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Sample records for membrane nitrate reductase

  1. Compensatory periplasmic nitrate reductase activity supports anaerobic growth of Pseudomonas aeruginosa PAO1 in the absence of membrane nitrate reductase

    Science.gov (United States)

    Van Alst, Nadine E.; Sherrill, Lani A.; Iglewski, Barbara H.; Haidaris, Constantine G.

    2009-01-01

    Nitrate serves as a terminal electron acceptor under anaerobic conditions in Pseudomonas aeruginosa. Reduction of nitrate to nitrite generates a transmembrane proton motive force allowing ATP synthesis and anaerobic growth. Inner membrane-bound nitrate reductase NarGHI is encoded within the narK1K2GHJI operon and the periplasmic nitrate reductase NapAB is encoded within the napEFDABC operon. The role of the two dissimilatory nitrate reductases in anaerobic growth, and the regulation of their expression were examined by using a set of deletion mutants in P. aeruginosa PAO1. NarGHI mutants were unable to grow anaerobically, but plate cultures remained viable up to 120 hr. In contrast, nitrate sensor-response regulator mutant ΔnarXL displayed growth arrest initially, but resumed growth after 72 hr and reached early stationary phase in liquid culture after 120 hr. Genetic, transcriptional, and biochemical studies demonstrated that anaerobic growth recovery by the NarXL mutant was the result of NapAB periplasmic nitrate reductase expression. A novel transcriptional start site for napEFDABC expression was identified in the NarXL mutant grown anaerobically. Furthermore, mutagenesis of a consensus NarL-binding site monomer upstream of the novel transcriptional start site restored anaerobic growth recovery in the NarXL mutant. The data suggest that during anaerobic growth of wild type P. aeruginosa PAO1, nitrate response regulator NarL directly represses expression of periplasmic nitrate reductase, while inducing maximal expression of membrane nitrate reductase. PMID:19935885

  2. Evidence for a plasma-membrane-bound nitrate reductase involved in nitrate uptake of Chlorella sorokiniana

    Science.gov (United States)

    Tischner, R.; Ward, M. R.; Huffaker, R. C.

    1989-01-01

    Anti-nitrate-reductase (NR) immunoglobulin-G (IgG) fragments inhibited nitrate uptake into Chlorella cells but had no affect on nitrate uptake. Intact anti-NR serum and preimmune IgG fragments had no affect on nitrate uptake. Membrane-associated NR was detected in plasma-membrane (PM) fractions isolated by aqueous two-phase partitioning. The PM-associated NR was not removed by sonicating PM vesicles in 500 mM NaCl and 1 mM ethylenediaminetetraacetic acid and represented up to 0.8% of the total Chlorella NR activity. The PM NR was solubilized by Triton X-100 and inactivated by Chlorella NR antiserum. Plasma-membrane NR was present in ammonium-grown Chlorella cells that completely lacked soluble NR activity. The subunit sizes of the PM and soluble NRs were 60 and 95 kDa, respectively, as determined by sodium-dodecyl-sulfate electrophoresis and western blotting.

  3. Differential nitrate accumulation, nitrate reduction, nitrate reductase ...

    African Journals Online (AJOL)

    use

    2011-12-07

    Dec 7, 2011 ... reductase activity and nitrite accumulation depend on the exogenous nitrate. Nitrite itself is reduced to ammonium by palstidic nitrite reductase. Nitrite reductase is activated by both nitrate and nitrite ions by positive feed forward, whereas nitrate metabolites, most likely ammonium and glutamine; down.

  4. NADH-Ferricyanide Reductase of Leaf Plasma Membranes : Partial Purification and Immunological Relation to Potato Tuber Microsomal NADH-Ferricyanide Reductase and Spinach Leaf NADH-Nitrate Reductase.

    Science.gov (United States)

    Askerlund, P; Laurent, P; Nakagawa, H; Kader, J C

    1991-01-01

    Plasma membranes obtained by two-phase partitioning of microsomal fractions from spinach (Spinacea oleracea L. cv Medania) and sugar beet leaves (Beta vulgaris L.) contained relatively high NADH-ferricyanide reductase and NADH-nitrate reductase (NR; EC 1.6.6.1) activities. Both of these activities were latent. To investigate whether these activities were due to the same enzyme, plasma membrane polypeptides were separated with SDS-PAGE and analyzed with immunoblotting methods. Antibodies raised against microsomal NADH-ferricyanide reductase (tentatively identified as NADH-cytochrome b(5) reductase, EC 1.6.2.2), purified from potato (Solanum tuberosum L. cv Bintje) tuber microsomes, displayed one single band at 43 kilodaltons when reacted with spinach plasma membranes, whereas lgG produced against NR from spinach leaves gave a major band at 110 kilodaltons together with a few fainter bands of lower molecular mass. Immunoblotting analysis using inside-out and right-side-out plasma membrane vesicles strongly indicated that NR was not an integral protein but probably trapped inside the plasma membrane vesicles during homogenization. Proteins from spinach plasma membranes were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl) dimethylammonio] 1-propane-sulfonate and separated on a Mono Q anion exchange column at pH 5.6 with fast protein liquid chromatography. One major peak of NADH-ferricyanide reductase activity was found after separation. The peak fraction was enriched about 70-fold in this activity compared to the plasma membrane. When the peak fractions were analyzed with SDS-PAGE the NADH-ferricyanide reductase activity strongly correlated with a 43 kilodalton polypeptide which reacted with the antibodies against potato microsomal NADH-ferricyanide reductase. Thus, our data indicate that most, if not all, of the truly membrane-bound NADH-ferricyanide reductase activity of leaf plasma membranes is due to an enzyme very similar to potato tuber

  5. Differential nitrate accumulation, nitrate reduction, nitrate reductase ...

    African Journals Online (AJOL)

    use

    2011-12-07

    Dec 7, 2011 ... nitrate salts supply on nitrate accumulation, amino acid biosynthesis, total protein production, nitrate reductase activity and carbohydrate biosynthesis in the roots and leaves of the plants. The results indicate that both sodium and potassium nitrate supplementation had stimulatory effects on all of the.

  6. Biochemical and spectroscopic characterization of the membrane-bound nitrate reductase from Marinobacter hydrocarbonoclasticus 617.

    Science.gov (United States)

    Correia, Cristina; Besson, Stéphane; Brondino, Carlos D; González, Pablo J; Fauque, Guy; Lampreia, Jorge; Moura, Isabel; Moura, José J G

    2008-11-01

    Membrane-bound nitrate reductase from Marinobacter hydrocarbonoclasticus 617 can be solubilized in either of two ways that will ultimately determine the presence or absence of the small (Iota) subunit. The enzyme complex (NarGHI) is composed of three subunits with molecular masses of 130, 65, and 20 kDa. This enzyme contains approximately 14 Fe, 0.8 Mo, and 1.3 molybdopterin guanine dinucleotides per enzyme molecule. Curiously, one heme b and 0.4 heme c per enzyme molecule have been detected. These hemes were potentiometrically characterized by optical spectroscopy at pH 7.6 and two noninteracting species were identified with respective midpoint potentials at Em=+197 mV (heme c) and -4.5 mV (heme b). Variable-temperature (4-120 K) X-band electron paramagnetic resonance (EPR) studies performed on both as-isolated and dithionite-reduced nitrate reductase showed, respectively, an EPR signal characteristic of a [3Fe-4S]+ cluster and overlapping signals associated with at least three types of [4Fe-4S]+ centers. EPR of the as-isolated enzyme shows two distinct pH-dependent Mo(V) signals with hyperfine coupling to a solvent-exchangeable proton. These signals, called "low-pH" and "high-pH," changed to a pH-independent Mo(V) signal upon nitrate or nitrite addition. Nitrate addition to dithionite-reduced samples at pH 6 and 7.6 yields some of the EPR signals described above and a new rhombic signal that has no hyperfine structure. The relationship between the distinct EPR-active Mo(V) species and their plausible structures is discussed on the basis of the structural information available to date for closely related membrane-bound nitrate reductases.

  7. Inhibition of nitrate transport by anti-nitrate reductase IgG fragments and the identification of plasma membrane associated nitrate reductase in roots of barley seedlings

    Science.gov (United States)

    Ward, M. R.; Tischner, R.; Huffaker, R. C.

    1988-01-01

    Membrane associated nitrate reductase (NR) was detected in plasma membrane (PM) fractions isolated by aqueous two-phase partitioning from barley (Hordeum vulgare L. var CM 72) roots. The PM associated NR was not removed by washing vesicles with 500 millimolar NaCl and 1 millimolar EDTA and represented up to 4% of the total root NR activity. PM associated NR was stimulated up to 20-fold by Triton X-100 whereas soluble NR was only increased 1.7-fold. The latency was a function of the solubilization of NR from the membrane. NR, solubilized from the PM fraction by Triton X-100 was inactivated by antiserum to Chlorella sorokiniana NR. Anti-NR immunoglobulin G fragments purified from the anti-NR serum inhibited NO3- uptake by more than 90% but had no effect on NO2- uptake. The inhibitory effect was only partially reversible; uptake recovered to 50% of the control after thorough rinsing of roots. Preimmune serum immunoglobulin G fragments inhibited NO3- uptake 36% but the effect was completely reversible by rinsing. Intact NR antiserum had no effect on NO3- uptake. The results present the possibility that NO3- uptake and NO3- reduction in the PM of barley roots may be related.

  8. Latent nitrate reductase activity is associated with the plasma membrane of corn roots

    Science.gov (United States)

    Ward, M. R.; Grimes, H. D.; Huffaker, R. C.

    1989-01-01

    Latent nitrate reductase activity (NRA) was detected in corn (Zea mays L., Golden Jubilee) root microsome fractions. Microsome-associated NRA was stimulated up to 20-fold by Triton X-100 (octylphenoxy polyethoxyethanol) whereas soluble NRA was only increased up to 1.2-fold. Microsome-associated NRA represented up to 19% of the total root NRA. Analysis of microsomal fractions by aqueous two-phase partitioning showed that the membrane-associated NRA was localized in the second upper phase (U2). Analysis with marker enzymes indicated that the U2 fraction was plasma membrane (PM). The PM-associated NRA was not removed by washing vesicles with up to 1.0 M NACl but was solubilized from the PM with 0.05% Triton X-100. In contrast, vanadate-sensitive ATPase activity was not solubilized from the PM by treatment with 0.1% Triton X-100. The results show that a protein capable of reducing nitrate is embedded in the hydrophobic region of the PM of corn roots.

  9. Mechanism of biological denitrification inhibition: procyanidins induce an allosteric transition of the membrane-bound nitrate reductase through membrane alteration.

    Science.gov (United States)

    Bardon, Clément; Poly, Franck; Piola, Florence; Pancton, Muriel; Comte, Gilles; Meiffren, Guillaume; Haichar, Feth el Zahar

    2016-05-01

    Recently, it has been shown that procyanidins from Fallopia spp. inhibit bacterial denitrification, a phenomenon called biological denitrification inhibition (BDI). However, the mechanisms involved in such a process remain unknown. Here, we investigate the mechanisms of BDI involving procyanidins, using the model strain Pseudomonas brassicacearum NFM 421. The aerobic and anaerobic (denitrification) respiration, cell permeability and cell viability of P. brassicacearum were determined as a function of procyanidin concentration. The effect of procyanidins on the bacterial membrane was observed using transmission electronic microscopy. Bacterial growth, denitrification, NO3- and NO2-reductase activity, and the expression of subunits of NO3- (encoded by the gene narG) and NO2-reductase (encoded by the gene nirS) under NO3 or NO2 were measured with and without procyanidins. Procyanidins inhibited the denitrification process without affecting aerobic respiration at low concentrations. Procyanidins also disturbed cell membranes without affecting cell viability. They specifically inhibited NO3- but not NO2-reductase.Pseudomonas brassicacearum responded to procyanidins by over-expression of the membrane-bound NO3-reductase subunit (encoded by the gene narG). Our results suggest that procyanidins can specifically inhibit membrane-bound NO3-reductase inducing enzymatic conformational changes through membrane disturbance and that P. brassicacearum responds by over-expressing membrane-bound NO3-reductase. Our results lead the way to a better understanding of BDI. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  10. Differential nitrate accumulation, nitrate reduction, nitrate reductase ...

    African Journals Online (AJOL)

    For most of the cultivated crops, nitrate is the major source of nitrogen. Most steps in the nitrate assimilatory pathway are nitrate inducible. In this study, Cucurbita pepo were grown in washed sand per pot at three potassium and sodium nitrate supplies (25, 50 and 100 mM) to investigate the effects of nitrate salts supply on ...

  11. Effect of ammonium and nitrate on ferric chelate reductase and nitrate reductase in Vaccinium species.

    Science.gov (United States)

    Poonnachit, U; Darnell, R

    2004-04-01

    Most Vaccinium species have strict soil requirements for optimal growth, requiring low pH, high iron availability and nitrogen primarily in the ammonium form. These soils are limited and are often located near wetlands. Vaccinium arboreum is a wild species adapted to a wide range of soils, including high pH, low iron, and nitrate-containing soils. This broader soil adaptation in V. arboreum may be related to increased efficiency of iron or nitrate uptake compared with the cultivated Vaccinium species. Nitrate, ammonium and iron uptake, and nitrate reductase (NR) and ferric chelate reductase (FCR) activities were compared in two Vaccinium species grown hydroponically in either nitrate or ammonia, with or without iron. The species studied were the wild V. arboreum and the cultivated V. corymbosum interspecific hybrid, which exhibits the strict soil requirements of most Vaccinium species. Ammonium uptake was significantly greater than nitrate uptake in both species, while nitrate uptake was greater in the wild species, V. arboreum, compared with the cultivated species, V. corymbosum. The increased nitrate uptake in V. arboreum was correlated with increased root NR activity compared with V. corymbosum. The lower nitrate uptake in V. corymbosum was reflected in decreased plant dry weight in this species compared with V. arboreum. Root FCR activity increased significantly in V. corymbosum grown under iron-deficient conditions, compared with the same species grown under iron-sufficient conditions or with V. arboreum grown under either iron condition. V. arboreum appears to be more efficient in acquiring nitrate compared with V. corymbosum, possibly due to increased NR activity and this may partially explain the wider soil adaptation of V. arboreum.

  12. On The Regulation of Spinach Nitrate Reductase 1

    Science.gov (United States)

    Sanchez, Juan; Heldt, Hans W.

    1990-01-01

    A coupled assay has been worked out to study spinach (Spinacea oleracea L.) nitrate reductase under low, more physiological concentrations of NADH. In this assay the reduction of nitrate is coupled to the oxidation of malate catalyzed by spinach NAD-malate dehydrogenase. The use of this coupled system allows the assay of nitrate reductase activity at steady-state concentrations of NADH below micromolar. We have used this coupled assay to study the kinetic parameters of spinach nitrate reductase and to reinvestigate the putative regulatory role of adenine nucleotides, inorganic phosphate, amino acids, and calcium and calmodulin. PMID:16667335

  13. Optimum conditions for cotton nitrate reductase extraction and ...

    African Journals Online (AJOL)

    GREGO

    mM of glutamine in the extraction buffer stimulates significantly, in vitro, the reduction of nitrate. Enzyme activity is moreover optimal when 1 M of exogenous nitrate, as substrate, is added to the reaction medium. At these optimum conditions of nitrate reductase activity determination, the substrate was completely reduced ...

  14. Nitrate reductase assay using sodium nitrate for rapid detection of multidrug resistant tuberculosis

    OpenAIRE

    Macedo, Ma?ra Bidart; Groll, Andrea Von; Fissette, Krista; Palomino, Juan Carlos; da Silva, Pedro Eduardo Almeida; Martin, Anandi

    2012-01-01

    We validated the nitrate reductase assay (NRA) for the detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) using sodium nitrate (NaNO3) in replacement of potassium nitrate (KNO3) as nitrate source. NaNO3 is cheaper than KNO3 and has no restriction on use which facilitates the implementation of NRA to detect MDR-TB.

  15. NADH-Ferricyanide Reductase of Leaf Plasma Membranes 1

    Science.gov (United States)

    Askerlund, Per; Laurent, Pascal; Nakagawa, Hiroki; Kader, Jean-Claude

    1991-01-01

    Plasma membranes obtained by two-phase partitioning of microsomal fractions from spinach (Spinacea oleracea L. cv Medania) and sugar beet leaves (Beta vulgaris L.) contained relatively high NADH-ferricyanide reductase and NADH-nitrate reductase (NR; EC 1.6.6.1) activities. Both of these activities were latent. To investigate whether these activities were due to the same enzyme, plasma membrane polypeptides were separated with SDS-PAGE and analyzed with immunoblotting methods. Antibodies raised against microsomal NADH-ferricyanide reductase (tentatively identified as NADH-cytochrome b5 reductase, EC 1.6.2.2), purified from potato (Solanum tuberosum L. cv Bintje) tuber microsomes, displayed one single band at 43 kilodaltons when reacted with spinach plasma membranes, whereas lgG produced against NR from spinach leaves gave a major band at 110 kilodaltons together with a few fainter bands of lower molecular mass. Immunoblotting analysis using inside-out and right-side-out plasma membrane vesicles strongly indicated that NR was not an integral protein but probably trapped inside the plasma membrane vesicles during homogenization. Proteins from spinach plasma membranes were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl) dimethylammonio] 1-propane-sulfonate and separated on a Mono Q anion exchange column at pH 5.6 with fast protein liquid chromatography. One major peak of NADH-ferricyanide reductase activity was found after separation. The peak fraction was enriched about 70-fold in this activity compared to the plasma membrane. When the peak fractions were analyzed with SDS-PAGE the NADH-ferricyanide reductase activity strongly correlated with a 43 kilodalton polypeptide which reacted with the antibodies against potato microsomal NADH-ferricyanide reductase. Thus, our data indicate that most, if not all, of the truly membrane-bound NADH-ferricyanide reductase activity of leaf plasma membranes is due to an enzyme very similar to potato tuber

  16. Analysis of nitrate reductase mRNA expression and nitrate reductase activity in response to nitrogen supply

    OpenAIRE

    Gholamreza Kavoosi; Sadegh Balotf; Homeira Eshghi; Hasan Hasani

    2014-01-01

    Nitrate is one of the major sources of nitrogen for the growth of plants. It is taken up by plant roots and transported to the leaves where it is reduced to nitrite in the. The main objective of this research was to investigate stimulatory effects of sodium nitrate, potassium nitrate, ammonia and urea on the production/generation of the nitrate reductase mRNA in Triticum aestivum plants. The plants were grown in standard nutrient solution for 21 days and then starved in a media without nitrat...

  17. Optimum conditions for cotton nitrate reductase extraction and ...

    African Journals Online (AJOL)

    Conditions of nitrate reductase extraction and activity measurement should be adapted to plant species, and to the organs of the same plant, because of extreme weaknesses and instabilities of the enzyme. Different extraction and reaction media have been compared in order to define the best conditions for cotton callus ...

  18. Transcriptional modulation of genes encoding nitrate reductase in ...

    African Journals Online (AJOL)

    2016-10-26

    Oct 26, 2016 ... The free aluminum (Al) content in soil can reach levels that are toxic to plants, and this has frequently limited increased productivity of cultures. Four genes encoding nitrate reductase (NR) were identified, named ZmNR1–4. With the aim of evaluating NR activity and the transcriptional modulation of the.

  19. Transcriptional modulation of genes encoding nitrate reductase in ...

    African Journals Online (AJOL)

    The free aluminum (Al) content in soil can reach levels that are toxic to plants, and this has frequently limited increased productivity of cultures. Four genes encoding nitrate reductase (NR) were identified, named ZmNR1–4. With the aim of evaluating NR activity and the transcriptional modulation of the ZmNR1, ZmNR2, ...

  20. Nitrate reductase gene involvement in hexachlorobiphenyl dechlorination by Phanerochaete chrysosporium

    International Nuclear Information System (INIS)

    De, Supriyo; Perkins, Michael; Dutta, Sisir K.

    2006-01-01

    Polychlorobiphenyl (PCB) degradation usually occurs through reductive dechlorination under anaerobic conditions and phenolic ring cleavage under aerobic conditions. In this paper, we provide evidence of nitrate reductase (NaR) mediated dechlorination of hexachlorobiphenyl (PCB-153) in Phanerochaete chrysosporium under non-ligninolytic condition and the gene involved. The NaR enzyme and its cofactor, molybdenum (Mo), were found to mediate reductive dechlorination of PCBs even in aerobic condition. Tungsten (W), a competitive inhibitor of this enzyme, was found to suppress this dechlorination. Chlorine release assay provided further evidence of this nitrate reductase mediated dechlorination. Commercially available pure NaR enzyme from Aspergillus was used to confirm these results. Through homology search using TBLASTN program, NaR gene was identified, primers were designed and the RT-PCR product was sequenced. The NaR gene was then annotated in the P. chrysosporium genome (GenBank accession no. AY700576). This is the first report regarding the presence of nitrate reductase gene in this fungus with the explanation why this fungus can dechlorinate PCBs even in aerobic condition. These fungal inoculums are used commercially as pellets in sawdust for enhanced bioremediation of PCBs at the risk of depleting soil nitrates. Hence, the addition of nitrates to the pellets will reduce this risk as well as enhance its activity

  1. Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription

    DEFF Research Database (Denmark)

    Cheng, Chi-Lien; Acedo, Gregoria N; Kristensen, Michael

    1992-01-01

    can replace light in eliciting an increase of nitrate reductase mRNA accumulation in dark-adapted green Arabidopsis plants. We show further that sucrose alone is sufficient for the full expression of nitrate reductase genes in etiolated Arabidopsis plants. Finally, using a reporter gene, we show......Nitrate reductase, the first enzyme in nitrate assimilation, is located at the crossroad of two energy-consuming pathways: nitrate assimilation and carbon fixation. Light, which regulates the expression of many higher-plant carbon fixation genes, also regulates nitrate reductase gene expression....... Located in the cytosol, nitrate reductase obtains its reductant not from photosynthesis but from carbohydrate catabolism. This relationship prompted us to investigate the indirect role that light might play, via photosynthesis, in the regulation of nitrate reductase gene expression. We show that sucrose...

  2. Gamma-irradiation activates biochemical systems: induction of nitrate reductase activity in plant callus.

    OpenAIRE

    Pandey, K N; Sabharwal, P S

    1982-01-01

    Gamma-irradiation induced high levels of nitrate reductase activity (NADH:nitrate oxidoreductase, EC 1.6.6.1) in callus of Haworthia mirabilis Haworth. Subcultures of gamma-irradiated tissues showed autonomous growth on minimal medium. We were able to mimic the effects of gamma-irradiation by inducing nitrate reductase activity in unirradiated callus with exogenous auxin and kinetin. These results revealed that induction of nitrate reductase activity by gamma-irradiation is mediated through i...

  3. Immunological comparison of the NADH:nitrate reductase from different cucumber tissues

    Directory of Open Access Journals (Sweden)

    Jolanta Marciniak

    2014-01-01

    Full Text Available Soluble nitrate reductase from cucumber roots (Cucumis sativus L. was isolated and purified with blue-Sepharose 4B. Specific antibodies against the NR protein were raised by immunization of a goat. Using polyclonal antibodies anti-NR properties of the nitrate reductase from various cucumber tissues were examined. Experiments showed difference in immuno-logical properties of nitrate reductase (NR from cotyledon roots and leaves.

  4. Optimisation of nitrate reductase enzyme activity to synthesise silver nanoparticles.

    Science.gov (United States)

    Khodashenas, Bahareh; Ghorbani, Hamid Reza

    2016-06-01

    Today, the synthesis of silver nanoparticles (Ag NPs) is very common since it has many applications in different areas. The synthesis of these nanoparticles is done by means of physical, chemical, or biological methods. However, due to its inexpensive and environmentally friendly features, the biological method is more preferable. In the present study, using nitrate reductase enzyme available in the Escherichia coli (E. coli) bacterium, the biosynthesis of Ag NPs was investigated. In addition, the activity of the nitrate reductase enzyme was optimised by changing its cultural conditions, and the effects of silver nitrate (AgNO(3)) concentration and enzyme amount on nanoparticles synthesis were studied. Finally, the produced nanoparticles were studied using ultraviolet -visible (UV-Vis) spectrophotometer, dynamic light scattering technique, and transmission electron microscopy. UV-Visible spectrophotometric study showed the characteristic peak for Ag NPs at wavelength 405-420 nm for 1 mM metal precursor solution (AgNO(3)) with 1, 5, 10, and 20 cc supernatant and 435 nm for 0.01M AgNO(3) with 20 cc supernatant. In this study, it was found that there is a direct relationship between the AgNO(3) concentration and the size of produced Ag NPs.

  5. Determination of Nitrate Reductase Assay Depending on the Microbial Growth

    International Nuclear Information System (INIS)

    El-Kabbany, H.M.

    2012-01-01

    A rapid micro-dilution assay for determination of the antimicrobial susceptibility of different bacterial isolates was developed. This assay is based on the ability of the most of viable organisms to reduce nitrates. The MIC or MBC could be determined by nitrate reductase (NR) only after 30 to 90 min of incubation depending on the behaviour of microbial growth. Bacterial viability is detected by a positive nitrite reduction rather than visible turbidity. The nitrate reduction assay was compared with standard micro-assay using 250 isolates of different taxa against 10 antibiotics belonging to different classes. An excellent agreement of 82.5 % was found between the two methods and only 17.5 % of 1794 trials showed difference in the determined MIC by tow-dilution interval above or below the MIC determined by the turbidimetric method under the same test conditions. However, the nitrate reduction assay was more rapid and sensitive in detecting viable bacteria and so, established an accurate estimate of the minimal inhibitory concentration (MIC) or the minimal bacterial concentration (MBC). The nitrate reduction assay offers the additional advantage that it could be used to determine the MBC without having to subculture the broth. 232 cases of resistance were detected by NR and 4 different media were tested for susceptibility test. The bacterial isolates were exposed to ultra violet (UV) light for different period

  6. Structural Basis of Eukaryotic Nitrate Reduction: Crystal Structures of the Nitrate Reductase Active Site

    Science.gov (United States)

    Fischer, Katrin; Barbier, Guillaume G.; Hecht, Hans-Juergen; Mendel, Ralf R.; Campbell, Wilbur H.; Schwarz, Guenter

    2005-01-01

    Nitrate assimilation in autotrophs provides most of the reduced nitrogen on earth. In eukaryotes, reduction of nitrate to nitrite is catalyzed by the molybdenum-containing NAD(P)H:nitrate reductase (NR; EC 1.7.1.1-3). In addition to the molybdenum center, NR contains iron-heme and flavin adenine dinucleotide as redox cofactors involved in an internal electron transport chain from NAD(P)H to nitrate. Recombinant, catalytically active Pichia angusta nitrate-reducing, molybdenum-containing fragment (NR-Mo) was expressed in P. pastoris and purified. Crystal structures for NR-Mo were determined at 1.7 and 2.6 Å. These structures revealed a unique slot for binding nitrate in the active site and identified key Arg and Trp residues potentially involved in nitrate binding. Dimeric NR-Mo is similar in overall structure to sulfite oxidases, with significant differences in the active site. Sulfate bound in the active site caused conformational changes, as compared with the unbound enzyme. Four ordered water molecules located in close proximity to Mo define a nitrate binding site, a penta-coordinated reaction intermediate, and product release. Because yeast NAD(P)H:NR is representative of the family of eukaryotic NR, we propose a general mechanism for nitrate reduction catalysis. PMID:15772287

  7. Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode

    Energy Technology Data Exchange (ETDEWEB)

    Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif, E-mail: e.erhan@gyte.edu.tr

    2012-01-01

    This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44-1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N = 3) with a relative standard deviation (RSD) of 5.4% (n = 7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 {mu}g/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday. - Highlights: Black-Right-Pointing-Pointer K{sub 3}Fe(CN){sub 6} has been used for the first time as mediator for nitrate reductase. Black-Right-Pointing-Pointer Better performance was obtained in comparison to other nitrate biosensor studies operated with various mediators. Black-Right-Pointing-Pointer Analytical parameters were better than standard nitrate analysis methods.

  8. Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode

    International Nuclear Information System (INIS)

    Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif

    2012-01-01

    This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44–1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N = 3) with a relative standard deviation (RSD) of 5.4% (n = 7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 μg/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday. - Highlights: ► K 3 Fe(CN) 6 has been used for the first time as mediator for nitrate reductase. ► Better performance was obtained in comparison to other nitrate biosensor studies operated with various mediators. ► Analytical parameters were better than standard nitrate analysis methods.

  9. Effect of Ammonium and Nitrate on Ferric Chelate Reductase and Nitrate Reductase in Vaccinium Species

    OpenAIRE

    POONNACHIT, U.; DARNELL, R.

    2004-01-01

    • Background and Aims Most Vaccinium species have strict soil requirements for optimal growth, requiring low pH, high iron availability and nitrogen primarily in the ammonium form. These soils are limited and are often located near wetlands. Vaccinium arboreum is a wild species adapted to a wide range of soils, including high pH, low iron, and nitrate‐containing soils. This broader soil adaptation in V. arboreum may be related to increased efficiency of iron or nitrate uptake compared with th...

  10. Nitrate decreases xanthine oxidoreductase-mediated nitrite reductase activity and attenuates vascular and blood pressure responses to nitrite

    Directory of Open Access Journals (Sweden)

    Célio Damacena-Angelis

    2017-08-01

    Full Text Available Nitrite and nitrate restore deficient endogenous nitric oxide (NO production as they are converted back to NO, and therefore complement the classic enzymatic NO synthesis. Circulating nitrate and nitrite must cross membrane barriers to produce their effects and increased nitrate concentrations may attenuate the nitrite influx into cells, decreasing NO generation from nitrite. Moreover, xanthine oxidoreductase (XOR mediates NO formation from nitrite and nitrate. However, no study has examined whether nitrate attenuates XOR-mediated NO generation from nitrite. We hypothesized that nitrate attenuates the vascular and blood pressure responses to nitrite either by interfering with nitrite influx into vascular tissue, or by competing with nitrite for XOR, thus inhibiting XOR-mediated NO generation. We used two independent vascular function assays in rats (aortic ring preparations and isolated mesenteric arterial bed perfusion to examine the effects of sodium nitrate on the concentration-dependent responses to sodium nitrite. Both assays showed that nitrate attenuated the vascular responses to nitrite. Conversely, the aortic responses to the NO donor DETANONOate were not affected by sodium nitrate. Further confirming these results, we found that nitrate attenuated the acute blood pressure lowering effects of increasing doses of nitrite infused intravenously in freely moving rats. The possibility that nitrate could compete with nitrite and decrease nitrite influx into cells was tested by measuring the accumulation of nitrogen-15-labeled nitrite (15N-nitrite by aortic rings using ultra-performance liquid chromatography tandem mass-spectrometry (UPLC-MS/MS. Nitrate exerted no effect on aortic accumulation of 15N-nitrite. Next, we used chemiluminescence-based NO detection to examine whether nitrate attenuates XOR-mediated nitrite reductase activity. Nitrate significantly shifted the Michaelis Menten saturation curve to the right, with a 3-fold increase in

  11. Comparative modelling and molecular docking of nitrate reductase from Bacillus weihenstephanensis (DS45

    Directory of Open Access Journals (Sweden)

    R. Seenivasagan

    2016-07-01

    Full Text Available Nitrate reductase catalyses the oxidation of NAD(PH and the reduction of nitrate to nitrite. NR serves as a central point for the integration of metabolic pathways by governing the flux of reduced nitrogen through several regulatory mechanisms in plants, algae and fungi. Bacteria express nitrate reductases that convert nitrate to nitrite, but mammals lack these specific enzymes. The microbial nitrate reductase reduces toxic compounds to nontoxic compounds with the help of NAD(PH. In the present study, our results revealed that Bacillus weihenstephanensis expresses a nitrate reductase enzyme, which was made to generate the 3D structure of the enzyme. Six different modelling servers, namely Phyre2, RaptorX, M4T Server, HHpred, SWISS MODEL and Mod Web, were used for comparative modelling of the structure. The model was validated with standard parameters (PROCHECK and Verify 3D. This study will be useful in the functional characterization of the nitrate reductase enzyme and its docking with nitrate molecules, as well as for use with autodocking.

  12. Studies on the kinetic mechanism of nitrate reductase from spinach (Spinacea oleracea).

    Science.gov (United States)

    de la Rosa, F F; Palacián, E; Castillo, F

    1980-09-01

    Based on Lineweaver-Burk plots of the initial velocities, at different concentrations of NADH and nitrate, and product inhibition patterns, an Iso Ping Pong Bi Bi steady state kinetic mechanism is proposed for the spinach nitrate reductase. This mechanism incorporates the concept that the oxidized enzyme is present in two isomeric forms.

  13. Nitrate reductase from Spinacea oleracea. FAD and the reactivation of the enzyme treated with p-Hydroxymercuribenzoate.

    Science.gov (United States)

    Castillo, F; de la Rosa, F F; Palacián, E

    1977-12-01

    Spinach nitrate reductase complex previously inactivated by treatment with mercurials p-hydroxymercuribenzoate or p-hydroxymercuriphenyl sulphonate can be reactivated by incubation with dithioerythritol. The reactivation of NADH-diaphorase seems to be FAD-dependent, whereas that of FNH2-nitrate reductase is not. The requirement of FAD for NADH-inactivation of nitrate reductase treated with p-hydroxymercuribenzoate disappears after treatment with dithioerythritol.

  14. Overexpression of Nitrate Reductase in Tobacco Delays Drought-Induced Decreases in Nitrate Reductase Activity and mRNA1

    Science.gov (United States)

    Ferrario-Méry, Sylvie; Valadier, Marie-Hélène; Foyer, Christine H.

    1998-01-01

    Transformed (cauliflower mosaic virus 35S promoter [35S]) tobacco (Nicotiana plumbaginifolia L.) plants constitutively expressing nitrate reductase (NR) and untransformed controls were subjected to drought for 5 d. Drought-induced changes in biomass accumulation and photosynthesis were comparable in both lines of plants. After 4 d of water deprivation, a large increase in the ratio of shoot dry weight to fresh weight was observed, together with a decrease in the rate of photosynthetic CO2 assimilation. Foliar sucrose increased in both lines during water stress, but hexoses increased only in leaves from untransformed controls. Foliar NO3− decreased rapidly in both lines and was halved within 2 d of the onset of water deprivation. Total foliar amino acids decreased in leaves of both lines following water deprivation. After 4 d of water deprivation no NR activity could be detected in leaves of untransformed plants, whereas about 50% of the original activity remained in the leaves of the 35S-NR transformants. NR mRNA was much more stable than NR activity. NR mRNA abundance increased in the leaves of the 35S-NR plants and remained constant in controls for the first 3 d of drought. On the 4th d, however, NR mRNA suddenly decreased in both lines. Rehydration at d 3 caused rapid recovery (within 24 h) of 35S-NR transcripts, but no recovery was observed in the controls. The phosphorylation state of the protein was unchanged by long-term drought. There was a strong correlation between maximal extractable NR activity and ambient photosynthesis in both lines. We conclude that drought first causes increased NR protein turnover and then accelerates NR mRNA turnover. Constitutive NR expression temporarily delayed drought-induced losses in NR activity. 35S-NR expression may therefore allow more rapid recovery of N assimilation following short-term water deficit. PMID:9576799

  15. Induction of the Nitrate Assimilation nirA Operon and Protein-Protein Interactions in the Maturation of Nitrate and Nitrite Reductases in the Cyanobacterium Anabaena sp. Strain PCC 7120.

    Science.gov (United States)

    Frías, José E; Flores, Enrique

    2015-07-01

    Nitrate is widely used as a nitrogen source by cyanobacteria, in which the nitrate assimilation structural genes frequently constitute the so-called nirA operon. This operon contains the genes encoding nitrite reductase (nirA), a nitrate/nitrite transporter (frequently an ABC-type transporter; nrtABCD), and nitrate reductase (narB). In the model filamentous cyanobacterium Anabaena sp. strain PCC 7120, which can fix N2 in specialized cells termed heterocysts, the nirA operon is expressed at high levels only in media containing nitrate or nitrite and lacking ammonium, a preferred nitrogen source. Here we examined the genes downstream of the nirA operon in Anabaena and found that a small open reading frame of unknown function, alr0613, can be cotranscribed with the operon. The next gene in the genome, alr0614 (narM), showed an expression pattern similar to that of the nirA operon, implying correlated expression of narM and the operon. A mutant of narM with an insertion mutation failed to produce nitrate reductase activity, consistent with the idea that NarM is required for the maturation of NarB. Both narM and narB mutants were impaired in the nitrate-dependent induction of the nirA operon, suggesting that nitrite is an inducer of the operon in Anabaena. It has previously been shown that the nitrite reductase protein NirA requires NirB, a protein likely involved in protein-protein interactions, to attain maximum activity. Bacterial two-hybrid analysis confirmed possible NirA-NirB and NarB-NarM interactions, suggesting that the development of both nitrite reductase and nitrate reductase activities in cyanobacteria involves physical interaction of the corresponding enzymes with their cognate partners, NirB and NarM, respectively. Nitrate is an important source of nitrogen for many microorganisms that is utilized through the nitrate assimilation system, which includes nitrate/nitrite membrane transporters and the nitrate and nitrite reductases. Many cyanobacteria

  16. EPR and redox properties of periplasmic nitrate reductase from Desulfovibrio desulfuricans ATCC 27774.

    Science.gov (United States)

    González, Pablo J; Rivas, María G; Brondino, Carlos D; Bursakov, Sergey A; Moura, Isabel; Moura, José J G

    2006-07-01

    Nitrate reductases are enzymes that catalyze the conversion of nitrate to nitrite. We report here electron paramagnetic resonance (EPR) studies in the periplasmic nitrate reductase isolated from the sulfate-reducing bacteria Desulfovibrio desulfuricans ATCC 27774. This protein, belonging to the dimethyl sulfoxide reductase family of mononuclear Mo-containing enzymes, comprises a single 80-kDa subunit and contains a Mo bis(molybdopterin guanosine dinucleotide) cofactor and a [4Fe-4S] cluster. EPR-monitored redox titrations, carried out with and without nitrate in the potential range from 200 to -500 mV, and EPR studies of the enzyme, in both catalytic and inhibited conditions, reveal distinct types of Mo(V) EPR-active species, which indicates that the Mo site presents high coordination flexibility. These studies show that nitrate modulates the redox properties of the Mo active site, but not those of the [4Fe-4S] center. The possible structures and the role in catalysis of the distinct Mo(V) species detected by EPR are discussed.

  17. Mo and W bis-MGD enzymes: nitrate reductases and formate dehydrogenases.

    Science.gov (United States)

    Moura, José J G; Brondino, Carlos D; Trincão, José; Romão, Maria João

    2004-10-01

    Molybdenum and tungsten are second- and third-row transition elements, respectively, which are found in a mononuclear form in the active site of a diverse group of enzymes that generally catalyze oxygen atom transfer reactions. Mononuclear Mo-containing enzymes have been classified into three families: xanthine oxidase, DMSO reductase, and sulfite oxidase. The proteins of the DMSO reductase family present the widest diversity of properties among its members and our knowledge about this family was greatly broadened by the study of the enzymes nitrate reductase and formate dehydrogenase, obtained from different sources. We discuss in this review the information of the better characterized examples of these two types of Mo enzymes and W enzymes closely related to the members of the DMSO reductase family. We briefly summarize, also, the few cases reported so far for enzymes that can function either with Mo or W at their active site.

  18. The Effect of Nitrate Levels and Harvest Times on Fe, Zn, Cu, and K, Concentrations and Nitrate Reductase Activity in Lettuce and Spinach

    Directory of Open Access Journals (Sweden)

    Z. Gheshlaghi

    2015-09-01

    Full Text Available Leafy vegetables are considered as the main sources of nitrate in the human diet. In order to investigate the effect of nitrate levels and harvest times on nitrate accumulation, nitrate reductase activity, concentrations of Fe, Zn, Cu and K in Lettuce and Spinach and their relation to nitrate accumulation in these leafy vegetables, two harvest times (29 and 46 days after transplanting, two vegetable species of lettuce and spinach and two concentrations of nitrate (10 and 20 mM were used in a hydroponics greenhouse experiment with a completely randomized design and 3 replications. Modified Hoagland and Arnon nutrient solutions were used for the experiment. The results indicated that by increasing nitrate concentration of solution, nitrate accumulation in roots and shoots of lettuce and spinach increased significantly (P ≤ 0.05, and the same trend was observed for the nitrate reductase activity in the shoots of the two species. Increasing the nitrate concentrations of solution, reduced the shoot dry weight and the concentration of Fe and Cu in both species, where as it increased the K and Zn concentrations in the shoots of the two species in each both harvest times, the nitrate accumulation increased, but the nitrate reductase activity decreased in the shoots of the two species over the course of the growth. The Concentration of Fe, Cu and K decreased in the shoots of lettuce and the spinach with the time, despite the increase in Zn concentration in the shoots. The results also indicated that increasing nitrate concentrations of solution to the levels greater than the plant capacity for reduction and net uptake of nitrate, leads to the nitrate accumulation in the plants. Nitrate accumulation in plant tissue led to decreases in fresh shoot yield and Fe and Cu concentrations and nitrate reductase activities in both lettuce and spinach.

  19. Variant Cell Lines of Haplopappus gracilis with Disturbed Activities of Nitrate Reductase and Nitrite Reductase.

    Science.gov (United States)

    Gilissen, L J; Barneix, A J; van Staveren, M; Breteler, H

    1985-07-01

    Selected variant cell lines of Haplopappus gracilis (Nutt) Gray that showed disturbed growth after transfer from an alanine medium to NO(3) (-) medium were characterized. The in vivo NO(3) (-) reductase activity (NRA) was lower in these lines than in the wild type. In vitro NRA assays suggest that decreased in vivo NRA was not caused by a lower amount of active enzyme. Cells of the variant lines revealed up to 75% lower extractable activity of NO(2) (-) reductase as compared with the wild type. This coincided with higher accumulation of NO(2) (-) by the variant than by the wild type cells after transfer from alanine medium to NO(3) (-) medium. NO(2) (-) accumulation was transient or continuous, depending on cell line, metabolic state of the cells, and light conditions.

  20. Azospirillum Inoculation Alters Nitrate Reductase Activity and Nitrogen Uptake in Wheat Plant Under Water Deficit Conditions

    OpenAIRE

    N. Aliasgharzad, N. Aliasgharzad; Heydaryan, Zahra; Sarikhani, M.R

    2014-01-01

    Water deficit stress usually diminishes nitrogen uptake by plants. There are evidences that some nitrogen fixing bacteria can alleviate this stress by supplying nitrogen and improving its metabolism in plants. Four Azospirillum strains, A. lipoferum AC45-II, A. brasilense AC46-I, A. irakense AC49-VII and A. irakense AC51-VI were tested for nitrate reductase activity (NRA). In a pot culture experiment using a sandy loam soil, wheat plants (Triticum aestivum L. cv. Sardari) were inoculated with...

  1. Effect of tungsten and vanadium on the in vitro assembly of assimilatory nitrate reductase utilizing Neurospora mutant nit-1

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.Y.; Erickson, R.; Pan, S.S.; Jones, G.; May, F.; Nason, A.

    1974-06-01

    Tungsten or vanadium in a nutrient medium containing nitrate, but not ammonia, as the sole nitrogen source inhibited the formation of assimilatory NADPH-nitrate reductase (but not nitrate-inducible NADPH-cytochrome c reductase) and growth of wild type Neurospora crassa. Inhibition was prevented by high levels of molybdate in the nutrient medium but was not reversed by adding molybdate to subsequently prepared cell-free enzyme preparations. Neither tungsten nor vanadium was inhibitory when added to partially purified wild type Neurospora NADPH-nitrate reductase. Cell-free preparations of uninduced wild type grown in increasing concentrations of tungsten or vanadium showed progressive inhibition of ability to assemble nitrate reductase in vitro (with extracts of nitrate-induced Neurospora mutant nit-1) which was partially or entirely restored by subsequent addition of molybdate to the extracts of the tungsten- or vanadium-grown uninduced wild type. Tungsten or vanadium added to acid-treated bovine milk xanthine oxidase or to extracts of uninduced wild type also inhibited in vitro enzyme assembly, with added molybdate partially preventing inhibition. The tungsten or vanadium analogue of nitrate reductase formed in vivo or by in vitro assembly is considerably more labile than its molybdenum counterpart as indicated by the complete loss of /sup 185/W or /sup 48/V from the enzyme as a result of trichloroacetic acid precipitation or heat treatment.

  2. The effect of ionic and non-ionic surfactants on the growth, nitrate reductase and nitrite reductase activities of Spirodela polyrrhiza (L. Schleiden

    Directory of Open Access Journals (Sweden)

    Józef Buczek

    2014-01-01

    Full Text Available Inclusion into the medium of 5 mg•dm-3 of non-ionic (ENF or ionic (DBST surfactant caused 50-60% inhibition of nitrite reductase MR activity in S. polyrrhiza. At the same time, increased accumulation of NO2- in the plant tissues and lowering of the total and soluble protein contents were found. DBST also lowered the nitrate reductase (NR activity and the dry mass of the plants.

  3. Rapid induction of GFP expression by the nitrate reductase promoter in the diatom Phaeodactylum tricornutum

    Science.gov (United States)

    Ewe, Daniela; Río Bártulos, Carolina; Kroth, Peter G.; Gruber, Ansgar

    2016-01-01

    An essential prerequisite for a controlled transgene expression is the choice of a suitable promoter. In the model diatom Phaeodactylum tricornutum, the most commonly used promoters for trans-gene expression are the light dependent lhcf1 promoters (derived from two endogenous genes encoding fucoxanthin chlorophyll a/c binding proteins) and the nitrate dependent nr promoter (derived from the endogenous nitrate reductase gene). In this study, we investigated the time dependent expression of the green fluorescent protein (GFP) reporter under control of the nitrate reductase promoter in independently genetically transformed P. tricornutum cell lines following induction of expression by change of the nitrogen source in the medium via flow cytometry, microscopy and western blotting. In all investigated cell lines, GFP fluorescence started to increase 1 h after change of the medium, the fastest increase rates were observed between 2 and 3 h. Fluorescence continued to increase slightly for up to 7 h even after transfer of the cells to ammonium medium. The subsequent decrease of GFP fluorescence was much slower than the increase, probably due to the stability of GFP. The investigation of several cell lines transformed with nr based constructs revealed that, also in the absence of nitrate, the promoter may show residual activity. Furthermore, we observed a strong variation of gene expression between independent cell lines, emphasising the importance of a thorough characterisation of genetically modified cell lines and their individual expression patterns. PMID:27635322

  4. Colour formation in fermented sausages by meat-associated staphylococci with different nitrite- and nitrate-reductase activities

    DEFF Research Database (Denmark)

    Gøtterup, Jacob; Olsen, Karsten; Knøchel, Susanne

    2008-01-01

    nitrate depended on the specific Staphylococcus strain. Strains with high nitrate-reductase activity showed a significantly faster rate of pigment formation, but other factors were of influence as well. Product stability for the sliced, packaged sausage was evaluated as surface colour and oxidation...

  5. Purification and biochemical characterization of simplified eukaryotic nitrate reductase expressed in Pichia pastoris.

    Science.gov (United States)

    Barbier, Guillaume G; Joshi, Rama C; Campbell, Ellen R; Campbell, Wilbur H

    2004-09-01

    NAD(P)H:nitrate reductase (NaR, EC 1.7.1.1-3) is a useful enzyme in biotechnological applications, but it is very complex in structure and contains three cofactors-flavin adenine dinucleotide, heme-Fe, and molybdenum-molybdopterin (Mo-MPT). A simplified nitrate reductase (S-NaR1) consisting of Mo-MPT-binding site and nitrate-reducing active site was engineered from yeast Pichia angusta NaR cDNA (YNaR1). S-NaR1 was cytosolically expressed in high-density fermenter culture of methylotrophic yeast Pichia pastoris. Total amount of S-NaR1 protein produced was approximately 0.5 g per 10 L fermenter run, and methanol phase productivity was 5 microg protein/g wet cell weight/h. Gene copy number in genomic DNA of different clones showed direct correlation with the expression level. S-NaR1 was purified to homogeneity in one step by immobilized metal affinity chromatography (IMAC) and total amount of purified protein per run of fermentation was approximately 180 mg. Polypeptide size was approximately 55 kDa from electrophoretic analysis, and S-NaR1 was mainly homo-tetrameric in its active form, as shown by gel filtration. S-NaR1 accepted electrons efficiently from reduced bromphenol blue (kcat = 2081 s(-1)) and less so from reduced methyl viologen (kcat = 159 s(-1)). The nitrate KM for S-NaR1 was 30 +/- 3 microM, which is very similar to YNaR1. S-NaR1 is capable of specific nitrate reduction, and direct electric current, as shown by catalytic nitrate reduction using protein film cyclic voltammetry, can drive this reaction. Thus, S-NaR1 is an ideal form of this enzyme for commercial applications, such as an enzymatic nitrate biosensor formulated with S-NaR1 interfaced to an electrode system.

  6. The uptake and accumulation of phosphorous and nitrates and the activity of nitrate reductase in cucumber seedlings treated with PbCl2 or CdCl2

    Directory of Open Access Journals (Sweden)

    Marek Burzyński

    2014-01-01

    Full Text Available Treatment of 4-day-old cucumber (Cucumis sativus L. seedlings with PbCl2 or CdCl2 caused a significant increase in the accumulation of heavy metals by the plants, especially in the roots. The accumulated Pb initially enhanced the uptake of phosphorous after the plants had been transferred to a nutrient medium (6, 24 hrs, but after only 48 Ins the uptake had dropped to below control level. The plants treated with Cd exhibited a constant decreased phosphorous uptake level. The accumulated lead and cadmium also inhibited nitrate uptake and the activity of nitrate reductase. It is suggested that the reason for the decreased nitrate reductase activity lay rather in the lower nitrate uptake than in a direct effect of the heavy metals on the enzyme.

  7. Comparison of the Stereospecificity and Immunoreactivity of NADH-Ferricyanide Reductases in Plant Membranes.

    Science.gov (United States)

    Fredlund, K. M.; Struglics, A.; Widell, S.; Askerlund, P.; Kader, J. C.; Moller, I. M.

    1994-11-01

    The substrate stereospecificity of NADH-ferricyanide reductase activities in the inner mitochondrial membrane and peroxisomal membrane of potato (Solanum tuberosum L.) tubers, spinach (Spinacea oleracea L.) leaf plasma membrane, and red beetroot (Beta vulgaris L.) tonoplast were all specific for the [beta]-hydrogen of NADH, whereas the reductases in wheat root (Triticum aestivum L.) endoplasmic reticulum and potato tuber outer mitochondrial membrane were both [alpha]-hydrogen specific. In all isolated membrane fractions one or several polypeptides with an apparent size of 45 to 55 kD cross-reacted with antibodies raised against a microsomal NADH-ferricyanide reductase on western blots.

  8. Acetaldehyde Oxime, A Product Formed during the In Vivo Nitrate Reductase Assay of Soybean Leaves.

    Science.gov (United States)

    Mulvaney, C S; Hageman, R H

    1984-09-01

    Evolution of nitrogen oxides (NO((x)), primarily as nitric oxide) from soybean (Glycine max [L.] Merr.) leaves during purged in vivo nitrate reductase assays had been reported; however, these reports were based on a method that had been used for determination of NO((x)) in air. This method also detects other N compounds. Preliminary work led us to doubt that the evolved N was nitric oxide. Studies were undertaken to identify the N compound evolved from the in vivo assay that had been reported as NO((x)). Material for identification was obtained by cryogenic trapping and fractional distillation, and by chemical trapping procedures. Mass spectrometry, ultraviolet spectroscopy, and (15)N-labeled nitrate were used to identify the compounds evolved and to determine whether these compounds were derived from nitrate. Acetaldehyde oxime was identified as the predominant N compound evolved and this compound is readily detected by the method for NO((x)) determination. Substantial quantities of acetaldehyde oxime (16.2 micromoles per gram fresh weight per hour) were evolved during the in vivo assay. Small amounts of nitrous oxide (0.63 micrograms N per gram fresh weight per hour) were evolved, but this compound is not detected as NO((x)). Acetaldehyde oxime and nitrous oxide were both produced as a result of nitrate ((15)NO(3) (-)) reduction during the assay.

  9. Acetaldehyde Oxime, A Product Formed during the In Vivo Nitrate Reductase Assay of Soybean Leaves 1

    Science.gov (United States)

    Mulvaney, Charlene S.; Hageman, Richard H.

    1984-01-01

    Evolution of nitrogen oxides (NO(x), primarily as nitric oxide) from soybean (Glycine max [L.] Merr.) leaves during purged in vivo nitrate reductase assays had been reported; however, these reports were based on a method that had been used for determination of NO(x) in air. This method also detects other N compounds. Preliminary work led us to doubt that the evolved N was nitric oxide. Studies were undertaken to identify the N compound evolved from the in vivo assay that had been reported as NO(x). Material for identification was obtained by cryogenic trapping and fractional distillation, and by chemical trapping procedures. Mass spectrometry, ultraviolet spectroscopy, and 15N-labeled nitrate were used to identify the compounds evolved and to determine whether these compounds were derived from nitrate. Acetaldehyde oxime was identified as the predominant N compound evolved and this compound is readily detected by the method for NO(x) determination. Substantial quantities of acetaldehyde oxime (16.2 micromoles per gram fresh weight per hour) were evolved during the in vivo assay. Small amounts of nitrous oxide (0.63 micrograms N per gram fresh weight per hour) were evolved, but this compound is not detected as NO(x). Acetaldehyde oxime and nitrous oxide were both produced as a result of nitrate (15NO3−) reduction during the assay. PMID:16663781

  10. Seasonal Patterns of Nitrate Reductase and Nitrogenase Activities in Phaseolus vulgaris L. 1

    Science.gov (United States)

    Franco, Alvilio A.; Pereira, Joao C.; Neyra, Carlos A.

    1979-01-01

    The patterns of nitrate reductase activity (NRA) in the leaves (in vivo assay) and root nodule nitrogenase activity (C2H2 reduction) were investigated throughout the season in field-grown Phaseolus vulgaris plants. Maximal NRA (per g fresh weight) occurred at early stages of leaf development but total activity (per leaf) was maximal when the leaf reached full size. In mature plants, most NRA was associated with the upper leaves. Nitrogenase activity was initiated about 2 weeks after sowing, reached a maximum at flowering (5 weeks after sowing) and declined rapidly thereafter. Nitrogenase activity followed the pattern of nodule development. After flowering, P. vulgaris was apparently able to take up and assimilate NO−3 as evidenced by the increase in NO−3 content of the stem and the high levels of NRA in the leaves. Total plant NRA was maximal after flowering and addition of NH4NO3 to the soil at flowering resulted in even higher levels of NRA through most of the pod-filling period, thus resulting in higher seed yields (59% over control). It is proposed that P. vulgaris can benefit from both N2 fixation and NO−3 assimilation and that nitrate reductase plays an important role in the assimilation of nitrogen after flowering. PMID:16660740

  11. Analysis of the combined effects of lanthanum and acid rain, and their mechanisms, on nitrate reductase transcription in plants.

    Science.gov (United States)

    Xia, Binxin; Sun, Zhaoguo; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

    2017-04-01

    Rare earth element (REE) pollution and acid rain are major global environmental concerns, and their spatial distributions overlap. Thus, both forms of pollution combine to act on plants. Nitrogen is important for plant growth, and nitrate reductase (NR) is a key plant enzyme that catalyzes nitrogen assimilation. Studying the combined effects of REEs and acid rain on plant nitrogen-based nutrients has important environmental significance. Here, soybean (Glycine max) plants, commonly used for toxicological studies, were exposed to lanthanum (La), a REE, and acid rain to study the NR activities and NR transcriptional levels in the roots. To explain how the pollution affected the NR transcriptional level, we simultaneously observed the contents of intracellular La and nutrient elements, protoplast morphology, membrane lipid peroxidation and intracellular pH. A combined treatment of 0.08mmol/L La and pH 4.5 acid rain increased the NR activity, decreased the NR transcriptional level, increased the intracellular nutrient elements' contents and caused deformations in membrane structures. Other combined treatments significantly decreased the aforementioned parameters and caused serious damage to the membrane structures. The variation in the amplitudes of combined treatments was greater than those of individual treatments. Compared with the control and individual treatments, combined treatments increased membrane permeability, the malondialdehyde content, and intracellular H + and La contents, and with an increasing La concentration or acid strength, the change in amplitude increased. Thus, the combined effects on NR gene transcription in soybean seedling roots were related to the intracellular nutrient elements' contents, protoplast morphology, membranous lipid peroxidation, intracellular pH and La content. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Nitrogen nutrition of Canna indica: Effects of ammonium versus nitrate on growth, biomass allocation, photosynthesis, nitrate reductase activity and N uptake rates

    DEFF Research Database (Denmark)

    Konnerup, Dennis; Brix, Hans

    2010-01-01

    The effects of inorganic nitrogen (N) source (NH4+, NO3- or both) on growth, biomass allocation, photosynthesis, N uptake rate, nitrate reductase activity and mineral composition of Canna indica were studied in hydroponic culture. The relative growth rates (0.05-0.06 g g-1 d-1), biomass allocation...

  13. The nitrate reductase activity of some root and stem parasites and their hosts

    International Nuclear Information System (INIS)

    Hunter, J.J.

    1984-12-01

    This investigation surveyed the nitrate reductase activity (NRA) of some South African root and stem parasites, as well as their hosts. Fourteen species - five stem and nine root parasites, representative of seven families - and eleven different hosts from eight families, were studied. Two methods were applied in the determination of the NRA of parasite and host, namely the in vivo and in vitro methods. Because of the limited literature on the NRA of parasitic flowering plants both the in vivo and in vitro methods were developed for the host species and subsequently applied to that specific species of parasite as well. Parasites and hosts were also investigated in their natural habitat. The NRA of the roots could, however, only be increased providing phorsynthetic products as a source of NADH, were available. By using [U- 14 C]-Sucrose it was confirmed that the parasite could have fulfilled this need. Generally, the investigation showed that the parasites that were studied, have not altogether lost their ability to reduce nitrate. However, it would appear that the host is used as a source of reduced nitrogen, rather than nitrate, under natural conditions

  14. Cold adaptation of the mononuclear molybdoenzyme periplasmic nitrate reductase from the Antarctic bacterium Shewanella gelidimarina

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, Philippa J.L. [School of Chemistry, University of Sydney, New South Wales 2006 (Australia); Codd, Rachel, E-mail: rachel.codd@sydney.edu.au [School of Chemistry, University of Sydney, New South Wales 2006 (Australia); School of Medical Sciences (Pharmacology) and Bosch Institute, University of New South Wales, New South Wales 2006 (Australia)

    2011-11-04

    Highlights: Black-Right-Pointing-Pointer Cold-adapted phenotype of NapA from the Antarctic bacterium Shewanella gelidimarina. Black-Right-Pointing-Pointer Protein homology model of NapA from S. gelidimarina and mesophilic homologue. Black-Right-Pointing-Pointer Six amino acid residues identified as lead candidates governing NapA cold adaptation. Black-Right-Pointing-Pointer Molecular-level understanding of designing cool-temperature in situ oxyanion sensors. -- Abstract: The reduction of nitrate to nitrite is catalysed in bacteria by periplasmic nitrate reductase (Nap) which describes a system of variable protein subunits encoded by the nap operon. Nitrate reduction occurs in the NapA subunit, which contains a bis-molybdopterin guanine dinucleotide (Mo-MGD) cofactor and one [4Fe-4S] iron-sulfur cluster. The activity of periplasmic nitrate reductase (Nap) isolated as native protein from the cold-adapted (psychrophilic) Antarctic bacterium Shewanella gelidimarina (Nap{sub Sgel}) and middle-temperature adapted (mesophilic) Shewanella putrefaciens (Nap{sub Sput}) was examined at varied temperature. Irreversible deactivation of Nap{sub Sgel} and Nap{sub Sput} occurred at 54.5 and 65 Degree-Sign C, respectively. When Nap{sub Sgel} was preincubated at 21-70 Degree-Sign C for 30 min, the room-temperature nitrate reductase activity was maximal and invariant between 21 and 54 Degree-Sign C, which suggested that Nap{sub Sgel} was poised for optimal catalysis at modest temperatures and, unlike Nap{sub Sput}, did not benefit from thermally-induced refolding. At 20 Degree-Sign C, Nap{sub Sgel} reduced selenate at 16% of the rate of nitrate reduction. Nap{sub Sput} did not reduce selenate. Sequence alignment showed 46 amino acid residue substitutions in Nap{sub Sgel} that were conserved in NapA from mesophilic Shewanella, Rhodobacter and Escherichia species and could be associated with the Nap{sub Sgel} cold-adapted phenotype. Protein homology modeling of Nap{sub Sgel} using a

  15. Periplasmic nitrate reductase revisited: a sulfur atom completes the sixth coordination of the catalytic molybdenum.

    Science.gov (United States)

    Najmudin, Shabir; González, Pablo J; Trincão, José; Coelho, Catarina; Mukhopadhyay, Abhik; Cerqueira, Nuno M F S A; Romão, Carlos C; Moura, Isabel; Moura, José J G; Brondino, Carlos D; Romão, Maria J

    2008-06-01

    Nitrate reductase from Desulfovibrio desulfuricans ATCC 27774 (DdNapA) is a monomeric protein of 80 kDa harboring a bis(molybdopterin guanine dinucleotide) active site and a [4Fe-4S] cluster. Previous electron paramagnetic resonance (EPR) studies in both catalytic and inhibiting conditions showed that the molybdenum center has high coordination flexibility when reacted with reducing agents, substrates or inhibitors. As-prepared DdNapA samples, as well as those reacted with substrates and inhibitors, were crystallized and the corresponding structures were solved at resolutions ranging from 1.99 to 2.45 A. The good quality of the diffraction data allowed us to perform a detailed structural study of the active site and, on that basis, the sixth molybdenum ligand, originally proposed to be an OH/OH(2) ligand, was assigned as a sulfur atom after refinement and analysis of the B factors of all the structures. This unexpected result was confirmed by a single-wavelength anomalous diffraction experiment below the iron edge (lambda = 1.77 A) of the as-purified enzyme. Furthermore, for six of the seven datasets, the S-S distance between the sulfur ligand and the Sgamma atom of the molybdenum ligand Cys(A140) was substantially shorter than the van der Waals contact distance and varies between 2.2 and 2.85 A, indicating a partial disulfide bond. Preliminary EPR studies under catalytic conditions showed an EPR signal designated as a turnover signal (g values 1.999, 1.990, 1.982) showing hyperfine structure originating from a nucleus of unknown nature. Spectropotentiometric studies show that reduced methyl viologen, the electron donor used in the catalytic reaction, does not interact directly with the redox cofactors. The turnover signal can be obtained only in the presence of the reaction substrates. With use of the optimized conditions determined by spectropotentiometric titration, the turnover signal was developed with (15)N-labeled nitrate and in D(2)O-exchanged Dd

  16. In situ assay of nitrate reductase activity using portable water bath.

    Science.gov (United States)

    Rajsz, Adam; Wojtuń, Bronisław; Bytnerowicz, Andrzej

    2017-07-01

    In environmental research (i.e., plant ecophysiology, environmental microbiology, and environmental chemistry), some assays require incubation of samples at controlled temperature and darkness. Until now, due to a lack of equipment providing such possibility in situ, researchers had to move collected samples to the laboratory for incubation. Obviously, a delayed incubation and the ex situ conditions could seriously affect the assays' results. A good example of analysis where water bath use is needed is the nitrate reductase activity (NRA) in vivo assay where plant tissue samples are incubated in buffer solution at a predetermined temperature. We designed a transportable water bath with a temperature control which enables in situ measurements in many types of environmental studies. The presented device is small in size featuring a thermally insulated chamber and an electronically controlled thermostat system powered by a 12-V battery. Due to its modular design, it can be transported comfortably in difficult terrain. The incubation process can be carried out continuously in stable temperature and darkness. In order to examine the field usability of the presented device, we conducted measurements of plant nitrate reductase activity in difficult field conditions. The in situ assays were carried out at high altitudes in the Karkonosze mountains, SW Poland. The NRA was studied in two alpine species (Deschampsia caespitosa and Homogyne alpina). Our results showed low NR activity in H. alpina (mean 0.31 μM NO 2 g -1 DW h -1 ) and higher NRA in D. caespitosa (mean 2.7 μM NO 2 g -1 DW h -1 ). The obtained results were highly reproducible and had small variability (low standard error values).

  17. Exogenous auxin-induced NO synthesis is nitrate reductase-associated in Arabidopsis thaliana root primordia.

    Science.gov (United States)

    Kolbert, Zsuzsanna; Bartha, Bernadett; Erdei, László

    2008-06-16

    Nitric oxide (NO) functions in various physiological and developmental processes in plants. However, the source of this signaling molecule in the diversity of plant responses is not well understood. It is known that NO mediates auxin-induced adventitious and lateral root (LR) formation. In this paper, we provide genetic and pharmacological evidence that the production of NO is associated with the nitrate reductase (NR) enzyme during indole-3-butyric acid (IBA)-induced lateral root development in Arabidopsis thaliana L. NO production was detected using 4,5-diaminofluorescein diacetate (DAF-2DA) in the NR-deficient nia1, nia2 and Atnoa1 (former Atnos1) mutants of A. thaliana. An inhibitor for nitric oxide synthase (NOS) N(G)-monomethyl-l-arginine (l-NMMA) was applied. Our data clearly show that IBA increased LR frequency in the wild-type plant and the LR initials emitted intensive NO-dependent fluorescence of the triazol product of NO and DAF-2DA. Increased levels of NO were restricted only to the LR initials in contrast to primary root (PR) sections, where NO remained at the control level. The mutants had different NO levels in their control state (i.e. without IBA treatment): nia1, nia2 showed lower NO fluorescence than Atnoa1 or the wild-type plant. The role of NR in IBA-induced NO formation in the wild type was shown by the zero effects of the NOS inhibitors l-NMMA. Finally, it was clearly demonstrated that IBA was able to induce NO generation in both the wild-type and Atnoa1 plants, but failed to induce NO in the NR-deficient mutant. It is concluded that the IBA-induced NO production is nitrate reductase-associated during lateral root development in A. thaliana.

  18. Antimicrobial activity and physical characterization of silver nanoparticles green synthesized using nitrate reductase from Fusarium oxysporum.

    Science.gov (United States)

    Gholami-Shabani, Mohammadhassan; Akbarzadeh, Azim; Norouzian, Dariush; Amini, Abdolhossein; Gholami-Shabani, Zeynab; Imani, Afshin; Chiani, Mohsen; Riazi, Gholamhossein; Shams-Ghahfarokhi, Masoomeh; Razzaghi-Abyaneh, Mehdi

    2014-04-01

    Nanostructures from natural sources have received major attention due to wide array of biological activities and less toxicity for humans, animals, and the environment. In the present study, silver nanoparticles were successfully synthesized using a fungal nitrate reductase, and their biological activity was assessed against human pathogenic fungi and bacteria. The enzyme was isolated from Fusarium oxysporum IRAN 31C after culturing on malt extract-glucose-yeast extract-peptone (MGYP) medium. The enzyme was purified by a combination of ultrafiltration and ion exchange chromatography on DEAE Sephadex and its molecular weight was estimated by gel filtration on Sephacryl S-300. The purified enzyme had a maximum yield of 50.84 % with a final purification of 70 folds. With a molecular weight of 214 KDa, it is composed of three subunits of 125, 60, and 25 KDa. The purified enzyme was successfully used for synthesis of silver nanoparticles in a way dependent upon NADPH using gelatin as a capping agent. The synthesized silver nanoparticles were characterized by X-ray diffraction, dynamic light scattering spectroscopy, and transmission and scanning electron microscopy. These stable nonaggregating nanoparticles were spherical in shape with an average size of 50 nm and a zeta potential of -34.3. Evaluation of the antimicrobial effects of synthesized nanoparticles by disk diffusion method showed strong growth inhibitory activity against all tested human pathogenic fungi and bacteria as evident from inhibition zones that ranged from 14 to 25 mm. Successful green synthesis of biologically active silver nanoparticles by a nitrate reductase from F. oxysporum in the present work not only reduces laborious downstream steps such as purification of nanoparticle from interfering cellular components, but also provides a constant source of safe biologically-active nanomaterials with potential application in agriculture and medicine.

