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Sample records for changing redox conditions

  1. Seasonal changes in magnetic parameters of sediments with changing redox conditions in Hiroshima Bay, Japan

    NASA Astrophysics Data System (ADS)

    Kawamura, Noriko; Amano, Yuka; Ishikawa, Naoto

    2016-07-01

    To describe and interpret the relationship between spatial and seasonal changes in the sedimentary environment of nearshore sediments and their magnetic properties, magnetic and geochemical analyses were performed on sediment samples from three stations in Hiroshima Bay, Japan. Vertical stratification of the water column in the bay changes throughout the year, and magnetic hysteresis parameters and mineralogy in the bay sediments vary in response to changes in redox conditions of bottom waters. Magnetite and hematite are present year-round at all stations. The presence of maghemitized magnetite is inferred at a station located at the entrance to the bay. Greigite is recognized at all stations in September 2011 but is not found at the entrance to the bay when water column stratification is disturbed from October 2011. The presence of maghemite and goethite is inferred at two stations in the inner bay when the sedimentary environment is oxic. The remanent coercivity/coercivity ratio (Hcr/Hc) also varies, both spatially and temporally, which reflects changes in magnetic mineralogy. Increased of Hcr/Hc values are likely to be caused by goethite and/or maghemite formation when water column stratification is disturbed and the seafloor is oxic. Concentration-dependent magnetic parameters do not respond to seasonal changes in the redox conditions of bottom waters. Reaction times and/or changes in chemical and physical conditions may be insufficient to affect these parameters in the sediments of Hiroshima Bay.

  2. Changes in the Precambrian ocean U cycle linked to the evolution of surficial redox conditions

    NASA Astrophysics Data System (ADS)

    Partin, C. A.; Bekker, A.; Scott, C.; Gill, B. C.; Lyons, T. W.

    2009-12-01

    The rise of atmospheric oxygen between 2.47 and 2.32 Ga undoubtedly had a significant impact on global biogeochemical cycles and particularly, the intensity of oxidative continental weathering. While the timing of atmospheric oxygenation is well-constrained, the redox -state of the deep ocean throughout the Proterozoic is less known. The distribution of redox-sensitive elements, such as uranium and molybdenum, in ancient sedimentary rocks provides insight into the response of the deep ocean to this dramatic geochemical change. Here we present a compilation of U concentrations in marine black shales, from the Archean to the present to track the coupled redox evolution of the atmosphere and oceans, and to decipher changes in the uranium cycle itself. Since riverine delivery represents the only significant source of uranium to the oceans, and scavenging by organic matter-rich sediments beneath suboxic to anoxic waters represents the only significant sink, uranium concentrations in black shales hold a record of the evolution of the uranium cycle through time. Temporal changes in the concentrations of U in black shales can be attributed to two first-order controls: variable delivery of riverine U to the ocean, a reflection of levels of oxygen in the atmosphere, and the extent of ocean anoxic conditions. The compiled data show a series of changes in the uranium cycle through time. Phanerozoic uranium enrichments are associated with ocean-wide anoxic events coupled with a fully developed oxidative continental weathering cycle. Enrichments are muted in Proterozoic sediments, reflecting either a weaker riverine delivery of uranium to the oceans, and/or a strong sink associated with widespread anoxia. Authigenic uranium enrichments significantly above crustal levels, which reflect strong oxidative continental weathering, do not appear until several hundred million years after the Great Oxidation Event. We propose that the U cycle in the Archean oceans was dominated by the

  3. A 22,000 year record of changing redox conditions from the Peruvian Oxygen Minimum Zone (OMZ): benthic foraminifera approach

    NASA Astrophysics Data System (ADS)

    Erdem, Z.; Schönfeld, J.; Glock, N.

    2015-12-01

    Benthic foraminifera have been used as proxies for the prevailing conditions at the sediment-water interface. Their distribution patterns are thought to facilitate reconstruction of past environmental conditions. Variations of bottom water oxygenation can be traced by the downcore distribution of benthic foraminifera and some of their morphological characters. Being one of the strongest and most pronounced OMZs in today's world oceans, the Peruvian OMZ is a key area to study such variations in relation with changing climate. Spatial changes or an extension of the OMZ through time and space are investigated using sediment cores from the lower OMZ boundary. We focus on time intervals Late Holocene, Early Holocene, Bølling Allerød, Heinrich-Stadial 1 and Last Glacial Maximum (LGM) to investigate changes in bottom-water oxygen and redox conditions. The recent distributions of benthic foraminiferal assemblages provide background data for an interpretation of the past conditions. Living benthic foraminiferal faunas from the Peruvian margin are structured with the prevailing bottom-water oxygen concentrations today (Mallon et al., 2012). Downcore distribution of benthic foraminiferal assemblages showed fluctuations in the abundance of the indicator species depicting variations and a decreasing trend in bottom water oxygen conditions since the LGM. In addition, changes in bottom-water oxygen and nitrate concentrations are reconstructed for the same time intervals by the pore density in tests of Planulina limbata and Bolivina spissa (Glock et al., 2011), respectively. The pore densities also indicate a trend of higher oxygen and nitrate concentrations in the LGM compared to the Holocene. Combination of both proxies provide information on past bottom-water conditions and changes of oxygen concentrations for the Peruvian margin. Glock et al., 2011: Environmental influences on the pore density of Bolivina spissa (Cushman), Journal of Foraminiferal Research, v. 41, no. 1, p

  4. Redox conditions and marine microbial community changes during the end-Ordovician mass extinction event

    NASA Astrophysics Data System (ADS)

    Smolarek, Justyna; Marynowski, Leszek; Trela, Wiesław; Kujawski, Piotr; Simoneit, Bernd R. T.

    2017-02-01

    The end-Ordovician (Hirnantian) crisis is the first globally distinct extinction during the Phanerozoic, but its causes are still not fully known. Here, we present an integrated geochemical and petrographic analysis to understand the sedimentary conditions taking place before, during and after the Late Ordovician ice age. New data from the Zbrza (Holy Cross Mountains) and Gołdap (Baltic Depression) boreholes shows that, like in other worldwide sections, the total organic carbon (TOC) content is elevated in the upper Katian and uppermost Hirnantian to Rhudannian black shales, but depleted (below 1%) during most of the Hirnantian. Euxinic conditions occurred in the photic zone in both TOC-rich intervals. This is based on the maleimide distribution, occurrence of aryl isoprenoids and isorenieratane, as well as a dominance of tiny pyrite framboids. Euxinic conditions were interrupted by the Hirnantian regression caused by glaciation. Sedimentation on the deep shelf changed to aerobic probably due to intense thermohaline circulation. Euxinia in the water column occurred directly during the time associated with the second pulse of the mass extinction with a termination of the end-Ordovician glaciation and sea level rise just at the Ordovician/Silurian (O/S) boundary. In contrast, we suggest based on inorganic proxies that bottom water conditions were generally oxic to dysoxic due to upwelling in the Rheic Ocean. The only episode of seafloor anoxia in the Zbrza basin was found at the O/S boundary, where all inorganic indicators showed elevated values typical for anoxia (U/Th > 1.25; V/Cr > 4.25; V/(V + Ni): 0.54-0.82 and Mo > 10-25 ppm). Significant differences in hopanes to steranes ratio and in C27-C29 sterane distribution between the Katian, Rhudannian and Hirnantian deposits indicate changes in marine microbial communities triggered by sharp climate change and Gondwana glaciation. The increase from biomarkers of cyanobacteria (2α-methylhopanes) after the O

  5. Rapid changes in the redox conditions of the western Tethys Ocean during the early Aptian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Westermann, Stéphane; Stein, Melody; Matera, Virginie; Fiet, Nicolas; Fleitmann, Dominik; Adatte, Thierry; Föllmi, Karl B.

    2013-11-01

    The early Aptian (125 to 121 Ma) records an episode of severe environmental change including a major perturbation of the carbon cycle, an oceanic anoxic event (OAE 1a, 122.5 Ma), a platform drowning episode and a biocalcification crisis. We propose to trace changes in the oxygenation state of the ocean during the early Aptian anoxic event using the redox-sensitive trace-element (RSTE) distribution, phosphorus accumulation rates (PARs) and organic-matter characterization in three different basins of the western Tethys. The following sections have been investigated: Gorgo a Cerbara (central Italy) in the Umbria Marche basin, Glaise (SE France) in the Vocontian basin and Cassis/La Bédoule (SE France) located in the Provencal basin. In the Gorgo a Cerbara section, RSTE distributions show a low background level along the main part of the section, contrasted by different maxima in concentrations within the Selli level. In the Glaise section, the Goguel level displays a weak increase in RSTE contents coeval with moderate TOC values. At Cassis/La Bédoule, no significant RSTE enrichments have been observed in sediments equivalent to the Selli level. These differences in the records of the geochemical proxies of the Selli level or its equivalent indicate the deposition under different redox conditions, probably related to the paleogeography. Our data indicate the development of anoxic-euxinic conditions in the deeper part of the Tethys during OAE 1a, whereas in the shallower environments, conditions were less reducing. Moreover, at Gorgo a Cerbara, the Selli level is characterized by rapid changes in the intensity of reducing conditions in the water column. Ocean eutrophication seems to be a major factor in the development and the persistence of anoxia as suggested by the PAR evolution. Higher PAR values at the onset of OAE 1a suggest an increase in nutrient input, whereas the return to lower values through the first part of the OAE 1a interval may be related to the

  6. Redox conditions for mantle plumes

    NASA Astrophysics Data System (ADS)

    Heister, L. E.; Lesher, C. E.

    2005-12-01

    The vanadium to scandium ratio (V/Sc) for basalts from mid-ocean ridge (MOR) and arc environments has been proposed as a proxy for fO2 conditions during partial melting (e.g. [1] and [2]). Contrary to barometric measurements of the fO2 of primitive lavas, the V/Sc ratio of the upper mantle at mid-ocean ridges and arcs is similar, leading previous authors to propose that the upper mantle has uniform redox potential and is well-buffered. We have attempted to broaden the applicability of the V/Sc parameter to plume-influenced localities (both oceanic and continental), where mantle heterogeneities associated with recycled sediments, mafic crust, and metasomatized mantle, whether of shallow or deep origin, exist. We find that primitive basalts from the North Atlantic Igneous Province (NAIP), Hawaii (both the Loa and Kea trends), Deccan, Columbia River, and Siberian Traps show a range of V/Sc ratios that are generally higher (average ~9) than those for MOR (average ~ 6.7) or arc (average ~7) lavas. Based on forward polybaric decompression modeling, we attribute these differences to polybaric melting and melt segregation within the garnet stability field rather than the presence of a more oxidized mantle in plume-influenced settings. Like MORB, the V/Sc ratios for plume-influenced basalts can be accounted for by an oxidation state approximately one log unit below the Ni-NiO buffer (NNO-1). Our analysis suggests that source heterogeneities have little, if any, resolvable influence on mantle redox conditions, although they have significant influence on the trace element and isotopic composition of mantle-derived melts. We suggest that variations in the redox of erupted lavas is largely a function of shallow lithospheric processes rather than intrinsic to the mantle source, regardless of tectonic setting. [1] Li and Lee (2004) EPSL, [2] Lee et al. (2005) J. of Petrology

  7. Minor Elements in Nakhlite Pyroxenes: Does Cr Record Changes in REDOX Conditions during Crystallization?

    NASA Technical Reports Server (NTRS)

    McKay, G.; Schwandt, C.; Le, L.; Mikouchi, T.

    2007-01-01

    Nakhlites are olivine-bearing clinopyroxene cumulates. Based on petrographic characteristics, they may be divided into groups that cooled at different rates and may have been formed at different depths in a single flow. The order of cooling rate from slowest to fastest is NWA998conditions under which these samples crystallized. Thus it is important to understand the major and minor element zoning in the cumulus pyroxenes. While major elements are nearly homogeneous, minor elements exhibit distinctive zoning patterns that vary from one nakhlite to another. This abstract reports unusual Cr zoning patterns in pyroxenes from MIL03346 (MIL) and contrast these with pyroxenes from Y593 and Nakhla.

  8. Method for characterization of the redox condition of cementitious materials

    SciTech Connect

    Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

    2015-12-22

    Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize an in situ redox indicator that is present in the cementitious materials as formed. The in situ redox indicator leaches from cementitious material and, when the leaching process is carried out under anaerobic conditions can be utilized to determine the redox condition of the material. The in situ redox indicator can exhibit distinct characteristics in the leachate depending upon the redox condition of the indicator.

  9. Changes in depth-transect redox conditions spanning the end-Permian mass extinction and their impact on the marine extinction: Evidence from biomarkers and sulfur isotopes

    NASA Astrophysics Data System (ADS)

    Kaiho, Kunio; Oba, Masahiro; Fukuda, Yoshihiko; Ito, Kosuke; Ariyoshi, Shun; Gorjan, Paul; Riu, Yuqing; Takahashi, Satoshi; Chen, Zhong-Qiang; Tong, Jinnan; Yamakita, Satoshi

    2012-08-01

    Changes in redox conditions during the Changhsingian to Griesbachian spanning the end-Permian mass extinction were recently reported based on analyses of organic molecules. We provide more precise organic-molecular data, that detail redox conditions spanning the end-Permian mass extinction at different palaeowater depths in the neritic Palaeotethys (estimated water depths: 10, 40, 100, and 200 m; Bulla, Huangzhishan, Meishan, and Chaohu sections, respectively) during this period. Here we propose that a change from occasional euxinia to anoxia in the shallow Palaeotethys occurred at the time of the mass extinction intercalated with oxic pulses. The second extinction at 0.7 myr after the main extinction was also caused by anoxia. New and published sulfur-isotope ratios (34S/32S) measured in carbonate-associated sulfate from the neritic Palaeotethys and in sulfide from pelagic central Panthalassa sediments show high values during the Changhsingian, consistent with the development of euxinia. The mass extinction coincided with a global fall in δ34S values, as well as a shift in δ13C values, indicating a global oxidation of H2S. This organic and isotopic geochemistry implies that accumulation of hydrogen sulfide in intermediate and deep waters followed by oxidation of hydrogen sulfide led to dissolved oxygen consumption, surface-water anoxia, and acidification, resulting in the end-Permian mass extinction in the seas.

  10. Behavioral responses of Escherichia coli to changes in redox potential.

    PubMed

    Bespalov, V A; Zhulin, I B; Taylor, B L

    1996-09-17

    Escherichia coli bacteria sensed the redox state in their surroundings and they swam to a niche that had a preferred reduction potential. In a spatial redox gradient of benzoquinone/benzoquinol, E. coli cells migrated to form a sharply defined band. Bacteria swimming out of either face of the band tumbled and returned to the preferred conditions at the site of the band. This behavioral response was named redox taxis. Redox molecules, such as substituted quinones, that elicited redox taxis, interact with the bacterial electron transport system, thereby altering electron transport and the proton motive force. The magnitude of the behavioral response was dependent on the reduction potential of the chemoeffector. The Tsr, Tar, Trg, Tap, and CheR proteins, which have a role in chemotaxis, were not essential for redox taxis. A cheB mutant had inverted responses in redox taxis, as previously demonstrated in aerotaxis. A model is proposed in which a redox effector molecule perturbs the electron transport system, and an unknown sensor in the membrane detects changes in the proton motive force or the redox status of the electron transport system, and transduces this information into a signal that regulates phosphorylation of the CheA protein. A similar mechanism has been proposed for aerotaxis. Redox taxis may play an important role in the distribution of bacterial species in natural environments.

  11. Multiple redox states of multiheme cytochromes may enable bacterial response to changing redox environments

    NASA Astrophysics Data System (ADS)

    Arbour, T.; Wrighton, K. C.; Mullin, S. W.; Castelle, C.; Luef, B.; Gilbert, B.; Banfield, J. F.

    2013-12-01

    Multiheme c-type cytochromes (MHCs) are key components in electron-transport pathways that enable some microorganisms to transfer electron byproducts of metabolism to a variety of minerals. As a response to changes in mineral redox potential, microbial communities may shift their membership, or individual organisms may adjust protein expression. Alternatively, the ability to respond may be conferred by the innate characteristics of certain electron-transport-chain components. Here, we used potentiostat-controlled microbial fuel cells (MFCs) to measure the timescale of response to imposed changes in redox conditions, thus placing constraints on the importance of these different mechanisms. In the experiments, a solid electrode acts as an electron-accepting mineral whose redox potential can be precisely controlled. We inoculated duplicate MFCs with a sediment/groundwater mixture from an aquifer at Rifle, Colorado, supplied acetate as an electron donor, and obtained stable, mixed-species biofilms dominated by Geobacter and a novel Geobacter-related family. We poised the anode at potentials spanning the range of natural Fe(III)-reduction, then performed cyclic voltammetry (CV) to characterize the overall biofilm redox signature. The apparent biofilm midpoint potential shifted directly with anode set potential when the latter was changed within the range from about -250 to -50 mV vs. SHE. Following a jump in set potential by 200 mV, the CV-midpoint shift by ~100 mV over a timescale of ~30 minutes to a few hours, depending on the direction of the potential change. The extracellular electron transfer molecules, whose overall CV signature is very similar to those of purified MHCs, appear to span a broad redox range (~200 mV), supporting the hypothesis that MHCs confer substantial redox flexibility. This flexibility may be a principle reason for the abundance of MHCs expressed by microorganisms capable of extracellular electron transfer to minerals.

  12. Modelling sulfamethoxazole degradation under different redox conditions

    NASA Astrophysics Data System (ADS)

    Sanchez-Vila, X.; Rodriguez-Escales, P.

    2015-12-01

    Sulfamethoxazole (SMX) is a low adsorptive, polar, sulfonamide antibiotic, widely present in aquatic environments. Degradation of SMX in subsurface porous media is spatially and temporally variable, depending on various environmental factors such as in situ redox potential, availability of nutrients, local soil characteristics, and temperature. It has been reported that SMX is better degraded under anoxic conditions and by co-metabolism processes. In this work, we first develop a conceptual model of degradation of SMX under different redox conditions (denitrification and iron reducing conditions), and second, we construct a mathematical model that allows reproducing different experiments of SMX degradation reported in the literature. The conceptual model focuses on the molecular behavior and contemplates the formation of different metabolites. The model was validated using the experimental data from Barbieri et al. (2012) and Mohatt et al. (2011). It adequately reproduces the reversible degradation of SMX under the presence of nitrite as an intermediate product of denitrification. In those experiments degradation was mediated by the transient formation of a diazonium cation, which was considered responsible of the substitution of the amine radical by a nitro radical, forming the 4-nitro-SMX. The formation of this metabolite is a reversible process, so that once the concentration of nitrite was back to zero due to further advancement of denitrification, the concentration of SMX was fully recovered. The forward reaction, formation of 4-nitro SMX, was modeled considering a kinetic of second order, whereas the backward reaction, dissociation of 4-nitro-SMX back to the original compound, could be modeled with a first order degradation reaction. Regarding the iron conditions, SMX was degraded due to the oxidation of iron (Fe2+), which was previously oxidized from goethite due to the degradation of a pool of labile organic carbon. As the oxidation of iron occurred on the

  13. Redox Conditions Among the Terrestrial Planets

    NASA Technical Reports Server (NTRS)

    Jones, J. H.

    2004-01-01

    Early solar system conditions should have been extremely reducing. The redox state of the early solar nebula was determined by the H2O/H2 of the gas, which is calculated (based on solar composition) to have been about IW-5. At high temperature under such conditions, ferrous iron would exist only as a trace element in silicates and the most common type of chondritic material should have been enstatite chondrites. The observation that E-chondrites form only a subset of the chondrite suite and that the terrestrial planets (Earth, Moon, Mars, Venus, 4 Vesta) contain ferrous and ferric iron as major and minor elements, respectively, implies that either most chondritic materials formed under conditions that were not solar or that early-formed metals oxidized at low temperature, producing FeO. For example, equilibrated ordinary chondrites (by definition, common chondritic materials), by their phase assemblage of olivine, orthopyroxene and metal, must fall not far from the QFI (Quartz-Fayalite-Iron) oxygen buffer. The QFI buffer is about IW-0.5 and, as we shall see, this fo2 is close to that inferred for many materials in the inner solar system.

  14. New lab scale approaches for quantification of redox conditions

    NASA Astrophysics Data System (ADS)

    Fernandez, P. M.; Dathe, A.; Nadeem, S.; Bakken, L. R.; Bloem, E.; French, H. K.; Binley, A. M.

    2013-12-01

    Degradation of organic chemicals in the unsaturated zone is a process highly relevant for developing remediation techniques for protecting groundwater. Degradation causes changes in chemical composition of the water phase and gas releases. These changes can potentially be mapped with electrical resistivity measurements in the bulk soil and gas measurements at the soil surface. The redox potential combined with the local geological conditions determines the composition of available electron acceptors as well as microbial degradation pathways and how the soil system is affected in the long term. After oxygen and nitrate are depleted, manganese and iron should be reduced. However, in experiments conducted in the unsaturated zone at Gardermoen airport, Norway, it was found that for the degradation of the de-icing agent propylene glycol (PG), manganese and iron were preferred over nitrate as electron acceptor. A key hypothesis for the work presented is that for a designated soil, the redox potential affects gas releases and soil solution composition profoundly. As the redox potential decreases, the reactants of the degradation change and therefore the composition of the soil-water system changes. These changes can be quantified dynamically by gas measurements and changes in electrical conductivity of the pore water and electrical resistivity of the bulk soil. Batch experiments were conducted to examine whether nitrate is a preferred electron acceptor over iron and manganese oxides as described in classical redox reaction theory. Gas releases during PG and glutamate degradation were measured in a sandy pristine soil with and without nitrate under anaerobic condition during two weeks of incubation. Chemical reactions were quantified with the modelling tool ORCHESTRA. We are currently investigating whether dynamical measurements of electrical conductivity and bulk resistivity are suited to trace which electron acceptors (nitrate, manganese or iron) are being reduced. First

  15. Mobility and phytoavailability of As and Pb in a contaminated soil using pine sawdust biochar under systematic change of redox conditions.

    PubMed

    Beiyuan, Jingzi; Awad, Yasser M; Beckers, Felix; Tsang, Daniel C W; Ok, Yong Sik; Rinklebe, Jörg

    2017-03-08

    Biochar has been adopted to control the mobility and phytoavailability of trace elements (TEs) in soils. To date, no attempt has been made to determine the mobility and phytoavailability of arsenic (As) and lead (Pb) in a contaminated soil with biochars as amendments under predefined redox potentials (EH). Thus, in this study, a soil contaminated with As and Pb (2047 and 1677 mg kg(-1), respectively) was pre-incubated for 105 days with three amendments (pine sawdust biomass (BM) and two biochars produced from the same feedstock at 300 °C (BC300) and 550 °C (BC550)). The aged samples were then exposed to dynamic EH conditions to evaluate the mobility and phytoavailability of As and Pb after immobilization. The BM amendment significantly decreased and the BC300 slightly reduced the mobility and phytoavailability of As and Pb, which may be related to the oxygen-containing functional groups on the surface of BM and BC300. In contrast, BC550 increased the mobility of As at -300 to -100 mV and 100 mV, enhanced the phytoavailability of As under oxidizing condition (>100 mV), but reduced the phytoavailability of Pb, which might be caused by the properties of amendments and redox chemistry of the TEs. The effectiveness of BM and biochars for the stabilization of As and Pb varied under dynamic EH conditions, which indicates that detailed investigations should be conducted before the applications of biochar as soil amendment under variable environmental conditions, especially for contaminated paddy soils.

  16. Conformational changes in redox pairs of protein structures

    PubMed Central

    Fan, Samuel W; George, Richard A; Haworth, Naomi L; Feng, Lina L; Liu, Jason Y; Wouters, Merridee A

    2009-01-01

    Disulfides are conventionally viewed as structurally stabilizing elements in proteins but emerging evidence suggests two disulfide subproteomes exist. One group mediates the well known role of structural stabilization. A second redox-active group are best known for their catalytic functions but are increasingly being recognized for their roles in regulation of protein function. Redox-active disulfides are, by their very nature, more susceptible to reduction than structural disulfides; and conversely, the Cys pairs that form them are more susceptible to oxidation. In this study, we searched for potentially redox-active Cys Pairs by scanning the Protein Data Bank for structures of proteins in alternate redox states. The PDB contains over 1134 unique redox pairs of proteins, many of which exhibit conformational differences between alternate redox states. Several classes of structural changes were observed, proteins that exhibit: disulfide oxidation following expulsion of metals such as zinc; major reorganisation of the polypeptide backbone in association with disulfide redox-activity; order/disorder transitions; and changes in quaternary structure. Based on evidence gathered supporting disulfide redox activity, we propose disulfides present in alternate redox states are likely to have physiologically relevant redox activity. PMID:19598234

  17. Copper dynamics under alternating redox conditions is influenced by soil properties and contamination source.

    PubMed

    Balint, Ramona; Said-Pullicino, Daniel; Ajmone-Marsan, Franco

    2015-02-01

    Understanding the effect of soil redox conditions on contaminant dynamics is of significant importance for evaluating their lability, mobility and potential transfer to other environmental compartments. Under changing redox conditions, soil properties and constituents such as Fe and Mn (hydr)oxides and organic matter (OM) may influence the behavior of associated metallic elements (MEs). In this work, the redox-driven release and redistribution of Cu between different soil pools was studied in three soils having different contamination sources. This was achieved by subjecting soil columns to a series of alternating reducing and oxidizing cycles under non-limiting C conditions, and assessing their influence on soil pore water, leachate and solid phase composition. Results showed that, in all soils, alternating redox conditions led to an increase in the distribution of Cu in the more labile fractions, consequently enhancing its susceptibility to loss. This was generally linked to the redox-driven cycling of Fe, Mn and dissolved organic matter (DOM). In fact, results suggested that the reductive dissolution of Fe and Mn (hydr)oxides and subsequent reprecipitation as poorly-ordered phases under oxic conditions contributed to the release and mobilization of Cu and/or Cu-containing organometallic complexes. However, the behavior of Cu, as well as the mechanisms controlling Cu release and loss with redox cycling, was influenced by both soil properties (e.g. pH, contents of easily reducible Fe and Mn (hydr)oxides) and source of Cu contamination.

  18. Distinct Redox Regulation in Sub-Cellular Compartments in Response to Various Stress Conditions in Saccharomyces cerevisiae

    PubMed Central

    Ayer, Anita; Sanwald, Julia; Pillay, Bethany A.; Meyer, Andreas J.; Perrone, Gabriel G.; Dawes, Ian W.

    2013-01-01

    Responses to many growth and stress conditions are assumed to act via changes to the cellular redox status. However, direct measurement of pH-adjusted redox state during growth and stress has never been carried out. Organellar redox state (EGSH) was measured using the fluorescent probes roGFP2 and pHluorin in Saccharomyces cerevisiae. In particular, we investigated changes in organellar redox state in response to various growth and stress conditions to better understand the relationship between redox-, oxidative- and environmental stress response systems. EGSH values of the cytosol, mitochondrial matrix and peroxisome were determined in exponential and stationary phase in various media. These values (−340 to −350 mV) were more reducing than previously reported. Interestingly, sub-cellular redox state remained unchanged when cells were challenged with stresses previously reported to affect redox homeostasis. Only hydrogen peroxide and heat stress significantly altered organellar redox state. Hydrogen peroxide stress altered the redox state of the glutathione disulfide/glutathione couple (GSSG, 2H+/2GSH) and pH. Recovery from moderate hydrogen peroxide stress was most rapid in the cytosol, followed by the mitochondrial matrix, with the peroxisome the least able to recover. Conversely, the bulk of the redox shift observed during heat stress resulted from alterations in pH and not the GSSG, 2H+/2GSH couple. This study presents the first direct measurement of pH-adjusted redox state in sub-cellular compartments during growth and stress conditions. Redox state is distinctly regulated in organelles and data presented challenge the notion that perturbation of redox state is central in the response to many stress conditions. PMID:23762325

  19. Distinct redox regulation in sub-cellular compartments in response to various stress conditions in Saccharomyces cerevisiae.

    PubMed

    Ayer, Anita; Sanwald, Julia; Pillay, Bethany A; Meyer, Andreas J; Perrone, Gabriel G; Dawes, Ian W

    2013-01-01

    Responses to many growth and stress conditions are assumed to act via changes to the cellular redox status. However, direct measurement of pH-adjusted redox state during growth and stress has never been carried out. Organellar redox state (E GSH) was measured using the fluorescent probes roGFP2 and pHluorin in Saccharomyces cerevisiae. In particular, we investigated changes in organellar redox state in response to various growth and stress conditions to better understand the relationship between redox-, oxidative- and environmental stress response systems. E GSH values of the cytosol, mitochondrial matrix and peroxisome were determined in exponential and stationary phase in various media. These values (-340 to -350 mV) were more reducing than previously reported. Interestingly, sub-cellular redox state remained unchanged when cells were challenged with stresses previously reported to affect redox homeostasis. Only hydrogen peroxide and heat stress significantly altered organellar redox state. Hydrogen peroxide stress altered the redox state of the glutathione disulfide/glutathione couple (GSSG, 2H(+)/2GSH) and pH. Recovery from moderate hydrogen peroxide stress was most rapid in the cytosol, followed by the mitochondrial matrix, with the peroxisome the least able to recover. Conversely, the bulk of the redox shift observed during heat stress resulted from alterations in pH and not the GSSG, 2H(+)/2GSH couple. This study presents the first direct measurement of pH-adjusted redox state in sub-cellular compartments during growth and stress conditions. Redox state is distinctly regulated in organelles and data presented challenge the notion that perturbation of redox state is central in the response to many stress conditions.

  20. Microbial functional gene diversity with a shift of subsurface redox conditions during In Situ uranium reduction.

    PubMed

    Liang, Yuting; Van Nostrand, Joy D; N'guessan, Lucie A; Peacock, Aaron D; Deng, Ye; Long, Philip E; Resch, C Tom; Wu, Liyou; He, Zhili; Li, Guanghe; Hazen, Terry C; Lovley, Derek R; Zhou, Jizhong

    2012-04-01

    To better understand the microbial functional diversity changes with subsurface redox conditions during in situ uranium bioremediation, key functional genes were studied with GeoChip, a comprehensive functional gene microarray, in field experiments at a uranium mill tailings remedial action (UMTRA) site (Rifle, CO). The results indicated that functional microbial communities altered with a shift in the dominant metabolic process, as documented by hierarchical cluster and ordination analyses of all detected functional genes. The abundance of dsrAB genes (dissimilatory sulfite reductase genes) and methane generation-related mcr genes (methyl coenzyme M reductase coding genes) increased when redox conditions shifted from Fe-reducing to sulfate-reducing conditions. The cytochrome genes detected were primarily from Geobacter sp. and decreased with lower subsurface redox conditions. Statistical analysis of environmental parameters and functional genes indicated that acetate, U(VI), and redox potential (E(h)) were the most significant geochemical variables linked to microbial functional gene structures, and changes in microbial functional diversity were strongly related to the dominant terminal electron-accepting process following acetate addition. The study indicates that the microbial functional genes clearly reflect the in situ redox conditions and the dominant microbial processes, which in turn influence uranium bioreduction. Microbial functional genes thus could be very useful for tracking microbial community structure and dynamics during bioremediation.

  1. Microbial Functional Gene Diversity with a Shift of Subsurface Redox Conditions during In Situ Uranium Reduction

    PubMed Central

    Liang, Yuting; Van Nostrand, Joy D.; N′Guessan, Lucie A.; Peacock, Aaron D.; Deng, Ye; Long, Philip E.; Resch, C. Tom; Wu, Liyou; He, Zhili; Li, Guanghe; Hazen, Terry C.; Lovley, Derek R.

    2012-01-01

    To better understand the microbial functional diversity changes with subsurface redox conditions during in situ uranium bioremediation, key functional genes were studied with GeoChip, a comprehensive functional gene microarray, in field experiments at a uranium mill tailings remedial action (UMTRA) site (Rifle, CO). The results indicated that functional microbial communities altered with a shift in the dominant metabolic process, as documented by hierarchical cluster and ordination analyses of all detected functional genes. The abundance of dsrAB genes (dissimilatory sulfite reductase genes) and methane generation-related mcr genes (methyl coenzyme M reductase coding genes) increased when redox conditions shifted from Fe-reducing to sulfate-reducing conditions. The cytochrome genes detected were primarily from Geobacter sp. and decreased with lower subsurface redox conditions. Statistical analysis of environmental parameters and functional genes indicated that acetate, U(VI), and redox potential (Eh) were the most significant geochemical variables linked to microbial functional gene structures, and changes in microbial functional diversity were strongly related to the dominant terminal electron-accepting process following acetate addition. The study indicates that the microbial functional genes clearly reflect the in situ redox conditions and the dominant microbial processes, which in turn influence uranium bioreduction. Microbial functional genes thus could be very useful for tracking microbial community structure and dynamics during bioremediation. PMID:22327592

  2. Transition from confined to phreatic conditions as the factor controlling salinization and change in redox state, Upper subaquifer of the Judea Group, Israel

    NASA Astrophysics Data System (ADS)

    Gavrieli, Ittai; Burg, Avi; Guttman, Joseph

    2002-08-01

    An increase in salinity and change from oxic to anoxic conditions are observed in the Upper subaquifer of the Judea Group in the Kefar Uriyya pumping field at the western foothills of the Judea Mountains, Israel. Hydrogeological data indicate that the change, which occurs over a distance of only a few kilometers, coincides with a transition from confined to phreatic conditions in the aquifer. The deterioration in the water quality is explained as a result of seepage of more saline, organic-rich water from above, into the phreatic "roofed" part of the aquifer. The latter is derived from the bituminous chalky rocks of the Mount Scopus Group, which confine the aquifer in its southeastern part. In this confined part, water in perched horizons within the Mount Scopus Group cannot leak down and flow westward while leaching organic matter and accumulating salts. However, upon reaching the transition area from confined to phreatic conditions, seepage to the Judea Upper subaquifer is possible, thereby allowing it to be defined as a leaky aquifer. The incoming organic matter consumes the dissolved oxygen and allows bacterial sulfate reduction. The latter accounts for the H2S in the aquifer, as indicated by sulfur isotopic analyses of coexisting sulfate and sulfide. Thus, from an aquifer management point of view, in order to maintain the high quality of the water in the confined southeastern part of the Kefar Uriyya field, care should be taken not to draw the confined-roofed transition area further east by over pumping.

  3. Microbial communities acclimate to recurring changes in soil redox potential status

    SciTech Connect

    DeAngelis, Kristen M.; Silver, Whendee; Thompson, Andrew; Firestone, Mary K.

    2010-12-03

    Rapidly fluctuating environmental conditions can significantly stress organisms, particularly when fluctuations cross thresholds of normal physiological tolerance. Redox potential fluctuations are common in humid tropical soils, and microbial community acclimation or avoidance strategies for survival will in turn shape microbial community diversity and biogeochemistry. To assess the extent to which indigenous bacterial and archaeal communities are adapted to changing in redox potential, soils were incubated under static anoxic, static oxic or fluctuating redox potential conditions, and the standing (DNA-based) and active (RNA-based) communities and biogeochemistry were determined. Fluctuating redox potential conditions permitted simultaneous CO{sub 2} respiration, methanogenesis, N{sub 2}O production and iron reduction. Exposure to static anaerobic conditions significantly changed community composition, while 4-day redox potential fluctuations did not. Using RNA: DNA ratios as a measure of activity, 285 taxa were more active under fluctuating than static conditions, compared with three taxa that were more active under static compared with fluctuating conditions. These data suggest an indigenous microbialcommunity adapted to fluctuating redox potential.

  4. Changes in productivity and redox conditions during the Last Glacial Maximum as recorded in high-resolution geochemical records from Alfonso Basin, Gulf of California

    NASA Astrophysics Data System (ADS)

    Choumiline, K.; Lyons, T. W.; Carriquiry, J. D.; Perez-Cruz, L. L.; Beaufort, L.

    2015-12-01

    The Last Glacial Maximum represents the most recent major sea level low stand in Earth history. Such changes in eustatic sea level impacted the oxygenation of marine basins, yet the characteristics and mechanisms of those impacts remain poorly known. Specific basin conditions are needed to develop, record, and preserve those paleoredox changes through time most effectively, including rapid sedimentation rates and silled basin morphologies. The anoxic Alfonso Basin, partially separated from the Gulf of California by a bathymetric sill, is such a place. The basin is located in a dry semiarid region dominated by dust inputs and only occasional tropical cyclone-induced fluvial contributions. We present the first multi-proxy reconstruction of southern Gulf of California paleoredox that covers an uninterrupted timespan from the Late Pleistocene to the present, with an emphasis on the Last Glacial Maximum. In this research we contrast geochemical data from a 47-meter-long sediment core (collected with the giant CALYPSO corer aboard the R/V Marion Dufresne) with the solid phase and pore water chemical data from a shorter but very detailed box core (collected on the R/V El Puma), both from Alfonso Basin. Our results show that during the Late Pleistocene and throughout the Holocene several paleoredox shifts occurred, often accompanied by differences in lamination (laminated/massive alternations) and trace element (Mo, V, U) compositions; detailed Fe chemistry (FeHR/FeTand Fe/Al ratios); as well as carbon and sulfur concentrations and isotope ratios. For example, FeHR/FeT ratios indicate values of roughly 0.15 during the Last Glacial Maximum (lower than theoretic threshold of 0.2 between oxic and anoxic), suggesting more oxic conditions, in comparison to 0.25 and higher in the Holocene. Most of the variability seen in these proxies is related to global sea level change, while some variability is instead related to local variations in paleoproductivity, often connected to

  5. Bicarbonate Induced Redox Proteome Changes in Arabidopsis Suspension Cells

    PubMed Central

    Yin, Zepeng; Balmant, Kelly; Geng, Sisi; Zhu, Ning; Zhang, Tong; Dufresne, Craig; Dai, Shaojun; Chen, Sixue

    2017-01-01

    Climate change as a result of increasing atmospheric CO2 affects plant growth and productivity. CO2 is not only a carbon donor for photosynthesis but also an environmental signal that can perturb cellular redox homeostasis and lead to modifications of redox-sensitive proteins. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, protein redox modifications and how they function in plant CO2 response remain unclear. Here a new iodoTMTRAQ proteomics technology was employed to analyze changes in protein redox modifications in Arabidopsis thaliana suspension cells in response to bicarbonate (mimic of elevated CO2) in a time-course study. A total of 47 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, transport, ROS scavenging, cell structure modulation and protein turnover. This inventory of previously unknown redox responsive proteins in Arabidopsis bicarbonate responses lays a foundation for future research toward understanding the molecular mechanisms underlying plant CO2 responses. PMID:28184230

  6. Pyrite framboid diameter distribution in the Lower Oligocene black shales of the Vrancea Nappe as an indicator of changes in redox conditions, Eastern Outer Carpathians, Romania

    NASA Astrophysics Data System (ADS)

    Wendorff, Małgorzata; Marynowski, Leszek; Rospondek, Mariusz

    2016-04-01

    Studies of recent and ancient sediments revealed that the diameter distribution of pyrite framboids may be reliably used to characterise oxygen-restricted environments and distinguish ancient euxinic conditions (water column hydrogen sulphide bearing thus oxygen-free) from anoxic, non-sulfidic or dysoxic (oxygen-poor) conditions. Such diagnoses are of great importance when reconstructing palaeoenvironments in ancient basins and the processes of source rocks formation. During Oligocene to early Miocene time an extensive accumulation of organic matter (OM)-rich sediments occurred in the entire Paratethys including the Carpathian Foredeep, which was closed forming fold-thrust belt of the Outer Carpathians. These OM-rich black shales are represented by so-called Menilite shales, widely considered as hydrocarbon source rocks, which constitute as well a detailed archive for palaeoenvironmental changes. The purpose of this preliminary study is to characterise the depositional environment of the Lower Oligocene black shales basing on the pyrite framboid diameter distribution. Five samples of finely laminated black shales were selected from the Nechit section outcropping in the Bistrica half-window of the Vrancea Nappe in the Eastern Outer Carpathians, E Romania. At least 100 framboid diameters were measured on polished blocks using scanning electron microscope in a back-scattered electron mode. Framboids from four samples starting from the lowermost part of the section exhibit a narrow range of diameters from 1.0 to 11.5 μm; mean value ranges from 3.65 to 4.85 μm. Small-sized framboids (< 6 μm) account for 70% up to 91% of all framboids, while large framboids (>10 μm) are absent or rare (max. 2%). Within the sample from the uppermost part of the section framboids reveal more variable sizes, 2 - 25 μm, with mean value of 6.63 μm. Small framboids are still numerous (54%), however the amount of framboids >10 μm increases to 15%. The domination of small framboids with

  7. Organic chemical degradation by remote study of the redox conditions

    NASA Astrophysics Data System (ADS)

    Fernandez, P. M.; Revil, A.; Binley, A. M.; Bloem, E.; French, H. K.

    2014-12-01

    Monitoring the natural (and enhanced) degradation of organic contaminants is essential for managing groundwater quality in many parts of the world. Contaminated sites often have limited access, hence non-intrusive methods for studying redox processes, which drive the degradation of organic compounds, are required. One example is the degradation of de-icing chemicals (glycols and organic salts) released to the soil near airport runways during winter. This issue has been broadly studied at Oslo airport, Gardermoen, Norway using intrusive and non-intrusive methods. Here, we report on laboratory experiments that aim to study the potential of using a self-potential, DCresistivity, and time-domain induced polarization for geochemical characterization of the degradation of Propylene Glycol (PG). PG is completely miscible in water, does not adsorb to soil particles and does not contribute to the electrical conductivity of the soil water. When the contaminant is in the unsaturated zone near the water table, the oxygen is quickly consumed and the gas exchange with the surface is insufficient to ensure aerobic degradation, which is faster than anaerobic degradation. Since biodegradation of PG is highly oxygen demanding, anaerobic pockets can exist causing iron and manganese reduction. It is hypothesised that nitrate would boost the degradation rate under such conditions. In our experiment, we study PG degradation in a sand tank. We provide the system with an electron highway to bridge zones with different redox potential. This geo-battery system is characterized by self-potential, resistivity and induced polarization anomalies. An example of preliminary results with self-potential at two different times of the experiment can be seen in the illustration. These will be supplemented with more direct information on the redox chemistry: in-situ water sampling, pH, redox potential and electrical conductivity measurements. In parallel, a series of batch experiments have been

  8. EQCM Measurements: Redox-Induced Changes in Solvent and Ion Content in Anchored Redox Monolayers of Organosulfur Compounds and Their Electrocatalysis on Gold Electrodes

    DTIC Science & Technology

    1990-08-01

    EQCM Mwasurements: Redox-Induced Changes in Solvent and M0 Content in Anchored Redox Monolayers of Organosulfur CD Compounds and their Electrocatalysis ...REDOX-INDUCED CHANGES IN SOLVENT AND ION CONTENT IN ANCHORED REDOX MONOLAYERS OF ORGANOSULFUR COMPOUNDS AND THEIR ELECTROCATALYSIS ON GOLD...Measurements: Redox-Induced Changes in Solvent and Ion Content in Anchored Redox Monolayers of Organosulfur Compounds and their Electrocatalysis on

  9. Bacterial adaptation of respiration from oxic to microoxic and anoxic conditions: redox control.

    PubMed

    Bueno, Emilio; Mesa, Socorro; Bedmar, Eulogio J; Richardson, David J; Delgado, Maria J

    2012-04-15

    Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments.

  10. Lignin decomposition and microbial community in paddy soils: effects of alternating redox conditions

    NASA Astrophysics Data System (ADS)

    Cerli, Chiara; Liu, Qin; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

    2013-04-01

    Paddy soils are characterised by interchanging cycles of anaerobic and aerobic conditions. Such fluctuations cause continuous changes in soil solution chemistry as well as in the composition and physiological responses of the microbial community. Temporary deficiency in oxygen creates conditions favourable to facultative or obligates anaerobic bacteria, while aerobic communities can thrive in the period of water absence. These alterations can strongly affect soil processes, in particular organic matter (OM) accumulation and mineralization. In submerged soils, lignin generally constitutes a major portion of the total OM because of hampered degradation under anoxic conditions. The alternating redox cycles resulting from paddy soil management might promote both degradation and preservation of lignin, affecting the overall composition and reactivity of total and dissolved OM. We sampled soils subjected to cycles of anoxic (rice growing period) and oxic (harvest and growth of other crops) conditions since 700 and 2000 years. We incubated suspended Ap material, sampled from the two paddy plus two corresponding non-paddy control soils under oxic and anoxic condition, for 3 months, interrupted by a short period of three weeks (from day 21 to day 43) with reversed redox conditions. At each sampling time (day 2, 21, 42, 63, 84), we determined lignin-derived phenols (by CuO oxidation) as well as phospholipids fatty acids contents and composition. We aimed to highlight changes in lignin decomposition as related to the potential rapid changes in microbial community composition. Since the studied paddy soils had a long history of wet rice cultivation, the microbial community should be well adapted to interchanging oxic and anoxic cycles, therefore fully expressing its activity at both conditions. In non-paddy soil changes in redox conditions caused modification of quantity and composition of the microbial community. On the contrary, in well-established paddy soils the microbial

  11. Adaptive changes in renal mitochondrial redox status in diabetic nephropathy

    SciTech Connect

    Putt, David A.; Zhong, Qing; Lash, Lawrence H.

    2012-01-15

    Nephropathy is a serious and common complication of diabetes. In the streptozotocin (STZ)-treated rat model of diabetes, nephropathy does not typically develop until 30 to 45 days post-injection, although hyperglycemia occurs within 24 h. We tested the hypothesis that chronic hyperglycemia results in a modest degree of oxidative stress that is accompanied by compensatory changes in certain antioxidants and mitochondrial redox status. We propose that as kidneys progress to a state of diabetic nephropathy, further adaptations occur in mitochondrial redox status. Basic parameters of renal function in vivo and several parameters of mitochondrial function and glutathione (GSH) and redox status in isolated renal cortical mitochondria from STZ-treated and age-matched control rats were examined at 30 days and 90 days post-injection. While there was no effect of diabetes on blood urea nitrogen, measurement of other, more sensitive parameters, such as urinary albumin and protein, and histopathology showed significant and progressive worsening in diabetic rats. Thus, renal function is compromised even prior to the onset of frank nephropathy. Changes in mitochondrial respiration and enzyme activities indicated existence of a hypermetabolic state. Higher mitochondrial GSH content and rates of GSH transport into mitochondria in kidneys from diabetic rats were only partially due to changes in expression of mitochondrial GSH carriers and were mostly due to higher substrate supply. Although there are few clear indicators of oxidative stress, there are several redox changes that occur early and change further as nephropathy progresses, highlighting the complexity of the disease. Highlights: ►Adaptive changes in renal mitochondrial and redox status in diabetic rats. ►Modest renal dysfunction even prior to onset of nephropathy. ►Elevated concentrations of mitochondrial GSH in diabetic kidneys. ►Change in GSH due partly to increased protein expression of transporter.

  12. Cadmium induced mitochondrial redox changes in germinating pea seed.

    PubMed

    Smiri, Moêz; Chaoui, Abdelilah; Rouhier, Nicolas; Kamel, Chibani; Gelhaye, Eric; Jacquot, Jean-Pierre; El Ferjani, Ezzedine

    2010-12-01

    Mitochondria play an essential role in producing the energy required for seedling growth following imbibition. Heavy metals, such as cadmium impair mitochondrial functioning in part by altering redox regulation. The activities of two protein redox systems present in mitochondria, thioredoxin (Trx) and glutaredoxin (Grx), were analysed in the cotyledons and embryo of pea (Pisum sativum L.) germinating seeds exposed to toxic Cd concentration. Compared to controls, Cd-treated germinating seeds showed a decrease in total soluble protein content, but an increase in -SH content. Under Cd stress conditions, Grx and glutathione reductase (GR) activities as well as glutathione (GSH) concentrations decreased both in cotyledons and the embryo. Similar results were obtained with the Trx system: Trx and NADPH-dependent thioredoxin reductase (NTR) activities were not stimulated, whereas total NAD(P) contents diminished in the embryo. However, Cd enhanced the levels of all components of the Trx system in the cotyledons. On the other hand, Cd caused a significant increase in oxidative stress parameters such as the redox ratio of coenzymes (oxidized to reduced forms) and NAD(P)H oxidase activities. These results indicate that Cd induces differential redox responses on different seed tissues. We suggest that neither Grx system nor Trx one may improve the redox status of mitochondrial thiols in the embryo of germinating pea seeds exposed to Cd toxicity, but in the cotyledons the contribution of Trx/NTR/NADPH can be established in despite the vulnerability of the coenzyme pools due to enzymatic oxidation.

  13. Mineralogical record of the redox conditions on early Mars

    NASA Astrophysics Data System (ADS)

    Dehouck, Erwin; Gaudin, Anne; Chevrier, Vincent; Mangold, Nicolas

    2016-06-01

    Sulfates and Fe-oxides identified on the martian surface by orbital and in situ missions indicate that oxidizing conditions have existed on early Mars, at least locally and/or episodically. In the context of rock alteration and weathering, redox conditions are especially critical for the behavior of iron, which is soluble in its divalent state but insoluble in its trivalent state. Here, we combine results from a series of laboratory experiments conducted under Mars-like conditions to address the influence of highly-oxidizing compounds such as hydrogen peroxide (H2O2) on the alteration pathways of primary materials. We show that, if early Mars had a dense CO2 atmosphere allowing for relatively "warm and wet" conditions and surface weathering, highly-oxidizing conditions would have strongly inhibited the formation of Fe/Mg-smectite clays from alteration of igneous ferromagnesian minerals, and possibly enhanced the formation of carbonates. But a decade of mineral mapping of the martian surface show abundant, widespread Fe/Mg-clays and rare carbonates, which we interpret here as a mineralogical record of poorly-oxidizing (or even reducing) conditions during most of the Noachian era. Oxidizing conditions would have occurred later in martian history as a consequence of a higher rate of H2 escape or of a lower rate of volcanic outgassing, or both.

  14. Bacterial Adaptation of Respiration from Oxic to Microoxic and Anoxic Conditions: Redox Control

    PubMed Central

    Bueno, Emilio; Mesa, Socorro; Bedmar, Eulogio J.; Richardson, David J.

    2012-01-01

    Abstract Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments. Antioxid. Redox Signal. 16, 819–852. PMID:22098259

  15. The influence of reactive oxygen species on local redox conditions in oxygenated natural waters

    NASA Astrophysics Data System (ADS)

    Rose, Andrew

    2016-11-01

    Redox conditions in natural waters are a fundamental control on biogeochemical processes and ultimately many ecosystem functions. While the dioxygen/water redox couple controls redox thermodynamics in oxygenated aquatic environments on geological timescales, it is kinetically inert in the extracellular environment on the much shorter timescales on which many biogeochemical processes occur. Instead, electron transfer processes on these timescales are primarily mediated by a relatively small group of trace metals and stable radicals, including the reactive oxygen species superoxide. Such processes are of critical biogeochemical importance because many of these chemical species are scarce nutrients, but may also be toxic at high concentrations. Furthermore, their bioavailability and potentially toxicity is typically strongly influenced by their redox state. In this paper, I examine to what extent redox conditions in oxygenated natural waters are expected to be reflected in the redox states of labile redox-active compounds that readily exchange electrons with the dioxygen/superoxide redox couple, and potentially with each other. Additionally, I present the hypothesis that that the relative importance of the dioxygen/superoxide and superoxide/hydrogen peroxide redox couples exerts a governing control on local redox conditions in oxygenated natural waters on biogeochemically important timescales. Given the recent discovery of widespread extracellular superoxide production by a diverse range of organisms, this suggests the existence of a fundamental mechanism for organisms to tightly regulate local redox conditions in their extracellular environment in oxygenated natural waters.

  16. Mantle Redox Conditions in the North Atlantic Igneous Province

    NASA Astrophysics Data System (ADS)

    Heister, L. E.; Gras, M. A.; Lesher, C. E.

    2004-12-01

    The North Atlantic igneous province (NAIP) has long been viewed as a region of anomalous mantle upwelling related to plume activity, continental rifting, and a heterogeneous mantle source. Prior to continental rifting in the Tertiary, the northern portion of the region was the site of closure of the Iapetus ocean basin. This tectonic event may have contributed to heterogeneities within the upper mantle and altered its oxidation state relative to the ambient mantle. Vanadium has been shown to be a useful indicator of redox conditions due to its multiple valence states (e.g. [1-2]). In mantle minerals, vanadium becomes increasingly incompatible under more oxidizing conditions [3]. Because both scandium and vanadium are moderately incompatible during melting, the Sc/V ratio of primitive basalts can be used to investigate the oxidation state of the mantle [1-3]. We have examined the Sc/V ratios of primitive lavas from the mid-Atlantic ridge (MAR), Iceland, and the East Greenland margin to determine if there are spatial or temporal variations in the oxidation state of the NAIP mantle. The Sc/V ratios for MAR basalts are 0.13-0.20 (GEOROC chemical database); while Icelandic basalts range from 0.10-0.25 with an average of 0.16 (1 σ =0.05). The entire range of Sc/V ratios of the Paleogene East Greenland basalts is 0.07-0.17 with an average of 0.10 (1 σ = 0.05). The Sc/V ratios of Icelandic basalts are similar to MAR basalts, but the East Greenland lavas are distinctly lower than both the MAR and Iceland. The Sc/V ratio also can vary as a function of mean pressure of melting (i.e. spinel versus garnet lherzolite). To test the relative importance of melting systematics, source composition, and oxygen fugacity on the Sc/V systematics for NAIP basalts, we incorporated the oxygen-fugacity-dependent V mineral-melt partitioning data of [3] into the polybaric decompression melting model REEBOX [4]. The best-fit model parameters for the majority of the Iceland and MAR basalts

  17. Combination of aquifer thermal energy storage and enhanced bioremediation: resilience of reductive dechlorination to redox changes.

    PubMed

    Ni, Zhuobiao; van Gaans, Pauline; Smit, Martijn; Rijnaarts, Huub; Grotenhuis, Tim

    2016-04-01

    To meet the demand for sustainable energy, aquifer thermal energy storage (ATES) is widely used in the subsurface in urban areas. However, contamination of groundwater, especially with chlorinated volatile organic compounds (CVOCs), is often being encountered. This is commonly seen as an impediment to ATES implementation, although more recently, combining ATES and enhanced bioremediation of CVOCs has been proposed. Issues to be addressed are the high water flow velocities and potential periodic redox fluctuation that accompany ATES. A column study was performed, at a high water flow velocity of 2 m/h, simulating possible changes in subsurface redox conditions due to ATES operation by serial additions of lactate and nitrate. The impacts of redox changes on reductive dechlorination as well as the microbial response of Dehalococcoides (DHC) were evaluated. The results showed that, upon lactate addition, reductive dechlorination proceeded well and complete dechlorination from cis-DCE to ethene was achieved. Upon subsequent nitrate addition, reductive dechlorination immediately ceased. Disruption of microorganisms' retention was also immediate and possibly detached DHC which preferred attaching to the soil matrix under biostimulation conditions. Initially, recovery of dechlorination was possible but required bioaugmentation and nutrient amendment in addition to lactate dosing. Repeated interruption of dechlorination and DHC activity by nitrate dosing appeared to be less easily reversible requiring more efforts for regenerating dechlorination. Overall, our results indicate that the microbial resilience of DHC in biosimulated ATES conditions is sensitive to redox fluctuations. Hence, combining ATES with bioremediation requires dedicated operation and monitoring on the aquifer geochemical conditions.

  18. Early diagenesis of carbohydrates and lignin in mangrove sediments subject to variable redox conditions (French Guiana)

    NASA Astrophysics Data System (ADS)

    Marchand, C.; Disnar, J. R.; Lallier-Vergès, E.; Lottier, N.

    2005-01-01

    A comparative study of lignin and neutral carbohydrate compositions, combined with C, N and δ 13C analyses, was carried out on sedimentary cores, and on various vascular plant species collected in mangrove swamps of French Guiana. The main purpose of this study was to assess the diagenesis of carbohydrates and lignin in brackish to hypersaline fine-grained mangrove sediments characterized by great changes in redox conditions. Distribution of carbohydrates in sediments reflects both the lability of these compounds and their efficient recycling. They are subject to selective degradation, cellulosic glucose and xylose appearing to be the two most labile neutral sugars. In contrast a relative increase in arabinose, rhamnose, fucose and hemicellulosic glucose between plants and sediments, suggests that they may be more refractory and/or that they also derive from microbial synthesis. The total carbon from lignin-derived phenols is higher in sediments than in mangrove plants as a consequence of their rather refractory character. Nevertheless, evidence of lignin decomposition was found to be independent of local environmental conditions. The various redox processes that occur in mangrove sediments depend on plant species, stages in forest development and season. Different redox conditions induce different mechanisms for the decomposition of lignin and thus induce changes in phenol distributions. At depth, in most mangroves, an increase in (Ad/Al) v ratios and in deoxy sugars (fucose and rhamnose) content was significantly correlated with increased proportions of oxidized allochthonous organic debris deriving from the Amazonian detrital discharge, thus suggesting a specific source effect rather than a diagenesis induced change. Therefore, this study illustrates that both lignin and cellulose, derived from vascular plant debris, can be degraded in waterlogged mangrove sediments, and that their distribution depends on environmental conditions.

  19. Nitroxides as redox probes of melanins: dark-induced and photoinduced changes in redox equilibria

    SciTech Connect

    Sarna, T.; Korytowski, W.; Sealy, R.C.

    1985-05-15

    The interaction of nitroxide free radicals and their reduced products (hydroxylamines) with synthetic and natural melanins has been studied. Electron spin resonance spectroscopy was used to measure changes in radical concentration in the dark and during irradiation with visible or uv light. Some reduction of nitroxide occurs in the dark, and is reversible: the nitroxide can be completely regenerated by the one-electron oxidant ferricyanide. The kinetics of the process depend strongly on radical charge and pH. For positively charged nitroxides the rate is much faster than for either neutral or anionic radicals. At pH 10 the rate is about 20 times faster than at pH 5. Oxidation of hydroxylamine also can occur so that a redox equilibrium is established. The equilibrium constant has been estimated for the reaction between a nitroxide and melanin from autoxidation of 3,4-dihydroxyphenylalanine. Results are also dependent upon the type of melanin used and chemical modification (oxidation or reduction) of the melanin. Redox equilibria are altered during irradiation with either visible or uv light. Rapid oxidation of hydroxylamine to nitroxide is apparent, together with a slower reduction of nitroxide. Action spectra for these processes are related to those for melanin radical production and oxygen consumption in nitroxide-free melanin systems. Reduction of nitroxide is inhibited by oxygen, suggesting a competition between nitroxide and oxygen for photoinduced reducing equivalents.

  20. Optical redox ratio identifies metastatic potential-dependent changes in breast cancer cell metabolism

    PubMed Central

    Alhallak, Kinan; Rebello, Lisa G.; Muldoon, Timothy J.; Quinn, Kyle P.; Rajaram, Narasimhan

    2016-01-01

    The development of prognostic indicators of breast cancer metastatic risk could reduce the number of patients receiving chemotherapy for tumors with low metastatic potential. Recent evidence points to a critical role for cell metabolism in driving breast cancer metastasis. Endogenous fluorescence intensity of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) can provide a label-free method for assessing cell metabolism. We report the optical redox ratio of FAD/(FAD + NADH) of four isogenic triple-negative breast cancer cell lines with varying metastatic potential. Under normoxic conditions, the redox ratio increases with increasing metastatic potential (168FARN>4T07>4T1), indicating a shift to more oxidative metabolism in cells capable of metastasis. Reoxygenation following acute hypoxia increased the redox ratio by 43 ± 9% and 33 ± 4% in the 4T1 and 4T07 cells, respectively; in contrast, the redox ratio decreased 14 ± 7% in the non-metastatic 67NR cell line. These results demonstrate that the optical redox ratio is sensitive to the metabolic adaptability of breast cancer cells with high metastatic potential and could potentially be used to measure dynamic functional changes that are indicative of invasive or metastatic potential. PMID:27895979

  1. Redox Conditions in Selected Principal Aquifers of the United States

    USGS Publications Warehouse

    McMahon, P.B.; Cowdery, T.K.; Chapelle, F.H.; Jurgens, B.C.

    2009-01-01

    Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami-nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+), hydrogen sulfide (H2S), and methane (CH4). Determining the kinds of redox processes that occur in an aquifer system, documenting their spatial distribution, and understanding how they affect concentrations of natural or anthropogenic contaminants are central to assessing and predicting the chemical quality of groundwater. This Fact Sheet extends the analysis of U.S. Geological Survey authors to additional principal aquifer systems by applying a framework developed by the USGS to a larger set of water-quality data from the USGS national water databases. For a detailed explanation, see the 'Introduction' in the Fact Sheet.

  2. Redox conditions in deep groundwater: recent accomplishments and future directions

    NASA Astrophysics Data System (ADS)

    Ioka, Seiichiro; Iwatsuki, Teruki; Sakai, Toshiaki; Ishijima, Yoji

    Redox potential (Eh) is one of the most important physico-chemical properties of groundwater. Groundwater Eh have been studied in terms of safety of high-level radioactive waste disposals, water resource management and so on. As the results, it is getting clear that redox potential of deep groundwater in sedimentary and crystalline rocks have a remarkable variability. For example, some reported Eh values of deep groundwater decrease with increasing depth, i.e. with residence time. However, there are few reports showing data measured in situ. Only some Eh values of deep groundwater measured from research borehole drilled at crystalline rocks in Japan and Sweden have been reported. Between 200 and 1000m depth, the Eh values of the deep groundwater range from about 0 to -400mV. This essay first briefly summarizes methodology for Eh measurement and reports Eh values of deep groundwater. Then, it discusses the remaining issues of Eh measurement that are to develop of measurement technology applicable for various geological environments and to understand the redox evolution process through the groundwater flow system.

  3. Limitations of ichnofossil approach for evaluating paleo-bottom-water redox conditions

    SciTech Connect

    Savrda, C.E.; Bottjer, D.

    1987-05-01

    Information on trace fossil diversity, burrow size, and depth of burrow penetration has been incorporated into an ichnofossil tiering model designed for the evaluation of paleo-bottom-water redox conditions. Previous applications to a variety of Phanerozoic strata indicate that this trace fossil approach is more effective than previously emphasized criteria for reconstructing relative degree of oxygenation as well as rates and magnitudes of temporal change in oxygenation. However, the trace fossil model is not without limitations. Presently, they recognize four factors that could limit the accuracy of ichnology-based redox reconstructions: (1) information loss - increases in penetration depth (associated with reoxygenation) that occur at rates in excess of sedimentation rate will destroy a portion of the previous record of oxygenation whereas extended residence times of deep-tier organisms may mask the record through excessive overprinting; (2) inadequate structure visibility - required information on trace fossil assemblage composition and cross cutting relationships is unobtainable for strata where original or diagenetically enhanced contrast between burrows and surrounding sediments is lacking; (3) complexity introduced by rapid deposition - periodic turbidite deposition can mask the desired oxygen signal through substrate modification, temporary modification of faunal composition and behavior, and/or temporary water chemistry changes; and (4) changes in substrate consistency - temporal variation in substrate stiffness (e.g., development of firmgrounds) may result in intrastratal variation in trace fossil tiering structure. The success of future applications of the ichnologic approach depends upon thorough consideration of these factors.

  4. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    SciTech Connect

    Lipson, David A.; Raab, Theodore K.; Parker, Melanie; Kelley, Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-08-01

    Summary This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes,

  5. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    SciTech Connect

    Lipson, David A.; Raab, Theodore K.; Parker, Melanie; Kelley, Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-07-21

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska, and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography, but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes).

  6. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils.

    PubMed

    Lipson, David A; Raab, Theodore K; Parker, Melanie; Kelley, Scott T; Brislawn, Colin J; Jansson, Janet

    2015-08-01

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes).

  7. Redox conditions and the efficiency of chlorinated ethene biodegradation: Field studies

    USGS Publications Warehouse

    Chapelle, F.H.; Bradley, P.M.

    2000-01-01

    The effect of redox conditions on the efficiency of chlorinated ethene biodegradation was investigated at two field sites. One site (NAS Cecil Field, FL) is characterized by predominantly Fe(III)-reducing conditions in the contaminant source area, grading to predominantly sulfate- reducing conditions downgradient. This sequence of redox conditions led to relatively inefficient biodegradation of chlorinated ethenes, with high concentrations of trichloroethene extending more than 400 meters downgradient of the source area. In contrast, a second site (NBS Kings Bay, GA) characterized by predominantly sulfate-reducing conditions in the source area followed by Fe(III)-reducing conditions downgradient. In this system perchloroethene (PCE) and TCE were rapidly biodegraded and extended less than 100 meters downgradient. Rates of ground- water transport are similar at the two sites (???0.2 m/d) indicating that the succession of redox processes, rather than other hydrologic factors, is the principal control on biodegradation. In particular, redox conditions that favor the initial reduction of highly chlorinated ethenes (methanogenic or sulfate-reducing conditions) followed by more oxidizing conditions (Fe(III)- reducing or oxic conditions) favors efficient biodegradation. Thus, documenting the succession of redox processes is an important step in understanding the efficiency of chlorinated ethene biodegradation in ground-water systems.

  8. Redox state changes in human skeletal muscle after isometric contraction.

    PubMed Central

    Henriksson, J; Katz, A; Sahlin, K

    1986-01-01

    Subjects maintained an isometric contraction of the quadriceps femoris muscle at two-thirds maximal voluntary contraction (m.v.c.) force for 5 s (5.0 +/- 0.3 s; mean +/- S.E. of mean; n = 6) or until fatigue (52 +/- 4 s; n = 13). Muscle biopsies were obtained at rest, immediately after the contractions and also at 1 and 4 min of recovery after contraction to fatigue. In all subjects 5 s isometric contraction resulted in an increase of muscle NADH (0.084 +/- 0.012 at rest to 0.203 +/- 0.041 mmol/kg dry wt.) and a decrease of phosphocreatine (PC; change in concentration = -17.3 +/- 3.8 mmol/kg dry wt.). Glucose-6-phosphate concentration was more than doubled whereas lactate increased in only four of the six subjects. The two subjects who did not show any increase in lactate also had the lowest increase in NADH. At fatigue NADH increased to 0.226 +/- 0.032 mmol/kg dry wt. which was not significantly different from the value after 5 s contraction. Muscle PC was nearly depleted and lactate increased 12-fold above resting levels. The major part (65%) of the NADH increase at fatigue had reverted after 1 min recovery but only a slight further decrease occurred between 1 and 4 min of recovery. In relative terms the time course of the changes in muscle NADH during the first minute of recovery was similar to that of PC resynthesis, suggesting a common regulator such as O2 availability. In contrast to the delayed return of NADH concentration, PC resynthesis continued during the later part of the recovery period and PC concentration was almost fully restored after 4 min of recovery. It is concluded that muscle NADH is already maximally increased in the first seconds of muscle contraction at two-thirds m.v.c. Indirect evidence indicates that this increase reflects a reduction of the mitochondrial NAD-NADH redox couple. The rapid establishment of a reduced mitochondrial redox state at the start of muscle contraction will probably lead to a reduction of the redox state in the

  9. Changes in the Mineral Assemblage of Paddy Soils upon Redox Cycles

    NASA Astrophysics Data System (ADS)

    Vogelsang, Vanessa; Fiedler, Sabine; Jahn, Reinhold

    2010-05-01

    Rice is one of the major cereal crops of global agriculture. World wide more than 10% of the arable land is used for rice production, mainly under temporarily waterlogged conditions. This leads to distinct redox cycles, governing the biogeochemistry of paddy soils. Yet, long-term effects of alternating redox conditions on the soil mineral matrix and properties are still not fully understood. The objective of the project is to elucidate the processes of mineral transformation as related to changing redox conditions and to time of rice cultivation. Long-term effects of rice cultivation on the mineral assemblage were studied along a chronosequence of paddy soils (100, 700 and 2000a paddy soils) developed in comparable parent material in the province of Zhejiang, China. Top soils were analysed for the mineral assemblage and physicochemical properties using x-ray diffraction and chemical analyses, respectively. All studied clay fractions showed a similar clay mineral assemblage (illite, chlorite, kaolinite, vermiculite, smectite). Differences among the paddy sites though could not be related to the time of cultivation. The CECpot of the clay fraction slightly increased from 100 to 2000 a paddy usage, which was partly attributed to a concurrent increase of Corg. With age the Feo/Fed-ratio in both the Alp and Ardp-horizon increased, with a maximum in the Ardp of the 2000 a paddy field. We conclude, that due to an increasing number of redox-cycles, long-term cultivation enhances the formation of microcrystalline Fe-hydroxides in the A-horizons of paddy soils. Chronological changes in the clay mineral assemblage could not be observed in this study.

  10. Transport of gadolinium- and arsenic-based pharmaceuticals in saturated soil under various redox conditions.

    PubMed

    Menahem, Adi; Dror, Ishai; Berkowitz, Brian

    2016-02-01

    The release of pharmaceuticals and personal care products (PPCPs) to the soil-water environment necessitates understanding of PPCP transport behavior under conditions that account for dynamic flow and varying redox states. This study investigates the transport of two organometallic PPCPs, Gd-DTPA and roxarsone (arsenic compound) and their metal salts (Gd(NO3)3, AsNaO2); Gd-DTPA is used widely as a contrasting agent for MRI, while roxarsone is applied extensively as a food additive in the broiler poultry industry. Here, we present column experiments using sand and Mediterranean red sandy clay soil, performed under several redox conditions. The metal salts were almost completely immobile. In contrast, transport of Gd-DTPA and roxarsone was affected by the soil type. Roxarsone was also affected by the different redox conditions, showing delayed breakthrough curves as the redox potential became more negative due to biological activity (chemically-strong reducing conditions did not affect the transport). Mechanisms that include adsorptive retardation for aerobic and nitrate-reducing conditions, and non-adsorptive retardation for iron-reducing, sulfate-reducing and biologically-strong reducing conditions, are suggested to explain the roxarsone behavior. Gd-DTPA is found to be a stable complex, with potential for high mobility in groundwater systems, whereas roxarsone transport through groundwater systems is affected by redox environments, demonstrating high mobility under aerobic and nitrate-reducing conditions and delayed transport under iron-reducing, sulfate-reducing and biologically-strong reducing conditions.

  11. EVALUATION OF IMMOBILIZED REDOX INDICATORS AS REVERSIBLE, IN SITU REDOX SENSORS FOR DETERMINING FE(III)-REDUCING CONDITIONS IN ENVIRONMENTAL SAMPLES. (R828772)

    EPA Science Inventory

    An in situ methodology based on immobilized redox indicators has been developed to determine when Fe(III)-reducing conditions exist in environmental systems. The redox indicators thionine (Thi, formal potential at pH 7 (E70') equals 66 mV), tol...

  12. Overexpression of the transcription factor Yap1 modifies intracellular redox conditions and enhances recombinant protein secretion

    PubMed Central

    Delic, Marizela; Graf, Alexandra B.; Koellensperger, Gunda; Haberhauer-Troyer, Christina; Hann, Stephan; Mattanovich, Diethard; Gasser, Brigitte

    2014-01-01

    Oxidative folding of secretory proteins in the endoplasmic reticulum (ER) is a redox active process, which also impacts the redox conditions in the cytosol. As the transcription factor Yap1 is involved in the transcriptional response to oxidative stress, we investigate its role upon the production of secretory proteins, using the yeast Pichia pastoris as model, and report a novel important role of Yap1 during oxidative protein folding. Yap1 is needed for the detoxification of reactive oxygen species (ROS) caused by increased oxidative protein folding. Constitutive co-overexpression of PpYAP1 leads to increased levels of secreted recombinant protein, while a lowered Yap1 function leads to accumulation of ROS and strong flocculation. Transcriptional analysis revealed that more than 150 genes were affected by overexpression of YAP1, in particular genes coding for antioxidant enzymes or involved in oxidation-reduction processes. By monitoring intracellular redox conditions within the cytosol and the ER using redox-sensitive roGFP1 variants, we could show that overexpression of YAP1 restores cellular redox conditions of protein-secreting P. pastoris by reoxidizing the cytosolic redox state to the levels of the wild type. These alterations are also reflected by increased levels of oxidized intracellular glutathione (GSSG) in the YAP1 co-overexpressing strain. Taken together, these data indicate a strong impact of intracellular redox balance on the secretion of (recombinant) proteins without affecting protein folding per se. Re-establishing suitable redox conditions by tuning the antioxidant capacity of the cell reduces metabolic load and cell stress caused by high oxidative protein folding load, thereby increasing the secretion capacity. PMID:28357216

  13. Effect of redox conditions on bacterial community structure in Baltic Sea sediments with contrasting phosphorus fluxes.

    PubMed

    Steenbergh, Anne K; Bodelier, Paul L E; Slomp, Caroline P; Laanbroek, Hendrikus J

    2014-01-01

    Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of bacteria in phosphorus release from sediments, we assessed the effect of redox conditions on the structure of bacterial communities. To do so, we incubated surface sediments from four sampling sites in the Baltic Sea under oxic and anoxic conditions and analyzed the fingerprints of the bacterial community structures in these incubations and the original sediments. This paper describes the effects of redox conditions, sampling station, and sample type (DNA, RNA, or whole-cell sample) on bacterial community structure in sediments. Redox conditions explained only 5% of the variance in community structure, and bacterial communities from contrasting redox conditions showed considerable overlap. We conclude that benthic bacterial communities cannot be classified as being typical for oxic or anoxic conditions based on community structure fingerprints. Our results suggest that the overall structure of the benthic bacterial community has only a limited impact on benthic phosphate fluxes in the Baltic Sea.

  14. Chromium Release from a COPR-Contaminated Soil at Varying Water Content and Redox Conditions.

    PubMed

    Matern, Katrin; Mansfeldt, Tim

    2016-07-01

    Many soils in the region of Kanpur, North India, are heavily affected by the leather industry and its upstream supplier sector, as indicated by elevated chromium (Cr) contents. Under reducing conditions-for instance, at water saturation after monsoon rain or flood irrigation-the dynamic and species distribution of Cr may be affected due to changes in redox potential (E). In this study, the influence of E on the speciation and release of Cr from a contaminated agricultural soil was investigated. A soil sample that was affected by hyperalkaline leachate from chromite ore processing residue, was taken and packed in soil columns, and subjected to a saturation-drainage-saturation cycle. After initial water saturation, the E dropped slowly to minimum values of around ‒100 mV (calculated to pH 7), while E was controlled by CrO/CrO(s), or CrO/(Fe,Cr)OOH redox couples. Soil drainage resulted in a quick return to oxidizing conditions; i.e., E > 300 mV. The Cr species distribution and release showed a clear trend with E. At the beginning of the experiment, under oxidizing and weakly reducing conditions (E range from >100 to 300 mV), Cr(VI) was released in particular. However, under moderately reducing conditions (E range from 100 to -100 mV), Cr was gradually immobilized and irreversible sequestered via reductive precipitation. The results presented in this study provide an improved understanding of the mobility of Cr(VI) in contaminated soils at varying water contents, which is essential for the evaluation of environmental risks in this region.

  15. The characterization of ferromanganese crust and its redox change, Western Pacific Magellan seamounts

    NASA Astrophysics Data System (ADS)

    Yang, K.; Kim, J. W.; Park, H.; Baik, H.; Park, K.; Kim, J.

