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Berlin Brandenburg

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  • 1
    In: Wilmott, March 2016, Vol.2016(82), pp.51-59
    Description: The year 2015 has furnished us with three examples of pegged-currency-rate regimes breaking in dramatic fashion, all of which we explore in this arti cle. On January 15, 2015, the longstanding Swiss National Bank (SNB) defense level of 1.20 for the Swiss franc (CHF) against the euro was breached - one...
    Keywords: Foreign Exchange Rates;
    ISSN: 1540-6962
    E-ISSN: 1541-8286
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  • 2
    Language: English
    In: Journal of Bacteriology, July, 2013, Vol.195(13-14), p.3260(9)
    Description: Phylogenetically diverse species of bacteria can catalyze the oxidation of ferrous iron [Fe(II)] coupled to nitrate (NO.sub.3.sup.-) reduction, often referred to as nitrate-dependent iron oxidation (NDFO). Very little is known about the biochemistry of NDFO, and though growth benefits have been observed, mineral encrustations and nitrite accumulation likely limit growth. Acidovorax ebreus, like other species in the Acidovorax genus, is proficient at catalyzing NDFO. Our results suggest that the induction of specific Fe(II) oxidoreductase proteins is not required for NDFO. No upregulated periplasmic or outer membrane redox-active proteins, like those involved in Fe(II) oxidation by acidophilic iron oxidizers or anaerobic photoferrotrophs, were observed in proteomic experiments. We demonstrate that while "abiotic" extracellular reactions between Fe(II) and biogenic (NO.sub.2.sup.-) /NO can be involved in NDFO, intracellular reactions between Fe(II) and periplasmic components are essential to initiate extensive NDFO. We present evidence that an organic cosubstrate inhibits NDFO, likely by keeping periplasmic enzymes in their reduced state, stimulating metal efflux pumping, or both, and that growth during NDFO relies on the capacity of a nitrate-reducing bacterium to overcome the toxicity of Fe(II) and reactive nitrogen species. On the basis of our data and evidence in the literature, we postulate that all respiratory nitrate-reducing bacteria are innately capable of catalyzing NDFO. Our findings have implications for a mechanistic understanding of NDFO, the biogeochemical controls on anaerobic Fe(II) oxidation, and the production of (NO.sub.2.sup.-), NO, and (NO.sub.2) in the environment.
    Keywords: Metal-reducing Bacteria -- Research ; Oxidation-reduction Reactions -- Research ; Periplasm -- Research
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: International Journal of Hydrogen Energy, August 2012, Vol.37(15), pp.11504-11513
    Description: Two-stage anaerobic digesters are ideally suited for hydrogen production because primary fermentation is separated from methanogenesis, allowing for optimization of both processes. At low hydrogen partial pressures, hydrogen forming reactions become thermodynamically favorable and there is a shift in fermentation toward the production of acetate and away from butyrate, alcohols, and solvents. Increased acetate yields in first stage reactors enhance acetoclastic methanogenesis in second stage reactors. We evaluated the effects of headspace pressure and reactor mixing, two parameters that can be controlled at the industrial scale, on hydrogen production and fermentation products using anaerobic batch reactors. Control of methanogenesis was achieved with low pH caused by high loading of non-fat powered milk (4 gVS ). In mixed reactors, hydrogen yields increased significantly from 87.5 to 121.4 ml (  = 0.056) and the acetate to butyrate ratio increased from 0.44 to 0.68 (  = 0.11). Control of headspace pressure below atmospheric levels did not have a significant effect on gas production. These results demonstrate the rapid production of hydrogen and inhibition of methanogenesis via substrate loading and mixing, and provide a practical method for enhancing energy recovery in two-stage anaerobic digesters. ► We evaluate methods for increasing hydrogen production in anaerobic digesters. ► Anaerobic fermentation using high substrate loading produces rich biogas. ► Mixing increases hydrogen by releasing entrained gas and preventing methanogenesis. ► Acetate/butyrate increases in mixed reactors, suggesting a fermentation shift. ► Increased acetate improves methane production in downstream methanogenic reactors.
    Keywords: Enhanced Biohydrogen Production ; Two-Stage Anaerobic Digestion ; Low Pressure ; Mixing ; Acetate to Butyrate Ratio ; Engineering
    ISSN: 0360-3199
    E-ISSN: 1879-3487
    Source: ScienceDirect Journals (Elsevier)
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  • 4
    Language: English
    In: Analytical chemistry, 16 January 2018, Vol.90(2), pp.1273-1279
    Description: Droplet microfluidics can identify and sort cells using digital reverse transcription polymerase chain reaction (RT-PCR) signals from individual cells. However, current methods require multiple microfabricated devices for enzymatic cell lysis and PCR reagent addition, making the process complex and prone to failure. Here, we describe a new approach that integrates all components into a single device. The method enables controlled exposure of isolated single cells to a high pH buffer, which lyses cells and inactivates reaction inhibitors but can be instantly neutralized with RT-PCR buffer. Using our chemical lysis approach, we distinguish individual cells' gene expression with data quality equivalent to more complex two-step workflows. Our system accepts cells and produces droplets ready for amplification, making single-cell droplet RT-PCR faster and more reliable.