  19. Three spinach leaf nitrate reductase-3-hydroxy-3-methylglutaryl-CoA reductase kinases that are regulated by reversible phosphorylation and/or Ca2+ ions.

    Science.gov (United States)

    Douglas, P; Pigaglio, E; Ferrer, A; Halfords, N G; MacKintosh, C

    1997-07-01

    In spinach (Spinacea oleracea L.) leaf extracts, three protein kinases (PKI, PKII and PKIII) were identified each of which phosphorylated spinach nitrate reductase on serine-543, and inactivated the enzyme in the presence of nitrate reductase inhibitor, 14-3-3. PKIII was also very active in phosphorylating and inactivating Arabidopsis (Landsberg erecta) 3-hydroxy-3-methylglutaryl-coenzyme A reductase 1 (HMGR1). PKI and PKII phosphorylated HMGR1 more slowly than PKIII, compared with their relative rates of phosphorylation of nitrate reductase. HMGR1 identical with those that are seen after phosphorylation of serine-577 by the sucrose non-fermenting (SNF1)-like PK, 3-hydroxy-3-methylglutaryl-Co A reductase kinase A (HRK-A), from cauliflower [Dale, Arró, Becerra, Morrice, Boronat, Hardie and Ferrer (1995) Eur. J. Biochem. 233, 506-513]. PKI was Ca2+-dependent when prepared in the absence of protein phosphatase (PP) inhibitors, and largely Ca2+-dependent when prepared in the presence of PP inhibitors (NaF and EGTA). The Ca2+-independent portion of PKI was inactivated by either PP2A or PP2C, while the Ca2+-dependent portion of PKI became increasingly activated during storage, which we presume was mimicking the effect of an unidentified PP. These findings indicate that PK1 is regulated by two functionally distinct phosphorylations. PKI had a molecular mass of 45 kDa on gel filtration and was active towards substrate peptides that terminated at the +2 residue from the phosphorylation site, whereas PKIII was inactive towards these peptides. PKII was Ca2+-stimulated under all conditions tested. PKIII was Ca2+-indepdented, inactivated by PP2A or PP2C, had a requirement for a hydrophobic residue in the +4 position of peptide substrates, had a molecular mass by gel filtration of approximately 140 kDa, and an antibody against the rye SNF1-related PK (RKIN1) recognized a 58 kDa subunit in fractions containing PKIII. These properties of PKIII are identical with those reported

  20. Three spinach leaf nitrate reductase-3-hydroxy-3-methylglutaryl-CoA reductase kinases that are required by reversible phosphorylation and/or Ca2+ ions.

    Science.gov (United States)

    Douglas, P; Pigaglio, E; Ferrer, A; Halfords, N G; MacKintosh, C

    1997-01-01

    In spinach (Spinacea oleracea L.) leaf extracts, three protein kinases (PKI, PKII and PKIII) were identified each of which phosphorylated spinach nitrate reductase on serine-543, and inactivated the enzyme in the presence of nitrate reductase inhibitor, 14-3-3. PKIII was also very active in phosphorylating and inactivating Arabidopsis (Landsberg erecta) 3-hydroxy-3-methylglutaryl-coenzyme A reductase 1 (HMGR1). PKI and PKII phosphorylated HMGR1 more slowly than PKIII, compared with their relative rates of phosphorylation of nitrate reductase. HMGR1 identical with those that are seen after phosphorylation of serine-577 by the sucrose non-fermenting (SNF1)-like PK, 3-hydroxy-3-methylglutaryl-Co A reductase kinase A (HRK-A), from cauliflower [Dale, Arró, Becerra, Morrice, Boronat, Hardie and Ferrer (1995) Eur. J. Biochem. 233, 506-513]. PKI was Ca2+-dependent when prepared in the absence of protein phosphatase (PP) inhibitors, and largely Ca2+-dependent when prepared in the presence of PP inhibitors (NaF and EGTA). The Ca2+-independent portion of PKI was inactivated by either PP2A or PP2C, while the Ca2+-dependent portion of PKI became increasingly activated during storage, which we presume was mimicking the effect of an unidentified PP. These findings indicate that PK1 is regulated by two functionally distinct phosphorylations. PKI had a molecular mass of 45 kDa on gel filtration and was active towards substrate peptides that terminated at the +2 residue from the phosphorylation site, whereas PKIII was inactive towards these peptides. PKII was Ca2+-stimulated under all conditions tested. PKIII was Ca2+-indepdented, inactivated by PP2A or PP2C, had a requirement for a hydrophobic residue in the +4 position of peptide substrates, had a molecular mass by gel filtration of approximately 140 kDa, and an antibody against the rye SNF1-related PK (RKIN1) recognized a 58 kDa subunit in fractions containing PKIII. These properties of PKIII are identical with those reported

  1. Ammonium Inhibits Chromomethylase 3-Mediated Methylation of the Arabidopsis Nitrate Reductase Gene NIA2

    Science.gov (United States)

    Kim, Joo Yong; Kwon, Ye Jin; Kim, Sung-Il; Kim, Do Youn; Song, Jong Tae; Seo, Hak Soo

    2016-01-01

    Gene methylation is an important mechanism regulating gene expression and genome stability. Our previous work showed that methylation of the nitrate reductase (NR) gene NIA2 was dependent on chromomethylase 3 (CMT3). Here, we show that CMT3-mediated NIA2 methylation is regulated by ammonium in Arabidopsis thaliana. CHG sequences (where H can be A, T, or C) were methylated in NIA2 but not in NIA1, and ammonium [(NH4)2SO4] treatment completely blocked CHG methylation in NIA2. By contrast, ammonium had no effect on CMT3 methylation, indicating that ammonium negatively regulates CMT3-mediated NIA2 methylation without affecting CMT3 methylation. Ammonium upregulated NIA2 mRNA expression, which was consistent with the repression of NIA2 methylation by ammonium. Ammonium treatment also reduced the overall genome methylation level of wild-type Arabidopsis. Moreover, CMT3 bound to specific promoter and intragenic regions of NIA2. These combined results indicate that ammonium inhibits CMT3-mediated methylation of NIA2 and that of other target genes, and CMT3 selectively binds to target DNA sequences for methylation. PMID:26834755

  2. Identification of Ser-543 as the major regulatory phosphorylation site in spinach leaf nitrate reductase

    Science.gov (United States)

    Bachmann, M.; Shiraishi, N.; Campbell, W. H.; Yoo, B. C.; Harmon, A. C.; Huber, S. C.; Davies, E. (Principal Investigator)

    1996-01-01

    Spinach leaf NADH:nitrate reductase (NR) responds to light/dark signals and photosynthetic activity in part as a result of rapid regulation by reversible protein phosphorylation. We have identified the major regulatory phosphorylation site as Ser-543, which is located in the hinge 1 region connecting the cytochrome b domain with the molybdenum-pterin cofactor binding domain of NR, using recombinant NR fragments containing or lacking the phosphorylation site sequence. Studies with NR partial reactions indicated that the block in electron flow caused by phosphorylation also could be localized to the hinge 1 region. A synthetic peptide (NR6) based on the phosphorylation site sequence was phosphorylated readily by NR kinase (NRk) in vitro. NR6 kinase activity tracked the ATP-dependent inactivation of NR during several chromatographic steps and completely inhibited inactivation/phosphorylation of native NR in vitro. Two forms of NRk were resolved by using anion exchange chromatography. Studies with synthetic peptide analogs indicated that both forms of NRk had similar specificity determinants, requiring a basic residue at P-3 (i.e., three amino acids N-terminal to the phosphorylated serine) and a hydrophobic residue at P-5. Both forms are strictly calcium dependent but belong to distinct families of protein kinases because they are distinct immunochemically.

  3. Nitrate reductase activity in the diatom Biddulphia longicruris: characterization and daily oscillation

    Directory of Open Access Journals (Sweden)

    Cristina S Asano

    1995-01-01

    Full Text Available Nitrate reductase (NR activity was studied in the marine diatom Biddulphia longicruris. During 24 hours of sampling, NR activity was found during day time and in the transition day-night. Nitrite anions, the product of nitrate reduction, was released by the cells at the times NR was active, and accumulated in the culture medium. Whenever the cultures of B. longicmris were submitted to nitrogen deprivation, NR activity could not be detected. In vitro determination of KM values for NR using nitrate or NADH were respectively 50//M and 80 /*M. Temperature and pH dependence of NR activity were also determined for this organism.A atividade de nitrato redutase (NR foi estudada na diatomácea marinha Biddulphia longicruris. A NR é a enzima responsável pelo processo de assimilação de nitrato. O nitrato é reduzido no interior da célula a nitrito pela ação da NR. Esta enzima é normalmente oligomérica e utiliza o NADH como substrato doador de elétrons. Em alguns organismos também são encontradas NRs capazes de utilizarem o NADPH como doador eletrônico para a redução do nitrato a nitrito. Para a diatomácea B. longicmris foram apresentadas evidências de que a sua NR é específica para NADH e que a redução de nitrato em presença de NADPH não acontece. Determinações in vitro dos valores das constantes de Michaelis-Menten (KM usando nitrato e NADH como substratos, são respectivamente 50µ e 80µM. A temperatura ótima de reação enzimática e a sua dependência ao pH também foram estudadas. Cultivos de B. longicmris foram acompanhados por períodos de 24 horas e foi mostrado que a atividade de NR é encontrada em maiores níveis durante os períodos de transição de luz/escuro. Os anions nitrito, produtos da redução de nitrato, são eliminados pelas células nos períodos de maior atividade de NR e se acumulam no meio de cultura. Células submetidas à ausência de nitrato apresentam uma repressão da expressão de NR, sendo

  4. Elevated CO2-induced production of nitric oxide (NO) by NO synthase differentially affects nitrate reductase activity in Arabidopsis plants under different nitrate supplies.

    Science.gov (United States)

    Du, Shaoting; Zhang, Ranran; Zhang, Peng; Liu, Huijun; Yan, Minggang; Chen, Ni; Xie, Huaqiang; Ke, Shouwei

    2016-02-01

    CO2 elevation often alters the plant's nitrate reductase (NR) activity, the first enzyme acting in the nitrate assimilation pathway. However, the mechanism underlying this process remains unknown. The association between elevated CO2-induced alterations of NR activity and nitric oxide (NO) was examined in Col-0 Arabidopsis fed with 0.2-10 mM nitrate, using NO donors, NO scavenger, and NO synthase (NOS) inhibitor. The noa1 mutant, in which most NOS activity was lost, and the NR activity-null mutant nia1 nia2 were also used to examine the above association. In response to CO2 elevation, NR activity increased in low-nitrate Col-0 plants but was inhibited in high-nitrate Col-0 plants. NO scavenger and NOS inhibitor could eliminate these two responses, whereas the application of NO donors mimicked these distinct responses in ambient CO2-grown Col-0 plants. Furthermore, in both low- and high-nitrate conditions, elevated CO2 increased NOS activity and NO levels in Col-0 and nia1 nia2 plants but had little effect on NO level and NR activity in noa1 plants. Considering all of these findings, this study concluded that, in response to CO2 elevation, either the NR activity induction in low-nitrate plants or the NR activity inhibition in high-nitrate plants is regulated by NOS-generated NO. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

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

    Science.gov (United States)

    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. Copyright © 2012. Published by Elsevier B.V.

  6. Donnan dialysis as membrane process for nitrate removal from drinking water: Membrane structure effect

    Directory of Open Access Journals (Sweden)

    S. Ben Hamouda

    2017-02-01

    Full Text Available Nitrates are extremely soluble in water and are considered as the renown pollutants of natural water and water table. Removing them through AMX, AM3, and RPA anion exchange membranes has been studied under donnan dialysis conditions as a function of concentration, pH and the nature of the feed phase. It was observed that the AMX membrane gives the highest nitrate transport efficiency and that the optimal concentration in the selected zone was in 6.2 g/L (0.1 M with 37.9%. It was also observed that the best pH for the concentration of 0.62 g/L is pH 10 with yield of 23%. Results are evaluated by the yield calculated with nitrates concentration detected by molecular absorption spectrometry in 212 nm.

  7. Identification of a regulatory phosphorylation site in the hinge 1 region of nitrate reductase from spinach (Spinacea oleracea) leaves.

    Science.gov (United States)

    Douglas, P; Morrice, N; MacKintosh, C

    1995-12-18

    Purified nitrate reductase (NR) from spinach leaves was phosphorylated in vitro by NR-inactivating kinase on Ser-543 which is located in the hinge 1 region between the molybdenum-cofactor and haem-binding domains. Phosphorylation of Ser-543 allowed NR to be inhibited by the inhibitor, NIP. Degraded NR preparations in which a proportion of the subunits had lost 45 amino acids from the N-terminus during purification could be phosphorylated by NR kinase on Ser-543, but could not subsequently be fully inhibited by NIP, suggesting a role for the N-terminal tail of NR in NIP binding.

  8. Nitrogenase and nitrate reductase activities in young Alnus glutinosa, relationship and effect of light-dark treatments

    International Nuclear Information System (INIS)

    Benamar, S.; Thiery, G.; Pizelle, G.

    1995-01-01

    Relations between in vivo nitrogenase (N-2-ase; EC 1.18.6.1) and nitrate reductase (NR; EC 1.6.6.1) activities were studied in young nodulated Alnus glutinosa (L. ) Gaertn. Positive correlations linked N-2-ase activity, constitutive (non-inducible by nitrate) leaf NR activity and plant growth. Light/dark treatments applied to the whole shoot or, separately, to the upper and lower part of shoot led to the finding that(a) the constitutive leaf NR activity depended on direct illumination of the leaf and did not appear subordinate to the N-2-ase activity; (b) the N-2-ase activity was much more efficiently supported by the illumination of the upper (young) leaves than by that of the lower (mature) leaves; (c) the maintenance of nitrate-inducible root NR activity required leaf illumination. The variations of both N-2-ase and root NR activities in response to light/dark treatments emphasize the importance of the photosynthesis for the reduction of dinitrogen and nitrate in nodulated roots of Alnus glutinosa

  9. Nitrate reduction associated with respiration in Sinorhizobium meliloti 2011 is performed by a membrane-bound molybdoenzyme.

    Science.gov (United States)

    Ferroni, Felix M; Rivas, María G; Rizzi, Alberto C; Lucca, María E; Perotti, Nora I; Brondino, Carlos D

    2011-10-01

    The purification and biochemical characterization of the respiratory membrane-bound nitrate reductase from Sinorhizobium meliloti 2011 (Sm NR) is reported together with the optimal conditions for cell growth and enzyme production. The best biomass yield was obtained under aerobic conditions in a fed-batch system using Luria-Bertani medium with glucose as carbon source. The highest level of Sm NR production was achieved using microaerobic conditions with the medium supplemented with both nitrate and nitrite. Sm NR is a mononuclear Mo-protein belonging to the DMSO reductase family isolated as a heterodimeric enzyme containing two subunits of 118 and 45 kDa. Protein characterization by mass spectrometry showed homology with respiratory nitrate reductases. UV-Vis spectra of as-isolated and dithionite reduced Sm NR showed characteristic absorption bands of iron-sulfur and heme centers. Kinetic studies indicate that Sm NR follows a Michaelis-Menten mechanism (K (m) = 97 ± 11 μM, V = 9.4 ± 0.5 μM min(-1), and k (cat) = 12.1 ± 0.6 s(-1)) and is inhibited by azide, chlorate, and cyanide with mixed inhibition patterns. Physiological and kinetic studies indicate that molybdenum is essential for NR activity and that replacement of this metal for tungsten inhibits the enzyme. Although no narGHI gene cluster has been annotated in the genome of rhizobia, the biochemical characterization indicates that Sm NR is a Mo-containing NR enzyme with molecular organization similar to NarGHI.

  10. Purification of a nitrate reductase kinase from Spinacea oleracea leaves, and its identification as a calmodulin-domain protein kinase.

    Science.gov (United States)

    Douglas, P; Moorhead, G; Hong, Y; Morrice, N; MacKintosh, C

    1998-10-01

    Spinach (Spinacea oleracea L.) nitrate reductase (NR) is inactivated by phosphorylation on serine-543, followed by binding of the phosphorylated enzyme to 14-3-3 proteins. We purified one of several chromatographically distinct NRserine-543 kinases from spinach leaf extracts, and established by Edman sequencing of 80 amino acid residues that it is a calcium-dependent (calmodulin-domain) protein kinase (CDPK), with peptide sequences very similar to Arabidopsis CDPK6 (accession no. U20623; also known as CPK3). The spinach CDPK was recognized by antibodies raised against Arabidopsis CDPK. Nitrate reductase was phosphorylated at serine-543 by bacterially expressed His-tagged CDPK6, and the phosphorylated NR was inhibited by 14-3-3 proteins. However, the bacterially expressed CDPK6 had a specific activity approx. 200-fold lower than that of the purified spinach enzyme. The physiological control of NR by CDPK is discussed, and the regulatory properties of the purified CDPK are considered with reference to current models for reversible intramolecular binding of the calmodulin-like domain to the autoinhibitory junction of CDPKs.

  11. Nitrate reductase and photosynthetic activities of wheat and their relationship with plant productivity under soil water deficit conditions (abstract)

    International Nuclear Information System (INIS)

    Ashraf, M.Y.; Sarwar, G.; Hussain, F.

    2005-01-01

    Experiments were conducted in lysimeters with wheat during two consecutive years. The first year experiment comprised of eight wheat genotypes with four water stress treatments, i.e. normal irrigation, pre-anthesis drought, post-anthesis drought and terminal drought, with four replications. The results showed that yield and yield parameters reduced with the severity of drought in all wheat lines. However, wheat lines Chakwal-86, DS-4 and Barani-83 had comparatively higher yield and yield components than others. The maximum reduction in all parameters was under terminal drought. The difference between pre- and post-anthesis drought was nonsignificant, particularly for grain yield. The second experiment was conducted with four wheat lines: two were tolerant (Chakwal-86 and DS-4) and two susceptible (Pavon and DS-17) under similar environments with same treatments to study the photosynthetic efficiency, nitrogen metabolism and their relationship with plant productivity (yield). The results showed that leaf area, transpiration, dry matter accumulation and nitrate reductase activity were reduced while diffusive resistance and total amino acids increased in all the wheat lines under water deficit conditions. The relationship between yield and leaf area, transpiration, dry matter accumulation and nitrate reductase activity was positive. The overall results showed that wheat lines Chakwal-86 and DS-4 showed better performance than others. (author)

  12. Heterologous expression and biochemical characterization of assimilatory nitrate and nitrite reductase reveals adaption and potential of Bacillus megaterium NCT-2 in secondary salinization soil.

    Science.gov (United States)

    Chu, Shaohua; Zhang, Dan; Wang, Daxin; Zhi, Yuee; Zhou, Pei

    2017-08-01

    Large accumulation of nitrate in soil has resulted in "salt stress" and soil secondary salinization. Bacillus megaterium NCT-2 which was isolated from secondary salinization soil showed high capability of nitrate reduction. The genes encoding assimilatory nitrate and nitrite reductase from NCT-2 were cloned and over-expressed in Escherichia coli. The optimum co-expression condition was obtained with E. coli BL21 (DE3) and 0.1mM IPTG for 10h when expression was carried out at 20°C and 120rpm in Luria-Bertani (LB) medium. The molecular mass of nitrate reductase was 87.3kDa and 80.5kDa for electron transfer and catalytic subunit, respectively. The large and small subunit of nitrite reductase was 88kDa and 11.7kDa, respectively. The purified recombinant enzymes showed broad activity range of temperature and pH. The maximum activities were obtained at 35°C and 30°C, pH 6.2 and 6.5, which was similar to the condition of greenhouse soils. Maximum stimulation of the enzymes occurred with addition of Fe 3+ , while Cu 2+ caused the maximum inhibition. The optimum electron donor was MV+Na 2 S 2 O 4 +EDTA and MV+Na 2 S 2 O 4 , respectively. Kinetic parameters of K m and V max were determined to be 670μM and 58U/mg for nitrate reductase, and 3100μM and 5.2U/mg for nitrite reductase. Results of quantitative real-time PCR showed that the maximum expression levels of nitrate and nitrite reductase were obtained at 50mM nitrate for 8h and 12h, respectively. These results provided information on novel assimilatory nitrate and nitrite reductase and their properties presumably revealed adaption of B. megaterium NCT-2 to secondary salinization condition. This study also shed light on the role played by the nitrate assimilatory pathway in B. megaterium NCT-2. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Nitric oxide generated by nitrate reductase increases nitrogen uptake capacity by inducing lateral root formation and inorganic nitrogen uptake under partial nitrate nutrition in rice.

    Science.gov (United States)

    Sun, Huwei; Li, Jiao; Song, Wenjing; Tao, Jinyuan; Huang, Shuangjie; Chen, Si; Hou, Mengmeng; Xu, Guohua; Zhang, Yali

    2015-05-01

    Increasing evidence shows that partial nitrate nutrition (PNN) can be attributed to improved plant growth and nitrogen-use efficiency (NUE) in rice. Nitric oxide (NO) is a signalling molecule involved in many physiological processes during plant development and nitrogen (N) assimilation. It remains unclear whether molecular NO improves NUE through PNN. Two rice cultivars (cvs Nanguang and Elio), with high and low NUE, respectively, were used in the analysis of NO production, nitrate reductase (NR) activity, lateral root (LR) density, and (15)N uptake under PNN, with or without NO production donor and inhibitors. PNN increased NO accumulation in cv. Nanguang possibly through the NIA2-dependent NR pathway. PNN-mediated NO increases contributed to LR initiation, (15)NH₄(+)/(15)NO₃(-) influx into the root, and levels of ammonium and nitrate transporters in cv. Nanguang but not cv. Elio. Further results revealed marked and specific induction of LR initiation and (15)NH₄(+)/(15)NO₃(-) influx into the roots of plants supplied with NH₄(+)+sodium nitroprusside (SNP) relative to those supplied with NH₄(+) alone, and considerable inhibition upon the application of cPTIO or tungstate (NR inhibitor) in addition to PNN, which is in agreement with the change in NO fluorescence in the two rice cultivars. The findings suggest that NO generated by the NR pathway plays a pivotal role in improving the N acquisition capacity by increasing LR initiation and the inorganic N uptake rate, which may represent a strategy for rice plants to adapt to a fluctuating nitrate supply and increase NUE. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  14. Developmental stage- and concentration-specific sodium nitroprusside application results in nitrate reductase regulation and the modification of nitrate metabolism in leaves of Medicago truncatula plants.

    Science.gov (United States)

    Antoniou, Chrystalla; Filippou, Panagiota; Mylona, Photini; Fasoula, Dionysia; Ioannides, Ioannis; Polidoros, Alexios; Fotopoulos, Vasileios

    2013-09-01

    Nitric oxide (NO) is a bioactive molecule involved in numerous biological events that has been reported to display both pro-oxidant and antioxidant properties in plants. Several reports exist which demonstrate the protective action of sodium nitroprusside (SNP), a widely used NO donor, which acts as a signal molecule in plants responsible for the expression regulation of many antioxidant enzymes. This study attempts to provide a novel insight into the effect of application of low (100 μΜ) and high (2.5 mM) concentrations of SNP on the nitrosative status and nitrate metabolism of mature (40 d) and senescing (65 d) Medicago truncatula plants. Higher concentrations of SNP resulted in increased NO content, cellular damage levels and reactive oxygen species (ROS) concentration, further induced in older tissues. Senescing M. truncatula plants demonstrated greater sensitivity to SNP-induced oxidative and nitrosative damage, suggesting a developmental stage-dependent suppression in the plant's capacity to cope with free oxygen and nitrogen radicals. In addition, measurements of the activity of nitrate reductase (NR), a key enzyme involved in the generation of NO in plants, indicated a differential regulation in a dose and time-dependent manner. Furthermore, expression levels of NO-responsive genes (NR, nitrate/nitrite transporters) involved in nitrogen assimilation and NO production revealed significant induction of NR and nitrate transporter during long-term 2.5 mM SNP application in mature plants and overall gene suppression in senescing plants, supporting the differential nitrosative response of M. truncatula plants treated with different concentrations of SNP.

  15. Rapid induction of GFP expression by the nitrate reductase promoter in the diatom Phaeodactylum tricornutum

    Czech Academy of Sciences Publication Activity Database

    Chu, L.; Ewe, Daniela; Bártulos, C.R.; Kroth, P. G.; Gruber, A.

    2016-01-01

    Roč. 4, AUG 25 (2016), e2344 ISSN 2167-8359 Institutional support: RVO:61388971 Keywords : Flow cytometry * Nitrogen source * Nitrate Subject RIV: EE - Microbiology, Virology Impact factor: 2.177, year: 2016

  16. Rapid induction of GFP expression by the nitrate reductase promoter in the diatom Phaeodactylum tricornutum

    Czech Academy of Sciences Publication Activity Database

    Chu, L.; Ewe, Daniela; Bártulos, C.R.; Kroth, P.G.; Gruber, A.

    2016-01-01

    Roč. 4, AUG 25 2016 (2016), e2344 ISSN 2167-8359 Institutional support: RVO:61388971 Keywords : Flow cytometry * Nitrogen source * Nitrate Subject RIV: EE - Microbiology, Virology Impact factor: 2.177, year: 2016

  17. Mutation of the regulatory phosphorylation site of tobacco nitrate reductase results in high nitrite excretion and NO emission from leaf and root tissue

    NARCIS (Netherlands)

    Lea, US; ten Hoopen, F; Provan, F; Kaiser, WM; Meyer, C; Lillo, C

    In wild-type Nicotiana plumbaginifolia Viv. and other higher plants, nitrate reductase (NR) is regulated at the post-translational level and is rapidly inactivated in response to, for example, a light-to-dark transition. This inactivation is caused by phosphorylation of a conserved regulatory serine

  18. NapGH components of the periplasmic nitrate reductase of Escherichia coli K-12: location, topology and physiological roles in quinol oxidation and redox balancing.

    OpenAIRE

    Brondijk, T Harma C; Nilavongse, Arjaree; Filenko, Nina; Richardson, David J; Cole, Jeffrey A

    2004-01-01

    Nap (periplasmic nitrate reductase) operons of many bacteria include four common, essential components, napD, napA, napB and napC (or a homologue of napC ). In Escherichia coli there are three additional genes, napF, napG and napH, none of which are essential for Nap activity. We now show that deletion of either napG or napH almost abolished Nap-dependent nitrate reduction by strains defective in naphthoquinone synthesis. The residual rate of nitrate reduction (approx. 1% of that of napG+ H+ ...

  19. The roles of tissue nitrate reductase activity and myoglobin in securing nitric oxide availability in deeply hypoxic crucian carp

    DEFF Research Database (Denmark)

    Hansen, Marie N; Lundberg, Jon O; Filice, Mariacristina

    2016-01-01

    . We also tested whether liver, muscle and heart tissue possess nitrate reductase activity that supplies nitrite to the tissues during severe hypoxia. Crucian carp exposed to deep hypoxia (1nitrite in red musculature to more than double the value in normoxic fish......In mammals, treatment with low doses of nitrite has a cytoprotective effect in ischemia/reperfusion events, as a result of nitric oxide formation and S-nitrosation of proteins. Interestingly, anoxia-tolerant lower vertebrates possess an intrinsic ability to increase intracellular nitrite...... concentration during anoxia in tissues with high myoglobin and mitochondria content, such as the heart. Here, we tested the hypothesis that red and white skeletal muscles develop different nitrite levels in crucian carp exposed to deep hypoxia and assessed whether this correlates with myoglobin concentration...

  20. Effect of NaCI and supplemental calcium on growth parameters and nitrate reductase activity in maize

    Directory of Open Access Journals (Sweden)

    Elżbieta Sacała

    2011-01-01

    Full Text Available In this study, investigated were the effects of NaCl (60 mmol/dm-3 and NaCl supplemented with different salts (5 mmol/dm-3 CaCl2, CaSO4, CaCO3, KCl, on growth of two maize varieties (Cyrkon and Limko. After 7 days of cultivation in nutrient solution the growth response to salinity of both maize varieties was similar. NaCl led to a dramatic decrease in growth of plants (approx. 50% reduction in fresh and dry weight of root, and 70% reduction in fresh weight of shoot. Addition of extra Ca2+ or K+ to nutrient solution containing NaCl did not definitely improve the growth parameters of maize. However, among the tested salts, CaCl2 had a beneficial visual effect on maize seedlings. In other cases the plants showed noticeable symptoms of salt damage. In long term exposure to salinity (two weeks growth of Cyrkon was more inhibited than Limko. Comparison of growth responses in short-term exposure to salinity (7 days with long-term (14 days showed that in Cyrkon variety the negative effects of NaCl were intensified and addition of CaCl2 to salinized solution had not positive effects on growth. On the contrary, in Limko variety, there was a significant improvement in growth (especially in root dry weight. This fact indicates that during longer exposure to salinity Limko was able to adapt to those conditions. Salinity caused a significant decrease in leaf nitrate reductase activity (60% and 30% reduction respectively in Limko and Cyrkon. Addition of CaCl2 to salinized nutrient solution resulted in greater enzyme inhibition in Cyrkon (50% decline in relation to plants grown under sole NaCl, and 30% increase in Limko. Inhibition of nitrate reductase activity did not cause a decrease in concentration of soluble protein in maize leaves.

  1. Nitrate reductase 15N discrimination in Arabidopsis thaliana, Zea mays, Aspergillus niger, Pichea angusta, and Escherichia coli

    Directory of Open Access Journals (Sweden)

    Eli eCarlisle

    2014-07-01

    Full Text Available Stable 15N isotopes have been used to examine movement of nitrogen (N through various pools of the global N cycle. A central reaction in the cycle involves nitrate (NO3– reduction to nitrite (NO2– catalyzed via nitrate reductase (NR. Discrimination against 15N by NR is a major determinant of isotopic differences among N pools. Here, we measured in vitro 15N discrimination by several NRs purified from plants, fungi, and a bacterium to determine the intrinsic 15N discrimination by the enzyme and to evaluate the validity of measurements made using 15N-enriched NO3–. Observed NR isotope discrimination ranged from 22‰ to 32‰ (kinetic isotope effects of 1.022 to 1.032 among the different isozymes at natural abundance 15N (0.37%. As the fractional 15N content of substrate NO3– increased from natural abundance, the product 15N fraction deviated significantly from that expected based on substrate enrichment and 15N discrimination measured at natural abundance. Additionally, isotopic discrimination by denitrifying bacteria used to reduce NO3– and NO2– in some protocols became a greater source of error as 15N enrichment increased. We briefly discuss potential causes of artifactual results with enriched 15N and recommend against the use of highly enriched 15N tracers to study N discrimination in plants or soils.

  2. Elevated CO2 levels affect the activity of nitrate reductase and carbonic anhydrase in the calcifying rhodophyte Corallina officinalis.

    Science.gov (United States)

    Hofmann, Laurie C; Straub, Sandra; Bischof, Kai

    2013-02-01

    The concentration of CO(2) in global surface ocean waters is increasing due to rising atmospheric CO(2) emissions, resulting in lower pH and a lower saturation state of carbonate ions. Such changes in seawater chemistry are expected to impact calcification in calcifying marine organisms. However, other physiological processes related to calcification might also be affected, including enzyme activity. In a mesocosm experiment, macroalgal communities were exposed to three CO(2) concentrations (380, 665, and 1486 µatm) to determine how the activity of two enzymes related to inorganic carbon uptake and nutrient assimilation in Corallina officinalis, an abundant calcifying rhodophyte, will be affected by elevated CO(2) concentrations. The activity of external carbonic anhydrase, an important enzyme functioning in macroalgal carbon-concentrating mechanisms, was inversely related to CO(2) concentration after long-term exposure (12 weeks). Nitrate reductase, the enzyme responsible for reduction of nitrate to nitrite, was stimulated by CO(2) and was highest in algae grown at 665 µatm CO(2). Nitrate and phosphate uptake rates were inversely related to CO(2), while ammonium uptake was unaffected, and the percentage of inorganic carbon in the algal skeleton decreased with increasing CO(2). The results indicate that the processes of inorganic carbon and nutrient uptake and assimilation are affected by elevated CO(2) due to changes in enzyme activity, which change the energy balance and physiological status of C. officinalis, therefore affecting its competitive interactions with other macroalgae. The ecological implications of the physiological changes in C. officinalis in response to elevated CO(2) are discussed.

  3. Loss of nitrate reductases NIA1 and NIA2 impairs stomatal closure by altering genes of core ABA signaling components in Arabidopsis.

    Science.gov (United States)

    Zhao, Chenchen; Cai, Shengguan; Wang, Yizhou; Chen, Zhong-Hua

    2016-06-02

    Nitrate reductases NIA1 and NIA2 determine NO production in plants and are critical to abscisic acid (ABA)-induced stomatal closure. However, the role for NIA1 and NIA2 in ABA signaling has not been paid much attention in nitrate reductase loss-of-function mutant nia1nia2. Recently, we have demonstrated that ABA-inhibited K(+)in current and ABA-enhanced slow anion current were absent in nia1nia2. Exogenous NO restored regulation of these channels for stomatal closure in nia1nia2. In this study, we found that mutating NIA1 and NIA2 impaired nearly all the key components of guard cell ABA signaling pathway in Arabidopsis. We also propose a simplified model for ABA signaling in the nia1nia2 mutant.

  4. Over-expression of a tobacco nitrate reductase gene in wheat (Triticum aestivum L. increases seed protein content and weight without augmenting nitrogen supplying.

    Directory of Open Access Journals (Sweden)

    Xiao-Qiang Zhao

    Full Text Available Heavy nitrogen (N application to gain higher yield of wheat (Triticum aestivum L. resulted in increased production cost and environment pollution. How to diminish the N supply without losing yield and/or quality remains a challenge. To meet the challenge, we integrated and expressed a tobacco nitrate reductase gene (NR in transgenic wheat. The 35S-NR gene was transferred into two winter cultivars, "Nongda146" and "Jimai6358", by Agrobacterium-mediation. Over-expression of the transgene remarkably enhanced T1 foliar NR activity and significantly augmented T2 seed protein content and 1000-grain weight in 63.8% and 68.1% of T1 offspring (total 67 individuals analyzed, respectively. Our results suggest that constitutive expression of foreign nitrate reductase gene(s in wheat might improve nitrogen use efficiency and thus make it possible to increase seed protein content and weight without augmenting N supplying.

  5. Purification and characterization of an NADH-hexacyanoferrate(III) reductase from spinach leaf plasma membrane.

    Science.gov (United States)

    Bérczi, A; Fredlund, K M; Møller, I M

    1995-06-20

    Plasma membranes were purified from spinach (Spinacea oleracea L.) leaves by aqueous two-phase partitioning. The NADH-hexacyanoferrate(III) reductase was released from the membrane by Chaps solubilization and purified 360-fold by ion-exchange chromatography followed by affinity chromatography and size-exclusion chromatography on FPLC. A major band of 45 kDa and a minor contaminant of 66 kDa were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The band at 45 kDa cross-reacted with antibodies raised against an NADH-hexacyanoferrate(III) reductase from potato tuber microsomes. The native size of the enzyme was 160 kDa as determined by size-exclusion chromatography indicating that it is a tetramer. Two-dimensional gel electrophoresis, isoelectric focusing, followed by SDS-PAGE revealed three main bands of identical molecular weight with pI of 5.3-5.6. The enzyme contained about one flavin adenine dinucleotide (FAD) per 45-kDa subunit as determined by fluorescence spectroscopy, was specific for the beta-hydrogen of NADH, preferred NADH over NADPH as electron donor, and preferred hexacyanoferrate(III) as electron acceptor, e.g., it reduced Fe3+-EDTA, cytochrome c, oxygen, and duroquinone at 70% whereas FAD, flavin mononucleotide, duroquinone, and ubiquinone0 did not affect the activity.

  6. Nafion {sup registered} /nitrated sulfonated poly(ether ether ketone) membranes for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Jie-Cheng; Kuo, Jen-Feng; Chen, Chuh-Yung [Department of Chemical Engineering, National Cheng-Kung University, Tainan, 70148 (China)

    2009-10-20

    Sulfonated poly(ether ether ketone)s (SPEEKs) are substituted on the main chain of the polymer by nitro groups and blended with Nafion {sup registered} to attain composite membranes. The sulfonation, nitration and blending are achieved with a simple, inexpensive process, and the blended membranes containing the nitrated SPEEKs reveal a liquid-liquid phase separation. The blended membranes have a lower water uptake compared to recast Nafion {sup registered}, and the methanol permeability is reduced significantly to 4.29 x 10{sup -7}-5.34 x 10{sup -7} cm{sup 2} s{sup -1} for various contents of nitrated SPEEK for S63N17, and 4.72 x 10{sup -7}-7.11 x 10{sup -7} cm{sup 2} s{sup -1} for S63N38, with a maximum proton conductivity of {proportional_to}0.085 S cm{sup -1}. This study examines the single-cell performance at 80 C of Nafion {sup registered} /nitrated SPEEK membranes with various contents of nitrated SPEEK and a degree of nitration of 23-25 mW cm{sup -2} for S63N17 and 24-29 mW cm{sup -2} for S63N38. Both the power density and open circuit voltage are higher than those of Nafion {sup registered} 115 and recast Nafion {sup registered}. (author)

  7. Properties of nitrogen fertilization are decisive in determining the effects of elevated atmospheric CO2 on the activity of nitrate reductase in plants.

    Science.gov (United States)

    Zhang, Ranran; Du, Shaoting

    2016-01-01

    The concentration of atmospheric CO2 is predicted to double by the end of this century. The response of higher plants to an increase in atmospheric CO2 often includes a change in nitrate reductase (NR) activity. In a recent study, we showed that, under elevated CO2 levels, NR induction in low-nitrate plants and NR inhibition in high-nitrate plants are regulated by nitric oxide (NO) generated via nitric oxide synthases. This finding provides an explanation for the diverse responses of plants to elevated CO2 levels, and suggests that the use of nitrogen fertilizers on soil will have a major influence on the nitrogen assimilation capacity of plants in response to CO2 elevation.

  8. Resolution of two native monomeric 90 kDa nitrate reductase active proteins from Shewanella gelidimarina and the sequence of two napA genes

    International Nuclear Information System (INIS)

    Simpson, Philippa J.L.; McKinzie, Audra A.; Codd, Rachel

    2010-01-01

    Research highlights: → Two monomeric 90 kDa nitrate reductase active proteins from Shewanella gelidimarina. → Sequence of napA from napEDABC-type operon and napA from NapDAGHB-type operon. → Isolation of NAP as NapA or NapAB correlated with NapA P47E amino acid substitution. -- Abstract: The reduction of nitrate to nitrite in the bacterial periplasm occurs in the 90 kDa NapA subunit of the periplasmic nitrate reductase (NAP) system. Most Shewanella genomes contain two nap operons: napEDABC and napDAGHB, which is an unusual feature of this genus. Two native, monomeric, 90 kDa nitrate reductase active proteins were resolved by hydrophobic interaction chromatography from aerobic cultures of Shewanella gelidimarina replete with reduced nitrogen compounds. The 90 kDa protein obtained in higher yield was characterized as NapA by electronic absorption and electron paramagnetic resonance spectroscopies and was identified by LC/MS/MS and MALDI-TOF/TOF MS as NapA from the napEDABC-type operon. The other 90 kDa protein, which was unstable and produced in low yields, was posited as NapA from the napDAGHB-type operon. Two napA genes have been sequenced from the napEDABC-type and napDAGHB-type operons of S. gelidimarina. Native NAP from S. putrefaciens was resolved as one NapA monomer and one NapAB heterodimer. Two amino acid substitutions in NapA correlated with the isolation of NAP as a NapA monomer or a NapAB heterodimer. The resolution of native, redox-active NapA isoforms in Shewanella provides new insight into the respiratory versatility of this genus, which has implications in bioremediation and the assembly of microbial fuel cells.

  9. Involvement of nitrate reductase (NR) in osmotic stress-induced NO generation of Arabidopsis thaliana L. roots.

    Science.gov (United States)

    Kolbert, Zsuzsanna; Ortega, Leandro; Erdei, László

    2010-01-01

    Nitric oxide (NO) is undoubtedly a potential signal molecule in diverse developmental processes and stress responses. Despite our extensive knowledge about the role of NO in physiological and stress responses, the source of this gaseous molecule is still unresolved. The aim of this study was to investigate the potential role of nitrate reductase (NR) as the source of NO accumulation in the root system of wild-type and NR-deficient nia1, nia2 mutant Arabidopsis plants under osmotic stress conditions induced by a polyethylene glycol (PEG 6000) treatment. Reduction of primary root (PR) length was detected as the effect of osmotic stress in wild-type and NR-deficient plants. We found that osmotic stress-induced lateral root (LR) initiation in wild-type, but not in NR-mutant plants. High levels of NO formation occurred in roots of Col-1 plants as the effect of PEG treatment. The mammalian nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA) had no effect on LR initiation or NO generation, while tungstate, an NR inhibitor, inhibited the later phase of osmotic stress-induced NO accumulation and slightly decreased the LR development. In nia1, nia2 roots, the PEG treatment induced the first phase of NO production, but later NO production was inhibited. We conclude that the first phase of PEG-induced NO generation is not dependent on NOS-like or NR activity. It is also suggested that the activity of NR in roots is required for the later phase of osmotic stress-induced NO formation.

  10. Direct nitrate reductase assay versus microscopic observation drug susceptibility test for rapid detection of MDR-TB in Uganda.

    Directory of Open Access Journals (Sweden)

    Freddie Bwanga

    Full Text Available The most common method for detection of drug resistant (DR TB in resource-limited settings (RLSs is indirect susceptibility testing on Lowenstein-Jensen medium (LJ which is very time consuming with results available only after 2-3 months. Effective therapy of DR TB is therefore markedly delayed and patients can transmit resistant strains. Rapid and accurate tests suitable for RLSs in the diagnosis of DR TB are thus highly needed. In this study we compared two direct techniques--Nitrate Reductase Assay (NRA and Microscopic Observation Drug Susceptibility (MODS for rapid detection of MDR-TB in a high burden RLS. The sensitivity, specificity, and proportion of interpretable results were studied. Smear positive sputum was collected from 245 consecutive re-treatment TB patients attending a TB clinic in Kampala, Uganda. Samples were processed at the national reference laboratory and tested for susceptibility to rifampicin and isoniazid with direct NRA, direct MODS and the indirect LJ proportion method as reference. A total of 229 specimens were confirmed as M. tuberculosis, of these interpretable results were obtained in 217 (95% with either the NRA or MODS. Sensitivity, specificity and kappa agreement for MDR-TB diagnosis was 97%, 98% and 0.93 with the NRA; and 87%, 95% and 0.78 with the MODS, respectively. The median time to results was 10, 7 and 64 days with NRA, MODS and the reference technique, respectively. The cost of laboratory supplies per sample was low, around 5 USD, for the rapid tests. The direct NRA and MODS offered rapid detection of resistance almost eight weeks earlier than with the reference method. In the study settings, the direct NRA was highly sensitive and specific. We consider it to have a strong potential for timely detection of MDR-TB in RLS.

  11. Impacts of some divalent cations on periplasmic nitrate reductase and dehydrogenase enzymes of Escherichia, Pseudomonas and Acinetobacter species

    Directory of Open Access Journals (Sweden)

    Christian E. Nwanyanwu

    2008-08-01

    Full Text Available The impacts of Hg2+, Cd2+ and Zn2+ on the activities of periplasmic nitrate reductase (NAP and dehydrogenase (DHA enzymes of three organisms isolated from soil and sediment-water interface were analysed in liquid culture studies. NAP and DHA activities were estimated from nitrite and triphenyl formazan were produced respectively after 4h incubation at 28 ± 2oC. Hg2+ completely inhibited NAP activity in Escherichia and Pseudomonas spp at all the concentrations (0.2 – 1mM while progressive inhibitions of NAP activity were observed in Escherichia and Pseudomonas spp with increasing concentrations of Zn2+ and Cd2+. Both metals were stimulatory to NAP of Acinetobacter sp at 0.2 – 1mM. Apart from stimulation of DHA activity by Zn2+ (0.2 – 1mM in Escherichia sp, Cd2+ (0.4 -1.0mM in Acinetobacter sp and (1.0mM in Pseudomonas sp, all the metals progressively inhibited DHA activities in the three organisms. In Escherichia sp, the activities of the two enzymes were negatively correlated on exposure to Zn2+ (r = -0.91 and positively correlated (r = >0.90 on exposure to Cd2+ and Hg2+. Based on IC50 values of the metals for the DHA and NAP enzymes, the most resistant of the three organisms were Escherichia sp and Acinetobacter sp respectively. Quantitatively, NAP with its lower IC50 values than DHA was a more sensitive toxicity measure for Hg2+ in all the organisms. The sensitivity of microbial metabolic enzymes to the toxic effects of metals varies with the type of enzyme, metal and the microorganism involved.

  12. [Effects of nitrogen application rate on nitrate reductase activity, nitric oxide content and gas exchange in winter wheat leaves].

    Science.gov (United States)

    Shangguan, Zhou-Ping

    2007-07-01

    In this paper, the effects of different nitrogen application rates on the nitrate reductase (NR) activity, nitric oxide (NO) content and gas exchange parameters in winter wheat (Triticum aestivum L.) leaves from tillering stage to heading stage and on grain yield were studied. The results showed that the photosynthetic rate (P(n)), transpiration rate (T(r)) and instantaneous water use efficiency (IWUE) of leaves as well as the grain yield were increased with increasing nitrogen application rate first but decreased then, with the values of all these parameters reached the highest in treatment N180. The NR activity increased with increasing nitrogen application rate, and there was a significant linear correlation between NR activity and NO content at tillering and jointing stages (R2 > or = 0.68, n = 15). NO content had a quadratic positive correlation with stomatal conductance (G(s)) (R2 > or = 0.43, n = 15). The lower NO content produced by lower NR activity under lower nitrogen application rate promoted the stoma opened, while the higher NO content produced by higher NR activity under higher nitrogen application rate induced the stoma closed. Although the leaf NO content had a quadratic positive correlation with stomatal conductance (R2 > or = 0.36, n = 15), no remarkable correlation was observed between NR activity and NO content at heading stage, suggesting that nitrogen fertilization could not affect leaf NO content through promoting NR activity, and further more, regulate the stomatal action. Under appropriate nitrogen application the leaf NR activity and NO content were lower, G(s), T(r) and IWUE were higher, and thus, the crop had a better drought-resistant ability, higher P(n), and higher grain yield.

  13. Ions transfer modeling through monopolar and bipolar membranes: Treatment of wastewater containing ammonium nitrate by electrodialysis

    Directory of Open Access Journals (Sweden)

    Mohamed Amine Ben Ali

    2015-05-01

    Full Text Available In this study, a mathematical model was proposed to illustrate the different transport modes contributing in transfer of all involved species through anion, cation and bipolar membranes. This study was led on a wastewater containing ammonium nitrate treated by bipolar membrane electrodialysis (BPMED. In this electrodialysis, different species are involved, in particular, ammonium ions NH4+, nitrates NO3-, ammoniac NH3, water H2O and protons H+. Calculations led from the material balance sheets equations obtained in bath mode, allowed to validate the proposed transfer model and to check balance sheets material on all involved species during electrodialysis.

  14. Process-driven bacterial community dynamics are key to cured meat colour formation by coagulase-negative staphylococci via nitrate reductase or nitric oxide synthase activities.

    Science.gov (United States)

    Sánchez Mainar, María; Leroy, Frédéric

    2015-11-06

    The cured colour of European raw fermented meats is usually achieved by nitrate-into-nitrite reduction by coagulase-negative staphylococci (CNS), subsequently generating nitric oxide to form the relatively stable nitrosomyoglobin pigment. The present study aimed at comparing this classical curing procedure, based on nitrate reductase activity, with a potential alternative colour formation mechanism, based on nitric oxide synthase (NOS) activity, under different acidification profiles. To this end, meat models with and without added nitrate were fermented with cultures of an acidifying strain (Lactobacillus sakei CTC 494) and either a nitrate-reducing Staphylococcus carnosus strain or a rare NOS-positive CNS strain (Staphylococcus haemolyticus G110), or by relying on the background microbiota. Satisfactory colour was obtained in the models prepared with added nitrate and S. carnosus. In the presence of nitrate but absence of added CNS, however, cured colour was only obtained when L. sakei CTC 494 was also omitted. This was ascribed to the pH dependency of the emerging CNS background microbiota, selecting for nitrate-reducing Staphylococcus equorum strains at mild acidification conditions but for Staphylococcus saprophyticus strains with poor colour formation capability when the pH decrease was more rapid. This reliance of colour formation on the composition of the background microbiota was further explored by a side experiment, demonstrating the heterogeneity in nitrate reduction of a set of 88 CNS strains from different species. Finally, in all batches prepared with S. haemolyticus G110, colour generation failed as the strain was systematically outcompeted by the background microbiota, even when imposing milder acidification profiles. Thus, when aiming at colour formation through CNS metabolism, technological processing can severely interfere with the composition and functionality of the meat-associated CNS communities, for both nitrate reductase and NOS activities

  15. Ekstraksi ion krom dalam asam nitrat dengan teknologi membran cair untuk limbah industri penyamakan kulit

    Directory of Open Access Journals (Sweden)

    Dwi Wahini Nurhajati

    1999-12-01

    Full Text Available The objective of the research was to use of liquid membrane emulsion technique for the extraction of chrom in the nitrate acid solution. The liquid membrane phase as emulsion consists of kerosene as the solvent, sorbitan monooleat (span-80 as the surfactant, trioktil amin, as the carrier, natrium hidroksida as the internal phase. The optimum conditions obtained for making membrane, the liquid membrane phase was consists of organic phase (O, the internal liquid phase (W with the ratio of O/W = 1, the concentration sorbitan monooleat (span-80 in the membrane phase was 4%(v/v, the optimum time to achieve a emulsion was 5 minutes, the rate of stirring for membrane 8000 rpm. The optimum conditions obtained for extraction chrom ion as of chrom nitrate from solution with percentage of liquid membrane extraction used of 97,8% and the percentage of liquid membrane extraction used of 97,8% and the percentage of liquid-liquid extraction of 81,24% were as follow : the concentration of nitric acid in external phase was 3M, the concentration of tri oktil amin in the membrane phase was 5% (v/v, the concentration of natrium hidroksida in internal phase was 1% (v/v, the extraction time was 15 minutes and volume ratio of membrane phase and external phase was 1 : 3. The addition of Fe and Zn ions solution decreased the percent extraction of chrom ion.

  16. Methane-supported nitrate removal from groundwater in a membrane biofilm reactor.

    Science.gov (United States)

    Luo, Jing-Huan; Chen, Hui; Yuan, Zhiguo; Guo, Jianhua

    2018-04-01

    The discovery of denitrifying anaerobic methane oxidation (DAMO) has not only improved our understanding of global methane and nitrogen cycles, but also provided new technology options for removal of nitrate from nitrate-contaminated water. Previous studies have demonstrated DAMO organisms could remove nitrate and nitrite from wastewater under strictly anaerobically conditions. In the study, we investigate the feasibility of nitrate removal from groundwater, which contains dissolved oxygen in addition to nitrate. A membrane biofilm reactor (MBfR), inoculated with DAMO co-culture, was capable of treating synthetic groundwater containing highly contaminated nitrate (50  mg N/L) and oxygen (7-9 mg O 2 /L), with a maximum volumetric nitrate removal rate of 45 mg N/L-d. Accumulations of acetate and propionate were observed in some transient periods, indicating the possible involvement of acetate and propionate as intermediates in methane oxidation. The 16 S rRNA gene amplicon sequencing revealed that Candidatus Methylomirabilis, a known bacterial DAMO organism able to couple nitrite reduction with anaerobic oxidation of methane (AOM), was the dominant population. No archaeal DAMO organisms that are capable of coupling nitrate to AOM were observed, however, considerable amount of denitrifiers were developed in this system. Based on known metabolisms of these microorganisms and a series of batch studies, it was assumed that methane was oxidized into volatile fatty acids (VFAs) under oxygen-limiting conditions, then the generated VFAs served as carbon sources for these heterotrophic denitrifiers to remove nitrate. This study offers a potential technology for nitrate removal from groundwater by DAMO process in MBfR. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Nitrate and Perchlorate Destruction and Potable Water Production Using Membrane Biofilm Reduction

    Science.gov (United States)

    2014-01-01

    Polypropylene Membrane b. c. Figure 1. Schematic of hydrogen-fed MBfR (a) membrane cross section, (b) woven fibers and biofilm...MBfR effluent goal of 6 µg/L perchlorate and 0.5 mg-N/L nitrate • Tracer Testing Start-Up • Varied feed flow rates • Varied recycle ratios • Batch...parameters including flow rate, recycle flow rate, hydrogen pressure, gas sparge frequency, and the gas used for sparging were varied during optimization

  18. The Effects of Dose Rhizoctonia Binucleat (BNR and Phosphorus to Nitrate Reductase Activity (NRA and Chlorophyll of Vanilla Seedling (Vanilla planifolia Andrews

    Directory of Open Access Journals (Sweden)

    Haryuni Haryuni

    2016-09-01

    Full Text Available Vanilla (Vanilla planifolia Andrews is one of the important exported commodities in Indonesia. Indonesia is one of top five major vanilla exporters in the world, that produce the high quality of Indonesian vanilla with high vanillin content (2.75%. The aims of this research were to determine the effects of dose binukleat Rhizoctonia (BNR and phosphorus as well as the interaction of the nitrate reductase activity (NRA and chlorophyll of the vanilla seedling (Vanilla planifolia Andrew. Method in this research used completely randomized factorial design, by involving two factors (dose of BNR inoculation and Phosphor. The first factor is without inoculation and inoculation BNR (M0, M1, M2, M3 wich consists of (0,5, 10, 15 g/polybag, the second factor is the dose of phosphorus fertilizer (P0, P1, P2, P3 which consists of (0, 3, 6, 9 g/polibag. The results showed that the inoculation dose of BNR and doses of phosphorus not significant and lower levels of NRA and chlorophyll while the interaction dose of BNR and phosphorus significantly and increase levels of NRA and chlorophyll of vanilla seedling. Nitrate Reductase Activity and chlorophyll has important role in metabolism process as a plant growth indicator.How to CiteHaryuni, H., & Dewi, T. S. K. (2016. The Effects of Dose Rhizoctonia Binucleat (BNR and Phosphorus to Nitrate Reductase Activity (NRA and Chlorophyll of Vanilla Seedling (Vanilla planifolia Andrews. Biosaintifika: Journal of Biology & Biology Education, 8(2, 141-147.

  19. Sterol-induced Dislocation of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase from Endoplasmic Reticulum Membranes into the Cytosol through a Subcellular Compartment Resembling Lipid Droplets*

    Science.gov (United States)

    Hartman, Isamu Z.; Liu, Pingsheng; Zehmer, John K.; Luby-Phelps, Katherine; Jo, Youngah; Anderson, Richard G. W.; DeBose-Boyd, Russell A.

    2010-01-01

    Sterol-induced binding to Insigs in the endoplasmic reticulum (ER) allows for ubiquitination of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. This ubiquitination marks reductase for recognition by the ATPase VCP/p97, which mediates extraction and delivery of reductase from ER membranes to cytosolic 26 S proteasomes for degradation. Here, we report that reductase becomes dislocated from ER membranes into the cytosol of sterol-treated cells. This dislocation exhibits an absolute requirement for the actions of Insigs and VCP/p97. Reductase also appears in a buoyant fraction of sterol-treated cells that co-purifies with lipid droplets, cytosolic organelles traditionally regarded as storage depots for neutral lipids such as triglycerides and cholesteryl esters. Genetic, biochemical, and localization studies suggest a model in which reductase is dislodged into the cytosol from an ER subdomain closely associated with lipid droplets. PMID:20406816

  20. Nitrate reductase, arginine deaminase, urease and dehydrogenase activities in natural soil (ridges with forest) and in cotton soil after acetamiprid treatments.

    Science.gov (United States)

    Singh, Dileep K; Kumar, Sunil

    2008-03-01

    Soil enzymes are indicators of microbial activities in soil and are often considered as an indicator of soil health and fertility. They are very sensitive to the agricultural practices, pH of the soil, nutrients, inhibitors and weather conditions. To understand the effect of an insecticide, acetamiprid (IUPAC Name: (E)-N1-[(6-chloro-3-pyridyl) methyl]-N2-cyano-N1-methyl acetamidine) on different soil enzyme activities, the experiments were conducted for three consecutive years (2003--2005) at control and cotton experimental fields of Indian Agricultural Research Institute (IARI) and natural area (ridges with forest) in Delhi. The combined results for all three years were presented here to understand the impact of acetamiprid on soil enzyme activities. Acetamiprid was applied three times in one crop season after 41, 48 and 73 days of sowing, to control the pest. Soil of treated fields was analyzed for insecticide residues immediately after first insecticide treatment and thereafter at definite period. The residues of acetamiprid in experimental soil was varied from 0.30+/-0.13 to 22.67+/-0.2 microg g(-1)d.wt. soil, during the crop period of 2003. The insecticide residues for 2004 ranged between 0.59+/-0.38 and 13.42+/-0.71 microg g(-1)d.wt. soil and for 2005 it ranged between 0.48+/-0.22 and 19.81+/-0.33 microg g(-1)d.wt. soil. An average half life of acetamiprid in our treated field was 11.2+/-1.7 days for all three years. Similarly, the soil from natural area and control were also tested for insecticide residues. No detectable insecticide residues had been found. Soil from three localities i.e. natural, control and experimental fields were tested for different enzyme activities. Nitrate reductase, arginine deaminase, urease and dehydrogenase activities were high in natural soil in comparison to control soil and insecticide treated soil in all three experimental years. At the same time, nitrate reductase activity was all time low in acetamiprid treated soil

  1. Heavy-metal-induced Inhibition of Aspergillus niger nitrate reductase: Applications for Rapid Contaminant Detection in Aqueous Samples

    Energy Technology Data Exchange (ETDEWEB)

    Apel, William Arnold; Aiken, Abigail Marie; Peyton, Brent Michael; Petersen, James N.

    2003-03-01

    Enzyme inhibition assays have the potential to rapidly screen and identify heavy metals in environmental samples. Inhibition of nitrate reductase (NR) was examined as a method for detecting toxic metals. The activity of NR (EC 1.6.6.2) from Aspergillus niger was assayed as a function of metal concentration in the presence of Cd2+, Cr3+, Cr6+, Cu2+, Ni2+, Pb2+, and Zn2+. NR exhibited sensitivity to these metals at concentrations below 10 µM. Various buffers were screened for their ability to protect NR activity from metal inhibition, and 3-(N-morpholino) propanesulfonic acid (MOPS) was selected as the buffering system for the NR assays as it exhibited the least interference with metal inhibition, thus providing increased assay sensitivity. The hypothesis that chelating agents could prevent the inhibition of NR activity by metal ions was also tested. Results indicated that 10 mM ethylenediaminetetraacetic acid (EDTA) could protect NR activity from inhibition by Cr3+, Cu2+, Cd2+, Ni2+, and Zn2+ at concentrations below 100 µM, but that the EDTA had no effect on NR inhibition by Cr6+. An amount of 10 mM nitrilotriacetic acid (NTA) prevented NR inhibition by Cd2+, Cu2+, Ni2+, Pb2+, and Zn2+ at metal concentrations below 100 µM. However, 10 mM NTA was unable to protect the enzyme from inhibition by either Cr3+ or Cr6+. These results indicated that through specific metal chelation, a NR-based method for individually quantifying Cr3+ and Cr6+ species in aqueous solutions could be developed. The ability to restore activity to NR which been previously inhibited by exposure to 100 µM Pb2+, Cd2+, Zn2+, Cu2+, and Cr3+ was explored to determine whether NR activity could be recovered by EDTA additions for use in consecutive metal inhibition assays. The results showed NR activity could not be regained after exposure to Cr3+ or Cu2+, but did partially recover activity after Cd2+, Pb2+, and Zn2+ exposure.

  2. Modeling of gadolinium recovery from nitrate medium with 8-hydroxyquinoline by emulsion liquid membrane

    International Nuclear Information System (INIS)

    Hasan, M.A.; Aglan, R.F.; El-Reefy, S.A.

    2009-01-01

    The extraction equilibrium of Gd(III) from nitrate medium by 8-hydroxyquinoline (HOX) in toluene was studied. Liquid-liquid investigations were first carried out. Based on the equilibrium results, the extraction of Gd(III) from aqueous nitrate medium into an emulsion liquid membrane system (ELM) containing 8-hydroxyquinoline in toluene as extractant, HNO 3 as stripping solution, Span-80 as surfactant was studied. The stability of the prepared ELM was studied in terms of the degree of membrane breakage. The different parameters affecting the permeation of gadolinium (III) were also studied. A general permeation model for the recovery of Gd(III) by the selected membrane is presented. The internal mass transfer in the water in oil (W/O) emulsion drop, the external mass transfer around the drop, the rates of formation and decomposition of the complex at the external aqueous-organic interface were considered.

  3. Enzyme kinetics, inhibitors, mutagenesis and electron paramagnetic resonance analysis of dual-affinity nitrate reductase in unicellular N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801.

    Science.gov (United States)

    Wang, Tung-Hei; Chen, Yung-Han; Huang, Jine-Yung; Liu, Kang-Cheng; Ke, Shyue-Chu; Chu, Hsiu-An

    2011-11-01

    The assimilatory nitrate reductase (NarB) of N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801 is a monomeric enzyme with dual affinity for substrate nitrate. We purified the recombinant NarB of Cyanothece sp. PCC 8801 and further investigated it by enzyme kinetics analysis, site-directed mutagenesis, inhibitor kinetics analysis, and electron paramagnetic resonance (EPR) spectroscopy. The NarB showed 2 kinetic regimes at pH 10.5 or 8 and electron-donor conditions methyl viologen or ferredoxin (Fd). Fd-dependent NR assay revealed NarB with very high affinity for nitrate (K(m)1, ∼1μM; K(m)2, ∼270μM). Metal analysis and EPR results showed that NarB contains a Mo cofactor and a [4Fe-4S] cluster. In addition, the R352A mutation on the proposed nitrate-binding site of NarB greatly altered both high- and low-affinity kinetic components. Furthermore, the effect of azide on the NarB of Cyanothece sp. PCC 8801 was more complex than that on the NarB of Synechococcus sp. PCC 7942 with its single kinetic regime. With 1mM azide, the kinetics of the wild-type NarB was transformed from 2 kinetic regimes to hyperbolic kinetics, and its activity was enhanced significantly under medium nitrate concentrations. Moreover, EPR results also suggested a structural difference between the two NarBs. Taken together, our results show that the NarB of Cyanothece sp. PCC 8801 contains only a single Mo-catalytic center, and we rule out that the enzyme has 2 independent, distinct catalytic sites. In addition, the NarB of Cyanothece sp. PCC 8801 may have a regulatory nitrate-binding site. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  4. The reactivation of nitrate reductase from spinach (Spinacea oleracea L.) inactivated by NADH and cyanide: effects of peroxidase and associated systems.

    Science.gov (United States)

    Maldonado, J M; Notton, B A; Hewitt, E J

    1982-12-01

    Nitrate reductase of spinach (Spinacea oleracea L.) leaves which had been inactivated in vitro by treatment with NADH and cyanide, was reactivated by incubation with oxidant systems and measured as FMNH2-dependent activity. Ferricyanide, a purely chemical oxidant, produced rapid maximal reactivation (100%) which was 90% complete in less than 3 min. Reactivation occurred slowly and less completely (30-75% in 30 or 60 min) when the enzyme was incubated with pure horseradish peroxidase alone, depending on using one or 20 units and time. Addition of glucose and glucose oxidase to generate hydrogen peroxide increased reactivation slightly (10-15%) with 20 units of peroxidase but more (30-50%) with one unit and to 75-90% of ferricyanide values. Adding catalase decreased reactivation by more than half either with or without glucose oxidase. Glucose and glucose oxidase alone did not cause reactivation. Addition of superoxide dismutase increased reactivation from 50-75% of ferricyanide values with one unit of peroxidase alone but had no effect on greater reactivation obtained in the presence of glucose oxidase. The addition of p-cresol and manganese together increased reactivation with one unit of peroxidase and in the presence of glucose oxidase by about double, but omission of manganese had no effect. However, as shown previously, although trivalent manganese was formed, the residual presence of manganous ions inhibited reactivation. Nevertheless, peroxidase systems either alone or with additionally generated hydrogen peroxide can induce substantial reactivation of nitrate reductase in physiologically relevant conditions.

  5. Cloning of a nitrate reductase inactivator (NRI) cDNA from Spinacia oleracea L. and expression of mRNA and protein of NRI in cultured spinach cells.

    Science.gov (United States)

    Sonoda, Masatoshi; Ide, Hiroaki; Nakayama, Shinya; Sasaki, Asako; Kitazaki, Shinei; Sato, Takahide; Nakagawa, Hiroki

    2003-04-01

    The spinach ( Spinacia oleracea L. (cv. Hoyo) nitrate reductase inactivator (NRI) is a novel protein that irreversibly inactivates NR. Using degenerate primers based on an N-terminal amino acid sequence of NRI purified from spinach leaves and a cDNA library, we isolated a full-length NRI cDNA from spinach that contains an open reading frame encoding 479 amino acid residues. This protein shares 67.4% and 51.1-68.3% amino acid sequence similarities with a nucleotide pyrophosphatase (EC 3.6.1.9) from rice and three types of the nucleotide pyrophosphatase-like protein from Arabidopsis thaliana, respectively. Immunoblot analysis revealed that NRI was constitutively expressed in suspension-cultured spinach cells; however, its expression level is quite low in 1-day-subcultured cells. Moreover, northern blot analysis indicated that this expression was regulated at the mRNA level. These results suggest that NRI functions in mature cells.

  6. Emulsion liquid membrane for selective extraction of bismuth from nitrate medium

    International Nuclear Information System (INIS)

    Mokhtari, Bahram; Pourabdollah, Kobra

    2013-01-01

    The novelty of this work is the selective extraction of bismuth ions from nitrate medium by emulsion liquid membrane. Di(2-ethylhexyl)phosphoric acid was used as extractant of bismuth ions from nitrate medium by emulsion liquid membrane, and Triton X-100 was used as the biodegradable surfactant in n-pentanol n-pentanol bulk membrane. The extraction of bismuth ions was evaluated by the yield of extraction. The experimental parameters were evaluated and were optimized. They included the ratio of di(2-ethylhexyl)phosphoric acid concentration to the concentration of /Triton X-100 concentration (1.0 : 0.5% w/w), nature of diluents (n-pentanol), nature and concentration of the stripping solution (sulfuric acid, 0.5M), stirring speed (1,800 rpm) and equilibrium time of extraction (20min), initial feed solution of bismuth (350 ppm) and the volume ratio of the internal stripping phase to the membrane phase (14 times). The experimental parameters of kinetic extraction revealed that the bismuth ions were extracted at 100% 97%

  7. Emulsion liquid membrane for selective extraction of bismuth from nitrate medium

    Energy Technology Data Exchange (ETDEWEB)

    Mokhtari, Bahram; Pourabdollah, Kobra [Islamic Azad University, Shahreza (Iran, Islamic Republic of)

    2013-07-15

    The novelty of this work is the selective extraction of bismuth ions from nitrate medium by emulsion liquid membrane. Di(2-ethylhexyl)phosphoric acid was used as extractant of bismuth ions from nitrate medium by emulsion liquid membrane, and Triton X-100 was used as the biodegradable surfactant in n-pentanol n-pentanol bulk membrane. The extraction of bismuth ions was evaluated by the yield of extraction. The experimental parameters were evaluated and were optimized. They included the ratio of di(2-ethylhexyl)phosphoric acid concentration to the concentration of /Triton X-100 concentration (1.0 : 0.5% w/w), nature of diluents (n-pentanol), nature and concentration of the stripping solution (sulfuric acid, 0.5M), stirring speed (1,800 rpm) and equilibrium time of extraction (20min), initial feed solution of bismuth (350 ppm) and the volume ratio of the internal stripping phase to the membrane phase (14 times). The experimental parameters of kinetic extraction revealed that the bismuth ions were extracted at 100% 97%.