    2015-12-01

    Biotic/abiotic redox reaction is a ubiquitous process in mineral formation and growth, and changes in elemental redox states, particularly Fe/Mn may reflect the redox conditions in the sediment/ocean when the mineral forms. Samples were dredged from the seamounts in the western Pacific, OSM11 in order to investigate the formation, growth and its implications to geological history. The crust consist of five well-defined layers (here after called "layer 1" (rim) through "layer 5" (core)). Quartz, feldspar, and hematite are detected only in the layer 1 in addition to the poorly crystallined Fe-rich vernadite, which is likely to be associated with slower growth rate compared to the layers 2-5. CFA were identified in layers 4 and 5 under XRD measurement. Visible size of white colored well crystallined CFA were only observed in layer 4; whereas nano-sized CFA in layer 5 were identified by TEM. Clay minerals such as smectite were observed by TEM with SAED pattern and EDX in layers 1 and 3. The oxidation states of Fe and Mn in Fe-rich vernadite in entire layers were determined by EELS analysis. All the layers of Mn oxide minerals was consisted with dominantly Mn4+, which is consistent with appearance of vernadite in Fe-Mn crust. Fe-rich vernadite in layers 1 and 4 were consisted with 26-52 % of Fe3+/Fetot, dominant reduced form of Fe compared to layers 2, 3, and 5. The observed alternative patterns of Fe oxidation state in five distinct layers of Fe-Mn crust is likely to be associated with the various redox conditions in seawater, changes in growth rate of crust resulting in the various oxygen exposure time, and uplift-subsidence of sea mounts. A non-cultivation-based molecular approach with T-RFLP indicated the presence of functional gene (CumA) association with Mn oxidizing bacteria in Fe-Mn crust layers. The presence of Mn oxidizing gene may suggest that the biotic Mn oxides precipitation may persist locally in the Fe-Mn crust; whereas functional gene of Fe

  16. Fate of Pharmaceuticals and Personal Care Products (PPCPs) in Saturated Soil Under Various Redox Conditions

    NASA Astrophysics Data System (ADS)

    Dror, I.; Menahem, A.; Berkowitz, B.

    2014-12-01

    The growing use of PPCPs results in their increasing release to the aquatic environment. Consequently, understanding the fate of PPCPs under environmentally relevant conditions that account for dynamic flow and varying redox states is critical. In this study, the transport of two organometallic PPCPs, Gd-DTPA and Roxarsone (As complex) and their metal salts (Gd(NO3)3, AsNaO2), is investigated. The former is used widely as a contrasting agent for MRI, while the latter is applied extensively as a food additive in the broiler poultry industry. Both of these compounds are excreted from the body, almost unchanged chemically. Gadolinium complexes are not fully eliminated in wastewater treatment and can reach groundwater via irrigation with treated wastewater; Roxarsone can enter groundwater via leaching from manure used as fertilizer. Studies have shown that the transport of PPCPs in groundwater is affected by environmental conditions such as redox states, pH, and soil type. For this study, column experiments using sand or Mediterranean red sandy clay soil were performed under several redox conditions: aerobic, nitrate-reducing, iron-reducing, sulfate-reducing, methanogenic, and very strongly chemical reducing. Batch experiments to determine adsorption isotherms were also performed for the complexes and metal salts. We found that Gd-DTPA transport was affected by the soil type and was not affected by the redox conditions. In contrast, Roxarsone transport was affected mainly by the different redox conditions, showing delayed breakthrough curves as the conditions became more biologically reduced (strong chemical reducing conditions did not affect the transport). We also observed that the metal salts show essentially no transport while the organic complexes display much faster breakthrough. The results suggest that transport of these PPCPs through soil and groundwater is determined by the redox conditions, as well as by soil type and the form of the applied metal (as salt

  17. Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils

    NASA Astrophysics Data System (ADS)

    Sauerwein, Meike; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

    2010-05-01

    Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils Meike Sauerwein1, Alexander Hanke2, Klaus Kaiser3, Karsten Kalbitz2 1) Dept. of Soil Ecology, Bayreuth Centre of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany, meike.sauerwein@gmail.com 2) Institute of ecosystem dynamics and biodiversity, University of Amsterdam, 1018 WV, Netherlands, a.hanke@uva.nl, k.kalbitz@uva.nl 3) Soil Sciences, Martin Luther University Halle, 06099 Halle, Germany, klaus.kaiser@landw.uni-halle.de Current knowledge on dissolved organic matter (DOM) in soils is based mainly on observations and experiments in aerobic environments. Adsorption to soil minerals is an important mechanism of DOM retention and stabilization against microbial decay under oxic conditions. Under anoxic conditions where hydrous iron oxides, the potential main adsorbents of DOM, possibly dissolve, the importance of adsorption seems questionable. Therefore, we studied the adsorption of DOM to selected soil minerals and to mineral soils under oxic and anoxic conditions. In detail, we tested the following hypotheses: 1. Minerals and soils adsorb less DOM under anoxic conditions than under oxic ones. 2. The reduced adsorption under anoxic conditions is result of the smaller adsorption to hydrous Fe oxides whereas adsorption to clay minerals and Al hydroxides is not sensitive to changes in redox conditions 3. DOM adsorption will increase with the number of redox cycles, thus time of soil formation, due to increasing contents of poorly crystalline Fe oxides. This will, however, cause a stronger sensitivity to redox changes as poor crystalline Fe oxides are more reactive. 4. Aromatic compounds, being preferentially adsorbed under oxic conditions, will be less strongly adsorbed under anoxic conditions. We chose paddy soils as models because their periodically and regular exposure to changing redox cycles, with

  18. An anaerobic field injection experiment in a landfill leachate plume, Grindsted, Denmark: 2. Deduction of anaerobic (methanogenic, sulfate-, and Fe (III)-reducing) redox conditions

    NASA Astrophysics Data System (ADS)

    Albrechtsen, Hans-JøRgen; Bjerg, Poul L.; Ludvigsen, Liselotte; Rügge, Kirsten; Christensen, Thomas H.

    1999-04-01

    Redox conditions may be environmental factors which affect the fate of the xenobiotic organic compounds. Therefore the redox conditions were characterized in an anaerobic, leachate-contaminated aquifer 15-60 m downgradient from the Grindsted Landfill, Denmark, where an field injection experiment was carried out. Furthermore, the stability of the redox conditions spatially and over time were investigated, and different approaches to deduce the redox conditions were evaluated. The redox conditions were evaluated in a set of 20 sediment and groundwater samples taken from locations adjacent to the sediment samples. Samples were investigated with respect to groundwater chemistry, including hydrogen and volatile fatty acids (VFAs) and sediment geochemistry, and bioassays were performed. The groundwater chemistry, including redox sensitive species for a large number of samples, varied over time during the experimental period of 924 days owing to variations in the leachate from the landfill. However, no indication of change in the redox environment resulting from the field injection experiment or natural variation was observed in the individual sampling points. The methane, Fe(II), hydrogen, and VFA groundwater chemistry parameters strongly indicated a Fe(III)-reducing environment. This was further supported by the bioassays, although methane production and sulfate-reduction were also observed in a few samples close to the landfill. On the basis of the calculated carbon conversion, Fe(III) was the dominant electron acceptor in the region of the aquifer, which was investigated. Because of the complexity of a landfill leachate plume, several redox processes may occur simultaneously, and an array of methods must be applied for redox characterization in such multicomponent systems.

  19. The Influence of Cooling History on the Redox Conditions of Subduction Zone Magmas

    NASA Astrophysics Data System (ADS)

    Parks, B. H.; Kelley, K. A.; Cottrell, E.; Posner, E. S.

    2009-12-01

    The availability of oxygen in the Earth’s interior controls mineral assemblages, magmatic crystallization and degassing, and trace element partitioning. Alternative views of redox conditions in the mantle argue either that it varies regionally in response to plate tectonic activity or that it is homogeneous throughout the upper mantle. Bulk analyses of global lava suites suggest that arc basalts are more oxidized than mid-ocean ridge basalts. This may be attributed to either more oxidized arc mantle sources or near-surface magmatic processes such as crystallization and degassing. Glass inclusions in olivine may record changes in the liquid magma as crystals and gases are progressively removed, offering a means of discriminating between these models. We assess the effects of crystallization and degassing on the redox conditions of basaltic arc magmas through the analysis of co-variations in major elements, volatiles (H2 O, CO2, S), and Fe oxidation state (i.e., Fe3+/ΣFe), in a new suite of olivine-hosted glass inclusions from one eruption of Agrigan volcano in the Mariana arc. We use Fe K-edge micro X-ray Absorption Near-Edge Structure spectroscopy to determine Fe3+/ΣFe ratios of glass inclusions at the same spatial scale as major and volatile element analyses of the same glasses. Fe3+/ΣFe ratios of the Agrigan melts (0.19-0.28) are more oxidized than mid-ocean ridge basalts (0.13-0.17). Major element compositions of the melt inclusions are consistent with fractional crystallization of olivine +/- plagioclase, although Fe3+/ΣFe decreases with decreasing MgO, which is not predicted by crystallization of these two phases. Loss of vapor phases during degassing (e.g., CO2, S, H2O) could also drive changes in the redox state of magmas. The Fe3+/ΣFe ratio does not vary systematically with CO2, indicating that redox conditions are unaffected by early stage degassing of CO2. Fe3+/ΣFe does decrease with decreasing S, revealing that a net reduction of Fe occurs as S

  20. Expression of Bradyrhizobium japonicum cbb(3) terminal oxidase under denitrifying conditions is subjected to redox control.

    PubMed

    Bueno, Emilio; Richardson, David J; Bedmar, Eulogio J; Delgado, María J

    2009-09-01

    Bradyrhizobium japonicum utilizes cytochrome cbb(3) oxidase encoded by the fixNOQP operon to support microaerobic respiration under free-living and symbiotic conditions. It has been previously shown that, under denitrifying conditions, inactivation of the cycA gene encoding cytochrome c(550), the electron donor to the Cu-containing nitrite reductase, reduces cbb(3) expression. In order to establish the role of c(550) in electron transport to the cbb(3) oxidase, in this work, we have analyzed cbb(3) expression and activity in the cycA mutant grown under microaerobic or denitrifying conditions. Under denitrifying conditions, mutation of cycA had a negative effect on cytochrome c oxidase activity, heme c (FixP and FixO) and heme b cytochromes as well as expression of a fixP'-'lacZ fusion. Similarly, cbb(3) oxidase was expressed very weakly in a napC mutant lacking the c-type cytochrome, which transfers electrons to the NapAB structural subunit of the periplasmic nitrate reductase. These results suggest that a change in the electron flow through the denitrification pathway may affect the cellular redox state, leading to alterations in cbb(3) expression. In fact, levels of fixP'-'lacZ expression were largely dependent on the oxidized or reduced nature of the carbon source in the medium. Maximal expression observed in cells grown under denitrifying conditions with an oxidized carbon source required the regulatory protein RegR.

  1. Mobilization and Release of colloidal Carbon from a Soil Column Under Redox Oscillation Condition

    NASA Astrophysics Data System (ADS)

    Afsar, M. Z.; Jin, Y.

    2015-12-01

    Dissolved organic matter (DOM), the most mobile form of carbon (C), strongly influences the cycling, distribution and behavior of C in soil. In wetlands, the reductive dissolution of iron and manganese oxy-hydroxides releases large quantities of DOM into the soil solution. The objective of this study is to quantify the changes in aqueous organic carbon concentration in different sized fractions induced by reduction of iron and increase in pH. Twenty four cm long soil columns were prepared. Columns were run under oxic (as control) and anoxic conditions. Two platinum redox probes were inserted at 10 and 17 cm depths from the soil surface to monitor the redox status of the column. Anoxic and oxic conditions were maintained by flushing with either nitrogen or oxygen gas through the soil. No additional organic sources were added. After 35 days of anoxic environment, column leachate samples were separated by differential centrifugation into five colloidal sized fractions (<450 nm, <220 nm, <100 nm, <50 nm and <2.3 nm). Immediately after the 1st reduction half cycle, the leachate samples were collected inside the glove box and the soil columns were flushed with oxygen to prepare for 2nd reduction half cycle. After 1st reduction half cycle, the pH, ionic strength and aqueous (Fe2+) concentration of the column extracts were increased whereas the Eh value was decreased. The range of pH, Eh, ionic strength and concentration of Fe2+ was 6.38 to 6.91, -219 to -275 mV, 13.74 to 18.84 mM and 1.8 to 3.41 mg L-1, respectively. Following the anoxic incubation, the total desorbed C was increased up to 139 mg L-1. The distribution of C across the five particle size fractions was 3.68-11.73% (> 450 nm), 0.59-5.12% (450-220 nm), 0.45-4.91% (220-100 nm), 0.18-2.91% (100-50 nm), 15.48-35.23% (50 nm - 2.3 nm) and 49.15-63.94% (<2.3 nm). The preliminary results confirmed the release of more nanoparticulate (50-2.3 nm) and truly dissolved (<2.3 nm) organic matter from the anoxic soil column

  2. The Cr Redox Record of fO2 Variation in Angrites. Evidence for Redox Conditions of Angrite Petrogenesis and Parent Body

    NASA Technical Reports Server (NTRS)

    Shearer, Charles K.; Bell, Aaron S.; Burger, Paul V.; Papike, James J.; Jones, John; Le, Loan

    2016-01-01

    Angrites represent some of the earliest stages of planetesimal differentiation. Not surprisingly, there is no simple petrogenetic model for their origin. Petrogenesis has been linked to both magmatic and impact processes. Studies demonstrated that melting of chondritic material (e.g. CM, CV) at redox conditions where pure iron metal is unstable (e.g., IW+1 to IW+2) produced angrite-like melts. Alternatively, angrites were produced at more reducing conditions (conditions of angrite crystallization are limited, and only preliminary attempts been made to understand the changes in fO2 that occurred during petrogenesis. Many of the angrites have phase assemblages which provide conflicting signals about redox conditions during crystallization (e.g., Fe metal and a Fe-Ti oxide with potential Fe3+. There have been several estimates of fO2 for angrites. Most notably, experiments examined the variation of DEu/DGd with fO2, between plagioclase and fassaitic pyroxene in equilibrium with an angrite melt composition. They used their observations to estimate the fO2 of crystallization to be approximately IW+0.6 for angrite LEW 86010. This estimate is only a "snapshot" of fO2 conditions during co-crystallization of plagioclase and pyroxene. Preliminary XANES analyses of V redox state in pyroxenes from D'Orbigny reported changes in fO2 from IW-0.7 during early pyroxene crystallization to IW+0.5 during latter episodes of pyroxene crystallization [15]. As this was a preliminary report, it presented limited information concerning the effects of pyroxene orientation and composition on the V valence measurements, and the effect of melt composition on valence and

  3. Influence of the redox condition dynamics on the removal efficiency of a laboratory-scale constructed wetland.

    PubMed

    Wiessner, A; Kappelmeyer, U; Kuschk, P; Kästner, M

    2005-01-01

    A laboratory reactor planted with Juncus effusus treating an artificial wastewater was used to investigate the short-term and long-term variations and interactions in the redox conditions as well as the removal efficiency of C and the N turnover. The permanent circulation of the process water enabled the micro-gradient processes to be evaluated for an operating period of 20 months. Steady-state conditions were achieved throughout the operating period with high mean removal efficiencies of 92.7% total organic carbon, 82.0% ammonia and 97.6% nitrate. Daily variations in the redox state of the rhizosphere of a few hundred mV were observed, ranging from about -200 to oxidized conditions of about +200 mV and driven by daylight. Variations in pH associated with changes in light and redox were linked to the dynamics of the fates of organic and inorganic carbon species. The ammonia removal processes were found to be firmly established, including for moderately reduced redox conditions with high efficiencies for E(h)>-50 mV. The enrichment of ammonia (up to 13 mg l(-1)) closely linked to the light, particularly during summertime, indicates the existence of hitherto unconsidered additional N turnover pathways in the rhizoplane involving N(2) produced by microbes or released by plants. C turnover was strongly related to the seasonal variation in illumination with minimum efficiencies during the dark season. In addition, it was characterized by oscillation with periods of approximately 1 month. The relationships found are dominant for biofilms on the rhizoplane and decisive for the removal efficiency of especially simple constructed and natural wetlands. The results highlight the importance of helophytes and their physiological specifics for removal processes.

  4. Nontronite (NAu-1) Structure Associated with Microbial Fe(III) Reduction in Various Redox Conditions

    NASA Astrophysics Data System (ADS)

    Koo, T.; Kim, S.; Kim, J.

    2011-12-01

    Shewanella oneidensis MR-1 respires the structural Fe(III) of smectite and promotes illite formation in O2-free environment (Kostka et al., 1996, Kim et al., 2004). Since S. oneidensis is a facultative iron reducing bacterium, it is crucial to understand the structural changes induced by bio-reduction of structural Fe(III) in various redox conditions. Furthermore, the changes in cation exchange capacity (CEC) of bio-reduced nontronite upon the modification of mineral structure has not been extensively studied in terms of Fe-cycling. In this present study, we reported the evolution of nontronite structure at various time points in various redox conditions and corresponding CEC upon reduction and re-oxidation. S. oneidensis MR-1 was incubated in M1 medium with Na-lactate as the electron donor and Fe in nontronite (NAu-1) as the sole electron acceptor at pH 7 in anaerobic chamber for 3 hrs, 12 hrs, 1 day, 2 days, 4 days, 7 days, 14 days, and 21 days. O2 gas bubbling was then applied to the sample at each time point for 24 hours for re-oxidation. The triplet samples at each time point for both reduction and re-oxidation experiments were prepared. The extent of Fe(III) reduction measured by 1,10-phenanthroline method (Stucki and Anderson, 1981) indicated that the structural Fe(III) was reduced up to 8.8% of total Fe(III) within 21 days. XRD data with various treatments such as air dried, glycolated and lithium-saturated showed that K-nontronite may be formed because no discrete 10-Å illite peak was observed in Li-saturated sample upon glycolation. The CEC increased from 747 meg/kg to 1145 meg/kg during Fe(III) reduction and decreased to 954 meg/kg upon re-oxidation, supporting the possible formation of K-nontronite. The direct observation by electron microscopy verified the structural changes in nontonite in various redox conditions. The long-term experiment for 6 months, is in progress in anaerobic chamber, and results will be discussed. Kim, J. W., Dong, H., Seabaugh

  5. Impacts of microbial redox conditions on the phase distribution of pyrene in soil-water systems.

    PubMed

    Kim, Han S; Roper, J Chadwick; Pfaender, Frederic K

    2008-03-01

    Variations in the soil/sediment organic matter (SOM)-hydrophobic organic contaminant (HOC) bindings upon microbially mediated redox conditions were examined. While the extractability of pyrene associated with soil declined after its biodegradation began during aerobic incubation, its variations were almost constant (+/-3.0-4.4%) during anoxic/anaerobic incubations. The dissolved organic matter released from the soil incubated under highly reduced conditions became more humified and aromatic, had a higher average molecular weight, and was more polydispersed compared to that obtained from oxic incubation, similar to the SOM alterations in the early stage of diagenesis (humification). The concentrations of pyrene in the aqueous phase increased significantly during the soil incubations under highly reduced conditions due to its favorable interaction with the altered DOM. Our results suggest that the microbially mediated redox conditions have significant impacts on SOM and should be considered for the transport, fate, bioavailability, and exposure risk of HOCs in the geo-environments.

  6. Molybdenum isotope fractionation in soils: Influence of redox conditions, organic matter, and atmospheric inputs

    NASA Astrophysics Data System (ADS)

    Siebert, C.; Pett-Ridge, J. C.; Opfergelt, S.; Guicharnaud, R. A.; Halliday, A. N.; Burton, K. W.

    2015-08-01

    soils are controlled by redox conditions, organic matter, and atmospheric inputs. In this way Mo isotopes have the potential to react to and record climate driven changes in the weathering environment. The presence of both isotopically light and heavy Mo (relative to parent material) across all sites and within individual soil profiles suggests that it is normal for multiple fractionation mechanisms to operate under the open-system conditions of soils.

  7. Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration

    PubMed Central

    Birkner, Nancy; Navrotsky, Alexandra

    2014-01-01

    Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings. PMID:24733903

  8. Does phosphate enhance the natural attenuation of crude oil in groundwater under defined redox conditions?

    NASA Astrophysics Data System (ADS)

    Ponsin, Violaine; Mouloubou, Olsen Raïnness; Prudent, Pascale; Höhener, Patrick

    2014-11-01

    After a crude oil spill caused by a broken pipeline in 2009 to a gravel aquifer in southern France, degradation processes under various redox conditions progressively established, but at rates that predict a long life-time of the source under natural attenuation after partial source removal. In this study, we aimed at identifying the rate-limiting factors for each redox condition, with special emphasis on phosphate as limiting nutrient. The study was conducted in laboratory microcosms assembled with material collected on site: sediments, water from monitoring wells, oil and microbial sludge. Redox conditions were promoted by adding electron acceptors (either oxygen, nitrate, limonite (FeO(OH)), cryptomelane (K(Mn4 +,Mn2 +)8O16), or sulfate). For each condition, the role of phosphate was studied by repeated additions for up to 290 days. The results showed a very strong stimulation of aerobic and denitrifying rates of oil degradation by phosphate, provided that oxygen and nitrate were repeatedly supplied. Phosphate caused also a marked stimulation of methanogenic degradation, and a relatively small stimulation of metal reduction. These anaerobic processes started only after marked lag phases, and phosphate shortened the lag phase for methanogenic degradation. Degradation of aromatic and aliphatic hydrocarbons with less than 8 carbons, including benzene, was confirmed even under unstimulated conditions. It is concluded that degradation rates at the site are limited by both, availability of electron acceptors and availability of phosphate needed for promoting microbial growth.

  9. Deepwater redox changes in the southern Okinawa Trough since the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Dou, Yanguang; Yang, Shouye; Li, Chao; Shi, Xuefa; Liu, Jihua; Bi, Lei

    2015-06-01

    In this study, rare earth element (REE) was treated as a paleo-redox proxy to investigate the changes of depositional environment in the southern Okinawa Trough since the last glacial maximum. The acid-leachable fraction (leachate) of the sediments recovered from the ODP Site 1202B is dominated by biogenic and authigenic components while detrital contamination is minor. The significant enrichment of middle REE suggests a large contribution from authigenic Mn oxyhydroxides and cerium (Ce) anomaly can indicate deepwater redox change. The REE parameters including Ce anomaly in the leachate exhibit remarkable and abrupt changes in the early Holocene (∼9.5 ka) and during LGM (∼20 ka). An increase of Ce anomaly at 28-22 ka implies the suboxic deepwater condition probably caused by increased primary productivity. Weak positive Ce anomalies during the last glacial maximum and deglaciation suggest an oxic depositional environment responding to the enhanced deepwater ventilation with the advection of the North Pacific Intermediate Water and/or South China Sea Intermediate Water into the trough. A decrease of Ce anomaly in the early Holocene might be caused by the intrusion and strengthening of the Kuroshio Current in the trough that enhanced the water stratification and induced a gradual development of suboxic depositional condition. Furthermore, an abrupt change of chemical composition at ca. 4 ka probably indicates a decrease of dissolved oxygen in deepwater and a weakening of ventilation in the Okinawa Trough. This study suggests that REE proxy can provide new insights into the linkage among surface current, deepwater circulation and sediment record in the continental margin where terrigenous input dominates.

  10. Global iridium anomaly, mass extinction, and redox change at the Devonian-Carboniferous boundary

    SciTech Connect

    Wang, K. Univ. of Calgary, Alberta ); Attrep, M. Jr.; Orth, C.J. )

    1993-12-01

    Iridium abundance anomalies have been found on a global scale in the Devonian-Carboniferous (D-C) boundary interval, which records one of the largest Phanerozoic mass-extinction events, an event that devastated many groups of living organisms, such as plants, ammonoids, trilobites, conodonts, fish, foraminiferans, brachiopods, and ostracodes. At or very close to the D-C boundary, there exists a geographically widespread black-shale interval, and Ir abundances reach anomalous maxima of 0.148 ppb (Montagne Noire, France), 0.138 ppb (Alberta, Canada) 0.140 ppb (Carnic Alps, Austria), 0.156 ppb (Guangxi, China), 0.258 ppb (Guizhou, China), and 0.250 ppb (Oklahoma). The discovery of global D-C Ir anomalies argues for an impact-extinction model. However, nonchondritic ratios of Ir to other important elements and a lack of physical evidence (shocked quartz, microtektites) do not support such a scenario. The fact that all Ir abundance maxima are at sharp redox boundaries in these sections leads us to conclude that the Ir anomalies likely resulted from a sudden change in paleo-redox conditions during deposition and/or early diagenesis. 36 refs., 2 figs., 1 tab.

  11. Changes in mitochondrial homeostasis and redox status in astronauts following long stays in space

    PubMed Central

    Indo, Hiroko P.; Majima, Hideyuki J.; Terada, Masahiro; Suenaga, Shigeaki; Tomita, Kazuo; Yamada, Shin; Higashibata, Akira; Ishioka, Noriaki; Kanekura, Takuro; Nonaka, Ikuya; Hawkins, Clare L.; Davies, Michael J.; Clair, Daret K. St; Mukai, Chiaki

    2016-01-01

    The effects of long-term exposure to extreme space conditions on astronauts were investigated by analyzing hair samples from ten astronauts who had spent six months on the International Space Station (ISS). Two samples were collected before, during and after their stays in the ISS; hereafter, referred to as Preflight, Inflight and Postflight, respectively. The ratios of mitochondrial (mt) to nuclear (n) DNA and mtRNA to nRNA were analyzed via quantitative PCR. The combined data of Preflight, Inflight and Postflight show a significant reduction in the mtDNA/nDNA in Inflight, and significant reductions in the mtRNA/nRNA ratios in both the Inflight and Postflight samples. The mtRNA/mtDNA ratios were relatively constant, except in the Postflight samples. Using the same samples, the expression of redox and signal transduction related genes, MnSOD, CuZnSOD, Nrf2, Keap1, GPx4 and Catalase was also examined. The results of the combined data from Preflight, Inflight and Postflight show a significant decrease in the expression of all of the redox-related genes in the samples collected Postflight, with the exception of Catalase, which show no change. This decreased expression may contribute to increased oxidative stress Inflight resulting in the mitochondrial damage that is apparent Postflight. PMID:27982062

  12. Changes in mitochondrial homeostasis and redox status in astronauts following long stays in space.

    PubMed

    Indo, Hiroko P; Majima, Hideyuki J; Terada, Masahiro; Suenaga, Shigeaki; Tomita, Kazuo; Yamada, Shin; Higashibata, Akira; Ishioka, Noriaki; Kanekura, Takuro; Nonaka, Ikuya; Hawkins, Clare L; Davies, Michael J; Clair, Daret K St; Mukai, Chiaki

    2016-12-16

    The effects of long-term exposure to extreme space conditions on astronauts were investigated by analyzing hair samples from ten astronauts who had spent six months on the International Space Station (ISS). Two samples were collected before, during and after their stays in the ISS; hereafter, referred to as Preflight, Inflight and Postflight, respectively. The ratios of mitochondrial (mt) to nuclear (n) DNA and mtRNA to nRNA were analyzed via quantitative PCR. The combined data of Preflight, Inflight and Postflight show a significant reduction in the mtDNA/nDNA in Inflight, and significant reductions in the mtRNA/nRNA ratios in both the Inflight and Postflight samples. The mtRNA/mtDNA ratios were relatively constant, except in the Postflight samples. Using the same samples, the expression of redox and signal transduction related genes, MnSOD, CuZnSOD, Nrf2, Keap1, GPx4 and Catalase was also examined. The results of the combined data from Preflight, Inflight and Postflight show a significant decrease in the expression of all of the redox-related genes in the samples collected Postflight, with the exception of Catalase, which show no change. This decreased expression may contribute to increased oxidative stress Inflight resulting in the mitochondrial damage that is apparent Postflight.

  13. Reconstruction of Redox Conditions and Productivity in Coastal Waters of the Bothnian Sea during the Holocene

    NASA Astrophysics Data System (ADS)

    Dijkstra, N.; Quintana Krupinski, N. B.; Slomp, C. P.

    2014-12-01

    Hypoxia is a growing problem in coastal waters worldwide, and is a well-known cause of benthic mortality. The semi-enclosed Baltic Sea is currently the world's largest human-induced dead zone. During the early Holocene, it experienced several periods of natural hypoxia following the intrusion of seawater into the previous freshwater lake. Recent studies suggest that at that time, the hypoxia expanded north to include the deep basin of the Bothnian Sea. In this study, we assess whether the coastal zone of the Bothnian Sea was also hypoxic during the early Holocene. We analysed a unique sediment record (0 - 30 mbsf) from the Ångermanälven estuary, which was retrieved during the International Ocean Discovery Programme (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. Using geochemical proxies and foraminifera abundances, we reconstruct the changes in redox conditions, salinity and productivity in the estuary. Our preliminary results suggest that bottom waters in this coastal basin became anoxic upon the intrusion of brackish seawater in the early Holocene and that the productivity was elevated. The presence of benthic foraminifera in this estuary during the mid-Holocene suggests more saline conditions in the Bothnian Sea than today. Due to isostatic uplift, the estuary likely gradually became more isolated from the Bothnian Sea, which itself became more isolated from the Baltic Sea. Both factors likely explain the subsequent re-oxygenation of bottom waters and gradual refreshening of the estuary as recorded in the sediments. Interestingly, the upper meters of sediment are enriched in minerals that contain iron, phosphorus and manganese. We postulate that the refreshening of the estuary triggered the formation of these minerals, thereby increasing the phosphorus retention in these sediments and further reducing primary productivity. This enhanced retention linked to refreshening may contribute to the current oligotrophic conditions in the Bothnian Sea.

  14. Subsurface Conditions Controlling Uranium Incorporation in Iron Oxides: A Redox Stable Sink

    SciTech Connect

    Fendorf, Scott

    2016-04-05

    Toxic metals and radionuclides throughout the U.S. Department of Energy Complex pose a serious threat to ecosystems and to human health. Of particular concern is the redox-sensitive radionuclide uranium, which is classified as a priority pollutant in soils and groundwaters at most DOE sites owing to its large inventory, its health risks, and its mobility with respect to primary waste sources. The goal of this research was to contribute to the long-term mission of the Subsurface Biogeochemistry Program by determining reactions of uranium with iron (hydr)oxides that lead to long-term stabilization of this pervasive contaminant. The research objectives of this project were thus to (1) identify the (bio)geochemical conditions, including those of the solid-phase, promoting uranium incorporation in Fe (hydr)oxides, (2) determine the magnitude of uranium incorporation under a variety of relevant subsurface conditions in order to quantify the importance of this pathway when in competition with reduction or adsorption; (3) identify the mechanism(s) of U(VI/V) incorporation in Fe (hydr)oxides; and (4) determine the stability of these phases under different biogeochemical (inclusive of redox) conditions. Our research demonstrates that redox transformations are capable of achieving U incorporation into goethite at ambient temperatures, and that this transformation occurs within days at U and Fe(II) concentrations that are common in subsurface geochemical environments with natural ferrihydrites—inclusive of those with natural impurities. Increasing Fe(II) or U concentration, or initial pH, made U(VI) reduction to U(IV) a more competitive sequestration pathway in this system, presumably by increasing the relative rate of U reduction. Uranium concentrations commonly found in contaminated subsurface environments are often on the order of 1-10 μM, and groundwater Fe(II) concentrations can reach exceed 1 mM in reduced zones of the subsurface. The redox-driven U(V) incorporation

  15. Detecting changes in the thiol redox state of proteins following a decrease in oxygen concentration using a dual labeling technique.

    PubMed

    Lui, James K C; Lipscombe, Richard; Arthur, Peter G

    2010-01-01

    Cells are routinely exposed to hyperoxic conditions when cultured in the presence of 95% air and 5% carbon dioxide. Hyperoxic conditions can increase the generation of reactive oxygen species and cause oxidative stress. Oxidative stress has been proposed to cause cells in culture to behave differently from cells in vivo. One route by which oxidative stress could affect cellular function is through alterations in protein function caused by the oxidation of thiol groups (-SH) of redox-sensitive cysteine residues. To test whether changes in oxygen concentration were sufficient to cause changes in the thiol redox state of proteins, we developed a sensitive method involving the labeling of reduced and oxidized cysteine residues with fluorescent tags. Using this dual labeling method, we found 62 of 411 protein spots that were significantly more reduced following a 30 min decrease in oxygen concentration. We conclude that the elevated oxygen concentration characteristic of typical cell culture conditions has the potential to affect cellular behavior through changes in the thiol redox state of proteins.

  16. Retinal proteins associated with redox regulation and protein folding play central roles in response to high glucose conditions.

    PubMed

    Wang, Ssu-Han; Lee, Wen-Chi; Chou, Hsiu-Chuan

    2015-03-01

    Diabetic retinopathy typically causes poor vision and blindness. A previous study revealed that a high blood glucose concentration induces glycoxidation and weakens the retinal capillaries. Nevertheless, the molecular mechanisms underlying the effects of high blood glucose induced diabetic retinopathy remain to be elucidated. In the present study, we cultured the retinal pigmented epithelial cell line ARPE-19 in mannitol-balanced 5.5, 25, and 100 mM glucose media and investigated protein level alterations. Proteomic analysis revealed significant changes in 137 protein features, of which 124 demonstrated changes in a glucose concentration dependent manner. Several proteins functionally associated with redox regulation, protein folding, or the cytoskeleton are affected by increased glucose concentrations. Additional analyses also revealed that cellular oxidative stress, including endoplasmic reticulum stress, was significantly increased after treatment with high glucose concentrations. However, the mitochondrial membrane potential and cell survival remained unchanged during treatment with high glucose concentrations. To summarize, in this study, we used a comprehensive retinal pigmented epithelial cell based proteomic approach for identifying changes in protein expression associated retinal markers induced by high glucose concentrations. Our results revealed that a high glucose condition can induce cellular oxidative stress and modulate the levels of proteins with functions in redox regulation, protein folding, and cytoskeleton regulation; however, cell viability and mitochondrial integrity are not significantly disturbed under these high glucose conditions.

  17. The Conditions of Institutional Change.

    ERIC Educational Resources Information Center

    Caskey, Owen L.

    The author proposes a method of examining and organizing the principles relating to the conditions of institutional change. Those conditions of change involve principles which relate to three elements--people, places, and things. Within these categories, principles may be enumerated which operate to facilitate or restrain change or innovation…

  18. Intermittent fasting results in tissue-specific changes in bioenergetics and redox state.

    PubMed

    Chausse, Bruno; Vieira-Lara, Marcel A; Sanchez, Angélica B; Medeiros, Marisa H G; Kowaltowski, Alicia J

    2015-01-01

    Intermittent fasting (IF) is a dietary intervention often used as an alternative to caloric restriction (CR) and characterized by 24 hour cycles alternating ad libitum feeding and fasting. Although the consequences of CR are well studied, the effects of IF on redox status are not. Here, we address the effects of IF on redox state markers in different tissues in order to uncover how changes in feeding frequency alter redox balance in rats. IF rats displayed lower body mass due to decreased energy conversion efficiency. Livers in IF rats presented increased mitochondrial respiratory capacity and enhanced levels of protein carbonyls. Surprisingly, IF animals also presented an increase in oxidative damage in the brain that was not related to changes in mitochondrial bioenergetics. Conversely, IF promoted a substantial protection against oxidative damage in the heart. No difference in mitochondrial bioenergetics or redox homeostasis was observed in skeletal muscles of IF animals. Overall, IF affects redox balance in a tissue-specific manner, leading to redox imbalance in the liver and brain and protection against oxidative damage in the heart.

  19. Intermittent Fasting Results in Tissue-Specific Changes in Bioenergetics and Redox State

    PubMed Central

    Chausse, Bruno; Vieira-Lara, Marcel A.; Sanchez, Angélica B.; Medeiros, Marisa H. G.; Kowaltowski, Alicia J.

    2015-01-01

    Intermittent fasting (IF) is a dietary intervention often used as an alternative to caloric restriction (CR) and characterized by 24 hour cycles alternating ad libitum feeding and fasting. Although the consequences of CR are well studied, the effects of IF on redox status are not. Here, we address the effects of IF on redox state markers in different tissues in order to uncover how changes in feeding frequency alter redox balance in rats. IF rats displayed lower body mass due to decreased energy conversion efficiency. Livers in IF rats presented increased mitochondrial respiratory capacity and enhanced levels of protein carbonyls. Surprisingly, IF animals also presented an increase in oxidative damage in the brain that was not related to changes in mitochondrial bioenergetics. Conversely, IF promoted a substantial protection against oxidative damage in the heart. No difference in mitochondrial bioenergetics or redox homeostasis was observed in skeletal muscles of IF animals. Overall, IF affects redox balance in a tissue-specific manner, leading to redox imbalance in the liver and brain and protection against oxidative damage in the heart. PMID:25749501

  20. Redox-triggered changes in the self-assembly of a ferrocene-peptide conjugate.

    PubMed

    Adhikari, Bimalendu; Kraatz, Heinz-Bernhard

    2014-05-30

    Ultrasonication of a ferrocene conjugate of a short amyloid peptide (Aβ18-20) in toluene causes formation of an organogel, which undergoes dramatic structural changes upon oxidation from a nanofibrillar network to spherical micelles. This morphological change is redox-controlled and reversible.

  1. Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting

    NASA Astrophysics Data System (ADS)

    Huck, Claire E.; van de Flierdt, Tina; Jiménez-Espejo, Francisco J.; Bohaty, Steven M.; Röhl, Ursula; Hammond, Samantha J.

    2016-03-01

    Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation. However, combined studies on sediments, pore waters, fish teeth, and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources.

  2. Changes in redox properties of humic acids upon sorption to alumina

    NASA Astrophysics Data System (ADS)

    Subdiaga, Edisson; Orsetti, Silvia; Jindal, Sharmishta; Haderlein, Stefan B.

    2016-04-01

    1. Introduction A prominent role of Natural Organic Matter (NOM) in biogeochemical processes is its ability to act as an electron shuttle, accelerating rates between a bulk electron donor and an acceptor. The underlying processes are reversible redox reactions of quinone moieties.1 This shuttling effect has been studied in two major areas: transformation of redox active pollutants and microbial respiration.2-3 Previous studies primarily compared effects in the presence or absence of NOM without addressing the redox properties of NOM nor its speciation. The interaction between humic acids (HA) and minerals might change properties and reactivity of organic matter. Specifically, we investigate whether changes in the redox properties of a HA occur upon sorption to redox inactive minerals. Since fractionation and conformational rearrangements of NOM moieties upon sorption are likely to happen, the redox properties of the NOM fractions upon sorption might differ as well. 2. Materials and methods Elliot Soil Humic Acid (ESHA), Pahokee Peat Humic Acid (PPHA) and Suwannee River Humic Acid (SRHA) were used as received from IHSS. Aluminum oxide (Al2O3) was suspended in 0.1M KCl. Sorption was studied at pH 7.0 in duplicate batch experiments for several HA/Al2O3 ratios. For the suspension (mineral + sorbed HA, plus dissolved HA), the filtrate (0.45μm) and the HA stock solution, the electron donating and accepting capacities (EDC and EAC) were determined following established procedures.4 3. Results All studied HA-Al2O3 systems showed similar behavior with regard to changes in redox properties. There was a significant increase in the EDC of the whole suspension compared to the stock solutions and the non-sorbed HA in the filtrate (up to 300% for PPHA). This effect was more pronounced with increasing amounts of sorbed HA in the suspension. Although ESHA had the highest sorption capacity on Al2O3 (~ 6 times higher than PPHA & SRHA), it showed the smallest changes in redox

  3. Global gene expression analysis of Saccharomyces cerevisiae grown under redox potential-controlled very-high-gravity conditions.

    PubMed

    Liu, Chen-Guang; Lin, Yen-Han; Bai, Feng-Wu

    2013-11-01

    Redox potential (ORP) plays a pivotal role in yeast viability and ethanol production during very-high-gravity (VHG) ethanol fermentation. In order to identify the correlation between redox potential profiles and gene expression patterns, global gene expression of Saccharomyces cerevisiae was investigated. Results indicated that significant changes in gene expression occurred at the periods of 0 - 6 h and 30 - 36 h, respectively. Changes noted in the period of 0 - 6 h were mainly related to carbohydrate metabolism. In contrast, gene expression variation at 30 - 36 h could be attributed primarily to stress response. Although CDC19 was down-regulated, expression of PYK2, PDC6 and ADH2 correlated inversely with ORP. Meanwhile, expression of GPD1 decreased due to the depletion of dissolved oxygen in the fermentation broth, but expression of GPD2 correlated with ORP. Transcription of genes encoding heat shock proteins was characterized by uphill, downhill, valley and plateau expression profiles, accordingly to specific function in stress response. These results highlight the role of ORP in modulating yeast physiology and metabolism under VHG conditions.

  4. Release of arsenic from a Haplic Gleysol under controlled redox conditions

    NASA Astrophysics Data System (ADS)

    Mansfeldt, T.; Overesch, M.

    2009-04-01

    The redox potential (EH) governs the solubility of trace elements in soils, mainly by the reductive dissolution of iron (hydr)oxides, which are important adsorbents. Similarly the species distribution of some trace elments in soils strongly depends on EH. Species distribution in turn affects the solubility and toxicity of trace elements. Hence, the EH is a master variable for the behaviour of trace elements in soil. Arsenic is such a redox-sensitive trace element. In the lowlands of southern Münsterland, North Rhine-Westphalia (Germany), various Gleysols under grassland recently have been found to be naturally enriched with arsenic. Field measurements at such a site revealed high variations in soil EH during the course of the time with a range of 900 mV. We initiated a laboratory study to determine the effects of different redox regimes (oxidizing, moderately reducing and reducing soil conditions) both on the solubility and speciation of As. The batch study was performed using the AhBg, Bg1 and Bg2 horizons from a Haplic Gleysol. Total arsenic contents increased with increasing soil depth from 121, 613 to 1.004 mg/kg As. Fixed redox potentials in stirred soil suspensions were achieved by flushing closed glass microcosms with either N2 or air during 40 days. Redox potential and pH of the suspension were continuously recorded. In intervals of 48 hours, subsamples of 40 ml were taken from a sampling port by a tube connected to a vacuum filtration device (0.45 µm). The filtrates were analyzed for DOC, TIC, nitrate, sulfate, phosphate, and total Mn, Fe and total As. Also, Fe2+ and As(III) were determined. First results indicate that lowering EH from 450 to -100 mV (pH 7) results in a significant increase of pH and concentrations of DOC, TIC, total Fe, Fe2+, Mn, and total As in solution. Significant concentrations of As(III) could be observed at EH values below 100 mV.

  5. Mosses influence phosphorus cycling in rich fens by driving redox conditions in shallow soils.

    PubMed

    Crowley, Katherine F; Bedford, Barbara L

    2011-09-01

    Mosses play an integral role in the hydrologic regimes of ecosystems where they cover the soil surface, and thus affect biogeochemical cycling of elements influenced by soil oxidation-reduction (redox) reactions, including the plant growth-limiting nutrients, nitrogen and phosphorus (P). In rich fens where P often limits plant growth, we hypothesized that feedbacks between mosses and redox conditions would determine P availability to shallow-rooted forb species that constitute much of these wetlands' unusually high plant species diversity. In a moss removal experiment in three fens, forb tissue P and microbial P were greater while anion exchange membrane (AEM) resin P was lower where mosses occurred than where they were removed, suggesting both higher availability and greater demand for P in moss-covered soils. Coupled physicochemical and biological mechanisms drove moss effects on P cycling, ultimately through effects on soil oxygenation or reduction: higher redox potential underlying mosses corresponded to greater microbial activity, phosphatase enzyme activity, and colonization by arbuscular mycorrhizal fungi (AMF), all of which can promote greater P availability to plants. These more oxidized soils stimulated: (1) greater microbial activity and root vigor; (2) correspondingly greater P demand via microbial uptake, forb uptake, and iron (Fe)-P reactions; and (3) greater P supply through soil and root phosphatase activity and AMF colonization. This work demonstrates that mosses improve vascular plant P acquisition by alleviating stresses caused by reducing conditions that would otherwise prevail in shallow underlying soils, thus providing a mechanism by which mosses facilitate plant species diversity in rich fens.

  6. Impact of hydroquinone used as a redox effector model on potential denitrification, microbial activity and redox condition of a cultivable soil.

    PubMed

    Perotti, Elda B R

    2015-01-01

    In this microcosm study, we analyzed the effect produced by hydroquinone on the expression of soil biological denitrification, in relation to the redox state of the soil, both in terms of intensity factor (Eh') and capacity factor (amount of oxidized or reduced compounds). The supplementation of an Argiudoll soil with hydroquinone decreased the soil apparent reduction potential (Eh') and soil dehydrogenase activity (formazan production from tetrazolium chloride reduction; redox capacity factor), the relationship between both factors being highly significative, r=0.99 (p<0.001). The bacterial population (measured by colony forming units) increased, and the production of N2O was greater (p<0.001) at 200 and 400μg/g dry soil doses. Furthermore, there was an inverse relationship between soil dehydrogenase activity and the number of bacteria (r=-0.82; p<0.05), increased denitrification activity and changes in the CO2/N2O ratio value. These results suggest that hydroquinone at supplemented doses modified the soil redox state and the functional structure of the microbial population. Acetate supplementation on soil with hydroquinone, to ensure the availability of an energy source for microbial development, confirmed the tendency of the results obtained with the supplementation of hydroquinone alone. The differences observed at increased doses of hydroquinone might be explained by differences on the hydroquinone redox species between treatments.

  7. Understanding redox conditions in the mid-Cretaceous Baffin Bay - a combined model-data approach

    NASA Astrophysics Data System (ADS)

    Lenniger, M.; Bjerrum, C. J.; Pedersen, G. K.; Azhar, M. Al

    2012-04-01

    Cretaceous events of widespread oceanic anoxia are characterized by perturbations in the global carbon cycle and accompanied increased carbon burial in marine sediments. Their occurrence is thought to have been linked to an interaction of greenhouse conditions, palaeogeography and increased nutrient discharge, which led to enhanced surface productivity and improved conditions for carbon preservation. One of the most widespread oceanic anoxic events is the Cenomanian-Turonian boundary event (OAE2). Evidence for anoxic or even euxinic conditions during OAE2 is mainly observed in the Western Interior Seaway and at low- and mid-palaeolatitudes in the proto-Atlantic. However, our understanding of the distribution and characteristics of OAE2 in high palaeolatitudes is still incomplete. In order to investigate the palaeoceanographic conditions in high palaeolatitudes in the mid-Cretaceous, we studied the Umiivik-I stratigraphic core from West Greenland using an integrated approach combining sedimentology and geochemistry with three dimensional regional ocean modeling. Sedimentary rocks from the Umiivik-I core show relative high TOC contents with values up to about 5 %. The organic carbon-to-pyrite sulphur ratio (C/S-ratio) indicates that the organic matter (OM) is predominantly of normal marine origin. Increased C/S-ratios are caused by intermittent input of terrestrial OM and indicate fluctuations in runoff. Redox sensitive trace metal concentrations (e.g. Mo, U and V) were measured in bulk rock samples in order to reconstruct the redox conditions during the deposition. The concentrations of the trace metals (TM) are relatively low and in the same range as reported for average shale reference material. The low TM concentrations in the Umiivik-I core are indicative of deposition under oxygenated bottom water conditions in contrast to usually observed high TM concentrations in anoxic depositional environments during the mid-Cretaceous. These findings are exceptional due to

  8. Evaluation of redox indicators for determining sulfate-reducing and dechlorinating conditions.

    PubMed

    Jones, Brian D; Ingle, James D

    2005-11-01

    An in situ methodology based on covalently bonded redox indicators has been developed for determining when sulfate-reducing conditions exist in environmental samples. Three immobilized redox indicators [thionine (Thi, formal potential at pH 7 (E(0')7) equals 52 mV), cresyl violet (CV, E(0')7 = -81 mV), and phenosafranine (PSaf, E(0')7 = -267 mV)] were tested for their response to sulfide in synthetic solutions and under sulfate-reducing conditions in wastewater slurries. The byproduct of the sulfate-reducing process, sulfide, was found to couple well to CV in the concentration range of 1-100 microM total sulfide ([S(-II)]) and the pH range of 6-8. Thi, the indicator with the highest formal potential, reacts rapidly with sulfide at levels well below 1 microM while PSaf, the indicator with the lowest formal potential, does not couple to sulfide at levels in excess of 100 microM [S(-II)]. The degree of reduction of the indicators (i.e., the fraction of cresyl violet oxidized) in contact with a given level of sulfide can be modeled qualitatively with an equilibrium expression for [S(-II)]-indicator based on the Nernst equation assuming that rhombic sulfur is the product of sulfide oxidation. In a groundwater sample with dechlorinating microbes, reduction of Thi and partial reduction of CV correlated with dechlorination of TCE to cis-DCE.

  9. Cu/ZnO nanocatalysts in response to environmental conditions: surface morphology, electronic structure, redox state and CO2 activation.

    PubMed

    Martínez-Suárez, Luis; Frenzel, Johannes; Marx, Dominik

    2014-12-21

    Methanol synthesis is one of the landmarks of heterogeneous catalysis due to the great industrial significance of methanol as a clean liquid fuel and as a raw material for industry. Understanding in atomistic detail the properties of the underlying metal/oxide catalyst materials as a function of temperature and composition of the reactive gas phase is of utmost importance in order to eventually improve the production process. By performing extensive density functional theory based slab calculations in combination with a thermodynamic formalism we establish an atomistic understanding of gas phase-induced changes of surface morphology, redox properties and reactivity of ZnO supported Cu nanocatalysts. Extending our recent insights [Phys. Rev. Lett., 2013, 110, 086108], we explore surface stabilization mechanisms and site-dependent redox states of both catalyst components as well as the pronounced electronic charge transfer processes across the metal-support interface. Moreover, ab initio molecular dynamics simulations unveil the vital role played by dynamical shape fluctuations of the deposited Cu8 cluster. The pronounced structural flexibility of the metal nanoparticle is found to enhance CO2 activation over Cu8 at the elevated temperature conditions of the industrial methanol synthesis process, in addition to activation of CO2via electronic charge transfer from the ZnO support.

  10. Modeling the Time-dependent Changes in Electrical Conductivity of Basaltic Melts With Redox State

    NASA Astrophysics Data System (ADS)

    Pommier, A.; Gaillard, F.; Pichavant, M.

    2008-12-01

    The electrical conductivity σ is an efficient probe of mass transfer processes within silicate melts and magmas. Little attention has been given to the influence of redox state (fO2) on the melts conductivity. We present an experimental setup allowing electrical conductivity measurements for basaltic melts under variable fO2. We demonstrate a significant dependence of σ with fO2, allowing to characterize in situ the mechanisms and kinetics of redox changes in the melt. Experiments were conducted on basalts from Pu'u 'O'o, Hawaii, and Mt.Vesuvius, Italy. Measurements were performed cylindrical glass samples (OD: 6mm, ID: 1mm, L: 8mm) using an impedance spectrometer. Experiments were conducted in a 1atm vertical furnace, from 1200°C to 1400°C. Variable gas atmosphere (air, CO2 or CO-CO2 gas mixtures) were used, imposing ΔNNO from -1 to +7. Electrical conductivities were determined for the two melts at constant fO2, different T (constant fO2) and constant T, different fO2 (variable fO2) obtained by changing the gas composition. Isothermal reduction and oxidation cycles were performed. Glasses quenched from different T and fO2 conditions were analyzed by electron microprobe, the FeO concentration was determined by wet chemistry. In constant fO2 experiments, a small but detectable effect of fO2 on σ is evidenced. At 1300°C, the difference in the Kilauea sample conductivity between reduced (ΔNNO=-1) and oxidized (ΔNNO=+7) fO2 is <1(ohm.m)-1, the sample being more conductive when reduced. The temperature dependence of σ was fitted using Arrhenian equations, the activation energy Ea being 100kJ/mol. Sodium was identified as the main charge carrier in the melts. The fO2-effect on σ can thus be attributed to the influence of the Fe2+/Fe3+ ratio on sodium mobility. The fO2-dependence of σ was included in the model of Pommier et al.(2008), allowing the conductivity of natural melts to be calculated as a function of T, P, H2O, and fO2. Variable fO2 experiments

  11. Instability of bottom-water redox conditions during accumulation of Quaternary sediment in the Japan Sea

    USGS Publications Warehouse

    Piper, D.Z.; Isaacs, C.M.

    1996-01-01

    The concentrations of Cd, Cr, Cu, Mo, Ni, Sb, U, V, and Zn were measured in early Quaternary sediment (1.32 to 1.08 Ma) from the Oki Ridge in the Japan Sea. The elements were partitioned between a detrital fraction, composed of terrigenous and volcaniclastic aluminosilicate debris, and a marine fraction, composed of biogenic and hydrogenous debris derived from seawater. The most important factors controlling minor-element accumulation rates in the marine fraction were (1) primary productivity in the photic zone, which largely controlled the flux of particulate organic-matter-bound minor elements settling through the water column and onto the seafloor, and (2) bottom-water redox, which determined the suite of elements that accumulated directly from seawater. This marine fraction of minor elements on Oki Ridge recorded six periods of high minor-element abundance. Assuming a constant bulk sediment accumulation rate, each period lasted roughly 5,000 to 10,000 years with a 41,000-year cycle. Accumulation rates of individual elements such as Cd, Mo, and U suggest sulfate-reducing conditions were established in the bottom water during the 10,000-year periods; accumulation rates of Cr and V during the intervening periods are indicative of less reducing, denitrifying conditions. Interelement ratios, for example, Cu:Mo, V:Cr, and Sb:Mo, further reflect bottom-water instability, such that bottom-water redox actually varied from sulfate reducing to denitrifying during the periods of highest minor-element accumulation rates; it varied from denitrifying to oxidizing during the intervening periods. Sediment lithology supports these interpretations of the minor-element distributions; the sediment is finely laminated for several of the periods represented by Cd, Mo, and U maxima and weakly laminated to bioturbated for the intervening periods. The geochemistry of this sediment demonstrates the unambiguous signal of Mo, principally, but of several other minor elements as well in

  12. Microcosm experiments to control anaerobic redox conditions when studying the fate of organic micropollutants in aquifer material

    NASA Astrophysics Data System (ADS)

    Barbieri, Manuela; Carrera, Jesús; Sanchez-Vila, Xavier; Ayora, Carlos; Cama, Jordi; Köck-Schulmeyer, Marianne; López de Alda, Miren; Barceló, Damià; Tobella Brunet, Joana; Hernández García, Marta

    2011-11-01

    The natural processes occurring in subsurface environments have proven to effectively remove a number of organic pollutants from water. The predominant redox conditions revealed to be one of the controlling factors. However, in the case of organic micropollutants the knowledge on this potential redox-dependent behavior is still limited. Motivated by managed aquifer recharge practices microcosm experiments involving aquifer material, settings potentially feasible in field applications, and organic micropollutants at environmental concentrations were carried out. Different anaerobic redox conditions were promoted and sustained in each set of microcosms by adding adequate quantities of electron donors and acceptors. Whereas denitrification and sulfate-reducing conditions are easily achieved and maintained, Fe- and Mn-reduction are strongly constrained by the slower dissolution of the solid phases commonly present in aquifers. The thorough description and numerical modeling of the evolution of the experiments, including major and trace solutes and dissolution/precipitation of solid phases, have been proven necessary to the understanding of the processes and closing the mass balance. As an example of micropollutant results, the ubiquitous beta-blocker atenolol is completely removed in the experiments, the removal occurring faster under more advanced redox conditions. This suggests that aquifers constitute a potentially efficient alternative water treatment for atenolol, especially if adequate redox conditions are promoted during recharge and long enough residence times are ensured.

  13. Organization of biogeochemical nitrogen pathways with switch-like adjustment in fluctuating soil redox conditions

    PubMed Central

    Lamba, Sanjay; Bera, Soumen; Rashid, Mubasher; Medvinsky, Alexander B.; Acquisti, Claudia; Li, Bai-Lian

    2017-01-01

    Nitrogen is cycled throughout ecosystems by a suite of biogeochemical processes. The high complexity of the nitrogen cycle resides in an intricate interplay between reversible biochemical pathways alternatively and specifically activated in response to diverse environmental cues. Despite aggressive research, how the fundamental nitrogen biochemical processes are assembled and maintained in fluctuating soil redox conditions remains elusive. Here, we address this question using a kinetic modelling approach coupled with dynamical systems theory and microbial genomics. We show that alternative biochemical pathways play a key role in keeping nitrogen conversion and conservation properties invariant in fluctuating environments. Our results indicate that the biochemical network holds inherent adaptive capacity to stabilize ammonium and nitrate availability, and that the bistability in the formation of ammonium is linked to the transient upregulation of the amo-hao mediated nitrification pathway. The bistability is maintained by a pair of complementary subsystems acting as either source or sink type systems in response to soil redox fluctuations. It is further shown how elevated anthropogenic pressure has the potential to break down the stability of the system, altering substantially ammonium and nitrate availability in the soil, with dramatic effects on biodiversity. PMID:28280580

  14. Redox interactions between Saccharomyces cerevisiae and Saccharomyces uvarum in mixed culture under enological conditions.

    PubMed

    Cheraiti, Naoufel; Guezenec, Stéphane; Salmon, Jean-Michel

    2005-01-01

    Wine yeast starters that contain a mixture of different industrial yeasts with various properties may soon be introduced to the market. The mechanisms underlying the interactions between the different strains in the starter during alcoholic fermentation have never been investigated. We identified and investigated some of these interactions in a mixed culture containing two yeast strains grown under enological conditions. The inoculum contained the same amount (each) of a strain of Saccharomyces cerevisiae and a natural hybrid strain of S. cerevisiae and Saccharomyces uvarum. We identified interactions that affected biomass, by-product formation, and fermentation kinetics, and compared the redox ratios of monocultures of each strain with that of the mixed culture. The redox status of the mixed culture differed from that of the two monocultures, showing that the interactions between the yeast strains involved the diffusion of metabolite(s) within the mixed culture. Since acetaldehyde is a potential effector of fermentation, we investigated the kinetics of acetaldehyde production by the different cultures. The S. cerevisiae-S. uvarum hybrid strain produced large amounts of acetaldehyde for which the S. cerevisiae strain acted as a receiving strain in the mixed culture. Since yeast response to acetaldehyde involves the same mechanisms that participate in the response to other forms of stress, the acetaldehyde exchange between the two strains could play an important role in inhibiting some yeast strains and allowing the growth of others. Such interactions could be of particular importance in understanding the ecology of the colonization of complex fermentation media by S. cerevisiae.

  15. Ageing-induced changes in the redox status of peripheral motor nerves imply an effect on redox signalling rather than oxidative damage

    PubMed Central

    McDonagh, Brian; Scullion, Siobhan M.; Vasilaki, Aphrodite; Pollock, Natalie; McArdle, Anne; Jackson, Malcolm J.

    2016-01-01

    Ageing is associated with loss of skeletal muscle fibres, atrophy of the remaining fibres and weakness. These changes in muscle are accompanied by disruption of motor neurons and neuromuscular junctions although the direct relationship between the nerve and muscle degeneration is not understood. Oxidative changes have been implicated in the mechanisms leading to age-related loss of muscle mass and in degeneration of the central nervous system, but little is known about age-related changes in oxidation in specific peripheral nerves that supply muscles that are affected by ageing. We have therefore examined the sciatic nerve of old mice at an age when loss of tibialis anterior muscle mass and function is apparent. Sciatic nerve from old mice did not show a gross increase in oxidative damage, but electron paramagnetic resonance (EPR) studies indicated an increase in the activity of superoxide and/or peroxynitrite in the nerves of old mice at rest that was further exacerbated by electrical stimulation of the nerve to activate muscle contractions. Proteomic analyses indicated that specific redox-sensitive proteins are increased in content in the nerves of old mice that may reflect an adaptation to regulate the increased superoxide/peroxynitrite and maintain redox homoeostasis. Analysis of redox active cysteines showed some increase in reversible oxidation in specific proteins in nerves of old mice, but this was not universally seen across all redox-active cysteines. Detailed analysis of the redox-active cysteine in one protein in the nerve of old mice that is key to redox signalling (Peroxiredoxin 6, Cys 47) showed a minor increase in reversible oxidation that would be compatible with a change in its redox signalling function. In conclusion, the data presented indicate that sciatic nerve from old mice does not show a gross increase in oxidative damage similar to that seen in the TA and other muscles that it innervates. Our results indicate an adaptation to increased

  16. Ageing-induced changes in the redox status of peripheral motor nerves imply an effect on redox signalling rather than oxidative damage.

    PubMed

    McDonagh, Brian; Scullion, Siobhan M; Vasilaki, Aphrodite; Pollock, Natalie; McArdle, Anne; Jackson, Malcolm J

    2016-05-01

    Ageing is associated with loss of skeletal muscle fibres, atrophy of the remaining fibres and weakness. These changes in muscle are accompanied by disruption of motor neurons and neuromuscular junctions although the direct relationship between the nerve and muscle degeneration is not understood. Oxidative changes have been implicated in the mechanisms leading to age-related loss of muscle mass and in degeneration of the central nervous system, but little is known about age-related changes in oxidation in specific peripheral nerves that supply muscles that are affected by ageing. We have therefore examined the sciatic nerve of old mice at an age when loss of tibialis anterior muscle mass and function is apparent. Sciatic nerve from old mice did not show a gross increase in oxidative damage, but electron paramagnetic resonance (EPR) studies indicated an increase in the activity of superoxide and/or peroxynitrite in the nerves of old mice at rest that was further exacerbated by electrical stimulation of the nerve to activate muscle contractions. Proteomic analyses indicated that specific redox-sensitive proteins are increased in content in the nerves of old mice that may reflect an adaptation to regulate the increased superoxide/peroxynitrite and maintain redox homoeostasis. Analysis of redox active cysteines showed some increase in reversible oxidation in specific proteins in nerves of old mice, but this was not universally seen across all redox-active cysteines. Detailed analysis of the redox-active cysteine in one protein in the nerve of old mice that is key to redox signalling (Peroxiredoxin 6, Cys 47) showed a minor increase in reversible oxidation that would be compatible with a change in its redox signalling function. In conclusion, the data presented indicate that sciatic nerve from old mice does not show a gross increase in oxidative damage similar to that seen in the TA and other muscles that it innervates. Our results indicate an adaptation to increased

  17. Macroform and microform-induced change in redox-sensitive chemistries of river channel surface sediments

    NASA Astrophysics Data System (ADS)

    Byrne, P.; Zhang, H.; Heathwaite, A. L.; Binley, A.; Ullah, S.; Kaeser, D.; Heppell, C. M.; Lansdown, K.; Trimmer, M.

    2012-04-01

    In-stream geomorphological features such as riffle-pool sequences (macroforms) can produce steep hydraulic gradients which induce flow in and out of the riverbed - hyporheic exchange flow (HEF). The acceleration of flow over channel obstacles such as large cobbles and boulders (microforms) can create variation in surface-subsurface pressure gradients and generation of HEF. HEF in shallow surface sediments affect the transformation of redox-sensitive chemical forms and, therefore, the attenuation or release of nutrients in river systems. Here, we examine the relationship between stream geomorphological environment (microform and macroform) and concentration profiles of redox-sensitive species (nitrate, sulphate, iron, manganese) in shallow (15cm) subsurface sediments. In-situ passive samplers (diffusive equilibrium in thin films - DET) are used to obtain biogeochemical data from armoured environments at fine scale (cm) depth resolution where there is strong upwelling. The probes were deployed in a 50m reach of the River Eden, Cumbria, UK, during baseflow conditions. The experimental setup allowed for the assessment of differences in redox-sensitive chemistries between a riffle and pool environment and between smooth and rough bed surfaces in the pool. The passive sensing basis of the DET methodology provided a means for investigating how HEF systems generated at two different geomorphological scales influence the concentration and spatial patterns of redox-sensitive species. DET's capability of measuring at high spatial resolution allowed the extent of hyporheic mixing to be targeted, even though it is often limited to the top few centimetres of sediment.

  18. Chromium Redox Equilibria in Fluids and Minerals under Hydrothermal and Subduction-zone Conditions

    NASA Astrophysics Data System (ADS)

    Hao, J.; Sverjensky, D. A.; Hazen, R. M.

    2015-12-01

    Chromium mobility and isotopic variations have been reported from a variety of high-temperature environments from hydrothermal to diamond-forming at elevated temperatures and pressures [1, 2, 3]. In addition, experiments under upper mantle conditions reported Cr-rich fluids in equilibrium with chromium oxide (Cr3+2O3) [4]. These studies suggest the need for theoretical models of the aqueous speciation of chromium in fluids and the stabilities of Cr minerals under deep crustal and upper mantle conditions. We estimated the thermodynamic properties of aqueous Cr2+, Cr3+, HCrO4-, CrO42-, and Cr2O72- using published data [5, 6] and the Deep Earth Water Model [7] to predict the different oxidation states of aqueous Cr to 1,000 °C and 5.0 GPa. We show that Cr(II) becomes the major redox state of Cr in hydrothermal fluids at 100 to 400 °C, with log fO2,g at magnetite/hematite over a wide range of pH values. In subduction zones, with log fO2,g at QFM to QFM - 2, a range of Cr redox states (II, III, and VI) may exist at 600 °C and 5 GPa depending on the pH. However, at higher temperatures (1000 °C), aqueous Cr(III) disappears and Cr(II) is favored relative to Cr(VI), again depending on the pH. Our predicted stability of Cr(II) in aqueous fluids at high temperatures suggests new mechanisms for redox/pH dependent Cr isotopic fractionation. We also estimated the thermodynamic properties of Cr(II)- and Cr(III)-garnets with the Sverjensky-Molling equation [8] to investigate the stability of Cr-garnet-fluid equilibria at elevated pressures and temperatures. References: [1] Schoenberg et al., 2008, Chem Geol 249, 294-306; [2] Farkaš et al., 2013, GCA 123, 74-92; [3] Stachel & Harris, 2008, Ore Geol. Rev, 34, 5-32; [4] Klein-BenDavid et al., 2011, Lithos 125, 122-130; [5] Ball & Nordstrom, 1998, J Chem Eng Data 43, 895-918; [6] Johnson & Nelson, 2012, Inorg Chem 51, 6116-6128; [7] Sverjensky et al. 2014, GCA 129, 125-145; [8] Sverjensky & Molling, 1992, Nature 356, 231-234.

  19. A system for conducting igneous petrology experiments under controlled redox conditions in reduced gravity

    NASA Technical Reports Server (NTRS)

    Williams, Richard J.

    1987-01-01

    The Space Shuttle and the planned Space Station will permit experimentation under conditions of reduced gravitational acceleration offering experimental petrologists the opportunity to study crystal growth, element distribution, and phase chemistry. In particular the confounding effects of macro and micro scale buoyancy-induced convection and crystal settling or flotation can be greatly reduced over those observed in experiments in the terrestrial laboratory. Also, for experiments in which detailed replication of the environment is important, the access to reduced gravity will permit a more complete simulation of processes that may have occurred on asteroids or in free space. A technique that was developed to control, measure, and manipulate oxygen fugacities with small quantities of gas which are recirculated over the sample. This system could be adaptable to reduced gravity space experiments requiring redox control.

  20. A system for conducting igneous petrology experiments under controlled redox conditions in reduced gravity

    NASA Technical Reports Server (NTRS)

    Williams, R. J.

    1986-01-01

    The Space Shuttle and the planned Space Station will permit experimentation under conditions of reduced gravitational acceleration offering experimental petrologists the opportunity to study crystal growth, element distribution, and phase chemistry. In particular the confounding effects of macro and micro scale buoyancy-induced convection and crystal settling or floatation can be greatly reduced over those observed in experiments in the terrestrial laboratory. Also, for experiments in which detailed replication of the environment is important, the access to reduced gravity will permit a more complete simulation of processes that may have occurred on asteroids or in free space. A technique that was developed to control, measure, and manipulate oxygen fugacites with small quantities of gas which are recirculated over the sample is described. This system should be adaptable to reduced gravity space experiments requiring redox control. Experiments done conventionally and those done using this technique yield identical results done in a 1-g field.

  1. Modeling microbial degradation of propylene glycol: electron acceptors and their related redox conditions

    NASA Astrophysics Data System (ADS)

    Dathe, Annette; Fernandez, Perrine M.; Bloem, Esther; Meeussen, Johannes C. L.; French, Helen K.

    2014-05-01

    De-icing chemicals are applied in large amounts at airports during winter conditions to keep the runways and aircrafts ice-free. The commonly used propylene glycol (PG) is easily degradable by local microbial communities, but anoxic zones develop and soluble Fe+2 and Mn+2 ions can reach the groundwater. To enhance microbial induced remediation and reduce the release of iron and manganese, it was proposed to add NO3- together with PG. However, experiments conducted in the unsaturated zone at Gardermoen airport, Norway, revealed that manganese and iron were preferred over NO3- as electron acceptor [1]. The objectives of this study are to quantify mechanisms which control the order of reduction processes in an unsaturated sandy soil, and to test whether measured redox potentials can help to determine underlying biogeochemical reactions. We are modelling the microbial degradation of PG using Monod kinetics described for the chemical equilibrium tool ORCHESTRA [2], following an approach of [1]. The model is calibrated against gas measurements of CO2, NO2 and N2 released from batch experiments performed under controlled conditions. Fe+2 and Mn+2 were measured for the start and end of the experiment, as well as bulk resistivity, pH and electrical conductivity. With the calibrated model we are working towards a tool to quantify microbial induced redox reactions under different soil water saturations to account for seasonal water fluxes especially during snowmelt. [1] Schotanus, D., Meeussen, J.C.L., Lissner, H., van der Ploeg, M.J., Wehrer, M., Totsche, K.U., van der Zee, S.E.A.T.M., 2013. Transport and degradation of propylene glycol in the vadose zone: model development and sensitivity analysis. Environ Sci Pollut Res Int. [2] Meeussen, J.C.L., 2003. ORCHESTRA: An Object-Oriented Framework for Implementing Chemical Equilibrium Models. Environ. Sci. Technol. 37, 1175-1182.

  2. Reconstructing the redox conditions of Paleoproterozoic oceans: Insights from the Zaonega Formation

    NASA Astrophysics Data System (ADS)

    Patel, Neel; Zerkle, Aubrey; Izon, Gareth; Romashkin, Alexander; Rychanchik, Dmtriy; Upraus, Kärt; Kirsimäe, Kalle; Wing, Boswell; Lepland, Aivo

    2015-04-01

    The Paleoproterozoic is marked by profound changes in global tectonics, climate and biogeochemical cycling of redox sensitive elements. Determining the redox state of marine environments at this point in Earth's history is fundamental in understanding the connections between the geosphere and biosphere, including possible microbially-assisted phosphogenesis. One hypothesis suggests that oxidative weathering following Earth's first significant rise in atmospheric oxygen, resulted in an increased supply of sulfate and phosphate to the oceans, culminating in the first significant phosphorite deposits some 300-400 Ma later (Lepland et al., 2013). Thus Paleoproterozoic ocean structure has been envisaged as stratified, through mildly oxygenated shallow water and anoxic deep water, with temporally and spatially variable phases of euxinia possibly linked to transient changes in the size of the seawater sulfate reservoir (Scott et al., 2014). New cores obtained from the upper part of the 2 Ga Zaonega Formation in the Onega Basin of Karelia, NW Russia, have recovered a variety of organic-rich mudstones and carbonate rocks, containing several discrete mm-cm scale P-rich beds that may represent seep or hydrothermally-influenced depositional settings (Lepland et al., 2013). Here we present new Fe-speciation data and pyrite derived S-isotope data spanning one of these new cores in order to: i) evaluate the redox state of the water column, determining the extent of water column euxinia, and ii) assess the potential influence of S-cycling on phosphogenesis. Preliminary Fe extractions show that total Fe is broadly dictated by lithology, but generally lower in samples where the P-rich intervals occur, possibly supporting extensive sulfate reduction and the formation of a euxinic water column. Further S-isotope analyses on associated pyrites will determine the extent to which additional biogeochemical S-cycling (e.g., sulfide oxidation) could also have contributed to the P

  3. Stability of uranium incorporated into Fe (hydr)oxides under fluctuating redox conditions.

    PubMed

    Stewart, Brandy D; Nico, Peter S; Fendorf, Scott

    2009-07-01

    Reaction pathways resulting in uranium-bearing solids that are stable (i.e., having limited solubility) under aerobic and anaerobic conditions will limit dissolved concentrations and migration of this toxin. Here, we examine the sorption mechanism and propensity for release of uranium reacted with Fe (hydr)oxides under cyclic oxidizing and reducing conditions. Upon reaction of ferrihydrite with Fe(II) under conditions where aqueous Ca-UO2-CO3 species predominate (3 mM Ca and 3.8 mM total CO3), dissolved uranium concentrations decrease from 0.16 mM to below detection limit (BDL) after 5-15 d, depending on the Fe(II) concentration. In systems undergoing 3 successive redox cycles (14 d of reduction, followed by 5 d of oxidation) and a pulsed decrease to 0.15 mM total CO3, dissolved uranium concentrations varied depending on the Fe(II) concentration during the initial and subsequent reduction phases. U concentrations resulting during the oxic "rebound" varied inversely with the Fe(II) concentration during the reduction cycle. Uranium removed from solution remains in the oxidized form and is found adsorbed onto and incorporated into the structure of newly formed goethite and magnetite. Our results reveal that the fate of uranium is dependent on anaerobic/ aerobic conditions, aqueous uranium speciation, and the fate of iron.

  4. Stability of uranium incorporated into Fe(hydr)oxides under fluctuating redox conditions

    SciTech Connect

    Stewart, B.D.; Nico, P.S.; Fendorf, S.

    2009-04-01

    Reaction pathways resulting in uranium bearing solids that are stable (i.e., having limited solubility) under both aerobic and anaerobic conditions will limit dissolved concentrations and migration of this toxin. Here we examine the sorption mechanism and propensity for release of uranium reacted with Fe (hydr)oxides under cyclic oxidizing and reducing conditions. Upon reaction of ferrihydrite with Fe(II) under conditions where aqueous Ca-UO{sub 2}-CO{sub 3} species predominate (3 mM Ca and 3.8 mM CO{sub 3}-total), dissolved uranium concentrations decrease from 0.16 mM to below detection limit (BDL) after 5 to 15 d, depending on the Fe(II) concentration. In systems undergoing 3 successive redox cycles (15 d of reduction followed by 5 d of oxidation) and a pulsed decrease to 0.15 mM CO{sub 3}-total, dissolved uranium concentrations varied depending on the Fe(II) concentration during the initial and subsequent reduction phases - U concentrations resulting during the oxic 'rebound' varied inversely with the Fe(II) concentration during the reduction cycle. Uranium removed from solution remains in the oxidized form and is found both adsorbed on and incorporated into the structure of newly formed goethite and magnetite. Our 15 results reveal that the fate of uranium is dependent on anaerobic/aerobic conditions, aqueous uranium speciation, and the fate of iron.

  5. Amendment of biochar reduces the release of toxic elements under dynamic redox conditions in a contaminated floodplain soil.

    PubMed

    Rinklebe, Jörg; Shaheen, Sabry M; Frohne, Tina

    2016-01-01

    Biochar (BC) can be used to remediate soils contaminated with potential toxic elements (PTEs). However, the efficiency of BC to immobilize PTEs in highly contaminated floodplain soils under dynamic redox conditions has not been studied up to date. Thus, we have (i) quantified the impact of pre-definite redox conditions on the release dynamics of dissolved aluminum (Al), arsenic (As), cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) in a highly contaminated soil (CS) (non-treated) and in the same soil treated with 10 g kg(-1) biochar based material (CS+BC), and (ii) assessed the efficacy of the material to reduce the concentrations of PTEs in soil solution under dynamic redox conditions using an automated biogeochemical microcosm apparatus. The impact of redox potential (EH), pH, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), iron (Fe), manganese (Mn), and sulfate (SO4(2-)) on dynamics of PTEs was also determined. The EH was lowered to +68 mV and afterwards increased stepwise to +535 mV. Significant negative correlation between EH and pH in CS and CS+BC was detected. The systematic increase of EH along with decrease of pH favors the mobilization of PTEs in CS and CS+BC. The material addition seems to have little effect on redox processes because pattern of EH/pH and release dynamics of PTEs was basically similar in CS and CS+BC. However, concentrations of dissolved PTEs were considerably lower in CS+BC than in CS which demonstrates that BC is able to decrease concentrations of dissolved PTEs even under dynamic redox conditions.

  6. Redox conditions and the efficiency of chlorinated ethene biodegradation: Laboratory studies

    USGS Publications Warehouse

    Bradley, P.M.; Chapelle, F.H.

