well as aromatic acids. Here, we express four CAR enzymes from different fungal origins to test their activity against fatty acids commonly produced in oleaginous microbes. These in vitro results will inform metabolic engineering strategies to conduct mild biological reduction of carboxylic acids in situ, which is conventionally done via hydrotreating catalysis at high temperatures and hydrogen pressures.

  12. Novel mechanism for scavenging of hypochlorite involving a periplasmic methionine-rich peptide and methionine sulfoxide reductase

    SciTech Connect

    Melnyk, Ryan A.; Youngblut, Matthew D.; Clark, Iain C.; Carlson, Hans K.; Wetmore, Kelly M.; Price, Morgan N.; Lavarone, Anthony T.; Deutschbauer, Adam M.; Arkin, Adam P.; Coates, John D.

    2015-05-12

    stressed in the environment by reactive chlorine species (RCS) of either anthropogenic or natural origin, but little is known of the defense mechanisms they have evolved. Using a microorganism that generates RCS internally as part of its respiratory process allowed us to uncover a novel defense mechanism based on RCS scavenging by reductive reaction with a sacrificial methionine-rich peptide and redox recycling through a methionine sulfoxide reductase. As a result, this system is conserved in a broad diversity of organisms, including some of clinical importance, invoking a possible important role in innate immune system evasion.

  13. Novel mechanism for scavenging of hypochlorite involving a periplasmic methionine-rich peptide and methionine sulfoxide reductase

    DOE PAGES

    Melnyk, Ryan A.; Youngblut, Matthew D.; Clark, Iain C.; ...

    2015-05-12

    either anthropogenic or natural origin, but little is known of the defense mechanisms they have evolved. Using a microorganism that generates RCS internally as part of its respiratory process allowed us to uncover a novel defense mechanism based on RCS scavenging by reductive reaction with a sacrificial methionine-rich peptide and redox recycling through a methionine sulfoxide reductase. As a result, this system is conserved in a broad diversity of organisms, including some of clinical importance, invoking a possible important role in innate immune system evasion.« less

  14. A Raman spectroscopic study of the arsenate mineral chenevixite Cu2Fe23+(AsO4)2(OH)4ṡH2O

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Scholz, Ricardo; Lana, Cristiano; Xi, Yunfei

    2015-01-01

    We have studied the mineral chenevixite from Manto Cuba Mine, San Pedro de Cachiyuyo District, Inca de Oro, Chañaral Province, Atacama Region, Chile, using a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous composition, with predominance of As, Fe, Al, Cu, Fe and Cu. Minor amounts of Si were also observed. Raman spectroscopy complimented with infrared spectroscopy has been used to assess the molecular structure of the arsenate minerals chenevixite. Characteristic Raman and infrared bands of the (AsO4)3- stretching and bending vibrations are identified and described. The observation of multiple bands in the (AsO4)3- bending region offers support for the loss of symmetry of the arsenate anion in the structure of chenevixite. Raman bands attributable to the OH stretching vibrations of water and hydroxyl units were analysed. Estimates of the hydrogen bond distances were made based upon the OH stretching wavenumbers.

  15. Pyrobaculum yellowstonensis Strain WP30 Respires on Elemental Sulfur and/or Arsenate in Circumneutral Sulfidic Geothermal Sediments of Yellowstone National Park

    PubMed Central

    Jay, Z. J.; Beam, J. P.; Dohnalkova, A.; Lohmayer, R.; Bodle, B.; Planer-Friedrich, B.; Romine, M.