  8. [Effects of silver nitrate on the phase state of model multibilayer membranes].

    Science.gov (United States)

    Vashchenko, O V; Iermak, Yu L; Krasnikova, A O; Lisetski, L N

    2015-01-01

    In order to study the effects caused by silver nitrate (AgNO3) on model lipid membranes, we studied multibilayer membranes based on L-α-dipalmitoylphosphatidylcholine (DPPC) and AgNO3 aqueous soluitions in a wide concentration range (up to 30 wt%) by means of differential scanning calorimetry. It has been shown that the presence of AgNO3 leads both to an increase in the main phase transition temperature (T(m)) and appearance of an additional phase transition peak (T(m)), suggesting increasing of both density and heterogeneity of the lipid membrane. The effect of nitrate ions (NO ) was shown to be of the opposite nature (bilayer fluidizing), so the integral densifying effect of AgNO3 can be referred solely to the action of silver ions (Ag(+)). With increasing AgNO3 concentration, the tendency was observed to opposite changes in T(m) and T'(m) peaks intensity, thereby at about 26. wt% of AgNO3 the initial peak (T(m)) disappeared. In the range of Ag+ therapeutic concentrations (up to 2 wt%) no significant changes in the DPPC membrane were revealed. This can be one of the reasons of the absence of a damaging effect of silver drugs on a host organism with simultaneous pronounced bactericidal effect.

  9. Overexpression of a GmCnx1 gene enhanced activity of nitrate reductase and aldehyde oxidase, and boosted mosaic virus resistance in soybean.

    Directory of Open Access Journals (Sweden)

    Zheng Zhou

    Full Text Available Molybdenum cofactor (Moco is required for the activities of Moco-dependant enzymes. Cofactor for nitrate reductase and xanthine dehydrogenase (Cnx1 is known to be involved in the biosynthesis of Moco in plants. In this work, a soybean (Glycine max L. Cnx1 gene (GmCnx1 was transferred into soybean using Agrobacterium tumefaciens-mediated transformation method. Twenty seven positive transgenic soybean plants were identified by coating leaves with phosphinothricin, bar protein quick dip stick and PCR analysis. Moreover, Southern blot analysis was carried out to confirm the insertion of GmCnx1 gene. Furthermore, expression of GmCnx1 gene in leaf and root of all transgenic lines increased 1.04-2.12 and 1.55-3.89 folds, respectively, as compared to wild type with GmCnx1 gene and in line 10 , 22 showing the highest expression. The activities of Moco-related enzymes viz nitrate reductase (NR and aldehydeoxidase (AO of T1 generation plants revealed that the best line among the GmCnx1 transgenic plants accumulated 4.25 μg g(-1 h(-1 and 30 pmol L(-1, respectively (approximately 2.6-fold and 3.9-fold higher than non-transgenic control plants.In addition, overexpression ofGmCnx1boosted the resistance to various strains of soybean mosaic virus (SMV. DAS-ELISA analysis further revealed that infection rate of GmCnx1 transgenic plants were generally lower than those of non-transgenic plants among two different virus strains tested. Taken together, this study showed that overexpression of a GmCnx1 gene enhanced NR and AO activities and SMV resistance, suggesting its important role in soybean genetic improvement.

  10. Impact of elevated atmospheric CO2 on nitrate reductase transcription and activity in leaves and roots of Plantago major

    NARCIS (Netherlands)

    Fonseca, F; Bowsher, CG; Stulen, [No Value

    Vegetative plants of an inbred line, A4, of Plantage major ssp. pleiosperma (L.) Pilger were grown at 350 mu l 1(-1) or at elevated (700 mu l l(-1)) CO2 in non-limiting nutrient solution with nitrate. Both the relative growth rate (RGR) and the root to total plant weight ratio (RWR) were increased

  11. Disguised as a sulfate reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate

    DEFF Research Database (Denmark)

    Thorup, Casper; Schramm, Andreas; Findlay, Alyssa Jean Lehsau

    2017-01-01

    This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D...... of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane......-anchored nitrite reductase....

  12. Tetrathionate reductase of Salmonella thyphimurium: a molybdenum containing enzyme

    International Nuclear Information System (INIS)

    Hinojosa-Leon, M.; Dubourdieu, M.; Sanchez-Crispin, J.A.; Chippaux, M.

    1986-01-01

    Use of radioactive molybdenum demonstrates that the tetrathionate reductase of Salmonella typhimurium is a molydenum containing enzyme. It is proposed that this enzyme shares with other molybdo-proteins, such as nitrate reductase, a common molybdenum containing cofactor the defect of which leads to the loss of the tetrathionate reductase and nitrate reductase activities

  13. Physical and mechanical properties of membrane polyvinilidene flouride with the addition of silver nitrate

    Directory of Open Access Journals (Sweden)

    Mataram Agung

    2018-01-01

    Full Text Available The membrane is a layer formed from fine fibers are used as a filter. In this research, measured the tensile strength and pore size of the membrane that is made in three variations of a specimen with a mixed composition of different Polyvinilidene Fluoride 17.5%, 20%, 22.5%., membrane made using Polyvinilidene Fluoride polimer granules and N,N-Dimethylformamide as solvent and silver nitrate. Membrane molded into standardized test specimens and tested with a device Adhesion Tearring Strength Tester. The results show an increase in the value of the tensile test of 404.8356 KPa to the composition of 17.5%, 507.3598 KPa for composition of 20% and 603.7218 KPa to a composition of 22.5%. For testing the microstructure using a Scanning Electron Microscopy with the resulting increase in pore diameter, for the range of 558.4 nm-781.8 nm are void to the composition of 17.5%, range 670.1 nm - 781.8 nm without voids for the composition of 20% and 1.117 μm-1.228μm without voids on a composition of 22.5

  14. Cytochrome b5 reductase is the component from neuronal synaptic plasma membrane vesicles that generates superoxide anion upon stimulation by cytochrome c

    Directory of Open Access Journals (Sweden)

    Alejandro K. Samhan-Arias

    2018-05-01

    Full Text Available In this work, we measured the effect of cytochrome c on the NADH-dependent superoxide anion production by synaptic plasma membrane vesicles from rat brain. In these membranes, the cytochrome c stimulated NADH-dependent superoxide anion production was inhibited by antibodies against cytochrome b5 reductase linking the production to this enzyme. Measurement of the superoxide anion radical generated by purified recombinant soluble and membrane cytochrome b5 reductase corroborates the production of the radical by different enzyme isoforms. In the presence of cytochrome c, a burst of superoxide anion as well as the reduction of cytochrome c by cytochrome b5 reductase was measured. Complex formation between both proteins suggests that cytochrome b5 reductase is one of the major partners of cytochrome c upon its release from mitochondria to the cytosol during apoptosis. Superoxide anion production and cytochrome c reduction are the consequences of the stimulated NADH consumption by cytochrome b5 reductase upon complex formation with cytochrome c and suggest a major role of this enzyme as an anti-apoptotic protein during cell death.

  15. Cytochrome b5 reductase is the component from neuronal synaptic plasma membrane vesicles that generates superoxide anion upon stimulation by cytochrome c.

    Science.gov (United States)

    Samhan-Arias, Alejandro K; Fortalezas, Sofia; Cordas, Cristina M; Moura, Isabel; Moura, José J G; Gutierrez-Merino, Carlos

    2018-05-01

    In this work, we measured the effect of cytochrome c on the NADH-dependent superoxide anion production by synaptic plasma membrane vesicles from rat brain. In these membranes, the cytochrome c stimulated NADH-dependent superoxide anion production was inhibited by antibodies against cytochrome b 5 reductase linking the production to this enzyme. Measurement of the superoxide anion radical generated by purified recombinant soluble and membrane cytochrome b 5 reductase corroborates the production of the radical by different enzyme isoforms. In the presence of cytochrome c, a burst of superoxide anion as well as the reduction of cytochrome c by cytochrome b 5 reductase was measured. Complex formation between both proteins suggests that cytochrome b 5 reductase is one of the major partners of cytochrome c upon its release from mitochondria to the cytosol during apoptosis. Superoxide anion production and cytochrome c reduction are the consequences of the stimulated NADH consumption by cytochrome b 5 reductase upon complex formation with cytochrome c and suggest a major role of this enzyme as an anti-apoptotic protein during cell death. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Nitrate reductase activity (NRA in the invasive alien Fallopia japonica: seasonal variation, differences among habitats types, and comparison with native species

    Directory of Open Access Journals (Sweden)

    Damian Chmura

    2016-09-01

    Full Text Available Nitrate reductase activity (NRA was studied in the invasive alien plant F. japonica (Japanese knotweed during the vegetation season and among natural, semi-natural, and human-made habitats and compared with NRA in selected native species. NRA was measured directly in the field from the beginning of May until the beginning of October. NRA was much higher than in the plant’s native range, i.e., East Asia, and showed a high degree of variation over time with the highest values being reached at the stage of fast vegetative growth and at the beginning of fruiting. NRA was highest on dumping sites probably due to the high nitrogen input into soils and near traffic and the emission of NOx by vehicles. A comparison of the enzyme activity in four selected native plant species indicated that NRA in F. japonica was the highest with the exception of Urtica dioica, which exhibited a similar activity of the enzyme. A detailed comparison with this species showed that differences between these species on particular dates were influenced by differences in the phenology of both plants. The initial results that were obtained suggest that nitrogen pollution in an environment can contribute to habitat invasibility and a high level of NRA, which in addition to the many plant traits that are commonly accepted as characteristic of invasiveness features, may be an important factor that enhances invasion success.

  17. Effects of elevated CO2 on the photosynthesis and nitrate reductase activity of Pyropia haitanensis (Bangiales, Rhodophyta) grown at different nutrient levels

    Science.gov (United States)

    Liu, Chunxiang; Zou, Dinghui

    2015-03-01

    Pyropia haitanensis, a commercially important species, was cultured at two CO2 concentrations (390×10-6 and 700×10-6 (parts per million)) and at low and high nutrient levels, to explore the effect of elevated CO2 on the species under nutrient enrichment. Results show that in CO2-enriched thalli, relative growth rate (RGR) was enhanced under nutrient enrichment. Elevated CO2 decreased phycobiliprotein (PB) contents, but increased the contents of soluble carbohydrates. Nutrient enrichment increased the contents of chlorophyll a (Chl a) and PB, while soluble carbohydrate content decreased. CO2 enrichment enhanced the relative maximum electronic transport rate and light saturation point. In nutrient-enriched thalli the activity of nitrate reductase (NRA) increased under elevated CO2. An instantaneous pH change in seawater (from 8.1 to 9.6) resulted in reduction of NRA, and the thalli grown under both elevated CO2 and nutrient enrichment exhibited less pronounced reduction than in algae grown at the ambient CO2. The thermal optima of NRA under elevated CO2 and/or nutrient enrichment shifted to a lower temperature (10-15°C) compared to that in ambient conditions (20°C). We propose that accelerated photosynthesis could result in growth increment. N assimilation remained high in acidified seawater and reflected increased temperature sensitivity in response to elevated CO2 and eutrophication.

  18. Nitrate reductase and nitrogenase activities in relation to N-uptake from soil, 15N-fertilizer and symbiotic fixation in soybean (Glycine max)

    International Nuclear Information System (INIS)

    Ruschel, A.P.; Saito, S.M.T.; Vose, P.B.

    1980-01-01

    Nitrate reductase (NRA) and nitrogenase (ARA) activities were evaluated in relation to nitrogen in the plant from soil (NFS), fertilizer (NFF) and symbiotic fixation (NFN 2 ) to study the pattern of utilization of nitrogen in nodulated and non nodulated soybean, 35, 55 and 75 days after planting. Three levels of ( 15 NH 4 ) 2 SO 4 - added to soil were used (0 - 25 and 50 kg N/ha), being the experiment conducted in the greenhouse, with a split plot statistical design and 4 replications. Maximum levels of RNA and ARA occurred 55 days after planting. Addition of 50 kg N/ha decreased NRA at all harvesting time studied; and nodule ARA only 75 days after planting. By that time the nodulated isoline showed higher NRA than the non nodulated one, the NFS and NFF of the isolines were not different 35 and 55 days after planting, but decreased at the last harvest, especially in nodulated soybean. Symbiotic N 2 -fixation increased plant-N after 55 days growth, contribution about 65% of plant-N in the period between 55 and 75 days after planting. Nodulated plant showed higher N than non nodulated, a sinergistic effect of the three sources of N studied on N increase of nodulated plants was observed. (Author) [pt

  19. Drought-Induced Effects on Nitrate Reductase Activity and mRNA and on the Coordination of Nitrogen and Carbon Metabolism in Maize Leaves1

    Science.gov (United States)

    Foyer, Christine H.; Valadier, Marie-Hélène; Migge, Andrea; Becker, Thomas W.

    1998-01-01

    Maize (Zea mays L.) plants were grown to the nine-leaf stage. Despite a saturating N supply, the youngest mature leaves (seventh position on the stem) contained little NO3− reserve. Droughted plants (deprived of nutrient solution) showed changes in foliar enzyme activities, mRNA accumulation, photosynthesis, and carbohydrate and amino acid contents. Total leaf water potential and CO2 assimilation rates, measured 3 h into the photoperiod, decreased 3 d after the onset of drought. Starch, glucose, fructose, and amino acids, but not sucrose (Suc), accumulated in the leaves of droughted plants. Maximal extractable phosphoenolpyruvate carboxylase activities increased slightly during water deficit, whereas the sensitivity of this enzyme to the inhibitor malate decreased. Maximal extractable Suc phosphate synthase activities decreased as a result of water stress, and there was an increase in the sensitivity to the inhibitor orthophosphate. A correlation between maximal extractable foliar nitrate reductase (NR) activity and the rate of CO2 assimilation was observed. The NR activation state and maximal extractable NR activity declined rapidly in response to drought. Photosynthesis and NR activity recovered rapidly when nutrient solution was restored at this point. The decrease in maximal extractable NR activity was accompanied by a decrease in NR transcripts, whereas Suc phosphate synthase and phosphoenolpyruvate carboxylase mRNAs were much less affected. The coordination of N and C metabolism is retained during drought conditions via modulation of the activities of Suc phosphate synthase and NR commensurate with the prevailing rate of photosynthesis. PMID:9576798

  20. Influence of the temporal and spatial variation of nitrate reductase, glutamine synthetase and soil composition in the N species content in lettuce (Lactuca sativa).

    Science.gov (United States)

    Pinto, Edgar; Fidalgo, Fernanda; Teixeira, Jorge; Aguiar, Ana A; Ferreira, Isabel M P L V O

    2014-04-01

    The variation of nitrate reductase (NR), glutamine synthetase (GS) and N content in lettuce was evaluated at 5 stages of lettuce growth. Soil physicochemical properties and its N content were also assessed to elucidate the soil-to-plant transfer of inorganic N and potential leaching to groundwater. A decrease of NR activity and an increase of NO3(-) and N-Kjeldahl content in lettuces were observed during plant growth, whereas GS activity and NH4(+) increased during the first few weeks of lettuce growth and then decreased. Although the temporal variation was similar in lettuces grown in different soils, quantitative differences were observed, indicating that high NO3(-) content in soil caused a higher NO3(-) accumulation in lettuce despite the higher NR activity during the initial stage of plant growth. Higher levels of NO3(-) and NH4(+) were correlated with higher levels of N-Kjeldahl in lettuce suggesting a positive effect of these N species in the biosynthesis of organic forms of N. Soil physicochemical properties influenced the mobility of inorganic N within the groundwater-soil-plant system. Sandy soils with low OM content allowed NO3(-) leaching, which was confirmed by higher NO3(-) levels in groundwater. Therefore, lettuces grown in those soils presented lower N content and the inputs of N to the environment were higher. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. Mathematical Modelling of Nitrate Removal from Water Using a Submerged Membrane Adsorption Hybrid System with Four Adsorbents

    Directory of Open Access Journals (Sweden)

    Mahatheva Kalaruban

    2018-01-01

    Full Text Available Excessive concentrations of nitrate in ground water are known to cause human health hazards. A submerged membrane adsorption hybrid system that includes a microfilter membrane and four different adsorbents (Dowex 21K XLT ion exchange resin (Dowex, Fe-coated Dowex, amine-grafted (AG corn cob and AG coconut copra operated at four different fluxes was used to continuously remove nitrate. The experimental data obtained in this study was simulated mathematically with a homogeneous surface diffusion model that incorporated membrane packing density and membrane correlation coefficient, and applied the concept of continuous flow stirred tank reactor. The model fit with experimental data was good. The surface diffusion coefficient was constant for all adsorbents and for all fluxes. The mass transfer coefficient increased with flux for all adsorbents and generally increased with the adsorption capacity of the adsorbents.

  2. Membrane-anchored MucR mediates nitrate-dependent regulation of alginate production in Pseudomonas aeruginosa

    KAUST Repository

    Wang, Yajie

    2015-04-29

    Alginates exhibit unique material properties suitable for medical and industrial applications. However, if produced by Pseudomonas aeruginosa, it is an important virulence factor in infection of cystic fibrosis patients. The alginate biosynthesis machinery is activated by c-di-GMP imparted by the inner membrane protein, MucR. Here, it was shown that MucR impairs alginate production in response to nitrate in P. aeruginosa. Subsequent site-specific mutagenesis of MucR revealed that the second MHYT sensor motif (MHYT II, amino acids 121–124) of MucR sensor domain was involved in nitrate sensing. We also showed that both c-di-GMP synthesizing and degrading active sites of MucR were important for alginate production. Although nitrate and deletion of MucR impaired alginate promoter activity and global c-di-GMP levels, alginate yields were not directly correlated with alginate promoter activity or c-di-GMP levels, suggesting that nitrate and MucR modulate alginate production at a post-translational level through a localized pool of c-di-GMP. Nitrate increased pel promoter activity in the mucR mutant while in the same mutant the psl promoter activity was independent of nitrate. Nitrate and deletion of mucR did not impact on swarming motility but impaired attachment to solid surfaces. Nitrate and deletion of mucR promoted the formation of biofilms with increased thickness, cell density, and survival. Overall, this study provided insight into the functional role of MucR with respect to nitrate-mediated regulation of alginate biosynthesis. © 2015 Springer-Verlag Berlin Heidelberg

  3. The outer membrane protein Omp35 affects the reduction of Fe(III, nitrate, and fumarate by Shewanella oneidensis MR-1

    Directory of Open Access Journals (Sweden)

    Myers Charles R

    2004-06-01

    Full Text Available Abstract Background Shewanella oneidensis MR-1 uses several electron acceptors to support anaerobic respiration including insoluble species such as iron(III and manganese(IV oxides, and soluble species such as nitrate, fumarate, dimethylsulfoxide and many others. MR-1 has complex branched electron transport chains that include components in the cytoplasmic membrane, periplasm, and outer membrane (OM. Previous studies have implicated a role for anaerobically upregulated OM electron transport components in the use of insoluble electron acceptors, and have suggested that other OM components may also contribute to insoluble electron acceptor use. In this study, the role for an anaerobically upregulated 35-kDa OM protein (Omp35 in the use of anaerobic electron acceptors was explored. Results Omp35 was purified from the OM of anaerobically grown cells, the gene encoding Omp35 was identified, and an omp35 null mutant (OMP35-1 was isolated and characterized. Although OMP35-1 grew on all electron acceptors tested, a significant lag was seen when grown on fumarate, nitrate, and Fe(III. Complementation studies confirmed that the phenotype of OMP35-1 was due to the loss of Omp35. Despite its requirement for wild-type rates of electron acceptor use, analysis of Omp35 protein and predicted sequence did not identify any electron transport moieties or predicted motifs. OMP35-1 had normal levels and distribution of known electron transport components including quinones, cytochromes, and fumarate reductase. Omp35 is related to putative porins from MR-1 and S. frigidimarina as well as to the PorA porin from Neisseria meningitidis. Subcellular fraction analysis confirmed that Omp35 is an OM protein. The seven-fold anaerobic upregulation of Omp35 is mediated post-transcriptionally. Conclusion Omp35 is a putative porin in the OM of MR-1 that is markedly upregulated anaerobically by a post-transcriptional mechanism. Omp35 is required for normal rates of growth on Fe

  4. Analytical properties of some commercially available nitrate reductase enzymes evaluated as replacements for cadmium in automated, semiautomated, and manual colorimetric methods for determination of nitrate plus nitrite in water

    Science.gov (United States)

    Patton, Charles J.; Kryskalla, Jennifer R.

    2013-01-01

    A multiyear research effort at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) evaluated several commercially available nitrate reductase (NaR) enzymes as replacements for toxic cadmium in longstanding automated colorimetric air-segmented continuous-flow analyzer (CFA) methods for determining nitrate plus nitrite (NOx) in water. This research culminated in USGS approved standard- and low-level enzymatic reduction, colorimetric automated discrete analyzer NOx methods that have been in routine operation at the NWQL since October 2011. The enzyme used in these methods (AtNaR2) is a product of recombinant expression of NaR from Arabidopsis thaliana (L.) Heynh. (mouseear cress) in the yeast Pichia pastoris. Because the scope of the validation report for these new automated discrete analyzer methods, published as U.S. Geological Survey Techniques and Methods 5–B8, was limited to performance benchmarks and operational details, extensive foundational research with different enzymes—primarily YNaR1, a product of recombinant expression of NaR from Pichia angusta in the yeast Pichia pastoris—remained unpublished until now. This report documents research and development at the NWQL that was foundational to development and validation of the discrete analyzer methods. It includes: (1) details of instrumentation used to acquire kinetics data for several NaR enzymes in the presence and absence of known or suspected inhibitors in relation to reaction temperature and reaction pH; and (2) validation results—method detection limits, precision and bias estimates, spike recoveries, and interference studies—for standard- and low-level automated colorimetric CFA-YNaR1 reduction NOx methods in relation to corresponding USGS approved CFA cadmium-reduction (CdR) NOx methods. The cornerstone of this validation is paired sample statistical and graphical analysis of NOx concentrations from more than 3,800 geographically and seasonally diverse surface

  5. β-Subunits of the SnRK1 Complexes Share a Common Ancestral Function Together with Expression and Function Specificities; Physical Interaction with Nitrate Reductase Specifically Occurs via AKINβ1-Subunit1[C][OA

    Science.gov (United States)

    Polge, Cécile; Jossier, Mathieu; Crozet, Pierre; Gissot, Lionel; Thomas, Martine

    2008-01-01

    The SNF1/AMPK/SnRK1 kinases are evolutionary conserved kinases involved in yeast, mammals, and plants in the control of energy balance. These heterotrimeric enzymes are composed of one α-type catalytic subunit and two γ- and β-type regulatory subunits. In yeast it has been proposed that the β-type subunits regulate both the localization of the kinase complexes within the cell and the interaction of the kinases with their targets. In this work, we demonstrate that the three β-type subunits of Arabidopsis (Arabidopsis thaliana; AKINβ1, AKINβ2, and AKINβ3) restore the growth phenotype of the yeast sip1Δsip2Δgal83Δ triple mutant, thus suggesting the conservation of an ancestral function. Expression analyses, using AKINβ promoter∷β-glucuronidase transgenic lines, reveal different and specific patterns of expression for each subunit according to organs, developmental stages, and environmental conditions. Finally, our results show that the β-type subunits are involved in the specificity of interaction of the kinase with the cytosolic nitrate reductase. Together with previous cell-free phosphorylation data, they strongly support the proposal that nitrate reductase is a real target of SnRK1 in the physiological context. Altogether our data suggest the conservation of ancestral basic function(s) together with specialized functions for each β-type subunit in plants. PMID:18768910

  6. Nitrate Sensing and Metabolism Modulate Motility, Biofilm Formation, and Virulence in Pseudomonas aeruginosa▿

    Science.gov (United States)

    Van Alst, Nadine E.; Picardo, Kristin F.; Iglewski, Barbara H.; Haidaris, Constantine G.

    2007-01-01

    Infection by the bacterial opportunist Pseudomonas aeruginosa frequently assumes the form of a biofilm, requiring motility for biofilm formation and dispersal and an ability to grow in nutrient- and oxygen-limited environments. Anaerobic growth by P. aeruginosa is accomplished through the denitrification enzyme pathway that catalyzes the sequential reduction of nitrate to nitrogen gas. Mutants mutated in the two-component nitrate sensor-response regulator and in membrane nitrate reductase displayed altered motility and biofilm formation compared to wild-type P. aeruginosa PAO1. Analysis of additional nitrate dissimilation mutants demonstrated a second level of regulation in P. aeruginosa motility that is independent of nitrate sensor-response regulator function and is associated with nitric oxide production. Because motility and biofilm formation are important for P. aeruginosa pathogenicity, we examined the virulence of selected regulatory and structural gene mutants in the surrogate model host Caenorhabditis elegans. Interestingly, the membrane nitrate reductase mutant was avirulent in C. elegans, while nitrate sensor-response regulator mutants were fully virulent. The data demonstrate that nitrate sensing, response regulation, and metabolism are linked directly to factors important in P. aeruginosa pathogenesis. PMID:17526746

  7. Smart membranes for nitrate removal, water purification, and selective ion transportation

    Science.gov (United States)

    Wilson, William D [Pleasanton, CA; Schaldach, Charlene M [Pleasanton, CA; Bourcier, William L [Livermore, CA; Paul, Phillip H [Livermore, CA

    2009-12-15

    A computer designed nanoengineered membrane for separation of dissolved species. One embodiment provides an apparatus for treatment of a fluid that includes ions comprising a microengineered porous membrane, a system for producing an electrical charge across the membrane, and a series of nanopores extending through the membrane. The nanopores have a pore size such that when the fluid contacts the membrane, the nanopores will be in a condition of double layer overlap and allow passage only of ions opposite to the electrical charge across the membrane.

  8. Nitrite Reductase NirS Is Required for Type III Secretion System Expression and Virulence in the Human Monocyte Cell Line THP-1 by Pseudomonas aeruginosa▿

    Science.gov (United States)

    Van Alst, Nadine E.; Wellington, Melanie; Clark, Virginia L.; Haidaris, Constantine G.; Iglewski, Barbara H.

    2009-01-01

    The nitrate dissimilation pathway is important for anaerobic growth in Pseudomonas aeruginosa. In addition, this pathway contributes to P. aeruginosa virulence by using the nematode Caenorhabditis elegans as a model host, as well as biofilm formation and motility. We used a set of nitrate dissimilation pathway mutants to evaluate the virulence of P. aeruginosa PA14 in a model of P. aeruginosa-phagocyte interaction by using the human monocytic cell line THP-1. Both membrane nitrate reductase and nitrite reductase enzyme complexes were important for cytotoxicity during the interaction of P. aeruginosa PA14 with THP-1 cells. Furthermore, deletion mutations in genes encoding membrane nitrate reductase (ΔnarGH) and nitrite reductase (ΔnirS) produced defects in the expression of type III secretion system (T3SS) components, extracellular protease, and elastase. Interestingly, exotoxin A expression was unaffected in these mutants. Addition of exogenous nitric oxide (NO)-generating compounds to ΔnirS mutant cultures restored the production of T3SS phospholipase ExoU, whereas nitrite addition had no effect. These data suggest that NO generated via nitrite reductase NirS contributes to the regulation of expression of selected virulence factors in P. aeruginosa PA14. PMID:19651860

  9. ACCUMULATION OF NITROGEN COMPOUNDS AND NITRATE REDUCTASE ACTIVITY IN LETTUCE CULTIVATED IN DIFFERENT CROP SYSTEMS ACÚMULO DE COMPOSTOS NITROGENADOS E ATIVIDADE DA REDUTASE DO NITRATO EM ALFACE PRODUZIDA EM DIFERENTES SISTEMAS DE CULTIVO

    Directory of Open Access Journals (Sweden)

    Fernanda Nunes Ibrahim

    2008-09-01

    Full Text Available

    Nitrate content determination is important for food quality evaluation, therefore when ingested nitrate is reduced the nitrite, which can generate harmful compounds to the human organism. Ahead of this, the present work had as objective to study the transport and accumulation of nitrogen compounds and the nitrate reductase activity in lettuce cultivar 'Vera' produced in Registro (SP in different cropping systems. Were collected samples of the xylem sap, aerial part and root for quantification of nitrogen compounds and of the reductase activity in vivo. The nitrate concentration in the xylem sap, the nitrate and amino acids contents, as well as the nitrate reductase activity, demonstrated more intense transport, accumulation and assimilation in plants cultivated in in hydroponic solution, followed of the conventional system and finally, of the organic. The stem of the plant in the three systems of culture presented high capacity of accumulation and assimilation the nitrogen compounds. The nitrate reductase activity in leaves was superior of the root. The content nitrate, independent of the culture system, varied of 24.32 the 800.06 mg kg-1 of FW in the different parts of the plant. However, it did not exceed the maximum

  10. Nitrate transport in cucumber leaves is an inducible process involving an increase in plasma membrane H+-ATPase activity and abundance

    Directory of Open Access Journals (Sweden)

    Nikolic Miroslav

    2012-05-01

    Full Text Available Abstract Background The mechanisms by which nitrate is transported into the roots have been characterized both at physiological and molecular levels. It has been demonstrated that nitrate is taken up in an energy-dependent way by a four-component uptake machinery involving high- and low- affinity transport systems. In contrast very little is known about the physiology of nitrate transport towards different plant tissues and in particular at the leaf level. Results The mechanism of nitrate uptake in leaves of cucumber (Cucumis sativus L. cv. Chinese long plants was studied and compared with that of the root. Net nitrate uptake by roots of nitrate-depleted cucumber plants proved to be substrate-inducible and biphasic showing a saturable kinetics with a clear linear non saturable component at an anion concentration higher than 2 mM. Nitrate uptake by leaf discs of cucumber plants showed some similarities with that operating in the roots (e.g. electrogenic H+ dependence via involvement of proton pump, a certain degree of induction. However, it did not exhibit typical biphasic kinetics and was characterized by a higher Km with values out of the range usually recorded in roots of several different plant species. The quantity and activity of plasma membrane (PM H+-ATPase of the vesicles isolated from leaf tissues of nitrate-treated plants for 12 h (peak of nitrate foliar uptake rate increased with respect to that observed in the vesicles isolated from N-deprived control plants, thus suggesting an involvement of this enzyme in the leaf nitrate uptake process similar to that described in roots. Molecular analyses suggest the involvement of a specific isoform of PM H+-ATPase (CsHA1 and NRT2 transporter (CsNRT2 in root nitrate uptake. At the leaf level, nitrate treatment modulated the expression of CsHA2, highlighting a main putative role of this isogene in the process. Conclusions Obtained results provide for the first time evidence that a saturable

  11. Nitrate and ammonia as nitrogen sources for deep subsurface microorganisms

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    Heini eKutvonen

    2015-10-01

    Full Text Available We investigated the N-utilizing bacterial community in anoxic brackish groundwater of the low and intermediate level nuclear waste repository cave in Olkiluoto, Finland, at 100 m depth using 15N-based stable isotope probing (SIP and enrichment with 14/15N-ammonium or 14/15N-nitrate complemented with methane. 28 days of incubation at 12°C increased the concentration of bacterial 16S rRNA and nitrate reductase (narG gene copies in the substrate amended microcosms simultaneously with a radical drop in the overall bacterial diversity and OTU richness. Hydrogenophaga/Malikia were enriched in all substrate amended microcosms and Methylobacter in the ammonium and ammonium+methane supplemented microcosms. Sulfuricurvum was especially abundant in the nitrate+methane treatment and the unamended incubation control. Membrane-bound nitrate reductase genes (narG from Polarimonas sp. were detected in the original groundwater, while Burkholderia, Methylibium and Pseudomonas narG genes were enriched due to substrate supplements. Identified amoA genes belonged to Nitrosomonas sp. 15N-SIP revealed that Burkholderiales and Rhizobiales clades belonging to the minority groups in the original groundwater used 15N from ammonium and nitrate as N source indicating an important ecological function of these bacteria, despite their low number, in the groundwater N cycle in Olkiluoto bedrock system.

  12. N-partitioning, nitrate reductase and glutamine synthetase activities in two contrasting varieties of maize Partição de nitrogênio e atividade das enzimas nitrato redutase e glutamina sintetase em duas cultivares contrastantes de milho

    Directory of Open Access Journals (Sweden)

    Altair Toledo Machado

    2001-02-01

    Full Text Available In order to identify useful parameters for maize genetic breeding programs aiming at a more efficient use of N, two maize varieties of contrasting N efficiency, Sol da Manhã NF (efficient and Catetão (inefficient were compared. Experiments were carried out under field and greenhouse conditions, at low and high N levels. The parameters analysed included total and relative plant and grain N content, biomass and the activities of nitrate reductase and glutamine synthetase in different parts of the plant. It was found that the translocation efficiency of N and photoassimilates to the developing seeds and the source-sink relations were significantly different for the two varieties. N content of the whole plant and grain, cob weight and the relative ear dry weight were useful parameters for characterizing the variety Sol da Manhã NF as to its efficient use of N. Enzymes activity of glutamine synthetase (transferase reaction and nitrate reductase did not differ among the varieties.Com o objetivo de identificar parâmetros que possam ser utilizados em programas de melhoramento genético em milho para uso eficiente de N, duas cultivares de milho contrastantes quanto ao uso deste nutriente, Sol da Manhã NF (eficiente e Catetão (não-eficiente, foram avaliadas em dois experimentos conduzidos no campo e em casa de vegetação, respectivamente, sob nível baixo e alto de N. Os caracteres avaliados foram: teor e conteúdo de N em diferentes partes da planta; massa seca; peso dos grãos e de diferentes partes da planta; biomassa, e atividade das enzimas nitrato redutase e glutamina sintetase. O mecanismo de translocação de N e de fotoassimilados para os grãos e a relação fonte/dreno foram importantes para diferenciar a cultivar eficiente da não-eficiente. Conteúdo de N nos grãos e total das plantas, peso do sabugo e relação peso de espiga/matéria seca foram importantes para caracterizar a cultivar Sol da Manhã NF eficiente no uso do N. A

  13. Effects of solar UV radiation on photosynthesis and enzyme activities (carbonic anhydrase and nitrate reductase) in marine macroalgae from southern Spain Efectos de la radiación solar UV sobre la fotosíntesis y actividades enzimáticas (anhidrasa carbónica y nitrato reductasa) en macralgas marinas del sur de España

    OpenAIRE

    FÉLIX L. FIGUEROA; BENJAMÍN VIÑEGLA

    2001-01-01

    The effects of solar ultraviolet (UV) radiation during daily cycles on photosynthesis and two key enzymes involved in carbon incorporation, the carbonic anhydrase, and in inorganic nitrogen reduction, the nitrate reductase, of macroalgae from southern Spain are presented. During daily cycles, photoinhibition in several intertidal macroalgae, expressed as decrease in the effective quantum yield from the morning to noon time, was linearly dependent on the daily integrated irradiance. However, r...

  14. Function of Ubiquinone in Electron Transport from Reduced Nicotinamide Adenine Dinucleotide to Nitrate and Oxygen in Aerobacter aerogenes

    Science.gov (United States)

    Knook, D. L.; Planta, R. J.

    1971-01-01

    The possible role of quinones in the electron transport system of Aerobacter aerogenes was investigated. The only quinone found in measurable amounts in bacteria grown in minimal media under both aerobic and anaerobic conditions was ubiquinone-8. Membrane-bound ubiquinone-8 could be removed by extraction with pentane, or destroyed by ultraviolet irradiation, with a concomitant loss of both reduced nicotinamide adenine dinucleotide (NADH) oxidase and NADH-linked respiratory nitrate reductase activity. In the extracted membrane preparations, these enzymatic activities could be restored, both to the same degree, by incorporation of ubiquinone-6, -8, or -10, but not by incorporation of menaquinones. The NADH oxidation and the nitrate reduction were sensitive to the respiratory inhibitors dicoumarol, lapachol, and cyanide. The results obtained indicate that ubiquinone-8 mediates the electron transport between NADH and oxygen as well as between NADH and nitrate. Branching of the electron transport chain to oxygen and nitrate occurs after an initial common pathway. PMID:4100202

  15. Growth of silicone-immobilized bacteria on polycarbonate membrane filters, a technique to study microcolony formation under anaerobic conditions.

    OpenAIRE

    Højberg, O; Binnerup, S J; Sørensen, J

    1997-01-01

    A technique was developed to study microcolony formation by silicone-immobilized bacteria on polycarbonate membrane filters under anaerobic conditions. A sudden shift to anaerobiosis was obtained by submerging the filters in medium which was depleted for oxygen by a pure culture of bacteria. The technique was used to demonstrate that preinduction of nitrate reductase under low-oxygen conditions was necessary for nonfermenting, nitrate-respiring bacteria, e.g., Pseudomonas spp., to cope with a...

  16. Nitrate reductase and glutamine synthetase activity in coffee leaves during fruit development Atividade da redutase do nitrato e glutamina sintetase em folhas de cafeeiro durante o desenvolvimento dos frutos

    Directory of Open Access Journals (Sweden)

    Andre Rodrigues Reis

    2009-04-01

    Full Text Available Nitrate reductase is the first enzyme in the pathway of nitrate reduction by plants, followed by glutamine synthetase, which incorporates ammonia to glutamine. The purpose of this study was to evaluate the nitrate reductase and glutamine synthetase activity, total soluble protein content, N and Ni content in coffee leaves during fruit development under field conditions to establish new informations to help assess the N nutritional status and fertilizer management. The experimental design was in randomized complete blocks, arranged in a 3 x 6 factorial design, with five replications. The treatments consisted of 3 N rates (0 - control, 150 and 300 kg ha-1 and six evaluation periods (January, February, March, April, May, and June in six-year-old coffee (Coffea arabica L. plants of Catuaí Vermelho IAC 44 cv. The nitrate reductase and glutamine synthetase activities, leaf soluble protein, and N concentrations increased linearly with the N rates. During fruit development, the enzyme activity, leaf soluble protein and N content decreased, due to the leaf senescence process caused by nutrient mobilization to other organs, e.g, to the berries. Leaf Ni increased during fruit development. Beans and raisin-fruits of plants well-supplied with N had higher Ni contents. Enzyme activities, total leaf N and leaf soluble protein, evaluated during the green fruit stage in March, were significantly correlated with coffee yield. These variables can therefore be useful for an early assessment of the coffee N nutritional status as well as coffee yield and N fertilization management.A redutase do nitrato (RN é a primeira enzima na via de redução de nitrato pelas plantas, seguida da glutamina sintetase (GS, a qual incorpora amônia à glutamina. O objetivo deste trabalho foi avaliar a atividade dessas enzimas, o teor de proteína solúvel total e a concentração de N e de Ni em folhas e grãos de cafeeiro durante o desenvolvimento dos frutos, em condições de

  17. Mutational analysis of the respiratory nitrate transporter NarK2 of Mycobacterium tuberculosis.

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    Michelle M Giffin

    Full Text Available Mycobacterium tuberculosis induces nitrate reductase activity in response to decreasing oxygen levels. This is due to regulation of both the transcription and the activity of the nitrate transporter NarK2. A model of NarK2 structure is proposed containing 12 membrane spanning regions consistent with other members of the major facilitator superfamily. The role of the proton gradient was determined by exposing M. tuberculosis to uncouplers. Nitrite production decreased indicating that the importation of nitrate involved an H(+/nitrate symporter. The addition of nitrite before nitrate had no effect, suggesting no role for a nitrate/nitrite antiporter. In addition the NarK2 knockout mutant showed no defect in nitrite export. NarK2 is proposed to be a Type I H(+/nitrate symporter. Site directed mutagenesis was performed changing 23 amino acids of NarK2. This allowed the identification of important regions and amino acids of this transporter. Five of these mutants were inactive for nitrate transport, seven produced reduced activity and eleven mutants retained wild type activity. NarK2 is inactivated in the presence of oxygen by an unknown mechanism. However none of the mutants, including those with mutated cysteines, were altered in their response to oxygen levels. The assimilatory nitrate transporter NasA of Bacillus subtilis was expressed in the M. tuberculosis NarK2 mutant. It remained active during aerobic incubation showing that the point of oxygen control is NarK2.

  18. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report

    Energy Technology Data Exchange (ETDEWEB)

    John F. Stolz

    2011-06-15

    A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory

  19. Membrane biological reactors to remove nitrate, digest biosolids, and eliminate water flushing requirements within replicated recirculation systems culturing rainbow trout

    Science.gov (United States)

    Nutrients, particularly nitrate (NO3), can accumulate to very high levels within low exchange recirculation aquaculture systems (RAS) and negatively impact a number of cultured species. To prevent the harmful effects of nitrate accumulation and to dispose of concentrated waste biosolids, many RAS ar...

  20. Iron reductases from Pseudomonas aeruginosa.

    Science.gov (United States)

    Cox, C D

    1980-01-01

    Cell-free extracts of Pseudomonas aeruginosa contain enzyme activities which reduce Fe(III) to Fe(II) when iron is provided in certain chelates, but not when the iron is uncomplexed. Iron reductase activities for two substrates, ferripyochelin and ferric citrate, appear to be separate enzymes because of differences in heat stabilities, in locations in fractions of cell-free extracts, in reductant specificity, and in apparent sizes during gel filtration chromatography. Ferric citrate iron reductase is an extremely labile activity found in the cytoplasmic fraction, and ferripyochelin iron reductase is a more stable activity found in the periplasmic as well as cytoplasmic fraction of extracts. A small amount of activity detectable in the membrane fraction seemed to be loosely associated with the membranes. Although both enzymes have highest activity reduced nicotinamide adenine dinucleotide, reduced glutathione also worked with ferripyochelin iron reductase. In addition, oxygen caused an irreversible loss of a percentage of the ferripyochelin iron reductase following sparge of reaction mixtures, whereas the reductase for ferric citrate was not appreciably affected by oxygen. PMID:6766439

  1. Functional properties and differential mode of regulation of the nitrate transporter from a plant symbiotic ascomycete

    Science.gov (United States)

    Montanini, Barbara; Viscomi, Arturo R.; Bolchi, Angelo; Martin, Yusé; Siverio, José M.; Balestrini, Raffaella; Bonfante, Paola; Ottonello, Simone

    2005-01-01

    Nitrogen assimilation by plant symbiotic fungi plays a central role in the mutualistic interaction established by these organisms, as well as in nitrogen flux in a variety of soils. In the present study, we report on the functional properties, structural organization and distinctive mode of regulation of TbNrt2 (Tuber borchii NRT2 family transporter), the nitrate transporter of the mycorrhizal ascomycete T. borchii. As revealed by experiments conducted in a nitrate-uptake-defective mutant of the yeast Hansenula polymorpha, TbNrt2 is a high-affinity transporter (Km=4.7 μM nitrate) that is bispecific for nitrate and nitrite. It is expressed in free-living mycelia and in mycorrhizae, where it preferentially accumulates in the plasma membrane of root-contacting hyphae. The TbNrt2 mRNA, which is transcribed from a single-copy gene clustered with the nitrate reductase gene in the T. borchii genome, was specifically up-regulated following transfer of mycelia to nitrate- (or nitrite)-containing medium. However, at variance with the strict nitrate-dependent induction commonly observed in other organisms, TbNrt2 was also up-regulated (at both the mRNA and the protein level) following transfer to a nitrogen-free medium. This unusual mode of regulation differs from that of the adjacent nitrate reductase gene, which was expressed at basal levels under nitrogen deprivation conditions and required nitrate for induction. The functional and expression properties, described in the present study, delineate TbNrt2 as a versatile transporter that may be especially suited to cope with the fluctuating (and often low) mineral nitrogen concentrations found in most natural, especially forest, soils. PMID:16201972

  2. Disguised as a Sulfate Reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate

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    Casper Thorup

    2017-07-01

    Full Text Available This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D. alkaliphilus. Instead, the genome contains all of the genes necessary for sulfate reduction, including a gene for a reductive-type dissimilatory bisulfite reductase (DSR. Despite this, growth by sulfate reduction was not observed. Transcriptomic analysis revealed a very high expression level of sulfate-reduction genes during growth by sulfide oxidation, while inhibition experiments with molybdate pointed to elemental sulfur/polysulfides as intermediates. Consequently, we propose that D. alkaliphilus initially oxidizes sulfide to elemental sulfur, which is then either disproportionated, or oxidized by a reversal of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane-anchored nitrite reductase.

  3. Progesterone receptor membrane component 1 inhibits the activity of drug-metabolizing cytochromes P450 and binds to cytochrome P450 reductase.

    Science.gov (United States)

    Szczesna-Skorupa, Elzbieta; Kemper, Byron

    2011-03-01

    Progesterone receptor membrane component 1 (PGRMC1) has been shown to interact with several cytochromes P450 (P450s) and to activate enzymatic activity of P450s involved in sterol biosynthesis. We analyzed the interactions of PGRMC1 with the drug-metabolizing P450s, CYP2C2, CYP2C8, and CYP3A4, in transfected cells. Based on coimmunoprecipitation assays, PGRMC1 bound efficiently to all three P450s, and binding to the catalytic cytoplasmic domain of CYP2C2 was much more efficient than to a chimera containing only the N-terminal transmembrane domain. Down-regulation of PGRMC1 expression levels in human embryonic kidney 293 and HepG2 cell lines stably expressing PGRMC1-specific small interfering RNA had no effect on the endoplasmic reticulum localization and expression levels of P450s, whereas enzymatic activities of CYP2C2, CYP2C8, and CYP3A4 were slightly higher in PGRMC1-deficient cells. Cotransfection of cells with P450s and PGRMC1 resulted in PGRMC1 concentration-dependent inhibition of the P450 activities, and this inhibition was partially reversed by increased expression of the P450 reductase (CPR). In contrast, CYP51 activity was decreased by down-regulation of PGRMC1 and expression of PGRMC1 in the PGRMC1-deficient cells increased CYP51 activity. In cells cotransfected with CPR and PGRMC1, strong binding of CPR to PGRMC1 was observed; however, in the presence of CYP2C2, interaction of PGRMC1 with CPR was significantly reduced, suggesting that CYP2C2 competes with CPR for binding to PGRMC1. These data show that in contrast to sterol synthesizing P450, PGRMC1 is not required for the activities of several drug-metabolizing P450s, and its overexpression inhibits those P450 activities. Furthermore, PGRMC1 binds to CPR, which may influence P450 activity.

  4. Nitrate biosensors and biological methods for nitrate determination.

    Science.gov (United States)

    Sohail, Manzar; Adeloju, Samuel B

    2016-06-01

    The inorganic nitrate (NO3‾) anion is present under a variety of both natural and artificial environmental conditions. Nitrate is ubiquitous within the environment, food, industrial and physiological systems and is mostly present as hydrated anion of a corresponding dissolved salt. Due to the significant environmental and toxicological effects of nitrate, its determination and monitoring in environmental and industrial waters are often necessary. A wide range of analytical techniques are available for nitrate determination in various sample matrices. This review discusses biosensors available for nitrate determination using the enzyme nitrate reductase (NaR). We conclude that nitrate determination using biosensors is an excellent non-toxic alternative to all other available analytical methods. Over the last fifteen years biosensing technology for nitrate analysis has progressed very well, however, there is a need to expedite the development of nitrate biosensors as a suitable alternative to non-enzymatic techniques through the use of different polymers, nanostructures, mediators and strategies to overcome oxygen interference. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Sodium Nitrate Induces Reactive Oxygen Species That Lower the Antioxidant Power, Damage the Membrane, and Alter Pathways of Glucose Metabolism in Human Erythrocytes.

    Science.gov (United States)

    Ansari, Fariheen Aisha; Mahmood, Riaz

    2015-12-09

    Nitrate salts are widely used as food additives and nitrogenous fertilizers and are present as contaminants in drinking water supplies. The effect of different concentrations (1-15 mM) of sodium nitrate (NaNO3) on human erythrocytes was studied under in vitro conditions. Treatment of erythrocytes with NaNO3 resulted in increases in methemoglobin levels, lipid peroxidation, and protein oxidation and a decrease in glutathione content. There were changes in the activities of all major antioxidant defense enzymes, and the pathways of glucose metabolism were also affected. Increased generation of reactive oxygen species (ROS) took place while the antioxidant power was impaired. The osmotic fragility of cells was increased, and membrane-bound enzymes were greatly inhibited. All changes were statistically significant at a probability level of P < 0.05 at all concentrations of NaNO3 except the lowest (1 mM). Thus, NaNO3 generates ROS that cause significant damage to human erythrocytes and interfere in normal cellular pathways.

  6. Disguised as a Sulfate Reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate.

    Science.gov (United States)

    Thorup, Casper; Schramm, Andreas; Findlay, Alyssa J; Finster, Kai W; Schreiber, Lars

    2017-07-18

    This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D. alkaliphilus Instead, the genome contains all of the genes necessary for sulfate reduction, including a gene for a reductive-type dissimilatory bisulfite reductase (DSR). Despite this, growth by sulfate reduction was not observed. Transcriptomic analysis revealed a very high expression level of sulfate-reduction genes during growth by sulfide oxidation, while inhibition experiments with molybdate pointed to elemental sulfur/polysulfides as intermediates. Consequently, we propose that D. alkaliphilus initially oxidizes sulfide to elemental sulfur, which is then either disproportionated, or oxidized by a reversal of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane-anchored nitrite reductase. IMPORTANCE Sulfide oxidation and sulfate reduction, the two major branches of the sulfur cycle, are usually ascribed to distinct sets of microbes with distinct diagnostic genes. Here we show a more complex picture, as D. alkaliphilus , with the genomic setup of a sulfate reducer, grows by sulfide oxidation. The high expression of genes typically involved in the sulfate reduction pathway suggests that these genes, including the reductive-type dissimilatory bisulfite reductases, are also involved in as-yet-unresolved sulfide oxidation pathways. Finally, D. alkaliphilus is closely related to cable bacteria, which grow by electrogenic sulfide oxidation. Since there are no pure cultures of cable bacteria, D. alkaliphilus may represent an

  7. Atividade da enzima nitrato redutase em milho cultivado sob diferentes níveis de adubação nitrogenada e potássica Activity of the enzyme reductase nitrate in corn cultivated under different levels of nitrogen and potassium fertilization

    Directory of Open Access Journals (Sweden)

    Sueli Maria da Silva

    2011-11-01

    Full Text Available Em função de seu uso na alimentação humana e animal e de um elevado potencial produtivo, o milho constitui-se num dos mais importantes cereais cultivados e comercializados no mundo. O objetivo deste trabalho foi avaliar o efeito de diferentes doses de nitrogênio e potássio na atividade da enzima redutase do nitrato na cultura do milho em casa de vegetação. Foram utilizadas cinco doses de nitrogênio (0; 50; 100; 150 e 200kg ha-1 e cinco doses de potássio (0; 40; 80; 120 e 160kg ha-1. A atividade da enzima foi estimada in vivo após as plantas atingirem quatro folhas totalmente desdobradas. Utilizou-se o método baseado no princípio de que a quantidade de nitrito liberada por fragmentos de tecidos vivos num tampão, na presença de uma agente permanente e do substrato, reflete a atividade potencial da enzima. A atividade da enzima nitrato redutase sofreu influência significativa da interação das doses de nitrogênio e potássio, já que a interação N=100kg ha-1 e K=40kg ha-1 proporcionou as melhores médias do experimento. A partir dessa dose, o aumento no fornecimento tanto de nitrogênio quanto de potássio promoveu redução da atividade enzimática.Because of the use in human feeding, animal, and high productive potential, corn is considered to be one of the most important cultivated and commercialized cereals in the world. The aim of this research was to evaluate the effect of different potassium doses and nitrogen in the activity of the enzyme nitrate reductase in the corn culture in a greenhouse environment. Five dosages of nitrogen (0; 50; 100; 150 and 200kg ha-1 and five potassium dosages (0; 40; 80; 120 and 160kg ha-1 were used. The activity of the nitrate reductase was esteemed, in vivo after the plants reached four leaves totally unfolded. The method that was used is based on the principle of the amount of nitrite liberated by fragments of alive tissue in a buffer in the presence of a permanent agent and substrate

  8. Respiratory arsenate reductase as a bidirectional enzyme

    Science.gov (United States)

    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.

  9. Ferrisiderophore reductase activity in Bacillus megaterium.

    Science.gov (United States)

    Arceneaux, J E; Byers, B R

    1980-01-01

    The release of iron from ferrisiderophores (microbial ferric-chelating iron transport cofactors) by cell-free extracts of Bacillus megaterium was demonstrated. Reductive transfer of iron from ferrisiderophores to the ferrous-chelating agent ferrozine was measured spectrophotometrically. This ferrisiderophore reductase activity (reduced nicotinamide adenine dinucleotide phosphate:ferrisiderophore oxidoreductase) was associated primarily with the cell soluble rather than particulate (membrane) fraction. Ferrisiderophore reductase was inhibited by oxygen and required the addition of a reductant (reduced nicotinamide adenine dinucleotide phosphate was most effective) for maximal activity. The activity was destroyed by both heat and protease treatments and was inhibited by iodoacetamide treatment. Ferrisiderophore reductase activity for several microbial ferrisiderophores was measured; highest activity was displayed for ferrischizokinen, the ferrisiderophore produced by this organism. The Km and Vmax values of the reductase for ferrischizokinen were 2.5 x 10(-4) M and 35.7 nmol/min per mg of the ferrisiderophore reductase reaction. Preliminary fractionation of the cell soluble material by gel filtration chromatography resulted in the demonstration of ferrisiderophore reductase activity in three peaks of different molecular weight. Ferrisiderophore reductase probably mediates entrance of iron into cellular metabolism. PMID:6444944

  10. Respiratory and dissimilatory nitrate-reducing communities from an extreme saline alkaline soil of the former lake Texcoco (Mexico).

    Science.gov (United States)

    Alcántara-Hernández, Rocio J; Valenzuela-Encinas, César; Marsch, Rodolfo; Dendooven, Luc

    2009-01-01

    The diversity of the dissimilatory and respiratory nitrate-reducing communities was studied in two soils of the former lake Texcoco (Mexico). Genes encoding the membrane-bound nitrate reductase (narG) and the periplasmic nitrate reductase (napA) were used as functional markers. To investigate bacterial communities containing napA and narG in saline alkaline soils of the former lake Texcoco, libraries of the two sites were constructed (soil T3 with pH 11 and electrolytic conductivity in saturated extract (EC(SE)) 160 dS m(-1) and soil T1 with pH 8.5 and EC(SE) 0.8 dS m(-1)). Phylogenetic analysis of napA sequences separated the clone families into two main groups: dependent or independent of NapB. Most of napA sequences from site T1 were grouped in the NapB-dependent clade, meanwhile most of the napA sequences from the extreme soil T3 were affiliated to the NapB-independent group. For both sites, partial narG sequences were associated with representatives of the Proteobacteria, Firmicutes and Actinobacteria phyla, but the proportions of the clones were different. Our results support the concept of a specific and complex nitrate-reducing community for each soil of the former lake Texcoco.

  11. Hydroxylated naphthoquinones as substrates for Escherichia coli anaerobic reductases.

    Science.gov (United States)

    Rothery, R A; Chatterjee, I; Kiema, G; McDermott, M T; Weiner, J H

    1998-01-01

    We have used two hydroxylated naphthoquinol menaquinol analogues, reduced plumbagin (PBH2, 5-hydroxy-2-methyl-1,4-naphthoquinol) and reduced lapachol [LPCH2, 2-hydroxy-3-(3-methyl-2-butenyl)-1, 4-naphthoquinol], as substrates for Escherichia coli anaerobic reductases. These compounds have optical, solubility and redox properties that make them suitable for use in studies of the enzymology of menaquinol oxidation. Oxidized plumbagin and oxidized lapachol have well resolved absorbances at 419 nm (epsilon=3.95 mM-1. cm-1) and 481 nm (epsilon=2.66 mM-1.cm-1) respectively (in Mops/KOH buffer, pH 7.0). PBH2 is a good substrate for nitrate reductase A (Km=282+/-28 microM, kcat=120+/-6 s-1) and fumarate reductase (Km=155+/-24 microM, kcat=30+/-2 s-1), but not for DMSO reductase. LPCH2 is a good substrate for nitrate reductase A (Km=57+/-35 microM, kcat=68+/-13 s-1), fumarate reductase (Km=85+/-27 microM, kcat=74+/-6 s-1) and DMSO reductase (Km=238+/-30 microM, kcat=191+/-21 s-1). The sensitivity of enzymic LPCH2 and PBH2 oxidation to 2-n-heptyl-4-hydroxyquinoline N-oxide inhibition is consistent with their oxidation occurring at sites of physiological quinol binding. PMID:9576848

  12. Avaliação do teste de nitrato redutase para a detecção rápida de resistência aos medicamentos de primeira linha em cepas de Mycobacterium tuberculosis isoladas de pacientes em um hospital geral Evaluation of the nitrate reductase assay for the rapid detection of resistance to first-line medications in Mycobacterium tuberculosis strains isolated from patients in a general hospital

    Directory of Open Access Journals (Sweden)

    Maria de Fátima Filardi Oliveira Mansur

    2012-04-01

    Full Text Available Comparamos o teste de nitrato redutase com o método de proporções, considerado como padrão ouro, em 57 cepas de Mycobacterium tuberculosis isoladas de pacientes atendidos no Hospital das Clínicas da Universidade Federal de Minas Gerais, em Belo Horizonte (MG. A sensibilidade, a especificidade e a acurácia para rifampicina e isoniazida foram de 100% para todas, enquanto essas foram, respectivamente, de 88,9%, 66,7% e 96,5% para estreptomicina e de 98,0%, 100% e 98,2% para etambutol. A média de tempo para a obtenção dos resultados foi de dez dias. Na amostra estudada, o teste de nitrato redutase mostrou grande acurácia e excelente concordância com o padrão ouro.We compared the nitrate reductase assay with the proportion method, which is considered the gold standard, in 57 Mycobacterium tuberculosis strains isolated from patients treated at the Federal University of Minas Gerais Hospital das Clínicas, located in the city of Belo Horizonte, Brazil. For rifampin and isoniazid, the sensitivity, specificity, and accuracy of the nitrate reductase assay were all 100%, whereas they were 100%, 88.9%, and 66.7%, respectively, for streptomycin and 98.0%, 100%, and 98.2%, respectively, for ethambutol. The mean time to results was ten days. In the study sample, the nitrate reductase assay proved highly accurate and showed excellent concordance with the gold standard.

  13. Growth of silicone-immobilized bacteria on polycarbonate membrane filters, a technique to study microcolony formation under anaerobic conditions

    DEFF Research Database (Denmark)

    Højberg, Ole; Binnerup, S. J.; Sørensen, Jan

    1997-01-01

    A technique was developed to study microcolony formation by silicone- immobilized bacteria on polycarbonate membrane filters under anaerobic conditions. A sudden shift to anaerobiosis was obtained by submerging the filters in medium which was depleted for oxygen by a pure culture of bacteria....... The technique was used to demonstrate that preinduction of nitrate reductase under low-oxygen conditions was necessary for nonfermenting, nitrate-respiring bacteria, e.g., Pseudomonas spp., to cope with a sudden lack of oxygen. In contrast, nitrate-respiring, fermenting bacteria, e.g., Bacillus and Escherichia...... spp, formed microcolonies under anaerobic conditions with or without the presence of nitrate and irrespective of aerobic or anaerobic preculture conditions....

  14. Fully automated multidimensional reversed-phase liquid chromatography with tandem anion/cation exchange columns for simultaneous global endogenous tyrosine nitration detection, integral membrane protein characterization, and quantitative proteomics mapping in cerebral infarcts.

    Science.gov (United States)

    Quan, Quan; Szeto, Samuel S W; Law, Henry C H; Zhang, Zaijun; Wang, Yuqiang; Chu, Ivan K

    2015-10-06

    Protein tyrosine nitration (PTN) is a signature hallmark of radical-induced nitrative stress in a wide range of pathophysiological conditions, with naturally occurring abundances at substoichiometric levels. In this present study, a fully automated four-dimensional platform, consisting of high-/low-pH reversed-phase dimensions with two additional complementary, strong anion (SAX) and cation exchange (SCX), chromatographic separation stages inserted in tandem, was implemented for the simultaneous mapping of endogenous nitrated tyrosine-containing peptides within the global proteomic context of a Macaca fascicularis cerebral ischemic stroke model. This integrated RP-SA(C)X-RP platform was initially benchmarked through proteomic analyses of Saccharomyces cerevisiae, revealing extended proteome and protein coverage. A total of 27 144 unique peptides from 3684 nonredundant proteins [1% global false discovery rate (FDR)] were identified from M. fascicularis cerebral cortex tissue. The inclusion of the S(A/C)X columns contributed to the increased detection of acidic, hydrophilic, and hydrophobic peptide populations; these separation features enabled the concomitant identification of 127 endogenous nitrated peptides and 137 transmembrane domain-containing peptides corresponding to integral membrane proteins, without the need for specific targeted enrichment strategies. The enhanced diversity of the peptide inventory obtained from the RP-SA(C)X-RP platform also improved analytical confidence in isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic analyses.

  15. Effects of solar UV radiation on photosynthesis and enzyme activities (carbonic anhydrase and nitrate reductase in marine macroalgae from southern Spain Efectos de la radiación solar UV sobre la fotosíntesis y actividades enzimáticas (anhidrasa carbónica y nitrato reductasa en macralgas marinas del sur de España

    Directory of Open Access Journals (Sweden)

    FÉLIX L. FIGUEROA

    2001-06-01

    Full Text Available The effects of solar ultraviolet (UV radiation during daily cycles on photosynthesis and two key enzymes involved in carbon incorporation, the carbonic anhydrase, and in inorganic nitrogen reduction, the nitrate reductase, of macroalgae from southern Spain are presented. During daily cycles, photoinhibition in several intertidal macroalgae, expressed as decrease in the effective quantum yield from the morning to noon time, was linearly dependent on the daily integrated irradiance. However, recovery, expressed as the increase in the effective quantum yield from noon to the afternoon, presented a different pattern; full recovery was found below daily integrated irradiance of 1.0 x10(4 kJ m-2. However, recovery reached only 50 % at higher irradiances. The existence of daily photoinhibition and full recovery in intertidal algae suggests that photoinhibition is a photoprotective mechanism against high solar radiation as in higher plants, and that patterns of photoinhibition and recovery are affected by accumulative doses. Activities of carbonic anhidrase and nitrate reductase were determined in three marine macroalgae (Plocamium cartilagineum, Ulva rigida and Fucus spiralis under full (PAR + UV-A + UV-B and excluded UV solar radiation (PAR. Under PAR + UV-A + UV-B, peaks of enzyme activity were found in P. cartilagineum during the evening, and accordingly to data previously published for other red macroalgae. This situation was modified by the absence of UV radiation since the increase in the activities was delayed several hours. In the three macroalgae and under full solar radiation, a significant and negative correlation was found only when data from nitrate reductase activity was shifted in time during at least four hours. This correlation is lost in Ulva rigida when UV radiation is excluded. The existence of these daily variations with a negative correlation of both enzyme activities could reflect a complex regulatory link between carbon and

  16. Does foliar application of salicylic acid protects nitrate reductase and ...

    African Journals Online (AJOL)

    The present study was conducted to assess whether exogenous applied salicylic acid (SA) as a foliar spray could ameliorate the adverse effects of virus infection in two maize cultivars (maize cv. sabaini and maize cv. Nab El-gamal). The plants were grown under normal field conditions for two weeks in sand clay soil, and ...

  17. Does foliar application of salicylic acid protects nitrate reductase and ...

    African Journals Online (AJOL)

    SAM

    2014-06-04

    Jun 4, 2014 ... interferes with tobacco mosaic virus replication via a novel salicylhydroxamic acid-sensitive mechanism. Plant Cell 9:547-557. Dat JF, Lopez DH, Foyer CH, Scott IM (1998). Parallel changes in H2O2 and catalase during thermotolerance induced by salicylic acid or heat acclimation in mustard seedlings.

  18. The dehydration of uranyl nitrate hexahydrate

    International Nuclear Information System (INIS)

    Badalov, A.; Kamalov, D.D.; Khamidov, B.O.; Mirsaidov, I.U.; Eshbekov, N.R.

    2010-01-01

    Present article is devoted to study of dehydration process of uranyl nitrate hexahydrate. The dehydration process of uranyl nitrate hexahydrate was studied by means of tensimeter method with membrane zero-manometer. The research was carried out under equilibrium conditions. It was defined that in studied temperature ranges (300-450 K) the dehydration process of UO 2 (NO 3 ) 2 has a three stage character.

  19. Electrochemical processing of nitrate waste solutions

    International Nuclear Information System (INIS)

    Genders, D.; Weinberg, N.; Hartsough, D.

    1992-01-01

    The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F - ions from the synthetic mix migrating across the cation exchange membrane and forming HF in the acid anolyte. Other possibilities for anode materials were explored. A membrane separation process was investigated which employs an anion and cation exchange membrane to remove nitrite and nitrate, recovering caustic and nitric acid. Present research has shown poor current efficiencies for nitrite and nitrate transport across the anion exchange membrane due to co-migration of hydroxide anions. Precipitates form within the anion exchange membranes which would eventually result in the failure of the membranes. Electrochemical processing offers a highly promising and viable method for the treatment of nitrate waste solutions

  20. Characterization of a heme c nitrite reductase from a non-ammonifying microorganism, Desulfovibrio vulgaris Hildenborough.

    Science.gov (United States)

    Pereira, I A; LeGall, J; Xavier, A V; Teixeira, M

    2000-08-31

    A cytochrome c nitrite reductase (NiR) was purified for the first time from a microorganism not capable of growing on nitrate, the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough. It was isolated from the membranes as a large heterooligomeric complex of 760 kDa, containing two cytochrome c subunits of 56 and 18 kDa. This complex has nitrite and sulfite reductase activities of 685 micromol NH(4)(+)/min/mg and 1.0 micromol H(2)/min/mg. The enzyme was studied by UV-visible and electron paramagnetic resonance (EPR) spectroscopies. The overall redox behavior was determined through a visible redox titration. The data were analyzed with a set of four redox transitions, with an E(0)' of +160 mV (12% of total absorption), -5 mV (38% of total absorption), -110 mV (38% of total absorption) and -210 mV (12% of total absorption) at pH 7.6. The EPR spectra of oxidized and partially reduced NiR show a complex pattern, indicative of multiple heme-heme magnetic interactions. It was found that D. vulgaris Hildenborough is not capable of using nitrite as a terminal electron acceptor. These results indicate that in this organism the NiR is not involved in the dissimilative reduction of nitrite, as is the case with the other similar enzymes isolated so far. The possible role of this enzyme in the detoxification of nitrite and/or in the reduction of sulfite is discussed.