    2000-01-01

    The potential for biodegradation of highly reduced groundwater contaminants is greatest under aerobic conditions and least under CO2-reducing (methanogenic) conditions. Laboratory studies conducted using [1,2-14C] vinyl chloride (VC) indicate the same pattern applies to the anaerobic oxidation of relatively reduced chloroethylenes. Recent studies, showing that CH4 can be a significant product of microbial degradation of VC under methanogenic conditions, clarified mechanisms underlying anaerobic VC mineralization and emphasized the redox dependence of this process. A microcosm study conducted with stream bed sediments demonstrated rapid degradation of [1,2-14C] VC and simultaneous production of 14CO2 and 14CH4. The results of acetate mineralization studies indicated that these sediments contained active acetotrophic methanogens. VC degradation involved an initial transformation to acetate via oxidative acetogenesis followed by acetotrophic methanogenesis to yield CO2 and CH4 as final products. Based on these recent results, a conceptual model for anaerobic microbial degradation of VC to non-chlorinated products can be proposed.

  7. Manganese oxide-coated redox bars as an indicator for reducing soil conditions

    NASA Astrophysics Data System (ADS)

    Dorau, Kristof; Mansfeldt, Tim

    2014-05-01

    Field identification of reducing soil conditions is of concern not only for soil pedogenesis but also for nutrient and pollutant dynamics in soils. We manufactured manganese (Mn) oxide-coated polyvinyl chloride (PVC) bars and proved their suitability for identification of reducing soil conditions in both the laboratory and field. Birnessite (δ-MnO2) was synthesized according to a recently published method and was coated onto white PVC bars. We used microcosm devices with adjusted redox potentials (EH) to distinguish the onset and intensity of depletion patterns along the Mn oxide-coating and soil column experiments combined with field application to validate the enhanced removal of Mn against Fe oxide-coated bars under anaerobe soil conditions. Field application was performed at a site with shallow and strongly fluctuating water tables where water table depth and soil temperature were monitored. Three microcosm experiments adjusted to oxidizing (EH ~500 mV, pH 7), weakly reducing (EH ~175 mV, pH 7) and moderately reducing conditions (EH ~25 mV, pH 7) showed depending on the EH no, slight, or intense removal of the Mn oxide-coating, respectively. Moreover, the removal of Mn oxide (225 mm2 d-1) in soil column experiments exceeded the removal of Fe oxide (118 mm2 d-1). The enhanced removal of the Mn oxide-coating was also found under anaerobe conditions in field application. Consequently, identifying of reducing conditions in soils by Mn oxide-coated bars is possible. We recommend using this methodology for short-term monitoring, e.g. on weekly basis, since tri- and tetravalent Mn is the preferred electron acceptor compared with trivalent Fe.

  8. Oxidative damage and redox change in pea seeds treated with cadmium.

    PubMed

    Smiri, Moêz; Chaoui, Abdelilah; Rouhier, Nicolas; Gelhaye, Eric; Jacquot, Jean-Pierre; El Ferjani, Ezzedine

    2010-01-01

    Pea seeds (Pisum sativum L.) were germinated by soaking in distilled water or 5mM CdCl2 for 5 days. The relationships among Cd treatment, germination rate, embryonic axis growth, NAD(P)H levels and NAD(P)H oxidase activities in mitochondrial and peroxisomal fractions of cotyledons and embryonic axis were investigated. Heavy metal stress provoked a diminution in germination percent and embryonic axis growth, as compared to the control. A drastic disorder in reducing power was imposed after exposure to cadmium. Heavy metal caused a significant increase in the redox ratio of coenzymes. NADPH oxidase is considered to be oxidative stress-related enzymes. The NAD(P)H oxidase activities were strongly stimulated after Cd exposure. The changes in redox and oxidative properties are discussed in relation to the delay in seed germination and embryonic axis growth.

  9. Linked redox precipitation of sulfur and selenium under anaerobic conditions by sulfate-reducing bacterial biofilms.

    PubMed

    Hockin, Simon L; Gadd, Geoffrey M

    2003-12-01

    A biofilm-forming strain of sulfate-reducing bacteria (SRB), isolated from a naturally occurring mixed biofilm and identified by 16S rDNA analysis as a strain of Desulfomicrobium norvegicum, rapidly removed 200 micro M selenite from solution during growth on lactate and sulfate. Elemental selenium and elemental sulfur were precipitated outside SRB cells. Precipitation occurred by an abiotic reaction with bacterially generated sulfide. This appears to be a generalized ability among SRB, arising from dissimilatory sulfide biogenesis, and can take place under low redox conditions and in the dark. The reaction represents a new means for the deposition of elemental sulfur by SRB under such conditions. A combination of transmission electron microscopy, environmental scanning electron microscopy, and cryostage field emission scanning electron microscopy were used to reveal the hydrated nature of SRB biofilms and to investigate the location of deposited sulfur-selenium in relation to biofilm elements. When pregrown SRB biofilms were exposed to a selenite-containing medium, nanometer-sized selenium-sulfur granules were precipitated within the biofilm matrix. Selenite was therefore shown to pass through the biofilm matrix before reacting with bacterially generated sulfide. This constitutes an efficient method for the removal of toxic concentrations of selenite from solution. Implications for environmental cycling and the fate of sulfur and selenium are discussed, and a general model for the potential action of SRB in selenium transformations is presented.

  10. Tailoring partially reduced graphene oxide as redox mediator for enhanced biotransformation of iopromide under methanogenic and sulfate-reducing conditions.

    PubMed

    Toral-Sánchez, Eduardo; Rangel-Mendez, J Rene; Ascacio Valdés, Juan A; Aguilar, Cristóbal N; Cervantes, Francisco J

    2016-10-22

    This work reports the first successful application of graphene oxide (GO) and partially reduced GO (rGO) as redox mediator (RM) to increase the biotransformation of the recalcitrant iodinated contrast medium, iopromide (IOP). Results showed that GO-based materials promoted up to 5.5 and 2.8-fold faster biotransformation of IOP by anaerobic sludge under methanogenic and sulfate-reducing conditions, respectively. Correlation between the extent of reduction of GO and its redox-mediating capacity was demonstrated, which was reflected in faster removal and greater extent of biotransformation of IOP. Further analysis indicated that the biotransformation pathway of IOP involved multiple reactions including deiodination, decarboxylation, demethylation, dehydration and N-dealkylation. GO-based materials could be strategically tailored and integrated in biological treatment systems to effectively enhance the redox conversion of recalcitrant pollutants commonly found in wastewater treatment systems and industrial effluents.

  11. Redox-coupled structural changes of the catalytic a' domain of protein disulfide isomerase.

    PubMed

    Inagaki, Koya; Satoh, Tadashi; Yagi-Utsumi, Maho; Le Gulluche, Anne-Charlotte; Anzai, Takahiro; Uekusa, Yoshinori; Kamiya, Yukiko; Kato, Koichi

    2015-09-14

    Protein disulfide isomerase functions as a folding catalyst in the endoplasmic reticulum. Its b' and a' domains provide substrate-binding sites and undergo a redox-dependent domain rearrangement coupled to an open-closed structural change. Here we determined the first solution structure of the a' domain in its oxidized form and thereby demonstrate that oxidation of the a' domain induces significant conformational changes not only in the vicinity of the active site but also in the distal b'-interfacial segment. Based on these findings, we propose that this conformational transition triggers the domain segregation coupled with the exposure of the hydrophobic surface.

  12. Selective detection of the structural changes upon photoreactions of several redox cofactors in photosystem II by means of light-induced ATR-FTIR difference spectroscopy

    NASA Astrophysics Data System (ADS)

    Okubo, Tatsunori; Noguchi, Takumi

    2007-04-01

    Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was applied for the first time to detect the structural changes upon photoreactions of redox cofactors in photosystem II (PSII). The PSII-enriched membranes from spinach were adsorbed on the surface of a silicon prism, and FTIR measurements of various redox cofactors were performed for the same sample but under different conditions by exchanging buffers in a flow cell. Light-induced FTIR difference spectra upon redox reactions of the oxygen-evolving Mn cluster, the primary quinone electron acceptor Q A, the redox-active tyrosine Y D, the primary electron acceptor pheophytin, and the primary electron donor chlorophyll P680 were successively recorded in buffers including different redox reagents and inhibitors. All of these cofactors remained active in the PSII membranes on the silicon surface, and the resultant spectra were basically identical to those previously recorded by the conventional transmission method. These ATR-FTIR measurements enable accurate comparison between reactions of different active sites in a single PSII sample. The present results demonstrated that the ATR-FTIR spectroscopy is a useful technique for investigation of the reaction mechanism of PSII.

  13. Physical Training Status Determines Oxidative Stress and Redox Changes in Response to an Acute Aerobic Exercise

    PubMed Central

    Damirchi, Arsalan; Farjaminezhad, Manoochehr

    2016-01-01

    Objective. To assess the influence of different physical training status on exercise-induced oxidative stress and changes in cellular redox state. Methods. Thirty male subjects participated in this study and were assigned as well-trained (WT), moderately trained (MT), and untrained (UT) groups. The levels of cortisol, creatine kinase, plasma reduced glutathione to oxidized glutathione (GSH/GSSG), cysteine/cystine (Cys/CySS), and GSH/GSSG ratio in red blood cells (RBCs) were measured immediately and 10 and 30 min after exercise. Results. Following the exercise, plasma GSH/GSSG (p = 0.001) and Cys/CySS (p = 0.005) were significantly reduced in all groups. Reduction in plasma GSH/GSSG ratio in all groups induced a transient shift in redox balance towards a more oxidizing environment without difference between groups (p = 0.860), while RBCs GSH/GSSG showed significant reduction (p = 0.003) and elevation (p = 0.007) in UT and MT groups, respectively. The highest level of RBCs GSH/GSSG ratio was recorded in MT group, and the lowest one was recorded in the WT group. Conclusion. Long term regular exercise training with moderate intensity shifts redox balance towards more reducing environment, versus intensive exercise training leads to more oxidizing environment and consequently development of related diseases. PMID:27064342

  14. Redox conditions in the atmosphere and shallow-marine environments during the first Huronian deglaciation: Insights from Os isotopes and redox-sensitive elements

    NASA Astrophysics Data System (ADS)

    Goto, Kosuke T.; Sekine, Yasuhito; Suzuki, Katsuhiko; Tajika, Eiichi; Senda, Ryoko; Nozaki, Tatsuo; Tada, Ryuji; Goto, Kazuhisa; Yamamoto, Shinji; Maruoka, Teruyuki; Ohkouchi, Naohiko; Ogawa, Nanako O.

    2013-08-01

    The Paleoproterozoic (2.5-2.0 Ga) is one of the most important periods in Earth's history, and was characterized by a rise in atmospheric oxygen levels and repeated (at least three) severe glaciations (the Huronian glaciations). In this study, we investigate redox conditions in the atmosphere and in shallow-marine environments immediately after the first Huronian glaciation based on the isotopic composition of Os, and the abundance of redox-sensitive elements (Os, Re, and Mo) in sedimentary rocks from the Huronian Supergroup, Canada. We found no significant authigenic enrichment of Os in the sedimentary rocks deposited during the first Huronian deglaciation. The initial isotopic composition of Os in the sediments was close to that of chondrite at the time of deposition (Os187/188Os=∼0.11). These results suggest that atmospheric O2 levels were insufficient to mobilize radiogenic Os through continental weathering (pO2<10-5-10-3 present atmospheric level (PAL)). In contrast, we found enrichment of Re in the sedimentary rocks, which suggests the occurrence of oxidative weathering of Re under mildly oxidizing conditions (>10-8-10-5 PAL). Despite the Re enrichment, low abundances of Mo imply possible non-sulfidic conditions in shallow-marine environments at the time of deposition. Together with the results of organic carbon and sulfur analyses, we suggest that atmospheric O2 remained at relatively low levels of around 10-8-10-5 PAL after the first Huronian deglaciation, which contrasts with proposed dramatic increases in O2 after the second and third Huronian deglaciations. These results imply that the second and third Huronian glaciations may have been global events, associated with climatic jumps from severe glaciations to super-greenhouse conditions and the subsequent blooming of photosynthetic cyanobacteria in the glacial aftermath.

  15. Decomposition of jellyfish carrion in situ: Short-term impacts on infauna, benthic nutrient fluxes and sediment redox conditions.

    PubMed

    Chelsky, Ariella; Pitt, Kylie A; Ferguson, Angus J P; Bennett, William W; Teasdale, Peter R; Welsh, David T

    2016-10-01

    Jellyfish often form blooms that persist for weeks to months before they collapse en masse, resulting in the sudden release of large amounts of organic matter to the environment. This study investigated the biogeochemical and ecological effects of the decomposition of jellyfish in a shallow coastal lagoon in New South Wales, Australia. Catostylus mosaicus carrion was added to the surface of shallow sub-tidal sediments and biogeochemical parameters and macrofaunal abundance immediately below the jellyfish carrion were measured over three days. Sediment plots without jellyfish served as controls. Sediment oxygen demand and carbon and nitrogen efflux increased by up to 60-fold in the jellyfish plots, compared to control plots, and dissolved organic nutrient fluxes were more sustained than in previous studies due to the use of fresh rather than frozen biomass. The decomposing jellyfish progressively altered sediment redox conditions, indicated by an increase in porewater iron (II) and sulfide concentrations measured by high-resolution in situ diffusive samplers. Abundance of some macrofaunal taxa in the jellyfish plots decreased relative to controls, however, the abundance of a carnivorous gastropod, which was presumably feeding on the carrion, increased in the jellyfish plots. While jellyfish carrion may be a food source for some macrofauna, low oxygen conditions coupled with the accumulation of toxic dissolved sulfides in the near-surface sediments may explain the overall change in the macroinfaunal community.

  16. Effects of redox mediators on azo dye decolorization by Shewanella algae under saline conditions.

    PubMed

    Meng, Xianming; Liu, Guangfei; Zhou, Jiti; Fu, Q Shiang

    2014-01-01

    Azo dye decolorization by Shewanella algae (SAL) in the presence of high concentrations of NaCl and different quinones or humic acids was investigated to reveal the effects of redox mediator under saline conditions. Growth of SAL and the other two marine Shewanella strains coupled to anthraquinone-2,6-disulfonate (AQDS) reduction was observed in a wide range of NaCl concentrations (0-7%). AQDS showed the best enhancing effects, whereas some other quinones demonstrated poorer stimulating or even inhibiting effects on acid red 27 (AR27) decolorization. Different humic acids could also enhance the decolorization. The correlation between specific AQDS-mediated reduction rate and initial AR27 concentration could be described with Michaelis-Menten kinetics (Km=0.2 mM and Vmax=9.3 μmol mg cell(-1) h(-1)). AQDS reduction by SAL was determined to be the rate-limiting step of mediated reduction. Mediated decolorization products of AR27 were determined to be less phytotoxic aromatic amines.

  17. Redox conditions and trace metal cycling in coastal sediments from the maritime Antarctic

    NASA Astrophysics Data System (ADS)

    Monien, Patrick; Lettmann, Karsten Alexander; Monien, Donata; Asendorf, Sanja; Wölfl, Anne-Cathrin; Lim, Chai Heng; Thal, Janis; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2014-09-01

    Redox-sensitive trace metals (Mn, Fe, U, Mo, Re), nutrients and terminal metabolic products (NO3-, NH4+, PO43-, total alkalinity) were investigated for the first time in pore waters of Antarctic coastal sediments. The results of this study reveal a high spatial variability in redox conditions in surface sediments from Potter Cove, King George Island, western Antarctic Peninsula. Particularly in the shallower areas of the bay the significant correlation between sulphate depletion and total alkalinity, the inorganic product of terminal metabolism, indicates sulphate reduction to be the major pathway of organic matter mineralisation. In contrast, dissimilatory metal oxide reduction seems to be prevailing in the newly ice-free areas and the deeper troughs, where concentrations of dissolved iron of up to 700 μM were found. We suggest a combination of several factors to be responsible for the domination of metal oxide reduction over sulphate reduction in these areas. These include the increased accumulation of fine-grained material with high amounts of reducible metal oxides, a reduced availability of metabolisable organic matter and an enhanced physical and biological disturbance by bottom water currents, ice scouring and burrowing organisms. Based on modelled iron fluxes we calculate the contribution of the Antarctic shelf to the pool of potentially bioavailable iron (Feb) to be 6.9 × 103 to 790 × 103 t yr-1. Consequently, these shelf sediments would provide an Feb flux of 0.35-39.5 mg m-2 yr-1 (median: 3.8 mg m-2 yr-1) to the Southern Ocean. This contribution is in the same order of magnitude as the flux provided by icebergs and significantly higher than the input by aeolian dust. For this reason suboxic shelf sediments form a key source of iron for the high nutrient-low chlorophyll (HNLC) areas of the Southern Ocean. This source may become even more important in the future due to rising temperatures at the WAP accompanied by enhanced glacier retreat and the

  18. Redox-linked conformation change and electron transfer between monoheme c-type cytochromes and oxides

    NASA Astrophysics Data System (ADS)

    Khare, Nidhi; Lovelace, David M.; Eggleston, Carrick M.; Swenson, Michael; Magnuson, Timothy S.

    2006-09-01

    Electron transfer between redox active proteins and mineral oxides is important in a variety of natural as well as technological processes, including electron transfer from dissimilatory metal-reducing bacteria to minerals. One of the pathways that could trigger electron transfer between proteins and minerals is redox-linked conformation change. We present electrochemical evidence that mitochondrial cytochrome c (Mcc) undergoes significant conformation change upon interaction with hematite and indium-tin oxide (ITO) surfaces. The apparent adsorption-induced conformation change causes the protein to become more reducing, which makes it able to transfer electrons to the hematite conduction band. Although Mcc is not a protein thought to be involved in interaction with mineral surfaces, it shares (or can be conformed so as to share) some characteristics with multiheme outer-membrane cytochromes thought to be involved in the transfer of electrons from dissimilatory iron-reducing bacteria to ferric minerals during respiration. We present evidence that a 10.1 kDa monohoeme cytochrome isolated and purified from Acidiphilium cryptum, with properties similar to those of Mcc, also undergoes conformation change as a result of interaction with hematite surfaces.

  19. Examination of Technetium Transport Through Soils Under Contrasting Redox Conditions: Batch and Column Work

    NASA Astrophysics Data System (ADS)

    Dozier, R.; Montgomery, D.; Wylie, E. M.; Dogan, M.; Moysey, S. M.; Powell, B. A.; Martinez, N. E.

    2015-12-01

    Experiments were performed under various reducing conditions to evaluate the transport behavior of technetium-99 (99Tc) in the presence of sandy clay loam soil from the Savannah River Site (SRS) and goethite, magnetite, and iron sulfide, which were selected for their increasing reducing potential. The experiments were conducted to investigate how redox reaction equilibria and rates affect the overall mobility of 99Tc as it transitions between the mobile Tc(VII) and immobile Tc(IV). Under oxygen-rich conditions, batch sorption isotherms measured for TcO4- across the concentration range 0.5 to 50 μg/L were linear with distribution coefficients (Kd) of 0.78 mL/g or lower, with decreasing sorption for goethite, magnetite, and iron sulfide, respectively. Addition of Na2S resulted in a marked increase in apparent 99Tc sorption to the solid phase, with Kd of 43 mL/g, 35 mL/g, and 29 mL/g, following the same mineral trend as previously. The increased Kd values are possibly due to reduction of Tc(VII) to Tc(IV), resulting in the formation of TcO2(s). SRS soil batch sorption isotherms measured for TcO4- across the same concentration range were also linear, with Kd of 0.7 mL/g for unadjusted pH, 5.1 mL/g for pH of around 6, and 6.7 mL/g for pH of around 4. Kinetic batch sorption tests showed less than 10% 99Tc sorption in an oxidizing environment and greater than 95% sorption in a reducing environment, with both reactions occurring on the order of minutes. In contrast, desorption experiments initiated by transferring the samples from a reducing environment (0.1% H2(g)/99.9% N2(g)) to atmospheric conditions resulted in a slow desorption step on the order of days. Column experiments conducted with the SRS sands indicate a retardation factor of 1.17 for 99Tc under oxygen rich conditions. Additional column experiments are being conducted to evaluate 99Tc transport dependencies on transitions between oxygen rich and poor conditions.

  20. Redox Redone.

    ERIC Educational Resources Information Center

    Petty, John T.

    1996-01-01

    Presents an extension of the change in oxidation number method that is used for balancing skeletal redox reactions in aqueous solutions. Retains most of the simplicity of the change in oxidation number method but provides the additional step-by-step process necessary for the beginner to balance an equation. (JRH)

  1. Redox imbalance and morphological changes in skin fibroblasts in typical Rett syndrome.

    PubMed

    Signorini, Cinzia; Leoncini, Silvia; De Felice, Claudio; Pecorelli, Alessandra; Meloni, Ilaria; Ariani, Francesca; Mari, Francesca; Amabile, Sonia; Paccagnini, Eugenio; Gentile, Mariangela; Belmonte, Giuseppe; Zollo, Gloria; Valacchi, Giuseppe; Durand, Thierry; Galano, Jean-Marie; Ciccoli, Lucia; Renieri, Alessandra; Hayek, Joussef

    2014-01-01

    Evidence of oxidative stress has been reported in the blood of patients with Rett syndrome (RTT), a neurodevelopmental disorder mainly caused by mutations in the gene encoding the Methyl-CpG-binding protein 2. Little is known regarding the redox status in RTT cellular systems and its relationship with the morphological phenotype. In RTT patients (n = 16) we investigated four different oxidative stress markers, F2-Isoprostanes (F2-IsoPs), F4-Neuroprostanes (F4-NeuroPs), nonprotein bound iron (NPBI), and (4-HNE PAs), and glutathione in one of the most accessible cells, that is, skin fibroblasts, and searched for possible changes in cellular/intracellular structure and qualitative modifications of synthesized collagen. Significantly increased F4-NeuroPs (12-folds), F2-IsoPs (7.5-folds) NPBI (2.3-folds), 4-HNE PAs (1.48-folds), and GSSG (1.44-folds) were detected, with significantly decreased GSH (-43.6%) and GSH/GSSG ratio (-3.05 folds). A marked dilation of the rough endoplasmic reticulum cisternae, associated with several cytoplasmic multilamellar bodies, was detectable in RTT fibroblasts. Colocalization of collagen I and collagen III, as well as the percentage of type I collagen as derived by semiquantitative immunofluorescence staining analyses, appears to be significantly reduced in RTT cells. Our findings indicate the presence of a redox imbalance and previously unrecognized morphological skin fibroblast abnormalities in RTT patients.

  2. Redox Imbalance and Morphological Changes in Skin Fibroblasts in Typical Rett Syndrome

    PubMed Central

    Amabile, Sonia; Belmonte, Giuseppe; Valacchi, Giuseppe; Galano, Jean-Marie; Ciccoli, Lucia; Renieri, Alessandra; Hayek, Joussef

    2014-01-01

    Evidence of oxidative stress has been reported in the blood of patients with Rett syndrome (RTT), a neurodevelopmental disorder mainly caused by mutations in the gene encoding the Methyl-CpG-binding protein 2. Little is known regarding the redox status in RTT cellular systems and its relationship with the morphological phenotype. In RTT patients (n = 16) we investigated four different oxidative stress markers, F2-Isoprostanes (F2-IsoPs), F4-Neuroprostanes (F4-NeuroPs), nonprotein bound iron (NPBI), and (4-HNE PAs), and glutathione in one of the most accessible cells, that is, skin fibroblasts, and searched for possible changes in cellular/intracellular structure and qualitative modifications of synthesized collagen. Significantly increased F4-NeuroPs (12-folds), F2-IsoPs (7.5-folds) NPBI (2.3-folds), 4-HNE PAs (1.48-folds), and GSSG (1.44-folds) were detected, with significantly decreased GSH (−43.6%) and GSH/GSSG ratio (−3.05 folds). A marked dilation of the rough endoplasmic reticulum cisternae, associated with several cytoplasmic multilamellar bodies, was detectable in RTT fibroblasts. Colocalization of collagen I and collagen III, as well as the percentage of type I collagen as derived by semiquantitative immunofluorescence staining analyses, appears to be significantly reduced in RTT cells. Our findings indicate the presence of a redox imbalance and previously unrecognized morphological skin fibroblast abnormalities in RTT patients. PMID:24987493

  3. Chemoreceptor discharges and cytochrome redox changes of the rat carotid body: Role of heme ligands

    PubMed Central

    Lahiri, Sukhamay; Ehleben, Wilhelm; Acker, Helmut

    1999-01-01

    In superfused in vitro rat carotid body, we recorded chemoreceptor discharges and the redox state of cytochromes simultaneously to identify the primary oxygen-sensing protein controlling transmitter release and electrical activity of the carotid sinus nerve. These parameters were tested under the influence of heme ligands such as oxygen, cyanide, 4-(2-aminoethyl)-benzenesulfonyl fluoride, and CO. During stimulation, there was an initial increase in discharge frequency followed by a decline or suppression of activity. Photometric changes lagged and were maintained as nerve activity decreased. Reducing mitochondrial cytochromes by cyanide or prolonged severe hypoxia, suppressed the chemoreceptor discharge. 4-(2-Aminoethyl)-benzenesulfonyl fluoride, a specific inhibitor of the phagocytic cytochrome b558, also silenced the chemoreceptors after an initial excitation. CO increased the chemoreceptor discharge under normoxia, an effect inhibited by light, when the cytochromes were not reduced. When the discharges were depressed by severe hypoxia, exposure to light excited the chemoreceptors and the cytochromes were reduced. The rapidity of the chemosensory responses to light and lack of effect on dopamine release from type I cells led us to hypothesize that carotid body type I cells and the apposed nerve endings use different mechanisms for oxygen sensing: the nerve endings generate action potentials in association with membrane heme proteins whereas cytosolic heme proteins signal the redox state, releasing modulators or transmitters from type I cells. PMID:10430959

  4. Changes in glutathione redox cycle during diapause determination and termination in the bivoltine silkworm, Bombyx mori.

    PubMed

    Zhao, Lin-Chuan; Hou, Yi-Sheng; Sima, Yang-Hu

    2014-02-01

    To explore whether glutathione regulates diapause determination and termination in the bivoltine silkworm Bombyx mori, we monitored the changes in glutathione redox cycle in the ovary of both diapause- and nondiapause-egg producers, as well as those in diapause eggs incubated at different temperatures. The activity of thioredoxin reductase (TrxR) was detected in ovaries but not in eggs, while neither ovaries nor eggs showed activity of glutathione peroxidase. A lower reduced glutathione/oxidized glutathione (GSH/GSSG) ratio was observed in the ovary of diapause-egg producers, due to weaker reduction of oxidized glutathione (GSSG) to the reduced glutathione (GSH) catalyzed by glutathione reductase (GR) and TrxR. This indicates an oxidative shift in the glutathione redox cycle during diapause determination. Compared with the 25°C-treated diapause eggs, the 5°C-treated diapause eggs showed lower GSH/GSSG ratio, a result of stronger oxidation of GSH catalyzed by thioredoxin peroxidase and weaker reduction of GSSG catalyzed by GR. Our study demonstrated the important regulatory role of glutathione in diapause determination and termination of the bivoltine silkworm.

  5. Diquat-induced cellular pyridine nucleotide redox changes and alteration of metabolic enzyme activities in colonic carcinoma cells.

    PubMed

    Circu, Magdalena L; Maloney, Ronald E; Aw, Tak Yee

    2017-02-25

    Previously we have shown that the redox cycler menadione (MQ) induced cellular pyridine nucleotide redox imbalance that was linked to a decrease in aerobic glycolysis and perturbation of the mitochondrial respiratory activity due to the redox cycling of the compound; these processes were potentiated by low glucose. In this study, we investigated how colonic epithelial cells maintained pyridine nucleotide (NAD(+)/NADH and NADP(+)/NADPH) redox homeostasis upon acute metabolic variation and exposure to the redox cycling diquat (DQ). Our results show that DQ challenge disrupted cellular NADH/NAD(+) redox status and enhanced cellular NADPH generation. Notably, DQ-induced NADH decrease was associated with enhanced lactate production, a process that was potentiated by glucose availability, but not by the mitochondrial substrates, succinate or malate/glutamate. In addition, DQ increased glucose 6-phoshate dehydrogenase (G6PDH) activity consistent with glucose diversion towards pentose phosphate pathway. As a consequence, steady-state NADPH levels were maintained during MQ challenge at normal glucose. In contrast and despite increased G6PDH and malic enzyme (ME) activities, DQ induced cellular NADPH-to-NADP(+) shift at low glucose, a situation that was reversed by mitochondrial substrates. Collectively, these results are consistent with increased aerobic glycolysis by DQ and specific metabolic changes leading to enhanced NADPH generation upon oxidative challenge.

  6. Prediction and visualization of redox conditions in the groundwater of Central Valley, California

    NASA Astrophysics Data System (ADS)

    Rosecrans, Celia Z.; Nolan, Bernard T.; Gronberg, JoAnn M.

    2017-03-01

    Regional-scale, three-dimensional continuous probability models, were constructed for aspects of redox conditions in the groundwater system of the Central Valley, California. These models yield grids depicting the probability that groundwater in a particular location will have dissolved oxygen (DO) concentrations less than selected threshold values representing anoxic groundwater conditions, or will have dissolved manganese (Mn) concentrations greater than selected threshold values representing secondary drinking water-quality contaminant levels (SMCL) and health-based screening levels (HBSL). The probability models were constrained by the alluvial boundary of the Central Valley to a depth of approximately 300 m. Probability distribution grids can be extracted from the 3-D models at any desired depth, and are of interest to water-resource managers, water-quality researchers, and groundwater modelers concerned with the occurrence of natural and anthropogenic contaminants related to anoxic conditions. Models were constructed using a Boosted Regression Trees (BRT) machine learning technique that produces many trees as part of an additive model and has the ability to handle many variables, automatically incorporate interactions, and is resistant to collinearity. Machine learning methods for statistical prediction are becoming increasing popular in that they do not require assumptions associated with traditional hypothesis testing. Models were constructed using measured dissolved oxygen and manganese concentrations sampled from 2767 wells within the alluvial boundary of the Central Valley, and over 60 explanatory variables representing regional-scale soil properties, soil chemistry, land use, aquifer textures, and aquifer hydrologic properties. Models were trained on a USGS dataset of 932 wells, and evaluated on an independent hold-out dataset of 1835 wells from the California Division of Drinking Water. We used cross-validation to assess the predictive performance of

  7. Prediction and visualization of redox conditions in the groundwater of Central Valley, California

    USGS Publications Warehouse

    Rosecrans, Celia Z.; Nolan, Bernard T.; Gronberg, JoAnn M.

    2017-01-01

    Regional-scale, three-dimensional continuous probability models, were constructed for aspects of redox conditions in the groundwater system of the Central Valley, California. These models yield grids depicting the probability that groundwater in a particular location will have dissolved oxygen (DO) concentrations less than selected threshold values representing anoxic groundwater conditions, or will have dissolved manganese (Mn) concentrations greater than selected threshold values representing secondary drinking water-quality contaminant levels (SMCL) and health-based screening levels (HBSL). The probability models were constrained by the alluvial boundary of the Central Valley to a depth of approximately 300 m. Probability distribution grids can be extracted from the 3-D models at any desired depth, and are of interest to water-resource managers, water-quality researchers, and groundwater modelers concerned with the occurrence of natural and anthropogenic contaminants related to anoxic conditions.Models were constructed using a Boosted Regression Trees (BRT) machine learning technique that produces many trees as part of an additive model and has the ability to handle many variables, automatically incorporate interactions, and is resistant to collinearity. Machine learning methods for statistical prediction are becoming increasing popular in that they do not require assumptions associated with traditional hypothesis testing. Models were constructed using measured dissolved oxygen and manganese concentrations sampled from 2767 wells within the alluvial boundary of the Central Valley, and over 60 explanatory variables representing regional-scale soil properties, soil chemistry, land use, aquifer textures, and aquifer hydrologic properties. Models were trained on a USGS dataset of 932 wells, and evaluated on an independent hold-out dataset of 1835 wells from the California Division of Drinking Water. We used cross-validation to assess the predictive performance of

  8. Exercise-induced changes in redox status of elite karate athletes.

    PubMed

    Pesic, Snezana; Jakovljevic, Vladimir; Djordjevic, Dusica; Cubrilo, Dejan; Zivkovic, Vladimir; Jorga, Vladimir; Mujovic, Vujadin; Djuric, Dragan; Stojimirovic, Biljana

    2012-02-29

    Regular training has been claimed to increase the activity of antioxidant enzymes and, consequently, augments the resistance to oxidative stress; however, large volumes of training performed by elite sportsmen could lead to a chronic oxidative stress state. The aim of our study was to assess the oxidative status of elite athletes at the beginning of the preparatory and the beginning of the competition training phases, so that the influence of three months of programmed physical activity on redox status could be determined. The chronic effects of exercise on the redox state of the athletes were compared to the effects of a single bout of karate training. Thirty elite karate athletes, 16-30 years old, were subjected to maximal graded exercise test to estimate their aerobic capacity; blood sampling was also performed to measure levels of superoxide anion radical (O₂⁻), hydrogen peroxide (H₂O₂), superoxide dismutase activity (SOD) and catalase activity (CAT). The only significant change after the three-month training process was found in the significantly decreased CAT activity (X ± SE: 7.95 ± 0.13 U/g Hb × 10³ in the preparatory period, 6.65 ± 0.28 U/g Hb × 10³ in the competition stage; P < 0.01). After a single karate training session, there was statistically significant decrease of O₂⁻(X ± SE: 32.7 ± 4.9 nmol/ml in the preparatory period, 24.5 ± 2.5 nmol/ml in the competition stage; P < 0.05) and increase of H₂O₂(X ± SE: 11.8 ± 1.0 nmol/ml in the preparatory period, 14.2 ± 0.9 nmol/ml in the competition stage; P < 0.01), as well as significant CAT increase (X ± SE: 6.6 ± 0.6 U/g Hb × 10³ in the preparatory period, 8.5 ± 0.5 U/g Hb × 10³ in the competition stage; P < 0.05). Although the three-month training process induced, at the first sight, negative changes in the redox state, expressed through the decrease in CAT activity, adequate response of the antioxidant system of our athletes to acute exercise was preserved.

  9. Efficient chemisorption of organophosphorous redox probes on indium tin oxide surfaces under mild conditions.

    PubMed

    Forget, Amélie; Limoges, Benoît; Balland, Véronique

    2015-02-17

    We report a mild and straightforward one-step chemical surface functionalization of indium tin oxide (ITO) electrodes by redox-active molecules bearing an organophosphoryl anchoring group (i.e., alkyl phosphate or alkyl phosphonate group). The method takes advantage of simple passive adsorption in an aqueous solution at room temperature. We show that organophosphorus compounds can adsorb much more strongly and stably on an ITO surface than analogous redox-active molecules bearing a carboxylate or a boronate moiety. We provide evidence, through quantitative electrochemical characterization (i.e., by cyclic voltammetry) of the adsorbed organophosphoryl redox-active molecules, of the occurrence of three different adsorbate fractions on ITO, exhibiting different stabilities on the surface. Among these three fractions, one is observed to be strongly chemisorbed, exhibiting high stability and resistance to desorption/hydrolysis in a free-redox probe aqueous buffer. We attribute this remarkable stability to the formation of chemical bonds between the organophosphorus anchoring group and the metal oxide surface, likely occurring through a heterocondensation reaction in water. From XPS analysis, we also demonstrate that the surface coverage of the chemisorbed molecules is highly affected by the degree of surface hydroxylation, a parameter that can be tuned by simply preconditioning the freshly cleaned ITO surfaces in water. The lower the relative surface hydroxide density on ITO, the higher was the surface coverage of the chemisorbed species. This behavior is in line with a chemisorption mechanism involving coordination of a deprotonated phosphoryl oxygen atom to the non-hydroxylated acidic metal sites of ITO.

  10. The redox conditions of anhydrous and hydrous xenoliths of suprasubduction and intraplate lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Bonadiman, C.; Coltorti, M.

    2012-12-01

    The oxidation state of the upper mantle, its relationship with C-H-O fluids speciation and tectonic settings has been debated for decades and the various modelling have considered the prevalent role of the hydrous minerals over nominally anhydrous minerals (and the opposite) as well as the dissolution of silicate minerals (as providers of Fe3+ to the system) as directly related to water activity and oxygen fugacity. Each of these modelling has different implications for mantle rheology, seismic structure, and the evolution of the lithosphere (i.e.: Karato and Jung, 1998, Hirshmann, 2006). Upper mantle is the only part of the Earth's mantle where the oxygen fugacity can be directly measured, its values/variation being dependent on various processes such as partial melting and metasomatism often operating in time and space without solution of continuity. Recent general reviews of oxygen thermobarometry measurements (Forst & McCammon, 2008; Foley, 2011) indicate that the oxygen fugacity at the top of the upper mantle falls within ±2 log units of the fayalite-magnetite-quartz (FMQ) oxygen buffer. There is also a general consensus in considering H2O as the strongest oxidizing agent in mantle metasomatic fluids, its activity leading to the formation of amphibole and raising the mantle redox state. This contribution presents fO2 and water activity results from three spinel-bearing mantle xenolith localities and distinct geodynamic settings: Ichinomegata (Japan) amphibole-bearing peridotites entrained in calc-alkaline basalts and Cerro Fraile (South Patagonia, Argentina), mostly anhydrous lherzolites and pirossenites brought up to the surface by alkaline basalts representing fragments of sub-arc mantle and Baker Rocks, Victoria Land (Antarctica), amphibole-bearing lherzolites representing portion of intraplate subcontinental lithospheric mantle. The three mantle sectors records fO2 values in the range of -1.9 to +0.8 log units of the FQM buffer. and low to very low aH2O

  11. Redox-dependent structural changes in an engineered heme-copper center in myoglobin: insights into chloride binding to CuB in heme copper oxidases.

    PubMed

    Zhao, Xuan; Nilges, Mark J; Lu, Yi

    2005-05-03

    The effects of chloride on the redox properties of an engineered binuclear heme-copper center in myoglobin (Cu(B)Mb) were studied by UV-vis spectroelectrochemistry and EPR spectroscopy. A low-spin heme Fe(III)-Cu(I) intermediate was observed during the redox titration of Cu(B)Mb only in the presence of both Cu(II) and chloride. Upon the first electron transfer to the Cu(B) center, one of the His ligands of Cu(B) center dissociates and coordinates to the heme iron, forming a six-coordinate low-spin ferric heme center and a reduced Cu(B) center. The second electron transfer reduces the ferric heme and causes the release of the coordinated His ligand. Thus, the fully reduced state of the heme-copper center contains a five-coordinate ferrous heme and a reduced Cu(B) center, ready for O(2) binding and reduction to water to occur. In the absence of a chloride ion, formation of the low-spin heme species was not observed. These redox reactions are completely reversible. These results indicate that binding of chloride to the Cu(B) center can induce redox-dependent structural changes, and the bound chloride and hydroxide in the heme-copper center may play different roles in the redox-linked enzymatic reactions of heme-copper oxidases, probably because of their different binding affinity to the copper center and the relatively high concentration of chloride under physiological conditions.

  12. Effect of redox conditions on bacterial and fungal biomass and carbon dioxide production in Louisiana coastal swamp forest sediment.

    PubMed

    Seo, Dong Cheol; DeLaune, Ronald D

    2010-08-01

    Fungal and bacterial carbon dioxide (CO2) production/emission was determined under a range of redox conditions in sediment from a Louisiana swamp forest used for wastewater treatment. Sediment was incubated in microcosms at 6 Eh levels (-200, -100, 0, +100, +250 and +400 mV) covering the anaerobic range found in wetland soil and sediment. Carbon dioxide production was determined by the substrate-induced respiration (SIR) inhibition method. Cycloheximide (C15H23NO4) was used as the fungal inhibitor and streptomycin (C21H39N7O12) as the bacterial inhibitor. Under moderately reducing conditions (Eh > +250 mV), fungi contributed more than bacteria to the CO2 production. Under highly reducing conditions (Eh < or = 0 mV), bacteria contributed more than fungi to the total CO2 production. The fungi/bacteria (F/B) ratios varied between 0.71-1.16 for microbial biomass C, and 0.54-0.94 for microbial biomass N. Under moderately reducing conditions (Eh > or = +100 mV), the F/B ratios for microbial biomass C and N were higher than that for highly reducing conditions (Eh < or = 0 mV). In moderately reducing conditions (Eh > or = +100 mV), the C/N microbial biomass ratio for fungi (C/N: 13.54-14.26) was slightly higher than for bacteria (C/N: 9.61-12.07). Under highly reducing redox conditions (Eh < or = 0 mV), the C/N microbial biomass ratio for fungi (C/N: 10.79-12.41) was higher than for bacteria (C/N: 8.21-9.14). For bacteria and fungi, the C/N microbial biomass ratios under moderately reducing conditions were higher than that in highly reducing conditions. Fungal CO2 production from swamp forest could be of greater ecological significance under moderately reducing sediment conditions contributing to the greenhouse effect (GHE) and the global warming potential (GWP). However, increases in coastal submergence associated with global sea level rise and resultant decrease in sediment redox potential from increased flooding would likely shift CO2 production to bacteria rather than

  13. Plant Defense Response to Fungal Pathogens (II. G-Protein-Mediated Changes in Host Plasma Membrane Redox Reactions).

    PubMed Central

    Vera-Estrella, R.; Higgins, V. J.; Blumwald, E.

    1994-01-01

    Elicitor preparations containing the avr5 gene products from races 4 and 2.3 of Cladosporium fulvum, and tomato (Lycopersicon esculentum L.) cells containing the resistance gene Cf5 were used to investigate the involvement of redox processes in the production of active oxygen species associated with the plant response to the fungal elicitors. Here we demonstrate that certain race-specific elicitors of C. fulvum induced an increase in ferricyanide reduction in enriched plasma membrane fractions of tomato cells. The addition of elicitors to plasma membranes also induced increases in NADH oxidase and NADH-dependent cytochrome c reductase activities, whereas ascorbate peroxidase activity was decreased. These results suggest that changes in the host plasma membrane redox processes, transferring electrons from reducing agents to oxygen, could be involved in the increased production of active oxygen species by the race-specific elicitors. Our results also show that the dephosphorylation of enzymes involved in redox reactions is responsible for the race-specific induced redox activity. The effects of guanidine nucleotide analogs and mastoparan on the activation of plasma membrane redox reactions support the role of GTP-binding proteins in the transduction of signals leading to the activation of the defense response mechanisms of tomato against fungal pathogens. PMID:12232307

  14. The Influence of the Biological Pump on Marine Redox Conditions During Earth History

    NASA Astrophysics Data System (ADS)

    Meyer, K. M.; Ridgwell, A.; Payne, J.

    2015-12-01

    Evidence for bottom-water anoxia on the continental shelves waned over the course of the Phanerozoic, which may be influenced by secular changes in the biological pump that led to weaker positive feedbacks within the oceans. The biological pump describes the transfer of carbon from the atmosphere to the deep ocean, which creates vertical gradients in nutrients and oxygen, both important influences in the structure of marine ecosystems. We used the cGENIE Earth system model to quantitatively test the hypothesis that reductions in the efficiency of the nutrient recycling loop of the biological pump during the past 550 Ma reduced the extent of anoxia on the shelves and acted as an important control on marine animal ecosystems. When the modeled remineralization depth is shallow relative to the modern ocean, anoxia tends to be more widespread at continental shelf depths. As the modeled remineralization depth increases toward modern conditions, anoxia is less prevalent and occurs at depths below the continental shelves. Reduced marine productivity in the closed system configuration of cGENIE cannot produce the frequent bottom-water anoxia conditions envisioned for the Paleozoic. We hypothesize that evidence for greater animal abundance and metabolic demand during the Phanerozoic was driven by progressive oxygenation of shelf environments related to changes in the biological pump rather than greater food availability. In general, these model simulations suggest changes in the depth distribution of organic carbon remineralization may have controlled observed shifts in ocean chemistry, biogeochemical cycling, and ecosystem structure during the Phanerozoic.

  15. Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

    NASA Astrophysics Data System (ADS)

    Harte, Philip T.; Ayotte, Joseph D.; Hoffman, Andrew; Révész, Kinga M.; Belaval, Marcel; Lamb, Steven; Böhlke, J. K.

    2012-09-01

    Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO{3/-}), iron (Fe2+), manganese (Mn2+), and sulfate (SO{4/2-}). Redox conditions were evaluated also based on methane (CH4), excess nitrogen gas (N2) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50-100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.

  16. Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

    USGS Publications Warehouse

    Harte, Philip T.; Ayotte, Joseph D.; Hoffman, Andrew; Revesz, Kinga M.; Belaval, Marcel; Lamb, Steven; Böhlke, J.K.

    2012-01-01

    Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO3-), iron (Fe2+), manganese (Mn2+), and sulfate (SO42-). Redox conditions were evaluated also based on methane (CH4), excess nitrogen gas (N2) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.

  17. An evaluation of benthic foraminiferal U/Ca and U/Mn proxies for deep ocean carbonate chemistry and redox conditions

    NASA Astrophysics Data System (ADS)

    Chen, Pujiao; Yu, Jimin; Jin, Zhangdong

    2017-02-01

    The deep ocean is thought to have played a crucial role in modulating atmospheric CO2 changes, and thus reconstructions of deep ocean conditions can place important constraints on the past global carbon cycle. Some previous studies suggested that foraminiferal U/Ca could be used to infer seawater carbonate chemistry changes, but others showed complications from diagenesis and temperature. A recent downcore study suggested that foraminiferal U/Mn may be used for sedimentary redox-conditions, but no core-top work has been done to investigate factors affecting U/Mn. We investigate controlling factors on U/Ca and U/Mn in two benthic foraminiferal species from 120 global core-tops and three Atlantic sediment cores. Our core-top data reveal no significant correlation between core-top benthic U/Ca and carbonate system parameters. The lack of an influence of deep-water [CO32-] on U/Ca is further supported by our downcore results. Together, our data highlight complications to use benthic U/Ca for deep-water carbonate chemistry reconstructions. Although no correlation is found between core-top U/Mn and hydrographic data, high-resolution U/Mn and U/Ca in core TNO57-21 show similar patterns to authigenic U (aU) and vary in tandem with atmospheric CO2 on millennial timescales. Changes in U/Mn, U/Ca and aU in TNO57-21 may reflect postdepositional diagenesis linked to sedimentary oxygen, which is controlled by subantarctic surface productivity and ventilation of deep South Atlantic in the past. We suggest that benthic U/Mn and U/Ca may be used as auxiliary indicators for past sedimentary redox-conditions and along with other proxies could reflect deep-water oxygenation.

  18. Modeling biogeochemical processes in subterranean estuaries: Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients

    NASA Astrophysics Data System (ADS)

    Spiteri, Claudette; Slomp, Caroline P.; Tuncay, Kagan; Meile, Christof

    2008-02-01

    A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO3-, NH4+, and PO4) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater-seawater mixing zone determine the extent of nutrient removal and the input of nitrogen and phosphorus to coastal waters. At low to moderate groundwater velocities, simultaneous nitrification and denitrification can lead to a reversal in the depth of freshwater NO3- and NH4+-PO4 plumes, compared to their original positions at the landward source. Model results suggest that autotrophic denitrification pathways with Fe2+ or FeS2 may provide an important, often overlooked link between nitrogen and phosphorus biogeochemistry through the precipitation of iron oxides and subsequent binding of phosphorus. Simulations also highlight that deviations of nutrient data from conservative mixing curves do not necessarily indicate nutrient removal.

  19. Normalized rare earth elements in water, sediments, and wine: identifying sources and environmental redox conditions

    USGS Publications Warehouse

    Piper, David Z.; Bau, Michael

    2013-01-01

    The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that reveal their partitioning between different sediment fractions and the sources of those fractions, for example, between terrestrial-derived lithogenous debris and seawater-derived biogenous detritus and hydrogenous metal oxides. The REE of ancient sediments support their partitioning into these same fractions and further contribute to the identification of the redox geochemistry of the sea water in which the sediments accumulated. The normalized curves of the REE that have been examined in several South American wine varietals can be interpreted to reflect the lithology of the bedrock on which the vines may have been grown, suggesting limited fractionation during soil development.

  20. Effects of redox conditions on the control of arsenic mobility in shallow alluvial aquifers on the Venetian Plain (Italy).

    PubMed

    Carraro, A; Fabbri, P; Giaretta, A; Peruzzo, L; Tateo, F; Tellini, F

    2015-11-01

    The Venetian Plain is known for the occurrence of areas with high concentrations of arsenic in groundwater (greater than 400 μg/L). The study area represents the typical residential, industrial and agricultural features of most Western countries and is devoid of hydrothermal, volcanic or anthropogenic sources of arsenic. The aim of the study is to model the arsenic mobilization and the water-rock interaction by a complete hydrogeochemical investigation (analyses of filtered and unfiltered groundwater sediment mineralogy and geochemistry). The groundwater arsenic contamination and redox conditions are highly variable. Groundwaters with oxidizing and strongly reducing potentials have much lower arsenic concentrations than do mildly reducing waters. The grain size of the aquifer sediments includes gravels, sands and silty-clays. A continuous range of organic material concentrations is observed (from zero to 40%). The amount of sedimentary organic matter is highly correlated with the arsenic content of the sediments (up to 300 mg/kg), whereas no relationships are detectable between arsenic and other chemical parameters. The occurrence of arsenic minerals was observed as a peculiar feature under the scanning electron microscope. Arsenic and sulfur are the sole constituents of small tufts or thin crystals concentrated in small masses. These arsenic minerals were clearly observed in the peat sediments, in agreement with the geochemical modeling that requires very reducing conditions for their precipitation from the groundwater. The modeling suggests that, under oxidizing conditions, arsenic is adsorbed; moreover, a continuous decrease in the redox potential causes increasing desorption of arsenic. If the reducing conditions become more intense, the formation of As-S minerals would explain the lower concentration of arsenic measured in the strongly reducing groundwater. Even if As-sulfides are rare under low-temperature conditions, the anomalous abundance of reductants

  1. Determination of Cr isotopic composition in low-level carbonates by MC-ICP-MS: a sensitive proxy for redox changes?

    NASA Astrophysics Data System (ADS)

    Bonnand, Pierre; Parkinson, Ian; James, Rachael; Karjalainen, Anne-Mari; Fehr, Manuela; Fairchild, Ian

    2010-05-01

    Geochemical data suggest that atmospheric oxygen increased during two major steps: the Great oxidation event (~2.4 Ga) and the Neoproterozoic (~1Ga-545Ma). The O2 concentration in the atmosphere is strongly linked to the redox condition of the oceans. Therefore the study of redox sensitive elements in marine sediments can be used to evaluate the evolution of O2 concentrations in the atmosphere. Chromium is a redox sensitive element which significantly fractionates its isotopes during the reduction of Cr(VI) to Cr(III) (Ellis et al., 2002). Thus, Cr isotopes can be used to assess redox changes in the past oceans. Chromium isotopic compositions in sedimentary rocks (BIFs) have been used to determine the evolution of the O2 concentration in the atmosphere during the Proterozoic (Frei et al., 2009). We have developed a chemical procedure for the purification of Cr in carbonates by using a single cation column to separate the Cr from the matrix, Fe, Ti and V. Cr isotopic compositions are determined used a 50Cr-54Cr double spike method and analysed on a ThermoFisher Neptune MC-ICP-MS using HR and MR in order to be able to discriminate Ar interferences. Standards and samples are analysed as 50ppb Cr solutions and yield an external reproducibility 50 and 70ppm. This new method allowed us to analyse samples with a Cr concentrations as low as 1ppm. We have analysed a suite of Neoproterozoic carbonates from Australia, but also modern ooids and oolithic limestones through the Phanerozoic. The Cr isotopic data for carbonates record a range of δ53Cr between -0.1 and +1.7. This range indicates that some of these carbonates clearly reflect oxidising conditions in the ocean. By comparison, the Neoproterozoic samples have Cr isotopic compositions close to the continental crust value (-0.1 to 0.1), indicating the Neoproterozoic samples reflect deposition under more reducing conditions These data suggests that the redox condition during the deposition of shallow-water carbonates

  2. Monitoring Intracellular Redox Changes in Ozone-exposed airway epithelial cells

    EPA Science Inventory

    Background: The toxicity of many compounds involves oxidative injury to cells. Direct assessment of mechanistic events involved in xenobiotic-induced oxidative stress is not easily achievable. Development of genetically-encoded probes designed for monitoring intracellular redox s...

  3. Tirapazamine has no Effect on Hepatotoxicity of Cisplatin and 5-fluorouracil but Interacts with Doxorubicin Leading to Side Changes in Redox Equilibrium.

    PubMed

    Mandziuk, Slawomir; Matysiak, Wlodzimierz; Korga, Agnieszka; Burdan, Franciszek; Pasnik, Iwona; Hejna, Marcin; Korobowicz-Markiewicz, Agnieszka; Grzycka-Kowalczyk, Luiza; Kowalczyk, Michal; Poleszak, Ewa; Jodlowska-Jedrych, Barbara; Dudka, Jaroslaw

    2016-09-01

    Tirapazamine is a hypoxia-activated prodrug which was shown to exhibit up to 300 times greater cytotoxicity under anoxic in comparison with aerobic conditions. Thus, the combined anticancer therapy of tirapazamine with a routinely used anticancer drug seems to be a promising solution. Because tirapazamine undergoes redox cycle transformation in this study, the effect of tirapazamine on redox hepatic equilibrium, lipid status and liver morphology was evaluated in rats exposed to cisplatin, doxorubicin and 5-fluorouracil. Rats were intraperitoneally injected with tirapazamine and a particular cytostatic. The animals were killed, and blood and liver were collected. Hepatic glucose, total cholesterol, triglycerides, NADH, NADPH glutathione and the activity of glucose-6-phosphate dehydrogenase were determined. Liver morphology and the immune expression of HMG-CoA-reductase were also assessed. Glucose, total cholesterol, triglycerides, bilirubin concentrations and the activity of aspartate and alanine aminotransferases were determined in the plasma. Tirapazamine displayed insignificant interactions with cisplatin and 5-fluorouracil referring to hepatic morphology and biochemical parameters. However, tirapazamine interacts with doxorubicin, thus leading to side changes in redox equilibrium and lipid peroxidation, but those effects are not severe enough to exclude that drug combination from further studies. Thus, tirapazamine seems to be a promising agent in successive studies on anticancer activity in similar schedules.

  4. Changes in the redox state of sediments following the 2010 BP blowout

    NASA Astrophysics Data System (ADS)

    Hastings, D. W.; Brooks, G.; Hollander, D. J.; Larson, R. A.; Morford, J. L.; Romero, I.; Hammaker, S.; Hogan, A.; Roeder, T. K.

    2012-12-01

    We have collected multi-core sediment cores from over 40 sites along the NE Gulf of Mexico continental slope following the 2010 Deepwater Horizon oil spill. We present the geochemical results from four select sites collected on August 2010, December 2010, February 2011, September 2011, and August 2012. Cores were extruded at 2 mm intervals, and sediments were analyzed for TOC, 13C, carbonate, short-lived radioisotopes (Pb-210, Cs-137, Be-7, Th-234) and grain size. Cores reveal a well-defined, internally stratified dark brown layer in the top 1-6 cm, with finer grain size than underlying sediments. Samples were digested at high temperature and pressure in concentrated nitric acid to dissolve both the oil and authigenic fractions, but not the detrital component. Samples were subsequently analyzed by ICP-MS. Although the Macondo crude oil is slightly enriched in Ni, V, and Co, with concentrations of 2.8, 0.9, and 0.08ppm, respectively, no significant enrichment of these metals is observed in Gulf of Mexico sediments. Sediment mass accumulation rates following the event range from 0.6 - 20 g/cm2/yr, which are one to two orders of magnitude higher than pre-spill rates. Organic and inorganic carbon deposition rates from the 2010 and February 2011 cores are also elevated one to two orders of magnitude. 13C signatures of this recent deposited material are slightly depleted relative to pre-oil event material. Large sedimentation rates, depleted 13C values and lack of bioturbation on the surface of the deep sediments studied supports the hypothesis of a large sea-snow-like blizzard event during the oil-spill in 2010. Bacterially mediated oxidation of organic matter is reflected in a well-established sequence of oxidation-reduction reactions. We exploit redox sensitive trace elements including Mn, Fe, Re, U, Mo, and V to infer changes in the redox state of sediments following this large pulse of organic matter to the seafloor.

  5. Arsenic uptake by rice is influenced by microbe-mediated arsenic redox changes in the rhizosphere.

    PubMed

    Jia, Yan; Huang, Hai; Chen, Zheng; Zhu, Yong-Guan

    2014-01-21

    Arsenic (As) uptake by rice is largely determined by As speciation, which is strongly influenced by microbial activities. However, little is known about interactions between root and rhizosphere microbes, particularly on arsenic oxidation and reduction. In this study, two rice cultivars with different radial oxygen loss (ROL) ability were used to investigate the impact of microbially mediated As redox changes in the rhizosphere on As uptake. Results showed that the cultivar with higher ROL (Yangdao) had lower As uptake than that with lower ROL (Nongken). The enhancement of the rhizospheric effect on the abundance of the arsenite (As(III)) oxidase gene (aroA-like) was greater than on the arsenate (As(V)) reductase gene (arsC), and As(V) respiratory reductase gene (arrA), resulting in As oxidation and sequestration in the rhizosphere, particularly for cultivar Yangdao. The community of As(III)-oxidizing bacteria in the rhizosphere was dominated by α-Proteobacteria and β-Proteobacteria and was influenced by rhizospheric effects, rice straw application, growth stage, and cultivar. Application of rice straw into the soil increased As release and accumulation into rice plants. These results highlighted that uptake of As by rice is influenced by microbial processes, especially As oxidation in the rhizosphere, and these processes are influenced by root ROL and organic matter application.

  6. Understanding Biogeochemical Transformations Of Trace Elements In Multi Metal-Rich Geomaterials Under Stimulated Redox Conditions

    EPA Science Inventory

    Natural and anthropogenic influences on hydrological conditions can induce periodic or long-term reduced conditions in geologic materials. Such conditions can cause significant impacts on biogeochemical processes of trace elements in subsurface or near surface environments. The...

  7. Redox transformations of iron in the presence of exudate from the cyanobacterium Microcystis aeruginosa under conditions typical of natural waters.

    PubMed

    Wang, Kai; Garg, Shikha; Waite, T David

    2017-02-24

    Interaction of the exudate secreted by a toxic strain of the cyanobacterium Microcystis aeruginosa with Fe(II) and Fe(III) was investigated here under both acidic (pH 4) and alkaline (pH 8) conditions. At the concentrations of iron and exudate used, iron was present as dissolved iron (< 0.025 µm) at pH 4 but principally as small (< 0.45 µm) iron oxyhydroxide particles at pH 8 with only ~3-27% present in the dissolved form as a result of iron binding by the organic exudate. The formation of strong Fe(III)-exudate and relatively weak Fe(II)-exudate complexes alters the reduction potential of the Fe(III)/Fe(II) redox couple facilitating more rapid oxidation of Fe(II) at pH 4 and 8 than was the case in the absence of exudate. Our results further show that the organic exudate contains Fe(III) reducing moieties resulting in production of measureable concentrations of Fe(II). However, these reducing moieties are short-lived (with a half-life of 1.9 hours) and easily oxidized in air-saturated environments. A kinetic model was developed that adequately describes the redox transformation of Fe in the presence of exudate both at pH 4 and pH 8.

  8. Surface and redox properties of cobalt-ceria binary oxides: On the effect of Co content and pretreatment conditions

    NASA Astrophysics Data System (ADS)

    Konsolakis, Michalis; Sgourakis, Michalis; Carabineiro, Sónia A. C.

    2015-06-01

    Ceria-based transition metal catalysts have recently received considerable attention both in heterogeneous catalysis and electro-catalysis fields, due to their unique physicochemical characteristics. Their catalytic performance is greatly affected by the surface local chemistry and oxygen vacancies. The present study aims at investigating the impact of Co/Ce ratio and pretreatment conditions on the surface and redox properties of cobalt-ceria binary oxides. Co-ceria mixed oxides with different Co content (0, 20, 30, 60, 100 wt.%) were prepared by impregnation method and characterized by means of N2 adsorption at -196 °C, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results shown the improved reducibility of Co/CeO2 mixed oxides compared to single oxides, due to a synergistic interaction between cobalt and cerium. Oxidation pretreatment results in a preferential localization of cerium species on the outer surface. In contrast, a uniform distribution of cobalt and cerium species over the entire catalyst surface is obtained by the reduction process, which facilitates the formation of oxygen vacancies though Co3+/Co2+ and Ce3+/Ce4+ redox cycles. Fundamental insights toward tuning the surface chemistry of cobalt-ceria binary oxides are provided, paving the way for real-life industrial applications.

  9. NOVELTY DETECTION UNDER CHANGING ENVIRONMENTAL CONDITIONS

    SciTech Connect

    H. SOHN; K. WORDER; C. R. FARRAR

    2001-04-01

    The primary objective of novelty detection is to examine a system's dynamic response to determine if the system significantly deviates from an initial baseline condition. In reality, the system is often subject to changing environmental and operation conditions that affect its dynamic characteristics. Such variations include changes in loading, boundary conditions, temperature, and moisture. Most damage diagnosis techniques, however, generally neglect the effects of these changing ambient conditions. Here, a novelty detection technique is developed explicitly taking into account these natural variations of the system in order to minimize false positive indications of true system changes. Auto-associative neural networks are employed to discriminate system changes of interest such as structural deterioration and damage from the natural variations of the system.

  10. Virgin coconut oil maintains redox status and improves glycemic conditions in high fructose fed rats.

    PubMed

    Narayanankutty, Arunaksharan; Mukesh, Reshma K; Ayoob, Shabna K; Ramavarma, Smitha K; Suseela, Indu M; Manalil, Jeksy J; Kuzhivelil, Balu T; Raghavamenon, Achuthan C

    2016-01-01

    Virgin Coconut Oil (VCO), extracted from fresh coconut kernel possess similar fatty acid composition to that of Copra Oil (CO), a product of dried kernel. Although CO forms the predominant dietary constituent in south India, VCO is being promoted for healthy life due to its constituent antioxidant molecules. High fructose containing CO is an established model for insulin resistance and steatohepatitis in rodents. In this study, replacement of CO with VCO in high fructose diet markedly improved the glucose metabolism and dyslipidemia. The animals fed VCO diet had only 17 % increase in blood glucose level compared to CO fed animals (46 %). Increased level of GSH and antioxidant enzyme activities in VCO fed rats indicate improved hepatic redox status. Reduced lipid peroxidation and carbonyl adducts in VCO fed rats well corroborate with the histopathological findings that hepatic damage and steatosis were comparatively reduced than the CO fed animals. These results suggest that VCO could be an efficient nutraceutical in preventing the development of diet induced insulin resistance and associated complications possibly through its antioxidant efficacy.

  11. Determination of dissolution rates of spent fuel in carbonate solutions under different redox conditions with a flow-through experiment

    NASA Astrophysics Data System (ADS)

    Röllin, S.; Spahiu, K.; Eklund, U.-B.

    2001-09-01

    Dissolution rates of spent UO 2 fuel have been investigated using flow-through experiments under oxidizing, anoxic and reducing conditions. For oxidizing conditions, approximately congruent dissolution rates were obtained in the pH range 3-9.3 for U, Np, Ba, Tc, Cs, Sr and Rb. For these elements, steady-state conditions were obtained in the flow rate range 0.02-0.3 ml min -1. The dissolution rates were about 3 mg d -1 m-2 for pH>6. For pH<6, dissolution rates were strongly increasing for decreasing pH. Incongruent dissolution was found for Zr, Mo, Ru, Rh, Pd, Am and the lanthanides. The dissolution rates with H 2(g) saturated solutions dropped by up to four orders of magnitude as compared to oxidizing conditions. Because of the very low concentrations, only U, Pu, Am, Mo, Tc and Cs could be measured. For anoxic conditions, both the redox potential and dissolution rates increased approaching the same values as under oxidizing conditions.

  12. Investigating redox processes under diffusive and advective flow conditions using a coupled omics and synchrotron approach

    NASA Astrophysics Data System (ADS)

    Kemner, K. M.; Boyanov, M.; Flynn, T. M.; O'Loughlin, E. J.; Antonopoulos, D. A.; Kelly, S.; Skinner, K.; Mishra, B.; Brooks, S. C.; Watson, D. B.; Wu, W. M.

    2015-12-01

    FeIII- and SO42--reducing microorganisms and the mineral phases they produce have profound implications for many processes in aquatic and terrestrial systems. In addition, many of these microbially-catalysed geochemical transformations are highly dependent upon introduction of reactants via advective and diffusive hydrological transport. We have characterized microbial communities from a set of static microcosms to test the effect of ethanol diffusion and sulfate concentration on UVI-contaminated sediment. The spatial distribution, valence states, and speciation of both U and Fe were monitored in situ throughout the experiment by synchrotron x-ray absorption spectroscopy, in parallel with solution measurements of pH and the concentrations of sulfate, ethanol, and organic acids. After reaction initiation, a ~1-cm thick layer of sediment near the sediment-water (S-W) interface became visibly dark. Fe XANES spectra of the layer were consistent with the formation of FeS. Over the 4 year duration of the experiment, U LIII-edge XANES indicated reduction of U, first in the dark layer and then throughout the sediment. Next, the microcosms were disassembled and samples were taken from the overlying water and different sediment regions. We extracted DNA and characterized the microbial community by sequencing 16S rRNA gene amplicons with the Illumina MiSeq platform and found that the community evolved from its originally homogeneous composition, becoming significantly spatially heterogeneous. We have also developed an x-ray accessible column to probe elemental transformations as they occur along the flow path in a porous medium with the purpose of refining reactive transport models (RTMs) that describe coupled physical and biogeochemical processes in environmental systems. The elemental distribution dynamics and the RTMs of the redox driven processes within them will be presented.

  13. Redox changes in the brains of reproductive female rats during aging.

    PubMed

    Heemann, Fernanda Maciel; da Silva, Ana Carolina Almeida; Salomon, Tiago Boeira; Putti, Jordana Salete; Engers, Vanessa Krüger; Hackenhaar, Fernanda Schäfer; Benfato, Mara Silveira

    2017-01-01

    Reproduction is a critical and demanding phase of an animal's life. In mammals, females usually invest much more in parental care than males, and lactation is the most energetically demanding period of a female's life. Here, we tested whether oxidative stress is a consequence of reproduction in the brains of female Wistar rats. We evaluated the activities of glutathione peroxidase, glutathione S-transferase, and superoxide dismutase; H2O2 consumption; protein carbonylation; NO2 & NO3 levels; and total glutathione, as well as sex hormone levels in brain tissue of animals at 3, 6, 12, and 24months of age. Animals were grouped according to reproductive experience: breeders or non-breeders. Most of the studied parameters showed a difference between non-breeders and breeders at 12 and 24months. At 24months of age, breeders showed higher superoxide dismutase activity, H2O2 consumption, glutathione peroxidase activity, and carbonyl levels than non-breeders. In 12-month-old non-breeders, we observed a higher level of H2O2 consumption and higher superoxide dismutase and glutathione peroxidase activities than breeders. By evaluating the correlation network, we found that there were a larger number of influential nodes and positive links in breeder animals than in non-breeders, indicating a greater number of redox changes in breeder animals. Here, we also demonstrated that the aging process caused higher oxidative damage and higher antioxidant defenses in the brains of breeder female rats at 24months, suggesting that the reproduction process is costly, at least for the female brain. This study shows that there is a strong potential for a link between the cost of reproduction and oxidative stress.

  14. Trace elements geochemistry of kerogen in Upper Cretaceous sediments, Chad (Bornu) Basin, northeastern Nigeria: Origin and paleo-redox conditions

    NASA Astrophysics Data System (ADS)

    Adegoke, Adebanji Kayode; Abdullah, Wan Hasiah; Hakimi, Mohammed Hail; Sarki Yandoka, Babangida M.; Mustapha, Khairul Azlan; Aturamu, Adeyinka Oluyemi

    2014-12-01

    Trace element contents in isolated kerogen from Upper Cretaceous sediments within Gongila and Fika formations in the Chad (Bornu) Basin, northeastern Nigeria were determined using Inductively-coupled plasma mass spectrometer (ICP-MS), in order to infer the origin of the organic matter and the paleo-redox conditions during their sedimentation. The concentrations of the elements in the kerogen samples varied from 1.01 to 24,740 ppm. The distribution of elements shows that Fe is the most abundant element in Chad (Bornu) Basin kerogen, followed by Ce. Among the biophile elements, V is the most abundant, followed by Ni and Co in that order. Statistical evaluation of the elemental composition data shows that As, Ce, Pb, V, Cr, Fe, Co, Ni and U exhibit good positive correlations with each other. Molybdenum, on the other hand displays no obvious correlation with most of the trace elements determined including TOC, but has good positive correlation with TS and negative correlation with Tmax, Ce and Th, which suggests that the concentration of Mo decreases with increasing maturity and vice versa. Some trace element concentrations and their ratios suggest mixed marine and terrigenous source input for the organic matter (kerogen) in Chad (Bornu) Basin. More so, the concentrations of redox-sensitive elements, such as V, Ni, Cu, Cr Mo and Mn, in the kerogen samples suggest dysoxic bottom water conditions within the Gongila and Fika sediments. Cross-plots of V and Ni and V/(V + Ni) ratio also indicate that the organic matter of these samples was deposited in slightly reducing environments.

  15. Changes in the redox state in the retina and brain during the onset of diabetes in rats.

    PubMed

    Salceda, R; Vilchis, C; Coffe, V; Hernández-Muñoz, R

    1998-06-01

    Diabetic retinopathy is thought to result from chronic changes in the metabolic pathways of the retina. Hyperglycemia leads to increased intracellular glucose concentrations, alterations in glucose degradation and an increase in lactate/pyruvate ratio. We measured lactate content in retina and other ocular and non-ocular tissues from normal and diabetic rats in the early stages of streptozotocin-induced diabetes. The intracellular redox state was calculated from the cytoplasmic [lactate]/[pyruvate] ratio. Elevated lactate concentration were found in retina and cerebral cortex from diabetic rats. These concentrations led to a significant and progressive decrease in the NAD+/NADH ratio, suggesting that altered glucose metabolism is an initial step of retinopathy. It is thus possible that tissues such as cerebral cortex have mechanisms that prevent the damaging effect of lactate produced by hyperglycemia and/or alterations of the intracellular redox state.

  16. From climate change to molecular response: redox proteomics of ozone-induced responses in soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ozone (O3) causes significant agricultural losses with soybean being highly sensitive to this oxidant. Here we assess the effect of elevated seasonal O3 exposure on the total and redox proteomes of soybean. To understand the molecular responses to O3 exposure, soybean grown at the Soybean Free Air C...

  17. Biodegradation of fat, oil and grease (FOG) deposits under various redox conditions relevant to sewer environment.

    PubMed

    He, Xia; Zhang, Qian; Cooney, Michael J; Yan, Tao

    2015-07-01

    Fat, oil and, grease (FOG) deposits are one primary cause of sanitary sewer overflows (SSOs). While numerous studies have examined the formation of FOG deposits in sewer pipes, little is known about their biodegradation under sewer environments. In this study, FOG deposit biodegradation potential was determined by studying the biodegradation of calcium palmitate in laboratory under aerobic, nitrate-reducing, sulfate-reducing, and methanogenic conditions. Over 110 days of observation, calcium palmitate was biodegraded to CO2 under aerobic and nitrate-reducing conditions. An approximate 13 times higher CO2 production rate was observed under aerobic condition than under nitrate-reducing condition. Under sulfate-reducing condition, calcium palmitate was recalcitrant to biodegradation as evidenced by small reduction in sulfate. No evidence was found to support calcium palmitate degradation under methanogenic condition in the simulated sewer environment. Dominant microbial populations in the aerobic and nitrate-reducing microcosms were identified by Illumina seqeuncing, which may contain the capability to degrade calcium palmitate under both aerobic and nitrate-reducing conditions. Further study on these populations and their functional genes could shed more light on this microbial process and eventually help develop engineering solutions for SSOs control in the future.

  18. Resveratrol and N-acetylcysteine influence redox balance in equine articular chondrocytes under acidic and very low oxygen conditions

    PubMed Central

    Collins, John A.; Moots, Robert J.; Clegg, Peter D.; Milner, Peter I.

    2015-01-01

    Mature articular cartilage is an avascular tissue characterized by a low oxygen environment. In joint disease, acidosis and further reductions in oxygen levels occur, compromising cartilage integrity.This study investigated how acidosis and very low oxygen levels affect components of the cellular redox system in equine articular chondrocytesand whether the antioxidants resveratrol and N-acetylcysteine could modulate this system. We used articular chondrocytes isolated from nondiseased equine joints and cultured them in a 3-D alginate bead system for 48 h in <1, 2, 5, and 21% O2 at pH 7.2 or 6.2 in the absence or presence of the proinflammatory cytokine, interleukin-1β (10 ng/ml).In addition, chondrocytes were cultured with resveratrol (10 µM) or N-acetylcysteine (NAC) (2 mM).Cell viability, glycosaminoglycan (GAG) release, mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS), GSH:GSSG ratio, and SOD1 and SOD2 protein expression were measured. Very low levels of oxygen (<1%), acidosis (pH 6.2), and exposure to IL-1β led to reductions in cell viability, increased GAG release, alterations in ΔΨm and ROS levels, and reduced GSH:GSSG ratio. In addition, SOD1 and SOD2 protein expressions were reduced. Both resveratrol and NAC partially restored ΔΨm and ROS levels and prevented GAG release and cell loss and normalized SOD1 and SOD2 protein expression. In particular NAC was highly effective at restoring the GSH:GSSG ratio.These results show that the antioxidants resveratrol and N-acetylcysteine can counteract the redox imbalance in articular chondrocytes induced by low oxygen and acidic conditions. PMID:25998424

  19. Redox chemistry of the molecular interactions between tea catechins and human serum proteins under simulated hyperglycemic conditions.

    PubMed

    Özyurt, Hazal; Luna, Carolina; Estévez, Mario

    2016-03-01

    Carbonylation is an irreversible modification in oxidized proteins that has been directly related to a number of health disorders including Type 2 diabetes. Dietary antioxidants have been proposed to counteract the oxidative stress occurring under hyperglycemic conditions. An understanding of the nature and consequences of the molecular interactions between phytochemicals and human plasma proteins is of utmost scientific interest. Three tea catechins namely epicatechin (EC), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG) were tested for (i) their affinity to bind to human serum albumin (HSA) and human hemoglobin (HH) and (ii) their ability to inhibit tryptophan (Trp) depletion and for the formation of specific protein carbonyls and pentosidine in the aforementioned proteins. Both proteins (20 mg mL(-1)) were allowed to react with postprandial plasmatic concentrations of the catechins (EC: 0.7 μM, EGC: 1.8 μM, and EGCG: 0.7 μM) under simulated hyperglycemic conditions (12 mM glucose/0.2 mM Fe(3+)/37 °C/10 days). The three catechins were able to inhibit Trp oxidation and protein carbonylation in both plasma proteins. Some anti-glycation properties were linked to their binding affinities. The molecular interactions reported in the present study may explain the alleged beneficial effects of tea catechins against the redox impairment linked to hyperglycemic conditions.

  20. Exploring correlation between redox potential and other edaphic factors in field and laboratory conditions in relation to methane efflux.

    PubMed

    Singh, S N

    2001-10-01

    Methane is primarily a biogenic gas, which is implicated in global warming. Although its production in the anoxic conditions is regulated by several edaphic factors, aquatic macrophytes also influence methane emission by providing aerenchyma to act as chimney for CH4 transport from the sediment to troposphere, by releasing root exudates to the sediment to serve as substrate for methanogenic bacteria and by transporting atmospheric O2 to rhizosphere, which stimulates CH4 consumption. Among the edaphic factors, redox potential (Eh) is the most important, which largely determines the action of methanogenic bacteria. Hence, a study was undertaken first to find out the correlation between CH4 emission and edaphic factors in the field conditions and then to understand the relationship between Eh and other edaphic factors. The field studies revealed that natural wetlands were the major source of CH4 emission, and the vegetation plays an important role in CH4 emission from the water bodies. However, it was very difficult to establish a strong relationship between the CH4 emission and the edaphic factors in the field conditions due to other limiting factors and their constant fluctuations. In this connection, the laboratory experiments exhibited that soil temperature, pH, moisture regime and incubation period were negatively correlated with Eh, which determines the initiation of methanogenic process. However, organic carbon and the water regime over the soil surface did not show any impact on Eh in this study.