    Keywords: Droplets ; Microfluidics ; Pcr:Polymerase-Chain-Reaction ; Complexity-Step ; Single-Machine ; Cell-Lysis ; Gene-Expression ; Data-Quality ; Tröpfchen ; Mikrofluidik ; Polymerase-Kettenreaktion ; Komplexitätsstufe ; Einzelmaschine ; Zelllösung ; Genexpression ; Datenqualität ; Engineering ; Chemistry;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 5
    Language: English
    In: Applied and Environmental Microbiology, 2011, Vol. 77(20), p.7401
    Description: A comparative analysis of the genomes of four dissimilatory (per)chlorate-reducing bacteria is performed to reveal a genomic island associated with perchlorate reduction. The genomic island, in addition to the characterized metabolic genes for perchlorate reductase and chlorite dismutase is found to contain multiple conserved uncharacterized genes possibly involved in electron transport and regulation.
    Keywords: Ammonium Perchlorate – Chemical Properties ; Anaerobic Bacteria – Physiological Aspects ; Microbial Respiration – Research ; Oxidation-Reduction Reactions – Analysis;
    ISSN: 1098-5336
    ISSN: 10985336
    ISSN: 00992240
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  • 6
    Language: English
    In: The Journal of biological chemistry, 22 April 2016, Vol.291(17), pp.9190-202
    Description: Perchlorate is an important ion on both Earth and Mars. Perchlorate reductase (PcrAB), a specialized member of the dimethylsulfoxide reductase superfamily, catalyzes the first step of microbial perchlorate respiration, but little is known about the biochemistry, specificity, structure, and mechanism of PcrAB. Here we characterize the biophysics and phylogeny of this enzyme and report the 1.86-Å resolution PcrAB complex crystal structure. Biochemical analysis revealed a relatively high perchlorate affinity (Km = 6 μm) and a characteristic substrate inhibition compared with the highly similar respiratory nitrate reductase NarGHI, which has a relatively much lower affinity for perchlorate (Km = 1.1 mm) and no substrate inhibition. Structural analysis of oxidized and reduced PcrAB with and without the substrate analog SeO3 (2-) bound to the active site identified key residues in the positively charged and funnel-shaped substrate access tunnel that gated substrate entrance and product release while trapping transiently produced chlorate. The structures suggest gating was associated with shifts of a Phe residue between open and closed conformations plus an Asp residue carboxylate shift between monodentate and bidentate coordination to the active site molybdenum atom. Taken together, structural and mutational analyses of gate residues suggest key roles of these gate residues for substrate entrance and product release. Our combined results provide the first detailed structural insight into the mechanism of biological perchlorate reduction, a critical component of the chlorine redox cycle on Earth.
    Keywords: Dmso Reductase Superfamily ; Mo-Bis-Mgd ; Enzyme Mechanism ; Iron-Sulfur Protein ; Molybdenum ; Perchlorate Reductase ; Structure-Function ; Substrate Access Tunnel ; Substrate Inhibition ; X-Ray Crystallography ; Bacterial Proteins -- Chemistry ; DNA Helicases -- Chemistry ; Oxidoreductases -- Chemistry ; Perchlorates -- Chemistry ; Rhodocyclaceae -- Enzymology
    E-ISSN: 1083-351X
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  • 7
    Language: English
    In: Journal of bacteriology, July 2013, Vol.195(14), pp.3260-8
    Description: Phylogenetically diverse species of bacteria can catalyze the oxidation of ferrous iron [Fe(II)] coupled to nitrate (NO(3)(-)) reduction, often referred to as nitrate-dependent iron oxidation (NDFO). Very little is known about the biochemistry of NDFO, and though growth benefits have been observed, mineral encrustations and nitrite accumulation likely limit growth. Acidovorax ebreus, like other species in the Acidovorax genus, is proficient at catalyzing NDFO. Our results suggest that the induction of specific Fe(II) oxidoreductase proteins is not required for NDFO. No upregulated periplasmic or outer membrane redox-active proteins, like those involved in Fe(II) oxidation by acidophilic iron oxidizers or anaerobic photoferrotrophs, were observed in proteomic experiments. We demonstrate that while "abiotic" extracellular reactions between Fe(II) and biogenic NO(2)(-)/NO can be involved in NDFO, intracellular reactions between Fe(II) and periplasmic components are essential to initiate extensive NDFO. We present evidence that an organic cosubstrate inhibits NDFO, likely by keeping periplasmic enzymes in their reduced state, stimulating metal efflux pumping, or both, and that growth during NDFO relies on the capacity of a nitrate-reducing bacterium to overcome the toxicity of Fe(II) and reactive nitrogen species. On the basis of our data and evidence in the literature, we postulate that all respiratory nitrate-reducing bacteria are innately capable of catalyzing NDFO. Our findings have implications for a mechanistic understanding of NDFO, the biogeochemical controls on anaerobic Fe(II) oxidation, and the production of NO(2)(-), NO, and N(2)O in the environment.