  1. Recent structural insights into the function of copper nitrite reductases.

    Science.gov (United States)

    Horrell, Sam; Kekilli, Demet; Strange, Richard W; Hough, Michael A

    2017-11-15

    Copper nitrite reductases (CuNiR) carry out the first committed step of the denitrification pathway of the global nitrogen cycle, the reduction of nitrite (NO 2 - ) to nitric oxide (NO). As such, they are of major agronomic and environmental importance. CuNiRs occur primarily in denitrifying soil bacteria which carry out the overall reduction of nitrate to dinitrogen. In this article, we review the insights gained into copper nitrite reductase (CuNiR) function from three dimensional structures. We particularly focus on developments over the last decade, including insights from serial femtosecond crystallography using X-ray free electron lasers (XFELs) and from the recently discovered 3-domain CuNiRs.

  2. Effects of arsenic on nitrate metabolism in arsenic hyperaccumulating and non-hyperaccumulating ferns

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Nandita [Soil and Water Science Department, University of Florida, Gainesville, Fl 32611-0290 (United States); Eco-Auditing group, National Botanical Research Institute, Rana Pratap Marg, Lucknow 226 001 (India); Ma, Lena Q., E-mail: lqma@ufl.ed [Soil and Water Science Department, University of Florida, Gainesville, Fl 32611-0290 (United States); Vu, Joseph C. [Chemistry Research Unit, CMAVE, USDA-ARS, Gainesville, FL 32608-1069 and Agronomy Department, University of Florida, Gainesville, FL 32611-0500 (United States); Raj, Anshita [Eco-Auditing group, National Botanical Research Institute, Rana Pratap Marg, Lucknow 226 001 (India)

    2009-08-15

    This study investigated the effects of arsenic on the in vitro activities of the enzymes (nitrate reductase and nitrite reductase) involved in nitrate metabolism in the roots, rhizomes, and fronds of four-month old Pteris vittata (arsenic - hyperaccumulator) and Pteris ensiformis (non-arsenic--hyperaccumulator) plants. The arsenic treatments (0, 150, and 300 muM as sodium arsenate) in hydroponics had adverse effects on the root and frond dry weights, and this effect was more evident in P. ensiformis than in P. vittata. Nitrate reductase and nitrite reductase activities of arsenate-treated plants were reduced more in P. ensiformis than in P. vittata. This effect was accompanied by similar decreases in tissue NO{sub 3}{sup -} concentrations. Therefore, this decrease is interpreted as being indirect, i.e., the consequence of the reduced NO{sub 3}{sup -} uptake and translocation in the plants. The study shows the difference in the tolerance level of the two Pteris species with varying sensitivity to arsenic. - Arsenic reduced the activity of nitrate and nitrite reductase more in Pteris ensiformis than Pteris vittata.

  3. Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts.

    Science.gov (United States)

    Karasu, Cimen; Cumaoğlu, Ahmet; Gürpinar, Ali Rifat; Kartal, Murat; Kovacikova, Lucia; Milackova, Ivana; Stefek, Milan

    2012-03-01

    The pomegranate, Punica granatum L., has been the subject of current interest as a medicinal agent with wide-ranging therapeutic indications. In the present study, pomegranate ethanolic seed and hull extracts were tested, in comparison with a commercial sample, for the inhibition of aldose reductase, an enzyme involved in the etiology of diabetic complications. In vitro inhibition of rat lens aldose reductase was determined by a conventional method. Pomegranate ethanolic hull extract and commercial pomegranate hull extract exhibited similar aldose reductase inhibitory activity characterized by IC(50) values ranging from 3 to 33.3 μg/ml. They were more effective than pomegranate ethanolic seed extract with IC(50) ranging from 33.3 to 333 μg/ml. Antioxidant action of the novel compounds was documented in a DPPH test and in a liposomal membrane model, oxidatively stressed by peroxyl radicals. All the plant extracts showed considerable antioxidant potential in the DPPH assay. Pomegranate ethanolic hull extract and commercial pomegranate hull extract executed similar protective effects on peroxidatively damaged liposomal membranes characterized by 10ethanolic seed extract showed significantly lower antioxidant activity compared to both hull extracts studied. Pomegranate extracts are thus presented as bifunctional agents combining aldose reductase inhibitory action with antioxidant activity and with potential therapeutic use in prevention of diabetic complications.

  4. Modeled Wet Nitrate Deposition

    Data.gov (United States)

    U.S. Environmental Protection Agency — Modeled data on nitrate wet deposition was obtained from Dr. Jeff Grimm at Penn State Univ. Nitrate wet depostion causes acidification and eutrophication of surface...

  5. DROUGHT-INDUCED EFFECTS AND RECOVERY OF NITRATE ASSIMILATION AND NODULE ACTIVITY IN COWPEA PLANTS INOCULATED WITH BRADYRHIZOBIUM SPP. UNDER MODERATE NITRATE LEVEL

    Directory of Open Access Journals (Sweden)

    Silveira Joaquim Albenísio Gomes da

    2001-01-01

    Full Text Available This study was carried out to establish comparative effects of drought and recovery on the nitrate assimilation and nodule activity related to N2 fixation in cowpea plants [Vigna unguiculata L. (Walp.] previously inoculated with Bradyrhizobium spp. BR-3256 (CB-756 strain in the presence of 5 mol m-3 NO-3. Twenty-eight-day-old nodulated plants were submitted to water deprivation during 4 consecutive days and afterwards resupplied with nutrient solution during 2 days. The water deprivation caused a rapid increase in the nitrate content in root and a marked reduction in leaf nitrate reductase (NR activity. In contrast nodule NR activity was slightly increased by water deprivation. Concomitantly, in nodules of water stressed plants, leghemoglobin and glutamine synthetase (GS activity declined and a progressive reduction in ureide-N concentration in xylem sap was observed. Leaf-NR activity increased rapidly after rehydration while leaf nitrate content declined. In contrast both GS activity and soluble protein content in the nodule continued to decline in rewatered plants. In addition the concentration of leghemoglobin recovered well, while the xylem ureide-N content experienced a slight increase after rehydration. Despite the nitrate assimilation in leaves and the nodule activity had been both severely affected by water stress, the rapid recovery of nitrate reductase activity suggests that the nitrate assimilation process is less sensitive to drought/rehydration cycle when cowpea plants are nodulated in presence of moderate nitrate level.

  6. An 15N study of the effects of nitrate, ammonium, and nitrate + ammonium nutrition on nitrogen assimilation in Zea mays L

    International Nuclear Information System (INIS)

    Murphy, A.T.

    1984-10-01

    A brief review of the literature on the effects of nitrate and ammonium nitrogen sources on plant growth, and the assimilation of those nitrogen sources, has been presented. It was concluded that ammonium nutrition produces optimum growth, with nitrate + ammonium being a better nitrogen source than only nitrate. Leaf blade nitrate reductase activity exceeded that of the root in nitrate-fed plants, suggesting that the shoot is the major region of nitrate assimilation. This is further supported by the results of xylem exudate analysis, where 93% of the newly-absorbed nitrogen exported by the roots was detected as nitrate. Evidence in support of this hypothesis was also obtained by studying the distribution of 15 N in the various nitrogenous compounds. The effects of nitrogen source on plant growth, organic nitrogen and inorganic nitrogen contents, and the rates of incorporation into nitrogenous compounds were studied. The observed differences were explained with reference to the effects of the various nitrogen sources on the physiology of the plants. The experimental techniques included assays of the enzymes nitrate reductase and glutamine synthetase, whole plant growth studies, and the analysis of nitrogenous compounds of xylem exudate and those extracted from the leaf blade, leaf base, and root regions of maize plants after feeding with a nutrient solution containing nitrogen as 15 N

  7. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources of...

  8. Determination of the total nitrate content of thorium nitrate solution with a selective electrode

    International Nuclear Information System (INIS)

    Wirkner, F.M.

    1979-01-01

    The nitrate content of thorium nitrate solutions is determined with a liquid membrane nitrate selective electrode utilizing the known addition method in 0.1 M potassium fluoride medium as ionic strength adjustor. It is studied the influence of pH and the presence of chloride, sulphate, phosphate, meta-silicate, thorium, rare earths, iron, titanium, uranium and zirconium at the same concentrations as for the aqueous feed solutions in the thorium purification process. The method is tested in synthetic samples and in samples proceeding from nitric dissolutions of thorium hidroxide and thorium oxicarbonate utilized as thorium concentrates to be purified [pt

  9. Nitrate accumulation in spinach

    NARCIS (Netherlands)

    Steingröver, Eveliene Geertruda

    1986-01-01

    Leafy vegetables, like spinach, may contain high concentrations of nitrate. In the Netherlands, about 75% of mean daily intake of nitrate orginates from the consumption of vegatables. Hazards to human health are associated with the reduction of nitrate to nitrite. Acute nitrite poisoning causes

  10. Bioinformatics approach of three partial polyprenol reductase genes in Kandelia obovata

    Science.gov (United States)

    Basyuni, M.; Wati, R.; Sagami, H.; Oku, H.; Baba, S.

    2018-03-01

    This present study describesthe bioinformatics approach to analyze three partial polyprenol reductase genes from mangrove plant, Kandeliaobovataas well aspredictedphysical and chemical properties, potential peptide, subcellular localization, and phylogenetic. The diversity was noted in the physical and chemical properties of three partial polyprenol reductase genes. The values of chloroplast were relatively high, showed that chloroplast transit peptide occurred in mangrove polyprenol reductase. The target peptide value of mitochondria varied from 0.088 to 0.198 indicated it was possible to be present. These results suggested the importance of understanding the diversity of physicochemical properties of the different amino acids in polyprenol reductase. The subcellular localization of two partial genes located in the plasma membrane. To confirm the homology among the polyprenol reductase in the database, a dendrogram was drawn. The phylogenetic tree depicts that there are three clusters, the partial genes of K. obovata joined the largest one: C23157 was close to Ricinus communis polyprenol reductase. Whereas, C23901 and C24171 were grouped with Ipomoea nil polyprenol reductase, suggested that these polyprenol reductase genes form distinct separation into tropical habitat plants.

  11. Ammonium nitrate explosion hazards

    Directory of Open Access Journals (Sweden)

    Negovanović Milanka

    2015-01-01

    Full Text Available Ammonium nitrate (AN primarily is used as a fertilizer but it is also very important compound in the production of industrial explosives. The application of ammonium nitrate in the production of industrial explosives was related with the early era of Nobel dynamite and widely increased with the appearance of blasting agents such as ANFO and Slurry, in the middle of the last Century. Throughout the world millions of tons of ammonium nitrate are produced annually and handled without incident. Although ammonium nitrate generally is used safely, accidental explosions involving AN have high impact resulting in loss of lives and destruction of property. The paper presents the basic properties of ammonium nitrate as well as hazards in handling of ammonium nitrate in order to prevent accidents. Several accidents with explosions of ammonium nitrate resulted in catastrophic consequences are listed in the paper as examples of non-compliance with prescribed procedures.

  12. Modulation of nitrate-nitrite conversion in the oral cavity.

    Science.gov (United States)

    van Maanen, J M; van Geel, A A; Kleinjans, J C

    1996-01-01

    The formation of nitrite from ingested nitrate can give rise to the induction of methemoglobinemia and endogenous nitrosation resulting in the formation of carcinogenic N-nitroso compounds. We investigated the possibility of modulation of the conversion of nitrate into nitrite in the oral cavity in order to seek ways of reducing the formation of the deleterious nitrite. We investigated the effectiveness of several mouthwash solutions with antibacterial constituents on the reduction of nitrate into nitrite in the oral cavity. In 15 studied subjects, the mean percentage of salivary nitrate reduced to nitrite after ingestion of 235 mg (3.8 mmol) nitrate was found to be 16.1 +/- 6.2%. The use of an antiseptic mouthwash with active antibacterial constituent chlorhexidine resulted in an almost complete decrease of the mean percentage of reduced nitrate, to 0.9 +/- 0.8%. Mouthwash solutions with antibacterial component triclosan or antimicrobial enzymes amyloglucosidase and glucose oxidase did not affect the reduction of nitrate into nitrite. A toothpaste with active components triclosan and zinc citrate with synergistic antiplaque activity was also without effect. Use of a pH-regulating chewing gum resulted in a rise in the pH in the oral cavity from 6.8 to 7.3. At 30 min after nitrate ingestion, this rise was accompanied by a significant increase in the salivary nitrite concentration, which might be explained by the pH being close to the optimal pH for nitrate reductase of 8. In conclusion, a limited number of possibilities of modulation of the conversion of nitrate into nitrite in the oral cavity are available.

  13. Isolated menthone reductase and nucleic acid molecules encoding same

    Science.gov (United States)

    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.

  14. Chloroplast Fe(III) chelate reductase activity is essential for seedling viability under iron limiting conditions

    OpenAIRE

    Jeong, Jeeyon; Cohu, Christopher; Kerkeb, Loubna; Pilon, Marinus; Connolly, Erin L.; Guerinot, Mary Lou

    2008-01-01

    Photosynthesis, heme biosynthesis, and Fe-S cluster assembly all take place in the chloroplast, and all require iron. Reduction of iron via a membrane-bound Fe(III) chelate reductase is required before iron transport across membranes in a variety of systems, but to date there has been no definitive genetic proof that chloroplasts have such a reduction system. Here we report that one of the eight members of the Arabidopsis ferric reductase oxidase (FRO) family, FRO7, localizes to the chloropla...

  15. Diversity of Nitrate-Reducing and Denitrifying Bacteria in a Marine Aquaculture Biofilter and their Response to Sulfide

    DEFF Research Database (Denmark)

    Krieger, Bärbel; Schwermer, Carsten U.; Rezakhani, Nastaran

    2006-01-01

    was developed containing a 3-stage biofilter for nitrification, denitrification/anaerobic sludge digestion, and sulfide oxidation. Sulfate reduction in the anaerobic part of the system leads to sulfide concentrations exceeding 5 mM, which may affect nitrate reduction and denitrification. Sulfide can inhibit...... nitrous oxide reductase, trigger a shift from denitrification to dissimilatory nitrate reduction to ammonium (DNRA), or be used as electron donor for nitrate reduction. The goal of this study was to identify and isolate nitrate-reducing and denitrifying bacteria from the biofilter and to investigate...

  16. Biomass accumulation, photochemical efficiency of photosystem II, nutrient contents and nitrate reductase activity in young rosewood plants (Aniba rosaeodora Ducke submitted to different NO3-:NH4+ ratios Acúmulo de biomassa, eficiência fotoquímica do fotossistema II, conteúdo de nutrientes e atividade da redutase do nitrato em plantas jovens de pau-rosa (Aniba rosaeodora Ducke submetidas a diferentes relações NO3-:NH4+

    Directory of Open Access Journals (Sweden)

    Denize Caranhas de Sousa Barreto

    2007-01-01

    Full Text Available The rosewood (Aniba rosaeodora Ducke is a native tree species of Amazon rainforest growing naturally in acidic forest soils with reduced redox potential. However, this species can also been found growing in forest gaps containing oxide soils. Variations in the forms of mineral nitrogen (NO3- or NH4+ may be predicted in these different edaphic conditions. Considering that possibility, an experiment was carried out to analyze the effects of different NO3-:NH4+ ratios on the growth performance, mineral composition, chloroplastid pigment contents, photochemical efficiency photosystem II (PSII, and nitrate redutase activity (RN, E.C.1.6.6.1 on A. rosaeodora seedlings. Nine-month-old seedlings were grown in pots with a washed sand capacity of 7.5 kg and submitted to different NO3-:NH4+ ratios (T1 = 0:100%, T2 = 25:75%, T3 = 50:50%, T4 = 75:25%, and T5 = 100:0%. The lowest relative growth rate was observed when the NO3-:NH4+ ratio was equal to 0:100%. In general, high concentrations of NO3- rather than NH4+ favored a greater nutrient accumulation in different parts of the plant. For the chloroplastid pigment, the highest Chl a, Chl b, Chl tot, Chl a/b and Chl tot/Cx+c contents were found in the treatment with 75:25% of NO3-:NH4+, and for Chl b and Cx+c it was observed no difference. In addition, there was a higher photochemical efficiency of PSII (Fv/Fm when high NO3- concentrations were used. A linear and positive response for the nitrate reductase activity was recorded when the nitrate content increased on the culture substrate. Our results suggest that A. rosaeodora seedlings have a better growth performance when the NO3- concentrations in the culture substrate were higher than the NH4+ concentrations.O pau-rosa (Aniba rosaeodora Ducke habita, naturalmente, solos florestais ácidos com potencial redox reduzido. No entanto, estas espécies têm sido encontradas também em clareiras que, teoricamente, apresentam solos mais oxidados. Nestas diferentes

  17. Potential testicular toxicity of sodium nitrate in adult rats.

    Science.gov (United States)

    Aly, Hamdy A A; Mansour, Ahmed M; Abo-Salem, Osama M; Abd-Ellah, Hala F; Abdel-Naim, Ashraf B

    2010-02-01

    Nitrate is a common contaminant in groundwater aquifers. Current study aimed at evaluating the potential testicular toxicity of sodium nitrate in rats. Sodium nitrate was given orally to rats at doses of 50, 100 or 200 mg/kg/day for 60 consecutive days. Sperm count and motility, daily sperm production and testis weight were significantly decreased specially at high doses. Testicular activity of lactate dehydrogenase-X, glucose-6-phosphate dehydrogenase, and acid phosphatase were inhibited in a dose-related manner. Lipid peroxides and hydrogen peroxide production were significantly increased in all treated animals. This was accompanied by inhibition of testicular activities of superoxide dismutase and glutathione peroxidase. Fifty mg/kg of sodium nitrate did not significantly alter catalase or glutathione reductase activity. Glutathione was significantly decreased by sodium nitrate in a dose-related manner. The decrease in sperm count and motility and daily sperm production was confirmed by histopathological studies which indicated chromatolysis, pyknosis and necrosis in spermatocytes. In conclusion, subchronic exposure of rats to sodium nitrate results in testicular toxicity as evidenced by decreased sperm count and motility, daily sperm production and testis weight, inhibited activity of enzyme markers of spermatogenesis and induction of histopathological changes. These effects are attributed, at least partly, to testicular oxidative stress. Copyright 2009. Published by Elsevier Ltd.

  18. Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism ...

    African Journals Online (AJOL)

    Administrator

    2011-10-19

    Oct 19, 2011 ... Polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are associated with abortion, early embryo loss and recurrent spontaneous abortion in human. However, information on the association between MTHFR polymorphism and cow abortion is scarce. In the present study, the effects.

  19. Association between methylenetetrahydrofolate reductase (MTHFR ...

    African Journals Online (AJOL)

    Association between methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism and risk of ischemic stroke in North Indian population: A hospital based case–control study. Amit Kumar, Shubham Misra, Anjali Hazarika, Pradeep Kumar, Ram Sagar, Abhishek Pathak, Kamalesh Chakravarty, Kameshwar ...

  20. Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism ...

    African Journals Online (AJOL)

    Polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are associated with abortion, early embryo loss and recurrent spontaneous abortion in human. However, information on the association between MTHFR polymorphism and cow abortion is scarce. In the present study, the effects of MTHFR ...

  1. Trametes versicolor carboxylate reductase uncovered.

    Science.gov (United States)

    Winkler, Margit; Winkler, Christoph K

    The first carboxylate reductase from Trametes versicolor was identified, cloned, and expressed in Escherichia coli . The enzyme reduces aromatic acids such as benzoic acid and derivatives, cinnamic acid, and 3-phenylpropanoic acid, but also aliphatic acids such as octanoic acid are reduced.

  2. Rhodobacter capsulatus gains a competitive advantage from respiratory nitrate reduction during light-dark transitions.

    Science.gov (United States)

    Ellington, M J K; Richardson, D J; Ferguson, S J

    2003-04-01

    Rhodobacter capsulatus N22DNAR(+) possesses a periplasmic nitrate reductase and is capable of reducing nitrate to nitrite under anaerobic conditions. In the absence of light this ability cannot support chemoheterotrophic growth in batch cultures. This study investigated the effect of nitrate reduction on the growth of R. capsulatus N22DNAR(+) during multiple light-dark cycles of anaerobic photoheterotrophic/dark chemoheterotrophic growth conditions in carbon-limited continuous cultures. The reduction of nitrate did not affect the photoheterotrophic growth yield of R. capsulatus N22DNAR(+). After a transition from photoheterotrophic to dark chemoheterotrophic growth conditions, the reduction of nitrate slowed the initial washout of a R. capsulatus N22DNAR(+) culture. Towards the end of a period of darkness nitrate-reducing cultures maintained higher viable cell counts than non-nitrate-reducing cultures. During light-dark cycling of a mixed culture, the strain able to reduce nitrate (N22DNAR(+)) outcompeted the strain which was unable to reduce nitrate (N22). The evidence indicates that the periplasmic nitrate reductase activity supports slow growth that retards the washout of a culture during anaerobic chemoheterotrophic conditions, and provides a protonmotive force for cell maintenance during the dark period before reillumination. This translates into a selective advantage during repeated light-dark cycles, such that in mixed culture N22DNAR(+) outcompetes N22. Exposure to light-dark cycles will be a common feature for R. capsulatus in its natural habitats, and this study shows that nitrate respiration may provide a selective advantage under such conditions.

  3. Nitrate leaching index

    Science.gov (United States)

    The Nitrate Leaching Index is a rapid assessment tool that evaluates nitrate (NO3) leaching potential based on basic soil and climate information. It is the basis for many nutrient management planning efforts, but it has considerable limitations because of : 1) an oversimplification of the processes...

  4. Agricultural nitrate pollution

    DEFF Research Database (Denmark)

    Anker, Helle Tegner

    2015-01-01

    Despite the passing of almost 25 years since the adoption of the EU Nitrates Directive, agricultural nitrate pollution remains a major concern in most EU Member States. This is also the case in Denmark, although a fairly strict regulatory regime has resulted in almost a 50 per cent reduction...

  5. Initial kinetics of 15N-nitrate labelling of root and shoot N fractions of barley cultured at different relative addition rates of nitrate-N

    International Nuclear Information System (INIS)

    Agrell, D.; Larsson, C.M.; Larsson, M.; MacKown, C.T.; Rufty, T.W.

    1997-01-01

    The reduction of absorbed nitrate in the root and N transport to the shoot were studied in young barley (Hordeum vulgare L.) plants growing at low external nitrate levels. Plants were grown at three relative addition rates (RA) of nitrate: 0.04, 0.09, and 0.14 d -1 , which represent different degrees of growth limiting nitrate supply. Root nitrate reduction and N transport in situ were estimated using 15 N labelled nitrate exposures ranging from 5 to 60 min. With increasing RA, nitrate uptake in absolute terms increased, but the proportion of absorbed 15 N-nitrate that was reduced in the root decreased markedly. After 10-20 min of exposure to the label, 75, 49 and 27 % of the 15 N taken up was recovered as reduced 15 N in the root at RAs 0.04, 0.09, and 0.14 d -1 , respectively. The response pattern was supported by root nitrate reductase activities and xylem sap nitrate measurements. The decreasing proportion of reduced 15 N in the root with higher nitrate supply rates was matched by a relative increase in 15 N-nitrate storage and, to some extent, an increase in N transport to the shoot. Although small amounts of 15 N were rapidly transported to the shoot, the accumulation of label in the shoot at the end of the 60 min period remained a relatively small proportion of total 15 N uptake, which indicates delayed movement of 15 N out of the root. The results clearly indicate that differing degrees of adjustment occur in important nitrate assimilation processes throughout the N deficiency range. (author)

  6. The cytochrome bd respiratory oxygen reductases.

    Science.gov (United States)

    Borisov, Vitaliy B; Gennis, Robert B; Hemp, James; Verkhovsky, Michael I

    2011-11-01

    Cytochrome bd is a respiratory quinol: O₂ oxidoreductase found in many prokaryotes, including a number of pathogens. The main bioenergetic function of the enzyme is the production of a proton motive force by the vectorial charge transfer of protons. The sequences of cytochromes bd are not homologous to those of the other respiratory oxygen reductases, i.e., the heme-copper oxygen reductases or alternative oxidases (AOX). Generally, cytochromes bd are noteworthy for their high affinity for O₂ and resistance to inhibition by cyanide. In E. coli, for example, cytochrome bd (specifically, cytochrome bd-I) is expressed under O₂-limited conditions. Among the members of the bd-family are the so-called cyanide-insensitive quinol oxidases (CIO) which often have a low content of the eponymous heme d but, instead, have heme b in place of heme d in at least a majority of the enzyme population. However, at this point, no sequence motif has been identified to distinguish cytochrome bd (with a stoichiometric complement of heme d) from an enzyme designated as CIO. Members of the bd-family can be subdivided into those which contain either a long or a short hydrophilic connection between transmembrane helices 6 and 7 in subunit I, designated as the Q-loop. However, it is not clear whether there is a functional consequence of this difference. This review summarizes current knowledge on the physiological functions, genetics, structural and catalytic properties of cytochromes bd. Included in this review are descriptions of the intermediates of the catalytic cycle, the proposed site for the reduction of O₂, evidence for a proton channel connecting this active site to the bacterial cytoplasm, and the molecular mechanism by which a membrane potential is generated. 2011 Elsevier B.V. All rights reserved.

  7. Seasonal variation in denitrification and dissimilatory nitrate reduction to ammonia process rates and corresponding key functional genes along an estuarine nitrate gradient

    Science.gov (United States)

    Smith, Cindy J.; Dong, Liang F.; Wilson, John; Stott, Andrew; Osborn, A. Mark; Nedwell, David B.

    2015-01-01

    This research investigated spatial-temporal variation in benthic bacterial community structure, rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) processes and abundances of corresponding genes and transcripts at three sites—the estuary-head, mid-estuary and the estuary mouth (EM) along the nitrate gradient of the Colne estuary over an annual cycle. Denitrification rates declined down the estuary, while DNRA rates were higher at the estuary head and middle than the EM. In four out of the six 2-monthly time-points, rates of DNRA were greater than denitrification at each site. Abundance of gene markers for nitrate-reduction (nitrate reductase narG and napA), denitrification (nitrite reductase nirS) and DNRA (DNRA nitrite reductase nrfA) declined along the estuary with significant relationships between denitrification and nirS abundance, and DNRA and nrfA abundance. Spatially, rates of denitrification, DNRA and corresponding functional gene abundances decreased along the estuary. However, temporal correlations between rate processes and functional gene and transcript abundances were not observed. PMID:26082763

  8. Thermodynamics of dehydration process of uranyl nitrate pentahydrate of thorium

    International Nuclear Information System (INIS)

    Khamidov, F.A.; Mirsaidov, I.U.; Nazarov, K.M.; Nasriddinov, S.K.; Badalov, A.B.

    2010-01-01

    Present article is devoted to thermodynamics of dehydration process of uranyl nitrate pentahydrate of thorium. The results of researches of dehydration process of uranyl nitrate pentahydrate of thorium Th(NO 3 ) 4 ·5H 2 O were considered. The researches were carried out by means of tensimeter method with membrane zero-manometer under equilibrium conditions and at 300-450 K temperature ranges. The thermodynamic characteristics of dehydration process of initial crystalline hydrate was defined.

  9. A soluble 3-hydroxy-3-methylglutaryl-CoA reductase in the protozoan Trypanosoma cruzi

    DEFF Research Database (Denmark)

    Pena Diaz, Javier; Montalvetti, A; Camacho, A

    1997-01-01

    of the splice acceptor sites clearly indicated that the corresponding mRNA apparently lacks sequences encoding a membrane N-terminal domain. The reductase gene is a single copy and is located on a chromosome of 1.36 Mb as determined by contour-clamped homogeneous electric field electrophoresis. The overall...

  10. NarK is a nitrite-extrusion system involved in anaerobic nitrate respiration by Escherichia coli

    NARCIS (Netherlands)

    Rowe, John J.; Ubbink-Kok, Trees; Molenaar, Douwe; Konings, Wilhelmus; Driessen, Arnold J.M.

    Escherichia coli can use nitrate as a terminal electron acceptor for anaerobic respiration. A polytopic membrane protein, termed NarK, has been implicated in nitrate uptake and nitrite excretion and is thought to function as a nitrate/nitrite antiporter. The longest-lived radioactive isotope of

  11. VT Nitrate Leaching Index

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) Nitrate Leaching Index data for the state of Vermont. This is a derivative product based on the SSURGO soils data for all counties except Essex...

  12. The Arabidopsis Nitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance[C][W

    Science.gov (United States)

    Li, Jian-Yong; Fu, Yan-Lei; Pike, Sharon M.; Bao, Juan; Tian, Wang; Zhang, Yu; Chen, Chun-Zhu; Zhang, Yi; Li, Hong-Mei; Huang, Jing; Li, Le-Gong; Schroeder, Julian I.; Gassmann, Walter; Gong, Ji-Ming

    2010-01-01

    Long-distance transport of nitrate requires xylem loading and unloading, a successive process that determines nitrate distribution and subsequent assimilation efficiency. Here, we report the functional characterization of NRT1.8, a member of the nitrate transporter (NRT1) family in Arabidopsis thaliana. NRT1.8 is upregulated by nitrate. Histochemical analysis using promoter-β-glucuronidase fusions, as well as in situ hybridization, showed that NRT1.8 is expressed predominantly in xylem parenchyma cells within the vasculature. Transient expression of the NRT1.8:enhanced green fluorescent protein fusion in onion epidermal cells and Arabidopsis protoplasts indicated that NRT1.8 is plasma membrane localized. Electrophysiological and nitrate uptake analyses using Xenopus laevis oocytes showed that NRT1.8 mediates low-affinity nitrate uptake. Functional disruption of NRT1.8 significantly increased the nitrate concentration in xylem sap. These data together suggest that NRT1.8 functions to remove nitrate from xylem vessels. Interestingly, NRT1.8 was the only nitrate assimilatory pathway gene that was strongly upregulated by cadmium (Cd2+) stress in roots, and the nrt1.8-1 mutant showed a nitrate-dependent Cd2+-sensitive phenotype. Further analyses showed that Cd2+ stress increases the proportion of nitrate allocated to wild-type roots compared with the nrt1.8-1 mutant. These data suggest that NRT1.8-regulated nitrate distribution plays an important role in Cd2+ tolerance. PMID:20501909

  13. Immunocytochemical localization of APS reductase and bisulfite reductase in three Desulfovibrio species

    NARCIS (Netherlands)

    Kremer, D.R.; Veenhuis, M.; Fauque, G.; Peck Jr., H.D.; LeGall, J.; Lampreia, J.; Moura, J.J.G.; Hansen, T.A.

    1988-01-01

    The localization of APS reductase and bisulfite reductase in Desulfovibrio gigas, D. vulgaris Hildenborough and D. thermophilus was studied by immunoelectron microscopy. Polyclonal antibodies were raised against the purified enzymes from each strain. Cells fixed with formaldehyde/glutaraldehyde were

  14. Electrochemical processing of nitrate waste solutions. Phase 2, Final report

    Energy Technology Data Exchange (ETDEWEB)

    Genders, D.; Weinberg, N.; Hartsough, D. [Electrosynthesis Co., Inc., Cheektowaga, NY (US)

    1992-10-07

    The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F{sup {minus}} ions from the synthetic mix migrating across the cation exchange membrane and forming HF in the acid anolyte. Other possibilities for anode materials were explored. A membrane separation process was investigated which employs an anion and cation exchange membrane to remove nitrite and nitrate, recovering caustic and nitric acid. Present research has shown poor current efficiencies for nitrite and nitrate transport across the anion exchange membrane due to co-migration of hydroxide anions. Precipitates form within the anion exchange membranes which would eventually result in the failure of the membranes. Electrochemical processing offers a highly promising and viable method for the treatment of nitrate waste solutions.

  15. Fatty acyl-CoA reductase

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Ammonium nitrate and iron nutrition effects on some nitrogen assimilation enzymes and metabolites in Spirulina platensis.

    Science.gov (United States)

    Esen, Merve; Ozturk Urek, Raziye

    2015-01-01

    The effect of various concentrations of ammonium nitrate (5-60 mM), an economical nitrogen source, on the growth, nitrate-ammonium uptake rates, production of some pigments and metabolites, and some nitrogen assimilation enzymes such as nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT) in Spirulina platensis (Gamont) Geitler was investigated. Ten millimolars of ammonium nitrate stimulated the growth, production of pigments and the other metabolites, and enzyme activities, whereas 30 and 60 mM ammonium nitrate caused inhibition. In the presence of 10 mM ammonium nitrate, different concentrations of iron were tried in the growth media of S. platensis. After achieving the best growth, levels of metabolite and pigment production, and enzyme activities in the presence of 10 mM ammonium nitrate as a nitrogen source, different iron concentrations (10-100 µM) were tried in the growth medium of S. platensis. The highest growth, pigment and metabolite levels, and enzyme activities were determined in the medium containing 50 µM iron and 10 mM ammonium nitrate. In this optimum condition, the highest dry biomass level, chlorophyll a, and pyruvate contents were obtained as 55.42 ± 3.8 mg mL(-1) , 93.114 ± 7.9 µg g(-1) , and 212.5 ± 18.7 µg g(-1) , respectively. The highest NR, NiR, GS, and GOGAT activities were 67.16 ± 5.1, 777.92 ± 52, 0.141 ± 0.01, and 44.45 ± 3.6, respectively. Additionally, 10 mM ammonium nitrate is an economical and efficient nitrogen source for nitrogen assimilation of S. platensis, and 50 µM iron is optimum for the growth of S. platensis. © 2014 International Union of Biochemistry and Molecular Biology, Inc.

  17. Comparison of nitrate accumulation, nitrogen uptake and utilization efficiency among different spinach (Spinacia oleracea L. genotypes

    Directory of Open Access Journals (Sweden)

    Zhou Jianjian

    2017-10-01

    Full Text Available A hydroponic experiment was conducted to study the difference of nitrate accumulation,nitrogen uptake and utilization efficiency between four spinach (Spinacia oleracea L. genotypes (So10,So13,So18 and So57. Results showed that So13 had the highest nitrate contents under two nitrate (NO3--N level (0.5 mmol·L-1,15 mmol·L-1 conditions,whereas So10 had the lowest nitrate contents. So18 had the similar nitrate contents with So13 under low NO3- level,while it showed no significant difference of nitrate contents with So57 under high NO3- treatment. The 15NO3--N uptake rates of So13 were the highest one among four genotypes,while the N utilization efficiency (NutE and N utilization ratio (NUR of So13 were significantly lower than those of So18 and So57. The shoot dry mass,nitrate reductase activity,NutE,NUR of So18 and So57 were higher than those of So13 and So10,while their 15NO3--N uptake rates were lower than those of So13. The shoot dry mass,nitrate reductase activity,NutE,N utilization ratio of So10 were significantly lower than those of So18 and So57,and its 15NO3--N uptake rate was significantly lower than those of So13. Among the four spinach genotypes,the So57 can be selected as elite germplasm using for spinach production for its relatively lower nitrate content and higher N efficiency.

  18. Oxygen and xenobiotic reductase activities of cytochrome P450.

    NARCIS (Netherlands)

    Goeptar, A.R.; Scheerens, H.; Vermeulen, N.P.E.

    1995-01-01

    The oxygen reductase and xenobiotic reductase activities of cytochrome P450 (P450) are reviewed. During the oxygen reductase activity of P450, molecular oxygen is reduced to superoxide anion radicals (O

  19. The Bradyrhizobium japonicum frcB Gene Encodes a Diheme Ferric Reductase ▿†

    Science.gov (United States)

    Small, Sandra K.; O'Brian, Mark R.

    2011-01-01

    Iron utilization by bacteria in aerobic environments involves uptake as a ferric chelate from the environment, followed by reduction to the ferrous form. Ferric iron reduction is poorly understood in most bacterial species. Here, we identified Bradyrhizobium japonicum frcB (bll3557) as a gene adjacent to, and coregulated with, the pyoR gene (blr3555) encoding the outer membrane receptor for transport of a ferric pyoverdine. FrcB is a membrane-bound, diheme protein, characteristic of eukaryotic ferric reductases. Heme was essential for FrcB stability, as were conserved histidine residues in the protein that likely coordinate the heme moieties. Expression of the frcB gene in Escherichia coli conferred ferric reductase activity on those cells. Furthermore, reduced heme in purified FrcB was oxidized by ferric iron in vitro. B. japonicum cells showed inducible ferric reductase activity in iron-limited cells that was diminished in an frcB mutant. Steady-state levels of frcB mRNA were strongly induced under iron-limiting conditions, but transcript levels were low and unresponsive to iron in an irr mutant lacking the global iron response transcriptional regulator Irr. Thus, Irr positively controls the frcB gene. FrcB belongs to a family of previously uncharacterized proteins found in many proteobacteria and some cyanobacteria. This suggests that membrane-bound, heme-containing ferric reductase proteins are not confined to eukaryotes but may be common in bacteria. PMID:21705608

  20. The Bradyrhizobium japonicum frcB gene encodes a diheme ferric reductase.

    Science.gov (United States)

    Small, Sandra K; O'Brian, Mark R

    2011-08-01

    Iron utilization by bacteria in aerobic environments involves uptake as a ferric chelate from the environment, followed by reduction to the ferrous form. Ferric iron reduction is poorly understood in most bacterial species. Here, we identified Bradyrhizobium japonicum frcB (bll3557) as a gene adjacent to, and coregulated with, the pyoR gene (blr3555) encoding the outer membrane receptor for transport of a ferric pyoverdine. FrcB is a membrane-bound, diheme protein, characteristic of eukaryotic ferric reductases. Heme was essential for FrcB stability, as were conserved histidine residues in the protein that likely coordinate the heme moieties. Expression of the frcB gene in Escherichia coli conferred ferric reductase activity on those cells. Furthermore, reduced heme in purified FrcB was oxidized by ferric iron in vitro. B. japonicum cells showed inducible ferric reductase activity in iron-limited cells that was diminished in an frcB mutant. Steady-state levels of frcB mRNA were strongly induced under iron-limiting conditions, but transcript levels were low and unresponsive to iron in an irr mutant lacking the global iron response transcriptional regulator Irr. Thus, Irr positively controls the frcB gene. FrcB belongs to a family of previously uncharacterized proteins found in many proteobacteria and some cyanobacteria. This suggests that membrane-bound, heme-containing ferric reductase proteins are not confined to eukaryotes but may be common in bacteria.

  1. Characterization of xylose reductase from Candida tropicalis ...

    African Journals Online (AJOL)

    USER

    2010-08-02

    Aug 2, 2010 ... Xylose reductase gene, enzyme cofactors and plasmids. E.coli BL21(DE3) was used as host strains for ... C. tropicalis xylose reductase gene was isolated from plasmid. pMD18-T (TaKaRa, Japan). Enzyme ..... the gels is instable, soft and even dissolve in the solution containing multivalent anions or high ...

  2. Serum nitrate levels as an index of endothelial function in pre-eclamsia and normal pregnancy.

    Science.gov (United States)

    Gupta, Rani; Maruthy, K N; Mhaskar, Arun M; Padmanabhan, Laxmi Devi

    2003-04-01

    The study was conducted in St. John's Medical College Hospital and Department of Physiology, with the aim of studying the serum nitrate levels in pre-eclampsia and normal pregnancy. The total number of subjects studied in various groups were 159, control (n = 55), first trimester (n = 13), second trimester normal (n = 42), second trimester pre-eclampsia/PET (n = 5), third trimester normal (n = 32), third trimester pre-eclampsia/PET (n = 12). The serum nitrate was measured by one step enzymatic assay using Nitrate reductase from Aspergillus species. The nitrate levels in the third trimester pre-eclamptic group was found to be significant lower (P = 0.02), as compared to normal subjects, however the renal functions were normal in all the subjects.

  3. Yttrium Nitrate mediated Nitration of Phenols at room temperature in ...

    Indian Academy of Sciences (India)

    Rapid nitration of electron rich phenols using Y(NO₃)₃.6H₂O in glacial acetic acid at room temperature was observed with good yield. The method allows nitration of phenols without oxidation, and isolation of nitration product in a rapid and simple way. The described method is selective for phenols.

  4. Yttrium Nitrate mediated Nitration of Phenols at room temperature in ...

    Indian Academy of Sciences (India)

    which resulted in many neurological disorders.1 Thus, the mechanism of nitration in biological system explains how environment and genetic factors induce neurological disorder. Conventional nitration involves use of concentrated H2SO4 and HNO3 mixture as the nitrating agent. Such a method suffers from drawbacks.

  5. Nitrate ammonification by Nautilia profundicola AmH: experimental evidence consistent with a free hydroxylamine intermediate.

    Directory of Open Access Journals (Sweden)

    Thomas E Hanson

    2013-07-01

    Full Text Available The process of nitrate reduction via nitrite controls the fate and bioavailability of mineral nitrogen within ecosystems; i.e. whether it is retained as ammonium (ammonification or lost as nitrous oxide or dinitrogen (denitrification. Here, we present experimental evidence for a novel pathway of microbial nitrate reduction, the reverse hydroxylamine:ubiquinone reductase module (reverse-HURM pathway. Instead of a classical ammonia-forming nitrite reductase that performs a 6 electron-transfer process, the pathway is thought to employ two catalytic redox modules operating in sequence: the reverse-HURM reducing nitrite to hydroxylamine followed by a hydroxylamine reductase that converts hydroxylamine to ammonium. Experiments were performed on Nautilia profundicola strain AmH, whose genome sequence led to the reverse-HURM pathway proposal. N. profundicola produced ammonium from nitrate, which was assimilated into biomass. Furthermore, genes encoding the catalysts of the reverse-HURM pathway were preferentially expressed during growth of N. profundicola on nitrate as an electron acceptor relative to cultures grown on polysulfide as an electron acceptor. Finally, nitrate-grown cells of N. profundicola were able to rapidly and stoichiometrically convert high concentrations of hydroxylamine to ammonium in resting cell assays. These experiments are consistent with the reverse-HURM pathway and a free hydroxylamine intermediate, but could not definitively exclude direct nitrite reduction to ammonium by the reverse-HURM with hydroxylamine as an off-pathway product. N. profundicola and related organisms are models for a new pathway of nitrate ammonification that may have global impact due to the wide distribution of these organisms in hypoxic environments and symbiotic or pathogenic associations with animal hosts.

  6. Gas transport and sub-Ig relaxations in unmodified and nitrated polyarylethersulfones

    NARCIS (Netherlands)

    Kamps, K.M.P.; Teunis, Hermannus A.; Teunis, H.A.; Wessling, Matthias; Smolders, C.A.; Smolders, C.A.

    1992-01-01

    Aromatic nitration has been used to modify the polymer main chain of polysulfone and polyethersulfone. Alteration in the gas separation characteristics of homogeneous membrane made out of these polymers could be observed upon nitration. Generally, separation factors for gas mixtures of CO2/CH4

  7. Nitrate Leaching Management

    Science.gov (United States)

    Nitrate (NO3) leaching is a significant nitrogen (N) loss process for agriculture that must be managed to minimize NO3 enrichment of groundwater and surface waters. Managing NO3 leaching should involve the application of basic principles of understanding the site’s hydrologic cycle, avoiding excess ...

  8. Oxalate synthesis in leaves is associated with root uptake of nitrate and its assimilation in spinach (Spinacia oleracea L.) plants.

    Science.gov (United States)

    Liu, Xiao Xia; Zhou, Kai; Hu, Yan; Jin, Rong; Lu, Ling Li; Jin, Chong Wei; Lin, Xian Yong

    2015-08-15

    Excessive accumulation of oxalate in numerous vegetables adversely affects their quality as food. While it is known that nitrate could effectively stimulate oxalate accumulation in many vegetables, little information is available about the mechanism of nitrate-induced oxalate accumulation. In this study, we examined the association of oxalate synthesis with nitrate uptake and assimilation in two genotypes of spinach (Spinacia oleracea L.), Heizhenzhu and Weilv. Increasing nitrate levels resulted in enhanced synthesis of oxalate, as well as increased root uptake of nitrate and leaf activities of nitrate reductase (NR) and glutamine synthetase (GS) for both genotypes. Correlation analysis revealed that oxalate accumulation in spinach leaves was positively related with rate of nitrate uptake by roots, as well as leaf activities of NR and GS. Addition of plasmalemma H(+)-ATPase inhibitor sodium vanadate (Na3VO4) significantly decreased leaf oxalate accumulation in both genotypes. Presence of NR or GS inhibitors led to reduction of leaf oxalate contents, GS/NR activities and decreased nitrate uptake rate. Significantly higher levels of nitrate root uptake, leaf NR and GS activities were observed in the high-oxalate genotype Heizhenzhu than in Weilv. Oxalate synthesis in leaves of spinach is not only positively associated with root uptake of nitrate, but also with its assimilation within the plants. © 2014 Society of Chemical Industry.

  9. Functioning of nitric oxide cycle in gastric mucosa of rats under excessive combined intake of sodium nitrate and fluoride.

    Science.gov (United States)

    Akimov, O Ye; Kostenko, V O

    2016-01-01

    In the article the function of nitric oxide (·NO) cycle in rat’s gastric mucosa was assessed under excessive combined chronic fluoride and nitrate intake during 30 days. It was estimated that general nitric oxide synthase activity (NOS) was increased during excessive sodium fluoride intake meanwhile influence on gene­ral nitrate reduction was not statistically significant, but general nitrite reduction was increased. General arginase activity decreased. Excessive sodium nitrate intake decreased NOS activity, but increased nitrate, nitrite reduction and general arginase activity. Combined sodium nitrate and fluoride intake increased NOS by 18.9%, nitrate reduction by 71.7%, nitrite by 161.5%, arginase activity increase by 61.4%. The highest amounts of peroxynitrite were obtained from excessive sodium fluoride intake group, excessive sodium nitrate intake showed the lowest levels and combined excessive sodium nitrate and fluoride intake levels had intermediate results. Summarizing the data obtained, the authors have made a conclusion that combined excessive sodium nitrate and fluoride intake creates optimal conditions for functioning of nitrate-nitrite reductases.

  10. Horizontal transfer of a nitrate assimilation gene cluster and ecological transitions in fungi: a phylogenetic study.

    Directory of Open Access Journals (Sweden)

    Jason C Slot

    Full Text Available High affinity nitrate assimilation genes in fungi occur in a cluster (fHANT-AC that can be coordinately regulated. The clustered genes include nrt2, which codes for a high affinity nitrate transporter; euknr, which codes for nitrate reductase; and NAD(PH-nir, which codes for nitrite reductase. Homologs of genes in the fHANT-AC occur in other eukaryotes and prokaryotes, but they have only been found clustered in the oomycete Phytophthora (heterokonts. We performed independent and concatenated phylogenetic analyses of homologs of all three genes in the fHANT-AC. Phylogenetic analyses limited to fungal sequences suggest that the fHANT-AC has been transferred horizontally from a basidiomycete (mushrooms and smuts to an ancestor of the ascomycetous mold Trichoderma reesei. Phylogenetic analyses of sequences from diverse eukaryotes and eubacteria, and cluster structure, are consistent with a hypothesis that the fHANT-AC was assembled in a lineage leading to the oomycetes and was subsequently transferred to the Dikarya (Ascomycota+Basidiomycota, which is a derived fungal clade that includes the vast majority of terrestrial fungi. We propose that the acquisition of high affinity nitrate assimilation contributed to the success of Dikarya on land by allowing exploitation of nitrate in aerobic soils, and the subsequent transfer of a complete assimilation cluster improved the fitness of T. reesei in a new niche. Horizontal transmission of this cluster of functionally integrated genes supports the "selfish operon" hypothesis for maintenance of gene clusters.

  11. Carboxylic acid reductase enzymes (CARs).

    Science.gov (United States)

    Winkler, Margit

    2018-04-01

    Carboxylate reductases (CARs) are emerging as valuable catalysts for the selective one-step reduction of carboxylic acids to their corresponding aldehydes. The substrate scope of CARs is exceptionally broad and offers potential for their application in diverse synthetic processes. Two major fields of application are the preparation of aldehydes as end products for the flavor and fragrance sector and the integration of CARs in cascade reactions with aldehydes as the key intermediates. The latest applications of CARs are dominated by in vivo cascades and chemo-enzymatic reaction sequences. The challenge to fully exploit product selectivity is discussed. Recent developments in the characterization of CARs are summarized, with a focus on aspects related to the domain architecture and protein sequences of CAR enzymes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Refining method for bismuth nitrate

    International Nuclear Information System (INIS)

    Shibata, Shigeyuki.

    1997-01-01

    The present invention concerns a method of separating and removing α ray emitting nuclides present in an aqueous solution of bismuth nitrate by an industrially convenient method. A nitric acid concentration in the aqueous solution of bismuth nitrate in which α ray emitting nuclides are dissolved is lowered to coprecipitate the bismuth oxynitrate and the α ray emitting nuclides. The coprecipitation materials are separated from the aqueous solution of bismuth nitrate to separate the α ray emitting nuclides dissolved in the aqueous solution of bismuth nitrate thereby refining the aqueous solution of bismuth nitrate. (T.M.)

  13. Nitrate in drinking water

    DEFF Research Database (Denmark)

    Schullehner, Jörg

    Annual nationwide exposure maps for nitrate in drinking water in Denmark from the 1970s until today will be presented based on the findings in Schullehner & Hansen (2014) and additional work on addressing the issue of private well users and estimating missing data. Drinking water supply in Denmark...... is highly decentralized and fully relying on simple treated groundwater. At the same time, Denmark has an intensive agriculture, making groundwater resources prone to nitrate pollution. Drinking water quality data covering the entire country for over 35 years are registered in the public database Jupiter....... In order to create annual maps of drinking water quality, these data had to be linked to 2,852 water supply areas, which were for the first time digitized, collected in one dataset and connected to the Jupiter database. Analyses of the drinking water quality maps showed that public water supplies...

  14. Nitrate in drinking water

    DEFF Research Database (Denmark)

    Schullehner, Jörg; Hansen, Birgitte; Sigsgaard, Torben

    is highly decentralized and fully relying on simple treated groundwater. At the same time, Denmark has an intensive agriculture, making groundwater resources prone to nitrate pollution. Drinking water quality data covering the entire country for over 35 years are registered in the public database Jupiter......Annual nationwide exposure maps for nitrate in drinking water in Denmark from the 1970s until today will be presented based on the findings in Schullehner & Hansen (2014) and additional work on addressing the issue of private well users and estimating missing data. Drinking water supply in Denmark....... In order to create annual maps of drinking water quality, these data had to be linked to 2,852 water supply areas, which were for the first time digitized, collected in one dataset and connected to the Jupiter database. Analyses of the drinking water quality maps showed that public water supplies...

  15. Subcellular distribution of nitroblue tetrazolium reductase (NBT-R) in human polymorphonuclear leukocytes (PMN).

    Science.gov (United States)

    Baehner, R L

    1975-11-01

    Subcellular distribution study of cytoplasmic organelles was performed on human polymorphonuclear leukocytes after homogenization in 0.34 molar sucrose by differential centrifugation and sucrose density gradient centrifugation of the homogenate. The whole homogenate and each fraction was assayed for nitroblue tetrazolium (NBT)-reductase with and without 1 mM potassium cyanide, and the distribution of this enzyme was compared to the distribution of lysozyme, peroxidase, beta-glucuronidase, and acid and alkaline phosphatase. Enzyme recovery was 97 per cent and ranged between 74 and 124 per cent. Latent activity of all enzymes except NBT-reductase, acid, and alkaline phosphatase was demonstrated by observing a four- to sixfold increase in activity after the addition of Triton-X 100. Maximal relative specific activity using either DPNH or without cyanide for NBT-reductase was found in the 100,000 x g differential centrifugation fraction and was concentrated in the less dense top fraction of the sucrose density gradient. The distribution pattern was similar to acid and alkaline phosphatase. In contrast, the maximal concentration of beta-glucuronidase and peroxidase was found in the heavier 7,200 x g granule fraction and in the more dense bottom fractions of the sucrose density gradient. Maximal lysozyme activity was concentrated in the 30,000 x g granule fraction and in the fractions located between the heaviest and lightest fractions of the sucrose density gradient. The lack of latent activity and the similarity of subcellular distribution of NBT-reductase to acid and alkaline phosphatase, two enzymes associated with microsomes and plasmalemal membranes in human polymorphonuclear leukocytes (PMN), indicates that NBT-reductase is also a nonlysosomal enzyme located in microsomes or in plasmalemal membranes. These findings support the previously described histochemical observations that initial reduction of NBT to formazan occurs on the PMN plasmalemal surface membrane at

  16. Enterosalivary nitrate metabolism and the microbiome: Intersection of microbial metabolism, nitric oxide and diet in cardiac and pulmonary vascular health.

    Science.gov (United States)

    Koch, Carl D; Gladwin, Mark T; Freeman, Bruce A; Lundberg, Jon O; Weitzberg, Eddie; Morris, Alison

    2017-04-01

    Recent insights into the bioactivation and signaling actions of inorganic, dietary nitrate and nitrite now suggest a critical role for the microbiome in the development of cardiac and pulmonary vascular diseases. Once thought to be the inert, end-products of endothelial-derived nitric oxide (NO) heme-oxidation, nitrate and nitrite are now considered major sources of exogenous NO that exhibit enhanced vasoactive signaling activity under conditions of hypoxia and stress. The bioavailability of nitrate and nitrite depend on the enzymatic reduction of nitrate to nitrite by a unique set of bacterial nitrate reductase enzymes possessed by specific bacterial populations in the mammalian mouth and gut. The pathogenesis of pulmonary hypertension (PH), obesity, hypertension and CVD are linked to defects in NO signaling, suggesting a role for commensal oral bacteria to shape the development of PH through the formation of nitrite, NO and other bioactive nitrogen oxides. Oral supplementation with inorganic nitrate or nitrate-containing foods exert pleiotropic, beneficial vascular effects in the setting of inflammation, endothelial dysfunction, ischemia-reperfusion injury and in pre-clinical models of PH, while traditional high-nitrate dietary patterns are associated with beneficial outcomes in hypertension, obesity and CVD. These observations highlight the potential of the microbiome in the development of novel nitrate- and nitrite-based therapeutics for PH, CVD and their risk factors. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Clone-Specific Response in Leaf Nitrate Reductase Activity among Unrelated Hybrid Poplars in relation to Soil Nitrate Availability

    Directory of Open Access Journals (Sweden)

    Julien Fortier

    2012-01-01

    Full Text Available In this field study, we used in vivo NRA activity in hybrid poplar leaves as an indicator of NO3- assimilation for five unrelated hybrid poplar clones. We also examined if leaf NRA of these clones is influenced to the same extent by different levels of soil NO3- availability in two riparian agroforestry systems located in pastures. Leaf NRA differences of more than one order of magnitude were observed between the clones, clearly showing their different abilities to reduce NO3- in leaves. Clone DxN-3570, a P. deltoides x P. nigra hybrid (Aigeiros intrasectional hybrid, always had the highest leaf NRA during the field assays. This clone was also the only one to increase its leaf NRA with increasing NO3- soil availability, which resulted in a significant Site x Clone interaction and a positive relationship between soil NO3- concentration and NRA. All of the four other clones studied had one or both parental species from the Tacamahaca section. They had relatively low leaf NRA and they did not increase their leaf NRA when grown on the NO3- rich site. These results provide evidence that NO3- assimilation in leaves varies widely among hybrid poplars of different parentages, suggesting potential preferences for N forms.

  18. Interspecific variation for thermal dependence of glutathione reductase in sainfoin.

    Science.gov (United States)

    Kidambi, S P; Mahan, J R; Matches, A G

    1990-05-01

    Understanding the biochemical and physiological consequences of species variation would expedite improvement in agronomically useful genotypes of sainfoin (Onobrychis spp.) Information on variation among sainfoin species is lacking on thermal dependence of glutathione reductase (B.C. 1.6.4.2.), which plays an important role in the protection of plants from both high and low temperature stresses by preventing harmful oxidation of enzymes and membranes. Our objective was to investigate the interspecific variation for thermal dependency of glutathione reductase in sainfoin. Large variation among species was found for: (i) the minimum apparent Km (0.4-2.5 μM NADPH), (ii) the temperature at which the minimum apparent Km was observed (15°-5°C), and (iii) the thermal kinetic windows (2°-30°C width) over a 15°-45°C temperature gradient. In general, tetraploid species had narrower (≤17°C) thermal kinetic windows than did diploid species (∼30°C), with one exception among the diploids. Within the tetraploid species, the cultivars of O. viciifolia had a broader thermal kinetic window (≥7°C) than the plant introduction (PI 212241, >2 °C) itself.

  19. A ferric-chelate reductase for iron uptake from soils.

    Science.gov (United States)

    Robinson, N J; Procter, C M; Connolly, E L; Guerinot, M L

    1999-02-25

    Iron deficiency afflicts more than three billion people worldwide, and plants are the principal source of iron in most diets. Low availability of iron often limits plant growth because iron forms insoluble ferric oxides, leaving only a small, organically complexed fraction in soil solutions. The enzyme ferric-chelate reductase is required for most plants to acquire soluble iron. Here we report the isolation of the FRO2 gene, which is expressed in iron-deficient roots of Arabidopsis. FRO2 belongs to a superfamily of flavocytochromes that transport electrons across membranes. It possesses intramembranous binding sites for haem and cytoplasmic binding sites for nucleotide cofactors that donate and transfer electrons. We show that FRO2 is allelic to the frd1 mutations that impair the activity of ferric-chelate reductase. There is a nonsense mutation within the first exon of FRO2 in frd1-1 and a missense mutation within FRO2 in frd1-3. Introduction of functional FRO2 complements the frd1-1 phenotype in transgenic plants. The isolation of FRO2 has implications for the generation of crops with improved nutritional quality and increased growth in iron-deficient soils.

  20. Thioredoxin Reductase and its Inhibitors

    Science.gov (United States)

    Saccoccia, Fulvio; Angelucci, Francesco; Boumis, Giovanna; Carotti, Daniela; Desiato, Gianni; Miele, Adriana E; Bellelli, Andrea

    2014-01-01

    Thioredoxin plays a crucial role in a wide number of physiological processes, which span from reduction of nucleotides to deoxyriboucleotides to the detoxification from xenobiotics, oxidants and radicals. The redox function of Thioredoxin is critically dependent on the enzyme Thioredoxin NADPH Reductase (TrxR). In view of its indirect involvement in the above mentioned physio/pathological processes, inhibition of TrxR is an important clinical goal. As a general rule, the affinities and mechanisms of binding of TrxR inhibitors to the target enzyme are known with scarce precision and conflicting results abound in the literature. A relevant analysis of published results as well as the experimental procedures is therefore needed, also in view of the critical interest of TrxR inhibitors. We review the inhibitors of TrxR and related flavoreductases and the classical treatment of reversible, competitive, non competitive and uncompetitive inhibition with respect to TrxR, and in some cases we are able to reconcile contradictory results generated by oversimplified data analysis. PMID:24875642

  1. [Manganese-dependent ribonucleotide reductase of Propionibacterium freudenreichii subsp. shermanii: partial purification, characterization, and role in DNA biosynthesis].

    Science.gov (United States)

    Iordan, E P; Bryukhanov, A L; Dunaevskiĭ, Ia E; Pryanishnikova, N I; Danilova, I V

    2000-01-01

    Like Lactobacillus leichmanii, Rhizobium meliloti, and Euglena gracilis, P. freudenreichii implicates cobalamin in DNA anabolism via adenosylcobalamin-dependent ribonucleotide reductase. However, in the absence of corrinoids, P. freudenreichii is able to synthesize DNA with the involvement of an alternative ribonucleotide reductase, which is independent of adenosylcobalamin. This enzyme is localized in both the cytoplasm (80% of activity) and the cytoplasmic membrane (20% of activity), being loosely bound to the latter. Experiments with crude ribonucleotide reductase isolated from extracts of corrinoid-deficient cells showed that manganese specifically stimulates this enzyme and that it is composed of two protein subunits, a feature that is typical of all metal-containing reductases activated by molecular oxygen. Low concentrations of manganese ions enhanced DNA synthesis in corrinoid-deficient manganese-limited cells. This effect was prevented by the addition of 80 mM hydroxyurea, a specific inhibitor of metal-containing aerobic ribonucleotide reductases. It was concluded that, in adenosylcobalamin-deficient P. freudenreichii cells, DNA synthesis is provided with deoxyribosyl precursors through the functioning of manganese-dependent aerobic ribonucleotide reductase composed of two subunits.

  2. Electrochemical processing of nitrate waste solutions

    Energy Technology Data Exchange (ETDEWEB)

    Genders, D.; Weinberg, N.; Hartsough, D. (Electrosynthesis Co., Inc., Cheektowaga, NY (United States))

    1992-10-07

    The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F[sup [minus

  3. Sustainable nitrate-contaminated water treatment using multi cycle ion-exchange/bioregeneration of nitrate selective resin.

    Science.gov (United States)

    Ebrahimi, Shelir; Roberts, Deborah J

    2013-11-15

    The sustainability of ion-exchange treatment processes using high capacity single use resins to remove nitrate from contaminated drinking water can be achieved by regenerating the exhausted resin and reusing it multiple times. In this study, multi cycle loading and bioregeneration of tributylamine strong base anion (SBA) exchange resin was studied. After each cycle of exhaustion, biological regeneration of the resin was performed using a salt-tolerant, nitrate-perchlorate-reducing culture for 48 h. The resin was enclosed in a membrane to avoid direct contact of the resin with the culture. The results show that the culture was capable of regenerating the resin and allowing the resin to be used in multiple cycles. The concentrations of nitrate in the samples reached a peak in first 0.5-1h after placing the resin in medium because of desorption of nitrate from resin with desorption rate of 0.099 ± 0.003 hr(-1). After this time, since microorganisms began to degrade the nitrate in the aqueous phase, the nitrate concentration was generally non-detectable after 10h. The average of calculated specific degradation rate of nitrate was -0.015 mg NO3(-)/mg VSS h. Applying 6 cycles of resin exhaustion/regeneration shows resin can be used for 4 cycles without a loss of capacity, after 6 cycles only 6% of the capacity was lost. This is the first published research to examine the direct regeneration of a resin enclosed in a membrane, to allow reuse without any disinfection or cleaning procedures. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Characterisation of a desmosterol reductase involved in phytosterol dealkylation in the silkworm, Bombyx mori.

    Directory of Open Access Journals (Sweden)

    Leonora F Ciufo

    Full Text Available Most species of invertebrate animals cannot synthesise sterols de novo and many that feed on plants dealkylate phytosterols (mostly C(29 and C(28 yielding cholesterol (C(27. The final step of this dealkylation pathway involves desmosterol reductase (DHCR24-catalysed reduction of desmosterol to cholesterol. We now report the molecular characterisation in the silkworm, Bombyx mori, of such a desmosterol reductase involved in production of cholesterol from phytosterol, rather than in de novo synthesis of cholesterol. Phylogenomic analysis of putative desmosterol reductases revealed the occurrence of various clades that allowed for the identification of a strong reductase candidate gene in Bombyx mori (BGIBMGA 005735. Following PCR-based cloning of the cDNA (1.6 kb and its heterologous expression in Saccharomyces cerevisae, the recombinant protein catalysed reduction of desmosterol to cholesterol in an NADH- and FAD-dependent reaction.Conceptual translation of the cDNA, that encodes a 58.9 kDa protein, and database searching, revealed that the enzyme belongs to an FAD-dependent oxidoreductase family. Western blotting revealed reductase protein expression exclusively in the microsomal subcellular fraction and primarily in the gut. The protein is peripherally associated with microsomal membranes. 2D-native gel and PAGE analysis revealed that the reductase is part of a large complex with molecular weight approximately 250 kDa. The protein occurs in midgut microsomes at a fairly constant level throughout development in the last two instars, but is drastically reduced during the wandering stage in preparation for metamorphosis. Putative Broad Complex transcription factor-binding sites detectable upstream of the DHCR24 gene may play a role in this down-regulation.

  5. BIOLOGICAL ROLE OF ALDO-KETO REDUCTASES IN RETINOIC ACID BIOSYNTHESIS AND SIGNALING

    Directory of Open Access Journals (Sweden)

    F. Xavier eRuiz

    2012-04-01

    Full Text Available Several aldo-keto reductase (AKR enzymes from subfamilies 1B and 1C show retinaldehyde reductase activity, having low Km and kcat values. Only AKR1B10 and 1B12, with all-trans-retinaldehyde, and AKR1C3, with 9-cis-retinaldehyde, display high catalytic efficiency. Major structural determinants for retinaldehyde isomer specificity are located in the external loops (A and C for AKR1B10, and B for AKR1C3, as assessed by site-directed mutagenesis and molecular dynamics. Cellular models have shown that AKR1B and 1C enzymes are well suited to work in vivo as retinaldehyde reductases and to regulate retinoic acid (RA biosynthesis at hormone pre-receptor level. An additional physiological role for the retinaldehyde reductase activity of these enzymes, consistent with their tissue localization, is their participation in β-carotene absorption. Retinaldehyde metabolism may be subjected to subcellular compartmentalization, based on enzyme localization. While retinaldehyde oxidation to RA takes place in the cytosol, reduction to retinol could take place in the cytosol by AKRs or in the membranes of endoplasmic reticulum by microsomal retinaldehyde reductases. Upregulation of some AKR1 enzymes in different cancer types may be linked to their induction by oxidative stress and to their participation in different signaling pathways related to cell proliferation. AKR1B10 and AKR1C3, through their retinaldehyde reductase activity, trigger a decrease in the RA biosynthesis flow, resulting in RA deprivation and consequently lower differentiation, with an increased cancer risk in target tissues. Rational design of selective AKR inhibitors could lead to development of novel drugs for cancer treatment as well as reduction of chemotherapeutic drug resistance.

  6. fHANT-AC genes of the ectomycorrhizal fungus Laccaria bicolor are not repressed by l-glutamine allowing simultaneous utilization of nitrate and organic nitrogen sources.

    Science.gov (United States)

    Kemppainen, Minna J; Alvarez Crespo, Maria C; Pardo, Alejandro G

    2010-08-01

    In boreal and temperate forest ectomycorrhizal fungi play a crucial role in nitrogen cycling by assimilating nitrogenous compounds from soil and transferring them to tree hosts. The expression profile of fHANT-AC genes, nitrate transporter (Lbnrt), nitrate reductase (Lbnr) and nitrite reductase (Lbnir), responsible for nitrate utilization in the ectomycorrhizal fungus Laccaria bicolor, was studied on variable N regimens. The three genes were shown to be under a common regulation: repressed in the presence of ammonium while growth on nitrate resulted in high transcripts accumulation. The presence of nitrate was shown not to be indispensable for activation of Laccaria fHANT-AC as also N starvation and growth on urea and l-asparagine resulted in high transcript levels. Equally high expression of Laccaria fHANT-AC genes was detected in mycelia grown on variable concentrations of l-glutamine. This finding shows that in L. bicolor N metabolite repression of fHANT-AC is not signalled via l-glutamine like described in ascomycetes. The expression patterns of Lbnrt and Lbnir were also studied in an Lbnr RNA-silenced Laccaria strain. No differences were observed on the N source regulation or the degree of transcript accumulation of these genes, indicating that the presence of high nitrate reductase activity is not a core regulator of L. bicolor fHANT-AC expression. The simultaneous utilization of nitrate and organic N sources, already suggested by high transcript levels of Laccaria fHANT-AC genes on organic N, was supported by the increase of culture medium pH as a result of nitrate transporter activity. The possible ecological and evolutionary significance of the herein reported high regulatory flexibility of Laccaria nitrate utilization pathway for ectomycorrizal fungi and the ectomycorrhizal symbiosis is discussed. © 2009 Society for Applied Microbiology and Blackwell Publishing Ltd.