  1. Mitochondria and Redox Signaling in Steatohepatitis

    PubMed Central

    Morris, E. Matthew; Rector, R. Scott; Thyfault, John P.

    2011-01-01

    Abstract Alcoholic and nonalcoholic fatty liver diseases are potentially pathological conditions that can progress to steatohepatitis, fibrosis, and cirrhosis. These conditions affect millions of people throughout the world in part through poor lifestyle choices of excess alcohol consumption, overnutrition, and lack of regular physical activity. Abnormal mitochondrial and cellular redox homeostasis has been documented in steatohepatitis and results in alterations of multiple redox-sensitive signaling cascades. Ultimately, these changes in signaling lead to altered enzyme function and transcriptional activities of proteins critical to mitochondrial and cellular function. In this article, we review the current hypotheses linking mitochondrial redox state to the overall pathophysiology of alcoholic and nonalcoholic steatohepatitis and briefly discuss the current therapeutic options under investigation. Antioxid. Redox Signal. 15, 485–504. PMID:21128703

  2. Differential neurogenic effects of casein-derived opioid peptides on neuronal stem cells: implications for redox-based epigenetic changes.

    PubMed

    Trivedi, Malav; Zhang, Yiting; Lopez-Toledano, Miguel; Clarke, Andrew; Deth, Richard

    2016-11-01

    Food-derived peptides, such as β-casomorphin BCM7, have potential to cross the gastrointestinal tract and blood-brain barrier and are associated with neurological disorders and neurodevelopmental disorders. We previously established a novel mechanism through which BCM7 affects the antioxidant levels in neuronal cells leading to inflammatory consequences. In the current study, we elucidated the effects of casein-derived peptides on neuronal development by using the neurogenesis of neural stem cells (NSCs) as an experimental model. First, the transient changes in intracellular thiol metabolites during NSC differentiation (neurogenesis) were investigated. Next, the neurogenic effects of food-derived opioid peptides were measured, along with changes in intracellular thiol metabolites, redox status and global DNA methylation levels. We observed that the neurogenesis of NSCs was promoted by human BCM7 to a greater extent, followed by A2-derived BCM9 in contrast to bovine BCM7, which induced increased astrocyte formation. The effect was most apparent when human BCM7 was administered for 1day starting on 3days postplating, consistent with immunocytochemistry. Furthermore, neurogenic changes regulated by bovine BCM7 and morphine were associated with an increase in the glutathione/glutathione disulfide ratio and a decrease in the S-adenosylmethionine/S-adenosylhomocysteine ratio, indicative of changes in the redox and the methylation states. Finally, bovine BCM7 and morphine decreased DNA methylation in differentiating NSCs. In conclusion, these results suggest that food-derived opioid peptides and morphine regulated neurogenesis and differentiation of NSCs through changes in the redox state and epigenetic regulation.

  3. Conformational Change Near the Redox Center of Dihydrolipoamide Dehydrogenase Induced by NAD(+) to Regulate the Enzyme Activity.

    PubMed

    Fukamichi, Tomoe; Nishimoto, Etsuko

    2015-05-01

    Dihydrolipoamide dehydrogenase (LipDH) transfers two electrons from dihydrolipoamide (DHL) to NAD(+) mediated by FAD. Since this reaction is the final step of a series of catalytic reaction of pyruvate dehydrogenase multi-enzyme complex (PDC), LipDH is a key enzyme to maintain the fluent metabolic flow. We reported here the conformational change near the redox center of LipDH induced by NAD(+) promoting the access of the DHL to FAD. The increase in the affinity of DHL to redox center was evidenced by the decrease in K M responding to the increase in the concentration of NAD(+) in Lineweaver-Burk plots. The fluorescence intensity of FAD transiently reduced by the addition of DHL was not recovered but rather reduced by the binding of NAD(+) with LipDH. The fluorescence decay lifetimes of FAD and Trp were prolonged in the presence of NAD(+) to show that FAD would be free from the electron transfer from the neighboring Tyrs and the resonance energy transfer efficiency between Trp and FAD lowered. These results consistently reveal that the conformation near the FAD and the surroundings would be so rearranged by NAD(+) to allow the easier access of DHL to the redox center of LipDH.

  4. Effect of redox conditions on MTBE biodegradation in surface water Sediments

    USGS Publications Warehouse

    Bradley, P.M.; Chapelle, F.H.; Landmeyer, J.E.

    2001-01-01

    Microbial degradation of methyl tert-butyl ether (MTBE) was observed in surface water-sediment microcosms under anaerobic conditions. The efficiency and products of anaerobic MTBE biodegradation were dependent on the predominant terminal electron-accepting conditions. In the presence of substantial methanogenic activity, MTBE biodegradation was nominal and involved reduction of MTBE to the toxic product, tert-butyl alcohol (TBA). In the absence of significant methanogenic activity, accumulation of [14C]TBA generally decreased, and mineralization of [U-14C]MTBE to 14CO2 generally increased as the oxidative potential of the predominant terminal electron acceptor increased in the order of SO4, Fe(III), Mn(IV) < NO3 < O2. Microbial mineralization of MTBE to CO2 under Mn(IV)or SO4-reducing conditions has not been reported previously. The results of this study indicate that microorganisms inhabiting the sediments of streams and lakes can degrade MTBE effectively under a range of anaerobic terminal electron-accepting conditions. Thus, anaerobic bed sediment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States.

  5. Redox-sensitive structural change in the A-domain of HMGB1 and its implication for the binding to cisplatin modified DNA

    SciTech Connect

    Wang, Jing; Tochio, Naoya; Takeuchi, Aya; Uewaki, Jun-ichi; Kobayashi, Naohiro; Tate, Shin-ichi

    2013-11-29

    Highlights: •The structure of the oxidized A-domain of human HMGB1 was solved. •Phe38 ring was flipped in the oxidized structure from that in the reduced form. •The flipped ring disables the intercalation into the cisplatinated lesions. •The functionally relevant redox-dependent structural change was described. -- Abstract: HMGB1 (high-mobility group B1) is a ubiquitously expressed bifunctional protein that acts as a nuclear protein in cells and also as an inflammatory mediator in the extracellular space. HMGB1 changes its functions according to the redox states in both intra- and extra-cellular environments. Two cysteines, Cys23 and Cys45, in the A-domain of HMGB1 form a disulfide bond under oxidative conditions. The A-domain with the disulfide bond shows reduced affinity to cisplatin modified DNA. We have solved the oxidized A-domain structure by NMR. In the structure, Phe38 has a flipped ring orientation from that found in the reduced form; the phenyl ring in the reduced form intercalates into the platinated lesion in DNA. The phenyl ring orientation in the oxidized form is stabilized through intramolecular hydrophobic contacts. The reorientation of the Phe38 ring by the disulfide bond in the A-domain may explain the reduced HMGB1 binding affinity towards cisplatinated DNA.

  6. One electron changes everything: a multispecies copper redox shuttle for dye-sensitized solar cells.

    SciTech Connect

    Hoffeditz, William L.; Katz, Michael J.; Deria, Pravas; Cutsail, George E.; Pellin, Michael J.; Farha, Omar K.; Hupp, Joseph T.

    2016-02-25

    Dye-sensitized solar cells (DSCs) are an established alternative photovoltaic technology that offers numerous potential advantages in solar energy applications. However, this technology has been limited by the availability of molecular redox couples that are both noncorrosive/nontoxic and do not diminish the performance of the device. In an effort to overcome these shortcomings, a copper-containing redox shuttle derived from 1,8-bis(2'-pyridyl)-3,6-dithiaoctane (PDTO) ligand and the common DSC additive 4-tert-butylpyridine (TBP) was investigated. Electrochemical measurements, single-crystal X-ray diffraction, and absorption and electron paramagnetic resonance spectroscopies reveal that, upon removal of one metal-centered electron, PDTO-enshrouded copper ions completely shed the tetradentate PDTO ligand and replace it with four or more TBP ligands. Thus, the Cu(I) and Cu(II) forms of the electron shuttle have completely different coordination spheres and are characterized by widely differing Cu(II/I) formal potentials and reactivities for forward versus reverse electron transfer. Notably, the coordination-sphere replacement process is fully reversed upon converting Cu(II) back to Cu(I). In cells featuring an adsorbed organic dye and a nano- and mesoparticulate, TiO2-based, photoelectrode, the dual species redox shuttle system engenders performance superior to that obtained with shuttles based on the (II/I) forms of either of the coordination complexes in isolation.

  7. The redox environment triggers conformational changes and aggregation of hIAPP in Type II Diabetes

    PubMed Central

    Rodriguez Camargo, Diana C.; Tripsianes, Konstantinos; Buday, Katalin; Franko, Andras; Göbl, Christoph; Hartlmüller, Christoph; Sarkar, Riddhiman; Aichler, Michaela; Mettenleiter, Gabriele; Schulz, Michael; Böddrich, Annett; Erck, Christian; Martens, Henrik; Walch, Axel Karl; Madl, Tobias; Wanker, Erich E.; Conrad, Marcus; de Angelis, Martin Hrabě; Reif, Bernd

    2017-01-01

    Type II diabetes (T2D) is characterized by diminished insulin production and resistance of cells to insulin. Among others, endoplasmic reticulum (ER) stress is a principal factor contributing to T2D and induces a shift towards a more reducing cellular environment. At the same time, peripheral insulin resistance triggers the over-production of regulatory hormones such as insulin and human islet amyloid polypeptide (hIAPP). We show that the differential aggregation of reduced and oxidized hIAPP assists to maintain the redox equilibrium by restoring redox equivalents. Aggregation thus induces redox balancing which can assist initially to counteract ER stress. Failure of the protein degradation machinery might finally result in β-cell disruption and cell death. We further present a structural characterization of hIAPP in solution, demonstrating that the N-terminus of the oxidized peptide has a high propensity to form an α-helical structure which is lacking in the reduced state of hIAPP. In healthy cells, this residual structure prevents the conversion into amyloidogenic aggregates. PMID:28287098

  8. GLOBAL CHANGE EFFECTS ON CORAL REEF CONDITION

    EPA Science Inventory

    Fisher, W., W. Davis, J. Campbell, L. Courtney, P. Harris, B. Hemmer, M. Parsons, B. Quarles and D. Santavy. In press. Global Change Effects on Coral Reef Condition (Abstract). To be presented at the EPA Science Forum: Healthy Communities and Ecosystems, 1-3 June 2004, Washington...

  9. Conditioned Reinforcement Value and Resistance to Change

    ERIC Educational Resources Information Center

    Shahan, Timothy A.; Podlesnik, Christopher A.

    2008-01-01

    Three experiments examined the effects of conditioned reinforcement value and primary reinforcement rate on resistance to change using a multiple schedule of observing-response procedures with pigeons. In the absence of observing responses in both components, unsignaled periods of variable-interval (VI) schedule food reinforcement alternated with…

  10. Disentangling the record of diagenesis, local redox conditions, and global seawater chemistry during the latest Ordovician glaciation

    NASA Astrophysics Data System (ADS)

    Ahm, Anne-Sofie C.; Bjerrum, Christian J.; Hammarlund, Emma U.

    2017-02-01

    The Late Ordovician stratigraphic record integrates glacio-eustatic processes, water-column redox conditions and carbon cycle dynamics. This complex stratigraphic record, however, is dominated by deposits from epeiric seas that are susceptible to local physical and chemical processes decoupled from the open ocean. This study contributes a unique deep water basinal perspective to the Late Ordovician (Hirnantian) glacial record and the perturbations in seawater chemistry that may have contributed to the Hirnantian mass extinction event. We analyze recently drilled cores and outcrop samples from the upper Vinini Formation in central Nevada and report combined trace- and major element geochemistry, Fe speciation (FePy /FeHR and FeHR /FeT), and stable isotope chemostratigraphy (δ13COrg and δ34SPy). Measurements of paired samples from outcrop and core reveal that reactive Fe is preserved mainly as pyrite in core samples, while outcrop samples have been significantly altered as pyrite has been oxidized and remobilized by modern weathering processes. Fe speciation in the more pristine core samples indicates persistent deep water anoxia, at least locally through the Late Ordovician, in contrast to the prevailing interpretation of increased Hirnantian water column oxygenation in shallower environments. Deep water redox conditions were likely decoupled from shallower environments by a basinal shift in organic matter export driven by decreasing rates of organic matter degradation and decreasing shelf areas. The variable magnitude in the record of the Hirnantian carbon isotope excursion may be explained by this increased storage of isotopically light carbon in the deep ocean which, in combination with increased glacio-eustatic restriction, would strengthen lateral- and vertical gradients in seawater chemistry. We adopt multivariate statistical methods to deconstruct the spatial and temporal re-organization of seawater chemistry during the Hirnantian glaciation and attempt to

  11. Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil.

    PubMed

    Shaheen, Sabry M; Rinklebe, Jörg

    2017-01-15

    The impact of sugar beet factory lime (SBFL) on the release dynamics and mobilization of toxic metals (TMs) under dynamic redox conditions in floodplain soils has not been studied up to date. Therefore, the aim of this study was to verify the scientific hypothesis that SBFL is able to immobilize Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn under different redox potentials (EH) in a contaminated floodplain soil. For this purpose, the non-treated contaminated soil (CS) and the same soil treated with SBFL (CS+SBFL) were flooded in the laboratory using a highly sophisticated automated biogeochemical microcosm apparatus. The experiment was conducted stepwise from reducing (-13 mV) to oxidizing (+519 mV) soil conditions. Soil pH decreased under oxic conditions in CS (from 6.9 to 4.0) and in CS+SBFL (from 7.5 to 4.4). The mobilization of Cu, Cr, Pb, and Fe were lower in CS+SBFL than in CS under both reducing/neutral and oxic/acidic conditions. Those results demonstrate that SBFL is able to decrease concentrations of these elements under a wide range of redox and pH conditions. The mobilization of Cd, Co, Mn, Mo, Ni, and Zn were higher in CS+SBFL than in CS under reducing/neutral conditions; however, these concentrations showed an opposite behavior under oxic/acidic conditions and were lower in CS+SBFL than in CS. We conclude that SBFL immobilized Cu, Cr, Pb, and Fe under dynamic redox conditions and immobilized Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, the latter elements were mobilized under reducing neutral conditions in the studied soil. Therefore, the addition of SBFL to acid floodplain soils contaminated with TMs might be an important alternative for ameliorating these soils with view to a sustainable management of these soils.

  12. Stable Chromium Isotopes as tracer of changes in weathering processes and redox state of the ocean during Neoproterozoic glaciation

    NASA Astrophysics Data System (ADS)

    Dossing, L. N.; Gaucher, C.; Boggiani, P. C.; Frei, R.

    2010-12-01

    The chemistry of surface environments on Earth has essentially evolved from early anoxic conditions to a present day oxic state. How in detail this transition occurred is still a matter of debate but the last 200 million years (My) of the Neoproterozoic Era [(1000 to 542 million years ago (Ma)] show an emerging picture of large scale fluctuations in the redox state of the oceans [1-2]. The reasons for these fluctuations are to be sought in Earth’s atmospheric oxygenation which led to the rapid radiation of oxygen-utilizing macroscopic metazoans, but details regarding the nature of these fluctuations remain unclear. The Late Neoproterozoic is known for a number of widespread glaciations causing the return of ferruginous oceans which were absent for more than a billion years of Earth history. This study elaborates on the idea that Chromium (Cr) stable isotopes in Fe-rich chemical sediments deposited during glacial events are suitable for tracing oxygenation of surface environments through Earth's history [3]. The focus of this study is to apply the Cr isotope system to one of the Marinoan (650-630 Ma) glacio-marine sequences (Jacadigo Group, Brazil) in order to get a detailed spatial and relative temporal resolution of changes in weathering processes and redox states of the respective ocean basin during the depositional period of the sediments. The Jacadigo Group is a glacio-marine succession which is composed of the Urucum Fm. (sandstones) at the base, the Santa Cruz Fm. (BIFs) and the Puga Fm. (Fe-rich glacial diamictites) at the top. Cr stable isotope measurements on various BIF horizons of the Santa Cruz Fm. yielded positive δ53/52Cr values range from +0.4 to+ 0.9‰, while the overlying Fe-rich glaciogenic diamictites of the Puga Fm. show δ53/52Cr values range from to +0.1 to+ 0.4‰. These positively fractionated values correspond to positive δ53/52Cr values measured in other Late Neoproterozoic BIFs and speak for the occurrence of potential oxygenation

  13. Conditioned reinforcement value and resistance to change.

    PubMed

    Shahan, Timothy A; Podlesnik, Christopher A

    2008-05-01

    Three experiments examined the effects of conditioned reinforcement value and primary reinforcement rate on resistance to change using a multiple schedule of observing-response procedures with pigeons. In the absence of observing responses in both components, unsignaled periods of variable-interval (VI) schedule food reinforcement alternated with extinction. Observing responses in both components intermittently produced 15 s of a stimulus associated with the VI schedule (i.e., S+). In the first experiment, a lower-valued conditioned reinforcer and a higher rate of primary reinforcement were arranged in one component by adding response-independent food deliveries uncorrelated with S+. In the second experiment, one component arranged a lower valued conditioned reinforcer but a higher rate of primary reinforcement by increasing the probability of VI schedule periods relative to extinction periods. In the third experiment, the two observing-response components provided similar rates of primary reinforcement but arranged different valued conditioned reinforcers. Across the three experiments, observing-response rates were typically higher in the component associated with the higher valued conditioned reinforcer. Resistance to change was not affected by conditioned reinforcement value, but was an orderly function of the rate of primary reinforcement obtained in the two components. One interpretation of these results is that S+ value does not affect response strength and that S+ deliveries increase response rates through a mechanism other than reinforcement. Alternatively, because resistance to change depends on the discriminative stimulus-reinforcer relation, the failure of S+ value to impact resistance to change could have resulted from a lack of transfer of S+ value to the broader discriminative context.

  14. Effect of H2 and redox condition on biotic and abiotic MTBE transformation

    USGS Publications Warehouse

    Bradley, P.M.; Chapelle, F.H.; Landmeyer, J.E.

    2006-01-01

    Laboratory studies conducted with surface water sediment from a methyl tert-butyl ether (MTBE)-contaminated site in South Carolina demonstrated that, under methanogenic conditions, [U-14C] MTBE was transformed to 14C tert-butyl alcohol (TBA) with no measurable production of 14CO2. Production of TBA was not attributed to the activity of methanogenic microorganisms, however, because comparable transformation of [U-14C] MTBE to 14C-TBA also was observed in heat-sterilized controls with dissolved H2 concentrations > 5 nM. The results suggest that the transformation of MTBE to TBA may be an abiotic process that is driven by biologically produced H2 under in situ conditions. In contrast, mineralization of [U-14C] MTBE to 14CO2 was completely inhibited by heat sterilization and only observed in treatments characterized by dissolved H2 concentrations < 2 nM. These results suggest that the pathway of MTBE transformation is influenced by in situ H2 concentrations and that in situ H2 concentrations may be an useful indicator of MTBE transformation pathways in ground water systems.

  15. Phosphorus recycling and burial in Baltic Sea sediments with contrasting redox conditions

    NASA Astrophysics Data System (ADS)

    Slomp, Caroline P.; Mort, Haydon P.; Reed, Dan C.; Jilbert, Tom; Gustafsson, Bo G.

    2010-05-01

    The Baltic Sea is a classical example of a coastal system that is subject to an increased intensity and spatial extent of hypoxia due to human activities. The expansion of hypoxia since the 1960s is the result of increased inputs of nutrients from land (both from fertilizer and wastewater) and is negatively affecting living conditions for benthic organisms. In addition, the biogeochemical cycling of carbon and nutrients has been significantly altered. Water column studies have shown that the availability of dissolved inorganic phosphorus (DIP) is positively correlated with hypoxia due to release of phosphorus from sediment Fe-oxides and from organic matter upon the transition from oxic to hypoxic conditions. Thus, a large internal source of phosphorus exists in the sediment that largely controls short-term variability in water column DIP concentrations. In this presentation, we focus on results of recent field and modeling work for various parts of the Baltic Sea that confirm the role of Fe-bound P from seasonally hypoxic sediments at intermediate water depths as a major source of DIP. We also show that extended hypoxia and anoxia leads to depletion of sediment Fe-bound P and, ultimately, lower rates of sediment-water exchange of P. Authigenic Ca-P minerals appear to be only a relatively minor burial sink for P. The lack of major inorganic P burial makes the Baltic Sea sensitive to the feedback loop between increased hypoxia, enhanced regeneration of P and increased primary productivity. Historical records of bottom water oxygen at two sites (Bornholm, Northern Gotland) show a decline over the past century which is accompanied by a rise in values of typical sediment proxies for anoxia (total sulfur, molybdenum and organic C/P ratios). While sediment reactive P concentrations in anoxic basins are equal to or higher than at oxic sites, burial rates of P at hypoxic and anoxic sites are up to 20 times lower because of lower sedimentation rates. Nevertheless, burial of

  16. The redox switch/redox coupling hypothesis.

    PubMed

    Cerdán, Sebastián; Rodrigues, Tiago B; Sierra, Alejandra; Benito, Marina; Fonseca, Luis L; Fonseca, Carla P; García-Martín, María L

    2006-01-01

    We provide an integrative interpretation of neuroglial metabolic coupling including the presence of subcellular compartmentation of pyruvate and monocarboxylate recycling through the plasma membrane of both neurons and glial cells. The subcellular compartmentation of pyruvate allows neurons and astrocytes to select between glucose and lactate as alternative substrates, depending on their relative extracellular concentration and the operation of a redox switch. This mechanism is based on the inhibition of glycolysis at the level of glyceraldehyde 3-phosphate dehydrogenase by NAD(+) limitation, under sufficiently reduced cytosolic NAD(+)/NADH redox conditions. Lactate and pyruvate recycling through the plasma membrane allows the return to the extracellular medium of cytosolic monocarboxylates enabling their transcellular, reversible, exchange between neurons and astrocytes. Together, intracellular pyruvate compartmentation and monocarboxylate recycling result in an effective transcellular coupling between the cytosolic NAD(+)/NADH redox states of both neurons and glial cells. Following glutamatergic neurotransmission, increased glutamate uptake by the astrocytes is proposed to augment glycolysis and tricarboxylic acid cycle activity, balancing to a reduced cytosolic NAD(+)/NADH in the glia. Reducing equivalents are transferred then to the neuron resulting in a reduced neuronal NAD(+)/NADH redox state. This may eventually switch off neuronal glycolysis, favoring the oxidation of extracellular lactate in the lactate dehydrogenase (LDH) equilibrium and in the neuronal tricarboxylic acid cycles. Finally, pyruvate derived from neuronal lactate oxidation, may return to the extracellular space and to the astrocyte, restoring the basal redox state and beginning a new loop of the lactate/pyruvate transcellular coupling cycle. Transcellular redox coupling operates through the plasma membrane transporters of monocarboxylates, similarly to the intracellular redox shuttles

  17. Permeable Reactive Barriers Designed To Mitigate Eutrophication Alter Bacterial Community Composition and Aquifer Redox Conditions.

    PubMed

    Hiller, Kenly A; Foreman, Kenneth H; Weisman, David; Bowen, Jennifer L

    2015-10-01

    Permeable reactive barriers (PRBs) consist of a labile carbon source that is positioned to intercept nitrate-laden groundwater to prevent eutrophication. Decomposition of carbon in the PRB drives groundwater anoxic, fostering microbial denitrification. Such PRBs are an ideal habitat to examine microbial community structure under high-nitrate, carbon-replete conditions in coastal aquifers. We examined a PRB installed at the Waquoit Bay National Estuarine Research Reserve in Falmouth, MA. Groundwater within and below the PRB was depleted in oxygen compared to groundwater at sites upgradient and at adjacent reference sites. Nitrate concentrations declined from a high of 25 μM upgradient and adjacent to the barrier to <0.1 μM within the PRB. We analyzed the total and active bacterial communities filtered from groundwater flowing through the PRB using amplicons of 16S rRNA and of the 16S rRNA genes. Analysis of the 16S rRNA genes collected from the PRB showed that the total bacterial community had high relative abundances of bacteria thought to have alternative metabolisms, such as fermentation, including candidate phyla OD1, OP3, TM7, and GN02. In contrast, the active bacteria had lower abundances of many of these bacteria, suggesting that the bacterial taxa that differentiate the PRB groundwater community were not actively growing. Among the environmental variables analyzed, dissolved oxygen concentration explained the largest proportion of total community structure. There was, however, no significant correlation between measured environmental parameters and the active microbial community, suggesting that controls on the active portion may differ from the community as a whole.

  18. Single-cell Sequencing of Thiomargarita Reveals Genomic Flexibility for Adaptation to Dynamic Redox Conditions.

    PubMed

    Winkel, Matthias; Salman-Carvalho, Verena; Woyke, Tanja; Richter, Michael; Schulz-Vogt, Heide N; Flood, Beverly E; Bailey, Jake V; Mußmann, Marc

    2016-01-01

    Large, colorless sulfur-oxidizing bacteria (LSB) of the family Beggiatoaceae form thick mats at sulfidic sediment surfaces, where they efficiently detoxify sulfide before it enters the water column. The genus Thiomargarita harbors the largest known free-living bacteria with cell sizes of up to 750 μm in diameter. In addition to their ability to oxidize reduced sulfur compounds, some Thiomargarita spp. are known to store large amounts of nitrate, phosphate and elemental sulfur internally. To date little is known about their energy yielding metabolic pathways, and how these pathways compare to other Beggiatoaceae. Here, we present a draft single-cell genome of a chain-forming "Candidatus Thiomargarita nelsonii Thio36", and conduct a comparative analysis to five draft and one full genome of other members of the Beggiatoaceae. "Ca. T. nelsonii Thio36" is able to respire nitrate to both ammonium and dinitrogen, which allows them to flexibly respond to environmental changes. Genes for sulfur oxidation and inorganic carbon fixation confirmed that "Ca. T. nelsonii Thio36" can function as a chemolithoautotroph. Carbon can be fixed via the Calvin-Benson-Bassham cycle, which is common among the Beggiatoaceae. In addition we found key genes of the reductive tricarboxylic acid cycle that point toward an alternative CO2 fixation pathway. Surprisingly, "Ca. T. nelsonii Thio36" also encodes key genes of the C2-cycle that convert 2-phosphoglycolate to 3-phosphoglycerate during photorespiration in higher plants and cyanobacteria. Moreover, we identified a novel trait of a flavin-based energy bifurcation pathway coupled to a Na(+)-translocating membrane complex (Rnf). The coupling of these pathways may be key to surviving long periods of anoxia. As other Beggiatoaceae "Ca. T. nelsonii Thio36" encodes many genes similar to those of (filamentous) cyanobacteria. In summary, the genome of "Ca. T. nelsonii Thio36" provides additional insight into the ecology of giant sulfur

  19. Single-cell sequencing of Thiomargarita reveals genomic flexibility for adaptation to dynamic redox conditions

    DOE PAGES

    Winkel, Matthias; Salman-Carvalho, Verena; Woyke, Tanja; ...

    2016-06-21

    Large, colorless sulfur-oxidizing bacteria (LSB) of the family Beggiatoaceae form thick mats at sulfidic sediment surfaces, where they efficiently detoxify sulfide before it enters the water column. The genus Thiomargarita harbors the largest known free-living bacteria with cell sizes of up to 750 μm in diameter. In addition to their ability to oxidize reduced sulfur compounds, some Thiornargarita spp. are known to store large amounts of nitrate, phosphate and elemental sulfur internally. To date little is known about their energy yielding metabolic pathways, and how these pathways compare to other Beggiatoaceae. Here, we present a draft single-cell genome of amore » chain-forming "Candidatus Thiomargarita nelsonii Thio36", and conduct a comparative analysis to five draft and one full genome of other members of the Beggiatoaceae. "Ca. T. nelsonii Thio36" is able to respire nitrate to both ammonium and dinitrogen, which allows them to flexibly respond to environmental changes. Genes for sulfur oxidation and inorganic carbon fixation confirmed that "Ca. T. nelsonii Thio36" can function as a chemolithoautotroph. Carbon can be fixed via the Calvin-Benson-Bassham cycle, which is common among the Beggiatoaceae. In addition we found key genes of the reductive tricarboxylic acid cycle that point toward an alternative CO2 fixation pathway. Surprisingly, "Ca. T. nelsonii Thio36" also encodes key genes of the C2-cycle that convert 2-phosphoglycolate to 3-phosphoglycerate during photorespiration in higher plants and cyanobacteria. Moreover, we identified a novel trait of a flavin-based energy bifurcation pathway coupled to a Na+-translocating membrane complex (Rnf). The coupling of these pathways may be key to surviving long periods of anoxia. As other Beggiatoaceae "Ca. T. nelsonii Thio36" encodes many genes similar to those of (filamentous) cyanobacteria. In conclusion, the genome of "Ca. T. nelsonii Thio36" provides additional insight into the ecology of giant sulfur

  20. Single-cell Sequencing of Thiomargarita Reveals Genomic Flexibility for Adaptation to Dynamic Redox Conditions

    PubMed Central

    Winkel, Matthias; Salman-Carvalho, Verena; Woyke, Tanja; Richter, Michael; Schulz-Vogt, Heide N.; Flood, Beverly E.; Bailey, Jake V.; Mußmann, Marc

    2016-01-01

    Large, colorless sulfur-oxidizing bacteria (LSB) of the family Beggiatoaceae form thick mats at sulfidic sediment surfaces, where they efficiently detoxify sulfide before it enters the water column. The genus Thiomargarita harbors the largest known free-living bacteria with cell sizes of up to 750 μm in diameter. In addition to their ability to oxidize reduced sulfur compounds, some Thiomargarita spp. are known to store large amounts of nitrate, phosphate and elemental sulfur internally. To date little is known about their energy yielding metabolic pathways, and how these pathways compare to other Beggiatoaceae. Here, we present a draft single-cell genome of a chain-forming “Candidatus Thiomargarita nelsonii Thio36”, and conduct a comparative analysis to five draft and one full genome of other members of the Beggiatoaceae. “Ca. T. nelsonii Thio36” is able to respire nitrate to both ammonium and dinitrogen, which allows them to flexibly respond to environmental changes. Genes for sulfur oxidation and inorganic carbon fixation confirmed that “Ca. T. nelsonii Thio36” can function as a chemolithoautotroph. Carbon can be fixed via the Calvin–Benson–Bassham cycle, which is common among the Beggiatoaceae. In addition we found key genes of the reductive tricarboxylic acid cycle that point toward an alternative CO2 fixation pathway. Surprisingly, “Ca. T. nelsonii Thio36” also encodes key genes of the C2-cycle that convert 2-phosphoglycolate to 3-phosphoglycerate during photorespiration in higher plants and cyanobacteria. Moreover, we identified a novel trait of a flavin-based energy bifurcation pathway coupled to a Na+-translocating membrane complex (Rnf). The coupling of these pathways may be key to surviving long periods of anoxia. As other Beggiatoaceae “Ca. T. nelsonii Thio36” encodes many genes similar to those of (filamentous) cyanobacteria. In summary, the genome of “Ca. T. nelsonii Thio36” provides additional insight into the ecology of

  1. Improvement of the Redox Balance Increases l-Valine Production by Corynebacterium glutamicum under Oxygen Deprivation Conditions

    PubMed Central

    Hasegawa, Satoshi; Uematsu, Kimio; Natsuma, Yumi; Suda, Masako; Hiraga, Kazumi; Jojima, Toru; Inui, Masayuki

    2012-01-01

    Production of l-valine under oxygen deprivation conditions by Corynebacterium glutamicum lacking the lactate dehydrogenase gene ldhA and overexpressing the l-valine biosynthesis genes ilvBNCDE was repressed. This was attributed to imbalanced cofactor production and consumption in the overall l-valine synthesis pathway: two moles of NADH was generated and two moles of NADPH was consumed per mole of l-valine produced from one mole of glucose. In order to solve this cofactor imbalance, the coenzyme requirement for l-valine synthesis was converted from NADPH to NADH via modification of acetohydroxy acid isomeroreductase encoded by ilvC and introduction of Lysinibacillus sphaericus leucine dehydrogenase in place of endogenous transaminase B, encoded by ilvE. The intracellular NADH/NAD+ ratio significantly decreased, and glucose consumption and l-valine production drastically improved. Moreover, l-valine yield increased and succinate formation decreased concomitantly with the decreased intracellular redox state. These observations suggest that the intracellular NADH/NAD+ ratio, i.e., reoxidation of NADH, is the primary rate-limiting factor for l-valine production under oxygen deprivation conditions. The l-valine productivity and yield were even better and by-products derived from pyruvate further decreased as a result of a feedback resistance-inducing mutation in the acetohydroxy acid synthase encoded by ilvBN. The resultant strain produced 1,470 mM l-valine after 24 h with a yield of 0.63 mol mol of glucose−1, and the l-valine productivity reached 1,940 mM after 48 h. PMID:22138982

  2. Redox Regulation of Plant Development

    PubMed Central

    Considine, Michael J.

    2014-01-01

    Abstract Significance: We provide a conceptual framework for the interactions between the cellular redox signaling hub and the phytohormone signaling network that controls plant growth and development to maximize plant productivity under stress-free situations, while limiting growth and altering development on exposure to stress. Recent Advances: Enhanced cellular oxidation plays a key role in the regulation of plant growth and stress responses. Oxidative signals or cycles of oxidation and reduction are crucial for the alleviation of dormancy and quiescence, activating the cell cycle and triggering genetic and epigenetic control that underpin growth and differentiation responses to changing environmental conditions. Critical Issues: The redox signaling hub interfaces directly with the phytohormone network in the synergistic control of growth and its modulation in response to environmental stress, but a few components have been identified. Accumulating evidence points to a complex interplay of phytohormone and redox controls that operate at multiple levels. For simplicity, we focus here on redox-dependent processes that control root growth and development and bud burst. Future Directions: The multiple roles of reactive oxygen species in the control of plant growth and development have been identified, but increasing emphasis should now be placed on the functions of redox-regulated proteins, along with the central roles of reductants such as NAD(P)H, thioredoxins, glutathione, glutaredoxins, peroxiredoxins, ascorbate, and reduced ferredoxin in the regulation of the genetic and epigenetic factors that modulate the growth and vigor of crop plants, particularly within an agricultural context. Antioxid. Redox Signal. 21, 1305–1326. PMID:24180689

  3. Redox Regulation of Mitochondrial Function

    PubMed Central

    Handy, Diane E.

    2012-01-01

    Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

  4. Hydroquinone-Mediated Redox Cycling of Iron and Concomitant Oxidation of Hydroquinone in Oxic Waters under Acidic Conditions: Comparison with Iron-Natural Organic Matter Interactions.

    PubMed

    Jiang, Chao; Garg, Shikha; Waite, T David

    2015-12-15

    Interactions of 1,4-hydroquinone with soluble iron species over a pH range of 3-5 in the air-saturated and partially deoxygenated solution are examined here. Our results show that 1,4-hydroquinone reduces Fe(III) in acidic conditions, generating semiquinone radicals (Q(•-)) that can oxidize Fe(II) back to Fe(III). The oxidation rate of Fe(II) by Q(•-)increases with increase in pH due to the speciation change of Q(•-) with its deprotonated form (Q(•-)) oxidizing Fe(II) more rapidly than the protonated form (HQ(•)). Although the oxygenation of Fe(II) is negligible at pH < 5, O2 still plays an important role in iron redox transformation by rapidly oxidizing Q(•-) to form benzoquinone (Q). A kinetic model is developed to describe the transformation of quinone and iron under all experimental conditions. The results obtained here are compared with those obtained in our previous studies of iron-Suwannee River fulvic acid (SRFA) interactions in acidic solutions and support the hypothesis that hydroquinone moieties can reduce Fe(III) in natural waters. However, the semiquinone radicals generated in pure hydroquinone solution are rapidly oxidized by dioxygen, while the semiquinone radicals generated in SRFA solution are resistant to oxidation by dioxygen, with the result that steady-state semiquinone concentrations in SRFA solutions are 2-3 orders of magnitude greater than in solutions of 1,4-hydroquinone. As a result, semiquinone moieties in SRFA play a much more important role in iron redox transformations than is the case in solutions of simple quinones such as 1,4-hydroquinone. This difference in the steady-state concentration of semiquinone species has a dramatic effect on the cycling of iron between the +II and +III oxidation states, with iron turnover frequencies in solutions containing SRFA being 10-20 times higher than those observed in solutions of 1,4-hydroquinone.

  5. Temperature micro-mapping and redox conditions of a chlorite zoning pattern in green-schist facies fault zone

    NASA Astrophysics Data System (ADS)

    Trincal, Vincent; Lanari, Pierre; Lacroix, Brice; Buatier, Martine D.; Charpentier, Delphine; Labaume, Pierre; Muñoz, Manuel

    2014-05-01

    Faults are major discontinuities driving fluid flows and playing a major role in precipitation of ore deposits. Mineral paragenesis and crystal chemistry depend on Temperature (T) condition, fluid composition but also on the redox environment of precipitation. The studied samples come from the Pic de Port Vieux thrust sheet, a minor thrust sheet associated to Gavarnie thrust fault zone (Central Pyrenees). The Pic de Port Vieux Thrust sheet comprises a 1-20 meter thick layer of Triassic red beds and mylonitized Cretaceous limestone. The thrust sheet is affected by faults and cleavage; the other important deformation product is a set of veins filled by quartz and chlorite. Microstructural and mineralogical investigations were performed based on the previous work of Grant (1992). The crystallization of chlorite is syn-tectonic and strongly controlled by the fluid circulation during the Gavarnie thrust sheet emplacement. Chlorite precipitated in extension veins, crack-seal shear veins or in open cavities. The chlorite filling the open cavities occurs as pseudo-uniaxial plates arranged in rosette-shaped aggregates. These aggregates appear to have developed as a result of radial growth of the chlorite platelets. According to point and microprobe X-ray images, these chlorites display oscillatory chemical zoning patterns with alternating iron rich and magnesium rich bands. The chlorite composition ranges from Fe rich pole (Si2.62Al1.38O10(Al1.47Fe1.87Mg2.61)6(OH)8) to Mg rich pole (Si2.68Al1.31O10(Al1.45Fe1.41Mg3.06)6(OH)8). In metamorphic rocks, zoning pattern or rimmed minerals results for varying P or T conditions and can be used to unravel the P-T history of the sample. In the present study, temperature maps are derived from standardized microprobe X-ray images using the program XMapTools (Lanari et al 2014). The (Fe3+/Fetot) value in chlorite was directly measured using μXANES spot analyses collected at the Fe-K edge. The results indicate a homogeneous temperature of

  6. Inorganic nanoparticles kill Toxoplasma gondii via changes in redox status and mitochondrial membrane potential.

    PubMed

    Adeyemi, Oluyomi Stephen; Murata, Yuho; Sugi, Tatsuki; Kato, Kentaro

    2017-01-01

    This study evaluated the anti-Toxoplasma gondii potential of gold, silver, and platinum nanoparticles (NPs). Inorganic NPs (0.01-1,000 µg/mL) were screened for antiparasitic activity. The NPs caused >90% inhibition of T. gondii growth with EC50 values of ≤7, ≤1, and ≤100 µg/mL for gold, silver, and platinum NPs, respectively. The NPs showed no host cell cytotoxicity at the effective anti-T. gondii concentrations; the estimated selectivity index revealed a ≥20-fold activity toward the parasite versus the host cell. The anti-T. gondii activity of the NPs, which may be linked to redox signaling, affected the parasite mitochondrial membrane potential and parasite invasion, replication, recovery, and infectivity potential. Our results demonstrated the antiparasitic potential of NPs. The findings support the further exploration of NPs as a possible source of alternative and effective anti-T. gondii agents.

  7. Inorganic nanoparticles kill Toxoplasma gondii via changes in redox status and mitochondrial membrane potential

    PubMed Central

    Adeyemi, Oluyomi Stephen; Murata, Yuho; Sugi, Tatsuki; Kato, Kentaro

    2017-01-01

    This study evaluated the anti-Toxoplasma gondii potential of gold, silver, and platinum nanoparticles (NPs). Inorganic NPs (0.01–1,000 µg/mL) were screened for antiparasitic activity. The NPs caused >90% inhibition of T. gondii growth with EC50 values of ≤7, ≤1, and ≤100 µg/mL for gold, silver, and platinum NPs, respectively. The NPs showed no host cell cytotoxicity at the effective anti-T. gondii concentrations; the estimated selectivity index revealed a ≥20-fold activity toward the parasite versus the host cell. The anti-T. gondii activity of the NPs, which may be linked to redox signaling, affected the parasite mitochondrial membrane potential and parasite invasion, replication, recovery, and infectivity potential. Our results demonstrated the antiparasitic potential of NPs. The findings support the further exploration of NPs as a possible source of alternative and effective anti-T. gondii agents. PMID:28280332

  8. Redox Changes Induced by General Anesthesia in Critically Ill Patients with Multiple Traumas

    PubMed Central

    Papurica, Marius; Rogobete, Alexandru Florin; Sandesc, Dorel; Dumache, Raluca; Nartita, Radu; Sarandan, Mirela; Cradigati, Alina Carmen; Luca, Loredana; Vernic, Corina; Bedreag, Ovidiu Horea

    2015-01-01

    The critically ill polytrauma patient is a constant challenge for the trauma team due to the complexity of the complications presented. Intense inflammatory response and infections, as well as multiple organ dysfunctions, significantly increase the rate of morbidity and mortality in these patients. Moreover, due to the physiological and biochemical imbalances present in this type of patients, the bioproduction of free radicals is significantly accelerated, thus installing the oxidative stress. In the therapeutic management of such patients, multiple surgical interventions are required and therefore they are being subjected to repeated general anesthesia. In this paper, we want to present the pathophysiological implications of oxidative stress in critically ill patients with multiple traumas and the implications of general anesthesia on the redox mechanisms of the cell. We also want to summarize the antioxidant treatments able to reduce the intensity of oxidative stress by modulating the biochemical activity of some cellular mechanisms. PMID:26693352

  9. Assessment of MTBE biodegradation pathways by two-dimensional isotope analysis in mixed bacterial consortia under different redox conditions.

    PubMed

    Youngster, Laura K G; Rosell, Mònica; Richnow, Hans H; Häggblom, Max M

    2010-09-01

    The fuel oxygenate, methyl tert-butyl ether (MTBE), although now widely banned or substituted, remains a persistent groundwater contaminant. Multidimensional compound-specific isotope analysis (CSIA) of carbon and hydrogen is being developed for determining the extent of MTBE loss due to biodegradation and can also potentially distinguish between different biodegradation pathways. Carbon and hydrogen isotopic fractionation factors were determined for MTBE degradation in aerobic and anaerobic laboratory cultures. The carbon isotopic enrichment factor (epsilonC) for aerobic MTBE degradation by a bacterial consortium containing the aerobic MTBE-degrading bacterium, Variovorax paradoxus, was -1.1 +/- 0.2 per thousand and the hydrogen isotope enrichment factor (epsilonH) was -15 +/- 2 per thousand. This corresponds to an approximated lambda value (Lambda = epsilonH/epsilonC) of 14. Carbon isotope enrichment factors for anaerobic MTBE-degrading enrichment cultures were -7.0 +/- 0.2 per thousand and did not vary based on the original inoculum source, redox condition of the enrichment, or supplementation with syringic acid as a co-substrate. The hydrogen enrichment factors of cultures without syringic acid were insignificant, however a strong hydrogen enrichment factor of -41 +/- 3 per thousand was observed for cultures which were fed syringic acid during MTBE degradation. The Lambda = 6 obtained for NYsyr cultures might be diagnostic for the stimulation of anaerobic MTBE degradation by methoxylated compounds by an as yet unknown pathway and mechanism. The stable-isotope enrichment factors determined in this study will enhance the use of CSIA for monitoring anaerobic and aerobic MTBE biodegradation in situ.

  10. Morphology Changing at Incipient Crystallization Condition

    NASA Astrophysics Data System (ADS)

    Toshima, Takeshi; Hamai, Ryo; Fujita, Saya; Takemura, Yuka; Takamatsu, Saori; Tafu, Masamoto

    2015-04-01

    Brushite (Dicalcium phosphate dihydrate, (DCPD), CaHPO4·2H2O) is one of key components in calcium phosphate system due to wide attractive material not only as bioceramics but also environmental materials. Morphology of DCPD crystals is important factor when one uses its functionality with chemical reaction; because its surface crystal face, shape and size rule the chemical reactivity, responsiveness. Moreover, physical properties are also changed the morphology; such as cohesion, dispersiveness, permeability and so on. If one uses DCPD crystals as environmental renovation materials to catch the fluoride ions, their shape require 020 crystal surfaces; which usually restricts their shape as plate-like structure. After the chemical reaction, the shape of sludge is not good for handling due to their agglutinate property. Therefore searching an effective parameter and developing the method to control the morphology of DCPD crystals is required. In past, we reported that initial concentration and pH value of starting solution, prepared by dissolving calcium nitrate, Ca(NO3)2 and ammonium dihydrogen phosphate, NH4H2PO4, changes the morphology of DCPD crystals and phase diagram of morphology of DCPD crystal depend on those parameter. The DCPD crystallization shows unique behaviour; products obtained higher initial concentration form single crystal-like structure and under lower condition, they form agglomerate crystal-like structure. These results contradict usual crystallization. Here we report that the effect of mixing process of two solutions. The morphology of DCPD crystals is changed from plate structure to petal structure by the arrangement. Our result suggests that morphology of DCPD crystals strongly depends at incipient crystallization condition and growth form is controllable by setting initial crystallization condition.

  11. Optimisation of the operational conditions of trichloroethylene degradation using Trametes versicolor under quinone redox cycling conditions using central composite design methodology.

    PubMed

    Vilaplana, Marcel; García, Ana Belén; Caminal, Gloria; Guillén, Francisco; Sarrà, Montserrat

    2012-04-01

    Extracellular radicals produced by Trametes versicolor under quinone redox cycling conditions can degrade a large variety of pollutant compounds, including trichloroethylene (TCE). This study investigated the effect of the agitation speed and the gas-liquid phase volume ratio on TCE degradation using central composite design (CCD) methodology for a future scale-up to a reactor system. The agitation speed ranged from 90 to 200 rpm, and the volume ratio ranged from 0.5 to 4.4. The results demonstrated the important and positive effect of the agitation speed and an interaction between the two factors on TCE degradation. Although the volume ratio did not have a significant effect if the agitation speed value was between 160 and 200 rpm, at lower speed values, the specific pollutant degradation was clearly more extensive at low volume ratios than at high volume ratios. The fitted response surface was validated by performing an experiment using the parameter combination in the model that maximised TCE degradation. The results of the experiments carried out using different biomass concentrations demonstrated that the biomass concentration had a positive effect on pollutant degradation if the amount of biomass present was lower than 1.6 g dry weight l(-1). The results show that the maximum TCE degradation was obtained at the highest speed (200 rpm), gas-liquid phase volume ratio (4.4), and a biomass concentration of 1.6 g dry weight l(-1).

  12. Fifty hertz extremely low-frequency electromagnetic field causes changes in redox and differentiative status in neuroblastoma cells.

    PubMed

    Falone, Stefano; Grossi, Maria R; Cinque, Benedetta; D'Angelo, Barbara; Tettamanti, Enzo; Cimini, Annamaria; Di Ilio, Carmine; Amicarelli, Fernanda

    2007-01-01

    The current study was designed to establish whether extremely low-frequency electromagnetic fields might affect neuronal homeostasis through redox-sensitive mechanisms. To this end, intracellular reactive oxygen species production, antioxidant and glutathione-based detoxifying capability and genomic integrity after extremely low-frequency electromagnetic fields exposure were investigated. Moreover, we also studied potential extremely low-frequency electromagnetic fields-dependent changes in the proliferative and differentiative cellular status. Results seem to support redox-mediated extremely low-frequency electromagnetic fields effects on biological models as, although no major oxidative damage was detected, after exposure we observed a positive modulation of antioxidant enzymatic expression, as well as a significant increase in reduced glutathione level, indicating a shift of cellular environment towards a more reduced state. In addition, extremely low-frequency electromagnetic fields treatment induced a more differentiated phenotype as well as an increased expression in peroxisome proliferators-activated receptor isotype beta, a class of transcription factors related to neuronal differentiation and cellular stress response. As second point, to deepen how extremely low-frequency electromagnetic fields treatment could affect neuroblastoma cell antioxidant capacity, we examined the extremely low-frequency electromagnetic fields-dependent modifications of cell susceptibility to pro-oxidants. Results clearly showed that 50 Hz extremely low-frequency electromagnetic fields exposure reduces cell tolerance towards oxidative attacks.

  13. Combining sedimentological, trace metal (Mn, Mo) and molecular evidence for reconstructing past water-column redox conditions: The example of meromictic Lake Cadagno (Swiss Alps)

    NASA Astrophysics Data System (ADS)

    Wirth, Stefanie B.; Gilli, Adrian; Niemann, Helge; Dahl, Tais W.; Ravasi, Damiana; Sax, Nadja; Hamann, Yvonne; Peduzzi, Raffaele; Peduzzi, Sandro; Tonolla, Mauro; Lehmann, Moritz F.; Anselmetti, Flavio S.

    2013-11-01

    Here, we present sedimentological, trace metal, and molecular evidence for tracking bottom water redox-state conditions during the past 12,500 years in nowadays sulfidic and meromictic Lake Cadagno (Switzerland). A 10.5 m long sediment core from the lake covering the Holocene period was investigated for concentration variations of the trace metals Mn and Mo (XRF core scanning and ICP-MS measurements), and for the presence of anoxygenic phototrophic sulfur bacteria (carotenoid pigment analysis and 16S rDNA real time PCR). Our trace metal analysis documents an oxic-intermediate-sulfidic redox-transition period beginning shortly after the lake formation ˜12.5 kyr ago. The oxic period is characterized by low sedimentary Mn and Mo concentrations, as well as by the absence of any remnants of anoxygenic phototrophic sulfur bacteria. Enhanced accumulation/preservation of Mn (up to 5.6 wt%) in the sediments indicates an intermediate, Mn-enriched oxygenation state with fluctuating redox conditions during a ˜2300-year long transition interval between ˜12.1 and 9.8 kyr BP. We propose that the high Mn concentrations are the result of enhanced Mn2+ leaching from the sediments during reducing conditions and subsequent rapid precipitation of Mn-(oxyhydr)oxide minerals during episodic and short-term water-column mixing events mainly due to flood-induced underflows. At 9800 ± 130 cal yr BP, a rapid transition to fully sulfidic conditions is indicated by the marked enrichment of Mo in the sediments (up to 490 ppm), accompanied by an abrupt drop in Mn concentrations and the increase of molecular biomarkers that indicate the presence of anoxygenic photosynthetic bacteria in the water column. Persistently high Mo concentrations >80 ppm provide evidence that sulfidic conditions prevailed thereafter until modern times, without any lasting hypolimnetic ventilation and reoxygenation. Hence, Lake Cadagno with its persistently stable chemocline offers a framework to study in great

  14. Clostridium thermocellum DSM 1313 transcriptional responses to redox perturbation

    DOE PAGES

    Sander, Kyle B.; Wilson, Charlotte M.; M. Rodriquez, Jr.; ...

    2015-12-12

    Clostridium thermocellum is a promising consolidated bioprocessing candidate organism capable of directly converting lignocellulosic biomass to ethanol. Current ethanol yields, productivities, and growth inhibitions are industrial deployment impediments for commodity fuel production by this bacterium. Redox imbalance under certain conditions and in engineered strains may contribute to incomplete substrate utilization and may direct fermentation products to undesirable overflow metabolites. As a result, towards a better understanding of redox metabolism in C. thermocellum, we established continuous growth conditions and analyzed global gene expression during addition of two stress chemicals (methyl viologen and hydrogen peroxide) which changed the fermentation redox potential.

  15. Rare Earth Elements of Methane-Derived Authigenic Carbonates and Its Constraints on Redox Condition in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Wang, S.; Magalhaes, V. H.; Fuentefria De Menezes Pinheiro, L. F.; Yan, W.

    2014-12-01

    The mineral composition, stable carbon and oxygen isotopes, and the rare earth elements (REE) concentrations in methane-derived authigenic carbonates collected from the Gulf of Cadiz were used to trace fluid sources and provide information on the associated biogeochemical processes during their formation. These samples are composed by a detrital fraction (mainly composed by quartz and clays) cemented by authigenic carbonates: aragonite and Mg-calcite, pure Mg-calcite, or dolomite and Mg-calcite. The δ13C values of the samples vary between -45.78‰ and -9.72‰ VPDB and δ18O values range from 3.67‰ to 6.92‰ VPDB. The δ13C composition is indicative of the methane-derived (probably from thermogenic gas or a mixed of thermogenic and biogenic gas) source of these carbonates. The total REE content (ΣREE) of these seep carbonates range from 13 to 31 ppm and average ΣREE values of 21 ppm, with most of samples lower than the typical marine carbonate value of ~28 ppm. This result suggests that the REE composition of the methane-derived authigenic carbonates is controlled primarily by the migrated methane-rich fluids from which they have precipitated. The results that the REE enrichment of the samples containing dolomite and Mg-calcite minerals is higher than samples with aragonite also suggest that the authigenic mineral composition and the formation setting are important factors on the REE concentration. The shale-normalized REE patterns of the seep carbonates show no abnormality or slight positive Ce anomalies, suggesting that the formation of these seep carbonates occurs in anoxic condition. The correlation results of Ce/Ce* and LaN/SmN, Ce/Ce* and DyN/SmN, Ce/Ce* and ΣREE have also suggested that the REE characteristics of most seep carbonate samples preserve the original redox conditions of their formation and that late diagenesis has little effect on the REE. Therefore, it is feasible to assume that these methane-derived authigenic carbonates represent

  16. Post-irradiation hypoxic incubation of X-irradiated MOLT-4 cells reduces apoptotic cell death by changing the intracellular redox state and modulating SAPK/JNK pathways.

    PubMed

    Hamasu, T; Inanami, O; Tsujitani, M; Yokoyama, K; Takahashi, E; Kashiwakura, I; Kuwabara, M

    2005-05-01

    To elucidate radiobiological effects of hypoxia on X-ray-induced apoptosis, MOLT-4 cells were treated under four set of conditions: (1) both X irradiation and incubation under normoxia, (2) X irradiation under hypoxia and subsequent incubation under normoxia, (3) X irradiation under normoxia and subsequent incubation under hypoxia, and (4) both X irradiation and incubation under hypoxia, and the induction of apoptosis was examined by fluorescence microscopy. About 28-33% apoptosis was observed in cells treated under conditions 1 and 2, but this value was significantly reduced to around 18-20% in cells treated under conditions 3 and 4, suggesting that post-irradiation hypoxic incubation rather than hypoxic irradiation mainly caused the reduction of apoptosis. The activation and expression of apoptosis signal-related molecules SAPK/JNK, Fas and caspase-3 were also suppressed by hypoxic incubation. Effects of hypoxic incubation were canceled when cells were treated under conditions 3 and 4 with an oxygen-mimicking hypoxic cell radiosensitizer, whereas the addition of N-acetyl-L-cysteine again reduced the induction of apoptosis. From these results it was concluded that hypoxia reduced the induction of apoptosis by changing the intracellular redox state, followed by the regulation of apoptotic signals in X-irradiated MOLT-4 cells.

  17. Role of redox metabolism for adaptation of aquatic animals to drastic changes in oxygen availability.

    PubMed

    Welker, Alexis F; Moreira, Daniel C; Campos, Élida G; Hermes-Lima, Marcelo

    2013-08-01

    Large changes in oxygen availability in aquatic environments, ranging from anoxia through to hyperoxia, can lead to corresponding wide variation in the production of reactive oxygen species (ROS) by animals with aquatic respiration. Therefore, animals living in marine, estuarine and freshwater environments have developed efficient antioxidant defenses to minimize oxidative stress and to regulate the cellular actions of ROS. Changes in oxygen levels may lead to bursts of ROS generation that can be particularly harmful. This situation is commonly experienced by aquatic animals during abrupt transitions from periods of hypoxia/anoxia back to oxygenated conditions (e.g. intertidal cycles). The strategies developed differ significantly among aquatic species and are (i) improvement of their endogenous antioxidant system under hyperoxia (that leads to increased ROS formation) or other similar ROS-related stresses, (ii) increase in antioxidant levels when displaying higher metabolic rates, (iii) presence of constitutively high levels of antioxidants, that attenuates oxidative stress derived from fluctuations in oxygen availability, or (iv) increase in the activity of antioxidant enzymes (and/or the levels of their mRNAs) during hypometabolic states associated with anoxia/hypoxia. This enhancement of the antioxidant system - coined over a decade ago as "preparation for oxidative stress" - controls the possible harmful effects of increased ROS formation during hypoxia/reoxygenation. The present article proposes a novel explanation for the biochemical and molecular mechanisms involved in this phenomenon that could be triggered by hypoxia-induced ROS formation. We also discuss the connections among oxygen sensing, oxidative damage and regulation of the endogenous antioxidant defense apparatus in animals adapted to many natural or man-made challenges of the aquatic environment.

  18. The effect of redox conditions and adaptation time on organic micropollutant removal during river bank filtration: A laboratory-scale column study.

    PubMed

    Bertelkamp, C; Verliefde, A R D; Schoutteten, K; Vanhaecke, L; Vanden Bussche, J; Singhal, N; van der Hoek, J P

    2016-02-15

    This study investigated the redox dependent removal and adaptive behaviour of a mixture of 15 organic micropollutants (OMPs) in laboratory-scale soil columns fed with river water. Three separate pilot systems were used consisting of: (1) two columns, (2) ten columns and (3) twenty two columns to create oxic, suboxic (partial nitrate removal) and anoxic (complete nitrate removal). The pilot set-up has some unique features--it can simulate fairly long residence times (e.g., 45 days using the 22 column system) and reduced conditions developed naturally within the system. Dimethoate, diuron, and metoprolol showed redox dependent removal behaviour with higher biodegradation rates in the oxic zone compared to the suboxic/anoxic zone. The redox dependent behaviour of these three OMPs could not be explained based on their physico-chemical properties (hydrophobicity, charge and molecular weight) or functional groups present in the molecular structure. OMPs that showed persistent behaviour in the oxic zone (atrazine, carbamazepine, hydrochlorothiazide and simazine) were also not removed under more reduced conditions. Adaptive behaviour was observed for five OMPs: dimethoate, chloridazon, lincomycin, sulfamethoxazole and phenazone. However, the adaptive behaviour could not be explained by the physico-chemical properties (hydrophobicity, charge and molecular weight) investigated in this study and only rough trends were observed with specific functional groups (e.g. ethers, sulphur, primary and secondary amines). Finally, the adaptive behaviour of OMPs was found to be an important factor that should be incorporated in predictive models for OMP removal during river bank filtration.

  19. Calcium Dynamics of Ex Vivo Long-Term Cultured CD8+ T Cells Are Regulated by Changes in Redox Metabolism

    PubMed Central

    Gran, Margaret A.; Potnis, Anish; Hill, Abby; Lu, Hang

    2016-01-01

    T cells reach a state of replicative senescence characterized by a decreased ability to proliferate and respond to foreign antigens. Calcium release associated with TCR engagement is widely used as a surrogate measure of T cell response. Using an ex vivo culture model that partially replicates features of organismal aging, we observe that while the amplitude of Ca2+ signaling does not change with time in culture, older T cells exhibit faster Ca2+ rise and a faster decay. Gene expression analysis of Ca2+ channels and pumps expressed in T cells by RT-qPCR identified overexpression of the plasma membrane CRAC channel subunit ORAI1 and PMCA in older T cells. To test whether overexpression of the plasma membrane Ca2+ channel is sufficient to explain the kinetic information, we adapted a previously published computational model by Maurya and Subramaniam to include additional details on the store-operated calcium entry (SOCE) process to recapitulate Ca2+ dynamics after T cell receptor stimulation. Simulations demonstrated that upregulation of ORAI1 and PMCA channels is not sufficient to explain the observed alterations in Ca2+ signaling. Instead, modeling analysis identified kinetic parameters associated with the IP3R and STIM1 channels as potential causes for alterations in Ca2+ dynamics associated with the long term ex vivo culturing protocol. Due to these proteins having known cysteine residues susceptible to oxidation, we subsequently investigated and observed transcriptional remodeling of metabolic enzymes, a shift to more oxidized redox couples, and post-translational thiol oxidation of STIM1. The model-directed findings from this study highlight changes in the cellular redox environment that may ultimately lead to altered T cell calcium dynamics during immunosenescence or organismal aging. PMID:27526200

  20. Redox condition of the late Neoproterozoic pelagic deep ocean: 57Fe Mössbauer analyses of pelagic mudstones in the Ediacaran accretionary complex, Wales, UK

    NASA Astrophysics Data System (ADS)

    Sato, Tomohiko; Sawaki, Yusuke; Asanuma, Hisashi; Fujisaki, Wataru; Okada, Yoshihiro; Maruyama, Shigenori; Isozaki, Yukio; Shozugawa, Katsumi; Matsuo, Motoyuki; Windley, Brian F.

    2015-11-01

    We report geological and geochemical analysis of Neoproterozoic pelagic deep-sea mudstones in an accretionary complex in Lleyn, Wales, UK. Ocean plate stratigraphy at Porth Felen, NW Lleyn, consists of mid-ocean ridge basalt (> 4 m), bedded dolostone (2 m), black mudstone (5 m), hemipelagic siliceous mudstone (1 m,) and turbiditic sandstone (15 m), in ascending order. The absence of terrigenous clastics confirms that the black and siliceous mudstone was deposited in a pelagic deep-sea. Based on the youngest U-Pb age (564 Ma) of detrital zircons separated from overlying sandstone, the deep-sea black mudstone was deposited in the late Ediacaran. The 5 m-thick black mudstone contains the following distinctive lithologies: (i) black mudstone with thin pyritic layers (0.8 m), (ii) alternation of black mudstone and gray/dark gray siliceous mudstone (2.4 m), (iii) thinly-laminated dark gray shale (1 m), and (iv) black mudstone with thin pyritic layers (1 m). 57Fe Mössbauer spectroscopy confirms that these black mudstones contain pyrite without hematite. In contrast, red bedded claystones (no younger than 542 Ma) in the neighboring Braich section contain hematite as their main iron mineral. These deep-sea mudstones in the Lleyn Peninsula record a change of redox condition on the pelagic deep-sea floor during the Ediacaran. The black mudstone at Porth Felen shows that deep-sea anoxia existed in the late Ediacaran. The eventual change from a reducing to an oxidizing deep-sea environment likely occurred in the late Ediacaran (ca. 564-542 Ma).

  1. Redox changes across the Triassic-Jurassic boundary: From anoxic to euxinic black shale deposition

    NASA Astrophysics Data System (ADS)

    Richoz, Sylvain; van de Schootbrugge, Bas; Püttmann, Wilhelm; Heunisch, Carmen; Quan, Tracy M.; Lindström, Sofie; Fiebig, Jens; Pross, Joerg

    2010-05-01

    The Triassic-Jurassic boundary (T-J; 201.6 Ma) marks one of the so called Big Five mass-extinction events that may have led to the extinction of more than 80% of all marine invertebrates. The extinction of marine and terrestrial biota is increasingly linked to the outgassing of large volumes of CO2 and SO2 during the emplacement of the Central Atlantic Magmatic Province. Here, we present multi-disciplinary data, including organic geochemical proxies, isotope (C, N), and palynological data, from cores in Luxemburg (Rosswinkel), and northern (Mariental) and southern Germany (Mingolsheim) that provide evidence for changes in type of black shale deposition that reflect major environmental perturbations across the T-J boundary. Prior to the T-J extinction, the Uppermost Rhaetian in Germany contains black shales that are rich in dinoflagellate cysts, and show high amplitude nitrogen isotope excursions. No biomarker evidence for photic zone euxinia was found in the Rhaetian. Because cyst-building dinoflagellates require oxygenated bottom waters, Rhaetian organic-rich sediments were deposited through high-productivity in well mixed shallow marine basins. Following the major overturn of terrestrial vegetation (fern spike) and the marine extinction level, black shales in the lowermost Hettangian reveal extremely low dinoflagellate cyst abundance, but high abundance of prasinophyte green algae and acritarchs. These black shales also show elevated quantities of the biomarker isorenieratane. Isorenieratane derives from the brown strains of photosynthetic green sulphur bacteria (Chlorobiaceae) that require both light and free hydrogen sulfide in the water column. The presence of abundant aryl isoprenoids (isorenieratane and its diagenetic products) in Luxemburg and N Germany suggests that marginal marine basins in NW Europe became salinity stratified and developed intense Photic Zone Euxinia (PZE) after the mass extinction event. This change in low oxygen conditions is

  2. Mouse redox histology using genetically encoded probes.

    PubMed

    Fujikawa, Yuuta; Roma, Leticia P; Sobotta, Mirko C; Rose, Adam J; Diaz, Mauricio Berriel; Locatelli, Giuseppe; Breckwoldt, Michael O; Misgeld, Thomas; Kerschensteiner, Martin; Herzig, Stephan; Müller-Decker, Karin; Dick, Tobias P

    2016-03-15

    Mapping the in vivo distribution of endogenous oxidants in animal tissues is of substantial biomedical interest. Numerous health-related factors, including diet, physical activity, infection, aging, toxins, or pharmacological intervention, may cause redox changes. Tools are needed to pinpoint redox state changes to particular organs, tissues, cell types, and subcellular organelles. We describe a procedure that preserves the in vivo redox state of genetically encoded redox biosensors within histological tissue sections, thus providing "redox maps" for any tissue and comparison of interest. We demonstrate the utility of the technique by visualizing endogenous redox differences and changes in the context of tumor growth, inflammation, embryonic development, and nutrient starvation.

  3. Sequential changes in redox status and nitric oxide synthases expression in the liver after bile duct ligation.

    PubMed

    Vázquez-Gil, M José; Mesonero, M José; Flores, Olga; Criado, Manuela; Hidalgo, Froilán; Arévalo, Miguel A; Sánchez-Rodríguez, Angel; Tuñón, M Jesús; López-Novoa, José M; Esteller, A

    2004-06-25

    Bile duct ligation (BDL) in rats induces portal fibrosis. This process has been linked to changes in the oxidative state of the hepatic cells and in the production of nitric oxide. Our objective was to find possible temporal connections between hepatic redox state, NO synthesis and liver injury. In this work we have characterized hepatic lesions 17 and 31 days after BDL and determined changes in hepatic function, oxidative state, and NO production. We have also analyzed the expression and localization of inducible NO synthase (NOS2) and constitutive NO synthase (NOS3). After 17 and 31 days from ligature, lipid peroxidation is increased and both plasma concentration and biliary excretion of nitrite+nitrate are rised. 17 days after BDL both NOS2 and NOS3 are expressed intensely and in the same regions. 31 days after BDL, the expression of NOS2 remains elevated and is localized mostly in preserved hepatocytes in portal areas and in neighborhoods of centrolobulillar vein. NOS3 is localized in vascular regions of portal spaces and centrolobulillar veins and in preserved sinusoids and although its expression is greater than in control animals (34%), it is clearly lower (50%) than 17 days after BDL. The time after BDL is crucial in the study of NO production, intrahepatic localization of NOS isoforms expression, and cell type involved, since all these parameters change with time. BDL-induced, peroxidation and fibrosis are not ligated by a cause-effect relationship, but rather they both seem to be the consequence of common inductors.

  4. Use of dimedone-based chemical probes for sulfenic acid detection evaluation of conditions affecting probe incorporation into redox-sensitive proteins.

    PubMed

    Klomsiri, Chananat; Nelson, Kimberly J; Bechtold, Erika; Soito, Laura; Johnson, Lynnette C; Lowther, W Todd; Ryu, Seong-Eon; King, S Bruce; Furdui, Cristina M; Poole, Leslie B

    2010-01-01

    Sulfenic acids, formed as transient intermediates during the reaction of cysteine residues with peroxides, play significant roles in enzyme catalysis and regulation, and are also involved in the redox regulation of transcription factors and other signaling proteins. Therefore, interest in the identification of protein sulfenic acids has grown substantially in the past few years. Dimedone, which specifically traps sulfenic acids, has provided the basis for the synthesis of a novel group of compounds that derivatize 1,3-cyclohexadione, a dimedone analogue, with reporter tags such as biotin for affinity capture and fluorescent labels for visual detection. These reagents allow identification of the cysteine sites and proteins that are sensitive to oxidation and permit identification of the cellular conditions under which such oxidations occur. We have shown that these compounds are reactive and specific toward sulfenic acids and that the labeled proteins can be detected at high sensitivity using gel analysis or mass spectrometry. Here, we further characterize these reagents, showing that the DCP-Bio1 incorporation rates into three sulfenic acid containing proteins, papaya papain, Escherichia coli fRMsr, and the Salmonella typhimurium peroxiredoxin AhpC, are significantly different and, in the case of fRMsr, are unaffected by changes in buffer pH from 5.5 and 8.0. We also provide protocols to label protein sulfenic acids in cellular proteins, either by in situ labeling of intact cells or by labeling at the time of lysis. We show that the addition of alkylating reagents and catalase to the lysis buffer is critical in preventing the formation of sulfenic acid subsequent to cell lysis. Data presented herein also indicate that the need to standardize, as much as possible, the protein and reagent concentrations during labeling. Finally, we introduce several new test or control proteins that can be used to evaluate labeling procedures and efficiencies.

  5. DNA and redox state induced conformational changes in the DNA-binding domain of the Myb oncoprotein.

    PubMed Central

    Myrset, A H; Bostad, A; Jamin, N; Lirsac, P N; Toma, F; Gabrielsen, O S

    1993-01-01

    The DNA-binding domain of the oncoprotein Myb comprises three imperfect repeats, R1, R2 and R3. Only R2 and R3 are required for sequence-specific DNA-binding. Both are assumed to contain helix-turn-helix (HTH)-related motifs, but multidimensional heteronuclear NMR spectroscopy revealed a disordered structure in R2 where the second HTH helix was predicted [Jamin et al. (1993) Eur. J. Biochem., 216, 147-154]. We propose that the disordered region folds into a 'recognition' helix and generates a full HTH-related motif upon binding to DNA. This would move Cys43 into the hydrophobic core of R2. We observed that Cys43 was accessible to N-ethylmaleimide alkylation in the free protein, but inaccessible in the DNA complex. Mutant proteins with charged (C43D) or polar (C43S) side chains in position 43 bound DNA with reduced affinity, while hydrophobic replacements (C43A, C43V and C43I) gave unaltered or improved DNA-binding. Specific DNA-binding enhanced protease resistance dramatically. Fluorescence emission spectra and quenching experiments supported a DNA-induced conformational change. Moreover, reversible oxidation of Cys43 had an effect similar to the inactivating C43D mutation. The highly oxidizable Cys43 could function as a molecular sensor for a redox regulatory mechanism turning specific DNA-binding on or off by controlling the DNA-induced conformational change in R2. Images PMID:8223472

  6. Redox chemistry changes in the Panthalassic Ocean linked to the end-Permian mass extinction and delayed Early Triassic biotic recovery

    PubMed Central

    Zhang, Guijie; Zhang, Xiaolin; Hu, Dongping; Li, Dandan; Algeo, Thomas J.; Farquhar, James; Henderson, Charles M.; Qin, Liping; Shen, Megan; Shen, Danielle; Schoepfer, Shane D.; Chen, Kefan; Shen, Yanan

    2017-01-01

    The end-Permian mass extinction represents the most severe biotic crisis for the last 540 million years, and the marine ecosystem recovery from this extinction was protracted, spanning the entirety of the Early Triassic and possibly longer. Numerous studies from the low-latitude Paleotethys and high-latitude Boreal oceans have examined the possible link between ocean chemistry changes and the end-Permian mass extinction. However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85–90% of the global ocean area, remain under debate. Here, we report multiple S-isotopic data of pyrite from Upper Permian–Lower Triassic deep-sea sediments of the Panthalassic Ocean, now present in outcrops of western Canada and Japan. We find a sulfur isotope signal of negative Δ33S with either positive δ34S or negative δ34S that implies mixing of sulfide sulfur with different δ34S before, during, and after the end-Permian mass extinction. The precise coincidence of the negative Δ33S anomaly with the extinction horizon in western Canada suggests that shoaling of H2S-rich waters may have driven the end-Permian mass extinction. Our data also imply episodic euxinia and oscillations between sulfidic and oxic conditions during the earliest Triassic, providing evidence of a causal link between incursion of sulfidic waters and the delayed recovery of the marine ecosystem. PMID:28167796

  7. Redox chemistry changes in the Panthalassic Ocean linked to the end-Permian mass extinction and delayed Early Triassic biotic recovery.

    PubMed

    Zhang, Guijie; Zhang, Xiaolin; Hu, Dongping; Li, Dandan; Algeo, Thomas J; Farquhar, James; Henderson, Charles M; Qin, Liping; Shen, Megan; Shen, Danielle; Schoepfer, Shane D; Chen, Kefan; Shen, Yanan

    2017-02-21

    The end-Permian mass extinction represents the most severe biotic crisis for the last 540 million years, and the marine ecosystem recovery from this extinction was protracted, spanning the entirety of the Early Triassic and possibly longer. Numerous studies from the low-latitude Paleotethys and high-latitude Boreal oceans have examined the possible link between ocean chemistry changes and the end-Permian mass extinction. However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85-90% of the global ocean area, remain under debate. Here, we report multiple S-isotopic data of pyrite from Upper Permian-Lower Triassic deep-sea sediments of the Panthalassic Ocean, now present in outcrops of western Canada and Japan. We find a sulfur isotope signal of negative Δ(33)S with either positive δ(34)S or negative δ(34)S that implies mixing of sulfide sulfur with different δ(34)S before, during, and after the end-Permian mass extinction. The precise coincidence of the negative Δ(33)S anomaly with the extinction horizon in western Canada suggests that shoaling of H2S-rich waters may have driven the end-Permian mass extinction. Our data also imply episodic euxinia and oscillations between sulfidic and oxic conditions during the earliest Triassic, providing evidence of a causal link between incursion of sulfidic waters and the delayed recovery of the marine ecosystem.

  8. Studying Iron Mineralogy to Understand Redox Conditions in the Mesoproterozoic Belt Basin, USA Using Complementary Microscopic, Spectroscopic, and Magnetic Techniques

    NASA Astrophysics Data System (ADS)

    Slotznick, S. P.; Webb, S.; Kirschvink, J. L.; Fischer, W. W.

    2015-12-01

    Observations of iron chemistry and mineralogy over time provide a valuable tool for studying paleoenvironments, but questions still remain as to the redox character of Proterozoic basins after the rise of oxygen. To evaluate the mechanisms of iron mineralization in Proterozoic samples, we developed an approach that pairs the microscale textural techniques of light microscopy, magnetic scanning microscopy, and (synchrotron-based) microprobe x-ray spectroscopy with sensitive bulk rock magnetic experiments. Samples were collected from stratigraphic sections across the ~1.4 Ga lower Belt Group, Belt Supergroup, MT and ID, USA with a focus on excellently preserved sedimentary rocks, but also including those altered by a variety of diagenetic, metamorphic, and metasomatic events. Results show that even in the best-preserved parts of the Belt Basin, late diagenetic and/or metasomatic fluids affected (in some cases very mildly) the primary iron phases as evidenced by prevalent post-depositional alterations such as rare base metal sulfides. In more heavily altered rocks, the appearance of pyrrhotite and other minerals signaled transformations in iron mineralogy through metamorphism and metasomatism. Despite these secondary phases crystallizing in an open fluid-rich system, primary records of redox chemistry were preserved in the recrystallized early diagenetic framboidal pyrite and (sub)micron-sized detrital magnetite grains. Detrital magnetite is not the most abundant iron-bearing phase in any of the samples (typically <0.01 wt%), but is widely observed in both proximal and deeper basin facies, illustrating an important detrital flux of iron to the basin and a highly reactive iron source for early diagenetic pyrite. Based on our analyses, we interpret the shallow waters of the Belt Basin to be oxic with sulfidic pore fluids and deeper waters in parts of the basin as likely euxinic, consistent with the results of some bulk geochemical proxies. This redox reconstruction also

  9. Soluble oligomers of amyloid-β cause changes in redox state, DNA methylation, and gene transcription by inhibiting EAAT3 mediated cysteine uptake.