    Keywords: Comamonadaceae -- Metabolism ; Ferrous Compounds -- Metabolism ; Nitrates -- Metabolism
    ISSN: 00219193
    E-ISSN: 1098-5530
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  • 8
    Language: English
    In: Risks, 01 July 2017, Vol.5(3), p.35
    Description: Much of the debate around a potential British exit (Brexit) from the European Union has centred on the potential macroeconomic impact. In this paper, we instead focus on understanding market expectations for price action around the Brexit referendum date. Extracting implied distributions from the GBPUSD option volatility surface, we originally estimated, based on our visual observation of implied probability densities available up to 13 June 2016, that the market expected that a vote to leave could result in a move in the GBPUSD exchange rate from 1.4390 (spot reference on 10 June 2016) down to a range in 1.10 to 1.30, i.e., a 10–25% decline—very probably with highly volatile price action. To quantify this more objectively, we construct a mixture model corresponding to two scenarios for the GBPUSD exchange rate after the referendum vote, one scenario for “remain” and one for “leave”. Calibrating this model to four months of market data, from 24 February to 22 June 2016, we find that a “leave” vote was associated with a predicted devaluation of the British pound to approximately 1.37 USD per GBP, a 4.5% devaluation, and quite consistent with the observed post-referendum exchange rate move down from 1.4877 to 1.3622. We contrast the behaviour of the GBPUSD option market in the run-up to the Brexit vote with that during the 2014 Scottish Independence referendum, finding the potential impact of Brexit to be considerably higher.
    Keywords: Brexit ; Foreign Exchange Options ; Implied Distributions ; Forecasting ; Event Risk ; Business
    E-ISSN: 2227-9091
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  • 9
    In: Molecular Microbiology, October 2014, Vol.94(1), pp.107-125
    Description: Previous work on respiratory chlorate reduction has biochemically identified the terminal reductase and the chlorite detoxifying enzyme . In  , genes encoding these enzymes reside on composite transposons whose core we refer to as the hlorate eduction composite transposon nterior (). To better understand this metabolism in , we used ‐seq and proteomics to predict carbon and electron flow during chlorate reduction and posit that formate is an important electron carrier with lactate as the electron donor, but that predominates on acetate. Chlorate‐specific transcription of electron transport chain components or the was not observed, but and transcription was attenuated by oxygen. The major chlorate‐specific response related to oxidative stress and was indicative of reactive chlorine species production. A genetic system based on ‐streptomycin counter selection was developed to further dissect the metabolism, but readily lost the via homologous recombination of the composite transposon's flanking insertion sequences. An engineered strain containing a single chromosomal did not grow on chlorate, but overexpression of and its neighbouring cytochrome restored growth. We postulate that the recently acquired underwent copy‐number expansion to circumvent insufficient expression of key genes in the pathway.
    Keywords: Gene Deletion ; Oxidative Stress ; Chlorates -- Metabolism ; Shewanella -- Metabolism;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 10
    Language: English
    In: Applied and environmental microbiology, April 2015, Vol.81(8), pp.2717-26
    Description: Two (per)chlorate-reducing bacteria, strains CUZ and NSS, were isolated from marine sediments in Berkeley and San Diego, CA, respectively. Strain CUZ respired both perchlorate and chlorate [collectively designated (per)chlorate], while strain NSS respired only chlorate. Phylogenetic analysis classified both strains as close relatives of the gammaproteobacterium Sedimenticola selenatireducens. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) preparations showed the presence of rod-shaped, motile cells containing one polar flagellum. Optimum growth for strain CUZ was observed at 25 to 30 °C, pH 7, and 4% NaCl, while strain NSS grew optimally at 37 to 42 °C, pH 7.5 to 8, and 1.5 to 2.5% NaCl. Both strains oxidized hydrogen, sulfide, various organic acids, and aromatics, such as benzoate and phenylacetate, as electron donors coupled to oxygen, nitrate, and (per)chlorate or chlorate as electron acceptors. The draft genome of strain CUZ carried the requisite (per)chlorate reduction island (PRI) for (per)chlorate respiration, while that of strain NSS carried the composite chlorate reduction transposon responsible for chlorate metabolism. The PRI of strain CUZ encoded a perchlorate reductase (Pcr), which reduced both perchlorate and chlorate, while the genome of strain NSS included a gene for a distinct chlorate reductase (Clr) that reduced only chlorate. When both (per)chlorate and nitrate were present, (per)chlorate was preferentially utilized if the inoculum was pregrown on (per)chlorate. Historically, (per)chlorate-reducing bacteria (PRB) and chlorate-reducing bacteria (CRB) have been isolated primarily from freshwater, mesophilic environments. This study describes the isolation and characterization of two highly related marine halophiles, one a PRB and the other a CRB, and thus broadens the known phylogenetic and physiological diversity of these unusual metabolisms.
    Keywords: Chlorates -- Metabolism ; Gammaproteobacteria -- Genetics ; Perchlorates -- Metabolism ; Water Pollutants, Chemical -- Metabolism
    ISSN: 00992240
    E-ISSN: 1098-5336
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