  7. dl-Asparaginium nitrate

    Directory of Open Access Journals (Sweden)

    Nabila Moussa Slimane

    2009-09-01

    Full Text Available In the title compound, C4H9N2O3+·NO3−, alternatively called (1RS-2-carbamoyl-1-carboxyethanaminium nitrate, the asymmetric unit comprises one asparaginium cation and one nitrate anion. The strongest cation–cation O—H...O hydrogen bond in the structure, together with other strong cation–cation N—H...O hydrogen bonds, generates a succession of infinite chains of R22(8 rings along the b axis. Additional cation–cation C—H...O hydrogen bonds link these chains into two-dimensional layers formed by alternating R44(24 and R42(12 rings. Connections between these layers are provided by the strong cation–anion N—H...O hydrogen bonds, as well as by one weak C—H...O interaction, thus forming a three-dimensional network. Some of the cation–anion N—H...O hydrogen bonds are bifurcated of the type D—H...(A1,A2.

  8. Fatty acyl-CoA reductases of birds

    Directory of Open Access Journals (Sweden)

    Hellenbrand Janine

    2011-12-01

    Full Text Available Abstract Background Birds clean and lubricate their feathers with waxes that are produced in the uropygial gland, a holocrine gland located on their back above the tail. The type and the composition of the secreted wax esters are dependent on the bird species, for instance the wax ester secretion of goose contains branched-chain fatty acids and unbranched fatty alcohols, whereas that of barn owl contains fatty acids and alcohols both of which are branched. Alcohol-forming fatty acyl-CoA reductases (FAR catalyze the reduction of activated acyl groups to fatty alcohols that can be esterified with acyl-CoA thioesters forming wax esters. Results cDNA sequences encoding fatty acyl-CoA reductases were cloned from the uropygial glands of barn owl (Tyto alba, domestic chicken (Gallus gallus domesticus and domestic goose (Anser anser domesticus. Heterologous expression in Saccharomyces cerevisiae showed that they encode membrane associated enzymes which catalyze a NADPH dependent reduction of acyl-CoA thioesters to fatty alcohols. By feeding studies of transgenic yeast cultures and in vitro enzyme assays with membrane fractions of transgenic yeast cells two groups of isozymes with different properties were identified, termed FAR1 and FAR2. The FAR1 group mainly synthesized 1-hexadecanol and accepted substrates in the range between 14 and 18 carbon atoms, whereas the FAR2 group preferred stearoyl-CoA and accepted substrates between 16 and 20 carbon atoms. Expression studies with tissues of domestic chicken indicated that FAR transcripts were not restricted to the uropygial gland. Conclusion The data of our study suggest that the identified and characterized avian FAR isozymes, FAR1 and FAR2, can be involved in wax ester biosynthesis and in other pathways like ether lipid synthesis.

  9. Nitrate storage and dissimilatory nitrate reduction by eukaryotic microbes

    DEFF Research Database (Denmark)

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly...... and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate...... storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described...

  10. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Science.gov (United States)

    2010-07-01

    ..., combustible liquids, corrosive liquids, chlorates, permanganates, finely divided metals, caustic soda... molten ammonium nitrate if a fire occurred (and thus become potential detonators for the storage piles...

  11. Engineered P450 biocatalysts show improved activity and regio-promiscuity in aromatic nitration.

    Science.gov (United States)

    Zuo, Ran; Zhang, Yi; Jiang, Chao; Hackett, John C; Loria, Rosemary; Bruner, Steven D; Ding, Yousong

    2017-04-12

    Nitroaromatics are among the most important and commonly used chemicals but their production often suffers from multiple unsolved challenges. We have previously described the development of biocatalytic nitration processes driven by an engineered P450 TxtE fusion construct. Herein we report the creation of improved nitration biocatalysts through constructing and characterizing fusion proteins of TxtE with the reductase domain of CYP102A1 (P450BM3, BM3R). The majority of constructs contained variable linker length while one was rationally designed for optimizing protein-protein interactions. Detailed biochemical characterization identified multiple active chimeras that showed improved nitration activity, increased coupling efficiency and higher total turnover numbers compared with TxtE. Substrate promiscuity of the most active chimera was further assessed with a substrate library. Finally, a biocatalytic nitration process was developed to nitrate 4-Me-DL-Trp. The production of both 4-Me-5-NO 2 -L-Trp and 4-Me-7-NO 2 -L-Trp uncovered remarkable regio-promiscuity of nitration biocatalysts.

  12. Decomposition of metal nitrate solutions

    International Nuclear Information System (INIS)

    Haas, P.A.; Stines, W.B.

    1982-01-01

    Oxides in powder form are obtained from aqueous solutions of one or more heavy metal nitrates (e.g. U, Pu, Th, Ce) by thermal decomposition at 300 to 800 deg C in the presence of about 50 to 500% molar concentration of ammonium nitrate to total metal. (author)

  13. Evaluation of nitrate destruction methods

    International Nuclear Information System (INIS)

    Taylor, P.A.; Kurath, D.E.; Guenther, R.

    1993-01-01

    A wide variety of high nitrate-concentration aqueous mixed [radioactive and Resource Conservation and Recovery Act (RCRA) hazardous] wastes are stored at various US Department of Energy (DOE) facilities. These wastes will ultimately be solidified for final disposal, although the waste acceptance criteria for the final waste form is still being determined. Because the nitrates in the wastes will normally increase the volume or reduce the integrity of all of the waste forms under consideration for final disposal, nitrate destruction before solidification of the waste will generally be beneficial. This report describes and evaluates various technologies that could be used to destroy the nitrates in the stored wastes. This work was funded by the Department of Energy's Office of Technology Development, through the Chemical/Physical Technology Support Group of the Mixed Waste Integrated Program. All the nitrate destruction technologies will require further development work before a facility could be designed and built to treat the majority of the stored wastes. Several of the technologies have particularly attractive features: the nitrate to ammonia and ceramic (NAC) process produces an insoluble waste form with a significant volume reduction, electrochemical reduction destroys nitrates without any chemical addition, and the hydrothermal process can simultaneously treat nitrates and organics in both acidic and alkaline wastes. These three technologies have been tested using lab-scale equipment and surrogate solutions. At their current state of development, it is not possible to predict which process will be the most beneficial for a particular waste stream

  14. Nitrate removal through combination of nanofiltration and electrocatalysis; Nitratentfernung durch Kombination von Nanofiltration und Elektrokatalyse

    Energy Technology Data Exchange (ETDEWEB)

    Roehricht, M.; Stadlbauer, E.A.; Happel, H. [Fachhochschule Giessen (Germany). Zentrum fuer Umwelttechnik

    1999-07-01

    In a new process combination, nitrate-containing ground water is first of all separated by nanofiltration into a concentrate stream (some 25 %) and a largely nitrate-free permeate (75 %). Then the enriched nitrate in the concentrate is converted into nitrogen by means of electrocatalytic nitrate reduction. Whereas, in nanofiltration, a concentration takes place, electrocatalytic nitrate reduction is a process by which nitrate is converted into elemental nitrogen and, thus, removed. Nanofiltration is a membrane separating process making use of 'open' reverse osmosis membranes, which are characterized by high flow but also reduced retention. (orig.) [German] In einer neuen Verfahrenskombination wird das nitrathaltige Grundwasser zuerst durch Nanofiltration in einen Konzentratstrom (ca. 25%) und ein weitgehend nitratfreies Permeat (75%) aufgeteilt. Im Konzentrat wird dann mittels Elektrokatalytischer Nitratreduktion (EKN) das angereicherte Nitrat zu Stickstoff umgewandelt. Waehrend bei der Nanofiltration eine Aufkonzentrierung erfolgt, wird durch die Elektrokatalytische Nitratreduktion das Nitrat in elementaren Stickstoff umgewandelt und so entfernt. Die Nanofiltration ist ein Membrantrennverfahren, bei dem 'offene' Umkehrosmosemembranen eingesetzt werden, die einen hohen Fluss aber auch eine verminderte Rueckhaltung aufweisen. (orig.)

  15. Nitrated type III collagen as a biological marker of nitric oxide-mediated synovial tissue metabolism in osteoarthritis

    DEFF Research Database (Denmark)

    Richardot, P; Charni-Ben Tabassi, N; Toh, L

    2009-01-01

    OBJECTIVES: Nitric oxide (NO) is a major mediator of joint tissue inflammation and damage in osteoarthritis (OA) and mediates the nitration of tyrosine (Y*) residues in proteins. We investigated the nitration of type III collagen, a major constituent of synovial membrane, in knee OA. METHODS: A p...... investigation of oxidative-related alterations of synovial tissue metabolism in OA....

  16. A study on ion separation through liquid membrane

    International Nuclear Information System (INIS)

    Kang, Young Ho; Kwon, Sun Kil; Joo, Jae Oh; Whang, Sung Chan; Kim, Jung Do; Ann, Hyun Suk

    1991-12-01

    The flux of uranyl nitrate across cellulose acetate was determined using TOPO as a carrier. TOPO particles were physically entrapped in the membrane, which prepared by phase inversion method. The dominating factors were the amount of plasticizer, CTA-TOPO ratio in the membrane, uranium concentration in the feed solution, acidity and the solution temperature. And the transport phenomena of uranyl nitrate across this membrane were microscopically analysed by SEM. The increase of the membrane stability was observed when TOPO was used as a carrier. Another new technology to economically reduce the low-level liquid waste through the membrane is tested in a laboratory scale. (Author)

  17. Studying solubility of praseodymium(3) nitrate with nitrates of aniline, guanidine in aqueous solution

    International Nuclear Information System (INIS)

    Kuznetsova, L.S.; Zhuravlev, E.F.

    1977-01-01

    The solubility in the systems praseodymium nitrate-aniline nitrate-water(1) and praseodymium nitrate-guanidine nitrate-water(2) has been studied at 20 and 40 deg C. In the given temperature range the state diagrams of the systems correspond to the isotherms of the simple eutonic type. Aniline nitrate and hexahydrate of praseodymium nitrate in the first system and guanidine nitrate and hexahydrate of praseodymium nitrate in the second system are equilibrium solid phases. The most developed crystallization fields are those of amine nitrates; eutonics are enriched with praseodymium nitrate

  18. Low level nitrate or nitroethane preconditioning enhances the bactericidal effect of suboptimal experimental chlorate treatment against Escherichia coli and Salmonella Typhimurium but not Campylobacter in swine.

    Science.gov (United States)

    Anderson, Robin C; Jung, Yong Soo; Genovese, Kenneth J; McReynolds, Jackson L; Callaway, Todd R; Edrington, Thomas S; Harvey, Roger B; Nisbet, David J

    2006-01-01

    An experimental chlorate product that targets the respiratory nitrate reductase enzyme of bacteria such as Salmonella and Escherichia coli has shown promising results in reducing concentrations of these bacteria in the gut of food animals. Because expression of the target enzyme is induced by nitrate, we administered short-duration, low level nitrate or nitroethane preconditioning treatments to finishing swine to see if these would enhance the ability of an experimental chlorate product to kill these bacteria. Results from these studies showed that preconditioning the gut microflora of swine with low levels of nitrate or nitrocompounds enhanced (more than tenfold) the ability of the chlorate product to kill Salmonella and E. coli, but not Campylobacter. Further studies are needed before these compounds can be fed as feed additives to animals, although it is likely that nitrate preconditioning may be more near to market than the nitrocompounds, which may require more comprehensive review by regulatory authorities.

  19. Chloroplast Fe(III) chelate reductase activity is essential for seedling viability under iron limiting conditions.

    Science.gov (United States)

    Jeong, Jeeyon; Cohu, Christopher; Kerkeb, Loubna; Pilon, Marinus; Connolly, Erin L; Guerinot, Mary Lou

    2008-07-29

    Photosynthesis, heme biosynthesis, and Fe-S cluster assembly all take place in the chloroplast, and all require iron. Reduction of iron via a membrane-bound Fe(III) chelate reductase is required before iron transport across membranes in a variety of systems, but to date there has been no definitive genetic proof that chloroplasts have such a reduction system. Here we report that one of the eight members of the Arabidopsis ferric reductase oxidase (FRO) family, FRO7, localizes to the chloroplast. Chloroplasts prepared from fro7 loss-of-function mutants have 75% less Fe(III) chelate reductase activity and contain 33% less iron per microgram of chlorophyll than wild-type chloroplasts. This decreased iron content is presumably responsible for the observed defects in photosynthetic electron transport. When germinated in alkaline soil, fro7 seedlings show severe chlorosis and die without setting seed unless watered with high levels of soluble iron. Overall, our results provide molecular evidence that FRO7 plays a role in chloroplast iron acquisition and is required for efficient photosynthesis in young seedlings and for survival under iron-limiting conditions.

  20. Variability of nitrate and phosphate

    Digital Repository Service at National Institute of Oceanography (India)

    Sardessai, S.; Sundar, D.

    and the high-nitrate waters farther upstream led to a sharp increase in nitrates in the first few kilometres from the mouth of the Mandovi. Thus, at the end of the summer monsoon, the channels of the Mandovi and Zuari have nitrate concentrations of the order... in June. Throughout this period, the properties of the waters at the mouth migrate upstream owing to horizontal mixing. One consequence of this mixing is a steady rise in salinity in the channels of the Mandovi and Zuari. Since the concentration June 13...

  1. Methylenetetrahydrofolate reductase A1298C polymorphism and ...

    African Journals Online (AJOL)

    Methylenetetrahydrofolate reductase A1298C polymorphism and breast cancer risk: A meta analysis of 33 studies. ... were searched for case‑control studies relating the association between MTHFR A1298C polymorphism and BC risk and estimated summary odds ratios (ORs) with confidence intervals (CIs) for assessment.

  2. Xylose reductase from the thermophilic fungus Talaromyces ...

    Indian Academy of Sciences (India)

    Given the potential application of xylose reductase enzymes that preferentially utilize the reduced form of nicotinamide adenine dinucleotide (NADH) rather than NADPH in the fermentation of five carbon sugars by genetically engineered microorganisms, the coenzyme selectivity of TeXR was altered by site-directed ...

  3. Methylenetetrahydrofolate reductase (MTHFR) C677T gene ...

    Indian Academy of Sciences (India)

    vitamin B12 and riboflavin that are required in Hcy metabolic pathway. Gene that encodes the methylenete- trahydrofolate reductase (MTHFR) enzyme that .... tors like climate, food habits, lifestyle and genetic makeup are common. Validation of the results of the present study in different ethnic groups with larger sample ...

  4. phenotype correlation of methylene tetrahydrofolate reductase ...

    African Journals Online (AJOL)

    Rabah M. Shawky

    2014-06-21

    Jun 21, 2014 ... ORIGINAL ARTICLE. Study of genotype–phenotype correlation of methylene tetrahydrofolate reductase (MTHFR) gene polymorphisms in a sample of Egyptian autistic children. Rabah M. Shawky a,. *, Farida El-baz b. , Tarek M. Kamal c. , Reham M. Elhossiny b. ,. Mona A. Ahmed b. , Ghada H. El Nady d.

  5. Scandium extraction by methyltrialkylammonium nitrate from nitrate solutions

    International Nuclear Information System (INIS)

    Stepanov, S.I.; Kiyatkina, N.G.; Fedotov, O.N.

    1987-01-01

    Chemistry of scandium extraction by methyltrialkylammonium (MTAA) nitrate in toluene from nitrate solutions is studied. Methods of saturation, equilibrium shift, physicochemical analysis, isomolar series and UV-spectroscopy are used to determine the composition of extracted complexes. It is shown that with low saturation degrees of extractant (R 4 N) 6 Sc(NO 3 ) 9 complex is formed in organic phase and with saturation - (R 4 N) 3 xSc(NO 3 ) 6 complex

  6. Rare earth(3) nitrates extraction with trialkylmethylammonium nitrate in toluene

    International Nuclear Information System (INIS)

    Pyartman, A.K.; Kovalev, S.V.; Keskinov, V.A.; Khokhlova, N.V.

    1997-01-01

    Extraction of rare earth(3) nitrates [praseodymium(3)-lutetium(3)] with trialkylmethylammonium nitrate in toluene at T = 298.15 K and pH 2 is studied. Extraction isotherms are described with regard to formation of compounds of (R 4 N) i [Ln(NO 3 ) 3+i ] composition (i = 2, 3) in organic phase. Values of extraction constants are calculated, they are decreasing in the praseodymium(3) - lutetium(3) series

  7. Characterization of FRO1, a Pea Ferric-Chelate Reductase Involved in Root Iron Acquisition1

    Science.gov (United States)

    Waters, Brian M.; Blevins, Dale G.; Eide, David J.

    2002-01-01

    To acquire iron, many plant species reduce soil Fe(III) to Fe(II) by Fe(III)-chelate reductases embedded in the plasma membrane of root epidermal cells. The reduced product is then taken up by Fe(II) transporter proteins. These activities are induced under Fe deficiency. We describe here the FRO1 gene from pea (Pisum sativum), which encodes an Fe(III)-chelate reductase. Consistent with this proposed role, FRO1 shows similarity to other oxidoreductase proteins, and expression of FRO1 in yeast conferred increased Fe(III)-chelate reductase activity. Furthermore, FRO1 mRNA levels in plants correlated with Fe(III)-chelate reductase activity. Sites of FRO1 expression in roots, leaves, and nodules were determined. FRO1 mRNA was detected throughout the root, but was most abundant in the outer epidermal cells. Expression was detected in mesophyll cells in leaves. In root nodules, mRNA was detected in the infection zone and nitrogen-fixing region. These results indicate that FRO1 acts in root Fe uptake and they suggest a role in Fe distribution throughout the plant. Characterization of FRO1 has also provided new insights into the regulation of Fe uptake. FRO1 expression and reductase activity was detected only in Fe-deficient roots of Sparkle, whereas both were constitutive in brz and dgl, two mutants with incorrectly regulated Fe accumulation. In contrast, FRO1 expression was responsive to Fe status in shoots of all three plant lines. These results indicate differential regulation of FRO1 in roots and shoots, and improper FRO1 regulation in response to a shoot-derived signal of iron status in the roots of the brz and dgl mutants. PMID:12011340

  8. Characterization of FRO1, a pea ferric-chelate reductase involved in root iron acquisition.

    Science.gov (United States)

    Waters, Brian M; Blevins, Dale G; Eide, David J

    2002-05-01

    To acquire iron, many plant species reduce soil Fe(III) to Fe(II) by Fe(III)-chelate reductases embedded in the plasma membrane of root epidermal cells. The reduced product is then taken up by Fe(II) transporter proteins. These activities are induced under Fe deficiency. We describe here the FRO1 gene from pea (Pisum sativum), which encodes an Fe(III)-chelate reductase. Consistent with this proposed role, FRO1 shows similarity to other oxidoreductase proteins, and expression of FRO1 in yeast conferred increased Fe(III)-chelate reductase activity. Furthermore, FRO1 mRNA levels in plants correlated with Fe(III)-chelate reductase activity. Sites of FRO1 expression in roots, leaves, and nodules were determined. FRO1 mRNA was detected throughout the root, but was most abundant in the outer epidermal cells. Expression was detected in mesophyll cells in leaves. In root nodules, mRNA was detected in the infection zone and nitrogen-fixing region. These results indicate that FRO1 acts in root Fe uptake and they suggest a role in Fe distribution throughout the plant. Characterization of FRO1 has also provided new insights into the regulation of Fe uptake. FRO1 expression and reductase activity was detected only in Fe-deficient roots of Sparkle, whereas both were constitutive in brz and dgl, two mutants with incorrectly regulated Fe accumulation. In contrast, FRO1 expression was responsive to Fe status in shoots of all three plant lines. These results indicate differential regulation of FRO1 in roots and shoots, and improper FRO1 regulation in response to a shoot-derived signal of iron status in the roots of the brz and dgl mutants.

  9. The nitrate-reduction gene cluster components exert lineage-dependent contributions to optimization of Sinorhizobium symbiosis with soybeans.

    Science.gov (United States)

    Liu, Li Xue; Li, Qin Qin; Zhang, Yun Zeng; Hu, Yue; Jiao, Jian; Guo, Hui Juan; Zhang, Xing Xing; Zhang, Biliang; Chen, Wen Xin; Tian, Chang Fu

    2017-12-01

    Receiving nodulation and nitrogen fixation genes does not guarantee rhizobia an effective symbiosis with legumes. Here, variations in gene content were determined for three Sinorhizobium species showing contrasting symbiotic efficiency on soybeans. A nitrate-reduction gene cluster absent in S. sojae was found to be essential for symbiotic adaptations of S. fredii and S. sp. III. In S. fredii, the deletion mutation of the nap (nitrate reductase), instead of nir (nitrite reductase) and nor (nitric oxide reductase), led to defects in nitrogen-fixation (Fix - ). By contrast, none of these core nitrate-reduction genes were required for the symbiosis of S. sp. III. However, within the same gene cluster, the deletion of hemN1 (encoding oxygen-independent coproporphyrinogen III oxidase) in both S. fredii and S. sp. III led to the formation of nitrogen-fixing (Fix + ) but ineffective (Eff - ) nodules. These Fix + /Eff - nodules were characterized by significantly lower enzyme activity of glutamine synthetase indicating rhizobial modulation of nitrogen-assimilation by plants. A distant homologue of HemN1 from S. sojae can complement this defect in S. fredii and S. sp. III, but exhibited a more pleotropic role in symbiosis establishment. These findings highlighted the lineage-dependent optimization of symbiotic functions in different rhizobial species associated with the same host. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. Biochemical, Physiological and Transcriptomic Comparison between Burley and Flue-Cured Tobacco Seedlings in Relation to Carbohydrates and Nitrate Content

    Directory of Open Access Journals (Sweden)

    Yafei Li

    2017-12-01

    Full Text Available Burley tobacco is a genotype of chloroplast-deficient mutant with accumulates high levels of tobacco-specific nitrosamines (TSNAs which would induce malignant tumors in animals. Nitrate is a principle precursor of tobacco-specific nitrosamines. Nitrate content in burley tobacco was significantly higher than that in flue-cured tobacco. The present study investigated differences between the two tobacco types to explore the mechanisms of nitrate accumulation in burley tobacco. transcripts (3079 related to the nitrogen and carbon metabolism were observed. Expression of genes involved in carbon fixation, glucose and starch biosynthesis, nitrate translocation and assimilation were significantly low in burley tobacco than flue-cured tobacco. Being relative to flue-cured tobacco, burley tobacco was significantly lower at total nitrogen and carbohydrate content, nitrate reductase and glutamine synthetase activities, chlorophyll content and photosynthetic rate (Pn, but higher nitrate content. Burley tobacco required six-fold more nitrogen fertilizers than flue-cured tobacco, but both tobaccos had a similar leaf biomass. Reduced chlorophyll content and photosynthetic rate (Pn might result in low carbohydrate formation, and low capacity of nitrogen assimilation and translocation might lead to nitrate accumulation in burley tobacco.

  11. Nitrate augmented myocardial viability assessment

    International Nuclear Information System (INIS)

    Wadhwa, S.; Mansberb, R.; Fernandes, V.B.

    1997-01-01

    Full text: 24 hour 201 TI reinjection imaging improves myocardial viability detection when compared to standard 3-4 hour redistribution imaging, however, it is a time-consuming approach and some images do not provide adequate quality due to high background activity on the delayed scan. We tested whether sensitivity of redistribution and same day reinjection imaging could be improved by giving short-acting nitrates immediately prior to redistribution and reinjection imaging. Eighteen patients underwent a stress test (exercise or pharmacological) and 4 hour redistribution 201 TI SPECT study. Immediately after redistribution imaging, each patient was given 600 μg of sublingual glyceryl trinitrate and reimaged 15-20 minutes later (nitrate augmented image). Immediately following nitrate augmentation imaging, each patient was reinjected with 30 MBq of 201 TI and reimaged 20 minutes later (nitrate augmented reinjection images). Each patient returned 24 hours later and was reinjected with 40 MBq of 201 TI and imaged 20 minutes later (24 hour reinjection images). In all, each patient had five SPECT images as follows: stress/redistribution/ nitrate augmented redistribution/nitrate augmented same day reinjection/ 24 hour reinjection. The myocardium was divided into 11 segments and perfusion to each segment was scored by consensus method (2 blinded assessors) on a 4 point graded scale (0 = no perfusion, 1 = minimal perfusion, 2 = moderate perfusion, 3 = normal perfusion). Perfusion scores were analysed on a segment by segment basis; as well, each patient was given an overall perfusion score equal to the sum of the perfusion score for each segment. 150 segments with reduced perfusion were identified, of these 23 (15.3%) showed improvement in the redistribution images, 60 (40%) segments improved in the nitrate augmented images, 49 (32.7%) improved in the nitrate augmented reinjection images and 52 (34.7%) improved in the 24 hour reinjection images. To assess overall cardiac

  12. Disentangling the rhizosphere effect on nitrate reducers and denitrifiers: insight into the role of root exudates.

    Science.gov (United States)

    Henry, S; Texier, S; Hallet, S; Bru, D; Dambreville, C; Chèneby, D; Bizouard, F; Germon, J C; Philippot, L

    2008-11-01

    To determine to which extent root-derived carbon contributes to the effects of plants on nitrate reducers and denitrifiers, four solutions containing different proportions of sugar, organic acids and amino acids mimicking maize root exudates were added daily to soil microcosms at a concentration of 150 microg C g(-1) of soil. Water-amended soils were used as controls. After 1 month, the size and structure of the nitrate reducer and denitrifier communities were analysed using the narG and napA, and the nirK, nirS and nosZ genes as molecular markers respectively. Addition of artificial root exudates (ARE) did not strongly affect the structure or the density of nitrate reducer and denitrifier communities whereas potential nitrate reductase and denitrification activities were stimulated by the addition of root exudates. An effect of ARE composition was also observed on N(2)O production with an N(2)O:(N(2)O + N(2)) ratio of 0.3 in microcosms amended with ARE containing 80% of sugar and of 1 in microcosms amended with ARE containing 40% of sugar. Our study indicated that ARE stimulated nitrate reduction or denitrification activity with increases in the range of those observed with the whole plant. Furthermore, we demonstrated that the composition of the ARE affected the nature of the end-product of denitrification and could thus have a putative impact on greenhouse gas emissions.

  13. Effect of pharmaceutical potential endocrine disruptor compounds on protein disulfide isomerase reductase activity using di-eosin-oxidized-glutathione.

    Directory of Open Access Journals (Sweden)

    Danièle Klett

    Full Text Available BACKGROUND: Protein Disulfide Isomerase (PDI in the endoplasmic reticulum of all cells catalyzes the rearrangement of disulfide bridges during folding of membrane and secreted proteins. As PDI is also known to bind various molecules including hormones such as estradiol and thyroxin, we considered the hypothesis that adverse effects of endocrine-disrupter compounds (EDC could be mediated through their interaction with PDI leading to defects in membrane or secreted proteins. METHODOLOGY/PRINCIPAL FINDINGS: Taking advantage of the recent description of the fluorescence self quenched substrate di-eosin-oxidized-glutathione (DiE-GSSG, we determined kinetically the effects of various potential pharmaceutical EDCs on the in-vitro reductase activity of bovine liver PDI by measuring the fluorescence of the reaction product (E-GSH. Our data show that estrogens (ethynylestradiol and bisphenol-A as well as indomethacin exert an inhibition whereas medroxyprogesteroneacetate and nortestosterone exert a potentiation of bovine PDI reductase activity. CONCLUSIONS: The present data indicate that the tested EDCs could not only affect endocrine target cells through nuclear receptors as previously shown, but could also affect these and all other cells by positively or negatively affecting PDI activity. The substrate DiE-GSSG has been demonstrated to be a convenient substrate to measure PDI reductase activity in the presence of various potential EDCs. It will certainly be usefull for the screening of potential effect of all kinds of chemicals on PDI reductase activity.

  14. Biogenesis of plasma membrane cholesterol

    International Nuclear Information System (INIS)

    Lange, Y.

    1986-01-01

    A striking feature of the molecular organization of eukaryotic cells is the singular enrichment of their plasma membranes in sterols. The authors studies are directed at elucidating the mechanisms underlying this inhomogeneous disposition. Cholesterol oxidase catalyzes the oxidation of plasma membrane cholesterol in intact cells, leaving intracellular cholesterol pools untouched. With this technique, the plasma membrane was shown to contain 95% of the unesterified cholesterol of cultured human fibroblasts. Cholesterol synthesized from [ 3 H] acetate moved to the plasma membrane with a half-time of 1 h at 37 0 C. They used equilibrium gradient centrifugation of homogenates of biosynthetically labeled, cholesterol oxidase treated cells to examine the distribution of newly synthesized sterols among intracellular pools. Surprisingly, lanosterol, a major precursor of cholesterol, and intracellular cholesterol both peaked at much lower buoyant density than did 3-hydroxy-3-methylglutaryl-CoA reductase. This suggests that cholesterol biosynthesis is not taken to completion in the endoplasmic reticulum. The cholesterol in the buoyant fraction eventually moved to the plasma membrane. Digitonin treatment increased the density of the newly synthesized cholesterol fractions, indicating that nascent cholesterol in transit is associated with cholesterol-rich membranes. The authors are testing the hypothesis that the pathway of cholesterol biosynthesis is spatially organized in various intracellular membranes such that the sequence of biosynthetic steps both concentrates the sterol and conveys it to the plasma membrane

  15. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    Science.gov (United States)

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  16. Fundamentals on the biochemistry of peroxynitrite and protein tyrosine nitration

    Directory of Open Access Journals (Sweden)

    Silvina Bartesaghi

    2018-04-01

    Full Text Available In this review we provide an analysis of the biochemistry of peroxynitrite and tyrosine nitration. Peroxynitrite is the product of the diffusion-controlled reaction between superoxide (O2•- and nitric oxide (•NO. This process is in competition with the enzymatic dismutation of O2•- and the diffusion of •NO across cells and tissues and its reaction with molecular targets (e.g. guanylate cyclase. Understanding the kinetics and compartmentalization of the O2•- / •NO interplay is critical to rationalize the shift of •NO from a physiological mediator to a cytotoxic intermediate. Once formed, peroxynitrite (ONOO- and ONOOH; pKa = 6,8 behaves as a strong one and two-electron oxidant towards a series of biomolecules including transition metal centers and thiols. In addition, peroxynitrite anion can secondarily evolve to secondary radicals either via its fast reaction with CO2 or through proton-catalyzed homolysis. Thus, peroxynitrite can participate in direct (bimolecular and indirect (through secondary radical intermediates oxidation reactions; through these processes peroxynitrite can participate as cytotoxic effector molecule against invading pathogens and/or as an endogenous pathogenic mediator. Peroxynitrite can cause protein tyrosine nitration in vitro and in vivo. Indeed, tyrosine nitration is a hallmark of the reactions of •NO-derived oxidants in cells and tissues and serves as a biomarker of oxidative damage. Protein tyrosine nitration can mediate changes in protein structure and function that affect cell homeostasis. Tyrosine nitration in biological systems is a free radical process that can be promoted either by peroxynitrite-derived radicals or by other related •NO-dependent oxidative processes. Recently, mechanisms responsible of tyrosine nitration in hydrophobic biostructures such as membranes and lipoproteins have been assessed and involve the parallel occurrence and connection with lipid

  17. Sodium nitrate ingestion increases skeletal muscle nitrate content in humans.

    Science.gov (United States)

    Nyakayiru, Jean; Kouw, Imre W K; Cermak, Naomi M; Senden, Joan M; van Loon, Luc J C; Verdijk, Lex B

    2017-09-01

    Nitrate ([Formula: see text]) ingestion has been shown to have vasoactive and ergogenic effects that have been attributed to increased nitric oxide (NO) production. Recent observations in rodents suggest that skeletal muscle tissue serves as an endogenous [Formula: see text] "reservoir." The present study determined [Formula: see text] contents in human skeletal muscle tissue in a postabsorptive state and following ingestion of a sodium nitrate bolus (NaNO 3 ). Seventeen male, type 2 diabetes patients (age 72 ± 1 yr; body mass index 26.5 ± 0.5 kg/m 2 ; means ± SE) were randomized to ingest a dose of NaNO 3 (NIT; 9.3 mg [Formula: see text]/kg body wt) or placebo (PLA; 8.8 mg NaCl/kg body wt). Blood and muscle biopsy samples were taken before and up to 7 h following [Formula: see text] or placebo ingestion to assess [Formula: see text] [and plasma nitrite ([Formula: see text])] concentrations. Additionally, basal plasma and muscle [Formula: see text] concentrations were assessed in 10 healthy young (CON-Y; age 21 ± 1 yr) and 10 healthy older (CON-O; age 75 ± 1 yr) control subjects. In all groups, baseline [Formula: see text] concentrations were higher in muscle (NIT, 57 ± 7; PLA, 61 ± 7; CON-Y, 80 ± 10; CON-O, 54 ± 6 µmol/l) than in plasma (NIT, 35 ± 3; PLA, 32 ± 3; CON-Y, 38 ± 3; CON-O, 33 ± 3 µmol/l; P ≤ 0.011). Ingestion of NaNO 3 resulted in a sustained increase in plasma [Formula: see text], plasma [Formula: see text], and muscle [Formula: see text] concentrations (up to 185 ± 25 µmol/l) in the NIT group (time effect P nitrate ingestion is usually limited to the changes observed in plasma nitrate and nitrite concentrations. The present investigation assessed the skeletal muscle nitrate content in humans during the postabsorptive state, as well as following dietary nitrate ingestion. We show that basal nitrate content is higher in skeletal muscle tissue than in plasma and that ingestion of a dietary nitrate bolus strongly increases both plasma

  18. Removal of Nitrate from Groundwater by Anoxic Biological Reactor

    Directory of Open Access Journals (Sweden)

    Salwa Hajar

    2013-05-01

    Full Text Available    Groundwater pollution by  nitrate is considered as an important problem that must be addressed because many of the populations experiencing a big shortage of drinking water. In this study, the anoxic biological reactor is used to remove nitrates from groundwater. In this reactor,  bacteria convert nitrate to nitrogen under anoxic conditions and  lack of availability of nutrients  to get the necessary energy.     Five types of membrane bio-pregnant carrier within the reactor namely:  activated carbon (1-3 mm, granules of polyethylene (thickness of 3 mm X 4 mm Dia., bentonite (0.5-1 mm,  red wood (2X2X2 cm  and black sand (0.6 - 1.2 mm are employed. Four types nutrients namely:   Four types of carbonate which are: ethanol, molasses, glucose and acetic acid with the addition of sodium ortho phosphate dihydrogen (NaH2PO4 are used.     Laboratory results showed that the use of activated carbon gave the best results with respect to the removal of nitrates. The results indicated also that  acetic acid and molasses are the best nutrients for the reduction of nitrate ions. However, molasses may cause deposits on the inside walls of pipes and pumps.     The removal  efficiency of nitrate reached to 92% when using molasses and reached  to 99.7%  for acetic acid while it reached 54% when using glucose.

  19. Lapachol inhibition of vitamin K epoxide reductase and vitamin K quinone reductase.

    Science.gov (United States)

    Preusch, P C; Suttie, J W

    1984-11-01

    Lapachol [2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone] has been shown to be a potent inhibitor of both vitamin K epoxide reductase and the dithiothreitol-dependent vitamin K quinone reductase of rat liver microsomes in vitro. These observations explain the anticoagulant activity of lapachol previously observed in both rats and humans. Lapachol inhibition of the vitamin K epoxide and quinone reductases resembled coumarin anticoagulant inhibition, and was observed in normal strain but not in warfarin-resistant strain rat liver microsomes. This similarity of action suggests that the lactone functionality of the coumarins is not critical for their activity. The initial-velocity steady-state inhibition patterns for lapachol inhibition of the solubilized vitamin K epoxide reductase were consistent with tight binding of lapachol to the oxidized form of the enzyme, and somewhat lower affinity for the reduced form. It is proposed that lapachol assumes a 4-enol tautomeric structure similar to that of the 4-hydroxy coumarins. These structures are analogs of the postulated hydroxyvitamin K enolate intermediate bound to the oxidized form of the enzyme in the chemical reaction mechanism of vitamin K epoxide reductase, thus explaining their high affinity.

  20. Interacting TCP and NLP transcription factors control plant responses to nitrate availability.

    Science.gov (United States)

    Guan, Peizhu; Ripoll, Juan-José; Wang, Renhou; Vuong, Lam; Bailey-Steinitz, Lindsay J; Ye, Dening; Crawford, Nigel M

    2017-02-28

    Plants have evolved adaptive strategies that involve transcriptional networks to cope with and survive environmental challenges. Key transcriptional regulators that mediate responses to environmental fluctuations in nitrate have been identified; however, little is known about how these regulators interact to orchestrate nitrogen (N) responses and cell-cycle regulation. Here we report that teosinte branched1/cycloidea/proliferating cell factor1-20 (TCP20) and NIN-like protein (NLP) transcription factors NLP6 and NLP7, which act as activators of nitrate assimilatory genes, bind to adjacent sites in the upstream promoter region of the nitrate reductase gene, NIA1 , and physically interact under continuous nitrate and N-starvation conditions. Regions of these proteins necessary for these interactions were found to include the type I/II Phox and Bem1p (PB1) domains of NLP6&7, a protein-interaction module conserved in animals for nutrient signaling, and the histidine- and glutamine-rich domain of TCP20, which is conserved across plant species. Under N starvation, TCP20-NLP6&7 heterodimers accumulate in the nucleus, and this coincides with TCP20 and NLP6&7-dependent up-regulation of nitrate assimilation and signaling genes and down-regulation of the G 2 /M cell-cycle marker gene, CYCB1;1 TCP20 and NLP6&7 also support root meristem growth under N starvation. These findings provide insights into how plants coordinate responses to nitrate availability, linking nitrate assimilation and signaling with cell-cycle progression.

  1. Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and age of onset in schizophrenia: A combined analysis of independent samples

    DEFF Research Database (Denmark)

    Saetre, Peter; Vares, Maria; Werge, Thomas

    2011-01-01

    Methylenetetrahydrofolate reductase (MTHFR) is involved in the one-carbon cycle, which is of importance for nucleotide synthesis and methylation of DNA, membranes, proteins and lipids. The MTHFR gene includes two common polymorphisms (rs1801133 or C677T; rs1801131 or A1298C) which both alter enzy...

  2. Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and age of onset in schizophrenia: a combined analysis of independent samples

    NARCIS (Netherlands)

    Saetre, P.; Vares, M.; Werge, T.; Andreassen, O.A.; Arinami, T.; Ishiguro, H.; Nanko, S.; Tan, E.; Han, D.H.; Roffman, J.L.; Muntjewerff, J.W.; Jagodzinski, P.P.; Kempisty, B.; Hauser, J.; Vilella, E.; Betcheva, E.; Nakamura, Y.; Regland, B.; Agartz, I.; Hall, H.; Terenius, L.; Jonsson, E.G.

    2011-01-01

    Methylenetetrahydrofolate reductase (MTHFR) is involved in the one-carbon cycle, which is of importance for nucleotide synthesis and methylation of DNA, membranes, proteins and lipids. The MTHFR gene includes two common polymorphisms (rs1801133 or C677T; rs1801131 or A1298C) which both alter enzyme

  3. Radiation chemistry of nitrate ices

    International Nuclear Information System (INIS)

    Kishore, K.; Moorthy, P.N.; Rao, K.N.

    1978-01-01

    The yields of various products formed in γ-irradiated nitrate ices, viz NO 2 - , H 2 O 2 , O 2 and H 2 , have been measured at different nitrate concentrations. Daniel's method of partition of yields has been employed to evaluate the direct and indirect effect contributions to the yields of the first three products. G(H 2 ) is close to zero at all nitrate concentrations above approximately 0.5 mol dm -3 . The mechanism of product formation has been discussed in the light of various reactions put forth to explain the radiolysis of fluid aqueous nitrate solutions. The effect of various scavengers for the primary species on the product yields has also been investigated. From this it is inferred that nitrate is able to scavenge both the reducing species, viz. H and e - sub(m) giving nitrite and possibly also the holes (h + sub(m)) giving O 2 , and excited water molecules (H 2 O*) giving H 2 O 2 and additional nitrite. (author)

  4. Changes of sodium nitrate, nitrite, and N-nitrosodiethylamine during in vitro human digestion.

    Science.gov (United States)

    Kim, Hyeong Sang; Hur, Sun Jin

    2017-06-15

    This study aimed to determine the changes in sodium nitrate, sodium nitrite, and N-nitrosodiethylamine (NDEA) during in vitro human digestion, and the effect of enterobacteria on the changes in these compounds. The concentrations of nitrate, nitrite, and NDEA were significantly reduced from 150, 150, and 1ppm to 42.8, 63.2, and 0.85ppm, respectively, during in vitro human digestion (pdigestion. This study is the first to report that E. coli can dramatically reduce the amount of nitrite during in vitro human digestion and this may be due to the effect of nitrite reductase present in E. coli. We therefore conclude that the amounts of potentially harmful substances and their toxicity can be decreased during human digestion. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...

  6. Leishmania chagasi: uptake of iron bound to lactoferrin or transferrin requires an iron reductase.

    Science.gov (United States)

    Wilson, Mary E; Lewis, Troy S; Miller, Melissa A; McCormick, Michael L; Britigan, Bradley E

    2002-03-01

    Leishmania chagasi can utilize iron bound to transferrin, lactoferrin, or other chelates. We investigated the mechanism of iron uptake. Promastigotes preferentially took up iron in a reduced rather than an oxidized form, suggesting that extracellular iron must be reduced prior to internalization. Similar to literature reports, a 70-kDa protein in promastigote membrane-containing microsomes bound to [125I]-labeled transferrin. However, [125I]lactoferrin and [125I]albumin also bound a similar 70-kDa protein, suggesting that binding might not be specific. Both total and fractionated promastigotes exhibited an NADPH-dependent iron reductase activity. In contrast to trypanosomes, which take up transferrin through a specific receptor, these data support a model in which a parasite-associated or secreted reductase reduces ferric to ferrous iron, decreasing its affinity for the extracellular chelate and allowing it to be readily internalized by the parasite. This could account for the ability of the parasite to utilize iron from multiple sources in diverse host environments. Index Descriptors and Abbreviations. Index descriptors: Cryptococcus neoformans, Histoplasma capsulatum, iron, iron reductase, lactoferrin, L. chagasi, leishmaniasis, nutrient acquisition, protozoan, Saccharomyces cerevisiae, Trypanosoma brucei, Trypanosoma cruzi, transferrin; Abbreviations used: DNA, deoxyribonucleic acid; DTT, dithiothreitol; HBSS, Hanks' balanced salt solution; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NEM, N-ethylmaleimide; RNA, ribonucleic acid.

  7. Research progress on the roles of aldose reductase in diabetic retinopathy

    Directory of Open Access Journals (Sweden)

    Hong-Zhe Li

    2015-07-01

    Full Text Available Aldose reductase(ARbelonging to nicotinamide-adenine dinucleotide phosphate(NADPH-dependent aldehyde-keto reductase superfamily, is the key rate-limiting enzyme in the polyol pathway which plays an important role in the body's high-sugar metabolism. AR is widely present in the kidneys, blood vessels, lens, retina, heart, skeletal muscle and other tissues and organs, converts glucose to sorbitol which easy permeability of cell membranes, cause cell swelling, degeneration, necrosis, and have a close relationship with the development of chronic complications of diabetes mellitus. Diabetic retinopathy(DRis a multifactorial disease, the exact cause is currently unknown, but polyol pathway has been demonstrated to play an important role in the pathogenesis of DR. Clinical risk factors such as blood sugar control, blood pressure and other treatments for DR only play a part effect of remission or invalid, if we can find out DR genes associated with the disease, this will contribute to a better understanding of the pathological mechanisms and contribute to the development of new treatments and drugs. The current research progress of AR, AR gene polymorphism, Aldose reductase inhibitors to DR was reviewed in this article.

  8. The relationship between the nitrogen and nitrate content and nitrate ...

    African Journals Online (AJOL)

    The interrelationships between the nitrate-N and nitrogen content and dry matter yield of Midmar ryegrass (Lolium multiflorum cv. Midmar) were investigated. Data were collected from N fertility trials, from two seasons (1985 and 1987) on four soil sites (Metz, Griffin, Clovelly and Katspruit) with N fertilizer rates ranging from 0 ...

  9. Proteomic analysis of peroxynitrite-induced protein nitration in isolated beef heart mitochondria.

    Science.gov (United States)

    Kohutiar, M; Eckhardt, A; Mikšík, I; Šantorová, P; Wilhelm, J

    2018-01-05

    Mitochondria are exposed to reactive nitrogen species under physiological conditions and even more under several pathologic states. In order to reveal the mechanism of these processes we studied the effects of peroxynitrite on isolated beef heart mitochondria in vitro. Peroxynitrite has the potential to nitrate protein tyrosine moieties, break the peptide bond, and eventually release the membrane proteins into the solution. All these effects were found in our experiments. Mitochondrial proteins were resolved by 2D electrophoresis and the protein nitration was detected by immunochemical methods and by nano LC-MS/MS. Mass spectrometry confirmed nitration of ATP synthase subunit beta, pyruvate dehydrogenase E1 component subunit beta, citrate synthase and acetyl-CoA acetyltransferase. Immunoblot detection using chemiluminiscence showed possible nitration of other proteins such as cytochrome b-c1 complex subunit 1, NADH dehydrogenase [ubiquinone] iron-sulfur protein 2, elongation factor Tu, NADH dehydrogenase [ubiquinone] flavoprotein 2, heat shock protein beta-1and NADH dehydrogenase [ubiquinone] iron-sulfur protein 8. ATP synthase beta subunit was nitrated both in membrane and in fraction prepared by osmotic lysis. The high sensitivity of proteins to nitration by peroxynitrite is of potential biological importance, as these enzymes are involved in various pathways associated with energy production in the heart.

  10. Efficiency of nitrate uptake in spinach : impact of external nitrate concentration and relative growth rate on nitrate influx and efflux

    NARCIS (Netherlands)

    Ter Steege, MW; Stulen, [No Value; Wiersema, PK; Posthumus, F; Vaalburg, W

    1999-01-01

    Regulation of nitrate influx and efflux in spinach (Spinacia oleracea L., cv. Subito), was studied in short-term label experiments with N-13- and N-15-nitrate. Nitrate fluxes were examined in relation to the N demand for growth, defined as relative growth rate (RGR) times plant N concentration.

  11. Nitrate and bicarbonate selective CHEMFETs

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Engbersen, Johannes F.J.; Reinhoudt, David

    1995-01-01

    The development of durable anion selective CHEMFET micro sensors is described. Selectivity in these sensors is either obtained from differences in hydration energy of the anions (the Hlofmeister series, giving nitrate selectivity) or by introduction of a new class of uranyl salophene ionophores

  12. Extreme nitrite tolerance in the clown knifefish Chitala ornata is linked to up-regulation of methaemoglobin reductase activity.

    Science.gov (United States)

    Gam, Le Thi Hong; Jensen, Frank Bo; Damsgaard, Christian; Huong, Do Thi Thanh; Phuong, Nguyen Thanh; Bayley, Mark

    2017-06-01

    The clown knifefish is a facultative air breather, which is widely farmed in freshwater ponds in Vietnam. Here we report a very high nitrite tolerance (96h LC 50 of 7.82mM) in this species and examine the effects of 1mM (LC 5 ) and 2.5mM (LC 10 ) ambient nitrite on haemoglobin (Hb) derivatives, electrolyte levels, acid-base status, and total body water content during 7days of exposure. Furthermore, we tested the hypothesis that erythrocyte methaemoglobin (metHb) reductase activity is upregulated by nitrite exposure. Plasma nitrite levels increased for 2-3days but stayed below environmental levels and fell towards control values during the last half of the exposure period. Plasma nitrate, in contrast, rose continuously, reflecting detoxification of nitrite to nitrate. MetHb generated from the reaction between nitrite and erythrocyte Hb reached 38% at day 2, but then decreased to 17% by the end of experiment. The first order rate constant for metHb reduction by erythrocyte metHb reductase increased from 0.01 in controls to 0.046min -1 after 6days of nitrite exposure, showing up-regulation of this enzyme. While such upregulation has been suggested in nitrite-exposed fish species, this study provides the first experimental evidence. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Human carbonyl reductase 4 is a mitochondrial NADPH-dependent quinone reductase.

    Science.gov (United States)

    Endo, Satoshi; Matsunaga, Toshiyuki; Kitade, Yukio; Ohno, Satoshi; Tajima, Kazuo; El-Kabbani, Ossama; Hara, Akira

    2008-12-26

    A protein encoded in the gene Cbr4 on human chromosome 4q32.3 belongs to the short-chain dehydrogenase/reductase family. Contrary to the functional annotation as carbonyl reductase 4 (CBR4), we show that the recombinant tetrameric protein, composed of 25-kDa subunits, exhibits NADPH-dependent reductase activity for o- and p-quinones, but not for other aldehydes and ketones. The enzyme was insensitive to dicumarol and quercetin, potent inhibitors of cytosolic quinone reductases. The 25-kDa CBR4 was detected in human liver, kidney and cell lines on Western blotting using anti-CBR4 antibodies. The overexpression of CBR4 in bovine endothelial cells reveals that the enzyme has a non-cleavable mitochondrial targeting signal. We further demonstrate that the in vitro quinone reduction by CBR4 generates superoxide through the redox cycling, and suggest that the enzyme may be involved in the induction of apoptosis by cytotoxic 9,10-phenanthrenequinone.

  14. Structure and mechanism of dimethylsulfoxide reductase, a molybdopterin-containing enzyme of DMSO reductase family

    International Nuclear Information System (INIS)

    McEwan, A.G.; Ridge, J.P.; McDevitt, C.A.; Hanson, G.R.

    2001-01-01

    Full text: Apart from nitrogenase, enzymes containing molybdenum are members of a superfamily, the molybdopterin-containing enzymes. Most of these enzymes catalyse an oxygen atom transfer and two electron transfer reaction. During catalysis the Mo at the active site cycles between the Mo(VI) and Mo(IV) states. The DMSO reductase family of molybdopterin-containing enzymes all contain a bis(molybdopterin guanine dinucleotide)Mo cofactor and over thirty examples have now been described. Over the last five years crystal structures of dimethylsulfoxide (DMSO) reductase and four other enzymes of the DMSO reductase family have revealed that enzymes of this family have a similar tertiary structure. The Mo atom at the active site is coordinated by four thiolate ligands provided by the dithiolene side chains of the two MGD molecules of the bis(MGD)Mo cofactor as well as a ligand provided by an amino acid side chain. In addition, an oxygen atom in the form of an oxo, hydroxo or aqua group is also coordinated to the Mo atom. In the case of dimethylsulfoxide reductase X-ray crystallography of the product-reduced species and Raman spectroscopy has demonstrated that the enzyme contains a single exchangeable oxo group that is H-bonded to W116

  15. Nitroreductase reactions of Arabidopsis thaliana thioredoxin reductase.

    Science.gov (United States)

    Miskiniene, V; Sarlauskas, J; Jacquot, J P; Cenas, N

    1998-09-07

    Arabidopsis thaliana NADPH:thioredoxin reductase (TR, EC 1.6.4.5) catalyzed redox cycling of aromatic nitrocompounds, including the explosives 2,4,6-trinitrotoluene and tetryl, and the herbicide 3,5-dinitro-o-cresol. The yield of nitro anion radicals was equal to 70-90%. Redox cycling of tetryl was accompanied by formation of N-methylpicramide. Bimolecular rate constants of nitroaromatic reduction (kcat/Km) and reaction catalytic constants (kcat) increased upon an increase in oxidant single-electron reduction potential (E(1)7). Using compounds with an unknown E(1)7 value, the reactivity of TR increased parallelly to the increase in reactivity of ferredoxin:NADP+ reductase of Anabaena PCC 7119 (EC 1.18.1.2). This indicated that the main factor determining reactivity of nitroaromatics towards TR was their energetics of single-electron reduction. Incubation of reduced TR in the presence of tetryl or 2,4-dinitrochlorobenzene resulted in a loss of thioredoxin reductase activity, most probably due to modification of reduced catalytic disulfide, whereas nitroreductase reaction rates were unchanged. This means that on the analogy of quinone reduction by TR (D. Bironaite, Z. Anusevicius, J.-P. Jacquot, N. Cenas, Biochim. Biophys. Acta 1383 (1998) 82-92), FAD and not catalytic disulfide of TR was responsible for the reduction of nitroaromatics. Tetryl, 2,4,6-trinitrotoluene and thioredoxin increased the FAD fluorescence intensity of TR. This finding suggests that nitroaromatics may bind close to the thioredoxin-binding site at the catalytic disulfide domain of TR, and induce a conformational change of enzymes (S.B. Mulrooney, C.H. Williams Jr., Protein Sci. 6 (1997) 2188-2195). Our data indicate that certain nitroaromatic herbicides, explosives and other classes of xenobiotics may interfere with the reduction of thioredoxin by plant TR, and confer prooxidant properties to this antioxidant enzyme.

  16. Genetics of nitrate accumulation in lettuce

    OpenAIRE

    Reinink, K.

    1993-01-01

    This study evaluated the prospects of breeding for low nitrate content in lettuce ( Lactuca sativa L.). A lettuce collection was screened and accessions with low nitrate content were identified. These were used to study the genetics of nitrate accumulation. Nitrate accumulation inherited quantitatively, in a mainly additive fashion with only minor effects of dominance. No important maternal effects were detected. Estimates of the additive genotypic variance and t...

  17. Structural basis for dynamic mechanism of nitrate/nitrite antiport by NarK.

    Science.gov (United States)

    Fukuda, Masahiro; Takeda, Hironori; Kato, Hideaki E; Doki, Shintaro; Ito, Koichi; Maturana, Andrés D; Ishitani, Ryuichiro; Nureki, Osamu

    2015-05-11

    NarK belongs to the nitrate/nitrite porter (NNP) family in the major facilitator superfamily (MFS) and plays a central role in nitrate uptake across the membrane in diverse organisms, including archaea, bacteria, fungi and plants. Although previous studies provided insight into the overall structure and the substrate recognition of NarK, its molecular mechanism, including the driving force for nitrate transport, remained elusive. Here we demonstrate that NarK is a nitrate/nitrite antiporter, using an in vitro reconstituted system. Furthermore, we present the high-resolution crystal structures of NarK from Escherichia coli in the nitrate-bound occluded, nitrate-bound inward-open and apo inward-open states. The integrated structural, functional and computational analyses reveal the nitrate/nitrite antiport mechanism of NarK, in which substrate recognition is coupled to the transport cycle by the concomitant movement of the transmembrane helices and the key tyrosine and arginine residues in the substrate-binding site.

  18. Nitrate transporters in leaves and their potential roles in foliar uptake of nitrogen dioxide

    Directory of Open Access Journals (Sweden)

    Yanbo eHu

    2014-07-01

    Full Text Available While plant roots are specialized organs for the uptake and transport of water and nutrients, the absorption of gaseous or liquid mineral elements by aerial plant parts has been recognized since more than one century. Nitrogen (N is an essential macronutrient which generally absorbed either as nitrate (NO3- or ammonium (NH4+ by plant roots. Gaseous nitrogen pollutants like N dioxide (NO2 can also be absorbed by plant surfaces and assimilated via the NO3– assimilation pathway. The subsequent NO3– flux may induce or repress the expression of various NO3–-responsive genes encoding for instance, the transmembrane transporters, NO3–/NO2– (nitrite reductase, or assimilatory enzymes involved in N metabolism. Based on the existing information, the aim of this review was to theoretically analyze the potential link between foliar NO2 absorption and N transport and metabolism. For such purpose, an overview of the state of knowledge on the NO3– transporter genes identified in leaves or shoots of various species and their roles for NO3– transport across the tonoplast and plasma membrane, in addition to the process of phloem loading is briefly provided. It is assumed that a NO2-induced ac-cumulation of NO3–/NO2– may alter the expression of such genes, hence linking transmembrane NO3– transporters and foliar uptake of NO2. It is likely that NRT1/NRT2 gene expression and spe-cies-dependent apoplastic buffer capacity may be also related to the species-specific foliar NO2 uptake process. It is concluded that further work focusing on the expression of NRT1 (NRT1.1, NRT1.7, NRT1.11 and NRT1.12, NRT2 (NRT2.1, NRT2.4 and NRT2.5 and chloride channel family genes (CLCa and CLCd may help us elucidate the physiological and metabolic response of plants fumigated with NO2.

  19. Nitrate tolerance impairs nitric oxide-mediated vasodilation in vivo

    DEFF Research Database (Denmark)

    Laursen, Jørn Bech; Boesgaard, Søren; Poulsen, Henrik E.

    1996-01-01

    Nitrates, Nitrate tolerence, Nitric oxide, acetylcholine, N-acetylcholine, N-acetylcysteine, L-NAME, Rat, Anesthetized......Nitrates, Nitrate tolerence, Nitric oxide, acetylcholine, N-acetylcholine, N-acetylcysteine, L-NAME, Rat, Anesthetized...

  20. 21 CFR 172.160 - Potassium nitrate.

    Science.gov (United States)

    2010-04-01

    ... Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN...

  1. 21 CFR 172.170 - Sodium nitrate.

    Science.gov (United States)

    2010-04-01

    ... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate. 172.170 Section 172.170 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN...

  2. 76 FR 47238 - Ammonium Nitrate From Russia

    Science.gov (United States)

    2011-08-04

    ... COMMISSION Ammonium Nitrate From Russia Determination On the basis of the record \\1\\ developed in the subject... order on ammonium nitrate from Russia would be likely to lead to continuation or recurrence of material... Commission are contained in USITC Publication 4249 (August 2011), entitled Ammonium Nitrate from Russia...

  3. Method of producing thin cellulose nitrate film

    International Nuclear Information System (INIS)

    Lupica, S.B.

    1975-01-01

    An improved method for forming a thin nitrocellulose film of reproducible thickness is described. The film is a cellulose nitrate film, 10 to 20 microns in thickness, cast from a solution of cellulose nitrate in tetrahydrofuran, said solution containing from 7 to 15 percent, by weight, of dioctyl phthalate, said cellulose nitrate having a nitrogen content of from 10 to 13 percent

  4. High temperature interaction studies on equimolar nitrate mixture of uranyl nitrate hexahydrate and gadolinium nitrate hexahydrate

    International Nuclear Information System (INIS)

    Kalekar, Bhupesh B.; Raje, Naina; Reddy, A.V.R.

    2015-01-01

    Rare earths including gadolinium form a sizeable fraction of the fission products in the nuclear fission of fissile material in the reactor. These fission products can interact with uranium dioxide fuel and can form various compounds which can alter the thermal behavior of the fuel. The mixed oxide formed due to the high temperature interactions of mixture of uranyl nitrate hexahydrate (UNH) and gadolinium nitrate hexahydrate (GdNH) has been studied using thermal and X- ray diffraction techniques. The equimolar mixture of UNH and GdNH was prepared by mixing the weighed amount of individual nitrates and grinding gently with mortar and pestle. Thermogravimetry (TG) measurements were carried out by separately heating 100 mg of mixture and individual nitrates at heating rate of 10°C min -1 using Netzsch thermal analyzer (Model No.: STA 409 PC Luxx) in high purity nitrogen atmosphere with a flow rate of 120 mL min -1 . The XRD measurement was carried out on a Philips X-ray diffractometer (Model PW1710) using nickel-filtered Cu-Kα radiation

  5. Biogenesis of membrane bound respiratory complexes in Escherichia coli

    OpenAIRE

    Price, Claire E.; Driessen, Arnold J.M.

    2010-01-01

    Escherichia colt is one of the preferred bacteria for studies on the energetics and regulation of respiration Respiratory chains consist of primary dehydrogenases and terminal reductases or oxidases linked by quinones. In order to assemble this complex arrangement of protein complexes, synthesis of the subunits occurs in the cytoplasm followed by assembly in the cytoplasm and/or membrane, the incorporation of metal or organic cofactors and the anchoring of the complex to the membrane In the c...

  6. Yttrium Nitrate mediated Nitration of Phenols at room temperature in ...

    Indian Academy of Sciences (India)

    chromatographic purification. 2.1 Procedure for Nitration of Phenol. Phenol (94 mg, 1 mmol) dissolved in 3 mL glacial acetic acid in a 50 mL test tube was treated with solid Y(NO3)3.6H2O. (383 mg, 1 mmol) with constant shaking at RT for 10 min. The reaction was monitored by TLC at 10% EtOAc in. Petroleum benzene.

  7. Methemoglobin reductase activity in intact fish red blood cells

    DEFF Research Database (Denmark)

    Jensen, Frank B; Nielsen, Karsten

    2018-01-01

    Red blood cells (RBCs) possess methemoglobin reductase activity that counters the ongoing oxidation of hemoglobin (Hb) to methemoglobin (metHb), which in circulating blood is caused by Hb autoxidation or reactions with nitrite. We describe an assay for determining metHb reductase activity in intact...

  8. 21 CFR 864.7375 - Glutathione reductase assay.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... reductase deficiency, or riboflavin deficiency. (b) Classification. Class II (performance standards). [45 FR...

  9. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration*

    OpenAIRE

    Olah, George A.; Narang, Subhash C.; Olah, Judith A.

    1981-01-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an α-nitronaphthalene to β-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aroma...

  10. Methionine sulfoxide reductase A protects neuronal cells against brief hypoxia/reoxygenation

    Science.gov (United States)

    Yermolaieva, Olena; Xu, Rong; Schinstock, Carrie; Brot, Nathan; Weissbach, Herbert; Heinemann, Stefan H.; Hoshi, Toshinori

    2004-02-01

    Hypoxia/reoxygenation induces cellular injury by promoting oxidative stress. Reversible oxidation of methionine in proteins involving the enzyme peptide methionine sulfoxide reductase type A (MSRA) is postulated to serve a general antioxidant role. Therefore, we examined whether overexpression of MSRA protected cells from hypoxia/reoxygenation injury. Brief hypoxia increased the intracellular reactive oxygen species (ROS) level in PC12 cells and promoted apoptotic cell death. Adenovirus-mediated overexpression of MSRA significantly diminished the hypoxia-induced increase in ROS and facilitated cell survival. Measurements of the membrane potentials of intact mitochondria in PC12 cells and of isolated rat liver mitochondria showed that hypoxia induced depolarization of the mitochondrial membrane. The results demonstrate that MSRA plays a protective role against hypoxia/reoxygenation-induced cell injury and suggest the therapeutic potential of MSRA in ischemic heart and brain disease.

  11. Localization of Methyl-Coenzyme M Reductase as Metabolic Marker for Diverse Methanogenic Archaea

    Directory of Open Access Journals (Sweden)

    Christoph Wrede

    2013-01-01

    Full Text Available Methyl-Coenzyme M reductase (MCR as key enzyme for methanogenesis as well as for anaerobic oxidation of methane represents an important metabolic marker for both processes in microbial biofilms. Here, the potential of MCR-specific polyclonal antibodies as metabolic marker in various methanogenic Archaea is shown. For standard growth conditions in laboratory culture, the cytoplasmic localization of the enzyme in Methanothermobacter marburgensis, Methanothermobacter wolfei, Methanococcus maripaludis, Methanosarcina mazei, and in anaerobically methane-oxidizing biofilms is demonstrated. Under growth limiting conditions on nickel-depleted media, at low linear growth of cultures, a fraction of 50–70% of the enzyme was localized close to the cytoplasmic membrane, which implies “facultative” membrane association of the enzyme. This feature may be also useful for assessment of growth-limiting conditions in microbial biofilms.

  12. Membrane fusion

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    At Stanford University, Boxer lab, I worked on membrane fusion of small unilamellar lipid vesicles to flat membranes tethered to glass surfaces. This geometry closely resembles biological systems in which liposomes fuse to plasma membranes. The fusion mechanism was studied using DNA zippering...... between complementary strands linked to the two apposing membranes closely mimicking the zippering mechanism of SNARE fusion complexes....

  13. Biobased Membrane

    NARCIS (Netherlands)

    Koenders, E.A.B.; Zlopasa, J.; Picken, S.J.

    2015-01-01

    The present invention is in the field of a composition for forming a bio-compatible membrane applicable to building material, such as concrete, cement, etc., to a meth od of applying said composition for forming a bio-compatible membrane, a biocompatible membrane, use of said membrane for various

  14. Polyether sulfone membrane modeling and construction for the ...

    African Journals Online (AJOL)

    Polyether sulfone membrane modeling and construction for the removal of nitrate from water using ion interference sulfate and iron nano-particle. ... The aim of this study was constructed the polyether sulfone membrane and modelling it, and for checking impact pressure, the amount of iron nanoparticles and sulfate iron ...

  15. Nitrate Removal from Ground Water: A Review

    Directory of Open Access Journals (Sweden)

    Archna

    2012-01-01

    Full Text Available Nitrate contamination of ground water resources has increased in Asia, Europe, United States, and various other parts of the world. This trend has raised concern as nitrates cause methemoglobinemia and cancer. Several treatment processes can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that biological denitrification is more acceptable for nitrate removal than reverse osmosis and ion exchange. This paper reviews the developments in the field of nitrate removal processes which can be effectively used for denitrifying ground water as well as industrial water.

  16. Inhibition of NADH-ubiquinone reductase activity by N,N'-dicyclohexylcarbodiimide and correlation of this inhibition with the occurrence of energy-coupling site 1 in various organisms

    International Nuclear Information System (INIS)

    Yagi, T.

    1987-01-01

    The NADH-ubiquinone reductase activity of the respiratory chains of several organisms was inhibited by the carboxyl-modifying reagent N,N'-dicyclohexylcarbodiimide (DCCD). This inhibition correlated with the presence of an energy-transducing site in this segment of the respiratory chain. Where the NADH-quinone reductase segment involved an energy-coupling site (e.g., in bovine heart and rat liver mitochondria, and in Paracoccus denitrificans, Escherichia coli, and Thermus thermophilus HB-8 membranes), DCCD acted as an inhibitor of ubiquinone reduction by NADH. By contrast, where energy-coupling site 1 was absent (e.g., in Saccharomyces cerevisiae mitochondria and BacilLus subtilis membranes), there was no inhibition of NADH-ubiquinone reductase activity by DCCD. In the bovine and P. denitrificans systems, DCCD inhibition was pseudo first order with respect to incubation time, and reaction order with respect to inhibitor concentration was close to unity, indicating that inhibition resulted from the binding of one inhibitor molecule per active unit of NADH-ubiquinone reductase. In the bovine NADH-ubiquinone reductase complex (complex I), [ 14 C]DCCD was preferentially incorporated into two subunits of molecular weight 49,000 and 29,000. The time course of labeling of the 29,000 molecular weight subunit with [ 14 C]DCCD paralleled the time course of inhibition of NADH-ubiquinone reductase activity

  17. Nitrate metabolism in the gromiid microbial universe

    DEFF Research Database (Denmark)

    Høgslund, Signe; Risgaard-Petersen, Nils; Cedhagen, Tomas

    Eukaryotic nitrate respiration supported by intracellular nitrate storages contributes substantially to the nitrogen cycle. Research focus is currently directed towards two phyla: Foraminifera and diatoms, but the widespread Gromia in the Rhizaria may be another key organism. These giant protists...... enclose and regulate a small biogeochemical universe within their cell. Their transparent proteinaceous cell wall surrounds a complex matrix consisting of sediment, bacteria and nitrate which is concentrated to hundreds of mM in the gromiid cell. The nitrate is respired to dinitrogen, but in contrast...... to the findings of eukaryotic mediated nitrate reduction in some foraminifera and diatoms, nitrate respiration in gromiids seems to be mediated by bacterial endosymbionts. The role of endobionts in nitrate accumulating eukaryotes is of fundamental importance for understanding the evolutionary path...

  18. Denitrification of nitrate waste solutions

    International Nuclear Information System (INIS)

    Michaels, S.L.; Michel, R.C.; Terpandjian, P.D.; Vora, J.N.