    PubMed

    Hodgson, Nathaniel; Trivedi, Malav; Muratore, Christina; Li, Shaomin; Deth, Richard

    2013-01-01

    Oxidative stress, hyperhomocysteinemia, altered DNA methylation, and insulin resistance in the brain are associated with Alzheimer's disease (AD), but the role of amyloid-β (Aβ) in these events remains unclear. Intracellular cysteine is rate-limiting for synthesis of the antioxidant glutathione (GSH), and factors regulating cysteine uptake exert a powerful influence over cellular redox status, especially in mature neurons where cysteine synthesis via transsulfuration of homocysteine (HCY) is restricted. We investigated the effect of soluble Aβ oligomers (oAβ) on basal and insulin-like growth factor-1 (IGF-1)-induced cysteine uptake mediated by the excitatory amino acid transporter 3 (EAAT3) in cultured human neuronal cells. We also examined the effect of oAβ on intracellular thiol metabolite levels, DNA methylation, and the transcription status of redox and methylation-associated genes. oAβ inhibited EAAT3-mediated cysteine uptake, causing a decrease in intracellular cysteine and GSH levels. The ratio of the methyl donor S-adenosylmethionine to the methylation inhibitor S-adenosylhomocysteine was decreased, in association with an increase in HCY and a global decrease in DNA methylation, indicative of decreased activity of the redox-sensitive enzyme methionine synthase. These metabolic effects of oAβ coincided with changes in the expression of redox and methylation pathway genes. The ability of oAβ to modulate gene expression via their redox and methylation-dependent epigenetic effects may contribute to the pathology of AD and recognition of this mechanism may lead to novel treatment approaches. We describe a role of IGF-1 signaling in regulating redox and methylation homeostasis, and propose this to be a pathogenic target of oAβ.

  10. Experimental evidence for non-redox transformations between magnetite and hematite under H 2-rich hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Otake, Tsubasa; Wesolowski, David J.; Anovitz, Lawrence M.; Allard, Lawrence F.; Ohmoto, Hiroshi

    2007-05-01

    Transformations of magnetite (Fe IIFe 2IIIO 4) to hematite (Fe 2IIIO 3) (and vice versa) have been thought by many scientists and engineers to require molecular O 2 and/or H 2. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H 2-rich aqueous solutions at 150 °C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O 2 or H 2: Fe3O 4(Mt) + 2H (aq)+ ↔ Fe 2O 3(Hm) + Fe (aq)2+ + H 2O. The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H 2. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

  11. Electrochemical response of a biofilm community to changes in electron-acceptor redox potential elucidated using microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Arbour, T.; Wrighton, K. C.; Mullin, S. W.; Luef, B.; Gilbert, B.; Banfield, J. F.

    2012-12-01

    Currently, we have limited insight into how mineral properties affect dissimilatory metal-reducing bacteria (DMRB) or the microbial communities that contain them. Advances in our understanding of DMRB metabolism have been achieved using microbial fuel cells (MFCs), which exploit the ability of these organisms to transfer electrons extracellularly. By replacing the mineral electron acceptor with a conductive electrode under potentiostat control, the activity of microorganisms capable of interfacial electron transfer can be quantified by the current flowing through the electrode and related to the thermodynamics of respiration. We seek to understand how communities and their individual members respond to changes in mineralogy, and expect mineral redox potential to be a primary control. The ability to precisely control the redox potential of the electron-accepting anodic electrode is our primary motivation for using MFCs. We inoculated duplicate MFCs containing 10 mM acetate in phosphate buffered media with a slurry of subsurface sediment and groundwater obtained from the Integrated Field-Scale Research Challenge Site at Rifle, CO. Electroactive biofilms were established on graphite anodes poised at a favorable potential (0.0 V vs. SHE) before poising at -0.2 V—a potential representative of natural iron reduction. The current was stable across both anodes over more than 100 days of operation, and the percentage of the electrons in acetate recovered as current ("Coulombic efficiency") was typically 70 to >90%. Current density reached 0.4 A/m2 at -0.2 V, to a max of over 1.0 A/m2 at or above ~0.0 V (based on geometric electrode surface area). Media exchanges and biofilm cyclic voltammetry (CV) experiments indicate that electrode-attached microbial communities were responsible for primary electron transfer. Cryo-electron and confocal fluorescence microscopies of the biofilm reveal numerous morphologies of viable microorganisms that are currently being characterized

  12. Studying the relationship between redox and cell growth using quantitative phase imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sridharan, Shamira; Leslie, Matthew T.; Bapst, Natalya; Smith, John; Gaskins, H. Rex; Popescu, Gabriel

    2016-03-01

    Quantitative phase imaging has been used in the past to study the dry mass of cells and study cell growth under various treatment conditions. However, the relationship between cellular redox and growth rates has not yet been studied in this context. This study employed the recombinant Glrx-roGFP2 redox biosensor targeted to the mitochondrial matrix or cytosolic compartments of A549 lung epithelial carcinoma cells. The Glrx-roGFP2s biosensor consists of a modified GFP protein containing internal cysteine residues sensitive to the local redox environment. The formation/dissolution of sulfide bridges contorts the internal chromophore, dictating corresponding changes in florescence emission that provide direct measures of the local redox potential. Combining 2-channel florescent imaging of the redox sensor with quantitative phase imaging allowed observation of redox homeostasis alongside measurements of cellular mass during full cycles of cellular division. The results indicate that mitochondrial redox showed a stronger inverse correlation with cell growth than cytoplasmic redox states; although redox changes are restricted to a 5% range. We are now studying the relationship between mitochondrial redox and cell growth in an isogenic series of breast cell lines built upon the MCF-10A genetic background that vary both in malignancy and metastatic potential.

  13. Dental Usage Under Changing Economic Conditions

    PubMed Central

    Manski, Richard J.; Moeller, John F.; Chen, Haiyan; Schimmel, Jody; St Clair, Patricia A.; Pepper, John V.

    2012-01-01

    Objective The purpose of this article is to examine the relationship between changes in household finances (wealth and income) and changes in dental utilization at the onset of the recent recession in a population of older Americans. Methods Data from the Health and Retirement Study (HRS) were analyzed for U.S. individuals aged 51 years and older during the 2006 and 2008 waves of the HRS. We estimated logistic models of (1) starting and (2) stopping dental use between 2006 and 2008 survey periods as a function of changes in household wealth and income, controlling for other potentially confounding covariates. Results We found that only when household wealth falls by 50 percent or more were older adults less likely to seek dental care. Changes in household income and other changes in household wealth were not associated with changes in dental utilization among this population. Conclusions Older Americans’ dental care utilization appeared to be fairly resilient to changes in household finances; only when wealth fell by 50 percent or more did individuals decrease dental use. This finding might extend to other health care services that are preventive, routine, and relatively inexpensive. PMID:22994647

  14. Changes in redox states of respiratory pigments recorded from the eyes of live blowflies exposed to light stimuli and hypoxia.

    PubMed

    Meglič, Andrej; Zupančič, Gregor

    2011-03-01

    Time courses of mitochondrial responses to illumination-induced physiological loads and to hypoxia, were recorded optically from eyes of blowflies Calliphora vicina chalky. We isolated changes in redox states of haems a(3), a, c, and b. Two types of responses to light stimulation were observed. Haems b and a(3) responded with transient oxidation and haems a and c with reduction. The same two groups emerged in response to anoxic exposure. The onset of reduction of haems a and c had virtually no latency, while haems a(3) and b exhibited a transient oxidation followed by reduction only after 10-20 s. The dependence of the steady-state reduction level on [Formula: see text] produced the same groups. Haems a and c were significantly reduced at [Formula: see text] levels around 10 kPa while with haems b and a(3) load-induced oxidation was only replaced by reduction below 2 kPa. We propose haems respond to physiological loads in accordance with their steady-state reduction, which in turn depends largely on barriers for electron transport imposed by the mitochondrial membrane potential. We also propose it may be possible to assess the values of tissue [Formula: see text] and O(2) consumption by monitoring haems that are highly oxidized at rest such as haem a.

  15. Long-term sulphur starvation of Arabidopsis thaliana modifies mitochondrial ultrastructure and activity and changes tissue energy and redox status.

    PubMed

    Ostaszewska, Monika; Juszczuk, Izabela M; Kołodziejek, Izabella; Rychter, Anna M

    2014-04-15

    Sulphur, as a constituent of amino acids (cysteine and methionine), iron-sulphur clusters, proteins, membrane sulpholipids, glutathione, glucosinolates, coenzymes, and auxin precursors, is essential for plant growth and development. Absence or low sulphur concentration in the soil results in severe growth retardation. Arabidopsis thaliana plants grown hydroponically for nine weeks on Knop nutrient medium without sulphur showed morphological symptoms of sulphur deficiency. The purpose of our study was to investigate changes that mitochondria undergo and the role of the highly branched respiratory chain in survival during sulphur deficiency stress. Ultrastructure analysis of leaf mesophyll cells of sulphur-deficient Arabidopsis showed heterogeneity of mitochondria; some of them were not altered, but the majority had swollen morphology. Dilated mitochondria displayed a lower matrix density and fewer cristae compared to control mitochondria. Disintegration of the inner and outer membranes of some mitochondria from the leaves of sulphur-deficient plants was observed. On the contrary, chloroplast ultrastructure was not affected. Sulphur deficiency changed the respiratory activity of tissues and isolated mitochondria; Complex I and IV capacities and phosphorylation rates were lower, but external NAD(P)H dehydrogenase activity increased. Higher external NAD(P)H dehydrogenase activity corresponded to increased cell redox level with doubled NADH/NAD ratio in the leaf and root tissues. Sulphur deficiency modified energy status in the tissues of Arabidopsis plants. The total concentration of adenylates (expressed as ATP+ADP), measured in the light, was lower in the leaves and roots of sulphur-deficient plants than in the controls, which was mainly due to the severely decreased ATP levels. We show that the changes in mitochondrial ultrastructure are compensated by the modifications in respiratory chain activity. Although mitochondria of Arabidopsis tissues are affected by

  16. Accelerated Oxygen Atom Transfer and C-H Bond Oxygenation by Remote Redox Changes in Fe3 Mn-Iodosobenzene Adducts.

    PubMed

    de Ruiter, Graham; Carsch, Kurtis M; Gul, Sheraz; Chatterjee, Ruchira; Thompson, Niklas B; Takase, Michael K; Yano, Junko; Agapie, Theodor

    2017-03-24

    We report the synthesis, characterization, and reactivity of [LFe3 (PhPz)3 OMn((s) PhIO)][OTf]x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzene-metal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, (57) Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe(III)2 Fe(II) Mn(II) vs. Fe(III)3 Mn(II) ) influence oxygen atom transfer in tetranuclear Fe3 Mn clusters. In particular, a one-electron redox change at a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude.

  17. Redox-coupled structural changes in nitrite reductase revealed by serial femtosecond and microfocus crystallography

    PubMed Central

    Fukuda, Yohta; Suzuki, Mamoru; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Iwata, So; Mizohata, Eiichi

    2016-01-01

    Serial femtosecond crystallography (SFX) has enabled the damage-free structural determination of metalloenzymes and filled the gaps of our knowledge between crystallographic and spectroscopic data. Crystallographers, however, scarcely know whether the rising technique provides truly new structural insights into mechanisms of metalloenzymes partly because of limited resolutions. Copper nitrite reductase (CuNiR), which converts nitrite to nitric oxide in denitrification, has been extensively studied by synchrotron radiation crystallography (SRX). Although catalytic Cu (Type 2 copper (T2Cu)) of CuNiR had been suspected to tolerate X-ray photoreduction, we here showed that T2Cu in the form free of nitrite is reduced and changes its coordination structure in SRX. Moreover, we determined the completely oxidized CuNiR structure at 1.43 Å resolution with SFX. Comparison between the high-resolution SFX and SRX data revealed the subtle structural change of a catalytic His residue by X-ray photoreduction. This finding, which SRX has failed to uncover, provides new insight into the reaction mechanism of CuNiR. PMID:26769972

  18. Detection of reactive oxygen species-sensitive thiol proteins by redox difference gel electrophoresis: implications for mitochondrial redox signaling.

    PubMed

    Hurd, Thomas R; Prime, Tracy A; Harbour, Michael E; Lilley, Kathryn S; Murphy, Michael P

    2007-07-27

    Reactive oxygen species (ROS) produced by the mitochondrial respiratory chain can be a redox signal, but whether they affect mitochondrial function is unclear. Here we show that low levels of ROS from the respiratory chain under physiological conditions reversibly modify the thiol redox state of mitochondrial proteins involved in fatty acid and carbohydrate metabolism. As these thiol modifications were specific and occurred without bulk thiol changes, we first had to develop a sensitive technique to identify the small number of proteins modified by endogenous ROS. In this technique, redox difference gel electrophoresis, control, and redox-challenged samples are labeled with different thiol-reactive fluorescent tags and then separated on the same two-dimensional gel, enabling the sensitive detection of thiol redox modifications by changes in the relative fluorescence of the two tags within a single protein spot, followed by protein identification by mass spectrometry. Thiol redox modification affected enzyme activity, suggesting that the reversible modification of enzyme activity by ROS from the respiratory chain may be an important and unexplored mode of mitochondrial redox signaling.

  19. The Association of Arsenic With Redox Conditions, Depth, and Ground-Water Age in the Glacial Aquifer System of the Northern United States

    USGS Publications Warehouse

    Thomas, Mary Ann

    2007-01-01

    More than 800 wells in the glacial aquifer system of the Northern United States were sampled for arsenic as part of U.S. Geological Survey National Water-Quality Assessment (NAWQA) studies during 1991-2003. Elevated arsenic concentrations (greater than or equal to 10 micrograms per liter) were detected in 9 percent of samples. Elevated arsenic concentrations were associated with strongly reducing conditions. Of the samples classified as iron reducing or sulfate reducing, arsenic concentrations were elevated in 19 percent. Of the methanogenic samples, arsenic concentrations were elevated in 45 percent. In contrast, concentrations of arsenic were elevated in only 1 percent of oxic samples. Arsenic concentrations were also related to ground-water age. Elevated arsenic concentrations were detected in 34 percent of old waters (recharged before 1953) as compared to 4 percent of young waters (recharged since 1953). For samples classified as both old and methanogenic, elevated arsenic concentrations were detected in 62 percent of samples, as compared to 1 percent for samples classified as young and oxic. Arsenic concentrations were also correlated with well depth and concentrations of several chemical constituents, including (1) constituents linked to redox processes and (2) anions or oxyanions that sorb to iron oxides. Observations from the glacial aquifer system are consistent with the idea that the predominant source of arsenic is iron oxides and the predominant mechanism for releasing arsenic to the ground water is reductive desorption or reductive dissolution. Arsenic is also released from iron oxides under oxic conditions, but on a more limited basis and at lower concentrations. Logistic regression was used to investigate the relative significance of redox, ground-water age, depth, and other water-quality constituents as indicators of elevated arsenic concentrations in the glacial aquifer system. The single variable that explained the greatest amount of variation in

  20. Experimental evidence for non-redox transformations between magnetite and hematite under H-2-rich hydrothermal conditions.

    SciTech Connect

    Otake, Tsubasa; Wesolowski, David J; Anovitz, Lawrence {Larry} M

    2007-05-01

    Transformations of magnetite (Fe{sup II}Fe{sub 2}{sup III}O{sub 4}) to hematite (Fe{sub 2}{sup III}O{sub 3}) (and vice versa) have been thought by many scientists and engineers to require molecular O{sub 2} and/or H{sub 2}. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H{sub 2}-rich aqueous solutions at 150 C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O{sub 2} or H{sub 2}: Fe{sub 3}O{sub 4}(Mt) + 2H{sub (aq)}{sup +} {leftrightarrow} Fe{sub 2}O{sub 3}(Hm) + Fe{sub (aq)}{sup 2+} + H{sub 2}O. The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H{sub 2}. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

  1. Experimental Evidence for Non-Redox Transformation Between Magnetite and Hermatite Under H2-Rich Hydrothermal Conditions

    SciTech Connect

    Otake, Tsubasa; Ohmoto, Hiroshi; Wesolowski, David J; Anovitz, Lawrence {Larry} M; Allard Jr, Lawrence Frederick

    2007-01-01

    Transformations of magnetite (Fe{sup II}Fe{sub 2}{sup III}O{sub 4}) to hematite (Fe{sub 2}{sup III}O{sub 3}) (and vice versa) have been thought by many scientists and engineers to require molecular O{sub 2} and/or H{sub 2}. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H{sub 2}-rich aqueous solutions at 150 C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O{sub 2} or H{sub 2}: Fe{sub 3}O{sub 4}(Mt) + 2H{sub (aq)}{sup +} {leftrightarrow} Fe{sub 2}O{sub 3}(Hm) + Fe{sub (aq)}{sup 2+} + H{sub 2}O The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H{sub 2}. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

  2. Reactive nitrogen species contribute to the rapid onset of redox changes induced by acute immobilization stress in rats.

    PubMed

    Chen, Hsiao-Jou Cortina; Spiers, Jereme G; Sernia, Conrad; Anderson, Stephen T; Lavidis, Nickolas A

    2014-12-01

    Acute stress leads to the rapid secretion of glucocorticoids, which accelerates cellular metabolism, resulting in increased reactive oxygen and nitrogen species generation. Although the nitrergic system has been implicated in numerous stress-related diseases, the time course and extent of nitrosative changes during acute stress have not been characterized. Outbred male Wistar rats were randomly allocated into control (n = 9) or 120 min acute immobilization stress (n = 9) groups. Serial blood samples were collected at 0 (baseline), 60, 90, and 120 min. Plasma corticosterone concentrations increased by approximately 350% at 60, 90, and 120 (p < 0.001) min of stress. The production of nitric oxide, measured as the benzotriazole form of 4-amino-5-methylamino-2',7'-difluorofluorescein, increased during stress exposure by approximately 5%, 10%, and 15% at 60 (p < 0.05), 90 (p < 0.01) and 120 (p < 0.001) min, respectively, compared to controls. Nitric oxide metabolism, measured as the stable metabolites nitrite and nitrate, showed a 40-60% increase at 60, 90, and 120 (p < 0.001) min of stress. The oxidative status of 2',7'-dichlorofluorescein in plasma was significantly elevated at 60 (p < 0.01), 90, and 120 (p < 0.001) min. A delayed decrease of approximately 25% in the glutathione redox ratio at 120 min (p < 0.001) also indicates stress-induced cellular oxidative stress. The peroxidation of plasma lipids increased by approximately 10% at 90 (p < 0.05) and 15% at 120 (p < 0.001) min, indicative of oxidative damage. It was concluded that a single episode of stress causes early and marked changes of both oxidative and nitrosative status sufficient to induce oxidative damage in peripheral tissues.

  3. Ultra-oxidized redox conditions in subduction mélanges? Decoupling between oxygen fugacity and oxygen availability in a metasomatic environment

    NASA Astrophysics Data System (ADS)

    Tumiati, Simone; Poli, Stefano; Godard, Gaston; Martin, Silvana; Malaspina, Nadia

    2014-05-01

    The manganese ore of Praborna (Italian Western Alps) is embedded within a metasedimentary sequence belonging to a subduction mélange equilibrated at high-pressure conditions (~2 GPa) during the Alpine orogenesis and record environmental conditions typical for a subducting slab setting. The pervasive veining of the ore and the growth of "pegmatoid" HP minerals suggest an open system with large fluid/rock ratio and a strong interaction with slab-derived fluids. This natural case provides an excellent natural laboratory for the study of the oxygen mobility in subducting oceanic slab mélanges at high-P, fluid-present conditions. The Mn-rich rocks in contact with the underlying sulphide- and magnetite-bearing metabasites, in textural and chemical equilibrium with the veins, contain braunite (Mn2+Mn3+6SiO12) + quartz + pyroxmangite (Mn2+SiO3), and minor hematite, omphacite, the epidote piemontite and spessartine-rich garnet. Similarly to Fe-bearing systems, Mn oxides and silicates can be regarded as natural redox-sensors, capable to monitor a process of fluid infiltration that could fix externally the intensive variable fO2 (or μO2). Sulphides are absent in these Mn-rich rocks, sulphates (barite, celestine) occurring instead together with As- and Sb oxides and silicates. On the basis of the observed assemblages, new thermodynamic calculations show that these mélange rocks are characterized by unrealistic ultra-oxidized states (ΔFMQ up to +12) if the chemical potential of oxygen (or the oxygen fugacity) is accounted for. However, if the molar quantity of oxygen in excess with reference to with reference to a system where all iron and manganese are considered to be ferrous, the ore appears only moderately oxidized, and comparable to typical subduction-slab mafic eclogites. Therefore, oxygen can be hardly considered a perfectly mobile component, even in the most favourable conditions. In the Earth's interior redox reactions take place mainly among solid oxides and

  4. Chromium Isotopes in Carbonates - a Tracer for Climate Change and for Reconstructing the Redox state of Ancient Seawater

    NASA Astrophysics Data System (ADS)

    Frei, R.; Gaucher, C.; Dossing, L. N.; Sial, A. N.

    2011-12-01

    the redox state of ancient seawater since positive values indicate that, at least locally, Neoproterozoic shallow ocean waters were sufficiently oxidized to fractionate chromium and/or that oxygen levels of the atmosphere were sufficient to transform Cr(III) into the more mobile hexavalent Cr(VI) formed during weathering processes on land. The fact that 87Sr/86Sr values, despite δ13C fluctuations, remain low (indicative of a strong hydrothermal input into the basin at his time) implies that CO2 limitation was the cause of negative δ13C and δ53Cr excursions in otherwise nutrient rich late Vendian basins, and that glaciation is only one more consequence of a tectonically driven, biologically mediated system. In such a scenario, glaciation acts as an amplifier of δ53Cr signals. These signals in marine carbonates are a sensitive tracer for redox processes in the ocean and/or on land and have the potential to contribute significantly to the reconstruction of climatic changes, particularly those that are associated with major glaciation periods in Earth's history.

  5. Chromium isotopes in carbonates — A tracer for climate change and for reconstructing the redox state of ancient seawater

    NASA Astrophysics Data System (ADS)

    Frei, R.; Gaucher, C.; Døssing, L. N.; Sial, A. N.

    2011-12-01

    powerful tool for reconstructing the redox state of ancient seawater since positive values indicate that, at least locally, Neoproterozoic shallow ocean waters were sufficiently oxidized to fractionate chromium and/or that oxygen levels of the atmosphere were sufficient to transform Cr(III) into the more mobile hexavalent Cr(VI) formed during weathering processes on land. The fact that 87Sr/ 86Sr values, despite δ 13C fluctuations, remain low (indicative of a strong hydrothermal input into the basin at his time) implies that CO 2 limitation was the cause of negative δ 13C and δ 53Cr excursions in otherwise nutrient rich late Neoproterozoic basins, and that glaciation is only one more consequence of a tectonically driven, biologically mediated system. In such a scenario, glaciation acts as an amplifier of δ 53Cr signals. These signals in marine carbonates are a sensitive tracer for redox processes in the ocean and/or on land and have the potential to contribute significantly, in combination with the other commonly used isotopic tracers, to the reconstruction of climatic changes, particularly those that are associated with major glaciation periods in Earth's history.

  6. High-throughput screening of cellular redox sensors using modern redox proteomics approaches.

    PubMed

    Jiang, Jingwen; Wang, Kui; Nice, Edouard C; Zhang, Tao; Huang, Canhua

    2015-01-01

    Cancer cells are characterized by higher levels of intracellular reactive oxygen species (ROS) due to metabolic aberrations. ROS are widely accepted as second messengers triggering pivotal signaling pathways involved in the process of cell metabolism, cell cycle, apoptosis, and autophagy. However, the underlying cellular mechanisms remain largely unknown. Recently, accumulating evidence has demonstrated that ROS initiate redox signaling through direct oxidative modification of the cysteines of key redox-sensitive proteins (termed redox sensors). Uncovering the functional changes underlying redox regulation of redox sensors is urgently required, and the role of different redox sensors in distinct disease states still remains to be identified. To assist this, redox proteomics has been developed for the high-throughput screening of redox sensors, which will benefit the development of novel therapeutic strategies for cancer treatment. Highlighted here are recent advances in redox proteomics approaches and their applications in identifying redox sensors involved in tumor development.

  7. Terrain on Europa under Changing Lighting Conditions

    NASA Technical Reports Server (NTRS)

    1997-01-01

    These images obtained by the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft show the same region of Europa under different lighting conditions. The upper image was obtained on June 28th, 1996 during Galileo's first orbit around Jupiter under 'high-sun' conditions -- the equivalent of taking a picture from a high altitude at noon (with the sun directly overhead). Note that albedo (light/dark) features are emphasized. Compare this to the lower image containing a higher-resolution inset. This (inset) image was taken on November 6th, 1996 during the spacecraft's third orbit under 'low-sun' illumination -- the equivalent of taking a picture from a high altitude at sunrise or sunset. Note that in this image the albedo features are not readily apparent. Instead, the topography of the terrain is emphasized. Planetary geologists use information from images acquired under a variety of lighting conditions to identify different types of structures and interpret how they formed. Note that the bright linear features in the upper image are seen to be ridges in the lower image. The circular feature on the right side of both images, Cilix, is approximately 25 kilometers (15 miles) across.

    The area seen in the upper image is 312 kilometers (187 miles) by 570 kilometers (342 miles) across; the area covered by the inset is 36 kilometers (22 miles) by 315 kilometers (190 miles) across. Both of these images are centered near 2 South latitude, 185 West longitude. North is to the top of the frames.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  8. Evaluation of I/Ca ratios in benthic foraminifera from the Peruvian oxygen minimum zone as proxy for redox conditions in the ambient water masses

    NASA Astrophysics Data System (ADS)

    Glock, N.; Liebetrau, V.; Eisenhauer, A.

    2014-12-01

    Tropical oxygen minimum zones (OMZs) are most important areas of oxygen depletion in today´s oceans and nutrient cycling in these regions has a large socio-economic impact because they account for about 17% of the global commercial fish catches(1). Possibly increasing magnitude and area of oxygen depletion in these regions, might endanger rich pelagic fish habitats in the future threatening the global marine food supply. By the use of a quantitative redox proxy in OMZs, reconstruction of the temporal variation in OMZ extension eventually providing information about past and future changes in oxygenation and the anthropogenic role in the recent trend of expanding OMZs(2). Recent work has shown that iodine/calcium (I/Ca) ratios in marine carbonates are a promising proxy for ambient oxygen concentration(3). Our study explores the correlation of I/Ca ratios in four benthic foraminiferal species (three calcitic, one aragonitic) from the Peruvian OMZ to bottom water oxygen concentrations ([O2]BW) and evaluates foraminiferal I/Ca ratios as a possible redox proxy for the ambient water masses. Our results show that all species have a positive trend in the I/Ca ratios as a function of [O2]BW. Only for the aragonitic species Hoeglundina elegans this trend is not significant. The highest significance has been found for Uvigerina striata (I/Ca = 0.032(±0.004).[O2]BW + 0.29(±0.03), R² = 0.61, F = 75, P < 0.0001). Although I/Ca ratios in benthic foraminifera appear to be a robust redox proxy there are some methodical issues which have to be considered. These "pitfalls" include: (i) the volatility of iodine in acidic solutions, (ii) a species dependency of the I/Ca-[O2]BW relationship which is either related to a strong vital effect or toa species dependency on the calcification depth within sediment, and (iii) the inter-test variability of I/Ca between different specimens from the same species and habitat. (1): FAO FishStat: Fisheries and aquaculture software. In: FAO

  9. Changes in Spatiotemporal Precipitation Patterns in Changing Climate Conditions

    NASA Astrophysics Data System (ADS)

    Chang, Won; Stein, Michael L.; Wang, Jiali; Kotamarthi, V. Rao; Moyer, Elisabeth J.

    2016-12-01

    Climate models robustly imply that some significant change in precipitation patterns will occur. Models consistently project that the intensity of individual precipitation events increases by approximately 6-7%/K, following the increase in atmospheric water content, but that total precipitation increases by a lesser amount (1-2 %/K in the global average in transient runs). Some other aspect of precipitation events must then change to compensate for this difference. We develop here a new methodology for identifying individual rainstorms and studying their physical characteristics - including starting location, intensity, spatial extent, duration, and trajectory - that allows identifying that compensating mechanism. We apply this technique to precipitation over the contiguous U.S. from both radar-based data products and high-resolution model runs simulating 80 years of business-as-usual warming. In model studies, we find that the dominant compensating mechanism is a reduction of storm size. In summer, rainstorms become more intense but smaller, in winter, rainstorm shrinkage still dominates, but storms also become less numerous and shorter duration. These results imply that flood impacts from climate change will be less severe than would be expected from changes in precipitation intensity alone. We show also that projected changes are smaller than model-observation biases, implying that the best means of incorporating them into impact assessments is via "data-driven simulations" that apply model-projected changes to observational data. We therefore develop a simulation algorithm that statistically describes model changes in precipitation characteristics and adjusts data accordingly, and show that, especially for summertime precipitation, it outperforms simulation approaches that do not include spatial information.

  10. Changing CS Features Alters Evaluative Responses in Evaluative Conditioning

    ERIC Educational Resources Information Center

    Unkelbach, Christian; Stahl, Christoph; Forderer, Sabine

    2012-01-01

    Evaluative conditioning (EC) refers to changes in people's evaluative responses toward initially neutral stimuli (CSs) by mere spatial and temporal contiguity with other positive or negative stimuli (USs). We investigate whether changing CS features from conditioning to evaluation also changes people's evaluative response toward these CSs. We used…

  11. Redox therapy in neonatal sepsis: reasons, targets, strategy, and agents.

    PubMed

    Bajčetić, Milica; Spasić, Snežana; Spasojević, Ivan

    2014-09-01

    Neonatal sepsis is one of the most fulminating conditions in neonatal intensive care units. Antipathogen and supportive care are administered routinely, but do not deliver satisfactory results. In addition, the efforts to treat neonatal sepsis with anti-inflammatory agents have generally shown to be futile. The accumulating data imply that intracellular redox changes intertwined into neonatal sepsis redox cycle represent the main cause of dysfunction of mitochondria and cells in neonatal sepsis. Our aim here is to support the new philosophy in neonatal sepsis treatment, which involves the integration of mechanisms that are responsible for cellular dysfunction and organ failure, the recognition of the most important targets, and the selection of safe agents that can stop the neonatal sepsis redox cycle by hitting the hot spots. Redox-active agents that could be beneficial for neonatal sepsis treatment according to these criteria include lactoferrin, interleukin 10, zinc and selenium supplements, ibuprofen, edaravone, and pentoxifylline.

  12. Modulation of Chlamydomonas reinhardtii flagellar motility by redox poise

    PubMed Central

    Wakabayashi, Ken-ichi; King, Stephen M.

    2006-01-01

    Redox-based regulatory systems are essential for many cellular activities. Chlamydomonas reinhardtii exhibits alterations in motile behavior in response to different light conditions (photokinesis). We hypothesized that photokinesis is signaled by variations in cytoplasmic redox poise resulting from changes in chloroplast activity. We found that this effect requires photosystem I, which generates reduced NADPH. We also observed that photokinetic changes in beat frequency and duration of the photophobic response could be obtained by altering oxidative/reductive stress. Analysis of reactivated cell models revealed that this redox poise effect is mediated through the outer dynein arms (ODAs). Although the global redox state of the thioredoxin-related ODA light chains LC3 and LC5 and the redox-sensitive Ca2+-binding subunit of the docking complex DC3 did not change upon light/dark transitions, we did observe significant alterations in their interactions with other flagellar components via mixed disulfides. These data indicate that redox poise directly affects ODAs and suggest that it may act in the control of flagellar motility. PMID:16754958

  13. Copper-catalyzed hydroquinone oxidation and associated redox cycling of copper under conditions typical of natural saline waters.

    PubMed

    Yuan, Xiu; Pham, A Ninh; Miller, Christopher J; Waite, T David

    2013-08-06

    A detailed kinetic model has been developed to describe the oxidation of Cu(I) by O2 and the reduction of Cu(II) by 1,4-hydroquinone (H2Q) in the presence of O2 in 0.7 M NaCl solution over a pH range of 6.5-8.0. The reaction between Cu(I) and O2 is shown to be the most important pathway in the overall oxidation of Cu(I), with the rate constant for this oxidation process increasing with an increasing pH. In 0.7 M NaCl solutions, Cu(II) is capable of catalyzing the oxidation of H2Q in the presence of O2 with the monoanion, HQ(-), the kinetically active hydroquinone form, reducing Cu(II) with an intrinsic rate constant of (5.0 ± 0.4) × 10(7) M(-1) s(-1). Acting as a chain-propagating species, the deprotonated semiquinone radical (SQ(•) (-)) generated from both the one-electron oxidation of H2Q and the one-electron reduction of 1,4-benzoquinone (BQ) also reacts rapidly with Cu(II) and Cu(I), with the same rate constant of (2.0 ± 0.5) × 10(7) M(-1) s(-1). In addition to its role in reformation of Cu(II) via continuous oxidation of Cu(I), O2 rapidly removes SQ(•) (-), resulting in the generation of O2(•) (-). Agreement between half-cell reduction potentials of different redox couples provides confirmation of the veracity of the proposed model describing the interactions of copper and quinone species in circumneutral pH saline solutions.

  14. Mixing interfaces, fluxes, residence times and redox conditions of the hyporheic zones induced by dune-like bedforms and ambient groundwater flow

    NASA Astrophysics Data System (ADS)

    Marzadri, Alessandra; Tonina, Daniele; Bellin, Alberto; Valli, Alberto

    2016-02-01

    Recent studies highlighted the importance of the interface between streams and their surrounding sediment, known as the hyporheic zone, where stream waters flow through the alluvium. These pore water fluxes stem from the interaction among streambed morphology, stream hydraulics and surrounding groundwater flow. We analytically model the hyporheic hydraulics induced by a spatially uniform ambient groundwater flow made of a horizontal, underflow, and a vertical, basal, component, which mimics gaining and losing stream conditions. The proposed analytical solution allows to investigate the control of simple hydromorphological quantities on the extent, residence time and redox conditions of the hyporheic zone, and the thickness of the mixing interface between hyporheic and groundwater cells. Our analysis shows that the location of the mixing zone shallows or deepens in the sediment as a function of bedform geometry, surface hydraulic and groundwater flow. The point of stagnation, where hyporheic flow velocities vanish and where the separation surface passes through, is shallower than or coincides with the deepest point of the hyporheic zone only due to underflow. An increase of the ambient flow causes a reduction of the hyporheic zone volume similarly in both losing and gaining conditions. The hyporheic residence time is lognormally distributed under neutral, losing and gaining conditions, with the residence time moments depending on the same set of parameters describing dune morphology and stream flow.

  15. Changes in the redox potential of the rabbit cerebral cortex accompanying episodes of ECoG arousal during slow-wave sleep.

    PubMed

    Shvets-Ténéta-Gurii, T B; Troshin, G I; Dubinin, A G

    2008-01-01

    The redox potential (E) is a useful measure of the intensity and quality of shifts in energy metabolism. Brain E depends on the ratio of the rates of processes occurred in two compartments of energy metabolism - the glycolysis compartment, in which glucose is split without oxygen, and the oxidative metabolism compartment. The present report describes recording of local changes in E using platinum electrodes implanted into several points in the cortex. In these conditions, decreases in E correspond to local increases in the rates of glycolytic processes in the tissue surrounding the electrode and are related to mitochondrial processes, while increases in E correspond to local acceleration of processes in oxidative metabolism in the tissues around the electrode. Our previous studies in rats showed that during episodes of slow-wave sleep (SWS), metabolically active points of the rat cerebral cortex show significant decreases in E, and it was suggested that these are associated with increases in the rate of glycolysis. At the same time, E showed characteristic oscillations lasting 20-40 sec with amplitudes of tens of millivolts. The experiments reported here demonstrated that slow oscillations in E developing during SWS are created by regular episodes of ECoG arousal occurring during SWS, accompanied by startling of the animal, decreases in E, and inhibition of respiration. We suggest that a homeostasis system operates during SWS to maintain the animal's level of consciousness at a particular level and that this, like any system with feedback, operates in an oscillatory fashion. The role of glycolysis in supplying energy to the cerebral cortex to support the elevated level of consciousness increases.

  16. Redox alters yellow dragonflies into red.

    PubMed

    Futahashi, Ryo; Kurita, Ryoji; Mano, Hiroaki; Fukatsu, Takema

    2012-07-31

    Body color change associated with sexual maturation--so-called nuptial coloration--is commonly found in diverse vertebrates and invertebrates, and plays important roles for their reproductive success. In some dragonflies, whereas females and young males are yellowish in color, aged males turn vivid red upon sexual maturation. The male-specific coloration plays pivotal roles in, for example, mating and territoriality, but molecular basis of the sex-related transition in body coloration of the dragonflies has been poorly understood. Here we demonstrate that yellow/red color changes in the dragonflies are regulated by redox states of epidermal ommochrome pigments. Ratios of reduced-form pigments to oxidized-form pigments were significantly higher in red mature males than yellow females and immature males. The ommochrome pigments extracted from the dragonflies changed color according to redox conditions in vitro: from red to yellow in the presence of oxidant and from yellow to red in the presence of reductant. By injecting the reductant solution into live insects, the yellow-to-red color change was experimentally reproduced in vivo in immature males and mature females. Discontinuous yellow/red mosaicism was observed in body coloration of gynandromorphic dragonflies, suggesting a cell-autonomous regulation over the redox states of the ommochrome pigments. Our finding extends the mechanical repertoire of pigment-based body color change in animals, and highlights an impressively simple molecular mechanism that regulates an ecologically important color trait.

  17. Redox alters yellow dragonflies into red

    PubMed Central

    Futahashi, Ryo; Kurita, Ryoji; Mano, Hiroaki; Fukatsu, Takema

    2012-01-01

    Body color change associated with sexual maturation—so-called nuptial coloration—is commonly found in diverse vertebrates and invertebrates, and plays important roles for their reproductive success. In some dragonflies, whereas females and young males are yellowish in color, aged males turn vivid red upon sexual maturation. The male-specific coloration plays pivotal roles in, for example, mating and territoriality, but molecular basis of the sex-related transition in body coloration of the dragonflies has been poorly understood. Here we demonstrate that yellow/red color changes in the dragonflies are regulated by redox states of epidermal ommochrome pigments. Ratios of reduced-form pigments to oxidized-form pigments were significantly higher in red mature males than yellow females and immature males. The ommochrome pigments extracted from the dragonflies changed color according to redox conditions in vitro: from red to yellow in the presence of oxidant and from yellow to red in the presence of reductant. By injecting the reductant solution into live insects, the yellow-to-red color change was experimentally reproduced in vivo in immature males and mature females. Discontinuous yellow/red mosaicism was observed in body coloration of gynandromorphic dragonflies, suggesting a cell-autonomous regulation over the redox states of the ommochrome pigments. Our finding extends the mechanical repertoire of pigment-based body color change in animals, and highlights an impressively simple molecular mechanism that regulates an ecologically important color trait. PMID:22778425

  18. Solution structure of horse heart ferricytochrome c and detection of redox-related structural changes by high-resolution 1H NMR.

    PubMed

    Qi, P X; Beckman, R A; Wand, A J

    1996-09-24

    A model for the solution structure of horse heart ferricytochrome c has been determined by nuclear magnetic resonance spectroscopy combined with hybrid distance geometry-simulated annealing calculations. Forty-four highly refined structures were obtained using a total of 1671 distance constraints based on the observed magnitude of nuclear Overhauser effects and 58 torsion angle restrains based on the magnitude of determined J-coupling constants. The model incorporates six long-lived water molecules detected by pseudo-two-dimensional NOESY-TOCSY spectra. The all-residue root mean square deviation about the average structure is 0.33 +/- 0.04 A for the backbone N, C alpha, and C' atoms and 0.83 +/- 0.05 A for all heavy atoms. The overall topology of the model for solution structure is very similar to that seen in previously reported models for crystal structures of homologous c-type cytochromes though there are a number of significant differences in detailed aspects of the structure. Two of the three main helices display localized irregularities in helical hydrogen bonding resulting in bifurcation of main chain hydrogen bond acceptor carbonyls. The N- and C-terminal helices are tightly packed and display several interhelical interactions not seen in reported crystal models. To provide an independent measure of the accuracy of the model for the oxidized protein, the expected pseudocontact shifts induced by the spin 1/2 iron were compared to the observed redox-dependent chemical shift changes. These comparisons confirm the general accuracy of the model for the oxidized protein and its observed differences with the structure of the reduced protein. The structures of the reduced and oxidized states of the protein provide a template to explain a range of physical and biological data spanning the redox properties, folding, molecular recognition, and stability of the cytochrome c molecule. For example, a redox-dependent reorganization of surface residues at the heme edge can

  19. Clostridium thermocellum DSM 1313 transcriptional responses to redox perturbation

    SciTech Connect

    Sander, Kyle B.; Wilson, Charlotte M.; M. Rodriquez, Jr.; Klingeman, Dawn Marie; Davison, Brian H.; Brown, Steven D.; Rydzak, T.

    2015-12-12

    Clostridium thermocellum is a promising consolidated bioprocessing candidate organism capable of directly converting lignocellulosic biomass to ethanol. Current ethanol yields, productivities, and growth inhibitions are industrial deployment impediments for commodity fuel production by this bacterium. Redox imbalance under certain conditions and in engineered strains may contribute to incomplete substrate utilization and may direct fermentation products to undesirable overflow metabolites. As a result, towards a better understanding of redox metabolism in C. thermocellum, we established continuous growth conditions and analyzed global gene expression during addition of two stress chemicals (methyl viologen and hydrogen peroxide) which changed the fermentation redox potential.

  20. Ediacaran Redox Fluctuations

    NASA Astrophysics Data System (ADS)

    Sahoo, S. K.; Jiang, G.; Planavsky, N. J.; Kendall, B.; Owens, J. D.; Anbar, A. D.; Lyons, T. W.

    2013-12-01

    Evidence for pervasive oxic conditions, and likely even deep ocean oxygenation has been documented at three intervals in the lower (ca. 632 Ma), middle (ca. 580 Ma) and upper (ca. 551 Ma) Ediacaran. The Doushantuo Formation in South China hosts large enrichments of redox-sensitive trace element (e.g., molybdenum, vanadium and uranium) in anoxic shales, which are indicative of a globally oxic ocean-atmosphere system. However, ocean redox conditions between these periods continue to be a topic of debate and remain elusive. We have found evidence for widespread anoxic conditions through much of the Ediacaran in the deep-water Wuhe section in South China. During most of the Ediacaran-early Cambrian in basinal sections is characterized by Fe speciation data and pyrite morphologies that indicate deposition under euxinic conditions with near-crustal enrichments of redox-sensitive element and positive pyrite-sulfur isotope values, which suggest low levels of marine sulfate and widespread euxinia. Our work reinforces an emerging view that the early Earth, including the Ediacaran, underwent numerous rises and falls in surface oxidation state, rather than a unidirectional rise as originally imagined. The Ediacaran ocean thus experienced repetitive expansion and contraction of marine chalcophilic trace-metal levels that may have had fundamental impact on the slow evolution of early animals and ecosystems. Further, this framework forces us to re-examine the relationship between Neoproterozoic oxygenation and metazoan diversification. Varying redox conditions through the Cryogenian and Ediacaran may help explain molecular clock and biomarker evidence for an early appearance and initial diversification of metazoans but with a delay in the appearance of most major metazoan crown groups until close to Ediacaran-Cambrian boundary.

  1. Hourly and daily variation of sediment redox potential in tidal wetland sediments

    USGS Publications Warehouse

    Catallo, W. James

    1999-01-01

    Variation of electrochemical oxidation-reduction (redox) potential was examined in surface salt march sediments under conditions of flooding and tidal simulation in mesocosms and field sites. Time series were generated of redox potential measured in sediment profiles at 2-10 cm depth using combination Pt-Ag/AgCl (ORP) electrodes. Redox potential data were acquired at rapid rates (1-55 samples/h) over extended periods (3-104 days) along with similar times series of temperature (water, air, soil) and pH. It was found that redox potential vaired as a result of water level changes and was unrelated to diurnal changes in temperature or pH, the latter of which changed by 370 mV redox potential decrease in under 48 hours). Attenuatoin of microbial activity by [gamma] y-radiation and toxic chemicals elimintated this response. In tidal salt marsh mesocosms where the sediment-plant assemblages were exposed to a simulated diurnal tide, redox potenial oscillations of 40-300 mV amplitude were recoded that has the same periodicity as the flood-drain cycle. Periodic redoc potential time series were observed repeatedly in sediments receiving tidal pulsing but not in those sediments exposed to static hydrological conditions. Data collected over 12 days from a coastal marsh site experiencing diurnal tides showed similar fluctuations in redox potential. Data from the experimentents indicated that (a) redox potential can be a dynamic, nonlinear variable in coastal and estuarine wetland sediments over hourly and daily scales, and the designs of biogeochemical experiments should reflect this, (b) redox potential can change rapidly and signigicantly in coastal wetland sediments in response of flooding and draining, (c) microbial community processes are primarily determinants of the time course of redox potential in wetland sediments, and elimination of inhibition of microbial activity (e.g. by pollutants) can significantly alter that behavior, and (d) fast redox potential dynamics appear

  2. Rare Earth Elements of the Permian-Triassic Conodonts from Shelf Basin to Shallow Platform: Implications for Oceanic Redox Conditions immediately After the End-Permian Mass Extinction

    NASA Astrophysics Data System (ADS)

    Li, Y.; Zhao, L.; Chen, Z.; Chen, J.; Chen, Y.

    2013-12-01

    Rare-earth elements (REEs) can provide information regarding the influence of weathering fluxes and hydrothermal inputs on seawater chemistry as well as processes that fractionate REEs between solid and aqueous phases. Of these, cerium (Ce) distributions may provide information about variations in dissolved oxygen in seawater, and thus assess the redox conditions. The short residence times of REEs in seawater (~300-1,000 yr) can result in unique REE signatures in local watermasses. REE patterns preserved in biogenic apatite such as conodonts are ideal proxies for revealing original seawater chemistry. Here, we measured the REE content of in-situ, single albid crowns using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in combination with an ArF (λ=193 nm) excimer laser (Lambda Physiks GeoLas 2005) and quadrupole ICP-MS (Agilent 7500a). LA-ICP-MS is ideally suited for analyzing conodonts due to its ability to measure compositional variation within single conodont elements. It has the capability to determine, with high spatial resolution, continuous compositional depth profiles through the concentric layered structure of component histologies. To evaluate paleoceanographic conditions immediately after the Permian-Triassic (P-Tr) mass extinction in various depositional settings, we sampled a nearly contemporaneous strata unit, the P-Tr boundary bed, just above the extinction horizon from six sections in South China. They represent various depositional settings from shelf basin (Chaohu and Daxiakou sections), lower part of ramp (Meishan section), normal shallow platform (Yangou section), and platform microbialite (Chongyang and Xiushui sections). The sampled unit is constrained by conodonts Hindeodus changxingensis, H. parvus, and H. staeschei Zones in Meishan. REE results obtained from conodont albid crowns show that the seawater in lower ramp and shelf basin settings contains much higher REE concentrations than that in shallow platform. Ce

  3. Effects of Varying RedoxConditions on Natural Attenuation of Inorganic Contaminants from the D-Area Coal Pile Runoff Basin (U)

    SciTech Connect

    Kaplan, D

    2004-05-30

    The objective of this study was to provide geochemical parameters to characterize the D-Area Coal Pile Runoff Basin (DCPRB) sediment as a potential source term. It is anticipated that the measured values will be used in risk calculations and will provide additional technical support for imposing Monitored Natural Attenuation at D-Area. This study provides a detailed evaluation of the DCPRB sediment and is part of another study that quantified the Monitored Natural Attenuation of inorganic contaminants more broadly at the D-Area Expanded Operable Unit, which includes the DCPRB (Powell et al. 2004). Distribution coefficients (K{sub d} values; a solid to liquid contaminant concentration ratio) and the Potentially Leachable Fraction (the percent of the total contaminant concentration in the sediment that can likely contribute to a contaminant plume) were measured in a DCPRB sediment as a function of redox conditions. Redox conditions at the DCPRB are expected to vary greatly as the system undergoes varying drying and flooding conditions. Conservative values; K{sub d} values that err on the side of being too low and Potentially Leachable Fraction values that err on the side of being too high, are presented. The K{sub d} values are high compared to conservative literature values, and underscores the importance of measuring site-specific values to provide estimates of sediments natural attenuation/sorption capacities. The Potentially Leachable Fraction indicates that as little as 27% of the As, but all of the Cu and Tl will be part of the source term. In the case of the As, the remaining 83% will likely never leach out of the sediment, thereby providing a form of natural attenuation. Importantly, Be, Cr, Cu, Ni, and V concentrations in the sediment were less-than twice background levels, indicating this sediment was not a potential source for these contaminants. K{sub d} values generally increased significantly (As, Cd, Co, Cr, Cu, Ni, Se, and Tl) when the sediment was

  4. Trial development of unit response changes during conditioning in cats.

    PubMed

    Packham, S C; O'Brien, J H

    1976-10-01

    Single-cell and evoked potential (EP) activity in the postcruciate cortex of acutely prepared cats was recorded during a classical conditioning procedure. The temporal pattern of response (PSH) of the neuron was separated into three components, and the trial development of learning changes for these components was examined individually. Changes over trials in the similarity of the EP waveform and the unit PSH were also examined. The unit response components showed changes in response at different trial periods; these changes could not be accounted for by changes at lower brain levels that projected to the cortex. This suggests that local learning changes were taking places in the cortex. The EP-PSH similarity decreased for neurons showing the largest changes in response during conditioning. Since the EP reflects the response of the whole population of neurons and a majority did not show learning changes, this could account for the observed decrease.

  5. Sensitive Measures of Condition Change in EEG Data

    SciTech Connect

    Hively, L.M.; Gailey, P.C.; Protopopescu, V.

    1999-03-10

    We present a new, robust, model-independent technique for measuring condition change in nonlinear data. We define indicators of condition change by comparing distribution functions (DF) defined on the attractor for time windowed data sets via L{sub 1}-distance and {chi}{sup 2} statistics. The new measures are applied to EEG data with the objective of detecting the transition between non-seizure and epileptic brain activity in an accurate and timely manner. We find a clear superiority of the new metrics in comparison to traditional nonlinear measures as discriminators of condition change.

  6. Redox control of plant growth and development.

    PubMed

    Kocsy, Gábor; Tari, Irma; Vanková, Radomíra; Zechmann, Bernd; Gulyás, Zsolt; Poór, Péter; Galiba, Gábor

    2013-10-01

    Redox changes determined by genetic and environmental factors display well-organized interactions in the control of plant growth and development. Diurnal and seasonal changes in the environmental conditions are important for the normal course of these physiological processes and, similarly to their mild irregular alterations, for stress adaptation. However, fast or large-scale environmental changes may lead to damage or death of sensitive plants. The spatial and temporal redox changes influence growth and development due to the reprogramming of metabolism. In this process reactive oxygen and nitrogen species and antioxidants are involved as components of signalling networks. The control of growth, development and flowering by reactive oxygen and nitrogen species and antioxidants in interaction with hormones at organ, tissue, cellular and subcellular level will be discussed in the present review. Unsolved problems of the field, among others the need for identification of new components and interactions in the redox regulatory network at various organization levels using systems biology approaches will be also indicated.

  7. Redox-Dependent Modulation of Anthocyanin Biosynthesis by the TCP Transcription Factor TCP15 during Exposure to High Light Intensity Conditions in Arabidopsis.

    PubMed

    Viola, Ivana L; Camoirano, Alejandra; Gonzalez, Daniel H

    2016-01-01

    TCP proteins integrate a family of transcription factors involved in the regulation of developmental processes and hormone responses. It has been shown that most members of class I, one of the two classes in which the TCP family is divided, contain a conserved Cys that leads to inhibition of DNA binding when oxidized. In this work, we describe that the class-I TCP protein TCP15 inhibits anthocyanin accumulation during exposure of plants to high light intensity by modulating the expression of transcription factors involved in the induction of anthocyanin biosynthesis genes, as suggested by the study of plants that express TCP15 from the 35SCaMV promoter and mutants in TCP15 and the related gene TCP14. In addition, the effect of TCP15 on anthocyanin accumulation is lost after prolonged incubation under high light intensity conditions. We provide evidence that this is due to inactivation of TCP15 by oxidation of Cys-20 of the TCP domain. Thus, redox modulation of TCP15 activity in vivo by high light intensity may serve to adjust anthocyanin accumulation to the duration of exposure to high irradiation conditions.

  8. Fasting, but Not Aging, Dramatically Alters the Redox Status of Cysteine Residues on Proteins in Drosophila melanogaster.

    PubMed

    Menger, Katja E; James, Andrew M; Cochemé, Helena M; Harbour, Michael E; Chouchani, Edward T; Ding, Shujing; Fearnley, Ian M; Partridge, Linda; Murphy, Michael P

    2015-06-30

    Altering the redox state of cysteine residues on protein surfaces is an important response to environmental challenges. Although aging and fasting alter many redox processes, the role of cysteine residues is uncertain. To address this, we used a redox proteomic technique, oxidative isotope-coded affinity tags (OxICAT), to assess cysteine-residue redox changes in Drosophila melanogaster during aging and fasting. This approach enabled us to simultaneously identify and quantify the redox state of several hundred cysteine residues in vivo. Cysteine residues within young flies had a bimodal distribution with peaks at ∼10% and ∼85% reversibly oxidized. Surprisingly, these cysteine residues did not become more oxidized with age. In contrast, 24 hr of fasting dramatically oxidized cysteine residues that were reduced under fed conditions while also reducing cysteine residues that were initially oxidized. We conclude that fasting, but not aging, dramatically alters cysteine-residue redox status in D. melanogaster.

  9. Degradation of Redox-Sensitive Proteins including Peroxiredoxins and DJ-1 is Promoted by Oxidation-induced Conformational Changes and Ubiquitination

    PubMed Central

    Song, In-Kang; Lee, Jae-Jin; Cho, Jin-Hwan; Jeong, Jihye; Shin, Dong-Hae; Lee, Kong-Joo

    2016-01-01

    Reactive oxygen species (ROS) are key molecules regulating various cellular processes. However, what the cellular targets of ROS are and how their functions are regulated is unclear. This study explored the cellular proteomic changes in response to oxidative stress using H2O2 in dose- and recovery time-dependent ways. We found discernible changes in 76 proteins appearing as 103 spots on 2D-PAGE. Of these, Prxs, DJ-1, UCH-L3 and Rla0 are readily oxidized in response to mild H2O2 stress, and then degraded and active proteins are newly synthesized during recovery. In studies designed to understand the degradation process, multiple cellular modifications of redox-sensitive proteins were identified by peptide sequencing with nanoUPLC-ESI-q-TOF tandem mass spectrometry and the oxidative structural changes of Prx2 explored employing hydrogen/deuterium exchange-mass spectrometry (HDX-MS). We found that hydrogen/deuterium exchange rate increased in C-terminal region of oxidized Prx2, suggesting the exposure of this region to solvent under oxidation. We also found that Lys191 residue in this exposed C-terminal region of oxidized Prx2 is polyubiquitinated and the ubiquitinated Prx2 is readily degraded in proteasome and autophagy. These findings suggest that oxidation-induced ubiquitination and degradation can be a quality control mechanism of oxidized redox-sensitive proteins including Prxs and DJ-1. PMID:27703196

  10. Degradation of Redox-Sensitive Proteins including Peroxiredoxins and DJ-1 is Promoted by Oxidation-induced Conformational Changes and Ubiquitination

    NASA Astrophysics Data System (ADS)

    Song, In-Kang; Lee, Jae-Jin; Cho, Jin-Hwan; Jeong, Jihye; Shin, Dong-Hae; Lee, Kong-Joo

    2016-10-01

    Reactive oxygen species (ROS) are key molecules regulating various cellular processes. However, what the cellular targets of ROS are and how their functions are regulated is unclear. This study explored the cellular proteomic changes in response to oxidative stress using H2O2 in dose- and recovery time-dependent ways. We found discernible changes in 76 proteins appearing as 103 spots on 2D-PAGE. Of these, Prxs, DJ-1, UCH-L3 and Rla0 are readily oxidized in response to mild H2O2 stress, and then degraded and active proteins are newly synthesized during recovery. In studies designed to understand the degradation process, multiple cellular modifications of redox-sensitive proteins were identified by peptide sequencing with nanoUPLC-ESI-q-TOF tandem mass spectrometry and the oxidative structural changes of Prx2 explored employing hydrogen/deuterium exchange-mass spectrometry (HDX-MS). We found that hydrogen/deuterium exchange rate increased in C-terminal region of oxidized Prx2, suggesting the exposure of this region to solvent under oxidation. We also found that Lys191 residue in this exposed C-terminal region of oxidized Prx2 is polyubiquitinated and the ubiquitinated Prx2 is readily degraded in proteasome and autophagy. These findings suggest that oxidation-induced ubiquitination and degradation can be a quality control mechanism of oxidized redox-sensitive proteins including Prxs and DJ-1.

  11. Redox crisis underlies conditional light-dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA.

    PubMed

    Diamond, Spencer; Rubin, Benjamin E; Shultzaberger, Ryan K; Chen, You; Barber, Chase D; Golden, Susan S

    2017-01-24

    Cyanobacteria evolved a robust circadian clock, which has a profound influence on fitness and metabolism under daily light-dark (LD) cycles. In the model cyanobacterium Synechococcus elongatus PCC 7942, a functional clock is not required for diurnal growth, but mutants defective for the response regulator that mediates transcriptional rhythms in the wild-type, regulator of phycobilisome association A (RpaA), cannot be cultured under LD conditions. We found that rpaA-null mutants are inviable after several hours in the dark and compared the metabolomes of wild-type and rpaA-null strains to identify the source of lethality. Here, we show that the wild-type metabolome is very stable throughout the night, and this stability is lost in the absence of RpaA. Additionally, an rpaA mutant accumulates excessive reactive oxygen species (ROS) during the day and is unable to clear it during the night. The rpaA-null metabolome indicates that these cells are reductant-starved in the dark, likely because enzymes of the primary nighttime NADPH-producing pathway are direct targets of RpaA. Because NADPH is required for processes that detoxify ROS, conditional LD lethality likely results from inability of the mutant to activate reductant-requiring pathways that detoxify ROS when photosynthesis is not active. We identified second-site mutations and growth conditions that suppress LD lethality in the mutant background that support these conclusions. These results provide a mechanistic explanation as to why rpaA-null mutants die in the dark, further connect the clock to metabolism under diurnal growth, and indicate that RpaA likely has important unidentified functions during the day.

  12. A Novel Redox State Heme a Marker in Cytochrome c Oxidase Revealed by Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Piccoli, C.; Perna, G.; Scrima, R.; Cela, O.; Rinaldi, R.; Boffoli, D.; Capozzi, V.; Capitanio, N.

    2005-01-01

    This study was aimed to characterize by Raman spectroscopy (excitation line 633 nm) different redox states of the mitochondrial cytochrome c oxidase. The results obtained from a systematic analysis carried out on the mitochondrial enzyme prepared under redox conditions, differently affecting the valence state of the metal prosthetic groups, and a comparison with homologous bacterial heme-copper oxidases, cytochrome c and pyridine hemo-chrome extract revealed a novel redox state marker specifically linked to the redox transition of heme a, peaking at 1645 cm-1, and tentatively assigned to the C=C and/or C=N streching mode of the imidazole ring of a proxymal histidine ligand. The possible involvment of this redox-linked conformational change in the catalytic activity of cytochrome oxidase is discussed.

  13. The Tumor Suppressor Mst1 Promotes Changes in the Cellular Redox State by Phosphorylation and Inactivation of Peroxiredoxin-1 Protein*

    PubMed Central

    Rawat, Sonali Jalan; Creasy, Caretha L.; Peterson, Jeffrey R.; Chernoff, Jonathan

    2013-01-01

    The serine/threonine protein kinases Mst1 and Mst2 can be activated by cellular stressors including hydrogen peroxide. Using two independent protein interaction screens, we show that these kinases associate, in an oxidation-dependent manner, with Prdx1, an enzyme that regulates the cellular redox state by reducing hydrogen peroxide to water and oxygen. Mst1 inactivates Prdx1 by phosphorylating it at Thr-90 and Thr-183, leading to accumulation of hydrogen peroxide in cells. These results suggest that hydrogen peroxide-stimulated Mst1 activates a positive feedback loop to sustain an oxidizing cellular state. PMID:23386615

  14. High resolution redox potential measurements: techniques, interpretation and value

    NASA Astrophysics Data System (ADS)

    Vorenhout, Michel; van der Geest, Harm G.

    2013-04-01

    The ongoing improvement of techniques for the in situ measurement of redox potentials has led to a large number of studies on redox variability in various environments. These studies originate from a wide array of scientific disciplines, amongst which ecology (sediment biogeochemistry), environmental chemistry (degradation studies) and archaeology (in situ preservation). To gain insight in the potential applications, this paper presents three examples of studies in which a newly developed measurement technique was used in soils and where spatial and temporal variation plays an important role. The first one is a microcosm study on the effects of biota on the dynamics of redox conditions in the toplayer of aquatic sediments, showing that the presence of microbiota has a direct influence on biogeochemical parameters. The second is the study of the redox potential in the world heritage site of Bryggen (Bergen, NO) that is under threat of oxidation. The oxidation, caused by a lowered groundwater table, causes soil degradation and unstable conditions for the monumental buildings of the Medieval site. The third study shows variability in a sandy flood plain in Bangladesh, where redox processes dictate the environmental behaviour of Arsenic. This toxic metal is present in many wells used for drinking water, but shows very local variation in dissolution dynamics. In these three studies, continuous measurements of (changes in) redox conditions revealed a strong variability in these systems and consequences for the interpretation of single point measurements or low frequency sampling campaigns are discussed. In these and many other cases, the continuous measurement of the redox potential in soil media will aid in the understanding of the system under study.

  15. Redox kinetics and colloid formation during water-chlorite interactions

    NASA Astrophysics Data System (ADS)

    Kim, E. G.; Ahn, H.; Ryu, J. H.; Jo, H. Y.

    2014-12-01

    For the isolation of high-level radioactive wastes from biosphere, the deep geological repository should be maintained reducing conditions. Surface groundwater can flow along fractures into the deep geological repository, which may cause oxic conditions. In the oxic conditions, uranium can be oxidized from U(Ⅳ) to U(Ⅵ) and U(Ⅵ) can easily migrate in groundwater due to its high mobility. Chlorite with Fe(Ⅱ), which is a phyllosilicate minerals generally occurred in fractures, can help maintenance of the reducing condition because chlorite can consume oxidizing agents by redox reactions. In this study, redox kinetics of chlorite were investigated by conducting redox batch kinetic tests at various conditions (i.e., concentration of oxidizing agent, pH, and presence of NaCl). Colloidal particle formation during redox reactions of chlorite was also investigated. Two types of chlorite samples: low iron content (CCa-2) and high iron content (Chlorite from Daejeon, South Korea) were used. Redox batch kinetic tests were conducted for 60 days. The solutions, reactants, and colloidal particles collected from the redox batch kinetic tests every 10 days were characterized. Results show that the concentration of oxidizing agent decreased more in the chlorite sample having higher Fe(Ⅱ) content than that having lower Fe(Ⅱ) content. After 10 days, both the chlorite samples tend to be reached steady-state conditions and then no changes in the concentration of oxidizing agent were observed. SEM analysis shows that surface and edge of the chlorite samples tend to be crispy and smoothy with increasing reaction time. SEM-EDS analysis on colloidal particles shows that colloidal particles consisted of Fe and O, which were identified as ferrihydrite.

  16. Thymoquinone: An edible redox-active quinone for the pharmacotherapy of neurodegenerative conditions and glial brain tumors. A short review.

    PubMed

    Elmaci, Ilhan; Altinoz, Meric A

    2016-10-01

    There exist few efficient agents in the neurological and neurosurgical armamentarium for treatment of neurotrauma, refractory seizures and high grade glial tumors. Pathophysiological conditions of diverse neural injuries have converging common pathways including oxidative stress and apoptosis. Targeted therapies have been throughly investigated, but limited success has been achieved until now. Phytochemical drugs may provide easily achievable and cheap adjunctive sources. Thymoquinone is an edible quinone obtained from Nigella sativa seed oil and exerts powerful antiinflammatory, antioxidant and antitumor activities in experimental models. Recently emerging studies conducted with animal models suggest that thymoquinone - bearing a very simple molecular structure - significantly crosses the blood brain barrier and exerts neuromodulatory activities. Indeed, in animal studies, the following actions of thymoquinone were demonstrated: 1-Protection against ischemic brain damage. 2-Reduction of epileptic seizures and associated cerebral oxidative injury. 3-Reduction of morphine tolerance and associated oxidative brain damage. 4-Anxiolytic effects and reduction of immobility stress-associated cerebral oxidative injury. 5-Reduction of diabetes-induced cerebral oxidative stress, 6-Reduction of cerebral oxidative injuries induced by noxious exposures including toluene, lead and ionizing radiation. Substantial in vitro data suggest that thymoquinone may be beneficial in treatment of glial tumors. However, there is no clinical study investigating its antitumor effects. In fact, thymoquinone suppresses growth and invasion, and induces apoptosis of glial tumor cells via degrading tubulins and inhibiting 20S proteasome, telomerase, autophagy, FAK and metalloproteinases. A simple and easily available agent may be a promising adjunctive treatment option in neurological and neurosurgical practice.

  17. Microbial Response to Experimentally Controlled Redox Transitions at the Sediment Water Interface

    PubMed Central

    Frindte, Katharina; Allgaier, Martin; Grossart, Hans-Peter; Eckert, Werner

    2015-01-01

    The sediment–water interface of freshwater lakes is characterized by sharp chemical gradients, shaped by the interplay between physical, chemical and microbial processes. As dissolved oxygen is depleted in the uppermost sediment, the availability of alternative electron acceptors, e.g. nitrate and sulfate, becomes the limiting factor. We performed a time series experiment in a mesocosm to simulate the transition from aerobic to anaerobic conditions at the sediment–water interface. Our goal was to identify changes in the microbial activity due to redox transitions induced by successive depletion of available electron acceptors. Monitoring critical hydrochemical parameters in the overlying water in conjunction with a new sampling strategy for sediment bacteria enabled us to correlate redox changes in the water to shifts in the active microbial community and the expression of functional genes representing specific redox-dependent microbial processes. Our results show that during several transitions from oxic-heterotrophic condition to sulfate-reducing condition, nitrate-availability and the on-set of sulfate reduction strongly affected the corresponding functional gene expression. There was evidence of anaerobic methane oxidation with NOx. DGGE analysis revealed redox-related changes in microbial activity and expression of functional genes involved in sulfate and nitrite reduction, whereas methanogenesis and methanotrophy showed only minor changes during redox transitions. The combination of high-frequency chemical measurements and molecular methods provide new insights into the temporal dynamics of the interplay between microbial activity and specific redox transitions at the sediment–water interface. PMID:26599000

  18. Ascorbate oxidase-dependent changes in the redox state of the apoplast modulate gene transcript accumulation leading to modified hormone signaling and orchestration of defense processes in tobacco.

    PubMed

    Pignocchi, Cristina; Kiddle, Guy; Hernández, Iker; Foster, Simon J; Asensi, Amparo; Taybi, Tahar; Barnes, Jeremy; Foyer, Christine H

    2006-06-01

    The role of the redox state of the apoplast in hormone responses, signaling cascades, and gene expression was studied in transgenic tobacco (Nicotiana tabacum) plants with modified cell wall-localized ascorbate oxidase (AO). High AO activity specifically decreased the ascorbic acid (AA) content of the apoplast and altered plant growth responses triggered by hormones. Auxin stimulated shoot growth only when the apoplastic AA pool was reduced in wild-type or AO antisense lines. Oxidation of apoplastic AA in AO sense lines was associated with loss of the auxin response, higher mitogen-activated protein kinase activities, and susceptibility to a virulent strain of the pathogen Pseudomonas syringae. The total leaf glutathione pool, the ratio of reduced glutathione to glutathione disulfide, and glutathione reductase activities were similar in the leaves of all lines. However, AO sense leaves exhibited significantly lower dehydroascorbate reductase and ascorbate peroxidase activities than wild-type and antisense leaves. The abundance of mRNAs encoding antioxidant enzymes was similar in all lines. However, the day/night rhythms in the abundance of transcripts encoding the three catalase isoforms were changed in response to the AA content of the apoplast. Other transcripts influenced by AO included photorespiratory genes and a plasma membrane Ca(2+) channel-associated gene. We conclude that the redox state of the apoplast modulates plant growth and defense responses by regulating signal transduction cascades and gene expression patterns. Hence, AO activity, which modulates the redox state of the apoplastic AA pool, strongly influences the responses of plant cells to external and internal stimuli.

  19. Thiol-Based Redox Switches

    PubMed Central

    Groitl, Bastian; Jakob, Ursula

    2014-01-01

    Regulation of protein function through thiol-based redox switches plays an important role in the response and adaptation to local and global changes in the cellular levels of reactive oxygen species (ROS). Redox regulation is used by first responder proteins, such as ROS-specific transcriptional regulators, chaperones or metabolic enzymes to protect cells against mounting levels of oxidants, repair the damage and restore redox homeostasis. Redox regulation of phosphatases and kinases is used to control the activity of select eukaryotic signaling pathways, making reactive oxygen species important second messengers that regulate growth, development and differentiation. In this review we will compare different types of reversible protein thiol modifications, elaborate on their structural and functional consequences and discuss their role in oxidative stress response and ROS adaptation. PMID:24657586

  20. Development of a stable ERroGFP variant suitable for monitoring redox dynamics in the ER

    PubMed Central

    Hoseki, Jun; Oishi, Asami; Fujimura, Takaaki; Sakai, Yasuyoshi

    2016-01-01

    The endoplasmic reticulum (ER) is an essential organelle for cellular metabolic homeostasis including folding and maturation of secretory and membrane proteins. Disruption of ER proteostasis has been implicated in the pathogenesis of various diseases such as diabetes and neurodegenerative diseases. The ER redox state, which is an oxidative environment suitable for disulfide-bond formation, is essential for ER protein quality control. Hence, detection of the ER redox state, especially in living cells, is essential to understand the mechanism by which the redox state of the ER is maintained. However, methods to detect the redox state of the ER have not been well-established because of inefficient folding and stability of roGFP variants with oxidative redox potential like roGFP-iL. Here we have improved the folding efficiency of ER-targeted roGFP-iL (ERroGFP-iL) in cells by introducing superfolder GFP (sfGFP) mutations. Four specific amino acid substitutions (S30R, Y39N, T105N and I171V) greatly improved folding efficiency in Escherichia coli and in the ER of HeLa cells, as well as the thermostability of the purified proteins. Introduction of these mutations also enhanced the dynamic range for redox change both in vitro and in the ER of living cells. ER-targeted roGFP-S4 (ERroGFP-S4) possessing these four mutations could detect physiological redox changes within the ER. ERroGFP-S4 is therefore a novel probe suitable for monitoring redox change in the ER. ERroGFP-S4 can be applied to detect aberrant ER redox states associated with various pathological conditions and to identify the mechanisms used to maintain the redox state of the ER. PMID:26934978

  1. Single-cell sequencing of Thiomargarita reveals genomic flexibility for adaptation to dynamic redox conditions

    SciTech Connect

    Winkel, Matthias; Salman-Carvalho, Verena; Woyke, Tanja; Richter, Michael; Schulz-Vogt, Heide N.; Flood, Beverly E.; Bailey, Jake V.; Mußmann, Marc

    2016-06-21

    Large, colorless sulfur-oxidizing bacteria (LSB) of the family Beggiatoaceae form thick mats at sulfidic sediment surfaces, where they efficiently detoxify sulfide before it enters the water column. The genus Thiomargarita harbors the largest known free-living bacteria with cell sizes of up to 750 μm in diameter. In addition to their ability to oxidize reduced sulfur compounds, some Thiornargarita spp. are known to store large amounts of nitrate, phosphate and elemental sulfur internally. To date little is known about their energy yielding metabolic pathways, and how these pathways compare to other Beggiatoaceae. Here, we present a draft single-cell genome of a chain-forming "Candidatus Thiomargarita nelsonii Thio36", and conduct a comparative analysis to five draft and one full genome of other members of the Beggiatoaceae. "Ca. T. nelsonii Thio36" is able to respire nitrate to both ammonium and dinitrogen, which allows them to flexibly respond to environmental changes. Genes for sulfur oxidation and inorganic carbon fixation confirmed that "Ca. T. nelsonii Thio36" can function as a chemolithoautotroph. Carbon can be fixed via the Calvin-Benson-Bassham cycle, which is common among the Beggiatoaceae. In addition we found key genes of the reductive tricarboxylic acid cycle that point toward an alternative CO2 fixation pathway. Surprisingly, "Ca. T. nelsonii Thio36" also encodes key genes of the C2-cycle that convert 2-phosphoglycolate to 3-phosphoglycerate during photorespiration in higher plants and cyanobacteria. Moreover, we identified a novel trait of a flavin-based energy bifurcation pathway coupled to a Na+-translocating membrane complex (Rnf). The coupling of these pathways may be key to surviving long periods of anoxia. As other Beggiatoaceae "Ca. T. nelsonii Thio36" encodes many genes similar to those of (filamentous) cyanobacteria. In conclusion, the

  2. Redox potential: An indicator of site productivity in forest management

    NASA Astrophysics Data System (ADS)

    Sajedi, Toktam; Prescott, Cindy; Lavkulich, Les

    2010-05-01

    less than +300 mv in the forest floor; whereas only 15 percent of the HA plots had such low values. Composition of the forest understory species was related to soil moisture/aeration. Soil aeration was the most important soil variable influencing plant species composition, explaining 25% of the plant community variability. Eh was always greater than +300 mv in the mineral soil of old growth HA forests but below +300 mv in HA clearcuts, suggesting paludification; however it was below or at this threshold in both CH forests and clearcuts. The reduction in measured redox without a noticeable change in the watertable in HA sites suggests that harvesting HA forests shifts the ecosystem towards more anaerobic conditions more similar to CH sites. In a complimentary study, the significance of redox was assessed in a cedar swamp cutover by exploring the relationships between soil redox potential and tree growth, and mineralization of C and soil C store along a gradient of moisture caused by drainage. Drainage improved aeration in the rooting zone, expressed as redox, and above- and below ground C storage; however C mineralization measured as CO2 evolution was not affected. Tree growth was positively correlated with redox potential. Our results indicate that drainage could be a useful silvicultural practice for improving the productivity of these ecosystems and that it may be possible to improve tree growth without stimulating loss of soil C. This requires that drainage improve aeration in the rooting zone while maintaining redox levels of less than +300 mV in the bulk soil, indicating that redox measurements should be incorporated into silviculture interventions to improve productivity of these forests.