    2015-01-01

    Thermoproteales (phylum Crenarchaeota) populations are abundant in high-temperature (>70°C) environments of Yellowstone National Park (YNP) and are important in mediating the biogeochemical cycles of sulfur, arsenic, and carbon. The objectives of this study were to determine the specific physiological attributes of the isolate Pyrobaculum yellowstonensis strain WP30, which was obtained from an elemental sulfur sediment (Joseph's Coat Hot Spring [JCHS], 80°C, pH 6.1, 135 μM As) and relate this organism to geochemical processes occurring in situ. Strain WP30 is a chemoorganoheterotroph and requires elemental sulfur and/or arsenate as an electron acceptor. Growth in the presence of elemental sulfur and arsenate resulted in the formation of thioarsenates and polysulfides. The complete genome of this organism was sequenced (1.99 Mb, 58% G+C content), revealing numerous metabolic pathways for the degradation of carbohydrates, amino acids, and lipids. Multiple dimethyl sulfoxide-molybdopterin (DMSO-MPT) oxidoreductase genes, which are implicated in the reduction of sulfur and arsenic, were identified. Pathways for the de novo synthesis of nearly all required cofactors and metabolites were identified. The comparative genomics of P. yellowstonensis and the assembled metagenome sequence from JCHS showed that this organism is highly related (∼95% average nucleotide sequence identity) to in situ populations. The physiological attributes and metabolic capabilities of P. yellowstonensis provide an important foundation for developing an understanding of the distribution and function of these populations in YNP. PMID:26092468

  16. Pyrobaculum yellowstonensis Strain WP30 Respires on Elemental Sulfur and/or Arsenate in Circumneutral Sulfidic Geothermal Sediments of Yellowstone National Park.

    PubMed

    Jay, Z J; Beam, J P; Dohnalkova, A; Lohmayer, R; Bodle, B; Planer-Friedrich, B; Romine, M; Inskeep, W P

    2015-09-01

    Thermoproteales (phylum Crenarchaeota) populations are abundant in high-temperature (>70°C) environments of Yellowstone National Park (YNP) and are important in mediating the biogeochemical cycles of sulfur, arsenic, and carbon. The objectives of this study were to determine the specific physiological attributes of the isolate Pyrobaculum yellowstonensis strain WP30, which was obtained from an elemental sulfur sediment (Joseph's Coat Hot Spring [JCHS], 80°C, pH 6.1, 135 μM As) and relate this organism to geochemical processes occurring in situ. Strain WP30 is a chemoorganoheterotroph and requires elemental sulfur and/or arsenate as an electron acceptor. Growth in the presence of elemental sulfur and arsenate resulted in the formation of thioarsenates and polysulfides. The complete genome of this organism was sequenced (1.99 Mb, 58% G+C content), revealing numerous metabolic pathways for the degradation of carbohydrates, amino acids, and lipids. Multiple dimethyl sulfoxide-molybdopterin (DMSO-MPT) oxidoreductase genes, which are implicated in the reduction of sulfur and arsenic, were identified. Pathways for the de novo synthesis of nearly all required cofactors and metabolites were identified. The comparative genomics of P. yellowstonensis and the assembled metagenome sequence from JCHS showed that this organism is highly related (∼95% average nucleotide sequence identity) to in situ populations. The physiological attributes and metabolic capabilities of P. yellowstonensis provide an important foundation for developing an understanding of the distribution and function of these populations in YNP.

  17. Sequential extraction of inorganic arsenic compounds and methyl arsenate in human urine using mixed-mode monolithic silica spin column coupled with gas chromatography-mass spectrometry.

    PubMed

    Namera, Akira; Takeuchi, Akito; Saito, Takeshi; Miyazaki, Shota; Oikawa, Hiroshi; Saruwatari, Tatsuro; Nagao, Masataka

    2012-09-01

    A sequential analytical method was developed for the detection of arsenite, arsenate, and methylarsenate in human urine by gas chromatography-mass spectrometry (GC-MS). The combination of a derivatization of trivalent arsenic compounds by 2,3-dithio-1-propanol (British antilewisite; BAL) and a reduction of pentavalent arsenic compounds (arsenate and methylarsenate) were accomplished to carry out the analysis of arsenic compounds in urine. The arsenic derivatives obtained using BAL were extracted in a stepwise manner using a monolithic spin column and analyzed by GC-MS. A linear curve was observed for concentrations of arsenic compounds of 2.0 to 200 ng/mL, where the correlation coefficients of calibration curves were greater than 0.996 (for a signal-to-noise (S/N) ratio >10). The detection limits were 1 ng/mL (S/N > 3). Recoveries of the targets in urine were in the range 91.9-106.5%, and RSDs of the intra- and interday assay for urine samples containing 5, 50, and 150 ng/mL of arsenic compounds varied between 2.95 and 13.4%. The results from real samples obtained from a patient suspected of having ingested As containing medications using this proposed method were in good agreement with those obtained using high-performance liquid chromatography with inductively coupled plasma mass spectrometry.