    1976-01-01

    Bacterial denitrification by Pseudomonas Stutzeri has been chosen as the method for removing nitrate from the effluent stream of the Y-12 uranium purification process. A model was developed to predict bacterial growth and carbon and nitrate depletion during the induction period and steady state operation. Modification of analytical procedures and automatic control of the pH in the reactor are recommended to improve agreement between the prediction of the model and experimental data. An initial carbon-to-nitrogen (C/N) mass ratio of 1.4-1.5 insures adequate population growth during the induction period. Further experiments in batch reactors and in steady state flow reactors are recommended to obtain more reliable kinetic rate constants

  19. 2-Amino-5-chloropyridinium nitrate

    Directory of Open Access Journals (Sweden)

    Donia Zaouali Zgolli

    2009-11-01

    Full Text Available The title structure, C5H6ClN2+·NO3−, is held together by extensive hydrogen bonding between the NO3− ions and 2-amino-5-chloropyridinium H atoms. The cation–anion N—H...O hydrogen bonds link the ions into a zigzag- chain which develops parallel to the b axis. The structure may be compared with that of the related 2-amino-5-cyanopyridinium nitrate.

  20. The influence of Metisevit on biochemical and morphological indicators of blood of piglets under nitrate loading

    Directory of Open Access Journals (Sweden)

    B. Gutyj

    2017-07-01

    Full Text Available The article presents the results of research on the influence of the developed complex preparation Metisevit on the dynamics of morphological and biochemical blood indicators of piglets under nitrate loading. The research established that sodium nitrate intoxication causes disbalance of the physiological level of hematological indicators of the tested animals’ organisms. This was indicated by the manifestations of subclinical chronic nitrate-nitrite toxicosis: the increase in the level of nitrates, nitrites and methemoglobin in the blood. After prolonged feeding of the piglets with sodium nitrate at a dose of 0.3 g nitrate ion/kg, the concentration of nitrates and nitrites in the blood serum reached its maximum on the 60th day of the experiment. Also, the number of leukocytes and erythrocytes in the blood increased, and the activity of aspartate- and alanineaminotransferase in the blood serum increased. We rank the extent of liver intoxication with nitrates according to intensity of aminotransferase in the blood serum of the tested piglets. The normalization of morphological and biochemical blood indicators of piglets under nitrate-nitrite intoxication requires usage of a preparation which contains vitamins, zeolites and antioxidants. If the fodder contains high doses of nitrates, 1.0 mg/kg dose of Metisevit is added to the fodder for preventing subclinical nitrate-nitrite toxicosis. Metisevit contains the following agents: phenozan acid, methionine, zeolite, selenium, vitamins E and C. The research conducted proved the feasibility of using Metisevit for preventing chronic nitrate-nitrite toxicosis in piglets. This preparation caused a decrease in the concentration of nitrates, nitrites and in the level of methemoglobin in the blood of piglets. Usage of Metisevit on piglets showed normalization of the number of erythrocytes and hemoglobin in the blood on the 10th day, and normalization of ASAT and ALAT on 30th and 90th days. The mechanism of

  1. Photochemical reduction of uranyl nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Duerksen, W.K.

    1993-10-20

    The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

  2. Investigation into common solubility of dysprosium nitrate with nitrates of aniline, pyridine in aqueous solutions

    International Nuclear Information System (INIS)

    Katamanov, V.L.; Zhuravlev, E.F.

    1976-01-01

    Data are given on solubility at 20 and 40 deg C in the systems: dysprosium nitrate - aniline nitrate -water and dysprosium nitrate - pyridine nitrate - water. Solubilities are determined by the method of sections. It is found that isotherms of the first system are of eutonic type, equilibrium solid phases of dysprosium hexahydrate nitrate and aniline nitrate correspond to non-variant points of intersection of lines of saturated solutions. The solubility of aniline nitrate is much lower than that of dysprosium hexahydrate nitrate. An increase in the concentration of Dy 3+ ions in a binary solution results in salting-out of aniline nitrate and in absence of any interaction in the system. The compound Dy(NO 3 ) 3 x2PyxHNO 3 is formed in a congruent way in the second system considered

  3. NO signaling is a key component of the root growth response to nitrate in Zea mays L.

    Science.gov (United States)

    Trevisan, Sara; Manoli, Alessandro; Quaggiotti, Silvia

    2014-01-01

    Roots are considered to be a vital organ system of plants due to their involvement in water and nutrient uptake, anchorage, propagation, storage functions, secondary metabolite (including hormones) biosynthesis, and accumulation. Crops are strongly dependent on the availability of nitrogen in soil and on the efficiency of nitrogen utilization for biomass production and yield. However, knowledge about molecular responses to nitrogen fluctuations mainly derives from the study of model species. Nitric oxide (NO) has been proposed to be implicated in plant adaptation to environment, but its exact role in the response of plants to nutritional stress is still under evaluation. Recently a novel role for NO production and scavenging, thanks to the coordinate spatio-temporal expression of nitrate reductase and non-symbiotic hemoglobins, in the maize root response to nitrate has been postulated. This control of NO homeostasis is preferentially accomplished by the cells of the root transition zone (TZ) which seem to represent the most nitrate responsive portion of maize root. The TZ is already known to function as a sensory center able to gather information from the external environment and to re-elaborate them in an adequate response. These results indicate that it could play a central role also for nitrate sensing by roots. A lot of work is still needed to identify and characterize other upstream and downstream signals involved in the "nitrate-NO" pathway, leading to root architecture adjustments and finally to stress adaptation.

  4. Studies on the reverse osmosis treatment of uranyl nitrate solution

    International Nuclear Information System (INIS)

    Prabhakar, S.; Panicker, S.T.; Misra, B.M.; Ramani, P.S.

    1992-01-01

    The aqueous effluent generated in uranium processing, particularly in the nuclear fuel fabrication step, contains mainly uranium nitrate. This requires treatment before discharge into the environment to meet stringent standards. This paper presents the performance of cellulose acetate membranes with regard to rejection of uranium under reverse osmotic conditions for feed concentrations up to 200 mg/l of uranium, which corresponds to the levels normally prevalent in the effluents. The use of additives like the disodium salt of ethylenediaminetetraacetic acid and sodium sulfate for the improvement of reverse osmosis performance of the above membranes was also investigated. In the light of the experimental results, the suitability of reverse osmosis for the decontamination of uranium effluents is discussed

  5. Structures of mammalian cytosolic quinone reductases.

    Science.gov (United States)

    Foster, C E; Bianchet, M A; Talalay, P; Faig, M; Amzel, L M

    2000-08-01

    The metabolism of quinone compounds presents one source of oxidative stress in mammals, as many pathways proceed by mechanisms that generate reactive oxygen species as by-products. One defense against quinone toxicity is the enzyme NAD(P)H:quinone oxidoreductase type 1 (QR1), which metabolizes quinones by a two-electron reduction mechanism, thus averting production of radicals. QR1 is expressed in the cytoplasm of many tissues, and is highly inducible. A closely related homologue, quinone reductase type 2 (QR2), has been identified in several mammalian species. QR2 is also capable of reducing quinones to hydroquinones, but unlike QR1, cannot use NAD(P)H. X-ray crystallographic studies of QR1 and QR2 illustrate that despite their different biochemical properties, these enzymes have very similar three-dimensional structures. In particular, conserved features of the active sites point to the close relationship between these two enzymes.

  6. Nitrous oxide emission by the non-denitrifying, nitrate ammonifier Bacillus licheniformis.

    Science.gov (United States)

    Sun, Yihua; De Vos, Paul; Heylen, Kim

    2016-01-19

    Firmicutes have the capacity to remove excess nitrate from the environment via either denitrification, dissimilatory nitrate reduction to ammonium or both. The recent renewed interest in their nitrogen metabolism has revealed many interesting features, the most striking being their wide variety of dissimilatory nitrate reduction pathways. In the present study, nitrous oxide production from Bacillus licheniformis, a ubiquitous Gram-positive, spore-forming species with many industrial applications, is investigated. B. licheniformis has long been considered a denitrifier but physiological experiments on three different strains demonstrated that nitrous oxide is not produced from nitrate in stoichiometric amounts, rather ammonium is the most important end-product, produced during fermentation. Significant strain dependency in end-product ratios, attributed to nitrite and ammonium, and medium dependency in nitrous oxide production were also observed. Genome analyses confirmed the lack of a nitrite reductase to nitric oxide, the key enzyme of denitrification. Based on the gene inventory and building on knowledge from other non-denitrifying nitrous oxide emitters, hypothetical pathways for nitrous oxide production, involving NarG, NirB, qNor and Hmp, are proposed. In addition, all publically available genomes of B. licheniformis demonstrated similar gene inventories, with specific duplications of the nar operon, narK and hmp genes as well as NarG phylogeny supporting the evolutionary separation of previously described distinct BALI1 and BALI2 lineages. Using physiological and genomic data we have demonstrated that the common soil bacterium B. licheniformis does not denitrify but is capable of fermentative dissimilatory nitrate/nitrite reduction to ammonium (DNRA) with concomitant production of N2O. Considering its ubiquitous nature and non-fastidious growth in the lab, B. licheniformis is a suitable candidate for further exploration of the actual mechanism of N2O

  7. Membranous nephropathy

    Science.gov (United States)

    ... check for hepatitis B, hepatitis C, and syphilis Complement levels Cryoglobulin test Treatment The goal of treatment ... not as helpful for people with membranous nephropathy. Medicines used treat membranous nephropathy include: Angiotensin-converting enzyme ( ...

  8. Nitrate contamination of groundwater and its countermeasures

    Energy Technology Data Exchange (ETDEWEB)

    Mitamura, Hisayoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    The inevitable increases of food production and energy consumption with an increase in world population become main causes of an increase of nitrate load to the environment. Although nitrogen is essential for the growth of animal and plant as a constituent element of protein, excessive nitrate load to the environment contaminates groundwater resources used as drinking water and leads to seriously adverse effects on the health of man and livestock. In order to clarify the problem of nitrate contamination of groundwater and search a new trend of technology development from the viewpoint of environment remediation and protection, the present paper has reviewed adverse effects of nitrate on human health, the actual state of nitrogen cycle, several kinds of nitrate sources, measures for reducing nitrate level, etc. (author)

  9. Alpha autoradiography by cellulose nitrate layer

    International Nuclear Information System (INIS)

    Simonovic, J.; Vukovic, J.; Antanasijevic, R.

    1977-01-01

    From domestic cellulose nitrate bulk material thin layers for α-particle autoradiography were prepared. An artificial test specimen of a uniformly alpha labelled grid source was used. The efficiency of autoradiography by cellulose nitrate was calculated comparing with data from an Ilford K2 nuclear emulsion exposed under the same conditions as the cellulose nitrate film. The resolution was determined as the distance from grid pitch edge at which the track density fell considerably. (Auth.)

  10. Alpha autoradiography by cellulose nitrate layer

    International Nuclear Information System (INIS)

    Simonovic, J.; Vukovic, J.; Antanasijevic, R.

    1976-01-01

    From domestic cellulose nitrate bulk material thin layers for α-particle autoradiography were prepared. An artifical test specimen of a uniformly alpha labelled grid source was used. The efficiency of autoradiographs by cellulose nitrate was calculated comparing with data from an Ilford K2 nuclear emulsion exposed under the same conditions as the cellulose nitrate film. The resolution was determined as the distance from grid pitch edge at which the track density fell considerably. (orig.) [de

  11. Nitrat i drikkevandet og vores sundhed

    DEFF Research Database (Denmark)

    Hansen, Birgitte; Schullehner, Jörg; Sigsgaard, Torben

    2014-01-01

    Nitrat i drikkevandet er uønsket, da det kan påvirke vores sundhed negativt. Den øvre grænse for hvor meget nitrat der tillades i drikkevandet er fastsat i forhold til risikoen for akut forgiftning med nitrit og blå børn-syndromet. Men nitrat i drikkevandet mistænkes også for at være medvirkende...

  12. Synthesis of cerous ammonium nitrate using ceric ammonium nitrate and anhydrous ammonia as a reducing agent

    International Nuclear Information System (INIS)

    Bourleaux, G.; Colombet, P.; Rouxel, J.; Gradeff, P.S.; Mauermann, H.

    1988-01-01

    The reduction of ceric ammonium nitrate by anhydrous ammonia has been studied. The reaction yields cerous ammonium nitrate complex. This is an easy method to prepare an anhydrous Ce (III) salt, suitable for synthesis of organo cerium (III) derivatives [fr

  13. Characterization of mitochondrial thioredoxin reductase from C. elegans

    International Nuclear Information System (INIS)

    Lacey, Brian M.; Hondal, Robert J.

    2006-01-01

    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 cat of 610 min -1 and a K m of 610 μM using E. coli thioredoxin as substrate. The reported k cat is 25% of the k 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

  14. Regulation of ribonucleotide reductase by Spd1 involves multiple mechanisms

    DEFF Research Database (Denmark)

    Nestoras, Konstantinos; Mohammed, Asma Hadi; Schreurs, Ann-Sofie

    2010-01-01

    The correct levels of deoxyribonucleotide triphosphates and their relative abundance are important to maintain genomic integrity. Ribonucleotide reductase (RNR) regulation is complex and multifaceted. RNR is regulated allosterically by two nucleotide-binding sites, by transcriptional control, and...

  15. Reduction of Folate by Dihydrofolate Reductase from Thermotoga maritima

    NARCIS (Netherlands)

    Loveridge, E Joel; Hroch, Lukas; Hughes, Robert L; Williams, Thomas; Davies, Rhidian L; Angelastro, Antonio; Luk, Louis Y P; Maglia, Giovanni; Allemann, Rudolf K

    2017-01-01

    Mammalian dihydrofolate reductases (DHFR) catalyse the reduction of folate more efficiently than the equivalent bacterial enzymes, despite typically having similar efficiencies for the reduction of their natural substrate dihydrofolate. In contrast, we show here that DHFR from the hyperthermophilic

  16. Membrane Biophysics

    CERN Document Server

    Ashrafuzzaman, Mohammad

    2013-01-01

    Physics, mathematics and chemistry all play a vital role in understanding the true nature and functioning of biological membranes, key elements of living processes. Besides simple spectroscopic observations and electrical measurements of membranes we address in this book the phenomena of coexistence and independent existence of different membrane components using various theoretical approaches. This treatment will be helpful for readers who want to understand biological processes by applying both simple observations and fundamental scientific analysis. It provides a deep understanding of the causes and effects of processes inside membranes, and will thus eventually open new doors for high-level pharmaceutical approaches towards fighting membrane- and cell-related diseases.

  17. The reduction of nitrate, nitrite and hydroxylamine to ammonia by enzymes from Cucurbita pepo L. in the presence of reduced benzyl viologen as electron donor

    Science.gov (United States)

    Cresswell, C. F.; Hageman, R. H.; Hewitt, E. J.; Hucklesby, D. P.

    1965-01-01

    1. Enzyme systems from Cucurbita pepo have been shown to catalyse the reduction of nitrite and hydroxylamine to ammonia in yields about 90–100%. 2. Reduced benzyl viologen serves as an efficient electron donor for both systems. Activity of the nitrite-reductase system is directly related to degree of dye reduction when expressed in terms of the function for oxidation–reduction potentials, but appears to decrease to negligible activity below about 9% dye reduction. 3. NADH and NADPH alone produce negligible nitrite loss, but NADPH can be linked to an endogenous diaphorase system to reduce nitrite to ammonia in the presence of catalytic amounts of benzyl viologen. 4. The NADH– or NADPH–nitrate-reductase system that is also present can accept electrons from reduced benzyl viologen, but shows relationships opposite to that for the nitrite-reductase system with regard to effect of degree of dye reduction on activity. The product of nitrate reduction may be nitrite alone, or nitrite and ammonia, or ammonia alone, according only to the degree of dye reduction. 5. The relative activities of nitrite-reductase and hydroxylamine-reductase systems show different relationships with degree of dye reduction and may become reversed in magnitude when effects of degree of dye reduction are tested over a suitable range. 6. Nitrite severely inhibits the rate of reduction of hydroxylamine without affecting the yield of ammonia as a percentage of total substrate loss, but hydroxylamine has a negligible effect on the activity of the nitrite-reductase system. 7. The apparent Km for nitrite (1 μm) is substantially less than that for hydroxylamine, for which variable values between 0·05 and 0·9mm (mean 0·51 mm) have been observed. 8. The apparent Km values for reduced benzyl viologen differ for the nitrite-reductase and hydroxylamine-reductase systems: 60 and 7·5 μm respectively. 9. It is concluded that free hydroxylamine may not be an intermediate in the reduction of nitrite

  18. Peroxynitrous acid induces structural and functional modifications to basement membranes and its key component, laminin

    DEFF Research Database (Denmark)

    Degendorfer, Georg; Chuang, Christine Y.; Hammer, Astrid

    2015-01-01

    Basement membranes (BM) are specialized extracellular matrices underlying endothelial cells in the artery wall. Laminin, the most abundant BM glycoprotein, is a structural and biologically active component. Peroxynitrous acid (ONOOH), a potent oxidizing and nitrating agent, is formed in vivo...

  19. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Science.gov (United States)

    2010-10-01

    ... ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed with..., blasting, type B, and Explosives, blasting, type E, Division 1.5 compatibility group D. (f) No mixture...

  20. Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts

    OpenAIRE

    Karasu, Çimen; Cumaoğlu, Ahmet; Gürpinar, Ali Rifat; Kartal, Murat; Kovacikova, Lucia; Milackova, Ivana; Stefek, Milan

    2012-01-01

    The pomegranate, Punica granatum L., has been the subject of current interest as a medicinal agent with wide-ranging therapeutic indications. In the present study, pomegranate ethanolic seed and hull extracts were tested, in comparison with a commercial sample, for the inhibition of aldose reductase, an enzyme involved in the etiology of diabetic complications. In vitro inhibition of rat lens aldose reductase was determined by a conventional method. Pomegranate ethanolic hull extract and comm...

  1. Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.

    Science.gov (United States)

    Bretherick, Leslie

    1989-01-01

    Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)

  2. Engineering Styrene Monooxygenase for Biocatalysis: Reductase-Epoxidase Fusion Proteins.

    Science.gov (United States)

    Heine, Thomas; Tucker, Kathryn; Okonkwo, Nonye; Assefa, Berhanegebriel; Conrad, Catleen; Scholtissek, Anika; Schlömann, Michael; Gassner, George; Tischler, Dirk

    2017-04-01

    The enantioselective epoxidation of styrene and related compounds by two-component styrene monooxygenases (SMOs) has targeted these enzymes for development as biocatalysts. In the present work, we prepare genetically engineered fusion proteins that join the C-terminus of the epoxidase (StyA) to the N-terminus of the reductase (StyB) through a linker peptide and demonstrate their utility as biocatalysts in the synthesis of Tyrain purple and other indigoid dyes. A single-vector expression system offers a simplified platform for transformation and expansion of the catalytic function of styrene monooxygenases, and the resulting fusion proteins are self-regulated and couple efficiently NADH oxidation to styrene epoxidation. We find that the reductase domain proceeds through a sequential ternary-complex mechanism at low FAD concentration and a double-displacement mechanism at higher concentrations of FAD. Single-turnover studies indicate an observed rate constant for FAD-to-FAD hydride transfer of ~8 s -1 . This step is rate limiting in the styrene epoxidation reaction and helps to ensure that flavin reduction and styrene epoxidation reactions proceed without wasteful side reactions. Comparison of the reductase activity of the fusion proteins with the naturally occurring reductase, SMOB, and N-terminally histidine-tagged reductase, NSMOB, suggests that the observed changes in catalytic mechanism are due in part to an increase in flavin-binding affinity associated with the N-terminal extension of the reductase.

  3. Nitration Study of Cyclic Ladder Polyphenylsilsesquioxane

    Directory of Open Access Journals (Sweden)

    LIANG Jia-xiang

    2017-05-01

    Full Text Available Several nitration reagents including fuming nitric acid, HNO3-H2SO4, KNO3-H2SO4, HNO3-KNO3, CH3COOH-KNO3, (CH3CO2O-HNO3 were used to nitrate cyclic ladder polyphenylsilsesquioxane (CL-PPSQ in different conditions in order to enhance the compatibility of the CL-PPSQ in polymers, the NO2-PPSQ was obtained. FTIR, element analysis, GPC, TGA and 1H NMR were used to characterize the structures of the nitrated products. The results show that the nitrating abilities of the fuming nitric acid, HNO3-H2SO4 and KNO3-H2SO4 are very strong. Many nitro groups can be linked with phenyl groups in CL-PPSQ, but with low molecular mass, fracture occurs in siloxane segment. However, the Mn of the product NO2-PPSQ sharply drops by 50% compared with that of CL-PPSQ, so the nitration reagents can break the cyclic structure of CL-PPSQ. The nitrating reagents of HNO3-KNO3 and CH3COOH-KNO3 have no nitration effects on CL-PPSQ. At last, NO2-CL-PPSQ was prepared using (CH3CO2O-HNO3 because of the moderate nitration process and ability. The cyclic structure of PPSQ is remained, although the number of —NO2 group is not too much. At the same time, the nitration mechanism using different nitration reagents was analyzed. A certain amount of NO2+, which is a kind of activator owning strong nitration ability, can be found in the fuming nitric acid and H2SO4-HNO3(KNO3 systems. As to the (CH3CO2O-HNO3 system, the main activator is CH3COONO2.

  4. Legacy Nitrate Impacts on Groundwater and Streams

    Science.gov (United States)

    Tesoriero, A. J.; Juckem, P. F.; Miller, M. P.

    2017-12-01

    Decades of recharge of high-nitrate groundwater have created a legacy—a mass of high-nitrate groundwater—that has implications for future nitrate concentrations in groundwater and in streams. In the United States, inorganic nitrogen fertilizer applications to the land surface have increased ten-fold since 1950, resulting in sharp increases in nitrate concentrations in recharging groundwater, which pose a risk to deeper groundwater and streams. This study assesses the factors that control time lags and eventual concentrations of legacy nitrate in groundwater and streams. Results from the USGS National Water-Quality Assessment Project are presented which elucidate nitrate trends in recharging groundwater, delineate redox zones and assess groundwater and stream vulnerability to legacy nitrate sources on a regional scale. This study evaluated trends and transformations of agricultural chemicals based on groundwater age and water chemistry data along flow paths from recharge areas to streams at 20 study sites across the United States. Median nitrate recharge concentrations in these agricultural areas have increased markedly over the last 50 years, from 4 to 7.5 mg N/L. The effect that nitrate accumulation in shallow aquifers will have on drinking water quality and stream ecosystems is dependent on the redox zones encountered along flow paths and on the age distribution of nitrate discharging to supply wells and streams. Delineating redox zones on a regional scale is complicated by the spatial variability of reaction rates. To overcome this limitation, we applied logistic regression and machine learning techniques to predict the probability of a specific redox condition in groundwater in the Chesapeake Bay watershed and the Fox-Wolf-Peshtigo study area in Wisconsin. By relating redox-active constituent concentrations in groundwater samples to indicators of residence time and/or electron donor availability, we were able to delineate redox zones on a regional scale

  5. A mutant of Paracoccus denitrificans with disrupted genes coding for cytochrome c550 and pseudoazurin establishes these two proteins as the in vivo electron donors to cytochrome cd1 nitrite reductase

    NARCIS (Netherlands)

    Pearson, Isobel V; Page, M Dudley; van Spanning, Rob J M; Ferguson, Stuart J

    2003-01-01

    In Paracoccus denitrificans, electrons pass from the membrane-bound cytochrome bc(1) complex to the periplasmic nitrite reductase, cytochrome cd(1). The periplasmic protein cytochrome c(550) has often been implicated in this electron transfer, but its absence, as a consequence of mutation, has

  6. Participation of Chlorophyll b Reductase in the Initial Step of the Degradation of Light-harvesting Chlorophyll a/b-Protein Complexes in Arabidopsis

    OpenAIRE

    Horie, Yukiko; Ito, Hisashi; Kusaba, Makoto; Tanaka, Ryouichi; Tanaka, Ayumi

    2009-01-01

    The light-harvesting chlorophyll a/b-protein complex of photosystem II (LHCII) is the most abundant membrane protein in green plants, and its degradation is a crucial process for the acclimation to high light conditions and for the recovery of nitrogen (N) and carbon (C) during senescence. However, the molecular mechanism of LHCII degradation is largely unknown. Here, we report that chlorophyll b reductase, which catalyzes the first step of chlorophyll b degradation, plays a central role in L...

  7. Methylenetetrahydrofolate Reductase Activity and Folate Metabolism

    Directory of Open Access Journals (Sweden)

    Nursen Keser

    2014-04-01

    Full Text Available Folate is a vital B vitamin which is easily water-soluble. It is a natural source which is found in the herbal and animal foods. Folate has important duties in the human metabolism, one of them is the adjustment of the level of plasma homocysteine. Reduction in MTHFR (methylenetetrahydrofolate reductase,which is in charge of the metabolism of homocysteine activity affects the level of homocysteine. Therefore MTHFR is an important enzyme in folate metabolism. Some of the mutations occurring in the MTHFR gene is a risk factor for various diseases and may be caused the hyperhomocysteinemia or the homocystinuria, and they also may lead to metabolic problems. MTHFR is effective in the important pathways such as DNA synthesis, methylation reactions and synthesis of RNA. C677T and A1298C are the most commonly occurring polymorphisms in the gene of MTHFR. The frequency of these polymorphisms show differences in the populations. MTHFR, folate distribution, metabolism of homocysteine and S-adenosylmethionine, by the MTHFR methylation the genetic defects have the potential of affecting the risk of disease in the negative or positive way.

  8. Interactions between inhibitors of dihydrofolate reductase.

    Science.gov (United States)

    Bowden, K; Hall, A D; Birdsall, B; Feeney, J; Roberts, G C

    1989-03-01

    The binding of substrates and inhibitors to dihydrofolate reductase was studied by steady-state kinetics and high-field 1H-n.m.r. spectroscopy. A series of 5-substituted 2,4-diaminopyrimidines were examined and were found to be 'tightly binding' inhibitors of the enzyme (Ki less than 10(-9) M). Studies on the binding of 4-substituted benzenesulphonamides and benzenesulphonic acids also established the existence of a 'sulphonamide-binding site' on the enzyme. Subsequent n.m.r. experiments showed that there are two binding sites for the sulphonamides on the enzyme, one of which overlaps the coenzyme (NADPH) adenine-ring-binding site. An examination of the pH-dependence of the binding of sulphonamides to the enzyme indicated the influence of an ionizable group on the enzyme that was not directly involved in the sulphonamide binding. The change in pKa value from 6.7 to 7.2 observed on sulphonamide binding suggests the involvement of a histidine residue, which could be histidine-28.

  9. Aldose reductase mediates retinal microglia activation

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Kun-Che; Shieh, Biehuoy; Petrash, J. Mark, E-mail: mark.petrash@ucdenver.edu

    2016-04-29

    Retinal microglia (RMG) are one of the major immune cells in charge of surveillance of inflammatory responses in the eye. In the absence of an inflammatory stimulus, RMG reside predominately in the ganglion layer and inner or outer plexiform layers. However, under stress RMG become activated and migrate into the inner nuclear layer (INL) or outer nuclear layer (ONL). Activated RMG in cell culture secrete pro-inflammatory cytokines in a manner sensitive to downregulation by aldose reductase inhibitors. In this study, we utilized CX3CR1{sup GFP} mice carrying AR mutant alleles to evaluate the role of AR on RMG activation and migration in vivo. When tested on an AR{sup WT} background, IP injection of LPS induced RMG activation and migration into the INL and ONL. However, this phenomenon was largely prevented by AR inhibitors or in AR null mice, or was exacerbated in transgenic mice that over-express AR. LPS-induced increases in ocular levels of TNF-α and CX3CL-1 in WT mice were substantially lower in AR null mice or were reduced by AR inhibitor treatment. These studies demonstrate that AR expression in RMG may contribute to the proinflammatory phenotypes common to various eye diseases such as uveitis and diabetic retinopathy. - Highlights: • AR inhibition prevents retinal microglial activation. • Endotoxin-induced ocular cytokine production is reduced in AR null mice. • Overexpression of AR spontaneously induces retinal microglial activation.

  10. Spectrophotometric determination of nitrate in vegetables using ...

    African Journals Online (AJOL)

    A rapid and sensitive spectrophotometric method for the determination of nitrate in vegetables is described. The method is based on the measurement of the absorbance of yellow sodium nitrophenoxide formed via the reaction of phenol with the vegetable-based nitrate in presence of sulphuric acid. The analytical ...

  11. The crystal structure of urea nitrate

    NARCIS (Netherlands)

    Harkema, Sybolt; Feil, D.

    1969-01-01

    The structure of urea nitrate has been solved, by the use of three-dimensional X-ray data. Data were collected using Cu Ke and Mo K0~ radiations. The structure consists of layers with urea and nitrate groups held together by hydrogen bonds. The positions of all hydrogen atoms were found. The final R

  12. Spectrophotometric Determination of Nitrate and Phosphate Levels ...

    African Journals Online (AJOL)

    MBI

    2013-04-09

    Apr 9, 2013 ... of high nitrate level in drinking water, treatment and prevention methods must be considered to protect ground water aquifers from nitrate leaching . Treatment through ion-exchange, reverse osmosis, etc can rehabilitate the already contaminated water, while prevention through reduced dependence on.

  13. 4-Methoxy-N,N′-diphenylbenzamidinium nitrate

    Directory of Open Access Journals (Sweden)

    Renata S. Silva

    2016-09-01

    Full Text Available The asymmetric unit of the title salt N,N′-diphenyl-4-methoxybenzamidinium nitrate, C20H19N2O+·NO3−, comprises two independent N,N′-diphenyl-4-methoxybenzamidinium cations and two nitrate anions. The crystal structure features N—H...O hydrogen bonds and C—H...O contacts responsible for the packing.

  14. Relationships between nitrate, chlorophyll and chromaticity values ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-28

    Nov 28, 2011 ... balanced diet with their mineral, vitamin and dietary fibre contents, and low carbohydrate content (Žnidarčič et al.,. 2011). However, leafy vegetables may accumulate high amounts of nitrate, and usually they are the major contributor of the daily nitrate intake changing between. 30 to 90% (Santamaria, ...

  15. Nitrate metabolism in the gromiid microbial universe

    DEFF Research Database (Denmark)

    Høgslund, Signe; Risgaard-Petersen, Nils; Cedhagen, Tomas

    enclose and regulate a small biogeochemical universe within their cell. Their transparent proteinaceous cell wall surrounds a complex matrix consisting of sediment, bacteria and nitrate which is concentrated to hundreds of mM in the gromiid cell. The nitrate is respired to dinitrogen, but in contrast...

  16. Spectrophotometric Determination of Nitrate in Vegetables Using ...

    African Journals Online (AJOL)

    DR. MIKE HORSFALL

    ABSTRACT: A rapid and sensitive spectrophotometric method for the determination of nitrate in vegetables is described. The method is based on the measurement of the absorbance of yellow sodium nitrophenoxide formed via the reaction of phenol with the vegetable-based nitrate in presence of sulphuric acid.

  17. Nitrate reduction in an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Boesen, Carsten; Kristiansen, Henning

    1991-01-01

    of total dissolved ions in the NO3- free anoxic zone indicates the downward migration of contaminants and that active nitrate reduction is taking place. Nitrate is apparently reduced to N2 because both nitrite and ammonia are absent or found at very low concentrations. Possible electron donors......Nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of Quaternary age. Groundwater chemistry was studied in a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land. Results show that plumes of nitrate...... processes of O2 and NO3- occur at rates that are fast compared to the rate of downward water transport. Nitrate-contaminated groundwater contains total contents of dissolved ions that are two to four times higher than in groundwater derived from the forested area. The persistence of the high content...

  18. The Nitrate Transporter (NRT) Gene Family in Poplar

    Science.gov (United States)

    Bai, Hua; Euring, Dejuan; Volmer, Katharina; Janz, Dennis; Polle, Andrea

    2013-01-01

    Nitrate is an important nutrient required for plant growth. It also acts as a signal regulating plant development. Nitrate is actively taken up and transported by nitrate transporters (NRT), which form a large family with many members and distinct functions. In contrast to Arabidopsis and rice there is little information about the NRT family in woody plants such as Populus. In this study, a comprehensive analysis of the Populus NRT family was performed. Sixty-eight PtNRT1/PTR, 6 PtNRT2, and 5 PtNRT3 genes were identified in the P. trichocarpa genome. Phylogenetic analysis confirmed that the genes of the NRT family are divided into three clades: NRT1/PTR with four subclades, NRT2, and NRT3. Topological analysis indicated that all members of PtNRT1/PTR and PtNRT2 have 8 to 12 trans-membrane domains, whereas the PtNRT3 proteins have no or up to two trans-membrane domains. Four PtNRT3 members were predicted as secreted proteins. Microarray analyses revealed tissue-specific expression patterns of PtNRT genes with distinct clusters of NRTs for roots, for the elongation zone of the apical stem segment and the developing xylem and a further cluster for leaves, bark and wood. A comparison of different poplar species (P. trichocarpa, P. tremula, P. euphratica, P. fremontii x P. angustifolia, and P. x canescens) showed that the tissue-specific patterns of the NRT genes varied to some extent with species. Bioinformatic analysis of putative cis-regulatory elements in the promoter regions of PtNRT family retrieved motifs suggesting the regulation of the NRT genes by N metabolism, by energy and carbon metabolism, and by phytohormones and stress. Multivariate analysis suggested that the combination and abundance of motifs in distinct promoters may lead to tissue-specificity. Our genome wide analysis of the PtNRT genes provides a valuable basis for functional analysis towards understanding the role of nitrate transporters for tree growth. PMID:23977227

  19. The nitrate transporter (NRT gene family in poplar.

    Directory of Open Access Journals (Sweden)

    Hua Bai

    Full Text Available Nitrate is an important nutrient required for plant growth. It also acts as a signal regulating plant development. Nitrate is actively taken up and transported by nitrate transporters (NRT, which form a large family with many members and distinct functions. In contrast to Arabidopsis and rice there is little information about the NRT family in woody plants such as Populus. In this study, a comprehensive analysis of the Populus NRT family was performed. Sixty-eight PtNRT1/PTR, 6 PtNRT2, and 5 PtNRT3 genes were identified in the P. trichocarpa genome. Phylogenetic analysis confirmed that the genes of the NRT family are divided into three clades: NRT1/PTR with four subclades, NRT2, and NRT3. Topological analysis indicated that all members of PtNRT1/PTR and PtNRT2 have 8 to 12 trans-membrane domains, whereas the PtNRT3 proteins have no or up to two trans-membrane domains. Four PtNRT3 members were predicted as secreted proteins. Microarray analyses revealed tissue-specific expression patterns of PtNRT genes with distinct clusters of NRTs for roots, for the elongation zone of the apical stem segment and the developing xylem and a further cluster for leaves, bark and wood. A comparison of different poplar species (P. trichocarpa, P. tremula, P. euphratica, P. fremontii x P. angustifolia, and P. x canescens showed that the tissue-specific patterns of the NRT genes varied to some extent with species. Bioinformatic analysis of putative cis-regulatory elements in the promoter regions of PtNRT family retrieved motifs suggesting the regulation of the NRT genes by N metabolism, by energy and carbon metabolism, and by phytohormones and stress. Multivariate analysis suggested that the combination and abundance of motifs in distinct promoters may lead to tissue-specificity. Our genome wide analysis of the PtNRT genes provides a valuable basis for functional analysis towards understanding the role of nitrate transporters for tree growth.

  20. Sodium nitrate combustion limit tests

    International Nuclear Information System (INIS)

    Beitel, G.A.

    1976-04-01

    Sodium nitrate is a powerful solid oxidant. Energetically, it is capable of exothermically oxidizing almost any organic material. Rate-controlling variables such as temperature, concentration of oxidant, concentration of fuel, thermal conductivity, moisture content, size, and pressure severely limit the possibility of a self-supported exothermic reaction (combustion). The tests reported in this document were conducted on one-gram samples at atmospheric pressure. Below 380 0 C, NaNO 3 was stable and did not support combustion. At moisture concentrations above 22 wt percent, exothermic reactions did not propagate in even the most energetic and reactive compositions. Fresh resin and paraffin were too volatile to enable a NaNO 2 -supported combustion process to propagate. Concentrations of NaNO 3 above 95 wt percent or below 35 wt percent did not react with enough energy release to support combustion. The influence of sample size and confining pressure, both important factors, was not investigated in this study

  1. Impact of Sulfide on Nitrate Conversion in Eutrophic Nitrate-Rich Marine Sludge

    DEFF Research Database (Denmark)

    Schwermer, Carsten U.; Krieger, Bärbel; Lavik, Gaute

    2006-01-01

    nitrate conversion from denitrification to dissimilatory nitrate-reduction to ammonium (DNRA). In situ microsensor profiling in stagnant sludge revealed the typical stratification of nitrate reduction on top of sulfate reduction. Increasing the bulk nitrate concentration lead to a downward shift....... The interaction of these processes is less understood. Our aim was to investigate the functional interaction of nitrate reduction, denitrification and sulfate reduction in an anaerobic marine sludge. We hypothesize that sulfide (from sulfate reduction) (i) causes incomplete denitrification, and (ii) directs...... of the nitrate-sulfide transition zone; within this zone, N2O accumulated to 260 µM. Batch incubations of sludge with sulfide and 15N-nitrate showed the formation of ammonium at the expense of N2 with increasing sulfide concentrations; an indication of the predicted shift from denitrification to DNRA. However...

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

    Directory of Open Access Journals (Sweden)

    Yeon Bok Kim

    2014-01-01

    Full Text Available 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.

  3. Isolation and characterization of cDNAs encoding leucoanthocyanidin reductase and anthocyanidin reductase from Populus trichocarpa.

    Directory of Open Access Journals (Sweden)

    Lijun Wang

    Full Text Available Proanthocyanidins (PAs contribute to poplar defense mechanisms against biotic and abiotic stresses. Transcripts of PA biosynthetic genes accumulated rapidly in response to infection by the fungus Marssonina brunnea f.sp. multigermtubi, treatments of salicylic acid (SA and wounding, resulting in PA accumulation in poplar leaves. Anthocyanidin reductase (ANR and leucoanthocyanidin reductase (LAR are two key enzymes of the PA biosynthesis that produce the main subunits: (+-catechin and (--epicatechin required for formation of PA polymers. In Populus, ANR and LAR are encoded by at least two and three highly related genes, respectively. In this study, we isolated and functionally characterized genes PtrANR1 and PtrLAR1 from P. trichocarpa. Phylogenetic analysis shows that Populus ANR1 and LAR1 occurr in two distinct phylogenetic lineages, but both genes have little difference in their tissue distribution, preferentially expressed in roots. Overexpression of PtrANR1 in poplar resulted in a significant increase in PA levels but no impact on catechin levels. Antisense down-regulation of PtrANR1 showed reduced PA accumulation in transgenic lines, but increased levels of anthocyanin content. Ectopic expression of PtrLAR1 in poplar positively regulated the biosynthesis of PAs, whereas the accumulation of anthocyanin and flavonol was significantly reduced (P<0.05 in all transgenic plants compared to the control plants. These results suggest that both PtrANR1 and PtrLAR1 contribute to PA biosynthesis in Populus.

  4. Purification and Properties of an NADPH-Aldose Reductase (Aldehyde Reductase) from Euonymus japonica Leaves

    Science.gov (United States)

    Negm, Fayek B.

    1986-01-01

    The enzyme aldose (aldehyde) reductase was partially purified (142-fold) and characterized from Euonymus japonica leaves. The reductase, a dimer, had an average molecular weight of 67,000 as determined by gel filtration on Sephadex G-100. The enzyme was NADPH specific and reduced a broad range of substrates including aldoses, aliphatic aldehydes, and aromatic aldehydes. Maximum activity was observed at pH 8 in phosphate and Tris-HCl buffers and at pH 8.6 to 9.0 in glycine-NaOH buffer using dl-glyceraldehyde or 3-pyridinecarboxaldehyde as substrate. NADP was a competitive inhibitor with respect to NADPH with a Ki of 60 micromolar. Glycerol was an uncompetitive inhibitor to dl-glyceraldehyde (K′i = 460 millimolar). The Euonymus enzyme was inhibited by sulfhydryl inhibitor, phenobarbital, and high concentrations of Li2SO4. Pyrazol and metal chelating agents inhibited the enzyme slightly. Enzyme activity was detected in the leaves and berries of Celastrus orbiculatus and several species of Euonymus. Probable function of this enzyme is to reduce d-galactose to galactitol, a characteristic metabolite in phloem sap of members of the Celastraceae family. Images Fig. 1 PMID:16664750

  5. Transmembrane topology of FRO2, a ferric chelate reductase from Arabidopsis thaliana.

    Science.gov (United States)

    Schagerlöf, Ulrika; Wilson, Greer; Hebert, Hans; Al-Karadaghi, Salam; Hägerhäll, Cecilia

    2006-09-01

    Iron uptake in Arabidopsis thaliana is mediated by ferric chelate reductase FRO2, a transmembrane protein belonging to the flavocytochrome b family. There is no high resolution structural information available for any member of this family. We have determined the transmembrane topology of FRO2 experimentally using the alkaline phosphatase fusion method. The resulting topology is different from that obtained by theoretical predictions and contains 8 transmembrane helices, 4 of which build up the highly conserved core of the protein. This core is present in the entire flavocytochrome b family. The large water soluble domain of FRO2, which contains NADPH, FAD and oxidoreductase sequence motifs, was located on the inside of the membrane.

  6. 5α-reductases in human physiology: an unfolding story.

    Science.gov (United States)

    Traish, Abdulmaged M

    2012-01-01

    5α-reductases are a family of isozymes expressed in a wide host of tissues including the central nervous system (CNS) and play a pivotal role in male sexual differentiation, development and physiology. A comprehensive literature search from 1970 to 2011 was made through PubMed and the relevant information was summarized. 5α reductases convert testosterone, progesterone, deoxycorticosterone, aldosterone and corticosterone into their respective 5α-dihydro-derivatives, which serve as substrates for 3α-hydroxysteroid dehydrogenase enzymes. The latter transforms these 5α-reduced metabolites into a subclass of neuroactive steroid hormones with distinct physiological functions. The neuroactive steroid hormones modulate a multitude of functions in human physiology encompassing regulation of sexual differentiation, neuroprotection, memory enhancement, anxiety, sleep and stress, among others. In addition, 5α -reductase type 3 is also implicated in the N-glycosylation of proteins via formation of dolichol phosphate. The family of 5α-reductases was targeted for drug development to treat pathophysiological conditions, such as benign prostatic hyperplasia and androgenetic alopecia. While the clinical use of 5α-reductase inhibitors was well established, the scope and the magnitude of the adverse side effects of such drugs, especially on the CNS, is still unrecognized due to lack of knowledge of the various physiological functions of this family of enzymes, especially in the CNS. There is an urgent need to better understand the function of 5α-reductases and the role of neuroactive steroids in human physiology in order to minimize the potential adverse side effects of inhibitors targeting 5α-reductases to treat benign prostatic hyperplasia and androgenic alopecia.

  7. Efficient Reduction of Vertebrate Cytoglobins by the Cytochrome b5/Cytochrome b5Reductase/NADH System.

    Science.gov (United States)

    Amdahl, Matthew B; Sparacino-Watkins, Courtney E; Corti, Paola; Gladwin, Mark T; Tejero, Jesús

    2017-08-01

    Cytoglobin is a heme-containing protein ubiquitous in mammalian tissues. Unlike the evolutionarily related proteins hemoglobin and myoglobin, cytoglobin shows a six-coordinated heme binding, with the heme iron coordinated by two histidine side chains. Cytoglobin is involved in cytoprotection pathways through yet undefined mechanisms, and it has recently been demonstrated that cytoglobin has redox signaling properties via nitric oxide (NO) and nitrite metabolism. The reduced, ferrous cytoglobin can bind oxygen and will react with NO in a dioxygenation reaction to form nitrate, which dampens NO signaling. When deoxygenated, cytoglobin can bind nitrite and reduce it to NO. This oxidoreductase activity could be catalytic if an effective reduction system exists to regenerate the reduced heme species. The nature of the physiological cytoglobin reducing system is unknown, although it has been proposed that ascorbate and cytochrome b 5 could fulfill this role. Here we describe that physiological concentrations of cytochrome b 5 and cytochrome b 5 reductase can reduce human and fish cytoglobins at rates up to 250-fold higher than those reported for their known physiological substrates, hemoglobin and myoglobin, and up to 100-fold faster than 5 mM ascorbate. These data suggest that the cytochrome b 5 /cytochrome b 5 reductase system is a viable reductant for cytoglobin in vivo, allowing for catalytic oxidoreductase activity.

  8. Clinical pharmacology and clinical trials of ribonucleotide reductase inhibitors: is it a viable cancer therapy?

    Science.gov (United States)

    Mannargudi, Mukundan Baskar; Deb, Subrata

    2017-08-01

    Ribonucleotide reductase (RR) enzymes (RR1 and RR2) play an important role in the reduction of ribonucleotides to deoxyribonucleotides which is involved in DNA replication and repair. Augmented RR activity has been ascribed to uncontrolled cell growth and tumorigenic transformation. This review mainly focuses on several biological and chemical RR inhibitors (e.g., siRNA, GTI-2040, GTI-2501, triapine, gemcitabine, and clofarabine) that have been evaluated in clinical trials with promising anticancer activity from 1960's till 2016. A summary on whether their monotherapy or combination is still effective for further use is discussed. Among the RR2 inhibitors evaluated, GTI-2040, siRNA, gallium nitrate and didox were more efficacious as a monotherapy, whereas triapine was found to be more efficacious as combination agent. Hydroxyurea is currently used more in combination therapy, even though it is efficacious as a monotherapy. Gallium nitrate showed mixed results in combination therapy, while the combination activity of didox is yet to be evaluated. RR1 inhibitors that have long been used in chemotherapy such as gemcitabine, cladribine, fludarabine and clofarabine are currently used mostly as a combination therapy, but are equally efficacious as a monotherapy, except tezacitabine which did not progress beyond phase I trials. Based on the results of clinical trials, we conclude that RR inhibitors are viable treatment options, either as a monotherapy or as a combination in cancer chemotherapy. With the recent advances made in cancer biology, further development of RR inhibitors with improved efficacy and reduced toxicity is possible for treatment of variety of cancers.

  9. Nitrogen nutrition of Salvinia natans: Effects of inorganic nitrogen form on growth, morphology, nitrate reductase activity and uptake kinetics of ammonium and nitrate

    DEFF Research Database (Denmark)

    Jampeetong, Arunothai; Brix, Hans

    2009-01-01

    In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO3-, NH4+, or both at equimolar concentrations (500 μM). Plants supplied with only NO3- had lower growth rates (0.17 ± 0.01 g g-1 d-1), shorter roots, smaller......+ is probably the main N source for S. natans, but plants probably also exploit NO3- when NH4+ concentrations are low. This is suggested based on the observation that the plants maintain high NRA in the roots at relatively high NH4+ levels in the water, even though the uptake capacity for NO3- is reduced under...

  10. Biochemical properties of human dehydrogenase/reductase (SDR family) member 7.

    Science.gov (United States)

    Stambergova, Hana; Skarydova, Lucie; Dunford, James E; Wsol, Vladimir

    2014-01-25

    Dehydrogenase/reductase (SDR family) member 7 (DHRS7, retSDR4, SDR34C1) is a previously uncharacterized member of the short-chain dehydrogenase/reductase (SDR) superfamily. While human SDR members are known to play an important role in various (patho)biochemical pathways including intermediary metabolism and biotransformation of xenobiotics, only 20% of them are considered to be well characterized. Based on phylogenetic tree and SDR sequence clusters analysis DHRS7 is a close relative to well-known SDR member 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) that participates in metabolism of endogenous and xenobiotic substances with carbonyl group. The aim of present study is to determine the basic biochemical properties of DHRS7 and its possible involvement in metabolism of substrates with carbonyl group. For the first time the computational predictions of this membrane protein and membrane topology were experimentally confirmed. DHRS7 has been demonstrated to be an integral protein facing the lumen of the endoplasmic reticulum with lack of posttranscriptional glycosylation modification. Subsequently, NADP(H) cofactor preference and enzymatic reducing activity of DHRS7 was determined towards endogenous substrates with a steroid structure (cortisone, 4-androstene-3,17-dion) and also toward relevant exogenous substances bearing a carbonyl group harmful to human health (1,2-naphtoquinone, 9,10-phenantrenequinone). In addition to 11β-HSD1, DHRS7 is another enzyme from SDR superfamily that have been proved, at least in vitro, to contribute to the metabolism of xenobiotics with carbonyl group. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  11. Atomic structure of nitrate-binding protein crucial for photosynthetic productivity

    Energy Technology Data Exchange (ETDEWEB)

    Koropatkin, Nicole M.; Pakrasi, Himadri B.; Smith, Thomas J.

    2006-06-27

    Cyanobacteria, blue-green algae, are the most abundant autotrophs in aquatic environments and form the base of all aquatic food chains by fixing carbon and nitrogen into cellular biomass. The single most important nutrient for photosynthesis and growth is nitrate, which is severely limiting in many aquatic environments particularly the open ocean (1, 2). It is therefore not surprising that NrtA, the solute-binding component of the high-affinity nitrate ABC transporter, is the single-most abundant protein in the plasma membrane of these bacteria (3). Here we describe the first structure of a nitratespecific receptor, NrtA from Synechocystis sp. PCC 6803, complexed with nitrate and determined to a resolution of 1.5Å. NrtA is significantly larger than other oxyanionbinding proteins, representing a new class of transport proteins. From sequence alignments, the only other solute-binding protein in this class is CmpA, a bicarbonatebinding protein. Therefore, these organisms created a novel solute-binding protein for two of the most important nutrients; inorganic nitrogen and carbon. The electrostatic charge distribution of NrtA appears to force the protein off of the membrane while the flexible tether facilitates the delivery of nitrate to the membrane pore. The structure not only details the determinants for nitrate selectivity in NrtA, but also the bicarbonate specificity in CmpA. Nitrate and bicarbonate transport are regulated by the cytoplasmic proteins NrtC and CmpC, respectively. Interestingly, the residues lining the ligand binding pockets suggest that they both bind nitrate. This implies that the nitrogen and carbon uptake pathways are synchronized by intracellular nitrate and nitrite.3 The nitrate ABC transporter of cyanobacteria is composed of four polypeptides (Figure 1): a high-affinity periplasmic solute-binding lipoprotein (NrtA), an integral membrane permease (NrtB), a cytoplasmic ATPase (NrtD), and a unique ATPase/solute-binding fusion protein (Nrt

  12. Pancreaticobiliary cancers with deficient methylenetetrahydrofolate reductase genotypes.

    Science.gov (United States)

    Matsubayashi, Hiroyuki; Skinner, Halcyon G; Iacobuzio-Donahue, Christine; Abe, Tadayoshi; Sato, Norihiro; Riall, Taylor Sohn; Yeo, Charles J; Kern, Scott E; Goggins, Michael

    2005-08-01

    Methyl group deficiency might promote carcinogenesis by inducing DNA breaks and DNA hypomethylation. We hypothesized that deficient methylenetetrahydrofolate reductase (MTHFR) genotypes could promote pancreatic cancer development. First, we performed a case-control study of germline MTHFR polymorphisms (C677T, A1298C) in 303 patients with pancreatic cancer and 305 matched control subjects. Pancreatic neoplasms frequently lose an MTHFR allele during tumorigenesis; we hypothesized that such loss could promote carcinogenesis. We therefore evaluated the cancer MTHFR genotypes of 82 patients with pancreaticobiliary cancers and correlated them to genome-wide measures of chromosomal deletion by using 386 microsatellite markers. Finally, MTHFR genotypes were correlated with global DNA methylation in 68 cancer cell lines. Germline MTHFR polymorphisms were not associated with an increased likelihood of having pancreatic cancer. Fractional allelic loss (a measure of chromosomal loss) trended higher in cancers with 677T genotypes than in cancers with other genotypes (P = .055). Among cancers with loss of an MTHFR allele, cancers with 677T MTHFR alleles had more deletions at folate-sensitive fragile sites (36.9%) and at tumor suppressor gene loci (68.5%) than 677C cancers (28.7% and 47.8%, P = .079 and .014, respectively). LINE1 methylation was lower in cancers with less functional 677T/TT genotypes (24.4%) than in those with 677CT (26.0%) and CC/C genotypes (32.5%) (P = .014). Cancers with defective MTHFR genotypes have more DNA hypomethylation and more chromosomal losses. Deficient MTHFR function due to loss of an MTHFR allele by an evolving neoplasm might, by promoting chromosomal losses, accelerate cancer development.

  13. Sulfite reductase protects plants against sulfite toxicity.

    Science.gov (United States)

    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.

  14. Molybdenum isotope fractionation by cyanobacterial assimilation during nitrate utilization and N₂ fixation.

    Science.gov (United States)

    Zerkle, A L; Scheiderich, K; Maresca, J A; Liermann, L J; Brantley, S L

    2011-01-01

    We measured the δ⁹⁸Mo of cells and media from molybdenum (Mo) assimilation experiments with the freshwater cyanobacterium Anabaena variabilis, grown with nitrate as a nitrogen (N) source or fixing atmospheric N₂. This organism uses a Mo-based nitrate reductase during nitrate utilization and a Mo-based dinitrogenase during N₂ fixation under culture conditions here. We also demonstrate that it has a high-affinity Mo uptake system (ModABC) similar to other cyanobacteria, including marine N₂-fixing strains. Anabaena variabilis preferentially assimilated light isotopes of Mo in all experiments, resulting in fractionations of -0.2‰ to -1.0‰ ± 0.2‰ between cells and media (ε(cells-media)), extending the range of biological Mo fractionations previously reported. The fractionations were internally consistent within experiments, but varied with the N source utilized and for different growth phases sampled. During growth on nitrate, A. variabilis consistently produced fractionations of -0.3 ± 0.1‰ (mean ± standard deviation between experiments). When fixing N₂, A. variabilis produced fractionations of -0.9 ± 0.1‰ during exponential growth, and -0.5 ± 0.1‰ during stationary phase. This pattern is inconsistent with a simple kinetic isotope effect associated with Mo transport, because Mo is likely transported through the ModABC uptake system under all conditions studied. We present a reaction network model for Mo isotope fractionation that demonstrates how Mo transport and storage, coordination changes during enzymatic incorporation, and the distribution of Mo inside the cell could all contribute to the total biological fractionations. Additionally, we discuss the potential importance of biologically incorporated Mo to organic matter-bound Mo in marine sediments. © 2010 Blackwell Publishing Ltd.

  15. Molybdenum isotope fractionation by cyanobacterial assimilation during nitrate utilization and N2fixation

    Science.gov (United States)

    Zerkle, A L; Scheiderich, K; Maresca, J A; Liermann, L J; Brantley, S L

    2011-01-01

    We measured the δ98Mo of cells and media from molybdenum (Mo) assimilation experiments with the freshwater cyanobacterium Anabaena variabilis, grown with nitrate as a nitrogen (N) source or fixing atmospheric N2. This organism uses a Mo-based nitrate reductase during nitrate utilization and a Mo-based dinitrogenase during N2 fixation under culture conditions here. We also demonstrate that it has a high-affinity Mo uptake system (ModABC) similar to other cyanobacteria, including marine N2-fixing strains. Anabaena variabilis preferentially assimilated light isotopes of Mo in all experiments, resulting in fractionations of −0.2‰ to −1.0‰ ± 0.2‰ between cells and media (εcells–media), extending the range of biological Mo fractionations previously reported. The fractionations were internally consistent within experiments, but varied with the N source utilized and for different growth phases sampled. During growth on nitrate, A. variabilis consistently produced fractionations of −0.3 ± 0.1‰ (mean ± standard deviation between experiments). When fixing N2, A. variabilis produced fractionations of −0.9 ± 0.1‰ during exponential growth, and −0.5 ± 0.1‰ during stationary phase. This pattern is inconsistent with a simple kinetic isotope effect associated with Mo transport, because Mo is likely transported through the ModABC uptake system under all conditions studied. We present a reaction network model for Mo isotope fractionation that demonstrates how Mo transport and storage, coordination changes during enzymatic incorporation, and the distribution of Mo inside the cell could all contribute to the total biological fractionations. Additionally, we discuss the potential importance of biologically incorporated Mo to organic matter-bound Mo in marine sediments. PMID:21092069

  16. Denitrification and environmental factors influencing nitrate removal in Guaymas Basin hydrothermally-altered sediments

    Directory of Open Access Journals (Sweden)

    Marshall W Bowles

    2012-10-01

    Full Text Available We measured potential nitrate removal and denitrification rates in hydrothermally altered sediments inhabited by Beggiatoa mats and adjacent brown oil stained sediments from the Guaymas Basin, Gulf of California. Sediments with Beggiatoa maintained slightly higher rates of potential denitrification than did brown sediments at 31.2 (±12.1 versus 21.9 (±1.4 μM N d-1, respectively. In contrast, the nitrate removal rates in brown sediments were higher than those observed in mat-hosting sediments at 418 ± 145 versus 174 ± 74 μM N d-1, respectively. Additional experiments were conducted to assess the responses of denitrifying communities to environmental factors (i.e. nitrate, sulfide, and dissolved organic carbon (DOC concentration. The denitrifying community had a high affinity for nitrate (Km = 137 ± 91 μΜ ΝΟ3-, in comparison to other environmental communities of denitrifiers, and were capable of high maximum rates of denitrification (vmax = 1164 ± 153 μM N d-1. The presence of sulfide resulted in significantly lower denitrification rates. Microorganisms with the potential to perform denitrification were assessed in these sediments using the bacterial16S rRNA gene and nitrous oxide reductase (nosZ functional gene libraries. The bacterial 16S rRNA gene clone library was dominated by Epsilonproteobacteria (38%, some of which (e.g. Sulfurimonas sp. have a potential for sulfide dependent denitrification. The nosZ clone library did not contain clones similar to pure culture denitrifiers; these clones were most closely associated with environmental clones.

  17. Development of an optochemical sensor for continuous reversible determination of nitrate in drinking water and ground water

    International Nuclear Information System (INIS)

    Lumpp, R.

    1993-09-01

    An optochemical sensor has been developed for continuous reversible determination of nitrate in drinking water and ground water. The sensor is based on the combination of the anion selective liquid ion exchanger Ni(II[bathophenanthroline] 3 2+ with phenolsulfonephtalein dyes in a polyvinylchloride membrane. (orig.) [de

  18. Thermolabile defect of methylenetetrahydrofolate reductase in coronary artery disease.

    Science.gov (United States)

    Kang, S S; Passen, E L; Ruggie, N; Wong, P W; Sora, H

    1993-10-01

    To determine whether or not a moderate genetic defect of homocysteine metabolism is associated with the development of coronary artery disease, we studied the prevalence of thermolabile methylenetetrahydrofolate reductase, which is probably the most common genetic defect of homocysteine metabolism. Three hundred thirty-nine subjects who underwent coronary angiography were classified into three groups: (1) patients with severe coronary artery stenosis (> or = 70% occlusion in one or more coronary arteries or > or = 50% occlusion in the left main coronary artery), (2) patients with mild to moderate coronary artery stenosis (< 70% occlusion in one or more coronary arteries or < 50% occlusion in the left main coronary artery), and (3) patients with non-coronary heart disease or noncardiac chest pain (nonstenotic coronary arteries). The thermolability of methylenetetrahydrofolate reductase was prospectively determined in all subjects. Plasma homocyst(e)ine levels were then measured in those with thermolabile methylenetetrahydrofolate reductase. The traditional risk factors for coronary artery disease were thereafter ascertained by chart review of all subjects. The prevalence of thermolabile methylenetetrahydrofolate reductase was 18.1% in group 1, 13.4% in group 2, and 7.9% in group 3. There was a significant difference between the prevalence of thermolabile methylenetetrahydrofolate reductase in groups 1 and 3 (P < .04). All individuals with thermolabile methylenetetrahydrofolate reductase irrespective of their clinical grouping had higher plasma homocyst(e)ine levels than normal (group 1, 14.86 +/- 5.85; group 2, 15.36 +/- 5.70; group 3, 13.39 +/- 3.80; normal, 8.50 +/- 2.8 nmol/mL). Nonetheless, there was no statistically significant difference in the plasma homocyst(e)ine concentrations of these patients with or without coronary artery stenosis. Using discriminant function analysis, thermolabile methylenetetrahydrofolate reductase was predictive of angiographically

  19. Synthesis and Characterization of Stable Anion Exchange Membranes: The Addition of Electron-withdrawing Group

    Directory of Open Access Journals (Sweden)

    Gülşen ALBAYRAK ARI

    2016-10-01

    Full Text Available Anion exchange membranes (AEM based on poly(2,6-dimethyl-1,4-phenylene oxide (PPO were used as polymer electrolyte membrane for fuel cell applications. The membranes were prepared via bromination, quaternization and nitration reactions and their fuel cell-related properties (water uptake, ion exchange capacity, ionic conductivity were determined. Also, the structures and thermal properties were studied with Fourier transform infrared spectroscopy (FTIR, Size exclusion chromatography (SEC and Differential scanning calorimetry (DSC. Nitration of quaternized PPO (Q-PPO leaded to a decrease in water uptake and ion exchange capacity of the AEM. However, Q-PPO membrane treated with nitration reaction (NO2-Q-PPO exhibited a significant alkaline stability compared to quaternized PPO (Q-PPO.   The results indicated that the addition of electron-withdrawing group, such as nitro, into the structure in order to improve in alkaline stability is a promising new route for preparation alkaline stable AEM membranes.

  20. The role of biliverdin reductase in colorectal cancer

    International Nuclear Information System (INIS)

    Bauer, M.

    2010-01-01

    In recent years, the effects of biliverdin and bilirubin have been studied extensively, and an inhibitory effect of bile pigments in cancer progression has been proposed. In this study we focused on the effects of biliverdin reductase, the enzyme that converts biliverdin to bilirubin, in colorectal cancer. For in vitro experiments we used a human colorectal carcinoma cell line and transfected it with an expression construct of shRNA specific for biliverdin reductase, to create cells with stable knock-down of enzyme expression. Cell proliferation was analyzed using the CASY model TT cell counting device. Western blot protein analysis was performed to study intracellular signaling cascades. Samples of human colorectal cancer were analyzed using immunohistochemistry. We were able to confirm the antiproliferative effects of bile pigments on cancer cells in vitro. However, this effect was attenuated in biliverdin reductase knock down cells. ERK and Akt activation seen under biliverdin and bilirubin treatment was also reduced in biliverdin reductase deficient cells. Immunohistochemical analysis of tumor samples from patients with colorectal cancer showed elevated biliverdin reductase levels. High enzyme expression was associated with lower overall and disease free patient survival. We conclude that BVR is required for bile pigment mediated effects regarding cancer cell proliferation and modulation of intracellular signaling cascades. The role of BVR overexpression in vivo and its exact influence on cancer progression and patient survival need to be further investigated. (author) [de

  1. Mechanical wounding induces a nitrosative stress by down-regulation of GSNO reductase and an increase in S-nitrosothiols in sunflower (Helianthus annuus) seedlings

    Science.gov (United States)

    Chaki, Mounira; Valderrama, Raquel; Fernández-Ocaña, Ana M.; Carreras, Alfonso; Gómez-Rodríguez, Maria. V.; Pedrajas, José R.; Begara-Morales, Juan C.; Sánchez-Calvo, Beatriz; Luque, Francisco; Leterrier, Marina; Corpas, Francisco J.; Barroso, Juan B.

    2011-01-01

    Nitric oxide (NO) and related molecules such as peroxynitrite, S-nitrosoglutathione (GSNO), and nitrotyrosine, among others, are involved in physiological processes as well in the mechanisms of response to stress conditions. In sunflower seedlings exposed to five different adverse environmental conditions (low temperature, mechanical wounding, high light intensity, continuous light, and continuous darkness), key components of the metabolism of reactive nitrogen species (RNS) and reactive oxygen species (ROS), including the enzyme activities L-arginine-dependent nitric oxide synthase (NOS), S-nitrosogluthathione reductase (GSNOR), nitrate reductase (NR), catalase, and superoxide dismutase, the content of lipid hydroperoxide, hydrogen peroxide, S-nitrosothiols (SNOs), the cellular level of NO, GSNO, and GSNOR, and protein tyrosine nitration [nitrotyrosine (NO2-Tyr)] were analysed. Among the stress conditions studied, mechanical wounding was the only one that caused a down-regulation of NOS and GSNOR activities, which in turn provoked an accumulation of SNOs. The analyses of the cellular content of NO, GSNO, GSNOR, and NO2-Tyr by confocal laser scanning microscopy confirmed these biochemical data. Therefore, it is proposed that mechanical wounding triggers the accumulation of SNOs, specifically GSNO, due to a down-regulation of GSNOR activity, while NO2-Tyr increases. Consequently a process of nitrosative stress is induced in sunflower seedlings and SNOs constitute a new wound signal in plants. PMID:21172815

  2. Membrane paradigm

    International Nuclear Information System (INIS)

    Price, R.H.; Thorne, K.S.

    1986-01-01

    The membrane paradigm is a modified frozen star approach to modeling black holes, with particles and fields assuming a complex, static, boundary-layer type structure (membrane) near the event horizon. The membrane has no effects on the present or future evolution of particles and fields above itself. The mathematical representation is a combination of a formalism containing terms for the shear and bulk viscosity, surface pressure, momentum, temperature, entropy, etc., of the horizon and the 3+1 formalism. The latter model considers a family of three-dimensional spacelike hypersurfaces in one-dimensional time. The membrane model considers a magnetic field threading the hole and undergoing torque from the hole rotation. The field is cleaned by the horizon and distributed over the horizon so that ohmic dissipation is minimized. The membrane paradigm is invalid inside the horizon, but is useful for theoretically probing the properties of slowly evolving black holes

  3. Membrane processes

    Science.gov (United States)

    Staszak, Katarzyna

    2017-11-01

    The membrane processes have played important role in the industrial separation process. These technologies can be found in all industrial areas such as food, beverages, metallurgy, pulp and paper, textile, pharmaceutical, automotive, biotechnology and chemical industry, as well as in water treatment for domestic and industrial application. Although these processes are known since twentieth century, there are still many studies that focus on the testing of new membranes' materials and determining of conditions for optimal selectivity, i. e. the optimum transmembrane pressure (TMP) or permeate flux to minimize fouling. Moreover the researchers proposed some calculation methods to predict the membrane processes properties. In this article, the laboratory scale experiments of membrane separation techniques, as well their validation by calculation methods are presented. Because membrane is the "heart" of the process, experimental and computational methods for its characterization are also described.

  4. Interaction of Yna1 and Yna2 Is Required for Nuclear Accumulation and Transcriptional Activation of the Nitrate Assimilation Pathway in the Yeast Hansenula polymorpha.

    Directory of Open Access Journals (Sweden)

    Lucia Silvestrini

    Full Text Available A few yeasts, including Hansenula polymorpha are able to assimilate nitrate and use it as nitrogen source. The genes necessary for nitrate assimilation are organised in this organism as a cluster comprising those encoding nitrate reductase (YNR1, nitrite reductase (YNI1, a high affinity transporter (YNT1, as well as the two pathway specific Zn(II2Cys2 transcriptional activators (YNA1, YNA2. Yna1p and Yna2p mediate induction of the system and here we show that their functions are interdependent. Yna1p activates YNA2 as well as its own (YNA1 transcription thus forming a nitrate-dependent autoactivation loop. Using a split-YFP approach we demonstrate here that Yna1p and Yna2p form a heterodimer independently of the inducer and despite both Yna1p and Yna2p can occupy the target promoter as mono- or homodimer individually, these proteins are transcriptionally incompetent. Subsequently, the transcription factors target genes containing a conserved DNA motif (termed nitrate-UAS determined in this work by in vitro and in vivo protein-DNA interaction studies. These events lead to a rearrangement of the chromatin landscape on the target promoters and are associated with the onset of transcription of these target genes. In contrast to other fungi and plants, in which nuclear accumulation of the pathway-specific transcription factors only occur in the presence of nitrate, Yna1p and Yna2p are constitutively nuclear in H. polymorpha. Yna2p is needed for this nuclear accumulation and Yna1p is incapable of strictly positioning in the nucleus without Yna2p. In vivo DNA footprinting and ChIP analyses revealed that the permanently nuclear Yna1p/Yna2p heterodimer only binds to the nitrate-UAS when the inducer is present. The nitrate-dependent up-regulation of one partner protein in the heterodimeric complex is functionally similar to the nitrate-dependent activation of nuclear accumulation in other systems.