  3. Two distinct redox cascades cooperatively regulate chloroplast functions and sustain plant viability

    PubMed Central

    Yoshida, Keisuke; Hisabori, Toru

    2016-01-01

    The thiol-based redox regulation system is believed to adjust chloroplast functions in response to changes in light environments. A redox cascade via the ferredoxin-thioredoxin reductase (FTR)/thioredoxin (Trx) pathway has been traditionally considered to serve as a transmitter of light signals to target enzymes. However, emerging data indicate that chloroplasts have a complex redox network composed of diverse redox-mediator proteins and target enzymes. Despite extensive research addressing this system, two fundamental questions are still unresolved: How are redox pathways orchestrated within chloroplasts, and why are chloroplasts endowed with a complicated redox network? In this report, we show that NADPH-Trx reductase C (NTRC) is a key redox-mediator protein responsible for regulatory functions distinct from those of the classically known FTR/Trx system. Target screening and subsequent biochemical assays indicated that NTRC and the Trx family differentially recognize their target proteins. In addition, we found that NTRC is an electron donor to Trx-z, which is a key regulator of gene expression in chloroplasts. We further demonstrate that cooperative control of chloroplast functions via the FTR/Trx and NTRC pathways is essential for plant viability. Arabidopsis double mutants impaired in FTR and NTRC expression displayed lethal phenotypes under autotrophic growth conditions. This severe growth phenotype was related to a drastic loss of photosynthetic performance. These combined results provide an expanded map of the chloroplast redox network and its biological functions. PMID:27335455

  4. Changes in phosphorylation of adenosine phosphate and redox state of nicotinamide-adenine dinucleotide (phosphate) in Geobacter sulfurreducens in response to electron acceptor and anode potential variation.

    PubMed

    Rose, Nicholas D; Regan, John M

    2015-12-01

    Geobacter sulfurreducens is one of the dominant bacterial species found in biofilms growing on anodes in bioelectrochemical systems. The intracellular concentrations of reduced and oxidized forms of nicotinamide-adenine dinucleotide (NADH and NAD(+), respectively) and nicotinamide-adenine dinucleotide phosphate (NADPH and NADP(+), respectively) as well as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) were measured in G. sulfurreducens using fumarate, Fe(III)-citrate, or anodes poised at different potentials (110, 10, -90, and -190 mV (vs. SHE)) as the electron acceptor. The ratios of CNADH/CNAD+ (0.088±0.022) and CNADPH/CNADP+ (0.268±0.098) were similar under all anode potentials tested and with Fe(III)-citrate (reduced extracellularly). Both ratios significantly increased with fumarate as the electron acceptor (0.331±0.094 for NAD and 1.96±0.37 for NADP). The adenylate energy charge (the fraction of phosphorylation in intracellular adenosine phosphates) was maintained near 0.47 under almost all conditions. Anode-growing biofilms demonstrated a significantly higher molar ratio of ATP/ADP relative to suspended cultures grown on fumarate or Fe(III)-citrate. These results provide evidence that the cellular location of reduction and not the redox potential of the electron acceptor controls the intracellular redox potential in G. sulfurreducens and that biofilm growth alters adenylate phosphorylation.

  5. Proteasome inhibitor-adapted myeloma cells are largely independent from proteasome activity and show complex proteomic changes, in particular in redox and energy metabolism

    PubMed Central

    Soriano, G P; Besse, L; Li, N; Kraus, M; Besse, A; Meeuwenoord, N; Bader, J; Everts, B; den Dulk, H; Overkleeft, H S; Florea, B I; Driessen, C

    2016-01-01

    Adaptive resistance of myeloma to proteasome inhibition represents a clinical challenge, whose biology is poorly understood. Proteasome mutations were implicated as underlying mechanism, while an alternative hypothesis based on low activation status of the unfolded protein response was recently suggested (IRE1/XBP1-low model). We generated bortezomib- and carfilzomib-adapted, highly resistant multiple myeloma cell clones (AMO-BTZ, AMO-CFZ), which we analyzed in a combined quantitative and functional proteomic approach. We demonstrate that proteasome inhibitor-adapted myeloma cells tolerate subtotal proteasome inhibition, irrespective of a proteasome mutation, and uniformly show an 'IRE1/XBP1-low' signature. Adaptation of myeloma cells to proteasome inhibitors involved quantitative changes in >600 protein species with similar patterns in AMO-BTZ and AMO-CFZ cells: proteins involved in metabolic regulation, redox homeostasis, and protein folding and destruction were upregulated, while apoptosis and transcription/translation were downregulated. The quantitatively most upregulated protein in AMO-CFZ cells was the multidrug resistance protein (MDR1) protein ABCB1, and carfilzomib resistance could be overcome by MDR1 inhibition. We propose a model where proteasome inhibitor-adapted myeloma cells tolerate subtotal proteasome inhibition owing to metabolic adaptations that favor the generation of reducing equivalents, such as NADPH, which is supported by oxidative glycolysis. Proteasome inhibitor resistance may thus be targeted by manipulating the energy and redox metabolism. PMID:27118406

  6. Ceramic production during changing environmental/climatic conditions

    NASA Astrophysics Data System (ADS)

    Oestreich, Daniela B.; Glasmacher, Ulrich A.

    2015-04-01

    Ceramics, with regard to their status as largely everlasting everyday object as well as on the basis of their chronological sensitivity, reflect despite their simplicity the technological level of a culture and therefore also, directly or indirectly, the adaptability of a culture with respect to environmental and/or climatic changes. For that reason the question arises, if it is possible to identify changes in production techniques and raw material sources for ceramic production, as a response to environmental change, e.g. climate change. This paper will present results of a research about Paracas Culture (800 - 200 BC), southern Peru. Through several investigations (e.g. Schittek et al., 2014; Eitel and Mächtle, 2009) it is well known that during Paracas period changes in climate and environmental conditions take place. As a consequence, settlement patterns shifted several times through the various stages of Paracas time. Ceramics from three different sites (Jauranga, Cutamalla, Collanco) and temporal phases of the Paracas period are detailed archaeometric, geochemical and mineralogical characterized, e.g. Raman spectroscopy, XRD, and ICP-MS analyses. The aim of this research is to resolve potential differences in the chemical composition of the Paracas ceramics in space and time and to compare the data with the data sets of pre-Columbian environmental conditions. Thus influences of changing environmental conditions on human societies and their cultural conditions will be discussed. References Eitel, B. and Mächtle, B. 2009. Man and Environment in the eastern Atacama Desert (Southern Peru): Holocene climate changes and their impact on pre-Columbian cultures. In: Reindel, M. & Wagner, G. A. (eds.) New Technologies for Archaeology. Berlin Heidelberg: Springer-Verlag. Schittek, K., Mächtle, B., Schäbitz, F., Forbriger, M., Wennrich, V., Reindel, M., and Eitel, B.. Holocene environmental changes in the highlands of the southern Peruvian Andes (14° S) and their

  7. Future Risks of Pest Species under Changing Climatic Conditions

    PubMed Central

    Biber-Freudenberger, Lisa; Ziemacki, Jasmin; Tonnang, Henri E. Z.; Borgemeister, Christian

    2016-01-01

    Most agricultural pests are poikilothermic species expected to respond to climate change. Currently, they are a tremendous burden because of the high losses they inflict on crops and livestock. Smallholder farmers in developing countries of Africa are likely to suffer more under these changes than farmers in the developed world because more severe climatic changes are projected in these areas. African countries further have a lower ability to cope with impacts of climate change through the lack of suitable adapted management strategies and financial constraints. In this study we are predicting current and future habitat suitability under changing climatic conditions for Tuta absoluta, Ceratitis cosyra, and Bactrocera invadens, three important insect pests that are common across some parts of Africa and responsible for immense agricultural losses. We use presence records from different sources and bioclimatic variables to predict their habitat suitability using the maximum entropy modelling approach. We find that habitat suitability for B. invadens, C. cosyra and T. absoluta is partially increasing across the continent, especially in those areas already overlapping with or close to most suitable sites under current climate conditions. Assuming a habitat suitability at three different threshold levels we assessed where each species is likely to be present under future climatic conditions and if this is likely to have an impact on productive agricultural areas. Our results can be used by African policy makers, extensionists and farmers for agricultural adaptation measures to cope with the impacts of climate change. PMID:27054718

  8. Biogeochemical Barriers: Redox Behavior of Metals and Metalloids

    EPA Science Inventory

    Redox conditions and pH are arguably the most important geochemical parameters that control contaminant transport and fate in groundwater systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting...

  9. Site-dependant redox ratio in healthy oral cavity

    NASA Astrophysics Data System (ADS)

    Shanmugam, Sivabalan; Koteeswaran, Dornadula; Aruna, Prakasarao; Ganesan, Singaravelu

    2011-03-01

    The metabolic coenzymes NADH and FAD are autofluorescent and can be monitored non-destructively and without exogenous labels, using optical techniques. These endogenous fluorophores which are present in the cells and tissues gives rise to different fluorescence emission/excitation spectra between the normal and different diseased conditions. In the resent years, finding the optical redox ratio i.e., the ratio of the fluorescence intensity of FAD and NADH, gives the relative change in the oxidation-reduction state of the cells. Unlike other organs oral cavity has lined with variety of mucosal types. We investigated in vivo Optical redox ratio for four different anatomical locations viz., cheek mucosa, vermilion border of the lip, Hard palate, dorsal side of the tongue of healthy oral cavity. We measured this ratio for 20 healthy subjects and the redox ratio was significantly different between the different anatomical locations. The statistical significance was also investigated.

  10. Effects of morin-5'-sulfonic acid sodium salt (NaMSA) on cyclophosphamide-induced changes in oxido-redox state in rat liver and kidney.

    PubMed

    Merwid-Ląd, A; Trocha, M; Chlebda, E; Sozański, T; Magdalan, J; Ksiądzyna, D; Kopacz, M; Kuźniar, A; Nowak, D; Pieśniewska, M; Fereniec-Gołębiewska, L; Kwiatkowska, J; Szeląg, A

    2012-08-01

    Cyclophosphamide (CPX) is an anticancer drug with immunosuppressive properties. Its adverse effects are partly connected to the induction of oxidative stress. Some studies indicate that water-soluble derivative of morin-morin-5'-sulfonic acid sodium salt (NaMSA) exhibits strong antioxidant activity. The aim of present study was to evaluate the effect of NaMSA on CPX-induced changes in oxido-redox state in rat. Experiment was carried out on Wistar rats divided in three experimental groups (N = 12) receiving: 0.9% saline, CPX (15 mg/kg) or CPX (15 mg/kg) + NaMSA (100 mg/kg), respectively, and were given intragastrically for 10 days. Malondialdehyde (MDA) and glutathione (GSH) concentrations and superoxide dismutase (SOD) activity were determined in liver and kidneys. Catalase (CAT) activity was assessed only in liver. Treatment with CPX resulted in significant decrease in MDA level in both tissues, which was completely reversed by NaMSA treatment only in liver. In comparison to the control group significant decrease in SOD activity were observed in both tissues of CPX receiving group. In kidneys this parameter was fully restored by NaMSA administration. CPX evoked significant decrease in GSH concentration in kidneys, which was completely reversed by NaMSA treatment. No significant changes were seen in GSH levels and CAT activity between all groups in liver. Results of our study suggest that CPX may exert significant impact on oxido-redox state in both organs. NaMSA fully reversed the CPX-induced changes, especially MDA level in liver, SOD activity and GSH concentration in kidneys and it may be done by enhancement of activity/concentration of endogenous antioxidants.

  11. Pushing the Limits of Delta Bonding in Metal-Chromium Complexes with Redox Changes and Metal Swapping.

    PubMed

    Eisenhart, Reed J; Rudd, P Alex; Planas, Nora; Boyce, David W; Carlson, Rebecca K; Tolman, William B; Bill, Eckhard; Gagliardi, Laura; Lu, Connie C

    2015-08-03

    Into the metalloligand Cr[N(o-(NCH2P((i)Pr)2)C6H4)3] (1, CrL) was inserted a second chromium atom to generate the dichromium complex Cr2L (2), which is a homobimetallic analogue of the known MCrL complexes, where M is manganese (3) or iron (4). The cationic and anionic counterparts, [MCrL](+) and [MCrL](-), respectively, were targeted, and each MCr pair was isolated in at least one other redox state. The solid-state structures of the [MCrL](+,0,-) redox members are essentially the same, with ultrashort metal-metal bonds between 1.96 and 1.74 Å. The formal shortness ratios (r) of these interactions are between 0.84 and 0.74 and are interpreted as triple to quintuple metal-metal bonds with the aid of theory. The trio of (d-d)(10) species [Cr2L](-) (2(red)), MnCrL (3), and [FeCrL](+) (4(ox)) are S = 0 diamagnets. On the basis of M-Cr bond distances and theoretical calculations, the strength of the metal-metal bond across the (d-d)(10) series increases in the order Fe < Mn < Cr. The methylene protons in the ligand are shifted downfield in the (1)H NMR spectra, and the diamagnetic anisotropy of the metal-metal bond was calculated as -3500 × 10(-36), -3900 × 10(-36), and -5800 × 10(-36) m(3) molecule(-1) for 2(red), 3, and 4(ox) respectively. The magnitude of diamagnetic anisotropy is, thus, affected more by bond polarity than by bond order. A comparative vis-NIR study of quintuply bonded 2(red) and 3 revealed a large red shift in the δ(4) → δ(3)δ* transition energy upon swapping from the (Cr2)(2+) to the (MnCr)(3+) core. Complex 2(red) was further investigated by resonance Raman spectroscopy, and a band at 434 cm(-1) was assigned as the Cr-Cr bond vibration. Finally, 4(ox) exhibited a Mössbauer doublet with an isomer shift of 0.18 mm/s that suggests a primarily Fe-based oxidation to Fe(I).

  12. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 9 2013-10-01 2013-10-01 false Changed conditions affecting security. 1542.107 Section 1542.107 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY...

  13. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 9 2010-10-01 2010-10-01 false Changed conditions affecting security. 1542.107 Section 1542.107 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY...

  14. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 9 2011-10-01 2011-10-01 false Changed conditions affecting security. 1542.107 Section 1542.107 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY...

  15. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 9 2012-10-01 2012-10-01 false Changed conditions affecting security. 1542.107 Section 1542.107 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY...

  16. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 9 2014-10-01 2014-10-01 false Changed conditions affecting security. 1542.107 Section 1542.107 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY...

  17. Breeding crops for improved mineral nutrition under climate change conditions.

    PubMed

    Pilbeam, David J

    2015-06-01

    Improvements in understanding how climate change may influence chemical and physical processes in soils, how this may affect nutrient availability, and how plants may respond to changed availability of nutrients will influence crop breeding programmes. The effects of increased atmospheric CO2 and warmer temperatures, both individually and combined, on soil microbial activity, including mycorrhizas and N-fixing organisms, are evaluated, together with their implications for nutrient availability. Potential changes to plant growth, and the combined effects of soil and plant changes on nutrient uptake, are discussed. The organization of research on the efficient use of macro- and micronutrients by crops under climate change conditions is outlined, including analysis of QTLs for nutrient efficiency. Suggestions for how the information gained can be used in plant breeding programmes are given.

  18. Organophosphate pesticides-induced changes in the redox status of rat tissues and protective effects of antioxidant vitamins.

    PubMed

    Mishra, Vibhuti; Srivastava, Nalini

    2015-04-01

    Organophosphates (OPs) pesticides are among the most toxic synthetic chemicals purposefully added in the environment. The common use of OP insecticides in public health and agriculture results in an environmental pollution and a number of acute and chronic poisoning events. Present study was aimed to evaluate the potential of monocrotophos and quinalphos to effect the redox status and glutathione (GSH) homeostasis in rat tissues and find out whether antioxidant vitamins have some protection on the pesticide-induced alterations. The results showed that these pesticides alone or in combination, caused decrease in the levels of GSH and the corresponding increase in the levels of GSSG, decreasing the GSH/GSSG ratio. The results also showed that NADPH/NADP(+) and NADH/NAD(+) ratios were decreased in the liver and brain of rats on exposure with mococrotophos, quinalphos, and their mixture. These pesticides, alone or in combination, caused alterations in the activities of GSH reductase and glucose-6-phosphate dehydrogenase in the rat tissues. However, the expression of the GSH recycling enzymes did not show significant alterations as compared to control. From the results, it can be concluded that these pesticides generate oxidative stress but their effects were not synergistic when given together and prior feeding of antioxidant vitamins tend to reduce the toxicities of these pesticides.

  19. Proteotoxic stress and ageing triggers the loss of redox homeostasis across cellular compartments

    PubMed Central

    Kirstein, Janine; Morito, Daisuke; Kakihana, Taichi; Sugihara, Munechika; Minnen, Anita; Hipp, Mark S; Nussbaum-Krammer, Carmen; Kasturi, Prasad; Hartl, F Ulrich; Nagata, Kazuhiro; Morimoto, Richard I

    2015-01-01

    The cellular proteostasis network integrates the protein folding and clearance machineries in multiple sub-cellular compartments of the eukaryotic cell. The endoplasmic reticulum (ER) is the site of synthesis and folding of membrane and secretory proteins. A distinctive feature of the ER is its tightly controlled redox homeostasis necessary for the formation of inter- and intra-molecular disulphide bonds. Employing genetically encoded in vivo sensors reporting on the redox state in an organelle-specific manner, we show in the nematode Caenorhabditis elegans that the redox state of the ER is subject to profound changes during worm lifetime. In young animals, the ER is oxidizing and this shifts towards reducing conditions during ageing, whereas in the cytosol the redox state becomes more oxidizing with age. Likewise, the redox state in the cytosol and the ER change in an opposing manner in response to proteotoxic challenges in C. elegans and in HeLa cells revealing conservation of redox homeostasis. Moreover, we show that organelle redox homeostasis is regulated across tissues within C. elegans providing a new measure for organismal fitness. PMID:26228940

  20. Free energy distribution and hydrothermal mineral precipitation in Hadean submarine alkaline vent systems: Importance of iron redox reactions under anoxic conditions

    NASA Astrophysics Data System (ADS)

    Shibuya, Takazo; Russell, Michael J.; Takai, Ken

    2016-02-01

    Thermodynamic calculations of mixing between hypothetical seawater and hydrothermal fluid in the Hadean deep ocean were carried out to predict saturation states of mineral precipitates and redox reactions that could occur in Hadean submarine alkaline hydrothermal systems associated with the serpentinization of ultramafic rocks. In the calculations, the seawater was assumed to be weakly acidic (pH = 5.5) and to include carbon dioxide, ferrous iron and silica, with or without nitrate, while the Hadean hydrothermal fluid was assumed to be highly alkaline (pH = 11) and to contain abundant molecular hydrogen, methane and bisulfide, based on the Archean geologic record, the modern low-temperature alkaline hydrothermal vent fluid (Lost City field), and experimental and theoretical considerations. The modeling indicates that potential mineral precipitates in the mixing zone (hydrothermal chimney structures) could consist mainly of iron sulfides but also of ferrous serpentine and brucite, siderite, and ferric iron-bearing minerals such as goethite, hematite and/or magnetite as minor phases. The precipitation of ferric iron-bearing minerals suggests that chemical iron oxidation would be made possible by pH shift even under anoxic condition. In the mixing zone, comprising an inorganic barrier precipitated at the interface of the two contrasting solutions, various redox reactions release free energy with the potential to drive endergonic reactions, assuming the involvement of coupling inorganic protoenzymes. Hydrogenotrophic methanogenesis and acetogenesis - long considered the most ancient forms of biological energy metabolisms - are able to achieve higher maximum energy yield (>0.5 kJ/kg hydrothermal fluid) than those in the modern serpentinization-associated seafloor hydrothermal systems (e.g., Kairei field). Furthermore, the recently proposed methanotrophic acetogenesis pathway was also thermodynamically investigated. It is known that methanotrophic acetogenesis would

  1. Forecasting conditional climate-change using a hybrid approach

    USGS Publications Warehouse

    Esfahani, Akbar Akbari; Friedel, Michael J.

    2014-01-01

    A novel approach is proposed to forecast the likelihood of climate-change across spatial landscape gradients. This hybrid approach involves reconstructing past precipitation and temperature using the self-organizing map technique; determining quantile trends in the climate-change variables by quantile regression modeling; and computing conditional forecasts of climate-change variables based on self-similarity in quantile trends using the fractionally differenced auto-regressive integrated moving average technique. The proposed modeling approach is applied to states (Arizona, California, Colorado, Nevada, New Mexico, and Utah) in the southwestern U.S., where conditional forecasts of climate-change variables are evaluated against recent (2012) observations, evaluated at a future time period (2030), and evaluated as future trends (2009–2059). These results have broad economic, political, and social implications because they quantify uncertainty in climate-change forecasts affecting various sectors of society. Another benefit of the proposed hybrid approach is that it can be extended to any spatiotemporal scale providing self-similarity exists.

  2. [Redox Molecular Imaging Using ReMI].

    PubMed

    Hyodo, Fuminori; Ito, Shinji; Utsumi, Hideo

    2015-01-01

    Tissue redox status is one of the most important parameters to maintain homeostasis in the living body. Numerous redox reactions are involved in metabolic processes, such as energy production in the mitochondrial electron transfer system. A variety of intracellular molecules such as reactive oxygen species, glutathione, thioredoxins, NADPH, flavins, and ascorbic acid may contribute to the overall redox status in tissues. Breakdown of redox balance may lead to oxidative stress and can induce many pathological conditions such as cancer, neurological disorders, and aging. Therefore imaging of tissue redox status and monitoring antioxidant levels in living organisms can be useful in the diagnosis of disease states and assessment of treatment response. In vivo redox molecular imaging technology such as electron spin resonance imaging (ESRI), magnetic resonance imaging (MRI), and dynamic nuclear polarization (DNP)-MRI (redox molecular imaging; ReMI) is emerging as a viable redox status imaging modality. This review focuses on the application of magnetic resonance technologies using MRI or DNP-MRI and redox-sensitive contrast agents.

  3. Hydrological Responses to Land-Use Change Scenarios under Constant and Changed Climatic Conditions.

    PubMed

    Zhang, Ling; Nan, Zhuotong; Yu, Wenjun; Ge, Yingchun

    2016-02-01

    This study quantified the hydrological responses to land-use change scenarios in the upper and middle Heihe River basin (HRB), northwest China, under constant and changed climatic conditions by combining a land-use/cover change model (dynamic conversion of land use and its effects, Dyna-CLUE) and a hydrological model (soil and water assessment tool, SWAT). Five land-use change scenarios, i.e., historical trend (HT), ecological protection (EP), strict ecological protection (SEP), economic development (ED), and rapid economic development (RED) scenarios, were established. Under constant climatic condition, hydrological variations are only induced by land-use changes in different scenarios. The changes in mean streamflow at the outlets of the upper and the middle HRB are not pronounced, although the different scenarios produce different outcomes. However, more pronounced changes are observed on a subbasin level. The frequency of extreme flood is projected to decrease under the SEP scenario, while under the other scenarios, no changes can be found. Two emission scenarios (A1B and B1) of three general circulation models (HadCM3, CGCM3, and CCSM3) were employed to generate future possible climatic conditions. Under changed climatic condition, hydrological variations are induced by the combination of land-use and climatic changes. The results indicate that the impacts of land-use changes become secondary when the changed climatic conditions have been considered. The frequencies of extreme flood and drought are projected to decrease and increase, respectively, under all climate scenarios. Although some agreements can be reached, pronounced difference of hydrological responses can be observed for different climate scenarios of different GCMs.

  4. Hydrological Responses to Land-Use Change Scenarios under Constant and Changed Climatic Conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Nan, Zhuotong; Yu, Wenjun; Ge, Yingchun

    2016-02-01

    This study quantified the hydrological responses to land-use change scenarios in the upper and middle Heihe River basin (HRB), northwest China, under constant and changed climatic conditions by combining a land-use/cover change model (dynamic conversion of land use and its effects, Dyna-CLUE) and a hydrological model (soil and water assessment tool, SWAT). Five land-use change scenarios, i.e., historical trend (HT), ecological protection (EP), strict ecological protection (SEP), economic development (ED), and rapid economic development (RED) scenarios, were established. Under constant climatic condition, hydrological variations are only induced by land-use changes in different scenarios. The changes in mean streamflow at the outlets of the upper and the middle HRB are not pronounced, although the different scenarios produce different outcomes. However, more pronounced changes are observed on a subbasin level. The frequency of extreme flood is projected to decrease under the SEP scenario, while under the other scenarios, no changes can be found. Two emission scenarios (A1B and B1) of three general circulation models (HadCM3, CGCM3, and CCSM3) were employed to generate future possible climatic conditions. Under changed climatic condition, hydrological variations are induced by the combination of land-use and climatic changes. The results indicate that the impacts of land-use changes become secondary when the changed climatic conditions have been considered. The frequencies of extreme flood and drought are projected to decrease and increase, respectively, under all climate scenarios. Although some agreements can be reached, pronounced difference of hydrological responses can be observed for different climate scenarios of different GCMs.

  5. Screening of redox couples and electrode materials

    NASA Technical Reports Server (NTRS)

    Giner, J.; Swette, L.; Cahill, K.

    1976-01-01

    Electrochemical parameters of selected redox couples that might be potentially promising for application in bulk energy storage systems were investigated. This was carried out in two phases: a broad investigation of the basic characteristics and behavior of various redox couples, followed by a more limited investigation of their electrochemical performance in a redox flow reactor configuration. In the first phase of the program, eight redox couples were evaluated under a variety of conditions in terms of their exchange current densities as measured by the rotating disk electrode procedure. The second phase of the program involved the testing of four couples in a redox reactor under flow conditions with a varity of electrode materials and structures.

  6. Bioconversion of Coal: Hydrologic indicators of the extent of coal biodegradation under different redox conditions and coal maturity, Velenje Basin case study, Slovenia

    NASA Astrophysics Data System (ADS)

    Kanduč, Tjaša; Grassa, Fausto; Lazar, Jerneja; Jamnikar, Sergej; Zavšek, Simon; McIntosh, Jennifer

    2014-05-01

    Underground mining of coal and coal combustion for energy has significant environmental impacts. In order to reduce greenhouse gas emissions, other lower -carbon energy sources must be utilized. Coalbed methane (CBM) is an important source of relatively low-carbon energy. Approximately 20% of world's coalbed methane is microbial in origin (Bates et al., 2011). Interest in microbial CBM has increased recently due to the possibility of stimulating methanogenesis. Despite increasing interest, the hydrogeochemical conditions and mechanisms for biodegradation of coal and microbial methane production are poorly understood. This project aims to examine geochemical characteristics of coalbed groundwater and coalbed gases in order to constrain biogeochemical processes to better understand the entire process of coal biodegradation of coal to coalbed gases. A better understanding of geochemical processes in CBM areas may potentially lead to sustainable stimulation of microbial methanogenesis at economical rates. Natural analogue studies of carbon dioxide occurring in the subsurface have the potential to yield insights into mechanisms of carbon dioxide storage over geological time scales (Li et al., 2013). In order to explore redox processes related to methanogenesis and determine ideal conditions under which microbial degradation of coal is likely to occur, this study utilizes groundwater and coalbed gas samples from Velenje Basin. Determination of the concentrations of methane, carbondioxide, nitrogen, oxygen, argon was performed with homemade NIER mass spectrometer. Isotopic composition of carbon dioxide, isotopic composition of methane, isotopic composition of deuterium in methane was determined with Europa-Scientific IRMS with an ANCA-TG preparation module and Thermo Delta XP GC-TC/CF-IRMS coupled to a TRACE GC analyzer. Total alkalinity of groundwater was measured by Gran titration. Major cations were analyzed by ICP-OES and anions by IC method. Isotopic composition of

  7. NASA Redox Project status summary

    NASA Technical Reports Server (NTRS)

    Hagedorn, N. H.

    1983-01-01

    This report is a summary of the results of the Redox Project effort during Cy 1982. It was presented at the Fifth U.S. Department of Energy Battery and Electrochemical Contractors Conference, Arlington, Va., Dec. 7-9, 1982. The major development during 1982 was the shift from Redox system operation at 25 C with unmixed reactants to operation at 65 C with mixed reactants. This change has made possible a two- or three-fold increase in operating current density, to about 65 mA/sq cm, and an increase in reactant utilization from 40% to about 90%. Both of these improvements will lead to significant system cost reductions. Contract studies have indicated that Redox reactant costs also will be moderate. A new catalyst for the chromuim electrode offers all the advantages of the conventional gold-lead catalyst while being easier to apply and more forgiving in use.

  8. Reassessing Rogers' necessary and sufficient conditions of change.

    PubMed

    Watson, Jeanne C

    2007-09-01

    This article reviews the impact of Carl Rogers' postulate about the necessary and sufficient conditions of therapeutic change on the field of psychotherapy. It is proposed that his article (see record 2007-14630-002) made an impact in two ways; first, by acting as a spur to researchers to identify the active ingredients of therapeutic change; and, second, by providing guidelines for therapeutic practice. The role of the necessary and sufficient conditions in process-experiential therapy, an emotion-focused therapy for individuals, and their limitations in terms of research and practice are discussed. It is proposed that although the conditions are necessary and important in promoting clients' affect regulation, they do not take sufficient account of other moderating variables that affect clients' response to treatment and may need to be balanced with more structured interventions. Notwithstanding, Rogers highlighted a way of interacting with clients that is generally acknowledged as essential to effective psychotherapy practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved).

  9. Using Modis Imagery to Track Changes in Forest Condition

    NASA Astrophysics Data System (ADS)

    Chastain, R. A.

    2011-12-01

    The objective of the Real-Time Forest Disturbance (RTFD) project is to provide timely information regarding changes in forest conditions to assist the digital aerial sketch-mapping community in flight mission planning. To this end, a digital change detection methodology has been developed and implemented over the conterminous 48 U.S. states (CONUS) in 2008, 2009, and 2010 to track forest disturbances in near real-time (updated every 8 days). The RTFD approach uses MODIS satellite imagery, which provides daily observations to track developing disturbances that may also be ephemeral in nature. Also, the spectral grain of MODIS data permits the calculation of spectral indices, which the RTFD approach uses to characterize changes in forest condition. Baseline image data used in the RTFD method are produced using MODIS data composited from five years prior to the current growing season. In 2011, an additional 3-year baseline has been used in the change detection process. The RTFD approach has detected and tracked numerous defoliation events in the eastern deciduous biome, decline and mortality associated with beetle activity in the western coniferous biome, and forest damage associated with severe weather events. A quantitative retrospective assessment of 2010 RTFD results was performed to identify potential modifications to the analytical logic of the RTFD approach in order to improve detection efficiency. This assessment was performed within six study areas wherein forest disturbances occurred during 2010. Various methodological alterations were assessed within these study areas; principally, the use of different vegetation indices and alterations in baseline definition. Two-date Landsat change detection results acted as reference data to which RTFD results were compared. Differences in levels of agreement between various RTFD results and Landsat results were evaluated for significance using McNemar's test. The findings of this retrospective assessment indicate that a

  10. Nitrate bioreduction in redox-variable low permeability sediments

    SciTech Connect

    Yan, Sen; Liu, Yuanyuan; Liu, Chongxuan; Shi, Liang; Shang, Jianying; Shan, Huimei; Zachara, John M.; Fredrickson, Jim K.; Kennedy, David W.; Resch, Charles T.; Thompson, Christopher J.; Fansler, Sarah J.

    2015-09-09

    Denitrification is a microbial process that reduces nitrate and nitrite to nitrous oxide (N2O) or dinitrogen (N2) with a strong implication to global nitrogen cycling and climate change. This paper reports the effect of sediment redox conditions on the rate and end product of denitrification. The sediments were collected from a redox transition zone consisting of oxic and reduced layers at US Department of Energy’s Hanford Site where N2O was locally accumulated in groundwater. The results revealed that denitrification rate and end product varied significantly with initial sediment redox state. The denitrification rate was relatively faster, limited by organic carbon content and bioavailability in the oxic sediment. In contrast, the rate was much slower in the reduced sediment, limited by biomass and microbial function. A significant amount of N2O was accumulated in the reduced sediment; while in the oxic sediment, N2O was further reduced to N2. RT-PCR analysis revealed that nosZ, the gene that codes for N2O reductase, was below detection in the reduced sediment. The results implied that redox transition zones can be important sinks or sources of N2O depending on local biogeochemical and microbial conditions, and are important systems for understanding and modeling denitrification in subsurface environments.

  11. Surface monitoring measurements of materials on environmental change conditions

    NASA Astrophysics Data System (ADS)

    Tornari, Vivi; Bernikola, Eirini; Bellendorf, Paul; Bertolin, Chiara; Camuffo, Dario; Kotova, Lola; Jacobs, Daniela; Zarnic, Roko; Rajcic, Vlatka; Leissner, Johanna

    2013-05-01

    Climate Change is one of the most critical global challenges of our time and the burdened cultural heritage of Europe is particularly vulnerable to be left unprotected. Climate for Culture2 project exploits the damage impact of climate change on cultural heritage at regional scale. In this paper the progress of the study with in situ measurements and investigations at cultural heritage sites throughout Europe combined with laboratory simulations is described. Cultural works of art are susceptible to deterioration with environmental changes causing imperceptibly slow but steady accumulation of damaging effects directly impacted on structural integrity. Laser holographic interference method is employed to provide remote non destructive field-wise detection of the structural differences occurred as climate responses. The first results from climate simulation of South East Europe (Crete) are presented. A full study in regards to the four climate regions of Europe is foreseen to provide values for development of a precise and integrated model of thermographic building simulations for evaluation of impact of climate change. Development of a third generation user interface software optimised portable metrology system (DHSPI II) is designed to record in custom intervals the surface of materials witnessing reactions under simulated climatic conditions both onfield and in laboratory. The climate conditions refer to real data-loggers readings representing characteristic historical building in selected climate zones. New generation impact sensors termed Glass Sensors and Free Water Sensors are employed in the monitoring procedure to cross-correlate climate data with deformation data. In this paper results from the combined methodology are additionally presented.

  12. S-Glutathionylation and Redox Protein Signaling in Drug Addiction.

    PubMed

    Womersley, Jacqueline S; Uys, Joachim D

    2016-01-01

    Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin.

  13. S-Glutathionylation and Redox Protein Signaling in Drug Addiction

    PubMed Central

    Womersley, Jacqueline S.; Uys, Joachim D.

    2016-01-01

    Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin. PMID:26809999

  14. Thioredoxins, Glutaredoxins, and Peroxiredoxins—Molecular Mechanisms and Health Significance: from Cofactors to Antioxidants to Redox Signaling

    PubMed Central

    Hanschmann, Eva-Maria; Godoy, José Rodrigo; Berndt, Carsten; Hudemann, Christoph

    2013-01-01

    Abstract Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and “antioxidants”. Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions. Antioxid. Redox Signal. 19, 1539–1605. PMID:23397885

  15. Physiological Response of Plants to Temporary Changes in Gravity Conditions

    NASA Astrophysics Data System (ADS)

    Pandolfi, Camilla; Mugnai, Sergio; Masi, Elisa; Azzarello, Elisa; Voigt, Boris; Baluska, Frantisek; Volkmann, Dieter; Mancuso, Stefano

    Gravity is the main factor that influences the direction of growth of plant organs, and has also a direct effect on the plant metabolism. When an organ, mainly roots, is turned by between 0 (vertical) and 90 (horizontal), the change of orientation is perceived by its organs producing the so-called gravitropic reaction, which involves a strong metabolic response. In order to study these reaction in real microgravity conditions, some experiments have been set up during six ESA parabolic flight campaign. Oxygen concentration in the solution, in which roots of Zea mays were placed, have been constantly monitored during normal, hyper-and microgravity conditions. An evident burst in oxygen fluxes started just 2.0 0.5 s after the imposition of microgravity conditions. No significant changes were noticed neither in normal nor in hyper-gravity conditions. These measurements were done using oxymeters, that revealed the onset of long lasting oxygen bursts appearing only during microgravity. Although the chemical nature of these oxygen bursts is still unknown, they may implicate a strong generation of reactive oxygen species as they exactly match the microgravity situation. Thus, our data strongly sug-gest that the sensing mechanism is not related to a general mechano-stress, which was imposed also during hypergravity, but is very specific of the microgravity situation. Moreover, it is well-known that stress rapidly induces reactive oxygen bursts which are associated with oxygen influx and reactive oxygen efflux from stressed plant tissues. Accordingly, our data indicate that microgravity represents a stress situation for plants, especially for root apices, and these bursts, probably ROS, are initiating and integrating adaptive responses of plant roots which resemble other unrelated stress situations. To validate this hypothesis we added to our ex-perimental set-up two very sensitive selective microelectrodes for H2 O2 and NO, and, even if the parabolic flights are not

  16. Changes in Environmental Conditions Modify Infection Kinetics of Dairy Phages.

    PubMed

    Zaburlin, Delfina; Quiberoni, Andrea; Mercanti, Diego

    2017-04-08

    Latent period, burst time, and burst size, kinetic parameters of phage infection characteristic of a given phage/host system, have been measured for a wide variety of lactic acid bacteria. However, most studies to date were conducted in optimal growth conditions of host bacteria and did not consider variations due to changes in external factors. In this work, we determined the effect of temperature, pH, and starvation on kinetic parameters of phages infecting Lactobacillus paracasei, Lactobacillus plantarum, and Leuconostoc mesenteroides. For kinetics assessment, one-step growth curves were carried out in MRS broth at optimal conditions (control), lower temperature, pH 6.0 and 5.0 (MRS6 and MRS5, respectively), or in medium lacking carbon (MRSN) or nitrogen (MRSC) sources. Phage infection was progressively impaired as environmental conditions were modified from optimal. At lower temperature or pH, infection was delayed, as perceived by longer latent and burst times. Burst size, however, was lower, equal or higher than for controls, but this effect was highly dependent on the particular phage-host system studied. Phage infection was strongly inhibited in MRSC, but only mildly impaired in MRSN. Nevertheless, growth of all the bacterial strains tested was severely compromised by starvation, without significant differences between MRSC and MRSN, indicating that nitrogen compounds are specifically required for a successful phage infection, beyond their influence on bacterial growth.

  17. Reversible structural transformation of FeO(x) nanostructures on Pt under cycling redox conditions and its effect on oxidation catalysis.

    PubMed

    Fu, Qiang; Yao, Yunxi; Guo, Xiaoguang; Wei, Mingming; Ning, Yanxiao; Liu, Hongyang; Yang, Fan; Liu, Zhi; Bao, Xinhe

    2013-09-21

    Understanding dynamic changes of catalytically active nanostructures under reaction conditions is a pivotal challenge in catalysis research, which has been extensively addressed in metal nanoparticles but is less explored in supported oxide nanocatalysts. Here, structural changes of iron oxide (FeO(x)) nanostructures supported on Pt in a gaseous environment were examined by scanning tunneling microscopy, ambient pressure X-ray photoelectron spectroscopy, and in situ X-ray absorption spectroscopy using both model systems and real catalysts. O-Fe (FeO) bilayer nanostructures can be stabilized on Pt surfaces in reductive environments such as vacuum conditions and H2-rich reaction gas, which are highly active for low temperature CO oxidation. In contrast, exposure to H2-free oxidative gases produces a less active O-Fe-O (FeO2) trilayer structure. Reversible transformation between the FeO bilayer and FeO2 trilayer structures can be achieved under alternating reduction and oxidation conditions, leading to oscillation in the catalytic oxidation performance.

  18. Propaganda, News, or Education: Reporting Changing Arctic Sea Ice Conditions

    NASA Astrophysics Data System (ADS)

    Leitzell, K.; Meier, W.

    2010-12-01

    The National Snow and Ice Data Center provides information on Arctic sea ice conditions via the Arctic Sea Ice News & Analysis (ASINA) website. As a result of this effort to explain climatic data to the general public, we have attracted a huge amount of attention from our readers. Sometimes, people write to thank us for the information and the explanation. But people also write to accuse us of bias, slant, or outright lies in our posts. The topic of climate change is a minefield full of political animosity, and even the most carefully written verbiage can appear incomplete or biased to some audiences. Our strategy has been to report the data and stick to the areas in which our scientists are experts. The ASINA team carefully edits our posts to make sure that all statements are based on the science and not on opinion. Often this means using some technical language that may be difficult for a layperson to understand. However, we provide concise definitions for technical terms where appropriate. The hope is that by communicating the data clearly, without an agenda, we can let the science speak for itself. Is this an effective strategy to communicate clearly about the changing climate? Or does it downplay the seriousness of climate change? By writing at a more advanced level and avoiding oversimplification, we require our readers to work harder. But we may also maintain the attention of skeptics, convincing them to read further and become more knowledgeable about the topic.

  19. Structural change in molten basalt at deep mantle conditions.

    PubMed

    Sanloup, Chrystèle; Drewitt, James W E; Konôpková, Zuzana; Dalladay-Simpson, Philip; Morton, Donna M; Rai, Nachiketa; van Westrenen, Wim; Morgenroth, Wolfgang

    2013-11-07

    Silicate liquids play a key part at all stages of deep Earth evolution, ranging from core and crust formation billions of years ago to present-day volcanic activity. Quantitative models of these processes require knowledge of the structural changes and compression mechanisms that take place in liquid silicates at the high pressures and temperatures in the Earth's interior. However, obtaining such knowledge has long been impeded by the challenging nature of the experiments. In recent years, structural and density information for silica glass was obtained at record pressures of up to 100 GPa (ref. 1), a major step towards obtaining data on the molten state. Here we report the structure of molten basalt up to 60 GPa by means of in situ X-ray diffraction. The coordination of silicon increases from four under ambient conditions to six at 35 GPa, similar to what has been reported in silica glass. The compressibility of the melt after the completion of the coordination change is lower than at lower pressure, implying that only a high-order equation of state can accurately describe the density evolution of silicate melts over the pressure range of the whole mantle. The transition pressure coincides with a marked change in the pressure-evolution of nickel partitioning between molten iron and molten silicates, indicating that melt compressibility controls siderophile-element partitioning.

  20. From structure to redox: the diverse functional roles of disulfides and implications in disease

    PubMed Central

    Bechtel, Tyler J.; Weerapana, Eranthie

    2017-01-01

    This review provides a comprehensive overview of the functional roles of disulfide bonds and their relevance to human disease. The critical roles of disulfide bonds in protein structure stabilization and redox regulation of protein activity are addressed. Disulfide bonds are essential to the structural stability of many proteins within the secretory pathway and can exist as intramolecular or inter-domain disulfides. The proper formation of these bonds often relies on folding chaperones and oxidases such as members of the protein disulfide isomerase (PDI) family. Many of the PDI family members catalyze disulfide-bond formation, reduction and isomerization through redox-active disulfides and perturbed PDI activity is characteristic of carcinomas and neurodegenerative diseases. In addition to catalytic function in oxidoreductases, redox-active disulfides are also found on a diverse array of cellular proteins and act to regulate protein activity and localization in response to oxidative changes in the local environment. These redox-active disulfides are either dynamic intramolecular protein disulfides or mixed disulfides with small-molecule thiols generating glutathionylation and cysteinylation adducts. The oxidation and reduction of redox-active disulfides are mediated by cellular reactive oxygen species and activity of reductases, such as glutaredoxin and thioredoxin. Dysregulation of cellular redox conditions and resulting changes in mixed disulfide formation are directly linked to diseases such as cardiovascular disease and Parkinson’s disease. PMID:28044432

  1. Dynamic Structural Changes of SiO₂ Supported Pt-Ni Bimetallic Catalysts over Redox Treatments Revealed by NMR and EPR

    SciTech Connect

    Xu, Suochang; Walter, Eric D.; Zhao, Zhenchao; Hu, Mary Y.; Han, Xiuwen; Hu, Jian Z.; Bao, Xinhe

    2015-08-18

    SiO2 supported Pt-Ni bimetallic catalysts with different nickel loadings were prepared and their structural changes after redox treatments were studied by XRD, NMR, and EPR. It is found that the paramagnetic Ni species are mainly located on the surface of silica lattice. The relaxation of detected 29Si nuclei in our samples is mainly governed by a spin-diffusion mechanism. The paramagnetic effects are reflected in the spin-lattice relaxation of Q4 species, with the oxidized samples presenting faster relaxation rates than the corresponding reduced ones. Meanwhile the Q3 species, which are in close contact with the paramagnetic nickel ions, are “spectrally invisible”. In reducing atmosphere Ni gradually diffuses into Pt NPs to form PtNi alloys. While under oxidization treatment, the alloyed Ni atoms migrate outward from the core of Pt NPs and are oxidized. The main EPR spectrum results from reduced nickel species, and the reduced samples show stronger EPR signal than the corresponding oxidized ones. However, in the reduced samples, the superparamagnetic or ferromagnetic metallic Ni particles were inside the PtNi NPs, making their influence on the 29Si relaxation in the SiO2 support weaker than the oxidized samples.

  2. Crystal structures of a poplar thioredoxin peroxidase that exhibits the structure of glutathione peroxidases: insights into redox-driven conformational changes.

    PubMed

    Koh, Cha San; Didierjean, Claude; Navrot, Nicolas; Panjikar, Santosh; Mulliert, Guillermo; Rouhier, Nicolas; Jacquot, Jean-Pierre; Aubry, André; Shawkataly, Omar; Corbier, Catherine

    2007-07-13

    Glutathione peroxidases (GPXs) are a group of enzymes that regulate the levels of reactive oxygen species in cells and tissues, and protect them against oxidative damage. Contrary to most of their counterparts in animal cells, the higher plant GPX homologues identified so far possess cysteine instead of selenocysteine in their active site. Interestingly, the plant GPXs are not dependent on glutathione but rather on thioredoxin as their in vitro electron donor. We have determined the crystal structures of the reduced and oxidized form of Populus trichocarpaxdeltoides GPX5 (PtGPX5), using a selenomethionine derivative. PtGPX5 exhibits an overall structure similar to that of the known animal GPXs. PtGPX5 crystallized in the assumed physiological dimeric form, displaying a pseudo ten-stranded beta sheet core. Comparison of both redox structures indicates that a drastic conformational change is necessary to bring the two distant cysteine residues together to form an intramolecular disulfide bond. In addition, a computer model of a complex of PtGPX5 and its in vitro recycling partner thioredoxin h1 is proposed on the basis of the crystal packing of the oxidized form enzyme. A possible role of PtGPX5 as a heavy-metal sink is also discussed.

  3. Functional aspects of redox control during neuroinflammation.

    PubMed

    Rosales-Corral, Sergio; Reiter, Russel J; Tan, Dun-Xian; Ortiz, Genaro G; Lopez-Armas, Gabriela

    2010-07-15

    Neuroinflammation is a CNS reaction to injury in which some severe pathologies, regardless of their origin, converge. The phenomenon emphasizes crosstalk between neurons and glia and reveals a complex interaction with oxidizing agents through redox sensors localized in enzymes, receptors, and transcription factors. When oxidizing pressures cause reversible molecular changes, such as minimal or transitory proinflammatory cytokine overproduction, redox couples provide a means of translating the presence of reactive oxygen or nitrogen species into useful signals in the cell. Additionally, thiol-based redox sensors convey information about localized changes in redox potential induced by physiologic or pathologic situations. They are susceptible to oxidative changes and become key events during neuroinflammation, altering the course of a signaling response or the behavior of specific transcription factors. When oxidative stress augments the pressure on the intracellular environment, the effective reduction potential of redox pairs diminishes, and cell signaling shifts toward proinflammatory and proapoptotic signals, creating a vicious cycle between oxidative stress and neuroinflammation. In addition, electrophilic compounds derived from the oxidative cascade react with key protein thiols and interfere with redox signaling. This article reviews the relevant functional aspects of redox control during the neuroinflammatory process.

  4. Millennial-scale Changes of Surface and Bottom Water Conditions in the Northwest Pacific during the Last Deglacial Period

    NASA Astrophysics Data System (ADS)

    Khim, B. K.; Kim, S.; Ikehara, K.; Itaki, T.; Shibahara, A.; Yamamoto, M.

    2015-12-01

    The last deglacial changes of the water column conditions in the Northwest Pacific were reconstructed using geochemical and isotope proxies (biogenic opal, CaCO3, total organic carbon (TOC), redox sensitive elements, bulk nitrogen isotopes (δ15N), and silicon isotopes (δ30Sidiatom) of diatom frustules) along with the published data (alkenone temperatures and benthic foraminiferal faunas) at core GH02-1030 recovered from the slope off Tokachi. Age model for core GH02-1030 was determined using both planktonic and benthic foraminiferal AMC 14C dates (Ikehara et al., 2006). Alkenone sea surface temperature (SST) shows that biogenic opal productivity was related to the degree of spring-summer mixed layer depth (MLD). Biogenic opal and TOC contents change almost in parallel. δ30Sidiatom values are high (~+1‰) during the Holocene and low (~-0.4‰) during the last glacial maximum. During the Bølling-Allerød (BA) and the Pre-Boreal (PB), silicic acid utilization represented by δ30Sidiatom increased when the biogenic opal productivity and export TOC productivity are high under shoaling of spring-summer MLD. The BA and the PB intervals contain laminated sediment layers, which are characterized by increases of CaCO3 contents, bulk δ15N values, and redox element concentrations (Mo/Al, Cd/Al, and U/Al). All these indicate low dissolved oxygen content of the bottom water during the BA and PB periods, which is supported by the good preservation of dysoxic benthic foraminifera. In addition, compared to the Holocene biogenic opal productivity and related silicic acid utilization, the high δ15N values during the BA and the PB seemed to be attributed more to denitrification through the water column rather than complete utilization of nitrate. Another distinct feature based on benthic foraminiferal assemblage, CaCO3 contents and redox element concentrations is that the dissolved oxygen content in bottom water was lower during the BA than the PB. Because biogenic opal

  5. WATERSHED BOUNDARY CONDITIONS FOR GLOBAL CHANGE IMPACT ANALYSIS

    EPA Science Inventory

    The US Global Change Research Program (USGCRP) studies (among other issues) the impact of global change on water quality. This field study evaluates the impact of global changes (land-use change and climate change) on source water quality. Changes in source water quality change...

  6. Effect of pH on Structural Changes in Perch Hemoglobin that Can Alter Redox Stability and Heme Affinity

    SciTech Connect

    Richards, Mark P.; Aranda, IV, Roman; He, Cai; Phillips, Jr., George N.

    2010-01-07

    pH can be manipulated to alter the oxidative stability of fish-based foods during storage. X-ray diffraction was used to investigate the ability of reduced pH to cause structural changes in fish hemoglobins that lead to enhanced oxidative degradation. Decreasing pH from 8.0 to 6.3 and 5.7 created a large channel for solvent entry into the heme crevice of perch hemoglobin beta chains. The proton-induced opening of this channel occurred between site CD3 and the heme-6-propionate. Solvent entry into the heme crevice can enhance metHb formation and hemin loss, processes that accelerate lipid oxidation. Reduced pH also decreased the distance between Ile at E11 in one of the alpha chains and the ligand above the heme iron atom. This sterically displaces O{sub 2} and protonated O{sub 2} which increases metHb formation. These studies demonstrate that pH reduction causes structural changes in perch hemoglobin which increase oxidative degradation of the heme pigment.

  7. Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams

    USGS Publications Warehouse

    Briggs, Martin A.; Lautz, Laura; Hare, Danielle K.

    2013-01-01

    ¨hler number seemed to overestimate the actual transition as indicated by multiple secondary electron acceptors, illustrating the gradient nature of anaerobic transition. Temporal flux variability in low-flux morphologies generated a much greater range in hyporheic redox conditions compared to high-flux zones, and chemical responses to changing flux rates were consistent with those predicted from the empirical relationship between redox condition and residence time. The Raz tracer revealed that hyporheic flow paths have strong net aerobic respiration, particularly at higher residence time, but this reactive exchange did not affect the net stream signal at the reach scale.

  8. Comparing Observed Hurricane Conditions Against Potential Future Climate Change Influences

    NASA Astrophysics Data System (ADS)

    Graham, W. D.

    2012-12-01

    Climate Adaptation Science Investigators: (CASI) is to advance and apply NASA's scientific expertise and products to develop climate adaptation strategies that support NASA's overall mission by minimizing risks to each center's operations, physical assets, and personnel. Using Hurricane Katrina observations as a baseline, we use ADCIRC to model surge extent with simple modifications of the storm track. We examine two time now (T0) scenarios of present-day climatological factors: 1) translating the 2005 path 7 km west; and 2) rotating the approach angle from due-north to WNW. Second, we examine two future time scenarios (TX) by infusing climate change conditions, such as sea level rise and increased storm intensity, into a T0 baseline to assess future impacts. The primary goal of this work entails planning and protecting NASA assets and infrastructure. The adjacent communities, state and local emergency managers, gain benefit from this NASA work as data and analysis includes the surrounding geography.

  9. Metabolic Control of Redox and Redox Control of Metabolism in Plants

    PubMed Central

    Fernie, Alisdair R.

    2014-01-01

    Abstract Significance: Reduction-oxidation (Redox) status operates as a major integrator of subcellular and extracellular metabolism and is simultaneously itself regulated by metabolic processes. Redox status not only dominates cellular metabolism due to the prominence of NAD(H) and NADP(H) couples in myriad metabolic reactions but also acts as an effective signal that informs the cell of the prevailing environmental conditions. After relay of this information, the cell is able to appropriately respond via a range of mechanisms, including directly affecting cellular functioning and reprogramming nuclear gene expression. Recent Advances: The facile accession of Arabidopsis knockout mutants alongside the adoption of broad-scale post-genomic approaches, which are able to provide transcriptomic-, proteomic-, and metabolomic-level information alongside traditional biochemical and emerging cell biological techniques, has dramatically advanced our understanding of redox status control. This review summarizes redox status control of metabolism and the metabolic control of redox status at both cellular and subcellular levels. Critical Issues: It is becoming apparent that plastid, mitochondria, and peroxisome functions influence a wide range of processes outside of the organelles themselves. While knowledge of the network of metabolic pathways and their intraorganellar redox status regulation has increased in the last years, little is known about the interorganellar redox signals coordinating these networks. A current challenge is, therefore, synthesizing our knowledge and planning experiments that tackle redox status regulation at both inter- and intracellular levels. Future Directions: Emerging tools are enabling ever-increasing spatiotemporal resolution of metabolism and imaging of redox status components. Broader application of these tools will likely greatly enhance our understanding of the interplay of redox status and metabolism as well as elucidating and

  10. Arctic hillslope hydrologic response to changing water storage conditions

    NASA Astrophysics Data System (ADS)

    Rushlow, C. R.; Godsey, S.

    2013-12-01

    Solute transport from terrestrial to aquatic environments depends on dynamics of water storage and flux. In the arctic, these dynamics are related to changes in permafrost and hydrological conditions that vary with climate across multiple scales. In order to predict the continued trajectory of arctic landscape and ecosystem evolution, observed changes to the hydrologic regime and riverine nutrient fluxes require properly scaled, mechanistic explanations. We address this issue at the hillslope scale by quantifying hydrologic response to changing storage as part of a collaborative effort to understand the coupled hydrology and biogeochemistry of arctic hillslopes. Hillslopes underlain by continuous permafrost experience gradual, summer-season increases in potential water storage through active layer thaw, as well as stochastic changes in available water storage as soil moisture conditions change due to storm events, evapotranspiration, and subsurface flow. Preferential flowpaths called water tracks are ubiquitous features draining arctic hillslopes and are the focus of our study. We predict that water track hydrologic response to precipitation is a function of snowmelt or storm characteristics and available storage. We hypothesize that ¬the ratio of runoff to precipitation will decrease as available storage increases, whether due to the seasonal increase in active layer thaw, or an extended dry period. Intensive snow and thaw depth surveys on a water track on the hillslopes of the Upper Kuparuk River watershed in northern Alaska during May to June 2013 reveal that snow persisted one week longer in a water track than the adjacent hillslope, and thus active layer thaw initiated earlier on the adjacent hillslope. Despite this earlier thaw timing, thaw depth in the water track exceeded that on the non-track hillslope within five days of being uncovered. Thaw, and thus subsurface storage, in water tracks remained greater than the rest of the hillslope for at least the

  11. Conditioned hearing sensitivity change in the harbor porpoise (Phocoena phocoena).

    PubMed

    Nachtigall, Paul E; Supin, Alexander Ya; Pacini, Aude F; Kastelein, Ronald A

    2016-08-01

    Hearing sensitivity, during trials in which a warning sound preceding a loud sound, was investigated in two harbor porpoises (Phocoena phocoena). Sensitivity was measured using pip-train test stimuli and auditory evoked potential recording. When a hearing test/warning stimulus, with a frequency of either 45 or 32 kHz, preceded a loud 32 kHz tone with a sound pressure level of 152 dB re 1 μPa root mean square, lasting 2 s yielding an sound exposure level (SEL) of 155 dB re 1 μPa(2)s, pooled hearing thresholds measured just before the loud sound increased relative to baseline thresholds. During two experimental sessions the threshold increased up to 17 dB for the test frequency of 45 kHz and up to 11 dB for the test frequency of 32 kHz. An extinction test revealed very rapid threshold recovery within the first two experimental sessions. The SEL producing the hearing dampening effect was low compared to previous other odontocete hearing change efforts with each individual trial equal to 155 dB re 1 μPa(2) but the cumulative SEL for each subsession may have been as high as 168 dB re 1 μPa(2). Interpretations of conditioned hearing sensation change and possible change due to temporary threshold shifts are considered for the harbor porpoise and discussed in the light of potential mechanisms and echolocation.

  12. The Tumorigenic Roles of the Cellular REDOX Regulatory Systems

    PubMed Central

    Castaldo, Stéphanie Anaís; Freitas, Joana Raquel; Conchinha, Nadine Vasconcelos; Madureira, Patrícia Alexandra

    2016-01-01

    The cellular REDOX regulatory systems play a central role in maintaining REDOX homeostasis that is crucial for cell integrity, survival, and proliferation. To date, a substantial amount of data has demonstrated that cancer cells typically undergo increasing oxidative stress as the tumor develops, upregulating these important antioxidant systems in order to survive, proliferate, and metastasize under these extreme oxidative stress conditions. Since a large number of chemotherapeutic agents currently used in the clinic rely on the induction of ROS overload or change of ROS quality to kill the tumor, the cancer cell REDOX adaptation represents a significant obstacle to conventional chemotherapy. In this review we will first examine the different factors that contribute to the enhanced oxidative stress generally observed within the tumor microenvironment. We will then make a comprehensive assessment of the current literature regarding the main antioxidant proteins and systems that have been shown to be positively associated with tumor progression and chemoresistance. Finally we will make an analysis of commonly used chemotherapeutic drugs that induce ROS. The current knowledge of cancer cell REDOX adaptation raises the issue of developing novel and more effective therapies for these tumors that are usually resistant to conventional ROS inducing chemotherapy. PMID:26682014

  13. Differential alkylation-based redox proteomics--Lessons learnt.

    PubMed

    Wojdyla, Katarzyna; Rogowska-Wrzesinska, Adelina

    2015-12-01

    Cysteine is one of the most reactive amino acids. This is due to the electronegativity of sulphur atom in the side chain of thiolate group. It results in cysteine being present in several distinct redox forms inside the cell. Amongst these, reversible oxidations, S-nitrosylation and S-sulfenylation are crucial mediators of intracellular redox signalling, with known associations to health and disease. Study of their functionalities has intensified thanks to the development of various analytical strategies, with particular contribution from differential alkylation-based proteomics methods. Presented here is a critical evaluation of differential alkylation-based strategies for the analysis of S-nitrosylation and S-sulfenylation. The aim is to assess the current status and to provide insights for future directions in the dynamically evolving field of redox proteomics. To achieve that we collected 35 original research articles published since 2010 and analysed them considering the following parameters, (i) resolution of modification site, (ii) quantitative information, including correction of modification levels by protein abundance changes and determination of modification site occupancy, (iii) throughput, including the amount of starting material required for analysis. The results of this meta-analysis are the core of this review, complemented by issues related to biological models and sample preparation in redox proteomics, including conditions for free thiol blocking and labelling of target cysteine oxoforms.

  14. Redox-controlled molecular permeability of composite-wall microcapsules

    NASA Astrophysics Data System (ADS)

    Ma, Yujie; Dong, Wen-Fei; Hempenius, Mark A.; Möhwald, Helmuth; Julius Vancso, G.

    2006-09-01

    Many smart materials in bioengineering, nanotechnology and medicine allow the storage and release of encapsulated drugs on demand at a specific location by an external stimulus. Owing to their versatility in material selection, polyelectrolyte multilayers are very promising systems in the development of microencapsulation technologies with permeation control governed by variations in the environmental conditions. Here, organometallic polyelectrolyte multilayer capsules, composed of polyanions and polycations of poly(ferrocenylsilane) (PFS), are introduced. Their preparation involved layer-by-layer self-assembly onto colloidal templates followed by core removal. PFS polyelectrolytes feature redox-active ferrocene units in the main chain. Incorporation of PFS into the capsule walls allowed us to explore the effects of a new stimulus, that is, changing the redox state, on capsule wall permeability. The permeability of these capsules could be sensitively tuned via chemical oxidation, resulting in a fast capsule expansion accompanied by a drastic permeability increase in response to a very small trigger. The substantial swelling could be suppressed by the application of an additional coating bearing common redox-inert species of poly(styrene sulfonate) (PSS-) and poly(allylamine hydrochloride) (PAH+) on the outer wall of the capsules. Hence, we obtained a unique capsule system with redox-controlled permeability and swellability with a high application potential in materials as well as in bioscience.

  15. Redox-controlled molecular permeability of composite-wall microcapsules.

    PubMed

    Ma, Yujie; Dong, Wen-Fei; Hempenius, Mark A; Möhwald, Helmuth; Vancso, G Julius

    2006-09-01

    Many smart materials in bioengineering, nanotechnology and medicine allow the storage and release of encapsulated drugs on demand at a specific location by an external stimulus. Owing to their versatility in material selection, polyelectrolyte multilayers are very promising systems in the development of microencapsulation technologies with permeation control governed by variations in the environmental conditions. Here, organometallic polyelectrolyte multilayer capsules, composed of polyanions and polycations of poly(ferrocenylsilane) (PFS), are introduced. Their preparation involved layer-by-layer self-assembly onto colloidal templates followed by core removal. PFS polyelectrolytes feature redox-active ferrocene units in the main chain. Incorporation of PFS into the capsule walls allowed us to explore the effects of a new stimulus, that is, changing the redox state, on capsule wall permeability. The permeability of these capsules could be sensitively tuned via chemical oxidation, resulting in a fast capsule expansion accompanied by a drastic permeability increase in response to a very small trigger. The substantial swelling could be suppressed by the application of an additional coating bearing common redox-inert species of poly(styrene sulfonate) (PSS(-)) and poly(allylamine hydrochloride) (PAH(+)) on the outer wall of the capsules. Hence, we obtained a unique capsule system with redox-controlled permeability and swellability with a high application potential in materials as well as in bioscience.

  16. Implications of phosphorus redox geochemistry

    NASA Astrophysics Data System (ADS)

    Pasek, Matthew

    2015-04-01

    Phosphorus is the limiting nutrient in many environments. Until recently, redox changes to phosphorus speciation have been confined to the realm of chemical laboratories as phosphorus was considered to be synonymous with phosphate in the natural environment. The few known phosphorus species with a reduced redox state, such as phosphine gas, were considered novelties. Recent work has revealed a surprising role for low redox state organophosphorus compounds -- the phosphonates -- in biogeochemistry. Additionally, phosphite and hypophosphite (the lower oxyanions of phosphorus) have been identified from natural sources, and microbial genomics suggests these compounds may be ubiquitous in nature. Recent work from our laboratory suggests that reduced phosphorus compounds such as phosphite and hypophosphite may be ubiquitous (Pasek et al. 2014). If so, then these species maybe important in the global phosphorus biogeochemical cycle, and could influence global phosphorus sustainability. Additionally, these compounds could have been relevant on the early earth environment, priming the earth with reactive phosphorus for prebiotic chemistry. Reference: Pasek, M. A., Sampson, J. M., & Atlas, Z. (2014). Redox chemistry in the phosphorus biogeochemical cycle. Proceedings of the National Academy of Sciences, 111(43), 15468-15473.

  17. [Changes of rat gastric mucosal barrier under stress conditions].

    PubMed

    Zhan, Xianbao; Li, Zhaoshen; Cui, Zhongmin; Duan, Yimin; Nie, Shinan; Liu, Jing; Xu, Guoming

    2002-06-01

    OBJECTIVE To explore the changes of rat gastric mucosal barrier under conditions of water immersion restraint stress. METHODS Eighty rats were randomly divided into Group A (20 rats), B (40 rats) and C (20 rats) after being fasted for 24 hours. And then Group A was divided into two subgroups with ten rats in each. The two subgroups in Group A were given normal saline or omeprazole respectively while under the stress condition. The changes of gastric acid or bicarbonate secretion were determined. Group B (40 rats) were randomly divided into four subgroups,which were subgroup control, 1h, 2h and 4h after beginning of the stress. The quantity of glandular mucosal adherent mucus, the thickness of mucus gel layer and ulcer index were measured after stress in Group B. The glandular mucosal samples were labeled by Lanthanum and observed by transmission electromicroscopy. Group C was randomly divided into two subgroups in the same way with Group A. And each subgroup received normal saline or omeprazole respectively H(+) loss in gastric lumen was calculated by determining the difference of acidity between lavage and drainage fluid H(+) concentration. RESULTS It was found that gastric alkaline secretion decreased progressively (P < 0.05), while gastric acid secretion increased progressively under stress conditions (P < 0.05). The mucus quantity(A/g) in the four subgroups in Group B were 0.137 +/- 0.030, 0.143 +/- 0.012, 0.066 +/- 0.016 and 0.016 +/- 0.016 respectively. The mucus gel thickness(microm) were 71.08 +/- 5.85, 74.50 +/- 12.85, 57.63 +/- 6.45 and 51.35 +/- 2.84 respectively. The ulcer index were 0.2 +/- 0.1,0.4 +/- 0.1,5.2 +/- 1.3 and 10.0 +/- 0.5 respectively. Statistics showed that the mucus quantity was correlated with the mucus gel thickness positively(r = 0.89), while either of them was correlated with the ulcer index negatively(r = 0.85 and "r = 0.83). And it was also found that Lanthanum rarely stained the glandular mucosa in control subgroup, while heavily

  18. Age-related changes in conditioned flavor preference in rats.

    PubMed

    Renteria, Adam F; Silbaugh, Bryant C; Tolentino, Jerlyn C; Gilbert, Paul E

    2008-03-17

    Age-related changes have been documented in regions of the brain shown to process reward information. However, few studies have examined the effects of aging on associative memory for reward. The present study tested 7- and 24-month-old rats on a conditioned flavor preference task. Half of the rats in each age group received an unsweetened grape-flavored solution (CS-) on odd-numbered days and a sweetened cherry-flavored solution (CS+) on even-numbered days. The remaining rats in each age group received a sweetened grape-flavored solution (CS+) on odd-numbered days and an unsweetened cherry-flavored solution (CS-) on even-numbered days. During the acquisition phase of testing, the designated solution (CS+ or CS-) was presented to each rat for 15 min daily across six consecutive days. On the preference phase, each rat received unsweetened cherry and unsweetened grape-flavored solutions simultaneously for 15 min daily across four consecutive days. The 7-month-old rats showed a significant preference for the flavor that was previously sweetened during the acquisition phase (CS+) compared to the previously unsweetened solution (CS-) when the two unsweetened solutions were presented simultaneously during the preference phase of testing. In contrast, the 24-month-old rats did not show a preference and consumed roughly equal amounts of the previously sweetened (CS+) and unsweetened (CS-) solutions. Thus, the data suggest that the ability to form flavor-reward associations declines with increasing age, resulting in impaired conditioned flavor preference.

  19. COMPOSITION CHANGES IN REFRIGERANT BLENDS FOR AUTOMOTIVE AIR CONDITIONING

    EPA Science Inventory

    Three refrigerant blends used to replace CFC-12 in automotive air conditioners were evaluated for composition changes due to typical servicing and leakage. When recommended service procedures were followed, changes in blend compositions were relatively small. Small changes in b...

  20. A high redox potential form of cytochrome c550 in photosystem II from Thermosynechococcus elongatus.

    PubMed

    Guerrero, Fernando; Sedoud, Arezki; Kirilovsky, Diana; Rutherford, A William; Ortega, José M; Roncel, Mercedes

    2011-02-25

    Cytochrome c(550) (cyt c(550)) is a component of photosystem II (PSII) from cyanobacteria, red algae, and some other eukaryotic algae. Its physiological role remains unclear. In the present work, measurements of the midpoint redox potential (E(m)) were performed using intact PSII core complexes preparations from a histidine-tagged PSII mutant strain of the thermophilic cyanobacterium Thermosynechococcus (T.) elongatus. When redox titrations were done in the absence of redox mediators, an E(m) value of +200 mV was obtained for cyt c(550). This value is ∼300 mV more positive than that previously measured in the presence of mediators (E(m) = -80 mV). The shift from the high potential form (E(m) = +200 mV) to the low potential form (E(m) = -80 mV) of cyt c(550) is attributed to conformational changes, triggered by the reduction of a component of PSII that is sequestered and out of equilibrium with the medium, most likely the Mn(4)Ca cluster. This reduction can occur when reduced low potential redox mediators are present or under highly reducing conditions even in the absence of mediators. Based on these observations, it is suggested that the E(m) of +200 mV obtained without mediators could be the physiological redox potential of the cyt c(550) in PSII. This value opens the possibility of a redox function for cyt c(550) in PSII.

  1. Sedimentary cobalt concentrations track marine redox evolution

    NASA Astrophysics Data System (ADS)

    Swanner, Elizabeth; Planavsky, Noah; Lalonde, Stefan; Robbins, Jamie; Bekker, Andrey; Rouxel, Olivier; Konhauser, Kurt O.; Mojzsis, Stephen J.

    2013-04-01

    Oxygen production by photosynthesis drove the redox evolution of the atmosphere and ocean. Primary productivity by oxygenic photosynthesizers in the modern surface ocean is limited by trace nutrients such as iron, but previous studies have also observed high Co uptake associated with natural cyanobacterial populations. Constraining the size and variation of the oceanic reservoir of Co through time will help to understand the regulation of primary productivity and hence oxygenation through time. In this study, Co concentrations from iron formations (IF), shales and marine pyrites deposited over nearly 4 billion years of Earth's history are utilized to reconstruct secular changes in the mechanisms of Co removal from the oceanic reservoir. The Co reservoir prior to ~2 Ga was dominated by hydrothermal inputs and Fe(III)oxyhydroxides were likely involved in the removal of Co from the water column. Fe(II) oxidation in the water column resulted in the deposition of IF in the Archean and Paleoproterozoic, and the Co inventory of IF records a large oceanic reservoir of Co during this time. Lower Co concentrations in sediments during the Middle Proterozoic signify a decrease in the oceanic reservoir due to the expansion euxinic environments, corresponding to the results of previous studies. A transition to an oxidized deep ocean in the Phanerozoic is evidenced by correlation between Co and manganese (Mn) concentrations in hydrothermal and exhalative deposits, and in marine pyrites. This relationship between Co and Mn, signifying deposition of Co in association with Mn(IV)oxides, does not occur in the Precambrian. Mn(II) oxidation occurs at higher redox potentials than that required for Fe(II) oxidation, and the extent of Mn redox cycling prior to full ventilation of the oceans at the end of the Neoproterozoic was likely limited to spatially restricted oxic surface waters. In this regard, Co is another valuable redox proxy for tracking the growth and decline in oxygenated

  2. Icing conditions over Northern Eurasia in changing climate

    NASA Astrophysics Data System (ADS)

    Bulygina, Olga N.; Arzhanova, Natalia M.; Groisman, Pavel Ya

    2015-02-01

    Icing conditions, particularly in combination with wind, affect greatly the operation of overhead communication and transmission lines causing serious failures, which result in tremendous economic damage. Icing formation is dangerous to agriculture, forestry, high seas fishery, for land and off coast man-made infrastructure. Quantitative icing characteristics such as weight, thickness, and duration are very important for the economy and human wellbeing when their maximum values exceed certain thresholds. Russian meteorological stations perform both visual and instrumental monitoring of icing deposits. Visual monitoring is ocular estimation of the type and intensity of icing and the date of ice appearance and disappearance. Instrumental monitoring is performed by ice accretion indicator that in addition to the type, intensity and duration of ice deposits reports also their weight and size. We used observations at 958 Russian stations for the period 1977-2013 to analyze changes in the ice formation frequency at individual meteorological stations and on the territory of quasi-homogeneous climatic regions in Russia. It was found that hoar frosts are observed in most parts of Russia, but icing only occurs in European Russia and the Far East. On the Arctic coast of Russia, this phenomenon can even be observed in summer months. Statistically significant decreasing trends in occurrence of icing and hoar frost events are found over most of Russia. An increasing trend in icing weights (IWs) was found in the Atlantic Arctic region in autumn. Statistically significant large negative trends in IWs were found in the Pacific Arctic in winter and spring.

  3. Redox regulation: an introduction.

    PubMed

    Dietz, Karl-Josef; Scheibe, Renate

    2004-01-01

    The redox-state is a critical determinate of cell function, and any major imbalances can cause severe damage or death. The cellular redox status therefore needs to be sensed and modulated before such imbalances occur. Various redox-active components are involved in these processes, including thioredoxins, glutaredoxins and other thiol/disulphide-containing proteins. The cellular reactions for cytoprotection and for signalling are integrated with physiological redox-reactions in photosynthesis, assimilation and respiration. They also determine the developmental fate of the cell and finally decide on proliferation or cell death. An international workshop on redox regulation, organized by the research initiative FOR 387 of the Deutsche Forschungsgemeinschaft, was held in Bielefeld, Germany in 2002. A selection of articles originating from the meeting is printed in this issue of Physiologia Plantarum.

  4. Mitochondria and redox homoeostasis as chemotherapeutic targets.

    PubMed

    Briehl, Margaret M; Tome, Margaret E; Wilkinson, Sarah T; Jaramillo, Melba C; Lee, Kristy

    2014-08-01

    Characteristics of cancer cells include a more oxidized redox environment, metabolic reprogramming and apoptosis resistance. Our studies with a lymphoma model have explored connections between the cellular redox environment and cancer cell phenotypes. Alterations seen in lymphoma cells made resistant to oxidative stress include: a more oxidized redox environment despite increased expression of antioxidant enzymes, enhanced net tumour growth, metabolic changes involving the mitochondria and resistance to the mitochondrial pathway to apoptosis. Of particular importance, the cells show cross-resistance to multiple chemotherapeutic agents used to treat aggressive lymphomas. Analyses of clinical and tumour data reveal the worst prognosis when patients' lymphomas have gene expression patterns consistent with the most oxidized redox environment. Lymphomas from patients with the worst survival outcomes express increased levels of proteins involved in oxidative phosphorylation, including cytochrome c. This is consistent with these cells functioning as metabolic opportunists. Using lymphoma cell models and primary lymphoma cultures, we observed enhanced killing using genetic and drug approaches which further oxidize the cellular redox environment. These approaches include increased expression of SOD2 (superoxide dismutase 2), treatment with a manganoporphyrin that oxidizes the glutathione redox couple, or treatment with a copper chelator that inhibits SOD1 and leads to peroxynitrite-dependent cell death. The latter approach effectively kills lymphoma cells that overexpress the anti-apoptotic protein Bcl-2. Given the central role of mitochondria in redox homoeostasis, metabolism and the intrinsic pathway to apoptosis, our studies support the development of new anti-cancer drugs to target this organelle.

  5. Icing Conditions Over Northern Eurasia in Changing Climate

    NASA Astrophysics Data System (ADS)

    Bulygina, O.; Arzhanova, N.; Groisman, P. Y.

    2013-12-01

    Climate of the Russian Federation for the national territory. This Reference Book addresses the current state of these weather phenomena. However, the ongoing and projected humidity changes in the high latitudes will strongly affect the circum-polar area (land and ocean) and impact the frequency and intensity of these potentially dangerous weather phenomena across the entire extratropical land area. Therefore the goal of the present study is to quantify icing conditions over the northern Eurasia. Our analysis includes data of 958 Russian stations from 1977 to 2012. Regional analysis of gololed characteristics was carried out using quasi-homogeneous climatic regions. Maps (climatology, trends) are presented mostly for visualization purposes. The area-averaging technique using station values converted to anomalies with respect to a common reference period (in this study, from 1977 to 2012). Anomalies were arithmetically averaged first within 1N x 2E grid cells and thereafter by a weighted average value derived over the quasi-homogeneous climatic regions. This approach provides a more uniform spatial field for averaging.