  18. A Novel NADPH-dependent flavoprotein reductase from Bacillus megaterium acts as an efficient cytochrome P450 reductase.

    PubMed

    Milhim, Mohammed; Gerber, Adrian; Neunzig, Jens; Hannemann, Frank; Bernhardt, Rita

    2016-08-10

    Cytochromes P450 (P450s) require electron transfer partners to catalyze substrate conversions. With regard to biotechnological approaches, the elucidation of novel electron transfer proteins is of special interest, as they can influence the enzymatic activity and specificity of the P450s. In the current work we present the identification and characterization of a novel soluble NADPH-dependent diflavin reductase from Bacillus megaterium with activity towards a bacterial (CYP106A1) and a microsomal (CYP21A2) P450 and, therefore, we referred to it as B. megaterium cytochrome P450 reductase (BmCPR). Sequence analysis of the protein revealed besides the conserved FMN-, FAD- and NADPH-binding motifs, the presence of negatively charged cluster, which is thought to represent the interaction domain with P450s and/or cytochrome c. BmCPR was expressed and purified to homogeneity in Escherichia coli. The purified BmCPR exhibited a characteristic diflavin reductase spectrum, and showed a cytochrome c reducing activity. Furthermore, in an in vitro reconstituted system, the BmCPR was able to support the hydroxylation of testosterone and progesterone with CYP106A1 and CYP21A2, respectively. Moreover, in view of the biotechnological application, the BmCPR is very promising, as it could be successfully utilized to establish CYP106A1- and CYP21A2-based whole-cell biotransformation systems, which yielded 0.3g/L hydroxy-testosterone products within 8h and 0.16g/L 21-hydroxyprogesterone within 6h, respectively. In conclusion, the BmCPR reported herein owns a great potential for further applications and studies and should be taken into consideration for bacterial and/or microsomal CYP-dependent bioconversions.

  19. [Respiratory treatments in neuromuscular disease].

    PubMed

    Martínez Carrasco, C; Cols Roig, M; Salcedo Posadas, A; Sardon Prado, O; Asensio de la Cruz, O; Torrent Vernetta, A

    2014-10-01

    In a previous article, a review was presented of the respiratory pathophysiology of the patient with neuromuscular disease, as well as their clinical evaluation and the major complications causing pulmonary deterioration. This article presents the respiratory treatments required to preserve lung function in neuromuscular disease as long as possible, as well as in special situations (respiratory infections, spinal curvature surgery, etc.). Special emphasis is made on the use of non-invasive ventilation, which is changing the natural history of many of these diseases. The increase in survival and life expectancy of these children means that they can continue their clinical care in adult units. The transition from pediatric care must be an active, timely and progressive process. It may be slightly stressful for the patient before the adaptation to this new environment, with multidisciplinary care always being maintained.

  20. Respiratory weight losses during exercise.

    NASA Technical Reports Server (NTRS)

    Mitchell, J. W.; Nadel, E. R.; Stolwijk, J. A. J.

    1972-01-01

    Evaporative water loss from the respiratory tract was determined over a wide range of exercise. The absolute humidity of the expired air was the same at all levels of exercise and equal to that measured at rest. The rate of respiratory water loss during exercise was found to be 0.019 of the oxygen uptake times (44 minus water vapor pressure). The rate of weight loss during exercise due to CO2-O2 exchange was calculated. For exercise at oxygen consumption rates exceeding 1.5 L/min in a dry environment with a water vapor pressure of 10 mm Hg, the total rate of weight loss via the respiratory tract is on the order of 2-5 g/min.