  5. Interaction of Yna1 and Yna2 Is Required for Nuclear Accumulation and Transcriptional Activation of the Nitrate Assimilation Pathway in the Yeast Hansenula polymorpha.

    Science.gov (United States)

    Silvestrini, Lucia; Rossi, Beatrice; Gallmetzer, Andreas; Mathieu, Martine; Scazzocchio, Claudio; Berardi, Enrico; Strauss, Joseph

    2015-01-01

    A few yeasts, including Hansenula polymorpha are able to assimilate nitrate and use it as nitrogen source. The genes necessary for nitrate assimilation are organised in this organism as a cluster comprising those encoding nitrate reductase (YNR1), nitrite reductase (YNI1), a high affinity transporter (YNT1), as well as the two pathway specific Zn(II)2Cys2 transcriptional activators (YNA1, YNA2). Yna1p and Yna2p mediate induction of the system and here we show that their functions are interdependent. Yna1p activates YNA2 as well as its own (YNA1) transcription thus forming a nitrate-dependent autoactivation loop. Using a split-YFP approach we demonstrate here that Yna1p and Yna2p form a heterodimer independently of the inducer and despite both Yna1p and Yna2p can occupy the target promoter as mono- or homodimer individually, these proteins are transcriptionally incompetent. Subsequently, the transcription factors target genes containing a conserved DNA motif (termed nitrate-UAS) determined in this work by in vitro and in vivo protein-DNA interaction studies. These events lead to a rearrangement of the chromatin landscape on the target promoters and are associated with the onset of transcription of these target genes. In contrast to other fungi and plants, in which nuclear accumulation of the pathway-specific transcription factors only occur in the presence of nitrate, Yna1p and Yna2p are constitutively nuclear in H. polymorpha. Yna2p is needed for this nuclear accumulation and Yna1p is incapable of strictly positioning in the nucleus without Yna2p. In vivo DNA footprinting and ChIP analyses revealed that the permanently nuclear Yna1p/Yna2p heterodimer only binds to the nitrate-UAS when the inducer is present. The nitrate-dependent up-regulation of one partner protein in the heterodimeric complex is functionally similar to the nitrate-dependent activation of nuclear accumulation in other systems.

  6. Two-stage Sequential Electrochemical Treatment of Nitrate Brine Wastes

    Energy Technology Data Exchange (ETDEWEB)

    Yu Jiefei; Kupferle, Margaret J. [University of Cincinnati, Department of Civil and Environmental Engineering (United States)], E-mail: Margaret.Kupferle@uc.edu

    2008-08-15

    Nitrates in concentrated brines can be electrochemically reduced in the cathodic chamber of a split-cell electrochemical reactor with formation of ammonium (and small amounts of nitrite). Fortunately, ammonium may be electrochemically oxidized to nitrogen gas in the anodic reaction chamber if a coupled sequential process is used. The presence of chloride in the brine waste is an important consideration in oxidative electrochemical processes, however, because it cycles through oxidized and reduced states at the electrode surfaces and in the bulk solution. Electrochemical oxidation converts chloride ions to 'active chlorine' species with additional oxidizing capability (chlorine, hypochlorous acid and hypochlorite - essentially bleach), as well as to chlorates, depending on the reaction conditions. The production of these active species improves treatment performance in the ammonium oxidation phase since oxidation is no longer limited to the electrode surface. However, the process must be engineered to minimize loss of process efficiency due to parasitic side reactions (chloramines and chlorate). In this study, two-stage batch electrolysis was conducted using a three-electrode (copper anode, platinum-coated titanium cathode, silver/silver chloride reference) electrochemical cell, with the anodic and cathodic chambers separated by a Nafion 117 membrane. Treatment of nitrate and ammonium was tested with and without the presence of chloride in the waste. No significant difference was observed in cathodic nitrate reduction with chloride present or absent. However, the presence of chloride in the solution favored overall soluble nitrogen elimination upon oxidation. Increasing applied current increased production of undesirable byproducts (especially chlorate)

  7. Participation of Chlorophyll b Reductase in the Initial Step of the Degradation of Light-harvesting Chlorophyll a/b-Protein Complexes in Arabidopsis*

    Science.gov (United States)

    Horie, Yukiko; Ito, Hisashi; Kusaba, Makoto; Tanaka, Ryouichi; Tanaka, Ayumi

    2009-01-01

    The light-harvesting chlorophyll a/b-protein complex of photosystem II (LHCII) is the most abundant membrane protein in green plants, and its degradation is a crucial process for the acclimation to high light conditions and for the recovery of nitrogen (N) and carbon (C) during senescence. However, the molecular mechanism of LHCII degradation is largely unknown. Here, we report that chlorophyll b reductase, which catalyzes the first step of chlorophyll b degradation, plays a central role in LHCII degradation. When the genes for chlorophyll b reductases NOL and NYC1 were disrupted in Arabidopsis thaliana, chlorophyll b and LHCII were not degraded during senescence, whereas other pigment complexes completely disappeared. When purified trimeric LHCII was incubated with recombinant chlorophyll b reductase (NOL), expressed in Escherichia coli, the chlorophyll b in LHCII was converted to 7-hydroxymethyl chlorophyll a. Accompanying this conversion, chlorophylls were released from LHCII apoproteins until all the chlorophyll molecules in LHCII dissociated from the complexes. Chlorophyll-depleted LHCII apoproteins did not dissociate into monomeric forms but remained in the trimeric form. Based on these results, we propose the novel hypothesis that chlorophyll b reductase catalyzes the initial step of LHCII degradation, and that trimeric LHCII is a substrate of LHCII degradation. PMID:19403948

  8. Intramolecular electron transfer in Pseudomonas aeruginosa cd(1) nitrite reductase

    DEFF Research Database (Denmark)

    Farver, Ole; Brunori, Maurizio; Cutruzzolà, Francesca

    2009-01-01

    The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa...... nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity...... is controlling this internal ET step. In this study we have investigated the internal ET in the wild-type and His369Ala mutant of P. aeruginosa nitrite reductases and have observed similar cooperativity to that of the Pseudomonas stutzeri enzyme. Heme-c was initially reduced, in an essentially diffusion...

  9. Electrophilic and free radical nitration of benzene and toluene with various nitrating agents*

    Science.gov (United States)

    Olah, George A.; Lin, Henry C.; Olah, Judith A.; Narang, Subhash C.

    1978-01-01

    Electrophilic nitration of toluene and benzene was studied under various conditions with several nitrating systems. It was found that high orthopara regioselectivity is prevalent in all reactions and is independent of the reactivity of the nitrating agent. The methyl group of toluene is predominantly ortho-para directing under all reaction conditions. Steric factors are considered to be important but not the sole reason for the variation in the ortho/para ratio. The results reinforce our earlier views that, in electrophilic aromatic nitrations with reactive nitrating agents, substrate and positional selectivities are determined in two separate steps. The first step involves a π-aromatic-NO2+ ion complex or encounter pair, whereas the subsequent step is of arenium ion nature (separate for the ortho, meta, and para positions). The former determines substrate selectivity, whereas the latter determines regioselectivity. Thermal free radical nitration of benzene and toluene with tetranitromethane in sharp contrast gave nearly statistical product distributions. PMID:16592503

  10. Biochemical characterization of the purple form of Marinobacter hydrocarbonoclasticus nitrous oxide reductase

    Science.gov (United States)

    Dell'Acqua, Simone; Pauleta, Sofia R.; Moura, José J. G.; Moura, Isabel

    2012-01-01

    Nitrous oxide reductase (N2OR) catalyses the final step of the denitrification pathway—the reduction of nitrous oxide to nitrogen. The catalytic centre (CuZ) is a unique tetranuclear copper centre bridged by inorganic sulphur in a tetrahedron arrangement that can have different oxidation states. Previously, Marinobacter hydrocarbonoclasticus N2OR was isolated with the CuZ centre as CuZ*, in the [1Cu2+ : 3Cu+] redox state, which is redox inert and requires prolonged incubation under reductive conditions to be activated. In this work, we report, for the first time, the isolation of N2OR from M. hydrocarbonoclasticus in the ‘purple’ form, in which the CuZ centre is in the oxidized [2Cu2+ : 2Cu+] redox state and is redox active. This form of the enzyme was isolated in the presence of oxygen from a microaerobic culture in the presence of nitrate and also from a strictly anaerobic culture. The purple form of the enzyme was biochemically characterized and was shown to be a redox active species, although it is still catalytically non-competent, as its specific activity is lower than that of the activated fully reduced enzyme and comparable with that of the enzyme with the CuZ centre in either the [1Cu2+ : 3Cu+] redox state or in the redox inactive CuZ* state. PMID:22451106

  11. Nitrite and nitrite reductases: from molecular mechanisms to significance in human health and disease.

    Science.gov (United States)

    Castiglione, Nicoletta; Rinaldo, Serena; Giardina, Giorgio; Stelitano, Valentina; Cutruzzolà, Francesca

    2012-08-15

    Nitrite, previously considered physiologically irrelevant and a simple end product of endogenous nitric oxide (NO) metabolism, is now envisaged as a reservoir of NO to be activated in response to oxygen (O(2)) depletion. In the first part of this review, we summarize and compare the mechanisms of nitrite-dependent production of NO in selected bacteria and in eukaryotes. Bacterial nitrite reductases, which are copper or heme-containing enzymes, play an important role in the adaptation of pathogens to O(2) limitation and enable microrganisms to survive in the human body. In mammals, reduction of nitrite to NO under hypoxic conditions is carried out in tissues and blood by an array of metalloproteins, including heme-containing proteins and molybdenum enzymes. In humans, tissues play a more important role in nitrite reduction, not only because most tissues produce more NO than blood, but also because deoxyhemoglobin efficiently scavenges NO in blood. In the second part of the review, we outline the significance of nitrite in human health and disease and describe the recent advances and pitfalls of nitrite-based therapy, with special attention to its application in cardiovascular disorders, inflammation, and anti-bacterial defence. It can be concluded that nitrite (as well as nitrate-rich diet for long-term applications) may hold promise as therapeutic agent in vascular dysfunction and ischemic injury, as well as an effective compound able to promote angiogenesis.

  12. Proanthocyanidin synthesis in Theobroma cacao: genes encoding anthocyanidin synthase, anthocyanidin reductase, and leucoanthocyanidin reductase.

    Science.gov (United States)

    Liu, Yi; Shi, Zi; Maximova, Siela; Payne, Mark J; Guiltinan, Mark J

    2013-12-05

    The proanthocyanidins (PAs), a subgroup of flavonoids, accumulate to levels of approximately 10% total dry weight of cacao seeds. PAs have been associated with human health benefits and also play important roles in pest and disease defense throughout the plant. To dissect the genetic basis of PA biosynthetic pathway in cacao (Theobroma cacao), we have isolated three genes encoding key PA synthesis enzymes, anthocyanidin synthase (ANS), anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR). We measured the expression levels of TcANR, TcANS and TcLAR and PA content in cacao leaves, flowers, pod exocarp and seeds. In all tissues examined, all three genes were abundantly expressed and well correlated with PA accumulation levels, suggesting their active roles in PA synthesis. Overexpression of TcANR in an Arabidopsis ban mutant complemented the PA deficient phenotype in seeds and resulted in reduced anthocyanidin levels in hypocotyls. Overexpression of TcANS in tobacco resulted in increased content of both anthocyanidins and PAs in flower petals. Overexpression of TcANS in an Arabidopsis ldox mutant complemented its PA deficient phenotype in seeds. Recombinant TcLAR protein converted leucoanthocyanidin to catechin in vitro. Transgenic tobacco overexpressing TcLAR had decreased amounts of anthocyanidins and increased PAs. Overexpressing TcLAR in Arabidopsis ldox mutant also resulted in elevated synthesis of not only catechin but also epicatechin. Our results confirm the in vivo function of cacao ANS and ANR predicted based on sequence homology to previously characterized enzymes from other species. In addition, our results provide a clear functional analysis of a LAR gene in vivo.

  13. Expression and site-directed mutagenesis of human dihydrofolate reductase

    Energy Technology Data Exchange (ETDEWEB)

    Prendergast, N.J.; Delcamp, T.J.; Smith, P.L.; Freisheim, J.H.

    1988-05-17

    A procaryotic high-level expression vector for human dihydrofolate reductase has been constructed and the protein characterized as a first step toward structure-function studies of this enzyme. A vector bearing the tac promoter, four synthetic oligodeoxynucleotides, and a restriction fragment from the dihydrofolate reductase cDNA were ligated in a manner which optimized the transcriptional and translational frequency of the enzyme mRNA. The reductase, comprising ca. 17% of the total soluble protein in the host bacteria, was purified to apparent homogeneity as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and characterized by amino acid composition, partial amino acid sequence, and steady-sate kinetic analysis. This expression vector has been used as a template for double-stranded plasmid DNA site-specific mutagenesis. Functional studies on a Cys-6 ..-->.. Ser-6 mutant enzyme support the contention that Cys-6 is obligatory for organomercurial activation of human dihydrofolate reductase. The Ser-6 mutant enzyme was not activated to any extent following a 24-h incubation with p-(hydroxymercuri)benzoate and nicotinamide adenine dinucleotide phosphate (reduced) (NADPH), whereas the k/sub cat/ for Cys-6 reductase increased 2-fold under identical conditions. The specific activities of the Cys-6 and Ser-6 enzymes were virtually identical as determined by methotrexate titration as were the K/sub m/ values for both dihydrofolate and NADPH. The Ser-6 mutant showed a decreased temperature stability and was more sensitive to inactivation by ..cap alpha..-chymotrypsin when compared to the wild-type enzyme. These results suggest that the Ser-6 mutant reductase is conformationally altered relative to the Cys-6 native enzyme.

  14. [Nitrate concentrations in tap water in Spain].

    Science.gov (United States)

    Vitoria, Isidro; Maraver, Francisco; Sánchez-Valverde, Félix; Armijo, Francisco

    2015-01-01

    To determine nitrate concentrations in drinking water in a sample of Spanish cities. We used ion chromatography to analyze the nitrate concentrations of public drinking water in 108 Spanish municipalities with more than 50,000 inhabitants (supplying 21,290,707 potential individuals). The samples were collected between January and April 2012. The total number of samples tested was 324. The median nitrate concentration was 3.47 mg/L (range: 0.38-66.76; interquartile range: 4.51). The water from 94% of the municipalities contained less than 15 mg/L. The concentration was higher than 25mg/L in only 3 municipalities and was greater than 50mg/L in one. Nitrate levels in most public drinking water supplies in municipalities inhabited by almost half of the Spanish population are below 15 mg/L. Copyright © 2014 SESPAS. Published by Elsevier Espana. All rights reserved.

  15. Nitrate Waste Treatment Sampling and Analysis Plan

    Energy Technology Data Exchange (ETDEWEB)

    Vigil-Holterman, Luciana R. [Los Alamos National Laboratory; Martinez, Patrick Thomas [Los Alamos National Laboratory; Garcia, Terrence Kerwin [Los Alamos National Laboratory

    2017-07-05

    This plan is designed to outline the collection and analysis of nitrate salt-bearing waste samples required by the New Mexico Environment Department- Hazardous Waste Bureau in the Los Alamos National Laboratory (LANL) Hazardous Waste Facility Permit (Permit).

  16. ROE Wet Nitrate Deposition 2011-2013

    Data.gov (United States)

    U.S. Environmental Protection Agency — The raster data represent the amount of wet nitrate deposition in kilograms per hectare from 2011 to 2013. Summary data in this indicator were provided by EPA’s...

  17. ROE Wet Nitrate Deposition 1989-1991

    Data.gov (United States)

    U.S. Environmental Protection Agency — The raster data represent the amount of wet nitrate deposition in kilograms per hectare from 1989 to 1991. Summary data in this indicator were provided by EPA’s...

  18. High dose potassium-nitrate chemical dosimeter

    International Nuclear Information System (INIS)

    Dorda de Cancio, E.M.; Munoz, S.S.

    1982-01-01

    This dosimeter is used to control 10 kGY-order doses (1 Mrad). Nitrate suffers a radiolitic reduction phenomena, which is related to the given dose. The method to use potassium nitrate as dosimeter is described, as well as effects of the temperature of irradiation, pH, nitrate concentration and post-irradiation stability. Nitrate powder was irradiated at a Semi-Industrial Plant, at Centro Atomico Ezeiza, and also in a Gammacell-220 irradiator. The dose rates used were 2,60 and 1,80 KGY/hour, and the given doses varied between 1,0 and 150 KGY. The uncertainty was +-3% in all the range. (author) [es

  19. Nitrate reduction in geologically heterogeneous catchments

    DEFF Research Database (Denmark)

    Refsgaard, Jens Christian; Auken, Esben; Bamberg, Charlotte A.

    2014-01-01

    In order to fulfil the requirements of the EU Water Framework Directive nitrate load from agricultural areas to surface water in Denmark needs to be reduced by about 40%. The regulations imposed until now have been uniform, i.e. the same restrictions for all areas independent of the subsurface...... conditions. Studies have shown that on a national basis about 2/3 of the nitrate leaching from the root zone is reduced naturally, through denitrification, in the subsurface before reaching the streams. Therefore, it is more cost-effective to identify robust areas, where nitrate leaching through the root...... the entire catchment. However, as distributed models often do not include local scale hydrogeological heterogeneities, they are typically not able to make accurate predictions at scales smaller than they are calibrated. We present a framework for assessing nitrate reduction in the subsurface...

  20. Thermolysis of urea complexes of uranyl nitrate

    International Nuclear Information System (INIS)

    Kostyuk, N. N.

    2005-01-01

    Quantitative parameters of thermolysis of uranyl nitrate urea complexes, [UO 2 (NO 3 ) 2 {(NH 2 ) 2 CO} 2 ], [UO 2 (H 2 O){(NH 2 ) 2 CO} 4 ](NO 3 ) 2 , and [UO 2 (H 2 O){(NH 2 ) 2 CO} 5 ](NO 3 ) 2 at 175, 200, and 225 deg C were measured. Thermolysis of [UO 2 (NO 3 ) 2 {(NH 2 ) 2 CO} 2 ] at 200 deg C affords the biuret complex of uranyl nitrate in a 90% yield. The urea ligands in the hydrated complexes completely transform into biuret at 175 deg C. Thermolysis of [UO 2 (H 2 O){(NH 2 ) 2 CO} 5 ](NO 3 ) 2 yields the biuret-cyanurate complexes of uranyl nitrate. The features of thermolysis of the uranyl nitrate complexes originate from the chemical transformations of urea at elevated temperatures [ru

  1. Mechanisms of Peroxynitrite Mediated Nitration of Tyrosine

    Science.gov (United States)

    Gunaydin, Hakan; Houk, K. N.

    2009-01-01

    The mechanisms of tyrosine nitration by peroxynitrous acid or nitrosoperoxycarbonate were investigated with the CBS-QB3 method. Either the protonation of peroxynitrite, or a reaction with carbon dioxide gives a reactive peroxide intermediate. Peroxynitrous acid mediated nitration of phenol occurs via the unimolecular decomposition to give nitrogen dioxide and hydroxyl radicals. Nitrosoperoxycarbonate also undergoes unimolecular decomposition to give carbonate and nitrogen dioxide radicals. The reactions of tyrosine with the hydroxyl or carbonate radicals give a phenoxy radical intermediate. The reaction of the nitrogen dioxide with this radical intermediate followed by tautomerization gives nitrated tyrosine in both cases. According to CBS-QB3 calculations, the rate-limiting step for the nitration of phenol is the decomposition of peroxynitrous acid or of nitrosoperoxycarbonate. PMID:19374346

  2. Primordial membranes

    DEFF Research Database (Denmark)

    Hanczyc, Martin M; Monnard, Pierre-Alain

    2017-01-01

    Cellular membranes, which are self-assembled bilayer structures mainly composed of lipids, proteins and conjugated polysaccharides, are the defining feature of cell physiology. It is likely that the complexity of contemporary cells was preceded by simpler chemical systems or protocells during...... the various evolutionary stages that led from inanimate to living matter. It is also likely that primitive membranes played a similar role in protocell 'physiology'. The composition of such ancestral membranes has been proposed as mixtures of single hydrocarbon chain amphiphiles, which are simpler versions...

  3. Plasmid-encoded diacetyl (acetoin) reductase in Leuconostoc pseudomesenteroides

    DEFF Research Database (Denmark)

    Rattray, Fergal P; Myling-Petersen, Dorte; Larsen, Dianna

    2003-01-01

    A plasmid-borne diacetyl (acetoin) reductase (butA) from Leuconostoc pseudomesenteroides CHCC2114 was sequenced and cloned. Nucleotide sequence analysis revealed an open reading frame encoding a protein of 257 amino acids which had high identity at the amino acid level to diacetyl (acetoin...... diacetyl (acetoin) reductase activity with NADH as coenzyme, but not with NADPH as coenzyme, suggesting the presence of another diacetyl (acetoin)-reducing activity in L. pseudomesenteroides. Plasmid-curing experiments demonstrated that the butA gene is carried on a 20-kb plasmid in L. pseudomesenteroides....

  4. 2'-Deoxymugineic acid promotes growth of rice (Oryza sativa L.) by orchestrating iron and nitrate uptake processes under high pH conditions.

    Science.gov (United States)

    Araki, Ryoichi; Kousaka, Kayoko; Namba, Kosuke; Murata, Yoshiko; Murata, Jun

    2015-01-01

    Poaceae plants release 2'-deoxymugineic acid (DMA) and related phytosiderophores to chelate iron (Fe), which often exists as insoluble Fe(III) in the rhizosphere, especially under high pH conditions. Although the molecular mechanisms behind the biosynthesis and secretion of DMA have been studied extensively, little information is known about whether DMA has biological roles other than chelating Fe in vivo. Here, we demonstrate that hydroponic cultures of rice (Oryza sativa) seedlings show almost complete restoration in shoot height and soil-plant analysis development (SPAD) values after treatment with 3-30 μm DMA at high pH (pH 8.0), compared with untreated control seedlings at normal pH (pH 5.8). These changes were accompanied by selective accumulation of Fe over other metals. While this enhanced growth was evident under high pH conditions, DMA application also enhanced seedling growth under normal pH conditions in which Fe was fairly accessible. Microarray and qRT-PCR analyses revealed that exogenous DMA application attenuated the increased expression levels of various genes related to Fe transport and accumulation. Surprisingly, despite the preferential utilization of ammonium over nitrate as a nitrogen source by rice, DMA application also increased nitrate reductase activity and the expression of genes encoding high-affinity nitrate transporters and nitrate reductases, all of which were otherwise considerably lower under high pH conditions. These data suggest that exogenous DMA not only plays an important role in facilitating the uptake of environmental Fe, but also orchestrates Fe and nitrate assimilation for optimal growth under high pH conditions. © 2014 The Authors The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

  5. Preformed Nitrate in the Glacial North Atlantic

    Science.gov (United States)

    Homola, K.; Spivack, A. J.; D'Hondt, S.; Estes, E. R.; Insua, T. L.; McKinley, C. C.; Murray, R. W.; Pockalny, R. A.; Robinson, R. S.; Sauvage, J.

    2015-12-01

    Atmospheric CO2 abundances are highly correlated with global temperature variations over the past 800,000 years. Consequently, understanding the feedbacks between climate and CO2 is important for predictions of future climate. Leading hypotheses to explain this feedback invoke changes in ocean biology, circulation, chemistry, and/or gas exchange rates to trap CO2 in the deep ocean, thereby reducing the greenhouse effect of CO2 in the atmosphere. To test these hypotheses, we use sediment pore water profiles of dissolved nitrate and oxygen to reconstruct paleo-preformed nitrate concentrations at two deep-water sites in the western North Atlantic (23°N 57°W, 5557 m water depth; 30°N 58°W, 5367 m water depth). Preformed nitrate increases down-core to 22.7 μM (25.6 m core depth) at the northern site, and to 28.5 μM (27.8 m core depth) at the southern site. The large preformed nitrate gradient between these sites reveals a paleo-boundary between a southern water source high in preformed nitrate and a northern water source with lower concentrations, similar to today's ocean. However, the boundary between these water masses occurs north of where their modern counterparts meet, indicating that Antarctic Bottom Water (AABW) extended farther north during the Last Glacial Maximum (LGM). In addition, the southern source had a higher preformed nitrate concentration than today's AABW (25 μM), contradicting hypotheses that nutrient utilization was more efficient in the Southern Ocean deep-water formation regions during the LGM. Comparison to our previous Pacific data reveals that the average preformed nitrate concentration of the deep ocean was slightly higher during the LGM than today. This result implies that the CO2-climate feedback was not principally due to more efficient nitrate utilization.

  6. Is beetroot juice more effective than sodium nitrate? The effects of equimolar nitrate dosages of nitrate-rich beetroot juice and sodium nitrate on oxygen consumption during exercise.

    Science.gov (United States)

    Flueck, Joelle Leonie; Bogdanova, Anna; Mettler, Samuel; Perret, Claudio

    2016-04-01

    Dietary nitrate has been reported to lower oxygen consumption in moderate- and severe-intensity exercise. To date, it is unproven that sodium nitrate (NaNO3(-); NIT) and nitrate-rich beetroot juice (BR) have the same effects on oxygen consumption, blood pressure, and plasma nitrate and nitrite concentrations or not. The aim of this study was to compare the effects of different dosages of NIT and BR on oxygen consumption in male athletes. Twelve healthy, well-trained men (median [minimum; maximum]; peak oxygen consumption: 59.4 mL·min(-1)·kg(-1) [40.5; 67.0]) performed 7 trials on different days, ingesting different nitrate dosages and placebo (PLC). Dosages were 3, 6, and 12 mmol nitrate as concentrated BR or NIT dissolved in plain water. Plasma nitrate and nitrite concentrations were measured before, 3 h after ingestion, and postexercise. Participants cycled for 5 min at moderate intensity and further 8 min at severe intensity. End-exercise oxygen consumption at moderate intensity was not significantly different between the 7 trials (p = 0.08). At severe-intensity exercise, end-exercise oxygen consumption was ~4% lower in the 6-mmol BR trial compared with the 6-mmol NIT (p = 0.003) trial as well as compared with PLC (p = 0.010). Plasma nitrite and nitrate concentrations were significantly increased after the ingestion of BR and NIT with the highest concentrations in the 12-mmol trials. Plasma nitrite concentration between NIT and BR did not significantly differ in the 6-mmol (p = 0.27) and in the 12-mmol (p = 0.75) trials. In conclusion, BR might reduce oxygen consumption to a greater extent compared with NIT.

  7. Energy transfer in crystalline alkali nitrates

    Energy Technology Data Exchange (ETDEWEB)

    Anan' ev, Vladimir [Department of Analytical Chemistry, Kemerovo State University, Krasnaya Str., 6, Kemerovo 650043 (Russian Federation)]. E-mail: eprlab@kemsu.ru

    2007-08-15

    The radiation annealing of peroxynitrite ions in pre-photolyzed (253.7nm) alkali nitrate crystals has been studied. This process is stated to be due to interaction with high-energy excited states of the nitrate ion symmetry E' than to low-energy excited states symmetry A{sub 1}{sup '}'. The distance of energy transfer has been found to be {approx}10nm.

  8. Data on nitrate and nitrate of Taham dam in Zanjan (Iran

    Directory of Open Access Journals (Sweden)

    Mohammadreza Massoudinejad

    2018-04-01

    Full Text Available In recent years, contamination of water resources, with pollutants such as nitrate and nitrite, has significantly increased. These compounds can have harmful effects on human health, especially children such as methemoglobinemia. The main objective of this study was to measure the concentration of nitrate and nitrite and its health-risk assessment in the rivers entering Taham dam in Zanjan. USEPA Method was used to assess the health-risk of nitrate and nitrite. According to the obtained results, the concentration of nitrate and nitrite was in the range of 0.51–14.93 mg/l and 0.001–0.061 mg/l, respectively. According to the results, the mean of the CDI for nitrate and nitrite was 9.52*10−2 and 3.63*10−4 mg/kg/day, respectively. Furthermore, the mean HI for nitrate and nitrite was 5.97*10−2 and 3.63*10−3, respectively. The concentration of nitrate and nitrite in rivers was lower than the WHO and Iran guidelines. Based on the results, the HI value in all samples was less than 1 which indicating the non-carcinogenic effects of nitrate and nitrite in these rivers. Keywords: Nitrate, Nitrite, Water quality, Dam

  9. Criticality parameters for uranyl nitrate or plutonium nitrate systems in tributyl phosphate/kerosine and water

    International Nuclear Information System (INIS)

    Weber, W.

    1985-01-01

    This report presents the calculated values of smallest critical masses and volumina and neutron physical parameters for uranyl nitrate (3, 4, 5% U-235) or plutonium nitrate (5% Pu-240), each in a 30 per cent solution of tributyl phosphate (TBP)/kerosine. For the corresponding nitrate-water solutions, newly calculated results are presented together with a revised solution density model. A comparison of the data shows to what extent the criticality of nitrate-TBP/kerosine systems can be assessed on the basis of nitrate-water parameters, revealing that such data can be applied to uranyl nitrate/water systems, taking into account that the smallest critical mass of uranyl nitrate-TBP/kerosine systems, up to a 5 p.c. U-235 enrichment, is by 4.5 p.c. at the most smaller than that of UNH-water solutions. Plutonium nitrate (5% Pu-240) in the TBP/kerosine solution will have a smallest critical mass of up to 7 p.c. smaller, as compared with the water data. The suitability of the computing methods and cross-sections used is verified by recalculating experiments carried out to determine the lowest critical enrichment of uranyl nitrate. The calculated results are well in agreement with experimental data. The lowest critical enrichment is calculated to be 2.10 p.c. in the isotope U-235. (orig.) [de

  10. Extreme nitrite tolerance in the clown knifefish Chitala ornata is linked to up-regulation of methaemoglobin reductase activity

    DEFF Research Database (Denmark)

    Gam, Le Thi Hong; Jensen, Frank Bo; Damsgaard, Christian

    2017-01-01

    and fell towards control values during the last half of the exposure period. Plasma nitrate, in contrast, rose continuously, reflecting detoxification of nitrite to nitrate. MetHb generated from the reaction between nitrite and erythrocyte Hb reached 38% at day 2, but then decreased to 17% by the end......The clown knifefish is a facultative air breather, which is widely farmed in freshwater ponds in Vietnam. Here we report a very high nitrite tolerance (96h LC50 of 7.82mM) in this species and examine the effects of 1mM (LC5) and 2.5mM (LC10) ambient nitrite on haemoglobin (Hb) derivatives......, electrolyte levels, acid-base status, and total body water content during 7days of exposure. Furthermore, we tested the hypothesis that erythrocyte methaemoglobin (metHb) reductase activity is upregulated by nitrite exposure. Plasma nitrite levels increased for 2-3days but stayed below environmental levels...

  11. Denitrification inhibition by high nitrate wastes

    International Nuclear Information System (INIS)

    Veydovec, W.; Silverstein, J.; Lehmkuhl, G.D.

    1994-01-01

    The processing of radioactive metal products at nuclear weapons plants and research labs has produced wastewaters containing high concentrations of nitrate, often greater than 50,000 mg/l N. The adaptation of activated sludge and inhibition of denitrification at high nitrate concentrations was studied using pH controlled bench-scale sequencing batch reactors (SBRs), operated with 50% of the SBR volume recycled (recycle volume = influent volume). Denitrification of 1,350 and 2,700 mg/l NO 3 - -N was completed after approximately 5 hours and 15 hours, respectively. No denitrification of 5,400 mg/l NO 3 - -N was observed. These results suggest that there is a progressive inhibition of denitrification as nitrate concentrations increase from 1,350 to 5,400 mg/l NO 3 - -N. In a subsequent series of experiments at an initial reactor nitrate concentration of 1,350 mg/l N, a significant accumulation of nitrate was observed, resulting once in destabilization with loss of denitrification and once in successful adaptation of the activated sludge. At a nitrate concentration of 1,350 mg/l N, the adaptation of activated sludge appears to be unstable, resulting sometimes in stable denitrification and sometimes in biomass washout

  12. Nitrate Adsorption on Clay Kaolin: Batch Tests

    Directory of Open Access Journals (Sweden)

    Morteza Mohsenipour

    2015-01-01

    Full Text Available Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112.5, 225, and 450 mgNO3-/L, with a constant pH equal to 2, constant temperature equal to 25°C, and exposure period varying from 0 to 150 minutes were considered. The capacity of nitrate adsorption on kaolin has also been studied involving two well-known adsorption isotherm models, namely, Freundlich and Longmuir. The results revealed that approximately 25% of the nitrate present in the solution was adsorbed on clay kaolin. The laboratory experimental data revealed that Freundlich adsorption isotherm model was more accurate than Longmuir adsorption model in predicting of nitrate adsorption. Furthermore, the retardation factor of nitrate pollution in saturated zone has been found to be approximately 4 in presence of kaolin, which indicated that kaolin can be used for natural scavenger of pollution in the environment.

  13. Anaerobic columnar denitrification of high nitrate wastewater

    International Nuclear Information System (INIS)

    Francis, C.W.; Malone, C.D.

    1975-01-01

    Anaerobic columns were used to test the effectiveness of biological denitrification of nitrate solutions ranging in concentration from 1 to 10 kg NO 3 /m 3 . Several sources of nitrate (Ca(CNO 3 ) 2 , NaNO 3 , NH 4 NO 3 , and actual nitrate wastes from a UO 2 fuel fabrication plant) were evaluated as well as two packing media. The packing media were anthracite coal particles, whose effective diameter size ranged between 2 and 3 mm, and polypropylene Raschig rings 1.6 x 1.6 diameter. The anthracite coal proved to be the better packing media as excessive hydraulic short circuiting occurred in a 120 x 15 cm diameter glass column packed with the polypropylene rings after 40 days operation. With anthracite coal, floatation of the bed occurred at flow rates greater than 0.80 cm 3 /s. Tapered columns packed with anthracite coal eliminated the floatation problem, even at flow rates as high as 5 cm 3 /s. Under optimum operating conditions the anthracite coal behaved as a fluidized bed. Maximum denitrification rates were 1.0--1.4 g NO 3 /m 3 /s based on initial bed volume. Denitrification kinetics indicated that rates of denitrification became substrate inhibited at nitrate concentrations greater than 6.5 kg NO 3 /m 3 Anaerobic columns packed with anthracite coal appear to be an effective method of nitrate disposal for nitrate rich wastewater generated at UO 2 fuel fabrication plants and fuel reprocessing facilities. (U.S.)

  14. Protein tyrosine nitration in the cell cycle

    International Nuclear Information System (INIS)

    Jia, Min; Mateoiu, Claudia; Souchelnytskyi, Serhiy

    2011-01-01

    Highlights: → Enrichment of 3-nitrotyrosine containing proteins from cells synchronized in different phases of the cell cycle. → Identification of 76 tyrosine nitrated proteins that change expression during the cell cycle. → Nineteen identified proteins were previously described as regulators of cell proliferation. -- Abstract: Nitration of tyrosine residues in proteins is associated with cell response to oxidative/nitrosative stress. Tyrosine nitration is relatively low abundant post-translational modification that may affect protein functions. Little is known about the extent of protein tyrosine nitration in cells during progression through the cell cycle. Here we report identification of proteins enriched for tyrosine nitration in cells synchronized in G0/G1, S or G2/M phases of the cell cycle. We identified 27 proteins in cells synchronized in G0/G1 phase, 37 proteins in S phase synchronized cells, and 12 proteins related to G2/M phase. Nineteen of the identified proteins were previously described as regulators of cell proliferation. Thus, our data indicate which tyrosine nitrated proteins may affect regulation of the cell cycle.

  15. Elevated CO2 levels affect the activity of nitrate reductase and carbonic anhydrase in the calcifying rhodophyte Corallina officinalis

    OpenAIRE

    Hofmann, Laurie C.; Straub, Sandra; Bischof, Kai

    2013-01-01

    The concentration of CO2 in global surface ocean waters is increasing due to rising atmospheric CO2 emissions, resulting in lower pH and a lower saturation state of carbonate ions. Such changes in seawater chemistry are expected to impact calcification in calcifying marine organisms. However, other physiological processes related to calcification might also be affected, including enzyme activity. In a mesocosm experiment, macroalgal communities were exposed to three CO2 concentrations (380, 6...

  16. Trace nitrate in oxic waters

    Science.gov (United States)

    Zafiriou, O. C.; Ball, L. A.; Hanley, Q.

    1992-08-01

    We describe a modified (Garside, 1982, Marine Chemistry, 11, 159-167) nitrite method that permits measurements down to subnanomolar concentrations and present datafrom Atlantic and Carribean deepwater profiles for comparison with a published Pacific section. This important intermediate in the nitrogen cycle was detected in all samples. Concentrations were consistently lowest (0.1-0.4 nM) in oligotrophic surface waters. Below 1 km, carribean and Southwest Sargasso sea nitrite concentrations were 0.4-1 nM, decreasing with increasing depth; reported Pacific [NO 2] averages are several times higher. Profiles in the upper kilometer beneath the classical primary nitrate maximum (PNM) were qualitatively similar, exhibiting a smooth supra-exponential drop with depth to vvalues of ˜1-4 nM at 1 km. Then nitrite inventory in this "tail" of the PNM above 1 km with 1 nM ≤[NO 2]≤50 nM roughly equals that in the classical PNM. Significant differences among profiles in the 0.1-1 km regionn are observed, consistent with nitrite pool turnover of 3-7 days estimated from Redfield stoichiometry and tritium-helium ages. Thus seasonal and/or regional variations in factors altering the nitrite production-consumption balance, rather than transport, seem to be responsible for nitrite variability. Nitrite profiles with anomalous midwater or near-bottom fine structure, including multi-point maxima and minima, were found along the Venezuelan continental margin and at ≈ 13°N. These featurers are tentatively ascribed to boundary effects, as hydrographic and circumstantial evidence suggests that these waters interacted previously with the bottom.

  17. Radiation-induced nitration of organic compounds in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Ershov, B.G.; Gordeev, A.V.; Bykov, G.L. [Russian Academy of Sciences, Moscow (Russian Federation). Frumkin Inst. of Physical Chemistry and Electrochemistry; Moisy, P. [CEA, Bagnols sur Ceze (France). Nuclear Energy Div.

    2012-07-01

    Radiolysis in aqueous nitrate and acetic acid solutions and nitrate/nitric acid and phenol was studied. The radiolysis of these solutes occurs with {sup circle} NO{sup 2} radical, which is the active nitrating agent. Accumulation of nitromethane and nitrite was determined during {gamma}-irradiation of aqueous solutions containing acetic and nitrate solutions. Irradiation of aqueous phenol-nitrate/nitric acid solutions results in the formation of 2- and 4-nitrophenols.

  18. Formation, Evaporation, and Hydrolysis of Organic Nitrates from Nitrate Radical Oxidation of Monoterpenes

    Science.gov (United States)

    Ng, N. L.; Takeuchi, M.; Eris, G.; Berkemeier, T.; Boyd, C.; Nah, T.; Xu, L.

    2017-12-01

    Organic nitrates play an important role in the cycling of NOx and secondary organic aerosol (SOA) formation, yet their formation mechanisms and fates remain highly uncertain. The interactions of biogenic VOCs with NO3 radicals represent a direct way for positively linking anthropogenic and biogenic emissions. Results from ambient studies suggest that organic nitrates have a relatively short lifetime, though corresponding laboratory data are limited. SOA and organic nitrates produced at night may evaporate the following morning due to increasing temperatures or dilution of semi-volatile compounds. Once formed, organic nitrates can also undergo hydrolysis in the presence of particle water. In this work, we investigate the formation, evaporation, and hydrolysis of organic nitrates generated from the nitrate radical oxidation of a-pinene, b-pinene, and limonene. Experiments are conducted in the Georgia Environmental Chamber facility (GTEC) under dry and humid conditions and different temperatures. Experiments are also designed to probe different peroxy radical pathways (RO2+HO2 vs RO2+NO3). Speciated gas-phase and particle-phase organic nitrates are continuously monitored by a Filter Inlet for Gases and AEROsols High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (FIGAERO-HR-ToF-CIMS). Bulk aerosol composition is measured by a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). A large suite of highly oxygenated gas- and particle-phase organic nitrates are formed rapidly. We find a resistance to aerosol evaporation when it is heated. The extent of organic nitrate hydrolysis in the humid experiments is evaluated. The dynamics of the speciated organic nitrates over the course of the experiments will also be discussed. Results from this chamber study provide fundamental data for understanding the dynamics of organic nitrate aerosols over its atmospheric lifetime.

  19. Nitrate in groundwater in the United States

    Science.gov (United States)

    Burow, K. R.; Nolan, B. T.; Rupert, M. G.; Dubrovsky, N. M.

    2009-12-01

    An assessment of nitrate concentrations in groundwater in the United States (US) indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high nitrogen inputs. During 1991-2003, 5,101 wells were sampled in 51 study areas throughout the US as part of the USGS National Water-Quality Assessment program. Well locations for individual 30-well networks were selected for sampling using a computerized, stratified, random site-selection procedure to minimize spatial bias. These well networks reflect the existing used resource in major aquifers represented by domestic wells (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations in groundwater were compared with nationally-available variables such as nonpoint-source nitrogen inputs, soils, water chemistry, and other aquifer and well construction characteristics to predict the conditions most vulnerable to high nitrate concentrations. Nitrate was detected at concentrations above background of 1.0 mg/L (as N) in 50% of the wells sampled. Shallow groundwater beneath agricultural land had the highest median concentration of nitrate (3.1 mg/L). Median nitrate in shallow groundwater beneath urban land (1.4 mg/L) was lower than beneath agricultural land, but was higher than the median in major aquifers (0.56 mg/L). Although most wells sampled in the shallow land-use studies were not used for drinking water, concentrations exceeded the US EPA drinking-water standard (MCL) of 10 mg/L in 20% of wells in the agricultural land-use setting. Concentrations exceeded the MCL in only 3% of wells in the urban land-use setting, and 4% of wells in major aquifers. Classification and regression tree analysis was used to identify the relative importance of nitrogen inputs, water chemistry, and physical aquifer properties on nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that

  20. Intraethnic variation in steroid-5-alpha-reductase polymorphisms in ...

    Indian Academy of Sciences (India)

    2015-06-01

    Jun 1, 2015 ... in prostate cancer patients: a potential factor implicated in 5-alpha-reductase inhibitor treatment. LUIS ALBERTO HENRÍQUEZ-HERNÁNDEZ1,2,3∗, ALMUDENA VALENCIANO2, PALMIRA FORO-ARNALOT4,. MARÍA JESÚS ÁLVAREZ-CUBERO5,6, JOSÉ MANUEL COZAR7, JOSÉ FRANCISCO ...

  1. Intraethnic variation in steroid-5-alpha-reductase polymorphisms in ...

    Indian Academy of Sciences (India)

    2015-06-01

    Jun 1, 2015 ... Herrera-Ramos E., Rodríguez-Gallego C. and Lara P. C. 2015 Intraethnic variation in steroid-5-alpha-reductase polymorphisms in prostate ... generation. This study was approved by the Research and. Ethics Committee of each institution participant in the study. DNA was isolated from 300 µL of ...

  2. Bioinformatic analysis of dihydrofolate reductase predicted in the ...

    African Journals Online (AJOL)

    ... 5 alpha helices and 8 beta-strands. Twelve binding site residues were predicted in KCA1_1610 relative to the template protein 2zzaA in protein database (PDB). The predicted structure of KCA1_1610 dihydrofolate reductase can serve as a new template as an addition to structural genomics and generation of models for ...

  3. Dizygotic twinning is not associated with methylenetetrahydrofolate reductase haplotypes

    NARCIS (Netherlands)

    Montgomery, GW; Zhao, Z.Z.; Morley, K.I.; Marsh, A.J.; Boomsma, D.I.; Martin, N.G.; Duffy, DL

    2003-01-01

    Background: Folate metabolism is critical to embryonic development, influencing neural tube defects (NTD) and recurrent early pregnancy loss. Polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR) have been associated with dizygotic (DZ) twinning through pregnancy loss. Methods: The C677T

  4. Cloning and expression analysis of dihydroxyflavonol 4-reductase ...

    African Journals Online (AJOL)

    Southern blot analysis indicate that DFR is presented as a single copy in the Ascocenda spp. genome. The AscoDFR gene was highly expressed in the flower stages 2 and 3 of development as well as in the sepal and petal of the orchid flower. Keywords: Orchid, dihydroxyflavonol 4-reductase, anthocyanins, gene cloning ...

  5. Crystallographic analysis of tricolosan bound to enoyl reductase.

    NARCIS (Netherlands)

    Roujeinikova, A.; Levy, C.W.; Rowsell, S.; Sedelnikova, S.; Baker, P.J.; Minshull, C.A.; Mistry, A.; Colls, J.G.; Camble, R.; Stuitje, A.R.; Slabas, A.R.; Rafferty, J.B.; Pauptit, R.A.; Viner, A; Rice, D.W.

    1999-01-01

    Molecular genetic studies with strains of Escherichia coli resistant to triclosan, an ingredient of many anti-bacterial household goods, have suggested that this compound works by acting as an inhibitor of enoyl reductase (ENR) and thereby blocking lipid biosynthesis. We present structural analyses

  6. Molecular Cloning and Expression of Bacterial Mercuric Reductase ...

    African Journals Online (AJOL)

    USER

    2010-06-21

    Jun 21, 2010 ... In order to characterize the bacterial mercuric reductase (merA) gene, mercury resistant (Hgr). Escherichia coli strains have been isolated from various mercury contaminated sites of India. Their minimum inhibitory concentration (MIC) for Hg and zone of inhibition for different antibiotics were measured, and ...

  7. Evaluation of the conserve flavin reductase gene from three ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-12-15

    Dec 15, 2009 ... means of PCR technique. The nucleic acid sequences of the PCR primers were designed using conserved nucleic acid sequences of the flavin reductase enzyme from. Rhodococcus sp. strain IGTS8. The oligonucleotide primers were as follows: 5'-GAA TTC ATG TCT GAC. AAG CCG AAT GCC-3' (forward) ...

  8. Dihydrofolate reductase: A potential drug target in trypanosomes and leishmania

    Science.gov (United States)

    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.

  9. The intramolecular electron transfer between copper sites of nitrite reductase

    DEFF Research Database (Denmark)

    Farver, O; Eady, R R; Abraham, Z H

    1998-01-01

    The intramolecular electron transfer (ET) between the type 1 Cu(I) and the type 2 Cu(II) sites of Alcaligenes xylosoxidans dissimilatory nitrite reductase (AxNiR) has been studied in order to compare it with the analogous process taking place in ascorbate oxidase (AO). This internal process is in...

  10. Molecular Cloning and Expression of Bacterial Mercuric Reductase ...

    African Journals Online (AJOL)

    In order to characterize the bacterial mercuric reductase (merA) gene, mercury resistant (Hgr) Escherichia coli strains have been isolated from various mercury contaminated sites of India. Their minimum inhibitory concentration (MIC) for Hg and zone of inhibition for different antibiotics were measured, and finally mer operon ...

  11. Determination of nitrite/nitrate in human biological material by the simple Griess reaction.

    Science.gov (United States)

    Guevara, I; Iwanejko, J; Dembińska-Kieć, A; Pankiewicz, J; Wanat, A; Anna, P; Gołabek, I; Bartuś, S; Malczewska-Malec, M; Szczudlik, A

    1998-06-22

    Since a number of pathological processes such as septic shock, inflammation, graft rejection, diabetes, etc. are associated with a release of nitric oxide (NO), rapid and accurate methods of monitoring of NO concentration are of interest. Various methods for measurement of nitrite and nitrate (NO2-, NO3- ) -- the stable metabolites of NO -- are commonly used for this purpose. In this paper we have shown that the proper Griess procedure for nitrite determination significantly increases the sensitivity of this method. This procedure, supplemented with deproteinization and reduction of nitrates to nitrites in the presence of NADPH-sensitive reductase, can be successfully applied for measurement of NOx levels in human body fluids (serum, urine and CSF). Deproteinization of samples with methanol/diethylether is required and does not influence the sensitivity of detection of NO metabolites. The recovery of the method is 88%+/-6% (n = 30). The NOx concentrations measured by this procedure ranged from 25.0 to 39.0 micromol/l in blood, 4.6 to 14.6 micromol/l in CSF and 0.37 to 2.52 mmol/l (adjusted to creatinine concentration) in urine. The coefficient of variation for this method was between 1.3-2.2%. This method can also be recommended for measurement of NOx produced by cells in tissue cell culture.

  12. Organic matrix based slow release fertilizer enhances plant growth, nitrate assimilation and seed yield of Indian mustard (Brassica juncea L.).

    Science.gov (United States)

    Sharma, Vinod K; Singh, Rana P

    2011-09-01

    Field experiments were conducted to study the effect of organic matrix based slow release fertilizers (SRFs) on plant growth, nitrate assimilation and seed yield of Brassica juncea L. cv, pusa bold. The agro-waste materials like cow dung, clay soil, neem leaves and rice bran were mixed together in 2:2:1:1 ratio and used as organic matrix for the immobilization of chemical fertilizer nutrients with commercial grade saresh (Acacia gum, 15% solution) as binder. Different fertilizer treatments were organic matrix based slow release fertilizers, SRF-I (542.0 kg ha(-1)); SRF-II (736.5 kg ha(-1)) and chemical fertilizer combinations, boron (3 kg ha(-1))+sulphur (15 kg ha(-1))+nitrogen (80 kg ha(-1)) and boron (3 kg ha(-1)) + sulphur (15 kg ha(-1))+nitrogen (80 kg ha(-1))+phosphorus (15 kg ha(-1))+potassium (100 kg ha(-1)). Organic matrix based SRF-II released ammonium up to 50-d in wetsoil under laboratory conditions which showed maximum retention of the nutrients. Avery significant increase in plant growth, nitrate assimilation and seed yield was recorded in organic matrix based SRF-II applied plants. The maximum percent increase in biomass production was observed with organic matrix based SRF-II (increase of 65.8% in root fresh weight, 38.0% in root dry weight, 45.9% in leaf fresh weight plant(-1) and 27.5 % in leaf dry weight plant(-1) in 60-d old plants). It also increased the acquisition and assimilation of nitrate from the plant's rhizosphere which was evident by 45.6% increase in nitrate, 27.5% in nitrite and 11.7% in nitrate reductase activity (NRA) in leaves of 45-d old plants over control. The organic matrix based SRF-II significantly increased the seed yield by 28% in Indian mustard. Cost analysis revealed thatthis formulation is cost effective as it is based on agro waste materials.

  13. Tyrosine nitration affects thymidylate synthase properties.

    Science.gov (United States)

    Dąbrowska-Maś, Elżbieta; Frączyk, Tomasz; Ruman, Tomasz; Radziszewska, Karolina; Wilk, Piotr; Cieśla, Joanna; Zieliński, Zbigniew; Jurkiewicz, Agata; Gołos, Barbara; Wińska, Patrycja; Wałajtys-Rode, Elżbieta; Leś, Andrzej; Nizioł, Joanna; Jarmuła, Adam; Stefanowicz, Piotr; Szewczuk, Zbigniew; Rode, Wojciech

    2012-01-14

    Highly purified preparations of thymidylate synthase, isolated from calf thymus, and L1210 parental and FdUrd-resistant cells, were found to be nitrated, as indicated by a specific reaction with anti-nitro-tyrosine antibodies, suggesting this modification to appear endogenously in normal and tumor tissues. Each human, mouse and Ceanorhabditis elegans recombinant TS preparation, incubated in vitro in the presence of NaHCO(3), NaNO(2) and H(2)O(2) at pH 7.5, underwent tyrosine nitration, leading to a V(max)(app) 2-fold lower following nitration of 1 (with human or C. elegans TS) or 2 (with mouse TS) tyrosine residues per monomer. Enzyme interactions with dUMP, meTHF or 5-fluoro-dUMP were not distinctly influenced. Nitration under the same conditions of model tripeptides of a general formula H(2)N-Gly-X-Gly-COOH (X = Phe, Tyr, Trp, Lys, Arg, His, Ser, Thr, Cys, Gly), monitored by NMR spectroscopy, showed formation of nitro-species only for H-Gly-Tyr-Gly-OH and H-Gly-Phe-Gly-OH peptides, the chemical shifts for nitrated H-Gly-Tyr-Gly-OH peptide being in a very good agreement with the strongest peak found in (15)N-(1)H HMBC spectrum of nitrated protein. MS analysis of nitrated human and C. elegans proteins revealed several thymidylate synthase-derived peptides containing nitro-tyrosine (at positions 33, 65, 135, 213, 230, 258 and 301 in the human enzyme) and oxidized cysteine (human protein Cys(210), with catalytically critical Cys(195) remaining apparently unmodified) residues.

  14. Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans.

    Science.gov (United States)

    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.

  15. The Polymorphisms in Methylenetetrahydrofolate Reductase, Methionine Synthase, Methionine Synthase Reductase, and the Risk of Colorectal Cancer

    Science.gov (United States)

    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

  16. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration.

    Science.gov (United States)

    Olah, G A; Narang, S C; Olah, J A

    1981-06-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an alpha-nitronaphthalene to beta-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aromatics. Moodie and Schoefield [Hoggett, J. G., Moodie, R. B., Penton, J. R. & Schoefield, K. (1971) Nitration and Aromatic Reactivity (Cambridge Univ. Press, London)], as well as Perrin, independently concluded that, in the general scheme of nitration of reactive aromatics, there is the necessity to introduce into the classical Ingold mechanism an additional step involving a distinct intermediate preceding the formation of the Wheland intermediate (sigma complexes). This view coincides with our two-step mechanistic picture [Kuhn, S. J. & Olah, G. A. (1961) J. Am. Chem. Soc. 83, 4564-4571] of the nitronium salt nitration of aromatic hydrocarbons (including benzene and toluene), in which low substrate selectivity but high positional selectivity was found, indicating the independence of substrate from positional selectivity.

  17. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration*

    Science.gov (United States)

    Olah, George A.; Narang, Subhash C.; Olah, Judith A.

    1981-01-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an α-nitronaphthalene to β-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aromatics. Moodie and Schoefield [Hoggett, J. G., Moodie, R. B., Penton, J. R. & Schoefield, K. (1971) Nitration and Aromatic Reactivity (Cambridge Univ. Press, London)], as well as Perrin, independently concluded that, in the general scheme of nitration of reactive aromatics, there is the necessity to introduce into the classical Ingold mechanism an additional step involving a distinct intermediate preceding the formation of the Wheland intermediate (σ complexes). This view coincides with our two-step mechanistic picture [Kuhn, S. J. & Olah, G. A. (1961) J. Am. Chem. Soc. 83, 4564-4571] of the nitronium salt nitration of aromatic hydrocarbons (including benzene and toluene), in which low substrate selectivity but high positional selectivity was found, indicating the independence of substrate from positional selectivity. PMID:16593026

  18. Identification of 5α-reductase isoenzymes in canine skin.

    Science.gov (United States)

    Bernardi de Souza, Lucilene; Paradis, Manon; Zamberlam, Gustavo; Benoit-Biancamano, Marie-Odile; Price, Christopher

    2015-10-01

    Alopecia X in dogs is a noninflammatory alopecia that may be caused by a hormonal dysfunction. It may be similar to androgenic alopecia in men that is caused by the effect of dihydrotestosterone (DHT). The 5α-reductase isoenzymes, 5αR1 and 5αR2, and a recently described 5αR3, are responsible for the conversion of testosterone into DHT. However, which 5α-reductases are present in canine skin has not yet been described. The main objective of this study was to determine the pattern of expression of 5α-reductase genes in canine skin. Skin biopsies were obtained from healthy, intact young-mature beagles (three males, four females) at three anatomical sites normally affected by alopecia X (dorsal neck, back of thighs and base of tail) and two sites generally unaffected (dorsal head and ventral thorax). Prostate samples (n = 3) were collected as positive controls for 5α-reductase mRNA abundance measurement by real-time PCR. We detected mRNA encoding 5αR1 and 5αR3 but not 5αR2. There were no significant differences in 5αR1 and 5αR3 mRNA levels between the different anatomical sites, irrespective of gender (P > 0.05). Moreover, the mean mRNA abundance in each anatomical site did not differ between males and females (P > 0.05). To the best of the authors' knowledge, this is the first study demonstrating the expression of 5α-reductases in canine skin and the expression of 5αR3 in this tissue. These results may help to elucidate the pathogenesis of alopecia X and to determine more appropriate treatments for this disorder. © 2015 ESVD and ACVD.

  19. Arabidopsis cpFtsY mutants exhibit pleiotropic defects including an inability to increase iron deficiency-inducible root Fe(III) chelate reductase activity.

    Science.gov (United States)

    Durrett, Timothy P; Connolly, Erin L; Rogers, Elizabeth E

    2006-08-01

    All plants, except for the grasses, must reduce Fe(III) to Fe(II) in order to acquire iron. In Arabidopsis, the enzyme responsible for this reductase activity in the roots is encoded by FRO2. Two Arabidopsis mutants, frd4-1 and frd4-2, were isolated in a screen for plants that do not induce Fe(III) chelate reductase activity in their roots in response to iron deficiency. frd4 mutant plants are chlorotic and grow more slowly than wild-type Col-0 plants. Additionally, frd4 chloroplasts are smaller in size and possess dramatically fewer thylakoid membranes and grana stacks when compared with wild-type chloroplasts. frd4 mutant plants express both FRO2 and IRT1 mRNA normally in their roots under iron deficiency, arguing against any defects in systemic iron-deficiency signaling. Further, transgenic frd4 plants accumulate FRO2-dHA fusion protein under iron-deficient conditions, suggesting that the frd4 mutation acts post-translationally in reducing Fe(III) chelate reductase activity. FRO2-dHA appears to localize to the plasma membrane of root epidermal cells in both Col-0 and frd4-1 transgenic plants when grown under iron-deficient conditions. Map-based cloning revealed that the frd4 mutations reside in cpFtsY, which encodes a component of one of the pathways responsible for the insertion of proteins into the thylakoid membranes of the chloroplast. The presence of cpFtsY mRNA and protein in the roots of wild-type plants suggests additional roles for this protein, in addition to its known function in targeting proteins to the thylakoid membrane in chloroplasts.

  20. Nitrate radical oxidation of γ-terpinene: hydroxy nitrate, total organic nitrate, and secondary organic aerosol yields

    Science.gov (United States)

    Slade, Jonathan H.; de Perre, Chloé; Lee, Linda; Shepson, Paul B.

    2017-07-01

    Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ONs) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic γ-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from γ-terpinene oxidation by the nitrate radical (NO3), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following γ-terpinene oxidation by NO3. Under dry conditions, the hydroxy nitrate yield = 4(+1/-3) %, total ON yield = 14(+3/-2) %, and SOA yield ≤ 10 % under atmospherically relevant particle mass loadings, similar to those for α-pinene + NO3. Using a chemical box model, we show that the measured concentrations of NO2 and γ-terpinene hydroxy nitrates can be reliably simulated from α-pinene + NO3 chemistry. This suggests that NO3 addition to either of the two internal double bonds of γ-terpinene primarily decomposes forming a relatively volatile keto-aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography-mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental US and the Midwest, where polyolefinic monoterpene emissions are greatest.

  1. Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases

    Science.gov (United States)

    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.; hide

    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.

  2. Triterpenes and meroterpenes from Ganoderma lucidum with inhibitory activity against HMGs reductase, aldose reductase and α-glucosidase.

    Science.gov (United States)

    Chen, Baosong; Tian, Jin; Zhang, Jinjin; Wang, Kai; Liu, Li; Yang, Bo; Bao, Li; Liu, Hongwei

    2017-07-01

    Seven new compounds including four lanostane triterpenoids, lucidenic acids Q-S (1-3) and methyl ganoderate P (4), and three triterpene-farnesyl hydroquinone conjugates, ganolucinins A-C (5-7), one new natural product ganomycin J (8), and 73 known compounds (9-81) were isolated from fruiting bodies of Ganoderma lucidum. The structures of the compounds 1-8 were determined by spectroscopic methods. Bioactivities of compounds isolated were assayed against HMG-CoA reductase, aldose reductase, α-glucosidase, and PTP1B. Ganolucidic acid η (39), ganoderenic acid K (44), ganomycin J (8), and ganomycin B (61) showed strong inhibitory activity against HMG-CoA reductase with IC 50 of 29.8, 16.5, 30.3 and 14.3μM, respectively. Lucidumol A (67) had relatively good effect against aldose reductase with IC 50 of 19.1μM. Farnesyl hydroquinones ganomycin J (8), ganomycin B (61), ganomycin I (62), and triterpene-farnesyl hydroquinone conjugates ganoleuconin M (76) and ganoleuconin O (79) possessed good inhibitory activity against α-glucosidase with IC 50 in the range of 7.8 to 21.5μM. This work provides chemical and biological evidence for the usage of extracts of G. lucidum as herbal medicine and food supplements for the control of hyperglycemic and hyperlipidemic symptoms. Copyright © 2017. Published by Elsevier B.V.

  3. Vulnerability of streams to legacy nitrate sources

    Science.gov (United States)

    Tesoriero, Anthony J.; Duff, John H.; Saad, David A.; Spahr, Norman E.; Wolock, David M.

    2013-01-01

    The influence of hydrogeologic setting on the susceptibility of streams to legacy nitrate was examined at seven study sites having a wide range of base flow index (BFI) values. BFI is the ratio of base flow to total streamflow volume. The portion of annual stream nitrate loads from base flow was strongly correlated with BFI. Furthermore, dissolved oxygen concentrations in streambed pore water were significantly higher in high BFI watersheds than in low BFI watersheds suggesting that geochemical conditions favor nitrate transport through the bed when BFI is high. Results from a groundwater-surface water interaction study at a high BFI watershed indicate that decades old nitrate-laden water is discharging to this stream. These findings indicate that high nitrate levels in this stream may be sustained for decades to come regardless of current practices. It is hypothesized that a first approximation of stream vulnerability to legacy nutrients may be made by geospatial analysis of watersheds with high nitrogen inputs and a strong connection to groundwater (e.g., high BFI).

  4. Isolation and characterization of Fe(III)-chelate reductase gene LeFRO1 in tomato.

    Science.gov (United States)

    Li, Lihua; Cheng, Xudong; Ling, Hong-Qing

    2004-01-01

    Tomato is a model plant for studying molecular mechanisms of iron uptake and metabolism in strategy I plants (dicots and non-graminaceous monocots). Reduction of ferric to ferrous iron on the root surface is an obligatory process for iron acquisition from soil in these plants. LeFRO1 encoding an Fe(III)-chelate reductase protein was isolated from the tomato genome. We show that expression of LeFRO1 in yeast increases Fe(III)-chelate reductase activity. In a transient expression analysis we found that LeFRO1 protein was targeted on the plasma membrane. LeFRO1 transcript was detected in roots, leaves, cotyledons, flowers and young fruits by RT-PCR analysis. Abundance of LeFRO1 mRNA was much lower in young fruits than in other tissues. The transcription intensity of LeFRO1 in roots is dependent on the iron status whereas it is constitutively expressed in leaves. These results indicate that LeFRO1 is required in roots and shoots as well as in reproductive organs for iron homeostasis and that its transcription in roots and shoots is regulated by different control mechanisms. The expression of LeFRO1 was disrupted in the iron-inefficient mutants chloronerva and T3238 fer, indicating that FER and CHLN genes are involved in the regulation of LeFRO1 expression in tomato roots. The differential expression of LeFRO1 and LeIRT1 (an iron-regulated metal transporter gene in tomato) in roots of T3238 fer under iron-deficient and -sufficient conditions suggests that the FER gene may regulate expression of LeFRO1 more directly than that of LeIRT1 in tomato roots.

  5. The nitric-oxide reductase from Paracoccus denitrificans uses a single specific proton pathway.

    Science.gov (United States)

    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.

  6. The influence of Glyceria maxima and nitrate input on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community

    NARCIS (Netherlands)

    Nijburg, J.W.; Laanbroek, H.J.

    1997-01-01

    The influence of nitrate addition and the presence of Glyceria maxima (reed sweetgrass) on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community was investigated. Anoxic freshwater sediment was incubated in pots with or without G. maxima and with or without

  7. The influence of Glyceria maxima and nitrate input on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community

    NARCIS (Netherlands)

    Nijburg, J.W.; Laanbroek, H.J.

    1997-01-01

    The influence of nitrate addition and the presence of Glyceria maxima (reed sweetgrass) on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community was investigated. Anoxic freshwater sediment was incubated in pots with or without G. maxima and with or

  8. Copper nitrate: a privileged reagent for organic synthesis.

    Science.gov (United States)

    Gao, Mingchun; Ye, Rongxuan; Shen, Weijia; Xu, Bin

    2018-04-18

    Copper has been explored as an ideal candidate for replacing noble metals in organic synthesis, especially for practical large scale preparation. Recent decades have witnessed the renaissance and improvement of copper-catalyzed and copper-mediated organic reactions. Copper nitrate is a common inorganic copper salt which has been proved to be a ubiquitous reactant in organic synthesis due to its commercial availability, stability, inexpensiveness and environmentally benign nature. Copper nitrate could be used as a nitration reagent, oxidant, catalyst or promoter, and Lewis acid as well. Remarkably, great attention has been devoted to the efficient transformation of copper nitrate into functionalized or complicated compounds through various reaction types including cyclization, C-H activation, difunctionalization, nitration, rearrangement and asymmetric synthesis with chiral ligands. Further modification of copper nitrate, such as solid-supported copper nitrate or copper nitrate complexes, extends its applications in organic synthesis. The present review highlights recent advances of copper nitrate in organic synthesis, along with the mechanisms.

  9. Recombinant pinoresinol/lariciresinol reductase, recombinant dirigent protein, and methods of use

    Science.gov (United States)

    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.

  10. Mechanisms of Chromium and Uranium Toxicity in Pseudomonas stutzeri RCH2 Grown under Anaerobic Nitrate-Reducing Conditions.

    Science.gov (United States)

    Thorgersen, Michael P; Lancaster, W Andrew; Ge, Xiaoxuan; Zane, Grant M; Wetmore, Kelly M; Vaccaro, Brian J; Poole, Farris L; Younkin, Adam D; Deutschbauer, Adam M; Arkin, Adam P; Wall, Judy D; Adams, Michael W W

    2017-01-01

    Chromium and uranium are highly toxic metals that contaminate many natural environments. We investigated their mechanisms of toxicity under anaerobic conditions using nitrate-reducing Pseudomonas stutzeri RCH2, which was originally isolated from a chromium-contaminated aquifer. A random barcode transposon site sequencing library of RCH2 was grown in the presence of the chromate oxyanion (Cr[VI][Formula: see text]) or uranyl oxycation (U[VI][Formula: see text]). Strains lacking genes required for a functional nitrate reductase had decreased fitness as both metals interacted with heme-containing enzymes required for the later steps in the denitrification pathway after nitrate is reduced to nitrite. Cr[VI]-resistance also required genes in the homologous recombination and nucleotide excision DNA repair pathways, showing that DNA is a target of Cr[VI] even under anaerobic conditions. The reduced thiol pool was also identified as a target of Cr[VI] toxicity and psest_2088 , a gene of previously unknown function, was shown to have a role in the reduction of sulfite to sulfide. U[VI] resistance mechanisms involved exopolysaccharide synthesis and the universal stress protein UspA. As the first genome-wide fitness analysis of Cr[VI] and U[VI] toxicity under anaerobic conditions, this study provides new insight into the impact of Cr[VI] and U[VI] on an environmental isolate from a chromium contaminated site, as well as into the role of a ubiquitous protein, Psest_2088.