  6. Morphogenetic changes occurring in the regenerating newt tail under changed gravity conditions

    NASA Astrophysics Data System (ADS)

    Radugina, Elena A.; Grigoryan, Eleonora N.; Dvorochkin, Natasha; Almeida, Eduardo

    2012-07-01

    It is widely accepted that gravity greatly affects animal physiology, development, and alters gene expression. Recently it became apparent that it can also affect tissue morphogenesis. In our work, we developed special laboratory conditions that allow us to produce the gravity-dependent alterations in tail regenerates of the newt Pleurodeles waltl. We examined the dynamic morphogenetic changes during 50-day tail regeneration using computer morphometric analysis. Changes that we observed under these conditions were comparable with those found earlier in our spaceflight experiments. The newts kept in aquarium deep water (low g) after 1/3 tail amputation developed normal lanceolate regenerates. In contrast, the animals that stayed on the moist mat (1g) developed tail regenerates curved ventrally, with tips almost touching the mat. The similar results were obtained with a 12-day centrifugation at 2g. The study of the regenerate morphology in low g, 1g, and 2g animal groups allowed us to determine the stage at which the morphological changes in regenerates become apparent, and to detect the main morphological events associated with the development of tail curve, such as bending of ependymal tube and reorientation of the forming cartilage. We describe cellular processes foregoing observed tissue morphogenetic changes, such as cell migration, condensation in cell population, and unequal proliferation in different areas of epidermis and blastema. Cell proliferation in epidermis and blastema of tails regenerated under the conditions of different gravitational load was evaluated by BrdU assay. In 1g newts, cell proliferation increased within the dorso-apical region of the regenerates compared with that in low g group. These results provide us with a valuable insight into the regenerative tissue homostasis that involves cell division, cell death, and migration in the newt regenerating tail. In addition, these findings could provide us with better understanding of the

  7. Selenium- and tellurium-containing multifunctional redox agents as biochemical redox modulators with selective cytotoxicity.

    PubMed

    Jamier, Vincent; Ba, Lalla A; Jacob, Claus

    2010-09-24

    Various human diseases, including different types of cancer, are associated with a disturbed intracellular redox balance and oxidative stress (OS). The past decade has witnessed the emergence of redox-modulating compounds able to utilize such pre-existing disturbances in the redox state of sick cells for therapeutic advantage. Selenium- and tellurium-based agents turn the oxidizing redox environment present in certain cancer cells into a lethal cocktail of reactive species that push these cells over a critical redox threshold and ultimately kill them through apoptosis. This kind of toxicity is highly selective: normal, healthy cells remain largely unaffected, since changes to their naturally low levels of oxidizing species produce little effect. To further improve selectivity, multifunctional sensor/effector agents are now required that recognize the biochemical signature of OS in target cells. The synthesis of such compounds provides interesting challenges for chemistry in the future.

  8. Redox Fluctuation Structures Microbial Communities in a Wet Tropical Soil

    PubMed Central

    Pett-Ridge, J.; Firestone, M. K.

    2005-01-01

    Frequent high-amplitude redox fluctuation may be a strong selective force on the phylogenetic and physiological composition of soil bacterial communities and may promote metabolic plasticity or redox tolerance mechanisms. To determine effects of fluctuating oxygen regimens, we incubated tropical soils under four treatments: aerobic, anaerobic, 12-h oxic/anoxic fluctuation, and 4-day oxic/anoxic fluctuation. Changes in soil bacterial community structure and diversity were monitored with terminal restriction fragment length polymorphism (T-RFLP) fingerprints. These profiles were correlated with gross N cycling rates, and a Web-based phylogenetic assignment tool was used to infer putative community composition from multiple fragment patterns. T-RFLP ordinations indicated that bacterial communities from 4-day oxic/anoxic incubations were most similar to field communities, whereas those incubated under consistently aerobic or anaerobic regimens developed distinctly different molecular profiles. Terminal fragments found in field soils persisted either in 4-day fluctuation/aerobic conditions or in anaerobic/12-h treatments but rarely in both. Only 3 of 179 total fragments were ubiquitous in all soils. Soil bacterial communities inferred from in silico phylogenetic assignment appeared to be dominated by Actinobacteria (especially Micrococcus and Streptomycetes), “Bacilli,” “Clostridia,” and Burkholderia and lost significant diversity under consistently or frequently anoxic incubations. Community patterns correlated well with redox-sensitive processes such as nitrification, dissimilatory nitrate reduction to ammonium (DNRA), and denitrification but did not predict patterns of more general functions such as N mineralization and consumption. The results suggest that this soil's indigenous bacteria are highly adapted to fluctuating redox regimens and generally possess physiological tolerance mechanisms which allow them to withstand unfavorable redox periods. PMID

  9. Composition changes in refrigerant blends for automotive air conditioning

    SciTech Connect

    Jetter, J.J.; Delafield, F.R.; Ng, A.S.; Ratanaphruks, K.; Tufts, M.W.

    1999-07-01

    Three refrigerant blends used to replace the chlorofluorocarbon R-12 in automotive air conditioners were evaluated for composition changes due to typical servicing and leakage. When recommended service procedures were followed, changes in blend compositions were relatively small. Small changes in blend compositions caused no significant changes in refrigeration capacities. However, when recommended procedures were not followed, changes in compositions were relatively large. The amount of change in composition and the resulting effect on performance varied among the three refrigerant blends that were tested. Of the three blends, a quaternary blend containing hydrochlorofluorocarbon R-22 had the greatest changes in composition, while a binary blend containing hydrofluorocarbon R-134a had the smallest changes in composition.

  10. Communicating Vulnerabilities to Climate Change: Existing Health Conditions

    EPA Pesticide Factsheets

    View and download fact sheets that highlight the health impacts of climate change at different stages of life and for certain populations of concern, as well as communications materials to help strengthen conversations about climate change and health.

  11. Redox dependent changes at the heme propionates in cytochrome c oxidase from Paracoccus denitrificans: direct evidence from FTIR difference spectroscopy in combination with heme propionate 13C labeling.

    PubMed

    Behr, J; Hellwig, P; Mäntele, W; Michel, H

    1998-05-19

    Specific isotope labeling at the carboxyl groups of the four heme propionates of cytochrome c oxidase from Paracoccus denitrificans was used in order to assign signals observed in electrochemically induced redox Fourier transform infrared (FTIR) difference spectra of this enzyme. For this purpose, the hemA gene of the P. denitrificans strain PD1222, coding for 5-aminolevulinate synthase, was deleted by partial replacement with a kanamycin resistance cartridge, resulting in a stable 5-aminolevulinic acid (ALA) auxotrophy. Normal growth of this deficient strain and cytochrome c oxidase yield comparable to that of P. dentrificans wild-type strain PD1222 could be obtained by supplementation with 0.1 mM ALA in the growth medium. Visible spectra and reduced-minus-oxidized FTIR spectra showed that the purified cytochrome c oxidase had spectral characteristics identical to those of the wild-type enzyme. The decrease of a negative signal at 1676 cm-1 in the reduced-minus-oxidized FTIR difference spectra of the 13C-labeled cytochrome c oxidase in comparison to those of the unlabeled protein allowed the assignment of this signal to a COOH vibration mode of at least one of the four heme propionates. Moreover, a negative band at approximately 1570 cm-1 shifted to smaller wavenumbers in the spectra of the 13C-labeled enzyme in comparison to the spectra of the unlabeled enzyme and was thus assigned to contributions from an antisymmetric COO- mode of one or more of the four heme propionates. Additionally, a positive signal at 1538 cm-1 shifted to approximately 1500 cm-1 in the spectra of the isotopically labeled protein and was therefore assigned to at least one antisymmetric COO- mode of the heme propionates. A negative signal at 1390 cm-1, which has been shifted to 1360 cm-1 in the spectra of the 13C-labeled enzyme, is due to a symmetric COO- mode from at least one heme propionate. These results suggest that at least two of the four heme propionates in cytochrome c oxidase

  12. Mycobacterium tuberculosis WhiB3 Responds to Vacuolar pH-induced Changes in Mycothiol Redox Potential to Modulate Phagosomal Maturation and Virulence*

    PubMed Central

    Mehta, Mansi; Rajmani, Raju S.; Singh, Amit

    2016-01-01

    The ability of Mycobacterium tuberculosis to resist intraphagosomal stresses, such as oxygen radicals and low pH, is critical for its persistence. Here, we show that a cytoplasmic redox sensor, WhiB3, and the major M. tuberculosis thiol, mycothiol (MSH), are required to resist acidic stress during infection. WhiB3 regulates the expression of genes involved in lipid anabolism, secretion, and redox metabolism, in response to acidic pH. Furthermore, inactivation of the MSH pathway subverted the expression of whiB3 along with other pH-specific genes in M. tuberculosis. Using a genetic biosensor of mycothiol redox potential (EMSH), we demonstrated that a modest decrease in phagosomal pH is sufficient to generate redox heterogeneity in EMSH of the M. tuberculosis population in a WhiB3-dependent manner. Data indicate that M. tuberculosis needs low pH as a signal to alter cytoplasmic EMSH, which activates WhiB3-mediated gene expression and acid resistance. Importantly, WhiB3 regulates intraphagosomal pH by down-regulating the expression of innate immune genes and blocking phagosomal maturation. We show that this block in phagosomal maturation is in part due to WhiB3-dependent production of polyketide lipids. Consistent with these observations, MtbΔwhiB3 displayed intramacrophage survival defect, which can be rescued bypharmacological inhibition of phagosomal acidification. Last, MtbΔwhiB3 displayed marked attenuation in the lungs of guinea pigs. Altogether, our study revealed an intimate link between vacuolar acidification, redox physiology, and virulence in M. tuberculosis and discovered WhiB3 as crucial mediator of phagosomal maturation arrest and acid resistance in M. tuberculosis. PMID:26637353

  13. Mycobacterium tuberculosis WhiB3 Responds to Vacuolar pH-induced Changes in Mycothiol Redox Potential to Modulate Phagosomal Maturation and Virulence.

    PubMed

    Mehta, Mansi; Rajmani, Raju S; Singh, Amit

    2016-02-05

    The ability of Mycobacterium tuberculosis to resist intraphagosomal stresses, such as oxygen radicals and low pH, is critical for its persistence. Here, we show that a cytoplasmic redox sensor, WhiB3, and the major M. tuberculosis thiol, mycothiol (MSH), are required to resist acidic stress during infection. WhiB3 regulates the expression of genes involved in lipid anabolism, secretion, and redox metabolism, in response to acidic pH. Furthermore, inactivation of the MSH pathway subverted the expression of whiB3 along with other pH-specific genes in M. tuberculosis. Using a genetic biosensor of mycothiol redox potential (EMSH), we demonstrated that a modest decrease in phagosomal pH is sufficient to generate redox heterogeneity in EMSH of the M. tuberculosis population in a WhiB3-dependent manner. Data indicate that M. tuberculosis needs low pH as a signal to alter cytoplasmic EMSH, which activates WhiB3-mediated gene expression and acid resistance. Importantly, WhiB3 regulates intraphagosomal pH by down-regulating the expression of innate immune genes and blocking phagosomal maturation. We show that this block in phagosomal maturation is in part due to WhiB3-dependent production of polyketide lipids. Consistent with these observations, MtbΔwhiB3 displayed intramacrophage survival defect, which can be rescued bypharmacological inhibition of phagosomal acidification. Last, MtbΔwhiB3 displayed marked attenuation in the lungs of guinea pigs. Altogether, our study revealed an intimate link between vacuolar acidification, redox physiology, and virulence in M. tuberculosis and discovered WhiB3 as crucial mediator of phagosomal maturation arrest and acid resistance in M. tuberculosis.

  14. Detailed Vertical and Lateral Delineation of Redox Zones in Contaminant Plumes Using Redox-Sensitive Tapes (RST)

    NASA Astrophysics Data System (ADS)

    Blum, P.; Oeste, F. D.; Melzer, R.; Martus, P.

    2006-12-01

    Innovative redox-sensitive tapes (RST) have been developed for a detailed vertical and lateral delineation of redox zones in contaminated aquifers. The RST have the potential to become an integral part of a data acquisition strategy for monitored natural attenuation (MNA). The tape material, consists of a 2 cm wide synthetic textile coated with reactive manganese dioxide minerals. The RST are submerged into existing monitoring wells for approximately one month. This time period is sufficient to allow for a reaction of the mineral coating with groundwater. The RST are aimed at investigating four different redox-zones in contaminated aquifers: Mn(II)-oxidizing, Mn(IV)-reducing, Fe(III)-reducing and sulfate-reducing. Two RST case studies are presented. The RST investigations on a coal tar contaminated site allowed for a precise lateral and vertical delineation of the contaminant plume using the existing monitoring well network. The RST investigations on a BTEX contaminated site yielded a good correlation of RST data with hydrochemical data at the wells sampled. In the majority of plume wells located 50 m downstream of the source area and beyond, Mn(IV)-reducing environment appeared to be prevailing. Comparing the RST data with hydrochemical data indicated evidence for the transport of transformation products with groundwater flow. The repeated application of the RST facilitated an assessment of the plume dynamics. No significant seasonal variation with respect to the redox zone distribution was observed within the contaminant plume. However, the assessment of the changes in redox conditions over a time period of 2.5 years showed that the iron-reducing zone is shrinking and the sulfate-reducing zone disappeared completely indicating that the contaminant plume might decrease in the near future. Thus, the application of the RST facilitated an assessment of the plume dynamics on a centimeter-scale without the necessity of pumping and treating contaminated groundwater.

  15. Redox conditions in the Late Cretaceous Chalk Sea: the possible use of cerium anomalies as palaeoredox indicators in the Cenomanian and Turonian Chalk of England

    NASA Astrophysics Data System (ADS)

    Jeans, Christopher V.; Wray, David S.; Williams, C. Terry

    2015-09-01

    The cerium anomalies preserved in the Chalk have been investigated as possible palaeoredox indicators of the Late Cretaceous Sea and its sediment. This has been based upon over a hundred new rare earth element analyses of selected samples and grain size fractions from the Chalk. Particular attention has been given to the methodology of differentiating between the cerium anomalies preserved in the bioclastic calcite and those in carbonate-fluorapatite preserved in the acetic acid insoluble residues of chalks. Variations in the cerium anomaly of different particle size fractions of uncemented chalks suggest that fractionation of rare earth elements between the Chalk's seawater and the various organisms that contributed skeletal material to the bioclastic calcite of the Chalk may have occurred. Post-depositional processes of calcite cementation and late diagenetic sulphidisation have had no apparent effect on the cerium anomaly of the acetic acid insoluble residues. The cerium anomalies associated with the acetic acid insoluble residues from (1) an alternating sequence of chalks and marls from Ballard Cliff (Dorset, UK) typical of Milankovitch cyclicity show a marked diagenetic pattern, whereas those from (2) non-volcanic and volcanic marls display a pattern that is best explained by the variations in the availability of phosphorus and the timing of argillisation of volcanic glass during diagenesis. The general conclusion is drawn that the cerium anomalies preserved in the Chalk can provide an insight into the changing palaeoredox conditions in the Late Cretaceous Sea as well as in the pore fluids of its sediments.

  16. Assessing the Practical Equivalence of Conversions when Measurement Conditions Change

    ERIC Educational Resources Information Center

    Liu, Jinghua; Dorans, Neil J.

    2012-01-01

    At times, the same set of test questions is administered under different measurement conditions that might affect the psychometric properties of the test scores enough to warrant different score conversions for the different conditions. We propose a procedure for assessing the practical equivalence of conversions developed for the same set of test…

  17. Ontogenetic Change in the Auditory Conditioned Stimulus Pathway for Eyeblink Conditioning

    ERIC Educational Resources Information Center

    Freeman, John H.; Campolattaro, Matthew M.

    2008-01-01

    Two experiments examined the neural mechanisms underlying the ontogenetic emergence of auditory eyeblink conditioning. Previous studies found that the medial auditory thalamus is necessary for eyeblink conditioning with an auditory conditioned stimulus (CS) in adult rats. In experiment 1, stimulation of the medial auditory thalamus was used as a…

  18. Oxidative shift in tissue redox potential increases beat-to-beat variability of action potential duration.

    PubMed

    Kistamás, Kornél; Hegyi, Bence; Váczi, Krisztina; Horváth, Balázs; Bányász, Tamás; Magyar, János; Szentandrássy, Norbert; Nánási, Péter P

    2015-07-01

    Profound changes in tissue redox potential occur in the heart under conditions of oxidative stress frequently associated with cardiac arrhythmias. Since beat-to-beat variability (short term variability, SV) of action potential duration (APD) is a good indicator of arrhythmia incidence, the aim of this work was to study the influence of redox changes on SV in isolated canine ventricular cardiomyocytes using a conventional microelectrode technique. The redox potential was shifted toward a reduced state using a reductive cocktail (containing dithiothreitol, glutathione, and ascorbic acid) while oxidative changes were initiated by superfusion with H2O2. Redox effects were evaluated as changes in "relative SV" determined by comparing SV changes with the concomitant APD changes. Exposure of myocytes to the reductive cocktail decreased SV significantly without any detectable effect on APD. Application of H2O2 increased both SV and APD, but the enhancement of SV was the greater, so relative SV increased. Longer exposure to H2O2 resulted in the development of early afterdepolarizations accompanied by tremendously increased SV. Pretreatment with the reductive cocktail prevented both elevation in relative SV and the development of afterdepolarizations. The results suggest that the increased beat-to-beat variability during an oxidative stress contributes to the generation of cardiac arrhythmias.

  19. A Changing Federalism: The Condition of the States.

    ERIC Educational Resources Information Center

    Adams, E. Kathleen

    A majority of the 50 states are currently experiencing budget problems as a result of recent changes in the fiscal roles of federal, state, and local governments. Four major factors are responsible for the recent deterioration of state budgets: (1) reductions in federal aid to states and localities, (2) changes in the federal corporate and…

  20. MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS

    SciTech Connect

    Beyenal, Haluk; McLEan, Jeff; Majors, Paul; Fredrickson, Jim

    2013-11-14

    The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in the subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.

  1. Multicriteria adaptation of robotic groups to dynamically changing conditions

    NASA Astrophysics Data System (ADS)

    Misyurin, S. Yu; Nelyubin, A. P.; Ivlev, V. I.

    2017-01-01

    A new approach is proposed to design complex robotic systems composed of many robots that can operate under different conditions and perform various tasks. Bio-inspired ideas of adaptation of robotic groups are discussed.

  2. Changes of the corrosion potential of iron in stagnation and flow conditions and their relationship with metal release.

    PubMed

    Fabbricino, Massimiliano; Korshin, Gregory V

    2014-10-01

    This study examined the behavior of corrosion potential (Ecorr) of iron exposed to drinking water during episodes of stagnation and flow. These measurements showed that during stagnation episodes, Ecorr values decrease prominently and consistently. This decrease is initially rapid but it becomes slower as the stagnation time increases. During flow episodes, the Ecorr values increase and reach a quasi-steady state. Experiments with varying concentrations of dissolved oxygen showed that the decrease of Ecorr values characteristic for stagnation is likely to be associated with the consumption of dissolved oxygen by the exposed metal. The corrosion potential of iron and its changes during stagnation were sensitive to the concentrations of sulfate and chloride ions. Measurements of iron release showed that both the absolute values of Ecorr measured prior to or after stagnation episodes were well correlated with the logarithms of concentrations of total iron. The slope of this dependence showed that the observed correlations between Ecorr values and Fe concentrations corresponded to the coupling between the oxidant consumption and changes of Fe redox status. These results demonstrate that in situ Ecorr measurements can be a sensitive method with which to ascertain effects of hydrodynamic conditions and short-term variations of water chemistry on metal release and corrosion in drinking water. This approach is valuable practically because Ecorr measurements are precise, can be carried out in situ with any desired time resolution, do not affect the state of exposed surface in any extent and can be carried out with readily available equipment.

  3. Redox Indicator Mice Stably Expressing Genetically Encoded Neuronal roGFP: Versatile Tools to Decipher Subcellular Redox Dynamics in Neuropathophysiology

    PubMed Central

    Wagener, Kerstin C.; Kolbrink, Benedikt; Dietrich, Katharina; Kizina, Kathrin M.; Terwitte, Lukas S.; Kempkes, Belinda; Bao, Guobin

    2016-01-01

    Abstract Aims: Reactive oxygen species (ROS) and downstream redox alterations not only mediate physiological signaling but also neuropathology. For long, ROS/redox imaging was hampered by a lack of reliable probes. Genetically encoded redox sensors overcame this gap and revolutionized (sub)cellular redox imaging. Yet, the successful delivery of sensor-coding DNA, which demands transfection/transduction of cultured preparations or stereotaxic microinjections of each subject, remains challenging. By generating transgenic mice, we aimed to overcome limiting cultured preparations, circumvent surgical interventions, and to extend effectively redox imaging to complex and adult preparations. Results: Our redox indicator mice widely express Thy1-driven roGFP1 (reduction–oxidation-sensitive green fluorescent protein 1) in neuronal cytosol or mitochondria. Negative phenotypic effects of roGFP1 were excluded and its proper targeting and functionality confirmed. Redox mapping by ratiometric wide-field imaging reveals most oxidizing conditions in CA3 neurons. Furthermore, mitochondria are more oxidized than cytosol. Cytosolic and mitochondrial roGFP1s reliably report cell endogenous redox dynamics upon metabolic challenge or stimulation. Fluorescence lifetime imaging yields stable, but marginal, response ranges. We therefore developed automated excitation ratiometric 2-photon imaging. It offers superior sensitivity, spatial resolution, and response dynamics. Innovation and Conclusion: Redox indicator mice enable quantitative analyses of subcellular redox dynamics in a multitude of preparations and at all postnatal stages. This will uncover cell- and compartment-specific cerebral redox signals and their defined alterations during development, maturation, and aging. Cross-breeding with other disease models will reveal molecular details on compartmental redox homeostasis in neuropathology. Combined with ratiometric 2-photon imaging, this will foster our mechanistic understanding

  4. Dynamic Redox Regulation of IL-4 Signaling

    PubMed Central

    Dwivedi, Gaurav; Gran, Margaret A.; Bagchi, Pritha; Kemp, Melissa L.

    2015-01-01

    Quantifying the magnitude and dynamics of protein oxidation during cell signaling is technically challenging. Computational modeling provides tractable, quantitative methods to test hypotheses of redox mechanisms that may be simultaneously operative during signal transduction. The interleukin-4 (IL-4) pathway, which has previously been reported to induce reactive oxygen species and oxidation of PTP1B, may be controlled by several other putative mechanisms of redox regulation; widespread proteomic thiol oxidation observed via 2D redox differential gel electrophoresis upon IL-4 treatment suggests more than one redox-sensitive protein implicated in this pathway. Through computational modeling and a model selection strategy that relied on characteristic STAT6 phosphorylation dynamics of IL-4 signaling, we identified reversible protein tyrosine phosphatase (PTP) oxidation as the primary redox regulatory mechanism in the pathway. A systems-level model of IL-4 signaling was developed that integrates synchronous pan-PTP oxidation with ROS-independent mechanisms. The model quantitatively predicts the dynamics of IL-4 signaling over a broad range of new redox conditions, offers novel hypotheses about regulation of JAK/STAT signaling, and provides a framework for interrogating putative mechanisms involving receptor-initiated oxidation. PMID:26562652

  5. Marine water quality under climate change conditions/scenarios

    NASA Astrophysics Data System (ADS)

    Rizzi, Jonathan; Torresan, Silvia; Critto, Andrea; Zabeo, Alex; Brigolin, Daniele; Carniel, Sandro; Pastres, Roberto; Marcomini, Antonio

    2016-04-01

    The increase of sea temperature and the changes in marine currents are generating impacts on coastal waters such as changes in water biogeochemical and physical parameters (e.g. primary production, pH, salinity) leading to progressive degradation of the marine environment. With the main aim of analysing the potential impacts of climate change on coastal water quality, a Regional Risk Assessment (RRA) methodology was developed and applied to coastal marine waters of the North Adriatic (i.e. coastal water bodies of the Veneto and Friuli Venezia Giulia regions, Italy). RRA integrates the outputs of regional models providing information on macronutrients (i.e. dissolved inorganic nitrogen e reactive phosphorus), dissolved oxygen, pH, salinity and temperature, etc., under future climate change scenarios with site-specific environmental and socio-economic indicators (e.g. biotic index, presence and extension of seagrasses, presence of aquaculture). The presented approach uses Geographic Information Systems to manage, analyse, and visualize data and employs Multi-Criteria Decision Analysis for the integration of stakeholders preferences and experts judgments into the evaluation process. RRA outputs are hazard, exposure, vulnerability, risk and damage maps useful for the identification and prioritization of hot-spot areas and vulnerable targets in the considered region. Therefore, the main aim of this contribution is to apply the RRA methodology to integrate, visualize, and rank according to spatial distribution, physical and chemical data concerning the coastal waters of the North Adriatic Sea in order to predict possible changes of the actual water quality.

  6. Redox Species of Redox Flow Batteries: A Review.

    PubMed

    Pan, Feng; Wang, Qing

    2015-11-18

    Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

  7. The Necessary and Sufficient Conditions of Therapeutic Personality Change.

    ERIC Educational Resources Information Center

    Rogers, Carl R.

    1992-01-01

    Presents reprint of original work published in 1957 in "Journal of Consulting Psychology" in which Carl Rogers takes one small segment of theory of psychotherapy, of personality, and of interpersonal relationships; spells it out more completely; and explores its meaning and usefulness. Rogers examines psychological conditions necessary and…

  8. Changes in osteoblastic activity due to simulated weightless conditions

    NASA Technical Reports Server (NTRS)

    Doty, S. B.; Morey-Holton, E. R.

    1982-01-01

    Using histochemistry and electron microscopy, the reduced bone formation which occurs in the hypokinetic, orthostatically treated adult rat has been studied. The two major changes noted occurred in the osteoblast population, indicated by a reduced alkaline phosphatase activity and reduced numbers of gap junctions between cells. These results were most noticeable in the periosteum and endosteum of the long bones. Changes in osteoblasts lining the surface of trabecular bone were not as evident. These results indicate that the cells lining the surfaces of weight bearing bones are most affected by hypokinesia and this reduction in cellular activity may be a mechanically induced effect.

  9. Pettaquamscutt Cove Salt Marsh: Environmental Conditions and Historical Ecological Change

    EPA Science Inventory

    Using historic air photos and U.S. Coast Survey maps, historic vegetation changes were identified. Using surveys of vegetation and elevation, we measure elevation of Narrow River salt marshes, and compare it with other salt marshes in Rhode Island and neighboring states. Water ...

  10. Living Conditions, Ecology and Social Changes in the Indian Context.

    ERIC Educational Resources Information Center

    Rao, D. Subba

    1984-01-01

    Major problems faced in India's development are discussed, including rapid industrialization and urbanization and needs for ecological protection as well as food and industry, literacy, and rapid social change in a multilingual and multireligious society. The roles of higher education and international cooperation are also examined. (MSE)

  11. Biological Redox Cycling Of Iron In Nontronite And Its Potential Application In Nitrate Removal

    SciTech Connect

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K.; Zeng, Qiang; Edelmann, Richard E.; Pentrak, Martin; Agrawal, Abinash

    2015-05-05

    Redox cycling of structural Fe in phyllosilicates provides a potential method to remediate nitrate contamination in natural environment. Past research has only studied chemical redox cycles or a single biologically mediated redox cycle of Fe in phyllosilicates. The objective of this research was to study three microbially driven redox cycles of Fe in one phyllosilicate, nontronite (NAu-2). During the reduction phase structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacteria Shewanella putrefaciens CN32 as mediator in bicarbonate-buffered and PIPES-buffered media. During the oxidation phase, biogenic Fe(II) served an electron donor, nitrate as electron acceptor, and nitrate-dependent Fe(II)-oxidizing bacteria Pseudogulbenkiania sp. strain 2002 as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo 3 redox cycles without significant reductive or oxidative dissolution. X-ray diffraction and scanning and transmission electron microscopy revealed that NAu-2 was the dominant residual mineral throughout the 3 redox cycles with some dissolution textures but no significant secondary mineralization. Mössbauer spectroscopy revealed that Fe(II) in bio-reduced samples likely occurred in two distinct environments, at edges and the interior of the NAu-2 structure. Nitrate was completely reduced to nitrogen gas under both buffer conditions and this extent and rate did not change with Fe redox cycles. Mössbauer spectroscopy further revealed that nitrate reduction was coupled to predominant/preferred oxidation of edge Fe(II). These results suggest that structural Fe in phyllosilicates may represent a renewable source to continuously remove nitrate in natural environments.

  12. Redox-sensitive probes for the measurement of redox chemistries within phagosomes of macrophages and dendritic cells☆

    PubMed Central

    Balce, Dale R.; Yates, Robin M.

    2013-01-01

    There is currently much interest in factors that affect redox chemistries within phagosomes of macrophages and dendritic cells. In addition to the antimicrobial role of reactive oxygen species generation within phagosomes, accumulating evidence suggests that phagosomal redox chemistries influence other phagosomal functions such as macromolecular degradation and antigen processing. Whilst the redox chemistries within many sub-cellular compartments are being heavily scrutinized with the increasing use of fluorescent probe technologies, there is a paucity of tools to assess redox conditions within phagosomes. Hence the systems that control redox homeostasis in these unique environments remain poorly defined. This review highlights current redox-sensitive probes that can measure oxidative or reductive activity in phagosomes and discusses their suitability and limitations of use. Probes that are easily targeted to the phagosome by using established approaches are emphasized. PMID:24191242

  13. Intracellular Redox Compartmentation and ROS-Related Communication in Regulation and Signaling1[OPEN

    PubMed Central

    2016-01-01

    Recent years have witnessed enormous progress in understanding redox signaling related to reactive oxygen species (ROS) in plants. The consensus view is that such signaling is intrinsic to many developmental processes and responses to the environment. ROS-related redox signaling is tightly wedded to compartmentation. Because membranes function as barriers, highly redox-active powerhouses such as chloroplasts, peroxisomes, and mitochondria may elicit specific signaling responses. However, transporter functions allow membranes also to act as bridges between compartments, and so regulated capacity to transmit redox changes across membranes influences the outcome of triggers produced at different locations. As well as ROS and other oxidizing species, antioxidants are key players that determine the extent of ROS accumulation at different sites and that may themselves act as signal transmitters. Like ROS, antioxidants can be transported across membranes. In addition, the intracellular distribution of antioxidative enzymes may be modulated to regulate or facilitate redox signaling appropriate to the conditions. Finally, there is substantial plasticity in organellar shape, with extensions such as stromules, peroxules, and matrixules playing potentially crucial roles in organelle-organelle communication. We provide an overview of the advances in subcellular compartmentation, identifying the gaps in our knowledge and discussing future developments in the area. PMID:27208308

  14. Biological redox cycling of iron in nontronite and its potential application in nitrate removal.

    PubMed

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K; Zeng, Qiang; Edelmann, Richard E; Pentrák, Martin; Agrawal, Abinash

    2015-05-05

    Biological redox cycling of structural Fe in phyllosilicates is an important but poorly understood process. The objective of this research was to study microbially mediated redox cycles of Fe in nontronite (NAu-2). During the reduction phase, structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens CN32 as mediator in bicarbonate- and PIPES-buffered media. During the oxidation phase, biogenic Fe(II) served as electron donor and nitrate as electron acceptor. Nitrate-dependent Fe(II)-oxidizing bacterium Pseudogulbenkiania sp. strain 2002 was added as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo three redox cycles without significant dissolution. Fe(II) in bioreduced samples occurred in two distinct environments, at edges and in the interior of the NAu-2 structure. Nitrate reduction to nitrogen gas was coupled with oxidation of edge-Fe(II) and part of interior-Fe(II) under both buffer conditions, and its extent and rate did not change with Fe redox cycles. These results suggest that biological redox cycling of structural Fe in phyllosilicates is a reversible process and has important implications for biogeochemical cycles of carbon, nitrogen, and other nutrients in natural environments.

  15. Interaction between heavy metals and thiol-linked redox reactions in germination.

    PubMed

    Smiri, M; Chaoui, A; Ferjani, E E

    2010-09-15

    Thioredoxin (TRX) proteins perform important biological functions in cells by changing the redox state of proteins via dithiol disulfide exchange. Several systems are able to control the activity, stability, and correct folding of enzymes through dithiol/disulfide isomerization reactions including the enzyme protein disulfide-isomerase, the glutathione-dependent glutaredoxin system, and the thioredoxin systems. Plants have devised sophisticated mechanisms to cope with biotic and abiotic stresses imposed by their environment. Among these mechanisms, those collectively referred to as redox reactions induced by endogenous systems. This is of agronomical importance since a better knowledge of the involved mechanisms can offer novel means for crop protection. In the plant life cycle, the seed and seedling stages are key developmental stages conditioning the final yield of crops. Both are very sensitive to heavy metal stress. Plant redox reactions are principally studied on adult plant organs and there is only very scarce informations about the onset of redox regulation at the level of seed germination. In the here presented study, we discussed the importance of redox proteins in plant cell metabolism and defence. Special focus is given to TRX, which are involved in detoxification of ROS and also to their targets.

  16. Redox control of teratogenesis.

    PubMed

    Hansen, Jason M; Harris, Craig

    2013-01-01

    A number of human teratogens elicit their deleterious effects through mechanisms involving the generation of reactive oxygen species (ROS) and oxidative stress. However, classic definitions of oxidative stress do not fully coincide with basic fundamental principles of teratology. Newer definitions of oxidative stress focus on the targeted redox modification of cysteine/thiol functional groups found in the regulatory domains of critical signaling pathway proteins, suggesting that the targeted disruption of signaling through specific redox couples may account for the specificity of teratogen-induced malformations which previously could not be rationalized. Here, we review examples of teratogens that induce ROS and oxidative injury, describe oxidative stress-related teratogenic mechanisms, and provide rationale for developmental periods of sensitivity and species susceptibility. Understanding how chemicals disrupt redox status, induce oxidative stress leading to dysmorphogenesis becomes important to identify potential teratogens and develop therapeutic interventions for attenuation of harmful chemical effects in utero following exposure.

  17. Effects of Changing Atmospheric Conditions on Wind Turbine Performance (Poster)

    SciTech Connect

    Clifton, A.

    2012-12-01

    Multi-megawatt, utility-scale wind turbines operate in turbulent and dynamic winds that impact turbine performance in ways that are gradually becoming better understood. This poster presents a study made using a turbulent flow field simulator (TurbSim) and a Turbine aeroelastic simulator (FAST) of the response of a generic 1.5 MW wind turbine to changing inflow. The turbine power output is found to be most sensitive to wind speed and turbulence intensity, but the relationship depends on the wind speed with respect to the turbine's rated wind speed. Shear is found to be poorly correlated to power. A machine learning method called 'regression trees' is used to create a simple model of turbine performance that could be used as part of the wind resource assessment process. This study has used simple flow fields and should be extended to more complex flows, and validated with field observations.

  18. Synthesis and atomic level in situ redox characterization in ceria and ceria zirconia

    NASA Astrophysics Data System (ADS)

    Wang, Ruigang

    2007-12-01

    Nanocrystalline ceria-based oxides are widely used in automotive three-way catalytic converters to reduce the emissions of carbon monoxide, nitrogen oxides, and unburned hydrocarbons. The primary function of ceria-based oxides in the catalytic process is to adjust the local oxygen partial pressure and maintain an air-to-fuel ratio near the stoichiometric value (˜14.5) required for the optimal catalyst performance for carbon monoxide, hydrocarbon oxidation, and nitrogen oxides reduction. In this dissertation, a study of the relationship between the nanoscale structure, chemistry, and the redox behavior on high surface area ceria and ceria zirconia is presented. Precipitation and spray freezing methods were used to synthesize nanocrystalline ceria and ceria zirconia solid solution powders respectively. The effect of thermal treatments in oxidizing and reducing atmospheres on the reducibility of the materials has been systematically investigated. X-ray diffraction and thermogravimetric analysis were used to characterize the average structure and reducibility. In situ environmental transmission electron microscope was exploited to visualize the dynamic changes during redox processes at the atomic level. This resulted in the identification of the nanoscale structure and chemistry for the most active nanoparticles in these oxides. The correlation between ex situ macroscopic redox properties and in situ redox behavior of individual nanoparticles is demonstrated. The addition of zirconia to ceria clearly enhances the reducibility and thermal stability of ceria. A fundamental difference between ceria and ceria zirconia during in situ redox processes is related to oxygen vacancy ordering. Ceria showed oxygen vacancy ordering during reduction, whereas ceria zirconia did not. It is suggested that the absence of oxygen vacancy ordering might be a fundamental factor for improved redox properties of ceria zirconia compared with pure ceria. The 50% ceria-50% zirconia solid

  19. Collaborative Research for Water Resource Management under Climate Change Conditions

    NASA Astrophysics Data System (ADS)

    Brundiers, K.; Garfin, G. M.; Gober, P.; Basile, G.; Bark, R. H.

    2010-12-01

    We present an ongoing project to co-produce science and policy called Collaborative Planning for Climate Change: An Integrated Approach to Water-Planning, Climate Downscaling, and Robust Decision-Making. The project responds to motivations related to dealing with sustainability challenges in research and practice: (a) state and municipal water managers seek research that addresses their planning needs; (b) the scientific literature and funding agencies call for more meaningful engagement between science and policy communities, in ways that address user needs, while advancing basic research; and (c) empirical research contributes to methods for the design and implementation of collaborative projects. To understand how climate change might impact water resources and management in the Southwest US, our project convenes local, state, and federal water management practitioners with climate-, hydrology-, policy-, and decision scientists. Three areas of research inform this collaboration: (a) the role of paleo-hydrology in water resources scenario construction; (b) the types of uncertainties that impact decision-making beyond climate and modeling uncertainty; and (c) basin-scale statistical and dynamical downscaling of climate models to generate hydrologic projections for regional water resources planning. The project engages all participants in the research process, from research design to workshops that build capacity for understanding data generation and sources of uncertainty to the discussion of water management decision contexts. A team of “science-practice translators” facilitates the collaboration between academic and professional communities. In this presentation we contextualize the challenges and opportunities of use-inspired science-policy research collaborations by contrasting the initial project design with the process of implementation. We draw from two sources to derive lessons learned: literature on collaborative research, and evaluations provided by

  20. Formation of CaS-MgS in Enstatite Chondrites and Achondrites as a Function of Redox Conditions and Temperature: Constraints on Their Evolution in a Planetesimal and in a Proto-planet

    NASA Technical Reports Server (NTRS)

    Malavergne, Valerie; Berthet, S.; Righter, K.

    2007-01-01

    The cubic monosulfide series with the general formula (Mg,Mn,Ca,Fe)S are common phases in the enstatite chondrite (EH) and aubrite meteorite groups. In the Earth s mantle, sulfide minerals are associated with peridotites and eclogites. Study of these sulfide mineral systems is of interest for the mineralogy and petrology of planetary mantles. For example, MgS could occur in the primitive Earth and because it remains a low density phase compared to metal, would stay a separate phase during the core formation process, and thus not segregate to the core. (Mg,Ca,Mn,Fe)S sulphides might thus be important phases even in planetary differentiation processes. The importance of such minerals, and their formation, composition and textural relationships for understanding the genesis of enstatite chondrites and aubrites, has long been recognized. The main objective of this experimental study is to understand the formation and evolution of (Mg,Ca,Mn,Fe)S sulphides, particularly the oldhamite CaS and ningerite MgS, with pressure, temperature but also with redox conditions because EH and aubrites are meteorites that formed under reduced conditions. Piston-cylinder (PC) and multi-anvil (MA) experiments at high pressure (HP) and high temperature (HT) have been performed in order to simulate the evolution of these phases in a small planetary body from a planetesimal (with PC experiments) up to a proto-planet (with MA experiments).

  1. The Measurement of Reversible Redox Dependent Post-translational Modifications and Their Regulation of Mitochondrial and Skeletal Muscle Function.

    PubMed

    Kramer, Philip A; Duan, Jicheng; Qian, Wei-Jun; Marcinek, David J

    2015-01-01

    Mitochondrial oxidative stress is a common feature of skeletal myopathies across multiple conditions; however, the mechanism by which it contributes to skeletal muscle dysfunction remains controversial. Oxidative damage to proteins, lipids, and DNA has received the most attention, yet an important role for reversible redox post-translational modifications (PTMs) in pathophysiology is emerging. The possibility that these PTMs can exert dynamic control of muscle function implicates them as a mechanism contributing to skeletal muscle dysfunction in chronic disease. Herein, we discuss the significance of thiol-based redox dependent modifications to mitochondrial, myofibrillar, and excitation-contraction (EC) coupling proteins with an emphasis on how these changes could alter skeletal muscle performance under chronically stressed conditions. A major barrier to a better mechanistic understanding of the role of reversible redox PTMs in muscle function is the technical challenges associated with accurately measuring the changes of site-specific redox PTMs. Here we will critically review current approaches with an emphasis on sample preparation artifacts, quantitation, and specificity. Despite these challenges, the ability to accurately quantify reversible redox PTMs is critical to understanding the mechanisms by which mitochondrial oxidative stress contributes to skeletal muscle dysfunction in chronic diseases.

  2. The Measurement of Reversible Redox Dependent Post-translational Modifications and Their Regulation of Mitochondrial and Skeletal Muscle Function

    SciTech Connect

    Kramer, Philip A.; Duan, Jicheng; Qian, Wei-Jun; Marcinek, David J.

    2015-11-25

    Mitochondrial oxidative stress is a common feature of skeletal myopathies across multiple conditions; however, the mechanism by which it contributes to skeletal muscle dysfunction remains controversial. Oxidative damage to proteins, lipids, and DNA has received the most attention, yet an important role for reversible redox post-translational modifications (PTMs) in pathophysiology is emerging. The possibility that these PTMs can exert dynamic control of muscle function implicates them as a mechanism contributing to skeletal muscle dysfunction in chronic disease. Herein, we discuss the significance of thiol-based redox dependent modifications to mitochondrial, myofibrillar and excitation-contraction (EC) coupling proteins with an emphasis on how these changes could alter skeletal muscle performance under chronically stressed conditions. A major barrier to a better mechanistic understanding of the role of reversible redox PTMs in muscle function is the technical challenges associated with accurately measuring the changes of site-specific redox PTMs. Here we will critically review current approaches with an emphasis on sample preparation artifacts, quantitation, and specificity. Despite these challenges, the ability to accurately quantify reversible redox PTMs is critical to understanding the mechanisms by which mitochondrial oxidative stress contributes to skeletal muscle dysfunction in chronic diseases.

  3. The Measurement of Reversible Redox Dependent Post-translational Modifications and Their Regulation of Mitochondrial and Skeletal Muscle Function

    PubMed Central

    Kramer, Philip A.; Duan, Jicheng; Qian, Wei-Jun; Marcinek, David J.

    2015-01-01

    Mitochondrial oxidative stress is a common feature of skeletal myopathies across multiple conditions; however, the mechanism by which it contributes to skeletal muscle dysfunction remains controversial. Oxidative damage to proteins, lipids, and DNA has received the most attention, yet an important role for reversible redox post-translational modifications (PTMs) in pathophysiology is emerging. The possibility that these PTMs can exert dynamic control of muscle function implicates them as a mechanism contributing to skeletal muscle dysfunction in chronic disease. Herein, we discuss the significance of thiol-based redox dependent modifications to mitochondrial, myofibrillar, and excitation-contraction (EC) coupling proteins with an emphasis on how these changes could alter skeletal muscle performance under chronically stressed conditions. A major barrier to a better mechanistic understanding of the role of reversible redox PTMs in muscle function is the technical challenges associated with accurately measuring the changes of site-specific redox PTMs. Here we will critically review current approaches with an emphasis on sample preparation artifacts, quantitation, and specificity. Despite these challenges, the ability to accurately quantify reversible redox PTMs is critical to understanding the mechanisms by which mitochondrial oxidative stress contributes to skeletal muscle dysfunction in chronic diseases. PMID:26635632

  4. Ultrastructural morphologic changes in mycobacterial biofilm in different extreme condition.

    PubMed

    Kumar, Virendra; Sachan, Tarun Kumar; Sharma, Pragya; Rawat, Krishna Dutta

    2015-02-01

    The aim of this study was to investigate the morphologic and ultrastructural features of biofilms of slow and fast-growing mycobacteria in different stress conditions, presence and absence of oleic acid albumin dextrose catalase (OADC) enrichment and at different temperatures: 30, 37 and 42 °C. Four hundred mycobacterial isolates were taken. The biomass of each biofilm was quantified using a modified microtiter plate assay method. Isolates were divided into those that formed fully established biofilms, moderately attached biofilms and weakly adherent biofilms by comparison with a known biofilm-forming strain. The large quantity of biofilm was produced by Mycobacterium smegmatis at temperature 37 and 42 °C as compared to 30 °C. Mycobacterium fortuitum and M. avium developed large amount of biofilm at 30 °C as compared to 37 and 42 °C. Mycobacterium tuberculosis developed strong biofilm at 37 °C and no biofilm at 30 and 42 °C in Sauton's media. The selected non-tuberculous mycobacteria and H37Rv developed strong biofilm in the presence of OADC enrichment in Sauton's medium. Microscopic examination of biofilms by scanning electron microscopy revealed that poorly adherent biofilm formers failed to colonize the entire surface of the microtiter well. While moderately adherent biofilm formers grew in uniform monolayers but failed to develop a mature three-dimensional structure. SEM analysis of an isolate representative of the group formed fully established biofilms with a textured, multi-layered, three-dimensional structure.

  5. Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations

    USGS Publications Warehouse

    Hohn, R.; Isenbeck-Schroter, M.; Kent, D.B.; Davis, J.A.; Jakobsen, R.; Jann, S.; Niedan, V.; Scholz, C.; Stadler, S.; Tretner, A.

    2006-01-01

    To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7????M) and bromide (1.6??mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of bromide (Br-), As(V), and As(III) as well as additional parameters characterizing the geochemical conditions was observed at various locations downstream of the injection well over a period of 104??days. After a short lag period, nitrate and dissolved oxygen from the injectate oxidized ferrous iron and As(V) became bound to the freshly formed hydrous iron oxides. Approximately one week after terminating the injection, anoxic conditions had been reestablished and increases in As(III) concentrations were observed within 1??m of the injection. During the observation period, As(III) and As(V) were transported to a distance of 4.5??m downgradient indicating significant retardation by sorption processes for both species. Sediment assays as well as elevated concentrations of hydrogen reflected the presence of As(V) reducing microorganisms. Thus, microbial As(V) reduction was thought to be one major process driving the release of As(III) during the tracer test in the Cape Cod aquifer. ?? 2006 Elsevier B.V. All rights reserved.

  6. Changes in intracellular and apoplastic peroxidase activity, ascorbate redox status, and root elongation induced by enhanced ascorbate content in Allium cepa L.

    PubMed

    Córdoba-Pedregosa, María del Carmen; Villalba, José Manuel; Córdoba, Francisco; González-Reyes, José Antonio

    2005-02-01

    Onions (Allium cepa L.) treated with external ascorbic acid or with the immediate precursor of its synthesis L-galactono-gamma-lactone show a stimulated elongation rate of the roots and an increase in the number of new radicles appearing at the bulb base. Treatment with both molecules resulted in an enhanced accumulation of ascorbate and dehydroascorbate along the root axis, but the distribution of these redox forms was not uniform along the root, as detected in intracellular (symplastic) and extracellular (apoplastic) compartments. Thus, those radicular zones metabolically more active, such as the meristem and the elongation zone, accumulated the highest amount of both redox forms of ascorbate. On the other hand, ascorbate and L-galactono-gamma-lactone also stimulated cytosolic glucose-6-phosphate dehydrogenase activity and inhibited peroxidase activity as deduced from in vivo and in vitro experiments. Differences were also found when comparing apoplastic and symplastic activities. These results are compatible with the idea of an ascorbate-mediated stimulation of root growth by inhibiting cell wall stiffening and increasing root metabolism.

  7. Evening and morning peroxiredoxin-2 redox/oligomeric state changes in obstructive sleep apnea red blood cells: Correlation with polysomnographic and metabolic parameters.

    PubMed

    Feliciano, Amélia; Vaz, Fátima; Torres, Vukosava M; Valentim-Coelho, Cristina; Silva, Rita; Prosinecki, Vesna; Alexandre, Bruno M; Carvalho, Ana S; Matthiesen, Rune; Malhotra, Atul; Pinto, Paula; Bárbara, Cristina; Penque, Deborah

    2017-02-01

    We have examined the effects of Obstructive Sleep Apnea (OSA) on red blood cell (RBC) proteome variation at evening/morning day time to uncover new insights into OSA-induced RBC dysfunction that may lead to OSA manifestations. Dysregulated proteins mainly fall in the group of catalytic enzymes, stress response and redox regulators such as peroxiredoxin 2 (PRDX2). Validation assays confirmed that at morning the monomeric/dimeric forms of PRDX2 were more overoxidized in OSA RBC compared to evening samples. Six month of positive airway pressure (PAP) treatment decreased this overoxidation and generated multimeric overoxidized forms associated with chaperone/transduction signaling activity of PRDX2. Morning levels of overoxidized PRDX2 correlated with polysomnographic (PSG)-arousal index and metabolic parameters whereas the evening level of disulfide-linked dimer (associated with peroxidase activity of PRDX2) correlated with PSG parameters. After treatment, morning overoxidized multimer of PRDX2 negatively correlated with fasting glucose and dopamine levels. Overall, these data point toward severe oxidative stress and altered antioxidant homeostasis in OSA RBC occurring mainly at morning time but with consequences till evening. The beneficial effect of PAP involves modulation of the redox/oligomeric state of PRDX2, whose mechanism and associated chaperone/transduction signaling functions deserves further investigation. RBC PRDX2 is a promising candidate biomarker for OSA severity and treatment monitoring, warranting further investigation and validation.

  8. Redox-based epigenetic status in drug addiction: a potential contributor to gene priming and a mechanistic rationale for metabolic intervention.

    PubMed

    Trivedi, Malav S; Deth, Richard

    2014-01-01

    Alcohol and other drugs of abuse, including psychostimulants and opioids, can induce epigenetic changes: a contributing factor for drug addiction, tolerance, and associated withdrawal symptoms. DNA methylation is a major epigenetic mechanism and it is one of more than 200 methylation reactions supported by methyl donor S-adenosylmethionine (SAM). Levels of SAM are controlled by cellular redox status via the folate and vitamin B12-dependent enzyme methionine synthase (MS). For example, under oxidative conditions MS is inhibited, diverting its substrate homocysteine (HCY) to the trans sulfuration pathway. Alcohol, dopamine, and morphine, can alter intracellular levels of glutathione (GSH)-based cellular redox status, subsequently affecting SAM levels and DNA methylation status. Here, existing evidence is presented in a coherent manner to propose a novel hypothesis implicating the involvement of redox-based epigenetic changes in drug addiction. Further, we discuss how a "gene priming" phenomenon can contribute to the maintenance of redox and methylation status homeostasis under various stimuli including drugs of abuse. Additionally, a new mechanistic rationale for the use of metabolic interventions/redox-replenishers as symptomatic treatment of alcohol and other drug addiction and associated withdrawal symptoms is also provided. Hence, the current review article strengthens the hypothesis that neuronal metabolism has a critical bidirectional coupling with epigenetic changes in drug addiction exemplified by the link between redox-based metabolic changes and resultant epigenetic consequences under the effect of drugs of abuse.

  9. Seasonality of temperatures and redox zonations during bank filtration - A modeling approach

    NASA Astrophysics Data System (ADS)

    Henzler, Aline F.; Greskowiak, Janek; Massmann, Gudrun

    2016-04-01

    Bank filtration (BF) is a common technique for supplying drinking water, using the ability of the infiltration zone and aquifer passage to attenuate or degrade undesired substances that infiltrate from surface waters to groundwater abstraction wells. Temporal and spatial changes of temperatures and redox conditions are often the controlling factors for the fate and behavior of micropollutants during subsurface passage and consequently for the extracted raw water quality. A 2-dimensional cross-sectional heat transport and multi-species reactive transport model was set up to simulate the seasonally varying temperatures and redox conditions on the infiltration path at a bank filtration site in Berlin, Germany. The calibrated model was able to capture the observed variations in O2 and NO3- when considering temperature dependence of the redox reaction kinetics. The observed Mn2+- and Fe2+-concentrations were not well replicated by the model, presumably due to mineral reactions that were not accounted for in the simulations. SO42- was found to behave conservative, i.e., the observed concentration could be well simulated without any reactions. The simulations reveal the transience of BF systems with regard to temperatures and redox conditions, which has important implications for the BF quality and should therefore be accounted for.

  10. Redox interplay between mitochondria and peroxisomes

    PubMed Central

    Lismont, Celien; Nordgren, Marcus; Van Veldhoven, Paul P.; Fransen, Marc

    2015-01-01

    Reduction-oxidation or “redox” reactions are an integral part of a broad range of cellular processes such as gene expression, energy metabolism, protein import and folding, and autophagy. As many of these processes are intimately linked with cell fate decisions, transient or chronic changes in cellular redox equilibrium are likely to contribute to the initiation and progression of a plethora of human diseases. Since a long time, it is known that mitochondria are major players in redox regulation and signaling. More recently, it has become clear that also peroxisomes have the capacity to impact redox-linked physiological processes. To serve this function, peroxisomes cooperate with other organelles, including mitochondria. This review provides a comprehensive picture of what is currently known about the redox interplay between mitochondria and peroxisomes in mammals. We first outline the pro- and antioxidant systems of both organelles and how they may function as redox signaling nodes. Next, we critically review and discuss emerging evidence that peroxisomes and mitochondria share an intricate redox-sensitive relationship and cooperate in cell fate decisions. Key issues include possible physiological roles, messengers, and mechanisms. We also provide examples of how data mining of publicly-available datasets from “omics” technologies can be a powerful means to gain additional insights into potential redox signaling pathways between peroxisomes and mitochondria. Finally, we highlight the need for more studies that seek to clarify the mechanisms of how mitochondria may act as dynamic receivers, integrators, and transmitters of peroxisome-derived mediators of oxidative stress. The outcome of such studies may open up exciting new avenues for the community of researchers working on cellular responses to organelle-derived oxidative stress, a research field in which the role of peroxisomes is currently highly underestimated and an issue of discussion. PMID:26075204

  11. Associative change in the representations acquired during conditional discriminations: further analysis of the nature of conditional learning.

    PubMed

    Allman, Melissa J; Ward-Robinson, Jasper; Honey, R C

    2004-04-01

    Three experiments with rats investigated how the associative strengths of the representations that underlie conditional learning change when they are conditioned in compound. The results of each experiment suggest that the representation whose associative strength is most discrepant from the asymptote supported by the outcome of the trial undergoes the greatest change in associative strength. These results parallel those from simple Pavlovian conditioning (e.g., R. A. Rescorla, 2000). are inconsistent with unique-cue and configural accounts of conditional learning, and support a connectionist analysis of learning in which a "winner-takes-all" rule applies to the hidden units that can be activated and acquire associative strength at a given point in time.

  12. Real-Time Imaging of the Intracellular Glutathione Redox Potential in the Malaria Parasite Plasmodium falciparum

    PubMed Central

    Kasozi, Denis; Mohring, Franziska; Rahlfs, Stefan; Meyer, Andreas J.; Becker, Katja

    2013-01-01

    In the malaria parasite Plasmodium falciparum, the cellular redox potential influences signaling events, antioxidant defense, and mechanisms of drug action and resistance. Until now, the real-time determination of the redox potential in malaria parasites has been limited because conventional approaches disrupt sub-cellular integrity. Using a glutathione biosensor comprising human glutaredoxin-1 linked to a redox-sensitive green fluorescent protein (hGrx1-roGFP2), we systematically characterized basal values and drug-induced changes in the cytosolic glutathione-dependent redox potential (EGSH) of drug-sensitive (3D7) and resistant (Dd2) P. falciparum parasites. Via confocal microscopy, we demonstrated that hGrx1-roGFP2 rapidly detects EGSH changes induced by oxidative and nitrosative stress. The cytosolic basal EGSH of 3D7 and Dd2 were estimated to be −314.2±3.1 mV and −313.9±3.4 mV, respectively, which is indicative of a highly reducing compartment. We furthermore monitored short-, medium-, and long-term changes in EGSH after incubation with various redox-active compounds and antimalarial drugs. Interestingly, the redox cyclers methylene blue and pyocyanin rapidly changed the fluorescence ratio of hGrx1-roGFP2 in the cytosol of P. falciparum, which can, however, partially be explained by a direct interaction with the probe. In contrast, quinoline and artemisinin-based antimalarial drugs showed strong effects on the parasites' EGSH after longer incubation times (24 h). As tested for various conditions, these effects were accompanied by a drop in total glutathione concentrations determined in parallel with alternative methods. Notably, the effects were generally more pronounced in the chloroquine-sensitive 3D7 strain than in the resistant Dd2 strain. Based on these results hGrx1-roGFP2 can be recommended as a reliable and specific biosensor for real-time spatiotemporal monitoring of the intracellular EGSH in P. falciparum. Applying this technique in further

  13. On the resolvent of multidimensional operators with frequently changing boundary conditions in the case of the homogenized Dirichlet condition

    SciTech Connect

    Sharapov, T F

    2014-10-31

    We consider an elliptic operator in a multidimensional domain with frequently changing boundary conditions in the case when the homogenized operator contains the Dirichlet boundary condition. We prove the uniform resolvent convergence of the perturbed operator to the homogenized operator and obtain estimates for the rate of convergence. A complete asymptotic expansion is constructed for the resolvent when it acts on sufficiently smooth functions. Bibliography: 41 titles.

  14. Axial Ligation and Redox Changes at the Cobalt Ion in Cobalamin Bound to Corrinoid Iron-Sulfur Protein (CoFeSP) or in Solution Characterized by XAS and DFT

    PubMed Central

    Schrapers, Peer; Mebs, Stefan; Goetzl, Sebastian; Hennig, Sandra E.; Dau, Holger; Dobbek, Holger; Haumann, Michael

    2016-01-01

    A cobalamin (Cbl) cofactor in corrinoid iron-sulfur protein (CoFeSP) is the primary methyl group donor and acceptor in biological carbon oxide conversion along the reductive acetyl-CoA pathway. Changes of the axial coordination of the cobalt ion within the corrin macrocycle upon redox transitions in aqua-, methyl-, and cyano-Cbl bound to CoFeSP or in solution were studied using X-ray absorption spectroscopy (XAS) at the Co K-edge in combination with density functional theory (DFT) calculations, supported by metal content and cobalt redox level quantification with further spectroscopic methods. Calculation of the highly variable pre-edge X-ray absorption features due to core-to-valence (ctv) electronic transitions, XANES shape analysis, and cobalt-ligand bond lengths determination from EXAFS has yielded models for the molecular and electronic structures of the cobalt sites. This suggested the absence of a ligand at cobalt in CoFeSP in α-position where the dimethylbenzimidazole (dmb) base of the cofactor is bound in Cbl in solution. As main species, (dmb)CoIII(OH2), (dmb)CoII(OH2), and (dmb)CoIII(CH3) sites for solution Cbl and CoIII(OH2), CoII(OH2), and CoIII(CH3) sites in CoFeSP-Cbl were identified. Our data support binding of a serine residue from the reductive-activator protein (RACo) of CoFeSP to the cobalt ion in the CoFeSP-RACo protein complex that stabilizes Co(II). The absence of an α-ligand at cobalt not only tunes the redox potential of the cobalamin cofactor into the physiological range, but is also important for CoFeSP reactivation. PMID:27384529

  15. Impact of microbial activities on the mineralogy and performance of column-scale permeable reactive iron barriers operated under two different redox conditions.

    PubMed

    Van Nooten, Thomas; Lieben, François; Dries, Jan; Pirard, Eric; Springael, Dirk; Bastiaens, Leen

    2007-08-15

    The present study focuses on the impact of microbial activities on the performance of various long-term operated laboratory-scale permeable reactive barriers. The barriers contained both aquifer and Fe0 compartments and had received either sulfate or iron(III)-EDTA to promote sulfate-reducing and iron(III)-reducing bacteria, respectively. After dismantlement of the compartments after almost 3 years of operation, DNA-based PCR-DGGE analysis revealed the presence of methanogenic, sulfate-reducing, metal-reducing, and denitrifying bacteria within as well as up- and downgradient of the Fe0 matrix. Under all imposed conditions, the main secondary phases were vivianite, siderite, ferrous hydroxy carbonate, and carbonate green rust as found by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). Under sulfate-reduction promoting conditions, iron sulfides were formed in addition, resulting in 7 and 10 times higher degradation rates for PCE and TCE, respectively, compared to unreacted iron. These results indicate that the presence of sulfate-reducing bacteria in or around iron barriers and the subsequent formation of iron sulfides might increase the barrier reactivity.

  16. Redox Flow Batteries, a Review

    SciTech Connect

    Knoxville, U. Tennessee; U. Texas Austin; U, McGill; Weber, Adam Z.; Mench, Matthew M.; Meyers, Jeremy P.; Ross, Philip N.; Gostick, Jeffrey T.; Liu, Qinghua

    2011-07-15

    Redox flow batteries are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of redox flow batteries with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.

  17. PGE, Re-Os, and Mo isotope systematics in Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth

    NASA Astrophysics Data System (ADS)

    Siebert, C.; Kramers, J. D.; Meisel, Th.; Morel, Ph.; Nägler, Th. F.

    2005-04-01

    Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for suites of fine clastic sediments and black shales from the Barberton Greenstone Belt, South Africa (Fig Tree and Moodies Groups, 3.25-3.15 Ga), the Belingwe Greenstone Belt, Zimbabwe (Manjeri Formation, ca. 2.7 Ga) and shales from the Witwatersrand, Ventersdorp and Transvaal Supergroups, South Africa ranging from 2.95 to 2.2 Ga. Moderately oxidizing conditions are required to mobilize Re and Mo in the environment, Mo fractionation only occurs in solution, and these parameters thus have potential use as paleoredox proxies for the early Earth. PGE + Re abundance patterns of Barberton Greenstone Belt sediments are uniform and very similar in shape to those of komatiites. This indicates (1) that the PGE came from a source of predominantly ultramafic composition and, (2) that PGE were transported and deposited essentially in particulate form. Sediments from the younger Belingwe Greenstone Belt show more fractionated PGE + Re patterns and have Re/Os ratios 10 to 100× higher than those of Barberton sediments. Their PGE abundance patterns and Re/Os ratios are intermediate between those of the mid-Archean shales and Neoproterozoic to Recent black shales. They reflect scavenging of Re from solution in the sedimentary environment. δ 98/95Mo values of black shales of all ages correlate with their concentrations. The Barberton Greenstone Belt samples have ˜1-3 ppm Mo, similar to a granitoid-basaltic source. This Mo has δ 98/95Mo between -1.9 and -2.4‰ relative to present day mean ocean water molybdenum, MOMO and is thus not isotopically fractionated relative to such a source. Similar to the PGE this indicates transport in solid form. Sediments from the Belingwe Greenstone Belt show in part enhanced Mo concentrations (up to 6 ppm) and Mo isotope fractionation (δ 98/95Mo up to -1.4‰ relative to MOMO). The combined PGE + Re and Mo data show mainly reducing conditions in the

  18. NASA Redox Storage System Development Project

    NASA Technical Reports Server (NTRS)

    Hagedorn, N. H.

    1984-01-01

    The Redox Storage System Technology Project was jointly supported by the U.S. Department of Energy and NASA. The objectives of the project were to develop the Redox flow battery concept and to probe its technical and economic viability. The iron and chromium redox couples were selected as the reactants. Membranes and electrodes were developed for the original mode of operating at 25 C with the reactants separated by an ion-exchange membrane. Analytical capabilities and system-level operating concepts were developed and verified in a 1-kW, 13-kWh preprototype system. A subsequent change was made in operating mode, going to 65 C and using mixed reactants. New membranes and a new electrode catalyst were developed, resulting in single cell operation as high as 80 mA/sq cm with energy efficiencies greater than 80 percent. Studies indicate a likely system cost of about $75/kWh. Standard Oil of Ohio (Sohio) has undertaken further development of the Redox system. An exclusive patent license was obtained from NASA by Sohio. Transfer of Redox technology to Sohio is supported by the NASA Technology Utilization Office.

  19. Lycopene inhibits NF-kB-mediated IL-8 expression and changes redox and PPARγ signalling in cigarette smoke-stimulated macrophages.

    PubMed

    Simone, Rossella E; Russo, Marco; Catalano, Assunta; Monego, Giovanni; Froehlich, Kati; Boehm, Volker; Palozza, Paola

    2011-01-01

    Increasing evidence suggests that lycopene, the major carotenoid present in tomato, may be preventive against smoke-induced cell damage. However, the mechanisms of such a prevention are still unclear. The aim of this study was to investigate the role of lycopene on the production of the pro-inflammatory cytokine IL-8 induced by cigarette smoke and the possible mechanisms implicated. Therefore, human THP-1 macrophages were exposed to cigarette smoke extract (CSE), alone and following a 6-h pre-treatment with lycopene (0.5-2 µM). CSE enhanced IL-8 production in a time- and a dose-dependent manner. Lycopene pre-treatment resulted in a significant inhibition of CSE-induced IL-8 expression at both mRNA and protein levels. NF-kB controlled the transcription of IL-8 induced by CSE, since PDTC prevented such a production. Lycopene suppressed CSE-induced NF-kB DNA binding, NF-kB/p65 nuclear translocation and phosphorylation of IKKα and IkBα. Such an inhibition was accompanied by a decrease in CSE-induced ROS production and NOX-4 expression. Lycopene further inhibited CSE-induced phosphorylation of the redox-sensitive ERK1/2, JNK and p38 MAPKs. Moreover, the carotenoid increased PPARγ levels which, in turn, enhanced PTEN expression and decreased pAKT levels in CSE-exposed cells. Such effects were abolished by the PPARγ inhibitor GW9662. Taken together, our data indicate that lycopene prevented CSE-induced IL-8 production through a mechanism involving an inactivation of NF-kB. NF-kB inactivation was accompanied by an inhibition of redox signalling and an activation of PPARγ signalling. The ability of lycopene in inhibiting IL-8 production, NF-kB/p65 nuclear translocation, and redox signalling and in increasing PPARγ expression was also found in isolated rat alveolar macrophages exposed to CSE. These findings provide novel data on new molecular mechanisms by which lycopene regulates cigarette smoke-driven inflammation in human macrophages.

  20. Cellular Redox Imbalance and Changes of Protein S-glutathionylation Patterns Are Associated with Senescence Induced by Oncogenic H-Ras

    PubMed Central

    Urbanelli, Lorena; Magini, Alessandro; Magherini, Francesca; Pugnaloni, Armanda; Piva, Francesco; Modesti, Alessandra; Emiliani, Carla; Principato, Giovanni

    2012-01-01

    H-Ras oncogene requires deregulation of additional oncogenes or inactivation of tumor suppressor proteins to increase cell proliferation rate and transform cells. In fact, the expression of the constitutively activated H-RasV12 induces cell growth arrest and premature senescence, which act like barriers in pre-neoplastic lesions. In our experimental model, human fibroblasts transfected with H-RasV12 show a dramatic modification of morphology. H-RasV12 expressing cells also show premature senescence followed by cell death, induced by autophagy and apoptosis. In this context, we provide evidence that in H-RasV12 expressing cells, the premature senescence is associated with cellular redox imbalance as well as with altered post-translation protein modification. In particular, redox imbalance is due to a strong reduction of total antioxidant capacity, and significant decrease of glutathione level. As the reversible addition of glutathione to cysteinyl residues of proteins is an important post-translational regulative modification, we investigated S-glutathionylation in cells expressing active H-Ras. In this contest we observed different S-glutathionylation patterns in control and H-RasV12 expressing cells. Particularly, the GAPDH enzyme showed S-glutathionylation increase and significant enzyme activity depletion in H-Ras V12 cells. In conclusion, we proposed that antioxidant defense reduction, glutathione depletion and subsequent modification of S-glutathionylation of target proteins contribute to arrest cell growth, leading to death of fibroblasts expressing constitutively active H-Ras oncogene, thus acting as oncogenic barriers that obstacle the progression of cell transformation. PMID:23284910

  1. Ce K edge XAS of ceria-based redox materials under realistic conditions for the two-step solar thermochemical dissociation of water and/or CO2.

    PubMed

    Rothensteiner, Matthäus; Sala, Simone; Bonk, Alexander; Vogt, Ulrich; Emerich, Hermann; van Bokhoven, Jeroen A

    2015-10-28

    X-ray absorption spectroscopy was used to characterise ceria-based materials under realistic conditions present in a reactor for solar thermochemical two-step water and carbon dioxide splitting. A setup suitable for in situ measurements in transmission mode at the cerium K edge from room temperature up to 1773 K is presented. Time-resolved X-ray absorption near-edge structure (XANES) data, collected for a 10 mol% hafnium-doped ceria sample (Ce0.9Hf0.1O2-δ) during reduction at 1773 K in a flow of inert gas and during re-oxidation by CO2 at 1073 K, enables the quantitative determination of the non-stoichiometry δ of the fluorite-type structure. XANES analysis suggests the formation of the hexagonal Ce2O3 phase upon reduction in 2% hydrogen/helium at 1773 K. We discuss the experimental limitations and possibilities of high-temperature in situ XAS at edges of lower energy as well as the importance of the technique for understanding and improving the properties of ceria-based oxygen storage materials for thermochemical solar energy conversion.

  2. Redox regulation of cardiac hypertrophy.

    PubMed

    Sag, Can M; Santos, Celio X C; Shah, Ajay M

    2014-08-01

    It is increasingly evident that redox-dependent modifications in cellular proteins and signaling pathways (or redox signaling) play important roles in many aspects of cardiac hypertrophy. Indeed, these redox modifications may be intricately linked with the process of hypertrophy wherein there is not only a significant increase in myocardial O2 consumption but also important alterations in metabolic processes and in the local generation of O2-derived reactive species (ROS) that modulate and/or amplify cell signaling pathways. This article reviews our current knowledge of redox signaling pathways and their roles in cardiac hypertrophy. This article is part of a Special Issue entitled "Redox Signalling in the Cardiovascular System".

  3. Apatite: A new redox proxy for silicic magmas?

    NASA Astrophysics Data System (ADS)

    Miles, A. J.; Graham, C. M.; Hawkesworth, C. J.; Gillespie, M. R.; Hinton, R. W.; Bromiley, G. D.

    2014-05-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this paper we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+ and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively (Stephens et al., 1985). This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46) Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions.

  4. Assessment of mycotoxin risk on corn in the Philippines under current and future climate change conditions.

    PubMed

    Salvacion, Arnold R; Pangga, Ireneo B; Cumagun, Christian Joseph R

    2015-01-01

    This study attempts to assess the risk of mycotoxins (aflatoxins and fumonisins) contamination on corn in the Philippines under current and projected climate change conditions using fuzzy logic methodology based on the published range of temperature and rainfall conditions that favor mycotoxin development. Based on the analysis, projected climatic change will reduce the risk of aflatoxin contamination in the country due to increased rainfall. In the case of fumonisin contamination, most parts of the country are at a very high risk both under current conditions and the projected climate change conditions.

  5. K-8th Grade Korean Students' Conceptions of 'Changes of State' and 'Conditions for Changes of State'. Research Report

    ERIC Educational Resources Information Center

    Paik, Seoung-Hey; Kim, Hyo-Nam; Cho, Boo-Kyoung; Park, Jae-Won

    2004-01-01

    This study investigates the various conceptions held by K-8th Korean grade students regarding the 'changes of state' and the 'conditions for changes of state'. The study used a sample of five kindergarteners, five secondgrade students, five fourth-grade students, five sixth-grade students, and five eighth-grade students. The 25 students attend…

  6. Eye-Blink Conditioning Is Associated with Changes in Synaptic Ultrastructure in the Rabbit Interpositus Nuclei

    ERIC Educational Resources Information Center

    Weeks, Andrew C. W.; Connor, Steve; Hinchcliff, Richard; LeBoutillier, Janelle C.; Thompson, Richard F.; Petit, Ted L.

    2007-01-01

    Eye-blink conditioning involves the pairing of a conditioned stimulus (usually a tone) to an unconditioned stimulus (air puff), and it is well established that an intact cerebellum and interpositus nucleus, in particular, are required for this form of classical conditioning. Changes in synaptic number or structure have long been proposed as a…

  7. Redox-capacitor to connect electrochemistry to redox-biology.

    PubMed

    Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; White, Ian M; Bentley, William E; Payne, Gregory F

    2014-01-07

    It is well-established that redox-reactions are integral to biology for energy harvesting (oxidative phosphorylation), immune defense (oxidative burst) and drug metabolism (phase I reactions), yet there is emerging evidence that redox may play broader roles in biology (e.g., redox signaling). A critical challenge is the need for tools that can probe biologically-relevant redox interactions simply, rapidly and without the need for a comprehensive suite of analytical methods. We propose that electrochemistry may provide such a tool. In this tutorial review, we describe recent studies with a redox-capacitor film that can serve as a bio-electrode interface that can accept, store and donate electrons from mediators commonly used in electrochemistry and also in biology. Specifically, we (i) describe the fabrication of this redox-capacitor from catechols and the polysaccharide chitosan, (ii) discuss the mechanistic basis for electron exchange, (iii) illustrate the properties of this redox-capacitor and its capabilities for promoting redox-communication between biology and electrodes, and (iv) suggest the potential for enlisting signal processing strategies to "extract" redox information. We believe these initial studies indicate broad possibilities for enlisting electrochemistry and signal processing to acquire "systems level" redox information from biology.

  8. Flow visualization by redox-reaction dyes

    NASA Astrophysics Data System (ADS)

    Lister, C. R. B.

    1992-08-01

    Colour generation by a direct oxidation or reduction reaction at an electrode in aqueous solution does not generate gas, as is necessary to obtain a pH change. Flow visualization in a closed apparatus or porous medium is therefore possible without the interference of bubbles or a detectable density change. A series of anthraquinone sulphonic acid salts has been found that produce good colours upon reduction at a cathode in mildly alkaline solution. Some are soluble enough to be used in salt gradients and react well below the potential needed to evolve hydrogen, so the electrode remains in stable condition. Platinum is not necessary for the cathode, is indeed undesirable. A number of commercial redox dyes that produce colour upon oxidation were also tested. The most practical is methylene blue, which needs a powerful reducing agent to be decolourised. It is instantly reoxidised by dissolved air, a feature that may be useful in studies of gas/liquid transfer or entrainment across stratified boundaries.

  9. The geochemistry of redox sensitive trace metals in sediments

    SciTech Connect

    Morford, J.L.; Emerson, S.

    1999-06-01

    The authors analyzed the redox sensitive elements V, Mo, U, Re and Cd in surface sediments from the Northwest African margin, the US Northwest margin and the Arabian Sea to determine their response under a range of redox conditions. Where oxygen penetrates 1 cm or less into the sediments, Mo and V diffuse to the overlying water as Mn is reduced and remobilized. Authigenic enrichments of U, Re and Cd are evident under these redox conditions. With the onset of sulfate reduction, all of the metals accumulate authigenically with Re being by far the most enriched. General trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes: oxic, reducing where oxygen penetrates {le} 1 cm, and anoxic conditions. Using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations, the authors calculate the area of sediments below 1,000 m water depth in which oxygen penetration is {le} 1 cm to be 4% of the ocean floor. They conclude that sediments where oxygen penetrates {le} 1 cm release Mn, V and Mo to seawater at rates of 140%--260%, 60%--150% and 5%--10% of their respective riverine fluxes, using the authigenic metal concentrations and accumulation rates from this work and other literature. These sediments are sinks for Re, Cd and U, with burial fluxes of 70%--140%, 30%--80% and 20%--40%, respectively, of their dissolved riverine inputs. They modeled the sensitivity of the response of seawater Re, Cd and V concentrations to changes in the area of reducing sediments where oxygen penetrates {le} 1 cm. The analysis suggests a negligible change in seawater Re concentration, whereas seawater concentrations of Cd and V could have decreased and increased, respectively, by 5%--10% over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10%--20% if the area increased by a factor of 3. The concentration variations for a factor of 2 increase in the area of

  10. Cytosolic NADH-NAD+ Redox Visualized in Brain Slices by Two-Photon Fluorescence Lifetime Biosensor Imaging

    PubMed Central

    Mongeon, Rebecca; Venkatachalam, Veena

    2016-01-01

    Abstract Aim: Cytosolic NADH-NAD+ redox state is central to cellular metabolism and a valuable indicator of glucose and lactate metabolism in living cells. Here we sought to quantitatively determine NADH-NAD+ redox in live cells and brain tissue using a fluorescence lifetime imaging of the genetically-encoded single-fluorophore biosensor Peredox. Results: We show that Peredox exhibits a substantial change in its fluorescence lifetime over its sensing range of NADH-NAD+ ratio. This allows changes in cytosolic NADH redox to be visualized in living cells using a two-photon scanning microscope with fluorescence lifetime imaging capabilities (2p-FLIM), using time-correlated single photon counting. Innovation: Because the lifetime readout is absolutely calibrated (in nanoseconds) and is independent of sensor concentration, we demonstrate that quantitative assessment of NADH redox is possible using a single fluorophore biosensor. Conclusion: Imaging of the sensor in mouse hippocampal brain slices reveals that astrocytes are typically much more reduced (with higher NADH:NAD+ ratio) than neurons under basal conditions, consistent with the hypothesis that astrocytes are more glycolytic than neurons. Antioxid. Redox Signal. 25, 553–563. PMID:26857245

  11. Microfluidic redox battery.

    PubMed

    Lee, Jin Wook; Goulet, Marc-Antoni; Kjeang, Erik

    2013-07-07

    A miniaturized microfluidic battery is proposed, which is the first membraneless redox battery demonstrated to date. This unique concept capitalizes on dual-pass flow-through porous electrodes combined with stratified, co-laminar flow to generate electrical power on-chip. The fluidic design is symmetric to allow for both charging and discharging operations in forward, reverse, and recirculation modes. The proof-of-concept device fabricated using low-cost materials integrated in a microfluidic chip is shown to produce competitive power levels when operated on a vanadium redox electrolyte. A complete charge/discharge cycle is performed to demonstrate its operation as a rechargeable battery, which is an important step towards providing sustainable power to lab-on-a-chip and microelectronic applications.

  12. Redox theory of aging

    PubMed Central

    Jones, Dean P.

    2015-01-01

    Metazoan genomes encode exposure memory systems to enhance survival and reproductive potential by providing mechanisms for an individual to adjust during lifespan to environmental resources and challenges. These systems are inherently redox networks, arising during evolution of complex systems with O2 as a major determinant of bioenergetics, metabolic and structural organization, defense, and reproduction. The network structure decreases flexibility from conception onward due to differentiation and cumulative responses to environment (exposome). The redox theory of aging is that aging is a decline in plasticity of genome–exposome interaction that occurs as a consequence of execution of differentiation and exposure memory systems. This includes compromised mitochondrial and bioenergetic flexibility, impaired food utilization and metabolic homeostasis, decreased barrier and defense capabilities and loss of reproductive fidelity and fecundity. This theory accounts for hallmarks of aging, including failure to maintain oxidative or xenobiotic defenses, mitochondrial integrity, proteostasis, barrier structures, DNA repair, telomeres, immune function, metabolic regulation and regenerative capacity. PMID:25863726

  13. Proton gradient regulation 5-mediated cyclic electron flow under ATP- or redox-limited conditions: a study of ΔATpase pgr5 and ΔrbcL pgr5 mutants in the green alga Chlamydomonas reinhardtii.

    PubMed

    Johnson, Xenie; Steinbeck, Janina; Dent, Rachel M; Takahashi, Hiroko; Richaud, Pierre; Ozawa, Shin-Ichiro; Houille-Vernes, Laura; Petroutsos, Dimitris; Rappaport, Fabrice; Grossman, Arthur R; Niyogi, Krishna K; Hippler, Michael; Alric, Jean

    2014-05-01

    The Chlamydomonas reinhardtii proton gradient regulation5 (Crpgr5) mutant shows phenotypic and functional traits similar to mutants in the Arabidopsis (Arabidopsis thaliana) ortholog, Atpgr5, providing strong evidence for conservation of PGR5-mediated cyclic electron flow (CEF). Comparing the Crpgr5 mutant with the wild type, we discriminate two pathways for CEF and determine their maximum electron flow rates. The PGR5/proton gradient regulation-like1 (PGRL1) ferredoxin (Fd) pathway, involved in recycling excess reductant to increase ATP synthesis, may be controlled by extreme photosystem I acceptor side limitation or ATP depletion. Here, we show that PGR5/PGRL1-Fd CEF functions in accordance with an ATP/redox control model. In the absence of Rubisco and PGR5, a sustained electron flow is maintained with molecular oxygen instead of carbon dioxide serving as the terminal electron acceptor. When photosynthetic control is decreased, compensatory alternative pathways can take the full load of linear electron flow. In the case of the ATP synthase pgr5 double mutant, a decrease in photosensitivity is observed compared with the single ATPase-less mutant that we assign to a decreased proton motive force. Altogether, our results suggest that PGR5/PGRL1-Fd CEF is most required under conditions when Fd becomes overreduced and photosystem I is subjected to photoinhibition. CEF is not a valve; it only recycles electrons, but in doing so, it generates a proton motive force that controls the rate of photosynthesis. The conditions where the PGR5 pathway is most required may vary in photosynthetic organisms like C. reinhardtii from anoxia to high light to limitations imposed at the level of carbon dioxide fixation.

  14. Redox effects on the microbial degradation of refractory organic matter in marine sediments

    NASA Astrophysics Data System (ADS)

    Reimers, Clare E.; Alleau, Yvan; Bauer, James E.; Delaney, Jennifer; Girguis, Peter R.; Schrader, Paul S.; Stecher, Hilmar A.

    2013-11-01

    Microbially mediated reduction-oxidation (redox) reactions are often invoked as being the mechanisms by which redox state influences the degradation of sedimentary organic matter (OM) in the marine environment. To evaluate the effects of elevated, oscillating and reduced redox potentials on the fate of primarily aged, mineral-adsorbed OM contained in continental shelf sediments, we used microbial fuel cells to control redox state within and around marine sediments, without amending the sediments with reducing or oxidizing substances. We subsequently followed electron fluxes in the redox elevated and redox oscillating treatments, and related sediment chemical, isotopic and bacterial community changes to redox conditions over a 748-day experimental period. The electron fluxes of the elevated and oscillating redox cells were consistent with models of organic carbon (OC) oxidation with time-dependent first-order rate constants declining from 0.023 to 0.005 y-1, in agreement with rate constants derived from typical OC profiles and down core ages of offshore sediments, or from sulfate reduction rate measurements in similar sediments. Moreover, although cumulative electron fluxes were higher in the continuously elevated redox treatment, incremental rates of electron harvesting in the two treatments converged over the 2 year experiment. These similar rates were reflected in chemical indicators of OM metabolism such as dissolved OC and ammonia, and particulate OC concentrations, which were not significantly different among all treatments and controls over the experimental time-scale. In contrast, products of carbonate and opal dissolution and metal mobilization showed greater enrichments in sediments with elevated and oscillating redox states. Microbial community composition in anode biofilms and surrounding sediments was assessed via high-throughput 16S rRNA gene sequencing, and these analyses revealed that the elevated and oscillatory redox treatments led to the

  15. Contrasting Redox Stories from Trace Metal and Iron Proxy Records of the Late Cretaceous Western Interior Seaway

    NASA Astrophysics Data System (ADS)

    Tessin, A. C.; Sheldon, N. D.; Hendy, I. L.; Chappaz, A.

    2015-12-01

    The sedimentary record of the Cretaceous Western Interior Seaway (North America) is characterized by periods of enhanced organic carbon burial known as Oceanic Anoxic Events (OAEs). Compared to more typical OAEs, the last Cretaceous OAE, the Coniacian-Santonian OAE 3 (~86 Ma), is enigmatic and its driving mechanism less understood. While OAE 3 was geographically limited to restricted basins and shallow seaways, it also had a longer duration (~3 myrs) of organic carbon burial than earlier OAEs., Constraining paleoredox conditions during organic carbon burial events, such as OAEs, is important for understanding the relationship between ocean anoxia and carbon burial. Iron proxies (FeHR/FeT, Fepy/FeHR, and FeT/Al) provide an important tool in the reconstruction of paleoredox conditions through geologic time. Here we present sequential Fe and pyrite Fe measurements from the Niobrara Formation recovered in the USGS #1 Portland core from Cañon City Basin, Colorado. The new results indicate that Fe redox proxies from the Portland core are not always in agreement with other redox proxies. Pyrite Fe measurements indicate a single stepwise change in seaway oxygen limitation, whereas other paleoredox proxies (Mo, Re, U, bioturbation indices) indicate fluctuating redox conditions and a variable degree of euxinia throughout the record. Interpretation of pyrite Fe values may be complicated by the development of a highly reactive Fe limitation. Another commonly used redox proxy, FeT/Al, indicates oxic conditions when other redox proxies suggest anoxia and vice versa. Interpretation FeT/Al may be complicated by a number of factors, including sequestration of Fe in diagenetic carbonate phases, variable supply of external Fe, atypical basin geometry, and the development of shallow marine euxinia. Taken together, these observations clearly support the importance of using a multi proxy approach to accurately reconstruct oceanic redox history.

  16. Co-variation of nitrogen isotopes and redox states through glacial-interglacial cycles in the Black Sea

    NASA Astrophysics Data System (ADS)

    Quan, Tracy M.; Wright, James D.; Falkowski, Paul G.

    2013-07-01

    In all aquatic environments, nitrogen cycling within the water column is strongly influenced by oxygen. We hypothesize that the nitrogen isotopic composition (δ15N) of organic matter deposited in the sediments is a proxy for the redox state of the water column at the time of deposition. We tested the hypothesis by measuring the bulk sedimentary δ15N values in a drill core from the Black Sea, a basin that alternates between oxic, less saline conditions and anoxic, marine conditions on glacial-interglacial time scales. We reconstructed these changes in Black Sea redox conditions using sedimentary δ15N, total organic carbon (TOC), total nitrogen (TN), redox-sensitive metals, and micropaleontological data from a deep-sea core (DSDP Site 380). The sedimentary data reveal that during the transitions between oxic and anoxic conditions, δ15N values increased relative to the preceding and succeeding quasi-steady-state oxic and anoxic periods. The results indicate that the reciprocal transitional states from anoxic to oxic conditions were accompanied by intense denitrification; during the quasi-stable oxic and anoxic states (characterized by glacial fresh water and interglacial marine conditions) nitrification and complete nitrate utilization, respectively, dominate the nitrogen cycle. While other factors may influence the δ15N record, our results support the hypothesis that the variations in nitrogen isotopic composition of organic matter are strongly influenced by changes in redox state in the Black Sea subphotic zone on glacial-interglacial time scales, and can be explained by a relatively simple model describing the effects of oxygen on the microbial processes that drive the nitrogen cycle in marine ecosystems. Our model suggests that the nitrogen isotopic composition of marine sediments, on geological time scales, can be used to reconstruct the redox state of the overlying water column.

  17. Changes in winter conditions impact forest management in north temperate forests.

    PubMed

    Rittenhouse, Chadwick D; Rissman, Adena R

    2015-02-01

    Climate change may impact forest management activities with important implications for forest ecosystems. However, most climate change research on forests has focused on climate-driven shifts in species ranges, forest carbon, and hydrology. To examine how climate change may alter timber harvesting and forest operations in north temperate forests, we asked: 1) How have winter conditions changed over the past 60 years? 2) Have changes in winter weather altered timber harvest patterns on public forestlands? 3) What are the implications of changes in winter weather conditions for timber harvest operations in the context of the economic, ecological, and social goals of forest management? Using meteorological information from Climate Data Online and Autoregressive Integrated Moving Average (ARIMA) models we document substantial changes in winter conditions in Wisconsin, including a two- to three-week shortening of frozen ground conditions from 1948 to 2012. Increases in minimum and mean soil temperatures were spatially heterogeneous. Analysis of timber harvest records identified a shift toward greater harvest of jack pine and red pine and less harvest of aspen, black spruce, hemlock, red maple, and white spruce in years with less frozen ground or snow duration. Interviews suggested that frozen ground is a mediating condition that enables low-impact timber harvesting. Climate change may alter frozen ground conditions with complex implications for forest management.

  18. Experimentally observed iron redox kinetics in silicic liquids: Implications for Fe/sup 3 +//Fe/sup 2 +/ variations in rhyolite lava

    SciTech Connect

    Naney, M.T.; Swanson, S.E.

    1989-01-01

    Iron redox kinetics in silicate liquids were investigated by melting 100 mg pellets of compacted rhyolite, pantellerite, pantelleritic trachyte, and andesite rock powders at 1243 and 1343/degree/C in a moderately reducing furnace atmosphere (log fO/sub 2/ = /minus/7.83) for periods of 1 to 4320 minutes. The redox state of glasses produced by quenching these liquids was determined by colorimetric analysis of the ferrous iron and total iron content. Redox equilibrium, indicated by the attainment of a constant FeO/FeO/sub tot/ ratio, was observed for all temperature-composition conditions studied, except for 1243/degree/C experiments with USGS rhyolite standard RGM-1. This is consistent with the low diffusivity of reacting components in high viscosity rhyolite liquids. In the 1243/degree/C experiments with RGM-1, no change in the FeO/FeO/sub tot/ ratio was observed after 4320 minutes. This implies that redox equilibrium is not maintained in natural rhyolite lavas which erupt as significantly lower temperatures (720--850/degree/C). We conclude that sluggish redox kinetics precludes major changes in the oxidation state of a rhyolite magma during the eruption process. If this is true, then the quenched magma, represented by glassy rhyolites, preserves the pre-eruption redox signature of the magma. 2 refs.

  19. Changing epistemologies under conditions of social change in two Arab communities in Israel.

    PubMed

    Weinstock, Michael

    2015-02-01

    The study of epistemic thinking focuses on how people understand and coordinate objective and subjective aspects of knowing and make sense of multiple and discrepant knowledge claims. Typically described in terms of normative development, cross-cultural studies show differences in epistemic development and characteristics of epistemic thinking. This study focuses on within-culture variations of epistemic thinking, with the assumption that social change will produce changes in development. Arab society in Israel has undergone notable change over the last half century. In this cross-sectional research design, cross-generational comparison and rural-urban comparison were used as proxies for longitudinal social change. Three generations of Muslim Arab women in a village in Israel (20 adolescents, 20 mothers and 20 grandmothers) and 20 Muslim Arab adolescents from a large, mixed city in the same region responded to six dilemmas invoking epistemic thinking. Village adolescents were more subjectivist than their mothers and grandmothers. Sociodemographic characteristics representing greater exposure to diverse people and ideas accounted for generational differences. Both urban and rural adolescents tended towards subjectivist perspectives, and they did not differ. Parents' education levels emerged as the sociodemographic variables most consistently related to epistemic thinking. Epistemic thinking mediated the relationship between generation and gender role/cross-sex relation values.

  20. The Iron Redox Engine Drives Carbon, Nitrogen, and Phosphorus Cycling in Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Silver, W. L.; Hall, S. J.; Liptzin, D.; Yang, W. H.

    2011-12-01

    ways. Iron oxidation can be coupled with NO3- or NO2- reduction resulting in N2, N2O, or NH4+ production. Iron reduction can catalyze NH4+ oxidation to N2, NO2-, or NO3- through a newly described process call Feammox. Nitrite or NO3- produced via Feammox can be subsequently reduced to N2O via denitrification or to NH4+ via dissimilatory reduction. Iron interacts with P cycling through the effects of redox on Fe-P bonds. Evidence suggests that P sorbed to Fe oxides is liberated during Fe reduction, and can re-react with Fe(III) under oxidizing conditions. This results in short pulses of P availability in fluctuating redox environments such as humid, upland soils. Fe-P redox dynamics may facilitate P retention and higher P-use efficiency in high rainfall environments. Our results show that Fe is a key biogeochemical engine in soil systems, particularly under conditions of fluctuating redox. Biogeochemical cycles coupled with Fe result in greenhouse gas production and impact nutrient availability in terrestrial ecosystems. The redox sensitivity of these reactions suggests that they are likely to be particularly responsive to changes in precipitation, temperature, and other drivers of soil water dynamics associated with climate change.

  1. Electronic Connection Between the Quinone and Cytochrome c Redox Pools and Its Role in Regulation of Mitochondrial Electron Transport and Redox Signaling

    PubMed Central

    Sarewicz, Marcin; Osyczka, Artur

    2015-01-01

    Mitochondrial respiration, an important bioenergetic process, relies on operation of four membranous enzymatic complexes linked functionally by mobile, freely diffusible elements: quinone molecules in the membrane and water-soluble cytochromes c in the intermembrane space. One of the mitochondrial complexes, complex III (cytochrome bc1 or ubiquinol:cytochrome c oxidoreductase), provides an electronic connection between these two diffusible redox pools linking in a fully reversible manner two-electron quinone oxidation/reduction with one-electron cytochrome c reduction/oxidation. Several features of this homodimeric enzyme implicate that in addition to its well-defined function of contributing to generation of proton-motive force, cytochrome bc1 may be a physiologically important point of regulation of electron flow acting as a sensor of the redox state of mitochondria that actively responds to changes in bioenergetic conditions. These features include the following: the opposing redox reactions at quinone catalytic sites located on the opposite sides of the membrane, the inter-monomer electronic connection that functionally links four quinone binding sites of a dimer into an H-shaped electron transfer system, as well as the potential to generate superoxide and release it to the intermembrane space where it can be engaged in redox signaling pathways. Here we highlight recent advances in understanding how cytochrome bc1 may accomplish this regulatory physiological function, what is known and remains unknown about catalytic and side reactions within the quinone binding sites and electron transfers through the cofactor chains connecting those sites with the substrate redox pools. We also discuss the developed molecular mechanisms in the context of physiology of mitochondria. PMID:25540143

  2. Apatite: a new redox proxy for silicic magmas?

    NASA Astrophysics Data System (ADS)

    Miles, Andrew; Graham, Colin; Hawkesworth, Chris; Gillespie, Martin; Bromiley, Geoff; Hinton, Richard

    2015-04-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this presentation we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively[1]. This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO2=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46) Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions[2]. [1] Stephens, W. E., Whitley, J. E., Thirlwall, M. F. and Halliday, A. N. (1985) The Criffell zoned pluton: correlated behaviour of rare earth element abundances with isotopic systems. Contributions to Mineralogy and

  3. Measuring E(GSH) and H2O2 with roGFP2-based redox probes.

    PubMed

    Morgan, Bruce; Sobotta, Mirko C; Dick, Tobias P

    2011-12-01

    Redox biochemistry plays an important role in a wide range of cellular events. However, investigation of cellular redox processes is complicated by the large number of cellular redox couples, which are often not in equilibrium with one another and can vary significantly between subcellular compartments and cell types. Further, it is becoming increasingly clear that different redox systems convey different biological information; thus it makes little sense to talk of an overall "cellular redox state". To gain a more differentiated understanding of cellular redox biology, quantitative, redox couple-specific, in vivo measurements are necessary. Unfortunately our ability to investigate specific redox couples or redox-reactive molecules with the necessary degree of spatiotemporal resolution is very limited. The development of genetically encoded redox biosensors offers a promising new way to investigate redox biology. Recently developed redox-sensitive green fluorescent proteins (roGFPs), genetically fused to redox-active proteins, allow rapid equilibration of the roGFP moiety with a specific redox couple. Two probes based on this principle are now available: Grx1-roGFP2 for the measurement of glutathione redox potential (E(GSH)) and roGFP2-Orp1 for measuring changes in H(2)O(2) concentration. Here we provide a detailed protocol for the use of these probes in both yeast and mammalian systems using either plate-reader- or microscopy-based measurements.

  4. Monitoring of WUT grand hall roof in conditions of high temperature changes

    NASA Astrophysics Data System (ADS)

    Wozniak, M.

    2009-04-01

    The geodetic control measurements of changes in object's geometry should satisfy high accuracy and reliability. New tacheometers equipped with Automatic Target Recognition automatically moves the telescope to the center of the prism and supports control points measurements. The accuracy of using ATR system and stability of instrument in precise measurements were controlled in laboratory and field conditions. This paper will present the results of monitoring measurements using Leica TDA 5005 during investigations of roof geometry in conditions of high temperature changes.

  5. Field, Experimental, and Modeling Study of Arsenic Partitioning across a Redox Transition in a Bangladesh Aquifer

    PubMed Central

    Jung, Hun Bok; Bostick, Benjamin C.; Zheng, Yan

    2012-01-01

    To understand the redox-dependent arsenic partitioning, we performed batch sorption and desorption experiments using aquifer sands subjected to chemical and mineralogical characterization. Sands collected from the redox transition zone between reducing groundwater and oxic river water at the Meghna riverbank with HCl extractable Fe(III)/Fe ratio ranging from 0.32 to 0.74, are representative of the redox conditions of aquifers common in nature. One brown suboxic sediment displayed a partitioning coefficient (Kd) of 7∼8 L kg−1 at equilibrium with 100 μg L−1 As(III), while two gray reducing sediments showed Kd of 1∼2 L kg−1. Lactate amendment to aquifer sands containing 91 mg kg−1 P-extractable As resulted in the reduction of As and Fe with sediment Fe(III)/Fe decreasing from 0.54 to 0.44, and mobilized an equivalent of 64 mg kg−1 As over a month. Desorption of As from non-lactate-amended sediment was negligible with little change in sediment Fe(III)/Fe. This release of As is consistent with microbial reduction of Fe(III) oxyhydroxides and the resulting decrease in the number of surface sites on Fe(III) oxyhydroxides. Arsenic partitioning (Kd) in iron-rich, sulfur-poor aquifers with circumneutral pH is redox-dependent and can be estimated by HCL leachable sediment Fe(III)/Fe ratio with typical Fe concentrations. PMID:22201284

  6. Oxidative stress and redox signalling in cardiac hypertrophy and heart failure

    PubMed Central

    Seddon, Mike; Looi, Yee H; Shah, Ajay M

    2007-01-01

    Substantial evidence suggests the involvement of oxidative stress in the pathophysiology of congestive heart failure and its antecedent conditions such as cardiac hypertrophy and adverse remodelling after MI. Oxidative stress describes an imbalance between antioxidant defences and the production of reactive oxygen species (ROS), which at high levels cause cell damage but at lower levels induce subtle changes in intracellular signalling pathways (termed redox signalling). ROS are derived from many sources including mitochondria, xanthine oxidase, uncoupled nitric oxide synthases and NADPH oxidases. The latter enzymes are especially important in redox signalling, being implicated in the pathophysiology of hypertension and atherosclerosis, and activated by diverse pathologically relevant stimuli. We review the contribution of ROS to heart failure pathophysiology and discuss potential therapies that may specifically target detrimental redox signalling. Indeed, drugs such as ACE inhibitors and statins may act in part through such mechanisms. A better understanding of redox signalling mechanisms may enable the development of new targeted therapeutic strategies rather than the non‐specific antioxidant approaches that have to date been disappointing in clinical trials. PMID:16670100

  7. Should flood regimes change in a warming climate? The role of antecedent moisture conditions

    NASA Astrophysics Data System (ADS)

    Woldemeskel, Fitsum; Sharma, Ashish

    2016-07-01

    Assessing changes to flooding is important for designing new and redesigning existing infrastructure to withstand future climates. While there is speculation that floods are likely to intensify in the future, this question is often difficult to assess due to inadequate records on streamflow extremes. An alternate way of determining possible extreme flooding is through assessment of the two key factors that lead to the intensification of floods: the intensification of causative rainfall and changes in the wetness conditions prior to rainfall. This study assesses global changes in the antecedent wetness prior to extreme rainfall. Our results indicate a significant increase in the antecedent moisture in Australia and Africa over the last century; however, there was also a decrease in Eurasia and insignificant change in North America. Given the nature of changes found in this study, any future flood assessment for global warming conditions should take into account antecedent moisture conditions.

  8. Homodimeric chicken galectin CG-1B (C-14): Crystal structure and detection of unique redox-dependent shape changes involving inter- and intrasubunit disulfide bridges by gel filtration, ultracentrifugation, site-directed mutagenesis, and peptide mass fingerprinting.

    PubMed

    López-Lucendo, María F; Solís, Dolores; Sáiz, José Luis; Kaltner, Herbert; Russwurm, Roland; André, Sabine; Gabius, Hans-Joachim; Romero, Antonio

    2009-02-20

    Intrafamily gene diversification has led to three prototype galectins in chicken [i.e., chicken galectin (CG)-1A, CG-1B, and CG-2] that show distinct expression profiles and developmental regulation. In order to pinpoint structural disparities among them, we determined the crystal structure of CG-1B. Alteration of the position of the Trp ring in the lectin site and the presence of only two ordered water molecules therein, as well as changes in the interface region between the two subunits, set the structure of CG-1B clearly apart from that of CG-1A. Intriguingly, the unique presence of two Cys residues at positions 2 and 7 in the N-terminal region translated into formation of an intersubunit disulfide bridge between the Cys7 residues of the homodimer in the crystal. In solution, oxidation is associated with significant shape changes in the dimeric protein and the additional occurrence of a compacted form with an intrasubunit disulfide bridge between Cys2 and Cys7. The single-site mutant C7S/C7V was not subjected to such changes, supporting the crucial role of Cys7 in redox-dependent shape changes. These results point to the functional significance of the distinctive presence of the two Cys residues in the N-terminal region of CG-1B.

  9. An Excel Workbook for Identifying Redox Processes in Ground Water

    USGS Publications Warehouse

    Jurgens, Bryant C.; McMahon, Peter B.; Chapelle, Francis H.; Eberts, Sandra M.

    2009-01-01

    The reduction/oxidation (redox) condition of ground water affects the concentration, transport, and fate of many anthropogenic and natural contaminants. The redox state of a ground-water sample is defined by the dominant type of reduction/oxidation reaction, or redox process, occurring in the sample, as inferred from water-quality data. However, because of the difficulty in defining and applying a systematic redox framework to samples from diverse hydrogeologic settings, many regional water-quality investigations do not attempt to determine the predominant redox process in ground water. Recently, McMahon and Chapelle (2008) devised a redox framework that was applied to a large number of samples from 15 principal aquifer systems in the United States to examine the effect of redox processes on water quality. This framework was expanded by Chapelle and others (in press) to use measured sulfide data to differentiate between iron(III)- and sulfate-reducing conditions. These investigations showed that a systematic approach to characterize redox conditions in ground water could be applied to datasets from diverse hydrogeologic settings using water-quality data routinely collected in regional water-quality investigations. This report describes the Microsoft Excel workbook, RedoxAssignment_McMahon&Chapelle.xls, that assigns the predominant redox process to samples using the framework created by McMahon and Chapelle (2008) and expanded by Chapelle and others (in press). Assignment of redox conditions is based on concentrations of dissolved oxygen (O2), nitrate (NO3-), manganese (Mn2+), iron (Fe2+), sulfate (SO42-), and sulfide (sum of dihydrogen sulfide [aqueous H2S], hydrogen sulfide [HS-], and sulfide [S2-]). The logical arguments for assigning the predominant redox process to each sample are performed by a program written in Microsoft Visual Basic for Applications (VBA). The program is called from buttons on the main worksheet. The number of samples that can be analyzed

  10. Tuning of Redox Regulatory Mechanisms, Reactive Oxygen Species and Redox Homeostasis under Salinity Stress

    PubMed Central

    Hossain, M. Sazzad; Dietz, Karl-Josef

    2016-01-01

    Soil salinity is a crucial environmental constraint which limits biomass production at many sites on a global scale. Saline growth conditions cause osmotic and ionic imbalances, oxidative stress and perturb metabolism, e.g., the photosynthetic electron flow. The plant ability to tolerate salinity is determined by multiple biochemical and physiological mechanisms protecting cell functions, in particular by regulating proper water relations and maintaining ion homeostasis. Redox homeostasis is a fundamental cell property. Its regulation includes control of reactive oxygen species (ROS) generation, sensing deviation from and readjustment of the cellular redox state. All these redox related functions have been recognized as decisive factors in salinity acclimation and adaptation. This review focuses on the core response of plants to overcome the challenges of salinity stress through regulation of ROS generation and detoxification systems and to maintain redox homeostasis. Emphasis is given to the role of NADH oxidase (RBOH), alternative oxidase (AOX), the plastid terminal oxidase (PTOX) and the malate valve with the malate dehydrogenase isoforms under salt stress. Overwhelming evidence assigns an essential auxiliary function of ROS and redox homeostasis to salinity acclimation of plants. PMID:27242807

  11. Eye-blink conditioning is associated with changes in synaptic ultrastructure in the rabbit interpositus nuclei

    PubMed Central

    Weeks, Andrew C.W.; Connor, Steve; Hinchcliff, Richard; LeBoutillier, Janelle C.; Thompson, Richard F.; Petit, Ted L.

    2007-01-01

    Eye-blink conditioning involves the pairing of a conditioned stimulus (usually a tone) to an unconditioned stimulus (air puff), and it is well established that an intact cerebellum and interpositus nucleus, in particular, are required for this form of classical conditioning. Changes in synaptic number or structure have long been proposed as a mechanism that may underlie learning and memory, but localizing these changes has been difficult. Thus, the current experiment took advantage of the large amount of research conducted on the neural circuitry that supports eye-blink conditioning by examining synaptic changes in the rabbit interpositus nucleus. Synaptic quantifications included total number of synapses per neuron, numbers of excitatory versus inhibitory synapses, synaptic curvature, synaptic perforations, and the maximum length of the synapses. No overall changes in synaptic number, shape, or perforations were observed. There was, however, a significant increase in the length of excitatory synapses in the conditioned animals. This increase in synaptic length was particularly evident in the concave-shaped synapses. These results, together with previous findings, begin to describe a sequence of synaptic change in the interpositus nuclei following eye-blink conditioning that would appear to begin with structural change and end with an increase in synaptic number. PMID:17551096

  12. Redox State of the Neoarchean Earth Environment

    NASA Technical Reports Server (NTRS)

    Zerkle, Aubrey L.; Claire, Mark W.; Domagal-Goldman, Shawn; Farquhar, James; Poulton, Simon W.

    2011-01-01

    A Titan-like organic haze has been hypothesized for Earth's atmosphere prior to widespread surface oxygenation approx.2.45 billion years ago (Ga). We present a high-resolution record of quadruple sulfur isotopes, carbon isotopes, and Fe speciation from the approx.2.65-2.5 Ga Ghaap Group, South Africa, which suggest a linkage between organic haze and the biogeochemical cycling of carbon, sulfur, oxygen, and iron on the Archean Earth. These sediments provide evidence for oxygen production in microbial mats and localized oxygenation of surface waters. However, this oxygen production occurred under a reduced atmosphere which existed in multiple distinct redox states that correlate to changes in carbon and sulfur isotopes. The data are corroborated by photochemical model results that suggest bi-stable transitions between organic haze and haze-free atmospheric conditions in the Archean. These geochemical correlations also extend to other datasets, indicating that variations in the character of anomalous sulfur fractionation could provide insight into the role of carbon-bearing species in the reducing Archean atmosphere.

  13. A lack of response of the financial behaviors of biodiversity conservation nonprofits to changing economic conditions

    PubMed Central

    Larson, Eric R; Boyer, Alison G; Armsworth, Paul R

    2014-01-01

    The effectiveness of conservation organizations is determined in part by how they adapt to changing conditions. Over the previous decade, economic conditions in the United States (US) showed marked variation including a period of rapid growth followed by a major recession. We examine how biodiversity conservation nonprofits in the US responded to these changes through their financial behaviors, focusing on a sample of 90 biodiversity conservation nonprofits and the largest individual organization (The Nature Conservancy; TNC). For the 90 sampled organizations, an analysis of financial ratios derived from tax return data revealed little response to economic conditions. Similarly, more detailed examination of conservation expenditures and land acquisition practices of TNC revealed only one significant relationship with economic conditions: TNC accepted a greater proportion of conservation easements as donated in more difficult economic conditions. Our results suggest that the financial behaviors of US biodiversity conservation nonprofits are unresponsive to economic conditions. PMID:25512840

  14. Redox- and Reactive Oxygen Species-Dependent Signaling into and out of the Photosynthesizing Chloroplast1[OPEN

    PubMed Central

    Dietz, Karl-Josef; Krieger-Liszkay, Anja

    2016-01-01

    Photosynthesis is a high-rate redox metabolic process that is subjected to rapid changes in input parameters, particularly light. Rapid transients of photon capture, electron fluxes, and redox potentials during photosynthesis cause reactive oxygen species (ROS) to be released, including singlet oxygen, superoxide anion radicals, and hydrogen peroxide. Thus, the photosynthesizing chloroplast functions as a conditional source of important redox and ROS information, which is exploited to tune processes both inside the chloroplast and, following retrograde release or processing, in the cytosol and nucleus. Analyses of mutants and comparative transcriptome profiling have led to the identification of these processes and associated players and have allowed the specificity and generality of response patterns to be defined. The release of ROS and oxidation products, envelope permeabilization (for larger molecules), and metabolic interference with mitochondria and peroxisomes produce an intricate ROS and redox signature, which controls acclimation processes. This photosynthesis-related ROS and redox information feeds into various pathways (e.g. the mitogen-activated protein kinase and OXI1 signaling pathways) and controls processes such as gene expression and translation. PMID:27255485

  15. Enhanced Colloidal Stability of CeO2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation.

    PubMed

    Liu, Xuyang; Ray, Jessica R; Neil, Chelsea W; Li, Qingyun; Jun, Young-Shin

    2015-05-05

    Due to the toxicity of cerium oxide (CeO2) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property changes of CeO2 NPs and their transport in natural and engineered aqueous systems is needed. This study investigates the impact of redox reactions with ferrous ions (Fe2+) on the colloidal stability of CeO2 NPs. We demonstrated that under anaerobic conditions, suspended CeO2 NPs in a 3 mM FeCl2 solution at pH 4.8 were much more stable against sedimentation than those in the absence of Fe2+. Redox reactions between CeO2 NPs and Fe2+ lead to the formation of 6-line ferrihydrite on the CeO2 surfaces, which enhanced the colloidal stability by increasing the zeta potential and hydrophilicity of CeO2 NPs. These redox reactions can affect the toxicity of CeO2 NPs by increasing cerium dissolution, and by creating new Fe(III) (hydr)oxide reactive surface layers. Thus, these findings have significant implications for elucidating the phase transformation and transport of redox reactive NPs in the environment.

  16. Rate of Conditioned Reinforcement Affects Observing Rate but Not Resistance to Change

    ERIC Educational Resources Information Center

    Shahan, Timothy A.; Podlesnik, Christopher A.

    2005-01-01

    The effects of rate of conditioned reinforcement on the resistance to change of operant behavior have not been examined. In addition, the effects of rate of conditioned reinforcement on the rate of observing have not been adequately examined. In two experiments, a multiple schedule of observing-response procedures was used to examine the effects…

  17. Effects of redox fluctuations on microbial community ecology post-wildfire in a high elevation mixed-conifer catchment in northern New Mexico.

    NASA Astrophysics Data System (ADS)

    Fairbanks, D.; Green, K.; Murphy, M. A.; Shepard, C.; Chorover, J.; Rich, V. I.; Gallery, R. E.

    2015-12-01

    Wildfires are increasing in size and severity across the western United States with impacts on regional biogeochemical cycling. The resiliency of resident soil microbial communities determines rates of nutrient transformations as well as forest structure and recovery. Redox conditions in soil determine metabolic activities of microorganisms, which first consume oxygen and a succession of alternative terminal electron acceptors to support growth and metabolism using a variety of carbon sources. Controls on redox zonation are largely unknown in dominantly oxic soils, and microbial community adaptation and response to fluctuations in redox potential in a sub-alpine forested post-disturbance catchment has not been studied. Previous work has shown that fluctuating or rising water tables result in redox-dynamic sites, which can be 'hot spots' of biogeochemical activity depending on landscape position. Fire-induced tree mortality results in altered hydrologic flow paths and decreased evapotranspiration, leading to potential for intensified hot spot activity. We are testing such coupling of microbial activity with fluctuations in redox status using field measurements and laboratory incubation experiments. The 2013 Thompson Ridge Fire in the Jemez River Basin (NM) Critical Zone Observatory provides a highly-contextualized opportunity to examine how disturbance regime affects changes in soil microbial community dynamics and fluctuations in reduction-oxidation potential (as quantified by continuous CZO measurements of O2, CO2 and Eh as a function of soil depth and landscape location). We hypothesize that areas of depositional convergence in the catchment, which have been shown to exhibit more reducing conditions, will host microbial communities that are better adapted to fluctuating redox conditions and exhibit a greater diversity in functional capabilities. In these mixed conifer forests we find shifts in redox potential status in relation to depth and topography where more

  18. Crossing redox boundaries--aquifer redox history and effects on iron mineralogy and arsenic availability.

    PubMed

    Banning, Andre; Rüde, Thomas R; Dölling, Bettina

    2013-11-15

    Cretaceous shallow marine sediments from northwestern Germany exhibit a distinct colour and geochemical boundary in a depth of several decametres, witnessing a terrestrial oxidative paleo redox process which resulted in cement loss and oxidation of Fe(II) phases. Sediment samples were obtained from boreholes drilled in near-coastal and further basinward paleo environments, including both reduced and oxidized redox facies, to characterize As and Fe occurrence in unaltered layers and redistributional consequences of the redox event. Geochemical and mineralogical composition and As fractionation were assessed. Arsenic resides in pyrite in the reduced section with a bulk rock maximum concentration of 39 μg g(-1), calculated Aspyrite is ~0.2 wt.%. Siderite concretions in the fine sands do not function as As sinks, neither does glauconite whose general As/Fe leaching behaviour was characterized. In the zone of redox transition, reduced and oxidized phases coexist and elevated As concentrations (up to 73 μg g(-1)) with high proportions of reactive As were detected. Arsenic behaviour changes from relatively homogeneous Fe sulphide-control in the unaltered sediments to very heterogeneous Fe hydroxide-control above the paleo redox boundary. The studied characteristics determine recent As availability in the subsurface and must be considered during groundwater extraction from this highly important aquifer.

  19. Mutual Comparative Filtering for Change Detection in Videos with Unstable Illumination Conditions

    NASA Astrophysics Data System (ADS)

    Sidyakin, Sergey V.; Vishnyakov, Boris V.; Vizilter, Yuri V.; Roslov, Nikolay I.

    2016-06-01

    In this paper we propose a new approach for change detection and moving objects detection in videos with unstable, abrupt illumination changes. This approach is based on mutual comparative filters and background normalization. We give the definitions of mutual comparative filters and outline their strong advantage for change detection purposes. Presented approach allows us to deal with changing illumination conditions in a simple and efficient way and does not have drawbacks, which exist in models that assume different color transformation laws. The proposed procedure can be used to improve a number of background modelling methods, which are not specifically designed to work under illumination changes.

  20. Trends in vegetation change under different karst terrain conditions, southwest China

    NASA Astrophysics Data System (ADS)

    Tong, Xiaowei; Wang, Kelin; Yue, Yuemin; Liao, Chujie

    2013-10-01

    Trends in vegetation change and their relationships with terrain conditions are significant to understand and evaluate the efficiency of ecological engineering implemented in karst regions, Southwest China. This study aimed to identify vegetation change trends in Hechi, Guangxi, China using time-series of SPOT-VGT NDVI data (1999-2010) and DEM. Linear trend analysis was applied to examine NDVI change trends. The results indicated that most of NDVI values had increased during this time period. There were spatial variations in NDVI change trends, which could be partiallly explained by different karst terrain conditions. The areas of most obviously positive trends in NDVI change were found at the elevation of 500-1000m and the relief amplitude between 200 and 500 m. Negative trends in NDVI change were appeared on slopes of south (sunlit) and west (semi-sunlit) aspect and at the elevation of 200 - 500 m, where were mainly due to human activities.

  1. Health and the war. Changing schemes and health conditions during the Spanish civil war.

    PubMed

    Barona, Josep L; Perdiguero-Gil, Enrique

    2008-01-01

    This paper focuses on the health reforms during the republican Spain (1931-1939) and the crisis derived from the three-year of civil war. It considers how the war affected the health system and the impairment of health conditions of the population during the late 1930s, considering the changing conditions caused by the conflict. Some of the specific topics analysed are the changing healthcare system, the adaptation of health organization after the outbreak of the war, the impact of the war on the health of the population and epidemiological changes, the problem of the refugees and the clinical studies by experts, mainly on undernourishment.

  2. Change of pH during excess sludge fermentation under alkaline, acidic and neutral conditions.

    PubMed

    Yuan, Yue; Peng, Yongzhen; Liu, Ye; Jin, Baodan; Wang, Bo; Wang, Shuying

    2014-12-01

    The change in pH during excess sludge (ES) fermentation of varying sludge concentrations was investigated in a series of reactors at alkaline, acidic, and neutral pHs. The results showed that the changes were significantly affected by fermentative conditions. Under different conditions, pH exhibited changing profiles. When ES was fermented under alkaline conditions, pH decreased in a range of (10±1). At the beginning of alkaline fermentation, pH dropped significantly, at intervals of 4h, 4h, and 5h with sludge concentrations of 8665.6mg/L, 6498.8mg/L, and 4332.5mg/L, then it would become moderate. However, under acidic conditions, pH increased from 4 to 5. Finally, under neutral conditions pH exhibited a decrease then an increase throughout entire fermentation process. Further study showed short-chain fatty acids (SCFAs), ammonia nitrogen and cations contributed to pH change under various fermentation conditions. This study presents a novel strategy based on pH change to predict whether SCFAs reach their stable stage.

  3. Redox processes and water quality of selected principal aquifer systems

    USGS Publications Warehouse

    McMahon, P.B.; Chapelle, F.H.

    2008-01-01

    Reduction/oxidation (redox) conditions in 15 principal aquifer (PA) systems of the United States, and their impact on several water quality issues, were assessed from a large data base collected by the National Water-Quality Assessment Program of the USGS. The logic of these assessments was based on the observed ecological succession of electron acceptors such as dissolved oxygen, nitrate, and sulfate and threshold concentrations of these substrates needed to support active microbial metabolism. Similarly, the utilization of solid-phase electron acceptors such as Mn(IV) and Fe(III) is indicated by the production of dissolved manganese and iron. An internally consistent set of threshold concentration criteria was developed and applied to a large data set of 1692 water samples from the PAs to assess ambient redox conditions. The indicated redox conditions then were related to the occurrence of selected natural (arsenic) and anthropogenic (nitrate and volatile organic compounds) contaminants in ground water. For the natural and anthropogenic contaminants assessed in this study, considering redox conditions as defined by this framework of redox indicator species and threshold concentrations explained many water quality trends observed at a regional scale. An important finding of this study was that samples indicating mixed redox processes provide information on redox heterogeneity that is useful for assessing common water quality issues. Given the interpretive power of the redox framework and given that it is relatively inexpensive and easy to measure the chemical parameters included in the framework, those parameters should be included in routine water quality monitoring programs whenever possible.

  4. Alternative Evaluation for the REDOX (202-S) Plutonium Loadout Hood

    SciTech Connect

    N. R. Kerr

    1999-09-20

    Located in the 200 Areas is the inactive 202-S Reduction Oxidation (REDOX) Facility, which is managed by the Bechtel Hanford, Inc. Surveillance/Maintenance and Transition project. This facility is contaminated from nuclear material processes related to nuclear material separation from Hanford Site facility operations. This alternative evaluation report describes the alternatives and selection criteria based on the necessary protective requirements to maintain the REDOX Plutonium Loadout Hood in a safe and stable condition awaiting a final waste response action.

  5. Cysteine Mutational Studies Provide Insight into a Thiol-Based Redox Switch Mechanism of Metal and DNA Binding in FurA from Anabaena sp. PCC 7120

    PubMed Central

    Botello-Morte, Laura; Pellicer, Silvia; Sein-Echaluce, Violeta C.; Contreras, Lellys M.; Neira, José Luis; Abián, Olga; Velázquez-Campoy, Adrián; Peleato, María Luisa; Fillat, María F.

    2016-01-01

    Abstract Aims: The ferric uptake regulator (Fur) is the main transcriptional regulator of genes involved in iron homeostasis in most prokaryotes. FurA from Anabaena sp. PCC 7120 contains five cysteine residues, four of them arranged in two redox-active CXXC motifs. The protein needs not only metal but also reducing conditions to remain fully active in vitro. Through a mutational study of the cysteine residues present in FurA, we have investigated their involvement in metal and DNA binding. Results: Residue C101 that belongs to a conserved CXXC motif plays an essential role in both metal and DNA binding activities in vitro. Substitution of C101 by serine impairs DNA and metal binding abilities of FurA. Isothermal titration calorimetry measurements show that the redox state of C101 is responsible for the protein ability to coordinate the metal corepressor. Moreover, the redox state of C101 varies with the presence or absence of C104 or C133, suggesting that the environments of these cysteines are mutually interdependent. Innovation: We propose that C101 is part of a thiol/disulfide redox switch that determines FurA ability to bind the metal corepressor. Conclusion: This mechanism supports a novel feature of a Fur protein that emerges as a regulator, which connects the response to changes in the intracellular redox state and iron management in cyanobacteria. Antioxid. Redox Signal. 24, 173–185. PMID:26414804

  6. Reactive oxygen species and redox compartmentalization.

    PubMed

    Kaludercic, Nina; Deshwal, Soni; Di Lisa, Fabio

    2014-01-01

    Reactive oxygen species (ROS) formation and signaling are of major importance and regulate a number of processes in physiological conditions. A disruption in redox status regulation, however, has been associated with numerous pathological conditions. In recent years it has become increasingly clear that oxidative and reductive modifications are confined in a spatio-temporal manner. This makes ROS signaling similar to that of Ca(2+) or other second messengers. Some subcellular compartments are more oxidizing (such as lysosomes or peroxisomes) whereas others are more reducing (mitochondria, nuclei). Moreover, although more reducing, mitochondria are especially susceptible to oxidation, most likely due to the high number of exposed thiols present in that compartment. Recent advances in the development of redox probes allow specific measurement of defined ROS in different cellular compartments in intact living cells or organisms. The availability of these tools now allows simultaneous spatio-temporal measurements and correlation between ROS generation and organelle and/or cellular function. The study of ROS compartmentalization and microdomains will help elucidate their role in physiology and disease. Here we will examine redox probes currently available and how ROS generation may vary between subcellular compartments. Furthermore, we will discuss ROS compartmentalization in physiological and pathological conditions focusing our attention on mitochondria, since their vulnerability to oxidative stress is likely at the basis of several diseases.

  7. Metabolic and morphological changes of an oil accumulating trebouxiophycean alga in nitrogen-deficient conditions.

    PubMed

    Ito, Takuro; Tanaka, Miho; Shinkawa, Haruka; Nakada, Takashi; Ano, Yoshitaka; Kurano, Norihide; Soga, Tomoyoshi; Tomita, Masaru

    2013-03-01

    Oil-rich algae have promising potential for a next-generation biofuel feedstock. Pseudochoricystis ellipsoidea MBIC 11204, a novel unicellular green algal strain, accumulates a large amount of oil (lipids) in nitrogen-deficient (-N) conditions. Although the oil bodies are easily visualized by lipophilic staining in the cells, little is known about how oil bodies are metabolically synthesized. Clarifying the metabolic profiles in -N conditions is important to understand the physiological mechanisms of lipid accumulations and will be useful to optimize culture conditions efficiently produce industrial oil. Metabolome and lipidome profiles were obtained, respectively, using capillary electrophoresis- and liquid chromatography-mass spectrometry from P. ellipsoidea in both nitrogen-rich (+N; rapid growth) and -N conditions. Relative quantities of more than 300 metabolites were systematically compared between these two conditions. Amino acids in nitrogen assimilation and N-transporting metabolisms were decreased to 1/20 the amount, or less, in -N conditions. In lipid metabolism, the quantities of neutral lipids increased greatly in -N conditions; however, quantities of nearly all the other lipids either decreased or only changed slightly. The morphological changes in +N and -N conditions were also provided by microscopy, and we discuss their relationship to the metabolic changes. This is the first approach to understand the novel algal strain's metabolism using a combination of wide-scale metabolome analysis and morphological analysis.

  8. An evaluation of resistance to change with unconditioned and conditioned reinforcers.

    PubMed

    Vargo, Kristina K; Ringdahl, Joel E

    2015-09-01

    Several reinforcer-related variables influence a response's resistance to change (Nevin, 1974). Reinforcer type (i.e., conditioned or unconditioned) is a reinforcer-related variable that has not been studied with humans but may have clinical implications. In Experiment 1, we identified unconditioned and conditioned reinforcers of equal preference. In Experiments 2, 3, and 4, we reinforced participants' behavior during a baseline phase using a multiple variable-interval (VI) 30-s VI 30-s schedule with either conditioned (i.e., token) or unconditioned (i.e., food; one type of reinforcement in each component) reinforcement. After equal reinforcement rates across components, we introduced a disruptor. Results of Experiments 2 and 3 showed that behaviors were more resistant to extinction and distraction, respectively, with conditioned than with unconditioned reinforcers. Results of Experiment 4, however, showed that when prefeeding disrupted responding, behaviors were more resistant to change with unconditioned reinforcers than with conditioned reinforcers.

  9. Redox Control of Inflammation in Macrophages

    PubMed Central

    Dehne, Nathalie; Grossmann, Nina; Jung, Michaela; Namgaladze, Dmitry; Schmid, Tobias; von Knethen, Andreas; Weigert, Andreas

    2013-01-01

    Abstract Macrophages are present throughout the human body, constitute important immune effector cells, and have variable roles in a great number of pathological, but also physiological, settings. It is apparent that macrophages need to adjust their activation profile toward a steadily changing environment that requires altering their phenotype, a process known as macrophage polarization. Formation of reactive oxygen species (ROS), derived from NADPH-oxidases, mitochondria, or NO-producing enzymes, are not necessarily toxic, but rather compose a network signaling system, known as redox regulation. Formation of redox signals in classically versus alternatively activated macrophages, their action and interaction at the level of key targets, and the resulting physiology still are insufficiently understood. We review the identity, source, and biological activities of ROS produced during macrophage activation, and discuss how they shape the key transcriptional responses evoked by hypoxia-inducible transcription factors, nuclear-erythroid 2-p45-related factor 2 (Nrf2), and peroxisome proliferator-activated receptor-γ. We summarize the mechanisms how redox signals add to the process of macrophage polarization and reprogramming, how this is controlled by the interaction of macrophages with their environment, and addresses the outcome of the polarization process in health and disease. Future studies need to tackle the option whether we can use the knowledge of redox biology in macrophages to shape their mediator profile in pathophysiology, to accelerate healing in injured tissue, to fight the invading pathogens, or to eliminate settings of altered self in tumors. Antioxid. Redox Signal. 19, 595–637. PMID:23311665

  10. Redox flow batteries: a review

    SciTech Connect

    Weber, Adam Z.; Mench, Matthew M; Meyers, Jeremy; Ross, Philip N.; Gostick, Jeffrey T.; Liu, Qinghua

    2011-01-01

    Redox flow batteries (RFBs) are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of RFBs with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.

  11. Microbial iron-redox cycling in subsurface environments.

    PubMed

    Roden, Eric E

    2012-12-01

    In addition to its central role in mediating electron-transfer reactions within all living cells, iron undergoes extracellular redox transformations linked to microbial energy generation through utilization of Fe(II) as a source of chemical energy or Fe(III) as an electron acceptor for anaerobic respiration. These processes permit microbial populations and communities to engage in cyclic coupled iron oxidation and reduction within redox transition zones in subsurface environments. In the present paper, I review and synthesize a few case studies of iron-redox cycling in subsurface environments, highlighting key biochemical aspects of the extracellular iron-redox metabolisms involved. Of specific interest are the coupling of iron oxidation and reduction in field and experimental systems that model redox gradients and fluctuations in the subsurface, and novel pathways and organisms involved in the redox cycling of insoluble iron-bearing minerals. These findings set the stage for rapid expansion in our knowledge of the range of extracellular electron-transfer mechanisms utilized by subsurface micro-organisms. The observation that closely coupled oxidation and reduction of iron can take place under conditions common to the subsurface motivates this expansion in pursuit of molecular tools for studying iron-redox cycling communities in situ.

  12. Genome-wide transcriptional response of a Saccharomyces cerevisiae strain with an altered redox metabolism.

    PubMed

    Bro, Christoffer; Regenberg, Birgitte; Nielsen, Jens

    2004-02-05

    The genome-wide transcriptional response of a Saccharomyces cerevisiae strain deleted in GDH1 that encodes a NADP(+)-dependent glutamate dehydrogenase was compared to a wild-type strain under anaerobic steady-state conditions. The GDH1-deleted strain has a significantly reduced NADPH requirement, and therefore, an altered redox metabolism. Identification of genes with significantly changed expression using a t-test and a Bonferroni correction yielded only 16 transcripts when accepting two false-positives, and 7 of these were Open Reading Frames (ORFs) with unknown function. Among the 16 transcripts the only one with a direct link to redox metabolism was GND1, encoding phosphogluconate dehydrogenase. To extract additional information we analyzed the transcription data for a gene subset consisting of all known genes encoding metabolic enzymes that use NAD(+) or NADP(+). The subset was analyzed for genes with significantly changed expression again with a t-test and correction for multiple testing. This approach was found to enrich the analysis since GND1, ZWF1 and ALD6, encoding the most important enzymes for regeneration of NADPH under anaerobic conditions, were down-regulated together with eight other genes encoding NADP(H)-dependent enzymes. This indicates a possible common redox-dependent regulation of these genes. Furthermore, we showed that it might be necessary to analyze the expression of a subset of genes to extract all available information from global transcription analysis.

  13. Iron Supplementation Effects on Redox Status following Aseptic Skeletal Muscle Trauma in Adults and Children

    PubMed Central

    Tsiokanos, Athanasios; Georgakouli, Kalliopi; Zalavras, Athanasios; Avloniti, Alexandra; Koutedakis, Yiannis

    2017-01-01

    Exercise-induced skeletal muscle microtrauma is characterized by loss of muscle cell integrity, marked aseptic inflammatory response, and oxidative stress. We examined if iron supplementation would alter redox status after eccentric exercise. In a randomized, double blind crossover study, that was conducted in two cycles, healthy adults (n = 14) and children (n = 11) received daily either 37 mg of elemental iron or placebo for 3 weeks prior to and up to 72 h after an acute eccentric exercise bout. Blood was drawn at baseline, before exercise, and 72 h after exercise for the assessment of iron status, creatine kinase activity (CK), and redox status. Iron supplementation at rest increased iron concentration and transferrin saturation (p < 0.01). In adults, CK activity increased at 72 h after exercise, while no changes occurred in children. Iron supplementation increased TBARS at 72 h after exercise in both adults and children; no changes occurred under placebo condition. Eccentric exercise decreased bilirubin concentration at 72 h in all groups. Iron supplementation can alter redox responses after muscle-damaging exercise in both adults and children. This could be of great importance not only for healthy exercising individuals, but also in clinical conditions which are characterized by skeletal muscle injury and inflammation, yet iron supplementation is crucial for maintaining iron homeostasis. This study was registered at Clinicaltrials.gov Identifier: NCT02374619. PMID:28203319

  14. Prolonged RNA changes in the Hermissenda eye induced by classical conditioning

    SciTech Connect

    Nelson, T.J.; Alkon, D.L. )

    1988-10-01

    The incorporation of {sup 32}P into mRNA and the total amount of mRNA were increased 3- to 4-fold in eyes isolated from Hermissenda crassicornis trained to associate light with rotation on a turntable compared with animals trained with equal numbers of light and rotation events presented randomly and with naive animals. Incorporation of {sup 32}P into poly(A){sup {minus}} RNA was reduced by as much as 60%. The RNA changes were strongly correlated with the degree of learning and could not be accounted for by changes in ({sup 32}P)ATP content. The RNA changes were maximal at 24 hr and were still detectable after 4 days, indicating that associative conditioning produces a period of increased DNA transcription that could be an intermediate step in memory consolidation. The RNA changes may in part account for recently observed conditioning-specific changes in the synthesis rates of specific proteins.

  15. CryoSat Estimates of Greenland Elevation Change, 2011-2014, under Varying Surface Melt Conditions.

    NASA Astrophysics Data System (ADS)

    McMillan, M.; Leeson, A.; Shepherd, A.; Briggs, K.; Armitage, T.; Muir, A.; Gilbert, L.; van den Broeke, M.; Kuipers Munneke, P.; Noel, B.

    2015-12-01

    Two decades of satellite observations have documented substantial mass loss from the Greenland Ice Sheet in response to ocean- and atmospheric-driven melting. During this period, ice mass has fluctuated over a range of timescales, from seasonal cycles in surface melt to decadal and longer responses to the surrounding climate. Mass loss is also highly variable in space, as a result of the distinct geometries and boundary conditions of different glaciological catchments. Resolving changes in ice sheet mass at both a high spatial resolution and temporal sampling frequency is necessary for understanding the timescales and drivers of glaciological change, but has remained a challenge for all satellite geodetic techniques. While radar altimetry has the potential to sample elevation change at a high (~ monthly) temporal frequency and with moderate (~ 5 km) spatial resolution, observations of Greenland Ice Sheet elevation change and mass balance have been challenging because of the kilometer scale resolution of pulse limited elevation measurements and the impact of highly variable snowpack conditions upon the backscattered echo. In this study we investigate the ability of CryoSat to derive estimates of Greenland Ice Sheet elevation change. We use an along-track approach to map ice sheet elevation changes between 2011 and 2014 and evaluate our results using ICEBridge airborne altimetry. Particular attention is given to the influence of changing snowpack conditions on the received echo, and the impact of the extensive 2012 summer melt event on the derived estimates of surface elevation change.

  16. Neptunium redox speciation at the illite surface

    NASA Astrophysics Data System (ADS)

    Marsac, Rémi; Banik, Nidhu lal; Lützenkirchen, Johannes; Marquardt, Christian Michael; Dardenne, Kathy; Schild, Dieter; Rothe, Joerg; Diascorn, Alexandre; Kupcik, Tomas; Schäfer, Thorsten; Geckeis, Horst

    2015-03-01

    Neptunium (Np(V)) sorption onto a purified illite is investigated as a function of pH (3-10) and [NpVO2+]tot(3 × 10-8-3 × 10-4 M) in 0.1 M NaCl under Ar atmosphere. After about one week reaction time, only insignificant variation of Np sorption is observed and the establishment of reaction equilibrium can be assumed. Surprisingly, solid-liquid distribution ratios (Rd) are clearly higher than those measured for Np(V) sorption onto illite under aerobic conditions. The observation that Rd increases with decreasing pe (pe = -log ae-) suggests partial reduction to Np(IV), although measured redox potentials (pe values) at a first glance suggest the predominance of Np(V). Reduction to Np(IV) at the illite surface could indeed be confirmed by X-ray absorption near-edge spectroscopy (XANES). Np speciation in presence of the purified Na-illite under given conditions is consistently described by applying the 2 sites protolysis non-electrostatic surface complexation and cation exchange model. Measured pe data are taken to calculate Np redox state and surface complexation constants for Np(IV) are derived by applying a data fitting procedure. Constants are very consistent with results obtained by applying an existing linear free energy relationship (LFER). Taking Np(IV) surface complexation constants into account shifts the calculated Np(V)/Np(IV) redox borderline in presence of illite surfaces by 3-5 pe units (0.2-0.3 V) towards redox neutral conditions. Our study suggests that Np(V) reduction in presence of a sorbing mineral phase is thermodynamically favored.

  17. Variable ecological conditions promote male helping by changing banded mongoose group composition

    PubMed Central

    Sanderson, Jennifer L.; Mwanghuya, Francis; Businge, Robert; Kyabulima, Solomon; Hares, Michelle C.; Inzani, Emma; Kalema-Zikusoka, Gladys; Mwesige, Kenneth; Thompson, Faye J.; Vitikainen, Emma I. K.; Cant, Michael A.

    2016-01-01

    Ecological conditions are expected to have an important influence on individuals’ investment in cooperative care. However, the nature of their effects is unclear: both favorable and unfavorable conditions have been found to promote helping behavior. Recent studies provide a possible explanation for these conflicting results by suggesting that increased ecological variability, rather than changes in mean conditions, promote cooperative care. However, no study has tested whether increased ecological variability promotes individual-level helping behavior or the mechanisms involved. We test this hypothesis in a long-term study population of the cooperatively breeding banded mongoose, Mungos mungo, using 14 years of behavioral and meteorological data to explore how the mean and variability of ecological conditions influence individual behavior, body condition, and survival. Female body condition was more sensitive to changes in rainfall leading to poorer female survival and pronounced male-biased group compositions after periods of high rainfall variability. After such periods, older males invested more in helping behavior, potentially because they had fewer mating opportunities. These results provide the first empirical evidence for increased individual helping effort in more variable ecological conditions and suggest this arises because of individual differences in the effect of ecological conditions on body condition and survival, and the knock-on effect on social group composition. Individual differences in sensitivity to environmental variability, and the impacts this has on the internal structure and composition of animal groups, can exert a strong influence on the evolution and maintenance of social behaviors, such as cooperative care. PMID:27418750

  18. Variable ecological conditions promote male helping by changing banded mongoose group composition.

    PubMed

    Marshall, Harry H; Sanderson, Jennifer L; Mwanghuya, Francis; Businge, Robert; Kyabulima, Solomon; Hares, Michelle C; Inzani, Emma; Kalema-Zikusoka, Gladys; Mwesige, Kenneth; Thompson, Faye J; Vitikainen, Emma I K; Cant, Michael A

    2016-01-01

    Ecological conditions are expected to have an important influence on individuals' investment in cooperative care. However, the nature of their effects is unclear: both favorable and unfavorable conditions have been found to promote helping behavior. Recent studies provide a possible explanation for these conflicting results by suggesting that increased ecological variability, rather than changes in mean conditions, promote cooperative care. However, no study has tested whether increased ecological variability promotes individual-level helping behavior or the mechanisms involved. We test this hypothesis in a long-term study population of the cooperatively breeding banded mongoose, Mungos mungo, using 14 years of behavioral and meteorological data to explore how the mean and variability of ecological conditions influence individual behavior, body condition, and survival. Female body condition was more sensitive to changes in rainfall leading to poorer female survival and pronounced male-biased group compositions after periods of high rainfall variability. After such periods, older males invested more in helping behavior, potentially because they had fewer mating opportunities. These results provide the first empirical evidence for increased individual helping effort in more variable ecological conditions and suggest this arises because of individual differences in the effect of ecological conditions on body condition and survival, and the knock-on effect on social group composition. Individual differences in sensitivity to environmental variability, and the impacts this has on the internal structure and composition of animal groups, can exert a strong influence on the evolution and maintenance of social behaviors, such as cooperative care.

  19. Prefrontal Single-Neuron Responses after Changes in Task Contingencies during Trace Eyeblink Conditioning in Rabbits

    PubMed Central

    2016-01-01

    Abstract A number of studies indicate that the medial prefrontal cortex (mPFC) plays a role in mediating the expression of behavioral responses during tasks that require flexible changes in behavior. During trace eyeblink conditioning, evidence suggests that the mPFC provides the cerebellum with a persistent input to bridge the temporal gap between conditioned and unconditioned stimuli. Therefore, the mPFC is in a position to directly mediate the expression of trace conditioned responses. However, it is unknown whether persistent neural responses are associated with the flexible expression of behavior when task contingencies are changed during trace eyeblink conditioning. To investigate this, single-unit activity was recorded in the mPFC of rabbits during extinction and reacquisition of trace eyeblink conditioning, and during training to a different conditional stimulus. Persistent responses remained unchanged after full extinction, and also did not change during reacquisition training. During training to a different tone, however, the generalization of persistent responses to the new stimulus was associated with an animal’s performance—when persistent responses generalized to the new tone, performance was high (>50% response rate). When persistent responses decreased to baseline rates, performance was poor (<50% response rate). The data suggest that persistent mPFC responses do not appear to mediate flexible changes in the expression of the original learning, but do appear to play a role in the generalization of that learning when the task is modified. PMID:27517083

  20. Growth rate changes of sodium chlorate crystals independent of growth conditions

    NASA Astrophysics Data System (ADS)

    Mitrović, M. M.; Žekić, A. A.; Baroš, Z. Z.

    2008-10-01

    Results of investigations of the growth rate changes inherent to the crystal are presented. It is shown that, in initial growth stage, there exist crystal growth rate changes independent of experimental conditions, with tendency to level during the time. Time evolution of sodium chlorate crystals growth rate dispersion is also presented. The results obtained show that these changes must be included in the interpretations of the growth rate changes affected by various parameters (supersaturation, temperature, fields, stress, impurities, etc.), which have not previously been taken into account. These results may improve the current crystal growth theories.

  1. Response of larch root development to annual changes of water conditions in eastern Siberia

    NASA Astrophysics Data System (ADS)

    Takenaka, Chisato; Miyahara, Mie; Ohta, Takeshi; Maximov, Trofim C.

    2016-06-01

    Eastern Siberia is characterized by continuous permafrost, and has recently been exposed to the effects of climate change. Larch, which is the dominant tree species, has been subject to major environmental changes including fluctuations in soil water content. The purpose of this study was to clarify the responses of mature larch tree roots to changes in soil water conditions. We established a treatment plot in a larch forest, and artificially changed the soil water conditions by covering the ground surface with a vinyl sheet, and from 2004 to 2006 monitored root development through root windows. The vinyl sheet maintained high levels of soil water content, even though the ambient conditions varied from dry in 2004 to wet in 2005 and dry in 2006. In the treatment plot the plants adapted to the wet conditions by decreasing vertical root development. In contrast, roots of plants in the control plot developed to the subsurface layer, even in 2005, and did not develop vertically in 2006 despite the drought. We conclude that larch adapted to the annual changes in soil water content by changing the vertical distribution of roots, and that this reflected a memory effect.

  2. Thermal conditions influence changes in body temperature induced by intragastric administration of capsaicin in mice.

    PubMed

    Mori, Noriyuki; Urata, Tomomi; Fukuwatari, Tsutomu

    2016-08-01

    Capsaicin has been reported to have unique thermoregulatory actions. However, changes in core temperature after the administration of capsaicin are a controversial point. Therefore, we investigated the effects of environmental thermal conditions on changes in body temperature caused by capsaicin in mice. We showed that intragastric administration of 10 and 15 mg/kg capsaicin increased tail temperature and decreased colonic temperatures in the core temperature (CT)-constant and CT-decreasing conditions. In the CT-increasing condition, 15 mg/kg capsaicin increased tail temperature and decreased colonic temperature. However, 10 mg/kg capsaicin increased colonic temperature. Furthermore, the amount of increase in tail temperature was greater in the CT-decreasing condition and lower in the CT-increasing condition, compared with that of the CT-constant condition. These findings suggest that the changes in core temperature were affected by the environmental thermal conditions and that preliminary thermoregulation state might be more important than the constancy of temperature to evaluate the effects of heat diffusion and thermogensis.

  3. Personality Development at Work: Workplace Conditions, Personality Changes, and the Corresponsive Principle

    PubMed Central

    Le, Kimdy; Donnellan, M. Brent; Conger, Rand

    2013-01-01

    Objective Investigations concerning adult personality development have increasingly focused on factors that are associated with apparent personality trait changes. The current study contributes to this literature by replicating and extending previous research concerning personality trait development in young adulthood and perceptions of workplace conditions. Method Analyses were based on up to 442 individuals who participated in the ongoing Family Transitions Project (e.g., Conger & Conger, 2002). The current analyses included personality trait data from 1994 and 2003, high-school grades and SES indicators from 1994, and reports about work conditions in 2001, 2003, and 2005. Results Personality attributes were prospectively associated with work conditions and income. Findings also support the corresponsive principle of personality development (e.g. Roberts, Caspi, & Moffitt, 2003): Traits that were prospectively associated with particular workplace conditions often seemed to be accentuated by those conditions. Conclusions Personality traits are prospectively associated with perceptions of the workplace. Workplace conditions are also associated with trait development. PMID:23336723

  4. Redox reactions of apo mammalian ferritin.

    PubMed

    Watt, R K; Frankel, R B; Watt, G D

    1992-10-13

    Apo horse spleen ferritin undergoes a 6.3 +/- 0.5 electron redox reaction at -310 mV at pH 6.0-8.5 and 25 degrees C to form reduced apoferritin (apoMFred). Reconstituted ferritin containing up to 50 ferric ions undergoes reduction at the same potential, taking up one electron per ferric ion and six additional electrons by the protein. We propose that apo mammalian ferritin (apoMF) contains six redox centers that can be fully oxidized forming oxidized apoferritin (apoMFox) or fully reduced forming apoMFred. ApoMFred can be prepared conveniently by dithionite or methyl viologen reduction. ApoMFred is slowly oxidized by molecular oxygen but more rapidly by Fe(CN)6(3-) to apoMFox. Fe(III)-cytochrome c readily oxidizes apoMFred to apoMFox with a stoichiometry of 6 Fe(III)-cytochrome c per apoMFred, demonstrating a rapid interprotein electron-transfer reaction. Both redox states of apoMF react with added Fe3+ and Fe2+. Addition of eight Fe2+ to apoMFox under anaerobic conditions produced apoMFred and Fe3+, as evidenced by the presence of a strong g = 4.3 EPR signal. Subsequent addition of bipyridyl produced at least six Fe(bipyd)3(2+) per MF, establishing the reversibility of this internal electron-transfer process between the redox centers of apoMF and bound iron. Incubation of apoMFred with the Fe(3+)-ATP complex under anaerobic conditions resulted in the formation and binding of two Fe2+ and four Fe3+ by the protein. The various redox states formed by the binding of Fe2+ and Fe3+ to apoMFox and apoMFred are proposed and discussed. The yellow color of apoMF appears to be an integral characteristic of the apoMF and is possibly associated with its redox activity.

  5. Redox mechanisms in hepatic chronic wound healing and fibrogenesis

    PubMed Central

    Novo, Erica; Parola, Maurizio

    2008-01-01

    Reactive oxygen species (ROS) generated within cells or, more generally, in a tissue environment, may easily turn into a source of cell and tissue injury. Aerobic organisms have developed evolutionarily conserved mechanisms and strategies to carefully control the generation of ROS and other oxidative stress-related radical or non-radical reactive intermediates (that is, to maintain redox homeostasis), as well as to 'make use' of these molecules under physiological conditions as tools to modulate signal transduction, gene expression and cellular functional responses (that is, redox signalling). However, a derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, can play a significant role in the pathogenesis of major human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis. This review has been designed to first offer a critical introduction to current knowledge in the field of redox research in order to introduce readers to the complexity of redox signalling and redox homeostasis. This will include ready-to-use key information and concepts on ROS, free radicals and oxidative stress-related reactive intermediates and reactions, sources of ROS in mammalian cells and tissues, antioxidant defences, redox sensors and, more generally, the major principles of redox signalling and redox-dependent transcriptional regulation of mammalian cells. This information will serve as a basis of knowledge to introduce the role of ROS and other oxidative stress-related intermediates in contributing to essential events, such as the induction of cell death, the perpetuation of chronic inflammatory responses, fibrogenesis and much more, with a major focus on hepatic chronic wound healing and liver fibrogenesis. PMID:19014652

  6. Redox properties of structural Fe in clay minerals: 3. Relationships between smectite redox and structural properties.

    PubMed

    Gorski, Christopher A; Klüpfel, Laura E; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B

    2013-01-01

    Structural Fe in clay minerals is an important redox-active species in many pristine and contaminated environments as well as in engineered systems. Understanding the extent and kinetics of redox reactions involving Fe-bearing clay minerals has been challenging due to the inability to relate structural Fe(2+)/Fe(total) fractions to fundamental redox properties, such as reduction potentials (EH). Here, we overcame this challenge by using mediated electrochemical reduction (MER) and oxidation (MEO) to characterize the fraction of redox-active structural Fe (Fe(2+)/Fe(total)) in smectites over a wide range of applied EH-values (-0.6 V to +0.6 V). We examined Fe(2+)/Fe(total )- EH relationships of four natural Fe-bearing smectites (SWy-2, SWa-1, NAu-1, NAu-2) in their native, reduced, and reoxidized states and compared our measurements with spectroscopic observations and a suite of mineralogical properties. All smectites exhibited unique Fe(2+)/Fe(total) - EH relationships, were redox active over wide EH ranges, and underwent irreversible electron transfer induced structural changes that were observable with X-ray absorption spectroscopy. Variations among the smectite Fe(2+)/Fe(total) - EH relationships correlated well with both bulk and molecular-scale properties, including Fe(total) content, layer charge, and quadrupole splitting values, suggesting that multiple structural parameters determined the redox properties of smectites. The Fe(2+)/Fe(total) - EH relationships developed for these four commonly studied clay minerals may be applied to future studies interested in relating the extent of structural Fe reduction or oxidation to EH-values.

  7. In vitro Real-time Measurement of the Intra-bacterial Redox Potential

    PubMed Central

    van der Heijden, Joris; Finlay, B. Brett

    2016-01-01

    All bacteria that live in oxygenated environments have to deal with oxidative stress caused by some form of exogenous or endogenous reactive oxygen species (ROS) (Imlay, 2013). Large quantities of ROS damage DNA, lipids and proteins which can eventually lead to bacterial cell death (Imlay, 2013). In contrast, smaller quantities of ROS can play more sophisticated roles in cellular signalling pathways affecting almost every process in the bacterial cell e.g. metabolism, stress responses, transcription, protein synthesis, etc. Previously, inadequate analytical methods prevented appropriate analysis of the intra-bacterial redox potential. Herein, we describe a method for the measurement of real-time changes to the intra-bacterial redox potential using redox-sensitive GFP (roGFP2) (van der Heijden et al., 2015). The roGFP2 protein is engineered to contain specific cysteine residues that form an internal disulfide bridge upon oxidation which results in a slight shift in protein conformation (Hanson et al., 2004). This shift results in two distinct protein isoforms with different fluorescence excitation spectra after excitation at 405 nm and 480 nm respectively. Consequently, the corresponding 405/480 nm ratio can be used as a measure for the intra-bacterial redox potential. The ratio-metric analysis excludes variations due to differences in roGFP2 concentrations and since the conformational shift is reversible the system allows for measurement of oxidizing as well as reducing conditions. In this protocol we describe the system by measuring the intra-bacterial redox potential inside Salmonella typhimurium (S. typhimurium) however this system can be adjusted for use in other Gram-negative bacteria. PMID:27617271

  8. Macromodel for changes in polishing pad surface condition caused by dressing and polishing

    NASA Astrophysics Data System (ADS)

    Isobe, Akira; Ogata, Kenjiro; Kurokawa, Shuhei

    2014-01-01

    A macromodel for changes in a pad surface by dressing and polishing is proposed. A polishing pad is divided into small areas and it is assumed that each area takes an “H” (= high) or “L” (= low) condition. The condition is changed by dressing or polishing, and the total chemical mechanical planarization (CMP) performance is determined by the average pad condition. The results from equations are compared with experimental data, and good correspondence is confirmed. Various CMP behaviors are well explained by the equations, such as polishing rate stabilization by dummy running, the differences in the stability time and polishing rate between in situ dressing and ex situ dressing, and polishing rate behaviors for patterned wafers. This new model can be used to predict process performances, to optimize process conditions, or to indicate the direction of consumable development.

  9. Redox proteomics in the mussel, Mytilus edulis.

    PubMed

    McDonagh, B; Tyther, R; Sheehan, D

    2006-07-01

    Pollutants (e.g. PAHs, metals) cause oxidative stress (OS) by forming reactive oxygen species. Redox proteomics provides a means for iden