  11. Mechanisms of Chromium and Uranium Toxicity in Pseudomonas stutzeri RCH2 Grown under Anaerobic Nitrate-Reducing Conditions

    Directory of Open Access Journals (Sweden)

    Michael P. Thorgersen

    2017-08-01

    Full Text Available Chromium and uranium are highly toxic metals that contaminate many natural environments. We investigated their mechanisms of toxicity under anaerobic conditions using nitrate-reducing Pseudomonas stutzeri RCH2, which was originally isolated from a chromium-contaminated aquifer. A random barcode transposon site sequencing library of RCH2 was grown in the presence of the chromate oxyanion (Cr[VI]O42− or uranyl oxycation (U[VI]O22+. Strains lacking genes required for a functional nitrate reductase had decreased fitness as both metals interacted with heme-containing enzymes required for the later steps in the denitrification pathway after nitrate is reduced to nitrite. Cr[VI]-resistance also required genes in the homologous recombination and nucleotide excision DNA repair pathways, showing that DNA is a target of Cr[VI] even under anaerobic conditions. The reduced thiol pool was also identified as a target of Cr[VI] toxicity and psest_2088, a gene of previously unknown function, was shown to have a role in the reduction of sulfite to sulfide. U[VI] resistance mechanisms involved exopolysaccharide synthesis and the universal stress protein UspA. As the first genome-wide fitness analysis of Cr[VI] and U[VI] toxicity under anaerobic conditions, this study provides new insight into the impact of Cr[VI] and U[VI] on an environmental isolate from a chromium contaminated site, as well as into the role of a ubiquitous protein, Psest_2088.

  12. Nitrite-Reductase and Peroxynitrite Isomerization Activities of Methanosarcina acetivorans Protoglobin

    Science.gov (United States)

    Ascenzi, Paolo; Leboffe, Loris; Pesce, Alessandra; Ciaccio, Chiara; Sbardella, Diego; Bolognesi, Martino; Coletta, Massimo

    2014-01-01

    Within the globin superfamily, protoglobins (Pgb) belong phylogenetically to the same cluster of two-domain globin-coupled sensors and single-domain sensor globins. Multiple functional roles have been postulated for Methanosarcina acetivorans Pgb (Ma-Pgb), since the detoxification of reactive nitrogen and oxygen species might co-exist with enzymatic activity(ies) to facilitate the conversion of CO to methane. Here, the nitrite-reductase and peroxynitrite isomerization activities of the CysE20Ser mutant of Ma-Pgb (Ma-Pgb*) are reported and analyzed in parallel with those of related heme-proteins. Kinetics of nitrite-reductase activity of ferrous Ma-Pgb* (Ma-Pgb*-Fe(II)) is biphasic and values of the second-order rate constant for the reduction of NO2– to NO and the concomitant formation of nitrosylated Ma-Pgb*-Fe(II) (Ma-Pgb*-Fe(II)-NO) are kapp1 = 9.6±0.2 M–1 s–1 and kapp2 = 1.2±0.1 M–1 s–1 (at pH 7.4 and 20°C). The kapp1 and kapp2 values increase by about one order of magnitude for each pH unit decrease, between pH 8.3 and 6.2, indicating that the reaction requires one proton. On the other hand, kinetics of peroxynitrite isomerization catalyzed by ferric Ma-Pgb* (Ma-Pgb*-Fe(III)) is monophasic and values of the second order rate constant for peroxynitrite isomerization by Ma-Pgb*-Fe(III) and of the first order rate constant for the spontaneous conversion of peroxynitrite to nitrate are happ = 3.8×104 M–1 s–1 and h0 = 2.8×10–1 s–1 (at pH 7.4 and 20°C). The pH-dependence of hon and h0 values reflects the acid-base equilibrium of peroxynitrite (pKa = 6.7 and 6.9, respectively; at 20°C), indicating that HOONO is the species that reacts preferentially with the heme-Fe(III) atom. These results highlight the potential role of Pgbs in the biosynthesis and scavenging of reactive nitrogen and oxygen species. PMID:24827820

  13. Nitrite-reductase and peroxynitrite isomerization activities of Methanosarcina acetivorans protoglobin.

    Directory of Open Access Journals (Sweden)

    Paolo Ascenzi

    Full Text Available Within the globin superfamily, protoglobins (Pgb belong phylogenetically to the same cluster of two-domain globin-coupled sensors and single-domain sensor globins. Multiple functional roles have been postulated for Methanosarcina acetivorans Pgb (Ma-Pgb, since the detoxification of reactive nitrogen and oxygen species might co-exist with enzymatic activity(ies to facilitate the conversion of CO to methane. Here, the nitrite-reductase and peroxynitrite isomerization activities of the CysE20Ser mutant of Ma-Pgb (Ma-Pgb* are reported and analyzed in parallel with those of related heme-proteins. Kinetics of nitrite-reductase activity of ferrous Ma-Pgb* (Ma-Pgb*-Fe(II is biphasic and values of the second-order rate constant for the reduction of NO2- to NO and the concomitant formation of nitrosylated Ma-Pgb*-Fe(II (Ma-Pgb*-Fe(II-NO are k(app1= 9.6 ± 0.2 M(-1 s(-1 and k(app2 = 1.2 ± 0.1 M(-1 s(-1 (at pH 7.4 and 20 °C. The k(app1 and k(app2 values increase by about one order of magnitude for each pH unit decrease, between pH 8.3 and 6.2, indicating that the reaction requires one proton. On the other hand, kinetics of peroxynitrite isomerization catalyzed by ferric Ma-Pgb* (Ma-Pgb*-Fe(III is monophasic and values of the second order rate constant for peroxynitrite isomerization by Ma-Pgb*-Fe(III and of the first order rate constant for the spontaneous conversion of peroxynitrite to nitrate are h(app = 3.8 × 10(4 M(-1 s(-1 and h0 = 2.8 × 10(-1 s(-1 (at pH 7.4 and 20 °C. The pH-dependence of hon and h0 values reflects the acid-base equilibrium of peroxynitrite (pKa = 6.7 and 6.9, respectively; at 20 °C, indicating that HOONO is the species that reacts preferentially with the heme-Fe(III atom. These results highlight the potential role of Pgbs in the biosynthesis and scavenging of reactive nitrogen and oxygen species.

  14. Global transcriptome analysis of Bacillus cereus ATCC 14579 in response to silver nitrate stress

    Directory of Open Access Journals (Sweden)

    Ganesh Babu Malli Mohan

    2011-11-01

    Full Text Available Abstract Silver nanoparticles (AgNPs were synthesized using Bacillus cereus strains. Earlier, we had synthesized monodispersive crystalline silver nanoparticles using B. cereus PGN1 and ATCC14579 strains. These strains have showed high level of resistance to silver nitrate (1 mM but their global transcriptomic response has not been studied earlier. In this study, we investigated the cellular and metabolic response of B. cereus ATCC14579 treated with 1 mM silver nitrate for 30 & 60 min. Global expression profiling using genomic DNA microarray indicated that 10% (n = 524 of the total genes (n = 5234 represented on the microarray were up-regulated in the cells treated with silver nitrate. The majority of genes encoding for chaperones (GroEL, nutrient transporters, DNA replication, membrane proteins, etc. were up-regulated. A substantial number of the genes encoding chemotaxis and flagellar proteins were observed to be down-regulated. Motility assay of the silver nitrate treated cells revealed reduction in their chemotactic activity compared to the control cells. In addition, 14 distinct transcripts overexpressed from the 'empty' intergenic regions were also identified and proposed as stress-responsive non-coding small RNAs.

  15. Global transcriptome analysis of Bacillus cereus ATCC 14579 in response to silver nitrate stress.

    Science.gov (United States)

    Babu, Malli Mohan Ganesh; Sridhar, Jayavel; Gunasekaran, Paramasamy

    2011-11-10

    Silver nanoparticles (AgNPs) were synthesized using Bacillus cereus strains. Earlier, we had synthesized monodispersive crystalline silver nanoparticles using B. cereus PGN1 and ATCC14579 strains. These strains have showed high level of resistance to silver nitrate (1 mM) but their global transcriptomic response has not been studied earlier. In this study, we investigated the cellular and metabolic response of B. cereus ATCC14579 treated with 1 mM silver nitrate for 30 & 60 min. Global expression profiling using genomic DNA microarray indicated that 10% (n = 524) of the total genes (n = 5234) represented on the microarray were up-regulated in the cells treated with silver nitrate. The majority of genes encoding for chaperones (GroEL), nutrient transporters, DNA replication, membrane proteins, etc. were up-regulated. A substantial number of the genes encoding chemotaxis and flagellar proteins were observed to be down-regulated. Motility assay of the silver nitrate treated cells revealed reduction in their chemotactic activity compared to the control cells. In addition, 14 distinct transcripts overexpressed from the 'empty' intergenic regions were also identified and proposed as stress-responsive non-coding small RNAs.

  16. Denitrification of high strength nitrate waste.

    Science.gov (United States)

    Dhamole, Pradip B; Nair, Rashmi R; D'Souza, Stanislaus F; Lele, S S

    2007-01-01

    The aim of the present work was to study the treatment of high strength nitrate waste (40000 ppm NO(3) i.e., 9032 ppm NO(3)-N) by acclimatizing sludge initially capable of degrading dilute streams (100-200 ppm NO(3)-N). Sludge from an effluent treatment plant of a fertilizer industry was acclimatized for 15 d each at 1694, 3388, 6774 and 9032 ppm NO(3)-N in a 4 L sequencing batch reactor. Complete denitrification of extremely concentrated nitrate waste (9032 ppm NO(3)-N) using acclimatized sludge was achieved in just 6 h. During the acclimatization period, increase in nitrite peak value from zero to 5907 ppm NO(2)-N was observed, as the concentration was increased from 1694 to 9032 ppm NO(3)-N. Kinetic analysis of the nitrate and nitrite profile could reasonably support microbiological explanations for nitrite build up and changes in sludge composition.

  17. Ammonium and nitrate tolerance in lichens

    Energy Technology Data Exchange (ETDEWEB)

    Hauck, Markus, E-mail: mhauck@gwdg.d [Department of Plant Ecology, Albrecht von Haller Institute of Plant Sciences, University of Goettingen, Untere Karspuele 2, 37073 Goettingen (Germany)

    2010-05-15

    Since lichens lack roots and take up water, solutes and gases over the entire thallus surface, these organisms respond more sensitively to changes in atmospheric purity than vascular plants. After centuries where effects of sulphur dioxide and acidity were in the focus of research on atmospheric chemistry and lichens, recently the globally increased levels of ammonia and nitrate increasingly affect lichen vegetation and gave rise to intense research on the tolerance of lichens to nitrogen pollution. The present paper discusses the main findings on the uptake of ammonia and nitrate in the lichen symbiosis and to the tolerance of lichens to eutrophication. Ammonia and nitrate are both efficiently taken up under ambient conditions. The tolerance to high nitrogen levels depends, among others, on the capability of the photobiont to provide sufficient amounts of carbon skeletons for ammonia assimilation. Lowly productive lichens are apparently predisposed to be sensitive to excess nitrogen. - Eutrophication has become a global threat for lichen diversity.

  18. Nitrate salt immobilization process development and implementation

    International Nuclear Information System (INIS)

    Petersen, R.D.; Johnson, A.J.; Peter, K.G.

    1986-01-01

    The waste nitrate salts generated at the Rocky Flats Plant (RFP) were determined to be unacceptable in their present form for shipment to and storage at the Nevada Test Site, according to the recently implemented Waste Acceptance Criteria. A reduction in the dispersibility and oxidizing potential of the salt was necessary. Various methods of immobilization were investigated to determine the waste form with the highest possible waste loading and the most cost effective processing. Portland cement was selected as the most effective binder (in terms of cost and performance), with a 55 wt % waste loading and a 1.5 water-to-cement ratio. A nitrate salt immobilization process has been installed in the liquid waste processing building. The process uses dry nitrate salts from the existing spray dryer, spray dryer feed solution, and Portland cement. The resulting waste grout is packaged in a plastic lined, corrugated fiberboard tri-wall box, and shipped to the Nevada Test Site for burial

  19. Removal of heavy metals and pollutants by membrane adsorption techniques

    Science.gov (United States)

    Khulbe, K. C.; Matsuura, T.

    2018-03-01

    Application of polymeric membranes for the adsorption of hazardous pollutants may lead to the development of next-generation reusable and portable water purification appliances. Membranes for membrane adsorption (MA) have the dual function of membrane filtration and adsorption to be very effective to remove trace amounts of pollutants such as cationic heavy metals, anionic phosphates and nitrates. In this review article, recent progresses in the development of MA membranes are surveyed. In addition, recent progresses in the development of advanced adsorbents such as nanoparticles are summarized, since they are potentially useful as fillers in the host membrane to enhance its performance. The future directions of R&D in this field are also shown in the conclusion section.

  20. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham

    2006-06-30

    A non-agglomerated and nanocrystalline-sized powder was successfully produced using ethylene glycol nitrate methods. The LSFT powder prepared using this method exhibits well dispersed and nano-sized particles about 100-200 nm. The density of LSFT sintered at 1300 C was about 90% of the theoretical density at which is 100 C less than that of the previous LSFT which was sintered at 1400 C. The sample sintered at 1400 C exhibited the evidence of a liquid phase at the grain boundaries and 2nd phase formation which probably caused low mechanical stability. The electrical conductivity and Seebeck coefficient were measured as a function of temperature. The LSFT-CGO specimens were cut from the as sintered bars and used for the evaluation of Mechanical Properties after polishing. The effect of strain rate on the flexural strength of the LSFT-CGO test specimens was studied. Three strain rates 6, 60 and 600 {micro}m/ min were chosen for this study. It is observed from the results that with increasing cross head speed the membrane takes higher loads to fail. A reduction in the strength of the membrane was observed at 1000 C in N{sub 2}. Two different routes were investigated to synthesis GDC using either formate or carbonate precursors. The precursor and CGO particle morphologies were examined by scanning electron microscopy. The thermal decomposition behaviors of Ce(Gd)(HCOO){sub 3} and Ce(Gd)(CO{sub 3})(OH) were determined by thermogravimetric analysis (TGA) at a rate of 3 C/min in air. The X-ray powder diffraction patterns of the precursor and CGO were collected and nitrogen adsorption isotherms were measured. Conductivity measurements were made by AC impedance spectroscopy on sintered disks in air using platinum electrodes.

  1. Robotic membranes

    DEFF Research Database (Denmark)

    Ramsgaard Thomsen, Mette

    2008-01-01

    , Vivisection and Strange Metabolisms, were developed at the Centre for Information Technology and Architecture (CITA) at the Royal Danish Academy of Fine Arts in Copenhagen as a means of engaging intangible digital data with tactile physical material. As robotic membranes, they are a dual examination...

  2. Effect of activated carbon in PSF-PEI-Ag symmetric membrane

    OpenAIRE

    Said Khairul Anwar Mohamad; George Genevieve Gadung; Alipah Nurul Ain Mohamed; Ismail Nor Zakirah; Jama’in Ramizah Liyana

    2017-01-01

    Polysulfone (Psf) composite membrane consist of activated carbon, polyethyleneimine and silver nitrate was prepared by phase inversion. The activated carbon (AC) act as adsorbent to adsorb heavy metal present in synthetic waste water while polysulfone membrane act as support. Phase inversion was carried out on different composition of activated carbon from 0 to 0.9% while other component are remain constant. The surface morphology of composite membrane was characterized by scanning electron m...

  3. COGEMA Experience in Uranous Nitrate Preparation

    International Nuclear Information System (INIS)

    Tison, E.; Bretault, Ph.

    2006-01-01

    Separation and purification of plutonium by PUREX process is based on a sequence of extraction and back extraction which requires reducing plutonium Pu IV (extractable form) into Pu III (inextractable form) Different reducers can be used to reduce Pu IV into Pu III. Early plants such as that for Magnox fuel at Sellafield used ferrous sulfamate while UP 1 at Marcoule used uranous sulfamate. These reducers are efficient and easy to prepare but generates ferric and/or sulphate ions and so complicates management of the wastes from the plutonium purification cycle. Recent plants such as UP3 and UP2 800 at La Hague, THORP at Sellafield, and RRP at Rokkasho Mura (currently under tests) use uranous nitrate (U IV) stabilized by hydrazinium nitrate (N 2 H 5 NO 3 ) and hydroxyl ammonium nitrate (HAN). In the French plants, uranous nitrate is used in U-Pu separation and alpha barrier and HAN is used in Pu purification. Compared to sulfamate, U IV does not generate extraneous chemical species and uranyl nitrate (U VI) generated by reducing Pu IV follows the main uranium stream. More over uranous nitrate is prepared from reprocessed purified uranyl nitrate taken at the outlet of the reprocessing plant. Hydrazine and HAN offer the advantage to be salt-free reagents. Uranous nitrate can be generated either by electrolysis or by catalytic hydrogenation process. Electrolytic process has been implemented in early plant UP 1 at Marcoule (when changing reducer from uranous sulfamate to uranous nitrate) and was used again in UP2 plant at La Hague. However, the electrolytic process presented several disadvantages such as a low conversion rate and problems associated with the use of mercury. Electrolysis cells with no mercury were developed for the Eurochemic plant in Belgium and then implemented in the first Japanese reprocessing plant in Tokai-Mura. But finally, in 1975, the electrolytic process was abandoned in favor of the catalytic hydrogenation process developed at La Hague. The

  4. Extraction of uranium with emulsion membrane process use tributylphosphate extractant

    International Nuclear Information System (INIS)

    Basuki, K.T.; Sudibyo, R.; Bambang EHB; Muhadi, A.W.

    1996-01-01

    To increase the effectiveness of extraction process with so for to occur, it was tried the extraction with a couple of extraction and stripping process. This couple process was called liquid membrane emulsion. As membrane was used mix surfactant (Span-80), tributylphosphate in kerosene, natrium carbonate, while as a feeder was uranium solution with 500 concentration ppm in 0.5 - 3 M nitrate acid. In this experiment the variable investigated were % surfactant (1 - 5 %), rotary speed for membrane making (2,500 - 10.000 rpm). The optimal condition result of experiment were 5 % surfactant, 3 M nitrate acid, rotary speed 10.000 rpm and (Kd eksU ) 57 %, and (Kd strippU ) 87 %, Kd eksU at liquid-liquid extraction is 44 %. (author)

  5. The evolution of the ribonucleotide reductases: much ado about oxygen.

    Science.gov (United States)

    Poole, Anthony M; Logan, Derek T; Sjöberg, Britt-Marie

    2002-08-01

    Ribonucleotide reduction is the only known biological means for de novo production of deoxyribonucleotides, the building blocks of DNA. These are produced from ribonucleotides, the building blocks of RNA, and the direction of this reaction has been taken to support the idea that, in evolution, RNA preceded DNA as genetic material. However, an understanding of the evolutionary relationships among the three modern-day classes of ribonucleotide reductase and how the first reductase arose early in evolution is still far off. We propose that the diversification of this class of enzymes is inherently tied to microbial colonization of aerobic and anaerobic niches. The work is of broader interest, as it also sheds light on the process of adaptation to oxygenic environments consequent to the evolution of atmospheric oxygen.

  6. Substrate specificity of an aflatoxin-metabolizing aldehyde reductase.

    OpenAIRE

    Ellis, E M; Hayes, J D

    1995-01-01

    The enzyme from rat liver that reduces aflatoxin B1-dialdehyde exhibits a unique catalytic specificity distinct from that of other aldo-keto reductases. This enzyme, designated AFAR, displays high activity towards dicarbonyl-containing compounds with ketone groups on adjacent carbon atoms; 9,10-phenanthrenequinone, acenaphthenequinone and camphorquinone were found to be good substrates. Although AFAR can also reduce aromatic and aliphatic aldehydes such as succinic semialdehyde, it is inactiv...

  7. Intraethnic variation in steroid-5-alpha-reductase polymorphisms in ...

    Indian Academy of Sciences (India)

    in prostate cancer patients: a potential factor implicated in. 5-alpha-reductase inhibitor treatment. Luis Alberto Henríquez-Hernández, Almudena Valenciano, Palmira Foro-Arnalot, María Jesús Álvarez-Cubero,. José Manuel Cozar, José Francisco Suárez-Novo, Manel Castells-Esteve, Pablo Fernández-Gonzalo,.

  8. Cloning and characterization of a nitrite reductase gene related to ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-03-01

    Mar 1, 2010 ... BL21 (DE3) strain with the recombinant expression vector pET-28A-GhNiR. NiR activity assay showed that the crude GhNiR protein had obvious activity to NaNO2 substrate. Key words: Cotton, nitrite reductase, prokaryotic expression, semi-quantitative RT-PCR, GenBank Accession. No: GQ389691.

  9. Xylose reductase from the thermophilic fungus Talaromyces emersonii

    Indian Academy of Sciences (India)

    Prakash

    action of xylose reductase (EC 1.1.1.21) and xylitol dehydrogenase (EC 1.1.1.9) is required to convert D-xylose to D-xylulose and all enzymes of the D-xylose pathway can be used in the L-arabinose pathway, where arabitol is oxidized by NAD+-dependent arabitol dehydrogenase (EC. 1.1.1.12) producing L-xylulose. This is ...

  10. IRON REDUCTASE SYSTEMS ON THE PLANT PLASMA-MEMBRANE - A REVIEW

    NARCIS (Netherlands)

    MOOG, PR; BRUGGEMANN, W

    1994-01-01

    Higher plant roots, leaf mesophyll tissue, protoplasts as well as green algae are able to reduce extra-cellular ferricyanide and ferric chelates. In roots of dicotyledonous and nongraminaceous, monocotyledonous plants, the rate of ferric reduction is increased by iron deficiency. This reduction is

  11. Generation of nitryl chloride from chlorotrimethylsilane-acetyl nitrate ...

    Indian Academy of Sciences (India)

    Administrator

    amyl nitrate does not yield NO2Cl with silicon reagent. However, acetyl nitrate reacts successfully with chlorotrimethylsi- lane to give nitryl chloride, which is characterized by its UV spectrum. If it is generated in presence of ketoximes ...

  12. The effect of prolonged dietary nitrate supplementation on atherosclerosis development

    NARCIS (Netherlands)

    Marsch, Elke; Theelen, Thomas L.; Janssen, Ben J. A.; Briede, Jacco J.; Haenen, Guido R.; Senden, Joan M. G.; van Loon, Lucas J. C.; Poeze, Martijn; Bierau, Jörgen; Gijbels, Marion J.; Daemen, Mat J. A. P.; Sluimer, Judith C.

    2016-01-01

    Short term dietary nitrate or nitrite supplementation has nitric oxide (NO)-mediated beneficial effects on blood pressure and inflammation and reduces mitochondrial oxygen consumption, possibly preventing hypoxia. As these processes are implicated in atherogenesis, dietary nitrate was hypothesized

  13. A toxicological study of gadolinium nitrate

    Energy Technology Data Exchange (ETDEWEB)

    London, J.E.

    1988-05-01

    The sensitization study in the guinea pig did not show gadolinium nitrate to have potential sensitizing properties. Skin application studies in the rabbit demonstrated that it was cutaneously a severe irritant. This material was considered an irritant in the rabbit eye application studies. 3 refs., 1 tab.

  14. Modular Regiospecific Synthesis of Nitrated Fatty Acids

    DEFF Research Database (Denmark)

    Hock, Katharina J.; Grimmer, Jennifer; Göbel, Dominik

    2016-01-01

    Endogenous nitrated fatty acids are an important class of signaling molecules. Herein a modular route for the efficient and regiospecific preparation of nitrooleic acids as well as various analogues is described. The approach is based on a simple set of alkyl halides as common building blocks...

  15. Spectrophotometric Determination of Nitrate and Phosphate Levels ...

    African Journals Online (AJOL)

    Twelve drinking water samples from boreholes were collected from various sampling sites around the vicinity of Kura irrigated farmlands using polythene plastic containers and were analysed for the nitrate and phosphate levels using uV – visible spectrophotometer. From the results, it was found that all the samples had ...

  16. The crystal structure of thiourea nitrate

    NARCIS (Netherlands)

    Feil, D.; Song Loong, W.

    1968-01-01

    The structure of thiourea nitrate has been determined by three-dimensional X-ray methods. Both Cu Ke and Mo K~ data were obtained with a single-crystal diffractometer and the final R values are 4.9% and 5.5% respectively. The space group is P211m and there are two molecules in the unit cell. All

  17. Denitration of High Nitrate Salts Using Reductants

    Energy Technology Data Exchange (ETDEWEB)

    HD Smith; EO Jones; AJ Schmidt; AH Zacher; MD Brown; MR Elmore; SR Gano

    1999-05-03

    This report describes work conducted by Pacific Northwest National Laboratory (PNNL), in conjunction with Idaho National Engineering and Environmental Laboratory (INEEL), to remove nitrates in simulated low-activity waste (LAW). The major objective of this work was to provide data for identifying and demonstrating a technically viable and cost-effective approach to condition LAW for immobilization (grout).

  18. Production of thorium nitrate from uranothorianite ores

    International Nuclear Information System (INIS)

    Brodsky, M.; Sartorius, R.; Sousseuer, Y.

    1959-01-01

    The separation of thorium and uranium from uranothorianite ores, either by precipitation or solvent-extraction methods, are discussed, and an industrial process for the manufacture of thorium nitrate is described. Reprint of a paper published in 'Progress in Nuclear Energy' Series III, Vol. 2 - Process Chemistry, 1959, p. 68-76 [fr

  19. Trend Analyses of Nitrate in Danish Groundwater

    DEFF Research Database (Denmark)

    Hansen, B.; Thorling, L.; Dalgaard, Tommy

    2012-01-01

    This presentation assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. Firstly, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribut......This presentation assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. Firstly, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis...... of distribution, trends and trend reversals in the groundwater nitrate concentration. Secondly, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Thirdly, groundwater recharge CFC (Chlorofluorocarbon) age determination allows linking of the first...... two dataset. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded...

  20. The Path to Nitrate Salt Disposition

    Energy Technology Data Exchange (ETDEWEB)

    Funk, David John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-16

    The topic is presented in a series of slides arranged according to the following outline: LANL nitrate salt incident as thermal runaway (thermally sensitive surrogates, full-scale tests), temperature control for processing, treatment options and down selection, assessment of engineering options, anticipated control set for treatment, and summary of the overall steps for RNS.

  1. Revitalising Silver Nitrate for Caries Management

    Directory of Open Access Journals (Sweden)

    Sherry Shiqian Gao

    2018-01-01

    Full Text Available Silver nitrate has been adopted for medical use as a disinfectant for eye disease and burned wounds. In dentistry, it is an active ingredient of Howe’s solution used to prevent and arrest dental caries. While medical use of silver nitrate as a disinfectant became subsidiary with the discovery of antibiotics, its use in caries treatment also diminished with the use of fluoride in caries prevention. Since then, fluoride agents, particularly sodium fluoride, have gained popularity in caries prevention. However, caries is an infection caused by cariogenic bacteria, which demineralise enamel and dentine. Caries can progress and cause pulpal infection, but its progression can be halted through remineralisation. Sodium fluoride promotes remineralisation and silver nitrate has a profound antimicrobial effect. Hence, silver nitrate solution has been reintroduced for use with sodium fluoride varnish to arrest caries as a medical model strategy of caries management. Although the treatment permanently stains caries lesions black, this treatment protocol is simple, painless, non-invasive, and low-cost. It is well accepted by many clinicians and patients and therefore appears to be a promising strategy for caries control, particularly for young children, the elderly, and patients with severe caries risk or special needs.

  2. 76 FR 46907 - Ammonium Nitrate Security Program

    Science.gov (United States)

    2011-08-03

    ... located in, under, or adjacent to any waters subject to the jurisdiction of the United States. Through its..., marking, labeling, placarding, security plans, emergency response information, training, etc.). f... ``solid ammonium nitrate that is chiefly the ammonium salt of nitric acid and contains not less than 33...

  3. EFFECT OF AMMONIUM NITRATE SOLUTIONS ON ...

    African Journals Online (AJOL)

    monium nitrate and the percentage fertilization as weD as the subsequent development of the embryos compared with controls. At 10 and 100 p.p.m. there is a marked reduction in fertilization. Abnor- mal fonns are common at 100 p.p.m. and some 95 % of the population fail to reach the gastrula stage. INTRODUCTION.

  4. Cloning, functional expression and characterization of a bifunctional 3-hydroxybutanal dehydrogenase /reductase involved in acetone metabolism by Desulfococcus biacutus.

    Science.gov (United States)

    Frey, Jasmin; Rusche, Hendrik; Schink, Bernhard; Schleheck, David

    2016-11-25

    The strictly anaerobic, sulfate-reducing bacterium Desulfococcus biacutus can utilize acetone as sole carbon and energy source for growth. Whereas in aerobic and nitrate-reducing bacteria acetone is activated by carboxylation with CO 2 to acetoacetate, D. biacutus involves CO as a cosubstrate for acetone activation through a different, so far unknown pathway. Proteomic studies indicated that, among others, a predicted medium-chain dehydrogenase/reductase (MDR) superfamily, zinc-dependent alcohol dehydrogenase (locus tag DebiaDRAFT_04514) is specifically and highly produced during growth with acetone. The MDR gene DebiaDRAFT_04514 was cloned and overexpressed in E. coli. The purified recombinant protein required zinc as cofactor, and accepted NADH/NAD + but not NADPH/NADP + as electron donor/acceptor. The pH optimum was at pH 8, and the temperature optimum at 45 °C. Highest specific activities were observed for reduction of C 3 - C 5 -aldehydes with NADH, such as propanal to propanol (380 ± 15 mU mg -1 protein), butanal to butanol (300 ± 24 mU mg -1 ), and 3-hydroxybutanal to 1,3-butanediol (248 ± 60 mU mg -1 ), however, the enzyme also oxidized 3-hydroxybutanal with NAD + to acetoacetaldehyde (83 ± 18 mU mg -1 ). The enzyme might play a key role in acetone degradation by D. biacutus, for example as a bifunctional 3-hydroxybutanal dehydrogenase/reductase. Its recombinant production may represent an important step in the elucidation of the complete degradation pathway.

  5. Inhibition or promotion of biodegradation of nitrate by Paracoccus sp. in the presence of nanoscale zero-valent iron

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Chenghong; Xu, Xuping [School of Life Science, Fujian Normal University, Fuzhou 350108, Fujian Province (China); Megharaj, Mallavarapu; Naidu, Ravendra [Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095 (Australia); Chen, Zuliang, E-mail: Zuliang.chen@unisa.edu.au [School of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095 (Australia)

    2015-10-15

    To investigate the effect of nanoscale zero-valent iron (nZVI) on the growth of Paracoccus sp. strain and biodenitrification under aerobic conditions, specific factors were studied, pH, concentration of nitrate, Fe (II) and carbon dioxide. Low concentration of nZVI (50 mg/L) promoted both cell growth and biodegradation of nitrate which rose from 69.91% to 76.16%, while nitrate removal fell to 67.10% in the presence of high nZVI concentration (1000 mg/L). This may be attributed to the ions produced in nZVI corrosion being used as an electron source for the biodegradation of nitrate. However, the excess uptake of Fe (II) causes oxidative damage to the cells. To confirm this, nitrate was completely removed after 20 h when 100 mg/L Fe (II) was added to the solution, which is much faster than the control (86.05%, without adding Fe (II)). However, nitrate removal reached only 45.64% after 20 h, with low cell density (OD{sub 600} = 0.62) in the presence of 300 mg/L Fe (II). Characterization techniques indicated that nZVI adhered to microorganism cell membranes. These findings confirmed that nZVI could affect the activity of the strain and consequently change the biodenitrification. - Highlights: • Biodenitrification by Paracoccus sp. in the presence of nZVI was studied. • Biodegradation was promoted at a low nZVI concentration. • Biodegradation was inhibited at a high nZVI concentration. • nZVI that adhered to microorganism cell membranes was characterized.

  6. DIHYDROFOLATE REDUCTASE AS A VERSATILE DRUG TARGET IN HEALTHCARE

    Directory of Open Access Journals (Sweden)

    Naira Rashid

    2016-09-01

    Full Text Available Dihydrofolate reductase is one of the important enzymes for thymidylate and purine synthesis. It has been used as a drug target for treatment of various diseases. A large number of pharmaceutical drugs have been designed to inhibit the activity of dihydrofolate reductase. However, over the period of time some organisms have developed resistance against some of these drugs. There is also a chance of cross reactivity for these drugs, as they may target the dihydrofolate reductase enzyme of other organisms. Although using NMR spectroscopy, phylogenetic sequence analysis, comparative sequence analysis between dihydrofolate enzymes of various organisms and molecular modeling studies, a lot has been unraveled about the difference in the structure of this enzyme in various organisms, yet there is a need for deeper understanding of these differences so as to design drugs that are specific to their targets and reduce the chance for cross reactivity. The dihydrofolate enzyme can also be explored for treatment of various other diseases that are associated with the folate cycle.

  7. Determination of the potency of a novel saw palmetto supercritical CO2 extract (SPSE for 5α-reductase isoform II inhibition using a cell-free in vitro test system

    Directory of Open Access Journals (Sweden)

    Pais P

    2016-04-01

    Full Text Available Pilar Pais, Agustí Villar, Santiago Rull Euromed, Barcelona, Spain Background: The nicotinamide adenine dinucleotide phosphate-dependent membrane protein 5α-reductase catalyses the conversion of testosterone to the most potent androgen – 5α-dihydrotestosterone. Two 5α-reductase isoenzymes are expressed in humans: type I and type II. The latter is found primarily in prostate tissue. Saw palmetto extract (SPE has been used extensively in the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH. The pharmacological effects of SPE include the inhibition of 5α-reductase, as well as anti-inflammatory and antiproliferative effects. Clinical studies of SPE have been inconclusive – some have shown significant results, and others have not – possibly the result of varying bioactivities of the SPEs used in the studies. Purpose: To determine the in vitro potency in a cell-free test system of a novel SP supercritical CO2 extract (SPSE, an inhibitor of the 5α-reductase isoenzyme type II. Materials and methods: The inhibitory potency of SPSE was compared to that of finasteride, an approved 5α-reductase inhibitor, on the basis of the enzymatic conversion of the substrate androstenedione to the 5α-reduced product 5α-androstanedione. Results: By concentration-dependent inhibition of 5α-reductase type II in vitro (half-maximal inhibitory concentration 3.58±0.05 µg/mL, SPSE demonstrated competitive binding toward the active site of the enzyme. Finasteride, the approved 5α-reductase inhibitor tested as positive control, led to 63%–75% inhibition of 5α-reductase type II. Conclusion: SPSE effectively inhibits the enzyme that has been linked to BPH, and the amount of extract required for activity is comparatively low. It can be confirmed from the results of this study that SPSE has bioactivity that promotes prostate health at a level that is superior to that of many other phytotherapeutic extracts. The

  8. The efficiency of a membrane bioreactor in drinking water denitrification

    Directory of Open Access Journals (Sweden)

    Petrovič Aleksandra

    2015-01-01

    Full Text Available The membrane bioreactor (MBR system was investigated regarding its nitrate removal capacity from drinking water. The performance of a pilot-scale MBR was tested, depending on the operational parameters, using sucrose as a carbon source. Drinking water from the source was introduced into the reactor in order to study the influence of flow-rate on the nitrate removal and denitrification efficiency of drinking water. The content of the nitrate was around 70 mg/L and the C/N ratio was 3:1. Nitrate removal efficiencies above 90% were obtained by flow-rates lower than 4.8 L/h. The specific denitrification rates varied between 0.02 and 0.16 g/L NO3/ (g/L MLSS•d. The efficiencies and nitrate removal were noticeably affected by the flow-rate and hydraulic retention times. At the maximum flow-rate of 10.2 L/h still 68% of the nitrate had been removed, whilst the highest specific denitrification rate was achieved at 0.2738 g/L NO3/ (g/L MLSS•d. The maximum reactor removal capacity was calculated at 8.75 g NO3/m3•h.

  9. Simultaneous removal of nitrate and hydrogen sulfide by autotrophic denitrification in nitrate-contaminated water treatment.

    Science.gov (United States)

    Liu, Yongjie; Chen, Nan; Liu, Ying; Liu, Hengyuan; Feng, Chuanping; Li, Miao

    2018-02-23

    Nitrate contamination is a risk to human health and may cause eutrophication, whereas H 2 S is an undesirable constituent in biogas. In order to better understand denitrification using gaseous H 2 S as electron donor, this study investigated denitrification at different molar ratios of sulfur and nitrogen (S/N ratios) and H 2 S dosages. Although nitrate continued to decrease, a lag in sulfate generation was observed, implying the generation of sulfide oxidizing intermediates, which accumulated even though nitrate was in excess at lower S/N ratios of 0.19 and 0.38. More addition of H 2 S could result in a longer lag of sulfate generation. Before depletion of dissolved sulfide, denitrification could proceed with little nitrite accumulation. High throughout sequencing analysis identified two major genera, Thiobacillus and Sulfurimonas, that were responsible for autotrophic denitrification. The simultaneous removal of nitrate and H 2 S using a wide range of concentrations could be able to be achieved.

  10. Unexpected nondenitrifier nitrous oxide reductase gene diversity and abundance in soils.

    Science.gov (United States)

    Sanford, Robert A; Wagner, Darlene D; Wu, Qingzhong; Chee-Sanford, Joanne C; Thomas, Sara H; Cruz-García, Claribel; Rodríguez, Gina; Massol-Deyá, Arturo; Krishnani, Kishore K; Ritalahti, Kirsti M; Nissen, Silke; Konstantinidis, Konstantinos T; Löffler, Frank E

    2012-11-27

    Agricultural and industrial practices more than doubled the intrinsic rate of terrestrial N fixation over the past century with drastic consequences, including increased atmospheric nitrous oxide (N(2)O) concentrations. N(2)O is a potent greenhouse gas and contributor to ozone layer destruction, and its release from fixed N is almost entirely controlled by microbial activities. Mitigation of N(2)O emissions to the atmosphere has been attributed exclusively to denitrifiers possessing NosZ, the enzyme system catalyzing N(2)O to N(2) reduction. We demonstrate that diverse microbial taxa possess divergent nos clusters with genes that are related yet evolutionarily distinct from the typical nos genes of denitirifers. nos clusters with atypical nosZ occur in Bacteria and Archaea that denitrify (44% of genomes), do not possess other denitrification genes (56%), or perform dissimilatory nitrate reduction to ammonium (DNRA; (31%). Experiments with the DNRA soil bacterium Anaeromyxobacter dehalogenans demonstrated that the atypical NosZ is an effective N(2)O reductase, and PCR-based surveys suggested that atypical nosZ are abundant in terrestrial environments. Bioinformatic analyses revealed that atypical nos clusters possess distinctive regulatory and functional components (e.g., Sec vs. Tat secretion pathway in typical nos), and that previous nosZ-targeted PCR primers do not capture the atypical nosZ diversity. Collectively, our results suggest that nondenitrifying populations with a broad range of metabolisms and habitats are potentially significant contributors to N(2)O consumption. Apparently, a large, previously unrecognized group of environmental nosZ has not been accounted for, and characterizing their contributions to N(2)O consumption will advance understanding of the ecological controls on N(2)O emissions and lead to refined greenhouse gas flux models.

  11. Identification of nitrate sources and discharge-depending nitrate dynamics in a mesoscale catchment

    Science.gov (United States)

    Mueller, Christin; Strachauer, Ulrike; Brauns, Mario; Musolff, Andreas; Kunz, Julia Vanessa; Brase, Lisa; Tarasova, Larisa; Merz, Ralf; Knöller, Kay

    2017-04-01

    During the last decades, nitrate concentrations in surface and groundwater have increased due to land use change and accompanying application of fertilizer in agriculture as well as increased atmospheric deposition. To mitigate nutrient impacts on downstream aquatic ecosystems, it is important to quantify potential nitrate sources, instream nitrate processing and its controls in a river system. The objective of this project is to characterize and quantify (regional) scale dynamics and trends in water and nitrogen fluxes of the entire Holtemme river catchment in central Germany making use of isotopic fingerprinting methods. Here we compare two key date sampling campaigns in 2014 and 2015, with spatially highly resolved measurements of discharge at 23 sampling locations including 11 major tributaries and 12 locations at the main river. Additionally, we have data from continuous runoff measurements at 10 locations operated by the local water authorities. Two waste water treatment plants contribute nitrogen to the Holtemme stream. This contribution impacts nitrate loads and nitrate isotopic signatures depending on the prevailing hydrological conditions. Nitrogen isotopic signatures in the catchment are mainly controlled by different sources (nitrified soil nitrogen in the headwater and manure/ effluents from WWTPs in the lowlands) and increase with raising nitrate concentrations along the main river. Nitrate loads at the outlet of the catchment are extremely different between both sampling campaigns (2014: NO3- = 97 t a-1, 2015: NO3- = 5 t a-1) which is associated with various runoff (2014: 0.8 m3 s-1, 2015: 0.2 m3 s-1). In 2015, the inflow from WWTP's raises the NO3- loads and enriches δ18O-NO3 values. Generally, oxygen isotope signatures from nitrate are more variable and are controlled by biogeochemical processes in concert with the oxygen isotopic composition of the ambient water. Elevated δ18O-NO3 in 2015 are most likely due to higher temperatures and lower

  12. Investigation of reduction and tolerance capability of lactic acid bacteria isolated from kimchi against nitrate and nitrite in fermented sausage condition.

    Science.gov (United States)

    Paik, Hyun-Dong; Lee, Joo-Yeon

    2014-08-01

    Lactobacillus brevis KGR3111, Lactobacillus curvatus KGR 2103, Lactobacillus plantarum KGR 5105, and Lactobacillus sakei KGR 4108 isolated from kimchi were investigated for their potential to be used as starter culture for fermented sausages with the capability to reduce and tolerate nitrate/nitrite. The reduction capability of tested strains for nitrate was not dramatic. All tested strains, however, showed the capability to produce nitrite reductase with the reduction amount of 58.46-75.80 mg/l of NO(2)(-). L. brevis and L. plantarum showed nitrate tolerance with the highest number of 8.71 log cfu/ml and 8.81 log cfu/ml, and L. brevis and L. sakei exhibited nitrite tolerance with the highest number of 8.24 log cfu/ml and 8.25 log cfu/ml, respectively. As a result, L. brevis, L. plantarum, and L. sakei isolated from kimchi showed a tolerance against nitrate or nitrite with a good nitrite reduction capability, indicating the satisfaction of one of the selection criteria to be used as starter culture for fermented sausages. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Evaluation of Nitrate Transport in Clay Soil

    Directory of Open Access Journals (Sweden)

    Morteza Seyedian

    2016-09-01

    Full Text Available  Background and purpose: With the increase in world population and the need to provide food, farmers are now using a variety of chemical fertilizers, organic pesticides have turned. Indiscriminate use of these inputs without considering its side effects, both environmental problems and brings in terms of human health. Among these, organic fertilizers contain soluble compounds such as nitrate. These compounds through precipitation or irrigation of the soil solution, groundwater and surface water resources are. The purpose of this study was to determine the amount of nitrate transport in clay and simulation software using HYDRUS2D. Methods: In order to perform it, 5 different height of soil column 20, 40, 60, 80 and 100 cm selected. In thicknesses of 20, 40, 60 and 80 cm respectively output levels after a period of 6, 12, 18 and 22 hours to input the concentration of nitrate (50 mg/lit is. In thicknesses of 20, 40, 60 and 80 cm, respectively, after the time of 5/6, 5/12, 21, and 25-hour concentration of 50 mg/lit is output. In thickness 20, 40, 60 and 80cm, outlet concentration after 6, 12, 18 and 22 minutes inlet concentration (50mg/lit. Results: The result showed that Hydrus software ability of simulates nitrate movement in soil and result of Hydrus software and laboratory data near. Conclusions: With increasing soil thickness difference HYDRUS2D results and experimental data more and more time to transfer nitrate were spent with increasing thickness. 

  14. Redução de nitrato em plantas jovens de café cultivadas em diferentes níveis de luz e de nitrogênio Nitrate reduction in young coffee trees grown under different levels of light and nitrogen

    Directory of Open Access Journals (Sweden)

    Maria Luiza Carvalho Carelli

    1990-01-01

    Full Text Available Foi estudado o efeito de níveis de luz e de nitrogênio na atividade da enzima redutase de nitrato e nos teores de nitrato e de açúcares nas folhas de plantas jovens de café (Coffea arabica L, assim como as possíveis relações entre a disponibilidade desses compostos e a atividade enzimática. Foram utilizadas plantas de dez meses de idade cultivadas em vasos contendo uma mistura de terra mais composto, e mantidas em condições ambientais em pleno sol e em 50% da luz solar. Metade das plantas de cada tratamento de luz foi suplementada semanalmente com nitrogênio. Os resultados mostraram que a atividade da redutase de nitrato, nos dois tratamentos de luz, foi maior nas plantas suplementadas com nitrogênio. Para um mesmo nível de nitrogênio, as plantas cultivadas em pleno sol apresentaram menor atividade da redutase de nitrato, maiores teores de nitrato e de açúcares e maiores taxas de transpiração, do que as cultivadas na sombra. Tais resultados indicam que a menor atividade da redutase de nitrato nas plantas cultivadas em pleno sol aparentemente não foi devida a limitações na disponibilidade de nitrato e de açúcares para fornecer a energia necessária para a redução de nitrato.The effect of levels of light and nitrogen on the activity of the enzyme nitrate reductase and its relationship with the availability of sugars and nitrate was studied in leaves of coffee plants (Coffea arabica L. cv. Catual. Ten month old plants were grown on pots containing a mixture of soil and compost, and were kept at full or 50% sunlight. Half of the plants of each light treatment received nitrogen supply. The results showed that the activity of nitrate reductase was higher on plants supplied with nitrogen at both light treatments. For the same nitrogen level, plants grown under full sunlight presented lower nitrate reductase activity, higher nitrate and sugars concentrations, and higher transpiration rates than plants kept at 50% sunlight

  15. 9 CFR 319.2 - Products and nitrates and nitrites.

    Science.gov (United States)

    2010-01-01

    ... and nitrates and nitrites. Any product, such as frankfurters and corned beef, for which there is a... without nitrate or nitrite and labeled with such standard name when immediately preceded with the term... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Products and nitrates and nitrites...

  16. Regioselective nitration of aromatic substrates in zeolite cages

    Indian Academy of Sciences (India)

    Phenol is nitrated regioselectively by fuming nitric acid inside the cages of faujasite zeolites (dependent on the loading level) and a remarkable orthoselectivity is observed in solid state nitration. Toluene and chlorobenzene also containing ortho-/para-orienting substituents, undergo faster nitration, though the ...

  17. A nitrate sensitive planar optode; performance and interferences

    DEFF Research Database (Denmark)

    Pedersen, Lasse; Dechesne, Arnaud; Smets, Barth F.

    2015-01-01

    We present a newly developed nitrate sensitive planar optode. It exhibits a linear response to nitrate from 1 to 50 mM at pH 8.0, a fast response time below 10 s and a good lifetime, allowing for fast two dimensional nitrate measurements over long periods of time. Interference from nitrite...

  18. Inactivation of Yersinia enterocolitica by nitrite and nitrate in food.

    Science.gov (United States)

    de Giusti, M; de Vito, E

    1992-01-01

    The antimicrobial effects of sodium nitrite and sodium and potassium nitrate against Yersinia enterocolitica were investigated in solution and in treated pork meat. Potassium nitrate and sodium nitrate showed only feeble antimicrobial activity in cultures; no antimicrobial activity was detected with sodium nitrite. Conversely, all three salts displayed apparent antimicrobial activity in pork meat, possibly due to selective effects on competitive flora.

  19. Nitrate ammonification in mangrove soils: A hidden source of nitrite?

    NARCIS (Netherlands)

    Balk, Melike; Laverman, A.M.; Keuskamp, Joost A.; Laanbroek, Hendrikus J.

    2015-01-01

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought

  20. Nitrate removal by electro-bioremediation technology in Korean soil

    International Nuclear Information System (INIS)

    Choi, Jeong-Hee; Maruthamuthu, Sundaram; Lee, Hyun-Goo; Ha, Tae-Hyun; Bae, Jeong-Hyo

    2009-01-01

    The nitrate concentration of surface has become a serious concern in agricultural industry through out the world. In the present study, nitrate was removed in the soil by employing electro-bioremediation, a hybrid technology of bioremediation and electrokinetics. The abundance of Bacillus spp. as nitrate reducing bacteria were isolated and identified from the soil sample collected from a greenhouse at Jinju City of Gyengsangnamdo, South Korea. The nitrate reducing bacterial species were identified by 16 s RNA sequencing technique. The efficiency of bacterial isolates on nitrate removal in broth was tested. The experiment was conducted in an electrokinetic (EK) cell by applying 20 V across the electrodes. The nitrate reducing bacteria (Bacillus spp.) were inoculated in the soil for nitrate removal process by the addition of necessary nutrient. The influence of nitrate reducers on electrokinetic process was also studied. The concentration of nitrate at anodic area of soil was higher when compared to cathode in electrokinetic system, while adding bacteria in EK (EK + bio) system, the nitrate concentration was almost nil in all the area of soil. The bacteria supplies electron from organic degradation (humic substances) and enhances NO 3 - reduction (denitrification). Experimental results showed that the electro-bio kinetic process viz. electroosmosis and physiological activity of bacteria reduced nitrate in soil environment effectively. Involvement of Bacillus spp. on nitrification was controlled by electrokinetics at cathode area by reduction of ammonium ions to nitrogen gas. The excellence of the combined electro-bio kinetics technology on nitrate removal is discussed.

  1. Nitrate concentration in drinking water supplies in selected ...

    African Journals Online (AJOL)

    Out of the 48 wells, 30 (62.5%) and 24 (50%) were located at ≤10 m from the septic tank/pit latrine and refuse dumps, respectively. Nitrate maps were developed using Georeferenced data for the water points. The nitrate exceedence map produced showed water sources within the study area with nitrate concentration ...

  2. Nitrate pollution of Neogene alluvium aquifer in Morogoro ...

    African Journals Online (AJOL)

    Concern over nitrate pollution of groundwater in integrated water quality management has been growing recently. The levels of nitrate in wells from septic tanks and urban agriculture with nitrogen fertilizers application may increase the potential groundwater pollution by nitrate. The purpose of this study was to determine the ...

  3. Occurrence of elevated nitrate in groundwaters of Krishna delta, India

    African Journals Online (AJOL)

    Nitrate concentrations were measured in the groundwater samples of Krishna delta, India. The results indicate a large variation of nitrate from 10 - 135 mg/l. In 79 groundwater samples, about 39% shows high nitrate contents (>50 mg/l), which is more than the permissible limits in drinking water. In north Krishna delta 49% ...

  4. Nitrate concentration in greenhouse lettuce: a modelling study

    NARCIS (Netherlands)

    Seginer, I.; Buwalda, F.; Straten, van G.

    1998-01-01

    A simple two-state-variable model was developed to describe the nitrate concentration in lettuce when nitrate supply is unlimited. A central element of the model is a negative correlation between the concentrations of soluble carbohydrates and nitrate in the cell sap, a correlation which reflects

  5. Headache characteristics during the development of tolerance to nitrates

    DEFF Research Database (Denmark)

    Christiansen, I; Iversen, Helle Klingenberg; Olesen, J

    2000-01-01

    Recent studies suggest that nitric oxide (NO) plays an important role in nitrate-induced headache and in spontaneous migraine attacks. Organic nitrates act as prodrugs for NO and headache is a predominant adverse effect of nitrates but often disappears during continuous treatment. Insight...

  6. 21 CFR 176.320 - Sodium nitrate-urea complex.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate-urea complex. 176.320 Section 176... Substances for Use Only as Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium... the provisions of this section. (a) Sodium nitrate-urea complex is a clathrate of approximately two...

  7. Effect of membrane characteristics on the performance of membrane bioreactors for oily wastewater treatment.

    Science.gov (United States)

    Mafirad, S; Mehrnia, M R; Sarrafzadeh, M H

    2011-01-01

    Influence of membrane material and pore size on the performance of a submerged membrane bioreactor (sMBR) for oily wastewater treatment was investigated. The sMBR had a working volume of about 19 L with flat sheet modules at the same hydrodynamic conditions. Five types of micro- and ultra-polymeric membranes containing cellulose acetate (CA), cellulose nitrate (CN), polyamide (PA), polyvinylidene difluoride (PVDF) and polyethersulfone (PES) were used and their filtration performance in terms of permeability, permeate quality and fouling intensity were evaluated. Characterization of the membranes was done by performing some analysis such as pore size distribution; contact angle and scanning electronic microscopy (SEM) microphotograph on all membranes. The quality of permeates from each membrane was identified by measuring chemical oxygen demand (COD). The results showed more irreversible fouling intensity for membranes with larger pore size which can be due to more permeation of bioparticles and colloids inside the pores. Membrane characteristics have a major role in the preliminary time of the filtration before cake layer formation so that the PA with the highest hydrophilicity had the lowest permeability decline by fouling in this period. Also, the PVDF and PES membranes had better performance according to better permeate quality in the preliminary time of the filtration related to smaller pore size and also their better fouling resistance and chemical stability properties. However, all membranes resulted in the same permeability and permeate quality after cake layer formation. An overall efficiency of about 95% in COD removal was obtained for oily wastewater treatment by the membranes used in this study.

  8. Ferric reductase activity of low molecular weight human milk fraction is associated with enhanced iron solubility and uptake in Caco-2 cells.

    Science.gov (United States)

    Pullakhandam, Raghu; Nair, Madhavan Krishnapillai; Kasula, Sunanda; Kilari, Sreenivasulu; Thippande, Tippeswamy Gowda

    2008-09-19

    It is known that the fractional absorption of extrinsic iron from human milk is higher in infants and adults. A low molecular weight milk fraction has been proposed to increase the bioavailability of iron from human milk. Nevertheless, the mechanisms remained elusive. Here in we demonstrate ferric reductase activity (Km7.73x10(-6)M) in low molecular weight human milk fraction (10kF, filtrate derived from ultra filtration of milk whey through 10kDa cutoff membrane), which increased ferric iron solubility and iron uptake in Caco-2 cells. The 10kF fraction was as effective as ascorbic acid (1:20 iron to ascorbic acid) in increasing the ferric iron solubility and uptake in Caco-2 cells. Further, gel filtration chromatography on peptide column led to co-elution of ferric reductase and iron solubilization activities at an apparent molecular mass of iron in Caco-2 cells. Thus, it is concluded that human milk possesses ferric reductase activity and is associated with ferric iron solubilization and enhanced absorption.

  9. Sodium nitrate supplementation does not enhance performance of endurance athletes.

    Science.gov (United States)

    Bescós, Raúl; Ferrer-Roca, Ventura; Galilea, Pedro A; Roig, Andreu; Drobnic, Franchek; Sureda, Antoni; Martorell, Miquel; Cordova, Alfredo; Tur, Josep A; Pons, Antoni

    2012-12-01

    Supplementation with inorganic nitrate has been suggested to be an ergogenic aid for athletes as nitric oxide donor. The purpose of this study was to determine whether ingestion of inorganic sodium nitrate benefits well-trained athletes performing a 40-min exercise test in laboratory conditions. In addition, we investigated the effect of this supplement on plasma levels of endothelin-1 (ET-1) and in nitrated proteins. Thirteen trained athletes participated in this randomized, double-blind, crossover study. They performed a 40-min cycle ergometer distance-trial test after two 3-d periods of dietary supplementation with sodium nitrate (10 mg·kg of body mass) or placebo. Concentration of plasma nitrate (256 ± 35 μM) and nitrite (334 ± 86 nM) increased significantly (P nitrate supplementation compared with placebo (nitrate: 44 ± 11 μM; nitrite: 187 ± 43 nM). In terms of exercise performance, there were no differences in either the mean distance (nitrate: 26.4 ± 1.1 km; placebo: 26.3 ± 1.2 km; P = 0.61) or mean power output (nitrate: 258 ± 28 W; placebo: 257 ± 28 W; P = 0.89) between treatments. Plasma ET-1 increased significantly (P nitrate (4.0 ± 0.8 pg·mL) and placebo (2.4 ± 0.4 pg·mL) conditions. This increase was significantly greater (P nitrate group. Levels of nitrated proteins did not differ between treatments (nitrate: preexercise, 91% ± 23%; postexercise, 81% ± 23%; placebo: preexercise, 95% ± 20%; postexercise, 99% ± 19%). Sodium nitrate supplementation did not improve a 40-min distance-trial performance in endurance athletes. In addition, concentration of plasma ET-1 increased significantly after exercise after supplementation with sodium nitrate.

  10. Protein Tyrosine Nitration: Selectivity, physicochemical and biological consequences, denitration and proteomics methods for the identification of tyrosine-nitrated proteins

    NARCIS (Netherlands)

    Abello, N.; Kerstjens, H.A.M.; Postma, D.S; Bischoff, Rainer

    2009-01-01

    Protein tyrosine nitration (PTN) is a post-translational modification occurring under the action of a nitrating agent. Tyrosine is modified in the 3-position of the phenolic ring through the addition of a nitro group (NO2). In the present article, we review the main nitration reactions and elucidate

  11. Protein Tyrosine Nitration : Selectivity, Physicochemical and Biological Consequences, Denitration, and Proteomics Methods for the Identification of Tyrosine-Nitrated Proteins

    NARCIS (Netherlands)

    Abello, Nicolas; Kerstjens, Huib A. M.; Postma, Dirkje S.; Bischoff, Rainer

    Protein tyrosine nitration (PTN) is a post-translational modification occurring under the action of a nitrating agent. Tyrosine is modified in the 3-position of the phenolic ring through the addition of a nitro group (NO(2)). In the present article, we review the main nitration reactions and

  12. Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.

    Science.gov (United States)

    Heyno, Eiri; Mary, Véronique; Schopfer, Peter; Krieger-Liszkay, Anja

    2011-07-01

    Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.

  13. Enzyme Mechanism and Slow-Onset Inhibition of Plasmodium falciparum Enoyl-Acyl Carrier Protein Reductase by an Inorganic Complex

    Science.gov (United States)

    de Medeiros, Patrícia Soares de Maria; Ducati, Rodrigo Gay; Basso, Luiz Augusto; Santos, Diógenes Santiago; da Silva, Luiz Hildebrando Pereira

    2011-01-01

    Malaria continues to be a major cause of children's morbidity and mortality worldwide, causing nearly one million deaths annually. The human malaria parasite, Plasmodium falciparum, synthesizes fatty acids employing the Type II fatty acid biosynthesis system (FAS II), unlike humans that rely on the Type I (FAS I) pathway. The FAS II system elongates acyl fatty acid precursors of the cell membrane in Plasmodium. Enoyl reductase (ENR) enzyme is a member of the FAS II system. Here we present steady-state kinetics, pre-steady-state kinetics, and equilibrium fluorescence spectroscopy data that allowed proposal of P. falciparum ENR (PfENR) enzyme mechanism. Moreover, building on previous results, the present study also evaluates the PfENR inhibition by the pentacyano(isoniazid)ferrateII compound. This inorganic complex represents a new class of lead compounds for the development of antimalarial agents focused on the inhibition of PfENR. PMID:21603269

  14. Histochemical localization of glutathione dependent NBT-reductase in mouse skin.

    Science.gov (United States)

    Shukla, Y

    2001-09-01

    Localization of the glutathione dependent Nitroblue tetrazolium (NBT) reductase in fresh frozen sections of mouse skin and possible dependence of NBT reductase on tissue thiol levels has been investigated. The fresh frozen tissue sections (8 m thickness) were prepared and incubated in medium containing NBT, reduced glutathione (GSH) and phosphate buffer. The staining for GSH was performed with mercury orange. The activity of the NBT-reductase in mouse skin has been found to be localized in the areas rich in glutathione and actively proliferating area of the skin. The activity of the NBT-reductase seems to be dependent on the glutathione contents.

  15. Silver nanoparticles can attenuate nitrative stress

    Directory of Open Access Journals (Sweden)

    Mariusz Zuberek

    2017-04-01

    Full Text Available We have reported previously that glucose availability can modify toxicity of silver nanoparticles (AgNPs via elevation of antioxidant defence triggered by increased mitochondrial generation of reactive oxygen species. In this study, we examined the effect of glucose availability on the production of reactive nitrogen species in HepG2 cells and modification of nitrative stress by AgNPs. We found that lowering the glucose concentration increased expression of genes coding for inducible nitric oxide syntheas, NOS2 and NOS2A resulting in enhanced production of nitric oxide. Surprisingly, AgNPs decreased the level of nitric oxide accelerated denitration of proteins nitrated by exogenous peroxynitrite in cells grown in the presence of lowered glucose concentration, apparently due to further induction of protective proteins.

  16. Photolysis of alkaline-earth nitrates

    Science.gov (United States)

    Kriger, L. D.; Miklin, M. B.; Dyagileva, E. P.; Anan'ev, V. A.

    2013-02-01

    Peroxynitrite and nitrite ions are the diamagnetic products of photolysis (with light at a wavelength of 253.7 nm) of alkaline-earth nitrates; the paramagnetic products and hydrogen peroxide were not found. The structural water in alkaline-earth nitrate crystals did not affect the qualitative composition of the photodecomposition products. The quantum yield of nitrite ions was 0.0012, 0.0038, 0.0078, and 0.0091 quanta-1 and that of peroxynitrite ions was 0.0070, 0.0107, 0.0286, and 0.0407 quanta-1 for Sr(NO3)2, Ba(NO3)2, Ca(NO3)2 · 4H2O, and Mg(NO3)2 · 6H2O, respectively.

  17. Purification of contaminated groundwater by membrane technology

    Energy Technology Data Exchange (ETDEWEB)

    Youn, In Soo; Chung, Chin Ki; Kim, Byoung Gon [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    The objective of this study is to apply the membrane separation technology to the purification of contaminated ground water in Korea. Under this scope, the purification was aimed to the drinking water level. The scale of the membrane system was chosen to a small filtration plant for local clean water supplies and/or heavy purifiers for buildings and public uses. The actual conditions of ground water contamination in Korea was surveyed to determine the major components to remove under the drinking water requirements. To set up a hybrid process with membrane methods, conventional purification methods were also investigated for the comparison purpose. The research results are summarized as follows : 1) Contamination of the groundwater in Korea has been found to be widespread across the country. The major contaminant were nitrate, bacteria, and organic chlorides. Some solvents and heavy metals are also supposed to exist in the ground water of industrial complexes, cities, and abandoned mines. 2) The purification methods currently used in public filtration plants appear not to be enough for new contaminants from recent industrial expanding. The advanced purification technologies generally adopted for this problem have been found to be unsuitable due to their very complicated design and operation, and lack of confidence in the purification performance. 3) The reverse osmosis tested with FilmTec FT30 membrane was found to remove nitrate ions in water with over 90 % efficiency. 4) The suitable membrane process for the contaminated groundwater in Korea has been found to be the treatments composed of activated carbon, microfiltration, reverse osmosis or ultrafiltration, and disinfection. The activated carbon treatment could be omitted for the water of low organic contaminants. The microfiltration and the reverse osmosis treatments stand for the conventional methods of filtration plants and the advanced methods for hardly removable components, respectively. It is recommended

  18. Regulation of AhFRO1, an Fe(III)-chelate reductase of peanut, during iron deficiency stress and intercropping with maize.

    Science.gov (United States)

    Ding, Hong; Duan, Lihong; Wu, Huilan; Yang, Rongxin; Ling, Hongqing; Li, Wen-Xue; Zhang, Fusuo

    2009-07-01

    Iron deficiency-induced chlorosis in peanut during anthesis was alleviated when peanut was intercropped with maize in field and pot experiments. Iron acquisition of graminaceous plants is characterized by the synthesis and secretion of the iron-chelating phytosiderophores. Compared to the roots of monocropped maize, the roots of maize intercropped with peanut always secreted higher amounts of phytosiderophores during peanut anthesis. For non-graminaceous plants, reduction of ferric to ferrous iron on the root surface is the rate-limiting step for mobilizing iron from soil. The full-length cDNA, AhFRO1, which is encoding an Fe(III)-chelate reductase, was isolated from peanut. AhFRO1 expression in yeast conferred Fe(III)-chelate reductase activity to the cells. Consistent with its function in iron uptake, AhFRO1 was determined to be a membrane protein by transient expression analysis. AhFRO1 mRNA accumulated under iron deficiency conditions. During pre-anthesis, the Fe(III)-chelate reductase activity and the transcript levels of AhFRO1 were similar in monocropped and intercropped peanut. When the iron deficiency-induced chlorosis developed in the monocropped peanuts, both the Fe(III)-chelate reductase activity of peanut and the transcript levels of AhFRO1 were higher in intercropped than in monocropped peanuts, which is consistent with the secretion of phytosiderophores by maize roots. We conclude that AhFRO1 in peanut and phytosiderophores from maize co-operate to improve the iron nutrition of peanut when intercropped with maize.

  19. Bioconversion of Nitramine Propellant Wastewaters - Triaminoguanidine Nitrate

    Science.gov (United States)

    1985-01-01

    o d i m sulfide for sneerobiasis. Batch and continuous cultures were inoculated with organisar from activated sludge (Marlborough Easterly Sewage ...Treatmtnt Plant, Marlborough, IU) anaerobic sludge digest (Nut Island Sewage T r e a b n t Plant. Boston. MA) and garden roil. One aL sampler of... BIOCONVERSION OF NITRAMINE PROPELLANT WASTEWATERS = TRIAMINOGUANIDINE 0 a NITRATE 80 BY DAVID L KAPLAN AND ARTHUR M. KAPLAN JANUARY 1985

  20. Genetic basis for nitrate resistance in Desulfovibrio strains

    Directory of Open Access Journals (Sweden)

    Hannah eKorte

    2014-04-01

    Full Text Available Nitrate is an inhibitor of sulfate-reducing bacteria (SRB. In petroleum production sites, amendments of nitrate and nitrite are used to prevent SRB production of sulfide that causes souring of oil wells. A better understanding of nitrate stress responses in the model SRB, Desulfovibrio vulgaris Hildenborough and Desulfovibrio alaskensis G20, will strengthen predictions of environmental outcomes. Nitrate inhibition of SRB has historically been considered to result from the generation of small amounts of nitrite, to which SRB are quite sensitive. Here we explored the possibility that nitrate might inhibit SRB by a mechanism other than through nitrite inhibition. We found that nitrate-stressed D. vulgaris cultures grown in lactate-sulfate conditions eventually grew in the presence of high concentrations of nitrate, and their resistance continued through several subcultures. Nitrate consumption was not detected over the course of the experiment, suggesting adaptation to nitrate. With high-throughput genetic approaches employing TnLE-seq for D. vulgaris and a pooled mutant library of D. alaskensis, we determined the fitness of many transposon mutants of both organisms in nitrate stress conditions. We found that several mutants, including homologs present in both strains, had a greatly increased ability to grow in the presence of nitrate but not nitrite. The mutated genes conferring nitrate resistance included the gene encoding the putative Rex transcriptional regulator (DVU0916/Dde_2702, as well as a cluster of genes (DVU0251-DVU0245/Dde_0597-Dde_0605 that is poorly annotated. Follow-up studies with individual D. vulgaris transposon and deletion mutants confirmed high-throughput results. We conclude that, in D. vulgaris and D. alaskensis, nitrate resistance in wild-type cultures is likely conferred by spontaneous mutations. Furthermore, the mechanisms that confer nitrate resistance may be different from those that confer nitrite resistance.